U.S. patent application number 16/888186 was filed with the patent office on 2020-12-03 for harmful substance removal system and method.
The applicant listed for this patent is HEARTLAND TECHNOLOGY PARTNERS LLC.. Invention is credited to Craig Clerkin, Benjamin N. Laurent.
Application Number | 20200376406 16/888186 |
Document ID | / |
Family ID | 1000004884999 |
Filed Date | 2020-12-03 |
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United States Patent
Application |
20200376406 |
Kind Code |
A1 |
Clerkin; Craig ; et
al. |
December 3, 2020 |
HARMFUL SUBSTANCE REMOVAL SYSTEM AND METHOD
Abstract
A harmful substance removal system and method include a direct
contact liquid concentrator having a gas inlet, a gas outlet, a
mixing chamber disposed between the gas inlet and the gas outlet,
and a liquid inlet for importing liquid into the mixing chamber.
Gas and liquid mixing in the are mixed chamber and a portion of the
liquid is vaporized. A demister is disposed downstream of the
mixing chamber. The demister includes at least one stage of mist
elimination having a first filter that removes particles greater
than 9 microns. A fan is coupled to the demister to assist gas flow
through the mixing chamber.
Inventors: |
Clerkin; Craig; (Stoughton,
WI) ; Laurent; Benjamin N.; (Cottage Grove,
WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HEARTLAND TECHNOLOGY PARTNERS LLC. |
St. Louis |
MO |
US |
|
|
Family ID: |
1000004884999 |
Appl. No.: |
16/888186 |
Filed: |
May 29, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62855563 |
May 31, 2019 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 1/14 20130101; C02F
2303/16 20130101; C02F 1/048 20130101; C02F 1/004 20130101; C02F
2301/046 20130101; C02F 2101/36 20130101; B01D 1/305 20130101; C02F
1/10 20130101; C02F 2103/06 20130101; C02F 1/283 20130101 |
International
Class: |
B01D 1/14 20060101
B01D001/14; B01D 1/30 20060101 B01D001/30; C02F 1/04 20060101
C02F001/04; C02F 1/10 20060101 C02F001/10; C02F 1/00 20060101
C02F001/00; C02F 1/28 20060101 C02F001/28 |
Claims
1. A harmful substance removal system, comprising: a direct contact
liquid concentrator including a gas inlet, a gas outlet, a mixing
chamber disposed between the gas inlet and the gas outlet, and a
liquid inlet for importing liquid into the mixing chamber, gas and
liquid mixing in the mixing chamber to vaporize a portion of the
liquid; a demister disposed downstream of the mixing chamber, the
demister including at least one stage of mist elimination
comprising a first filter that removes particles greater than 9
microns; and a fan coupled to the demister to assist gas flow
through the mixing chamber.
2. The harmful substance removal system of claim 1, wherein the
filter is located downstream of the fan.
3. The harmful substance removal system of claim 1, further
comprising a second filter in the demister, the second filter
removing particles greater than 15 microns, the second filter being
located upstream of the first filter.
4. The harmful substance removal system of claim 1, further
comprising a third filter in the demister, the third filter being a
coarse filter, the third filter being located upstream of the
second filter.
5. The harmful substance removal system of claim 1, wherein the
first filter removes particles greater than 5 microns and
preferably greater than 1 micron.
6. (canceled)
7. (canceled)
8. The harmful substance removal system of claim 1, wherein the
first filter comprises one of a mesh pad, a mesh pad and chevron, a
chevron, a flat pad, or a cylindrical pad.
9. The harmful substance removal system of claim 1, wherein the
demister includes a wash system that sprays cleaning water on the
first filter.
10. (canceled)
11. The harmful substance removal system of claim 1, wherein the
liquid comprises one of landfill leachate, power plant leachate,
and military wastewater.
12. The harmful substance removal system of claim 1, further
including a PFAS binding system applied to the evaporation system
or to the residual material after evaporation.
13. The harmful substance removal system of claim 12, wherein the
PFAS binding system includes an injection mechanism for injecting
an adsorbent, such as granular activated carbon.
14. The harmful substance removal system of claim 1, wherein the
harmful substance is a polyfluoroalkyl substance (PFAS).
15. The harmful substance removal system of claim 1, wherein the
first filter is removable.
16. The harmful substance removal system of claim 1, further
including a re-circulating circuit disposed between reservoir and
the mixing corridor to transport liquid within the reservoir to the
mixing corridor.
17. The harmful substance removal system of claim 16, wherein the
re-circulating circuit is coupled to the liquid inlet of the
concentrator section.
18-20. (canceled)
21. The harmful substance removal system of claim 1, further
including a sprayer disposed within the demister, the sprayer
positioned to spray liquid on the first filter to clean the first
filter.
22. The harmful substance removal system of claim 1, further
comprising a thermal destruction system.
23. The harmful substance removal system of claim 22, wherein the
thermal destruction system is a vapor thermal destruction system
located downstream of the demister.
24. (canceled)
25. The harmful substance removal system of claim 22, wherein the
thermal destruction system is a liquid thermal destruction system
that is used on the concentrated liquid portion of the
leachate.
26-33. (canceled)
34. The harmful substance removal system of claim 1, wherein the
first filter removes particles greater than 0.5 microns.
35. A method of moving PFAS from a liquid, the method comprising:
providing a source of heat; moving heat through a direct contact
liquid concentrator, the direct contact liquid concentrator
comprising: a heat inlet; a heat outlet; a liquid inlet; and a
mixing chamber connecting the heat inlet and the heat outlet,
injecting a liquid into the mixing chamber through the liquid
inlet; mixing the heat and the liquid, energy in the heat at least
partially evaporating the liquid; and removing entrained liquid
droplets greater than 9 microns in size from the waste heat.
Description
FIELD OF THE DISCLOSURE
[0001] This application relates generally to liquid concentrators,
and more specifically to compact, portable, inexpensive wastewater
concentrators that remove harmful substances from waste water
streams.
