CFD MODELING OF VORTEX AFTERBURNING OF BIOMASS GASIFICATION PRODUCTS IN A FLUIDIZED BED FURNACE

CFD modeling of the afterburning of biomass gasification products in a fluidized bed furnace with a vortex supply of secondary air has been carried out. The effect of secondary air heating on the ecological characteristics of flue gases has been determined. Modeling has shown that gasification products swirl in the primary chamber with the formation of a central vortex, which obeys the law of solid-body rotation. An increase in the temperature of the secondary air leads to an increase in its tangential velocity and, as a consequence, to an increase in centrifugal mass forces. Calculations have shown that with an increase in the secondary air temperature, the maximum of the kinetic energy of turbulence shifts to the periphery and increases in absolute value. This results in more efficient mixing of the central (producer gas) and peripheral (secondary air) streams. As a result, this leads to a more complete combustion. The influence of secondary air heating on the ecological characteristics of the furnace has been determined. As a result of air heating from 30° C to 300° C, the concentration of carbon monoxide decreases by more than 1.5 times. The concentration of nitrogen oxides practically does not change and amounts to 3.5 mg /nm3.

Chemistry of the Gasification of Carbonaceous Raw Material

The paper represents the studies of the process of carbonaceous raw material gasification. The initial material is represented by bituminous coal of grade H with the carbon (C) content of 79.2-85.3 %. Experimental studies have been used to substantiate the parameters of combustible generator gases (СО, Н2, СН4) output depending on the temperature of a reduction zone of the reaction channel and gas flow velocity along its length. It has been identified that the volume of the raw material input to be used for gasification process changes in direct proportion depending on the amount of burnt-out carbon and blow velocity. The gasification is intensified in terms of equal concentration of oxygen and carbon in the reaction channel of an underground gas generator. The gasification rate is stipulated by the intensity of chemical reactions, which depend immediately on the modes of blow mixture supply. Moreover, they depend directly on the intensity of oxygen supply to the coal mass and removal of the gasification products.

OPTIMIZATION OF ENERGY EFFICIENCY OF A HEAT RECUPERATOR ON THE BASIS OF UNDERGROUND COAL GASIFICATION

Mining of the off-balanced and balanced reserves of mines, being under closure or completing their operation, required the implementation of mobile, complex, and environmentally friendly development technologies based on the processes of well underground coal gasification (WUCG) that unites mining of coal and its energy-chemical use. Environmental friendliness of the WUCG process is possible due to its controllability, hermeticity of the underground gas generator, and complex use of cogeneration technologies in the closed cycle of purification and processing of gasification products. The set engineering tasks were performed using analytical studies, bench studies and field studies. Efficiency of thermal energy generation were studies using rocks enclosing the underground gasifier and generator gases. These sources being the basic heat generating segments of energy chemical complex for coal gasification being formed at the territories of operating coal mines or mines at the stage of their closure. Prospects of coal gasification and thermal energy generation using rock disposals of coal mines have been estimated.

THE COMPUTER SIMULATION OF THE COMBUSTION OF THE GASIFICATION PRODUCTS IN FLUIDIZED BED OF SOLID FUEL IN UPPER BED LAYER WITH VORTEX BURNING

The swirl afterburning is a promising method of improving the combustion of solid fuels. The aim of the work is to verify the ANSYS CFX software package for calculating the vortex chamber of cyclone-ball furnaces afterburning. As a result of the study it was determined that to simulate the combustion of gasification products of solid fuel in a fluidized bed in a upper bed space with vortex afterburning, it is advisable to use a two-stage mechanism of methane oxidation, supplemented by hydrogen oxidation reaction. The parameters of the Eddy Dissipation model are determined, which allow obtaining results on temperature fields and fields of concentrations of the main components with satisfactory accuracy, both qualitatively and quantitatively.