U.S. patent application number 16/372325 was filed with the patent office on 2019-07-25 for heat utilization in orc systems.
The applicant listed for this patent is Bitzer US, Inc.. Invention is credited to Paul Hughes, David C. Williams.
Application Number | 20190226363 16/372325 |
Document ID | / |
Family ID | 55437087 |
Filed Date | 2019-07-25 |
United States Patent
Application |
20190226363 |
Kind Code |
A1 |
Williams; David C. ; et
al. |
July 25, 2019 |
Heat Utilization in ORC Systems
Abstract
Apparatus, systems and methods are provided for the improved use
of waste heat recovery systems which utilize the organic Rankine
cycle (ORC) to generate mechanical and/or electric power from heat
sources generating power from byproducts of water purification
process(es). Waste heat energy obtained from heat source(s) is
provided to one or more ORC system(s) which may be operatively
coupled to electric generator(s). A heat coupling subsystem
provides the requisite condensation of ORC working fluid by
transferring heat from ORC working fluid to one or more other
process(es) or system(s), such as anaerobic digester tank(s), to
provide heat energy that enhances the production of fuel for the
prime mover(s) without requiring the consumption of additional
energy for that purpose.
Inventors: |
Williams; David C.; (Carson
City, NV) ; Hughes; Paul; (Reno, NV) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bitzer US, Inc. |
Flowery Branch |
GA |
US |
|
|
Family ID: |
55437087 |
Appl. No.: |
16/372325 |
Filed: |
April 1, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14944213 |
Nov 18, 2015 |
10247045 |
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16372325 |
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14625616 |
Feb 18, 2015 |
9702271 |
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14944213 |
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13758941 |
Feb 4, 2013 |
8997490 |
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14625616 |
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61594168 |
Feb 2, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 2209/02 20130101;
F02B 43/08 20130101; C02F 3/28 20130101; F01K 23/04 20130101; F01K
13/006 20130101; Y02T 10/12 20130101; C02F 2303/10 20130101; F01K
25/08 20130101; F01K 13/00 20130101; F01K 23/064 20130101; F01K
25/10 20130101; Y02W 10/30 20150501; C02F 3/303 20130101; Y02W
30/40 20150501; F01K 7/16 20130101; F01K 9/003 20130101; Y02E 50/30
20130101; Y02P 20/145 20151101 |
International
Class: |
F01K 7/16 20060101
F01K007/16; F01K 25/08 20060101 F01K025/08; F01K 9/00 20060101
F01K009/00; F01K 25/10 20060101 F01K025/10; F01K 13/00 20060101
F01K013/00; F02B 43/08 20060101 F02B043/08; F01K 23/04 20060101
F01K023/04; F01K 23/06 20060101 F01K023/06 |
Claims
1. A method of recovering energy from a wastewater treatment
system, the method comprising steps of: A. apportioning a quantity
of heat energy among one or more heat consuming water purification
process(es) using one or more valve(s); B. using at least some of
said heat energy by at least one of said one or more water
purification process(es) to produce at least one byproduct suitable
to generate heat by one or more source(s) of heat energy; C.
communicating some or all of said at least one byproduct to one or
more source(s) of heat energy; D. generating heat energy by said
one or more source(s) of heat energy using said some or all of said
at least one byproduct; E. communicating at least a portion of said
generated heat energy to a working fluid; and F. generating
mechanical power via expansion of said working fluid in a working
fluid expander.
2. The method of claim 1 wherein said one or more source(s) of heat
energy comprise at least one of any of a prime mover, an internal
combustion engine, a boiler, a fuel cell, and a microturbine.
3. The method of claim 1 wherein at least one of said one or more
water purification process(es) comprises at least one of any of an
anaerobic digestion process, an aerobic process, a biological
nutrient removal processes, and a combustible gas generation
process.
4. The method of claim 1 wherein said at least one byproduct
comprises at least one of any of a biogas, methane, hydrogen, and a
residual solid effluent.
5. The method of claim 1 wherein said mechanical power is
communicated to at least one of any of an electric generator, a
prime mover, a pump, a combustion engine, a fan, a turbine, and a
compressor.
6. The method of claim 1 wherein the steps of communicating heat
energy to a working fluid and generating mechanical power are
performed via an organic Rankine system.
7. The method of claim 1 wherein said quantity of heat energy
apportioned among said one or more heat consuming water
purification process(es) comprises at least a portion of the heat
energy generated by said one or more source(s) of heat energy.
8. The method of claim 1 further comprising a step of apportioning
at least some of said quantity of heat energy to at least one
radiator.
9. The method of claim 8 wherein said quantity of heat energy
apportioned among said one or more heat consuming water
purification process(es) and said at least one radiator comprises
at least a portion of the heat energy generated by said one or more
source(s) of heat energy.
10. The method of claim 1 wherein said quantity of heat energy
apportioned among said one or more heat consuming water
purification processes comprises heat energy received from an
organic Rankine cycle system.
11. The method of claim 10 wherein said heat energy received from
an organic Rankine cycle system is communicated via an alternate
medium.
12. The method of claim 11 wherein said alternate medium is at
least one of any of air, treated aqueous effluent, and water.
13. A wastewater treatment heat energy management method comprising
steps of: A. using at least one heat consuming water purification
process to generate at least one byproduct suitable for use in heat
generation; B. generating heat energy by consuming said byproduct
by at least one source of heat energy; C. communicating at least a
portion of said generated heat energy to a working fluid to create
heated working fluid; D. generating mechanical power by expanding
said heated working fluid in a working fluid expander; E.
apportioning and communicating at least a portion of heat energy
remaining in said expanded working fluid to said at least one heat
consuming water purification process using one or more valves; and
F. consuming some or all of said communicated expanded working
fluid heat energy by said at least one water purification
process.
14. The method of claim 13 wherein said at least one source of heat
energy comprises at least one of any of a prime mover, an internal
combustion engine, a boiler, a fuel cell, and a microturbine.
15. The method of claim 13 wherein said at least one water
purification process comprises at least one of any of an anaerobic
digestion process, an aerobic process, a biological nutrient
removal processes, and a combustible gas generation process.
16. The method of claim 13 wherein said at least one byproduct
comprises at least one of any of a biogas, methane, hydrogen, and a
residual solid effluent.
17. The method of claim 13 wherein said mechanical power is
communicated to at least one of any of an electric generator, a
prime mover, a pump, a combustion engine, a fan, a turbine, and a
compressor.
18. The method of claim 13 wherein the steps of creating heated
working fluid and expanding said heated working fluid in a working
fluid expander are performed using an organic Rankine cycle
system.
19. The method of claim 13 wherein the step of apportioning and
communicating heat energy further comprises a step of apportioning
and communicating at least some of said heat energy to at least one
radiator.
20. The method of claim 13 wherein said apportioned and
communicated heat energy comprises at least a portion of the heat
energy generated by said one or more source(s) of heat energy.
21. The method of claim 20 wherein the step of apportioning and
communicating heat energy further comprises a step of apportioning
and communicating at least some of said heat energy to said at
least one radiator.
22. The method of claim 13 whereon said quantity of heat energy
apportioned among said one or more heat consuming water
purification processes comprises heat energy communicated from an
organic Rankine cycle system.
23. The method of claim 22 wherein said heat energy communicated
from an organic Rankine cycle system is communicated via an
alternate medium.
24. The method of claim 23 wherein said alternate medium is at
least one of any of air, treated aqueous effluent, and water.
Description
RELATED APPLICATIONS
[0001] This application is a Continuation and claims domestic
benefit of co-owned of pending U.S. Nonprovisional patent
application Ser. No. 14/944,213 entitled "Heat Utilization in ORC
Systems" filed Nov. 18, 2015, which is a Continuation-in-Part and
claims domestic benefit of co-owned pending U.S. Nonprovisional
patent application Ser. No. 14/625,616, now U.S. Pat. No.
9,702,271, entitled "Heat Utilization in ORC Systems" filed Feb.
18, 2015, which is a Continuation of co-owned Nonprovisional patent
application Ser. No. 13/758,941, now U.S. Pat. No. 8,997,490,
entitled "Improved Heat Utilization in ORC Systems" filed Feb. 4,
2013, which in turn claimed benefit of co-owned U.S. Provisional
Patent Application 61/594,168 entitled "Improved Heat Utilization
in ORC Systems" filed Feb. 2, 2012. All four of said applications
(Ser. Nos. 14/944,213, 14/625,616, 13/758,941, and 61/594,168) are
incorporated herein by reference in their entireties for all useful
purposes. In the event of inconsistency between anything stated in
this specification and anything incorporated by reference in this
specification, this specification shall govern.
FIELD OF INVENTION
[0002] The present invention relates to the apparatus, systems, and
methods of utilizing organic Rankine cycle systems for the
generation of power from waste heat sources.
BACKGROUND
[0003] Many physical processes are inherently exothermic, meaning
that some energy previously present in another form is converted to
heat by the process. While the generation of heat energy may be the
desired outcome of such a process, as with a boiler installed to
provide radiant heat to a building using a network of conduits
which circulate hot water to radiators or a furnace used for the
smelting of metals, in many other instances unwanted heat is
produced as a byproduct of the primary process. One such example is
that of the internal combustion engine of an automobile where the
primary function is to provide motive force but where the
generation of significant unwanted heat is unavoidable. Even in
those processes where the generation of heat energy is desired,
some degree of residual heat unavoidably escapes or remains which
can be managed and/or dissipated. Whether generated intentionally
or incidentally, this residual, or waste, heat represents that
portion of the input energy which was not successfully applied to
the primary function of the process in question. This wasted energy
detracts from the performance, efficiency, and cost effectiveness
of the system.
