WO2018079370A1

WO2018079370A1 - Method for using recompressed vapor and plant

Info

Publication number: WO2018079370A1
Application number: PCT/JP2017/037672
Authority: WO
Inventors: 充宏河野; 木村　聡; 和久当房; 和史竹田; 鈴木　要
Original assignee: 株式会社ダイセル
Priority date: 2016-10-28
Filing date: 2017-10-18
Publication date: 2018-05-03
Also published as: CN109890476B; MY195815A; CN109890476A; JP7032319B2; JPWO2018079370A1

Abstract

The present invention is a method for using recompressed vapor comprising a main step for generating process vapor that includes a condensable gas component and recovering a condensate of the condensable gas component in the process vapor generated, a recompression step 5 for adiabatic compression of at least part of the process vapor by a compressor, increasing temperature, and obtaining recompressed vapor, a heat exchange step 7 using the recompressed vapor as a heat source, and a circulation step 9 for returning the non-condensed components of the recompressed vapor supplied to the heat exchange step 7 to the main step, wherein the method includes at least a holding step 8 for retaining the condensate condensed in the heat exchange step 7 and holding pressure of a back-pressure space downstream of the compressor. With this method, process vapor (recompressed vapor) that has been heated by adiabatic compression can be used efficiently as a heat source.

Description

Recompressed steam utilization method and plant

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

In chemical processes involving the generation of steam (for example, reaction of chemical substances, separation of mixtures, etc.), in order to reduce the amount of energy or running cost of the entire process, the amount of generated process steam is effectively used as a heat source. A method has been proposed. For example, vapor recompression (Vapor Re-Compression: VRC) that raises the temperature by adiabatically compressing process steam and uses the amount of heat of the compressed process steam (recompressed steam) as a heat source in processes such as evaporation, distillation, and drying ) Methods are being studied.

For example, in International Publication No. 2015/033935 (Patent Document 1), in the VRC method, by providing a circulation step for returning a gas component such as uncondensed recompressed steam existing downstream of the compressor to the main step. A method of using 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 stagnation of the gas component downstream of the compressor can be suppressed by the circulation step.

However, with this method, depending on the operating conditions of the plant, it may not be possible to smoothly recompress, 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, with regard to the degree of freedom in process design, if a new VRC system facility is added to an existing plant with other heat source facilities installed, the amount of process steam required to operate both facilities stably will be increased. In some cases, it could not be secured.

WO2015 / 033935 (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 capable of stably (or smoothly) operating a plant equipped with a VRC system using recompressed steam, and the plant.

Still another object of the present invention is to provide a method for using 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 used in the VRC method, and a plant using this method.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have generated a process steam containing a condensable gas component, and a main process for recovering the condensable gas component of the generated process steam as a condensate, A recompression process in which at least a part of the process steam is adiabatically compressed by a compressor to raise the temperature to obtain recompressed steam, a heat exchange process using the recompressed steam as a heat source, and a recombination provided for the heat exchange process. Among the compressed steam, in the method of using recompressed steam including a circulation process for returning non-condensed non-condensed components to the main process, the condensate condensed in the heat exchange process is retained without forcibly cooling or quenching. Thus, maintaining the pressure in the back pressure space downstream of the compressor (or suppressing (or preventing) the decrease in back pressure) can not only use recompressed steam more efficiently, but also stabilize the process (or plant). (Or smooth) found that can be operated (or running), and completed the present invention.

That is, the method of using the recompressed steam of the present invention generates a process steam containing a condensable gas component, and collects the condensable gas component of the generated process steam as a condensate, and at least the process steam. Of the recompressing process in which a part is adiabatically compressed with a compressor to increase the temperature to obtain recompressed steam, the heat exchanging process using the recompressed steam as a heat source, and the recompressed steam used in the heat exchanging process A method of using recompressed steam including a circulation step for returning non-condensed non-condensed components to the main step, the condensate condensed in the heat exchange step being retained, and the back pressure space downstream of the compressor At least a holding step for holding the pressure.

The condensate may be retained in the hold step without being forcibly cooled on the upstream side of the hold step. Further, in the processes after the heat exchange process, the generated condensate may be kept warm or heated, and the temperature of the condensate retained in the hold process is the outlet of the heat exchange process (or the heat exchange unit outlet side). The temperature T may be about (T-50) ° C. to (T + 20) ° C. In the hold step, the condensate may be retained for about 0.5 minutes to 10 hours by adjusting the outflow amount. In the holding 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 for cooling the condensate flowing out from the hold step. The method of the present invention also includes a gas introduction step for introducing a non-condensable gas into the back pressure space downstream of the compressor, and a deaeration for degassing the dissolved non-condensable gas from the condensate discharged in the hold step. And an air step. Furthermore, the method of the present invention may include a flashing step in which the condensate discharged in the holding step is flash-evaporated and separated into a volatile component and a non-volatile component. At least a part of the volatile components separated in the flash step may be used as a heat source for another process.

The present invention also includes a steam generator for generating 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 remainder of the process steam. Among the recompressed steam supplied to the heat exchange unit, the heat recompression 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 comprising a circulation line for returning non-condensed non-condensed components to the main unit, the condensate condensed in the heat exchange unit being retained and downstream of the steam recompressing unit A recompressed steam utilization plant having at least a holding unit for holding the pressure in the back pressure space is also included.

The plant may include a hold tank that retains the condensate without being provided with a cooling unit for forcibly cooling the condensate upstream of the hold unit. At least a part of the unit and line forming the back pressure space downstream of the vapor recompression unit may be kept warm or heated, and the temperature of the condensate in which the hold unit stays is the temperature at the outlet side of the heat exchange unit. The temperature may be maintained 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 condensate and retaining the condensate for about 0.5 minutes to 10 hours.

The hold unit has a gas-liquid separation function, and holds the condensate from the hold tank among the hold tank, the gas phase in the hold tank, and the back pressure space downstream of the vapor recompression unit. May also have an air ring line for connecting the gas phase space on the upstream side. In addition, the hold unit includes a hold tank for retaining the condensate, a gas-liquid separator disposed upstream of the hold tank, and a gas component separated by the gas-liquid separator. An air ring line for returning to the gas phase space upstream of the gas-liquid separator in the back pressure space downstream of the unit may be provided.

The plant of the present invention may further include a cooling unit for cooling the condensate flowing out of the hold unit. The plant of the present invention also removes the non-condensable gas dissolved in the condensate flowing out from the gas introduction unit for introducing the non-condensable gas into the back pressure space downstream of the vapor recompression unit and the hold unit. And a deaeration unit for taking care of. Furthermore, the plant of this invention may be equipped with the flash unit which flash-evaporates the condensate which flows out from a hold unit, and isolate | separates into a volatile component and a non-volatile component. The plant may include a line for using 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 (step) in which a unit operation involving a gas-liquid phase change is incorporated.

