The new legislative provisions, regulating the solid fuel trade in Poland, and the resolutions of

provincial assemblies assume, inter alia, a ban on the household use of lignite fuels and solid fuels

produced with its use; this also applies to coal sludge, coal flotation concentrates, and mixtures

produced with their use. These changes will force the producers of these materials to find new

ways and methods of their development, including their modification (mixing with other products

or waste) in order to increase their attractiveness for the commercial power industry. The presented

paper focuses on the analysis of coal sludge, classified as waste (codes 01 04 12 and 01 04 81)

or as a by-product in the production of coals of different types. A preliminary analysis aimed at

presenting changes in quality parameters and based on the mixtures of hard coal sludge (PG SILESIA)

with coal dusts from lignite (pulverized lignite) (LEAG) has been carried out. The analysis

of quality parameters of the discussed mixtures included the determination of the calorific value,

ash content, volatile matter content, moisture content, heavy metal content (Cd, Tl, Hg, Sb, As, Pb,

Cr, Co, Cu, Mn, Ni, and W), and sulfur content. The preliminary analysis has shown that mixing

coal sludge with coal dust from lignite and their granulation allows a product with the desired quality

and physical parameters to be obtained, which is attractive to the commercial power industry.

Compared to coal sludge, granulates made of coal sludge and coal dust from lignite with or without

ground dolomite have a higher sulfur content (in the range of 1–1.4%). However, this is still an

acceptable content for solid fuels in the commercial power industry. Compared to the basic coal

sludge sample, the observed increase in the content of individual toxic components in the mixture

samples is small and it therefore can be concluded that the addition of coal dust from lignite or carbonates

has no significant effect on the total content of the individual elements. The calorific value

is a key parameter determining the usefulness in the power industry. The size of this parameter for

coal sludge in an as received basis is in the range of 9.4–10.6 MJ/kg. In the case of the examined

mixtures of coal sludge with coal dust from lignite, the calorific value significantly increases to

the range of 14.0–14.5 MJ/kg (as received). The obtained values increase the usefulness in the

commercial power industry while, at the same time, the requirements for the combustion of solid

fuels are met to a greater extent. A slight decrease in the calorific value is observed in the case of

granulation with the addition of CaO or carbonates. Taking the analyzed parameters into account,

it can be concluded that the prepared mixtures can be used in the combustion in units with flue gas

desulfurization plants and a nominal thermal power not less than 1 MW. At this stage of work no

cost analysis was carried out.

Significant quantities of coal sludge are created during the coal enrichment processes in the mechanical processing plants of hard coal mines (waste group 01). These are the smallest grain classes with a grain size below 1 mm, in which the classes below 0.035 mm constitute up to 60% of their composition and the heat of combustion is at the level of 10 MJ/kg. The high moisture of coal sludge is characteristic, which after dewatering on filter presses reaches the value of 16–28% (Wtot r) (archival paper PG SILESIA). The fine-grained nature and high moisture of the material cause great difficulties at the stage of transport, loading and unloading of the material. The paper presents the results of pelletizing (granulating) grinding of coal sludge by itself and the piling of coal sludge with additional material, which is to improve the sludge energy properties. The piling process itself is primarily intended to improve transport possibilities. Initial tests have been undertaken to show changes in parameters by preparing coal sludge mixtures (PG SILESIA) with lignite coal dusts (LEAG). The process of piling sludge and their mixtures on an AGH laboratory vibratory grinder construction was carried out. As a result of the tests, it can be concluded that all mixtures are susceptible to granulation. This process undoubtedly broadens the transport possibilities of the material. The grain composition of the obtained material after granulation is satisfactory. Up to 2 to 20 mm granules make up 90–95% of the product weight. The strength of the fresh pellets is satisfactory and comparable for all mixtures. Fresh lumps subjected to a test for discharges from a height of 700 mm can withstand from 7 to 14 discharges. The strength of the pellets after longer seasoning, from the height of 500 mm, shows different values for the analyzed samples. The values obtained for hard coal sludge and their blends with brown coal dust are at the level from 4 to 5 discharges. The strength obtained is sufficient to determine the possibility of their transport. At this stage of the work it can be stated that the addition of coal dust from lignite does not cause the deterioration of the material’s strength with respect to clean coal sludge. Therefore, there is no negative impact on the transportability of the granulated material. As a result of mixing with coal dusts, it is possible to increase their energy value (Klojzy-Karczmarczyk at al. 2018). The cost analysis of the analyzed project was not carried out.

Hard coal sludge is classified as group 01 waste or it is a by-product in the production of a hard coal with variable energy importance. Pulverized lignite is not waste but a final product of drying and the very fine pulverization of lignite with a high calorific value. The study comprised the basic material before granulation such as coal sludge (PG SILESIA) and pulverized lignite (LEAG) as well as their prepared blends after the granulation on a pipe vibration granulator designed at AGH. The pulverized lignite of the LEAG company shows a low sulfur contents. In the analyzed samples its average content (Stot d) is 0.61%. An average value of this parameter in the analyzed coal sludge samples is 0.55%. The addition of pulverized lignite does not have a significant impact on the total content of sulfur and of analyzed toxic elements (Hg, As, Cd, Cr, Co, Cu, Mn, Ni, Pb, Sb, Tl, and W) in the samples. The calorific value of coal sludge falls within the range of 11.0−12.4 MJ/kg (on a dry basis). For the coal sludge and pulverized lignite blends the calorific value clearly increases to values of 14.8−17.7 MJ/kg (on dry basis). The calorific value slightly decreases in the