Numerical Simulation And Measurements Of Slag Discharge In Entrained Flow Gasifier

The entrained flow coal gasification technology become one of the important means and directions in clean coal and coal conversion technology in our country. Blocking slag and water wall "burn out" by failure of slag discharge restrict long term stable operation of entrained flow gasifier. So it is necessary to research into the entrained flow gasifier. In today's large-scale coal gasification technology shell coal gasification technology has significant competitive. Therefore this article take shell coal gasification technology as the example, Firstly, an entrained flow gasifier wall model is established by finite element method. The effect of the thickness of solid slag, slag nail length, the thermal conductivity of slag nail, the water-side heat transfer coefficient and the temperature of the gasifier furnace on temperature distribution were investigated, to study the working principle of "the slag resists the slag". Secondly, make a relatively systemic research about the coal-ash viscosity, black water (circulating water from slag pool), criterion of big slag generation and stack height of slag, using acoustic emission (AE), expectation early-warning of Fault in the gasifier. The innovative results can be summarized as follows:1. An entrained flow gasifier wall temperature distribution model is established by finite element method, the effect of the thickness of solid slag, slag nail length, the thermal conductivity of slag nail, the water-side heat transfer coefficient and the temperature of the gasifier furnace on temperature distribution were investigated. When the thickness of solid slag increases, the temperature at the interface between solid slag and liquid slag increases, the temperature of slag nail decreases, the temperature of water cooled tube and metal wall unchanged; when slag nail length increases, the temperature at the interface between solid slag and liquid slag decreases, the temperature of slag nail increases, the temperature of water cooled tube and metal wall unchanged; when the thermal conductivity of slag nail increases, the temperature of slag nail decreases, the temperature of water cooled tube increases, the temperature of metal wall decreases; when the water-side heat transfer coefficient increases, the temperature of water cooled tube, metal wall and slag nail increases; when the temperature of the gasifier furnace increases, the temperature of water cooled tube metal wall and slag nail unchanged.According to results, solid slag and liquid slag comprise the main thermal resistance of water wall, seclude water cooled tube, metal wall and slag nail from high temperature gas in the gasifier, ensure them not to be high temperature corrosion, high temperature corrosion ablative and high temperature fretting corrosion, to achieve "the slag resists the slag".2. The viscosity prediction models for Carboxymethylcellulose(CMC)-water system are obtained, desire to on-line inspection for viscosity of liquid slag. A characteristic frequency band of acoustic emission (AE) signals, was obtained by using wavelet transform. Then it was observed that the energy of AE signals at dominant frequency changed regularly with increasing fluid viscosity. A new method for building prediction model of viscosity was presented based on this regular behavior, that isμ=aΔf+b, whichΔfis displacement of dominant frequency, a and b is fitting parameters, this new method show that the correlation coefficient(r), average relative deviation (ARD) and root mean square error of cross validation (RMSECV) between actual viscosity and predictive values obtained by prediction model, were 0.979, 5.47% and 0.074, respectively. It is concluded that multi-scale analysis of AE is feasible for predicting fluid viscosity.3. The viscosity prediction models for sucrose-water system are obtained, desire to on-line inspection for viscosity of circulating water from slag pool. A characteristic frequency band of acoustic emission (AE) signals was obtained by using wavelet transform and Hurst analysis. Then it was observed that the energy of AE signals at different frequencies changed regularly with increasing black water viscosity. A new method for building prediction model of black water viscosity was presented based on this regular behavior. This new method was verified by the aqueous sucrose solutions system in a stirred vessel, which showed that the correlation coefficient(r), average relative deviation (ARD) and root mean square error of cross validation (RMSECV) between actual viscosity and predictive values obtained by prediction model, were 0.970,11.9% and 1.228. respectively. It is concluded that multi-scale analysis of AE is feasible for predicting black water viscosity.4. A criterion for the generation of large slag is presented based on acoustic emission (AE), namely the curve of energy and variance appears spike means that the generation of large slag, namely, energy E>1.5Eo, variance S>1.2S0, the average absolute relative deviation (AARD) is 0.34% when compared with ones by the method of visual observation. So this criterion cans detection the generation of large slag.5. A characteristic frequency band of acoustic emission (AE) signals, which represented the impact of the slag on the wall, was obtained by using wavelet transform and Hurst analysis. Then it was observed that the energy of AE signals at different frequencies changed regularly with increasing the height of slag pool, namely the height of the first step change in the characteristic energy curve is the stack height. Take water-glass beads for example, the average absolute relative deviation (AARD) is 3.94% when compared with ones by the method of visual observation. So this criterion cans detection the stack height.