“Recompressed steam” means process steam that has been compressed and heated to be used as a heat source in the steam recompression system (VRC system).

“Back pressure space” means all spaces and lines (including air ring lines) that reach (or transmit) the discharge pressure of the compressor in the VRC system (VRC process).

“Non-condensable gas” means a gas capable of maintaining a gaseous state under temperature and pressure in a back pressure space downstream of the compressor.

“Non-condensable component” is used to mean both non-condensable gas components and non-condensable gas components among the condensable gas components in the VRC method (VRC process).

“Volatile component” means a gas (or volatile) component evaporated by flash evaporation of condensate in the flash process, and “nonvolatile component” does not evaporate by flash evaporation of condensate in the flash process. Liquid (or low volatility) component.

In the present invention, the condensate condensed in the heat exchange step is retained, and the pressure in the back pressure space downstream of the compressor is maintained (or the pressure drop is suppressed). Therefore, process steam (recompressed steam) is used as an efficient heat source. In addition to improving the energy saving effect, the plant equipped with the VRC system can be operated stably (or smoothly). In addition, it is easy to deal with plants with large fluctuations in throughput and operating conditions, and has excellent process design flexibility. Moreover, by introducing a non-condensable gas, the stability (or smoothness) of plant operation provided with the VRC system and the flexibility of process design can be further improved. Furthermore, the volatile component produced | generated by flash evaporation of the condensate discharged | emitted from a VRC process (or outflow) can be utilized for another heat-source utilization process. Therefore, even if many process steams are used in the VRC system, other heat source utilization processes can be operated smoothly and safely in parallel, and the process design flexibility and energy saving effect can be further improved.

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

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 includes a distillation tower 1 as a process steam generator that discharges process steam containing a condensable gas component, and the process steam is discharged from the distillation tower 1. This discharge line branches off at a pipe branch point 4. One of the branched lines is provided with 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, and the condensability in the process steam is provided. The gas component (condensable component) is cooled by

condensers

2 and 3 and recovered as a condensate. The main unit includes the distillation column 1, the first condenser 2 and the second condenser 3.

In the other branched line, the remainder of the process steam is adiabatically compressed to increase the temperature via a line provided with flow control valves (or valves) 15 and 17 as flow control units. Compressor 5 (for example, a turbo compressor) as a steam recompression unit for obtaining recompressed steam, heat exchanger 7 as a heat exchange unit for using recompressed steam as a heat source, and heat exchange A hold tank (or storage tank) 8 is disposed as a hold unit for separating the process fluid that has passed through the vessel 7 into gas and liquid and retaining the separated condensed liquid (or condensed component).

The gas component (or non-condensed component) separated in the hold tank 8 passes through the air ring line (or pressure equalizing pipe) 8a of the hold tank 8 from the air ring line (or pressure equalizing pipe) 9a of the heat exchanger 7. Is returned to the main unit by a first circulation line 9 provided with a flow control valve 11 as a flow control device. The first circulation line 9 is connected to a line between the first condenser 2 and the second condenser 3 via a connection part (or a pipe connection part) 10 and passes through the first condenser 2. The process fluid (process vapor and / or condensate) is joined, 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 a flow control valve 13 as a flow control device, and condensed as a cooling unit. It is cooled by the liquid cooler 18 and collected together with the condensate 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 that connects an inlet side line and an outlet side line 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 a line between the

flow control valves

15 and 17 on the line on the inlet side of the compressor.

The method or plant of the present invention includes a distillation column 1, a first condenser 2, and a second condenser 3 as necessary, generates a process vapor containing a condensable gas component, cools and condenses. VRC which includes a main process (main process), a compressor 5, a heat exchanger 7 and a hold tank 8, and generates recompressed steam whose temperature is increased by adiabatically compressing process steam with a compressor and using it as a heat source Process (VRC process). Also in this specification and FIGS. 2 to 8, the same components as those in FIG. 1 are denoted by the same reference numerals.

In the plant (apparatus) having such a configuration, the operation is performed only in the main process before the start of the VRC 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 condensable gas component (condensable component). It is recovered as a condensate.

Next, the flow

rate control valves

11, 12 and 17 are fully opened, the flow rate control valve 15 is gradually opened while the flow rate control valve 13 is closed, and the predetermined opening degree is adjusted. At this time, 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 of the main process, and the system in the VRC process is also replaced by this process steam. The temperature rises. Thereafter, the flow control valve 17 is adjusted to a predetermined opening degree (for example, when the discharge pressure of the turbo compressor 5 becomes too low, the opening degree of the flow control valves 11 and / or 12 is adjusted as necessary. After adjusting the amount of process steam introduced into the compressor (by adjusting the flow rate to reduce the flow rate), the turbo compressor 5 is started and stabilized at the rated rotational speed. At this point, the process steam passing through the turbo-type compressor 5 is hardly loaded with a discharge pressure, but a process in which heat of the compressor shaft power × mechanical efficiency × (1−adiabatic efficiency) passes through the compressor. The temperature rises by transferring heat to the steam. When the flow control valve 12 is in an 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 the heat transfer from the compressor, and the temperature rise width 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 through the first circulation line 9 without being condensed, and is recovered by cooling condensation.

In this way, the first circulation line in the VRC process can return the uncondensed steam to the main process, so that it is possible to suppress stagnation of process steam due to heat transfer failure in the heat exchange unit, etc. It is possible to prevent the compressor from being damaged due to stagnation of gas distribution.

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

Next, when the flow rate 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) In (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 of the flow control valve 11.

However, such control only by adjusting the opening degree of the flow control valve 11 is not yet sufficient to effectively exert the effect of the VRC method. For example, in the VRC process, the condensation of recompressed steam (condensable gas component) in the heat exchange process and the like, and the non-condensable gas (for example, compressor bearings) for the condensate (condensate of the condensable gas component) Pressure (or back pressure on the downstream side of the compressor) drops (or stagnation of pressure rise) and accompanying temperature drop (or stagnation of temperature rise) due to dissolution of sealing gas leaking into the process) ) Occurs. Even if such a situation is dealt with only by adjusting the opening degree of the flow control valve 11, a predetermined pressure may not be maintained (or maintained). In order to maintain the predetermined pressure, it is unavoidable to limit the amount of condensable gas components condensed in the heat exchange process (or the amount of raw material charged in the heat exchanger (VRC evaporator)). Therefore, the pressure control on the downstream side of the compressor is not easy, and the energy saving effect is reduced. In addition, because of the pressure drop (or stagnation of pressure rise), that is, the compressor is idle (the state where the compressor is simply blowing without being compressed), the plant (or recompression) equipped with the VRC system The unit (or process)) cannot be smoothly operated, and the function (or operation) as an inherent energy saving plant may be stopped.

