JP6429698B2 - Solvent recovery method and apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus for recovering a solvent, wherein a water-containing material such as sludge is organic sludge, and moisture contained in the organic sludge is dehydrated using an absorbent made of a hydrophilic solvent such as an organic solvent, and the solvent is removed. It relates to the technology to collect.

  Conventionally, as a device for dewatering sludge generated from a sewage treatment plant, a water purification plant, a factory wastewater treatment facility, a civil engineering construction site, etc., there are various devices such as a centrifugal dehydrator and a filter press. However, depending on the properties of the sludge, it is difficult to remove moisture from the sludge.

  For this reason, for example, the invention described in Patent Document 1 is intended to increase the drying speed of the dewatered sludge and reduce the volume in a short time, and to the concentrated mud obtained after the coagulation sedimentation treatment Add volatile organic solvent such as methanol, ethanol, isopropyl alcohol and other alcohol-based organic solvents, dehydrate the mixed organic solvent, and remain in the dewatered sludge by volatilization of the added organic solvent. It promotes moisture vaporization and reduces the water content of the dehydrated sludge.

  The invention described in Patent Document 2 dehydrates organic sludge mixed with an organic solvent that is liquid and volatile at normal temperature and pressure with a dehydrator equipped with a heating means. The sludge is heated to a first predetermined temperature equal to or higher than the boiling point of the organic solvent, the organic solvent mixed in the organic sludge is vaporized, and the organic solvent is discharged from the dehydration unit and collected.

JP2011-2000811 JP2014-193438

  In the conventional configuration described above, the organic solvent is kneaded and dehydrated, and the water content of the dehydrated sludge is reduced to reduce the volume. In addition to the problem of being consumed, there is a problem that the organic solvent contained in the dehydrated filtrate is vaporized and volatilized to consume the organic solvent.

  For this reason, when recovering the solvent, in order to reduce the volatilization loss of the solvent as much as possible, a step of condensing and recovering the solvent by cooling the gas-liquid mixed fluid that is a dehydrated filtrate in various places of the solvent recovery mechanism is performed. Therefore, the energy consumption of the cold water production apparatus required for cooling the dehydrated filtrate and the like was great. Further, when purifying the dehydrated filtrate or the like in the distillation tower, a large amount of energy is required to reheat the dehydrated filtrate once cooled.

Furthermore, the dehydrated filtrate has a large amount of contaminants, and if the contaminants adhere to or accumulate in the distillation tower, there may be a case where sufficient separation efficiency cannot be obtained due to deterioration of heat transfer efficiency.
The present invention solves the above-described problems, and an object of the present invention is to provide a solvent recovery method and apparatus that can reduce energy consumption required for solvent recovery.

In order to solve the above problems, the solvent recovery method of the present invention is characterized in that the hydrophilic solvent functions as an absorbing liquid that absorbs moisture in the organic sludge and has a boiling point lower than that of the water. The gas-liquid mixed fluid that separates from the solid-liquid mixture with sludge contains the water separated from the organic sludge and the hydrophilic solvent, and the gas-liquid mixed fluid is gas-liquid separated in an uncooled condition in the gas - liquid separation step. The primary treatment liquid is collected, the primary treatment gas generated in the gas-liquid separation step is condensed in the condensation step, the secondary treatment liquid is collected, and the secondary treatment gas generated in the condensation step is dissolved in the dissolution process at room temperature water . The liquid is brought into contact with gas and liquid to recover the tertiary treatment liquid, and the primary treatment liquid, the secondary treatment liquid, and the tertiary treatment liquid are purified in a distillation column in the regeneration step to recover the hydrophilic solvent.

