Chlorine-containing waste gas treatment device and method

Abstract

The invention provides a chlorine-containing waste gas treatment device and method, and the device comprises a ferrous washing unit which is communicated with an external chlorine-containing waste gas pipeline and is used for preparing a ferrous chloride solution and carrying out primary spray washing on chlorine-containing waste gas; and the alkali washing unit is communicated with the tail gas outlet of the ferrous washing unit and is used for storing an alkaline solution and carrying out secondary spraying washing on the chlorine-containing waste gas. Through two-stage dechlorination, alkali liquor consumption can be reduced, by-products can be produced, and therefore the added value of dechlorination is increased.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment, and more particularly to a device and method for treating chlorine-containing waste gas. Background Technology

[0002] In chemical production processes using chlorine as a raw material, there is often a situation where residual chlorine-containing tail gas needs to be treated to meet emission standards. To treat this chlorine gas, alkaline solution (15%-30% NaOH solution) is usually used for absorption. However, this increases the consumption of alkaline solution, and the resulting waste alkaline solution (NaClO waste liquid) has no utilization value and needs further treatment before it can be discharged. Summary of the Invention

[0003] To reduce alkali consumption and increase the added value of dechlorination, a chlorine-containing waste gas treatment device is proposed in the first aspect of the present invention, comprising: a ferrous washing unit connected to an external chlorine-containing waste gas pipeline for preparing a ferrous chloride solution and performing a primary spray washing on the chlorine-containing waste gas; and an alkaline washing unit connected to the tail gas outlet of the ferrous washing unit for storing an alkaline solution and performing a secondary spray washing on the chlorine-containing waste gas.

[0004] In one or more embodiments, the ferrous washing unit includes: a ferrous washing tank for preparing and storing a ferrous chloride solution; a ferrous washing tower disposed above the ferrous washing tank, with its bottom connected to the ferrous washing tank and its side connected to an external chlorine-containing waste gas pipeline; and a first spray pipe disposed inside the ferrous washing tower and near its top, pumped to the ferrous washing tank, for obtaining the ferrous chloride solution from the ferrous washing tank and spraying it into the ferrous washing tower for initial spray washing of the chlorine-containing waste gas.

[0005] In one or more embodiments, the ferrous washing unit further includes: a density detector, installed on the ferrous washing tank, with a probe extending into the ferrous washing tank to detect the solution density; a discharge valve, installed on the ferrous washing tank, for controlled connection between the ferrous washing tank and an external iron material tank; and a first controller, connected to the density detector and the discharge valve respectively, configured to control the discharge valve to discharge iron material into the ferrous washing tank according to the solution density.

[0006] In one or more embodiments, the ferrous washing unit further includes: a first liquid level detector, installed on the ferrous washing tank, with a probe extending into the ferrous washing tank to detect the liquid level of the solution; a first replenishment valve, installed on the ferrous washing tank, for controlled connection between the ferrous washing tank and an external storage tank; a first drain valve, installed on the ferrous washing tank, for controlled connection to the external environment; the first controller is also connected to the first liquid level detector, the first replenishment valve, and the first drain valve respectively, and is configured to control the first drain valve to discharge solution according to the solution density of the ferrous washing tank, and to control the first replenishment valve to replenish acidic solution according to the liquid level of the solution.

[0007] In one or more embodiments, the acidic solution includes: hydrochloric acid solution or sulfuric acid solution.

[0008] In one or more embodiments, the alkaline washing unit includes: an alkaline washing tank for storing an alkaline solution; an alkaline washing tower disposed above the alkaline washing tank, with its bottom communicating with the alkaline washing tank and its side communicating with the ferrous washing tower; and a second spray pipe disposed inside the alkaline washing tower and near its top, pumped to the alkaline washing tank, for obtaining an alkaline solution from the alkaline washing tank and spraying it into the alkaline washing tower for secondary spray washing of the chlorine-containing waste gas.