In order to cope with such a situation, in the method or plant of the present invention, the condensate condensed in the heat exchange step (or heat exchange unit (heat exchanger 7)) is not forcibly cooled or rapidly cooled (predetermined). At least hold to maintain the pressure in the back pressure space downstream of the compressor (or the steam recompression unit (compressor 5)) in the recompression process. A process (or a hold unit having the hold tank 8) is provided. The condensate retained in the hold process (or hold unit) is a condensate from the heat exchange process (or heat exchange unit) and is at a relatively high temperature (for example, a temperature close to the boiling point of the condensate in the back pressure space). Therefore, by utilizing the high vapor pressure (or saturated vapor pressure) of this condensate, 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, a process in which the VRC system functions effectively even if a large amount of recompressed steam is condensed (for example, the condensable gas component is totally condensed) in the heat exchange step ( Or a plant) design becomes possible (or easy), and the energy saving effect can be further improved. In addition, the hold process (or hold unit) can easily control the pressure on the downstream side (back pressure space) of the compressor, and the plant (or the steam recompression unit (or recompression process)) equipped with the VRC system. Can be operated (or operated or operated) smoothly (or easily). For this reason, it is easy to apply to a plant with large fluctuations in throughput and operating conditions, and the process design is excellent in flexibility.

In the present specification and claims, the “back pressure space” refers to the space and line from the compressor downstream to the flow rate control device, for example, from the compressor downstream via the heat exchange unit, hold unit, etc. And a space and a line up to the flow rate control device arranged in each of the first circulation line and the condensate discharge line (or condensate discharge line), and the second circulation line from the compressor downstream It means the gas phase part of the space including the space and the line leading to the flow control device.

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

On the other hand, non-condensable gases such as non-condensed recompressed steam (non-condensed steam) and seal gas not dissolved in the process condensate are air components connected to the hold tank 8 as gas components (non-condensed components). It returns 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 unit 10 is usually cooled and condensed by the second condenser 3 on the downstream side of the connection unit 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 for the processes after the condensation process of the main process and the steam recompression process 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-condensed component). In the process shown in FIG. 2, in addition to the hold tank 8, the air ring line (or pressure equalizing pipe) 8 a and the flow rate control valve 13, the hold unit supplies the process fluid from the heat exchanger 7 to the upstream side of the hold tank 8. A gas-liquid separator 19 for separating a gas component (non-condensed component) and a liquid component (condensate), and an air ring 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 shown in FIG.

In the example of FIG. 2, since the gas-liquid separator 19 is provided on the upstream side of the hold tank 8, a process fluid (condensate) from which a gas component (non-condensed component) is separated can flow into the hold tank 8. is there. Therefore, the amount of condensate introduced into the hold tank 8 can be more accurately managed, and the amount of condensate retained in the hold tank 8 and the residence time can be more easily controlled. In addition, even if 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, the phenomenon such as steam hammer can be effectively suppressed, so the VRC process can be stabilized. I can drive.

The method (or plant) of the present invention is not necessarily required, but may have a gas introduction step (or a gas introduction unit) for introducing a non-condensable gas into the back pressure space. The process shown in FIG. 3 includes a gas introduction line 20 for introducing a non-condensable gas to the upstream side (back pressure space side) of the flow control valve 11 in the first circulation line 9 (or the circulation step) and the non-condensable gas. A flow control valve 21 (gas introduction unit or gas introduction step) for adjusting the amount of condensable gas introduced is provided, and further, a non-dissolved solution in the condensate is provided downstream 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 Otherwise, it is the same as the process of FIG.

When the unit and / or line forming the back pressure space such as the hold tank is cooled and the temperature is low at the start of VRC process operation (or at the beginning of operation), it is difficult to hold the pressure of the back pressure space by the hold unit. There is a case. Since the process shown in FIG. 3 includes a gas introduction unit (or a gas introduction step), even if a pressure drop (or a condensate temperature drop) occurs in the back pressure space due to an abnormal situation as described above. 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 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 includes recompressed steam (non-condensed steam) that has not been condensed in the heat exchanger 7, seal gas that has not been dissolved in the process condensate, and the like. The main unit (or the main unit) is separated as a gas component by the hold tank 8 and via the first circulation line 9 via the air ring line 8a of the hold tank 8 and / or the air ring line 9a of the heat exchanger 7. Return to step).

On the other hand, in the deaeration unit (or the deaeration process), the condensate from the condensate cooler 18 stays in the condensate deaeration tank 22, so that the non-condensable gas dissolved in the condensate 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 condensate. The degassed gas component (non-condensable gas) is discharged from a scrubber or other detoxification facility (or discharge facility), and the liquid component (condensate) is recovered together with the condensate of the main unit (or main process). The Therefore, the non-condensable gas dissolved in the condensate does not re-evaporate and does not affect the recovery destination unit (or process).

Also, the method (or plant) of the present invention may use the heat amount of the condensate flowing out of the hold unit in the VRC process and / or other processes. The process shown in FIG. 4 includes a flash tank (or flash evaporator) 24 (flash unit or flash evaporator) for flash evaporation of the condensate flowing out of the hold unit between the flow control valve 13 and the (condensate) cooler 18. And a third circulation line 25 for returning a gas component (volatile component) generated by the flash evaporation to the main unit (or main step), and at least one of process steam generated in the main unit (or main step). The process is the same as the process of FIG. 1 except that a part is branched through an introduction line (or an air supply line) 26 and provided with another unit (or another process) for use as a heat source in another process. . In addition, the liquid component (nonvolatile component) separated by the flash unit (or the flash process) is recovered as a condensate 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 starting the VRC process. That is, the flow control valve 15 is closed, and at least a part of the process vapor discharged from the distillation column 1 is condensed by the first condenser 2 and the second condenser 3. When another process is operating, it is collected together with the condensate condensed in the other process.

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

The volatile component 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. In other words, the flash unit (or the flash process) has a complicated apparatus or the like arranged so that the sensible heat of the condensate discharged (or outflowed) in the VRC process can be reused as the latent heat of the vapor by the flash process. Without installation, the energy saving effect can be further improved with minimum capital investment. 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 vapor, the amount of process vapor relative to the amount of volatile component vapor is overwhelmingly large. Will not be adversely affected.

