Abstract
Ensuring the reliable operation of the dust fuel preparation system at thermal power plants (TPP) is a topical issue since it determines the energy strategy of any country that fires coals for thermal energy production. This unit is one of the most energy-intensive units in TPP. Those systems are outdated, poorly automated and high energy-intensive. Furthermore, they must ensure efficient and safe operation of the facility while being environmentally friendly. The current work focuses on the process of grinding coals in ball drum mills for further pulverized combustion. An experimental study was performed in order to determine the main factors (rotational speed of the drum mill, the degree of loading with the grinding balls, and the velocity of the supplied air) that affect the efficiency of the fuel preparation system. The obtained experimental data and performed mathematical modeling resulted in regression equations describing the energy performance of the mill. Three regression equations for mill productivity, power consumed, and specific surface area of the final product were obtained and validated. The study reveals that the lowest specific energy consumption is achieved when the relative rotational speed of the mill is between 0.81 and 0.87; the weighted average diameter of the balls ranges from 33.5 up to 34.5 mm; the load factor of the grinding media ranges from 0.325 up to 0.335, the supplied air velocity is between 0.2 and 0.3 m/s. The proposed methodology allows adjustment of the operating parameters of the grinding process to achieve the lowest energy consumption. The power consumption for the preparation can be reduced up to 5 % for the selected operation mode of the grinding facility.
Highlights
Worldwide, thermal power plants (TPP) are facilities that are used for the simultaneous production of thermal and electric energy
The main distinguishing features of the solid fuel preparation system at the TPP-2 include: – defrosting of fuel is carried out only in exceptional cases via hot air produced in a steam boiler at very low air temperatures; – in other cases, the coals are dried with hot air from the air heater of the steam boilers right before the fuel is supplied to the BDM, and the balance of the supplied primary and secondary air is disturbed; – currently, preliminary stages of coal crushing are not provided, as a result, coal with large lumps is fed into the mill
– high specific metal and energy intensity; – low coefficient of performance (COP), less than 15 %; – low energy intensity of the grinding process, due to the low speed of the action of grinding bodies on the crushed material – about 50 % of grinding bodies do not participate in the grinding process; the working volume of the mill is used by 35 %; – high specific consumption of grinding media and mill lining material
Summary
TPPs are facilities that are used for the simultaneous production of thermal and electric energy. Different types of primary energy carriers such as natural gas, coals, biomass are used to run facilities. Some of them are directly used but the others must be initially processed before combustion. The fuel preparation process is energy-intensive, which results in an increased final energy price. To reduce final costs for energy production, mechanisms are being sought to improve the energy efficiency of each unit of the plant. Eastern-European Journal of Enterprise Technologies ISSN 1729-3774
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