CA2214542A1 - Process for recycling of gases during the manufacturing of components for lithium batteries - Google Patents
Process for recycling of gases during the manufacturing of components for lithium batteries Download PDFInfo
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Abstract
Provided herein is a method of recovering an aprotic solvent in a process for manufacturing lithium ion batteries comprising: (a) releasing an aprotic carrier solvent from a slurry coated onto a metal substrate wherein said slurry comprises the solvent and material used to fabricate electrodes for use in lithium ion batteries; (b) mixing the released solvent with a gas stream comprising a gas and water vapor; and (c) condensing the released solvent. Specific aprotic solvents include akyl substituted pyrrolidones such as N-methyl pyrrolidone.
Description
CA 02214~42 1997-09-19 PROC~SS FOR ~YCT.ING OF GA~S nURING T~F. ~PNUFACTURING OF
COMPONENTS FOR TITHIUM BATTERIES
FIELD OF THE INVENTION
This invention relates generally to the field of battery manufacturing and the recycling of solvents during such manufacturing. More particularly, the invention relates to the recovery of solvents in lithium ion battery processes.
BACKGROUND OF T~ INV~NTION
Lithium metal batteries are made of various constructions and by various methods. In one type of battery lithium metal is used to make the anode of the battery and lithium dioxy cobaltate is employed to make the cathode. In this particular battery, a LiCF3So3 salt dissolved in N-methyl pyrrolidone (NMP) acts as the liquid electrolyte for the battery.
In other lithium metal batteries, the anode is made from either lithium metal or a lithium aluminum alloy, and the cathode is made from a lithium manganese oxide.
Lithium metal batteries are used as electrical storage devises that are re-chargeable and re-useable. These batteries are used in electronic devices such as video cameras, cellular phones, computers, and cameras. Since the batteries can be recharged they are effective for increasing the portable nature of electronic devices. They also provide an economic energy source.
There are however a few drawbacks associated with the use of lithium metal batteries. One drawback is that the presence of lithium metal in a battery poses a potential fire hazard because lithium metal reacts violently when brought into contact with water. Another drawback is that lithium metal batteries require higher operating temperatures. A further drawback is that discarded lithium metal batteries may leak and CA 02214~42 1997-09-19 contaminate soil and water when they are disposed of in landfills.
The above drawbacks, along with othe~ commercial reasons, prompted the battery industry to develop batteries having improved safety, environmental and performance features.
Accordingly, lithium ion secondary batteries were developed.
Lithium ion secondary batteries do not contain a lithium metal electrode but instead contain electrodes made by coating thick slurries of carbonaceous materials and polymeric binders onto thin metal substrates. The slurries can also contain lithium alloys.
Because the slurries formed from carbonaceous materials and polymeric binders are highly viscous, and in some cases can almost be gel-like in their consistency, solvents are added to the slurries to decrease their viscosity. The solvents generally used are aprotic solvents having low vapor pressures and high flash points. These solvents may be mixed with a lower boiling oxygenated solvent such as ether, ester, alcohol or ketone. These lower boiling solvents are added to change the drying properties and rates of the applied slurries.
For example, anodes are made from alloys that allow lithium ions to be held in them (lithium - intercalatable). In forming these anode~, oxides or carbon are mixed with polytrifluoro ethylene binders and a carrier solve~lt such as methyl ethyl ketone, ethyl acetate or NMP. The electrolyte used is a non-aqueous solution containing LiCF3 S03 .
Lithium ion batteries are known that have a carbonaceous material/polyvinylidene fluoride mixture applied to a metal substrate. NMP is used as the carrier solvent for application of the mixture to the metal substrate. The electrolyte system in the battery construction is a solution of LiC104 in propylene carbonate and di-methoxyethane.
Lithium ion batteries, known as rechargeable polymer electrolyte batteries, have a carbon anode, a lithium nickel oxide cathode and a polyacrylonitrile or polyvinyl chloride matrix that contains an electrolyte made of lithium salts and CA 02214~42 1997-09-19 small amounts of solvent within the polymer matrix.
Typically, when electrodes for use in lithium ion batteries are manufactured, the metal substrate is coated with a slurry and drawn through a drying oven using a roll coating apparatus. Warm air moving over the surface of the coating pulls the solvent from the slurry. The solvent laden heated air is pulled by an exhaust fan and exits the drying oven through an exhaust stack.