[0004] With respect to the internal combustion engine common to
most automobiles, considerable waste heat energy is generated by
the combustion of fuel and the friction of moving parts within the
engine. Automobiles are equipped with extensive systems that
transfer the heat energy away from the source locations and
distribute that energy throughout a closed-loop recirculating
system, which usually employs a water-based coolant medium flowing
under pressure through jackets within the engine coupled to a
radiator across which the imposition of forced air dissipates a
portion of the undesired heat energy into the environment. This
cooling system is managed to permit the engine to operate at the
desired temperature, removing some but not all of the heat energy
generated by the engine.
[0005] As a secondary function, a portion of the heat energy
captured by the engine cooling system may be used to indirectly
provide warm air as desired to the passenger compartment for the
operator's comfort. This recaptured and re-tasked portion of the
waste heat energy generated as a byproduct of the engine's primary
function represents one familiar example of the beneficial use of
waste heat.
[0006] Very large internal combustion engines are widely used in
heavy industry in numerous applications. For example, General
Electric's Jenbacher gas engine division produces a full range of
engines with output power capabilities ranging from 250 kW to over
4,000 kW (by comparison, a typical mid-class automobile engine
produces about 150 kW of usable output power). The Jenbacher
engines can be powered by a variety of fuels, including but not
limited to natural gas, biogas (such as provided by anaerobic
digestion), and other combustible gasses including those from
landfills, sewage, and coal mines. One common use of large
combustion engines, such as the Jenbacher model 312 and 316
engines, is to co-locate them at a biogas generation facility. This
consolidates, at one location, (i) the elimination of biodegradable
waste products that release chemical energy in the form of
combustible biogas and (ii) the capture and combustion of the
biogas in large combustion engines to generate useful power.
[0007] These engines are frequently employed to drive electric
power generators, converting the rotational mechanical energy from
the energy of combustion into electrical energy. One such example
of an anaerobic digestion system specifically designed for the
generation of electric power from biogas is offered by Harvest
Power of Waltham, Mass.
[0008] In operation, these engines generate tremendous amounts of
waste heat energy that has historically been dissipated into the
environment. In the case of the combined Jenbacher model 316 engine
and generator system with a maximum electric power output of
approximately 835 kW, approximately 460 kW of heat energy is lost
in the exhaust gas (at an approximate temperature of 950.degree.
F.) and approximately another 570 kW is lost in the cooling system
(with a typical jacket water coolant temperature of approximately
200.degree. F.). From this data, it can be seen that less than half
of the system's power output is in the desired form (in this case,
electric power output from the system generator). Unless recaptured
and repurposed, however, the portion of the input energy converted
to heat is lost. In many prior art systems, this heat energy is
lost and additional energy is required to cool the recirculating
jacket water. The heat from exhaust gas generally escapes into the
atmosphere, and the recirculating jacket water is cooled by an
outboard apparatus (such as by large external condensing radiators
driven by forced air sources), which consume additional electric
power to function and further reduce the efficiency of the
system.
[0009] Additionally, the dissipation of this waste heat energy into
the environment can have deleterious effects. Localized heating may
adversely affect local fauna and flora and can require additional
power, either generated locally or purchased commercially, to
provide additional or specialized cooling. Further, the noise
generated by forced air cooling of the jacket water heat radiators
can have undesirable secondary effects.
[0010] With regard to engines fueled by
anaerobic-digestion-generated biofuel, a variety of techniques,
including the use of electrical heating systems, have been employed
to provide heat energy to anaerobic digestion processes necessary
for relatively efficient generation of biogas by heated
microorganisms. These systems consume considerable energy and
therefore have an attendant cost of operation and maintenance. For
example, the anaerobic digester heating systems offered by Walker
Process Equipment of Aurora, Ill. produce hot water in excess of
160.degree. F. using electric power with boilers fueled by biogas,
natural gas, or fuel oil as input energy. In addition to the energy
consumed to provide this hot water, additional electric energy must
be consumed to manage the waste heat from this apparatus.
[0011] Waste heat energy systems employing the organic Rankine
cycle (ORC) system have been developed and employed to recapture
waste heat from sources such as the Jenbacher 312 and 316
combustion engines. One typical prior art ORC system for electric
power generation from waste heat is depicted in FIG. 1. Heat
exchanger 101 receives a flow of a heat exchange medium in a closed
loop system heated by energy from a large internal combustion
engine at port 106.
[0012] For example, this heat energy may be directly supplied from
the combustion engine via the jacket water heated when cooling the
combustion engine, or it may be coupled to the ORC system via an
intermediate heat exchanger system installed proximate to the
source of exhaust gas of one or more combustion engines. In either
event, heated matter from the combustion engine or heat exchanger
is pumped to port 106 or its dedicated equivalent. The heated
matter flows through heat exchanger 101 and exits at port 107 after
transferring a portion of its latent heat energy to the separate
but thermally coupled closed loop ORC system which typically
employs an organic refrigerant as a working fluid. Under pressure
from the system pump 105, the heated working fluid, predominantly
in a gaseous state, is applied to the input port of expander 102,
which may be a positive displacement machine of various
configurations, including but not limited to a twin screw expander
or a turbine. Here, the heated and pressurized working fluid is
allowed to expand within the device, and such expansion produces
rotational kinetic energy that is operatively coupled to drive
electrical generator 103 and produce electric power which then may
be delivered to a local, isolated power grid or the commercial
power grid. The expanded working fluid at the output port of the
expander, which typically is a mixture of liquid and gaseous
working fluid, is then delivered to condenser subsystem 104 where
it is cooled until it has returned to a sufficiently liquid
state.
[0013] The condenser subsystem sometimes includes an array of
air-cooler radiators or another system of equivalent performance
through which the working fluid is circulated until it reaches the
desired temperature and state, at which point it is applied to the
input of system pump 105. System pump 105 provides the motive force
to pressurize the entire system and supply the liquid working fluid
to heat exchanger 101, where it once again is heated by the energy
supplied by the combustion engine waste heat and experiences a
phase change to its gaseous state as the organic Rankine cycle
repeats. The presence of working fluid throughout the closed loop
system ensures that the process is continuous as long as sufficient
heat energy is present at input port 106 to provide the requisite
energy to heat the working fluid to the necessary temperature. See,
for example, Langson U.S. Pat. No. 7,637,108 ("Power Compounder")
which is hereby incorporated by reference.
[0014] As a result of the transfer of waste heat energy from the
combustion engine to the ORC system, these types of prior art ORC
systems serve two functions. They convert this waste heat energy,
which would otherwise be lost, into productive power and they
simultaneously provide a beneficial, and sometimes a necessary,
cooling or condensation function for the combustion engine. In
turn, the ORC system's shaft output power has been used in a
variety of ways, such as to drive an electric power generator or to
provide mechanical power to the combustion engine, a pump, or some
other mechanical apparatus.
[0015] ORC systems can extract as much useful heat energy as is
practicable from one or more waste heat sources (often referred to
as the "prime mover"), but owing to various physical limitations
they cannot convert all available waste heat to mechanical or
electric power via the expansion process discussed above. Similar
in some respects to the cooling requirements of the prime mover,
the ORC system requires post-expansion cooling (condensation) of
its working fluid prior to repressurization of the working fluid by
the system pump and delivery of the working fluid to the heat
exchanger. The heat energy lost in this condensation process,
however, represents wasted energy which detracts from the overall
efficiency of the system.
[0016] Some prior art combined prime mover/ORC engine applications
have utilized heat generated by the ORC condensation process in a
conventional ORC system condenser while simultaneously providing
power (electrical and/or mechanical) for various purposes. Combined
heat and power ("CHP") ORC systems have typically fulfilled a
secondary purpose by using a portion of the heat energy from the
prime mover and/or heat energy remaining in the post-expansion
working fluid. FIG. 5 depicts a prior art ORC system including
combustion engine heat energy output port 501 and condenser heat
energy output port 502.
[0017] In one prior art ORC application, residual heat extracted
from a dedicated ORC condenser during the cooling of post-expansion
ORC working fluid at condenser heat energy output port 502 is used
to provide domestic hot water, radiant heating, or both. This
process requires the use of a conventional ORC condenser system
well known in the art. The energy flow of such an application is
depicted in the block diagram of FIG. 6. Here, a heat generating
engine 601 is operatively coupled to electric generator 602 and
provides waste heat energy 603 to the ORC system 604, which is
operatively coupled to drive electric generator 605. Heat energy
from the prime mover 601 is delivered to heat energy output port
501 and, in some prior art systems, is extracted to (i) a first
heat energy input port 606 (such as for radiant heating) and (ii) a
second heat energy input port 607 (such as for hot water heating).
In those ORC systems known by the applicants, the utilization of
residual heat from the post-expansion working fluid is
intentionally extracted from the system but is not utilized for
further system optimization of the prime mover or, for example, for
heating a production material such as microorganisms to generate
biofuel.
