The elemental sulfur in coal with calcium based methods such as solid fixed to prevent the formation of SO2 combustion, the desulfurization technology at home and abroad and domestic electric power industry desulfurization pilot plant introduction of research and analysis, the desulfurization method can be divided into pre combustion desulfurization, desulfurization during combustion and after combustion desulfurization 3.

The post combustion desulfurization, flue gas desulfurization (also known as Flue gas desulfurization, referred to as FGD), in FGD, according to the type of desulfurization agent, can be divided into the following five methods: CaCO3 (LimestoneCalcium) method based on MgO based method, magnesium, sodium method based on Na2SO3 method based on NH3, ammonia, organic alkali method with organic alkali based. The commercialization of technology widely used in the world is the calcium, the proportion of more than 90%. PressAbsorbentAndDesulfurization productsIn the wet state desulfurization process can also beDesulfurization technologyDivided into wet, dry and semi dry (wet) method. FGD technology is the wet desulfurization products by solution or slurry containing absorbent desulfurization in wet state and processing, this method has the desulfurization reaction speed, simple equipment,The desulfurization efficiencyThe advantages, but there exist some serious corrosion, high cost and easy operation and maintenance problems caused two pollution etc.. The treatment of dry desulfurization absorption and product FGD technology were carried out in the dry state, this method has noSewageThe waste acid discharged, the corrosion of the equipment to a lesser extent, no significant cooling, flue gas purification after high smoke temperature, conducive to the purification processChimneyExhaustThe advantages of the two diffusion, less pollution, but the desulfurization efficiency is low, the reaction speed is slow, large equipment etc.. FGD technology is a kind of semi dry desulfurization in the dry state, the desulfurization in wet stateRegeneration(such as washingActivated carbonRegeneration process), desulfurization, or in wet state in the dry state processing of desulfurization products (such as spray drying method) of flue gas desulfurization technology. In particular, semi dry desulfurization desulfurization treatment in dry conditions in wet condition, with bothWet desulfurizationThe advantages of fast reaction speed, high desulfurization efficiency, and dry, no sewage waste acid discharged after desulfurization products are easy to processing advantage and extensive attention by people. According to the use of desulfurization products, can be divided intoAbandonTwo kinds of method and recovery method.

-- limestoneDesulfurization gypsumIs a process of desulfurization technique is most widely used in the world, japan,GermanyUSA, theThermal power plantFlue gas desulfurization device used in about 90% by using this technology.

Its working principle is: the lime powder with water into slurry as absorbent absorber pump into full contact with the gas mixture, in flue gasSulfur dioxideWith the calcium carbonate slurry and the oxidation reaction of calcium sulfate from the lower part of the tower drum into the air, calcium sulfate reached a certain saturation, the crystallization of two water gypsum. The absorber from the gypsum slurry by condensation, dehydration, the moisture content is less than 10%, then sent to the conveyor stacking gypsum silo, the flue gas desulfurization through the mist eliminator to remove droplet, then afterHeat exchangerAfter heating, from the chimney into the atmosphere. Because of the absorption tower of absorbent slurry through the circulating pump repeated contact with the flue gas, absorption rate is very high, relatively low calcium and sulfur, desulfurization efficiency is greater than 95%.

(1) limestone storage and transportation system

(2) the limestone slurry preparation and supply system

(3) flue gas system

(4) SO2 absorption system

(5) gypsum dewatering system

(6) gypsum storage and transportation system

(7) slurry discharge system

(8) the process water system

(9) the compressed air system

(10) wastewater treatment system

(11) the oxidation air system

(12) electric control system

The absorbent, wide scope of application: the FGD device can be used in various kinds of absorbers, including limestone, lime, magnesite, waste soda solution etc.;

The fuel, wide scope of application: suitable for burning coal, heavy oil, oil, and gas boiler coke fuel processing;

The range of adaptability, fuel sulfur: flue gas can handle up to 8% of the sulfur content in fuel;

Finally, unit load adaptability: can meet the unit in 15 to 100% in the range of load stable operation;

Accordingly, high desulfurization efficiency: more than 95%, the highest reached 98%;

6, patent tray technology: effectively reduce liquid / gas ratio, is conducive to the tower of distributioin, saving material consumption and energy consumption, convenient maintenance of absorption tower;

Water absorbent, high utilization rate: the ratio of calcium to sulfur as low as 1.02 ~ 1.03;

Therefore, the deputy high purity of products: production reached a purity of more than 95% commercial grade gypsum;

Only, coal-fired boiler flue gas dust removal efficiency is high: 80% ~ 90%;

30, cross spray pipe layout: to reduce the height of absorption tower.