Also, if the VRC process and another process using the process steam of the main process are provided 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 the separate process There are cases where both cannot be operated (or operated) effectively. In particular, when the type of the compressor is a turbo type, there is a risk of equipment damage due to surging if the amount of inflow of process steam is small, 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 tends to be insufficient, and the energy saving effect may be extremely reduced. However, in the present invention, since the deficient amount of steam is compensated by the volatile component by the flash process, both the VRC process and the separate process can be operated effectively (or compatible). 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), and process design flexibility is further increased. It 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 process steam is generated. For example, the process steam generator is a device whose temperature is controlled by heating and evaporating with a heat source and then cooling and circulating. Specifically, it may be a reactor, an evaporator, a crystallizer, a dryer, or the like. Among these, a distillation column is preferable because the VRC process is easily incorporated into the heat source of the main process. The distillation tower is provided with a condenser for discharging process steam from the top of the tower and cooling and condensing the process steam, and a reboiler for gas charging of the raw material at the bottom of the distillation tower. The evaporator may be used as a heat source in combination with the reboiler at the bottom of the tower.

The process steam only needs to contain at least a condensable gas component, and may contain a non-condensable gas component, which will be described later. However, it is difficult to contribute as a heat source and is economically disadvantageous. Is preferably free of non-condensable gas components (or very small amounts of non-condensable gas components). 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), ketones ( Acetone, ethyl methyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), aldehydes (acetaldehyde, propionaldehyde, etc.), carboxylic acids (acetic acid, propionic acid, etc.), ethers (chain ethers such as dimethyl ether and diethyl ether, dioxane, Cyclic ethers such as tetrahydrofuran), hydrocarbons (aliphatic hydrocarbons such as hexane, alicyclic hydrocarbons such as cyclohexane, aromatics such as benzene, toluene, xylene, etc. Hydrogen such like), halogenated hydrocarbons (methylene chloride, chloroform, etc.) and the like. These organic solvents can be used alone or in combination of two or more. Of these organic solvents, esters (especially acetates) and hydrocarbons (especially aromatic hydrocarbons) are widely used. For example, esters / hydrocarbons are represented by esters / hydrocarbons = 99 / It may be mixed in a weight ratio of about 1 to 10/90, preferably 90/10 to 30/70, more preferably about 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, about 30 to 150 ° C., preferably 50 to 120 ° C., 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 5 to 20 kPa, and more preferably about 10 to 15 kPa. .

The proportion 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, for example, 30 to 99% by weight, preferably 50 to It may be about 98% by weight, more preferably about 80 to 95% by weight (particularly 85 to 93% by weight).

The temperature of the process vapor can be selected according to the type of condensable gas, and is not particularly limited, but is, for example, about 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 atmospheric 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 independent, but it is possible to efficiently condense the condensable gas component in the process steam and to suppress the circulation of uncondensed steam in the VRC process. Are preferably arranged in series. For example, two capacitors may be arranged in series. The capacity | capacitance of a condenser is not specifically limited, Usually, the capacity | capacitance which can condense the condensable gas component in a process vapor | steam by the single operation of the main process which does not operate a VRC process is selected. When the condenser is provided alone, the first circulation line is connected to the upstream side of the condenser. When arranging a plurality of capacitors, a plurality of capacitors may be arranged in series, and the first circulation line may be connected upstream of the first capacitor, but downstream of the first capacitor, And a line upstream of the last capacitor (a line between adjacent capacitors, and when two capacitors are arranged in series, a line between the first capacitor and the second capacitor) By connecting 1 circulation line, it can suppress that the condensable gas component in the non-condensed recompressed steam from the 1st circulation line circulates (backflows) to the VRC process. The plurality of condensers may be different condensers or the same condenser, but usually the first condenser (condensable gas in the process steam during steady operation only with the first condenser (upstream)). A condenser is used that has the capacity to condense all of the components.

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 material of the process steam generator in a gaseous state. In particular, in the case of a distillation column, as described above, the main process evaporator may be a column bottom reboiler, and a heat exchanger (such as a VRC evaporator) in the VRC process is used as a heat source for the main process together with the column bottom reboiler. May be used.

The process steam discharge line in the main process branches into a main line for cooling and condensing the process steam by the condenser and a VRC line supplied to the VRC process. In the VRC line supplied to the VRC process, flow control is performed. Although an apparatus is not essential, it is preferable to arrange | position the flow volume control apparatus for controlling the flow volume of the process steam to a VRC process upstream for the stable operation | movement of a 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) during steady operation when the VRC process is stable. The ratio of the process steam distributed between the main line and the VRC line can be appropriately selected according to the capacity of the compressor. From the viewpoint of energy saving, it is preferable that the ratio supplied to the VRC line is larger. At times, the entire amount of process steam may be distributed to the VRC line, but usually some of the process steam is supplied to the main line and the remainder is supplied to the VRC line.

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

As described above, in the example of FIG. 1, the utilization method of the recompressed steam was explained by the plant equipped with the turbo compressor, but in the plant equipped with the screw compressor, before the pressurization of the compressor ( The process steam circulation method in the VRC process (before the start of condensation) is slightly different. Specifically, in a plant equipped with a screw type compressor, as a device constituting the plant, in addition to different types of compressors, a flow control device adjacent to the upstream side of the compressor (the flow control valve in FIG. 1). It differs from a plant equipped with a turbo compressor in that 17) is not provided. As the process steam circulation operation, in a plant equipped with a screw-type compressor, the screw-type compressor is started and the flow rate disposed in the second circulation line is confirmed after being stabilized at the rated rotational speed. In the point which closes a control device (flow control valve 12 in Drawing 1), it differs from a plant provided with a turbo type compressor. Specifically, although the discharge pressure is hardly applied to the process steam that has passed through the screw compressor, as described above, the heat of the compressor shaft power x mechanical efficiency x (1-adiabatic efficiency) passes through the compressor. Heat transfer to the process steam causes a slight temperature rise. A part of the process steam whose temperature is slightly raised is circulated to the suction side of the compressor through the second circulation line. If the circulation continues, the temperature may exceed the upper limit of the compressor. After the operation state of the machine is stabilized, the flow control device disposed in the second circulation line is closed. Even if the flow control device disposed in the second circulation line is closed, the uncondensed recompressed steam circulating through the VRC process can be returned to the main process by the first circulation line. Circulation can be stopped in the second circulation line before the compressor is heated above the upper limit temperature. Therefore, the equipment for cooling the compressor heated up by the circulation of the second circulation line is also unnecessary. Thus, although the circulation method before the start of condensation differs depending on the type of the compressor, in any compressor, the recompressed steam can be safely and easily reused as a heat source.

