Study On Deposition Behavior Of Shell Coal Gasification Fly Ash By Cold Model

In recent years, the problem of fly ash adhering and depositing on syngas cooler in Sinopec Shell coal gasification device, which impacts company’s normal production. Therefore, it is very necessary to study on the deposition characteristics of fly ash. Shell coal gasification fly ash (FC, FD) and power plant fly ash (FA, FB) were used in the study. The particle size distribution, chemical composition, surface topography and powder characteristics of fly ash samples were studied by laser particle size analyzer, X-ray fluorescence spectrometer and scanning electron microscopy respectively and powder characteristics tester respectively. The differences between physical and chemical properties of fly ash were studied as well. And the Shell coal gasification fly ash cold simulation experiment platform was used to test the fly ash deposition experiment to look for the influence law of difference chemical composition, particle size, powder characteristics and gas flow rate on fly ash deposition behavior, then simulated the trajectories of fly ash. The results showed as follows:1. The melting temperature of Shell coal gasification fly ash was low. The content of calcium, sulfur was high. The particle size was small, and the range of particle size distribution was relatively narrow. However, the melting temperature of power plant fly ash was high. The content of silicon and aluminum was high. The particle size was big, and the range of particle size distribution was relatively wide. The different production conditions led to the differences between the physical and chemical properties of Shell coal gasification fly ash and power plant fly ash.2. The deposition quality of FA and FB was more than that of FC and FD. The range of FA and FB fly ash particle size distribution was wider than that of FC and FD fly ash. And the median size was larger. From the fly ash chemical composition data, the content of Al2O3was FA> FB> FC> FD. The rest angle of FA fly ash was relatively larger. And the rest angle of the other three kinds of fly ash was smaller. The jet-flow index size in the order was FB>FA>FC>FD. The wide particle size distribution, big median size, large content of Al2O3, the big fly ash rest angle and the high jet-flow index were the reasons led to fly ash deposition. Then the wide particle size distribution and the big median size were the main reasons. 3. In the fly ash deposition process, the content of tiny particles (0-5μm FA, FB and0～1μm FC, FD) increased gradually. The content of fly ash particles (38-75μm) was the maximum in the early deposition process (30s or60s). It showed that tiny particles were easier to deposit. And the particles (38-75μm) were easier to deposit than other size particles in the early deposition process. The fly ash deposition quality increased as the increased of gas flow rate. It showed that increasing the air flow within a certain range was beneficial to fly ash deposition. With the increasing of gas flow rate, the median diameter showed a trend of decrease after the first increase. Through the numerical simulation, the effect of fly ash particle size was not obvious on flight trajectory, its flight trajectory was near a curve.