阅读说明：本技术 一种丙烯腈制备装置的四效蒸发系统 (Four-effect evaporation system of acrylonitrile preparation device ) 是由 石喆 李大伟 刘清娟 于 2019-09-05 设计创作，主要内容包括：本发明涉及一种丙烯腈制备装置的四效蒸发系统,包括依次串联设置的一效蒸发器蒸发器、二效蒸发器、三效蒸发器和四效蒸发器；一效蒸发器底部设置有用于其底部溶液循环换热的一效换热器,二效蒸发器底部设置有用于其底部溶液循环换热的二效换热器,三效蒸发器底部设置有用于其底部溶液循环换热的三效换热器,四效蒸发器底部设置有用于其底部溶液循环换热的四效换热器,以及输出釜底残液的残液泵；一效换热器并联设置有一效备用换热器,二效换热器并联设置有二效备用换热器,三效换热器并联设置有三效备用换热器,四效换热器并联设置有四效备用换热器；四效蒸发器中可选择的切出其中一个蒸发器及与其相配的换热器。根据本发明的四效蒸发系统稳定性高。(The invention relates to a four-effect evaporation system of an acrylonitrile preparation device, which comprises a first-effect evaporator, a second-effect evaporator, a third-effect evaporator and a four-effect evaporator which are sequentially connected in series; the bottom of the first-effect evaporator is provided with a first-effect heat exchanger for circulating heat exchange of a solution at the bottom of the first-effect evaporator, the bottom of the second-effect evaporator is provided with a second-effect heat exchanger for circulating heat exchange of the solution at the bottom of the second-effect evaporator, the bottom of the third-effect evaporator is provided with a third-effect heat exchanger for circulating heat exchange of the solution at the bottom of the third-effect evaporator, the bottom of the fourth-effect evaporator is provided with a fourth-effect heat exchanger for circulating heat exchange of; the first-effect heat exchanger is provided with a first-effect standby heat exchanger in parallel, the second-effect heat exchanger is provided with a second-effect standby heat exchanger in parallel, the third-effect heat exchanger is provided with a third-effect standby heat exchanger in parallel, and the fourth-effect heat exchanger is provided with a fourth-effect standby heat exchanger in parallel; one of the four-effect evaporators and the heat exchanger matched with the evaporator can be selectively cut out. The four-effect evaporation system provided by the invention has high stability.)

1. A four-effect evaporation system of an acrylonitrile preparation device is characterized by comprising a first-effect evaporator (11), a second-effect evaporator (12), a third-effect evaporator (13) and a four-effect evaporator (14) which are sequentially connected in series;

the bottom of the first-effect evaporator (11) is provided with a first-effect heat exchanger (111) for solution circulation heat exchange at the bottom of the first-effect evaporator, the bottom of the second-effect evaporator (12) is provided with a second-effect heat exchanger (121) for solution circulation heat exchange at the bottom of the second-effect evaporator, the bottom of the third-effect evaporator (13) is provided with a third-effect heat exchanger (131) for solution circulation heat exchange at the bottom of the third-effect evaporator, the bottom of the fourth-effect evaporator (14) is provided with a fourth-effect heat exchanger (141) for solution circulation heat exchange at the bottom of the fourth-effect evaporator;

the double-effect heat exchanger (121) is provided with a double-effect standby heat exchanger (121b) in parallel, the triple-effect heat exchanger (131) is provided with a triple-effect standby heat exchanger (131b) in parallel, and the four-effect heat exchanger (141) is provided with a four-effect standby heat exchanger (141b) in parallel;

one evaporator and a heat exchanger matched with the evaporator can be selectively cut out from the four-effect evaporation system.

2. The four-effect evaporation system according to claim 1, wherein a first communication pipeline (1m) is connected between the first-effect evaporator inlet material line and the second-effect evaporator inlet material line, and a first cut-off valve (11m) for controlling the cut-off of the first communication pipeline is arranged on the first communication pipeline;

a second communicating pipeline (1a) is connected between the inlet steam line of the first-effect heat exchanger and the inlet steam line of the second-effect heat exchanger, and a second cut-off valve (11a) for controlling the on-off of the second communicating pipeline is arranged on the second communicating pipeline.

3. The four-effect evaporation system according to claim 1, wherein a third communication pipeline (1c) is connected between the second-effect evaporator inlet material line and the third-effect evaporator inlet material line, and a third cut-off valve (11c) for controlling the on-off of the third communication pipeline is arranged on the third communication pipeline;

a fourth communicating pipeline (1f) is connected between the inlet steam line of the two-effect heat exchanger and the inlet steam line of the three-effect heat exchanger, and a fourth cut-off valve (11f) for controlling the on-off of the fourth communicating pipeline is arranged on the fourth communicating pipeline.

4. The four-effect evaporation system according to claim 1, wherein a fifth communication pipeline (1g) is connected between the three-effect evaporator inlet material line and the four-effect evaporator inlet material line, and a fifth cut-off valve (11g) for controlling the on-off of the fifth communication pipeline is arranged on the fifth communication pipeline;

and a sixth communication pipeline (1j) is connected between the inlet steam line of the three-effect heat exchanger and the inlet steam line of the four-effect heat exchanger, and a sixth cut-off valve (11j) for controlling the on-off of the sixth communication pipeline is arranged on the sixth communication pipeline.

5. The four-effect evaporation system according to claim 1, wherein a seventh communication pipeline (1h) is connected between a circulating pump inlet material line connected with the inlet of the three-effect heat exchanger and a residual liquid pump inlet material line, and a seventh cut-off valve (11h) for controlling the on-off of the seventh communication pipeline is arranged on the seventh communication pipeline;

an eighth communication pipeline (1k) is connected between the four-effect heat exchanger inlet steam line and the four-evaporator distillate condenser inlet steam line, and an eighth cut-off valve (11k) for controlling the on-off of the eighth communication pipeline is arranged on the eighth communication pipeline.

