U.S. patent application number 14/587806 was filed with the patent office on 2015-04-23 for methods for periodic removal of contaminated working fluid from organic rankine cycle power systems.
The applicant listed for this patent is KALEX, LLC. Invention is credited to Alexander I. Kalina.
Application Number | 20150107250 14/587806 |
Document ID | / |
Family ID | 52117132 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150107250 |
Kind Code |
A1 |
Kalina; Alexander I. |
April 23, 2015 |
METHODS FOR PERIODIC REMOVAL OF CONTAMINATED WORKING FLUID FROM
ORGANIC RANKINE CYCLE POWER SYSTEMS
Abstract
An optimized Rankine thermodynamic cycle system and method
include utilizing a working fluid including a base component and an
effective amount of a lower boiling point component, where the
effective amount is sufficient to raise a power utilization
efficiency of the systems by up to 10%, without changing a weight
of the fluid reducing turbine efficiency for the particular base
component and for optimizing output control valves for adjusting
the working fluid composition and temperature sensors measuring an
initial temperature of a coolant medium and a final temperature of
a heat source stream to computer control valves to continuously
adjust a pressure and a flow rate of a working fluid stream to be
vaporized so that a heat utilization of the system is about 99%
increasing output by approximately 3% to 6% on a sustained and
permanent yearly basis.
Inventors: |
Kalina; Alexander I.;
(Hillsborough, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KALEX, LLC |
Belmont |
CA |
US |
|
|
Family ID: |
52117132 |
Appl. No.: |
14/587806 |
Filed: |
December 31, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14023134 |
Sep 10, 2013 |
8925320 |
|
|
14587806 |
|
|
|
|
Current U.S.
Class: |
60/649 |
Current CPC
Class: |
F01K 25/08 20130101;
F01K 13/02 20130101; F05D 2220/31 20130101; F03G 7/04 20130101;
F01K 21/06 20130101 |
Class at
Publication: |
60/649 |
International
Class: |
F01K 21/06 20060101
F01K021/06; F03G 7/04 20060101 F03G007/04 |
Claims
1. A method for removing oil contamination from an organic Rankine
cycle system comprising: a condenser subsystem comprising at least
one first heat exchange unit that condenses a spent working fluid
stream to form a condensed working fluid stream, a pressure and
flow rate adjusting subsystem comprising a feed pump to form a
pressurized condensed working fluid stream, a vaporization or
boiling subsystem comprising at least one heat exchange unit that
vaporizes the pressurized condensed working fluid stream to form a
vaporized working fluid stream, an energy conversion subsystem
comprising at least one turbine, an admission valve, and a turbine
bypass valve that extracts a portion of thermal energy from the
vaporized working fluid stream to form the spent working fluid
stream, and a working fluid reserve tank subsystem including a
reserve tank, a first valve for stopping a flow of working fluid to
the vaporization subsystem, a second valve for stopping a flow of
working fluid to the reserve tank, and a third valve for directing
working fluid from the reserve tank back into the system, where the
method comprising the steps of: concurrently, stopping the feed
pump, closing the admission valve and the first valve to stop the
flow of working fluid through the system, and opening the second
valve and the turbine bypass valve to direct cleaned working fluid
into the reserve tank, continuing a flow of a heat source stream
into the vaporization or boiling subsystem and a flow of a cooling
stream into the condensation subsystem so that residual working
fluid contaminated with a turbine lubricating oil boils in the
vaporization or boiling subsystem to form a highly contaminated
working fluid and a cleaned vaporized working fluid, which is
condensed in the condensation subsystem to form a cleaned condensed
working fluid, which is collected in the reserve tank, removing the
highly contaminated working fluid from the vaporization or boiling
subsystem, adding an amount of working fluid to the reserve tank to
account for the removed highly contaminated working fluid,
concurrently, opening the third valve, closing the second valve,
and charging the working fluid from the reserve tank into the
system, concurrently closing the third valve, starting the feed
pump, opening the admission valve and the first valve, and closing
the turbine bypass valve restarting the system of clean or
substantially cleaned working fluid, and periodically repeating the
steps on a periodic basis.
2. The method of claim 1, wherein the periodic basis occurs when a
degree of oil contamination of the working fluid decreases a
performance of the system.
3. The method of claim 1, wherein the periodic basis is yearly.
4. The method of claim 1, wherein the method occurs in a time
period of less than 1 day.
5. The method of claim 4, wherein the time period is between about
4 and about 24 hours.
6. The method of claim 5, wherein the time period is between about
6 and about 24 hours.
7. The method of claim 1, wherein as the amount of working fluid in
the vaporization or boiling subsystem is reduced, a concentration
of contaminating oil in a remaining working fluid in the
vaporization subsystem goes up and a temperature in the
vaporization or boiling subsystem goes up, when this temperature
reaches a desired level only a small amount of heavily contaminated
working fluid is left in the vaporization or boiling subsystem,
which is safely removed from the system for disposal removing all
or substantially all of the oil contamination from the system.
8. The method of claim 7, wherein the small amount of the heavily
contaminated working fluid is between 5% and 10% of the entire
working fluid amount.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 14/023,134, filed Sep. 10, 2013.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention relate to optimize the
performance of organic Rankine cycle (ORC) power systems that
utilize a working fluid and a geothermal heat source or similar
heat sources.
[0004] More specifically, embodiments of the present invention
relate to optimize the performance of organic Rankine cycle power
systems that utilize a working fluid and a geothermal heat source
or similar heat sources, where the cycles are binary power systems
of an organic Rankine cycles utilizing a flow of a geothermal fluid
or a similar heat source fluid. The present power cycles provide
three improvements, all of which are intended to work together.
Current, ORC systems have several limitations, which the present
invention is intended to improve, overcome or solve.
[0005] 2. Description of the Related Art
[0006] One primary limitation of an ORC system is the fact that the
geofluid commonly used as a heat source fluid is usually highly
mineralized, which limits the minimum temperature to which this
geofluid can fluid can be cooled to provide heat for a geothermal
power system. If it is cooled further than this limit, the
mineralization will be deposited on the heat exchange apparatus,
fouling it and interfering with the operation of the power
system.
[0007] However, ORC power systems in current operation do not make
maximum allowable utilization of their heat sources. Because the
temperature of the cooling medium (air or water) varies over the
course of each day, as well as by season and in response to the
weather, the working fluid enters and exits the system's feed pump
with different temperatures, depending on the coolant temperature.
Thus, in real-world operation, an ORC system must operate so that,
even on the coldest day (corresponding to the coldest possible
temperature of the cooling medium), the exit temperature of the
heat source always remains above the limit imposed by issues of
mineralization.
[0008] Another factor that must be considered is that, the higher
the boiler pressure, the higher the boiling temperature becomes.
This means that as the pressure in the boiler is increased, the
portion of heat available for the process of vaporization becomes
smaller. That is, all of the heat available from a given heat
source may be conceptually divided into two portions; the heat used
for the vaporization of the working fluid and the heat used for the
pre-heating of the working fluid from the temperature at the point
just after the feed pump up to the boiling temperature of the
working fluid.
