JP7032319B2 - How to use recompressed steam and plant - Google Patents

Description

The present invention relates to a method of efficiently utilizing the recompressed steam obtained by adiabatic compression of the steam in a process involving generation of steam as a heat source, and a plant using this method.

In a chemical process involving the generation of steam (for example, reaction of chemical substances, separation of a mixture, etc.), the amount of heat of the generated process steam is effectively utilized as a heat source in order to reduce the amount of energy required in the entire process or the running cost. A method has been proposed. For example, steam re-compression (VRC) that raises the temperature by adiabatic compression of process steam and uses the heat of the compression process steam (recompressed steam) as a heat source in processes such as evaporation, distillation, and drying. ) Methods such as methods are being studied.

For example, International Publication No. 2015/033935 (Patent Document 1) is provided with a circulation process for returning gas components such as uncondensed recompressed steam existing downstream of the compressor to the main process in the VRC method. , A method of utilizing process steam while preventing damage to equipment such as a compressor is disclosed. In this method, it is described that the process steam can be used safely and easily because the retention of the gas component in the downstream of the compressor can be suppressed by the circulation step.

However, this method may not be able to be smoothly recompressed depending on the operating conditions of the plant, the energy saving effect is not sufficient, and the degree of freedom in process design (or application of the VRC method) is limited. In addition, regarding the degree of freedom in process design, if VRC type equipment is newly added to the existing plant where other heat source utilization equipment is installed, the amount of process steam required for stable operation of both equipment can be obtained. In some cases, it could not be secured.

International Publication No. 2015/03393 (Claims, paragraphs [0005] [0009], Examples, FIGS. 1, 2 and 4)

Therefore, an object of the present invention is to provide a method of efficiently using process steam (recompressed steam) heated by adiabatic compression as a heat source, and a plant using this method.

Another object of the present invention is to provide a method for stably (or smoothly) operating a plant equipped with a VRC method using recompressed steam, and a plant thereof.

Still another object of the present invention is to provide a method of utilizing recompressed steam having excellent process design flexibility, and a plant using the method.

Another object of the present invention is to provide a method capable of operating other heat source utilization processes in parallel even if many process steams are utilized in the VRC method, and a plant using this method.

As a result of diligent studies to achieve the above problems, the present inventors generate a process vapor containing a condensable gas component, and recover the condensable gas component of the generated process vapor as a condensate. A re-condensation process in which at least a part of the process steam is adiabatically compressed by a compressor to raise the temperature to obtain re-condensed steam, a heat exchange process using the re-condensed steam as a heat source, and a re-condensation process. In the method of using the recompressed steam including the circulation step of returning the non-condensed component of the compressed steam to the main step, the condensed liquid condensed in the heat exchange step is retained without being forcibly cooled or rapidly cooled. Therefore, if the pressure in the back pressure space downstream of the compressor is maintained (or the decrease in back pressure is suppressed (or prevented)), not only the recondensed steam can be used more efficiently, but also the process (or plant) becomes more stable. The present invention has been completed by finding that it can be operated (or smoothly) (or smoothly).

That is, the method of utilizing the recompressed vapor of the present invention includes a main step of generating a process vapor containing a condensable gas component and recovering the condensable gas component of the generated process vapor as a condensate, and at least the above-mentioned process vapor. Of the re-condensation process in which a part is adiabatically compressed with a compressor to raise the temperature to obtain re-condensed steam, the heat exchange process using the re-condensed steam as a heat source, and the re-condensed steam used in the heat exchange process. It is a method of using recompressed steam including a circulation step of returning uncondensed non-condensed components to the main step, in which the condensed liquid condensed in the heat exchange step is retained to form a back pressure space downstream of the compressor. It includes at least a holding step to hold the pressure.

The condensed liquid may be retained in the hold step on the upstream side of the hold step without being forcibly cooled. Further, in the steps after the heat exchange step, the generated condensed liquid may be kept warm or heated, and the temperature of the condensed liquid retained in the hold step is the outlet (or the heat exchange unit outlet side) of the heat exchange step. It may be about (T-50) ° C. to (T + 20) ° C. with respect to the temperature T in. The condensed liquid may be retained in the holding step for about 0.5 minutes to 10 hours by adjusting the outflow amount. In the hold step, the condensed liquid and the non-condensed component may be gas-liquid separated.

The method of the present invention may further include a cooling step of cooling the condensate flowing out of the hold step. Further, the method of the present invention is a gas introduction step of introducing a non-condensable gas into the back pressure space downstream of the compressor, and a degassing of the dissolved non-condensable gas from the condensate flowing out in the hold step. It may include a gas process. Further, the method of the present invention may include a flash step of flash-evaporating the condensed liquid flowing out in the hold step to separate the volatile component and the non-volatile component. At least a part of the volatile components separated in this flash step may be used as a heat source for another process.

Further, the present invention includes a steam generator that generates process steam containing a condensable gas component, a main unit having a condenser for cooling and condensing a part of the generated process steam, and the balance of the process steam. Of the steam recompression unit for adiabatic compression and raising the temperature to obtain recompressed steam, the heat exchange unit for using the recompressed steam as a heat source, and the recompressed steam provided to the heat exchange unit. A recompressed steam utilization plant equipped with a circulation line for returning uncondensed non-condensed components to the main unit, where the condensed liquid in the heat exchange unit is retained and downstream of the steam recompression unit. It also includes a recompressed steam utilization plant equipped with at least a hold unit for holding the pressure in the back pressure space.

The plant may be provided with a hold tank for forcibly cooling the condensed liquid on the upstream side of the hold unit, without providing a cooling unit for forcibly cooling the condensed liquid. At least a part of the unit and the line forming the back pressure space downstream of the steam recompression unit may be kept warm or heated, and the temperature of the condensed liquid in which the hold unit stays is the temperature at the outlet side of the heat exchange unit. It may be kept at about (T-50) ° C. to (T + 20) ° C. with respect to T. The hold unit may have a flow rate control device for adjusting the outflow amount of the condensed liquid and allowing the condensed liquid to stay for about 0.5 minutes to 10 hours.

The hold unit has a gas-liquid separation function, and is a hold tank for retaining the condensed liquid, and the gas phase portion in the hold tank and the back pressure space downstream of the steam recompression unit from the hold tank. May also have an airing line for connecting to the vapor phase space on the upstream side. In addition, the hold unit steam recompresses the hold tank for retaining the condensed liquid, the gas-liquid separator disposed on the upstream side of the hold tank, and the gas component separated by this gas-liquid separator. Of the back pressure space downstream of the unit, it may have an airing line for returning to the gas phase space upstream of the gas-liquid separator.

The plant of the present invention may further include a cooling unit for cooling the condensate flowing out of the hold unit. Further, in the plant of the present invention, the gas introduction unit for introducing the non-condensable gas into the back pressure space downstream of the steam recompression unit and the non-condensable gas dissolved in the condensate flowing out from the hold unit are removed. It may be equipped with a degassing unit for care. Further, the plant of the present invention may include a flash unit that flash-evaporates the condensed liquid flowing out from the hold unit to separate it into a volatile component and a non-volatile component. The plant may be provided with a line for utilizing at least a part of the volatile components separated by the flash unit as a heat source for another process.

In the present specification and claims, "process steam" means steam generated in a manufacturing process (process) in which a unit operation accompanied by a phase change of gas and liquid is incorporated.

The "recompressed steam" means a process steam that has been compressed and raised in temperature for use as a heat source in the steam recompression method (VRC method).

"Back pressure space" means all spaces and lines (including airing lines) to which (or transmit) the discharge pressure of the compressor in the VRC method (VRC process).

The "non-condensable gas" means a gas capable of maintaining a gas state under temperature and pressure in the back pressure space downstream of the compressor.

The term "non-condensable component" is used in the VRC method (VRC process) to mean that both the non-condensed gas component and the non-condensable gas component are included in the condensable gas component.

The "volatile component" means a gas (or volatile) component evaporated by the flash evaporation of the condensate in the flash process, and the "nonvolatile component" does not evaporate by the flash evaporation of the condensate in the flash process. Means a liquid (or low volatility) component.

In the present invention, the condensed liquid condensed in the heat exchange step is retained to maintain the pressure in the back pressure space downstream of the compressor (or suppress the pressure drop), so that the process steam (recompressed steam) is used as a heat source for efficiency. Not only can the energy saving effect be improved, but also the plant equipped with the VRC method can be operated stably (or smoothly). In addition, it is easy to handle plants with large fluctuations in processing volume and operating conditions, and it has excellent process design flexibility. Further, by introducing the non-condensable gas, the stability (or smoothness) of the plant operation provided with the VRC method and the flexibility of the process design can be further improved. Further, the volatile components generated by the flash evaporation of the condensed liquid discharged (or outflowed) from the VRC process can be used for other heat source utilization processes. Therefore, even if a large amount of process steam is used in the VRC method, other heat source utilization processes can be operated smoothly and safely in parallel, and the flexibility of process design and the energy saving effect can be further improved.