BACKGROUND
[0002] Per- and polyfluoroalkyl substances (PFAS) are commonly used
in a wide range of consumer products, such as non-stick cooking
pans, due to the oil and water repellant properties of these
substances, as well as good thermal resistance and friction
reduction. Other consumer products, such as textiles, paper
products, and furniture make use of protective sprays that use
these substances. Because these consumer products are regularly
replaced, the worn out products usually end up in a landfill where
the PFAS is eventually released and congregates in the landfill
leachate.
[0003] Recent studies have found that PFAS may be harmful to humans
and animals in small quantities if ingested. As a result, many
government agencies are beginning to draft regulations directed
towards mitigating PFAS in landfills so that the PFAS does not
eventually seep into local drinking water.
[0004] Currently there are no known solutions that remove PFAS in
wastewater concentrators or evaporators.
SUMMARY
[0005] According to a first embodiment, a harmful substance removal
system includes a direct contact liquid concentrator having a gas
inlet, a gas outlet, a mixing chamber disposed between the gas
inlet and the gas outlet, and a liquid inlet for importing liquid
into the mixing chamber. Gas and liquid mixing in the are mixed
chamber and a portion of the liquid is vaporized. A demister is
disposed downstream of the mixing chamber. The demister includes at
least one stage of mist elimination having a first filter that
removes particles greater than 9 microns. A fan is coupled to the
demister to assist gas flow through the mixing chamber.
[0006] According to a second embodiment, a method of moving PFAS
from a liquid includes providing a source of heat. Heat is moved
through a direct contact liquid concentrator. The direct contact
liquid concentrator includes a heat inlet, a heat outlet, a liquid
inlet, and a mixing chamber connecting the heat inlet and the heat
outlet. Liquid is injected into the mixing chamber through the
liquid inlet. Heat and the liquid are mixed and energy in the heat
at least partially evaporates the liquid. Entrained liquid droplets
greater than 9 microns in size are removed.
[0007] The foregoing embodiments may further include any one or
more of the following optional features, structures, and/or
forms.
[0008] In one optional form, the filter is located downstream of
the fan.
[0009] In another optional form, a second filter is disposed in the
demister, the second filter removing particles greater than 15
microns, the second filter being located upstream of the first
filter.
[0010] In other optional forms, a third filter is disposed in the
demister, the third filter being a coarse filter, the third filter
being located upstream of the second filter.
[0011] In other optional forms, the first filter removes particles
greater than 5 microns and preferably greater than 1 micron.
[0012] In other optional forms, a vapor condenser is included.
[0013] In other optional forms, a selective reduction catalyst
treatment system is included.
[0014] In other optional forms, the first filter comprises one of a
mesh pad, a mesh pad and chevron, a chevron, a flat pad, or a
cylindrical pad.
[0015] In other optional forms, the demister includes a wash system
that sprays cleaning water on the first filter.
[0016] In other optional forms, the cleaning water comprises one of
service water, treated water, or wastewater.
[0017] In other optional forms, the liquid comprises one of
landfill leachate, power plant leachate, and military
wastewater.
[0018] In other optional forms, a PFAS binding system is applied to
the evaporation system or to the residual material after
evaporation.
[0019] In other optional forms, the PFAS binding system includes an
injection mechanism for injecting an adsorbent, such as granular
activated carbon.
[0020] In other optional forms, the harmful substance is a
polyfluoroalkyl substance (PFAS).
[0021] In other optional forms, the first filter is removable.
[0022] In other optional forms, a re-circulating circuit is
disposed between reservoir and the mixing corridor to transport
liquid within the reservoir to the mixing corridor.
[0023] In other optional forms, the re-circulating circuit is
coupled to the liquid inlet of the concentrator section.
[0024] In other optional forms, a baffle is disposed in the mixing
corridor adjacent to the further liquid inlet so that the
concentrated liquid from the re-circulating circuit impinges on the
baffle and disperses into the mixing corridor in small
droplets.
[0025] In other optional forms, an adjustable flow restriction is
included in the mixing corridor.
[0026] In other optional forms, the fan is an induction fan located
downstream of the demister to provide a negative pressure gradient
through the demister.
[0027] In other optional forms, a sprayer is disposed within the
demister, the sprayer being positioned to spray liquid on the first
filter to clean the first filter.
[0028] In other optional forms, a thermal destruction system is
included.
[0029] In other optional forms, the thermal destruction system is a
vapor thermal destruction system located downstream of the
demister.
[0030] In other optional forms, a condenser is located upstream of
the thermal destruction system.
[0031] In other optional forms, the thermal destruction system is a
liquid thermal destruction system that is used on the concentrated
liquid portion of the leachate.
[0032] In other optional forms, a second volume reduction step is
included, for example, an evaporator, a sludge dryer, or a
centrifuge followed by thermal destruction of the residual material
from the second volume reduction step.
[0033] In other optional forms, the thermal destruction device is
an incinerator fueled by natural gas, landfill gas, or propane.
[0034] In other optional forms, the system includes a vessel having
an interior adapted to receive a contaminated liquid, and a tube
disposed within the vessel and adapted to transport a gas into the
interior of the vessel.
[0035] In other optional forms, a baffle is disposed above a fluid
in the vessel.
[0036] In other optional forms, the baffle is attached to the
tube.
[0037] In other optional forms, the baffle is attached to an
interior wall of the vessel.
[0038] In other optional forms, the tube includes a gas exit
disposed below a surface of the process fluid within the
vessel.
[0039] In other optional forms, the gas is forced into the vessel
with a blower.
[0040] In other optional forms, the first filter removes particles
greater than 0.5 microns.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a general schematic diagram of a compact liquid
concentrator that is used to concentrate landfill leachate;
[0042] FIG. 2 is a perspective view of a compact liquid
concentrator which implements the concentration process illustrated
in FIG. 1, and which may be used to mitigate PFAS;
[0043] FIG. 3 is a side view of a portion of the compact liquid
concentrator of FIG. 2, including a PFAS removal scrubber.
[0044] FIG. 4 is a schematic view of an alternative embodiment of a
compact liquid concentrator that may be used in combination with
the PFAS removal scrubber of FIG. 3.
DETAILED DESCRIPTION
[0045] The PFAS removal systems and methods described herein may be
used in direct contact liquid concentrators and/or evaporators,
such as the liquid concentrator disclosed in U.S. Pat. No.