BRIEF SUMMARY OF SOME ASPECTS OF DISCLOSURE
[0018] The applicants have invented apparatus, systems, and methods
that productively utilize heat energy generated by ORC working
fluid condensation to produce fuel or other power or energy for use
by the prime mover. In some embodiments, the prime mover can use
the fuel, power, or energy to drive a prime mover.
[0019] In certain embodiments, the system includes: (i) a biogas
generation system providing combustible biogas to fuel the prime
mover; (ii) a prime mover that provides heat energy to drive an ORC
engine; and (iii) an ORC engine that provides heat energy to drive
the biogas generation system. In some embodiments, the biogas
generation system utilizes an anaerobic digestion process which can
utilize ORC heat energy to maintain the temperature for the
anaerobic process to take place.
[0020] In some embodiments, the prime mover may provide mechanical
power to drive one or more electric generators. In some
embodiments, such generators can be connected to a power
distribution grid.
[0021] In some applications, the biogas generation system can be
co-located with prime mover and ORC system(s) so that (i) one or
more prime mover(s) provide waste heat to drive one or more
co-located ORC system(s), (ii) one or more ORC system(s) provides
waste heat to microorganisms to drive the co-located biogas
generation system, and (iii) resulting biogas can provide fuel for
one or more co-located prime mover(s). In some of these
applications, one or more prime mover(s) and one or more ORC
system(s) can simultaneously provide productive power for an of a
wide variety of devices and applications, locally or otherwise.
Alternatively or in addition, the ORC system(s) may provide waste
heat to co-located heat consuming system(s) other than biogas
generation system(s). In some applications, the prime mover may
receive fuel from more than one source. For example, a prime mover
may run on locally-generated biogas during a portion of its
operating schedule and another fuel during other portions of its
operating schedule. Such other fuels may include but are not
limited to stored biogas, biogas imported from other sources, other
forms of combustible gasses, or alternate fuels (liquid, solid, or
gaseous) suited to the requirements of the prime mover. In some
applications, fuels from multiple sources may be mixed together and
that mixture supplied to the prime mover. This technique would
allow the operator to control the composition of the fact and the
exhaust emissions of the prime mover based in its availability and
to maximize performance and cost efficiency of its operation.
[0022] In some instances, waste heat energy obtained from the
exhaust gasses and/or cooling jacket water of the prime mover is
provided to one or more ORC system(s) which are operatively coupled
to one or more separate electrical generator(s) that are similarly
connected to the commercial power distribution grid. The heat
coupling subsystem can comprise a heat exchanger which is
operatively coupled to provide the requisite condensation of ORC
working fluid by transferring heat energy from said fluid to one or
more anaerobic digester tank(s). That heat energy can help optimize
production of biogas from the anaerobic digestion process used to
power the prime mover, and, when operated in concert with an ORC
system also generating electric power, improve the efficiency of,
and maximize the economic benefit of, the combined system.
[0023] The prime mover of some embodiments can be any system,
apparatus, or combination of apparatus, that converts some or all
of its input energy into heat energy or waste heat energy in a form
and quantity sufficient for use by one or more ORC system(s). In
some embodiments, the only purpose of the prime mover will be to
generate heat for the ORC system(s). All heat energy sources
co-located, compatible for use with, and utilized by one or more
ORC system(s) fall within the scope of the term "waste heat" for
the purpose of this application.
[0024] In some systems, a prime mover can generate and deliver
mechanical power to an electric power generator in addition to
providing waste heat energy for the ORC system(s). In certain
embodiments, a prime mover can simultaneously generate more than
one form of waste heat, including but not limited to cooling water,
hot exhaust gas, or radiated heat. The waste heat energy may be
captured and provided to the ORC system in any practicable manner,
either directly or via one or more intermediate heat exchanger
systems.
[0025] In some instances, one or more prime movers may provide
waste heat energy to one or more ORC systems. In some embodiments,
a single heat exchanger may be employed for any ORC system, any
prime mover, any source of heat energy from each prime mover, or
for more than one ORC system, prime mover, or heat energy source.
These heat exchangers may have separate input ports and separate
output ports for the energy source(s) or a single input and/or
output port may be utilized for more than one source.
[0026] In certain embodiments, one or more ORC system(s) operate
with a closed loop refrigerant cycle to prevent intermixture of
working fluid between systems. Similarly, in some instances one or
more prime mover(s) operate with a closed loop jacket water cooling
system to prevent any intermixture of jacket water between systems.
In other embodiments, a single exhaust gas heat recovery system is
employed to recover waste heat energy from more than one prime
mover and provide such heat energy to more than one associated ORC
system. In some embodiments, a heat recovery system receives heat
energy input from one or more sources and/or provides heat energy
to more than one ORC system.
[0027] In some systems, one or more additional heat sources provide
heat input to the ORC system(s). For example, a portion of the
biogas generated by the anaerobic digestion process may be burned a
separate boiler and used to provide heat input to the ORC system(s)
in addition to, or in lieu of, waste heat input from one or more
prime mover(s).
[0028] in certain embodiments, a portion of the waste heat energy
from the prime mover may be applied directly to the anaerobic
digestion process without having been first applied to the ORC
system(s). This can be beneficial in the event that the anaerobic
digestion heating requirements exceed the residual heat energy
available from the post-expansion working fluid in the ORC
system(s).
[0029] In some applications, one or more ORC systems constitute the
entire jacket water cooling system for the prime mover(s). In such
cases, the ORC systems may replace alternative prime mover cooling
systems, which consume, rather than generate, power during
operation and therefore usually have a significant cost of
operation in addition to their cost of installation. Such power
consuming dedicated prime mover cooling systems typically have a
significantly larger footprint than an ORC system; and therefore
they may have additional physical space requirements at the
generation facility. They may also generate noise and unwanted
environmental heat pollution as a consequence of operation.
Employing one or more ORC system(s) in lieu of power consuming
dedicated prime mover cooling systems, which are net consumers of
power under such circumstances, can be economically, physically,
and environmentally beneficial.
[0030] In some embodiments, the waste heat recovery system(s)
include one or more power generating system, which may be ORC
system(s), and one or more power receiving apparatus, which may be
but are not limited to electric power generator(s), prime mover(s),
pump(s), combustion engine(s), fan(s), turbine(s), compressor(s),
and the like. The rotational mechanical power generated by the
power generating system(s) is delivered to the power receiving
component.
[0031] In some embodiments, the ORC system(s) provide a portion of
the cooling system for the prime mover(s) and operate in
conjunction with one or more additional cooling system(s). In some
embodiments, electric power generated by the ORC systems may be
applied to the operation of said additional cooling systems for the
prime mover as well as provide electric power for other purposes at
the site or elsewhere. This can be particularly advantageous if,
for example, the prime mover is configured to solely provide
mechanical power output and a commercial source of electric power
is not readily available.
[0032] In some embodiments, one or more ORC system(s) may provide
heat energy to one or more anaerobic digestion tanks or other
anaerobic digestion structure. In some instances, multiple ORC
systems can provide heat energy to a single anaerobic digestion
tank. In some embodiments, the anaerobic digestion heating system
includes the entire condenser subsystem for the ORC system(s). In
other embodiments, the anaerobic digestion heating system comprises
a portion of the ORC condenser subsystem(s) in combination with one
or more other condensing system(s) which may operate on a regular
or intermittent basis dictated by a number of factors including
seasonal requirements. The ambient environmental conditions, the
number of ORC systems and their ratings, and/or the number,
configuration, location, or volume of the anaerobic digestion tanks
may each be factors in determining the configuration and operation
of the condenser portion of the ORC systems.
[0033] In some embodiments, the heat energy supplied by the ORC
system to the anaerobic digestion process can reduce or even
completely obviate the need for a supplemental anaerobic digestion
tank heating system. In some instances, this can reduce or even
eliminate the cost of installation, maintenance, and operation of
such supplemental system, including costs associated with electric
power and/or other fuels which may have previously been consumed by
its operation. In some cases, the ORC system can provide heat to
the anaerobic digestion process in combination with one or more
other heating systems, which can serve to reduce rather than
eliminate the attendant costs.
[0034] In some embodiments, the ORC system supplies all heat
required by the anaerobic digestion system via the transfer of heat
energy from the ORC process. In some embodiments, some or all of
the electric power generated by the ORC system can be supplied to
electrical heating systems to heat the anaerobic digestion tank(s).
This heating can be in addition to, or in lieu of, the direct
transfer of heat energy from the ORC system to the anaerobic
digestion system and can vary based on factors such as the
availability of heat energy and/or other electrical power, heating
requirements, and the like. In some embodiments, a portion of
electric power output generated by the ORC system is supplied to
other components or systems operatively connected (either
electrically, mechanically, or thermally) to the combined ORC and
anaerobic digestion system, including but not limited to other
heating systems, cooling systems, fans, pumps, compressors,
circulation systems, filtration equipment, stirring systems, and
the like.
