Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
  • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/34—Regenerating or reactivating

Definitions

• the present invention relates to an organic solvent recovery system.
• the organic solvent recovery system is equipped with a treatment tank that uses an adsorbent to adsorb the organic solvent in the gas to be treated, a treated gas supply device and a desorption gas supply device for each treatment tank, and employs a mechanism for switching between an adsorption process that supplies the gas to be treated to the treatment tank and a desorption process that supplies the desorption gas.
• Patent Document 1 discloses a gas treatment device equipped with three treatment tanks, a treated gas supply unit, a connecting flow path, a steam supply unit, and a dilution gas supply path.
• the treated gas supply unit supplies the treated gas containing the organic solvent to each treatment tank.
• Each treatment tank has an adsorbent capable of adsorbing the organic solvent contained in the treated gas.
• the connecting flow path connects two of the three treatment tanks in series. Specifically, the treated gas treated in the treatment tank used in the first adsorption step is introduced through the connecting flow path into the treatment tank used in the second adsorption step, where the organic solvent is further recovered from the treated gas.
• the gas treated in the second adsorption step is taken out of the system as clean air.
• the steam supply unit supplies each treatment tank with steam for desorbing the organic solvent adsorbed to the adsorbent from the adsorbent.
• the steam supply unit supplies steam to the remaining treatment tanks not used in the first adsorption step and the second adsorption step.
• the adsorption process is carried out continuously in two treatment tanks, while the desorption process is carried out in the remaining treatment tank.
• the treatment tank in which the desorption process has been carried out is then used in the second adsorption process, and thereafter in the first adsorption process.
• nonwoven activated carbon fiber is preferably used as an adsorbent capable of adsorbing organic solvents.
• Activated carbon fiber adsorbs organic solvents much faster than granular activated carbon, so it can reliably adsorb and remove organic solvents.
• activated carbon fiber has an extremely fast rate of adsorbing and desorbing organic solvents, the weight of the fiber packed into the treatment tank can be reduced to about 1/15 to 1/100 of that of granular activated carbon.
• activated carbon fiber has a porosity of 90 to 98%, which is very bulky compared to granular activated carbon, which has a porosity of 33 to 45%, so the weight of activated carbon fiber that can be packed per unit volume of the treatment tank is smaller than that of granular activated carbon.
• activated carbon fiber exhibits high removal performance even with a small packed weight, which results in the organic solvent recovery device being made smaller (Non-Patent Document 1).
• Patent Document 2 also discloses an activated carbon desorption device that reduces the amount of water vapor used by connecting the condensation side of a heat exchanger to the desorption steam outlet of an activated carbon adsorber (treatment tank), supplying water to the evaporation side of the heat exchanger, and installing a pressure reducing blower in a line connecting the evaporation side of the heat exchanger to the desorption water vapor inlet of the activated carbon adsorber, and evaporating the water on the evaporation side using the heat of the desorption steam to generate water vapor for desorption.
• an activated carbon desorption device that reduces the amount of water vapor used by connecting the condensation side of a heat exchanger to the desorption steam outlet of an activated carbon adsorber (treatment tank), supplying water to the evaporation side of the heat exchanger, and installing a pressure reducing blower in a line connecting the evaporation side of the heat exchanger to the desorption water vapor inlet of the activated carbon adsorber, and evaporating
• JP 2014-147863 A Japanese Utility Model Application Publication No. 58-161636
• activated carbon fiber has a higher porosity than general granular activated carbon or powdered activated carbon, so it takes time to replace the gas to be treated remaining in the treatment tank with the desorption water vapor in the desorption process.
• activated carbon fiber has an extremely fast rate of desorbing organic solvents compared to general granular activated carbon or powdered activated carbon, so the organic solvent adsorbed on the activated carbon fiber is rapidly desorbed in the early stage of the desorption process.
• the temperature of the desorption outlet gas discharged from the treatment tank hardly increases until the desorbed organic solvent is replaced by the desorption steam.