FIG. 1 is a process flow diagram for explaining a method of using the recompressed steam of the present invention and an example of a plant (apparatus). FIG. 2 is a process flow diagram for explaining a method of using the recompressed steam of the present invention and another example of a plant (equipment). FIG. 3 is a process flow diagram for explaining a method of using the recompressed steam of the present invention and still another example of the plant (equipment). FIG. 4 is a process flow diagram for explaining a method of using the recompressed steam of the present invention and another example of the plant (apparatus). FIG. 5 is a process flow diagram for explaining a method of using the recompressed steam of Example 1 and a plant (apparatus). FIG. 6 is a process flow diagram for explaining a method of using the recompressed steam of Comparative Example 1 and a plant (apparatus). FIG. 7 is a process flow diagram for explaining a method of using the recompressed steam of Example 2 and a plant (apparatus). FIG. 8 is a process flow diagram for explaining a method of using the recompressed steam of Reference Example 1 and a plant (equipment).

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings as necessary.

In the example of FIG. 1, the recompressed steam utilization plant is provided with a distillation column 1 as a process steam generator for discharging the process steam containing a condensable gas component, and the process steam is discharged from the distillation column 1. The discharge line is branched at the piping branch point 4. A first condenser 2 and a second condenser 3 for cooling and condensing a part of the process steam discharged from the distillation column 1 are arranged on one of the branched lines, and the condensability in the process steam is arranged. The gas component (condensable component) is cooled by the condensers 2 and 3 and recovered as a condensate. The main unit includes the distillation column 1, a first condenser 2, and a second condenser 3.

Further, in the other branched line, the balance of the process steam is adiabatically compressed and the temperature is raised via the line in which the flow control valves (or valves) 15 and 17 as the flow control unit are arranged. A compressor 5 as a steam recompressor unit for obtaining recompressed steam (for example, a turbo type compressor), a heat exchanger 7 as a heat exchange unit for using the recompressed steam as a heat source, and heat exchange. A hold tank (or storage tank) 8 is provided as a hold unit for separating the process fluid that has passed through the vessel 7 into gas and liquid and retaining the separated condensate (or condensate component).

The gas component (or non-condensed component) separated by the hold tank 8 passes from the air ring line (or pressure equalizing tube) 9a of the heat exchanger 7 via the airing line (or pressure equalizing tube) 8a of the hold tank 8. It merges with the gas of the above and is returned to the main unit by the first circulation line 9 provided with the flow rate control valve 11 as the flow rate control device. The first circulation line 9 is connected to the line between the first capacitor 2 and the second capacitor 3 via a connection portion (or a pipe connection portion) 10, and passes through the first capacitor 2. It is merged with the resulting process fluid (process vapor and / or condensate), and the condensate is recovered via the second condenser 3.

On the other hand, the condensate retained in the hold tank 8 is discharged (or outflowed) from a line (condensate discharge line or condensate outflow line) provided with the flow control valve 13 as a flow control device, and is condensed as a cooling unit. It is cooled by the liquid cooler 18 and recovered together with the condensed liquid that has passed through the second condenser 3 in the main unit.

Further, the (turbo type) compressor 5 is provided with a second circulation line 6 connecting a line on the inlet side and a line on the outlet side of the compressor, and a flow rate control valve 12 as a flow rate control device. ing. The second circulation line 6 is connected to the line between the flow control valves 15 and 17 in the line on the inlet side of the compressor.

The method or plant of the present invention includes a distillation column 1, a first compressor 2, and a second compressor 3 if necessary, and generates process steam containing a condensable gas component, which is cooled and condensed. A VRC that includes a main process (main process), a compressor 5, a heat exchanger 7, and a hold tank 8 and adiabatically compresses the process steam with a compressor to generate recompressed steam whose temperature has been raised and uses it as a heat source. It has a process (VRC process). Further, also in the present specification and FIGS. 2 to 8, the same components as those in FIG. 1 are assigned the same numbers.

In a plant (equipment) having such a configuration, before the start of the VRC process, it is operated only in the main process. That is, the flow control valve 15 is closed, and the process steam discharged from the distillation column 1 is cooled and condensed by the first condenser 2 and the second condenser 3 in the entire amount of the condensable gas component (condensable component). , Is recovered as a condensate.

Next, the flow rate control valves 11, 12 and 17 are fully opened, and the flow rate control valve 15 is gradually opened with the flow rate control valve 13 closed to adjust the opening to a predetermined value. At this time, a part of the process steam discharged from the distillation column 1 is replaced with the seal gas of the line in the VRC process through the branch point 4 of the discharge line in the main process, and the process steam in the system of the VRC process is also used. The temperature rises. After that, the flow rate control valve 17 is adjusted to a predetermined opening degree (for example, when the discharge pressure of the turbo type compressor 5 becomes too low, the opening degree of the flow rate control valve 11 and / or 12 is necessary. After adjusting the amount of process steam introduced into the compressor (adjusting in the direction of reducing the flow rate), the turbo type compressor 5 is started and stabilized at the rated rotation speed. At this point, almost no discharge pressure is applied to the process steam passing through the turbo type compressor 5, but the process in which the heat of the compressor shaft power × mechanical efficiency × (1-insulation efficiency) passes through the compressor. The heat transfer to the steam causes a temperature rise. When the flow control valve 12 is in the open state, it is closed so that the process steam flowing through the VRC process basically passes through the compressor only once. Therefore, the temperature rise is only heat transfer from the compressor, and the temperature rise range is small. Since the temperature difference between the process steam that has passed through the turbo compressor 5 and the boiling point of the internal process of the heat exchanger 7 is not sufficient, heat transfer is insufficient and condensation does not occur much. Therefore, most of the process steam (condensable gas component in the process steam) is returned to the pipe connection portion 10 of the main process by the first circulation line 9 in an uncondensed state, and is recovered by cooling condensation.

In this way, since the uncondensed steam can be returned to the main process by the first circulation line in the VRC process, it is possible to suppress the retention of process steam due to poor heat transfer in the heat exchange unit, and it is possible to suppress the retention of process steam in the compressor. It is possible to prevent damage to the compressor due to stagnation of gas flow.

The flow rate control valve 13 may be opened at an appropriate opening degree and / or frequency after confirming the liquid level of the condensed liquid in the hold tank 8, and the condensed liquid may be sent to a subsequent step. Further, in a plant equipped with a turbo compressor, the second circulation line 6 may be used to secure a circulation flow rate in order to avoid surging in an emergency in addition to controlling the circulation method of process steam. good.

Next, when the flow control valve 11 is gradually closed and the discharge pressure of the compressor 5 is gradually increased, the temperature of the compressed process steam (recompressed steam) rises, so that the heat exchange step (or heat exchange unit) (Heat exchanger 7)), it can be effectively used as a heat source. In order to maintain a predetermined pressure (or back pressure on the downstream side of the compressor) and temperature, the compression ratio in the compressor 5 is controlled by adjusting the opening degree of the flow control valve 11.

However, such control by adjusting the opening degree of the flow rate control valve 11 is not yet sufficient to effectively exert the effect of the VRC method. For example, in the VRC process, from the condensation of recompressed steam (condensable gas component) in the heat exchange process, etc., and from the non-condensable gas (for example, the bearing of the compressor) to the condensate (condensate of the condensable gas component). Decrease in pressure (or back pressure on the downstream side of the compressor) (or stagnation of pressure rise) due to dissolution of seal gas leaking into the process, etc., and accompanying decrease in temperature (or stagnation of temperature rise) ) Occurs. Even if such a situation is dealt with only by adjusting the opening degree of the flow rate control valve 11, the predetermined pressure may not be maintained (or maintained). In order to maintain a predetermined pressure, it is necessary to limit the amount of condensation of the condensable gas component in the heat exchange step (or the amount of raw material charged in the heat exchanger (VRC evaporator)). Therefore, it is not easy to control the pressure on the downstream side of the compressor, and the energy saving effect is reduced. In addition, the plant (or recompression) equipped with the VRC method due to the decrease in pressure (or the stagnation of pressure increase), that is, the state in which the compressor is idle (the state in which air is simply blown without compression). The unit (or process) may not operate smoothly, and the original function (or operation) of the energy-saving plant may stop.

In order to cope with such a situation, in the method or plant of the present invention, the condensed liquid condensed in the heat exchange step (or heat exchange unit (heat exchanger 7)) is not forcibly cooled or rapidly cooled (predetermined). Hold at least to retain pressure in the back pressure space downstream of the compressor (or steam recompression unit (compressor 5)) in the recompression step by accumulating (while preserving the temperature and / or steam pressure of). It comprises a step (or a hold unit having a hold tank 8). The condensed liquid retained in the hold step (or hold unit) is the condensed liquid from the heat exchange step (or heat exchange unit), and is in a relatively high temperature state (for example, a temperature close to the boiling point of the condensed liquid in the back pressure space). By utilizing the high vapor pressure (or saturated vapor pressure) of this condensed liquid, the pressure in the back pressure space can be effectively maintained (or the decrease is suppressed). Since such a hold step (or hold unit) is included, the VRC method functions effectively even if a large amount of recompressed vapor is condensed (for example, the condensable gas component is completely condensed) in the heat exchange step (for example). Or plant) design becomes possible (or easy), and the energy saving effect can be further improved. Further, by this hold step (or hold unit), the pressure on the downstream side (back pressure space) of the compressor can be easily controlled, and the plant (or steam recompression unit (or recompression step)) equipped with the VRC method). Can be smoothly (or easily) operated (or operated, operated). Therefore, it is easy to apply to plants with large fluctuations in processing amount and operating conditions, and it is also excellent in process design flexibility.

