With the spreading of intermittent renewable power, coal-fired power units should cycle frequently to balance the load between power supply side and demand side. Coal consumption rate of coal-fired units operating in dynamic processes is influenced by many factors, including thermal system, control system, heat storage variation, etc. Therefore, it is very difficult to evaluate the energy efficiency of coal-fired units operating in dynamic processes. It is important to ascertain the basic coal consumption rate in dynamic processes, which is the basis to evaluate the operation performance of coal-fired units.

In this study, an off-design calculation model of 660MW ultra-supercritical coal-fired units is developed and validated with design parameters. The developed models can be used to predict the coal consumption rates under steady-state off-design conditions. The basic coal consumption means the coal consumption of coal-fired units with operating parameters the same as target values. To calculate the basic coal consumption rate, a load change process is differentiated into lots of short time periods, and every period is regarded as a steady-state condition with constant load, therefore the coal consumption rate in every period are equal to that of the corresponding steady-state condition. The calculation formula of average coal consumption rates in load change processes is derived for dynamic processes where the load changes linearly with time.

On the basis of the off-design calculation model and assumption of idealized condition, average coal consumption rates during different processes with constant load change rates can be calculated and analyzed. Results show that if the initial and final loads are both settled, the basic coal consumption rate remains unchanged and is independent of load change rate. When the initial load is settled, the basic coal consumption rate increases with the decrease of final load. For example, if the initial load is set at 100%, the basic coal consumption rates with final load at 90%, 80%, 70% and 60% are 280.70, 281.17, 282.37 and 283.97g/kWh respectively. Otherwise, if the load change amplitude remains unchanged, the basic coal consumption rate increases as the initial load decrease. The study aims to provide benchmark values for the energy consumption analysis in actual dynamic processes, and further study on coal consumption characteristics in dynamic processes will be developed based on it.


Study on Basic Coal Consumption Characteristics in Dynamic Process of 660MW Ultra-Supercritical Coal-Fired Unit

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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