Research On The Boiler Of 1000MW Ultra Supercritical Double Reheat Units

With China's rapid development of economy, the dual pressure of the total energy and environment protection will place new demands on energy conservation and emission reduction continuously. Under the present social circumstances, it is becoming a major goal and an advancing direction in the energy fields to develop the 1000 MW ultra supercritical double reheat units. In the article, the research was launched typically on 1000 MW ultra supercritical double reheat boilers in Taizhou by China Guodian Corporation. The new calculation models were put forward for thermal calculation on 1000 MW double reheat boilers and different paremeters on different conditions of different coal were calculated mainly based on thermal calculation standards of year 1998 by Excel VBA. Parameter characteristics were analysed and operation characteristics were optimized on the 1000 MW ultra supercritical double reheat boiler. The results were as follows:Arrangements of heating surfaces in double reheat units were analysed and the forms including parallel arrangement for reheaters, adding flue gas damper, combined heating surfaces and some others were summarized. There were four thermal calculation models proposed to solve heat transfer problems of furnace, high-temperature surfaces, lowtemperature surfaces and auxiliary heating surfaces. The model calculation showed that the results were just close to the designed values and parameters could be calculated accurately. The whole thermal calculation for double reheat boilers was established using all the models above and all the results were got.On BMCR working condition, the steam temperature was 607.0?/615.6 ? /617.2 ?. The maximum deviation was only 3.9 ? and the temperature variation curve coincided well with the designed value curve. As load decreased, the deviation between calculation and design grew graduately and the maximum would be 10-20?, mainly coming from algorithm in the furnace. When using different kinds of coal, the maximum deviation would be 7? correspondingly. The parameters in the double reheat boiler were analysed. Compared to the single reheat boiler with the same capacity, working fluid flow was reduced by 245t/h and heat transfer in double reheaters was increased by 9.7%. At the same time, flue exhaust temperature was reduced by 6?and fuel comsumption was reduced by 33.3t/h, which would produce economic benefits for about 46 million yuan in one year. Finally, the operation mode in the double reheat boiler was optimized and thermal controlling means was put forward.Finally, the influence of adjusting flue damper opening on operating parameter was discussed in detail. Independent adjusting would produce variation of 50? between-39.1? to +16.4? on the side of first reheater, while 30? between-17.9? to +9.7? on the side of second reheater. The smaller the flow, the wider the variation. In general, temperature adjustment should be mainly based on swinging burners and adjusting flue damper while spray desuperheating was a kind of means of fine tuning and emergency. It was pointed that the 1000 MW ultra supercritical double reheat boiler had great developing potential and was worth carrying out further studies.