In the present specification and the scope of the claim, the "back pressure space" is a space and a line from the downstream of the compressor to the flow rate control device, for example, from the downstream of the compressor via a heat exchange unit, a hold unit, and the like. The space and line leading to the flow rate control device arranged in each of the first circulation line and the condensate discharge line (or the condensate outflow line), and arranged in the second circulation line from the downstream of the compressor. It means the gas phase part of the space including the space and the line leading to the flow rate control device.

The amount of condensed liquid staying in the hold tank 8 is adjusted by the flow control valve 13 arranged in the condensed liquid discharge or outflow (extraction) line (condensate outflow line or condensed liquid extraction line). By doing so, it is controlled by maintaining a predetermined liquid level. By such control, the condensed liquid in the hold tank is extracted before it is cooled by heat dissipation, and new condensed liquid from the heat exchange unit is retained, so that the temperature drop of the retained condensed liquid can be effectively suppressed. Due to the high pressure in the back pressure space, the condensed liquid can flow out (or pressure-feed) smoothly (or stably) without using a liquid-feeding pump or the like. Since the discharged condensate has a high temperature (for example, a temperature higher than the boiling point of the condensate at atmospheric pressure), it is cooled by the cooler (or condensate cooler) 18 (or cooling step), and the second condenser 3 of the main unit 3 It is recovered together with the condensed liquid that has passed through. In the cooling step (or cooling unit (condensate cooler 18)), for example, by cooling the condensate to a temperature below the boiling point at atmospheric pressure (or normal pressure), the pressure is lower than the back pressure space (for example, about atmospheric pressure). ) Even if the condensed liquid flows out (or is discharged) into the space, it can be recovered stably (easily or smoothly) while preventing flash evaporation.

On the other hand, non-condensable gas such as uncondensed recompressed steam (non-condensed steam) and seal gas not dissolved in the process condensate is air connected to the hold tank 8 as a gas component (non-condensed component). It is returned to the main process via the first circulation line 9 via the ring line 8a and / or the air ring line 9a connected to the heat exchanger 7. The condensable gas component (non-condensed vapor) contained in the non-condensed component returned to the connection portion 10 is usually cooled and condensed by the second condenser 3 on the downstream side of the connection portion 10, but for some reason the compressor Even if it flows into the side (upstream side), it is cooled and condensed by the first condenser 2. Therefore, even if it merges with the process steam discharged from the distillation column 1, the gas flow rate does not become excessive with respect to the steps after the condensation step of the main process and the steam recompression step of the VRC process.

The hold unit may have a gas-liquid separator for separating a liquid component (condensate) and a gas or gas component (non-condensation component). In the process shown in FIG. 2, the hold unit transfers the process fluid from the heat exchanger 7 to the upstream side of the hold tank 8 in addition to the hold tank 8, the air ring line (or pressure equalizing pipe) 8a, and the flow control valve 13. A gas-liquid separator 19 for separating a gas component (non-condensed component) and a liquid component (condensed liquid), and an airing line 19a for returning the gas component separated by the gas-liquid separator 19 to the first circulation line 9. The process is the same as that of FIG. 1 except that the above is provided.

In the example of FIG. 2, since the gas-liquid separator 19 is provided on the upstream side of the hold tank 8, the process fluid (condensate) separated from the gas component (non-condensed component) can flow into the hold tank 8. be. Therefore, it is easy to more accurately control the amount of the condensed liquid introduced into the hold tank 8, and it is possible to more easily control the amount of the condensed liquid staying in the hold tank 8 and the staying time. In addition, since the line connecting the heat exchanger 7 and the hold tank 8 is long and the amount of condensation in the VRC evaporator is small, phenomena such as steam hammer can be effectively suppressed, so that the VRC process can be stabilized. You can drive.

The method (or plant) of the present invention may have a gas introduction step (or gas introduction unit) for introducing a non-condensable gas into the back pressure space, although it is not always necessary. In the process shown in FIG. 3, the gas introduction line 20 for introducing the non-condensable gas and its non-condensable gas on the upstream side (back pressure space side) of the flow control valve 11 in the first circulation line 9 (or the circulation step). A flow control valve 21 (gas introduction unit or gas introduction step) for adjusting the amount of condensable gas introduced is provided, and a non-dissolved non-condensate solution is provided on the downstream side of the condensate cooler 18 (cooling unit or cooling step). A condensate degassing tank (or degassing tank) 22 for degassing (vaporizing or separating) the condensable gas component from the condensate, and a gas discharge line 23 (degassing unit) for discharging the degassed non-condensable gas component. Alternatively, the process is the same as that shown in FIG. 1 except that the degassing step) is provided.

At the start of VRC process operation (or at the beginning of operation), when the unit and / or line forming the back pressure space such as the hold tank is cooled and the temperature is low, it is difficult for the hold unit to hold the pressure in the back pressure space. In some cases. Since the process shown in FIG. 3 includes a gas introduction unit (or a gas introduction step), even if a pressure drop (or a drop in the temperature of the condensed liquid) occurs in the back pressure space due to the above-mentioned abnormal situation. By introducing a non-condensable gas as an auxiliary, the pressure in the back pressure space can be effectively maintained. Therefore, the operability (or ease) of the pressure control in the back pressure space is improved, and the VRC process can be operated (or operated) more stably (or smoothly).

The non-condensable gas introduced into the back pressure space from the gas introduction line 20 is together with the recompressed steam (non-condensed steam) that was not condensed by the heat exchanger 7, the seal gas that was not dissolved in the process condensate, and the like. , Separated by the hold tank 8 as a gas component, via the air ring line 8a of the hold tank 8 and / or via the air ring line 9a of the heat exchanger 7, and via the first circulation line 9, the main unit (or main unit). It is returned to the process).

On the other hand, in the degassing unit (or degassing step), the condensed liquid from the condensed liquid cooler 18 stays in the condensed liquid degassing tank 22, so that the non-condensable gas dissolved in the condensed liquid under the pressure of the back pressure space. (For example, a gas introduced from a gas introduction unit, a non-condensable gas such as a seal gas leaking from a compressor bearing, etc.) is degassed (vaporized or separated) from the condensed liquid. The degassed gas component (non-condensable gas) is discharged from the abatement equipment (or discharge equipment) such as a scrubber, and the liquid component (condensate) is recovered together with the condensate of the main unit (or main process). To. Therefore, the non-condensable gas dissolved in the condensate does not revaporize and affect the recovery destination unit (or process).

Further, in the method (or plant) of the present invention, the calorific value of the condensed liquid flowing out from the hold unit may be utilized in the VRC process and / or other processes. The process shown in FIG. 4 is a flash tank (or flash evaporator) 24 (flash unit or) for flash evaporation of the condensate flowing out of the hold unit between the flow control valve 13 and the (condensate) cooler 18. It is equipped with a third circulation line 25 that returns the gas component (volatile component) generated by the flash process) and the flash evaporation to the main unit (or main process), and further, at least one of the process vapors generated in the main unit (or main process). It is the same as the process of FIG. 1 except that the unit is branched via the introduction line (or the air supply line) 26 and is provided with another unit (or another process) for use as a heat source in another process. .. The liquid component (nonvolatile component) separated by the flash unit (or the flash step) is recovered as a condensed liquid via the cooler 18.

In the process of FIG. 4, only the main process or both the main process and another process are operating (or operating) before the start of the VRC process. That is, the flow control valve 15 is closed, and at least a part of the process steam discharged from the distillation column 1 is condensed by the first condenser 2 and the second condenser 3. If another process is running, it is collected with the condensed liquid in another process.

When the VRC process is started in the same manner as in the process of FIG. 1, the condensed liquid flowing out from the flow control valve 13 (hold unit or hold step) is not cooled and has a lower pressure than the back pressure space (for example, a large pressure). The liquid is sent to the flash tank 24 (about the pressure), and the flash evaporates. The gas component (volatile component) generated by the flash evaporation is returned to the line between the distillation column 1 and the branch point 4 of the main unit (or the main step) via the third circulation line 25, and is flash evaporated. The non-volatile component produced by the above is recovered together with the condensate of the main unit (or the main step) via the condensate cooler 18 (cooling unit or cooling step).

The volatile components returned to the main unit (or main process) can be used as a heat source in the VRC process and / or another process together with the process steam. That is, the flash unit (or the flash process) is equipped with a complicated device or the like in order to make the sensible heat of the condensed liquid discharged (or outflow) in the VRC process reusable as latent heat of steam by the flash process. The energy saving effect can be further improved with the minimum capital investment without installing. When the volatile component of the process steam is a mixture, the composition of the volatile component of the flash unit is often almost the same as the composition of the process steam. Even if the composition of the volatile component is slightly different from the composition of the process steam, the amount of steam of the process steam is overwhelmingly larger than the amount of steam of the volatile component, so even if the volatile component is returned to the main process, the post-process Does not adversely affect.