8,568,557, and the submerged gas evaporator disclosed in U.S. Pat.
No. 8,382,075, each of which is hereby incorporated by reference
herein.
[0046] A number of governmental agencies have started to regulate
certain PFAS (PFOA, PFOS and others) in drinking water. To meet the
new regulations, water treatment plants are required to limit the
amount of PFAS that can be discharged to the water going to a
treatment plant. One significant source of PFAS is landfill
leachate. PFAS in trash make their way into the leachate. Most
landfill leachate ends up at wastewater treatment plants.
[0047] Currently, some landfills evaporate some of the liquid
portion of landfill leachate before sending the concentrated
leachate to a water treatment plant to reduce costs. The wastewater
concentrators identified in the U.S. Patents above are sometimes
used to evaporate a portion of landfill leachate. If possible,
keeping PFAS in the landfill may be an important advantage for a
landfill and possibly a requirement, because water treatment plants
may refuse to accept leachate having PFAS or other
contaminates.
[0048] In a leachate evaporation process, such as the processes
described above and below, there are two places PFAS can end up:
one is in the vapor stream leaving the concentrator and the other
in the concentrated residual liquid. Currently, the total amount of
PFAS in leachate is a very, very small quantity, about 2 lb/yr for
an average landfill. Measurement of PFAS is typically reported in
the parts per trillion range.
[0049] PFAS in the vapor stream of a concentrator is not desirable
since PFAS may be deposited in places that might contact water and
find its way to drinking water. PFAS can enter the vapor stream in
the following ways. First, PFAS in Vapor Phase (gas phase)--Vapor
phase PFAS will be very small. Chemical properties of PFAS (vapor
pressure, pH range of leachate) are such that very, very little
should transfer to the vapor phase. However, there are thousands of
different PFAS compounds and only a few have published detail
chemical properties, so proving low vapor phase for all PFAS based
on chemical properties is not possible. PFAS traveling with
particles in vapor stream--solid PFAS particles may bind to
entrained liquid particles and travel with the vapor stream. PFAS
traveling in mist--PFAS is expected to be in ionic form in leachate
residual. PFAS may be emitted with vapor as a mist. Current
concentrator systems remove large articles (e.g., greater than 50
microns) from a vapor stream that may contain PFAS but generally do
not remove small particles, typically less than 10 microns.
[0050] PFAS that does not make it to the vapor steam of a
concentrator ends up in the residual concentrate, which is
desirable because the residual may be returned to the landfill and
not sent to the water treatment facility. However, eventually PFAS
returned to the landfill in the residual liquid may begin to cycle
up and eventually reach higher levels. If landfill leachate reaches
a concentration of PFAS that is unacceptable, the PFAS may be
removed through thermal destruction in which the PFAS in liquid
form is taken offsite to an incinerator or an incinerator could be
placed in the landfill. Incineration is an expensive option but
should address any/all concerns. Alternatively, the PFAS may be
stabilized. Stabilized PFAS containing sludges are mixed with an
adsorbent, such as granular activated carbon, that ties up or binds
some/all PFAS in the liquid.
[0051] Tuning now to FIG. 1, a generalized schematic diagram of a
liquid concentrator 10 is illustrated that includes a gas inlet 20,
a gas exit 22 and a flow corridor 24 connecting the gas inlet 20 to
the gas exit 22. The flow corridor 24 includes a narrowed portion
26 that accelerates the flow of gas through the flow corridor 24
creating turbulent flow within the flow corridor 24 at or near this
location. The narrowed portion 26 in this embodiment may formed by
a venturi device. In other concentrators, the flow corridor 24 may
not include a narrowed portion. A liquid inlet 30 injects a liquid
to be concentrated (via evaporation) into a liquid concentration
chamber in the flow corridor 24 at a point upstream of the narrowed
portion 26, and the injected liquid joins with the gas flow in the
flow corridor 24. The liquid inlet 30 may include one or more
replaceable nozzles 31 for spraying the liquid into the flow
corridor 24. The inlet 30, whether or not equipped with a nozzle
31, may introduce the liquid in any direction from perpendicular to
parallel to the gas flow as the gas moves through the flow corridor
24. A baffle 33 may also be located near the liquid inlet 30 such
that liquid introduced from the liquid inlet 30 impinges on the
baffle and disperses into the flow corridor in small droplets.
[0052] As the gas and liquid flow through the narrowed portion 26,
the venturi principle creates an accelerated and turbulent flow
that thoroughly mixes the gas and liquid in the flow corridor 24 at
and after the location of the inlet 30. As a result of the
turbulent mixing, a portion of the liquid rapidly vaporizes and
becomes part of the gas stream. As the gas-liquid mixture moves
through the narrowed portion 26, the direction and/or velocity of
the gas/liquid mixture may be changed by an adjustable flow
restriction, such as a venturi plate 32, which is generally used to
create a large pressure difference in the flow corridor 24 upstream
and downstream of the venturi plate 32. The venturi plate 32 may be
adjustable to control the size and/or shape of the narrowed portion
26 and may be manufactured from a corrosion resistant material
including a high alloy metal such as those manufactured under the
trade names of Hastelloy.RTM., Inconel.RTM., AL6XN, and
Monel.RTM..
[0053] After leaving the narrowed portion 26, the gas-liquid
mixture passes through a demister 34 (also referred to as a fluid
scrubber) coupled to the gas exit 22. The demister 34 removes
entrained liquid droplets from the gas stream. The demister 34
includes a gas-flow passage. The removed liquid collects in a
liquid collector or sump 36 in the gas-flow passage, the sump 36
may also include a reservoir for holding the removed liquid. A pump
40 fluidly coupled to the sump 36 and/or reservoir moves the liquid
through a re-circulating circuit 42 back to the liquid inlet 30
and/or flow corridor 24. In this manner, the liquid may be reduced
through evaporation to a desired concentration. Fresh or new liquid
to be concentrated is input to the re-circulating circuit 42
through a liquid inlet 44. This new liquid may instead be injected
directly into the flow corridor 24 upstream of the venturi plate
32. The rate of fresh liquid input into the re-circulating circuit
42 may be equal to the rate of evaporation of the liquid as the
gas-liquid mixture flows through the flow corridor 24 plus the rate
of liquid extracted through a concentrated fluid extraction port 46
located in or near the reservoir in the sump 40. The ratio of
re-circulated liquid to fresh liquid may generally be in the range
of approximately 1:1 to approximately 100:1, and is usually in the
range of approximately 5:1 to approximately 25:1. For example, if
the re-circulating circuit 42 circulates fluid at approximately 10
gal/min, fresh or new liquid may be introduced at a rate of
approximately 1 gal/min (i.e., a 10:1 ratio). A portion of the
liquid may be drawn off through the extraction port 46 when the
liquid in the re-circulating circuit 42 reaches a desired
concentration.