In the solvent recovery method of the present invention, in the regeneration step, the primary treatment liquid, the secondary treatment liquid, and the tertiary treatment liquid are supplied to different temperature ranges in the distillation tower according to the respective solvent concentrations, and a treatment liquid having a low solvent concentration is supplied. It supplies to the high temperature side of the lower part of a distillation column, and supplies the process liquid with a high solvent concentration to the low temperature side of the upper part of a distillation column .
In the solvent recovery method of the present invention, in the condensing step, the primary process gas is condensed using the normal temperature water as the cooling medium in the former stage condenser, and the primary process gas is condensed using the cooling water as the cooling medium in the latter stage condenser. And

In the solvent recovery method of the present invention, the normal temperature water is sewage treated water produced in a sewage treatment facility, and the organic sludge is a dehydrated cake produced in the sewage treatment facility.
In the solvent recovery method of the present invention, the dehydration step is performed before the gas-liquid separation step, and in the dehydration step, the solid-liquid mixture of the hydrophilic solvent and the organic sludge is dehydrated with a heated filter press, and the dehydrated filtrate from the organic sludge. The filtrate-containing absorption liquid desorbed as is recovered as a gas-liquid mixed fluid.

The solvent recovery method of the present invention is characterized in that warm water used for pressurization by a warming filter press is used for the regeneration step .

The dehydration system of the present invention includes a dehydrator for dehydrating a solid-liquid mixture of a hydrophilic solvent and organic sludge with a heating filter press to desorb a dehydrated filtrate composed of a gas-liquid mixed fluid, and a non- gas-liquid mixed fluid. A gas-liquid separator device that recovers a primary processing liquid by gas-liquid separation under cooling conditions, a condenser device that condenses the primary processing gas discharged from the gas-liquid separator device and recovers a secondary processing liquid, and a condenser The secondary treatment gas discharged from the equipment can be brought into contact with the normal temperature water of the dissolution liquid to recover the tertiary treatment liquid, and the primary treatment liquid, secondary treatment liquid, and tertiary treatment liquid can be supplied to different stages. Equipped with a simple distillation tower device,
The hydrophilic solvent functions as an absorbing liquid that absorbs water in the organic sludge and has a boiling point lower than that of water, and the dehydrated filtrate contains water separated from the organic sludge and the hydrophilic solvent. It is characterized by that.

  In the dehydration system of the present invention, the condenser device includes a first stage condenser that condenses the primary process gas using normal temperature water as a cooling medium, and a second stage that condenses the primary process gas that passes through the first stage condenser using cooling water as a cooling medium. It is characterized by having a condenser.

  As described above, according to the present invention, in the gas-liquid separation step, the gas-liquid mixed fluid is supplied into the tank in which the filtrate-containing absorbent is stored, and the gas-phase solvent is gas-liquid mixed in an uncooled natural state. By separating the fluid from the fluid, the filtrate-containing absorbing solution whose solvent concentration is lowered by promoting the volatilization of the solvent as compared with the conventional case involving cooling is taken out as the primary treatment liquid without energy consumption required for cooling.

  In the condensation step, the primary treatment gas with a small amount of impurities separated in the gas-liquid separation step is condensed, so that a secondary treatment liquid having a high solvent concentration is obtained while suppressing energy consumption. In the dissolving step, the secondary processing gas that has undergone the condensation step is dissolved in the dissolving solution by gas-liquid contact under an uncooled natural state, so that a tertiary processing solution having a low solvent concentration is obtained without energy consumption. Therefore, by collecting the solvent in the gas-liquid separation process, condensation process, and dissolution process, the energy consumption required for solvent recovery can be reduced, and the supply temperature of the processing liquid supplied to the distillation tower can be increased. Energy consumption for heating in the distillation tower can be reduced.

  In the regeneration process, the primary treatment liquid, the secondary treatment liquid, and the tertiary treatment liquid are supplied to different temperature ranges in the distillation tower according to the respective solvent concentrations, and the treatment liquid having a low solvent concentration is supplied to the high temperature in the lower part of the distillation tower. By supplying to the side and supplying the processing liquid having a high solvent concentration to the lower temperature side of the upper part in the distillation column, the amount of heating required for distillation can be reduced by suppressing the ring flow rate in the distillation column.