Further, if the VRC process and another process using the process steam of the main process are installed side by side as in the process of FIG. 4, the amount of process steam generated in the main process is insufficient, and the VRC process and another process It may not be possible to operate (or operate) both effectively. In particular, when the type of compressor is a turbo type, if the inflow of process steam is small, the equipment may be damaged by surging, and it is necessary to send more than a predetermined amount of process steam to the compressor. The amount of process steam to another process is likely to be insufficient, and the energy saving effect may be extremely reduced. However, in the present invention, since the insufficient amount of steam is supplemented by the volatile component by the flash process, it is easy to operate both the VRC process and another process effectively (or both). Therefore, the VRC unit (VRC process or VRC method) can be easily applied to an existing plant having a main unit (or main process) and another unit (separate process), further increasing the flexibility of process design. Can be improved.

[Main process (main unit)]
In the main process (main unit), the process steam generator is not limited to a distillation column as long as it generates process steam, and is, for example, a device whose temperature is controlled by heating and evaporating with a heat source and then cooling and circulating. It may be present, and specifically, it may be a reactor, an evaporator, a crystallizer, a dryer, or the like. Of these, a distillation column is preferable because the VRC process can be easily incorporated into the heat source of the main process. The distillation column is equipped with a condenser in which process steam is discharged from the top of the column and cools and condenses the process steam, and a reboiler for charging raw materials into gas at the bottom of the column. The evaporator) may be used as a heat source in combination with the reboiler at the bottom of the column.

The process vapor may contain at least a condensable gas component and may contain a non-condensable gas component described later, but it is practically disadvantageous from the viewpoint of being difficult to contribute as a heat source and economically disadvantageous. It is preferable that the non-condensable gas component is not contained (or the non-condensable gas component is extremely small). Usually, the condensable gas component contains water and / or an organic solvent. Examples of the organic solvent include alcohols (alkyl alcohols such as ethanol, propanol and isopropanol, glycols such as ethylene glycol and propylene glycol), esters (methyl acetate, ethyl acetate, butyl acetate and the like), and ketones (such as methyl acetate, ethyl acetate and butyl acetate). Acetone, ethyl methyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), aldehydes (acetaldehyde, propionaldehyde, etc.), carboxylic acids (acetic acid, propionic acid, etc.), ethers (dimethyl ether, diethyl ether, etc. chain ethers, dioxane, Cyclic ethers such as tetrahydrofuran), hydrocarbons (aliphatic hydrocarbons such as hexane, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene, toluene, xylene, etc.), halogenated hydrocarbons, etc. Examples include hydrogens (methylene chloride, chloroform, etc.). These organic solvents can be used alone or in combination of two or more. Among these organic solvents, esters (particularly acetic acid esters) and hydrocarbons (particularly aromatic hydrocarbons) are widely used, and esters and hydrocarbons can be used, for example, esters / hydrocarbons = 99 /. It may be mixed in a weight ratio of 1 to 10/90, preferably 90/10 to 30/70, and more preferably 80/20 to 50/50.

The boiling point of the organic solvent is determined by the type of the organic solvent, but is not particularly limited, and is, for example, 30 to 150 ° C., preferably 50 to 120 ° C., and more preferably about 60 to 100 ° C.

The vapor pressure (25 ° C.) of the organic solvent is determined by the type of the organic solvent, but is not particularly limited, and is, for example, about 1 to 30 kPa, preferably about 5 to 20 kPa, and more preferably about 10 to 15 kPa. ..

The ratio of the organic solvent can be selected according to the type of the organic solvent and is not particularly limited, but may be 10% by weight or more with respect to the entire process steam, for example, 30 to 99% by weight, preferably 50 to 50% by weight. It may be about 98% by weight, more preferably 80 to 95% by weight (particularly 85 to 93% by weight).

The temperature of the process steam can be selected depending on the type of condensable gas and is not particularly limited, but is, for example, 20 to 200 ° C, preferably 30 to 150 ° C, and more preferably about 50 to 100 ° C. The pressure of the process steam may be normal pressure steam or pressurized steam. The flow rate of the process steam (discharge flow rate from the process steam generator) is, for example, about 0.1 to 100 m ³ / sec, preferably 1 to 50 m ³ / sec, and more preferably about 3 to 10 m ³ / sec.

The condenser in the main process may be a single capacitor, but a plurality of capacitors can be used because they can efficiently condense the condensable gas component in the process steam and suppress the circulation of uncondensed steam in the VRC process. Is preferably arranged in series, and for example, two capacitors may be arranged in series. The capacity of the condenser is not particularly limited, and usually, the capacity to condense the condensable gas component in the process vapor is selected by the independent operation of the main process in which the VRC process is not operated. When the capacitor is arranged independently, the first circulation line is connected to the upstream side of the capacitor. When arranging a plurality of capacitors, a plurality of capacitors may be arranged in series and the first circulation line may be connected on the upstream side of the first capacitor, but it is on the downstream side of the first capacitor. And the line on the upstream side of the last capacitor (the line between adjacent capacitors, and when two capacitors are arranged in series, the line between the first capacitor and the second capacitor) By connecting the circulation line No. 1, it is possible to prevent the condensable gas component in the uncondensed recompressed steam from the first circulation line from circulating (backflowing) to the VRC process. The plurality of capacitors may be different capacitors or the same capacitor, but usually, as the first capacitor, only the first (upstream) capacitor is used and the condensable gas in the process steam during steady operation. Capacitors capable of condensing the entire amount of ingredients are used.

The main process may further include a heat exchanger such as a reboiler. The heat exchanger may be, for example, a main process evaporator for charging the raw materials of the process steam generator in the form of gas. In particular, in the case of a distillation column, as described above, the main process evaporator may be a bottom reboiler, and a heat exchanger in the VRC process (such as a VRC evaporator) is used as a heat source for the main process together with this bottom reboiler. You may use it.

The process steam discharge line in the main process is branched into a main line for cooling and condensing the process steam by the condenser and a VRC line supplied to the VRC process, and the flow rate is controlled in the VRC line supplied to the VRC process. Although the device is not essential, it is preferable to dispose a flow control device upstream for controlling the flow rate of the process steam to the VRC process for stable operation of the plant. Normally, the flow rate control device gradually increases the opening degree from the closed state at the start of operation, and is adjusted to a constant opening degree (for example, fully open) at the time of steady operation in which the VRC process is stable. The ratio of the process steam distributed to the main line and the VRC line can be appropriately selected according to the capacity of the compressor, and from the viewpoint of energy saving, it is preferable that the ratio supplied to the VRC line is large, for example, steady operation. At times, the entire amount of process steam may be distributed to the VRC line, but usually some process steam is fed to the main line and the rest is fed to the VRC line.

[Recompression process (steam recompression unit)]
In the VRC process, the type of the steam recompression unit is not particularly limited, and a conventional type, for example, various types of compressors such as a screw type, a turbo type, and a reciprocating type can be used. Of these, the screw type and the turbo type are preferable because they have a large effect of improving safety and convenience.

As described above, in the example of FIG. 1, the method of using the recompressed steam was described by the plant equipped with the turbo type compressor, but in the plant equipped with the screw type compressor, before the start of boosting of the compressor ( The method of circulating the process vapor in the VRC process before the start of condensation) is slightly different. Specifically, in a plant equipped with a screw type compressor, in addition to different types of compressors as devices constituting the plant, a flow rate control device adjacent to the upstream side of the compressor (flow control valve in FIG. 1). It differs from a plant equipped with a turbo compressor in that 17) is not arranged. As for the process steam circulation operation, in a plant equipped with a screw type compressor, the screw type compressor is started, and after confirming that it is stable at the rated rotation speed, the flow rate is arranged in the second circulation line. It differs from a plant equipped with a turbo compressor in that the control device (flow control valve 12 in FIG. 1) is closed. Specifically, although the discharge pressure is hardly loaded on the process steam that has passed through the screw type compressor, as described above, the heat of the compressor shaft power × mechanical efficiency × (1-insulation efficiency) passes through the compressor. The heat transfer to the steam causes a slight temperature rise. Then, a part of the process steam that has been slightly heated is circulated to the suction side of the compressor through the second circulation line, and if the circulation continues, the temperature may exceed the upper limit of the compressor, so that the compression is performed. After the operating condition of the machine stabilizes, the flow control device arranged in the second circulation line is closed. Even if the flow control device arranged in the second circulation line is closed, the uncondensed recompressed steam circulating in the VRC process can be returned to the main process by the first circulation line, so that the second circulation line can be used. By circulating, the circulation in the second circulation line can be stopped before the compressor is heated to the upper limit temperature or higher. Therefore, there is no need for equipment for cooling the compressor that has been heated by the circulation of the second circulation line. As described above, although the circulation method before the start of condensation differs depending on the type of compressor, the recompressed steam can be safely and easily reused as a heat source in any of the compressors.

The discharge pressure of the steam recompression unit can be selected according to the type of process steam, but the steady-state pressure is, for example, 30 kPaG (gauge pressure) or more (for example, 30 to 400 kPaG), preferably 40 to 200 kPaG, more preferably. Is about 50 to 100 kPaG.

