Experimental Study On Water Recovery And Particle Matter Control Of Flue Gas Condensation In Coal-fired Power Plants

The water resource situation in China is becoming increasingly tense.Coal-fired power plants consume a lot of water resources.The flue gas after the wet desulfurization system of the power plant contains a large amount of water,but it is rarely used effectively.The moisture in the flue gas recovered through condensation method can be solved the water demand in power plants.At the same time,the improvement of environmental protection standards has also put forward higher requirements for the emission of particulate matter and other air pollutants.The existing ultra-low emission transformation increases energy consumption inevitably.The use of flue gas condensation to remove particulate matter and other pollutants to achieve Ultra-low emissions and even near-zero emissions have received increasing attention.Through theoretical research and field test comparison,the flue gas state after the wet desulfurization system is explored,and the favorable working conditions for its water recovery and collaborative removal of particulate matter is determined.Experiments were conducted to study the water recovery characteristics and condensation heat transfer characteristics of wet flue gas,and to determine the important parameter indexes of flue gas condensate water recovery.The test method for particle concentration was optimized and selected for field test.The removal effect of particulate matter and other soluble components by flue gas condensation and recovery was obtained.The variation rules of each component of particulate matter during the condensation gas recovery process were analyzed.The analysis of flue gas and water recovery,particulate matter control,and waste heat utilization were analyzed,and four engineering application technical schemes were summarized and proposed.The main research conclusions obtained are as follows:First,the flue gas is basically in a saturated or supersaturated state after the wet desulfurization system,which contains a large amount of water,and is a favorable place for water condensation recovery and particulate nucleation removal.Second,the drop in flue gas temperature is linearly related to the recovery rate of smoke water.When the relative flow of cooling water is low,the influence of the relative flow of cooling water on the drop of flue gas temperature is very significant,but when the relative flow of cooling water reaches about 3kg/kg,the decrease of the flue gas temperature becomes stable,and the maximum heat exchange capacity under this operating condition is basically realized.With this condition,the convective condensation heat transfer coefficient is about 9 times the pure convective heat transfer coefficient,and the total heat transfer coefficient is very close to the flue gas side convective condensation heat transfer coefficient.The effect of water recovery in flue gas condenser is general,and the separator needs to further recover the condensed water.For the660MW unit,when the flue gas temperature drops by 10?,the condensate recovery water is about 60t/h,which can meet the water replenishment needs of the desulfurization system under the test conditions.Third,when the temperature of the flue gas drops by about 9?,the particulate matter removal efficiency of the system is 25%,the flue gas condenser has a better removal effect of the condensable particulate matter,and the separator has a higher removal efficiency of the filterable particulate matter.The separator is easier to remove 2.5-10?m filterable particles,and the particles smaller than 1?m in the flue gas condenser are easier to remove by nucleation.The system can achieve 20%removal efficiency of organic components in condensable particles and 30%of inorganic components;the increase of the system's fume temperature drop can help the collaborative removal of particles.Among them,the filtered particles are more affected by the fume temperature drop than the condensable particles.The inorganic component in the condensable particles is more affected by the temperature drop than the organic component.Flue gas condensation can simultaneously achieve the removal of soluble ions.The removal efficiency of Cl^-,Ca²⁺,NH₄⁺are high,and the proportion of SO₄^2-is the largest portion.