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, by adjusting the flow rate returned from the first circulation line (circulation step) to the main unit and controlling the process steam compression ratio (discharge pressure / suction pressure) (absolute pressure) by the steam recompression unit, Adjust the temperature of the recompressed steam to the desired temperature. In the present invention, if the flow rate returned to the main unit from the first circulation line is suppressed by the flow rate control device, the compression ratio increases, and the temperature increases due to the increase in the compression ratio, thereby improving the heat exchange efficiency. The compression ratio can be appropriately selected according to the target temperature of the recompressed steam. For example, it is 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, it is set to a discharge temperature that is, for example, 5 ° C. higher than the temperature of the process steam before being supplied to the steam recompression unit. For example, the discharge temperature may be set higher by 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 (return pipe of the compressor) is not essential, but since the VRC process can be stably operated, the second recirculation line provided with the flow rate control device is provided. May be. In the turbo compressor, the VRC line introduced into the compressor may further include a flow control device in the line after joining the second circulation line. In a plant equipped with a turbo compressor, the flow rate of the process steam introduced into the compressor is adjusted by adjusting the opening of the flow control device even before the compressor is started and during stable operation of the process. May be. Further, in the second circulation line in the plant equipped with the screw type compressor, in the initial stage of the VRC process operation (cold start), the flow rate control device is opened, and the process steam is circulated to the second circulation line. It may be used only for a short period of time until the rotating part reaches a stable rotational speed at the start of operation. A compressor having a function of a second circulation line in its mechanism is also commercially available.

In addition, in the present specification and claims, in addition to the above definition, the recompressed steam is a process steam that has passed through a steam recompression unit (step) (the degree of compression and the degree of compression). Steam with a small temperature rise) may also be referred to as recompressed steam.

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

The heat exchange unit is connected to the first circulation line, and gas components that have not been condensed in the heat exchange unit (non-condensed components including non-condensable vapor and non-condensable gas) are included in the heat exchange unit and / or It returns to the main process by the first circulation line via the air ring line of the hold unit. In the heat exchanging unit (heat exchanging step or condensing step), since the temperature rise of the recompressed steam is low at the initial stage of operation until the vapor recompressing unit becomes stable, most of the process fluid remains in the gaseous state in the first circulation line. Is returned to the main process. On the other hand, when the vapor recompression unit is stable, the process may be designed so that a part of the recompressed steam is condensed. However, all the condensable gas components in the recompressed steam are condensed (totally condensed). Thus, it is preferable to process-design the heat exchange unit (or heat exchange step). In the heat exchange process designed in this way, since most of the condensable gas component in the recompressed steam is condensed, there is almost no uncondensed steam (condensable gas component) supplied to the first circulation line. . In addition, as long as the effect of the present invention is not adversely affected, a part of the recompressed steam may be flowed to the first circulation line for maintaining the back pressure without being fully condensed.

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 held by the hold unit. However, the VRC method is easy to apply, and the process design flexibility is excellent.

[Hold process (hold unit)]
In the present invention, the hold unit (hold process) only needs to 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 condensate condensed by the heat exchange unit and the non-condensed components that have not been condensed. The hold unit having such a gas-liquid separation function may have a hold tank capable of gas-liquid separation, or may be formed of a gas-liquid separator and a hold tank. And 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 that allows gas-liquid separation, and the separated gas component (non-condensed component) is used as a back pressure space. It is only necessary to have an air ring line (or a pressure equalizing pipe) for returning (or communicating), and it is only necessary that the condensate can be separated into a gas phase and a liquid phase. If the capacity of the tank is too large, it is necessary to lengthen the residence time. Therefore, the temperature of the condensate may be reduced due to heat radiation from the tank surface, and the back pressure may not be effectively maintained.

Further, the gas-liquid separator is not particularly limited as long as the gas component and the condensate can be separated. The gas-liquid separator is usually connected to the upstream side of the hold tank in order to send the separated liquid component, and the separated gas component (non-condensed component) is returned to the back pressure space ( In many cases, it has an air ring line (or pressure equalizing pipe) for communication).

The gas component (non-condensed component) that is separated from the gas is separated from the steam that cannot be condensed in the heat exchange unit, the non-condensable gas introduced from the gas introduction unit, and the compressor bearing. Among the sealing gas (such as nitrogen gas) leaked into the gas, a gas component that was not completely dissolved in the process condensate, a vapor generated by the vapor-liquid equilibrium of the condensate remaining in the hold tank, and the like may be included. These non-condensed components may be returned to the main process and processed by the first circulation line via a hold tank capable of gas-liquid separation and / or an air ring line of the gas-liquid separator.

The air ring line of the hold tank capable of gas-liquid separation includes a gas phase space in the hold tank and a gas pressure space upstream of the hold tank (for example, the first gas pressure space). A circulation line) may be used. In addition, the air ring line of the gas-liquid separator is a gas-phase space (e.g., upstream of the gas-liquid separator in the back pressure space downstream of the vapor recompression unit). , The first return line). The position where each air ring line is connected is not particularly limited as long as it is a back pressure space. 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. Usually, it is often connected to the first circulation line (upstream side of the flow control valve 11 in FIG. 1).

When the hold tank has an air ring line (or gas-liquid separation function), the vapor pressure (or saturated vapor pressure) of the condensate that is retained (or stored) is effectively functioned to maintain the back pressure. This is preferable. Note that the line through which the condensate flows into the hold tank is sufficiently large with respect to the inflow of the condensate, and the gas phase space and the back pressure space (for example, the heat exchange unit) in the hold tank are blocked with the condensate. The air ring line is not always necessary when communicating (or communicating) without escaping (when the vapor pressure of the condensate that remains is connected to the extent that it can be used to maintain the back pressure) In many cases, a line is provided.

The hold unit (or hold process) has a hold tank that retains the condensate, but usually a hold tank (or condensate tank) that temporarily retains (or stores) the condensate is installed. From the viewpoint of reducing the load caused by equipment maintenance, it is common to install a condensate cooler upstream of the tank to cool the condensate so that the tank does not become a high-pressure gas facility in accordance with regulations. However, in the present invention, the condensate is kept at a relatively high temperature (for example, a temperature near the boiling point of the condensate under the pressure in the back pressure space) without forcibly cooling or quenching the condensate. The pressure holding effect can be improved effectively. From such a viewpoint, in the hold unit, the condensate is retained in the hold tank without providing a cooling unit for cooling the condensate upstream of the hold tank.

From the same point of view, 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 retention 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 not impairing the energy saving effect. Good.