In the present invention, the flow rate returned from the first circulation line (circulation step) to the main unit is adjusted, and the compression ratio (discharge pressure / suction pressure) (absolute pressure) of the process steam by the steam recompression unit is controlled. Adjust the temperature of the recompressed steam to the desired temperature. In the present invention, if the flow rate control device suppresses the flow rate returned from the first circulation line to the main unit, the compression ratio rises, and the temperature rises due to the rise in the compression ratio, so that the heat exchange efficiency can be improved. The compression ratio can be appropriately selected depending on the target temperature of the recompressed steam, and is, for example, 2 to 5 (for example, 2.2 to 4.5), preferably 2.4 to 4, and more preferably 2. It may be adjusted to about 5 to 3.5 (for example, 2.7 to 3.3).

The discharge temperature of the steam recompression unit can be selected according to the type of process steam. For example, the discharge temperature is set to be 5 ° C. or higher higher than the temperature of the process steam before being supplied to the steam recompression unit. It may be set to, for example, a discharge temperature as high as 5 to 100 ° C., preferably 10 to 80 ° C., and more preferably 15 to 50 ° C.

In the steam recompression unit, the second circulation line (compressor return pipe) is not essential, but it is equipped with a second circulation line in which a flow control device is arranged so that the VRC process can be operated stably. You may. In the turbo type compressor, the VRC line introduced in the compressor may further include a flow control device in the line after merging with the second circulation line. In a plant equipped with a turbo compressor, the flow rate of the process steam introduced into the compressor can be adjusted by adjusting the opening degree of this flow control device even before the compressor is started and during stable operation of the process. You may. Further, in the second circulation line in the plant equipped with the screw type compressor, at the initial stage of operation (cold start) of the VRC process, the flow control device is opened to circulate the process steam to the second circulation line of the compressor. It may be used only for a short period of time until the rotating portion reaches a stable rotation rate at the start of operation. As for the compressor, a type having a function of a second circulation line in the mechanism is also commercially available.

In addition to the above definition, in the present specification and the scope of the claim, if the process steam has passed through the steam recompression unit (process), the process steam at the time of cold start (degree of compression and degree of compression and) Steam with a small temperature rise) may also be referred to as recompressed steam.

[Heat exchange process (heat exchange unit)]
As the heat exchange unit, a conventional heat exchanger (for example, an evaporator such as a multi-tube heat exchanger) can be used, and as described above, this heat exchange unit is used together with the main process evaporator of the main process. Since it can be used as a heat source for the plant, it can be used as a resource-saving and energy-saving facility. When the heat exchange unit is used as the heat source for the main process, the ratio of the charged amount of the VRC evaporator is the total charged amount (the total amount of the charged amount of the VRC evaporator and the charged amount of the main process evaporator). For example, it may be 50% or more, preferably 60% or more (for example, 65 to 95%), and more preferably 70% or more (for example, 75 to 90%). The ratio of the charged amount of the VRC evaporator may be% by weight or% by volume. In the method of the present invention, as the amount of evaporation in the heat exchange unit (VRC evaporator) increases, the amount charged in the main process evaporator is appropriately reduced for operation.

The heat exchange unit is connected to the first circulation line, and the non-condensed gas components (non-condensed components including non-condensed steam and non-condensable gas) in the heat exchange unit are the heat exchange unit and / or It is returned to the main process by the first circulation line via the airing line of the hold unit. In the heat exchange unit (heat exchange step or condensation step), in the initial stage of operation until the steam recompression unit stabilizes, the temperature rise of the recompressed steam is low, so most of the process fluid remains gaseous and the first circulation line. Is returned to the main process. On the other hand, when the steam recompression unit is stable, the process may be designed so that a part of the recompressed steam is condensed, but all the condensable gas components in the recompressed steam are condensed (total condensation). It is preferable to design the process of the heat exchange unit (or heat exchange process) as described above. In the heat exchange process designed in this way, most of the condensable gas components in the recompressed steam are condensed, so that there is almost no uncondensed steam (condensable gas components) supplied to the first circulation line. .. As long as the effect of the present invention is not impaired, a part of the recompressed steam may be flowed through the first circulation line to maintain the back pressure without being completely condensed.

Further, in the present invention, even if the heat exchange unit has a large heat transfer area and can handle a large amount of processing, the back pressure can be effectively maintained by the hold unit, so that the processing amount and operating conditions fluctuate greatly for the plant. However, it is easy to apply the VRC method and it has excellent process design flexibility.

[Hold process (hold unit)]
In the present invention, the hold unit (holding step) may have at least one hold tank, and may have a plurality of hold tanks. When having a plurality of hold tanks, the hold tanks may be connected in series and / or in parallel, respectively.

The hold unit may usually have a gas-liquid separation function for separating the condensed liquid condensed by the heat exchange unit and the non-condensed component that has not been condensed. The hold unit having such a gas-liquid separation function may have a hold tank capable of gas-liquid separation, may be formed by a gas-liquid separator and a hold tank, and may be formed by a hold tank capable of gas-liquid separation. And may have both a gas-liquid separator.

The hold tank capable of gas-liquid separation is not particularly limited. For example, the hold tank has an appropriate capacity to the extent that gas-liquid separation is possible, and the separated gas component (non-condensable component) is placed in the back pressure space. It suffices to have an airing line (or pressure equalizing tube) for returning (or contacting), and it is sufficient that the gas phase and the liquid phase can be separated by retaining the condensed liquid. If the capacity of the tank is too large, it is necessary to lengthen the residence time, so that the temperature of the condensed liquid may drop due to heat radiation from the tank surface, and the back pressure may not be effectively maintained.

The gas-liquid separator is not particularly limited as long as it can separate the gas component and the condensed liquid. In addition, since the gas-liquid separator usually sends the separated liquid component, it is often connected to the upstream side of the hold tank, and the separated gas component (non-condensed component) is returned to the back pressure space ( Or have an airing line (or pressure equalizing tube) for contacting) in many cases.

The gas component (non-condensable component) separated by gas and liquid is in the process from the steam that could not be condensed in the heat exchange unit, the non-condensable gas introduced from the gas introduction unit, and the bearing of the compressor. Among the sealing gas (nitrogen gas, etc.) leaked into, the gas component that was not completely dissolved in the process condensate, the vapor generated by the gas-liquid equilibrium of the condensate staying in the hold tank, and the like may be contained. These non-condensed components may be returned to the main process and processed by the first circulation line via the gas-liquid separable hold tank and / or the airing line of the gas-liquid separator.

The air ring line of the hold tank that can separate gas and liquid is the gas phase space in the hold tank and the back pressure space downstream of the steam recompression unit, which is upstream of the hold tank (for example, the first gas phase space). It may be a line connecting to the circulation line). Further, in the gas-liquid separator airing line, the gas component separated by the gas-liquid separator is put into the gas phase space on the upstream side of the gas-liquid separator in the back pressure space downstream of the steam recompression unit (for example). , The first circulation line) may be a line to return. The position where each air ring line is connected is not particularly limited as long as it is a back pressure space, and for example, even if it is connected to a line between the steam recompression unit and the heat exchange unit, a heat exchange unit, or the like. However, it is usually connected to the first circulation line (upstream side of the flow rate control valve 11 in FIG. 1).

When the hold tank has an airing line (or gas-liquid separation function), the vapor pressure (or saturated vapor pressure) of the condensed liquid to be retained (or stored) is effectively functioned to maintain the back pressure. It is preferable because it can be used. The line in which the condensed liquid flows into the hold tank is sufficiently large with respect to the inflow amount of the condensed liquid, and the vapor phase space and the back pressure space (for example, a heat exchange unit) in the hold tank are blocked by the condensed liquid. If the communication (or communication) is performed without disconnection (when the vapor pressure of the accumulated condensate is connected to the extent that it can be used to maintain the back pressure), the airing line is not always necessary, but the airing Lines are often provided.

The hold unit (or hold step) has a hold tank for retaining the condensed liquid, but usually, when a hold tank (or a condensed liquid tank) for temporarily retaining (or storing) the condensed liquid is installed. From the viewpoint of reducing the load due to equipment maintenance, it was common to install a condensate cooler on the upstream side of the tank to cool the condensate so that the tank does not become a high-pressure gas facility under the regulations. However, in the present invention, the back pressure due to vapor pressure is used by keeping the condensate at a relatively high temperature (for example, the temperature near the boiling point of the condensate under the pressure of the back pressure space) without forcibly cooling or quenching the condensate. The pressure holding effect can be effectively improved. From this point of view, in the hold unit, the condensed liquid is retained in the hold tank without providing a cooling unit for cooling the condensed liquid on the upstream side of the hold tank.

From the same viewpoint, it is preferable that at least a part (particularly, the hold tank) of the unit and the line forming the back pressure space including the hold unit is kept warm. The heat retaining method is not particularly limited, and may be a method of keeping warm with a conventional heat insulating material or the like, or a method of keeping warm (or heating) using a heater or the like within a range that does not impair the energy saving effect. good.

