Hydrogen chloride pressure control system in production of PVC (polyvinyl chloride) prepared by calcium carbide method

Abstract

The utility model belongs to the field of chlor-alkali production equipment, and particularly relates to a hydrogen chloride pressure control system in PVC (polyvinyl chloride) production by a calcium carbide method, which comprises a hydrogen chloride synthesis furnace, a polyvinyl chloride production unit, an absorption hydrochloric acid preparation unit and a pressure control unit, the pressure control unit comprises a controller and a flow regulating valve group; the flow regulating valve group is arranged at the output end of the hydrogen chloride synthesis furnace; an in-furnace pressure transmitter is arranged in the hydrogen chloride synthesis furnace, and the hydrogen chloride synthesis furnace is respectively communicated with the absorption hydrochloric acid preparation unit and the polyvinyl chloride production unit through a flow regulating valve group. By additionally arranging the pressure control unit, the pressure control unit controls the opening degree of a valve according to the pressure in the hydrogen chloride synthesis furnace and adjusts the distribution amount of hydrogen chloride entering the absorption hydrochloric acid preparation unit and the polyvinyl chloride production unit, so that the dynamic balance of the gas pressure in the hydrogen chloride synthesis furnace is realized, and the pressure in the hydrogen chloride synthesis furnace is prevented from being too high; and production safety accidents are avoided.

Description

Technical Field

[0001] The utility model belongs to the field of chlor-alkali production equipment, in particular to a hydrogen chloride pressure control system in the production of PVC by the calcium carbide process. Background Art

[0002] Hydrochloric acid, also known as the aqueous solution of hydrochloric acid, is also one of the most basic inorganic acids and chemical raw materials in chlor-alkali enterprises. It is also a key product for balancing the production capacity of chlorine products.

[0003] The main process of hydrogen chloride synthesis is as follows: qualified hydrogen and chlorine from the hydrogen chloride treatment section pass through a flame arrester and enter the hydrogen chloride synthesis furnace in a certain ratio, and burn on the lamp head in the furnace. The generated hydrogen chloride gas is led out from the bottom of the cooler of the hydrogen chloride synthesis furnace, one way is supplied to the polyvinyl chloride (PVC) production unit, and the other way is absorbed by desalted water to make hydrochloric acid. The hydrogen chloride gas that is used to absorb hydrochloric acid is absorbed by the absorption tower, and the tail gas is naturally discharged after qualified analysis. The finished acid comes out from the bottom of the absorption tower and enters the hydrochloric acid metering tank. After qualified analysis, it is pumped into the hydrochloric acid product storage tank for sale.

[0004] During the start-up and shutdown of the polyvinyl chloride production unit, the pressure in the hydrogen chloride synthesis furnace changes greatly. The existing system generally detects the pressure in the synthesis furnace and manually adjusts the valve of the hydrogen chloride gas pipeline to control the hydrogen chloride gas from entering the polyvinyl chloride production unit or absorbing it to make hydrochloric acid. However, the existing manual adjustment requires manual operation, and the control of the valve is more dependent on the operating experience of the personnel. In practice, there are unreasonable control of the valve opening, or untimely regulation, which can easily lead to excessive pressure in the hydrogen chloride synthesis furnace and cause production safety accidents. Utility Model Content

[0005] The utility model aims to provide a hydrogen chloride pressure control system in the production of PVC by the calcium carbide process, so as to solve the problem that the existing hydrogen chloride synthesis system proposed in the above background technology needs to manually adjust the control valve based on experience, and there are unreasonable control of the control valve opening, or the regulation is not timely, resulting in excessive pressure in the hydrogen chloride synthesis furnace.