• the activated carbon fiber has a large external surface area, it rapidly absorbs the heat of the desorption steam in the early stage of the desorption process. As a result, the temperature of the desorption outlet gas discharged from the treatment tank hardly increases until the temperature of the activated carbon fiber has risen sufficiently.
• the present invention has been developed in consideration of the above problems, and its purpose is to provide an organic solvent system that can improve the efficiency of organic solvent recovery and significantly reduce the amount of water vapor used by the entire facility.
• the organic solvent recovery system of the present invention has the following configuration.
• an organic solvent recovery apparatus including at least four treatment tanks each containing an adsorbent that adsorbs and removes an organic solvent from a gas to be treated that contains the organic solvent, the treatment tanks sequentially carrying out an adsorption process in which the gas to be treated is brought into contact with the adsorbent to discharge a treatment gas, a desorption process in which the organic solvent is desorbed from the adsorbent using desorption steam and a desorbed gas is discharged, and a purging process in which the treatment tank is purged with a purge gas; a desorption water vapor inlet passage for introducing the desorption water vapor into a desorption treatment tank which is a treatment tank selected from the plurality of treatment tanks; a purge gas supply passage for supplying the purge gas to a purge treatment tank which is another treatment tank selected from the plurality of treatment tanks; a connecting flow path that connects the remaining plurality of adsorption treatment tanks in series in multiple stages; a gas supply passage for introducing the gas to be
• the organic solvent recovery device may include a condensate reservoir that accumulates the condensate discharged from the cooling section
• the heat exchanger may include a desorption gas outlet receiving section in which the desorption gas accumulates after indirect heating, a piping path that supplies the uncondensed desorption gas from the desorption gas outlet receiving section to the cooling section, and a piping path that supplies the desorption gas that has become condensed from the desorption gas outlet receiving section to the condensate reservoir.
• the desorption gas discharged from the treatment tank may be supplied to the cooling section during the early stage of the desorption process, and the desorption gas discharged from the treatment tank may be supplied to the heat generating section of the heat exchanger during the later stage of the desorption process.
• the heat exchanger may be a multi-tube heat exchanger having a tube portion, which is the heat generating portion, inside a container portion, which is the heat absorbing portion.
• the water vapor supply unit that supplies the desorption water vapor to the organic solvent recovery device may be connected to a direct path that supplies the desorption water vapor from the water vapor supply unit directly to the organic solvent recovery device, and a mixing path that mixes the desorption water vapor with the regenerated water vapor and supplies it to the organic solvent recovery device.
• the present invention provides an organic solvent system that can significantly reduce the amount of water vapor used by the entire facility while maintaining a high organic solvent recovery rate.
• FIG. 1 is a schematic diagram showing a configuration of an organic solvent recovery system according to a first embodiment.
• 4 is a graph showing a reduction rate of water vapor usage by the organic solvent recovery system according to the first embodiment.
• FIG. 11 is a schematic diagram showing a configuration of an organic solvent recovery system according to a second embodiment.
• FIG. 11 is a diagram showing a time chart illustrating the temporal switching of each treatment process of the organic solvent recovery system according to the second embodiment.
• the organic solvent in the present invention is methylene chloride, chloroform, carbon tetrachloride, ethylene chloride, trichloroethylene, tetrachloroethylene, o-dichlorobenzene, m-dichlorobenzene, fluorocarbon-112, fluorocarbon-113, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), other perfluoroalkyl compounds and polyfluoroalkyl compounds (PFAS), propyl bromide, butyl iodide, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, vinyl acetate, methyl propionate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, diethyl carbonate, ethyl formate, diethyl ether, dipropy
• FIG. 1 is a diagram showing a configuration of an organic solvent recovery system 1A according to the embodiment 1.
• the organic solvent recovery system 1A is a system that separates and recovers an organic solvent from a gas to be treated that contains the organic solvent.
• the organic solvent recovery system 1A includes an organic solvent recovery device 100, a heat exchanger 115, and a condenser 130 as a cooling section.
• the organic solvent recovery device 100 includes treatment tanks 101 to 104.