[0009] But at the same time, the higher the boiler pressure, the
more power output the system yields per given weight unit (pound,
kilogram, etc.,) of working fluid. Thus higher pressure in the
boiler increases output per weight unit of working fluid but
decreases the total amount of working fluid that may be vaporized
by the heat source. The goal in actual operation is to attain a
point which corresponds to maximum power output, rather than just
maximum heat source utilization. For each given allowable
condensation temperature, there will be an optimal desired pressure
in the boiler at which the system output will be maximized; this
may or may not correspond to maximum possible heat source
utilization. In certain parameters, higher pressure in the boiler
will allow for increased output per unit of heat source fluid, even
if the outlet temperature of the heat source fluid is not at the
lowest allowable point.
[0010] Yet another limitation on the operation of ORC plants is
that, because the working fluid is a hydrocarbon (e.g.,
isopentane), it must not be allowed to form a potentially
explosive, fuel-air mixture at any point in the system. This is a
potential issue in the system's condenser, and due to this fact,
the pressure in the condenser must always be maintained at a
pressure above atmospheric pressure; the usual operational standard
is to maintain a pressure in the condenser of 15.693 psia or 1
psig, i.e., 1 psi above atmospheric pressure.
[0011] At sea level, this pressure corresponds to a temperature of
condensation for the isopentane working fluid of 85.53.degree. F.
When the temperature of the cooling air becomes substantially lower
than this temperature, the temperature of condensation must still
remain constant. To that end, the flow of cooling air is reduced so
that the temperature of condensation remains at 85.53.degree. F. or
higher, and thus the corresponding pressure remains at 1 psig. Thus
any potential increase in power output that would otherwise be
available from such a decrease in the temperature of the cooling
media cannot be utilized. There is some economy attained from
reducing the work of the fans that bring in the cooling air, but
this is relatively small; the system's gross output is unchanged
but the reduced fan energy costs do slightly improve net output.
None the less, most of the potential for increased output available
from the cooler air is not be utilized.
[0012] The need to keep the outlet temperature of the heat source
above the point at which mineralization begins to occur, the need
to keep the pressure in the condenser above its mandatory minimum,
and the desire to establish an optimal pressure in the boiler to
obtain optimal power output for the system are all subject to a
limitation inherent in a conventional ORC system.
[0013] In order to attain the optimum set of parameters of a power
system, it is necessary to vary the boiling pressure and the flow
rate of the working fluid, based on the coolant temperature, while
carefully keeping both heat source outlet temperature and condenser
pressure above their required minimums. However, the work done by
the feed pump in a conventional ORC system is such that, for any
given difference of pressure between the points before and after
the feed pump, there is one specific and invariable flow rate of
working fluid through the system.
[0014] At the same time, the flow rate that would be required for
the optimal operation of the power system at a given pressure is
not the same as the flow rate inevitably corresponding to that
given pressure. Because a conventional ORC system has no capability
to vary its flow rate independent of its pressure, a conventional
ORC system operates in a suboptimal regime, i.e., chosen to
maximize output as best as possible, while carefully staying within
the limits imposed by the mineralization-based minimal allowable
heat-source outlet temperature and minimal allowable condenser
pressure.
[0015] One more additional issue with the conventional ORC
technology is that, in order to regulate the flow rate through the
turbine, i.e., a required capability, as the turbine has a maximum
flow rate that it can accept and this must not be exceeded, an
admission valve is installed prior to the turbine. The admission
valve allows the flow rate through the turbine to be controlled,
preventing the turbine from excess flow rate, but such use of an
admission valve results in a pressure loss and corresponding loss
of possible output.
[0016] Thus, there is a need in the art for systems and methods for
implementing the systems that address these output limitations of
conventional ORC power system.
SUMMARY OF THE INVENTION
[0017] Embodiments of the present invention provide methods for
optimizing the operation of geothermal organic Rankine cycle (ORC)
power systems so that the utilization of the heat source is
increased. The methods include adding an effective amount of a
lower boiling point component to a single component working fluid,
where the effective amount is sufficient to raise a power
utilization efficiency of the methods by up to 10%, without
substantially changing a weight of the working fluid, which would
reduce turbine efficiency. In certain embodiments, the effective
amount of the lower boiling point component is adjusted to maximize
power output or heat utilization. In other embodiments, the
effective amount of the lower boiling point component added to the
single component working fluid is sufficient to maximize power
output of the methods based on the base component and the lower
boiling point component. In other embodiments, the effective amount
of the lower boiling point component added to the single component
working fluid is less than or equal to about 5 wt. %. In other
embodiments, the effective amount of the lower boiling point
component added to the single component working fluid is between
about 1 wt. % and about 5 wt. %. In certain embodiments, the
effective amount of the lower boiling point component added to the
single component working fluid is less than or equal to about 5 wt.
%. In certain embodiments, the effective amount of the lower
boiling point component added to the single component working fluid
is between about 1 wt. % and about 5 wt. %. In other embodiments,
the effective amount of the lower boiling point component added to
the single component working fluid is between about 2 wt. % and
about 4 wt. %. In other embodiments, the effective amount of the
lower boiling point component added to the single component working
fluid is between about 2 wt. % and about 3 wt. %.
[0018] Embodiments of the present invention provide systems for
optimizing the operation of geothermal organic Rankine cycle (ORC)
power systems so that the utilization of the heat source is
increased, where the systems include a working fluid including a
base component and an effective amount of a lower boiling point
component, where the effective amount is sufficient to raise a
power utilization efficiency of the systems by up to 10%, without
changing a weight of the fluid reducing turbine efficiency for the
particular base component. In certain embodiments, the system
include a source of the base component and a source of the lower
boiling point components and flow control units so that the
effective amount of the base component and the lower boiling point
component may be adjusted to maximize power output or heat
utilization. In other embodiments, the effective amount of the
lower boiling point component added to the single component working
fluid is sufficient to maximize power output of the methods based
on the base component and the lower boiling point component. In
other embodiments, the effective amount of the lower boiling point
component added to the single component working fluid is less than
or equal to about 5 wt. %. In other embodiments, the effective
amount of the lower boiling point component added to the single
component working fluid is between about 1 wt. % and about 5 wt. %.
In certain embodiments, the effective amount of the lower boiling
point component added to the single component working fluid is less
than or equal to about 5 wt. %. In certain embodiments, the
effective amount of the lower boiling point component added to the
single component working fluid is between about 1 wt. % and about 5
wt. %. In other embodiments, the effective amount of the lower
boiling point component added to the single component working fluid
is between about 2 wt. % and about 4 wt. %. In other embodiments,
the effective amount of the lower boiling point component added to
the single component working fluid is between about 2 wt. % and
about 3 wt. %.