[0009] In one or more embodiments, the alkaline washing unit further includes: a pH meter installed on the alkaline washing tank, with its probe extending into the alkaline washing tank to detect the pH of the solution; a second replenishment valve installed on the alkaline washing tank for controlled connection between the alkaline washing tank and an external alkaline solution storage tank; and a second controller connected to the pH meter and the second replenishment valve, configured to control the second replenishment valve to replenish alkaline solution into the alkaline washing tank according to the solution pH.

[0010] In one or more embodiments, the alkaline washing unit further includes: a second liquid level detector, installed on the alkaline washing tank, with a probe extending into the alkaline washing tank to detect the liquid level height of the solution; a second drain valve, installed on the alkaline washing tank, for controlled connection to the external environment; and a second controller, which is also connected to the second liquid level detector and the second drain valve respectively, and configured to control the second drain valve to discharge the solution in the alkaline washing tank according to the liquid level height of the solution.

[0011] In one or more embodiments, the alkaline solution includes: sodium hydroxide solution, sodium carbonate solution, or sodium bicarbonate solution.

[0012] In a second aspect of the present invention, a method for treating chlorine-containing waste gas is provided. The method is based on the chlorine-containing waste gas treatment device of the present invention and includes: repeatedly spraying and washing the chlorine-containing tail gas with ferrous chloride solution to obtain byproducts; and spraying and washing the tail gas after chlorination by ferrous chloride solution with an alkaline solution to completely remove chlorine.

[0013] The beneficial effects of the present invention include: the present invention can reduce the consumption of alkali solution and produce by-products through two-stage dechlorination, thereby increasing the added value of dechlorination, and can automatically control the amount of reactants added and the timing of by-product output. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of a chlorine-containing waste gas treatment device according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the process of a chlorine-containing waste gas treatment method according to an embodiment of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0017] To reduce alkali consumption and enhance the added value of dechlorination, in a first aspect of this invention, a chlorine-containing waste gas treatment device is proposed. This device utilizes the reducing properties of ferrous chloride solution to react with chlorine gas to generate ferric chloride, which, as a byproduct, can be used as a flocculant for wastewater treatment. The chlorine-containing waste gas treatment device of this invention includes the following embodiments: In one embodiment, such as Figure 1As shown, the chlorine-containing waste gas treatment device of the present invention includes: a ferrous washing unit 10, connected to an external chlorine-containing waste gas pipeline, used to prepare a ferrous chloride solution and perform initial spray washing on the chlorine-containing waste gas; and an alkaline washing unit 20, connected to the tail gas outlet of the ferrous washing unit 10, used to store an alkaline solution and perform secondary spray washing on the chlorine-containing waste gas. In this embodiment, the ferrous washing unit 10 and the alkaline washing unit 20 are each a set of spray washing units, which can realize multi-stage washing of chlorine-containing tail gas. Compared with the traditional method of using only alkaline solution for one-time washing, the present invention can greatly reduce the amount of alkaline solution used and generate by-products by utilizing the first-stage washing (i.e., the initial washing), thereby reducing the cost of treating chlorine-containing tail gas.

[0018] In a further embodiment, the ferrous washing unit 10 includes: a ferrous washing tank 11 for preparing and storing a ferrous chloride solution; a ferrous washing tower 12 disposed above the ferrous washing tank, with its bottom connected to the ferrous washing tank 11 and its side connected to an external chlorine-containing waste gas pipeline; and a first spray pipe 13 disposed inside the ferrous washing tower 12 and near its top, pumped to the ferrous washing tank 11, for obtaining the ferrous chloride solution from the ferrous washing tank 11 and spraying it into the ferrous washing tower 12 for initial spray washing of the chlorine-containing waste gas. In this embodiment, the ferrous chloride solution can be prepared by simultaneously adding iron and hydrochloric acid solution to the ferrous washing tank 11, or by directly injecting the prepared ferrous chloride solution into the ferrous washing tank 11. During use, the first spray pipe 13 is used to atomize the ferrous chloride solution, enabling it to fully contact and react with chlorine gas, as shown in the following reaction formula: 2FeCl₂ + Cl₂ = 2FeCl₃; Of course, not all ferrous chloride can be converted into ferric chloride in a single spray washing process. Therefore, in actual use, it is necessary to repeatedly extract the mixed solution (containing ferrous chloride and ferric chloride) in the ferrous washing tank 11 to wash the chlorine gas. This operation will be repeated many times before the liquid is discharged to increase the ferric chloride content in the mixed solution.