A rate limiting factor of the coating operation is lo the speed at which the oven can cause the liquid to be removed form the coating. An increase in the speed of drying means the roll coating apparatus can be operated at a fast rate. Thus, rapid removal of solvent from the slurry coatings is desired.
Up to 30 pounds per hour of solvent are evaporated during production of the electrodes. Many production facilities operate continuously so that substantial amounts of evaporated solvents are generated. The solvents that exit through an exhaust vent are handled in various ways. One method of handling the solvent vapors generated from evaporating the solvent is to simply allow the vapors to be emitted into the atmosphere.
Another method of handling the solvent is to pass the solvent vapors, after they have exited the drying oven, through a thermal oxidizer which burns the vapors thereby,l emitting carbon dioxide, carbon monoxide, and water into atmosphere.
Although this method drastically reduces the amount of solvent emission, it is an expensive process since it destroys the solvent.
A further method of handling the solvent vapor is to direct the vapors into a condensing chamber where the vapors are condensed onto metal surfaces that are kept at a temperature cooler than the exhaust air. The temperature of the metal surfaces is maintained by circulating a cooling liquid that is provided by a chiller system. These cooling units consume large amounts of energy and are expensive to maintain.
CA 02214~42 1997-09-19 As will become apparent from the discussion below, it is an object of the present invention to provide a cost efficient means to recycle and reclaim solve~ts used to manufacture electrodes of lithium ion batteries. It is another object of the present invention to provide a closed loop continuous feed condensation process. It is yet a further object of the present invention to reduce the amount of solvents destroyed and to prevent the release of such solvents into the atmosphere. Other objects and advantages of the present invention will be readily apparent from the description of the invention as set out in the specification and claims below.
SUMMARY OF THE INVENTION
Provided herein is a method of recovering a solvent in a process for manufacturing lithium ion batteries. In practicing the invention, a carrier solvent is released from a slurry coated onto a metal substrate. The slurry contains both the carrier solv~nt and the material used to fabricate electrodes for use in lithium ion batteries. In fabricating the electrodes, the solvent is mixed with a gas stream comprising a gas and water after which the solvent is condensed. The invention as described herein may also comprise a closed looped and continuous process for the capture and re-use of the solvent.
The invention provides a substantial improvement in processes that require the removal of carrier solvent during the forced air drying of paste-like films or slurries used to manufacture electrodes for lithium ion batteries. The improvements comprise an inexpensive means of recovering the carrier solvent.
DF~TAIT~n D~.~CRIPTION OF T~ INV~NTION
In one aspect of the invention, anode construction begins with the mixing together of: 1) a slurry of a CA 02214~42 1997-09-19 carbonaceous material, usually graphite; 2) a polymeric binder, usually polyvinylidene fluoride, polyethylene, or polytrifluoro ethylene; and 3) a carrier. The preferred carrier comprises an aprotic solvent having a low vapor pressure and a high flash point. The carrier may be a combinatioh of an aprotic solvent and oxygenated solvents having low boiling temperatures such as an ether, ester, alcohol, or ketone. These solvents are added to change the drying rates of the solvents from the metal substrates. The preferred aprotic solvent is an alkyl substituted pyrrolidone, most preferably N-methyl pyrrolidone.
The preferred combination of solvents used to make up the carrier solvent is an akyl substituted pyrrolidone and methyl ethyl ketone.
In manufacturing an anode according to an embodiment of the present invention, a reverse roll coating apparatus has strung through it a metal foil substrate, usually thin copper (0.0005 - 0.002 inches thick). The copper foil is usually several feet wide and is strung through the coating apparatus from rolls of the copper foil that are usually several hundred yards in length. The slurry is placed into a slurry containment area of the reverse roll coating apparatus. The coating apparatus is started up and the slurry is applied to one face of the metal foil. The metal foil is usually moving at a rate of several yards per minute, usually 1 to 3~1yards per minute. Next, the slurry coated metal foil enters a drying oven. The slurry at this point is still a highly viscous liquid.
The drying oven is typically about 10 - 30 yards in length. Heated air is provided in the oven and is pulled over the surface of the slurry in order to dry the solvent out of slurry. Typically the temperature of the air passing over the surface of the slurry is about 200 ~F to 300 ~F. The air drawn into the oven is preferably at room temperature with a relative humidity at about 30%. The air drawn into the oven is pulled preferably at a rate of about 5000 to about 8000 scfm. The solvent is evaporated into the gas stream to create a solvent CA 02214~42 1997-09-19 laden hot air gas stream. The solvent laden hot air gas is pulled out of the oven and into a condenser where the solvent is condensed. In another embodiment of the invention, the water content of the air stream is increased ranging from about greater than 30% to about 50%, by introducing the water into the air stream after it exits the drying oven and before the aprotic solvent is condensed.
