Process steam recovery system and method

Abstract

The invention provides a process steam recovery system and method, and belongs to the technical field of steam recovery. The recovery system comprises a reactor exhaust tower, a spray water inlet is formed in the upper part of the side wall of the reactor exhaust tower, and a steam outlet is formed in the top of the reactor exhaust tower; a spray water inlet of the reactor exhaust tower is communicated with a spray water tank; and a steam outlet of the reactor exhaust tower is respectively communicated with a concentration tank and a steam pocket through pipelines. The device can effectively remove hexamethylenediamine and oligomer in process steam, reduces emission pollution, effectively utilizes the process steam to provide a heat source for the concentration tank, produces low-pressure steam with much waste heat for other users to use, consumes less spray water, absorbs a small amount of hexamethylenediamine and oligomer in exhaust gas of the reactor, and improves the production efficiency. And the waste water is discharged from the tower kettle as process waste water, is directly conveyed to an external sewage treatment system for sewage treatment, does not need to be independently recycled, and can achieve the purposes of energy conservation and consumption reduction.

Description

Technical Field

[0001] The invention belongs to the technical field of steam recovery, and in particular relates to a system and method for recovering process steam. Background Art

[0002] In the process of producing nylon 66 using nylon 66 polymerization reactor with domestic technology, a large amount of process steam will be discharged, and the process steam contains a small amount of hexamethylenediamine and oligomers. In the prior art, the process steam is treated by passing the process steam into a spray tower, and most of the process steam is condensed by spray spraying and other measures, and a small amount of non-condensable gas is emptied. This process includes a spray tower, a spray water collection tank, a spray water circulation pump, a spray water filter, a spray water cooler and other equipment. The recycled circulating spray water is filtered to remove impurities, and a certain amount of industrial water is added and then cooled and returned to the spray tower for recycling. The process steam temperature is as high as 240°C or above, the waste heat is not effectively utilized, and the circulating spray water flow is large. The spray water recovery system equipment occupies a large area. In addition, the spray water cooler and circulating pump consume circulating cooling water and electricity. Summary of the invention

[0003] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art and to provide a system and method for recovering process steam.

[0004] The present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a process steam recovery system, comprising a reactor exhaust tower, wherein the reactor exhaust tower is provided with a spray water inlet at the upper portion of the side wall and a steam outlet at the top;

[0006] The spray water inlet of the reactor exhaust tower is connected to a spray water tank;

[0007] The steam outlet of the reactor exhaust tower is connected to a concentration tank and a steam drum through pipelines.

[0008] A further improvement of the present invention is:

[0009] The reactor exhaust tower comprises an exhaust tower body, the top of the exhaust tower body is provided with a steam outlet, the bottom is provided with a wastewater outlet, the lower part of the side wall is provided with a process steam inlet, the upper part of the side wall is provided with a spray water inlet, and a plurality of sieve plates are provided in the exhaust tower body from the spray water inlet to the process steam inlet;

[0010] A spray water pipe is provided at the spray water inlet, one end of which extends into the interior of the exhaust tower body and is bent downward at 90 degrees, and at least one nozzle is provided at the end, and the other end of the spray water pipe is connected to the spray water tank through a pump;

[0011] A baffle is arranged inside the exhaust tower body at the process steam inlet.

[0012] A further improvement of the present invention is:

[0013] The steam outlet is connected to an exhaust pipe, and a first valve is arranged on the exhaust pipe. The first valve and a first pressure transmitter arranged on the top of the exhaust tower body form a pressure control loop.

[0014] A further improvement of the present invention is:

[0015] A second valve and a flow transmitter are provided on the pipeline connecting the spray water tank and the spray water inlet. The flow transmitter and the second valve form a flow control loop for controlling the amount of spray water entering the reactor exhaust tower.

[0016] A further improvement of the present invention is:

[0017] The exhaust pipe connected to the steam outlet of the reactor exhaust tower is connected to the inlet of the concentration tank jacket and the steam drum through the first pipe and the second pipe respectively;

[0018] A temperature-pressure cascade control loop is provided at the inlet of the concentration tank jacket to control the flow rate of process steam entering the concentration tank jacket.

