Structure for reducing content of ethylene glycol in process tail gas condensed wastewater

Abstract

The utility model discloses a structure for reducing the content of ethylene glycol in process tail gas condensed wastewater, which comprises a process tower, a heat exchanger, a generator set, a cooling plate heat exchanger and a condensate collecting tank, and the process tower, the heat exchanger and the condensate collecting tank are connected in series through pipelines. The process tower, the generator set, the cooling plate heat exchanger and the condensate collecting tank are sequentially connected in series through pipelines, and valves are arranged on an inlet pipeline and an outlet pipeline of the heat exchanger, an inlet pipeline of the generator set and an inlet pipeline and an outlet pipeline of the cooling plate heat exchanger. The device is characterized in that a flow dividing pipe is arranged between an outlet of the heat exchanger and an inlet pipeline of the cooling plate heat exchanger, and a ball valve is arranged on the flow dividing pipe. The bottleneck problem that the content of ethylene glycol in esterified water is high due to high condensate temperature when a process tower tail gas system of the device starts tail gas refrigeration in summer is solved, the transformation cost is low, and the COD biochemical treatment pressure of a sewage station is low.

Description

Technical Field

[0001] This utility model relates to the technical field of polyester production, specifically to a structure for reducing the ethylene glycol content in the condensate wastewater from process tail gas. Background Technology

[0002] Currently, in polyester production plants, to improve the utilization rate of waste heat from process exhaust gases in the process towers, the process exhaust gases are used not only for power generation by generator sets but also for heat exchange and power generation by refrigeration units. Generally, from June to October, the process exhaust gases are mainly used for condensate heating in the heat exchangers of the refrigeration units; during the remaining time, they can be used for heating and power generation by generator sets. When the process exhaust gases are used for power generation by generator sets, the exhaust gases, after being cooled by the generator sets, enter a cooling plate heat exchanger to be cooled again to ambient temperature before being discharged. However, when the process tower exhaust gases in the polyester plant are used for refrigeration in the summer, the process exhaust gases enter a heat exchanger for heat exchange, and the condensate from the cooled exhaust gases is discharged into an intermediate tank for further cooling before being uniformly discharged into the wastewater treatment plant. However, after the process tower exhaust gases are used for refrigeration in the summer, because the temperature of the condensate from the esterification water is higher than the temperature when waste heat power generation is used, coupled with the prolonged period of high temperatures above 40°C, the EG content in the esterification water remains between 0.22% and 0.41%. Figure 2 As shown, the higher the temperature, the higher the content, which puts considerable pressure on the biochemical treatment of COD in wastewater treatment plants. Summary of the Invention

[0003] In order to solve one or more technical problems existing in the prior art, the purpose of this application is to provide a structure that reduces the ethylene glycol content in the condensate wastewater of the process tail gas. This solves the bottleneck problem of high ethylene glycol content in the esterification water due to the high condensate temperature when the tail gas system of the process tower is turned on for cooling in summer. The modification cost is low and the pressure of COD biochemical treatment in the wastewater treatment plant is low.

[0004] To address the aforementioned technical problems, the objective of this application is achieved through the following technical solution:

[0005] A structure for reducing the ethylene glycol content in process tail gas condensate wastewater includes a process tower, a heat exchanger, a generator set, a cooling plate heat exchanger, and a condensate collection tank. The process tower, the heat exchanger, and the condensate collection tank are connected in series via pipelines. The process tower, the generator set, the cooling plate heat exchanger, and the condensate collection tank are sequentially connected in series via pipelines. Valves are provided on the inlet and outlet pipelines of the heat exchanger, the inlet pipeline of the generator set, and the inlet and outlet pipelines of the cooling plate heat exchanger. A diversion pipe is provided between the outlet of the heat exchanger and the inlet pipeline of the cooling plate heat exchanger, and a ball valve is provided on the diversion pipe.

[0006] Preferably, the outlet of the heat exchanger and the inlet pipe of the cooling plate heat exchanger are connected by removing material, and the diameter of the connection hole is 95mm.

[0007] Preferably, the diversion pipe includes several stainless steel pipes and stainless steel elbows, with the stainless steel pipes at both ends fixed to the outside of the connection hole by welding, and adjacent stainless steel pipes connected in series by the stainless steel elbows.

[0008] Preferably, the stainless steel pipe is DN100.

[0009] Preferably, the ball valve is connected to the stainless steel pipes at both ends via flanges.