In a preferred method a "precooling" heat exchanger is used to precool the solvent laden air stream prior to its entering a condensing exchanger. Using this method the air cooled in the condensing exchanger is recycled back into the "precooling" heat exchanger where it is used to cool the air stream exiting the drying oven.
Once the aprotic solvent is condensed it can be distilled from the water and recycled in a closed system wherein the solvent is reintroduced into the slurry. The water is separated from the NMP in the distillation unit.
In another embodiment of the invention a water scrubber is introduced into the system in order to absorb NMP
vapors that remain in the air stream after it leaves the condenser. Preferably, the scrubber is a packed column that removes residual solvent vapors out of the exhaust air with water mist. The water stream generated by the mist can be recycled into a distillation unit to remove the residual NMP.
A portion of the air exiting the water wash packed column scrubber can be re-used as the air entering the drying oven.
As the solvent is driven from the oven a construction is formed from the carbon/polymer composite bonded to the metal foil. The construction is wound into rolls and the rolls are put through the same coating/drying process. The final composite that is made into the anode has the metal foil coated on both sides with the carbon/polymer composition.
The cathode is constructed using the same process used to make the anode with some minor differences. One difference is in the composition of the slurry. In constructing the cathode, the slurry comprises a large amount CA 02214~42 1997-09-19 of a lithium oxide, such as LiCoO2 or LiNio2. Another difference is that aluminum foil is used as the metal substrate. The aluminum foil cathode is coated in much the same way as is the copper foil that is used for the anode.
The following examples are illustrative only and are not meant to limit the invention in any manner.
Example 1 (30% Relative humidity air stream at 75~F) This example illustrates the use of a condenser for condensing solvent vapor from an air stream exiting a drying oven and the subsequent recovery of the solvent in a distillation column. It also illustrates the use of a heat exchanger to "precool" a solvent laden air stream before it enters a primary condenser.
Room temperature air at approximately 75~F and with a relative humidity of about 30% is drawn into the oven through a reverse coating apparatus at a rate of about 5000 scfm using exhaust fans. The temperature of the air rises from about 24~C
to about 150~C by the time it exits the oven. As the coated metal foil passes through the drying oven, a total of about 100 lb/hr of NMP is evaporated from its surface into the air-stream. The concentration of NMP vapor in the a~ir stream leaving the drying oven is about 12% (by volume).
The solvent-laden air stream is pulled from the drying oven through a series of two finned-typed heat exchangers. The bulk of the NMP is condensed in the second heat-exchanger that uses a chilled water-and glycol solution as its cooling medium. When the oven is initially started-up, the second exchanger cools the air stream to preferably the dew point of the NMP. The air exiting the second exchanger is then recycled to the first "precooling" exchanger where it is used to cool air exiting the drying oven. When the system reaches steady state, the precooling exchanger reduces the cooling load in the second exchanger. The air stream exiting the final CA 02214~42 1997-09-19 condenser contains only 15 ppmv NMP and has a temperature of about -6~C (the dew point of the NMP and water vapor mixture).
The air can be recycled or treated further.
The NMP and water condensed in the second heat exchanger are pumped from a reservoir to a distillation column to recover the NMP from the water. The column feed has a composition of about 70 weight percent NMP and about 30 weight percent water. The column is best operated under a vacuum.
The temperature of the reboiler at the bottom of the is between about 100 to 180~C. The temperature in the overhead condenser is between about 25 to 55OC. The NMP is recovered as the bottoms product from the column at a concentration in the bottoms of 99.99 % (by weight). When the system reaches steady state, the bottoms product is used to preheat the feed to the distillation column.
Example 2 (50% Relative Humidity Air, at 75~F) This example illustrates the rise in the dew point caused by the addition of water vapor to the NMP-containing air stream of Example 1. The equipment and conditions described in this example are the same as those of Example 1 with the following exceptions: Room temperature air at 75~F a,,nd with a relative humidity of about 50% is drawn into the oven through a reverse roll coating apparatus at a rate of about 5000 scfm by the drying oven's exhaust fans. The air temperature rises through the oven to about 150~C and a total of about 100 lb/hr of NMP is evaporated into the air stream. The concentration of NMP in the air is 12% (vol.).
