Wet biogas desulfurization refers to the application of liquid absorbents (such as water or alkaline solutions) to wash flue gas and remove SO2 from flue gas. Its advantages are high desulfurization efficiency, small equipment, low investment, easy operation, easy control, and small footprint; The disadvantage is that it is easy to cause secondary pollution, there is a problem of wastewater post-treatment, high energy consumption, especially the low temperature of the flue gas after washing, which is not conducive to the diffusion of chimney exhaust, easy to generate "white smoke", requires secondary heating, and severe corrosion. The main methods are

石灰石-石膏法该工艺是利用石灰石/石灰石浆液洗涤烟道气，使之与SO2反应，生成亚硫酸钙(CaSO3)，经分离的亚硫酸钙可以抛弃，也可以通入空气强制氧化和加入一些添加剂，以石膏形式进行回收。为了减轻SO2洗涤设备的负荷，先要将烟道气除尘，然后再进入除尘设备与吸收液发生反应。石灰/石灰石-石膏法技术比较成熟，吸收剂价廉易得，运行可靠，应用最广，脱硫效率可达90%以上。

The limestone gypsum method is a process that uses limestone/limestone slurry to wash the flue gas and react with SO2 to generate calcium sulfite (CaSO3). The separated calcium sulfite can be discarded, or air can be introduced for forced oxidation and some additives can be added to recover it in the form of gypsum. In order to reduce the load of SO2 washing equipment, the flue gas needs to be removed from the dust first, and then it enters the dust removal equipment to react with the absorption liquid. The lime/limestone gypsum method technology is relatively mature, with inexpensive and easily available absorbers, reliable operation, and the widest application, with a desulfurization efficiency of over 90%.

钠法此法是用氢氧化钠、碳酸钠、或亚硫酸钠溶液为吸收剂吸收烟气中的SO2，因该法具有对SO2吸收速度快，管路和设备不易堵塞等优点，所以应用比较广泛，吸收液可以经无害化处理后弃去或适当方法处理后获得副产品NaSO3晶体、石膏、硫酸等。 镁法此法具有代表性的工艺有西德WilhlmGrillo公司发明的基里洛法和美国ChemicalConstructionCo发明的凯米克法。

Sodium method: This method uses sodium hydroxide, sodium carbonate, or sodium sulfite solution as absorbent to absorb SO2 in flue gas. Due to its advantages of fast SO2 absorption speed, less clogging of pipelines and equipment, it is widely used. The absorption solution can be discarded after harmless treatment or processed by appropriate methods to obtain by-products such as NaSO3 crystals, gypsum, sulfuric acid, etc. The representative processes of magnesium method include the Kirilo method invented by Wilhlm Grillo Company in West Germany and the Kemmick method invented by Chemical Construction Co. in the United States. Kirilot method

是用吸收性能好并容易再生的MgxMnOy为吸收剂吸收烟气中的SO2，此法所得副产物H2SO4的浓度可达98%。凯米克法又称氧化镁法，用串联两个文丘里除尘器除去烟气中微小的尘粒，并用MgO溶液吸收烟气中的SO2。吸收过程中生成的MgSO4·7H2O和MgSO4·6H2O的晶体与焦碳一起在1000℃下加热分解得到SO2和MgO。再生的MgO可重新用作吸收剂。

MgxMnOy with good absorption performance and easy regeneration is used as an absorbent to absorb SO2 in flue gas. The concentration of by-product H2SO4 obtained by this method can reach 98%. The Kemmick method, also known as the magnesium oxide method, uses two Venturi dust collectors in series to remove small dust particles from the flue gas, and uses a MgO solution to absorb SO2 from the flue gas. The crystals of MgSO4.7H2O and MgSO4.6H2O generated during the absorption process are heated and decomposed with coke at 1000 ℃ to obtain SO2 and MgO. The regenerated MgO can be reused as an absorbent.

氨法此法是用氨水为吸收剂吸收烟气中的SO2，其中间产物为亚硫酸铵和亚硫酸氢铵，采用不同方法处理中间产物可回收硫酸铵、石膏、单体硫等副产品。

Ammonia method This method uses ammonia water as an absorbent to absorb SO2 in flue gas, and the intermediate products are ammonium sulfite and ammonium bisulfite. Different methods are used to treat the intermediate products, which can recover by-products such as ammonium sulfate, gypsum, and monomer sulfur.

磷铵复肥法该法是利用天然磷矿石和氨为原料，在烟气脱硫过程中副产品为磷铵复合肥料，工艺流程主要包括四个过程，即:活性炭一级脱硫并制得稀硫酸;稀硫酸萃取磷矿制得稀硫酸溶液;磷酸和氨的中和液[(NH4)2HPO4]二级脱硫;料浆浓缩干燥制磷铵复肥。脱硫效率为95%以上。

The ammonium phosphate compound fertilizer method uses natural phosphorus ore and ammonia as raw materials, and the by-product in the flue gas desulfurization process is ammonium phosphate compound fertilizer. The process mainly includes four processes, namely: primary desulfurization with activated carbon and preparation of dilute sulfuric acid; Extracting phosphate rock with dilute sulfuric acid to obtain a dilute sulfuric acid solution; Neutralizing solution of phosphoric acid and ammonia [(NH4) 2HPO4] for secondary desulfurization; Concentrate and dry the slurry to produce ammonium phosphate compound fertilizer. The desulfurization efficiency is above 95%.