[0019] A further improvement of the present invention is:

[0020] The temperature-pressure cascade control loop includes a third valve arranged on the first pipeline, a second pressure transmitter arranged at the inlet of the concentration tank jacket, and a temperature transmitter arranged on the concentration tank.

[0021] A further improvement of the present invention is:

[0022] The recovery system also includes a control unit, which is respectively connected to the first pressure transmitter, the flow transmitter, the second pressure transmitter and the temperature transmitter through signals, and is also respectively connected to the first valve, the second valve and the third valve through signals, and is used to respectively receive the detection values ​​transmitted by the first pressure transmitter, the flow transmitter, the second pressure transmitter and the temperature transmitter, and calculate the difference between the detection value and the set value, and adjust the valve opening corresponding to each transmitter according to the difference between the detection value and the set value.

[0023] A second aspect of the present invention provides a method for recovering process steam, which uses the process steam recovery system as described above to recover the process steam.

[0024] A further improvement of the present invention is:

[0025] The reactor exhaust tower top pressure is 0.9-1.3 MPaG, preferably 1.0-1.2 MPaG; and / or,

[0026] The mass ratio of the spray water fed into the exhaust tower of the reactor to the process steam fed into the exhaust tower of the reactor is 0.1 to 0.5:1, preferably 0.2 to 0.3:1.

[0027] A further improvement of the present invention is:

[0028] The pressure at the inlet of the concentration tank jacket is controlled at 0.8-1.1 MPaG;

[0029] The temperature in the concentration tank is controlled at 130°C to 160°C.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention can not only effectively remove hexamethylenediamine and oligomers in process steam and reduce emission pollution, but also effectively utilize process steam to provide heat source for concentration tank, and use excess heat to produce low-pressure steam for use by other users. The spray water consumption is small, and the spray water absorbs a small amount of hexamethylenediamine and oligomers in the exhaust gas of the reactor, and is discharged from the tower bottom as process wastewater, and is directly sent to an off-site sewage treatment system for sewage treatment, without the need for separate recovery, thereby achieving the purpose of energy saving and consumption reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of a process steam recovery system in an embodiment of the present invention;

[0033] Figure 2 Schematic diagram of the structure of the reactor exhaust tower in the embodiment of the present invention.

[0034] In the figure, 1. reactor exhaust tower, 101. exhaust tower body, 102. steam outlet, 102. wastewater outlet, 104. process steam inlet, 105. spray water inlet, 106. sieve plate, 107. baffle, 2. spray water tank, 3. concentration tank, 4. steam drum, 5. exhaust pipe, 6. first valve, 7. first pressure transmitter, 8. second valve, 9. flow transmitter, 10. first pipe, 11. second pipe, 12. third valve, 13. second pressure transmitter, 14. temperature transmitter. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0036] [Example 1]

[0037] like Figure 1As shown, an embodiment of the present invention provides a process steam recovery system, comprising a reactor exhaust tower 1, wherein the upper part of the side wall of the reactor exhaust tower 1 is provided with a spray water inlet, and the top is provided with a steam outlet;

[0038] The spray water inlet of the reactor exhaust tower 1 is connected to the spray water tank 2;

[0039] The steam outlet of the reactor exhaust tower 1 is connected to the concentration tank 3 and the steam drum 4 through pipelines.

[0040] The process steam discharged from the polymerization reactor for producing nylon 66 enters the reactor exhaust tower 1 from the bottom, and the spray water in the spray water tank 2 enters the reactor exhaust tower 1 through the top spray water inlet. The two are fully contacted in the reactor exhaust tower, and the spray water absorbs a small amount of hexamethylenediamine and oligomers in the process steam, and is discharged from the tower bottom as process wastewater to the off-site sewage treatment system; the process steam discharged from the tower top steam outlet is divided into two parts, one part goes to the jacket of the concentration tank 3 to replace the medium-pressure steam to heat the medium in the concentration tank, and the rest of the process steam is passed into the pipe side of the drum 4 to heat the steam condensate in the drum 4, and the produced low-pressure steam goes to the low-pressure steam network for use by other users.