Because of the additional water vapor present in the air stream, the temperature required for condensing the NMP
from vapor is about 11~C. This is 5~C higher than the condensation temperature (dew point) of Example 1. Despite the higher dew point, the air stream exiting the final condenser still contains only 14 ppmv NMP. The air can be recycled, CA 02214~42 1997-09-19 treated or discharged. The condensed NMP is recovered from the water in a distillation column as in Example 1.
Example 3 (30% Relative Humidity Air at 75~F) This example illustrates the use of a water scrubber downstream of the primary condenser for use in absorbing NMP
vapor remaining in the air stream exiting the condenser.
Air containing residual NMP, after it passes through the condenser, is scrubbed by a water scrubber, such as a packed column exhaust air scrubbing unit. The water stream, containing about 2 weight percent NMP and about 9 weight percent water, can be discharged from the system or sent to a distillation column. Preferably, the whole process takes place in a closed loop system. The air discharged from the scrubber and containing about 1 ppm NMP can also be discharged from the system or recycled back into the air stream prior to condensation.
The invention has been described with reference to various specific embodiments. However, many variations and modifications may be made while remaining within the scope and spirit of the invention.
l1
COMPONENTS FOR TITHIUM BATTERIES
FIELD OF THE INVENTION
This invention relates generally to the field of battery manufacturing and the recycling of solvents during such manufacturing. More particularly, the invention relates to the recovery of solvents in lithium ion battery processes.
BACKGROUND OF T~ INV~NTION
Lithium metal batteries are made of various constructions and by various methods. In one type of battery lithium metal is used to make the anode of the battery and lithium dioxy cobaltate is employed to make the cathode. In this particular battery, a LiCF3So3 salt dissolved in N-methyl pyrrolidone (NMP) acts as the liquid electrolyte for the battery.
In other lithium metal batteries, the anode is made from either lithium metal or a lithium aluminum alloy, and the cathode is made from a lithium manganese oxide.
Lithium metal batteries are used as electrical storage devises that are re-chargeable and re-useable. These batteries are used in electronic devices such as video cameras, cellular phones, computers, and cameras. Since the batteries can be recharged they are effective for increasing the portable nature of electronic devices. They also provide an economic energy source.
There are however a few drawbacks associated with the use of lithium metal batteries. One drawback is that the presence of lithium metal in a battery poses a potential fire hazard because lithium metal reacts violently when brought into contact with water. Another drawback is that lithium metal batteries require higher operating temperatures. A further drawback is that discarded lithium metal batteries may leak and CA 02214~42 1997-09-19 contaminate soil and water when they are disposed of in landfills.
The above drawbacks, along with othe~ commercial reasons, prompted the battery industry to develop batteries having improved safety, environmental and performance features.
Accordingly, lithium ion secondary batteries were developed.
Lithium ion secondary batteries do not contain a lithium metal electrode but instead contain electrodes made by coating thick slurries of carbonaceous materials and polymeric binders onto thin metal substrates. The slurries can also contain lithium alloys.
Because the slurries formed from carbonaceous materials and polymeric binders are highly viscous, and in some cases can almost be gel-like in their consistency, solvents are added to the slurries to decrease their viscosity. The solvents generally used are aprotic solvents having low vapor pressures and high flash points. These solvents may be mixed with a lower boiling oxygenated solvent such as ether, ester, alcohol or ketone. These lower boiling solvents are added to change the drying properties and rates of the applied slurries.
For example, anodes are made from alloys that allow lithium ions to be held in them (lithium - intercalatable). In forming these anode~, oxides or carbon are mixed with polytrifluoro ethylene binders and a carrier solve~lt such as methyl ethyl ketone, ethyl acetate or NMP. The electrolyte used is a non-aqueous solution containing LiCF3 S03 .
Lithium ion batteries are known that have a carbonaceous material/polyvinylidene fluoride mixture applied to a metal substrate. NMP is used as the carrier solvent for application of the mixture to the metal substrate. The electrolyte system in the battery construction is a solution of LiC104 in propylene carbonate and di-methoxyethane.
Lithium ion batteries, known as rechargeable polymer electrolyte batteries, have a carbon anode, a lithium nickel oxide cathode and a polyacrylonitrile or polyvinyl chloride matrix that contains an electrolyte made of lithium salts and CA 02214~42 1997-09-19 small amounts of solvent within the polymer matrix.