[0035] The foregoing is a brief summary of only some of the novel
features, problem solutions, and advantages variously provided by
the various embodiments. It is to be understood that the scope of
the invention is to be determined by the claims as issued and not
by whether a claim addresses an issue noted in the Background or
provide a feature, solution, or advantage set forth in this Brief
Summary. Further, there are other novel features, solutions, and
advantages disclosed in this specification; they will become
apparent as this specification proceeds.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Without limiting the invention to the features and
embodiments depicted, certain aspects this disclosure, including
the preferred embodiment, are described in association with the
appended figures in which;
[0037] FIG. 1 is a block diagram of a prior art ORC system used to
convert waste heat energy into electric power;
[0038] FIG. 2A is a block diagram of a heat coupling subsystem with
heat exchangers to transfer heat energy from a closed loop system
to an anaerobic digestion tank;
[0039] FIG. 2B is a block diagram of a single ORC system used to
convert waste heat energy into electric power while simultaneously
providing heat energy to a single anaerobic digestion tank that
provides condensing functionality for the ORC system;
[0040] FIG. 2C is a block diagram of a single ORC system used to
convert waste heat energy into electric power while simultaneously
providing heat energy to a single anaerobic digestion tank that
provides partial condensing functionality for the ORC system,
augmented by the presence of a separate condenser;
[0041] FIG. 2D is a block diagram of an embodiment of this
invention comprising multiple heat exchangers and valve(s)
operative to apportion heat energy there between;
[0042] FIG. 3 is a block diagram of multiple ORC systems
simultaneously delivering heat energy to a single anaerobic
digestion tank while providing condensing functionality for the ORC
systems;
[0043] FIG. 4 is a block diagram of a single ORC system
simultaneously delivering heat energy to a multiple anaerobic
digestion tanks while providing condensing functionality for the
ORC system;
[0044] FIG. 5 is a block diagram of a prior art ORC system used to
convert waste heat energy into electric power including heat
extraction ports that can be used to provide heat for other
applications;
[0045] FIG. 6 is a block diagram of the energy flow in a prior art
system comprising a prime mover, an ORC system used to convert
waste heat energy into electric power, and heat extraction ports
for other non-system applications;
[0046] FIG. 7 is a block diagram of the energy flow in a system
comprising a prime mover, an ORC system used to convert waste heat
energy into electric power, and heat extraction from the prime
mover used to improve system efficiency;
[0047] FIG. 8 is a block diagram of the energy flow in a system
comprising a prime mover, an ORC system used to convert waste heat
energy into electric power, and heat extraction from the ORC system
used to improve system efficiency;
[0048] FIG. 9 is a block diagram of the energy flow in a system
comprising a prime mover, an ORC system used to convert waste heat
energy into electric power, and heat extraction from the prime
mover and from ORC system used to improve system efficiency;
and
[0049] FIG. 10 is a block diagram of a single ORC system used to
convert waste heat energy into electric power while simultaneously
providing heat energy to a single anaerobic digestion tank that
provides condensing functionality for the ORC system, including
heat extraction ports that can be used to provide heat for other
applications.
DETAILED DESCRIPTION OF THE PREFERRED AND OTHER EMBODIMENTS
[0050] The process of anaerobic digestion is well known in the art.
Certain strains of bacteria, in the absence of oxygen, are employed
to break down, or digest, certain biodegradable material including
food, yard, or other waste into byproducts such as combustible
gasses consisting of methane, hydrogen, and other trace components,
as well as a residual solid effluent byproduct. This effluent, or
sludge, contains ammonia, phosphorous, potassium, and other trace
materials and is beneficial to agriculture as a supplemental
enrichment fertilizer for soil or as a resource suitable for
combustion fuel to generate heat energy for any useful purpose.
[0051] The anaerobic digestion process involves three basic stages
involving different microorganisms, and the temperature of the
cultures can play a very significant role in the efficiency of the
digestion process. Mesophilic digestion, occurring at medium
temperatures, can be applied to discrete batches of biodegradable
waste while thermophilic digestion, occurring at higher
temperatures, may preferably be utilized on a continuous basis.
Although the anaerobic digestion microorganisms can survive within
the range from below freezing to above 135.degree. F., optimal
digestion occurs at 98.degree. F. for mesophilic organisms and
130.degree. F. for thermophilic organisms. Bacterial activity and
therefore biogas production is significantly reduced at greater
temperatures and declines at a somewhat lesser rate at cooler
temperatures. The requirement for heating of the cultures may vary
over time (over the course of a single day and, as seasons change,
throughout the year) based on ambient temperatures.
[0052] With reference now to FIG. 2A, a heat coupling subsystem 201
can be used to transfer heat energy to the anaerobic digestion
process while maintaining media isolation between a heat source and
an anaerobic digestion system in the heating tank 208, owing to
potentially different media requirements of the two systems. The
heat coupling subsystem 201 includes (i) an intermediate heat
exchanger 204, (ii) an anaerobic digestion tank heat exchanger 207
within, as part of the wall of, or otherwise in direct thermal
communication with, the anaerobic digestion tank 208, (iv) pumping
apparatus 209 between the tank heat exchanger 207 and the
intermediate heat exchanger 204, (v) operative coupling between the
various components described below, and (vi) secondary media (which
may be the same as or different from the primary medium depending
on system requirements) flowing within the isolated closed loop
provided by the tank-side (secondary) portion of the heat coupling
subsystem 201 via the input port 206 and the output port 205, the
anaerobic digestion tank heat exchanger 207, and the pumping
apparatus 209. Heat coupling subsystem 201 may also include storage
reservoirs (not shown) for a quantity of both the primary medium
and the secondary medium as necessary to insure that sufficient
media is available for the proper operation of each closed loop
systems on the primary and secondary sides.
[0053] The primary side of the intermediate heat exchanger 204
includes a primary side input port 202 to receive the heated
primary media (not shown) from the heat source, which may be an ORC
system, a prime mover, or any other source of heat energy, a
primary side heat exchanger section 204A, and a primary side output
port 203. This flow provides heat energy from the ORC system for
transfer to, and use by, the anaerobic digestion tank(s), e.g.,
208. The heated primary media can be ORC working fluid, water, a
mixture of water and ethyl glycol, a mixture of water and one or
more other components, or any other fluid or gaseous substance
compatible with the application and apparatus. The heated primary
media passes through the primary side 204A of intermediate heat
exchanger 204 and exits at primary side exit port 203. Heat energy
from the heated primary media is transferred to the secondary side
of the intermediate heat exchanger 204, through which a suitable
secondary media (not shown) enters at secondary side input port
206, flows through secondary side heat exchanger section 204B, and
exits at secondary side output port 205. This heated secondary
media then flows through anaerobic digestion tank heat exchanger
207, where heat energy is transferred from the heated secondary
media to the contents of anaerobic digestion tank 208 before being
pressurized by pumping apparatus 209 and returned to secondary side
of the intermediate heat exchanger 204 at the secondary side input
port 206.
[0054] With reference now to FIG. 2B, an ORC system, generally 200,
utilizes the heat coupling subsystem 201 within, as part of the
wall of, or otherwise in direct thermal communication within
anaerobic digestion tank 208 to provide cooling for the
post-expansion working fluid exiting from the expander 102. The ORC
working fluid exits the expander 102 and enters input port 202,
travels through the heat coupling subsystem 201, and then exits the
output port 203 and enters the system pump 105. The heat coupling
subsystem 201 and anaerobic digestion tank 208 therefore provide an
integrated working fluid condensation and heat consumption system.
That is, the anaerobic digestion tank heat exchanger 207, when
coupled to the ORC system via intermediate heat exchanger 204 in
the manner shown in FIG. 2A and described in detail above, comprise
heat coupling subsystem 201 which may be considered to function as
a single heat exchanger for the purposes of the ORC system.
Analogous to the performance of a transformer in an electrical
system, heat coupling subsystem 201 serves as a "thermal
transformer" which transfers heat energy from its primary (ORC)
side to its secondary (tank) side while maintaining isolation
between the separate media flowing in each closed loop. This
provides the equivalent performance of a condenser known in the
prior art with significant improvements. This particular system is
also a production system, meaning that the heat coupling subsystem
201 provides heat energy, via anaerobic digestion tank heat
exchanger 207, directly for production and not for mere disposition
of the heat as waste. In this example, the anaerobic digestion tank
heat exchanger 207 directly heats the contents of the anaerobic
digestion tank 208, yielding production of biogas. The temperature
of the post-expansion working fluid entering input port 202 should
be about 125.degree. F., which is nearly ideal for the purpose of
supplying heat to a continuous mesophilic anaerobic digestion
process including the heat energy losses from an intervening
intermediate heat exchanger.
[0055] Referring to both FIGS. 2A and 2B, in an embodiment
utilizing an intermediate heat exchanger 204, less heat energy will
be delivered to the anaerobic digestion tank(s) than is provided to
the primary side, i.e., through input port 202, of heat coupling
subsystem 201 due to the unavoidable loss of heat energy during the
heat transfer process from the primary medium to the secondary
medium via intermediate heat exchanger 204. However, for
applications with reduced anaerobic digestion heating requirements,
such as mesophilic digestion processes, this loss of heat energy
can be beneficial and can eliminate the requirement for a dedicated
supplemental condensing apparatus. This method may be applied to
any configuration of the anaerobic digestion heating apparatus.
