In the processes of coal mining, preparation and combustion, the rejects and by-products are generated. These are, among others, the rejects from the coal washing and dry deshaling processes as well as the coal combustion by-products (fly ash and slag). Current legal and industry regulations recommend determining the content of mercury in them. The regulations also define the acceptable content of mercury. The aim of the paper was to determine the mercury content in the rejects derived from the coal cleaning processes as well as in the combustion by-products in respect of their utilization. The mercury content in the representative samples of the rejects derived from the coal washing and dry deshaling processes as well as in the coal combustion by products derived from 8 coal-fired boilers was determined. The mercury content in the rejects from the coal washing process varied from 54 to 245 μg/kg, (the average of 98 μg/kg) and in the rejects from the dry deshaling process it varied from 76 to 310 μg/kg (the average of 148 μg/kg). The mercury content in the fly ash varied from 70 to 1420 μg/kg, (the average of 567 μg/kg) and in the slag it varied from 8 to 58 μg/kg (the average of 21 μg/kg). At the moment, in light of the regulations from the point of view of mercury content in the rejects from the coal preparation processes and in the coal combustion by-products, there are no significant barriers determining the way of their utilization. Nevertheless, in the future, regulations limiting the maximum content of mercury as well as the acceptable amount of leachable mercury may be introduced. Therefore, preparing for this situation by developing other alternative methods of using the rejects and by-products is recommended.
The engine simulations have become an integral part of engine design and development. They are based on approximations and assumptions. The precision of the results depends on the accuracy of these hypotheses. The simplified models of frozen composition, chemical equilibrium and chemical kinetics provide the compositions of combustion products for engine cycle simulations. This paper evaluates the effects of different operating conditions and hypotheses on the exergetic analysis of a spark-ignition engine. The Brazilian automotive market has the highest number of flex-fuel vehicles. Therefore, a flex-fuel engine is considered for simulations in order to demonstrate the effects of these different hypotheses. The stroke length and bore diameter have the same value of 80 mm. The in-cylinder irreversibility is calculated for each case at the closed part of the engine cycle. A comparative analysis of these hypotheses provides a comprehensive evaluation of their effects on exergetic analysis. Higher values of accumulated irreversibility are observed for the oversimplified hypothesis.
The work contains a description of a developed experimental and theoretical method of modeling of solid waste combustion in a device equipped with a moving grate and capability to optimize the work of waste incineration plant. Implementation of this issue was based on results of experimental studies made on a laboratory scale boiler. This was possible by defining and testing indicators of quantitative assessment of combustion such as: reaction front rate, ignition rate, the rate of combusted mass loss and the heat release rate. These indicators as measurable "criteria indicators" allow transfer of parameters from a laboratory-scale unit, working in the transient regime into an industrial full scale grate device working continuously in stable determined conditions. This allows for wide optimization possibilities in the operation of a waste incineration plant, in particular the combustion chamber, equipped with a moving grate system.
The article concerns fly ashes generated from the combustion of hard coal and deposited on landfills. Investigation results describing fly ash taken from a combustion waste landfill are presented in the article. The investigation results indicate a possibility for combusting the coal reclaimed by separation from the fly ash and utilizing the remaining fly ash fractions.
A forecast of the negative impact exerted on the environment by selected trace elements in “Bełchatów” Power Plant has been prepared on the basis of the results of investigations into these elements’ distribution carried out as part of earlier research on coal from “Bełchatów” Field and the data on updated analyses of the content of these elements in 55 brown coal samples from test boreholes. Work in “Bełchatów” Power Plant, which is supplied with coal from “Szczerców” Field, will be accompanied by trace elements transfer. On the basis of the conducted investigations it has been found that the biosphere is most threatened by mercury emissions. As shown by the presented results of analyses and calculations, the emissions of mercury in “Bełchatów” Power Plant are low. Mercury is accumulated chiefl y in gypsum produced in the FGD plant. The content of mercury in slag and ash is low.