6. The four-effect evaporation system according to any one of claims 1 to 5, wherein a one-effect output pump (3a) is further arranged on the outlet pipeline of the one-effect heat exchanger, a two-effect output pump (3b) is further arranged on the outlet pipeline of the two-effect heat exchanger, a three-effect output pump (3c) is further arranged on the outlet pipeline of the three-effect heat exchanger, and a four-effect output pump (3d) is further arranged on the outlet pipeline of the four-effect heat exchanger;

and outlet pipelines of the two-effect output pump (3b), the three-effect output pump (3c) and the four-effect output pump (3d) are respectively provided with a flow meter (4).

7. The four-effect evaporation system according to claim 6, wherein a ninth communication pipeline (1b) is arranged between the first-effect output pump inlet condensate line and the second-effect output pump inlet condensate line, and a ninth cut-off valve (11b) for controlling the on-off of the ninth communication pipeline is arranged on the ninth communication pipeline.

8. The four-effect evaporation system according to claim 1, wherein the heat exchange area ratio a of the two-effect backup heat exchanger (121b) to the two-effect heat exchanger (121) is such that: a is less than or equal to 1;

the heat exchange area ratio a of the three-effect standby heat exchanger (131b) to the three-effect heat exchanger (131) satisfies: a is less than or equal to 1;

the heat exchange area ratio a of the four-effect spare heat exchanger (141b) to the four-effect heat exchanger (141) satisfies: a is less than or equal to 1.

9. The four-effect evaporation system according to claim 8, wherein the heat exchange area ratio a of the two-effect backup heat exchanger (121b) to the two-effect heat exchanger (121) is such that: a is more than or equal to 0.4 and less than 1;

the heat exchange area ratio a of the three-effect standby heat exchanger (131b) to the three-effect heat exchanger (131) satisfies: a is more than or equal to 0.4 and less than 1;

the heat exchange area ratio a of the four-effect spare heat exchanger (141b) to the four-effect heat exchanger (141) satisfies: a is more than or equal to 0.4 and less than 1.

10. The four-effect evaporation system according to claim 1, wherein the two-effect heat exchanger (121), the three-effect heat exchanger (131), and the four-effect heat exchanger (141) are floating head heat exchangers.

11. The four-effect evaporation system according to claim 1, wherein one or a combination of two of wire mesh defoamers (15), vapor lift cap trays (16) are disposed in each of the first-effect evaporator (11), the second-effect evaporator (12), the third-effect evaporator (13) and the four-effect evaporator (14).

12. The four-effect evaporation system according to claim 11, wherein the lift cap tray (16) is further provided with a weep head on its underside.

13. The four-effect evaporation system according to claim 12, wherein the weep head is a bent pipe with an inlet and an outlet facing in the same direction, and one end of the weep head is communicated with the weep hole on the lift cap tray, and the other end of the weep head is a free end.

14. The four-effect evaporation system according to any one of claims 11 to 13, wherein the distance h between the upper end of the wire mesh demister (15) and the connection position of the evaporator top head and the evaporator satisfies: h is less than or equal to 800 mm.

15. The four-effect evaporation system according to claim 14, wherein the distance L between said lift cap tray (16) and the evaporator top head and evaporator connection locations is such that: l is less than or equal to 1500 mm.

Technical Field

The invention relates to the field of chemical industry, in particular to a four-effect evaporation system of an acrylonitrile preparation device.

Background

The production technology of acrylonitrile at home and abroad mainly adopts a propylene ammoxidation method. The process is developed for more than 50 years, and the process technology is mature. Since the advent, there has been no major improvement in the process, mainly aiming at the research of novel catalysts and the development of novel fluidized bed reactors, and simultaneously developing the process technology improvement aiming at the purposes of energy saving, consumption reduction, environmental protection and the like to improve the efficiency of the device. The propylene ammoxidation method has the advantages of easily obtained raw materials, simple process, stable operation, convenient product refining, low product cost and the like.

In the four-effect evaporation unit in the existing domestic acrylonitrile production device, a gas-phase product separated by an evaporator contains a large amount of polymers due to liquid foam carried by high flow velocity, so that a two-effect heat exchanger, a three-effect heat exchanger and a four-effect heat exchanger are easy to block, the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger need to be cleaned once every 3-6 months, and the four-effect evaporation unit stops running when the heat exchanger is cleaned, so that the long-period stable running of the device is influenced.

Disclosure of Invention

The invention aims to provide a four-effect evaporation system of an acrylonitrile preparation device, which can stably operate for a long time.

In order to realize the aim, the invention provides a four-effect evaporation system of an acrylonitrile preparation device, which comprises a first-effect evaporator, a second-effect evaporator, a third-effect evaporator and a four-effect evaporator which are sequentially connected in series;

the bottom of the first-effect evaporator is provided with a first-effect heat exchanger for circulating heat exchange of a solution at the bottom of the first-effect evaporator, the bottom of the second-effect evaporator is provided with a second-effect heat exchanger for circulating heat exchange of the solution at the bottom of the second-effect evaporator, the bottom of the third-effect evaporator is provided with a third-effect heat exchanger for circulating heat exchange of the solution at the bottom of the third-effect evaporator, the bottom of the fourth-effect evaporator is provided with a fourth-effect heat exchanger for circulating heat exchange of the solution at the;

the double-effect heat exchanger is provided with a double-effect standby heat exchanger in parallel, the triple-effect heat exchanger is provided with a triple-effect standby heat exchanger in parallel, and the quadruple-effect heat exchanger is provided with a quadruple-effect standby heat exchanger in parallel;

one of the four-effect evaporators and the heat exchanger matched with the evaporator can be selectively cut out.