[0056] With reference now to FIG. 2C, the structure and operation
of the system is identical to that of FIG. 2B with the addition of
an ORC condenser subsystem 104 between the input port 202 and the
outlet port 203. Condenser subsystem 104 functions as a heat
exchanger removing energy from the post-expansion working fluid to
restore the working fluid to a sufficiently liquid state. The
energy removed from the working fluid, in the form of heat, is
transferred to an alternate medium, such as air or a liquid, for
removal from the ORC system. In this embodiment comprising both
heat coupling subsystem 201 and condenser subsystem 104,
post-expansion ORC working fluid can thus travel through either or
both (i) the condenser subsystem 104 and (ii) the heat coupling
subsystem 201 associated with the anaerobic digestion tank 208.
This embodiment may be used when insufficient condensing capacity
might be provided by the anaerobic digestion tank 208 or during
periods of ORC operation when the anaerobic digestion tank 208 is
not in service. This embodiment permits the flow of post-expansion
working fluid directly from the outlet port 203 of the expander 102
directly to either condenser subsystem 104 or through heat coupling
subsystem 201. This will generally provide the greatest temperature
working fluid to heat coupling subsystem 201 and will permit
complete disassociation of heat coupling subsystem 201 from ORC
operation via the use of appropriate valves (not shown) at the
junctions of heat coupling subsystem 201 and the inlet and outlet
of condenser subsystem 104. Condenser subsystem 104 may generally
be any type of condenser system best suited for the particular
application and factors that govern the installation and operation
of the ORC system, including but not limited to the mass flow rate
of working fluid in the ORC system, ambient temperature conditions
including both diurnal and seasonal variations, equipment
footprint, installation and maintenance cost, and the like. In one
embodiment, condenser subsystem 104 may comprise one or more air
cooled radiators with forced air, as the medium, being driven
through the radiator(s) by one or more fans. In one embodiment,
condenser subsystem 104 may comprise one or more radiators wherein
a flow of a liquid medium is in heat transfer communication with
the post-expansion working fluid. In both embodiments, the media is
either discharged from the system or circulated and adequately
cooled in a separate system. All other configurations of condensing
subsystems known in the art and applicable to ORC systems are also
envisioned by this disclosure.
[0057] In a related embodiment shown in FIG. 2D, a condensing
transfer system 220 comprises an intermediate heat transfer unit
104A, condensing subsystem pump 221, one or more valve(s) 222,
anaerobic digester heat exchanger 223, and one or more secondary
heat exchanger(s) 228, all in heat energy transfer communication
via a separate condenser heat transfer medium flowing between said
elements. Post-expansion working fluid is conveyed to condensing
transfer system 220 via intermediate heat transfer unit 104A
through which the separate condenser heat transfer medium, in heat
transfer receiving communication with the working fluid, is
circulated via motive force provided by condensing subsystem pump
221. Said medium is separate from the ORC working fluid and may
comprise water, oil, an organic refrigerant, an inorganic compound,
or any other fluid or combinations of fluids of suitable
performance to accept heat energy from the working fluid and
provide said heat energy to one or more condensing subsystems
comprising the remainder of condensing transfer system 220. Heat
energy is transferred from the post-expansion working fluid to the
condenser heat transfer medium in intermediate heat transfer unit
104A, thereby heating the condenser heat transfer medium and
restoring the post-expansion working fluid to a sufficiently liquid
state suitable for pressurization by system pump 105 for reheating
and subsequent expansion in the ORC system as described elsewhere
herein.
[0058] Condensing subsystem pump 221 provides pressurization of the
heated condenser heat transfer medium necessary to convey said
heated medium to heat exchangers 223, 228, and others similarly
connected via the one or more valve(s) 222 that permit the flow of
heated condenser heat transfer medium to be controllably
distributed in any desired proportion as necessary and desirable
for system optimization. One or more valve(s) 222 are configured
receive the condenser heat transfer medium from pump 221 and direct
all of said heated condenser heat transfer medium to any one of
said heat exchangers, direct any portion of said heated condenser
heat transfer medium to any one heat exchanger and any other
portion(s) to any other heat exchanger(s), or to direct no heated
condenser heat transfer medium to any one or more than one of the
heat exchangers. However, as described below, at least a portion of
heated condenser heat transfer medium must be directed to at least
one heat exchanger. In this manner, the most efficient and
effective use of the heat energy removed from the post-expansion
working fluid may be realized.
[0059] FIG. 2D depicts anaerobic digester heat exchanger 223 in
heated condenser heat transfer medium receiving communication with
valve(s) 222. In one embodiment, anaerobic digester heat exchanger
223 may be intermediate heat exchanger 201 disclosed elsewhere
herein and depicted in FIG. 2A as being a component of heat
coupling subsystem 201. In this embodiment, primary side input port
202 and primary side output port 203 of intermediate heat exchanger
201 correspond to primary side input port 224 and primary side
output port 226, respectively, of anaerobic digester heat exchanger
223. Further, secondary side input port 206 and secondary side
output port 205 of intermediate heat exchanger 201 correspond to
secondary side input port 227 and secondary side output port 225 of
anaerobic digester heat exchanger 223. The primary and secondary
sides of anaerobic digester heat exchanger 223 are in thermal
transfer communication, allowing heat energy to be transferred from
the heated condenser heat transfer medium in the primary side to a
separate medium flowing in the secondary side. Said separate medium
may comprise water, oil, an organic refrigerant, an inorganic
compound, or any other fluid or combination of fluids of suitable
performance. The remaining components of intermediate heat
exchanger 201 may be identically configured as described and
depicted in FIG. 2A in this embodiment.
[0060] In one embodiment, anaerobic digester heat exchanger 223 may
be configured to provide heat energy to an anaerobic digestion tank
in any other manner described herein or otherwise known in the art.
By way of example and not limitation, anaerobic digester heat
exchanger 223 may be used in conjunction with the embodiments
depicted herein as FIG. 3, 4, 8, 9 or 10.
[0061] FIG. 2D also depicts secondary heat exchanger(s) 228 in
heated condenser heat transfer medium receiving communication with
valve(s) 222. Here, primary side input port 229 receives a flow of
heated condenser heat transfer medium from valve(s) 222 which
passes through the primary side of secondary heat exchanger(s) 228
and exits at output port 231. An additional and separate heat
transfer medium, which may comprise water, oil, an organic
refrigerant, an inorganic compound, or any other fluid or
combination of fluids of suitable performance, enters the secondary
side of secondary heat exchanger(s) 228 at input port 232, passes
through the secondary side of secondary heat exchanger(s) 228, and
exits at output port 230. The primary and secondary sides of
secondary heat exchanger(s) 228 are in thermal transfer
communication, thereby allowing heat energy to be transferred from
the heated condenser heat transfer medium in the primary side to
the separate medium flowing in the secondary side. In this manner,
heat energy from the heated condenser heat transfer medium is
transferred to the separate medium and thereby removed from
condensing transfer system 220.
[0062] Although only one exemplary secondary heat exchanger 228 is
depicted in FIG. 2D for clarity, it should be understood that the
instant disclosure provides for more than one such heat exchanger
in a similar or functionally equivalent arrangement (not shown).
Additional valve(s) 222 may be utilized to provide a controllable
portion, ranging from none to all, of the heated condenser heat
transfer medium from said valves to any of one or more heat
exchanger(s) 228 deemed necessary or desirable to provide
sufficient cooling for the ORC system and to provide and utilize
heat for any other desired purpose known in the art or later
developed.
[0063] In one embodiment, secondary heat exchanger(s) 228 comprise
one or more air cooled radiators subjected to forced air cooling
provided by electric fans. In this manner, heat energy from the
heated condenser heat transfer medium is transferred to the forced
air flow and thereby removed from condensing transfer system 220.
Said electric fans may be powered by electric power from a
commercial power grid, by electric power provided by one or more
generator(s) driven by mechanical power derived from the ORC
expander(s), by electric power provided by another local generator
associated with the prime mover(s) or anaerobic digestion system,
by mechanical power provided directly or indirectly by a rotating
shaft in or associated with one or more ORC expander(s), by
mechanical power provided directly or indirectly by another
rotating shaft in or associated with the prime mover(s) or
anaerobic digestion system, or by any other preferred source of
electric or mechanical power.
[0064] In one embodiment, secondary heat exchanger(s) 228 comprise
one or more liquid cooled radiators through which a flow of cooling
liquid, including but not limited to water, is passed through the
secondary side in heat energy receiving communication with the
heated condenser heat transfer medium flowing in the primary side
such that heat energy from the heated condenser heat transfer
medium is transferred to cooling liquid and thereby removed from
condensing transfer system 220. In one embodiment, the cooling
liquid may be cooled via any preferred means and re-circulated back
to the secondary side of secondary heat exchanger(s) 228 in a
closed-loop circuit. In an alternative embodiment, and preferably
when the cooling liquid is water, when a large supply of water is
available, and when the discharge of water heated by the condenser
heat transfer medium is both feasible and preferred, no attempt is
made to intentionally cool and re-circulate the cooling water. For
example, cooling water may be extracted from a source such as, but
not limited to, a well, a pond, or a large reservoir, provided to
secondary heat exchanger(s) 228 for cooling purposes, and then
discharged back into the same source or a different source. In one
embodiment, such cooling water may be extracted at or near a cool
point of the source and, after passing through secondary heat
exchanger(s) 228, be discharged at or near a warm point. In warm
summer months, the coolest point may be at the greatest depth of
the source and the warmest point may be at the surface. In cold
winter months, the upper surface of the source may be at or near
freezing temperatures while the warmest point may be at the
greatest depth. In the latter case, even the warmest temperature
will likely be sufficient for use by secondary heat exchanger(s)
228, and discharging water warmed by the heat transfer process at
the surface may be preferred to prevent the source from freezing.