[0019] Embodiments of the present invention provide methods for
optimizing the operation of geothermal power systems so that the
utilization of the heat source is maximized at all possible coolant
temperatures. In certain embodiments, the methods based on binary
power systems or so called organic Rankine cycles (ORCs). In
certain embodiments, the effective amount of the lower boiling
point component is adjusted to maximize power output or heat
utilization. In other embodiments, the effective amount of the
lower boiling point component added to the single component working
fluid is sufficient to maximize power output of the methods based
on the base component and the lower boiling point component. In
other embodiments, the effective amount of the lower boiling point
component added to the single component working fluid is less than
or equal to about 5 wt. %. In other embodiments, the effective
amount of the lower boiling point component added to the single
component working fluid is between about 1 wt. % and about 5 wt. %.
In certain embodiments, the effective amount of the lower boiling
point component added to the single component working fluid is less
than or equal to about 5 wt. %. In certain embodiments, the
effective amount of the lower boiling point component added to the
single component working fluid is between about 1 wt. % and about 5
wt. %. In other embodiments, the effective amount of the lower
boiling point component added to the single component working fluid
is between about 2 wt. % and about 4 wt. %. In other embodiments,
the effective amount of the lower boiling point component added to
the single component working fluid is between about 2 wt. % and
about 3 wt. %.
[0020] Embodiments of the present invention provide apparatuses for
optimizing the operation of geothermal power systems so that the
utilization of the heat source is maximized at all possible coolant
temperatures. In certain embodiments, the apparatuses are binary
power systems or so call organic Rankine cycles (ORCs). In certain
embodiments, the system include a source of the base component and
a source of the lower boiling point components and flow control
units so that the effective amount of the base component and the
lower boiling point component may be adjusted to maximize power
output or heat utilization. In other embodiments, the effective
amount of the lower boiling point component added to the single
component working fluid is sufficient to maximize power output of
the methods based on the base component and the lower boiling point
component. In other embodiments, the effective amount of the lower
boiling point component added to the single component working fluid
is less than or equal to about 5 wt. %. In other embodiments, the
effective amount of the lower boiling point component added to the
single component working fluid is between about 1 wt. % and about 5
wt. %. In certain embodiments, the effective amount of the lower
boiling point component added to the single component working fluid
is less than or equal to about 5 wt. %. In certain embodiments, the
effective amount of the lower boiling point component added to the
single component working fluid is between about 1 wt. % and about 5
wt. %. In other embodiments, the effective amount of the lower
boiling point component added to the single component working fluid
is between about 2 wt. % and about 4 wt. %. In other embodiments,
the effective amount of the lower boiling point component added to
the single component working fluid is between about 2 wt. % and
about 3 wt. %.
[0021] Embodiments of the present invention provide methods for
removing oil build up in the working fluid by running the working
fluid through system, while bypassing the turbine subsystem and
capturing the condensed working fluid in a reserve tank, until a
small amount of highly oil contaminated working fluid remains in
the system. At this point, the remaining working fluid is removed,
removing the oil. The working fluid in the reserve tank is
reintroduced into the system and a small amount of additional
working fluid is added to compensate for the quantity of oil
contaminated working fluid removed and the cycle is re-initialized.
These steps are repeated as needed or on a periodic bases to reduce
oil contamination without having to replace the working fluid and
with minimal disruption in power generation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention can be better understood with reference to the
following detailed description together with the appended
illustrative drawings in which like elements are numbered the
same:
[0023] FIG. 1 depicts an embodiment of an improved Rankine power
generation system using geofluids and a working fluid including a
base component and an effective amount of a lower boiling point
component.
[0024] FIG. 2 depicts another embodiment of an improved Rankine
power generation system using geofluids including a computer tuned
recycle loop and a working fluid including a base component and an
effective amount of a lower boiling point component.
[0025] FIG. 3A depicts an embodiment of an optimized power
generation system using geofluids.
[0026] FIG. 3B depicts another embodiment of an optimized power
generation system using geofluids.
DEFINITIONS USED IN THE INVENTION
[0027] The term "substantially" means that the value of the value
or property that the term modifies is within about 10% of the
related value or property. In other embodiments, the term means
that the value or property is withing 5% of the related value or
property. In other embodiments, the term means that the value or
property is withing 2.5% of the related value or property. In other
embodiments, the term means that the value or property is withing
1% of the related value or property. For example, the term
"substantially" used in the reduction in the unit weight of the
working fluid due to the addition of the lower boiling component
mean that the weight does not reduce or only minimally reduces
turbine efficiency. Stated differently, the term significantly
changing the weight of the working fluid means that the weight of
the working fluid is reduced by no more than 5%. In other
embodiments, the significantly changing the weight of the working
fluid means that the weight of the working fluid is reduced by no
more than 2.5%. In other embodiments, the significantly changing
the weight of the working fluid means that the weight of the
working fluid is reduced by no more than 1%.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The inventor has found that an optimized thermodynamic
cycle, in particular, an optimized organic Rankine cycle (ORC)
maybe implemented, where the methods and apparatuses establishing
the cycle continuously monitor and adjust a boiling pressure and a
flow rate of the working fluid entering the vaporization subsystem
based on a final temperature of a heat source stream and a
temperature of a condensed working fluid corresponding to an
initial temperature of a coolant used to condense the working
fluid. In order to attain this optimum set of parameters for the
power systems of this invention, it is necessary to vary the
boiling pressure and the flow rate of the working fluid, based on
the coolant temperature. However, the work done by the feed pump is
such that, for any given difference in pressure between the stream
at a location before and after the feed pump, there is one specific
and invariable flow rate of the working fluid through the system.
At the same time, the flow rate required for the optimal operation
of the power systems of this invention at a given pressure is not
the same as the actual flow rate that that given pressure
inevitably corresponds to. Thus, in order to achieve the optimal
operation of the power systems of this invention, it is necessary
to have the capability to change the pressure and flow rate
separately and independent of each other.
[0029] An embodiment of a system of this invention for implement a
thermodynamic cycle including a condenser subsystem comprising at
least one first heat exchange unit that condenses a spent working
fluid stream to form a condensed working fluid stream. The system
also includes a vaporization or boiling subsystem comprising at
least one heat exchange unit that vaporizes the flow rate and
pressure adjusted vaporization subsystem input stream to form a
vaporized energy conversion subsystem input stream, and an energy
conversion subsystem comprising at least one turbine that extracts
a portion of thermal energy from the vaporized energy conversion
subsystem input stream to form the spent working fluid stream. The
working fluid used the system comprises a base component and an
effective amount of a lower boiling point component, where the
effective amount is sufficient to increase a power utilization
efficiency of the system, without changing a weight of the fluid
reducing turbine efficiency for the particular base component. The
system may further include a working fluid pressure and flow
control subsystem comprising at least a feed pump, a control valve,
a bypass valve, a first temperature sensor, a second temperature
sensor, a dividing valve, and mixing valve, where the processing
unit adjusts a flow rate and a pressure of a vaporization subsystem
input stream from the condensed working fluid stream, where the
control valve and the bypass valve are flow control valves and are
controlled by the processing unit controlled in such a way as to
optimize the pressure and flow rate of the flow rate and pressure
adjusted vaporization subsystem input stream optimizing a power
output of the system based on a condensation temperature of the
condensed working fluid stream and a final heat source temperature
increasing system output between about 3% and 6% on a yearly basis.