[0006] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0007] A hydrogen chloride pressure control system in the production of PVC by calcium carbide process, comprising a hydrogen chloride synthesis furnace, a polyvinyl chloride production unit, an absorption hydrochloric acid production unit and a pressure control unit;

[0008] The pressure control unit includes a controller and a flow regulating valve group, the flow regulating valve group is arranged at the output end of the hydrogen chloride synthesis furnace, and the flow regulating valve group is connected to the controller;

[0009] The hydrogen chloride synthesis furnace is provided with a furnace pressure transmitter, which is connected to a controller. The hydrogen chloride synthesis furnace is connected to the absorption hydrochloric acid production unit and the polyvinyl chloride production unit through a flow regulating valve group.

[0010] Furthermore, the flow regulating valve group includes a first flow regulating valve and a second flow regulating valve, and the first flow regulating valve and the second flow regulating valve are electrically connected to the controller respectively; the first flow regulating valve is arranged on the connecting pipeline between the hydrogen chloride synthesis furnace and the polyvinyl chloride production unit, and the second flow regulating valve is arranged on the connecting pipeline between the hydrogen chloride synthesis furnace and the absorption hydrochloric acid production unit.

[0011] Furthermore, a desalted water unit is provided at the desalted water inlet end of the absorption hydrochloric acid production unit, and a third flow valve is provided on the connecting pipeline between the desalted water unit and the absorption hydrochloric acid production unit.

[0012] Furthermore, a flow transmitter is also arranged on the connecting pipeline between the desalted water unit and the absorption hydrochloric acid production unit, and the flow transmitter and the third flow valve are arranged in sequence.

[0013] Furthermore, it also includes a dilute alkali solution storage tank, which is connected to the tail gas outlet of the absorption hydrochloric acid production unit.

[0014] Furthermore, a fourth flow regulating valve is also provided on the connecting pipeline between the dilute alkali solution storage tank and the absorption hydrochloric acid production unit.

[0015] Furthermore, it also includes a hydrochloric acid product storage tank, which is connected to the hydrochloric acid outlet of the absorption hydrochloric acid production unit.

[0016] Furthermore, it also includes an audible and visual alarm, which is connected to the controller.

[0017] Compared with the prior art, the utility model has the beneficial effects of: by adding a pressure control unit, the pressure control unit includes a controller and a flow regulating valve group that is easy to control, and the pressure control unit controls the opening and closing and the opening of each flow regulating valve according to the pressure in the hydrogen chloride synthesis furnace, adjusts the distribution amount of hydrogen chloride entering the absorption hydrochloric acid unit, realizes dynamic control of the pressure in the hydrogen chloride synthesis furnace, ensures the dynamic balance of the gas pressure in the hydrogen chloride synthesis furnace, prevents the excessive pressure in the hydrogen chloride synthesis furnace due to unreasonable artificial control of the valve opening during the start-up and shutdown of the polyvinyl chloride production unit, and untimely regulation, thereby avoiding production safety accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a system block diagram of Embodiment 1 of the utility model;

[0019] Figure 2 This is a system block diagram of Embodiment 2 of the present utility model;

[0020] Figure 3 This is a system block diagram of Embodiment 3 of the present utility model;

[0021] Among them, 1-hydrogen chloride synthesis furnace, 11-furnace pressure transmitter, 12-first flow regulating valve, 13-second flow regulating valve, 2-desalting water unit, 21-flow transmitter, 22-third flow valve, 3-polyvinyl chloride production unit, 4-absorption hydrochloric acid unit, 41-primary absorption tank, 42-secondary absorption tank, 43-tail gas absorption tank, 5-hydrochloric acid product storage tank, 6-dilute alkali solution storage tank, 61-fourth flow regulating valve, 7-hydraulic ejector, 8-gas-liquid separator. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention, but the present invention is not limited to the implementation methods described below.

[0023] Example 1

[0024] See also Figure 1 The present embodiment provides a hydrogen chloride pressure control system in the production of PVC by calcium carbide process, comprising a hydrogen chloride synthesis furnace 1, a desalted water unit 2, a polyvinyl chloride production unit 3, an absorption hydrochloric acid unit 4, a hydrochloric acid product storage tank 5 and a pressure control unit.

[0025] The hydrogen chloride synthesis furnace 1 burns hydrogen and chlorine from the hydrogen chloride treatment section, and the generated hydrogen chloride gas is discharged from the bottom of the cooler of the hydrogen chloride synthesis furnace 1. An in-furnace pressure transmitter 11 is arranged in the hydrogen chloride synthesis furnace 1. The in-furnace pressure transmitter 11 is preferably a Dewell MXS series pressure transmitter, which has the advantages of high precision, good stability, small size, etc., and is cost-effective.

[0026] One path of the hydrogen chloride outlet of the hydrogen chloride synthesis furnace 1 is connected to the polyvinyl chloride production unit 3, and a first flow regulating valve 12 is arranged between the hydrogen chloride synthesis furnace 1 and the polyvinyl chloride production unit 3, and the first flow regulating valve 12 is used to regulate the amount of hydrogen chloride gas entering the polyvinyl chloride production unit 3. The polyvinyl chloride production unit 3 is a conventional production process flow, and the utility model will not be repeated here; another path of the hydrogen chloride outlet of the hydrogen chloride synthesis furnace 1 is connected to the absorption hydrochloric acid production unit 4, and a second flow regulating valve 13 is arranged between the hydrogen chloride synthesis furnace 1 and the absorption hydrochloric acid production unit 4, and the second flow regulating valve 13 is used to regulate the amount of hydrogen chloride gas entering the absorption hydrochloric acid production unit 4; the first flow regulating valve 12 and the second flow regulating valve 13 are used together to regulate the gas pressure in the hydrogen chloride synthesis furnace 1.

[0027] The absorption hydrochloric acid production unit 4 is connected to the desalted water unit 2 at another port relative to the hydrogen chloride synthesis furnace 1. The desalted water unit 2 provides desalted water for the absorption hydrochloric acid production unit 4. The absorption hydrochloric acid production unit 4 absorbs the incoming hydrogen chloride gas using the desalted water.

[0028] Specifically, the absorption hydrochloric acid production unit 4 includes three-stage absorption tanks, namely a primary absorption tank 41, a secondary absorption tank 42 and a tail gas absorption tank 43. The hydrogen chloride gas produced in the hydrogen chloride synthesis furnace 1 first enters the primary absorption tank 41, and then enters the secondary absorption tank 42 and the tail gas absorption tank 43 in sequence. The desalted water in the desalted water unit 2 passes through the tail gas absorption tank 43, the secondary absorption tank 42 and the primary absorption tank 41 in sequence.

[0029] The desalted water that absorbs the hydrogen chloride gas obtains a hydrochloric acid product with a qualified concentration, which is discharged from the primary absorption tank 41 and temporarily stored in the hydrochloric acid product storage tank 5; the other tail gas after the hydrogen chloride gas is absorbed is absorbed by the tail gas absorption tank 43 and then discharged.

[0030] The utility model also includes a pressure control unit, which includes a controller and the above-mentioned first flow regulating valve 12 and second flow regulating valve 13. The controller can jointly control the opening and closing and the opening degree of the first flow regulating valve 12 and the second flow regulating valve 13 according to the gas pressure in the furnace pressure transmitter 11.

[0031] Specifically, the controller is preferably a DeltaV MX controller commercially available from Emerson, and the furnace pressure transmitter 11, the first flow regulating valve 12, and the second flow regulating valve 13 are all electrically connected to the DeltaV MX controller; the furnace pressure transmitter 11 detects the pressure in the hydrogen chloride synthesis furnace 1 and sends the pressure signal to the DeltaV MX controller. The DeltaV MX controller sets a minimum pressure threshold and a maximum pressure threshold. According to actual process requirements, the minimum pressure threshold is set to 75kPa and the maximum pressure threshold is set to 90kPa. The DeltaV MX controller controls the opening of the first flow regulating valve 12 and the second flow regulating valve 13 according to the pressure value detected by the furnace pressure transmitter 11, and controls the opening and closing of the first flow regulating valve 12 and the second flow regulating valve 13 when the pressure value exceeds the pressure threshold, so as to prevent the polyvinyl chloride section from not timely adjusting the output flow of hydrogen chloride gas during the start-up and shutdown of the equipment, resulting in excessive pressure in the hydrogen chloride synthesis furnace 1, causing production safety accidents, and at the same time avoiding abnormal discharge of hydrogen chloride gas to cause environmental pollution and corrode on-site steel equipment, pipelines and auxiliary steel facilities. In this embodiment, the first flow regulating valve 12 and the second flow regulating valve 13 are preferably corrosion-resistant and high-temperature-resistant electromagnetic flow valves commercially available from Richter of Germany.

[0032] Furthermore, the hydrogen chloride pressure control system in the production of PVC by the calcium carbide process in this embodiment is also provided with an audible and visual alarm, which is electrically connected to the DeltaV MX controller. When the pressure in the hydrogen chloride synthesis furnace 1 exceeds the minimum pressure threshold and the maximum pressure threshold, the audible and visual alarm sends out an alarm message, so that the on-site and central control personnel can open and close the first flow regulating valve 12 or the second flow regulating valve 13 in time, and the control system stops to avoid causing a larger production safety accident.

[0033] The utility model realizes the principle of dynamic control of gas pressure in the absorption hydrogen chloride synthesis furnace 1: when the gas outlet pressure of the hydrogen chloride synthesis furnace 1 is normal, the first flow regulating valve 12 is fully opened, and the hydrogen chloride gas enters the polyvinyl chloride production unit 3 to synthesize polyvinyl chloride; when the gas outlet pressure of the hydrogen chloride synthesis furnace 1 is too high, the second flow regulating valve 13 is opened and its opening is adjusted, and part of the hydrogen chloride gas is switched to the absorption hydrochloric acid production unit 4 for absorption to prepare hydrochloric acid by-product, thereby ensuring the dynamic balance of the gas pressure in the hydrogen chloride synthesis furnace 1, avoiding excessive pressure in the hydrogen chloride synthesis furnace 1, and avoiding abnormal emission of hydrogen chloride waste gas.

[0034] Example 2

[0035] See also Figure 2 In order to facilitate the adjustment of the concentration of the hydrochloric acid product, the present embodiment controls the flow of the desalted water, and a third flow valve 22 is provided between the tail gas absorption tank 43 and the desalted water unit 2. The third flow valve 22 is preferably an electromagnetic flow valve that is easy to control and resistant to acid, alkali and high temperature. A flow transmitter 21 is provided between the tail gas absorption tank 43 and the desalted water unit 2. The flow transmitter 21 is preferably a metal tube rotor flow meter. The metal tube rotor flow meter is commonly used to measure the flow of liquids and gases. It is provided with a PTFE lining material for corrosive media, has reliable operation, is convenient for piping design, has strong interchangeability and is easy to maintain. The flow transmitter 21 monitors the flow of the desalted water; it is convenient for the operator to adjust and control the flow of the desalted water according to the concentration of the hydrochloric acid product, while saving desalted water resources.

[0036] Example 3

[0037] See also Figure 3 In actual production, in order to meet environmental protection requirements and reduce the small amount of hydrogen chloride gas carried in the tail gas, a dilute alkali liquid storage tank 6, a hydraulic ejector 7 and a gas-liquid separator 8 are set at the gas outlet of the tail gas absorption tank 43. The tail gas discharged from the tail gas absorption tank 43 is neutralized with the dilute alkali liquid ejected from the hydraulic ejector 7, further ensuring that the outlet emission gas meets the standard. The dilute alkali liquid storage tank 6 provides the system with the dilute alkali liquid required for neutralization. The gas-liquid mixture after neutralization by the hydraulic ejector 7 enters the gas-liquid separator 8, and the gas-liquid separator 8 separates the hydrochloric acid after absorbing a small amount of hydrogen chloride gas from other non-condensable gases, and discharges the separated non-condensable gases.

[0038] In order to facilitate the control of the flow rate of the dilute alkali solution in the present embodiment, a fourth flow regulating valve 61 is arranged between the dilute alkali solution storage tank 6 and the absorption hydrochloric acid production unit 4. The fourth flow regulating valve 61 is preferably an acid- and alkali-resistant electromagnetic flow valve; it enables the operator to adjust the flow rate of the dilute alkali solution during the start-up and shutdown of the polyvinyl chloride production unit, reduce the hydrogen chloride gas carried in the exhaust gas, and save dilute alkali solution resources.

[0039] The above embodiments are all relatively preferred implementation methods of the utility model, but they cannot be used as limitations on the technical solutions protected by the utility model. Any replacement solutions obtained by ordinary technicians in this field without making any creative work based on the technical ideas of the utility model are within the scope of protection of the utility model.

Claims

1. A hydrogen chloride pressure control system in the production of PVC by calcium carbide process, characterized in that: It comprises a hydrogen chloride synthesis furnace (1), a polyvinyl chloride production unit (3), an absorption hydrochloric acid production unit (4) and a pressure control unit; The pressure control unit comprises a controller and a flow regulating valve group, wherein the flow regulating valve group is arranged at the output end of the hydrogen chloride synthesis furnace (1), and the flow regulating valve group is connected to the controller; The hydrogen chloride synthesis furnace (1) is provided with an in-furnace pressure transmitter (11), and the in-furnace pressure transmitter (11) is connected to a controller. The hydrogen chloride synthesis furnace (1) is connected to the absorption hydrochloric acid production unit (4) and the polyvinyl chloride production unit (3) respectively through a flow regulating valve group.

2. The hydrogen chloride pressure control system in the production of PVC by calcium carbide process according to claim 1, characterized in that: The flow regulating valve group comprises a first flow regulating valve (12) and a second flow regulating valve (13), the first flow regulating valve (12) and the second flow regulating valve (13) being electrically connected to a controller respectively; the first flow regulating valve (12) is arranged on a connecting pipeline between a hydrogen chloride synthesis furnace (1) and a polyvinyl chloride production unit (3), and the second flow regulating valve (13) is arranged on a connecting pipeline between a hydrogen chloride synthesis furnace (1) and an absorption hydrochloric acid production unit (4).

3. The hydrogen chloride pressure control system in the production of PVC by calcium carbide process according to claim 1, characterized in that: A desalted water unit (2) is provided at the desalted water inlet end of the absorption hydrochloric acid production unit (4), and a third flow valve (22) is provided on the connecting pipeline between the desalted water unit (2) and the absorption hydrochloric acid production unit (4).

4. The hydrogen chloride pressure control system in the production of PVC by calcium carbide process according to claim 3, characterized in that: A flow transmitter (21) is also provided on the connecting pipeline between the desalted water unit (2) and the absorption hydrochloric acid production unit (4), and the flow transmitter (21) and the third flow valve (22) are provided in sequence.

5. The hydrogen chloride pressure control system in the production of PVC by the calcium carbide process according to any one of claims 1 to 4, characterized in that: It also comprises a dilute alkali solution storage tank (6), wherein the dilute alkali solution storage tank (6) is connected to the tail gas outlet of the absorption hydrochloric acid production unit (4).

6. The hydrogen chloride pressure control system in the production of PVC by calcium carbide process according to claim 5, characterized in that: A fourth flow regulating valve (61) is also provided on the connecting pipeline between the dilute alkali solution storage tank (6) and the absorption hydrochloric acid production unit (4).

7. The hydrogen chloride pressure control system in the production of PVC by calcium carbide process according to claim 5, characterized in that: It also includes a hydrochloric acid product storage tank (5), which is connected to the hydrochloric acid outlet of the absorption hydrochloric acid production unit (4).

8. The hydrogen chloride pressure control system in the production of PVC by calcium carbide process according to claim 1, characterized in that: It also includes an audible and visual alarm, which is connected to the controller.

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