[0041] [Example 2]

[0042] like Figure 2 As shown, the reactor exhaust tower 1 includes an exhaust tower body 101, a steam outlet 102 is provided on the top of the exhaust tower body 101, a wastewater outlet 103 is provided on the bottom, a process steam inlet 104 is provided on the lower part of the side wall, a spray water inlet 105 is provided on the upper part of the side wall, and a spray water pipe is provided at the spray water inlet 105. One end of the spray water pipe extends into the exhaust tower body 101 and is bent downward at 90 degrees, and at least one nozzle is provided at the end, so that the spray water entering the reactor exhaust tower 1 through the spray water pipe can be evenly dispersed, and then can fully contact with the process steam to fully absorb the hexamethylenediamine and oligomers in the process steam; the other end of the spray water pipe is connected to the spray water tank 2 through a pump.

[0043] A baffle 107 is provided at the process steam inlet 104 in the exhaust tower body 101 to control the speed and direction of the process steam entering the exhaust tower body 101 to ensure that the process steam can fully contact with the spray water.

[0044] Multiple sieve plates 106 are arranged in the exhaust tower body 101 from the spray water inlet 105 to the process steam inlet 104. The sieve plates 106 are large-aperture sieve plates to prevent solid particles from clogging the tower plates. The liquid phase flows through each layer of sieve plates 106 from top to bottom, and a certain height of liquid layer is maintained on each layer of sieve plates 106. The gas phase passes through the sieve holes on the sieve plates 106 from bottom to top, passes through each layer of sieve plates, and is dispersed into the liquid layer, so as to achieve the purpose of sufficient gas-liquid contact and mass transfer.

[0045] The top of the reactor exhaust tower 1 adopts a pressure control loop to ensure that the operating pressure at the top of the tower is stable and the temperature of the process steam discharged from the top of the tower will not be too low. Specifically, the steam outlet 102 is connected to the exhaust pipe 5, and the exhaust pipe 5 is provided with a first valve 6. The first valve 6 and the first pressure transmitter 7 provided at the top of the exhaust tower body 101 form a pressure control loop. The opening of the first valve 6 will be adjusted according to the difference between the detection value of the first pressure transmitter 7 and the set value, so that the pressure at the top of the reactor exhaust tower 1 is 0.9-1.3MPaG, preferably 1.0-1.2MPaG.

[0046] The temperature of the process steam before entering the reactor exhaust tower 1 is above 240°C, and the temperature of the process steam discharged from the top of the reactor exhaust tower can reach 180-230°C, preferably 190-210°C.

[0047] [Example 3]

[0048] In order to fully absorb hexamethylenediamine and oligomers in the process steam, the mass ratio of the spray water fed into the reactor exhaust tower 1 to the process steam entering the reactor exhaust tower 1 is controlled at 0.1-0.5:1, preferably 0.2-0.3:1.

[0049] Compared with the prior art, to treat the same exhaust volume of process steam, the amount of circulating spray water used in the prior art is 30-50 times the amount of spray water used in the present invention.

[0050] like Figure 1 As shown, a second valve 8 and a flow transmitter 9 are provided on the pipeline connecting the spray water tank 2 and the spray water inlet 105. The flow transmitter 9 and the second valve 8 form a flow control loop for controlling the amount of spray water entering the reactor exhaust tower 1. The opening of the second valve 8 is adjusted according to the difference between the detection value of the flow transmitter 9 and the set value.

[0051] [Example 4]

[0052] like Figure 1 As shown, the exhaust pipe 5 connected to the steam outlet 102 on the reactor exhaust tower 1 is connected to the inlet of the jacket of the concentration tank 3 and the steam drum 4 through the first pipeline 10 and the second pipeline 11 respectively, and the process steam discharged from the top of the reactor exhaust tower is divided into two paths, one path goes to the jacket of the concentration tank 3 to replace the medium-pressure steam to heat the medium in the concentration tank, and the remaining process steam is passed into the pipe side of the steam drum 4 to heat the steam condensate in the steam drum 4, and the produced low-pressure steam goes to the low-pressure steam network for use by other users.

[0053] A temperature-pressure cascade control loop is provided at the inlet of the jacket of the concentration tank 3 to automatically adjust the flow rate of the process steam from the top of the exhaust tower into the jacket of the concentration tank, so as to keep the temperature in the kettle of the concentration tank constant.