In certain embodiments, the mixing valve combines the condensed
working fluid stream and a pressure adjusted recirculation stream
exiting the bypass valve to form a feed pump input stream, the feed
pump pumps the feed pump input stream to a higher pressure to form
a pressurized stream, the dividing valve divides the pressurized
stream into a control valve input stream and a recirculation
stream, the control valve adjusts a pressure and a flow rate of the
control valve output stream to form the flow rate and pressure
adjusted vaporization subsystem input stream, and the bypass valve
adjusts a pressure and a flow rate of the recirculation stream to
form the pressure adjusted recirculation stream. In other
embodiments, the mixing valve combines the condensed working fluid
stream and a pressure adjusted recirculation stream exiting the
bypass valve to form a feed pump input stream, the feed pump pumps
the feed pump input stream to a higher pressure to form a
pressurized control valve input stream, the control valve adjusts a
pressure and a flow rate of the pressurized control valve input
stream to form a pressure adjusted stream, the dividing valve
divides the pressurized adjusted stream into the flow rate and
pressure adjusted vaporization subsystem input stream and a
recirculation stream, and the bypass valve adjusts a pressure and a
flow rate of the recirculation stream to form the pressure adjusted
recirculation stream. In certain embodiments, the base component is
selected from the group consisting of a hydrocarbon and a freon,
and the lower boiling point component is selected from the groups
consisting a hydrocarbon or a freon, having a boiling point lower
than the boiling point of the base component. In other embodiments,
the base component is isopentane and the lower boiling point
component comprises propane.
[0030] An embodiment of a method for implement a thermodynamic
cycle comprising the steps of condensing a spent working fluid
stream in counterflow with a coolant stream in a condenser
subsystem comprising at least one first heat exchange unit to form
a condensed working fluid stream. The method also includes the step
of vaporizing the vaporization subsystem input stream in a
vaporization or boiling subsystem comprising at least one heat
exchange unit to form a vaporized energy conversion subsystem input
stream. The method also includes the step of converting a portion
of the thermal energy in the vaporized energy conversion subsystem
input stream in an energy conversion subsystem comprising at least
one turbine to form the spent working fluid stream. In the method,
the working fluid including a base component and an effective
amount of a lower boiling point component, where the effective
amount is sufficient to raise a power utilization efficiency of the
systems by up to 10%, without changing a weight of the fluid
reducing turbine efficiency for the particular base component. In
other embodiments, the method further comprising the step of prior
to the vaporizing step, producing a vaporization subsystem input
stream in a working fluid pressure and flow control subsystem
comprising at least a feed pump, a control valve, a bypass valve, a
first temperature sensor, a second temperature sensor, a processing
unit, a dividing valve, mixing valve and a processing unit from the
condensed working fluid stream, where the control valve and the
bypass valve are flow control valves and are controlled by the
processing unit controlled in such a way as to optimize the
pressure and flow rate of the flow rate and pressure adjusted
vaporization subsystem input stream optimizing a power output of
the system based on an initial coolant temperature and a final heat
source temperature and where the system increases system output
between about 3% and 6% on a yearly basis. In certain embodiments,
the method further including the steps of combining the condensed
working fluid stream and a pressure adjusted recirculation stream
exiting the bypass valve in the mixing valve to form a feed pump
input stream, pumping the feed pump input stream to a higher
pressure in the feed pump to form a pressurized stream, dividing
the pressurized stream into a control valve input stream and a
recirculation stream in the dividing valve, adjusting a pressure
and a flow rate of the control valve input stream in the control
valve to form the vaporization subsystem input stream, and
adjusting a pressure and a flow rate of the recirculation stream in
the bypass valve to form the pressure adjusted recirculation
stream. In other embodiments, the method further including the
steps of mixing the condensed working fluid stream and a pressure
adjusted recirculation stream exiting the bypass valve in the
mixing valve to form a feed pump input stream, pumping the feed
pump input stream to a higher pressure in the feed pump to form a
pressurized control valve input stream, adjusting a pressure and a
flow rate of the pressurized control valve input stream in the
control valve to form a pressure adjusted stream, dividing the
pressure adjusted stream in the dividing valve into the
vaporization subsystem input stream and a recirculation stream, and
adjusting a pressure and a flow rate of the recirculation stream in
the bypass valve to form the pressure adjusted recirculation
stream. In other embodiments, the base component is selected from
the group consisting of a hydrocarbon and a freon, and the lower
boiling point component is selected from the groups consisting a
hydrocarbon or a freon, having a boiling point lower than the
boiling point of the base component. In other embodiments, the base
component is isopentane and the lower boiling point component is
propane.
[0031] An embodiment of a system for implement a thermodynamic
cycle including a condenser subsystem comprising at least one first
heat exchange unit that condenses a spent working fluid stream to
form a condensed working fluid stream. The system also includes a
working fluid pressure and flow control subsystem comprising at
least a feed pump, a control valve, a bypass valve, a first
temperature sensor, a second temperature sensor, a dividing valve,
and mixing valve, where the processing unit adjusts a flow rate and
a pressure of a vaporization subsystem input stream from the
condensed working fluid stream and a vaporization or boiling
subsystem comprising at least one heat exchange unit that vaporizes
the flow rate and pressure adjusted vaporization subsystem input
stream to form a vaporized energy conversion subsystem input
stream. The system also includes an energy conversion subsystem
comprising at least one turbine that extracts a portion of thermal
energy from the vaporized energy conversion subsystem input stream
to form the spent working fluid stream. The control valve and the
bypass valve are flow control valves and are controlled by the
processing unit controlled in such a way as to optimize the
pressure and flow rate of the flow rate and pressure adjusted
vaporization subsystem input stream optimizing a power output of
the system based on a condensation temperature of the condensed
working fluid stream and a final heat source temperature increasing
system output between about 3% and 6% on a yearly basis. In certain
embodiments, the mixing valve combines the condensed working fluid
stream and a pressure adjusted recirculation stream exiting the
bypass valve to form a feed pump input stream, the feed pump pumps
the feed pump input stream to a higher pressure to form a
pressurized stream, the dividing valve divides the pressurized
stream into a control valve input stream and a recirculation
stream, the control valve adjusts a pressure and a flow rate of the
control valve output stream to form the flow rate and pressure
adjusted vaporization subsystem input stream, and the bypass valve
adjusts a pressure and a flow rate of the recirculation stream to
form the pressure adjusted recirculation stream. In certain
embodiments, the mixing valve combines the condensed working fluid
stream and a pressure adjusted recirculation stream exiting the
bypass valve to form a feed pump input stream, the feed pump pumps
the feed pump input stream to a higher pressure to form a
pressurized control valve input stream, the control valve adjusts a
pressure and a flow rate of the pressurized control valve input
stream to form a pressure adjusted stream, the dividing valve
divides the pressurized adjusted stream into the flow rate and
pressure adjusted vaporization subsystem input stream and a
recirculation stream, and the bypass valve adjusts a pressure and a
flow rate of the recirculation stream to form the pressure adjusted
recirculation stream. In certain embodiments, the working fluid
comprises a base component and an effective amount of a lower
boiling point component, where the effective amount is sufficient
to increase a power utilization efficiency of the system, without
changing a weight of the fluid reducing turbine efficiency for the
particular base component, where the base component is selected
from the group consisting of a hydrocarbon and a freon, and a lower
boiling point component is selected from the groups consisting a
hydrocarbon or a freon, having a boiling point lower than the
boiling point of the base component. In other embodiments, the base
component is isopentane and the lower boiling point component
comprises propane.