[0010] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0011] Through online modification, the bottleneck problem of high ethylene glycol content in esterification water caused by high condensate temperature when the process tower tail gas system is activated for cooling in summer was solved with relatively small investment. This modification does not require unit maintenance, is simple and easy to implement, has a short modification time and low cost, and the entire modification process has no impact on production. After the modified pipeline was put into operation, the ethylene glycol content in the esterification water decreased significantly, stably, and controllably. By reducing EG consumption, the unit's production costs were reduced, while also alleviating the pressure on the subsequent COD biological treatment at the wastewater treatment plant. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of this utility model;

[0013] Figure 2 This is a table showing the EG content detection data in the esterified water before modification in this utility model.

[0014] Figure 3 This is a table showing the detection data of EG content in the modified esterified water of this utility model;

[0015] In the diagram: 1. Process tower; 2. Heat exchanger; 3. Ball valve; 4. Diverter pipe; 41. Stainless steel pipe; 42. Stainless steel elbow; 5. Generator set; 6. Cooling plate heat exchanger; 7. Condensate collection tank. Detailed Implementation

[0016] The present application will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0017] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0018] The terms "first," "second," etc., used in this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, without limiting the number of objects; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0019] like Figure 1 and Figure 3 As shown, a structure for reducing the ethylene glycol content in process tail gas condensate wastewater includes a process tower 1, a heat exchanger 2, a generator set 5, a cooling plate heat exchanger 6, and a condensate collection tank 7. The process tower 1, the heat exchanger 2, and the condensate collection tank 7 are connected in series via pipelines. The process tower 1, the heat exchanger 2, the cooling plate heat exchanger 6, and the condensate collection tank 7 are sequentially connected in series via pipelines. Valves are provided on the inlet and outlet pipelines of the heat exchanger 2, the inlet pipeline of the generator set 5, and the inlet and outlet pipelines of the cooling plate heat exchanger 6. A diversion pipe 4 is provided between the outlet of the heat exchanger 2 and the inlet pipeline of the cooling plate heat exchanger 6, and a ball valve 3 is provided on the diversion pipe 4.

[0020] This structure is based on the modification of the existing pipeline connecting the exhaust gas from process tower 1 to generator set 5 and chiller unit. A diversion pipe 4 with a ball valve 3 is added between the outlet of heat exchanger 2 in the chiller unit pipeline and the inlet pipe of cooling plate heat exchanger 6 in the generator unit pipeline. This splits the exhaust gas from process tower 1 into two new paths: the first path: the exhaust gas from process tower 1 is delivered to generator set 5 for heating and power generation after the valve on the pipeline is opened; the exhaust gas after power generation flows out from the outlet pipe and enters the cooling system. The first route involves cooling the wastewater through heat exchanger 6, followed by the flow of the cooled wastewater into condensate collection tank 7. The esterified water is then discharged into the wastewater treatment plant via the outlet pipe of condensate collection tank 7. The second route involves the exhaust gas from process tower 1, which enters heat exchanger 2 after the valve on the pipeline is opened. After heat exchange, the esterified water vapor from the exhaust gas flows along the diversion pipe 4 to the cooling heat exchanger 6 for further heat exchange and cooling. Finally, it flows into condensate collection tank 7 via the outlet pipe of cooling heat exchanger 6. When modifying the added diversion pipe 4 with ball valve 3, the modification of one end of heat exchanger 2 can be carried out in real time when the refrigeration unit is not working. Simply make a hole at the outlet of heat exchanger 2 and weld one end of diversion pipe 4 to the hole. For the other end, simply close the inlet and outlet valves of cooling plate heat exchanger 6 briefly before making a hole and welding diversion pipe 4. The entire modification process can be carried out online, with low investment and low cost. Moreover, when the waste heat power generation of process tower 1 is not in use, the generator condensate cooling plate heat exchanger 6 is effectively utilized, which effectively solves the bottleneck problem of incomplete heat consumption of process tower 1 after the tail gas refrigeration is started in summer, coupled with the lack of temperature adjustment of cooling water in hot weather, resulting in high temperature of process wastewater and high ethylene glycol content. Furthermore, this modification does not need to be carried out under the condition of unit maintenance, is simple and easy to implement, has a short modification time and low modification cost, and the entire modification process has no impact on production. After the modified pipeline was put into operation, the ethylene glycol content in the esterification water decreased significantly, stably, and controllably. By reducing EG consumption, the production cost of the equipment was reduced, while the pressure on the subsequent COD biochemical treatment of the wastewater treatment plant was alleviated.