[0054] Specifically, the temperature-pressure cascade control loop includes a third valve 12 arranged on the first pipeline 10, a second pressure transmitter 13 arranged at the inlet of the jacket of the concentrator tank 3, which is used to detect the pressure value of the process steam entering the jacket of the concentrator tank 3, and a temperature transmitter 14 arranged on the concentrator tank 3, which is used to detect the temperature in the concentrator tank 3. When it is detected that the pressure in the jacket of the concentrator tank 3 or the temperature in the concentrator tank 3 is greater than the set value, the third valve 12 is controlled to be closed or closed, so as to control the flow rate of the process steam entering the jacket of the concentrator tank 3.

[0055] Further preferably, the pressure at the inlet of the jacket of the concentration tank 3 is generally controlled at 0.8-1.1 MPaG.

[0056] More preferably, the temperature in the concentration tank 3 is generally controlled at 130°C to 160°C.

[0057] The remaining process steam enters the steam drum 4, which adopts a kettle-type heat exchanger. Steam condensate is added from the bottom of the shell side, and the low-pressure steam generated by heating is discharged from the top of the shell side.

[0058] It has been calculated that the waste heat of the process steam released from the exhaust tower of the reactor is much greater than the heat required for heating the concentrator. If all the heating medium of the concentrator jacket is used, the temperature in the concentrator kettle may be too high. Therefore, the present invention divides the process steam into two parts, which not only prevents the temperature in the concentrator kettle from being too high, but also makes more thorough use of the waste heat of the process steam and achieves better energy-saving effect.

[0059] The wastewater discharged from the exhaust tower kettle has a relatively high content of hexamethylenediamine and oligomers, which is discharged to the off-site sewage treatment system. The wastewater from the concentration tank and the steam drum is relatively clean and is used as washing water in the exhaust washing tower of the concentration tank.

[0060] [Example 5]

[0061] An embodiment of the present invention provides a process steam recovery system, which also includes a control unit (not shown in the figure), which is respectively connected to the first pressure transmitter 7, the flow transmitter 9, the second pressure transmitter 13 and the temperature transmitter 14 through signals, and is also respectively connected to the first valve 6, the second valve 8 and the third valve 12 through signals, and is used to respectively receive detection signals transmitted by the first pressure transmitter 7, the flow transmitter 9, the second pressure transmitter 13 and the temperature transmitter 14, and convert the detection signal into a detection value, and then calculate the difference with the set value, and adjust the valve opening corresponding to each transmitter according to the difference between the detection value and the set value.

[0062] Specifically, the control unit is connected to the first valve 6 and the first pressure transmitter 7 through signals respectively. The first pressure transmitter 7 detects the pressure signal at the top of the exhaust tower body 101 in real time and transmits it to the control unit. The control unit receives the pressure signal transmitted by the first pressure transmitter 7 and converts it into a pressure value, calculates the difference between the pressure value and the set value, and adjusts the opening of the first valve 6 according to the difference, so that the top pressure of the reactor exhaust tower 1 is 0.9-1.3MPaG, preferably 1.0-1.2MPaG, thereby ensuring that the temperature of the process steam discharged from the top of the tower is not too low. Preferably, the temperature of the process steam before entering the reactor exhaust tower is above 240°C, and the temperature of the process steam discharged from the top of the reactor exhaust tower can reach 180-230°C, and is further preferably 190-210°C.

[0063] The control unit is connected to the flow transmitter 9 and the second valve 8 through signals respectively. The flow transmitter 9 detects the flow signal of the spray water entering the reactor exhaust tower 1 in real time and transmits it to the control unit. The control unit receives the flow signal transmitted by the flow transmitter 9 and converts it into a flow value, calculates the difference between the flow value and the set value, and adjusts the opening of the second valve 8 according to the difference, so as to control the mass ratio of the spray water sent into the reactor exhaust tower 1 to the process steam entering the reactor exhaust tower 1 to be 0.1-0.5:1, preferably 0.2-0.3:1.