  In the condensing step, the primary processing gas is condensed using the normal temperature water as the cooling medium in the former stage condenser, and the primary processing gas is condensed using the cooling water as the cooling medium in the latter stage condenser, thereby cooling the condenser used in the latter stage. The required amount of water can be reduced, and the energy consumption required for the production can be suppressed.

The schematic diagram which shows the absorption dehydration apparatus in embodiment of this invention Schematic showing the solvent recovery device in the same embodiment Schematic diagram showing the distillation tower in the same embodiment Graph showing the relationship between the vapor-liquid equilibrium line of methanol-water mixture and the boiling point of the mixture The schematic diagram which shows the solvent collection | recovery apparatus in other embodiment of this invention. Schematic diagram showing the distillation tower in the same embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, organic sludge 101 is generated from a sewage treatment plant, a water purification plant, a factory wastewater treatment facility, and the like, and here is a dehydrated cake.

  The absorption liquid 103 used in the absorption dehydration apparatus 102 is a hydrophilic solvent. Here, an alcoholic solvent that is liquid at normal temperature such as methanol or ethanol is used as the hydrophilic solvent.

  The absorption dehydration apparatus 102 has a circulation system that goes around the absorption liquid storage tank 104, the stirring tank 105, the dehydration apparatus 106, the solvent recovery apparatus 107, and the solvent regeneration apparatus 108, and the absorption liquid 103 circulates in the circulation system. .

The absorption liquid storage tank 104 stores the absorption liquid 103, and adjusts the concentration of the solvent by adding a new solvent or dilution water as necessary.
The agitation tank 105 forms an agitation unit that agitates and mixes the absorbing liquid 103 supplied from the absorbing liquid storage tank 104 and the organic sludge 101 with a rotating agitating blade, and takes charge of the agitation process of making the organic sludge 101 into a solid-liquid mixed phase mixture. It promotes the contact between the water contained in the organic sludge 101 and the solvent of the absorbing liquid 103.

  The dehydrator 106 is responsible for a dehydration step of dehydrating the solid-liquid mixture in the stirring tank 105, and here, a heating filter press is used. The warming filter press warms the filter plate with hot water of about 90 ° C., raises the temperature of the solid-liquid mixture in the filter cloth disposed in the filter chamber between the filter plates to 65 to 78 ° C. or higher, and The dehydration process dehydrates the filtrate-containing absorption liquid 1 as a dehydrated filtrate by dehydrating the pressure. The filtrate-containing absorption liquid 1 is a gas-liquid mixed fluid containing the moisture of the organic sludge 101, the liquid phase of the absorption liquid 103, and the organic solvent in the gas phase.

The solvent regeneration device 108 is responsible for a regeneration step of regenerating the absorbent 103 by separating moisture from the filtrate-containing absorbent of the solvent recovery device 107, and here comprises a distillation column 7 described later.
The dehydration system of the present invention is composed of at least a dehydration device 106, a solvent recovery device 107, and a solvent regeneration device 108, and the entire absorption dehydration device 102 including the absorption liquid storage tank 104 and the agitation tank 105 can be used as a dehydration system. It is.

  As shown in FIGS. 2 and 3, the solvent recovery device 107 supplies the filtrate-containing absorption liquid as the gas-liquid mixed fluid 1 to the gas-liquid separator device 2. The gas-liquid separator device 2 is composed of a sealed filtrate tank. The gas-liquid mixed fluid 1 having a predetermined temperature recovered by the absorption dehydration device is gas-liquid separated in an uncooled natural state, and the gas phase solvent is removed. The primary treatment liquid 21 is recovered by being separated from the liquid mixture fluid. For this reason, the energy consumption required for cooling is not accompanied, and the volatilization of the solvent is promoted by utilizing the heat at a predetermined temperature given by the absorption dehydration apparatus. Therefore, the solvent concentration is lower than in the conventional case involving cooling. The resulting filtrate-containing absorption liquid can be taken out as a primary treatment liquid, and the heat given by the absorption dehydration apparatus can be used in a regeneration process in a subsequent process.