• the treatment tank 101 includes a cylindrical activated carbon fiber 101A
• the treatment tank 102 includes a cylindrical activated carbon fiber 102A
• the treatment tank 103 includes a cylindrical activated carbon fiber 103A
• the treatment tank 104 includes a cylindrical activated carbon fiber 104A.
• the activated carbon fibers 101A to 104A are passed from the outside to the inside to perform an adsorption process (adsorption process), passed from the inside to the outside to perform a desorption process (desorption process), and passed from the inside to the outside to perform a purge process (purge process).
• adsorption process adsorption process
• desorption process desorption process
• purge process purge process
• the treatment tanks 101 to 104 are connected to the treated gas supply line L10 and the desorption gas line L50. To open and close the connection to the treated gas supply line L10 and the desorption gas line L50, the treatment tanks 101 to 104 are provided with on-off valves V11 to V14 and on-off dampers V101 to V104, respectively.
• opening and closing dampers V201-V204 are provided, respectively, to control the flow of the gas A to be treated.
• the adsorption process of the organic solvent by the activated carbon fibers 101A-104A, the desorption process of the organic solvent from the activated carbon fibers 101A-104A, and the purging process of the treatment tanks 101-104 after the desorption process are performed alternately.
• the details are as follows.
• a first adsorption process is performed in which the organic solvent is adsorbed from the gas A to be treated by the activated carbon fibers
• a second adsorption process is performed in which the organic solvent is adsorbed by the activated carbon fibers from the gas to be treated (first adsorption process gas) after being treated in the treatment tank used in the first adsorption process, and clean gas is discharged.
• a desorption process is performed in which the organic solvent is desorbed from the activated carbon fibers.
• FIG. 1 shows a state in which the first adsorption process is performed in the treatment tank 101, the second adsorption process is performed in the treatment tank 102, the purging process is performed in the treatment tank 103, and the desorption process is performed in the treatment tank 104.
• the treatment tank in which the first adsorption process and the second adsorption process are performed is also called the adsorption treatment tank.
• the treatment tank in which the purging process is performed is also called the purge treatment tank.
• the treatment tank in which the desorption process is performed is also called the desorption treatment tank.
• the treated gas supply line L10 is a flow path for supplying the treated gas A to the treatment tanks 101-104.
• the upstream end of the treated gas supply line L10 is connected to a treated gas supply source.
• the treated gas supply line L10 is provided with a treated gas blower F1.
• a cooler C1 and a heater H1 are provided in the treated gas supply line L10 at a portion upstream of the treated gas blower F1 to adjust the temperature and humidity of the treated gas flowing into the treatment tanks 101-104 to the desired range.
• These devices may be installed as appropriate depending on the pressure, temperature, and humidity of the treated gas.
• connection lines L21 to L24 connect one treatment tank to another treatment tank so that the first adsorption process gas after the organic solvent is adsorbed by the activated carbon fiber in one of the treatment tanks 101 to 104 (the treatment tank used in the first adsorption process) is introduced into the treated gas supply port in the other treatment tank (the treatment tank used in the second adsorption process) different from the one of the treatment tanks 101 to 104.
• the connection line L21 connects the treated gas exhaust port in the treatment tank 101 to the treated gas supply port in the treatment tank 102.
• the connection line L22 connects the treated gas exhaust port in the treatment tank 102 to the treated gas supply port in the treatment tank 103.
• the connection line L23 connects the treated gas exhaust port in the treatment tank 103 to the treated gas supply port in the treatment tank 104.
• the connection line L24 connects the treatment gas exhaust port in the treatment tank 104 to the treated gas supply port in the treatment tank 101.
• connection lines L21 to L24 have a connection line L20 where they merge with each other.
• a second adsorption gas blower F2 is provided in the connection line L20.
• the clean gas lines L31 to L34 are flow paths for extracting the clean gas after adsorption processing in the treatment tanks 101 to 104.
• the clean gas lines L31 to L34 are connected to the treated gas exhaust ports in each of the treatment tanks 101 to 104.
• the clean gas lines L31 to L34 have a clean gas line L30 where they merge with each other.