Any preferred combinations of water extraction and return are
obvious to a person of ordinary skill in the art and are therefore
envisioned by this disclosure. In this manner, the temperature
characteristics of the source of cooling water may be controlled to
some degree, although such control is a potential advantage
secondary to that of the energy conversion and creation advantages
described elsewhere herein. Although extracting and returning the
water to and from, respectively, the same source allows for some or
all of the same water to be used more than once, the open nature of
this arrangement is distinguishable from the recirculating closed
loop embodiment described above because new (additional) water may
be added and previously-used water may be removed from the system
at any time, including via evaporation, unlike in a typical closed
loop system where a finite quantity of water is re-circulated
without addition or subtraction in the normal course of operation.
In one embodiment, water obtained for cooling from one source may
be returned to a different source whenever beneficial for any other
secondary purpose.
[0065] With reference now to FIG. 3, a series of ORC systems 301,
302, 303 are combined to provide heat energy to an anaerobic
digestion tank 308. Although three ORC systems are depicted, any
number of ORC systems can be included to provide the desired level
of heat transfer to the anaerobic digestion tank 308. This
embodiment may be particularly advantageous for large anaerobic
digestion facilities in order to maintain a uniform temperature
throughout a large volume anaerobic digestion tank 308. Since the
temperature of the medium circulating within the anaerobic
digestion heating system can be higher at its point of entry into
the tank and generally lowest at its point of exit as the heat
energy is transferred to the contents of the tank, the introduction
of several independent ORC systems, e.g., 301, 302, 303 at
different locations in the anaerobic tank 308 can provide for a
more even distribution of heat and corresponding uniform
temperature than would be possible from a single source.
[0066] The same or similar result may be achieved by a single ORC
system (not shown) using a specially designed manifold system (not
shown) having multiple heat coupling subsystems 201. For larger
digestion tanks, however, the finite heat energy available from a
single ORC system may be insufficient to maintain the temperature
of the tank contents uniformly at its desired, and in some
instances, optimal value. Any configuration of heat coupling
subsystems 201 may be employed to provide optimal results.
[0067] In order to provide the desired results, the geometry and
configuration of an anaerobic digestion tank heat exchanger 201
used to simultaneously heat the contents of the anaerobic digestion
tank(s) and provide condensation of the post-expansion working
fluid can be designed and implemented in view of the desired
performance of both subsystems. In one embodiment, the heated
medium (the post-expansion working fluid) flowing within the
anaerobic digestion tank heat exchanger 201 may directly circulate
within a series of interconnected pipes and/or manifolds (not
shown) inside the anaerobic digestion tank(s). These structures can
be essentially planar with media flows in a single plane
(neglecting the thickness of the components) or may be more three
dimensional with heated medium flows in two or more planes. The
configuration of the anaerobic digestion tank heat exchanger 201
may be designed with, as shown in FIGS. 2B and 2C, a single input
port 202 and output port 203 or may be configured with, as shown in
FIG. 3, multiple input ports 202 and output ports 203 to provide a
more uniform distribution of heat throughout the anaerobic
digestion tank 308. Further, the interconnected pipes and/or
manifolds may include a series of valves that permit control and
redirection of the heated medium to various regions of the
anaerobic digestion tank 308 as may be desired to achieve the
preferred distribution of heat. In another embodiment, the heated
medium may circulate through sealed channels embedded in the walls
of the anaerobic digestion tank(s), thereby heating the contents of
the tank at its interior boundaries or side wall(s).
[0068] With reference now to FIG. 4, a single ORC system 400 may be
used to provide heat energy to more than one anaerobic digestion
tank (not shown) via multiple heat coupling subsystems 401, 402,
and 403. In this embodiment, the available heat energy from
post-expansion working fluid from an ORC system 400 is distributed
to anaerobic digestion tank heat exchangers (not shown) in each of
three discrete anaerobic digestion tanks (not shown) via heat
coupling subsystems 401, 402, and 403. Each of these heat coupling
subsystems 401, 402, 403 may be comparable to heat coupling
subsystem 201 shown in FIG. 2A. The specific distribution of
post-expansion working fluid provided to each heat coupling
subsystem 401, 402, 403 can be controlled, varying it as needed to
allocate the available heat energy among the several tanks. In some
instances, this method can be well suited for smaller tanks,
systems with reduced requirements for anaerobic digestion heating,
or lower temperature mesophilic batch processing, particularly
where not all tanks are in simultaneous use. Although three tanks
are referenced here, any number of tanks are envisioned that
provide the requisite performance.
[0069] These combined ORC and anaerobic digestion systems are
distinguished from known prior combined heat and power systems in
that the prior technology merely siphons some portion of heat
energy from ports added to known ORC systems. The known prior art
does not teach, for example, the replacement of ORC condenser
systems, in whole or in part, with an alternate system including
one that simultaneously provides, via one heat coupling subsystem:
(i) heating directly to a heat consuming process which provides
some beneficial function and (ii) an equivalent cooling and
condensation function for the ORC working fluid primary media,
which may be heated post-expansion working fluid from the ORC. In
this regard, known prior art ORC systems typically require
significant electric power to drive fans or an equivalent cooling
system. The economic advantage of generating power from waste heat
energy is greatly reduced when a large portion of the generated
power is consumed by the system's internal requirements (sometimes
referred to as the "parasitic load"). The combined ORC and
anaerobic digestion system thus provides a double economic
advantage; not only is the requisite cooling provided for the
primary media, which in the case of an ORC will be heated
post-expansion working fluid, without additional electric power
consumption, but the electric power normally required to maintain
the anaerobic digestion tanks at the optimal temperature is no
longer required due to the transfer of heat energy from the
companion ORC system. While the known prior art requires electric
power to simultaneously cool the ORC media and heat the anaerobic
digestion tanks, the combined ORC and anaerobic digestion system
reduces or eliminates both requirements for electric power by
transferring unwanted heat energy directly via heat coupling
subsystem 201 from the ORC system to the anaerobic digestion
system. As a result, the net electric power generated by the
combined ORC and anaerobic digestion system is significantly
greater than in the present art, providing greater economic benefit
while conserving resources necessary to produce electric power.
[0070] In some embodiments of the present application, anaerobic
digestion-based biogas power generation systems can be enhanced by
integrating the functions of an ORC waste heat energy generation
system with the biogas-burning prime mover and the anaerobic
digestion process which generates the biogas for the prime mover.
Both the heat input and heat output of the ORC system can be
coupled to other components within the overall system. Unlike the
known prior art, which does not integrate all three subsystems into
a single optimized energy conversion system, some embodiments of
the present application provide for increased and possibly maximum
efficiency by utilizing more and possibly all available heat energy
within the system to a greater, and possibly the greatest, extent
practicable.
[0071] In certain embodiments, no heat energy is intentionally
dissipated or redirected to any non-system application. In certain
instances, as some or all of the lowest grade residual waste heat
energy remaining after two stages of electric power generation is
returned to enhance, and in some instances optimize, the production
of fuel for the primary electric power generation process, the
system forms a novel and more effective three stage
closed-energy-loop.
[0072] More specifically, the novel combined prime mover, ORC, and
anaerobic digestion system taught herein uniquely allows for each
of the three component systems to provide operational benefits of
the other two. Specifically, the anaerobic digestion system can, in
certain embodiments, be the anaerobic digestion system offered by
Harvest Power as described above. In certain embodiments, the prime
mover(s), which can be the Jenbacher 312 or 316 internal combustion
engines also described above, are fueled by biogas produced by the
anaerobic digestion process and cooled, in whole or in part, by one
or more ORC system(s) which remove undesired waste heat energy and
convert it to useful mechanical and/or electrical power. In this
manner, the ORC system(s), which in certain embodiments can be
Power+.TM. ORC system(s) offered by ElectraTherm, Inc. of Reno,
Nev., receive their input energy in the form of waste heat from the
prime mover(s) and provide post-expansion heat energy to the
anaerobic digestion process to enhance the production of biogas
fuel for the prime mover(s). Additionally, the heat energy from the
ORC that is absorbed by the anaerobic digestion process system
provides the necessary cooling condensation of post-expansion ORC
working fluid, obviating the need for a separate ORC condenser and
the attendant cost of operation. As each of the three component
system enhance the operation of the other two, all available heat
energy is utilized to the greatest extent possible and the need for
additional energy, particularly electrical energy, to provide
cooling and/or heating as in the present art is minimized or
eliminated.
[0073] In one embodiment depicted in FIG. 7, the prime mover 601
can simultaneously contribute heat energy and/or waste heat energy
603 to the ORC system 604 and heat energy 702 to the anaerobic
digestion tank 701, which provides the biogas fuel for the prime
mover 601.
[0074] In an embodiment depicted in FIG. 8, the ORC system 604 can
obtain its heat input from the waste heat energy 603 of prime mover
601 and deliver its own waste heat energy 801 to the anaerobic
digestion process. Heat energy flow 801 may be provided from the
post-expansion working fluid to anaerobic digestion tank 701.