[0019] In a further embodiment, to ensure sufficient FeCl2 in the circulating liquid and to achieve automatic control, the ferrous washing unit 10 further includes: a density detector 14, installed on the ferrous washing tank 11, with a probe extending into the ferrous washing tank 11 to detect the density of the solution (i.e., the circulating liquid); a discharge valve 15, installed on the ferrous washing tank 11, for controlled connection between the ferrous washing tank 11 and an external iron material tank (not shown); and a first controller (not shown), connected to the density detector 14 and the discharge valve 15 respectively, configured to control the discharge valve 15 to discharge iron material into the ferrous washing tank 11 according to the solution density. In this embodiment, the discharge valve 15 can be a star-shaped discharge valve to better control the discharge amount. The discharged iron material will undergo a reduction reaction with ferric chloride, reducing ferric chloride to ferrous chloride. The reaction formula is as follows: FeCl3 + Fe = 3 FeCl2; To ensure a complete reaction, iron filings are preferred as the iron material introduced in this embodiment.

[0020] During use, the concentration of ferric chloride in the circulating liquid will increase, and the density of the circulating liquid will also increase accordingly. Therefore, the amount of iron required each time must also increase. Calculations show that the amount of iron filings added is 0.8 times the theoretical amount of chlorine (P), but this needs to be corrected based on the density (D) of the circulating liquid in the ferrous circulating tank. The specific relationship between the amount of iron filings added and the density D of the circulating liquid is shown in the table below:

[0021] When the concentration of the circulating liquid is greater than 2.5 g / ml, the circulating liquid can be discharged from the ferrous washing tank 11 to collect the byproduct ferric chloride. This step will cause a significant drop in the liquid level in the ferrous washing tank 11. If further dechlorination is required, water or hydrochloric acid solution needs to be added to the ferrous washing tank 11 again. In order to automate this process, the present invention also proposes the following implementation: In a further embodiment, the ferrous washing unit 10 further includes: a first liquid level detector 16, installed on the ferrous washing tank 11, with a probe extending into the ferrous washing tank 11 to detect the liquid level of the solution (i.e., the circulating liquid); a first replenishment valve 17, installed on the ferrous washing tank 11, for controlled connection between the ferrous washing tank 11 and an external storage tank, which stores hydrochloric acid and solution / or water; a first drain valve 18, installed on the ferrous washing tank 11, for controlled connection to the external environment; and a first controller (not shown) is also connected to the first liquid level detector 16, the first replenishment valve 17, and the first drain valve 18, and configured to control the first drain valve 18 to discharge solution according to the solution density in the ferrous washing tank 11, and to control the first replenishment valve 17 to replenish acidic solution according to the liquid level of the solution.

[0022] In an optional embodiment, if the density detector 14 and the first liquid level detector 16 are programmable signal-emitting elements, the density detector 14 can directly control the discharge valve 14 and the first drain valve 18 without using a control unit. That is, when the solution concentration is greater than 2.5 g / ml, the circulating liquid can be discharged from the ferrous washing tank 11; and the first liquid level detector 16 can directly control the first replenishment valve 17, that is, when the liquid level drops to a preset height, automatic replenishment is performed.

[0023] In an optional implementation, to ensure safety during use, the initial amount of ferrous chloride solution added to the ferrous washing tank 11 should be less than or equal to 70% of the capacity of the ferrous washing tank 11.

[0024] In an alternative embodiment, the ferrous chloride solution can also be replaced by other ferrous salt solutions, such as ferrous sulfate solution, whose byproduct is ferric sulfate, which can also be used for water purification.