[0054] After passing through the demister 34 the gas stream passes
through an induction fan 50 that draws the gas through the flow
corridor 24 and demister gas-flow corridor under negative pressure.
Of course, the concentrator 10 could operate under positive
pressure produced by a blower (not shown) prior to the liquid inlet
30. Finally, the gas is vented to the atmosphere or directed for
further processing through the gas exit 22.
[0055] The concentrator 10 may include a pre-treatment system 52
for treating the liquid to be concentrated, which may be a
wastewater feed. For example, an air stripper may be used as a
pre-treatment system 52 to remove substances that may produce foul
odors or be regulated as air pollutants. In this case, the air
stripper may be any conventional type of air stripper or may be a
further concentrator of the type described herein, which may be
used in series as the air stripper. The pre-treatment system 52
may, if desired, heat the liquid to be concentrated using any
desired heating technique. Additionally, the gas and/or wastewater
feed circulating through the concentrator 10 may be pre-heated in a
pre-heater 54. Pre-heating may be used to enhance the rate of
evaporation and thus the rate of concentration of the liquid. The
gas and/or wastewater feed may be pre-heated through combustion of
renewable fuels such as wood chips, bio-gas, methane, or any other
type of renewable fuel or any combination of renewable fuels,
fossil fuels and waste heat. Furthermore, the gas and/or wastewater
may be pre-heated through the use of waste heat generated in a
landfill flare or stack. Also, waste heat from an engine, such as
an internal combustion engine, may be used to pre-heat the gas
and/or wastewater feed. Additionally, the gas streams ejected from
the gas exit 22 of the concentrator 10 may be transferred into a
flare or other post treatment device 56 which treats the gas before
releasing the gas to the atmosphere. More specifically, the post
treatment device 56 may be a thermal destruction device or a PFAS
binding system. In other embodiments, the post treatment device 56
may be preceded by a condenser that condenses water vapor in the
exhaust gas. In yet other embodiments, the post treatment device
may include a thermal destruction device for the residual
wastewater.
[0056] The liquid concentrator 10 described herein may be used to
concentrate a wide variety of wastewater streams, such as waste
water from industry, runoff water from natural disasters (floods,
hurricanes), refinery caustic, leachate such as landfill leachate,
etc. The liquid concentrator 10 is practical, energy efficient,
reliable, and cost-effective. In order to increase the utility of
this liquid concentrator, the liquid concentrator 10 is readily
adaptable to being mounted on a trailer or a moveable skid to
effectively deal with wastewater streams that arise as the result
of accidents or natural disasters or to routinely treat wastewater
that is generated at spatially separated or remote sites. The
liquid concentrator 10 described herein has all of these desirable
characteristics and provides significant advantages over
conventional wastewater concentrators, especially when the goal is
to manage a broad variety of wastewater streams.
[0057] Moreover, the concentrator 10 may be largely fabricated from
highly corrosion resistant, yet low cost materials such as
fiberglass and/or other engineered plastics. This is due, in part,
to the fact that the disclosed concentrator is designed to operate
under minimal differential pressure. For example, a differential
pressure generally in the range of only 10 to 30 inches water
column is required. Also, because the gas-liquid contact zones of
the concentration processes generate high turbulence within
narrowed (compact) passages at or directly after the venturi
section of the flow path, the overall design is very compact as
compared to conventional concentrators where the gas liquid contact
occurs in large process vessels. As a result, the amount of high
alloy metals required for the concentrator 10 is quite minimal.
Also, because these high alloy parts are small and can be readily
replaced in a short period of time with minimal labor, fabrication
costs may be cut to an even higher degree by designing some or all
of these parts to be wear items manufactured from lesser quality
alloys that are to be replaced at periodic intervals. If desired,
these lesser quality alloys (e.g., carbon steel) may be coated with
corrosion and/or erosion resistant liners, such as engineered
plastics including elastomeric polymers, to extend the useful life
of such components. Likewise, the pump 40 may be provided with
corrosion and/or erosion resistant liners to extend the life of the
pump 40, thus further reducing maintenance and replacement
costs.
[0058] As will be understood, the liquid concentrator 10 provides
direct contact of the liquid to be concentrated and the hot gas,
effecting highly turbulent heat exchange and mass transfer between
hot gas and the liquid, e.g., wastewater, undergoing concentration.
Moreover, the concentrator 10 employs highly compact gas-liquid
contact zones, making it minimal in size as compared to known
concentrators. The direct contact heat exchange feature promotes
high energy efficiency and eliminates the need for solid surface
heat exchangers as used in conventional, indirect heat transfer
concentrators. Further, the compact gas-liquid contact zone
eliminates the bulky process vessels used in both conventional
indirect and direct heat exchange concentrators. These features
allow the concentrator 10 to be manufactured using comparatively
low cost fabrication techniques and with reduced weight as compared
to conventional concentrators. Both of these factors favor
portability and cost-effectiveness. Thus, the liquid concentrator
10 is more compact and lighter in weight than conventional
concentrators, which make it ideal for use as a portable unit.
Additionally, the liquid concentrator 10 is less prone to fouling
and blockages due to the direct contact heat exchange operation and
the lack of solid heat exchanger surfaces. The liquid concentrator
10 can also process liquids with significant amounts of suspended
solids because of the direct contact heat exchange. As a result,
high levels of concentration of the process fluids may be achieved
without need for frequent cleaning of the concentrator 10.