[0075] In an embodiments depicted in FIG. 9, both the prime mover
601 and the ORC system 604 provide heat energy to anaerobic
digestion tank 701 as depicted in FIG. 9 via heat flows 702 and
801, respectively.
[0076] In addition to the heat energy being transferred from the
primary media (which in some embodiments may be post-expansion ORC
working fluid) to the anaerobic digestion process to increase the
efficiency of the overall system, heat energy may also be extracted
for other purposes. With reference now to FIG. 10, a prime mover
(not shown in FIG. 10) can provide heated prime mover media to the
heat exchanger 101 of an ORC system 1000 and to a prime mover heat
energy output port 501. Post-expansion working fluid heat energy
can be provided to the anaerobic digestion tank heat exchanger 201
and to an output port 1001; and post-anaerobic digestion tank heat
exchanger heat energy can be provided to output port 1002. Any
combination of these ports may be utilized to provide heat energy
for one or more purposes not related to the operation of the CHP
system.
[0077] One or more embodiments of this invention are particularly
well-suited for use in wastewater treatment systems where anaerobic
digestion systems are common and excess biogas produced by said
digestion systems is often burned as flares simply for disposal
purposes without providing any beneficial use or other advantage.
For the purposes of this disclosure, the phrase "wastewater
treatment" shall refer to any or all of the individual processes
known in the art whereby chemical, biological, or any other
contaminates are removed from an aqueous solution so as to reduce
the level of said contaminants, particularly but not necessarily to
a level wherein said aqueous solution is suitable for human
consumption or unrestricted use. Examples of wastewater treatment
facilities include, but are not limited to, sewage treatment
plants, irrigation water reclamation processing facilities, and the
like. In one wastewater treatment embodiment, the prime mover
providing heat to the ORC system may be an internal combustion
engine fueled at least in part by the biogas generated as a
byproduct of the anaerobic digestion system as disclosed elsewhere
herein. Heat energy from the engine jacket cooling water or exhaust
gas may be utilized by the ORC. In one embodiment, input heat
energy for the ORC system may be provided by one or more boilers
fueled by the biogas generated by the anaerobic digestion system or
other co-located process as disclosed elsewhere herein. Whenever
the term is used anywhere within the scope or applies to any
understanding of this disclosure, a co-located device, system or
process is one at or sufficiently proximate to the system disclosed
herein such that any input or output of said device, system or
process may be communicated to any input or output of any device,
system or processes directly or indirectly associated with the
disclosed system. Means of such communication between devices,
systems, or processes may be via any useful means, including but
not limited to wires, cable, conductors, electromagnetic waves,
pipes, tubing, conduit, raceways, rigid or flexible mechanical
devices such as rods, shafts, or linkages of any kind, heat energy
radiation, heat energy conduction, or by any other known or
subsequently developed means. In one embodiment, input heat energy
for the ORC system may be provided by any combination of internal
combustion engines or boilers. In one embodiment, input heat for
the ORC system may be provided by one or more fuel cells or
microturbines. In one embodiment, the dry sludge biosolid
byproducts of the anaerobic digestion process or any other
co-located process may also be incinerated in one or more boiler(s)
and the heat energy of said incineration supplied to the input of
the ORC system.
[0078] In one non-limiting exemplary embodiment pertinent to
wastewater treatment, heat energy may be delivered to system input
port 106 of FIG. 2D at an approximate temperature of 240.degree. F.
from one or more sources of heat comprising at least one of any of
boiler(s) or internal combustion engine(s) consuming some or all of
the biogas generated by the local anaerobic digestion system or by
any other co-located system or process. The ORC system operates as
described elsewhere herein, generating mechanical power via the
expansion of heated working fluid in expander 102 and either
conveying that mechanical power to generator 103 to provide
electrical power output or using the mechanical power directly for
some other beneficial purpose.
[0079] ORC condensing transfer system 220 is provided to remove
residual unwanted heat energy from the post-expansion ORC working
fluid and thereby return said working fluid to a sufficiently
liquid state. At inlet 233 of intermediate heat transfer unit 104A,
condenser heat transfer medium is provided at an approximate
temperature of 55.degree.-75.degree. F. at a flow rate of
approximately 200 gallons per minute. After receiving heat energy
transferred by the post-expansion working fluid, condenser heat
transfer medium, now heated to an approximate temperature of
110.degree.-113.degree. F., exits intermediate heat transfer unit
104A at outlet 234 and is pressurized by condensing subsystem pump
221 and conveyed to one or more valve(s) 222.
[0080] In one mode of operation of this embodiment, at least a
portion of the heated condenser heat transfer medium is provided
from said one or more valve(s) 222 to anaerobic digester heat
exchanger 223 via input port 224. Here, heat energy is transferred
from the heated condenser heat transfer medium to the anaerobic
digestion system to maintain the temperature of the cultures in the
range of 100.degree.-103.degree. F. for certain cultures and
generally within a broader range of 95.degree.-105.degree. suitable
for most mesophilic organisms. It should be appreciated the
quantity of heat energy available from the system, the temperature
of the heated condenser heat transfer medium applied to
intermediate heat transfer unit 104A, the volume of the anaerobic
digestion tanks, the ambient temperature, and a myriad of other
factors will require some degree of regulation in the amount of
heat energy necessary to maintain the cultures at their optimum
temperature. Such regulation may be provided by the one or more
valve(s) 222 via regulation of the mass flow rate of heated
condenser heat transfer medium flowing there through. Preferably,
the anaerobic digestion tank(s) and condensing transfer system 220
disclosed in detail below each comprise one or more temperature
sensors disposed at advantageous points in the system so that the
one or more valve(s) 222 may be continuously configured to maintain
the temperature of the cultures as desired. When heat energy is
required by the cultures, said one or more valve(s) 222 may be
operative to provide the requisite heat energy via an increased
flow of heated condenser heat transfer medium to anaerobic digester
heat exchanger 223. When additional heat energy is no longer
required by the cultures, the one or more valve(s) 222 may be
operative to reduce or discontinue the flow of heated condenser
heat transfer medium to anaerobic digester heat exchanger 223.
[0081] It is important to appreciate that under many circumstances,
the heat requirements of anaerobic cultures is wholly independent
of the cooling requirements of the ORC system and that the system
must be configurable to adequately, and preferably optimally,
ensure both requirements are simultaneously achieved at all times.
Under certain conditions, the ORC system may require additional
cooling while the anaerobic digestion system requires additional
heat energy; these simultaneous requirements are complementary
since the additional heat extracted from the ORC system would be
available to the anaerobic digestion system. However, conditions
such as high ambient temperature will generally require additional
ORC cooling while also reducing the amount of heat required by the
cultures, and these simultaneous requirements are contradictory
rather than complementary. Excess heat extracted via the ORC
cooling process may not be transferred to the cultures without
exceeding their optimal temperature, but it must still be extracted
from the ORC system to provide proper working fluid condensation
and then dissipated or consumed elsewhere.
[0082] Accordingly, in another mode of operation, the one or more
valve(s) 222 are operative to reduce or discontinue the flow of
heated condenser heat transfer medium to anaerobic digester heat
exchanger 223 while simultaneously increasing the flow of heated
condenser heat transfer medium to the one or more secondary heat
exchanger(s) 228. In this manner, the one or more secondary heat
exchanger(s) 228 provide a safety valve of sorts for the ORC system
which cannot operate without adequate cooling and condensation of
the post-expansion working fluid. Preferably, the ORC system, the
anaerobic digestion system, and the associated condensing transfer
system 220 which operatively connects the two will be provided with
sufficient operational flexibility to provide heat energy to the
anaerobic digestion cultures under all reasonable conditions and
sufficient capacity to provide working fluid condensation/cooling
to the ORC system under all reasonable conditions. To accomplish
this purpose, the ORC system will also preferably comprise one or
more temperature sensors disposed at advantageous points in the
system so that the one or more valve(s) 222 may be continuously
configured to provide the necessary ORC cooling as desired.
[0083] In this and other embodiments, the one or more secondary
heat exchanger(s) 228 may comprise any configuration disclosed
above, any known otherwise in the art, or any that may be later
developed. However, the presence of large reservoirs of treated
effluent at wastewater treatment plants enable the preferred use of
liquid-cooled radiators described above. At such facilities, the
temperature of the on-site treated effluent is not typically
regulated or maintained within any specific range, and given the
massive aggregate volume of available treated effluent and the
relatively low mass flow rate required to provide ORC cooling, the
heat energy of any portion of, or all portions of, the heated
condenser heat transfer medium may be easily consumed by said
treated effluent with only incidental incremental cost and with
minimal change in temperature to the aggregate volume thereof. In
lieu of massive air-cooled radiators driven by large fans consuming
electric power, one or more compact and relatively inexpensive
liquid-cooled radiators may be provided. Such radiators, broadly
described as heat exchangers, transfer heat energy from the ORC
working fluid to an external sink directly or via intermediate
means. Specifically, in one embodiment, a flow of heated condenser
heat transfer medium in the primary side of a standard heat
exchanger functioning as a radiator may be provided in heat energy
transfer communication with treated effluent from the wastewater
facility counterflowing in the secondary side, where said effluent
may provide up to all of the cooling capacity required by the ORC
system, even during periods when such cooling requirements are
maximized while heat consumption by the anaerobic digestion system
is minimized. Further, said effluent may be obtained and discharged
into the same reservoirs without the need for a closed loop
circulation system with active cooling known in the present art.