1, 200MW and above in large building or reforming unit;

Secondly, the sulfur content of coal in 0.5 ~ 5% and above;

The requirements, the desulfurization efficiency of more than 95%;

The limestone, abundant gypsum comprehensive utilization of wide area

Spray dryingThe desulphurization process with lime as desulfurization absorbent, lime and water made by digestionLimeMilk, milk of lime by the pump into the absorption tower is located in the atomization device, in the absorption tower, the atomized absorbent small droplets in contact with flue gas mixture, a chemical reaction between CaSO3 and SO2 in flue gas, flue gas SO2 removal. At the same time, the water evaporates rapidly into the absorbent and dry, the flue gas temperature decreases. The desulfurization reaction products and unused absorbent particles to form with dry flue gas out of the absorption tower, enterA dusterIs collected. The flue gas desulfurization by precipitator after discharge. In order to improve the utilization rate of desulfurization absorbent, the general part of dust collection addedPulpSystem for recycling. This process has two kinds of aerosol in different forms are available, a rotary spray atomization wheel, a gas-liquid two-phase flow.

Spray dry desulfurization technology has mature technology, simple process,The reliability of the systemEtc., the desulfurization rate can reach more than 85%. In the process of America andWestern EuropeSome countries have a certain scope of application (8%). Desulfurization ash can be used to make bricks, road construction, but is abandoned to the ash field or mine waste backfill.

Ammonium phosphate fertilizer FGD technology belongs to the recovery method, its by-product ammonium phosphate named. This process is mainly composed of adsorption (activated carbon desulfurization acid), extraction (decomposition of dilute sulfuric acid, phosphoric acid and phosphate) (ammonium phosphate neutralization liquid preparation), absorption (ammonium phosphate fertilizer, oxidation desulfurization liquid) (ammonium sulfite oxidation), concentrating and drying (solid fertilizer preparation) unit. It is divided into two systems:

The flue gas desulfurization system -- flue gas through efficient dust remover after the dust content is less than 200mg/Nm3, with the fan will smoke pressure is increased to 7000Pa, the first venturi spray cooling humidity, activated carbon and then enter the four parallel towerThe desulfurization towerGroup (one tower periodic switching control, a regeneration) the desulfurization rate is greater than or equal to 70%, and was about 30% concentrationSulfuric acidA flue gas after desulfurization, level to level two with ammonium phosphate slurry washing desulfurization tower desulfurization, flue gas after purification separation mist after discharge.

Fertilizer preparation system -- in the conventional single slot multi slurry extraction tank, the same level of desulfurization prepared by sulfuric acid decomposition of phosphate rock (P2O5 content is more than 26%), obtained after filtering dilute phosphoric acid (concentration greater than 10%), prepared after neutralization by ammonia phosphorus ammonia, as two desulfurizer slurry, two after desulfurization concentrated dried ammonium phosphate compound fertilizer.

Furnace calcium injection with flue gas wet desulfurization technology is based on furnace calcium injection desulfurization process inBoilerThe tail is additionally provided with a humidifying section, in order to improve the desulfurization efficiency. The process in limestone as absorbent, limestone powder by the gas is sprayed into the furnace temperature of 850~1150 DEG C, limestone thermal decomposition of calcium oxide and carbon dioxide, sulfur dioxide and calcium oxide in flue gasCalcium sulfite. Due to the reaction between gas and solid two-phase, influenced by the mass transfer process, the reaction is slow, the low utilization rate of absorbent. Humidification in the tailReactorInside, the humidifying water to spray into, and calcium oxide unreacted calcium hydroxide and then generate contact reaction with sulfur dioxide in flue gas. WhenThe ratio of calcium to sulfurIn 2.0~2.5, the desulfurization rate can reach 65~80%. Due to the addition of humidifying water makes the smoke temperature, outlet gas temperature is higher than that of normal controlThe dew point temperature10~15 C, humidification water due to smoke temperature heating is rapid evaporation, absorbent, reaction products of unreacted in dry state with flue gas discharge, were collected by dust collector.