Typically, when electrodes for use in lithium ion batteries are manufactured, the metal substrate is coated with a slurry and drawn through a drying oven using a roll coating apparatus. Warm air moving over the surface of the coating pulls the solvent from the slurry. The solvent laden heated air is pulled by an exhaust fan and exits the drying oven through an exhaust stack.
A rate limiting factor of the coating operation is lo the speed at which the oven can cause the liquid to be removed form the coating. An increase in the speed of drying means the roll coating apparatus can be operated at a fast rate. Thus, rapid removal of solvent from the slurry coatings is desired.
Up to 30 pounds per hour of solvent are evaporated during production of the electrodes. Many production facilities operate continuously so that substantial amounts of evaporated solvents are generated. The solvents that exit through an exhaust vent are handled in various ways. One method of handling the solvent vapors generated from evaporating the solvent is to simply allow the vapors to be emitted into the atmosphere.
Another method of handling the solvent is to pass the solvent vapors, after they have exited the drying oven, through a thermal oxidizer which burns the vapors thereby,l emitting carbon dioxide, carbon monoxide, and water into atmosphere.
Although this method drastically reduces the amount of solvent emission, it is an expensive process since it destroys the solvent.
A further method of handling the solvent vapor is to direct the vapors into a condensing chamber where the vapors are condensed onto metal surfaces that are kept at a temperature cooler than the exhaust air. The temperature of the metal surfaces is maintained by circulating a cooling liquid that is provided by a chiller system. These cooling units consume large amounts of energy and are expensive to maintain.
CA 02214~42 1997-09-19 As will become apparent from the discussion below, it is an object of the present invention to provide a cost efficient means to recycle and reclaim solve~ts used to manufacture electrodes of lithium ion batteries. It is another object of the present invention to provide a closed loop continuous feed condensation process. It is yet a further object of the present invention to reduce the amount of solvents destroyed and to prevent the release of such solvents into the atmosphere. Other objects and advantages of the present invention will be readily apparent from the description of the invention as set out in the specification and claims below.
SUMMARY OF THE INVENTION
Provided herein is a method of recovering a solvent in a process for manufacturing lithium ion batteries. In practicing the invention, a carrier solvent is released from a slurry coated onto a metal substrate. The slurry contains both the carrier solv~nt and the material used to fabricate electrodes for use in lithium ion batteries. In fabricating the electrodes, the solvent is mixed with a gas stream comprising a gas and water after which the solvent is condensed. The invention as described herein may also comprise a closed looped and continuous process for the capture and re-use of the solvent.
The invention provides a substantial improvement in processes that require the removal of carrier solvent during the forced air drying of paste-like films or slurries used to manufacture electrodes for lithium ion batteries. The improvements comprise an inexpensive means of recovering the carrier solvent.
DF~TAIT~n D~.~CRIPTION OF T~ INV~NTION
In one aspect of the invention, anode construction begins with the mixing together of: 1) a slurry of a CA 02214~42 1997-09-19 carbonaceous material, usually graphite; 2) a polymeric binder, usually polyvinylidene fluoride, polyethylene, or polytrifluoro ethylene; and 3) a carrier. The preferred carrier comprises an aprotic solvent having a low vapor pressure and a high flash point. The carrier may be a combinatioh of an aprotic solvent and oxygenated solvents having low boiling temperatures such as an ether, ester, alcohol, or ketone. These solvents are added to change the drying rates of the solvents from the metal substrates. The preferred aprotic solvent is an alkyl substituted pyrrolidone, most preferably N-methyl pyrrolidone.
The preferred combination of solvents used to make up the carrier solvent is an akyl substituted pyrrolidone and methyl ethyl ketone.
In manufacturing an anode according to an embodiment of the present invention, a reverse roll coating apparatus has strung through it a metal foil substrate, usually thin copper (0.0005 - 0.002 inches thick). The copper foil is usually several feet wide and is strung through the coating apparatus from rolls of the copper foil that are usually several hundred yards in length. The slurry is placed into a slurry containment area of the reverse roll coating apparatus. The coating apparatus is started up and the slurry is applied to one face of the metal foil. The metal foil is usually moving at a rate of several yards per minute, usually 1 to 3~1yards per minute. Next, the slurry coated metal foil enters a drying oven. The slurry at this point is still a highly viscous liquid.
