Thermal Treatment Of Municipal Waste Research Articles

Analysis of the Possibility of Using Slags from the Thermal Treatment of Municipal Waste as Potential Component of Cement-Case Study.

In Europe there are nearly 500 incinerators. There are over 2000 of them in the world. It is estimated that the combustion of 1 ton (Mg) of waste produces about 250–300 kg of slag. Due to the large amounts of this waste, the construction industry’s demand for raw materials and the reduction of CO2 emissions, research was undertaken to use slags as a cement component. The problem was complex because slags generated in the thermal treatment of municipal waste have different chemical compositions and physical properties and contain variable amounts of impurities. The choice of chemical analyses of slag was dictated by the potential influence on the properties of cement mortars. The total moisture of raw slag (4–10%), the bulk density (600–1267 kg/m3) and the specific surface after grinding (over 3000 cm2/g) were determined. The pH (11.9) and the content of sulphates (3.5% by weight), chlorides (0.3% by weight) and selected heavy metals (Cd, Cu, Fe, Mn, Zn, Pb) were measured in the aqueous extract. The obtained results of the washing test were compared with the values resulting from the currently binding legal regulations. In the next step, cement mortars with 30% addition of tested slags were designed and made. The article presents the results of compressive strength tests, which were compared with the results of samples without the addition of slag. The addition of slag to the cement mortar decreased S_MSWI 1 by 64% and S_MSWI 2 by 31%. The high loss of strength and the swelling of the S_MSWI 1 test led to the activation of the NaOH slag. In the endurance test, an increase from 16 to 32 MPa was recorded. Preliminary studies show that the addition of slag in the cement mortar allows obtaining the strength at the level of 30–32 MPa.

Thermal Treatment of Municipal Waste in Poland on Example of RDF Pyrolysis

In the face of the constant tightening of environmental regulations, alternative sources of fuels and energy are being increasingly sought. The European Union strives to introduce waste-free or low-waste closed-loop technologies using material and energy recovery to manage natural resources in a rational manner. Therefore, European regulations require member states to progressively restrict the amount of landfill waste. In Poland, these requirements have been included in the Act on waste and the Act on order and cleanliness in the commune. In addition, since 1 January 2016, it has been forbidden to store waste with a calorific value exceeding 6 MJ/kg, which is why in recent years there has been an increase in interest in the thermal transformation of municipal waste. Therefore, the article presents the current shape of waste management in Poland, and also introduces the dominant form of RDF management in the cement industry. Nevertheless, the capacity of cement plants is limited, and the energy use of fuels from waste encounters difficulties related to a significant reduction in pollutant emissions, which is why the use of modern installations for the thermal conversion of waste such as pyrolysis and gasification is increasingly considered. Taking into account the promising energy properties of secondary fuels obtained during the pyrolysis process, the chemical composition of gas from RDF pyrolysis was modeled for a pilot installation operating in Poland using CHEMKIN-PRO software. Determination of the combustible components allowed the calorific value of pyrolytic gas to be estimated, ranging from 28.2 - 28.7 MJ/m3. The obtained calorific value is much higher than the average calorific value of RDF (11-18MJ/kg) [1], which encourages wider use of the waste pyrolysis process in order to obtain secondary fuels with promising energy parameters. It will contribute to a further reduction in the amount of deposited waste, and thus to creating environmentally-friendly closed-loop waste management.

Decomposition of Gaseous Terephthalic Acid in the Presence of CaO

The decomposition of PET during thermal treatment of municipal waste results in the formation of sublimating substances such as terephthalic acid (TPA) and benzoic acid, causing blockage and corrosion of pipes in the treatment facilities. To prevent these effects, TPA can be decarboxylated in the presence of calcium oxide (CaO) to obtain benzene as the main product. However, high concentrations of TPA cause the formation of large char fractions, reducing the yield of desired products. In this investigation, TPA was decarboxylated using a fixed-bed reactor filled with CaO. To increase the yield of benzene and reduce the carbonaceous residue, the effects of pyrolysis temperature and TPA feed rate were investigated. The best results were achieved at 500 °C and a TPA feed rate of 51 mg L−1, yielding 67% benzene with a purity of 99.2% and a carbonaceous residue containing 18% of the initial carbon.

Utilization of waste materials by means of thermal and materials conversion

The extraordinary increase of waste quantities during the 1980s led to the development of numerous new technologies and principles which were aimed at a maximum possible reutilization of waste materials as valuable substances or as raw materials. As far as industrial waste management is concerned, more research was implemented concerning the principle of production-integrated environmental protection. For municipal waste management, new alternative technologies to thermal treatment of municipal waste were developed. The following contains an overview of the various methods for the treatment of solid, liquid and gaseous wastes as well as a presentation of the principles used to evaluate these methods in view of entropy aspects.