Generally, such effluent is available for use by the one or more
secondary heat exchanger(s) 228 within the range of
50.degree.-70.degree. F., sufficient to cool the heated condenser
heat transfer medium to the specified range of
55.degree.-75.degree. F. for application to inlet 233 of
intermediate heat transfer unit 104A. Generally, a treated effluent
flow of 250-350 gallons per minute will be required for an ORC
system configured to generate a net electric power output of 75-92
kWe, which is optimal for the Power+.TM. ORC system(s) offered by
ElectraTherm, Inc. In other embodiments, any other configuration of
heat exchanger may be utilized to remove heat from the heated
condenser heat transfer medium. For example, a series of manifolds
or ducting may be disposed within reservoirs of treated effluent or
other media of an appropriate temperature and the heated condenser
heat transfer medium cooled by passage through said manifolds or
ducting in thermal transfer communication with the treated effluent
or other media without the need to establish an active flow of
cooling media through a particular apparatus.
[0084] In one embodiment, the heat consumed from the post-expansion
working fluid by condensing transfer system 220 may also be used to
enhance biological nutrient removal processes when the system is
deployed at a wastewater treatment plant. As one example not
limiting upon the scope of this invention, certain aspects of
biological nutrient removal involve an aerobic process comprising
nitrification of effluent ammonia into nitrites via one or more
first classes of organisms and via one or more second classes of
organisms to convert said nitrites into nitrates. Following the
nitrification process, denitrification is performed by exposing the
produced nitrates to reaction with heterotrophic bacteria cultures
in an anoxic environment to yield nitrogen gas. These nitrification
and subsequent denitrification processes convert the nitrogen
present in effluent ammonia into free nitrogen gas and other
non-effluent byproducts, principally water and gasses including
hydrogen, oxygen, and carbon dioxide. In this manner, biological
nutrients are removed from the wastewater effluent as a part of the
overall process of water purification and reclamation.
[0085] Proper temperature is critical to the nitrification process.
A temperature in the range of 85.degree.-95.degree. F. is preferred
to maximize the rate of nitrification, with a reduction of about
18.degree. F. below this level causing a decrease in said
nitrification rate of approximately 30%. This lower efficiency
would require an increase in the mixed liquor suspended solids
(MLSS) of the effluent/organism mixture of approximately 300% to
maintain a constant level of nitrification. Such increase is
typically required on a seasonal basis for wastewater treatment
plants in locations where temperatures vary throughout the year,
and operators are presently faced with the unenviable task of
determining and adjusting MLSS for proper operation of their
facilities. If the temperature of the aerobic nitrification process
could be maintained within the desired range of
85.degree.-95.degree. F. throughout the year without incurring any
additional operational cost, such as the consumption of electric
power to provide heat for this purpose, a substantial advantage
over the present art would be realized. Consistent operation could
be achieved without the need to adjust MLSS content in bioreactors
to compensate for seasonal ambient temperature variations as
required by present art systems.
[0086] In one embodiment of the present invention, one or more
secondary heat exchanger(s) 228 may be configured to provide heat
from the heated condenser heat transfer medium to the nitrification
process so as to maintain the temperature of said process at its
optimal rate. In this embodiment, the one or more valve(s) 222 are
configured to adjust the flow of heated condenser heat transfer
medium to the nitrification process in any desired portion, said
portion determined by the availability of said heated condenser
heat transfer medium considered along with the demands of any
anaerobic digestion process, demands from any other heat consuming
application of the condensing transfer system 220, and the relative
priority of all of said applications considered on the whole.
Hydrogen gas is produced as a byproduct of the biological nutrient
removal process, and in some embodiments, this gas may be captured
and burned, either in a boiler or an internal combustion engine, to
produce input heat energy for the ORC process in a manner identical
to that of the anaerobic digestion process described elsewhere
herein. Present art systems typically dispose of hydrogen
byproducts via an on-site flare. The capture and re-integration of
as many incidental sources of energy as possible, where such
sources are presently discarded by systems known in the art,
represents a significant advantage over said known systems and
provides increased energy efficiency and performance.
[0087] In one embodiment of the present invention, anaerobic
digester heat exchanger 223 may be replaced with a heat exchanger
configured to provide heat energy to the aerobic nitrification
component of biological nutrient removal process in lieu of the
anaerobic digestion process (not shown). As the biological nutrient
removal process produces hydrogen gas as described above, said
hydrogen gas is suitable for combustion in either an ICE or a
boiler in a manner identical to that employed with biogas generated
via the anaerobic digestion process. Accordingly, this application
of residual heat energy removed from the ORC working fluid via the
condensation process contributes to the generation of fuel for
consumption by the source of input heat energy for the ORC via the
biological nutrient removal process just as it does with the
anaerobic digestion process described elsewhere herein.
[0088] In one embodiment, heat energy for biological nutrient
removal may be extracted directly from the source of heat energy
also supplying input heat to the ORC system as depicted in FIG. 6,
FIG. 7, and FIG. 9. Said heat energy may be in addition to, or in
lieu of, heat energy provided by condensing transfer system 220,
with the preferred point(s) of extraction of said heat energy
determined at least in part by the amount of heat energy available
from either or both sources, heat energy requirements of this or
other processes associated with the system, or based upon any other
criteria or according to any other preferences.
[0089] Although the disclosure of this example is directed toward
the removal of nitrogen from ammonia, a person of ordinary skill in
the art will recognize that the teaching herein is applicable to
any other biological nutrient removal process requiring or
preferring a consistent operating temperature. One or more
secondary heat exchanger(s) 228 may be configured to provide heat
energy from the heated condenser heat transfer medium to any other
process that contributes, in whole or in part, to the removal of
biological nutrients or the processing and purification of
wastewater. Similarly, in one embodiment, any co-located process or
system requiring consumption (removal) of heat energy may be
configured to supply heat energy to the ORC working fluid via one
or more additional heat exchangers in heat transfer communication
with said working fluid (not shown). Alternatively, in one
embodiment, heat energy may be removed from any co-located process
or system using components similar or identical to the one or more
secondary heat exchanger(s) 228 described above. Further, in
additional embodiments, processes including but not limited to
desalination and distillation may benefit from heat energy
extracted from post-expansion ORC working fluid in connection with
one or more water purification processes.
[0090] The advantages of this and other related embodiments of the
invention are considerable. Primarily, mechanical and electric
power is generated from the biogas waste product of the anaerobic
digestion or other fuel-generating process. Said power may be
consumed locally by the wastewater treatment plant for onsite
purposes, including but not limited to pumping and stirring,
thereby reducing or eliminating consumption of commercial power as
is now practiced. Locally-generated electric power may also be
applied to the commercial power grid for distribution to other
customers, producing an offset to the cost of power consumed
whenever the ORC system is offline. A considerable additional
advantage is realized by the reduction or elimination of flares now
used to burn biogas generated via the anaerobic digestion process.
Such flares produce emissions, unsightly visual effects, and
potential hazards that would preferably be eliminated when the
biogas is consumed by one or more boilers to provide input heat
energy for an ORC system. The liquid cooled radiators utilizing
treated effluent for heat consumption from the post-expansion ORC
working fluid are both considerably smaller, less expensive to
install and maintain, and more environmentally compatible than
their air-cooled counterparts. The advantages of using anaerobic
digestion, biological nutrient removal systems, or other co-located
processes to consume heat energy from the ORC system in lieu of
consuming electric power or burning only a portion of the generated
biogas in separate boiler(s) to heat the process cultures is
described in great detail elsewhere herein. And finally, the
flexibility of a system that converts waste material into useful
mechanical or electric power and biogas, which biogas is then
additionally consumed by the same system to optimally generate
additional mechanical or electric power, provides a high degree of
operational redundancy not known in the prior art.
[0091] In addition to anaerobic digestion systems, any application
benefiting from significant heat energy may be similarly integrated
with an ORC system as a heat receiving system with condensation
capacity in the manner taught herein. The anaerobic digestion
tank(s) function as a single subsystem providing combined working
fluid condensation and the consumption of heat energy for
beneficial use. As with the heating of anaerobic digestion tank(s),
any application in which coupled heat energy from the primary media
may replace the generation of heat energy via the consumption of
electric power will operate with greater efficiency and economic
benefit and may serve as a heat receiving system with condensation
capacity. Such applications may include but are not limited to the
heating of water in swimming pools, preheating water for boiler
systems, space heating, industrial or large scale domestic hot
water systems, combined heat and power systems, and the like. As a
result, these systems will also provide the dual benefit of
providing heat energy normally produced by electric power while
simultaneously eliminating the need for a separate ORC cooling and
condensing system in the present art.
[0092] In some embodiments where insufficient cooling and
condensation functionality may be available from the anaerobic
digestion system for proper operation of the ORC, a supplemental or
alternate system may be required if it is desirable to run the ORC.
In some embodiments, the ORC may serve as a primary cooling system
for the prime mover(s). The description of this invention is
intended to be enabling and not it will be evident to those skilled
in the art that numerous combinations of the embodiments described
above may be implemented together as well as separately, and all
such combinations constitute embodiments effectively described
herein.
* * * * *