[0032] An embodiment of a method for implement a thermodynamic
cycle comprising the steps of condensing a spent working fluid
stream in counterflow with a coolant stream in a condenser
subsystem comprising at least one first heat exchange unit to form
a condensed working fluid stream. The method also includes
producing a vaporization subsystem input stream in a working fluid
pressure and flow control subsystem comprising at least a feed
pump, a control valve, a bypass valve, a first temperature sensor,
a second temperature sensor, a processing unit, a dividing valve,
mixing valve and a processing unit from the condensed working fluid
stream, and vaporizing the vaporization subsystem input stream in a
vaporization or boiling subsystem comprising at least one heat
exchange unit to form a vaporized energy conversion subsystem input
stream. The method also includes converting a portion of the
thermal energy in the vaporized energy conversion subsystem input
stream in an energy conversion subsystem comprising at least one
turbine to form the spent working fluid stream. The control valve
and the bypass valve are flow control valves and are controlled by
the processing unit controlled in such a way as to optimize the
pressure and flow rate of the flow rate and pressure adjusted
vaporization subsystem input stream optimizing a power output of
the system based on an initial coolant temperature and a final heat
source temperature and where the system increases system output
between about 3% and 6% on a yearly basis. In certain embodiments,
the method further includes the steps of combining the condensed
working fluid stream and a pressure adjusted recirculation stream
exiting the bypass valve in the mixing valve to form a feed pump
input stream, pumping the feed pump input stream to a higher
pressure in the feed pump to form a pressurized stream, dividing
the pressurized stream into a control valve input stream and a
recirculation stream in the dividing valve, adjusting a pressure
and a flow rate of the control valve input stream in the control
valve to form the vaporization subsystem input stream, and
adjusting a pressure and a flow rate of the recirculation stream in
the bypass valve to form the pressure adjusted recirculation
stream. In other embodiments, the method further includes the steps
of mixing the condensed working fluid stream and a pressure
adjusted recirculation stream exiting the bypass valve in the
mixing valve to form a feed pump input stream, pumping the feed
pump input stream to a higher pressure in the feed pump to form a
pressurized control valve input stream, adjusting a pressure and a
flow rate of the pressurized control valve input stream in the
control valve to form a pressure adjusted stream, dividing the
pressure adjusted stream in the dividing valve into the
vaporization subsystem input stream and a recirculation stream, and
adjusting a pressure and a flow rate of the recirculation stream in
the bypass valve to form the pressure adjusted recirculation
stream. In certain embodiments, the working fluid comprises a base
component and an effective amount of a lower boiling point
component, where the effective amount is sufficient to increase a
power utilization efficiency of the system, without changing a
weight of the fluid reducing turbine efficiency for the particular
base component, where the base component is selected from the group
consisting of a hydrocarbon and a freon, and a lower boiling point
component is selected from the groups consisting a hydrocarbon or a
freon, having a boiling point lower than the boiling point of the
base component. In other embodiments, the base component is
isopentane and the lower boiling point component is propane.
[0033] An embodiment of a method for removing oil contamination
from an organic Rankine cycle system comprising a condenser
subsystem comprising at least one first heat exchange unit that
condenses a spent working fluid stream to form a condensed working
fluid stream, a pressure and flow rate adjusting subsystem
comprising a feed pump, a vaporization or boiling subsystem
comprising at least one heat exchange unit that vaporizes the
pressurized condensed working fluid stream to form a vaporized
working fluid stream, an energy conversion subsystem comprising at
least one turbine, an admission valve, and a turbine bypass valve
that extracts a portion of thermal energy from the vaporized
working fluid stream to form the spent working fluid stream, and a
working fluid reserve tank subsystem including a reserve tank, a
first valve for stopping a flow of working fluid to the
vaporization subsystem, a second valve for stopping a flow of
working fluid to the reserve tank, and a third valve for directing
working fluid from the reserve tank back into the system. The
method includes the steps of concurrently, stopping the feed pump,
closing the admission valve and the first valve to stop the flow of
working fluid through the system, and opening the second valve and
the turbine bypass valve to direct cleaned working fluid into the
reserve tank. The method also includes the steps of continuing a
flow of a heat source stream into the vaporization or boiling
subsystem and a flow of a cooling stream into the condensation
subsystem so that residual working fluid contaminated with a
turbine lubricating oil boils in the vaporization or boiling
subsystem to form a highly contaminated working fluid and a cleaned
vaporized working fluid, which is condensed in the condensation
subsystem to form a cleaned condensed working fluid, which is
collected in the reserve tank, and removing the highly contaminated
working fluid from the vaporization or boiling subsystem, adding an
amount of working fluid to the reserve tank to account for the
removed highly contaminated working fluid. The method also includes
the steps of concurrently, opening the third valve, closing the
second valve, and charging the working fluid from the reserve tank
into the system, concurrently closing the third valve, starting the
feed pump, opening the admission valve and the first valve, and
closing the turbine bypass valve restarting the system of clean or
substantially cleaned working fluid, and periodically repeating the
steps on a period basis. In certain embodiments, the period basis
occurs when a degree of oil contamination of the working fluid
reaches as given level, where the given level causes a given
decrease in system performance. In other embodiments the period
basis is yearly.
Suitable Reagents And Equipment
[0034] The working fluids used in the systems of this invention
include a base component and an effective amount of a lower boiling
point component. The base component comprises a hydrocarbon or a
freon. The lower boiling point component comprises a hydrocarbon or
a freon, having a boiling point lower than the boiling point of the
base component. Exemplary examples of the base component and lower
boiling point component include, without limitation, propane,
n-butane, n-pentane, n-hexane, n-heptane, n-octane, isobutane,
isopentane, isoheptane, isooctane, or higher n-alkanes or higher
n-isoalkanes, where the base component has a higher boiling point
than the lower boiling point component. Thus, for a Rankine cycle
system using isopentane as the base component, the lower boiling
point component may be propane, iso-butane, or n-butane.
[0035] It should be recognized by an ordinary artisan that at those
points in the systems of this invention were a stream is split into
two or more sub-streams, dividing valves that affect such stream
splitting are well known in the art and may be manually adjustable
or dynamically adjustable so that the splitting achieves the
desired stream flow rates and system efficiencies. Similarly, when
stream are combined, combining valve that affect combining are also
well known in the art and may be manually adjustable or dynamically
adjustable so that the splitting achieves the desired stream flow
rates and system efficiencies.