[0059] More specifically, in liquid concentrators that employ
indirect heat transfer, the heat exchangers are prone to fouling
and are subject to accelerated effects of corrosion at the normal
operating temperatures of the hot heat transfer medium that is
circulated within them (steam or other hot fluid). Each of these
factors places significant limits on the durability and/or costs of
building conventional indirectly heated concentrators, and on how
long they may be operated before it is necessary to shutdown and
clean or repair the heat exchangers. By eliminating the bulky
process vessels, the weight of the liquid concentrators and both
the initial costs and the replacement costs for high alloy
components are greatly reduced. Moreover, due to the temperature
difference between the gas and liquid, the relatively small volume
of liquid contained within the system, and the reduced relative
humidity of the gas prior to mixing with the liquid, the
concentrator 10 operates at close to the adiabatic saturation
temperature for the particular gas/liquid mixture, which is
typically in the range of about 150 degrees Fahrenheit to about 215
degrees Fahrenheit (i.e., this concentrator is a "low momentum"
concentrator).
[0060] Moreover, the concentrator 10 is designed to operate under
negative pressure, a feature that greatly enhances the ability to
use a very broad range of fuel or waste heat sources as an energy
source to affect evaporation. In fact, due to the draft nature of
these systems, pressurized or non-pressurized burners may be used
to heat and supply the gas used in the concentrator 10. Further,
the simplicity and reliability of the concentrator 10 is enhanced
by the minimal number of moving parts and wear parts that are
required. In general, only two pumps and a single induced draft fan
are required for the concentrator when it is configured to operate
on waste heat such as stack gases from engines (e.g., generators or
vehicle engines), industrial process stacks, gas compressor
systems, and flares, such as landfill gas flares. These features
provide significant advantages that reflect favorably on the
versatility and the costs of buying, operating and maintaining the
concentrator 10.
[0061] A typical concentrator 10 may be capable of treating as much
as one-hundred thousand gallons or more per day of wastewater,
while larger, stationary units, such as those installed at
landfills, sewage treatment plants, or natural gas or oil fields,
may be capable of treating multiples of one-hundred thousand
gallons of wastewater per day.
[0062] Turning now to FIG. 2, an embodiment of the compact liquid
concentrator 110 operates to concentrate wastewater, such as
landfill leachate, using exhaust or waste heat. For example, many
landfills include a flare which is used to burn landfill gas to
eliminate methane and other gases prior to release to the
atmosphere. Typically, the gas exiting the flare is between 1000
and 1500 degrees Fahrenheit and may reach 1800 degrees
Fahrenheit.
[0063] As illustrated in FIG. 2, the compact liquid concentrator
110 generally includes or is connected to a flare assembly 115, and
includes a heat transfer assembly 117 (shown in more detail in FIG.
4), an air pre-treatment assembly 119, a concentrator assembly 120
(shown in more detail in FIG. 5), a fluid scrubber 122, and an
exhaust section 124. Importantly, the flare assembly 115 includes a
flare 130, which burns landfill gas therein according to any known
principles, and an optional flare cap assembly 132. The flare cap
assembly 132 includes a moveable cap 134 (e.g., a flare cap, an
exhaust gas cap, etc.) which covers the top of the flare 130, or
other type of stack (e.g., a combustion gas exhaust stack), to seal
off the top of the flare 130 when the flare cap 134 is in the
closed position, or to divert a portion of the flare gas in a
partially closed position, and which allows gas produced within the
flare 130 to escape to the atmosphere through an open end that
forms a primary gas outlet 143, when the flare cap 134 is in an
open or partially open position. The flare cap assembly 132 also
includes a cap actuator 135, such as a motor (e.g., an electric
motor, a hydraulic motor, a pneumatic motor, etc.) which moves the
flare cap 134 between the fully open and the fully closed
positions.
[0064] If desired, the flare 130 may include an adapter section 138
including the primary combustion gas outlet 143 and a secondary
combustion gas outlet 141 upstream of the primary combustion gas
outlet 143. When the flare cap 130 is in the closed position,
combustion gas is diverted through the secondary combustion gas
outlet 141. The adapter section 138 may include a connector section
139 that connects the flare 130 (or exhaust stack) to the heat
transfer section 117 using a 90 degree elbow or turn. Other
connector arrangements are possible. For example, the flare 130 and
heat transfer section 117 may be connected at virtually any angle
between 0 degrees and 180 degrees. In this case, the flare cap
assembly 132 is mounted on the top of the adaptor section 138
proximate the primary combustion gas outlet 143.
[0065] As illustrated in FIG. 2, the heat transfer assembly 117
includes a transfer pipe 140, which connects to an inlet of the air
pre-treatment assembly 119 to the flare 130 and, more particularly,
to the adaptor section 138 of the flare 130. A support member 142,
in the form of a vertical bar or pole, supports the heat transfer
pipe 140 between the flare 130 and the air pre-treatment assembly
119 at a predetermined level or height above the ground. The heat
transfer pipe 140 is connected to the connector section 139 or the
adapter section 138 at the secondary combustion gas outlet 141, the
transfer pipe forming a portion of a fluid passageway between the
adapter section 138 and a secondary process, such as a fluid
concentrating process. The support member 142 is typically
necessary because the heat transfer pipe 140 will generally be made
of metal, such as carbon or stainless steel, and may be refractory
lined with materials such as aluminum oxide and/or zirconium oxide,
to withstand the temperature of the gas being transferred from the
flare 130 to the air pre-treatment assembly 119. Thus, the heat
transfer pipe 140 will typically be a heavy piece of equipment.
However, because the flare 130, on the one hand, and the air
pre-treatment assembly 119 and the concentrator assembly 120, on
the other hand, are disposed immediately adjacent to one another,
the heat transfer pipe 140 generally only needs to be of a
relatively short length, thereby reducing the cost of the materials
used in the concentrator 110, as well as reducing the amount of
support structure needed to bear the weight of the heavy parts of
the concentrator 110 above the ground. As illustrated in FIG. 2,
the heat transfer pipe 140 and the air pre-treatment assembly 1119
form an upside-down U-shaped structure.
