Abstract
The possibility of increasing the efficiency of drying coal concentrate unit on the basis of pipe-dryers has been investigated by converting the heat of flue gases outlet into electrical energy and the heat potential of hot water supply system with a heat power generation unit operating on low-boiling working fluids. A method and an algorithm for calculating the thermal mode of the unit under the conditions of specified limitations on temperature pressures in heat exchangers have been developed. On the basis of mathematical modeling of thermal conditions, it has been found that under the conditions of PD-11 pipe-dryers, when the heat power generation unit operates with butane-pentane mixture, 204 kW of electricity can be generated with the condensation cycle, and 1780 kW of heat and 65 kW of electric energy can be generated with the heating cycle.
Highlights
In the coal preparation and coal briquette factories, pipe-dryers are widely used for drying coal concentrate and fine product with a grain size of up to 13 – 15 mm [1, 2]
The conversion of heat of such a potential into mechanical work and electrical energy is possible with the help of a power generation unit (PGU) operating on low-boiling working fluids according to the Rankine cycle
The thermal model of PGU have been modeled with the initial data which are as follows: flue gas volume flow rate is 22.5 m3/s, which corresponds to the nominal value for the PD-11 pipe dryer; the initial temperature of the flue gases is 130 °C; the condensation temperature of the low-boiling working fluid in the condenser is 30 °C; in the water heater for the hot water supply system is 55 °C; the minimum temperature pressure at the outlet of heat exchangers is 10 °C; isentropic and mechanical turbine efficiency are 0.7 and 0.9; efficiency of the electric generator is 0.97; isentropic and mechanical efficiency of pumps are 0.7 and 0.97 respectively; efficiency of electric motors of pumps is 0.97
Summary
In the coal preparation and coal briquette factories, pipe-dryers are widely used for drying coal concentrate and fine product with a grain size of up to 13 – 15 mm [1, 2]. In these devices, the concentrate particles are picked up by a stream of hot flue gases and moved along with them, while in suspension. It is possible to increase the efficiency of installations by utilizing the residual heat of the leaving flue gases. Utilization of waste low-grade heat in Ukraine is currently receiving much attention [3 – 6]
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