  Next, the primary process gas 22 volatilized in the gas-liquid separator device 2 is supplied to the condenser device 3. In the condenser device 3, the primary processing gas 22 with a small amount of impurities separated by the gas-liquid separator device 2 is condensed, so that a secondary processing liquid 41 having a high solvent concentration can be obtained while suppressing energy consumption. . In the present embodiment, the condenser device 3 includes a plurality of condensers 31 and 32. The pre-stage condenser 31 condenses the primary process gas 22 using normal temperature water, that is, water in a natural state where energy is intentionally consumed and not cooled, as a cooling medium. Here, sewage treated water having a predetermined temperature (generally about 15 ° C.) generated in a sewage treatment facility is used as room temperature water.

  The latter-stage condenser 32 condenses the primary processing gas 22 by using cooling water, that is, cooling water intentionally consumed at a temperature lower than the above-described normal temperature water as a cooling medium. Here, as the cooling water, cooling water that is forcibly cooled to a predetermined low temperature (about 5 ° C.) by a cold water production apparatus (such as a chiller unit) is used.

  Therefore, by cooling as much as possible with the sewage treated water that is room temperature water at a predetermined temperature in the front-stage condenser 31, the cooling energy used in the rear-stage condenser 32, that is, the required amount of cooling water is reduced, or the cooling water By increasing the required temperature, the energy consumption required for the production can be suppressed. As shown in FIG. 5, the condenser device 3 can be constituted by a single condenser.

  The secondary process gas 42 discharged from the condenser device 3 is supplied to the dissolution and recovery device 5. In the dissolution and recovery device 5, the secondary treatment gas 42 discharged from the condenser device 3 is brought into gas-liquid contact with a dissolution liquid, here, room temperature water, and the tertiary treatment liquid 51 is recovered. Sewage treated water can also be used for this room temperature water. The treated sewage water is less subject to seasonal fluctuations in water temperature than water, etc., and even in the summer, the temperature rise is less than that in the water, and the reduction in solvent recovery rate can be suppressed. The tertiary processing gas 52 discharged from the dissolution and recovery device 5 is discharged out of the system such as a processing facility by the fan device 6.

  Therefore, it is divided into the gas-liquid separator device (gas-liquid separation step) 2, the condenser device (condensation step) 3, and the dissolution and recovery device (dissolution step) 5, and by recovering the solvent without excessively lowering the temperature. The energy consumption required for the recovery of the solvent can be reduced, and the consumption energy for heating in the distillation column 7 can be reduced by increasing the supply temperature of the treatment liquid supplied to the distillation column 7.

  In the dissolution and recovery apparatus 5, the water temperature of the dissolution liquid is preferably 15 ° C. or lower, and the solvent recovery rate is somewhat improved when cooling is performed. However, if the amount of increase in the solvent obtained by cooling in the dissolution and recovery apparatus 5 is compared with the energy required to heat the cooled solvent to a predetermined temperature in the distillation column 7, it is better not to cool as a whole. .

  Further, in the dissolution and recovery apparatus 5, there is a case where the solvent is condensed and generates heat when dissolved in water. However, in the present embodiment, since the condenser device 3 for cooling with cooling water is provided in the pre-process of the dissolution and recovery device 5, the gas phase solvent is introduced into the dissolution and recovery device 5 in a cooled state. Therefore, the temperature rise in the dissolution recovery device 5 can be suppressed.

  In the distillation column 7, the vapor 8 is distilled as a heat source for indirect heating to purify the solvent. In the present embodiment, the distillation column 7 is of a multistage type, and the primary treatment liquid 21, the secondary treatment liquid 41, and the tertiary treatment liquid 51 are mixed in different temperature ranges (different stages) of the distillation tower 7 according to the respective solvent concentrations. However, as shown in FIG. 6, the primary treatment liquid 21, the secondary treatment liquid 41, and the tertiary treatment liquid 51 may be collected and supplied to one place of the distillation column 7 at a temperature corresponding to the solvent concentration. Is possible.

