Basic laws of the processes and the principle of minimum energy consumption during pneumatic transport and distribution of pulverized fuel in direct pulverized fuel preparation systems

Abstract

The paper presents analysis of the basic laws and a calculation-based investigation of processes related to the low-concentration pneumatic transport and the distribution of finely dispersed pulverized fuel in direct pulverized fuel preparation systems of boiler units. Based on the principle of the minimum energy consumption, it is shown that, at high (standard) velocities of the turbulent gas flow—of 25–30 m/s, which is by 1.5–2 times higher than the critical speeds—the finely dispersed pulverized fuel can be transported simultaneously in the form of a low-concentration flow in pipelines and a concentrated, to 30% of the flow rate, thin layer on the pipeline walls with the height of the layer equal to 0.02–0.04 of the pipe radius. Consideration of this phenomenon is of great significance in terms of securing the efficient operation of pulverized fuel distribution units. The basic characteristics of the process have been determined and validated by test bench investigations using both model systems and pulverized fuel distribution systems of a number of power-generating units. The obtained results underlie a methodological approach to developing high-efficiency adjustable pulverized fuel distribution units. Also, results of industrial testing are presented that confirm the results of the analysis and of experimental studies.