CN1597061A

CN1597061A - Fuel coal smoke low oxidation rate desulfur method

Info

Publication number: CN1597061A
Application number: CN 03158258
Authority: CN
Inventors: 徐长香; 罗静; 傅国光
Original assignee: ZHENJIANG JIANGNAN ENVIRONMENTAL PROTECTION EQUIPMENT INST
Current assignee: Jiangsu New Century Jiangnan Environmental Protection Co ltd
Priority date: 2003-09-17
Filing date: 2003-09-17
Publication date: 2005-03-23
Anticipated expiration: 2023-09-17
Also published as: CN1283346C

Abstract

A low-oxidization method for desulfurizing the fume generated by burning coal includes such steps as spraying water for cooling and dusting the fume, stage-one absorption by spraying the absorbing liquid A, stage-two absorption by spraying the absorbing liquid B, spraying water for defrosting, and exhausting.

Description

Low-oxidation-rate desulfurization method for coal-fired flue gas

Technical Field

The invention belongs to the environment-friendly technology, and relates to a method for recycling sulfur dioxide in coal-fired boiler flue gas, in particular to a low-oxidation-rate desulfurization method for coal-fired flue gas.

Background

The flue gas generated by the coal-fired boiler contains a large amount of SO which can pollute the environment₂And the waste gas can be discharged after being subjected to desulfurization treatment. Among the treatment methods of coal-fired flue gas, ammonia desulfurization is currently usedOne of the main methods adopted is that sulfur ammonia fertilizer and high-purity SO which can be used for producing sulfuric acid can be by-produced due to ammonia desulfurization₂Has better market value, thereby reducing the desulfurization cost and even being profitable.

The ammonia desulphurization and the sulfur dioxide recycling mechanism are as follows:

1. and (3) desulfurization main reaction: reaction of sulfur dioxide with ammonia to form an ammonium sulfite salt

(X＝1.2-1.6)

2. And (3) desulfurization side reaction: the iminium salt is oxidized into sulfate by the residual oxygen in the flue gas

3. The mechanism for producing sulfuric acid by desorbing sulfur dioxide is as follows:

from the above mechanism, when the side reaction oxidation rate is Y, sulfuric acid (1-Y-X/2) and ammonium sulfate (Y + X/2) are co-produced in the whole process, that is, the less the side reaction is oxidized, the more sulfuric acid is produced and the less ammonia is used.

In the ammonia desulfurization process, ammonium sulfite is generally used as a main desulfurization product because the oxidation of ammonium sulfite is inevitable due to low gas-liquid reaction temperature, high oxygen content in flue gas, sufficient gas-liquid contact and the like. However, the ammonium sulfate market has a large limitation, and from the economic viewpoint, the ammonium sulfate production should be reduced, and the sulfur dioxide production should be increased, so as to produce sulfuric acid or liquid sulfur dioxide and other byproducts with higher market value. That is, reducing the oxidation rate during desulfurization is beneficial to embodying and improving the value of sulfur dioxide.

Disclosure of Invention

The invention aims to solve the technical problem of providing a low-oxidation-rate desulfurization method for coal-fired flue gas, which can reduce the oxidation rate in the ammonia-process desulfurization process and improve the utilization value of byproducts.

The method is carried out in a desulfurizing tower, three stages of flue gas treatment sections are arranged in the desulfurizing tower, and are a cooling and dedusting section, a first stage absorption section and a second stage absorption section in sequence, each stage of flue gas treatment section is provided with a spraying device, and the technological process and parameters are as follows:

a. cooling and dedusting: firstly, spraying and washing the flue gas entering the tower to reduce the temperature of the flue gas to 40-50 ℃ within 2-3 seconds;

b. first-stage absorption: spraying and absorbing by using an ammonium salt absorption liquid with the concentration of 500-650 g/l and the pH value of 5.2-6.2;

c. and (3) second-stage absorption: spraying and absorbing by using ammonium salt absorption liquid with the concentration of 300-500g/l and the pH value of 5.4-6.5;

d. washing and demisting the flue gas after absorption treatment, and emptying after eluting the absorption liquid carried in the flue gas.