If the temperature of the condensate retained in the hold tank (or hold unit) is higher than the boiling point (boiling point under the pressure of the back pressure space) of at least one component constituting the condensate, the back pressure is effectively used. Easy to maintain or hold. Therefore, if necessary, the temperature of the condensate may be increased by heating. Typically, the temperature of the condensate to be retained is, for example, (T−50) ° C. to (T + 20) ° C. (for example, with respect to the temperature T at the outlet (or outlet of the heat exchange unit) in 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.), more preferably (T-10 ) ° C. to (T + 3) ° C. (for example, (T-5) ° C. to T ° C.). In the present specification and claims, 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 stably operated. It means the temperature of the condensate immediately after (or in the vicinity of). The specific temperature of the condensate staying is, for example, 40 to 150 ° C. (eg 50 to 130 ° C.), preferably 60 to 120 ° C. (eg 70 to 110 ° C.), 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 the back pressure.

The hold unit may not have a flow rate control device (flow rate control valve or valve) for controlling the flow rate of the condensate, but can effectively hold the back pressure and operate the VRC process stably. To adjust the outflow amount of the condensate and hold a predetermined amount of condensate in the hold tank (or to control the liquid level of the condensate to a predetermined position (liquid level) in the hold tank). In order to adjust the condensate extraction amount from the tank to suppress (or keep warm) the temperature drop of the condensate staying, and / or to suppress the pressure drop due to abrupt extraction, it has a flow control device. May be. The condensate residence time (or average residence time) in the hold unit (or hold step) is, for example, 0.5 minutes to 10 hours (eg, 1 minute to 5 hours), preferably 1.5 minutes to 3 hours ( For example, it may be about 2 minutes to 1 hour), more preferably about 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 or it becomes difficult to maintain the back pressure, so there is a possibility that the VRC process cannot be stably operated. On the other hand, if the length is too long, the temperature of the condensate decreases due to heat dissipation, and it becomes difficult to maintain the back pressure or a large capacity hold tank, which may make it difficult to save space in the equipment.

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

The condensate retention amount 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 ), and 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 (heat exchange process) (for example, 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 reduced per unit time during steady operation) is lower than that of the conventional VRC method in which it is difficult to maintain the back pressure. For example, it can be improved by 30 to 100%, preferably 40 to 80% (for example, 50%).

[Cooling process (cooling unit)]
In the present invention, if necessary, a cooling unit for cooling the condensate may be provided downstream of the hold unit. The cooling unit includes 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 include one or a plurality of the cooling devices, and in the case where a plurality of the cooling devices are provided, they may be connected in series and / or in parallel, respectively. Moreover, as long as it is downstream of the hold unit, one cooling unit may be provided, or a plurality of cooling units may be provided with other units (or processes) in between. With such a cooling unit, even if the condensate is discharged (or outflowed) into a space lower in pressure (eg, atmospheric pressure) than the back pressure space, it can be recovered stably (or smoothly) without flash evaporation. . When a flash unit is provided downstream of the hold unit, a cooling unit may be provided in a line that discharges (or flows out) the non-volatile components separated by the flash unit.

The cooling unit may further include a flow rate control device (flow rate control valve or valve) for adjusting the flow rate of the cooled condensate as necessary. The flow rate control device may be provided upstream (most upstream) of the cooling device (or cooler) or between a plurality of cooling devices, but is usually provided downstream (most downstream) of the cooling device. There are many cases. In addition, when the hold unit is not provided with the flow control device, the condensate extraction amount from the hold tank may be adjusted by the flow control device of the cooling unit.

[Gas introduction process (gas introduction unit)]
In the present invention, the gas introduction unit may not be provided, but the temperature of the condensate is temporarily reduced by the hold unit due to some circumstances (for example, the unsteady operation at the initial stage of operation as described above). In order to cope with the situation, a gas introduction unit may be provided.

The gas introduction unit may be connected to at least a position where the pressure of 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 joining portion of each air ring line and the upstream side of the flow rate control device of the first circulation line. That is, it is preferable to introduce non-condensable gas in the circulation step downstream of the heat exchange step and / or the hold step. In the circulation process, by introducing the non-condensable gas, the amount of non-condensable gas that reduces the contact frequency for heat exchange between the recompressed steam and the heat exchange unit decreases through the heat exchange unit, Since heat can be exchanged efficiently, the size of the facility (or heat exchange unit) can be reduced. Moreover, since the contact frequency of the non-condensable gas to be introduced and the process condensate can be reduced, dissolution of the non-condensable gas into the process condensate can also be suppressed. As long as the effects of the present invention are not impaired, 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). When a gas introduction unit is connected to the compressor, the non-condensable gas to be introduced may be used as a seal gas (or shaft seal gas) of the compressor, and further, a seal gas leaking from the seal portion of the compressor ( Non-condensable gas) may be used for maintaining the back pressure.

As a non-condensable gas introduced from the gas introduction unit, the gas state is maintained under the temperature and pressure in the back pressure space of the vapor recompression unit (compressor) from the viewpoint of securing a predetermined pressure in the back pressure space. The gas is preferably a gas, the temperature of the back pressure space is, for example, about 25 to 300 ° C., preferably about 40 to 230 ° C., more preferably about 65 to 150 ° C., and the pressure is, for example, 30 to 400 kPaG. (For example, 30 to 300 kPaG), preferably 40 to 200 kPaG, 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 that is difficult to dissolve in the process condensate (condensate of the condensable gas component) (a gas that is insoluble or hardly soluble). ) Is preferred.

As typical non-condensable gas, for example, an inert gas (for example, nitrogen, air, carbon dioxide, carbon monoxide, rare gas (for example, argon, helium, etc.), etc.) that does not react with process vapor or the like can be mentioned. It is done. In the present specification and claims, “inert gas” means process steam or equipment (or non-condensable) under the conditions of the VRC process (for example, temperature and pressure in the back pressure space). As long as it is a gas that does not react with the material of the inner surface of the equipment that comes into contact with the gas, there is no particular limitation, and under conditions other than the conditions of the VRC process, gas that is reactive with process steam, process steam, and equipment are configured. It is used to mean including a gas that is reactive with a material other than the material.

These non-condensable gases can be used alone or in combination of two or more as a mixed gas. Of these non-condensable gases, nitrogen is preferable 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 a gas derived from a process [for example, a main process of a plant or other process (or other reaction process) Non-condensable gas generated (or by-product), preferably air contained in a trace amount in the process steam generated from the main process, seal gas leaked from equipment (such as a compressor) having a seal part such as a bearing part, etc.] May be supplied as a non-condensable gas. From the viewpoint of simplicity, the gas is preferably introduced from outside the process.

