According to data of the Central Statistical Office, the amount of sludge produced in municipal wastewater treatment plants in 2010 amounted to 526000 Mg d.m. The forecast of municipal sewage sludge amount in 2015 according to KPGO2014 will reach 642400 Mg d.m. and is expected to increase in subsequent years. Significant amounts of sludge will create problems due to its utilization. In order to solve this problem the use of thermal methods for sludge utilization is expected. According to the National Waste Management Plan nearly 30% of sewage sludge mass should be thermally utilized by 2022. The article presents the results of co-combustion of coal and municipal sewage sludge in a bubbling fluidized bed boiler made by SEFAKO and located in the Municipal Heating Company in Morag. Four tests of hard coal and sewage sludge co-combustion have been conducted. Boiler performance, emissions and ash quality were investigated.

The paper presents proposal of a model of the fluidized bed boiler adapted for use in model-based controllers e.g. predictive, adaptive or internal model control (IMC). The model has been derived in the form of transfer function matrix which allows its direct implementation in the controller structure. Formulated model takes into consideration the principal cross-coupling between process variables which enables the opportunity to search for feasibility of decoupling control. The results of the identification of the dynamics of the 2 MW industrial bubbling fluidized bed boiler using the proposed model form was presented. According to the experimental data it was found that despite of introduced simplifications presented model allows the boiler behavior prediction.

The paper presents the method of on-line diagnostics of the bed temperature controller for the fluidized bed boiler. Proposed solution is based on the methods of statistical process control. Detected decrease of the bed temperature control quality is used to activate the controller self-tuning procedure. The algorithm that provides optimal tuning of the bed temperature controller is also proposed. The results of experimental verification of the presented method is attached. Experimental studies were carried out using the 2 MW bubbling fluidized bed boiler.

The currently applicable legal provisions and also the economic concepts emphasize the importance of circular economy. In this aspect, it is very important to reduce the waste production respectively planning and running a business. Technical research is the key to finding a new applications for waste, in particular disposed on landfilling. Mining and energy industries belong to the biggest producers of waste in Poland. The total share of these two branches in waste production is up to 70% (mining and quarrying 53%; electricity, gas, steam and air conditioning supplay 17%). In environment, economy and social aspect, it is very important to develop this waste. The paper presents research on the physico-mechanical properties of the aggregates based on colliery shale supplemented by fly ash (20% - 40% supplement of fly ash). The following tests should be mentioned among performed: particle size distribution, the sand equivalent test, freeze resistance and direct shear tests. Also the chemical properties found in the literature was invoked. The research shows good physico-mechanical properties of the mixes, such as cohesion (44.62 kPa - 68.57 kPa) or internal firiction angle (34.74° - 40.52°). Though low resistance to weathering and a large susceptibility to frost heave (the mass loss after the freezing cycles is 76%) may limit its applicatin in road engineering. The sand equivalent tests were made only for aggregates. Tested materials shows usefulness for earthen structures. However, the research should be supplemented by chemical tests and also observations of the material properties changes as the effect of time. The research on the leachability of chemical pollutants, which will determine the acceptable share of ash in the mix, could be especially significant. The fact that fly ash contains a lot of sulphates and chlorides, which leach into the environment may pose a threat to living organisms.