Research On Economical Efficiency On Wet Desulfurization With The Utilization Of Low Temperature Waste Heat From Coal-fired Boiler

Coal-fired power station is the main source of SO2 emissions while providing the main electric power. The implementation of "ultra low emission" standards plays an important role in the implementation of the national energy conservation and emissions reduction strategy. However, the loss of smoke extraction in coal-fired boiler is the main heat loss, which still has the huge utilization potential of low temperature waste heat. Thus, the key to save energy substantially of power station boiler is how to effectively exploit the waste heat from smoke extraction in coal-fired power station.The economic influence of desulfurization system under the utilization of the low temperature waste heat utilization was analyzed in this paper by the tube furnace desulfurization tower experiment, CFD numerical simulation, and the low temperature waste heat utilization efficiency calculation. And this paper aimed at researching the influence on desulfurization efficiency and power consumption and water consumption of the desulfurization system under the utilization of the low temperature waste heat and providing theoretical basis for the reform scheme for the utilization of low temperature waste heat.The influence on desulfurization efficiency of different temperature of desulfurization tower inlet flue gas and different concentration of inlet flue gas SO2 were studied using a lab-scale tube furnace desulfurization tower. The following conclusions can be drawn: With the increase of temperature of desulfurization tower inlet flue gas, the temperature of desulfurization tower flue gas outlet also increased in a small scale, and the desulfurization efficiency decreased gradually. When the temperature of desulfurization tower inlet flue gas was 129℃ with a fixed spray amount, the desulfurization efficiency first rises then falls with the increasing concentration of sulfur dioxide. When the concentration of sulfur dioxide was 1200 ppm, the desulfurization efficiency was up to 94.08%.Base on computational fluid dynamics(CFD) technology and structuralized-non-structuralized hybrid grid technology, the standard k-ε turbulent model which describe the flue gas turbulent motion in the tower, the Discrete Phase Models which trace the movement of droplets, Discrete Random Walk model which describe droplets distribution, SO2 concentration field in the scrubber was determined by desulfurization model which build up non-steady state mass transfer theory, the gas-liquid fluid flow field in spraying tower was simulated with the SIMPLE calculation method. The numerical calculation of the scrubber of a 300 MW power unit was taken. The calculation results of desulfurization was in good agreement with the results researched by Zhejiang University, which meant the established model was feasible. Finally, the model was used to research the influence on the desulfurization efficiency of low temperature waste heat utilization, and the calculation results was consistent with the data provided by power plant of a scrubber in Guangdong. The efficiency of desulfurization is 98.03% with the utilization of low temperature waste heat, an 0.63% increase from unutilized occasion. Thus, the utilization of low temperature waste heat is advantageous to the desulfurization reactionWith the low temperature economizer installed in the power plant boiler, the flue gas side resistance increased leading the increase of the energy consumption of booster fan. But with the increasing depth of utilization of low temperature waste heat, the variable quantity of energy consumption from booster fan and the energy consumption of oxidation fan decreases. The flue gas carrying water vapor was a major cause of water consumption in the desulfurization system. When a certain 1000 MW ultra supercritical unit under 100% load and the depth of utilization of low temperature waste heat was 50℃, the total energy consumption increased 637.74 k W and the auxiliary power rate increased by 0.064%.But the generated power increased 2.4198 MW. After the deduction of the increase of energy consumption, the increment of the generated power was 1.7821 MW and the water consumption of desulfurization system reduces by 43.7t/h.