CA1080970A - Apparatus and method for enriching combustion air with oxygen - Google Patents
Apparatus and method for enriching combustion air with oxygenInfo
- Publication number
- CA1080970A CA1080970A CA297,412A CA297412A CA1080970A CA 1080970 A CA1080970 A CA 1080970A CA 297412 A CA297412 A CA 297412A CA 1080970 A CA1080970 A CA 1080970A
- Authority
- CA
- Canada
- Prior art keywords
- oxygen
- liquid
- air
- tower
- chamber
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/32—Direct CO2 mitigation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
Landscapes
- Gas Separation By Absorption (AREA)
- Air Supply (AREA)
- Combustion Of Fluid Fuel (AREA)
- Oxygen, Ozone, And Oxides In General (AREA)
Abstract
Abstract of the Disclosure An apparatus and method used in the oxygen enrichment of combustion air which for example, is mixed with a fuel in a burner of an industrial furnace or oven. Air, containing normal amounts of oxygen, is brought into contact with a liquid which absorbs at least some of the oxygen from the air. The oxygen enriched liquid is then heated by hot flue gases from the furnace, to liberate oxygen from the liquid for combination with the combustion air. prior to the mixture of the combustion air with the fuel. The oxygen depleted liquid is cooled and re-cycled for reuse in the process.
Description
~ 8~t7C~ , s Background of the Invention The invention is particularly useful in industrial furnaces or ovens from which hot exhaust gases exit through a ~lue into the ambient atmosphere. Much energy is lost as the hot flue gases exit the furnace. This energy, if recaptured, can be utilized to preheat the combustion air to increase the efficiency o the fuel. Such energy can ~lso be used in the enrichmen~ of combustion air with oxygen to reduce heat losses by lowering the amount of waste or exhaust gases. To enrich combustion air with oxygen, it is necessary to increase the amount of oxygen from a normal 21 percent to 25-50 percent. It has been found that the resulting flue gases have a lower level of ~` -nitrogen, thereby reducing the amount of heat wasted for heating nitrogen. It has been found that even a small enrichment of combustion air to 25 percent oxygen produces substantial savings in fuel.
,.
Combustion equipment, designed to use pure oxygen, has special refractories and water cooled members. At present7 it is uneconomical to use more than a 50 percent oxygen enrichment of air because of the special equipment needed. Thus, the term "conventional burner", as used in the specification and claims~
means any regular burner that can operate with up to 50 percent oxygen content in the combustion air. The savings in fuel pro-duced by the oxygen enrichment of combustion air, compares favorably with the savings experienced from using a recuperator for preheating the combustion air. For examp].e, most industrial recuperators produce combustion air at a temperature of 1000F.
or less. The enrichment of combustion air with oxygen to about 50 percent at high temperature is equivalent to preheating the conbustion air to l/-~00F. Tlle invention is directed to the en~
richrnent of combustion air.
tf~
.', . ' - ' ' ' '' ' ' . ' '', ' ', " `., ~ ,'' ,, ',, ~ In one particular aspect the present invention provides a m~thod oE enriching combustion air with oxygen comprising circulating air, containing normal quantities of oxygen, into contact with a liquid which absorbs oxygen from the air to form an oxygen enriched liquid, and then subsequently liberating the oxygen from the oxygen enriched liquid and mixing the liberated oxygen with air containing normal quantities of oxygen, to form oxygen enriched combustion air for subsequent mixing with a combustile fuel.
In another particular aspect the present invention provides in combination:
(a) a first tower with a vertically elongated chamber .
sealed from the ambient atmosphere;
(b) a second tower disposed in spaced relation from the first tower and also having a vertically elongate chamber ::
sealed from the ambient atmosphere;
(c) means for circulating air, containing normal quantities of oxygen, separately to the chambers of the towers;
(d) means for circulating an oxygen absorbing liquid to the chamber of the first tower for contact with air circulated therein, to form an oxygen enriched liquid;
(e) means for circulating the oxygen enriched liquid from the first tower to the chamber of the second tower;
(f) means for causing liberation of oxygen from the oxygen enriched liquid in the chamber of the second tower, .
for contact with air circulated in said chamber, to enrich said air with oxygen; and ~ -(g) means for removing the oxygen enriched air from the ::
chamber of the second tower. .
Description of the Drawing The following description of the invention will be better understood by having reference to the annexed drawing, which ~ 2-~.~
7~
,, .
is schematic and illustrates a furnace and an apparatus which is made in accordance with the invention for enriching with oxygen, combustion air circulated to the furnace.
Detailed Description of the Drawing With reference to the drawing, there is shown an industrial furnace 5 which is used, for example, in the heat treatment of metals. The furnace 5 has a heat chamber 6 and connecting flue 7 through which hot exhaust gases exit the furnace 5.
A conventional burner 8 is provided for heating metals disposed within the heat chamber 6 of the furnace 5. The burner 8 essentially comprises a nozzle 9 for receiving any -suitable fuel, e.g. gas or oil, under pressure; and a burner block 11 composed of any suitable refractory material. The ;
burner block 11 comprises ~-'", ,~.
,:; . :; : .
'-' ' : ;
~ ~
., .
. .~ '' ~, .
~', ' .
,, ;.,',: ' . ~ . -,......
~ 2a-... .... .
D
.--~ ''~
, ' . ~ ' ' ' ' , .