The drying oven is typically about 10 - 30 yards in length. Heated air is provided in the oven and is pulled over the surface of the slurry in order to dry the solvent out of slurry. Typically the temperature of the air passing over the surface of the slurry is about 200 ~F to 300 ~F. The air drawn into the oven is preferably at room temperature with a relative humidity at about 30%. The air drawn into the oven is pulled preferably at a rate of about 5000 to about 8000 scfm. The solvent is evaporated into the gas stream to create a solvent CA 02214~42 1997-09-19 laden hot air gas stream. The solvent laden hot air gas is pulled out of the oven and into a condenser where the solvent is condensed. In another embodiment of the invention, the water content of the air stream is increased ranging from about greater than 30% to about 50%, by introducing the water into the air stream after it exits the drying oven and before the aprotic solvent is condensed.
In a preferred method a "precooling" heat exchanger is used to precool the solvent laden air stream prior to its entering a condensing exchanger. Using this method the air cooled in the condensing exchanger is recycled back into the "precooling" heat exchanger where it is used to cool the air stream exiting the drying oven.
Once the aprotic solvent is condensed it can be distilled from the water and recycled in a closed system wherein the solvent is reintroduced into the slurry. The water is separated from the NMP in the distillation unit.
In another embodiment of the invention a water scrubber is introduced into the system in order to absorb NMP
vapors that remain in the air stream after it leaves the condenser. Preferably, the scrubber is a packed column that removes residual solvent vapors out of the exhaust air with water mist. The water stream generated by the mist can be recycled into a distillation unit to remove the residual NMP.
A portion of the air exiting the water wash packed column scrubber can be re-used as the air entering the drying oven.
As the solvent is driven from the oven a construction is formed from the carbon/polymer composite bonded to the metal foil. The construction is wound into rolls and the rolls are put through the same coating/drying process. The final composite that is made into the anode has the metal foil coated on both sides with the carbon/polymer composition.
The cathode is constructed using the same process used to make the anode with some minor differences. One difference is in the composition of the slurry. In constructing the cathode, the slurry comprises a large amount CA 02214~42 1997-09-19 of a lithium oxide, such as LiCoO2 or LiNio2. Another difference is that aluminum foil is used as the metal substrate. The aluminum foil cathode is coated in much the same way as is the copper foil that is used for the anode.
The following examples are illustrative only and are not meant to limit the invention in any manner.
Example 1 (30% Relative humidity air stream at 75~F) This example illustrates the use of a condenser for condensing solvent vapor from an air stream exiting a drying oven and the subsequent recovery of the solvent in a distillation column. It also illustrates the use of a heat exchanger to "precool" a solvent laden air stream before it enters a primary condenser.
Room temperature air at approximately 75~F and with a relative humidity of about 30% is drawn into the oven through a reverse coating apparatus at a rate of about 5000 scfm using exhaust fans. The temperature of the air rises from about 24~C
to about 150~C by the time it exits the oven. As the coated metal foil passes through the drying oven, a total of about 100 lb/hr of NMP is evaporated from its surface into the air-stream. The concentration of NMP vapor in the a~ir stream leaving the drying oven is about 12% (by volume).
The solvent-laden air stream is pulled from the drying oven through a series of two finned-typed heat exchangers. The bulk of the NMP is condensed in the second heat-exchanger that uses a chilled water-and glycol solution as its cooling medium. When the oven is initially started-up, the second exchanger cools the air stream to preferably the dew point of the NMP. The air exiting the second exchanger is then recycled to the first "precooling" exchanger where it is used to cool air exiting the drying oven. When the system reaches steady state, the precooling exchanger reduces the cooling load in the second exchanger. The air stream exiting the final CA 02214~42 1997-09-19 condenser contains only 15 ppmv NMP and has a temperature of about -6~C (the dew point of the NMP and water vapor mixture).
The air can be recycled or treated further.
The NMP and water condensed in the second heat exchanger are pumped from a reservoir to a distillation column to recover the NMP from the water. The column feed has a composition of about 70 weight percent NMP and about 30 weight percent water. The column is best operated under a vacuum.
The temperature of the reboiler at the bottom of the is between about 100 to 180~C. The temperature in the overhead condenser is between about 25 to 55OC. The NMP is recovered as the bottoms product from the column at a concentration in the bottoms of 99.99 % (by weight). When the system reaches steady state, the bottoms product is used to preheat the feed to the distillation column.