According to one aspect of the invention, a first communication pipeline is connected between the first-effect evaporator inlet material line and the second-effect evaporator inlet material line, and a first cut-off valve for controlling the first communication pipeline to be cut off is arranged on the first communication pipeline;

a second communicating pipeline is connected between the first-effect heat exchanger inlet steam line and the second-effect heat exchanger inlet steam line, and a second cut-off valve for controlling the on-off of the second communicating pipeline is arranged on the second communicating pipeline.

According to one aspect of the invention, a third communication pipeline is connected between the second-effect evaporator inlet material line and the third-effect evaporator inlet material line, and a third cut-off valve for controlling the on-off of the third communication pipeline is arranged on the third communication pipeline;

a fourth communicating pipeline is connected between the inlet steam line of the two-effect heat exchanger and the inlet steam line of the three-effect heat exchanger, and a fourth cut-off valve for controlling the on-off of the fourth communicating pipeline is arranged on the fourth communicating pipeline.

According to one aspect of the invention, a fifth communication pipeline is connected between the three-effect evaporator inlet material line and the four-effect evaporator inlet material line, and a fifth cut-off valve for controlling the on-off of the fifth communication pipeline is arranged on the fifth communication pipeline;

and a sixth communicating pipeline is connected between the inlet steam line of the triple-effect heat exchanger and the inlet steam line of the quadruple-effect heat exchanger, and a sixth cut-off valve for controlling the on-off of the sixth communicating pipeline is arranged on the sixth communicating pipeline.

According to one aspect of the invention, a seventh communication pipeline is connected between a circulating pump inlet material line connected with an inlet of the three-effect heat exchanger and a residual liquid pump inlet material line, and a seventh cut-off valve for controlling the on-off of the seventh communication pipeline is arranged on the seventh communication pipeline;

an eighth communicating pipeline is connected between an inlet steam line of the four-effect heat exchanger and an inlet steam line of the four-evaporator distillate condenser, and an eighth cut-off valve for controlling the on-off of the eighth communicating pipeline is arranged on the eighth communicating pipeline.

According to one aspect of the invention, a primary-effect output pump is further arranged on an outlet pipeline of the primary-effect heat exchanger, a secondary-effect output pump is further arranged on an outlet pipeline of the secondary-effect heat exchanger, a tertiary-effect output pump is further arranged on an outlet pipeline of the tertiary-effect heat exchanger, and a quaternary-effect output pump is further arranged on an outlet pipeline of the quaternary-effect heat exchanger;

and outlet pipelines of the two-effect output pump, the three-effect output pump and the four-effect output pump are respectively provided with a flowmeter.

According to one aspect of the invention, a ninth communication pipeline is arranged between the first-effect output pump inlet condensate line and the second-effect output pump inlet condensate line, and a ninth cut-off valve for controlling the on-off of the ninth communication pipeline is arranged on the ninth communication pipeline.

According to one aspect of the invention, the heat exchange area ratio a of the double-effect spare heat exchanger to the double-effect heat exchanger satisfies: a is less than or equal to 1;

the heat exchange area ratio a of the three-effect standby heat exchanger to the three-effect heat exchanger meets the following requirements: a is less than or equal to 1;

the heat exchange area ratio a of the four-effect standby heat exchanger to the four-effect heat exchanger meets the following requirements: a is less than or equal to 1.

According to one aspect of the invention, the heat exchange area ratio a of the double-effect spare heat exchanger to the double-effect heat exchanger satisfies: a is more than or equal to 0.4 and less than 1;

the heat exchange area ratio a of the three-effect standby heat exchanger to the three-effect heat exchanger meets the following requirements: a is more than or equal to 0.4 and less than 1;

the heat exchange area ratio a of the four-effect standby heat exchanger to the four-effect heat exchanger meets the following requirements: a is more than or equal to 0.4 and less than 1.

According to one aspect of the invention, the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger are floating head heat exchangers.

According to one aspect of the invention, one or a combination of two of a wire mesh demister and a vapor cap tray is arranged in each of the first-effect evaporator, the second-effect evaporator, the third-effect evaporator and the fourth-effect evaporator.

According to one aspect of the invention, the lower side of the lift cap tray is further provided with a weep head.

According to one aspect of the invention, the weep head is a bent pipe with an inlet and an outlet facing in the same direction, one end of the bent pipe is communicated with the weep hole on the lift cap tray, and the other end of the bent pipe is a free end.

According to one aspect of the invention, the distance h between the upper end of the wire mesh demister and the connecting position of the evaporator top head and the evaporator meets the following requirements: h is less than or equal to 800 mm.

According to one aspect of the invention, the distance L between the lift cap tray and the evaporator top head and evaporator connection location satisfies: l is less than or equal to 1500 mm.

According to one scheme of the invention, by the method for switching out any one-effect evaporator and heat exchanger provided by the invention, if one effect is blocked, the one-effect evaporator and the heat exchanger can be switched out and then overhauled and cleaned, and other evaporators and heat exchangers can be kept in normal operation. Thereby guaranteed the quadruple effect evaporation unit, can not take place to block up because of one of them effect, and the whole quadruple effect evaporation unit that leads to stops up, and then guaranteed the long period steady operation of acrylonitrile device quadruple effect evaporation unit.

According to the scheme of the invention, the floating head type heat exchanger is adopted, so that the outer wall of the heat exchanger can be cleaned more thoroughly after the heat exchanger tube bundle is drawn out. Particularly, the device prevents the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger from being blocked by polymer adhesion in the operation process of the four-effect evaporator of the acrylonitrile production device, and ensures the normal operation of the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger.