Specific Embodiments
Generalized Improved Rankine or Organic Rankine Cycles
First Generalized Embodiment
[0036] Referring now to FIG. 1, an embodiment of this invention,
generally 100, is shown to include: (a) a condenser subsystem 152
comprising at least one first heat exchange unit and at least one
feed pump, (b) a vaporization or boiling subsystem 156 comprising
at least one heat exchange unit, and (c) an energy conversion
subsystem 158 comprising at least one turbine. It should be noted
that the systems of this invention utilize a working fluid stream
and all the streams in the systems have the same working fluid
composition. Therefore, the term "stream" refers to a working fluid
stream and is to be understood in that manner throughout the
descriptions set forth below. As stated above, the working fluid
includes the base component and an effective amount of the lower
boiling point component, where the effective amount is sufficient
to maximize the power output of the system 100, while maintaining
substantially the same unit weight of the working fluid.
[0037] The condensation subsystem 152 condenses and pressurizes a
spent working fluid stream S106 to form a higher pressure condensed
working fluid stream S101. The higher pressure condensed stream
S101 is then forwarded to the vaporization and boiler subsystem
156, where the higher pressure condensed stream S101 is vaporized
or fully vaporized or fully vaporized and superheated to form a
higher pressure vaporized stream or a fully vaporized stream or a
fully vaporized and superheated stream S105. The stream S105 is
then forwarded to the energy conversion subsystem 158, where a
portion of its thermal energy is converted to mechanical and/or
electrical energy, a usable form of energy to produce a spent
stream S106.
[0038] In this embodiments, for an isopentane ORC system the lower
boiling component, ideally propane, is added to the isopentane
working fluid, so that the final working fluid includes an
effective amount of propane, where the effective amount is 3.5%
propane in the isopentane working fluid. In certain embodiments,
the effective amount is 3.0% propane in the isopentane working
fluid. In certain embodiments, the effective amount is 2.5% propane
in the isopentane working fluid. This change in the working fluid
composition has several beneficial effects.
[0039] The change in working fluid composition reduces a minimum
allowable temperature of condensation, which corresponds to a
minimum allowable safe condensation pressure of 1 psig, from
85.53.degree. F. to 65.58.degree. F. A pressure of condensation
will remain the same, but the minimum allowable temperature of
condensation will be much lower. This dramatically increases the
thermodynamic reversibility of the process and allows the use of
cooler air to increase the total output of the system.
[0040] The change of working fluid composition also lowers an
initial boiling point temperature of the working fluid, increasing
the available heat for vaporization and allows better utilization
of the heat source stream. Likewise, because the modified working
fluid enters the vaporization subsystem with a lower temperature,
it is possible, in some circumstances, to cool the heat source
closer to its safe (mineralization-based) minimum outlet
temperature and thus utilize even more heat from the heat source.
Both of these factors may allow for the delivery of more power
output.
[0041] The change in working fluid composition also makes the
working fluid a mixture, which means that it now boils and
condenses at variable temperatures providing a better "match"
between the heat source and the working fluid, as well as a better
match between the working fluid and the coolant and reducing
temperature differences in both the vaporization subsystem and in
the condenser, which in turn further reduces energy losses (in the
vaporization and condensation subsystems), yet further increasing
the system power output.
Second Generalized Embodiment
[0042] Referring now to FIG. 2, an embodiment of this invention,
generally 200, is shown to include: (a) a condenser subsystem 252
comprising at least one first heat exchange unit and at least one
pump, (b) a pressure and flow rate control subsystem 254 comprising
a feed pump, valves, temperature sensors and a processing unit, (c)
a vaporization or boiling subsystem 258 comprising at least one
heat exchange unit, and (d) an energy conversion subsystem 260
comprising at least one turbine. It should be noted that the
systems of this invention utilize a working fluid stream and all
the streams in the systems have the same working fluid composition.
Therefore, the term "stream" refers to a working fluid stream and
is to be understood in that manner throughout the descriptions set
forth below. In a variant of this system, the working fluid
includes a base component and an effective amount of the lower
boiling point component, where the effective amount is sufficient
to maximize the power output of the system 200, while maintaining
substantially the same unit weight of the working fluid.
[0043] The condensation subsystem 252 condenses a spent working
fluid stream S206 to form a condensed working fluid stream S201.
The condensed stream S201 is then forwarded to the pressure and
flow rate control subsystem 262, where the subsystem 262 diverts or
bypasses an amount of the condensed working fluid stream to form a
pressure and flow rate adjusted working fluid stream S203 by
pressurizing and pressure adjusting the stream. The pressure and
flow rate adjusted working fluid stream S203 is then forwarded to
the vaporization and boiler subsystem 256, where the stream S203 is
vaporized or fully vaporized or fully vaporized and superheated to
form a pressure and flow rate adjusted vaporized or fully vaporized
or fully vaporized and superheated stream S205. The stream S205 is
then forwarded to the energy conversion subsystem 258, where a
portion of its thermal energy is converted to mechanical and/or
electrical energy, a usable form of energy to produce a spent
working fluid stream S206.
Specific Improved Rankine or Organic Rankine Cycles
First Specific Embodiment
[0044] Referring now to FIG. 3A, an embodiment of an improved ORC
power system of this invention, generally 300, is shown to include:
(a) a condenser subsystem 352 comprising a first heat exchange unit
or condenser HE1, (b) a pressure and flow control subsystem 354
comprising a feed pump P1, a control valve CV, a bypass valve BV, a
first temperature sensor t.sub.1, a second temperature sensor
t.sub.2, a digital or analog processing unit (DPU/APU), a dividing
valve DV, a mixing valve MV, and optionally a first flow diversion
valve V1, a second flow diversion valve V2, a third flow diversion
valve V3, and a reserve tank R, (c) a vaporization or boiling
subsystem 356 comprising a second heat exchange unit HE2 and a
third heat exchange unit HE3, and (d) an energy conversion
subsystem 358 comprising an addition valve AV, a turbine T, and
optionally a turbine by-pass valve TBV. Both the control valve CV
and the bypass valve BV are flow control valves controlled by the
DPU/APU in such a way as to optimize the power output of the system
300 at all coolant temperatures and all heat source temperatures.
The feed pump P1 has a capacity that is maximized for a maximum
possible flow rate for any given pressure, where the pressure is
greater than what is required to attain optimal operation of the
power system 300. It should be noted that the systems of this
invention utilize a working fluid stream and all the streams in the
systems have the same working fluid composition. Therefore, the
term "stream" refers to a working fluid stream and is to be
understood in that manner throughout the descriptions set forth
below. In certain embodiments, the working fluid includes a base
component and an effective amount of the lower boiling point
component, where the effective amount is sufficient to maximize the
power output of the system 300, while maintaining substantially the
same unit weight of the working fluid.