'. , ' . ' ' ' .. ' . ' ' , ' ,. ' ' '' , ' "' ' ,~' ' ., ' ,. ' ' ' ', ~, ' " , ' ' ' ~'' ' ' ' ' ' " " . ' " . ' ' " ', ' ' , ' ' . ' '' ' " ' ' ' a mixing chamber 12 in which the combustion air and fuel are thoroughly mixed and ignited for subsequent passage into a flame tunnel 13 from which a flame 14 and hot gases, including the products of combustion, are discharged into the heat chamber 6 of the furnace 5. ~n apparatus, generally indicated at 15, is provided for enriching the combustion air with oxygen, prior to the mixture of the air with the fuel in the burner 8.
O~ygen Enrichment A~paratus 15 :
The apparatus 15, used in the enrichment of the combustion ~-air with oxygen, essentially comprises an absorption tower 16 ; ~
in which oxygen lS removed from air containing normal amounts : :
of oxygen, and a desorption tower 17 in which o~ygen is liberated .~ :
for combination with the combustion air being circulated to the :~.
burner 8. The towers 16, 17 are essentially.the same in that : ~ -both have a vertically elongated chamber 18, a downwardly ~ :
; directed spray 19 adjacent the top 20 of the chamber 18, and a:
bed 21 of conventional tower packing material, e.g. ceramic or plastic chips, disposed within the chamber 18 intermediate the spray 19 and.bottom 22 of the chamber 18. The tower packing ~
material provides a more efficient mass transfer of o~ygen within .-the towers 16, 17.
Air, containing normal amounts of oxygen, is continuously circulated, under pressure, to the absorption tower 1~ by any suitable blower 2~, after passage through a conventional dryer 24. A portion of the dry air is also circulated directly to the desorption tower 17. The air pressure within the absorption ~ .
tower 16 is mai.ntained from atmospheric to 15 pounds.per square inch (psi~
37~ -An oxygen absorbing liquid 25 is pumped to the absorption -and desorption towers 16, 17 from any convenient source of supply 26. Any suitable liquid having an affinity for oxygen may be utilized. Broadly speaking, the oxygen absorbing liquid 25 should have high oxygen releasing characteristics.
The mass flow rate of liquid through the apparatus 15 is considerably greater than that of the gas. Therefore, the major portion of the power required to operate the various fans and pumps of the apparatus 15, is used to circulate the liquid.
I0 Accordingly, the density and viscosity of any liquid used in the system or process, should be as low as possible to reduce the power requirements to a minimum.
The consumption of power in moving a liquid is directly proportional to the flow rate of the liquid, the specific gravity of the liquid, and a fractional power of the viscosity of the liquid. The flow rate of the liquid is inversely proportional -to the oxygen releasing power of the liquid. Mathematically, it :
can be stated that: ;
p ~ (SG3- nZj~ , S
where: P is the liquid pumping power, SG is the specific gravity of the liquid in lbs./cubic foot, n is the viscosity of the liquid in centipoise, and S is the oxygen releasing power of the liquid measured in cubic feet of oxygen released per cubic foot of liquid.
An oxygen absorbing liquid 25 having a parametric value for (SG) n~ of 60, was successfully used-in a prototype apparatus.
For economieal reasons, the parametric value of any commercially used oxygen absorbing llquid 25 should not exceed 30.
The speciEic heat o~ an oxygen absorbing liquid 25 should preferably be lower than 0.4 B~u/lb./F. for temperature swing operations, wherein there is a variation in the temperatures of the liquid (temperature swing) in the absorption and desorption ;;~
towèrs 16, 17.
The maximum oxygen enrichment o~ a liquid is also dependent on the separation characteristic of the liquid for oxygen and nitrogen. This is measurable by a so-called separation factor . which is the ratio of the solubility of oxygen in the liquid to the solubility o~ nitrogen in the liquid under the same tempera-ture and partial pressure conditions. The o~ygen absorbing liquid 25 should have a separation ~actor o~ at least 1.25 which produces a maximum enrichment of about 25%.- Higher levels o~ :
enrichment are achieved by liquids with larger separation ~actors.
The characteristic temperature (k) for an oxy~en absorbing Iiquid 25 should be greater than 1000R. in a system employing ~ .
temperature swing only. There is no advantage in using tempera-ture swing when the characteristic temperature (k) is less than 200R. so a pressure swing is utilized, pressure swing being a variation in the gas pressures in the absorption and desorption towers 16, 17. For economical reasons, a combina-tion of pressure .and temperature s~ing is used when the characteristic temperature (k) is in the range of from 200R. to 1000 R. Mathematicall~, the characteristic temperature (k) can be expressed as:
f S P ~ ~ Ta Td~ ~
k ~ ~ ln a - ln ~ ) where: ~n is the natural logarithm, Sa is the volumetric solu-b;lity of oxyten in the liquid in the absorption tower, Sd lS
" ~
the volumetric solubility of oxygen in the liquid in the de, sorption tower, Pa and Pd are partial pressures of oxygen in the absorption and desorption towers, respectively, and Ta and Td ;~
are temperatures (R) in the absorption and desorption towers, "
respectively. The characteristic temperature (k) is const~mt for a particular liquid, but varies with different liquids.
A dimethyl polysiloxane fluid having a standard vicosity of 50 centistokes at 25C., e.g. a silicone fluid bearing the trademark SF-96 of the General Electric Company, was effectively used as an oxygen absorbing liquid 25. Such fluids are clear, water-white, oily fluids which are non-toxic, inert, tasteless and odorless.