Example 2 (50% Relative Humidity Air, at 75~F) This example illustrates the rise in the dew point caused by the addition of water vapor to the NMP-containing air stream of Example 1. The equipment and conditions described in this example are the same as those of Example 1 with the following exceptions: Room temperature air at 75~F a,,nd with a relative humidity of about 50% is drawn into the oven through a reverse roll coating apparatus at a rate of about 5000 scfm by the drying oven's exhaust fans. The air temperature rises through the oven to about 150~C and a total of about 100 lb/hr of NMP is evaporated into the air stream. The concentration of NMP in the air is 12% (vol.).
Because of the additional water vapor present in the air stream, the temperature required for condensing the NMP
from vapor is about 11~C. This is 5~C higher than the condensation temperature (dew point) of Example 1. Despite the higher dew point, the air stream exiting the final condenser still contains only 14 ppmv NMP. The air can be recycled, CA 02214~42 1997-09-19 treated or discharged. The condensed NMP is recovered from the water in a distillation column as in Example 1.
Example 3 (30% Relative Humidity Air at 75~F) This example illustrates the use of a water scrubber downstream of the primary condenser for use in absorbing NMP
vapor remaining in the air stream exiting the condenser.
Air containing residual NMP, after it passes through the condenser, is scrubbed by a water scrubber, such as a packed column exhaust air scrubbing unit. The water stream, containing about 2 weight percent NMP and about 9 weight percent water, can be discharged from the system or sent to a distillation column. Preferably, the whole process takes place in a closed loop system. The air discharged from the scrubber and containing about 1 ppm NMP can also be discharged from the system or recycled back into the air stream prior to condensation.
The invention has been described with reference to various specific embodiments. However, many variations and modifications may be made while remaining within the scope and spirit of the invention.
l1
Claims (34)
1. A method of recovering an aprotic solvent in a process for manufacturing lithium ion batteries comprising:
(a) releasing an aprotic carrier solvent from a slurry coated onto a metal substrate wherein said slurry comprises the solvent;
(b) mixing the released solvent with a gas stream comprising a gas and water vapor; and (c) condensing the released solvent.
(a) releasing an aprotic carrier solvent from a slurry coated onto a metal substrate wherein said slurry comprises the solvent;
(b) mixing the released solvent with a gas stream comprising a gas and water vapor; and (c) condensing the released solvent.
2. The method as recited in claim 1 comprising releasing the solvent in a drying oven.
3. The method as recited in claim 1 wherein the gas comprises air.
4. The method as recited in claim 2 wherein the gas comprises air.
5. The method as recited in claim 4 comprising mixing the air and the water vapor in a drying oven.
6. The method as recited in claim 5 wherein the amount of water in the air in the drying oven exceeds the amount of water in the ambient air.
7. The method as recited in claim 1 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
8. The method as recited in claim 2 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
9. The method as recited in claim 3 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
10. The method as recited in claim 4 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
11. The method as recited in claim 5 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
12. The method as recited in claim 6 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
13. The method as recited in claim 7 wherein the pyrrolidone comprises N-methyl pyrrolidone.
14. The method as recited in claim 8 wherein the pyrrolidone comprises N-methyl pyrrolidone.
15. The method as recited in claim 9 wherein the pyrrolidone comprises N-methyl pyrrolidone.
16. The method as recited in claim 10 wherein the pyrrolidone comprises N-methyl pyrrolidone.
17. The method as recited in claim 11 wherein the pyrrolidone comprises N-methyl pyrrolidone.
18. The method as recited in claim 12 wherein the pyrrolidone comprises N-methyl pyrrolidone.
19. A method of recovering an aprotic solvent in a process for manufacturing lithium ion batteries:
(a) releasing an aprotic carrier solvent from a slurry coated onto a metal substrate;
(b) mixing the released solvent with a gas stream to form a solvent laden gas stream;
(c) adding water to the solvent laden gas stream;
(d) condensing said released solvent from said gas stream.
(a) releasing an aprotic carrier solvent from a slurry coated onto a metal substrate;
(b) mixing the released solvent with a gas stream to form a solvent laden gas stream;
(c) adding water to the solvent laden gas stream;
(d) condensing said released solvent from said gas stream.