• the desorption steam supply lines L41 to L44 are flow paths for supplying desorption steam to each treatment tank 101 to 104 in order to desorb the organic solvent adsorbed on the activated carbon fibers 101A to 104A from the activated carbon fibers 101A to 104A.
• the desorption steam is supplied from a steam compressor 122.
• the desorption steam supply lines L41 to L44 branch off from the desorption steam supply line L40 connected to the steam compressor 122.
• the desorption gas lines L51 to L54 are flow paths for recovering gas (desorption gas) containing the organic solvent desorbed from the activated carbon fibers 101A to 104A.
• Each of the desorption gas lines L51 to L54 is connected to each of the treatment tanks 101 to 104.
• Each of the desorption gas lines L51 to L54 has a desorption gas line L50 that merges with each other.
• a heat exchanger 115 is connected to the desorption gas line L50.
• the heat exchanger 115 has a desorption gas inlet chamber 115C to which the desorption gas line L50 is connected.
• the heat exchanger 115 also has a desorption gas outlet chamber 115D, which is a desorption gas outlet receiving section to which the heat exchanger outlet gas line L60 and the heat exchanger condensate line L61 are connected.
• makeup water C is supplied to the evaporation side of the heat exchanger 115.
• the makeup water C is sent to the evaporation side of the heat exchanger 115 by, for example, a liquid delivery pump.
• the heat exchanger 115 indirectly heats the make-up water C with the desorption gas supplied from the desorption gas line L50, thereby evaporating the make-up water C and generating water vapor.
• the evaporation side of the heat exchanger 115 is decompressed so that the boiling point is, for example, 70°C to 97°C, preferably 75°C to 95°C, and the generated water vapor is supplied to the steam compressor 122 as regenerated water vapor through the regenerated water vapor line L70 connected to the heat exchanger 115.
• the steam compressor 122 is a mechanism that uses high-pressure water vapor as a driving source (hereinafter, driving water vapor) to draw in constant-pressure water vapor (hereinafter, suction water vapor) in a reduced pressure state and increase the pressure to medium-pressure water vapor (hereinafter, discharge water vapor).
• the regenerated water vapor is sucked in as suction water vapor through the regenerated water vapor line L70, and the desorption water vapor, which is a mixture of water vapor D and regenerated water vapor, is discharged as discharge water vapor through the desorption water vapor supply line L40.
• the water vapor D is connected to a water vapor generation source.
• the desorption steam discharged from the steam compressor 122 is supplied to the treatment tanks 101 to 104 where the desorption process is being performed through the desorption steam supply line L40.
• the steam compressor 122 may be replaced by a compressor having a similar effect, such as a roots blower or turbo blower.
• the heat exchanger 115 is a multi-tube heat exchanger.
• a multi-tube heat exchanger is a heat exchanger in which a large number of tubes are arranged inside a cylinder called a shell, which is a container part.
• the surface of the tubes acts as a heat transfer surface, and heat is exchanged between the fluid flowing inside the tube 115B (hereinafter, the tube side) and the fluid flowing between the outside of the tube 115B and the inside of the shell 115A (hereinafter, the shell side).
• the tube 115B is a heat generating part that provides heat
• the shell 115A is a heat absorbing part that receives heat.
• the tube 115B connects the desorption gas inlet chamber 115C and the desorption gas outlet chamber 115D.
• the heat exchanger 115 of the present invention is arranged so that the tube 115B faces horizontally, and the tube side acts as the condensation side that supplies the desorption gas, and the shell side acts as the evaporation side that supplies the makeup water
• makeup water 115E In shell 115A, makeup water 115E always remains in an amount that contacts a part of tube 115B. When makeup water 115E comes into contact with tube 115B, makeup water 115E receives heat from the desorbed gas and evaporates. In addition, tube 115B also serves to heat makeup water up to the evaporation temperature, so there is no need to provide a separate makeup water heating facility for heating makeup water C.
• the heat exchanger 115 preferably adjusts the water level of the make-up water 115E so that a part of the tube 115B does not come into contact with the make-up water 115E.