The air and liquid 25 are brought together in-the absorption tower 16, where the liquid 21 absorbs at lea$t a portion of the oxygen in the air. The liquid 25 is-generally at room temperature, or at a relatively low temperature of from ~0F; to 100F. The :, ,~', . ' oxygen deficient air, or air from which oxygen has been removedJ
is discharged from the top 10 of the chamber 18 of the absorption tower 16 which is also supplied with a suitable mechanism through which liquid can be drained from the chamber 1~.
The liquid, now enriched with oxygen, i.e. the oxygen en-riched liquid 25, is circulated by a pump 27 under a relatively high pressure of from 25 psi to 100 psi to a heat exchanger 28 for preheating and then to the desorption tower 17, where the preheated oxygen enriched liquid 25 is brought into heat exchan~-ing relation with hot exhaust gases exiting the flue 7 of the furnace 5. The oxygen enriched liquid 25 is forced from the - spra~ 19 onto the bed 21 o~ tower packing material in the de-sorption tower 17. A conventionally designed heat exchanger 29 composed, for example, of a series of vertically disposed inter-. :,.. . .
- 6- . ~
.. . . .... .
',' ' , ,"','''' ', connected tubes, is embedded in the bed 21 of tower packing material. The oxygen enriched liquid 25 trickles downwardly through the bed 21 and is heated by the hot exhaust gas passing through the heat exchanger 29 to liberate oxygen which is com-bined with normal oxygen containing air that is being drawn up-wardly through the bed 21 and discharged from the desorption tower 17 through an exhaust port 30 in the top 20 of the chamber 18 by a vacuum pump or fan 31 which is disposed in the air line between the desorption tower 17 and burner 8. The vacuum pump 31 can be a steam ejector, in which case, a portion of the hot exhaust gases, exiting the flue 7, can be utiiized in the generation of steam necessary to operate the steam ejector.
The air pressure within the desorption tower 17 is not greater than, and preferably less than the air pressùre within the absorption tower 16. In most cases, the air pressure within the desorption tower 17 is less than atmospheric pressure which is the air pressure within the absorption tower 16. The tempera-ture of the oxygen enriched liquid 25 is raised to a temperature - of from 150F. to 400F., depending on the liquid used, as it comes into heat exchanging relation with the hot exhaust gases being circulated through the heat exchanger 29 within the de-sorption tower 17. The oxygen combines with the combustion air which is enriched from a normal 21 percent to a perferred 25-5 percent. The vacuum pump 31 forces-the enriched combustion air to the gas burner 8 for mixture with the fuel in the mixing chamber 12 ; ;
The hot liquld from which oxygen has been liberated, or the oxygen-lean liquid 32, remalning in the bo-ttom 22 of the .~ ,:
-7- ~
.
: .. .: : . . : . . , , ': ::
. :, . : ... . . . .: . . : :
7~
desorption tower 17, is circulated, under pressure, back to the absorption tower 16 by any suitable pump 33. It is important to cool the oxygen-lean liquid 32 before it is passed into the absorption tower 16 for reuse in the process. Accordingly, the oxygen-lean liquid 32 is passed through the preheater 28 and into heat exchanging relation with oxygen enriched liquid 25 being continuously circulated to the desorption tower 17. It has been found necessary to further cool the oxygen-lean liquid 32, so the liquid is subsequen-tly circulated through another heat exchanger 3~ through which cold water is separately circula~ed.
The properly cooled oxygen-lean liquid 32 is then recycled back to the absorption tower 16 for reuse in the process.
It is important to note that the hot exhaust gases also preheat the oxygen enriched combustion air being forced upwa~dly through the bed 21 of tower packing material in the desorption tower 17. If desired, a portion o~ the exhaust gas can be used ~ -outside the desorption tower 17 to further preheat the oxygen enriched combustion air being circulated to the burner 8. It is also important to note that the air flows countercurrent to the liquid trickling downwardly through the beds 21 of tower packing material of the towers 16, 17.
The solubility of a gas in a liquid increases with the increase in the pressure of the gas above the liquid and de-creases with the increase in temperature of the liquid. The above described process utilizes a variation in pressures (pressure swing), or a variation in temperatures (temperature swing), or a combination of both between the absorption and desorption towers 16, 17. A ternperature swing between the absorption arld desorption towers 16, 17 i.s preferred because of the readily available heat in the systern, i.e. the heat of the ' . . , . ~ ~', "'' : . , , ; :
hot exhaust gases. In this particular instance, the absorption tower 16 is operated at a lower temperature and higher pressure~
whereas the desorption tower 17 is operated at a higher tempera-ture and lower pressure. Thus, both a pressure and temperature swing are utilized. The air pressure within the absorption tower 16 is controlled by the regulation of the inlet and exhaust air valves 35, 36 in the air lines leading to and from the absorption tower 16, whereas a desired vacuum is established in thedesorption tower 17 by the regulation of the inlet and ex-haust air valves 37, 38 in the air lines leading to and fromthe desorption tower 17.
As previously indicated, the degree of pressure swing and temperature swing for a liquid depends on the physical characteristics and oxygen solubility behavior of the liqu~d as a function of temperature and partial pressure of oxygen. An oxygen concentration of 27.3 percent was achieved when pressures in the absorption and desorption towers 16~ 17 were 2 psi and -18.6 inches mercury, respectively, and the temperatures in said towers 16, 17 were 60F. and 170F., respectively. The enriched air flow was 3.5 standard cubic feet per hour, measured at 30 degrees mercury and 70F., with a liquid flow rate of 0.5 gallons per mlnute. The flow rate of the liquid through the system is dependent on the oxygen releasing capacity of the liquid. The higher the oxygen releasing capacity, the lower will ~
be the flow rate for a specific oxygen generation rate. It is ::
more economical to use a lower flow rate because the power input is severely reduced.
