| Thermal efficiency is the important indicator of power plant.Under the promise of the safe operation of the power plant,it is the final goal of every electrical enterprise to maximize the economic benefit of power plant. Improving the heat economy of power plant can make a huge beneficial influence in power plants and society. This paper started a research in heat economy of power plant.In the view of the problem that the heat consumption rate calculation is inaccurate in present power plants, a new calculation method of real-time heat consumption rate based on power measurement is developed in this paper. Firstly, through the analysis of design data and thermal performance test results, the operating characteristics of steam turbine were received. Secondly, the model of power plant was established based on the principle of thermal equilibrium, material balance and energy conservation. The high and low pressure heaters' extraction, steam parameters and Low pressure cylinder efficiency were obtained combining with the practical operation of the power plant. To get the heat consumption rate in real time, we can use the counterbalance method to calculate extraction steam flow in different tubes and main steam flow rate without measuring the condensate flow. The method has been applied in a power plant and the monitor results show that the model of heat consumption rate of high accuracy and stability. It supports the accurate evaluation of power plant thermal efficiency.We use the distribution calculation method to study the cleaning degree of the condenser. The overall heat resistance of condenser can be divided into water-side convective heat resistance, gas-side condensation heat resistance, tube-wall conductive heat resistance and fouling conductive resistance calculated by the distribution calculation. Apart from that, we also take the influence on overall heat transfer coefficient by the inlet temperature of circulating water and the number of circulating water flow, and the influence on the gas-side condensation heat transfer by the non-condensable gas into account, respectively. Taking a 660 MW unit as the study object, the change of fouling resistance is to be calculated by the model of cleanliness. By analysis, the model has the ability to show the clean level of the water-side condenser, which can provide certain reference to the operation of condenser.The loss differential analysis model of the heat regenerative system is established according to the method of matrix analysis. Then based on the constant power condition, the upper and the lower terminal temperature difference and the exhaust steam pressure loss of heater is analyzed by changing them respectively. The effect of terminal temperature difference and the backpressure on the heat consumption rate about a domestic 660 MW unit is conducted. The results of the study show that the most influential factor on heat economy of the unit is back pressure. And the loss differential of upper terminal temperature in the NO.1 high pressure heater is the biggest in all of the heater terminal temperature difference. These conclusions can provide theoretical basis for repairing.On those basises, the equipments state analysis system was constructed by using computer and network technology, achieving the monitoring of heat consumption rate and analyzing the cost difference of the regenerative system. It can provide the theory foundation for the decision-making of maintenance. |
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