[0066] The air pre-treatment assembly 119 includes a vertical
piping section 150 and an ambient air valve disposed at the top of
the vertical piping section 150. The ambient air valve (also
referred to as a bleed valve) forms a fluid passageway between the
heat transfer pipe 140 (or air pre-treatment assembly 119) and the
atmosphere. The ambient air valve operates to allow ambient air to
flow through a mesh bird screen 152 (typically wire or metal) and
into the interior of the air pre-treatment assembly 119 to mix with
the hot gas coming from the flare 130. If desired, the air
pre-treatment assembly 119 may include a permanently open section
proximate to the bleed valve which always allows some amount of
bleed air into the air pre-treatment assembly 119, which may be
desirable to reduce the size of the required bleed valve and for
safety reasons. While the control of the ambient air or bleed valve
will be discussed in greater detail hereinafter, this valve
generally allows the gas from the flare 130 to be cooled to a more
useable temperature before entering into the concentrator assembly
120. The air pre-treatment assembly 119 may be supported in part by
cross-members 154 connected to the support member 142. The
cross-members 154 stabilize the air pre-treatment assembly 119,
which is also typically made of heavy carbon or stainless steel or
other metal, and which may be refractory-lined to improve energy
efficiency and to withstand the high temperature of the gases
within this section of the concentrator 110. If desired, the
vertical piping section 150 may be extendable to adapt to or
account for flares of differing heights so as to make the liquid
concentrator 110 easily adaptable to many different flares or to
flares of different heights. This concept is illustrated in more
detail in FIG. 2. As shown in FIG. 2, the vertical piping section
150 may include a first section 150A (shown using dotted lines)
that rides inside of a second section 150B thereby allowing the
vertical piping section 150 to be adjustable in length
(height).
[0067] Generally speaking, the air pre-treatment assembly 119
operates to mix ambient air provided through the ambient air valve
beneath the screen 152 and the hot gas flowing from the flare 130
through the heat transfer pipe 140 to create a desired temperature
of gas at the inlet of the concentrator assembly 120.
[0068] The liquid concentrator assembly 120 includes a lead-in
section 156 having a reduced cross-section at the top end thereof
which mates the bottom of the piping section 150 to a quencher 159
of the concentrator assembly 120. The concentrator assembly 120
also includes a first fluid inlet 160, which injects new or
untreated liquid to be concentrated, such as landfill leachate,
into the interior of the quencher 159. While not shown in FIG. 2,
the inlet 160 may include a coarse sprayer with a large nozzle for
spraying the untreated liquid into the quencher 159. Because the
liquid being sprayed into the quencher 159 at this point in the
system is not yet concentrated, and thus has large amount of water
therein, and because the sprayer is a coarse sprayer, the sprayer
nozzle is not subject to fouling or being clogged by the small
particles within the liquid. As will be understood, the quencher
159 operates to quickly reduce the temperature of the gas stream
(e.g., from about 900 degrees Fahrenheit to less than 200 degrees
Fahrenheit) while performing a high degree of evaporation on the
liquid injected at the inlet 160. If desired, but not specifically
shown in FIG. 2, a temperature sensor may be located at or near the
exit of the piping section 150 or in the quencher 159 and may be
used to control the position of the ambient air valve to thereby
control the temperature of the gas present at the inlet of the
concentrator assembly 120.
[0069] As shown in FIG. 2, the quencher 159 is connected to liquid
injection chamber which is connected to narrowed portion or venturi
section 162 which has a narrowed cross section with respect to the
quencher 159 and which has a venturi plate 163 (shown in dotted
line) disposed therein. The venturi plate 163 creates a narrow
passage through the venturi section 162, which creates a large
pressure drop between the entrance and the exit of the venturi
section 162. This large pressure drop causes turbulent gas flow
within the quencher 159 and the top or entrance of the venturi
section 162, and causes a high rate of gas flow out of the venturi
section 162, both of which lead to thorough mixing of the gas and
liquid in the venturi section 162. The position of the venturi
plate 163 may be controlled with a manual control rod connected to
the pivot point of the plate 163, or via an electric control
mechanism, such as motor.
[0070] A re-circulating pipe 166 extends around opposite sides of
the entrance of the venturi section 162 and operates to inject
partially concentrated (i.e., re-circulated) liquid into the
venturi section 162 to be further concentrated and/or to prevent
the formation of dry particulate within the concentrator assembly
120 through multiple fluid entrances located on one or more sides
of the flow corridor. While not explicitly shown in FIG. 2, a
number of pipes, such as three pipes of, for example, 1/2 inch
diameter, may extend from each of the opposites legs of the pipe
166 partially surrounding the venturi section 162, and through the
walls and into the interior of the venturi section 162. Because the
liquid being ejected into the concentrator 110 at this point is
re-circulated liquid, and is thus either partially concentrated or
being maintained at a particular equilibrium concentration and more
prone to plug a spray nozzle than the less concentrated liquid
injected at the inlet 160, this liquid may be directly injected
without a sprayer so as to prevent clogging. However, if desired, a
baffle in the form of a flat plate may be disposed in front of each
of the openings of the 1/2 inch pipes to cause the liquid being
injected at this point in the system to hit the baffle and disperse
into the concentrator assembly 120 as smaller droplets. In any
event, the configuration of this re-circulating system distributes
or disperses the re-circulating liquid better within the gas stream
flowing through the concentrator assembly 120.
[0071] The combined hot gas and liquid flows in a turbulent manner
through the venturi section 162. As noted above, the venturi
section 162, which has a moveable venturi plate 163 disposed across
the width of the concentrator assembly 120, causes turbulent flow
and complete mixture of the liquid and gas, causing rapid
evaporation of the liquid within the gas. Because the mixing action
caused by the venturi section 162 provides a high degree of
evaporation, the gas cools substantially in the concentrator
assembly 120, and exits the venturi section 162 into a flooded
elbow 164 at high rates of speed. In fact, the temperature of the
gas-liquid mixture at this point may be about 160 degrees
Fahrenheit.