In operation, a desired amount of oxygen absorbing licluicl 25 is pumped into the bottom 22 of the absorption and desorption towers 16, 17. The necessary fans and pumps are operated to ~. . .
. .
.
.' , ,.. . , . :
,, ., ~, . , , - , ;~ , .... . . . , , : ..
- " :
cause circulation of the liquid through the system. The cooled liquid is forced from the spray head 19 onto the bed 21 of packing material of the absorption tower 16. Air, containing normal amounts of oxygen, is forced under pressure, upwardly through the bed 21 into contact with the oxygen absorbing liquid 25 trickling downwardly through the bed 21 into the bottom 22 of the absorption tower 16 from where it is removed and circulated, under pressure, to the desorption tower 17. The now oxygen enriched liquid is sprayed from the head 19 onto the bed 21 of tower packing material and trickles downwardly through the bed into contact with the heat exchanger 29 through which hot exhaust gases are separately circulated. The oxygen enriched liquid is heated and the oxygen stripped or liberated ~rom the liquid for combination with combustion air being forced upwardly through the bed 21 of tower packing material in the desorption tower l7. The now oxygen-lean liquid 32 is cooled and circulated back to the absorption tower 16 for reuse in the process. The heat from the oxygen-lean liquid 13 is utilized to preheat the oxygen enriched liquid 25 being circulated to the desorption tower 17. Thus, oxygen absorbing liquid is continuously being .
circulated between the towers 16, 17. Oxygen deficient air from the absorption tower 16 is exhausted into the ambient atmosphere , as is the cooled exhaust gas from the desorption tower 17.
Thus, there has been provided a very simple and economical method and apparatus for enriching combustion air with oxygen.
Further, normally lost heat from hot exhal1st gases exiting the flue of a furnace, are utllized in the enrichment of the com-bustion air with oxygen and in the preheating of the enriched combustion air, as previously indicated or mentioned.
: :
-- 1 o-- . , .
' . . .. ..
,.
Combustion equipment, designed to use pure oxygen, has special refractories and water cooled members. At present7 it is uneconomical to use more than a 50 percent oxygen enrichment of air because of the special equipment needed. Thus, the term "conventional burner", as used in the specification and claims~
means any regular burner that can operate with up to 50 percent oxygen content in the combustion air. The savings in fuel pro-duced by the oxygen enrichment of combustion air, compares favorably with the savings experienced from using a recuperator for preheating the combustion air. For examp].e, most industrial recuperators produce combustion air at a temperature of 1000F.
or less. The enrichment of combustion air with oxygen to about 50 percent at high temperature is equivalent to preheating the conbustion air to l/-~00F. Tlle invention is directed to the en~
richrnent of combustion air.
tf~
.', . ' - ' ' ' '' ' ' . ' '', ' ', " `., ~ ,'' ,, ',, ~ In one particular aspect the present invention provides a m~thod oE enriching combustion air with oxygen comprising circulating air, containing normal quantities of oxygen, into contact with a liquid which absorbs oxygen from the air to form an oxygen enriched liquid, and then subsequently liberating the oxygen from the oxygen enriched liquid and mixing the liberated oxygen with air containing normal quantities of oxygen, to form oxygen enriched combustion air for subsequent mixing with a combustile fuel.
In another particular aspect the present invention provides in combination:
(a) a first tower with a vertically elongated chamber .
sealed from the ambient atmosphere;
(b) a second tower disposed in spaced relation from the first tower and also having a vertically elongate chamber ::
sealed from the ambient atmosphere;
(c) means for circulating air, containing normal quantities of oxygen, separately to the chambers of the towers;
(d) means for circulating an oxygen absorbing liquid to the chamber of the first tower for contact with air circulated therein, to form an oxygen enriched liquid;
(e) means for circulating the oxygen enriched liquid from the first tower to the chamber of the second tower;
(f) means for causing liberation of oxygen from the oxygen enriched liquid in the chamber of the second tower, .
for contact with air circulated in said chamber, to enrich said air with oxygen; and ~ -(g) means for removing the oxygen enriched air from the ::
chamber of the second tower. .
Description of the Drawing The following description of the invention will be better understood by having reference to the annexed drawing, which ~ 2-~.~
7~
,, .
is schematic and illustrates a furnace and an apparatus which is made in accordance with the invention for enriching with oxygen, combustion air circulated to the furnace.
Detailed Description of the Drawing With reference to the drawing, there is shown an industrial furnace 5 which is used, for example, in the heat treatment of metals. The furnace 5 has a heat chamber 6 and connecting flue 7 through which hot exhaust gases exit the furnace 5.
A conventional burner 8 is provided for heating metals disposed within the heat chamber 6 of the furnace 5. The burner 8 essentially comprises a nozzle 9 for receiving any -suitable fuel, e.g. gas or oil, under pressure; and a burner block 11 composed of any suitable refractory material. The ;
burner block 11 comprises ~-'", ,~.
,:; . :; : .
'-' ' : ;
~ ~
., .
. .~ '' ~, .
~', ' .
,, ;.,',: ' . ~ . -,......
~ 2a-... .... .
D
.--~ ''~
, ' . ~ ' ' ' ' , .