If the temperature of the condensed liquid retained in the hold tank (or hold unit) is higher than the boiling point of at least one component constituting the condensed liquid (boiling point under pressure in the back pressure space), the back pressure is effective. Easy to maintain or hold. Therefore, if necessary, the temperature of the condensed liquid may be raised by heating. The temperature of the condensed liquid to be retained is typically, for example, (T-50) ° C. to (T + 20) ° C. (for example) with respect to the temperature T at the outlet (or heat exchange unit outlet side) of the heat exchange step. , (T-40) ° C to (T + 15) ° C), preferably (T-30) ° C to (T + 10) ° C (eg, (T-20) ° C to (T + 5) ° C), and more preferably (T-10). ) ° C. to (T + 3) ° C. (for example, (T-5) ° C. to T ° C.). In the present specification and the scope of the claim, the "temperature T at the outlet of the heat exchange process" is discharged from the heat exchange unit (or heat exchanger) in a state where the VRC process is operating stably. It means the temperature of the condensate immediately after (or near). The specific temperature of the stagnant condensed liquid is, for example, 40 to 150 ° C. (for example, 50 to 130 ° C.), preferably 60 to 120 ° C. (for example, 70 to 110 ° C.), and more preferably 80 to 105 ° C. It may be about (for example, 85 to 100 ° C.). If the temperature of the condensate is too low, it may be difficult to maintain back pressure.

The hold unit does not have to be equipped with a flow control device (flow control valve or valve) for controlling the outflow amount of the condensate, but the back pressure can be effectively maintained and the VRC process can be operated stably. Therefore, the outflow amount of the condensate is adjusted so that a predetermined amount of the condensate stays in the hold tank (or the liquid level of the condensate is controlled to a predetermined position (liquid level) in the hold tank). It has a flow control device to adjust the amount of condensate withdrawn from the tank to suppress (or keep warm) the temperature drop of the accumulated condensate, and / or to suppress the pressure drop due to sudden withdrawal. You may. The residence time (or average residence time) of the condensate in the hold unit (or hold step) is, for example, 0.5 minutes to 10 hours (for example, 1 minute to 5 hours), preferably 1.5 minutes to 3 hours (for example, 1 minute to 5 hours). For example, it may be about 2 minutes to 1 hour), more preferably 2.5 to 30 minutes (for example, 3 to 10 minutes). If the residence time is too short, the fluctuation range of the back pressure becomes large and it becomes difficult to maintain the back pressure, so that the VRC process may not be operated stably. On the other hand, if it is too long, the temperature of the condensed liquid will drop due to heat dissipation, and it will be difficult to maintain the back pressure, or a hold tank with a large capacity will be required, which may make it difficult to save space in the equipment.

The amount of condensed liquid extracted (or average amount) in the hold unit (or holding step) is, for example, about 1 to 100 tons / hr, preferably 10 to 50 tons / hr, and more preferably about 20 to 40 tons / hr. The amount may be the same as the amount of the condensed liquid introduced from the heat exchange unit (heat exchange step) during the steady operation of the VRC process.

The retention amount of the condensate in the hold unit is, for example, 0.1 to 20 m ³ (for example, 0.3 to 10 m ³ ), preferably 0.5 to 5 m ³ (for example, 0.8 to 3 m ³ ), more preferably. May be about 1 to 2 m ³ (for example, 1.2 to 1.8 m ³ ).

In the present invention, the pressure in the back pressure space can be easily controlled by the hold unit (or hold process), and the condensable gas component in the recompressed steam is effectively condensed (for example, in the heat exchange unit). Since it is possible to completely condense), the energy saving effect can be further improved. For example, when the entire amount of recompressed steam is condensed (total condensation), the energy efficiency (for example, the amount of heat source steam reduction per unit time for steady operation) is higher than that of the conventional VRC method in which back pressure is difficult to maintain. For example, it can be improved by about 30 to 100%, preferably about 40 to 80% (for example, 50%).

[Cooling process (cooling unit)]
In the present invention, if necessary, a cooling unit for cooling the condensed liquid may be provided downstream of the hold unit. The cooling unit is provided with at least a cooling device (or a cooler) for cooling the condensate, and a conventional cooling device can be used as the cooling device. The cooling unit may be provided with one or a plurality of the cooling devices, and when a plurality of the cooling devices are provided, they may be connected in series and / or in parallel, respectively. Further, as long as it is downstream of the hold unit, one cooling unit may be arranged, or a plurality of cooling units may be arranged with another unit (or a process) in between. With such a cooling unit, even if the condensate is discharged (or outflowed) into a space lower than the back pressure space (for example, atmospheric pressure), it can be stably (or smoothly) recovered without flash evaporation. .. When the flash unit is provided downstream of the hold unit, the cooling unit may be arranged on the line that discharges (or flows out) the non-volatile components separated by the flash unit.

Further, the cooling unit may further include a flow rate control device (flow control valve or valve) for adjusting the flow rate of the cooled condensate, if necessary. The flow rate control device may be provided on the upstream side (most upstream side) of the cooling device (or cooler) or between a plurality of cooling devices, but is usually provided on the downstream side (most downstream side) of the cooling device. In many cases. If the hold unit does not have a flow rate control device, the flow rate control device of the cooling unit may be used to adjust the amount of condensed liquid withdrawn from the hold tank.

[Gas introduction process (gas introduction unit)]
In the present invention, the gas introduction unit may not be provided, but for some reason (for example, unsteady operation at the initial stage of operation as described above), the temperature of the condensed liquid temporarily drops in the hold unit. A gas introduction unit may be provided to respond to the situation.

The gas introduction unit may be connected to at least a position where the pressure in the back pressure space can be controlled (for example, between the downstream side of the compressor and the upstream side of the flow control device of the first circulation line). In particular, it is preferable that the heat exchange unit and the hold unit are connected to a line between the confluence of the respective air ring lines and the upstream side of the flow control device of the first circulation line. That is, it is preferable to introduce a non-condensable gas in the circulation step downstream of the heat exchange step and / or the hold step. By introducing a non-condensable gas in the circulation process, the amount of the non-condensable gas that reduces the contact frequency for heat exchange between the recompressed steam and the heat exchange unit is reduced, and the amount of the non-condensable gas passing through the heat exchange unit is reduced. Since heat can be exchanged efficiently, the size of the equipment (or heat exchange unit) can be reduced. Further, since the contact frequency between the non-condensable gas to be introduced and the process condensate can be reduced, the dissolution of the non-condensable gas in the process condensate can be suppressed. The gas introduction unit may be connected to a compressor or a main unit (for example, a line connecting the main unit and the recompression unit) as long as the effect of the present invention is not impaired. When connecting the gas introduction unit to the compressor, the non-condensable gas to be introduced may be used as the seal gas (or shaft seal gas) of the compressor, and further, the seal gas leaking from the seal portion of the compressor ( Non-condensable gas) may be used to maintain back pressure.

The non-condensable gas introduced from the gas introduction unit maintains a gas state under the temperature and pressure in the back pressure space of the steam recompression unit (compressor) from the viewpoint of ensuring a predetermined pressure in the back pressure space. It is preferably a possible gas, the temperature of the back pressure space is, for example, 25 to 300 ° C, preferably 40 to 230 ° C, more preferably about 65 to 150 ° C, and the pressure is, for example, 30 to 400 kPaG. It may be a gas that can maintain a gaseous state in an environment of (for example, 30 to 300 kPaG), preferably 40 to 200 kPaG, and more preferably about 50 to 100 kPaG. Similarly, from the viewpoint of ensuring a predetermined pressure in the back pressure space, the non-condensable gas is a gas (insoluble or sparingly soluble) that is difficult to dissolve in the process condensate (condensate of the condensable gas component). ) Is preferable.

Typical non-condensable gases include, for example, inert gases that do not react with process vapors (eg, nitrogen, air, carbon dioxide, carbon monoxide, noble gases (eg, argon, helium, etc.)). Will be. In addition, in the present specification and the claims, "inert gas" means process vapor or equipment (or non-condensable) under the conditions of VRC process (for example, under the temperature and pressure in the back pressure space). The gas is not particularly limited as long as it is a gas that does not react with the material of the equipment (inner surface of the equipment that the gas comes into contact with), and constitutes a gas that is reactive with the process vapor or the like under conditions other than the conditions of the VRC process, or the process vapor or the equipment. It is used to mean that it contains a gas that is reactive with materials other than the material.

These non-condensable gases can also be used alone or in combination of two or more as a mixed gas. Of these non-condensable gases, nitrogen is preferred from the viewpoint of ease of introduction (or supply). In addition, the non-condensable gas may be supplied from a gas cylinder (or a compressed gas container), a gas generator, or the like, and the gas derived from the process [for example, in the main step of the plant or another step (or other reaction step). Non-condensable gas generated (or by-produced), preferably air contained in a small amount in the process vapor generated from the main process, seal gas leaking from equipment having a seal part such as a bearing part (compressor, etc.)] May be supplied as a non-condensable gas. From the viewpoint of convenience and the like, the gas introduced from outside the process is preferable.

The introduction flow rate of the non-condensable gas can be appropriately selected (or adjusted) according to the operating condition, but is, for example, 0.01 to 3% by volume, preferably 0. It may be about 03 to 1% by volume, more preferably about 0.05 to 0.5% by volume. The introduction ratio of this non-condensable gas is the volume ratio of the process steam generated in the main process under the temperature and pressure.

