The process of dry desulfurization is mostly gas solid reaction, the velocity is relatively low, the flow velocity of the flue gas in the reactor is slow and the reaction time is prolonged, so the equipment is large, but the flue gas after the desulphurization is less cooling or not cooling, so it does not need to be reheated (less energy consumption), which can satisfy the demand of emission diffusion. Besides, the two pollution is less, no scaling, blockage and high reliability.
1. Dry fly ash desulphurization
The desulphurizer is made from fly ash, hydrated lime and gypsum as raw material and granulated into a absorber. When the desulfurizer moves up and down from the tower to the tower, the calcium hydroxide of the desulfurizer reacts with the sulfur dioxide in the flue gas to produce gypsum, while the fly ash and gypsum in the desulfurizer play the role of active media. The desulfurizer after use can also be used as raw material for producing desulfurizer.
2 and BF moving bed activated carbon desulphurization
用活性炭作脱硫剂，在脱硫移动床中与约100℃烟气错流接触，以脱除二氧化硫，脱硫率90％以上。吸附了二氧化硫的活性炭在再生移动床中与 500～ 600 ℃热砂（或其它热载）体合，被炭还原成二氧化硫逸出，用于制硫酸，向烟气中添加氨用双层床处理，可同时脱除80%的二氧化氮。
Activated carbon is used as desulfurizer to cross the contact with flue gas at about 100 degrees in a desulphurization mobile bed to remove sulfur dioxide, and the desulfurization rate is over 90%. The activated carbon adsorbed sulfur dioxide in the regenerated mobile bed is combined with hot sand (or other hot load) at 500~600 C, and is reduced to sulfur dioxide by carbon. It is used to make sulphuric acid, and the ammonia is added to the flue gas to be treated with a double layer bed, and 80% nitrogen dioxide can be removed at the same time.
3. Spray drying method
It was developed in 70s. It uses lime as a desulphurizer, and uses atomizer to spray lime solution into the absorption tower. The lime slurry contacts the sulfur dioxide in the flue gas with very fine droplets. A chemical reaction was made to form calcium sulfite and calcium sulphate. Using the heat in the flue gas to vaporize the water of the droplet, the dried powder is not taken away with the flue gas after the desulphurization, and the desulfurization rate is 70 ~ 90%. When Ca / S - 1.5, the desulfurization rate is 85%, which is the kind of desulfurization in the wet state. The method of treating desulfurization products under dry condition is also called semi dry. The rate of desulphurization can reach more than 90%. The sulfur content of the allowed coal can reach 3%. It can compete with the wet process. The main feature of this method is that the waste from the absorption tower is dry. Compared with the wet limestone method, the huge waste disposal system is saved and the process is simplified. The key technology is the atomizer of limestone slurry and the absorption drying tower. The most widely used is the centrifugal rotary atomizer. Therefore, the application of this method is good in our country.
4. Electron beam irradiation
The principle is that water containing water is irradiated by electron beam, and the water in the flue gas is activated cracking into strong oxidants such as HO, O and so on. It can quickly oxidize sulfur dioxide and nitrogen dioxide into three sulphur oxide and nitrogen pentoxide, and then synthesize ammonium sulphate and ammonium nitrate with the added ammoniation. The desulphurization rate is 90%, and the denitrification rate is 80%. The whole unit has a high power consumption, accounting for about 10% of the plant's power generation.