A Study On De-oiled Asphalt Gasification Process And Its Application In IGCC Systems

In the IGCC poly-generation system with de-oiled asphalt gasification as the core process, gasification is the most critical technology which leads the whole system. This thesis focuses on the core process of de-oiled asphalt gasification, problems occurred in industrial gasification units, and the need to optimize the whole system. Based on large-scale cold model experiment results, the author studied the atomization performance of the burner and the flow field characteristics formed by the burner and the matching gasifier, and analyzed the characteristics of de-oiled asphalt gasification. Temperature and concentration distribution inside the gasifier are investigated through numerical simulation, and the effect of process conditions on the gasification process is discussed. Based on the above, the author developed a new de-oiled asphalt gasification burner, conducted industrial operation test, and applied the ASPEN software for simulation and optimization of the IGCC-Hydrogen poly-generation system with de-oiled asphalt as the raw material. The main contents of the thesis are as follows:1. Characterizing the rheology and viscosity-temperature characteristics of de-oiled asphalt, and selecting the glycerol with similar properties as the simulation medium, the experiment on atomization performance of multi-channel de-oiled asphalt gasification burner was performed using Malvern Laser Particle Analyzer. Results showed that when using the air and water as the working fluid, the atomization angle of the burner is about 20■, and the average SMD is less than 100μm under different operation conditions. Using a high-speed camera and image processing software, the author analyzed the breakup regime, characteristic length, and breakup duration of the liquid drop under different conditions in detail, and discussed the secondary regime of liquid drops.2. Velocity distribution and turbulence intensity of the gasifier were measured using a Dynamic Laser Doppler Particle Analyzer on a large scale cold-model ofΦ1000. Results showed that there is a significant gradient of axial and radial velocity and an obvious recirculation zone in the upper part of the gasifier. Based on Realizable k-εmodel, the velocity distribution and residence time distribution in the gasifier were simulated, and the simulated values show good agreement with the experimental values.3. Analyzing the gasification process based on cold-model and industrial practice, a mathematical model was set up to numerically simulate the turbulent reactive flow inside the gasifier, and to figure out the velocity distribution, temperature distribution, and concentration distribution inside the furnace. Results showed that the gasifier was a confined jet flow, and the jet zone and recirculation zone situated between burner exit and 1/2 height of the straight section, and that protective steam in the outermost channel can effectively decrease the temperature near the nozzle top. Investigation and simulation of the effect of process conditions on gasification process showed that:with the increase of oxygen asphalt ratio by 0.01, the temperature in the gasifier increases up to 25～35℃; there is a optimum value for effective gas production rate in correspondence with variation of oxygen asphalt ratio, as the value of steam asphalt varies, and the corresponding ratio of oxygen asphalt lies in the range of 0.66～0.68; as steam asphalt ratio increased by 0.05, the temperature at the gasifier exit decreases up to15～20℃.4. In order to solve the problem of short lifetime and ablation of the existing burners, based on the measurements of atomization, flow field and numerical simulations, the author proposed a new burner structure for de-oiled asphalt gasification. The primary concept of the new burner is to create a steam film between the oxygen and de-oiled asphalt, so as to avoid ablation at the nozzle end. Industrial tests have proved that the new burner performs well and enjoys a longer life cycle, with a more reasonable temperature distribution in the gasifier, a 4% oxygen consumption saving, a 12% steam consumption saving, and about 0.1 Mpa pressure difference reduction.5. Based on the ASPEN software, a simulation calculation of de-oiled asphalt gasification IGCC poly-generation systems was conducted to investigate the effect of various factors on the efficiency of IGCC power generation; on such basis, a process optimization program for IGCC system was proposed.