Numerical Simulation And Optimization Research On Physical Field In Annular Gap Scrubber

With strong ability of top pressure controlling and dust removing, Bischoff tower has been widely used in iron and steel industry. In order to ensure better dust-removing results and higher power generation of unit iron, it is very important to determine the right pressure loss of the tower. Based on the project of "Optimization research in TRT (Top Pressure Recovery Turbine Unit) system", this thesis is aimed at solving the problems about lower power generation of unit iron, which exists in the running process commonly. Based on a large number of literature study and on-site testing research, the physical fields of gas-liquid two-phase flow of the Annular Gap Scrubber (AGE) in Bischoff tower were researched and the operating parameters were optimized numerically. The main contents and conclusions include:(1) The on-site testing research results of the Bischoff-tower in No.6 blast furnace at Lianyuan Iron and Steel Corporation show that, after maintenance, the Bischoff system performs better effectiveness of dust removal and stability in top-pressure, whereas, the pressure loss was bigger and power generation of unit iron was lower.(2) The Annular Gap Scrubber in Bischoff tower was investigated. Then the mathematical model of gas-liquid two-phase flow in AGE was built and studied numerically. Results show that, the inlet speed of droplets and gas is lower, then it grows dramatically after entering the annular gap because the area reduced, and finally the speed reaches its maximum at the outlet of annular gap. After the outlet of annular gap, the air-flow was disorder with obvious vortices which were good for dusting. The simulation results were compared with that of measurements. Because the numerical calculation ignored solid, forecasting results were smaller than testing results with an average relative error about 4%. The simulation results agree well with measurements and the model mainly reflects the law of actual pressure change.(3) Using this mathematical model, the pressure loss in AGE was analyzed numerically under different conditions of annular-gap travel, coal-gas flow, water-gas ratio. Results show that:1) annular-gap travel, coal gas flow and water-gas ratio has different effects in differential pressure of AGE. And the most important factor is annular-gap travel, the second one is coal gas flow, and water-gas ratio is of lest importance/significance); 2) the smaller annular gap travel, the greater pressure loss is. Pressure loss inversely proportional to annular gap travel, and pressure loss decreases more rapidly under smaller travel condition;3) the greater the coal gas flow, the greater the pressure loss is, coal gas flow is proportional to pressure drop, and pressure drops more under smaller travel; 4) water-gas ratio is proportional to pressure drop, the greater water/gas ratio, the greater the pressure drop; 5) When the annular gap travel is controlled between 300-400mm, and coal gas flow controlled between 3.8×105～3.9×105 Nm3/h, the pressure is slightly larger than 30kPa. As a result, it can meet the request of dusting and it is good for the stability of blast furnace top pressure. Finally, it can improve the power generation of unit iron.