[0025] In a further embodiment, the alkaline washing unit 20 includes: an alkaline washing tank 21 for storing an alkaline solution; an alkaline washing tower 21 disposed above the alkaline washing tank 21, with its bottom connected to the alkaline washing tank 21 and its side connected to the ferrous washing tower 12; and a second spray pipe 23 disposed inside the alkaline washing tower 22 and near its top, pumped to the alkaline washing tank 21, for obtaining alkaline solution from the alkaline washing tank 21 and spraying it into the alkaline washing tower 22 for secondary scrubbing of the chlorine-containing waste gas. In this embodiment, the second spray pipe is used to atomize the alkaline solution, thereby fully reacting with the chlorine gas; furthermore, since the alkaline washing unit 20 is a two-stage chlorine removal unit, its chlorine removal capacity is greatly reduced, thereby greatly reducing the consumption of alkaline solution. During use, alkaline solution will be continuously drawn from the alkaline washing tank 21 to react with the chlorine gas, resulting in a decrease in the pH of the alkaline solution.

[0026] During operation, any remaining chlorine gas will be introduced from the top gas of the ferrous scrubbing tower 12 into the alkaline scrubbing tower 22 via pipeline. In the alkaline scrubbing tower 22, a 15% NaOH solution is used to spray the residual chlorine gas, ensuring that the exhaust gas meets emission standards.

[0027] In a further embodiment, to ensure the pH of the alkaline solution, the alkaline washing unit 20 further includes: a pH meter 24, installed on the alkaline washing tank 21, with its probe extending into the alkaline washing tank 21 to detect the pH of the solution; a second replenishment valve 25, installed on the alkaline washing tank 21, for controlled connection between the alkaline washing tank 21 and an external alkaline solution storage tank (not shown); and a second controller (not shown), connected to the pH meter 24 and the second replenishment valve 25 respectively, configured to control the second replenishment valve to replenish alkaline solution into the alkaline washing tank according to the solution pH.

[0028] In a further embodiment, the alkaline washing unit 20 further includes: a second liquid level detector 26, installed on the alkaline washing tank 21, with a probe extending into the alkaline washing tank 21 to detect the liquid level of the solution; a second drain valve 27, installed on the alkaline washing tank 21, for controlled connection to the external environment; and a second controller connected to the second liquid level detector 26 and the second drain valve 27 respectively, configured to control the second drain valve 27 to drain the solution in the alkaline washing tank 21 and replenish new alkaline solution according to the liquid level of the solution.

[0029] In one alternative embodiment, the alkaline solution includes: sodium hydroxide solution, sodium carbonate solution, or sodium bicarbonate solution.

[0030] In an optional implementation, if the pH meter 24 and the second liquid level meter 26 are programmable signal-emitting elements, then the second control unit can be omitted and the pH meter 24 and the second liquid level meter 26 can directly control the replenishment and the drainage.

[0031] In a second aspect of the invention, as Figure 2 As shown, a method for treating chlorine-containing waste gas is also proposed, which includes: step S1, repeatedly using ferrous chloride solution to perform initial spray washing on the chlorine-containing tail gas and obtain ferric chloride as a byproduct; step S2, using an alkaline solution to perform secondary spray washing on the tail gas after chlorine removal by ferrous chloride solution to completely remove chlorine.

[0032] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0033] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0034] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0035] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A chlorine-containing waste gas treatment device, characterized in that, include: The ferrous chloride scrubbing unit is connected to an external chlorine-containing waste gas pipeline and is used to prepare ferrous chloride solution and perform initial spray scrubbing on the chlorine-containing waste gas. The alkaline washing unit is connected to the exhaust gas outlet of the ferrous washing unit and is used to store alkaline solution and perform secondary spray washing on chlorine-containing waste gas.

