Limestone gypsum wet flue gas desulfurization equipment

1、 Introduction
At present, there are dozens of types of flue gas desulfurization technologies both domestically and internationally. According to whether water is added during the desulfurization process and the dry and wet forms of the desulfurization products, flue gas desulfurization can be divided into three categories: wet, semi dry, and dry desulfurization processes. Wet flue gas desulfurization technology is one of the commonly used techniques nowadays.
Wet flue gas desulfurization (WFGD) uses alkaline slurry or solution as an adsorbent to spray and wash flue gas containing sulfur dioxide in an absorption tower, allowing sulfur dioxide to react with the adsorbent to produce sulfite and sulfate.
Wet flue gas desulfurization processes include limestone gypsum method, magnesium oxide method, ammonia method, etc. The following content will focus on the limestone gypsum method.
2、 Working principle
Limestone or lime is used as a desulfurization absorbent. Limestone is crushed into powder and mixed with water to form an absorbent slurry. When lime is used as the absorbent, the lime powder is digested and treated with water to make the absorbent slurry. In the absorption tower, the absorption slurry is mixed with the flue gas, and the sulfur dioxide in the flue gas reacts chemically with the calcium carbonate in the slurry and the injected oxidizing air to be removed. The final reaction product is gypsum.
3、 Process flow
Boiler/kiln ->Dust collector ->Induced draft fan ->Absorption tower ->Chimney
The flue gas from the boiler or kiln enters the absorption tower under the action of the induced draft fan after dust removal. The absorption tower is a countercurrent spray empty tower structure, integrating absorption and oxidation functions. The upper part is the absorption zone and the lower part is the oxidation zone. The flue gas after dust removal comes into reverse contact with the circulating slurry in the absorption tower. The system is generally equipped with 3-5 slurry circulation pumps, each corresponding to a layer of atomization spray layer. When only one unit is running or the load is low, 1-2 spray layers can be shut down, and the system still maintains a high liquid to gas ratio, thus achieving the desired desulfurization effect. The upper part of the absorption zone is equipped with a secondary defogger, and the free moisture in the flue gas at the outlet of the defogger does not exceed 75mg/Nm3. After absorbing SO2, the slurry enters the circulating oxidation zone, where calcium sulfite is oxidized into gypsum crystals by the air blown in. At the same time, fresh limestone slurry is supplied from the absorbent preparation system to the absorption oxidation system to supplement the consumed limestone and maintain a certain pH value of the absorption slurry. When the reaction product slurry reaches a certain density, it is discharged into the desulfurization by-product system and dehydrated to form gypsum.
4、 Comparison of advantages and disadvantages
Advantages: Limestone gypsum desulfurization is the most commonly used wet desulfurization method. The main advantages of gypsum method are: a wide range of applicable coal types, high desulfurization efficiency (some devices have desulfurization efficiency greater than 90% when Ca/S=1), high utilization rate of absorbent (can be greater than 90%), high equipment operation rate (can reach over 90%), high reliability of operation (currently the most mature flue gas desulfurization process), and abundant and inexpensive source of desulfurizer limestone. When choosing flue gas desulfurization equipment for thermal power plants both domestically and internationally, the limestone/gypsum forced oxidation system has become the preferred wet flue gas desulfurization process.
Disadvantages: The initial investment cost is too high, the operating cost is high, the land area is large, the system management operation is complex, the wear and corrosion phenomenon is severe, the by-product gypsum is difficult to treat (due to sales problems, it can only be stacked), and the wastewater is difficult to treat.
The desulfurization processes used in different operating conditions are slightly different. If you have any questions, please call our technical hotline at 15511766866 0317-4644981