Ren Zhongjing, Fu Shanren 1 . Foreword China's energy composition is dominated by coal, and its consumption accounts for about 70% of total primary energy consumption. This situation will not change in the long run. Thermal power plants use coal as the main fuel for power generation, and direct combustion of coal releases large amounts of SO 2 , causing atmospheric pollution, and SO 2 emissions are also increasing with the increase in installed capacity . Strengthening environmental protection is an important guarantee for our country to implement a sustainable development strategy. Therefore, it is very urgent and necessary to increase the control of SO 2 in thermal power plants . There are three control methods for SO 2 : desulfurization before combustion, desulfurization during combustion, and desulfurization after combustion (FGD). Currently, flue gas desulfurization is considered to be the most effective way to control SO 2 . Flue gas desulfurization is mainly dry , semi-dry, and wet methods. 2. The basic principle of flue gas desulfurization SO 2 in smoke  Is essentially acidic, SO 2 from the flue gas can be removed by reaction with a suitable alkaline substance. The most common flue gas off the basic substance is limestone (calcium carbonate), lime (calcium oxide, Ca O) and hydrated lime (calcium hydroxide). Limestone is abundant in production and therefore relatively inexpensive. Quicklime and hydrated lime are produced by heating limestone. Other alkaline substances such as sodium carbonate ( soda ash ) , magnesium carbonate, and ammonia are sometimes used .  The alkaline material used reacts with the SO 2 in the flue gas to produce a mixture of sulfites and sulfates ( depending on the alkaline material used, these salts may be calcium, sodium, magnesium, or Ammonium salt ) . The ratio between sulfite and sulfate depends on the process conditions. In some processes, all sulfites are converted to sulfates.  The reaction between SO 2 or with a basic substance (wet flue gas desulfurization) occur in an alkaline solution, or the occurrence of (dry or semi-dry flue gas desulfurization) in the wet surface of the solid alkaline substance.   In the wet flue gas desulfurization system, the alkaline material ( usually an alkali solution, more often an alkaline slurry ) meets the flue gas in the spray tower. SO 2 in the flue gas dissolves in water to form a dilute acid solution, which then neutralizes with alkaline substances dissolved in water. The sulfites and sulphates formed by the reaction precipitate out of the aqueous solution and the precipitation depends on the relative solubility of the different salts present in the solution. For example, calcium sulfate is relatively poorly soluble and therefore easily precipitates. The solubility of sodium sulfate and ammonium sulfate is much better.   In both dry and semi-dry flue gas desulfurization systems, the solid alkaline absorbent either fluees the flue gas through the bed of alkaline absorbent and is injected into the flue gas stream to contact the flue gas phase. In either case, SO 2 are directly reacted with the solid alkaline material to produce the corresponding sulfite and sulfate. In order for this reaction to proceed, the solid alkaline material must be very loose or rather finely divided. In the semi-dry flue gas desulfurization system, water is added to the flue gas to form a liquid film on the surface of the basic material particles, SO 2 dissolved in the liquid film, accelerates the reaction with the solid basic substance. 3 Flue gas desulfurization technology   At present, the main flue gas desulfurization technologies include limestone - lime abandonment, limestone - gypsum, double-alkali, magnesium oxide, Welman-Lodd, ammonia, and sea water desulphurization, and wet desulfurization technologies, as well as rotary spray. Drying method, dry tailings, semi-dry flue gas desulphurization technology, such as calcining tail activation, circulating fluidized bed desulphurization, charged dry desulphurization, electron beam irradiation, and pulse corona plasma . Limestone-gypsum wet flue gas desulfurization is mainly achieved through six steps: (1) diffusion of gaseous SO 2 in the gas stream, gas diffusion through the membrane; (2) SO 2 is absorbed and dissociated into sulphite and hydrogen ions; (3) Hydrogen ions react with calcium carbonate to generate calcium ions; (4) Sulfite ions are oxidized to sulfate ions; (5) Under acidic conditions, sulfate reacts with calcium ions to form sulfates; (6) Sulfate crystals produce gypsum. The main factors influencing the limestone-gypsum flue gas desulfurization efficiency are absorption temperature, limestone quality, particle size, liquid-gas ratio, calcium-sulfur ratio, pH of slurry, flow rate and temperature of flue gas, oxygen content in flue gas, pulp tank The liquid holding capacity, gypsum supersaturation, etc. Here we will focus on the quality of limestone and the effect of slurry particle size on desulfurization efficiency. The main component of limestone is CaCO 3 . The higher the CaCO 3 content, the greater the activity of limestone and the more favorable it is for desulfurization. In general, the smaller the particle size of limestone, the larger the specific surface area and the more liquid-solid contact, which can effectively reduce the resistance of the liquid phase, so that its dissolution and reflection in the liquid phase is faster and more fully, and it is beneficial to improve the absorbent. Utilization and desulfurization efficiency. However, the smaller the particle size, the grinding energy consumption and equipment investment will be greatly increased. Considering the above two aspects, the general requirements of limestone fineness of 250-325 mesh (47 μ m -61 μ m) . 4  summary Limestone-gypsum flue gas desulphurization is characterized by mature technologies, high desulfurization efficiency, low cost and easy availability of absorbents, wide range of coal types, large flue gas desulfurization requirements, desulfurization by-products, and strong adaptability to load changes. , To adapt to 30% -100% load changes, and significantly reduce the possibility of project cost and other significant advantages of the world's most mature and most widely used flue gas desulfurization process. Micro-nano instruments: As the name implies, Round Molded Graphiteis a cylindrical product of graphite electrode, which is made of graphite block materials by crushing, screening, batching, shaping, cooling, roasting, dipping and graphitization of post section petroleum coke and medium temperature coal tar pitch. It has the advantages of high temperature resistance, corrosion resistance, good conductivity and light weight. It is mainly used for large DC resistance furnaces, blast furnace bricks, conductive electrodes, lining anti-corrosion and other purposes. Round Rod Graphite,Graphite Round Stock,Round Molded Graphite,Graphite Round Square Shape Henan Carbon Road New Material Technology Co., Ltd , https://www.kygraphiteblock.com
The high-purity graphite, graphite block and Molded Graphite produced by Pingdingshan Carbon Graphite Factory for many years are excellent, and the specifications of Round Molded Graphite are as follows: φ 450*800, φ 520*400 φ 630*420, φ 660*620 φ 780*600, φ 820*350~500 φ 900*350~400, φ 1050*350~400 φ 980~350*400, φ 1160*350~680 φ 1260*350~680, φ 1330*400 φ 1420*400, φ 1520*400 φ 1630*350, φ 1800*350 φ 2000*350, φ 520~2000*680