• a part of the tube 115B is located in the gas phase part in the shell 115A between the water level of the make-up water 115E and the regenerated steam line L70.
• the regenerated steam is heated by the tube 115B located in the gas phase part in the shell 115A, and it is possible to prevent the regenerated steam from condensing before being sucked into the steam compressor 122.
• a means for adjusting the water level of the make-up water 115E for example, a control method using a float type, a spacer type, a differential pressure type, or a capacitance type liquid level gauge can be considered.
• the desorbed gas outlet chamber 115D of the heat exchanger 115 is connected to the heat exchanger outlet gas line L60 and is connected to the condenser 130. Inside the condenser 130, heat exchange occurs between the desorbed gas that has completed heat exchange in the heat exchanger 115 and the cooling water, and the desorbed gas is cooled and condensed.
• the condensate condensed in the condenser 130 is supplied to a separator 131, which is a condensate reservoir, through a condenser condensate line L62.
• the separator 131 separates the condensate sent from the condenser condensate line L62 into a layer of recovered solvent 131A and a layer of separated wastewater 131B.
• the separated wastewater 131B may be discharged after being purified by an aeration device 132. Since an aeration gas containing an organic solvent is generated from the aeration device 132, an aeration gas line L64 is provided for returning the aeration gas to the treated gas supply line L10.
• the aeration device may be any other wastewater treatment device capable of separating organic solvents, such as a wastewater treatment device using an adsorbent or a separation membrane device.
• the heat exchanger condensate line L61 is connected to the desorption gas outlet chamber 115D of the heat exchanger 115.
• the heat exchanger condensate line L61 is connected to the separator 131.
• the desorption gas that has completed heat exchange in the tube 115B of the heat exchanger 115 is separated into uncondensed desorption gas and condensed condensate, and is supplied to the desorption gas outlet chamber 115D.
• the condensate of the desorption gas supplied to the desorption gas outlet chamber 115D is directly supplied to the separator 131 through the heat exchanger condensate line L61.
• the return gas line L63 is connected to the gas phase portion of the condenser 130 and the gas phase portion of the separator 131.
• the return gas line L63 is introduced into the treated gas supply line L10.
• the gas returned from the return gas line L63 to the treated gas supply line L10 should be introduced so as to flow in a counter flow direction to the flow direction of the treated gas A.
• the discharged steam from the steam compressor 122 i.e., the desorption steam, is supplied to each treatment tank 101-104 through the desorption steam supply line L40.
• the purge gas supply lines L81 to L84 are flow paths that supply purge gas to each of the treatment tanks 101 to 104 to exhaust the mixed gas of desorption water vapor and organic solvent remaining in each of the treatment tanks 101 to 104 from each of the treatment tanks 101 to 104.
• the purge gas supply lines L81 to L84 branch off from the purge gas supply line L80.
• the purge outlet gas lines L91 to L94 are flow paths for discharging the desorption water vapor and organic solvent (purge outlet gas) remaining in each of the treatment tanks 101 to 104 from each of the treatment tanks 101 to 104.
• Each of the purge outlet gas lines L91 to L94 is connected to each of the treatment tanks 101 to 104.
• Each of the purge outlet gas lines L91 to L94 has a purge outlet gas line L90 that merges with each other.
• the purge outlet gas line L90 is connected to the condenser 130.
• the purge outlet gas is supplied to the treated gas supply line L10 via the condenser 130 and the return gas line L63.
• the purge outlet gas can be outside air, a portion of the clean gas B, nitrogen, argon, etc., but using a portion of the clean gas B is preferable because it reduces the amount of clean gas B released into the atmosphere.
• each damper In the organic solvent recovery system 1 having the above configuration, the operation and opening/closing of each damper, each on-off valve, heat exchanger 115, steam compressor 122, condenser 130, separator 131, and each blower, each heater, and each cooler are appropriately controlled by a control device (not shown) to realize the gas treatment method described below.
• a gas treatment method using the organic solvent recovery system 1A having the above configuration will be described.