'. , ' . ' ' ' .. ' . ' ' , ' ,. ' ' '' , ' "' ' ,~' ' ., ' ,. ' ' ' ', ~, ' " , ' ' ' ~'' ' ' ' ' ' " " . ' " . ' ' " ', ' ' , ' ' . ' '' ' " ' ' ' a mixing chamber 12 in which the combustion air and fuel are thoroughly mixed and ignited for subsequent passage into a flame tunnel 13 from which a flame 14 and hot gases, including the products of combustion, are discharged into the heat chamber 6 of the furnace 5. ~n apparatus, generally indicated at 15, is provided for enriching the combustion air with oxygen, prior to the mixture of the air with the fuel in the burner 8.
O~ygen Enrichment A~paratus 15 :
The apparatus 15, used in the enrichment of the combustion ~-air with oxygen, essentially comprises an absorption tower 16 ; ~
in which oxygen lS removed from air containing normal amounts : :
of oxygen, and a desorption tower 17 in which o~ygen is liberated .~ :
for combination with the combustion air being circulated to the :~.
burner 8. The towers 16, 17 are essentially.the same in that : ~ -both have a vertically elongated chamber 18, a downwardly ~ :
; directed spray 19 adjacent the top 20 of the chamber 18, and a:
bed 21 of conventional tower packing material, e.g. ceramic or plastic chips, disposed within the chamber 18 intermediate the spray 19 and.bottom 22 of the chamber 18. The tower packing ~
material provides a more efficient mass transfer of o~ygen within .-the towers 16, 17.
Air, containing normal amounts of oxygen, is continuously circulated, under pressure, to the absorption tower 1~ by any suitable blower 2~, after passage through a conventional dryer 24. A portion of the dry air is also circulated directly to the desorption tower 17. The air pressure within the absorption ~ .
tower 16 is mai.ntained from atmospheric to 15 pounds.per square inch (psi~
37~ -An oxygen absorbing liquid 25 is pumped to the absorption -and desorption towers 16, 17 from any convenient source of supply 26. Any suitable liquid having an affinity for oxygen may be utilized. Broadly speaking, the oxygen absorbing liquid 25 should have high oxygen releasing characteristics.
The mass flow rate of liquid through the apparatus 15 is considerably greater than that of the gas. Therefore, the major portion of the power required to operate the various fans and pumps of the apparatus 15, is used to circulate the liquid.
I0 Accordingly, the density and viscosity of any liquid used in the system or process, should be as low as possible to reduce the power requirements to a minimum.
The consumption of power in moving a liquid is directly proportional to the flow rate of the liquid, the specific gravity of the liquid, and a fractional power of the viscosity of the liquid. The flow rate of the liquid is inversely proportional -to the oxygen releasing power of the liquid. Mathematically, it :
can be stated that: ;
p ~ (SG3- nZj~ , S
where: P is the liquid pumping power, SG is the specific gravity of the liquid in lbs./cubic foot, n is the viscosity of the liquid in centipoise, and S is the oxygen releasing power of the liquid measured in cubic feet of oxygen released per cubic foot of liquid.
An oxygen absorbing liquid 25 having a parametric value for (SG) n~ of 60, was successfully used-in a prototype apparatus.
For economieal reasons, the parametric value of any commercially used oxygen absorbing llquid 25 should not exceed 30.
The speciEic heat o~ an oxygen absorbing liquid 25 should preferably be lower than 0.4 B~u/lb./F. for temperature swing operations, wherein there is a variation in the temperatures of the liquid (temperature swing) in the absorption and desorption ;;~
towèrs 16, 17.
The maximum oxygen enrichment o~ a liquid is also dependent on the separation characteristic of the liquid for oxygen and nitrogen. This is measurable by a so-called separation factor . which is the ratio of the solubility of oxygen in the liquid to the solubility o~ nitrogen in the liquid under the same tempera-ture and partial pressure conditions. The o~ygen absorbing liquid 25 should have a separation ~actor o~ at least 1.25 which produces a maximum enrichment of about 25%.- Higher levels o~ :
enrichment are achieved by liquids with larger separation ~actors.
The characteristic temperature (k) for an oxy~en absorbing Iiquid 25 should be greater than 1000R. in a system employing ~ .
temperature swing only. There is no advantage in using tempera-ture swing when the characteristic temperature (k) is less than 200R. so a pressure swing is utilized, pressure swing being a variation in the gas pressures in the absorption and desorption towers 16, 17. For economical reasons, a combina-tion of pressure .and temperature s~ing is used when the characteristic temperature (k) is in the range of from 200R. to 1000 R. Mathematicall~, the characteristic temperature (k) can be expressed as:
f S P ~ ~ Ta Td~ ~
k ~ ~ ln a - ln ~ ) where: ~n is the natural logarithm, Sa is the volumetric solu-b;lity of oxyten in the liquid in the absorption tower, Sd lS
" ~
the volumetric solubility of oxygen in the liquid in the de, sorption tower, Pa and Pd are partial pressures of oxygen in the absorption and desorption towers, respectively, and Ta and Td ;~
are temperatures (R) in the absorption and desorption towers, "
respectively. The characteristic temperature (k) is const~mt for a particular liquid, but varies with different liquids.
A dimethyl polysiloxane fluid having a standard vicosity of 50 centistokes at 25C., e.g. a silicone fluid bearing the trademark SF-96 of the General Electric Company, was effectively used as an oxygen absorbing liquid 25. Such fluids are clear, water-white, oily fluids which are non-toxic, inert, tasteless and odorless.
The air and liquid 25 are brought together in-the absorption tower 16, where the liquid 21 absorbs at lea$t a portion of the oxygen in the air. The liquid 25 is-generally at room temperature, or at a relatively low temperature of from ~0F; to 100F. The :, ,~', . ' oxygen deficient air, or air from which oxygen has been removedJ
is discharged from the top 10 of the chamber 18 of the absorption tower 16 which is also supplied with a suitable mechanism through which liquid can be drained from the chamber 1~.
