| Waste incineration fly ash is the residue collected in the flue gas purification system of the waste incineration plant.It is mainly composed of flue ash and other chemical substances.Because fly ash from waste incineration contains heavy metals,dioxin and other harmful substances,the state has designated it as a hazardous waste and must carry out harmless treatment of fly ash.The co-processing technology of cement kiln has the advantages of solidifying heavy metals,adsorbing acid gas,completely decomposing dioxin,and no waste residue,which has attracted wide attention.However,during the calcination process,the chloride ions in the fly ash will corrode the steel bars in the concrete and adversely affect the normal operation of the cement kiln.Therefore,before the fly ash enters the kiln,the fly ash should be treated with water eluting chlorine.After washing,the fly ash can be safely put into the cement production process.In addition to chloride ions,there are sodium,potassium,calcium,lead,chromium and other ions in the fly ash washing liquid,and the sodium,potassium,and chlorine contents are relatively high.If potassium chloride in the washing liquid can be recovered,it will alleviate the lack of potassium resources in China.Must be positive.This article takes fly ash from a waste incineration plant in Beijing as an example to study the process of fly ash water eluting chlorine,fly ash water washing to remove impurities,concentration,separation and recovery of sodium chloride and potassium chloride,and to recycle waste incineration fly ash The engineering design used is instructive.Based on the single-factor water elution chlorine experiment on the four factors of water washing temperature,stirring speed,water washing time,and water solids ratio,the experimental conditions of chlorine elution of waste incineration fly ash water were optimized and tested by response surface methodology,Use Design-Expert8.0 software to fit the experimental data,establish a mathematical model of the fly ash water eluting chlorine,and obtain the degree of influence of 4 factors on the water eluting chlorine by analysis of variance: water washing solid ratio> water washing time > Water washing temperature>Stirring speed.When the solid ratio of the washing liquid is 10 ml · g-1,the washing time is28 min,the washing temperature is 30 ℃,and the stirring speed is 450 r · min-1,the removal rate of chloride ion through two cycles of washing reaches 93.3%,which meets Fly ash is required for chloride ion in cement production.Sodium carbonate and sodium sulfide were used to remove impurities in the fly ash water wash.When the amount of sodium carbonate reached 0.8g,the calcium,magnesium,aluminum,zinc,lead and chromium ions in the water wash were calculated as 30 ml water wash.The removal rate is 100%,100%,100%,100%,99.5%,45% in turn;when the addition amount of sodium sulfide is 0.2g,the removal rate of zinc,lead,chromium ions in the washing liquid is 100%,100 %,97%.The analysis shows that the process of removing impurities is to add sodium carbonate first and then sodium sulfide to achieve the purpose of first removing calcium,magnesium,aluminum,zinc and other ions in the washing liquid,and then removing lead and chromium ions.The water washing liquid after the impurity removal is concentrated by a roll-type reverse osmosis membrane,and the reduction of the concentrated liquid is about 50%.By analyzing the equilibrium phase diagram of the same anion and double salt system,the concentration and separation process of double-effect cocurrent evaporation is determined to achieve the separation and crystallization of sodium chloride and potassium chloride.The effects of different simulated operating conditions on the amount of generated steam and heat exchange area are analyzed.Comparing the investment and operating costs under different operating conditions,it is concluded that the cost is the lowest when the heating steam is 200 KPa and the final effect pressure is 10 KPa. |
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