[0064] The control unit is connected to the second pressure transmitter 13, the temperature transmitter 14 and the third valve 12 through signals respectively. The second pressure transmitter 13 detects the pressure signal of the process steam entering the jacket of the concentration tank 3 in real time and transmits it to the control unit. The temperature transmitter 14 detects the temperature signal in the concentration tank 3 in real time and transmits it to the control unit. The control unit receives the pressure signal transmitted by the second pressure transmitter 13 and the temperature signal transmitted by the temperature transmitter 14, converts them into pressure values ​​and temperature values ​​respectively, calculates the difference between the pressure value or the temperature value and the set value respectively, and adjusts the opening of the third valve 12 according to the difference between the pressure value and the set value or according to the difference between the temperature value and the set value, so that the pressure at the inlet of the concentration tank jacket is controlled at 0.8-1.1MPaG, and the temperature in the concentration tank is controlled at 130°C-160°C.

[0065] Preferably, the control unit may be a separately arranged control system, or may be a subunit or subsystem integrated into an existing DCS system in the nylon 66 polymerization reaction device, which is not specifically limited here.

[0066] [Example 6]

[0067] An embodiment of the present invention provides a process steam recovery method, which uses the process steam recovery system as described above to recover the process steam.

[0068] like Figure 1As shown, the process steam recovery system comprises a reactor exhaust tower 1, the upper part of the side wall of the reactor exhaust tower 1 is provided with a spray water inlet, and the top is provided with a steam outlet;

[0069] The spray water inlet of the reactor exhaust tower 1 is connected to the spray water tank 2;

[0070] The steam outlet of the reactor exhaust tower 1 is connected to the concentration tank 3 and the steam drum 4 through pipelines.

[0071] Further preferably, the pressure control loop is used at the top of the reactor exhaust tower to control the pressure at the top of the reactor exhaust tower, so as to ensure that the operating pressure at the top of the tower is stable and the temperature of the process steam discharged from the top of the tower is not too low. Specifically, the pressure at the top of the reactor exhaust tower is 0.9-1.3 MPaG, preferably 1.0-1.2 MPaG, so as to ensure that the temperature of the process steam discharged from the top of the tower is not too low. Preferably, the temperature of the process steam before entering the reactor exhaust tower is above 240°C, and the temperature of the process steam discharged from the top of the reactor exhaust tower can reach 180-230°C, and more preferably 190-210°C.

[0072] Further preferably, the spray water inlet of the reactor exhaust tower adopts a flow control loop to control the flow rate of the spray water entering the reactor exhaust tower, and then the mass ratio of the spray water entering the reactor exhaust tower to the process steam entering the reactor exhaust tower is controlled at 0.1 to 0.5:1, preferably 0.2 to 0.3:1.

[0073] Further preferably, a temperature-pressure cascade control loop is used at the inlet of the concentrator tank jacket to automatically adjust the flow rate of process steam from the top of the exhaust tower entering the concentrator tank jacket, so that the temperature in the concentrator tank kettle is constant, so that the pressure at the inlet of the concentrator tank jacket is controlled at 0.8-1.1 MPaG, and the temperature in the concentrator tank is controlled at 130°C-160°C.

[0074] The process steam discharged from the polymerization reactor for producing nylon 66 enters the reactor exhaust tower from the lower part of the side wall, and the spray water in the spray water tank enters the reactor exhaust tower through the top spray water inlet. The two are fully contacted in the reactor exhaust tower, and the spray water absorbs a small amount of hexamethylenediamine and oligomers in the process steam, and is discharged from the tower kettle as process wastewater to the off-site sewage treatment system. The process steam discharged from the steam outlet at the top of the tower is divided into two parts. One part goes to the jacket of the concentration tank to replace the medium-pressure steam to heat the medium in the concentration tank. The remaining process steam is passed into the drum pipe side to heat the steam condensate in the drum. The low-pressure steam produced goes to the low-pressure steam network for use by other users.

[0075] The wastewater discharged from the exhaust tower kettle has a relatively high content of hexamethylenediamine and oligomers, which is discharged to the off-site sewage treatment system. The wastewater from the concentration tank and the steam drum is relatively clean and is used as washing water in the exhaust washing tower of the concentration tank.

