Experimental And Numerical Study On Slag Flow At Slag Tap Hole Of Gasifier

There was slag blockage at the slag tap hole during long tome operation of gasifier sometimes, which is a great threat to the economic, safe and stable operation of device. According to the flow direction of syngas and slag, there were two ways of slag discharge: gas-slag countercurrent flow and gas-slag concurrent flow. Cold model experiment was carried out for observing the simulated slag flow characteristic under the slag tap hole. A dynamic model was developed to clarify the slag deposition、transition and growth on the membrane wall. The reason of slag blockage at the slag tap hole of Shell gasifier was tried to explore and corresponding measures to eliminate slag block were also put forward. The deposition behavior on the membrane wall under the slag tap hole of cold model experiment of gas-slag concurrent flow was also analysised.The slag discharge at the slag tap hole of Shell gasifier is gas-slag countercurrent flow process. Cold model experiment study on slag flow at the tap hole region of Shell gasifier was set up and the syrup was used as medium. The results indicate the simulated slag was broke up to slender liquid fragments and a part of the liquid fragments deposit on the screen wall, other than flow into the slag bath under the force of gravity. The deposition rate of slag deposition on the screen wall increases with increasing air velocity at the slag tap hole, whereas it decreases with increasing slag velocity; the liquid fragments of simulated slag and the deposition rate on the screen wall increase with decreasing viscosity and increasing operating load; the use of nozzle has a great influence on the simulated slag flow characteristic at the tap hole region. The simulated slag deposit on certain region of screen wall under experimental conditions using adjacent nozzle or three nozzle.A dynamic model of slag flow、transition and growth on the wall of slag tap hole region of Shell gasifier was performed. When the slag surface temperature is lower than critical temperature, the molten slag is totally solidified. When the slag surface temperature is above critical temperature, the solid slag layer is coated with a molten slag layer at equilibrium. the solid slag thickness increases along slag flow; as the operating temperature and deposition rate are decreased, the solid slag thickness and characteristic time increase. When the operating temperature and deposition rate keep constant, viscosity-temperature characteristic has no effect on the solid slag thickness and characteristic time; increasing the operating load and operating temperature make the solid slag become thin, when the operating load and operating temperature increase, the solid slag thickness keeps decreasing until it stabilizes after hundreds of hours or more.Cold model experiment of gas-slag concurrent flow was carried out for studying the effect of sudden expansion ratio on the slag flow behavior under the slag tap hole and deposition behavior on the membrane wall. The syrup as used as medium. The results indicate the sudden expansion ratio has a great effect on the flow behavior under the slag tap hole. When the gas velocity at the slag tap hole、operatong load、slag velocity and viscosity of simulated medium keep constant, the liquid fragments of simulated slag and the deposition rate on the membrane wall decrease with increasing sudden expansion ratio, while the distance between deposition region and slag tap hole increases with increasing sudden expansion ratio.Cold model experiment of gas-slag concurrent flow was systematacially carried out for observing the simulated slag flow behavior in the upper region of radiant syngas cooler. The results indicate that when the air velocity and operating load is fairly low, the simulated slag doesn’t deposit on the wall, but as the air velocity and operating load is fairly high, a part of the simulated slag deposit on the wall by an air jet in the inlet zone and the air entrainment in the recirculation region; the liquid fragments of simulated slag and the deposition rate on the wall increase with increasing operating load and air velocity at the slag tap hole, whereas the distance between deposition region and slag tap hole increases with decreasing operating load and air velocity; the liquid fragments of simulated slag and the deposition rate on the wall increase with decreasing viscosity and slag velocity, whereas the distance between deposition region and slag tap hole increases with increasing viscosity and slag velocity.