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

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

The deaeration unit has at least a condensate deaeration tank. The condensate degassing tank only needs to have a sufficiently large capacity for retaining the condensate and degassing, and a conventional tank can be used. Moreover, the deaeration unit may have a gas discharge line for discharging the non-condensable gas component deaerated in the condensate deaeration tank. The gas discharge line may be connected to a conventional abatement equipment (or discharge equipment) such as a scrubber. The deaeration 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 deaeration unit may have a flow rate control device for controlling the condensate discharge (or outflow) amount from the condensate deaeration tank and adjusting the retention amount. The condensate discharged from the deaeration unit (deaeration step) may be recovered as it is or via a cooling unit (cooling step).

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

The flash evaporation may be performed by a constant temperature flash that heats the condensate and depressurizes, an adiabatic flash that depressurizes the condensate without heating, or a flash that combines these flash conditions. In flash evaporation, the temperature of the condensate is, for example, 40 to 200 ° C. (eg, 50 to 180 ° C.), preferably 60 to 150 ° C. (eg, 70 to 120 ° C.), and more preferably 80 to 110 ° C. (eg, 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 about 80 to 500 kPa, and more preferably about 100 to 300 kPa.

It is sufficient that at least a part of the volatile component generated in the flash process is available as at least a part of a heat source of another process, and the amount (or flow rate) of the volatile component generated in the flash process is a condensate introduced into the flash process. 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%. It may be about wt% (for example, 10 to 15 wt%).

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

The separate unit may have an introduction line (or an air supply line) for introducing the volatile component and / or process steam. The connection position of the introduction line is not particularly limited as long as the volatile component and / or process steam can be introduced. For example, the connection position is connected to the flash unit or a third circulation line for connecting the flash unit and the main unit. In general, the main unit, for example, the process steam generator of the main unit (main process) (distillation column 1 in FIG. 1) and the condenser (the first in FIG. In many cases, it is connected to a line between the condenser 2) (especially a line downstream of the third circulation line).

The proportion of the volatile component introduced into the separate unit is, for example, 0 to 100% by weight (eg 10 to 99% by weight), preferably 30 to 100% by weight (eg 50 to 97% by weight), more preferably about 70 to 100% by weight (for example, 80 to 95% by weight). Note that the remainder of the volatile components generated in the flash process may be returned to the main unit for processing.

Although not necessarily required, the plant of the present invention connects the flash unit (flash process) and the main unit (main process), and returns a third part for returning a part of the volatile components generated in the flash process to the main process. A circulation line may be provided. The connection position of the third circulation line is not particularly limited as long as it is upstream of the condenser (for example, the second condenser 3 in FIG. 1) from the process steam generator (distillation column 1 in FIG. 1). , A line between a branch point (branch point 4 in FIG. 1) for branching the process steam to the VRC process and the main process, and a flow control device (valve 15 in FIG. 1) on the VRC line, two connected in series It may be a line between the condensers (a line between the first condenser 2 and the second condenser 3 in FIG. 1), but from the viewpoint of improving the energy saving effect by using it as a heat source, process steam generation It is preferable to install in the line between the branch point (branch point 4 in FIG. 1) where the process steam branches from the top of the vessel to 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 a cooling unit. Similarly, the condensate condensed in another process may be recovered together with the condensate of the main unit as it is or via a cooling unit. When the process steam generator is a distillation column, a part of the recovered condensate may be used as the reflux liquid of the distillation column, and the remainder may be sent to the subsequent process as an 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 process) includes a distillation column 1, and the charged liquid was evaporated by a main process evaporator (first heat exchanger) 14 and charged into the distillation column 1 in a gas state. When the main process alone is stably operated, the process vapor discharged from the top of the distillation column 1 is atmospheric pressure (atmospheric pressure), the temperature is about 80 ° C., the composition is 60% by weight of ethyl acetate, benzene The flow rate was 4 m ³ / sec at 30 wt% and water 10 wt%. As the compressor of the VRC process, a turbo 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. Process steam replacement in the VRC process line-Start-up of the compressor-Start of pressurization of the compressor (before the start of condensation)
(1) It was confirmed that the

valves

11, 12, 13, 15, and 17 were fully closed.

(2) The valve 11 of the first circulation line, the valve 12 of the second circulation line, and the valve 17 on the compressor suction side are 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 to replace the VRC process line with process steam, and the temperature of 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 speed (after about 10 to 20 seconds), the compressor discharge pressure rise is less than 50 kPaG in the steady continuous operation state. 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 rose to 115 kPaG. The discharge temperature was about 105 ° C.

2. Compressor pressurization (after the start of condensation) to existing evaporator load reduction (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 with the VRC evaporator (second heat exchanger) 7. The recompressed steam finally reached almost total condensation in the VRC evaporator 7, and the condensate temperature discharged was 95 ° C. The condensate tank 8 finally reached a tank internal temperature of 95 ° C. The liquid level of the condensate tank 8 was controlled to 1.5 m ³ by intermittently opening and closing the liquid level control valve 13 to flow out. The average residence time of the condensate was 3 minutes, and the condensate introduction amount from the heat exchange unit and the condensate outflow amount (or withdrawal amount) from the hold tank were 30 tons / hr. The discharged condensate was cooled to 45 ° C. by heat exchange with 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 of charge from the VRC evaporator exceeds 70% of the maximum value, the flow rate of the heat source steam 16 to the main process evaporator is adjusted to be reduced while maintaining the minimum load of the main process evaporator 14, The opening of the valve 17 was gradually increased to increase the suction amount of the compressor, and the charge amount from the main process evaporator was adjusted.

(3) When the operation of the entire process was stabilized, the discharge pressure of the compressor was stabilized by opening and closing the valve 11 with a slight opening. When the operation was stable, the heat source steam load of the main process evaporator was reduced by 6 tons / hr compared to 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 a plant including the conventional VRC process including the gas-liquid separator 19 without including the condensate tank 8 and the condensate cooler 18 in the plant illustrated in FIG. 5. The operation was started as follows using the same process steam (pressure, temperature, composition, flow rate) as in Example 1 and a turbo compressor.

1. Process steam replacement in the VRC process line-Start-up of the compressor-Start of pressurization of the compressor (before the start of condensation)
As described in Example 1, The operation of the VRC process was started in the same procedure as (1) to (5). As in Example 1, 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. Pressurization of the compressor (after the start of condensation) to reducing 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 to discharge The temperature was set to 110 ° C., and heat exchange was performed with the VRC evaporator (second heat exchanger) 7. The recompressed steam does not reach full condensation in the VRC evaporator (second heat exchanger) 7, and a part of the recompressed steam is passed through the first circulation line to the main process as an uncondensed gas component. I was back. In addition, the condensate separated by the gas-liquid separator 19 was collected in a slightly thicker pipe (condensate drain line) and was opened and closed intermittently. The average residence time of the condensate was 5 seconds.