[0045] The system 300 operates as follows: a condensed stream S301
having parameters as at a point 1 exits the first heat exchange
unit or condenser HE1. The condensed stream S301 is combined by the
mixing valve MV with a pressure adjusted recirculation stream S304
having parameters as at a point 4 forming a feed pump input stream
S303 having parameters at as a point 3. A pressure of the feed pump
input stream S303 is the same as a pressure of the condensed stream
S301 having the parameters as the point 1. It should be recognized
that the parameters of all streams comprise all characteristics and
properties of each stream including at least pressure, temperature,
composition, and flow rate.
[0046] The feed pump input stream S303 is then pumped to a higher
pressure in the feed pump P1 to form a pressurized feed pump output
stream S307 having parameters as at a point 7. The pressurized feed
pump output stream S307 is then forwarded to the control valve CV,
where a pressure of the pressurized feed pump output stream S307 is
reduced to a desired pressure forming a pressure adjusted stream
S308 having parameters as a point 8. The desired pressure of the
stream S308 is an optimal pressure for the specific boundary
conditions at which the power system 300 operates at any given
moment and is set by the DPU/APU, which controls the control valve
CV as explained more fully below.
[0047] If the entire flow of the stream S308 exiting the control
valve CV, then a flow rate of the stream entering the vaporization
or boiling subsystem 356 would be higher than needed for optimal
performance. Thus, the stream S308 is divided by the dividing valve
DVI into two substreams: a flow rate adjusted stream S302 having
parameters as at a point 2 and a diverted or recirculation stream
S309 having parameters as at a point 9.
[0048] The stream S309 is then sent through a bypass valve BV,
where its pressure is reduced to a pressure equal to a pressure of
the working fluid stream S301 having the parameters as at the point
1 forming the stream S304 having the parameters as at the point 4.
The stream S304 is then combined by the mixing valve MV with the
stream S301, thereby recirculating the excess working fluid flow
through the pump P1 in the form of the combined stream S303.
[0049] As a result, the pressure and flow rate stream S302 enters
the vaporization or boiler subsystem 356 of the system 300 are kept
at values that are optimal for operating the system 300. The
optimal pressure of the stream S308 having the parameters at the
point 8 is established by the control valve CV. The operation of
the control valve CV is controlled by the DPU/APU based on
measuring a condensation temperature of the condensed stream S301
corresponding to an initial coolant temperature of a cooling stream
S350 having parameters as at a point 50. The condensation
temperature is measured by a first temperature sensor t.sub.1, a
response of the first temperature sensor t.sub.1 is then forwarded
to the DPU/APU, which in turn uses the condensation temperature to
control the control valve CV.
[0050] The optimal flow rate of the pressure adjusted feed pump
output stream S308 is independently established by the operation of
the bypass valve BV, the operation of which is controlled the
DPU/APU based on measuring a final heat source temperature of a
spent heat source stream S342 having parameters as at a point 42
exiting the vaporization subsystem 356. In actual fact, the system
300 needs to monitor a flow rate of the flow rate adjusted stream
S302, but this flow rate is linearly related to the temperature of
the spent heat source stream S342, after being cooled in heat
exchange processes 2-10 or 41-42 and 10-16 or 40-41.
[0051] The control valve CV is thus operated and controlled by the
processing unit subsystem DPU/APU based on the condensation
temperature of the condensed stream S201 measured by the second
temperature sensor t.sub.2 as it exits the condenser HE1, which is
used to set the pressure of the pressures adjusted stream S308
exiting the control valve CV. The bypass valve BV may be operated
and controlled in the same manner by the processing subsystem
DPU/APU based on the final temperature of the spent heat source
stream S342 measured by the first temperature sensor t.sub.1, which
is used to set the flow rate of the pressure adjusted recirculation
stream S304.
[0052] The pressure and flow rate adjusted stream S302 is then
forwarded into the vaporization subsystem 356. The stream S302
first enters the second heat exchange unit HE2, where the stream
S302 is heated in counterflow with a cooled heat source stream S341
having parameters as at a point 41 to form a heated or a partially
vaporized stream S310 having parameters as at a point 10 and the
spend heat source stream S342 having the parameters as at the point
42. The stream S310 is then forwarded into the third heat exchange
system HE3, where the stream S310 is vaporized and/or superheated
in counterflow with a heat source stream S340 having parameters as
at a point 40 to form a vaporized or vaporized and superheated
stream S316 having parameters as at a point 16 and the cooled heat
source stream S341.
[0053] The vaporized or vaporized and superheated stream S316 is
then forwarded to the heat conversion subsystem 358. The stream
S316 then enters the turbine T forming a spent stream S318 having
parameters as at a point 18 and a portion of the heat in the stream
S316 is extracted and converted to a usable form of energy such as
mechanical and/or electrical.
[0054] The spent stream S318 enters the condenser HE1, where the
stream S318 is condensed in counterflow with a coolant stream S350
having parameters as at a point 50 to form the condensed stream
S301 and a spent coolant stream S351 having parameters as at a
point 51.
Second Specific Embodiment
[0055] Referring now to FIG. 3B, a variant of the improved ORC
power system embodiment of the present system 300 comprises an
alternate arrangement of the control valve CV, the bypass valve BV,
the dividing valve DV and the mixing valve MV. The pressurized feed
pump output stream S307 in this variant is divided by the dividing
valve DV to form a flow rate adjusted stream S308a having
parameters as at a point 8a and the recirculation stream S309. The
flow rate adjusted stream S308a is then forwarded to the control
valve CV adjusting its pressure to form the pressure and flow rate
adjusted stream S202, while the recirculation stream S309 is feed
to the bypass valve BV to from the pressure adjusted recirculation
stream S304. In this variant, the operation of the bypass valve BV
does not affect the operation of the control valve CV; this lack of
feedback has advantages, in terms of stability, but also
disadvantages, due to the lack of feedback. However, either variant
is viable. In such a variant, the operation of the bypass valve BV
affects the operation of the control valve CV; this feedback has
some disadvantages, however either variant is viable.
[0056] As well as allowing for independent control of pressure and
flow rate through the vaporization or boiling subsystem 356, the
embodiments of this invention described above have the additional
advantage that these system may fully regulate the flow rate of the
stream through the turbine, without needing to use the admission
valve AV installed prior to the turbine T to reduce the flow rate;
the admission valve AV may then be left fully open, substantially
reducing pressure losses. This then has the effect of reducing a
pressure in the vaporization subsystem 356, which reduces a
temperature of vaporization therein and increases the amount of
heat from the heat source that can be used to vaporize the working
fluid, thus increasing heat source utilization. All of these
factors further increase the efficiency and output of the
system.
Calculated Output of Nominal Megawatt ORC System
[0057] Calculations show that over the course of an average year of
operations of an ORC geothermal power system, performance is
improved as shown in Table 1 for the systems of this invention. In
Table 1, ORC represents a conventional organic Rankine cycle
system; CPFR ORC represents an organic Rankine cycle system
modified to allow independent control of pressure and flow rate of
the stream entering the vaporization subsystem; and WFCPFR ORC
represents an organic Rankine cycle system modified to operate with
a mixed propane-isopentane working fluid and independent control of
pressure and flow rate of the stream entering the vaporization
subsystem.