• a first adsorption step is carried out in a treatment tank 101 of an organic solvent recovery apparatus 100
• a second adsorption step is carried out in a treatment tank 102
• a purging step is carried out in a treatment tank 103
• a desorption step is carried out in a treatment tank 104.
• each treatment tank the process is repeated in the following order: first adsorption process ⁇ desorption process ⁇ purging process ⁇ second desorption process ⁇ first desorption process ⁇ ....
• the on-off valves V11, V22, V32, V44, V83, and V93 and the on-off dampers V101, V102, V103, V201, V202, and V203 are open, and the on-off valves V12, V13, V14, V21, V23, V24, V31, V33, V34, V41, V42, V43, V81, V82, V84, V91, V92, and V94 and the on-off dampers V104 and V204 are closed.
• the gas to be treated is supplied from a gas supply source to the first treatment tank 101 through the gas to be treated supply line L10, and the organic solvent contained in the gas to be treated is adsorbed to the activated carbon fiber 101A in the treatment tank 101 (first adsorption step).
• the gas to be treated is then supplied to the treatment tank 102 through the first connecting line L21, and the organic solvent contained in the gas supplied to the activated carbon fiber 102A is further adsorbed (second adsorption step).
• the activated carbon fiber 102A is dried by the supplied gas.
• this system can be used even if the drying performed in the second adsorption step is a system separated as a drying step, that is, even if each treatment tank performs treatment in the order of the first adsorption step ⁇ desorption step ⁇ purge step ⁇ drying step ⁇ second adsorption step ⁇ first adsorption step ⁇ ...
• Desorption steam is supplied to the treatment tank 104 through a desorption steam supply line L40, whereby the organic solvent is desorbed from the activated carbon fibers 104A.
• the steam for desorption is generated by mixing steam D and regenerated steam in the steam compressor 122.
• the steam compressor 122 is driven by steam D supplied through the steam line L71 for the steam compressor, sucks in regenerated steam in a reduced pressure state through the regenerated steam line L70, and discharges the desorption steam, which is a mixture of steam D and regenerated steam, through the desorption steam supply line L40.
• the desorption steam is ejected, and the organic solvent adsorbed on the activated carbon fiber 104A is desorbed from the activated carbon fiber 104A.
• the desorption gas which is a mixture of the desorbed organic solvent and the steam, is sent to the heat exchanger 115 through the desorption gas lines L54 and L50.
• the desorbed gas is supplied to the tube side of the heat exchanger 115 and exchanges heat with the make-up water 115E that is retained on the shell side of the heat exchanger 115. Specifically, the make-up water 115E is indirectly heated through the heat transfer surface.
• the desorption gas After the desorption gas has completed heat exchange with makeup water 115E in heat exchanger 115, it is separated into uncondensed desorption gas and condensed condensate.
• the uncondensed desorption gas is supplied to condenser 130 through heat exchanger outlet gas line 117. Inside condenser 130, heat exchange occurs between the desorption gas and cooling water, and the desorption gas is cooled and condensed. Meanwhile, the condensate of the desorption gas condensed in heat exchanger 115 is supplied to separator 131 through heat exchanger condensate line L61.
• Figure 2 is a graph showing the reduction rate of water vapor usage in organic solvent recovery system 1A.
• the horizontal axis in the graph of Fig. 2 indicates the value of A/B, which is the ratio of the weight A [kg] of the activated carbon fiber contained in the treatment tank of the organic solvent recovery apparatus of the present invention to the internal volume B [ m3 ] of the treatment tank.
• the vertical axis in the graph of Fig. 2 indicates the reduction rate (%) of the amount of water vapor used.
• the reduction rate of the amount of water vapor used can be calculated by the following formula (1).
• [Reduction rate of water vapor consumption (%)] [amount of regenerated water vapor (g/min)] ⁇ [amount of water vapor for desorption (g/min)] ⁇ 100 (1)
• the amount of water vapor desorbed can be measured, for example, by an ultrasonic, orifice, vortex, or area-type water vapor flow meter.