In the present embodiment, a treatment liquid having a low solvent concentration is supplied to the high temperature side of the lower part of the distillation column 7, and a treatment liquid having a high solvent concentration is supplied to the low temperature side of the upper part of the distillation column 7.
That is, the tertiary treatment liquid 51 having a solvent concentration of 20-30% is supplied to the first supply position 71 at about 80 ° C. in the lower part of the distillation column 7, and the primary treatment liquid 41 having a solvent concentration of 35-45% is the first treatment position 41. The second treatment liquid 41 having a solvent concentration of 70-80% is supplied to the second supply position 72 at about 76 ° C. above the first supply position 71, and the third supply at about 68 ° C. above the second supply position 72 is supplied. Supply to position 73.

  As shown in FIG. 4, the boiling point of the mixture of methanol and water, which is the solvent in the present embodiment, is about 80 ° C. when the solvent concentration is 20-30%, and about 76 ° C. when the solvent concentration is 35-45%. The solvent concentration is about 70 to 80% and about 68 ° C. Therefore, in the present embodiment, the primary treatment liquid 21, the secondary treatment liquid 41, and the tertiary treatment liquid 51 are supplied to a temperature range corresponding to the boiling point according to each solvent concentration.

  For this reason, the required heating amount required for distillation can be reduced by suppressing the ring flow rate of the treatment liquid in the distillation column 7. The solvent concentration of the distillate 9 exiting from the top of the distillation column 7 is increased, and the solvent concentration of the bottoms 10 exiting from the bottom of the distillation column 7 is reduced, thereby increasing the separation efficiency in the distillation column 7. .

  In addition, the primary treatment liquid 21 with a large amount of contaminants having a solvent concentration of 35 to 45% is not cooled in the filtrate tank of the gas-liquid separator device 2, or the cooling water and the sewage treatment water are used. Thus, the solvent concentration is lower than that in the case where the solvent is actively cooled as in the prior art. For this reason, the supply position in the distillation column 7 is lower than that in the prior art, the range in which impurities are deposited and deposited inside the distillation column 7 is reduced, and deterioration of the solvent separation efficiency is suppressed. The hot water used in the heating filter press is used for heating the distillation column 7 and steam production, or the waste heat from the distillation column 7 is supplied to the absorption dehydrator and used for the production of hot water. Use efficiency increases. Further, the bottoms 10 of the distillation column 7 is discharged out of the system by sewage discharge or the like.

  In the present invention, as shown in FIG. 5, the gas-liquid separator device 2 can be cooled with room temperature water, and sewage treated water at a predetermined temperature (generally about 15 ° C.) generated at room temperature water in a sewage treatment facility. Can also be used.

  By using sewage treated water, the energy for producing cooling water can be reduced as in the prior art, and the temperature of the filtrate tank liquid is not lowered too much, and the amount of heat required for heating in the distillation tower 7 can also be reduced. Furthermore, the cooling water used for cooling the condenser device 3 can be reused for cooling the gas-liquid separator device 2. By reusing the cooling water in this way, the energy for producing the cooling water as in the conventional case can be reduced as in the case of using the sewage treated water.

  In the present embodiment, the use of sewage treated water as room temperature water has been described. However, water that has a temperature necessary for solvent recovery and that does not consume energy and is not cooled can be used. For example, well water or river water Cooling drainage after use for cooling can be used.