TABLE-US-00001 TABLE 1 Output for a Nominal 10 Megawatt ORC System
Installation Cooling Air CPFR % I.sup.c CPFR WFCPFR % I.sup.c
WFCPFR Temperature ORC ORC ORC ORC ORC 40.degree. F. 10,582.7 kW
10,823.3 kW 2.27% 11,445.9 kW 8.16% 50.degree. F. 10,471.6 kW
10,690.5 kW 2.09% 11,249.7 kW 7.43% 53.degree. F..sup.a 10,418.8 kW
10,629.4 kW 2.02% 11,127.8 kW 6.81% 55.degree. F..sup.b 10,283.1 kW
10,572.8 kW 2.82% 10,940.7 kW 6.39% 59.degree. F. 10,000.1 kW
10,350.6 kW 3.51% 10,584.4 kW 5.84% 70.degree. F. 9,203.2 kW
9,537.7 kW 3.63% 9,623.6 kW 4.57% 80.degree. F. 8,433.7 kW 8,639.6
kW 2.44% 8,774.8 kW 4.04% .sup.aaverage annual temperature;
.sup.bISO conditions; .sup.c% I--percent improvement.
Embodiments for Decontamination Working Fluid in ORC Systems
[0058] In any ORC system, the turbines are lubricated by a
lubricating oil, which ends up contaminating the organic working
fluid. This contamination is a substantial problem in the operation
of ORC system, which leads, over time, to a degradation of ORC
system power output. Specifically, this degradation occurs because
turbines in ORCs are lubricated with a lubricating oil, which
inevitably comes into contact with the organic working fluid, e.g.,
hydrocarbon based or freon based. This contact allows some amount
of the lubricating oil to mix with the working fluid, so that the
working fluid vapor exiting the turbine contains some amount of the
lubricating oil.
[0059] As this oil-bearing working fluid enters the condensation
subsystem, it condenses completely and the oil carried therein
dissolves in the working fluid. As a result, the condensate is
actually a mixture of the working fluid and the lubricating oil.
This condensate eventually enters into the vaporization or boiling
subsystem. Crucially, in the process of boiling, the vapor produced
contains almost none of the lubricating oil that was dissolved in
the condensate during condensation. Thus, the concentration of the
lubricating oil in the liquid in the boiler constantly increases as
the ORC system continues operation.
[0060] If, in such a case, the pressure in the boiler is maintained
at a constant level, then the temperature of the boiling point of
the working fluid goes up. This causes a corresponding increase in
a "pinch point" temperature of the heat source. Since a relative
flow rate of the heat source remains constant, the total amount of
heat available for vaporization is reduced. This, in turn, reduces
the amount of vapor produced in the boiler and so less vapor is
sent to the turbine.
[0061] If, on the other hand, the pressure in the boiler is
adjusted (reduced) so that the temperature of the boiling point
remains constant, then the pressure of the vapor sent to the
turbine is reduced.
[0062] Either way, the power output of the turbine will be reduced
and the degree of this reduction of power output may be
substantial. This degradation of output caused by the lubricating
oil contaminating the organic working fluid has been observed in
all ORC systems using a lubricating oil to lubrication the
turbine.
[0063] Observation of existing ORC systems show that over the
course of several years, the reduction of power output may be as
high as 30% to 40% of the nominal output of the systems.
[0064] In the prior art, the only method of dealing with this issue
is to fully remove the contaminated working fluid, and either
discarding the oil-contaminated working fluid and replacing it with
clean working fluid or else cleaning via vaporization the
contaminated working fluid in some other apparatus, collecting the
clean vapor, condensing the clean vapor, and then returning the
cleaned working fluid to the power system. In the prior art, both
of these options are complicated and costly to implement, but both
will mitigate the issue of oil contamination of the working fluid
for a time (on order of 1 year) before new contamination makes the
issue return again. Either way, using the techniques available in
the prior art, such repeated replacement or "cleaning" of the
working fluid are not very practical.
[0065] The present method for decontaminating lubricating oil
contaminated working fluid utilizing existing apparatus of the
system of FIG. 3A or FIG. 3B in a novel manner. Periodically, the
system is taken off-line for a period of time. During this period,
the turbine T and the feed pump P1 are stopped. In addition, the
control valve CV and the turbine admission valve AV are fully
closed, while the turbine bypass valve TBV is fully opened. At the
same time, the valve V1 is closed and the valve V2 is opened. It
should be recognized that the bypass valve TBV, is already part of
conventional ORC systems. In certain embodiments, the period is
less than 1 day. In other embodiments, the period is between about
4 and about 24 hours. In other embodiments, the period is between
about 6 and about 24 hours.
[0066] Meanwhile, the heat source stream S340 is still sent through
the vaporization subsystem 356, allowing the working fluid already
in the vaporization subsystem 356 to vaporize, bypassing the
turbine T and passing through the turbine bypass valve TBV to form
a bypass vapor stream S316a having parameters as at a point 16a,
which is then forwarded to the condensation subsystem 352, where it
is condensed. This condensed stream is oil-free or substantially
oil-free, as the vapor leaving the vaporization subsystem leaving
almost all of the oil contamination behind in the boiler and no new
contamination is picked up from the turbine T, which is being
bypassed. This cleaned working fluid is then sent from the
condenser HE1 to be collected in the reserve tank R. The reserve
tank R is already a part of conventional ORC systems.
[0067] As the amount of working fluid in the vaporization subsystem
is reduced, the concentration of contaminating oil in the remaining
working fluid in the vaporization subsystem goes up. Thus, as
explained above, the temperature in the boiler goes up. When this
temperature reaches a desired level, which may be determined by one
experienced in the art, the entire process is stopped. At this
point, only a small amount (5% to 10% of the working fluid) of
heavily contaminated working fluid is left in the vaporization
subsystem. This heavily contaminated working fluid is then safely
removed from the system for disposal removing all or substantially
all of the oil contamination from the system. New uncontaminated
working fluid is then added from inventory to the reserve tank R to
make up the loss of working fluid removed. Once this is done, the
control valve CV and the admission valve AV are opened as set forth
in the embodiments of FIG. 3A and FIG. 3B. The valve V3 is then
fully opened and the working fluid in the reserve tank R reenters
into the system. Once the working fluid reenters the system, the
valve V2 is closed and the valve V1 is opened and the system is put
back in normal operation, with a substantially clean working fluid,
i.e., a working fluid free or substantially free of the lubricating
fluid. Oil contamination will immediately begin to build up again,
but since this cleaning process may be done in less than a single
day, and is relatively low cost and simple to execute. The
procedure may be repeated on a periodic basis such as a yearly
basis, thus keeping oil contamination of the working fluid under
control and preventing the very substantial loss of power output
that high degrees of oil-contamination cause in an ORC system.
[0068] All references cited herein are incorporated by reference.
Although the invention has been disclosed with reference to its
preferred embodiments, from reading this description those of skill
in the art may appreciate changes and modification that may be made
which do not depart from the scope and spirit of the invention as
described above and claimed hereafter.
* * * * *