| Coal is and will be the most important fuel to electricity generation according to domestic energy resource structure. In 2014, National Development and Reform Commission demanded to promote energy production and consumption revolution, and to further enhance the level of clean coal technology. Net coal consumption of newly constructed coal-fired units and active units should be lower than 300 gce/kWh and 310 gce/kWh by the end of 2020, respectively. Therefore, it is of great significance to develop high efficient coal-fired power generation technology.The thermal performance of Pyrolysis Bridged Hybrid Power System which is proposed by Institute of process engineering, Chinese academy of sciences is studied. Based on both Aspen Plus and Thermoflex software, a simulation platform of coal pyrolysis hybrid power generation system is established to study the thermal performance and energy-saving potential, especially focus on pyrolysis energy conversion efficiency and the thermal performance of integrated system.By the simulation, the effects of pyrolysis gas yields and moisture content of coal on the pyrolysis energy conversion efficiency are analyzed. It is demonstrated that the pyrolysis energy conversion efficiency declines with the increase of pyrolysis gas yield. The moisture content of coal increases energy consumption of pyrolysis. The pyrolysis energy conversion efficiency of Huolinhe lignite (20% moisture content) and Victoria lignite (50% moisture content) is 93.3% and 82.0%, respectively.Base on the Pyrolysis Bridged Hybrid Power System, a new power system coupling steam drying (called IPE power) is proposed. Net electric efficiency of the new system is higher than that of conventional power plants with the same steam pressure and temperature. The results show that net electric efficiency of IPE subcritical power systems and supercritical power system is 42% and 44%(net coal consumption:293 gce/kWh and gce/kWh), respectively.The IPE power system can be applied for the retrofitting of existing power units. The retrofitted projects of 300 MW subcritical unit and 50 MW thermal power plant are studied. Net electric efficiency of the former is upgraded from 34.63% to 40.65% (Net coal consumption is decreased from 355 gce/kWh and 303 gce/kWh), while that of the latter plant is increased from 14.80% to 20.37%(Net coal consumption is decreased from 316 gce/kWh and 269 gce/kWh). Thus, it is a promising and efficient way to upgrade the efficiency of existing power units by IPE system.The principle of steam integration can also be applied to small biomass-fired power unit or natural gas combined cycle (NGCC) power unit to increase the efficiency of power generation. The steam of biomass-fired boiler could be integrated with that of large coal-fired power unit with higher steam pressure and temperature. The thermal performance of coal-biomass power unit with steam integration is studied, and the effects of system parameters on thermal performance are considered. So does the steam generating unit in the natural gas combined cycle. It is indicated that net electric efficiency of coal-biomass power unit with steam integration increases from 29.40% to 38.42%, while that of steam generating unit with steam integration in the combined cycle rises from 32.89% to 34.47%.The economic evaluation of IPE system is carried out. The results show that it is feasible to have preferable profitability, especially available to retrofitted power plant. The projects have high profit margin of investment by making use of existing equipment as much as possible.This work shows that the thermal performance of IPE power system is better than that of conventional power system and the project is economically feasible. Meanwhile, the efficiency of the system could be further improved. The system can be applied not only to the newly constructed units, but also to existing power unit. This thesis can provide some advices for future engineering application of IPE power system. |
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