[0021] Among them, the esterified water gas flowing out of heat exchanger 2 is cooled by cooling plate heat exchanger 6, which can reduce the temperature of the process esterified water condensate discharged into condensate collection tank 7 by about 33°C, thereby reducing the EG content in the esterified water from the original 0.22-0.41% to 0.06-0.14%, reaching and exceeding the level before tail gas cooling. The COD of the sewage treatment plant also decreased from 6000 to about 3000, greatly reducing the pressure of biological treatment of sewage COD.

[0022] A further improvement is that a connection hole with a diameter of 95mm is made on the outlet of the heat exchanger 2 and the inlet pipe of the cooling plate heat exchanger 6 by removing material.

[0023] The connection holes on the outlet of heat exchanger 2 and the inlet of cooling plate heat exchanger 6 are all made with a hole opener. The diameter of the connection hole is 95mm. It is used with DN100 stainless steel pipe 41, which can make the distributor pipe 4 completely wrapped after welding, thus improving the convenience of operation.

[0024] A further improvement is that the diversion pipe 4 includes several stainless steel pipes 41 and stainless steel elbows 42. The stainless steel pipes 41 at both ends are fixed to the outside of the connection hole by welding, and two adjacent stainless steel pipes 41 are connected in series through the stainless steel elbows 42.

[0025] To achieve corrosion resistance, heat resistance, pressure resistance, and wear resistance, stainless steel is selected as the material for the diversion pipe 4. Among them, four stainless steel elbows 42 with a diameter of 90° and a diameter of 114.3mm*3.5mm are selected, along with 31 DN100 ball valves to ensure the stability of the tail gas condensate pipe of process tower 1.

[0026] The modification is simple, the old pipes and equipment can be dismantled and reused, the cost is low, and it is a modification on the original waste heat power generation cooling plate heat exchanger 6, so there is no need to buy a new plate heat exchanger; after being put into use, the temperature of the condensate collection tank 7 is reduced, and the liquid level is more controllable.

[0027] A further improvement is made in that the stainless steel pipe 41 is DN100; the ball valve 3 is connected to the stainless steel pipe 41 at both ends via flanges.

[0028] By combining ball valve 3 with the valve in the original outlet pipeline, the condensate flow direction can be switched randomly to control the reflux temperature.

[0029] The above embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of protection of this application. Any non-substantial changes and substitutions made by those skilled in the art based on this application shall fall within the scope of protection claimed by this application.

Claims

1. A structure for reducing the ethylene glycol content in condensate wastewater from process tail gas, comprising a process tower (1), a heat exchanger (2), a generator set (5), a cooling plate heat exchanger (6), and a condensate collection tank (7), wherein the process tower (1), the heat exchanger (2), and the condensate collection tank (7) are connected in series via pipes, and the process tower (1), the generator set (5), the cooling plate heat exchanger (6), and the condensate collection tank (7) are sequentially connected in series via pipes, and valves are provided on the inlet and outlet pipes of the heat exchanger (2), the inlet pipe of the generator set (5), and the inlet and outlet pipes of the cooling plate heat exchanger (6), characterized in that: A diversion pipe (4) is provided between the outlet of the heat exchanger (2) and the inlet pipe of the cooling plate heat exchanger (6), and a ball valve (3) is provided on the diversion pipe (4).

2. The structure for reducing the content of ethylene glycol in the process tail gas condensate wastewater according to claim 1, characterized in that: The outlet of the heat exchanger (2) and the inlet pipe of the cooling plate heat exchanger (6) are connected by removing material, and the diameter of the connection hole is 95mm.

3. The structure for reducing the content of ethylene glycol in the process tail gas condensate wastewater according to claim 2, characterized in that: The diversion pipe (4) includes several stainless steel pipes (41) and stainless steel elbows (42). The stainless steel pipes (41) at both ends are fixed outside the connection hole by welding. Two adjacent stainless steel pipes (41) are connected in series through the stainless steel elbows (42).

4. The structure for reducing the content of ethylene glycol in the process tail gas condensate wastewater according to claim 3, characterized in that: The stainless steel pipe (41) is DN100.

5. The structure for reducing the content of ethylene glycol in the process tail gas condensate wastewater according to claim 3, characterized in that: The ball valve (3) is connected to the stainless steel pipes (41) at both ends by flanges.

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