The liquid, now enriched with oxygen, i.e. the oxygen en-riched liquid 25, is circulated by a pump 27 under a relatively high pressure of from 25 psi to 100 psi to a heat exchanger 28 for preheating and then to the desorption tower 17, where the preheated oxygen enriched liquid 25 is brought into heat exchan~-ing relation with hot exhaust gases exiting the flue 7 of the furnace 5. The oxygen enriched liquid 25 is forced from the - spra~ 19 onto the bed 21 o~ tower packing material in the de-sorption tower 17. A conventionally designed heat exchanger 29 composed, for example, of a series of vertically disposed inter-. :,.. . .
- 6- . ~
.. . . .... .
',' ' , ,"','''' ', connected tubes, is embedded in the bed 21 of tower packing material. The oxygen enriched liquid 25 trickles downwardly through the bed 21 and is heated by the hot exhaust gas passing through the heat exchanger 29 to liberate oxygen which is com-bined with normal oxygen containing air that is being drawn up-wardly through the bed 21 and discharged from the desorption tower 17 through an exhaust port 30 in the top 20 of the chamber 18 by a vacuum pump or fan 31 which is disposed in the air line between the desorption tower 17 and burner 8. The vacuum pump 31 can be a steam ejector, in which case, a portion of the hot exhaust gases, exiting the flue 7, can be utiiized in the generation of steam necessary to operate the steam ejector.
The air pressure within the desorption tower 17 is not greater than, and preferably less than the air pressùre within the absorption tower 16. In most cases, the air pressure within the desorption tower 17 is less than atmospheric pressure which is the air pressure within the absorption tower 16. The tempera-ture of the oxygen enriched liquid 25 is raised to a temperature - of from 150F. to 400F., depending on the liquid used, as it comes into heat exchanging relation with the hot exhaust gases being circulated through the heat exchanger 29 within the de-sorption tower 17. The oxygen combines with the combustion air which is enriched from a normal 21 percent to a perferred 25-5 percent. The vacuum pump 31 forces-the enriched combustion air to the gas burner 8 for mixture with the fuel in the mixing chamber 12 ; ;
The hot liquld from which oxygen has been liberated, or the oxygen-lean liquid 32, remalning in the bo-ttom 22 of the .~ ,:
-7- ~
.
: .. .: : . . : . . , , ': ::
. :, . : ... . . . .: . . : :
7~
desorption tower 17, is circulated, under pressure, back to the absorption tower 16 by any suitable pump 33. It is important to cool the oxygen-lean liquid 32 before it is passed into the absorption tower 16 for reuse in the process. Accordingly, the oxygen-lean liquid 32 is passed through the preheater 28 and into heat exchanging relation with oxygen enriched liquid 25 being continuously circulated to the desorption tower 17. It has been found necessary to further cool the oxygen-lean liquid 32, so the liquid is subsequen-tly circulated through another heat exchanger 3~ through which cold water is separately circula~ed.
The properly cooled oxygen-lean liquid 32 is then recycled back to the absorption tower 16 for reuse in the process.
It is important to note that the hot exhaust gases also preheat the oxygen enriched combustion air being forced upwa~dly through the bed 21 of tower packing material in the desorption tower 17. If desired, a portion o~ the exhaust gas can be used ~ -outside the desorption tower 17 to further preheat the oxygen enriched combustion air being circulated to the burner 8. It is also important to note that the air flows countercurrent to the liquid trickling downwardly through the beds 21 of tower packing material of the towers 16, 17.
The solubility of a gas in a liquid increases with the increase in the pressure of the gas above the liquid and de-creases with the increase in temperature of the liquid. The above described process utilizes a variation in pressures (pressure swing), or a variation in temperatures (temperature swing), or a combination of both between the absorption and desorption towers 16, 17. A ternperature swing between the absorption arld desorption towers 16, 17 i.s preferred because of the readily available heat in the systern, i.e. the heat of the ' . . , . ~ ~', "'' : . , , ; :
hot exhaust gases. In this particular instance, the absorption tower 16 is operated at a lower temperature and higher pressure~
whereas the desorption tower 17 is operated at a higher tempera-ture and lower pressure. Thus, both a pressure and temperature swing are utilized. The air pressure within the absorption tower 16 is controlled by the regulation of the inlet and exhaust air valves 35, 36 in the air lines leading to and from the absorption tower 16, whereas a desired vacuum is established in thedesorption tower 17 by the regulation of the inlet and ex-haust air valves 37, 38 in the air lines leading to and fromthe desorption tower 17.
As previously indicated, the degree of pressure swing and temperature swing for a liquid depends on the physical characteristics and oxygen solubility behavior of the liqu~d as a function of temperature and partial pressure of oxygen. An oxygen concentration of 27.3 percent was achieved when pressures in the absorption and desorption towers 16~ 17 were 2 psi and -18.6 inches mercury, respectively, and the temperatures in said towers 16, 17 were 60F. and 170F., respectively. The enriched air flow was 3.5 standard cubic feet per hour, measured at 30 degrees mercury and 70F., with a liquid flow rate of 0.5 gallons per mlnute. The flow rate of the liquid through the system is dependent on the oxygen releasing capacity of the liquid. The higher the oxygen releasing capacity, the lower will ~
be the flow rate for a specific oxygen generation rate. It is ::
more economical to use a lower flow rate because the power input is severely reduced.