• the amount of regenerated water vapor can be measured, for example, by an ultrasonic, orifice, vortex, or area-type water vapor flow meter, or by weighing the flow rate of make-up water.
• the reduction rate in water vapor usage is greater than 0%, it indicates that recycled water vapor is being generated, and energy savings can be achieved.
• energy savings can be achieved when the A/B value is in the range of 12.0 or more.
• measures must be taken to reduce the dead space in the on-off dampers and on-off valves connected to the treatment tank.
• the amount of water vapor used for desorption can be reduced by satisfying the condition that the above-mentioned A/B value is 12.0 or more.
• the condensate of the desorbed gas condensed in the condenser 130 is supplied to the separator 131 through the condenser condensate line L62. In the separator 131, it is separated into a layer of recovered solvent 131A and a layer of separated wastewater 131B.
• the return gas remaining in the condenser 130 and separator 131 is pushed out by the desorbed gas and introduced into the treated gas supply line L10 through the return gas line L63, where it is mixed with the treated gas A.
• the treated gas A and the return gas introduced from the treated gas supply line L10 are sent to the treatment tank 101.
• a purge gas is supplied to the treatment tank 103 through the purge gas supply line L83, whereby the organic solvent and desorption water vapor remaining in the treatment tank 103 are discharged from the treatment tank 103.
• the organic solvent concentration in the clean gas discharged from the treatment tank at the beginning of the next second adsorption step can be reduced, and the removal performance of the organic solvent recovery system 1A is improved.
• the purge outlet gas which is a mixture of the organic solvent and desorption steam discharged from the treatment tank 103, is sent to the condenser 130 through the purge outlet gas lines L93 and L90.
• the organic solvent and desorption steam are condensed in the condenser 130, and the condensate is supplied to the separator 131 through the condenser condensate line L62.
• the purge outlet gas may be treated in a separate organic solvent recovery device instead of being sent to the condenser 130, but sending it to the condenser 130 can simplify the organic solvent recovery system 1A.
• the first adsorption process, second adsorption process, desorption process, and purging process are switched over, with treatment tank 101 performing the desorption process, treatment tank 102 performing the first adsorption process, treatment tank 103 performing the second adsorption process, and treatment tank 104 performing the purging process.
• the organic solvent recovery system 1A continuously recovers recovered solvent 131A.
• FIG. 3 is a diagram showing the configuration of an organic solvent recovery system 2 according to the second embodiment.
• an organic solvent recovery system 1B includes an on-off valve V100 and a condenser line L100 in addition to the configuration of the organic solvent recovery system 1A described in the first embodiment.
• FIG. 4 is a time chart showing the time-dependent switching of each process of the organic solvent recovery apparatus 100 of the second embodiment shown in FIG. 3. Below, the method of recovering organic solvent by the organic solvent recovery system 1B of the second embodiment will be described with reference to FIG. 4.
• the basic configuration of the organic solvent recovery system 1B of the second embodiment is the same as that of the organic solvent recovery system 1A described in the first embodiment above. The difference is that in the organic solvent recovery system 1B of the second embodiment, a three-way on-off valve V100 is provided on the desorption gas line L50 from the organic solvent recovery device 100. One downstream end of the on-off valve V100 is connected to the desorption gas inlet chamber 115C of the heat exchanger 115, and the other downstream end is connected to the condenser 130 via the condenser line L100.
• the on-off valve V100 can switch between supplying the desorption gas to the heat exchanger 115 or to the condenser 130. Note that a similar switching operation may be performed by using multiple two-way on-off valves instead of the three-way on-off valve V100.
• the organic solvent recovery device 100 of the second embodiment operates in a desorption process divided into a first desorption process in the early stage and a second desorption process in the later stage.
• the desorption gas is supplied to the condenser 130 through the condenser line L100 by operating the three-way on-off valve V100.
