The topic raised in this paper concerns an important aspect regarding the possibilities of the combustion and co-combustion of biomass substrates (energetic willow/sewage sludge), in light of the renewable energy source (RES) regulations, with fuel from waste defined here as RDF. Particular interest in these fuels and their mixtures results from a search by the thermal power engineering sector for fuels whose combustion will be associated with benefits, e.g., the acquisition of energy origin licenses, availability and lower cost of obtaining fuel (RDF), as well as moderate investment contributions using the existing base of coal grate boilers. This article indicates the possible variants of the combustion and co-combustion of the abovementioned fuels, referring to the use of technical and technological capabilities of coal grate furnaces. It was possible by comparing the mechanical and thermal load of grates, as well as so-called indicators for the quantitative assessment of combustion (i.e., ignition rate and mass loss rate). The result of the combustion of the fuel as above in a laboratory-scale furnace (samples weighing up to 1 kg), as well as their thermogravimetric analysis, indicates a great similarity of the mass loss curve, temperature profiles and combustion phases, as well as indicators of a quantitative assessment in the process of biomass and RDF oxidation. The obtained results of the mechanical and thermal load capacity of the grates constitute the basis for further analyses of fuel conversion, without the risk of thermal and/or mechanical grate overload. Relying on the research of the indicators for the quantitative assessment of combustion, it was found that the combustion process of the tested fuels could be carried out while maintaining the quality of burning the fuel layer. Based on the conducted research, it can be assumed that it is possible to replace coal fuels with biomass, RDF fuel, sewage sludge using coal furnaces for their combustion, which means a hybrid nature of the furnace due to the type of fuel.

Currently, there is a lot of interest in implementing the idea of a circular economy along with searching for optimal methods of waste management in terms of raw materials and energy. Waste wood-based floor panels are part of this discussion with regard to its management. The interest in this waste results from statistics and the prediction of its future quantities on the waste market. The separation and testing of individual layers of the waste floor panel was undertaken to answer the following question: Is it reasonable to mechanically separate the contaminated upper panel layer from the remaining part (which is suitable for material recycling) and subject it to thermal transformation methods? Thermogravimetric studies did not confirm the rationale of mechanical separation of layers for further management. Therefore, the use of pyrolysis was proposed as an alternative by showing the advantages of this process in the thermal transformation of the tested waste. The analyzed kinetics of this process included: mass loss, the influence of heating rate on the decomposition process, the impact of volatile parts in the substrate on the rate of mass loss, and the share of coke residue. Empirical formulas of the tested substrates in the molecular formula C–H–O–N (carbon-hydrogen-oxygen-nitrogen) were also proposed to assess its energy usefulness by entering the analyzed waste into a Van Krevelen diagram.

The amount of generated waste, which increases every year, is a serious problem of the modern world. In particular, attention should be paid to hazardous waste and methods of its disposal. One of the most used in this context is thermal treatment in dedicated incinerators equipped with a rotary kiln. Conducting the process requires, inter alia, supplying the furnace with a batch of batch material with appropriate parameters. Improper operation in this regard may cause negative environmental effects and operational problems. The key here is to select different types of hazardous waste and compose batch portions. The paper presents an application that optimizes the work of waste incineration plant operators. At the same time, this tool can be described as ensuring security at this stage of the process. The application implements an ant colony algorithm that selects the optimal solution to the problem, which has been formulated here as the types and masses of the batch mixture components with given parameters. The application has been tested in the laboratory and real conditions with satisfactory results.

Thermal transformation of waste carried out in a rotary kiln is a complex process, usually involving hazardous waste. Due to the great diversity of these wastes and their specific properties, the process of their thermal transformation may be associated with various types of operational problems. The reasons for their occurrence include, among others, processes potentially affecting the deterioration of the condition of the rotary kiln lining. In order to minimize problems, a tool is proposed to support the work of incineration plant operators. This is an application that enables generation of input material portions in subsequent kiln feeds. It is characterized by wide functionality, including the ability to assign higher weights to selected parameters. The application is based on an algorithm that takes into account the key waste parameters from the point of view of the thermal process, which have been given specific value ranges. Two series of simulations were performed with the same assumptions except for change in the weight for one of the parameters in the second case. In the first series, the following ranges of the considered parameters were obtained: calorific value 14.96–20.66 MJ/kg, pH 5.59–8.11, content of alkaline salts 1.42–7.39, content of chlorine 1.1–3.83, content of halogens 0.08–0.97. In the second series of simulations, the favored parameter was the calorific value, which ranged from 17.08 MJ/kg to 18.69 MJ/kg. The range of values for the remaining parameters changed slightly, with all meeting the criteria. Application tests showed the generation of waste mixtures with parameters consistent with the established ranges.

Biomass includes diverse raw materials of plant or animal origin that are biodegradable. It also constitutes a significant fraction of municipal waste burned in waste incineration plants. Grate technology is one of the more commonly used technologies in the thermal conversion of biomass. The mass transport of material on the grate is a complex issue. The article presents a model for determining selected mass flow parameters on the grate, primarily the distribution of residence time, degree of mixing, and dispersion. The model is a description of mechanical mass transport on the grates of thermal waste conversion devices and represents the kinetics of the processes occurring on the grate. It allows for the design of the details of the specific movement of the material particles on the grates depending on their size and density. In addition, experimental tests of flow parameters realized on a laboratory stand simulating the operation of the grate are presented. Tests were conducted on different types of grates and with selected types of biomass materials. They included variants of the operating parameters of the grates, such as the speed and pitch of the grates an their inclination, simultaneously with the fulfillment of the 1:1 scale condition of the size of the laboratory stand to the actual size of the industrial grate (its section). A general trend can be seen in the mean residence time of the material on the grate, which is higher in the case of a reciprocating grate. The degree of dispersion is mainly influenced for moving and reciprocating grates by the inclination angle of the grate. The analysis of the test results made it possible to clarify the mechanism of material mass transport on different types of grates. It is also proposed to use the results in modeling the process of biomass combustion in grate chambers as well as their design and operation.

The motion of input material in a rotary kiln is an important aspect of its operation. This can be observed especially in the case of the implementation of the hazardous waste incineration process in this device. The values of the flow parameters, mainly the residence time and the degree of mixing, can determine the proper and safe treatment of waste. The relationships that occur in the layer of solid material in a rotary kiln have not been completely recognized. This article presents a research method that involves an experiment on a laboratory stand simulating a rotary kiln in association with a dedicated algorithm. Multi-criteria tests were carried out. The adopted research method was the tracer method. It used a tracer which, subject to the same transport conditions as other material particles, provided information on the characteristic of the motion of tested materials in the rotating cylinder. The application based on the residence time distribution (RTD) algorithm returned information about the characteristics of the motion of the material in the rotary cylinder in terms of residence time distribution and the degree of mixing. This tracer method, together with stimulus impulses on the grate and a dedicated RTD algorithm, was used here as a sensor method to examine the characteristics of material motion on various grate systems. The data obtained as a result of this research may include, among others, the boundary conditions for numerical simulations of processes carried out in a rotary kiln.