The method of the invention has the following advantages:

1. the temperature of the flue gas is suddenly reduced to 40-50 ℃ for desulfurization, so that the desulfurization effect can be ensured. Because of the fact thatSO₂The ammonia and the sulfur can fully react only when the temperature is lower than 40-50 ℃, so that the desulfurization reaction enters the optimal condition as soon as possible, and the total desulfurization efficiency is ensured;

2. the rate of conversion of sulfite to sulfate can be reduced by reducing the temperature, which is beneficial to reducing the oxidation rate of the whole process;

3. the temperature of the flue gas is reduced, the corrosion of the medium to the equipment is greatly reduced, and the service life of the equipment is prolonged.

4. By utilizing the special relation between the ammoxidation reaction of the sulfurous acid and the salt concentration of the solution, the high-concentration ammonium salt is used for absorption in the first-stage absorption process, thereby effectively reducing the oxidation rate in the whole process. Because in general, the oxidation rate of ammonium sulfite increases with increasing concentration over a certain concentration range; however, when the concentration exceeds a certain value, the oxidation rate decreases with increasing concentration, and at higher concentrations the oxidation rate of ammonium sulfite is low.

Drawings

FIG. 1 is a schematic diagram of the method and apparatus used in the present invention.

The numbers in the figure illustrate the following: 1 is a cooling and dedusting section of a desulfurizing tower; 2 is a first-stage absorption section of the desulfurizing tower; 3 is a second-stage absorption section of the desulfurizing tower; 4 is a spraying device; 5. 8, 10 are circulating pumps; 6. 7 and 9 are circulation tanks.

Detailed Description

One embodiment of the invention is as follows:

75t/h coal-fired industrial boiler, with the flue gas amount of 110000Nm³The coal consumption of the boiler is 18.48t/h, the total sulfur of the fire coal is 3 percent, the exhaust gas temperature is 170 ℃, and the original dust content is 6500mg/Nm³And the electric precipitation efficiency is 98.5 percent. The desulfurizing tower phi 4500 XH 24000 has a structure as shown in figure 1, and is provided with three stages of fume treating sections, including one temperature lowering and dedusting section 1, one first stage absorbing section 2 and one second stage absorbing sectionAnd 3, each stage of flue gas treatment section is provided with a spraying device 4.

The flue gas treatment process and parameters are as follows:

cooling and dedusting, namely spraying and washing the flue gas entering the tower from the lower part with water, wherein the spraying amount is 120m³The washing liquid is 32 ℃ boiler waste water and make-up water, the temperature of the flue gas discharged from the temperature-reducing and dust-removing section is 47 ℃, and the make-up water is 8m³H is used as the reference value. The washing water is recycled after being filtered, and part of the washing water is used for dosing.

First-stage absorption, wherein the concentration of absorption liquid is 620g/l, the pH value is 6.1, and the spraying amount is 120m³H is used as the reference value. The absorbed liquid is divided into three parts, one part is sent to the sulfur dioxide desorption process, the other part flows into the second-stage absorption liquid in series, and the rest is added with ammonia to regulate the PH value and then circulates.

Second-stage absorption-the concentration of the ammonium salt absorption solution is 320g/l, the PH value is 5.7, and the spraying amount is 120m³H is used as the reference value. The absorbed liquid is divided into two parts, one part flows into the first-stage absorption liquid in series, the rest is added with ammonia to adjust the PH value, and the circulation is carried out after the ammonia is supplemented with cooling water

Water washing demisting-water spraying quantity5m³/h

As a result:

the ammonium salt by-products comprise 193g/l ammonium sulfite, 436g/l ammonium bisulfite and 32g/l ammonium sulfate, i.e. the oxidation rate is 3.85 percent and the ammonia consumption is 0.346t/tSO₂. The sulfur dioxide content in the tail gas is 89mg/Nm³Ammonia content in the tail gas of 12mg/Nm³。

Claims

1. A low-oxidation-rate desulfurization method for coal-fired flue gas is characterized by comprising the following steps: the method is carried out in a desulfurizing tower, wherein three stages of flue gas treatment sections are arranged in the desulfurizing tower, namely a cooling and dedusting section (1), a first stage absorption section (2) and a second stage absorption section (3), each stage of flue gas treatment section is provided with a spraying device (4), and the technological process and parameters are as follows:

a. cooling and dedusting: firstly, spraying and washing the flue gas entering the tower at a low temperature by using water, and reducing the temperature of the flue gas to 40-50 ℃ within 2-3 seconds;