In operation, a desired amount of oxygen absorbing licluicl 25 is pumped into the bottom 22 of the absorption and desorption towers 16, 17. The necessary fans and pumps are operated to ~. . .
. .
.
.' , ,.. . , . :
,, ., ~, . , , - , ;~ , .... . . . , , : ..
- " :
cause circulation of the liquid through the system. The cooled liquid is forced from the spray head 19 onto the bed 21 of packing material of the absorption tower 16. Air, containing normal amounts of oxygen, is forced under pressure, upwardly through the bed 21 into contact with the oxygen absorbing liquid 25 trickling downwardly through the bed 21 into the bottom 22 of the absorption tower 16 from where it is removed and circulated, under pressure, to the desorption tower 17. The now oxygen enriched liquid is sprayed from the head 19 onto the bed 21 of tower packing material and trickles downwardly through the bed into contact with the heat exchanger 29 through which hot exhaust gases are separately circulated. The oxygen enriched liquid is heated and the oxygen stripped or liberated ~rom the liquid for combination with combustion air being forced upwardly through the bed 21 of tower packing material in the desorption tower l7. The now oxygen-lean liquid 32 is cooled and circulated back to the absorption tower 16 for reuse in the process. The heat from the oxygen-lean liquid 13 is utilized to preheat the oxygen enriched liquid 25 being circulated to the desorption tower 17. Thus, oxygen absorbing liquid is continuously being .
circulated between the towers 16, 17. Oxygen deficient air from the absorption tower 16 is exhausted into the ambient atmosphere , as is the cooled exhaust gas from the desorption tower 17.
Thus, there has been provided a very simple and economical method and apparatus for enriching combustion air with oxygen.
Further, normally lost heat from hot exhal1st gases exiting the flue of a furnace, are utllized in the enrichment of the com-bustion air with oxygen and in the preheating of the enriched combustion air, as previously indicated or mentioned.
: :
-- 1 o-- . , .
' . . .. ..
Claims (16)
1. A method of enriching combustion air with oxygen comprising circulating air, containing normal quantities of oxygen, into contact with a liquid which absorbs oxygen from the air to form an oxygen enriched liquid, and then subsequently liberating the oxygen from the oxygen enriched liquid and mixing the liberated oxygen with air containing normal quantities of oxygen, to form oxygen enriched combustion air for subsequent mixing with a combustible fuel.
2. The method of claim 1, wherein oxygen is liberated from the enriched liquid by heating the enriched liquid to a temperature sufficient to liberate the oxygen.
3. The method of claim 1, wherein the pressure of the air from which oxygen is absorbed, is greater than the pressure of the air being enriched with oxygen.
4. The method of claim 1, wherein the pressure of the air from which oxygen is absorbed, is greater than the pressure of the air being enriched with oxygen, and the temperature of the liquid, at the time of absorbing oxygen, is considerably less than the temperature of the liquid immediately after oxygen has been liberated therefrom.
5. The method of claim 4, which includes heating oxygen en-riched liquid with hot exhaust gases, normally wasted to -the atmosphere, to liberate oxygen therefrom.
6. The method of claim 5, which includes cooling oxygen-lean liquid from which oxygen has been liberated and recycling said oxygen-lean liquid back into contact with air, containing normal quantities of oxygen, to absorb oxygen from the air.
7. The method of claim 6, wherein oxygen enriched liquid and oxygen-lean liquid are trickled, by gravity, through separate beds of tower packing material through which air, containing normal quantities of oxygen, is forced in directions opposite that in which the liquids trickle through the beds.
8. In combination:
(a) a first tower with a vertically elongated chamber sealed from the ambient atmosphere;
(b) a second tower disposed in spaced relation from the first tower and also having a vertically elongate chamber sealed from the ambient atmosphere;
(c) means for circulating air, containing normal quantities of oxygen, separately to the chambers of the towers;
(d) means for circulating an oxygen absorbing liquid to the chamber of the first tower for contact with air circulated therein, to form an oxygen enriched liquid;
(e) means for circulating the oxygen enriched liquid from the first tower to the chamber of the second tower;
(f) means for causing liberation of oxygen from the oxygen enriched liquid in the chamber of the second tower, for contact with air circulated in said chamber, to enrich said air with oxygen; and (g) means for removing the oxygen enriched air from the chamber of the second tower.
(a) a first tower with a vertically elongated chamber sealed from the ambient atmosphere;
(b) a second tower disposed in spaced relation from the first tower and also having a vertically elongate chamber sealed from the ambient atmosphere;
(c) means for circulating air, containing normal quantities of oxygen, separately to the chambers of the towers;
(d) means for circulating an oxygen absorbing liquid to the chamber of the first tower for contact with air circulated therein, to form an oxygen enriched liquid;
(e) means for circulating the oxygen enriched liquid from the first tower to the chamber of the second tower;
(f) means for causing liberation of oxygen from the oxygen enriched liquid in the chamber of the second tower, for contact with air circulated in said chamber, to enrich said air with oxygen; and (g) means for removing the oxygen enriched air from the chamber of the second tower.
9. The combination of claim 8, wherein the means for causing liberation of oxygen from the oxygen enriched liquid in the chamber of the second tower includes;
(h) means for creating a pressure differential in the air in the chambers of the first and second towers; and (i) means for creating a temperature differential in the oxygen absorbing liquid in the first tower and the oxygen en-riched liquid in the second tower.
(h) means for creating a pressure differential in the air in the chambers of the first and second towers; and (i) means for creating a temperature differential in the oxygen absorbing liquid in the first tower and the oxygen en-riched liquid in the second tower.
