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The article discusses the influence of briquetting/compaction parameters. This includes the effects of pressure and temperature on material density and the thermal conductivity of biomass compacted into briquette samples. Plant biomass mainly consists of lignin and cellulose which breaks down into simple polymers at the elevated temperature of 200 °C. Hence, the compaction pressure, compaction temperature, density, and thermal conductivity of the tested material play crucial roles in the briquetting and the torrefaction process to transform it into charcoal with a high carbon content. The tests were realized for samples of raw biomass compacted under pressure in the range from 100 to 1000 bar and at two temperatures of 20 and 200 °C. The pressure of 200 bar was concluded as the most economically viable in briquetting technology in the tests conducted. The conducted research shows a relatively good log relationship between the density of the compacted briquette and the compaction pressure. Additionally, higher compaction pressure resulted in higher destructive force of the compacted material, which may affect the lower abrasion of the material. Regarding heat transfer throughout the sample, the average thermal conductivity for the compacted biomass was determined at a value of 0.048 ± 0.001 W/(K∙m). Finally, the described methodology for thermal conductivity determination has been found to be a reliable tool, therefore it can be proposed for other applications. [ABSTRACT FROM AUTHOR]

As known, dried sewage sludge, is a by-product produced from waste water treatment, contains significant amounts of organic content, and makes up to 60% with overall calorific value from 9 to 12 MJ/kg. Hence, it can be considered as material for thermal processing focusing on heat and power production. Among thermal conversion technologies, gasification is seen as the effective one because it can be easily combined with heat and power cogeneration units. On the other hand, due to high mineral content (40–50%) in the sludge, it is difficult to be gasified and obtain syngas with calorific value satisfactory enough for fueling the internal combustion engine. The dried sludge can be subjected to be gasified at temperature above 850 °C. However, large amounts of mineral content do not provide favorable conditions to obtain this required temperature. Thus, it is proposed to enrich the sewage sludge with biomass characterized with significantly higher calorific value. In the article, co-gasification of sewage sludge and Virginia Mallow—energetic crops was investigated. Results from experimental and numerical investigation have been presented. The dried sewage sludge enriched with Virginia Mallow at a mass ratio of 0/100%, 50/50% and 100/0% in tests and in the range from 0 to 100% for theoretical analysis was applied in order to achieve effective gasification process. As observed, lignocellulosic biomass like Virginia Mallow contains low amounts of mineral content below 2%, which makes it appropriate for thermal processing. It contributes to more stable and efficient gasification process. Additionally, Virginia Mallow caused that the process temperature possible to achieve, was 950 °C. Thus, sewage sludge was mixed with this high-energy component in order to improve the gasification parameters and obtain syngas with higher calorific value. A zero-dimensional, two-zone model was developed with aid of the POLIMI kinetics mechanism developed by CRECK Modeling Group to simulate gasification of low calorific substances enriched with high calorific biomass. Obtained results showed that sewage sludge can be completely gasified at presence of Virginia Mallow. Syngas calorific value of approximately 5 MJ/Nm3 was produced from this gasification process. The maximal percentage of Virginia Mallow in the mixture with the sewage sludge was set at 50% due to economic aspects of the technology. It was found, that satisfactory conditions for effective gasification were achieved at this 50/50% percentage of sewage sludge and Virginia Mallow. Potential intensity of gasification was predicted from this 0-D 2-zones model, which calculates area of reduction zone to area of combustion zone. This reduction-to-combustion area ratio for the sewage sludge-Virginia Mallow mixture was estimated at value of 2. Finally, the model was successfully verified with results from tests, hence it was proposed as a tool for preliminary investigation on poor fuels gasification. [ABSTRACT FROM AUTHOR]