2. The chlorine-containing waste gas treatment device according to claim 1, characterized in that, The ferrous washing unit includes: Ferrous washing tank, used for preparing and storing ferrous chloride solution; The ferrous scrubbing tower is located above the ferrous scrubbing tank, with its bottom connected to the ferrous scrubbing tank and its side connected to an external chlorine-containing waste gas pipeline. The first spray pipe is installed inside the ferrous washing tower and near the top, and is connected to the pump of the ferrous washing tank. It is used to obtain ferrous chloride solution from the ferrous washing tank and spray it into the ferrous washing tower for initial spray washing of chlorine-containing waste gas.

3. The chlorine-containing waste gas treatment device according to claim 2, characterized in that, The ferrous washing unit also includes: A density meter is installed on the ferrous washing tank, with its probe extending into the ferrous washing tank to detect the density of the solution. A discharge valve is installed on the ferrous washing tank and is used to controllably connect the ferrous washing tank to an external iron tank. The first controller is connected to the density detector and the feeding valve, respectively, and is configured to control the feeding valve to feed iron material into the ferrous washing tank according to the solution density.

4. The chlorine-containing waste gas treatment device according to claim 3, characterized in that, The ferrous washing unit also includes: The first liquid level detector is installed on the ferrous washing tank, and the probe extends into the ferrous washing tank to detect the liquid level height of the solution; The first replenishment valve is installed on the ferrous washing tank and is used to controllably connect the ferrous washing tank and the external storage tank. The first drain valve is installed on the ferrous washing tank for controlled connection to the external environment; The first controller is also connected to the first liquid level detector, the first replenishment valve and the first drain valve respectively, and is configured to control the first drain valve to discharge the solution according to the solution density of the ferrous washing tank, and to control the first replenishment valve to replenish the acidic solution according to the liquid level of the solution.

5. The chlorine-containing waste gas treatment device according to claim 4, characterized in that, The acidic solution includes: hydrochloric acid solution or sulfuric acid solution.

6. The chlorine-containing waste gas treatment device according to claim 2, characterized in that, The alkaline washing unit includes: Alkaline washing tank, used to store alkaline solutions; An alkaline washing tower is located above the alkaline washing tank, with its bottom connected to the alkaline washing tank and its side connected to the ferrous washing tower. The second spray pipe is installed inside the alkali scrubbing tower and near the top, and is connected to the alkali scrubbing tank pump. It is used to obtain alkaline solution from the alkali scrubbing tank and spray it into the alkali scrubbing tower for secondary scrubbing of chlorine-containing waste gas.

7. The chlorine-containing waste gas treatment device according to claim 6, characterized in that, The alkaline washing unit further includes: A pH meter is installed on the alkaline washing tank, with its probe extending into the alkaline washing tank to detect the pH of the solution. The second replenishment valve is installed on the alkaline washing tank and is used to controllably connect the alkaline washing tank to an external alkaline solution storage tank. The second controller is connected to both the pH detector and the second replenishment valve, and is configured to control the second replenishment valve to replenish alkaline solution into the alkaline washing tank according to the solution pH.

8. The chlorine-containing waste gas treatment device according to claim 7, characterized in that, The alkaline washing unit further includes: The second liquid level detector is installed on the alkaline washing tank, and the probe extends into the alkaline washing tank to detect the liquid level height of the solution. The second drain valve is installed on the alkaline washing tank for controlled connection to the external environment; The second controller is also connected to the second liquid level detector and the second drain valve, respectively, and is configured to control the second drain valve to discharge the solution in the alkaline washing tank according to the liquid level height of the solution.

9. The chlorine-containing waste gas treatment device according to claim 8, characterized in that, The alkaline solution includes: sodium hydroxide solution, sodium carbonate solution, or sodium bicarbonate solution.

10. A method for treating chlorine-containing waste gas, characterized in that, The method is based on the chlorine-containing waste gas treatment device according to any one of claims 1-9, and the method includes: The chlorine-containing tail gas was repeatedly sprayed and washed with ferrous chloride solution to obtain byproducts. The tail gas after dechlorination with ferrous chloride solution is subjected to a second spray washing using an alkaline solution to completely remove chlorine.

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