According to one scheme of the invention, the liquid foam entrained in a vapor phase in an evaporator can be effectively intercepted by arranging the wire mesh demister and/or the gas lift cap tray, so that the polymer entering a downstream heat exchanger is reduced. The measure can effectively improve the operation time of the first-effect heat exchanger, the second-effect heat exchanger, the third-effect heat exchanger and the fourth-effect heat exchanger, and reduce the maintenance frequency of the on-line heat exchanger, thereby reducing the occurrence of unstable production operation caused by the maintenance of the heat exchanger.

According to one scheme of the invention, after the second, third and fourth heat exchangers are additionally provided with the standby heat exchangers, when one heat exchanger is blocked due to the adhesion of polymers such as acrylonitrile or hydrocyanic acid and the like, the inlet and outlet valves of the blocked heat exchanger can be closed, and the inlet and outlet valves of the standby heat exchanger are opened at the same time, and then the blocked heat exchanger is overhauled and cleaned. The whole four-effect evaporation unit can not be stopped due to the blockage of the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger, thereby ensuring the stable operation of the four-effect evaporator of the acrylonitrile device.

According to the scheme of the invention, after the flow meter is additionally arranged at the outlet of the output pump of the two-three-four-effect evaporator, the metering condition of the flow meter can be directly used for accurately judging which effect heat exchanger shell pass is blocked, and then a corresponding switching maintenance scheme is adopted.

Drawings

FIG. 1 schematically illustrates a block diagram of a four-effect evaporator according to one embodiment of the present invention;

FIG. 2 is a schematic representation of a wire mesh demister installation configuration according to an embodiment of the present invention;

figure 3 schematically illustrates a lift cap tray installation configuration according to one embodiment of the present invention.

Detailed Description

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship that is based on the orientation or positional relationship shown in the associated drawings, which is for convenience and simplicity of description only, and does not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus, the above-described terms should not be construed as limiting the present invention.

The present invention is described in detail below with reference to the drawings and the specific embodiments, which are not repeated herein, but the embodiments of the present invention are not limited to the following embodiments.

As shown in fig. 1, according to one embodiment of the present invention, the four-effect evaporator for producing acrylonitrile of the present invention comprises a one-effect evaporator 11, a two-effect evaporator 12, a three-effect evaporator 13 and a four-effect evaporator 14, which are sequentially arranged in series. In this embodiment, the bottom of the first-effect evaporator 11 is provided with a first-effect heat exchanger 111 for circulating heat exchange of the solution at the bottom thereof, the bottom of the second-effect evaporator 12 is provided with a second-effect heat exchanger 121 for circulating heat exchange of the solution at the bottom thereof, the bottom of the third-effect evaporator 13 is provided with a third-effect heat exchanger 131 for circulating heat exchange of the solution at the bottom thereof, and the bottom of the fourth-effect evaporator 14 is provided with a fourth-effect heat exchanger 141 for circulating heat exchange of the solution at the bottom thereof. In the present embodiment, a two-effect backup heat exchanger 121b is provided corresponding to the two-effect heat exchanger 121, a three-effect backup heat exchanger 131b is provided corresponding to the three-effect heat exchanger 131, and a four-effect backup heat exchanger 141b is provided corresponding to the four-effect heat exchanger 141.

As shown in fig. 1, according to one embodiment of the present invention, the bottom of the first effect evaporator 11 is provided with a first pipeline 112 connecting the first effect evaporator 11 with a first residual liquid pump 113, the first residual liquid pump 113 is connected with the first effect heat exchanger 111 with a second pipeline 114, and the bottom liquid passing through the first effect heat exchanger 111 is returned back to the evaporator from the side line of the first effect evaporator 11. External low-pressure steam is input into the single-effect heat exchanger 111 through a third pipeline 117, exchanges heat with bottom liquid flowing through the single-effect heat exchanger, and then is conveyed to the normal-pressure steam condensate tank. The upper part of the first effect evaporator 11 is fed with the recovery tower bottom liquid through the fourth pipe 118.

As shown in FIG. 1, according to one embodiment of the present invention, the bottom of the second effect evaporator 12 is provided with a fifth pipeline 122 connecting the second effect evaporator 12 with a second residual liquid pump 123, the second residual liquid pump 123 is connected with the second effect heat exchanger 121 with a sixth pipeline 124, and the bottom liquid passing through the second effect heat exchanger 121 is returned back to the evaporator from the side line of the second effect evaporator 12. A seventh pipe 115 leads from the first pipe 112 to send a part of the bottom liquid in the first pipe 112 to the upper part of the second effect evaporator 12. An eighth pipeline 116 is led out from the top of the first-effect evaporator 11 and communicated with the second-effect heat exchanger 121, so that the material flow output from the top of the first-effect evaporator 11 exchanges heat with the bottom liquid in the second-effect heat exchanger 121 and is sent to the low-pressure steam condensate tank. In the present embodiment, a tenth communication line 1e is connected between the first pipe line 112 and the fifth pipe line 122, and a tenth shutoff valve 11e is provided on the ninth communication line.

In the present embodiment, the second-effect backup heat exchanger 121b is communicated with the eighth pipeline 116 through the first connection pipe 2a and communicated with the sixth pipeline 124 through the second connection pipe 2b, so that the second-effect backup heat exchanger 121b is connected in parallel with the second-effect heat exchanger 121. Shut-off valves may be provided in the first connection pipe 2a and the second connection pipe 2b to control the connection and disconnection of the secondary heat exchanger 121 b.