In the desulfurization processFinlandAmerican, Canada,FranceApplication of other countries, the largest single capacity has reached 300000 kilowatts desulfurization technology.

Circulating fluidized bed flue gas desulfurization process by absorbent preparation, absorption tower, desulfurization ash recycling, dust collector and control system components. This process generally uses dry lime powder as the stateAbsorbentOn the other, can also be usedSulfur dioxideYesThe absorption reactionThe dry powder or slurry as absorbent.

The boiler discharged untreated flue gas from the absorption tower (i.e. fluidized bed) into the bottom. The bottom of the absorption tower for aVenturiDeviceVenturi, the flue gas flowed through the tube speed, and then with a very fineAbsorbentThe powder mixed with each other, between particles between gas and particles, intense friction, formed in fluidized bed, spray mist evenly reduce the smoke temperature, CaSO4 and sulfur dioxide in flue gas and CaSO3 absorber. After carrying large amounts of desulfurizationSolidParticles in the flue gas discharged from the top of the absorption column, enterRecyclingDust collector, separated by the middle particle ash bin return absorption tower, due to solid particles repeated 100 times, the higher utilization rate of absorbent.

The by-product of this process is a dry powder, its chemical composition and spray dry desulfurization process is similar, mainly composed of fly ash, CaSO3, CaSO4 and unreacted sorbent Ca (OH) 2 etc., suitable for mine backfill, road foundation void.

Circulating fluidized bed flue gas desulfurization process of typical, when the sulfur content of coal is about 2%, the ratio of calcium to sulfur is not greater than 1.3, the desulfurization rate can reach above 90%, the exhaust gas temperature of about 70 DEG C. This process in foreign countries is currently used in 10~20 million kilowatt class units. Because of its small occupied area, low investment, especially suitable for old unitsFlue gas desulfurization.

The seaThe desulfurization process is a desulfurization method using seawater alkalinity to SO2 removal in flue gas. In the desulfurization absorption tower, a lot of water spray washing into the absorption towerCoalIn the flue gas, flue gasSulfur dioxideAbsorbed by seawater is removed, the flue gas after purification separation, the flue gas heat exchanger heating after discharge. AbsorptionSulfur dioxideAfter the sea water and not a lot of desulfurizationThe sea waterThen, byAerationPool aeration treatment, in which SO32- was oxidized into stable SO42-, and the pH value of water and adjust COD meet emission standards after the discharge of the sea. Seawater desulfurization process is generally applicable to the seaside, the diffusion condition is good, use seawater as cooling water, burning low sulfur coal power plant. In the process of seawater desulfurizationNorwayIs widely used in refinery, the refinery etc.Industrial furnacesThe flue gas desulfurization, there have been more than 20 sets of desulfurization equipment put into operation. In recent years, seawater desulfurization technology has made rapid progress in the application of. The biggest problem in this process is possible after flue gas desulfurizationHeavy metalDeposition and onMarine environmentThe influence of long time need to observe in order to draw a conclusion, so inEnvironmental qualitySensitive andEnvironmental protectionHigh area to be carefully considered.

The process consists of the smoke dust, ammonia flue gas cooling, pre charging, electron beam irradiation and by-product trapping processes. The smoke exhaust of the boiler, after processing into the coarse filter dust collectorCooling towerInjection, cooling water in the cooling tower, cooling to the flue gas desulfurization,DenitrationThe temperature (about 70 DEG C). The dew point of flue gas is usually about 50 DEG C, cooling water mist is sprayed completely by evaporation in the cooling tower, therefore, does not produce waste water. Through the flue gas cooling tower after flowing into theReactorIn the reactor, the inlet will beAmmoniaThe compressed air, and water is sprayed into the mixture, adding the amount of ammonia depends on SOx concentration and NOx concentration, after electron beam irradiation, SOx and NOx under the action of the free radicals generated intermediates sulfate (H2SO4) and nitrate (HNO3). Then, sulfuric acid and nitric acid with the coexistence of ammonia neutralization reaction, producing the powder particles (ammonium sulfate (NH4) mixed powder of 2SO4 and ammonium nitrate NH4NO3). The part of the powder particles settle to the bottom of the reactor, through the conveyor discharge, the rest is the by-product of dust separation and trapping, after the granulation process was sent to the warehouse storage products. After purification of flue gas desulfurization by fan chimney emissions to the atmosphere.