(2) The amount of feed from the main process evaporator was adjusted by adjusting the flow rate of the heat source steam 16 to the main process evaporator as the amount of evaporation in the VRC evaporator 7 increased.

(3) When the operation was stabilized, the discharge pressure of the compressor was stabilized by opening and closing the valve 11 intermittently with a small opening. In a stable operation, the heat source steam load of the main process evaporator was reduced by 4 tons / hr as compared to 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 normal pressure (atmospheric pressure), the temperature is about 72.5 ° C., the composition is ethyl acetate 66 wt%, benzene 24 wt%, water 10 wt%, 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 purifier used in another process. As shown in FIG. 7, a VRC process was added, but from the viewpoint of investment recovery, 30 tons / hr of process steam was processed by the compressor 5 to evaporate heat of the charged liquid in the distillation column 1. I found it necessary to use as. A turbo compressor (“f44C2” manufactured by IHI Corporation) was used as the compressor of the VRC process. The temperature of the condensate produced 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 condensing was performed, so the flow rate was 30 tons / hr. Met. When this condensate was flushed under normal pressure in the flash tank 24, the resulting vapor had a temperature of 69.5 ° C. and a flow rate of 3.8 ton / hr, and the composition was 65% by weight of ethyl acetate and 26% by weight of benzene. And 9% by weight of water. This steam was joined to 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 was branched to the VRC process side. The remainder of the combined steam is at a temperature of 72 ° C. and a flow rate of 28.8 ton / hr. The composition immediately after the merge (or at the start of operation) is 65.93 wt% ethyl acetate, 24.13 wt% benzene, water The composition after the stable operation of 9.94% by weight is ethyl acetate 63.97% by weight, benzene 26.70% by weight, water 9.33% by weight, and is discharged from the top of the distillation column 1 There was no significant change from the composition of process steam. When the remainder of the combined steam was sent to a hot water heater (hot water purifier) in another process, the previous 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 that does not include the flash tank 24 and the third circulation line 25 in the plant shown in FIG. The VRC process is installed in the same manner as in Example 2 except that the condensate generated in the VRC process is cooled to 45 ° C. by the condensate cooler 18 without passing through the flash tank 24 and merged with the condensate of the main process. It was put into operation. When only the remaining process steam introduced into the VRC process is sent to the heat exchanger (hot water purifier) of another process through the line 26 to another process, the material balance is matched, but there is no allowance for the flow rate. Stable air supply (or introduction) was not possible, which hindered hot water production in a separate process.

The method of using recompressed steam of the present invention can be used in various plants that generate process steam, such as distillation plants.

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 tank)
8a, 9a, 19a ... Air ring line (equal pressure equalization pipe)
18 ... Condensate cooler (cooler)
19 ... Gas-liquid separator 20 ... Gas introduction line 22 ... Condensate deaeration tank (deaeration tank)
24 ... Flash tank (flash evaporator)

Claims

A main process of generating process steam containing condensable gas components and recovering the condensable gas components of the generated process steam as a condensate, and adiabatically compressing at least a part of the process steam with a compressor to increase the temperature Among the recompression process to obtain recompressed steam, the heat exchange process using the recompressed steam as a heat source, and the non-condensed components that are not condensed among the recompressed steam used in the heat exchange process are returned to the main process. A re-compression steam including a circulation step, and at least a re-compression that includes a condensate condensed in the heat exchange step and retains the pressure in the back pressure space downstream of the compressor How to use steam.
The method according to claim 1, wherein the condensate is retained in the hold step without forcibly cooling the condensate upstream of the hold step.
The method according to claim 1 or 2, wherein the temperature of the condensate retained in the holding 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 the condensate is retained for 0.5 minutes to 10 hours by adjusting an outflow amount of the condensate in the holding step.
The method according to any one of claims 1 to 4, wherein the condensate and the non-condensed component are gas-liquid separated in the holding step.
And a degassing step of degassing the dissolved noncondensable gas from the condensate flowing out in the hold step. Item 6. The method according to Item 4 or 5.
The method according to any one of claims 4 to 6, further comprising a flashing step in which the condensate flowing out in the holding step is flash-evaporated and separated into a volatile component and a non-volatile component.
The method according to claim 7, 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 for generating 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 is adiabatically compressed to reduce the temperature. Steam recompression unit for obtaining recompressed steam by raising, heat exchange unit for using recompressed steam as a heat source, and non-condensed non-condensing among recompressed steam provided to heat exchange unit A recompressed steam utilization plant equipped with a circulation line for returning the components to the main unit, where the condensate condensed in the heat exchange unit is retained to reduce the pressure in the back pressure space downstream of the steam recompressing unit. Recompressed steam utilization plant having at least a holding unit for holding.
The plant according to claim 9, further comprising a hold tank that retains the condensate without being provided with a cooling unit for forcibly cooling the condensate upstream of the hold unit.
The temperature of the condensate in which at least a part of the unit and line forming the back pressure space downstream of the vapor recompression unit is kept warm and the hold unit stays is set to a temperature T at the outlet side of the heat exchange unit ( The plant according to claim 9 or 10, wherein the plant is maintained at (T-50) ° C to (T + 20) ° C.
The plant according to any one of claims 9 to 11, wherein the hold unit has a flow rate control device for adjusting the outflow amount of the condensate and retaining the condensate for 0.5 minutes to 10 hours.
The hold unit has a gas-liquid separation function and holds the condensate from the hold tank, and the gas phase section in the hold tank and the back pressure space downstream of the vapor recompression unit. The plant according to any one of claims 9 to 12, further comprising an air ring line for connecting the gas phase space on the upstream side.
The hold unit holds the condensate, the gas-liquid separator disposed upstream of the hold tank, and the gas component separated by the gas-liquid separator The plant according to any one of claims 9 to 12, further comprising an air ring line for returning to the gas phase space upstream of the gas-liquid separator in the downstream back pressure space.
Furthermore, a gas introduction unit for introducing a non-condensable gas into the back pressure space downstream of the vapor recompression unit, and a deaeration for degassing the non-condensable gas dissolved in the condensate flowing out from the hold unit. The plant according to any one of claims 9 to 14, comprising a unit.
The plant according to any one of claims 9 to 15, further comprising a flash unit that flash-evaporates the condensate flowing out of the hold unit and separates it into a volatile component and a non-volatile component.
The plant according to claim 16, further comprising a line for using at least a part of the volatile components separated by the flash unit as a heat source for another process.