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The main objective of the research was to develop a method of biomass grindability determination (Biomass Grindability Index), which would allow for a clear classification of different types of solid biofuels in terms of their milling properties. The objective of the research included also the assessment of the possibility of adaptation of the existing coal grindability determination methods for evaluation of biomass milling. In the course of research, the biomass grindability determination method was modified to obtain the highest possible reliability of the developed index. The scope of laboratory tests being focused on influence of circumferential speed of test mill beaters, particle size distribution of sample, test time, mass and volume of sample. The results of laboratory and industrial tests have shown that the grindability index based on mean particle sizes of feed and product is unreliable. Grindability of different types of biomass, comminuted in beater mills, can be clearly determined by the index expressed as the ratio of energy consumption during the test to the amount of specified product size fraction. During the study laboratory test results obtained for proposed grindability index were compared to other grindability indices determined for utilized in research types of biomass.

Up to now, a few studies on the efficiency of heavy metal(-oid)s capture by a sorbent directly mixed with fuel, have been performed. For this reason, the main objective of the study is to determine whether or not such a solution is effective when RDF is incinerated. The paper presents a two-step analysis of the impact of three sorbents (ammonium sulphate, kaolinite and halloysite) in three dosages (2, 4 and 8 wt%) on heavy metal(-oid)s retention in the bottom ash. 12 heavy metal(-oid)s were taken into consideration - As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, V and Zn. Samples were incinerated in a lab-scale tubular reactor at two temperatures - 900 °C and 1100 °C. The first step of investigation constitutes ICP analysis of heavy metal(-oid)s content in the bottom ash, coupled with SEM/EDS analysis. Afterwards, the second step was to determine the stability of formed additive-heavy metal(-oid)s complexes via leachability tests in neutral and acid environments. The performed research has shown that ammonium sulphate is effective in Cr, Cu and Hg capture, halloysite – in Cd, Co, V and Mn capture, whereas kaolinite – in Pb capture.

A method for choosing the optimum fineness of coal in pulverised-fuel boilers is presented. This method is based on economic criteria and takes into account variations of the power unit load as well as the durability and the output of pulverisers. Calculations are performed for short periods of time (e.g. 1 h), provided that it is possible to change the fineness of the coal by controlling the angle of the classifier guide vanes. Therefore, the optimum value, adapted to the current parameters, may be easily set. A program was created in MS Excel to perform the optimization calculations. It enables making decisions concerning the modernisation of grinding systems and their proper operation when changing the fuel characteristics as well as the load and costs of power unit operation. The work is based on tests of pulverisers of a 650 t/h pulverized fuel boiler (OP 650) in a Polish power plant. On the basis of these studies, relationships were derived between the fineness of the produced pulverized fuel and operating parameters, the efficiency of the boiler and parameters of the milling system, e.g., energy consumption of the mill and its fan. The influence of variation of excess air in the boiler on the maximum grain size that can burn at an acceptable unburned combustibles level is also shown. The analysis of the impact of the composition of the mineral part of the Polish hard coal to the abrasion of mills was made. Based on the measurements carried out and the actual periods between overhauls of mills, which were determined during the operation, a correlation was found to determine the abrasive wear rate of the elements of ring-ball mills with nominal output of 33 t/h (type MKM 33). Exemplary calculations of optimum value of R0.09 were also performed.

The motivation of this paper is new NOx emission regulations according to IED Directive 2010/75/EU of EU which introduce the BAT’s conclusions as binding. The paper presents the methodology and results of research on the effectiveness of SCR catalysts during combustion of pulverised coal in a model furnace installed at the Institute of Power Engineering and Turbomachinery of the Silesian University of Technology (IPET). The aim of the research was to search for catalysts that could be placed in a regenerative rotary air heater - RAH-SCR. Two catalysts were tested: a commercial plate-type based on V2O5 and a prototype ceramic based on platinum. Presented results of investigation demonstrate a potentially high efficiency of RAH-SCR installations which can meet new environmental regulations of NOx emission. The highest NOx reduction efficiency (92.87%) was obtained for an industrial catalyst at 329°C, from about 436.3 to 31.1 mg/m3 as NO2 @ 6%O2 to 31,1. At lower temperature, 260°C maximum efficiency of NOx reduction does not exceed 60%, from 440,0 to 169,6 mg/m3. The placement of the catalyst in the RAH can also be a support for SNCR installations due to the increase in DeNOx efficiency and reduction of NH3 slip.

The paper presents slagging and fouling properties of ashes when hard coal was fired in a pulverized coal-fired boiler (230 t/h capacity) and the change of fouling indices of resulting fly ash when halloysite fireside additive was used. During reported full-scale study the pulverized coal-fired boiler was fired with hard coal with the addition of pulverized halloysite injected directly into furnace through the designed spray-nozzles in the upper part of boiler furnace. Chemical analysis of fuel properties and collected from the ESP (electrostatic precipitator) fly ash samples was carried out to obtain the following information: • determine chemical properties of coal and its ash produced during combustion in order to determine its propensity for slagging versus reference study conducted without the use of additive • identify the slagging and fouling indicators when halloysite additive was used. The tests results are intended to determine the effectiveness of the pulverized halloysite injection to the furnace in terms of reducing slagging and fouling of heating surfaces, in particular the evaporator and convective section of the boiler. The required halloysite feeding is determined by comparing the change in chemical composition (ash modification effectiveness) between fly ashes produced in the reference and test case so as it is corrected according to the fuel slagging properties (fuel slagging index).

The paper presents results of investigations on using halloysite as an additive in biomass-fired boilers. It has been shown that in the case of a few different agricultural biomasses the halloysite addition increased the ash sintering temperature to the values noted for coals. This is an effect of bonding sodium and potassium in the form of chlorides and other compounds. In practical terms the halloysite additive may reduce slagging and fouling of boiler heating surfaces as well as deteriorate the agglomeration processes in fluidized beds. Moreover, addition of halloysite reduces the amount of KCl and NaCl present in ash (and therefore in ash deposits) thus decreasing the rate of high temperature corrosion.