[Degassing process (degassing unit)]
A degassing unit is not always necessary, but if necessary, the non-condensable gas dissolved in the condensate under the pressure of the back pressure space is degassed (vaporized or vaporized) from the outflowing condensate downstream of the hold unit. It may be arranged for separation). When a gas introduction step is provided, it is preferable to install a degassing unit because the amount of non-condensable gas dissolved tends to be large.

The degassing unit has at least a condensate degassing tank. The condensate degassing tank may have a capacity sufficiently large to retain and degas the condensate, and a conventional tank can be used. Further, the degassing unit may have a gas discharge line for discharging the non-condensable gas component degassed in the condensate degassing tank. The gas discharge line may be connected to a conventional abatement equipment (or discharge equipment) such as a scrubber. The degassing unit may be provided with a decompression pump or the like on the gas discharge line to shorten the processing time and / or reduce the tank capacity.

The degassing unit may have a flow rate control device for controlling the amount of condensed liquid discharged (or outflow) from the condensed liquid degassing tank and adjusting the amount of retention. The condensed liquid discharged from the degassing unit (degassing step) may be recovered as it is or via the cooling unit (cooling step).

[Flash process (flash unit)]
The flash unit is not always necessary, but if necessary, the condensed liquid discharged (or outflowed) in the hold unit (hold process) is flash-evaporated to separate the generated volatile component and the non-volatile component. May be. By utilizing such flash evaporation, a part of the heat (or sensible heat) of the condensate is transferred to the heat (or latent heat) of the volatile component, and the heat of at least a part of the volatile component is transferred to another process (or another unit). Can be used as a heat source for.

The flash evaporation may be performed by a constant temperature flash that heats and reduces the pressure of the condensed liquid, an adiabatic flash that reduces the pressure of the condensed liquid without heating, or a flash that combines these flash conditions. In flash evaporation, the temperature of the condensate is, for example, 40-200 ° C. (eg, 50-180 ° C.), preferably 60-150 ° C. (eg, 70-120 ° C.), and more preferably 80-110 ° C. (eg, 80-110 ° C.). It may be about 85 to 105 ° C.). The pressure (absolute pressure) in the flash tank (or flash evaporator) may be, for example, about 50 to 1000 kPa, preferably 80 to 500 kPa, and more preferably about 100 to 300 kPa.

It is sufficient that at least a part of the volatile components generated in the flash process can be used as at least a part of the heat source of another process, and the amount (or flow rate) of the volatile components generated in the flash process is the condensate introduced in the flash process. With respect to the amount (or flow rate) of, for example, 1 to 70% by weight (for example, 3 to 50% by weight), preferably 5 to 30% by weight (for example, 8 to 25% by weight), and more preferably 10 to 20% by weight. It may be about% by weight (for example, 10 to 15% by weight).

In another process (separate unit), at least a part of the volatile components generated in the flash process and / or the process steam generated in the main process may be used as a heat source.

The separate unit may have an introduction line (or air supply line) for introducing the volatile components and / or process steam. The connection position of the introduction line is not particularly limited as long as the volatile component and / or the process vapor can be introduced, and is connected to, for example, a flash unit or a third circulation line for connecting the flash unit and the main unit. Usually, the main unit, for example, the process steam generator of the main unit (main step) (distillation column 1 in FIG. 1) and the capacitor first condensed in the main unit (first in FIG. 1). It is often connected to the line between the condenser 2) (particularly, the line downstream from the third circulation line).

The proportion of the volatile components introduced into the separate unit is, for example, 0 to 100% by weight (for example, 10 to 99% by weight), preferably 30 to 100% by weight (for example, 30 to 100% by weight) with respect to the total volatile components generated in the flash step. It may be about 50 to 97% by weight), more preferably 70 to 100% by weight (for example, 80 to 95% by weight). The balance of the volatile components generated in the flash step may be returned to the main unit for processing.

Although not always necessary, in the plant of the present invention, a third unit for connecting a flash unit (flash process) and a main unit (main process) to return a part of volatile components generated in the flash process to the main process. It may be provided with a circulation line of. The connection position of the third circulation line is not particularly limited as long as it is upstream from the process steam generator (distillation tower 1 in FIG. 1) and the condenser (for example, the second condenser 3 in FIG. 1), for example. , The line between the branch point (branch point 4 in FIG. 1) for branching the process steam to the VRC process and the main process and the flow control device (valve 15 in FIG. 1) on the VRC line, two connected in series. The line between the condensers (the line between the first condenser 2 and the second condenser 3 in FIG. 1) may be used, but the process steam generation can be used as a heat source to improve the energy saving effect. It is preferably installed on the line from the top of the vessel to the branch point (branch point 4 in FIG. 1) where the process vapor is branched into the VRC process and the main process.

On the other hand, the non-volatile component (condensate) separated by the flash unit may be recovered together with the condensate of the main unit as it is or via the cooling unit. Similarly, the condensed liquid condensed in another process may be recovered together with the condensed liquid of the main unit as it is or via the cooling unit. When the process steam generator is a distillation column, a part of the recovered condensed liquid may be used as a reflux liquid of the distillation column, and the rest may be sent to a subsequent process as a effluent.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

(Example 1)
FIG. 5 shows a process flow diagram. The main process (main step) includes a distillation column 1, and the charging liquid is evaporated by the main process evaporator (first heat exchanger) 14 and charged into the distillation column 1 in the state of gas. When stable operation is performed only by the main process, the process steam discharged from the top of the distillation column 1 is at normal pressure (atmospheric pressure) and the temperature is about 80 ° C., its composition is ethyl acetate 60% by weight, and benzene. It was 30% by weight, 10% by weight of water, and the flow rate was 4 m ³ / sec. As a compressor for the VRC process, a turbo type compressor (“f44C2” manufactured by IHI Corporation) was used. In FIG. 5, the compressor 5, the heat exchanger 7, the hold tank 8, and the line connecting them that form the back pressure space are heat-insulated with a heat insulating material.

1. 1. Process steam replacement of VRC process line-Compressor start-Compressor pressurization start (before condensation start)
(1) It was confirmed that the valves 11, 12, 13, 15 and 17 were fully closed.

(2) The valve 11 on the first circulation line, the valve 12 on the second circulation line, and the valve 17 on the suction side of the compressor were fully opened.

(3) The valve 15 of the line from the top of the distillation column 1 to the VRC process side was gradually opened, the line of the VRC process was replaced with process steam, and the temperature inside the system was raised over about 10 minutes. The valve 12 was fully closed and the valves 11 and 17 were set to a predetermined opening degree.

(4) After the compressor 5 is started and the impeller reaches the rated rotation speed (about 10 to 20 seconds later), the discharge pressure rise of the compressor is less than 50 kPaG in the steady continuous operation state, and the compressor It was confirmed that there were no abnormalities (abnormal noise, vibration, etc.). At this time, the shaft power of the compressor 5 was 250 kW, the suction gas flow rate was 3 m ³ / sec, and the discharge gas temperature of the compressor was 20 ° C. higher than the inlet temperature.

(5) The valve 11 of the first circulation line was gradually closed. At this time, the discharge pressure of the compressor 5 increased to 115 kPaG. The discharge temperature was about 105 ° C.

2. 2. Pressurization of the compressor (after the start of condensation) to reduction of the load on the existing evaporator (1) While observing the balance between the discharge pressure of the compressor 5 and the condensation, the valve 11 of the first circulation line was gradually closed. The discharge temperature was set to 110 ° C., and heat exchange was started by the VRC evaporator (second heat exchanger) 7. The recompressed steam finally reached almost total condensation in the VRC evaporator 7, and the temperature of the discharged condensate was 95 ° C. The temperature inside the condensate tank 8 finally reached 95 ° C. The liquid level of the condensate tank 8 was controlled to 1.5 m ³ by intermittently opening and closing the valve 13 for controlling the liquid level and flowing out. The average residence time of the condensed liquid was 3 minutes, and the amount of condensed liquid introduced from the heat exchange unit and the amount of condensed liquid outflow (or withdrawn amount) from the hold tank were 30 tons / hr. The discharged condensate was cooled to 45 ° C. by heat exchange with the cooling water in the condensate cooler 18, and returned to the main process.

(2) As the amount of evaporation in the VRC evaporator 7 increased, the amount charged from the VRC evaporator gradually increased. When the amount charged from the VRC evaporator exceeds 70% of the maximum value, adjust the flow rate of the heat source steam 16 to the main process evaporator while maintaining the minimum load of the main process evaporator 14 to reduce the flow rate. The opening degree of the valve 17 was gradually increased to increase the suction amount of the compressor, and the amount charged from the main process evaporator was adjusted.

(3) When the operation of the entire process was stable, the valve 11 was intermittently opened and closed with a small opening to stabilize the discharge pressure of the compressor. In the stable operation, the heat source steam load of the main process evaporator was reduced by 6 tons / hr as compared with the steady operation in which the VRC process was not operated.

(Comparative Example 1)
FIG. 6 shows a process flow diagram. The plant shown in FIG. 6 is the plant shown in FIG. 5 which is equipped with a conventional VRC process equipped with a gas-liquid separator 19 without a condensate tank 8 and a condensate cooler 18. Using the same process steam (pressure, temperature, composition, flow rate) and turbo compressor as in Example 1, the operation was started as follows.

