Approximate-Analytical Study on Thermal Preparation and Combustion of a Coal Particle

Abstract

The main amount of heat and electricity in the world is produced with application of coal. Following development of power engineering plans application of low-grade coals, including those of new deposits (Salomatov VV, Nature conservation technologies at thermal and atomic power plants, Novosibirsk, NSTU, 2006). Massive Shive-Ovoos open-cast is among such low developed deposits of Mongolia. This deposit requires a set of investigations on thermal preparation and combustion of coal, aimed at extensive and efficient energy utilization. Calculation of flame combustion of coals is based on dependences, which determine the whole combustion process of separate coal particles. For particles of natural coals these processes include complex transformations of organic and mineral parts of coal matrix, heating, devolatization, ignition and burning of coke residue. Such detailed elaboration requires complex physical and mathematical simulation.

Five successive stages of thermal preparation and combustion of a coal particle with initial humidity and ash content were distinguished by experimental results:

• 1. Heating. The particle is heated; the temperature increases, and the mass stays constant.

• 2. Drying. Liquid inside a wet particle evaporates and mass reduces.

• 3. Devolatization.

• 4. Ignition of slightly dried carbon layer by fuel gases. Residual moisture is still kept in the particle.

• 5. Burning. Two successive conditions are considered:

  • (a) simultaneous burning of dried carbon layer and evaporation;

  • (b) burning of absolutely dry coke residue.