Study On Zero-emission Technology For Desulfurization Wastewater Using Flue Gas Waste Heat Concentration Combined With Solidification

At present,there are many technical problems to be solved in the zero discharge of desulfurization wastewater from coal-fired power plants.The use of flue gas waste heat from the low temperature section of a power plant for wastewater concentration reduction has attracted industry attention due to its low operating costs and simple system.This paper proposes a new set of zero discharge process route of desulfurization wastewater from power plants.First,the flue gas waste heat after the electric precipitator is used to evaporate and reduce the desulfurization wastewater.Finally,the concentrated high-concentration wastewater is cemented and fixed to achieve zero wastewater discharge.For the concentration and reduction of waste gas waste heat,two technologies are studied in this paper.One is to set up a spray device inside the flue in front of the desulfurization tower after the electrostatic precipitator,and pump the waste water into the flue for spray atomization.After the dust collector,the entire flue gas volume is used to evaporate the waste water;Second,a bypass concentration tower is set up between the dust collector and the desulfurization tower.After the electrostatic precipitator is extracted,part of the flue gas is brought into contact with the wastewater in the concentration tower to exchange heat with the wastewater,so that the wastewater is concentrated.For the evaporation of waste water from the entire flue gas volume,in order to avoid nozzle clogging,a new“water curtain”nozzle spray method is proposed in this paper.The influence of the flue gas volume,inlet flue gas temperature,inlet water flow and different salt concentration on evaporation capacity was investigated by using control variable method;orthogonal experiments were used to determine the primary and secondary effects of different factors on evaporation capacity,from primary to secondary in order:the flue gas volume,inlet flue gas temperature,and inlet water flow;the water and salt carried by flue gas during spraying were investigated by connecting the flue gas outlet to the bubble tower;the evaporation capacity of desulfurization wastewater by the concentration system and the scale formation of the concentration system were investigated by using the actual waste water from the power plant.For the bypass concentration and washing integrated device that extracts part of the flue gas volume,the device consists of three parts:a concentration room,a defogging room,and a washing room.Eliminated the defogging device,set up a defogging room,and removed the large droplets and salt carried by the flue gas in the defogging room,and explored the influence of liquid-gas ratio,inlet gas temperature,and initial salt concentration on the evaporation capacity of wastewater;explored the influence of liquid-gas ratio on chlorine escape amount and the effect of washing chamber on chlorine removal;the scale samples inside the concentration system were characterized and analyzed.The main component of the scale sample was Ca SO₄.Then,the effects of concentration of various metal ions,p H and wastewater temperature on crystallization were investigated,and the crystallization salt produced by each experimental component was characterized and analyzed.Finally,a device for automatic separation of crystalline salt by swirling sedimentation tank was proposed.The concentrated liquid after flue gas waste heat reduction was cemented and fixed.The effects of different curing raw material ratios,water-binder ratio,mud-cement ratio,and river sand amount on the compressive strength of the solidified body were investigated.The solidified body has stable performance and meets the requirements for the use of building materials such as curbs.The zero-emission technology for desulfurization wastewater using flue gas waste heat concentration combined with solidification not only achieves zero discharge of waste water,but also simplifies the technical complexity and reduces the cost of wastewater treatment.The research results have important theoretical value for the engineering application of this technology.