• the treatment tank 104 discharges the gas to be treated remaining in the previous second adsorption process and the organic solvent desorbed from the activated carbon fiber 104A, and the heat of the desorption steam is rapidly absorbed by the activated carbon fiber 104A, so that the temperature of the desorption outlet gas discharged from the treatment tank 104 becomes low. Therefore, by supplying the desorption gas discharged from the treatment tank 104 directly to the condenser 130 without supplying it to the heat exchanger 115, the tube 115B of the heat exchanger 115 can be maintained at a high temperature, and as a result, the evaporation of the makeup water 115E is efficiently performed.
• the three-way on-off valve V100 is operated to supply the desorption gas to the heat exchanger 115, starting the second desorption process in the treatment tank 104 (i.e., between t1 and t2 shown in Figure 4).
• the timing for switching from the first desorption process to the second desorption process may be determined by measuring in advance the time it takes for the temperature of the desorption gas discharged from the treatment tank to reach a high temperature in the first desorption process.
• a temperature sensor 152 may be provided to measure the temperature of the desorption gas discharged from the treatment tank, and the control unit 150 may control the process to automatically switch from the first desorption process to the second desorption process when the temperature of the desorption gas detected by the temperature sensor 152 reaches a high temperature.
• the organic solvent recovery system 1B of the second embodiment can achieve the same effects as the organic solvent recovery system 1A of the first embodiment.
• the organic solvent recovery process is described as using the treatment tanks 101 to 104 as treatment tanks, but the organic solvent recovery process is not limited to using these four treatment tanks, and there may be five or more treatment tanks.
• the above system may also be provided with a steam compressor bypass line that directly connects the water vapor supply unit and the organic solvent recovery device 100. If a steam compressor bypass line is provided, when the flow rate of the water vapor for desorption is insufficient in the desorption process, the opening of the adjustment valve provided on the steam compressor bypass line can be adjusted to supplement the water vapor for desorption, thereby stabilizing the flow rate of the water vapor for desorption.
• Example 1 The following treatment was carried out using the organic solvent recovery system 1A shown in FIG. 1 described above.
• the gas to be treated was 45° C. and contained 4,000 ppm of ethyl acetate, and the gas was blown into the treatment tank 101 in the first adsorption step by the gas blower F1.
• Activated carbon fibers manufactured by Toyobo Co. , Ltd. were used for the activated carbon fibers 101A to 104A.
• the A/B ratios of the treatment tanks 101 to 104 were all set to 19.0 by reducing the dead space of the opening and closing dampers V101 to V104 of the treatment tanks 101 to 104.
• the first adsorption step gas discharged from the treatment tank 101 was blown into the treatment tank 102 in the second adsorption step.
• the gas to be treated was supplied to the treatment tank 101 in the first adsorption step for 11 minutes, the first adsorption step, desorption step, purge step, and second adsorption step were switched, and desorption steam was introduced into the treatment tank 101 to carry out the desorption step.
• the flow rate of steam D was adjusted to 284 g/min.
• the water level of make-up water 115E was adjusted by supplying make-up water C so that tube 115B of heat exchanger 115 was immersed in make-up water 115E, and regenerated steam was generated.
• the generated regenerated steam was sucked into steam compressor 122, mixed with steam D, and then supplied to treatment tank 101 as desorption steam.
• the first adsorption process, desorption process, purging process, and second adsorption process were switched, and purging gas was supplied to treatment tank 101 to perform the purging process.
• the purge step a part of the clean gas B was used as a purge gas, and a part of the clean gas B was blown into the treatment tank 101 by the purge gas blower F3.
• the air volume of the purge gas was 0.3 Nm3 /min.
• the first adsorption process, desorption process, purging process, and second adsorption process described above were each repeated 10 cycles.
• the ethyl acetate concentration in clean gas B after 10 cycles was 1.0 ppm.
• the reduction rate of water vapor usage which is the quotient of the amount of water vapor used for desorption and the amount of water vapor used for regeneration after 10 cycles, was 20%.
• the present invention makes it possible to provide an organic solvent recovery system that is energy-saving and improves the efficiency of organic solvent recovery, making a great contribution to the industrial world.

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• 2024
  • 2024-05-09 WO PCT/JP2024/017244 patent/WO2024247641A1/ja not_active Ceased
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