The desulfurization process using ammonia as absorbent, by-productAmmonium sulphateChemical fertilizer. Boiler flue gas discharged by the flue gas heat exchanger is cooled to 90~100 DEG C, pre washed into the scrubber to remove HCI and HF, the flue gas after washing through droplet separator to remove water droplets into pre scrubber. In the pre scrubber, ammonia spray washing of flue gas from the top of the tower, SO2 in the flue gas is absorbed and removed by water washing, washing the flue gas discharged after carrying removal by droplet separator, into the desulfurization scrubber. In the flue gas scrubber was further washed by,Washing towerThe top of the mist eliminator to remove droplets, into the scrubber. The flue gas heat exchanger after heating the stack. The concentration of ammonium sulfate solution produced in the washing process of about 30% from the washing tower, can be sent to the fertilizer plant for further processing or directly as a liquid fertilizer for sale, can also put this solution further evaporation drying processed into particles, crystals or bulk fertilizers for sale.

Combustion desulfurization before coal combustion is in the coal in the sulfur removal, pre combustion desulfurization technology are mainly physical and chemical method, coal washing, coal washing method adding sulfur fixing agent, coal gasification and liquefaction, coal water slurry technology. The washing is the use of physical, chemical or biological methods used in boilersRaw coalFor cleaning, remove the sulfur in coal, coal to purify and produce different specifications of products, quality.MicroorganismDesulfurization technologyIt is also a kind of chemical method in essence, it is thePulverized coalSuspended in the air bubble liquid containing bacteria, bacteria produce enzymes can promote the oxidation of sulfur into sulfate, so as to achieve the purpose of desulfurization; microbial desulfurization technology at present desulfurizing bacteria commonly used are: genera ThiobacillusThiobacillus ferrooxidans,Sulfur trioxideColi, archaea Sulfolobus, heat etc.. Add toSolid sulfurAgent refers to the addition of sulfur fixation material in coal, which is made of all kinds of coal, in the combustion process, the sulfur compounds in coal and sulfur fixing agent and reaction of sulfate in the residue, will not form SO2. CoalGasificationRefers to the water,Steam,OxygenOr airOxidantIn,High temperatureWith coalChemical reactionH2, CO, CH4, to generate combustibleMixed gas(calledGasProcess).CoalLiquefaction isThe conversion of coalFor cleaning liquidFuel(Gasoline,Diesel engineAviation kerosene, etc.) an advanced clean coal technology or chemical raw materials.Coal water slurry(Coal Water Mixture, referred to as CWM) isAshLess than 10%, sulfur is less than 0.5%,VolatileHigh raw coal, grinding into 250~300 m finePulverized coalAccording to 65%~70%, 30%~35%, additive coal water and about 1% of the proportion, the coal water slurry can be transported, storage and combustion as fuel oil, coal water slurry ejected from the nozzle at high speed combustion 50~70 m, atomized into droplets, in the preheating to 600~700 degrees furnace rapid evaporation, and with the micro explosion, coal devolatilization and ignition, the ignition temperature of pulverized coal is lower than.

Before combustion desulfurization technology in physical coal cleaning technology has been mature, the most widely used, the most economical, but only removal of inorganic sulfur; biological desulfurization, chemical method can not only remove inorganic sulfur, organic sulfur removal can also, but the cost is expensive, there are still a large distance from the industrial application; coal gasification and liquefaction remains to be studied further. Perfect; microbial desulfurization technology is developing; coal water slurry is a new type of low pollution fuel oil, which can not only maintain the original physical properties of coal and oil, has the same fluidity and stability, known as liquid coal products, huge market potential, currently has commercial conditions.