[0072] The bottom of the flooded elbow 164 has liquid disposed
therein, and the gas-liquid mixture exiting the venturi section 162
at high rates of speed impinges on the liquid in the bottom of the
flooded elbow 164 as the gas-liquid mixture is forced to turn 90
degrees to flow into the fluid scrubber 122. The interaction of the
gas-liquid stream with the liquid within the flooded elbow 164
removes liquid droplets from the gas-liquid stream and prevents
suspended particles within the gas-liquid stream from hitting the
bottom of flooded elbow 164 at high rates of speeds, thereby
preventing erosion of the metal wall of the flooded elbow 164.
[0073] After leaving the flooded elbow 164, the gas-liquid stream
in which evaporated liquid and some liquid and other particles
still exist, flows through the fluid scrubber 122 which is, in this
case, a cross-flow fluid scrubber. The fluid scrubber 122 includes
various screens or filters 169, 170 which aid in removal of
entrained liquids from the gas-liquid stream and removes other
particles that might be present with the gas-liquid stream.
[0074] As is typical in cross flow scrubbers, liquid captured by
the filters 169 and 170 gravity drains into a reservoir or sump 172
located at the bottom of the fluid scrubber 122. The sump 172,
which may hold, for example 200 gallons of liquid or more, thereby
collects concentrated fluid containing dissolved and suspended
solids removed from the gas-liquid stream and operates as a
reservoir for a source of re-circulating concentrated liquid back
to the concentrator assembly 120 to be further treated and/or to
prevent the formation of dry particulate within the concentrator
assembly 120. In one embodiment, the sump 172 may include a sloped
V-shaped bottom (not shown in the drawings) having a V-shaped
groove extending from the back of the fluid scrubber 122 (furthest
away from the flooded elbow 164) to the front of the fluid scrubber
122 (closest to the flooded elbow 164), wherein the V-shaped groove
is sloped such that the bottom of the V-shaped groove is lower at
the end of the fluid scrubber 122 nearest the flooded elbow 164
than at an end farther away from the flooded elbow 164. In other
words, the V-shaped bottom may be sloped with the lowest point of
the V-shaped bottom proximate the exit port 173 and/or the pump
182. Additionally, a washing circuit (not shown in the drawings)
may pump concentrated fluid from the sump 172 to a sprayer (not
shown) within the cross flow scrubber 122, the sprayer being aimed
to spray liquid at the V-shaped bottom. Alternatively, the sprayer
may spray unconcentrated liquid or clean water at the V-shaped
bottom and/or on the chevrons 170. The sprayer may periodically or
constantly spray liquid onto the surface of the V-shaped bottom to
wash solids and prevent solids buildup on the V-shaped bottom or at
the exit port 173 and/or the pump 182. As a result of this V-shaped
sloped bottom and pump, liquid collecting in the sump 172 is
continuously agitated and renewed, thereby maintaining a relatively
constant consistency and maintaining solids in suspension. If
desired, the spraying circuit may be a separate circuit using a
separate pump with, for example, an inlet inside of the sump 173,
or may use a pump 182 associated with a concentrated liquid
re-circulating circuit described below to spray concentrated fluid
from the sump onto the V-shaped bottom of the sump 172. In some
cases, the sprayer may incorporate the use of anti-foam agents or
foam suppressors.
[0075] As illustrated in FIG. 2, a return line 180, as well as a
pump 182, operate to re-circulate fluid removed from the gas-liquid
stream from the sump 172 back to the concentrator 120 and thereby
complete a fluid or liquid re-circulating circuit. Likewise, a pump
184 may be provided within an input line 186 to pump new or
untreated liquid, such as landfill leachate, to the input 160 of
the concentrator assembly 120. Also, one or more sprayers 185 may
be disposed inside the fluid scrubber 122 adjacent the chevrons 170
and may be operated periodically to spray clean water or a portion
of the wastewater feed on the chevrons 170 to keep them clean. A
chevron 170 is a type of filter, and other types of filters may be
substituted for the chevrons 170 illustrated in the drawings.
[0076] Concentrated liquid also be removed from the bottom of the
fluid scrubber 122 via the exit port 173 and may be further
processed or disposed of in any suitable manner in a secondary
re-circulating circuit. In particular, the concentrated liquid
removed by the exit port 173 contains a certain amount of suspended
solids, which preferably may be separated from the liquid portion
of the concentrated liquid and removed from the system using a
secondary re-circulating circuit. For example, concentrated liquid
removed from the exit port 173 may be transported through a
secondary concentrated wastewater circuit (not shown) to a
solid/liquid separating device, such as a settling tank, a
vibrating screen, a rotary vacuum filter, a filter press, or a
centrifuge. After the suspended solids and liquid portion of the
concentrated wastewater are separated by the solid/liquid
separating device, the liquid portion of the concentrated
wastewater may be returned to the sump 172 for further processing
in the first or primary re-circulating circuit connected to the
concentrator.
[0077] The gas, which flows through and out of the fluid scrubber
122 with the liquid and suspended solids removed therefrom, exits
out of piping or ductwork at the back of the fluid scrubber 122
(downstream of the chevrons 170) and flows through an induced draft
fan 190 of the exhaust assembly 124, from where it is exhausted to
the atmosphere in the form of the cooled hot inlet gas mixed with
the evaporated water vapor. Of course, an induced draft fan motor
192 is connected to and operates the fan 190 to create negative
pressure within the fluid scrubber 122 so as to ultimately draw gas
from the flare 130 through the transfer pipe 140, the air
pre-treatment assembly 119 and the concentrator assembly 120. As
described above with respect to FIG. 1, the induced draft fan 190
needs only to provide a slight negative pressure within the fluid
scrubber 122 to assure proper operation of the concentrator
110.
[0078] Turning now to FIG. 3, a fluid scrubber 222 is illustrated
that includes a harmful substance removal assembly 222a in the form
of a series of filters or screens 269a, 270a, 270b, 270c. More
specifically, the filter 269a is a coarse filter as described
above. Filters 270a, and 270b are fine filters as described above,
and the addition of an ultra fine filter 270c captures droplets
having diameters of less than 9 microns, preferably less than 5
microns, and more preferably less than 1 micron, and even more
preferably less than 0.5 microns. Filtering dropets of these sizes
has been found to be very effective at removing PFAS from the
system. The filters 269a, 270a, 270b, 270c may be removable from
the fluid scrubber 222. The fluid scrubber 222 illustrated in FIG.