DESCRIPTION OF SYMBOLS 1 Gas-liquid mixed fluid 2 Gas-liquid separator apparatus 3 Condenser apparatus 5 Dissolution recovery apparatus 6 Fan apparatus 7 Distillation tower 8 Steam 9 Distillate 10 Bottom liquid 21 Primary process liquid 22 Primary process gas 31, 32 Condenser 41 2 Next treatment liquid 42 Secondary treatment gas 51 Tertiary treatment liquid 52 Tertiary treatment gas 71 First supply position 72 Second supply position 73 Third supply position 101 Organic sludge 102 Absorption dehydrator 103 Absorption liquid 104 Absorption liquid storage tank 105 Stirring tank 106 Dehydrator 107 Solvent recovery unit 108 Solvent regenerator

Claims (8)

A gas-liquid mixed fluid that functions as an absorbing liquid that absorbs moisture in organic sludge and has a boiling point lower than that of water, and that separates from the solid-liquid mixture of the hydrophilic solvent and organic sludge is the organic solvent. The primary treatment gas containing the water separated from the sludge and the hydrophilic solvent, and recovering the primary treatment liquid by separating the gas-liquid mixed fluid under a non-cooled condition in the gas-liquid separation step and recovering the primary treatment liquid. In the condensation step, the secondary treatment liquid is recovered, and the secondary treatment gas generated in the condensation step is brought into gas-liquid contact with the room temperature water of the dissolution liquid in the dissolution step to recover the tertiary treatment solution, A solvent recovery method, comprising purifying a secondary treatment liquid and a tertiary treatment liquid in a distillation column in a regeneration step to recover a hydrophilic solvent. In the regeneration step, the primary treatment liquid, the secondary treatment liquid, and the tertiary treatment liquid are supplied to different temperature ranges in the distillation tower according to the respective solvent concentrations, and the treatment liquid having a low solvent concentration is supplied to the high temperature side at the lower part of the distillation tower. The solvent recovery method according to claim 1, wherein a treatment liquid having a high solvent concentration is supplied to the low temperature side of the upper part of the distillation column .   In the condensation step, the primary process gas is condensed using normal temperature water as a cooling medium in the former stage condenser, and the primary process gas is condensed using the cooling water as a cooling medium in the latter stage condenser. The solvent recovery method as described.   The solvent recovery method according to claim 3, wherein the room temperature water is sewage treated water generated in a sewage treatment facility, and the organic sludge is a dehydrated cake generated in the sewage treatment facility.   A dehydration step is performed before the gas-liquid separation step, and in the dehydration step, the solid-liquid mixture of the hydrophilic solvent and organic sludge is dehydrated with a heated filter press and desorbed from the organic sludge as a dehydrated filtrate. The solvent recovery method according to any one of claims 1 to 4, wherein the solvent is recovered as a gas-liquid mixed fluid.   6. The solvent recovery method according to claim 5, wherein warm water used for pressurization by a heating filter press is used for the regeneration step. A dehydration device that dehydrates a solid-liquid mixture of a hydrophilic solvent and organic sludge with a heated filter press and desorbs the dehydrated filtrate consisting of a gas-liquid mixed fluid, and gas-liquid separation of the gas - liquid mixed fluid under non-cooling conditions A gas-liquid separator device for collecting the primary treatment liquid, a condenser device for condensing the primary treatment gas discharged from the gas-liquid separator device and collecting the secondary treatment liquid, and a secondary treatment discharging from the condenser device A dissolution and recovery device that recovers the tertiary treatment liquid by bringing the gas into gas-liquid contact with normal temperature water of the dissolution liquid, and a distillation tower device that can supply the primary treatment liquid, the secondary treatment liquid, and the tertiary treatment liquid to different stages,
The hydrophilic solvent functions as an absorbing liquid that absorbs water in the organic sludge and has a boiling point lower than that of water, and the dehydrated filtrate contains water separated from the organic sludge and the hydrophilic solvent. A dehydration system characterized by that.   The condenser device has a first-stage condenser that condenses the primary processing gas using normal temperature water as a cooling medium, and a second-stage condenser that condenses the first processing gas that passes through the first-stage condenser using cooling water as a cooling medium. 8. The dehydration system according to claim 7, characterized in that

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