1. 1. Process steam replacement of VRC process line-Compressor start-Compressor pressurization start (before condensation start)
1. Described in Example 1. The operation of the VRC process was started in the same procedure as in (1) to (5). As in the first embodiment, when the valve 11 was gradually closed, the discharge pressure of the compressor 5 increased to 115 kPaG, and the temperature was about 105 ° C.

2. 2. Pressurization of the compressor (after the start of condensation) -Reduction of the load on the existing evaporator (1) While observing the balance between the discharge pressure of the compressor 5 and the condensation, gradually close the valve 11 of the first circulation line and discharge. The temperature was set to 110 ° C., and heat exchange was performed with the VRC evaporator (second heat exchanger) 7. The recompressed steam did not reach full condensation in the VRC evaporator (second heat exchanger) 7, and a part of the recompressed steam became the main process via the first circulation line as an uncondensed gas component. I was back. The condensate separated by the gas-liquid separator 19 was collected in a slightly thick pipe (condensate extraction line) and recovered by intermittently opening and closing the valve 13. The average residence time of the condensate was 5 seconds.

(2) As the amount of evaporation in the VRC evaporator 7 increased, the amount charged from the main process evaporator was adjusted by adjusting the flow rate of the heat source steam 16 to the main process evaporator in a direction of reducing the flow rate.

(3) When the operation was stable, the valve 11 was intermittently opened and closed with a small opening to stabilize the discharge pressure of the compressor. In the stable operation, the heat source steam load of the main process evaporator was reduced by 4 tons / hr as compared with the steady operation in which the VRC process was not operated.

(Example 2)
FIG. 7 shows a process flow diagram. The process steam discharged from the top of the distillation column 1 is at normal pressure (atmospheric pressure) and has a temperature of about 72.5 ° C., its composition is 66% by weight of ethyl acetate, 24% by weight of benzene, and 10% by weight of water, and the flow rate is. It was 55 tons / hr. Conventionally, 25 tons / hr of the process steam has been used as a heat source for a hot water purification device used in another process. As shown in FIG. 7, it was decided to add a VRC process, but from the viewpoint of investment recovery, 30 tons / hr of process steam was processed by the compressor 5, and the heat source for evaporation of the liquid charged in the distillation column 1 was generated. It turns out that it should be used as. As the compressor of the VRC process, a turbo type compressor (“f44C2” manufactured by IHI Corporation) was used. The temperature of the condensate generated after using 30 tons / hr of process steam as a heat source was 97 ° C., the pressure in the back pressure space was 340 kPa (absolute pressure), and the total condensation was performed, so the flow rate was 30 tons / hr. Met. When this condensed liquid was flushed under normal pressure in the flash tank 24, the generated vapor had a temperature of 69.5 ° C. and a flow rate of 3.8 tons / hr, and had a composition of 65% by weight of ethyl acetate and 26% by weight of benzene. , 9% by weight of water. This steam was merged into the line between the top of the distillation column 1 and the branch point 4 via the third circulation line 25. At the branch point 4, a part of the merged steam branched to the VRC process side. The balance of the merged steam has a temperature of 72 ° C. and a flow rate of 28.8 tons / hr, and the composition immediately after the merge (or at the beginning of operation) is 65.93% by weight of ethyl acetate, 24.13% by weight of benzene, and water. The composition is 9.94% by weight, the composition after the operation is stabilized is 63.97% by weight of ethyl acetate, 26.70% by weight of benzene, and 9.33% by weight of water, and is discharged from the top of the distillation column 1. There was no significant change from the composition of the process steam. When the rest of the combined steam was sent to a water heater (hot water purification device) of another process, the conventional hot water could be obtained without any trouble.

(Reference example 1)
FIG. 8 shows a process flow diagram. The plant shown in FIG. 8 is a plant shown in FIG. 7 that does not have a flash tank 24 and a third circulation line 25. The VRC process is installed in the same manner as in Example 2 except that the condensed liquid generated in the VRC process is cooled to 45 ° C. by the condensed liquid cooler 18 without going through the flash tank 24 and merged with the condensed liquid of the main process. It was put into operation. When I tried to send only the remaining process steam introduced into the VRC process to the heat exchanger (hot water purification device) of another process on line 26 to another process, the mass balance was consistent, but there was no margin in the flow rate. Stable air supply (or introduction) could not be performed, which hindered the production of hot water by another process.

The method of utilizing the recompressed steam of the present invention can be used in various plants that generate process steam, for example, a distillation plant.

1 ... Distiller (distillation tower)
2, 3 ... Condenser 4 ... Piping branch point 5 ... Compressor 6, 9, 25 ... Circulation line 7, 14 ... Heat exchanger (evaporator)
8 ... Hold tank (condensate tank, condensate receiving tank)
8a, 9a, 19a ... Airing line (pressure equalizing pipe)
18 ... Condensate cooler (cooler)
19 ... Gas-liquid separator 20 ... Gas introduction line 22 ... Condensate degassing tank (degassing tank)
24 ... Flash tank (flash evaporator)

Claims (15)

The main step of generating the process vapor containing the condensable gas component and recovering the condensable gas component of the generated process vapor as a condensate, and the adiabatic compression of at least a part of the process vapor with a compressor to raise the temperature. Of the recompressed steam to obtain recompressed steam, the heat exchange step using the recompressed steam as a heat source, and the recompressed steam used in the heat exchange step, the uncondensed non-condensed components are returned to the main process. A method of utilizing recompressed steam including a circulation step, which includes at least a hold step for retaining the condensed liquid condensed in the heat exchange step and holding the pressure in the back pressure space downstream of the compressor. A method of using recompressed steam in which the outflow amount of the condensed liquid is adjusted and the condensed liquid is retained for 0.5 minutes to 10 hours in the holding step . The method according to claim 1, wherein the condensed liquid is retained in the hold step without forcibly cooling the condensed liquid on the upstream side of the hold step. The method according to claim 1 or 2, wherein the temperature of the condensed liquid retained in the hold step is (T-50) ° C to (T + 20) ° C with respect to the temperature T at the outlet of the heat exchange step. The method according to any one of claims 1 to 3 , wherein in the hold step, the condensed liquid and the non-condensed component are separated into gas and liquid. Further, a claim including a gas introduction step of introducing a non-condensable gas into the back pressure space downstream of the compressor and a degassing step of degassing the dissolved non-condensable gas from the condensed liquid flowing out in the hold step. Item 8. The method according to any one of Items 1 to 4 . The method according to any one of claims 1 to 5 , further comprising a flash step of flash-evaporating the condensed liquid flowing out in the hold step to separate the volatile component and the non-volatile component. The method according to claim 6 , wherein at least a part of the volatile components separated in the flash step is used as a heat source for another process. A steam generator that generates process steam containing a condensable gas component, a main unit having a condenser for cooling and condensing a part of the generated process steam, and the rest of the process steam are adiabatic and compressed to control the temperature. Of the steam recompression unit for raising and obtaining recompressed steam, the heat exchange unit for using the recompressed steam as a heat source, and the recompressed steam provided to the heat exchange unit, non-condensed non-condensed. It is a recompressed steam utilization plant equipped with a circulation line for returning components to the main unit, and the condensed liquid condensed in the heat exchange unit is retained to reduce the pressure in the back pressure space downstream of the steam recompression unit. Recompression comprising at least a hold unit for holding , wherein the hold unit has a flow control device for adjusting the outflow of the condensate and allowing the condensate to stay for 0.5 minutes to 10 hours. Steam utilization plant. The plant according to claim 8 , further comprising a hold tank for forcibly cooling the condensed liquid on the upstream side of the hold unit, without providing a cooling unit for forcibly cooling the condensed liquid. The temperature of the condensate in which at least a part of the unit and the line forming the back pressure space downstream of the steam recompression unit is kept warm and the hold unit stays is set with respect to the temperature T on the outlet side of the heat exchange unit. The plant according to claim 8 or 9 , which is maintained at T-50) ° C to (T + 20) ° C. The hold unit has a gas-liquid separation function and is a hold tank for retaining condensed liquid, and the gas phase portion in the hold tank and the back pressure space downstream of the steam recompression unit from the hold tank. The plant according to any one of claims 8 to 10 , also having an airing line for connecting to the gas phase space on the upstream side. The hold unit combines the hold tank for retaining the condensed liquid, the gas-liquid separator disposed on the upstream side of the hold tank, and the gas component separated by this gas-liquid separator into the steam recompression unit. The plant according to any one of claims 8 to 10 , further comprising an airing line for returning to the gas phase space on the upstream side of the gas-liquid separator in the downstream back pressure space. Further, a gas introduction unit for introducing a non-condensable gas into the back pressure space downstream of the vapor recompression unit and a degassing for degassing the non-condensable gas dissolved in the condensate flowing out from the hold unit. The plant according to any one of claims 8 to 12 , comprising a unit. The plant according to any one of claims 8 to 13 , further comprising a flash unit that flash-evaporates the condensate flowing out of the hold unit to separate it into a volatile component and a non-volatile component. 14. The plant according to claim 14 , further comprising a line for utilizing at least a part of the volatile components separated by the flash unit as a heat source for another process.

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