3 may replace the fluid scrubber 122 of FIG. 2, or the fluid
scrubber 22 of FIG. 1. Moreover, the fluid scrubber 222 of FIG. 3
may be used to replace any filter and or fluid scrubber in a SGE
type concentrator. In other embodiments, the ultra fine filter 270c
may be located downstream of the induction fan, in the exhaust
stack. Filters are considered to remove 99% of particles of the
stated size for the filter. For example, a 5 micron filter removes
99% of particles greater than 5 microns.
[0079] Turning now to FIG. 4, an alternative compact liquid
concentrator 310 is described that may be used with the fluid
scrubber 222 of FIG. 3. The compact liquid concentrator 310
includes a vessel 330 having an interior adapted to receive a
contaminated liquid. A weir 340 that extends around a gas inlet
tube 322. The compact liquid concentrator 310 in this example may
be a submerged gas evaporator, a submerged gas reactor or a
combination submerged gas evaporator/reactor. A blower device (not
shown in FIG. 3) delivers heated gas to the gas inlet tube 322. The
vessel 330 has a dished bottom and an interior volume. The gas
inlet tube 322 is at least partially disposed within the interior
volume of the vessel 230. The weir 340 forms an annular confined
volume 370 within vessel 330 between the weir 340 and the gas inlet
tube. In the embodiment of FIG. 4, twelve sparge ports 324 are
disposed near the bottom of the gas inlet tube 322. The sparge
ports 324 in this example are substantially rectangular in shape,
although other shapes may be used. Additionally, the sparge ports
324 of this embodiment are arranged generally parallel to the flow
direction of the gas/liquid phase, further reducing the possibility
of the sparge ports 324 becoming clogged.
[0080] The heated gas exits the gas inlet tube 322 through the
sparge ports 324 into the confined volume 370 formed between the
gas inlet tube 322 and the tubular shaped weir 340. In this case,
the weir 340 has a circular cross-sectional shape and encircles the
lower end of the gas inlet tube 322. Additionally, the weir 340 is
located at an elevation which creates a lower circulation gap 336
between a first end 341 of the weir 340 and a bottom dished surface
331 of the vessel 330. The second end 342 of the weir 340 is
located at an elevation below a normal or at rest operating level
of the process fluid 390 within the vessel 330. Further, a baffle
or shield 338 is disposed within the vessel 330 above the second
end 342 of the weir 340. The baffle 338 is circular in shape and
extends radially outwardly from the gas inlet tube 322.
Additionally, the baffle 338 is illustrated as having an outer
diameter somewhat greater than the outer diameter of the weir 340.
However, the baffle 338 may have the same, a greater or smaller
diameter than the diameter of the weir 340 if desired. Several
support brackets 333 are mounted to the bottom surface 331 of the
vessel 330 and are attached to the weir 340 near the first end 341
of the weir 340. Additionally, a gas inlet tube stabilizer ring 335
is attached to the support brackets 333 and substantially surrounds
the bottom end 326 of the gas inlet tube 322 to stabilize the gas
inlet tube 322 during operation.
[0081] During operation headed gas is ejected through the sparge
ports 324 into the confined volume 370 between the gas inlet tube
322 and the weir 342 creating a mixture of gas and process fluid
390 within the confined volume 370 that is significantly reduced in
bulk density compared to the average bulk density of the fluid
located in a volume 371 outside of the wall of the weir 340. This
reduction in bulk density of the gas/liquid mixture within confined
volume 370 creates an imbalance in head pressure at all elevations
between the process fluid 390 surface and the first end 341 of the
weir 340 The reduced head pressure induces a flow pattern of liquid
from the higher head pressure regions of volume 371 through the
circulation gap 336 and into the confined volume 370. Once
established, this induced flow pattern provides vigorous mixing
action both within the confined volume 370 and throughout the
volume 371 as liquid from the surface and all locations within the
volume 371 is drawn downward through the circulation gap 336 and
upward through the confined volume 370 where the gas/liquid mixture
flows outward over the second end 342 of the weir 340 and over the
surface confined within the vessel 330.
[0082] At the point where gas/liquid mixture flowing upward within
confined volume 370 reaches the elevation of the surface and having
passed beyond the second edge 342 of the weir 340, the difference
in head pressure between the gas/liquid mixture within the confined
volume 370 and the gas/liquid mixture within volume 371 is
eliminated. Absent the driving force of differential head pressure
and the confining effect of the wall of the weir 340, gravity and
the resultant buoyancy of the gas phase within the liquid phase
become the primary outside forces affecting the continuing flow
patterns of the gas/liquid mixture exiting the confined space 370.
The combination of the force of gravity and the barrier created by
the baffle 338 in the vertical direction eliminates the vertical
velocity and momentum components of the flowing gas/liquid mixture
at or below the elevation of the bottom of the baffle 338 and
causes the velocity and momentum vectors of the flowing gas/liquid
mixture to be directed outward through a gap 339 created by the
second end 342 of the weir 340 and the bottom surface of the baffle
338 and downwards near the surface within the vessel 230. Discrete
and discontinuous regions of gas coalesce and ascend vertically
within the continuous liquid phase. As the ascending gas regions
within the gas/liquid mixture reach the surface, buoyancy causes
the discontinuous gas phase to break through the surface and to
coalesce into a continuous gas phase that is directed upward within
the confines of the vessel 330 and into a gas exit port 360 under
the influence of the differential pressure created by the blower or
blowers (not shown in FIG. 4). The fluid scrubber 222 of FIG. 3 may
be fluidly connected to the gas exit port 360 of FIG. 4 to perform
the hazardous substance removal described above.
[0083] While certain representative embodiments and details have
been shown for purposes of illustrating the invention, it will be
apparent to those skilled in the art that various changes in the
methods and apparatus disclosed herein may be made without
departing from the scope of the invention.
* * * * *