[0076] It has been calculated that the waste heat of the process steam released from the exhaust tower of the reactor is much greater than the heat required for heating the concentrator. If all the heating medium of the concentrator jacket is used, the temperature in the concentrator kettle may be too high. Therefore, the present invention divides the process steam into two parts, which not only prevents the temperature in the concentrator kettle from being too high, but also makes more thorough use of the waste heat of the process steam and achieves better energy-saving effect.

[0077] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0078] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0079] The above technical solution is only one implementation mode of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the principles disclosed in the present invention, and it is not limited to the technical solution described in the above specific embodiments of the present invention. Therefore, the above description is only preferred and does not have a restrictive meaning.

Claims

1. A process steam recovery system, characterized in that: It comprises a reactor exhaust tower, wherein the upper part of the side wall of the reactor exhaust tower is provided with a spray water inlet, and the top is provided with a steam outlet; The spray water inlet of the reactor exhaust tower is connected to a spray water tank; The steam outlet of the reactor exhaust tower is connected to a concentration tank and a steam drum through pipelines.

2. The process steam recovery system according to claim 1, characterized in that: The reactor exhaust tower comprises an exhaust tower body, the top of the exhaust tower body is provided with a steam outlet, the bottom is provided with a wastewater outlet, the lower part of the side wall is provided with a process steam inlet, the upper part of the side wall is provided with a spray water inlet, and a plurality of sieve plates are provided in the exhaust tower body from the spray water inlet to the process steam inlet; A spray water pipe is provided at the spray water inlet, one end of which extends into the interior of the exhaust tower body and is bent downward at 90 degrees, and at least one nozzle is provided at the end, and the other end of the spray water pipe is connected to the spray water tank through a pump; A baffle is arranged inside the exhaust tower body at the process steam inlet.

3. The process steam recovery system according to claim 1, characterized in that: The steam outlet is connected to an exhaust pipe, and a first valve is arranged on the exhaust pipe. The first valve and a first pressure transmitter arranged on the top of the exhaust tower body form a pressure control loop.

4. The process steam recovery system according to claim 3, characterized in that: A second valve and a flow transmitter are provided on the pipeline connecting the spray water tank and the spray water inlet. The flow transmitter and the second valve form a flow control loop for controlling the amount of spray water entering the reactor exhaust tower.

5. The process steam recovery system according to claim 4, characterized in that: The exhaust pipe connected to the steam outlet of the reactor exhaust tower is connected to the inlet of the concentration tank jacket and the steam drum through the first pipe and the second pipe respectively; A temperature-pressure cascade control loop is provided at the inlet of the concentration tank jacket to control the flow rate of process steam entering the concentration tank jacket.

6. The process steam recovery system according to claim 5, characterized in that: The temperature-pressure cascade control loop includes a third valve arranged on the first pipeline, a second pressure transmitter arranged at the inlet of the concentration tank jacket, and a temperature transmitter arranged on the concentration tank.

7. The process steam recovery system according to claim 6, characterized in that: The recovery system also includes a control unit, which is respectively connected to the first pressure transmitter, the flow transmitter, the second pressure transmitter and the temperature transmitter through signals, and is also respectively connected to the first valve, the second valve and the third valve through signals, and is used to respectively receive the detection values ​​transmitted by the first pressure transmitter, the flow transmitter, the second pressure transmitter and the temperature transmitter, and calculate the difference between the detection value and the set value, and adjust the valve opening corresponding to each transmitter according to the difference between the detection value and the set value.

8. A method for recovering process steam, characterized in that: The process steam is recovered by using the process steam recovery system as described in any one of claims 1 to 7.

9. The process steam recovery method according to claim 8, characterized in that: The reactor exhaust tower top pressure is 0.9-1.3 MPaG, preferably 1.0-1.2 MPaG; and / or, The mass ratio of the spray water fed into the exhaust tower of the reactor to the process steam fed into the exhaust tower of the reactor is 0.1 to 0.5:1, preferably 0.2 to 0.3:

1.

10. The process steam recovery method according to claim 8, characterized in that: The pressure at the inlet of the concentration tank jacket is controlled at 0.8-1.1 MPaG; The temperature in the concentration tank is controlled at 130°C to 160°C.

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