10. The combination of claim 9, wherein the means for creating a temperature differential in said liquids includes means for heating the oxygen enriched liquid to a temperature which is higher than that of the oxygen absorbing liquid in the chamber of the first tower.
11. The combination of claim 10, wherein the means for creating the temperature differential in said liquids includes means for maintaining the temperature of the oxygen absorbing liquid in the chamber of the first tower at a temperature in the range of from 40°F. to 100°F. and means for heating the oxygen en-riched liquid in the chamber of the second tower to a temperature in the range of from 150°F. to 400°F.
12. The combination of claim 10, wherein the means for creating a gas pressure differential in the air includes means for cre-ating in the chamber of the first tower an air pressure of from atmospheric to 15 psi, and means for creating in the chamber of the second tower an air pressure which is less than the air pressure in the chamber of the first tower.
13. The combination of claim 12, which includes a bed of tower packing material disposed in each of the chambers intermediate opposing, vertically spaced ends thereof, means for causing oxygen absorbing liquid and oxygen enriched liquid to flow, by gravity, through the beds of the first and second towers, respectively, and means for causing air, under pressure, to flow through the beds in a direction which is opposite that which the liquid flows therethrough.
14. The combination of claim 13, which includes:
(j) a furnace having a heat chamber and a flue from which hot exhaust gases exit the heat chamber;
(k) a burner mounted within the heat chamber of the furnace for discharging a flame and hot gases, including hot products of combustion, into the heat chamber;
(l) means for circulating fuel to the burner;
(m) means for circulating oxygen enriched air from the second tower to the burner for mixture with the fuel.
(j) a furnace having a heat chamber and a flue from which hot exhaust gases exit the heat chamber;
(k) a burner mounted within the heat chamber of the furnace for discharging a flame and hot gases, including hot products of combustion, into the heat chamber;
(l) means for circulating fuel to the burner;
(m) means for circulating oxygen enriched air from the second tower to the burner for mixture with the fuel.
15. The combination of claim 14, which includes means for circulating at least a portion of the hot exhaust gases from the flue to the desorption tower and into heat exchanging relation with oxygen enriched liquid therein.
16. The combination of claim 15, which includes means for cooling oxygen absorbing liquid remaining after oxygen is removed from the oxygen enriched liquid in the desorption tower, and means for recirculating cooled oxygen absorbing liquid back to the absorption tower for reuse in the process.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US81160077A | 1977-06-30 | 1977-06-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1080970A true CA1080970A (en) | 1980-07-08 |
Family
ID=25207008
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA297,412A Expired CA1080970A (en) | 1977-06-30 | 1978-02-21 | Apparatus and method for enriching combustion air with oxygen |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5413489A (en) |
| CA (1) | CA1080970A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5715816A (en) * | 1980-07-02 | 1982-01-27 | Matsushita Electric Ind Co Ltd | Apparatus for oxygen pump |
| JPS60211216A (en) * | 1984-03-02 | 1985-10-23 | エアー．プロダクツ．アンド．ケミカルス．インコーポレーテツド | Method of burning coal/water slurry |
| JPS60204603A (en) * | 1984-03-27 | 1985-10-16 | Osaka Gas Co Ltd | Apparatus for producing oxygen-enriched gas |
| US4617182A (en) * | 1985-08-26 | 1986-10-14 | Air Products And Chemicals, Inc. | Cascade heat recovery with coproduct gas production |
-
1978
- 1978-02-21 CA CA297,412A patent/CA1080970A/en not_active Expired
- 1978-05-01 JP JP5260378A patent/JPS5413489A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5413489A (en) | 1979-01-31 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4332643A (en) | Method of removing water from glycol solutions | |
| CN101472662B (en) | Heat recovery gas absorption process | |
| US7531030B2 (en) | Natural gas dehydrator and system | |
| US4280867A (en) | Glycol regeneration | |
| US5117623B1 (en) | Operating flexibility in igcc stations | |
| JPS5533595A (en) | Method of heating heat medium in heating system* and boiler | |
| US3867112A (en) | Reconcentrating solute-rich liquid absorbent | |
| US1934472A (en) | Method of separating carbon dioxide from a gas mixture | |
| CA1080970A (en) | Apparatus and method for enriching combustion air with oxygen | |
| US4017277A (en) | Direct contact water heating system and process | |
| JPS5515632A (en) | Dehumidifier | |
| GB2112517A (en) | Heating apparatus | |
| US1988759A (en) | Heat recovery system | |
| US4071322A (en) | Apparatus for producing an inert gas | |
| JPS6252106A (en) | Continuous manufacture of oxygen from purified dry air and liquid oxygen receptor and temperature change chemical air separation | |
| US2635039A (en) | Apparatus for purifying products of combustion | |
| CA1091574A (en) | Humidification and heating of gases | |
| US4953356A (en) | Geothermal reboiler apparatus and method | |
| GB2214835A (en) | Method and apparatus for desalination | |
| JPS61240009A (en) | Method for decreasing nox content and increasing heat recovery efficiency in exhaust gas | |
| JPH029414A (en) | Apparatus for treating combustion gas | |
| JPS55121318A (en) | Method of preventing generation of white exhaust smoke | |
| CN206688483U (en) | The processing equipment of acid Process Gas during a kind of carbon disulphide production | |
| JPS57187523A (en) | Reheating method of treated gas in flue gas desulfurization | |
| SU1537986A1 (en) | Heating/refrigerating unit |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |