Three-cycle desulphurization method for wet type ammonia-process desulphurization and flue gas desulfurization tower or system

Abstract

The invention relates to the field of environmental protection and discloses a three-cycle desulphurization method for wet type ammonia-process desulphurization. The desulphurization method is implemented with a first slurry circulating loop, a second slurry circulating loop and a third slurry circulating loop, wherein in the first slurry circulating loop, slurry having mass concentration of 10%-20% and a pH value of 4.0-5.0 is used for carrying out cycle spraying treatment on flue gas, and the temperature of the flue gas treated by the slurry is 50-60 DEG C; in the second slurry circulating loop, slurry having mass concentration of 10%-15% and a pH value of 5.0-6.0 is used for carrying out cycle spraying treatment on the flue gas; and in the third slurry circulating loop, slurry having mass concentration of 3%-10% is used for carrying out cycle spraying treatment on the flue gas. The invention also discloses a flue gas desulfurization tower or system using the three-cycle desulphurization method. According to the three-cycle desulphurization method, the three independent circulating loops are divided according to the concentration of the slurry, the circulating loops separately control the slurry having different concentrations and pH values for treatment of the flue gas, and the contradiction of high desulphurization efficiency and high oxygenation efficiency of by-products is solved.

Description

technical field [0001] The invention relates to the field of environmental protection, in particular to a three-cycle desulfurization method and a flue gas desulfurization tower or system. Background technique [0002] The National Development and Reform Commission, the Ministry of Environmental Protection and the National Energy Administration issued the "Coal Power Energy Conservation and Emission Reduction Upgrading and Transformation Action Plan" (2014-2020) issued in 2014. "(4) Strictly control the emission of air pollutants. New coal-fired power generation Units (including units under construction and whose projects have been included in the national thermal power construction plan) should simultaneously build advanced and efficient desulfurization, denitrification and dust removal facilities, and flue gas bypasses are not allowed. The air pollutants of new coal-fired power generation units in the eastern region (11 provinces and cities) The emission concentration basi...

AI Technical Summary

Problems solved by technology

[0006] (1) In the traditional spray tower, in order to improve the sulfur dioxide removal rate, it is often necessary to choose a larger liquid-gas ratio, resulting in an increase in ammonia escape and more aerosols, which is uneconomical in operation , is not even allowed

[0007] (2) In the traditional spray tower, the design desulfurization efficiency is above 95%, but in the actual operation process, the desulfurization efficiency is often only 80%-90%, which is lower than the design value

[0008] (3) In the traditional spray tower, the flue gas in the tower is often unevenly distributed, resulting in a large amount of flue gas on the local section of the absorption tower. When the amount of spray slurry is constant, the removal rate of sulfur dioxide is low, only 80% %-95%, which cannot meet the new environmental protection requirements of the existing ultra-low emissions

[0009] (4) In the traditional spray empty tower, there is only one concentration of slurry (15%-20%). In order to obtain sufficient slurry residence time (solid residence time ≥ 15h), the operating slurry density is generally higher ( 1070-1100Kg / m3)

[0010] (5) In the traditional spray empty tower, the oxidation of the intermediate product ammonium sulfite will become more difficult as the density of the slurry increases, and the oxidation effect of ammonium sulfite is poor when operating under the condition of higher slurry density. At the same time, some unreacted desulfurizers will be coated in the discharged ammonium sulfate slurry, which will directly affect the quality of by-products

[0011] (6) In the traditional spraying empty tower, in order to improve the desulfurization efficiency of sulfur dioxide, the pH value of the slurry is generally controlled at a higher pH value of 5.0-6.0, and the lower pH value of 4.0 required for the oxidation and crystallization of by-products is often ignored -5.0

[0012] At present, the state has raised the sulfur dioxide emission standards for coal-fired boilers, and the traditional spray empty tower wet ammonia desulfurization process can no longer meet the environmental protection requirements.

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