In the present embodiment, the heat exchange area ratio a between the dual-purpose backup heat exchanger 121b and the dual-purpose heat exchanger 121 satisfies: a is less than or equal to 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than or equal to that of the heat exchanger, so that the four-effect evaporator can be improved by adopting the standby heat exchanger with low cost.

Further, the heat exchange area ratio a between the two-effect backup heat exchanger 121b and the two-effect heat exchanger 121 satisfies: a is more than or equal to 0.2 and less than 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than that of the heat exchanger, so that the standby heat exchanger is prevented from being blocked in the process of maintaining the heat exchanger, smooth maintenance is guaranteed, and long-time stable operation of the four-effect evaporator is guaranteed.

Further, the heat exchange area ratio a between the two-effect backup heat exchanger 121b and the two-effect heat exchanger 121 satisfies: a is more than or equal to 0.4 and less than 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than that of the heat exchanger, so that the standby heat exchanger is prevented from being blocked in the process of maintaining the heat exchanger, smooth maintenance is guaranteed, and long-time stable operation of the four-effect evaporator is guaranteed.

As shown in FIG. 1, according to one embodiment of the present invention, the bottom of the triple-effect evaporator 13 is provided with a ninth pipeline 132 connecting the triple-effect evaporator 13 with a third residual liquid pump 133, the third residual liquid pump 133 is connected with the triple-effect heat exchanger 131 with a tenth pipeline 134, and the bottom liquid passing through the triple-effect heat exchanger 131 is returned to the evaporator from the side line of the triple-effect evaporator 13. An eleventh line 125 leads from the fifth line 122 to send a portion of the bottoms liquid in the fifth line 122 to the upper portion of the three-effect evaporator 13. A twelfth pipeline 126 is led out from the top of the second-effect evaporator 12 and communicated with the three-effect heat exchanger 131, so that the material flow output from the top of the second-effect evaporator 12 exchanges heat with the bottom liquid in the three-effect heat exchanger 131 and is sent to the low-pressure steam condensate tank.

In the present embodiment, the triple-effect backup heat exchanger 131b is communicated with the twelfth pipeline 126 through the third connection pipe 2c and communicated with the tenth pipeline 134 through the fourth connection pipe 2d, so that the triple-effect backup heat exchanger 131b is connected in parallel with the triple-effect heat exchanger 131. A shut-off valve may be provided in the third connection pipe 2c and the fourth connection pipe 2d to control the switching-on and switching-off of the triple-effect backup heat exchanger 131 b.

In the present embodiment, the heat exchange area ratio a between the three-effect backup heat exchanger 131b and the three-effect heat exchanger 131 satisfies: a is less than or equal to 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than or equal to that of the heat exchanger, so that the four-effect evaporator can be improved by adopting the standby heat exchanger with low cost.

Further, the heat exchange area ratio a between the three-effect backup heat exchanger 131b and the three-effect heat exchanger 131 satisfies: a is more than or equal to 0.2 and less than 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than that of the heat exchanger, so that the standby heat exchanger is prevented from being blocked in the process of maintaining the heat exchanger, smooth maintenance is guaranteed, and long-time stable operation of the four-effect evaporator is guaranteed.

Further, the heat exchange area ratio a between the three-effect backup heat exchanger 131b and the three-effect heat exchanger 131 satisfies: a is more than or equal to 0.4 and less than 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than that of the heat exchanger, so that the standby heat exchanger is prevented from being blocked in the process of maintaining the heat exchanger, smooth maintenance is guaranteed, and long-time stable operation of the four-effect evaporator is guaranteed.

As shown in fig. 1, according to an embodiment of the present invention, a thirteenth pipeline 142 connecting the four-effect evaporator 14 and a fourth residual liquid pump 143 is provided at the bottom of the four-effect evaporator 14, the fourth residual liquid pump 143 and the four-effect heat exchanger 141 are connected with a fourteenth pipeline 144, and the bottom liquid passing through the four-effect heat exchanger 141 is returned to the evaporator from the side of the four-effect evaporator 14. A fifteenth line 135 leads from the ninth line 132 to send a portion of the bottoms liquid in the ninth line 132 to the upper portion of the four-effect evaporator 14. And a sixteenth pipeline 136 is led out from the top of the three-effect evaporator 13 and communicated with the four-effect heat exchanger 141, so that the material flow output from the top of the three-effect evaporator 13 exchanges heat with bottom liquid in the four-effect heat exchanger 141 and then is sent to a low-pressure steam condensate tank. A seventeenth pipeline 145 leads from the thirteenth pipeline 142 to convey part of the bottom liquid to the subsequent section, and an eighteenth pipeline 146 leads from the top of the four-effect evaporator 14 to convey the stream led from the top of the four-effect evaporator 14 to the subsequent section for treatment.

In the present embodiment, the four-effect backup heat exchanger 141b is communicated with the sixteenth pipeline 136 through the fifth connection pipe 2e and communicated with the fourteenth pipeline 144 through the sixth connection pipe 2f, so that the four-effect backup heat exchanger 141b is connected in parallel with the four-effect heat exchanger 141. Shut-off valves may be provided in the fifth and sixth connection pipes 2e and 2f to control the switching on and off of the four-effect backup heat exchanger 141 b.

In the present embodiment, the heat exchange area ratio a between the four-effect backup heat exchanger 141b and the four-effect heat exchanger 141 satisfies: a is less than or equal to 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than or equal to that of the heat exchanger, so that the four-effect evaporator can be improved by adopting the standby heat exchanger with low cost.

Further, the heat exchange area ratio a between the four-effect backup heat exchanger 141b and the four-effect heat exchanger 141 satisfies: a is more than or equal to 0.2 and less than 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than that of the heat exchanger, so that the standby heat exchanger is prevented from being blocked in the process of maintaining the heat exchanger, smooth maintenance is guaranteed, and long-time stable operation of the four-effect evaporator is guaranteed.

Further, the heat exchange area ratio a between the four-effect backup heat exchanger 141b and the four-effect heat exchanger 141 satisfies: a is more than or equal to 0.4 and less than 1. Through the arrangement, the heat exchange area of the standby heat exchanger is selected to be smaller than that of the heat exchanger, so that the standby heat exchanger is prevented from being blocked in the process of maintaining the heat exchanger, smooth maintenance is guaranteed, and long-time stable operation of the four-effect evaporator is guaranteed.

As shown in fig. 1, one of the four-effect evaporators of the present invention and its associated heat exchanger can be selectively cut out according to one embodiment of the present invention.

As shown in figure 1, the first-effect evaporator and the first-effect heat exchanger are in short circuit by additionally arranging a communication pipeline, so that the second-effect evaporator, the third-effect evaporator and the fourth-effect evaporator, as well as the second-effect heat exchanger, the third-effect heat exchanger and the fourth-effect heat exchanger can normally operate. In the present embodiment, a first communication line 1m is connected between the first-effect evaporator inlet material line (i.e., the fourth line 118) and the second-effect evaporator inlet material line (i.e., the seventh line 115), and the first communication line 1m is provided with a first shut-off valve 11m for controlling the on/off of the first communication line. In this embodiment, a second communication pipeline 1a is connected between an inlet steam line of the first-effect heat exchanger 111 (i.e. a section where the third pipeline 117 is connected to the inlet of the first-effect heat exchanger 111) and an inlet steam line of the second-effect heat exchanger (i.e. a section where the eighth pipeline 116 is connected to the inlet of the second-effect heat exchanger 121), and a second cut-off valve 11a for controlling the on-off of the second communication pipeline 1a is arranged on the second communication pipeline. In this embodiment, a ninth communication pipeline 1b is connected between the steam line at the outlet of the first-effect heat exchanger 111 (i.e., the section of the third pipeline 117 connected to the outlet of the first-effect heat exchanger 111) and the steam line at the outlet of the second-effect heat exchanger (i.e., the section of the eighth pipeline 116 connected to the outlet of the second-effect heat exchanger 121), and a ninth cut-off valve 11b for controlling the on-off of the ninth communication pipeline 1b is arranged on the ninth communication pipeline 1 b. In the present embodiment, when the respective shut valves on the first communication line 1m, the second communication line 1a and the ninth communication line 1b are connected, the first-effect evaporator 11 and the corresponding first-effect heat exchanger 111 can be short-circuited by the communication lines, so that the first-effect evaporator 11 and the first-effect heat exchanger 111 are switched off in the operating state, and the second-effect evaporator 12, the third-effect evaporator 13 and the fourth-effect evaporator 14, and the corresponding second-effect heat exchanger 121, the third-effect heat exchanger 131 and the fourth-effect heat exchanger 141 can continue to operate normally.

As shown in fig. 1, according to an embodiment of the present invention, the first-effect evaporator, the third-effect evaporator, the fourth-effect evaporator, the first-effect heat exchanger, the third-effect heat exchanger, and the fourth-effect heat exchanger are normally operated by adding the communication lines to short-circuit the second-effect evaporator, the second-effect heat exchanger, and the second-effect backup heat exchanger. In the present embodiment, a third communication line 1c is connected between the inlet material line (i.e., the seventh pipeline 115) of the second effect evaporator 12 and the inlet material line (i.e., the eleventh pipeline 125) of the third effect evaporator 13, and the third communication line 1c is provided with a third cut-off valve 11c for controlling the on/off of the third communication line. In this embodiment, a fourth communication pipeline 1f is connected between an inlet steam line of the two-effect heat exchanger 121 (i.e., a section of the eighth pipeline 116 connected to the inlet of the two-effect heat exchanger 121) and an inlet steam line of the three-effect heat exchanger (i.e., a section of the twelfth pipeline 126 connected to the inlet of the three-effect heat exchanger), and a fourth cut-off valve 11f for controlling the on-off of the fourth communication pipeline 1f is arranged on the fourth communication pipeline 1 f. In the present embodiment, when the respective shut valves on the third communication line 1c and the fourth communication line 1f are connected, the second-effect evaporator 12 and the corresponding second-effect heat exchanger 121 can be short-circuited by the communication lines, so that the second-effect evaporator 12 and the second-effect heat exchanger 121 are switched off in the working state, and the first-effect evaporator 11, the third-effect evaporator 13 and the fourth-effect evaporator 14, and the corresponding first-effect heat exchanger 111, the third-effect heat exchanger 131 and the fourth-effect heat exchanger 141 can continue to operate normally.

As shown in fig. 1, according to an embodiment of the present invention, the triple-effect evaporator, the triple-effect heat exchanger and the triple-effect backup heat exchanger are short-circuited by adding the communication pipeline, so that the single-effect evaporator, the double-effect evaporator, the four-effect evaporator, the single-effect heat exchanger, the double-effect heat exchanger and the four-effect heat exchanger can normally operate. In the present embodiment, a fifth communication pipeline 1g is added between the triple-effect evaporator inlet material line (i.e., the eleventh pipeline 125) and the fourth-effect evaporator inlet material line (i.e., the fifteenth pipeline 135), and the fifth communication pipeline 1g is provided with a fifth cut-off valve 11g for controlling the on/off of the fifth communication pipeline. In this embodiment, a sixth communication pipeline 1j is added between an inlet steam line of the three-effect heat exchanger 131 (i.e., a section of the twelfth pipeline 126 connected to the inlet of the three-effect heat exchanger) and an inlet steam line of the four-effect heat exchanger 141 (i.e., a section of the sixteenth pipeline 136 connected to the inlet of the four-effect heat exchanger 141), and the sixth communication pipeline 1j is provided with a sixth cut-off valve 11j for controlling the on-off state of the sixth cut-off valve. In the present embodiment, when the respective shut valves on the fifth communication line 1g and the sixth communication line 1j are connected, the triple-effect evaporator 13 and the corresponding triple-effect heat exchanger 131 can be short-circuited by the communication lines, so that the triple-effect evaporator 13 and the triple-effect heat exchanger 131 are switched off in the working state, and the single-effect evaporator 11, the double-effect evaporator 12 and the four-effect evaporator 14, and the corresponding single-effect heat exchanger 111, the double-effect heat exchanger 121 and the four-effect heat exchanger 141 can continue to operate normally.

As shown in fig. 1, according to an embodiment of the present invention, the four-effect evaporator, the four-effect heat exchanger, and the four-effect backup heat exchanger are short-circuited by adding the communication pipeline, so that the one-effect evaporator, the two-effect evaporator, the three-effect evaporator, and the one-effect heat exchanger, the two-effect heat exchanger, and the three-effect heat exchanger operate normally. In the present embodiment, a seventh communication line 1h is connected between the ninth pipe line 132 (i.e., the circulation pump inlet material line) and the seventeenth pipe line 145 (i.e., the circulation pump inlet material line), and the seventh communication line 1h is provided with a seventh shut-off valve 11h for controlling the on/off of the seventh communication line. In the present embodiment, an eighth communication line 1k is connected between the four-effect heat exchanger inlet steam line (i.e., the section of the sixteenth pipeline 136 connected to the inlet of the four-effect heat exchanger 141) and the four-evaporator distillate condenser inlet steam line (i.e., the eighteenth pipeline 146), and the eighth cut-off valve 11k for controlling the on-off of the eighth communication line 1k is provided. In the present embodiment, when the respective shut valves on the seventh communication line 1h and the eighth communication line 1k are connected, the four-effect evaporator 14 and the corresponding four-effect heat exchanger 141 can be short-circuited by the communication lines, so that the four-effect evaporator 14 and the four-effect heat exchanger 141 are switched off in the operating state, and the first-effect evaporator 11, the second-effect evaporator 12, and the third-effect evaporator 13, and the corresponding first-effect heat exchanger 111, the second-effect heat exchanger 121, and the third-effect heat exchanger 131 can continue to operate normally.

As shown in fig. 1, according to an embodiment of the present invention, a first-effect output pump 3a is further disposed on an outlet pipeline of the first-effect heat exchanger 111 (i.e., a section of the third pipeline 117 connected to the outlet of the first-effect heat exchanger 111), a second-effect output pump 3b is further disposed on an outlet pipeline of the second-effect heat exchanger 121 (i.e., a section of the eighth pipeline 116 connected to the outlet of the second-effect heat exchanger 121), a third-effect output pump 3c is further disposed on an outlet pipeline of the third-effect heat exchanger 131 (i.e., a section of the twelfth pipeline 126 connected to the outlet of the third-effect heat exchanger 131), and a fourth-effect output pump 3d is further disposed on an outlet pipeline of the fourth-effect heat exchanger 141 (i.e., a section of the sixteenth pipeline 136 connected. In the present embodiment, one flow meter 4 is provided to each of the outlet lines of the two-effect delivery pump 3b, the three-effect delivery pump 3c, and the four-effect delivery pump 3 d.

According to one embodiment of the present invention, the two-effect heat exchanger 121, the three-effect heat exchanger 131, and the four-effect heat exchanger 141 are floating head heat exchangers. In the present embodiment, the two-effect heat exchanger 121, the three-effect heat exchanger 131, and the four-effect heat exchanger 141 may be a hook-and-loop floating head heat exchanger or a removable floating head heat exchanger. Through adopting floating head heat exchanger, can be convenient for the heat exchanger tube bank take out the back, more thorough to the washing of heat exchanger outer wall. Particularly, the device prevents the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger from being blocked by polymer adhesion in the operation process of the four-effect evaporator of the acrylonitrile production device, and ensures the normal operation of the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger.

According to one embodiment of the invention, one end of the first-effect evaporator 11, the second-effect evaporator 12, the third-effect evaporator 13 and the fourth-effect evaporator 14 adjacent to the top end socket is internally provided with one or a combination of two of a wire mesh demister and a steam rising cap tray respectively. Liquid foam entrained in a vapor phase in the evaporator can be effectively intercepted by arranging the wire mesh demister and/or the steam raising cap tray, so that the polymer entering a downstream heat exchanger is reduced. The measure can effectively improve the operation time of the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger, and reduce the maintenance frequency of the on-line heat exchanger, thereby reducing the occurrence of unstable production operation caused by the maintenance of the heat exchanger.

Referring to fig. 1 and 2, according to an embodiment of the present invention, wire mesh defoamers 15 are respectively disposed inside one ends of the first effect evaporator 11, the second effect evaporator 12, the third effect evaporator 13 and the fourth effect evaporator 14 adjacent to the top head. By arranging the wire mesh demister 15, liquid foam entrained in the vapor phase in the evaporator can be effectively intercepted, thereby reducing polymer entering a downstream heat exchanger. The measure can effectively improve the operation time of the two-effect heat exchanger, the three-effect heat exchanger and the four-effect heat exchanger, and reduce the maintenance frequency of the on-line heat exchanger, thereby reducing the occurrence of unstable production operation caused by the maintenance of the heat exchanger.

Referring to fig. 1 and 2, according to one embodiment of the present invention, the distance h between the upper end of the wire mesh demister 15 and the connecting position of the top head and the evaporator satisfies: h is less than or equal to 800 mm. Through the arrangement, the wire mesh demister 15 has enough distance to the top seal head, so that a small amount of foam can be effectively prevented from being delivered to the heat exchanger through the top seal head pipeline, and the long-time stable operation of the heat exchanger is further ensured.

Referring to fig. 1 and 2, according to one embodiment of the present invention, the distance h between the upper end of the wire mesh demister 15 and the connecting position of the top head and the evaporator satisfies: h is more than or equal to 200mm and less than 800 mm. Through the arrangement, the wire mesh demister 15 has enough distance to the top seal head, so that a small amount of foam can be effectively prevented from being delivered to the heat exchanger through the top seal head pipeline, and the long-time stable operation of the heat exchanger is further ensured.

Referring to fig. 1 and 2, according to one embodiment of the present invention, the distance h between the upper end of the wire mesh demister 15 and the connecting position of the top head and the evaporator satisfies: h is more than or equal to 300mm and less than or equal to 700 mm. Through the arrangement, the wire mesh demister 15 has enough distance from the top end socket, so that a small amount of foam can be effectively prevented from being delivered to the heat exchanger through the top end socket pipeline, and the long-time stable operation of the heat exchanger is further ensured.

Referring to fig. 1 and 2, according to one embodiment of the present invention, the distance h between the upper end of the wire mesh demister 15 and the connecting position of the top head and the evaporator satisfies: h is more than or equal to 400mm and less than or equal to 600 mm. Through the arrangement, the wire mesh demister 15 has enough distance from the top end socket, so that a small amount of foam can be effectively prevented from being delivered to the heat exchanger through the top end socket pipeline, and the long-time stable operation of the heat exchanger is further ensured.

Referring to fig. 1 and 3, according to one embodiment of the present invention, a single effect evaporator 11, a double effect evaporator 12, a triple effect evaporator 13, and a quadruple effect evaporator 14 are optionally provided with a riser cap tray 16. In this embodiment, the plurality of gas-lifting caps permeable to gas are arranged on the gas-lifting cap tray 16 in an array manner, so that it is effectively ensured that the foam in the liquid is blocked by the gas-lifting caps, the foam is prevented from being sent to the heat exchanger, and the normal operation of the heat exchanger is ensured. In this embodiment, a weep head 161 is further disposed on the side of the lift cap tray 16 away from the lift cap, the weep head 161 is a curved pipe with an inlet and an outlet facing in the same direction, and one end of the weep head is connected to a weep opening on the lift cap tray 16, and the other end is a free end extending toward the lift cap tray 16. Through the arrangement, the liquid staying on the gas cap tray 16 can be timely discharged to the lower side, the normal work of the gas cap is prevented from being influenced by excessive liquid, the accumulation of foam on the gas cap tray 16 is also avoided, and particularly when the wire mesh demister 15 and the gas cap tray 16 are arranged simultaneously, the reduction of the foam amount flowing into the wire mesh demister 15 is facilitated, and the foam sent to the heat exchanger is further reduced. In addition, the liquid leakage head 161 is a hook-shaped bent pipe, so that the liquid below can be effectively prevented from directly flowing to the upper part of the lift cap tray 16 through the liquid leakage head 161, and the normal operation of the lift cap tray 16 is ensured.

According to one embodiment of the invention, the distance L between the riser cap tray 16 and the location where the head and four-effect evaporator 14 are connected is such that: l is less than or equal to 1500 mm. Through the arrangement, the lift cap tower tray 16 and the top seal head can have enough distance, a small amount of foam can be effectively prevented from being sent to the heat exchanger through the top seal head pipeline, and the long-time stable operation of the heat exchanger is further ensured.

According to one embodiment of the invention, the distance L between the riser cap tray 16 and the location where the head and four-effect evaporator 14 are connected is such that: l is more than or equal to 800mm and less than 1500 mm. Through the arrangement, the lift cap tower tray 16 and the top seal head can have enough distance, a small amount of foam can be effectively prevented from being sent to the heat exchanger through the top seal head pipeline, and the long-time stable operation of the heat exchanger is further ensured.

According to one embodiment of the invention, the distance L between the riser cap tray 16 and the location where the head and four-effect evaporator 14 are connected is such that: l is more than or equal to 850mm and less than or equal to 1300 mm. Through the arrangement, the lift cap tower tray 16 and the top seal head can have enough distance, a small amount of foam can be effectively prevented from being sent to the heat exchanger through the top seal head pipeline, and the long-time stable operation of the heat exchanger is further ensured.

According to one embodiment of the invention, the distance L between the riser cap tray 16 and the location where the head and four-effect evaporator 14 are connected is such that: l is more than or equal to 900mm and less than or equal to 1100 mm. Through the arrangement, the lift cap tower tray 16 and the top seal head can have enough distance, a small amount of foam can be effectively prevented from being sent to the heat exchanger through the top seal head pipeline, and the long-time stable operation of the heat exchanger is further ensured.

Referring to fig. 1 and 2, according to an embodiment of the present invention, when the wire mesh demister 15 and the hood tray 16 are provided in the evaporator, the hood tray 16 is located below the wire mesh demister 15, and the arrangement is favorable for ensuring the normal operation of the evaporator, so that the defoaming effect is better, and more foam is prevented from being sucked into the pipeline connected to the heat exchanger.

The foregoing is merely exemplary of particular aspects of the present invention and devices and structures not specifically described herein are understood to be those of ordinary skill in the art and are intended to be implemented in such conventional ways.

The above description is only one embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.