20. The method as recited in claim 19 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
21. The method as recited in claim 19 wherein the pyrrolidone comprises N-methyl pyrrolidone.
22. The method as recited in claim 20 wherein the pyrrolidone comprises N-methyl pyrrolidone.
23. A method of recovering an aprotic solvent from a slurry coated onto a metal substrate in a drying oven, wherein said slurry comprises the solvent and material used to fabricate lithium ion batteries, comprising:
(a) drawing air through the oven creating a hot air gas stream;
(b) evaporating the solvent into the gas stream to create a solvent laden hot air gas stream;
(c) pulling the solvent laden hot air gas out of the oven and into a condenser;
(d) condensing the solvent.
(a) drawing air through the oven creating a hot air gas stream;
(b) evaporating the solvent into the gas stream to create a solvent laden hot air gas stream;
(c) pulling the solvent laden hot air gas out of the oven and into a condenser;
(d) condensing the solvent.
24. The method as recited in claim 23 wherein the condenser comprises a plurality of heat exchangers wherein the air exiting a second heat exchanger is then recycled to a first precooling exchanger.
25. The method as recited in claim 23 further comprising pumping the solvent and water generated in the condenser into a distillation column.
26. The method as recited in claim 24 further comprising pumping the solvent and water generated in the condenser into a distillation column.
27. The method as recited in claim 23 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
28. The method as recited in claim 24 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
29. The method as recited in claim 25 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
30. The method as recited in claim 26 wherein the aprotic solvent comprises an akyl substituted pyrrolidone.
31. The method as recited in claim 27 wherein the pyrrolidone comprises N-methyl pyrrolidone.
32. The method as recited in claim 28 wherein the pyrrolidone comprises N-methyl pyrrolidone.
33. The method as recited in claim 29 wherein the pyrrolidone comprises N-methyl pyrrolidone.
34. The method as recited in claim 30 wherein the pyrrolidone comprises N-methyl pyrrolidone.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US71929996A | 1996-09-19 | 1996-09-19 | |
| US08/719,299 | 1996-09-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2214542A1 true CA2214542A1 (en) | 1998-03-19 |
Family
ID=24889531
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2214542 Abandoned CA2214542A1 (en) | 1996-09-19 | 1997-09-19 | Process for recycling of gases during the manufacturing of components for lithium batteries |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2214542A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110152338A (en) * | 2019-06-04 | 2019-08-23 | 深圳市华尔信环保科技有限公司 | The recycling of NMP steam condensate and technique of zero discharge in lithium battery production |
| WO2021007295A1 (en) * | 2019-07-11 | 2021-01-14 | Durr Systems, Inc. | Apparatus and method for solvent recovery from drying process |
| DE102022000536A1 (en) | 2021-12-22 | 2023-06-22 | Dürr Systems Ag | Method and device for treating process air |
| WO2023116978A1 (en) | 2021-12-22 | 2023-06-29 | Dürr Systems Ag | Method and device for treating process air |
| WO2023227152A1 (en) | 2022-05-24 | 2023-11-30 | Dürr Systems Ag | Method and apparatus for treatment of process gas |
| WO2024120577A1 (en) * | 2022-12-07 | 2024-06-13 | Dürr Systems Ag | Apparatus and method for treating process gas |
-
1997
- 1997-09-19 CA CA 2214542 patent/CA2214542A1/en not_active Abandoned
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110152338A (en) * | 2019-06-04 | 2019-08-23 | 深圳市华尔信环保科技有限公司 | The recycling of NMP steam condensate and technique of zero discharge in lithium battery production |
| WO2021007295A1 (en) * | 2019-07-11 | 2021-01-14 | Durr Systems, Inc. | Apparatus and method for solvent recovery from drying process |
| US11130091B2 (en) | 2019-07-11 | 2021-09-28 | Durr Systems, Inc. | Apparatus and method for solvent recovery from drying process |
| CN113993610A (en) * | 2019-07-11 | 2022-01-28 | 杜尔系统有限公司 | Apparatus and method for recovering solvent from drying process |
| US11731073B2 (en) | 2019-07-11 | 2023-08-22 | Durr Systems, Inc. | Apparatus and method for solvent recovery from drying process |
| DE102022000536A1 (en) | 2021-12-22 | 2023-06-22 | Dürr Systems Ag | Method and device for treating process air |
| WO2023116978A1 (en) | 2021-12-22 | 2023-06-29 | Dürr Systems Ag | Method and device for treating process air |
| WO2023227152A1 (en) | 2022-05-24 | 2023-11-30 | Dürr Systems Ag | Method and apparatus for treatment of process gas |
| WO2024120577A1 (en) * | 2022-12-07 | 2024-06-13 | Dürr Systems Ag | Apparatus and method for treating process gas |
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