Steam gasification of rapeseed, wood, sewage sludge and miscanthus biochars for the production of a hydrogen-rich syngas

Steam gasification of biochars has emerged as a promising method for generating syngas that is rich in hydrogen. In this study four biochars formed via intermediate pyrolysis (wood pellet, sewage sludge, rapeseed and miscanthus) were gasified in a quartz tubular reactor using steam. The dynamic behaviour of the process and effects of temperature, steam flow and particle size were studied. The results show that increases in both steam flow and temperature significantly increase the dry gas yield and carbon conversion, but hydrogen volume fraction decreases at higher temperatures whilst particle size has little effect on gaseous composition. The highest volume fraction of hydrogen, 58.7%, was obtained at 750 °C from the rapeseed biochar

A comparative study on the pyrolysis of metal- and ash-enriched wood and the combustion properties of the gained char

This study aims to investigate the pyrolysis behaviour of metal-contaminated wood and the combustion properties of char derived from wood pyrolysis. Seven metals (Na, Mg, Ca, Zn, Cd, Pb and Fe(III)) were introduced to willow in cation form by ion-exchange and the thermal behaviour of demineralised samples and samples with additional ash were also investigated. The results show that the char yield increased from 21% to 24-28% and levoglucosan yield in vapour phase decreased from 88% to 62-29% after the addition of inorganic compounds, even though the metal binding capacity of wood varied from one metal ion to another. While char yield seems to be effected mainly by the concentration of the metal ions, levoglucosan yield was more dependent on the ionic species especially when sodium ions were present. When combustion experiments were carried out with char made of the metal enriched wood, two consecutive steps were observed, both effected by the presence of inorganic compounds. The first step was identified as the release and combustion of volatiles, while the second peak of the burning profile is the actual combustion of the fixed carbon. The burnout temperatures, estimated ignition indices and the conversion indicate that the type and not the amount of metal ions were the determining factors during the second step of combustion

Thermocatalytic-Reforming (TCR®) and TCR®-biochar properties

The thermo-catalytic reforming (TCR®) is an endothermic two stage process developed by Fraunhofer UMSICHT, able to process biomass and biomass residues with high ash and moisture contents as well as with low ash melting points. The process is a combination of an intermediate pyrolysis reactor and a reforming stage. The pyrolysis stage is typically running at temperatures between 400 and 500 °C and the reforming stage between 600 and 700 °C. In the first stage pyrolysis vapors and biochar are produced. In the second stage the vapors has to pass a continuous removed biochar bed in the reformer where they (the permanent gas as well as the oil) are upgraded. The temperatures can be varied to modify the products yield, quality and properties in specific ranges. The products are a synthesis gas, biochar and an oil-water fraction which can be separated easily. The products have high quality. Please click on the file below for full content of the abstract

EN-fuels from solid waste biomass by thermo-catalytic reforming

Intermediate pyrolysis describes a process of converting feedstock by heating it up in the absence of oxygen under moderate, “intermediate” conditions. Typical conditions are a residence time for solids between 5 to 30 minutes, low heating rates and temperatures between 350 °C - 450 °C. Due to these conditions intermediate pyrolysis has remarkable advantages regarding the feedstock, compared to other processes based on flash pyrolysis. Large particles, like pellets or chips can be used. Dry matter content can be below 50% from a technical point of view. For economic reasons the dry matter should be more than 70 % to avoid using energy mainly for drying. However, this dry matter is still very low compared to the requirements of most flash pyrolysis reactors. Another advantage is the use of variable and heterogeneous feedstock, preferably residue and waste biomass. The feedstock can vary from agricultural residues, biogas digestate, municipal and industrial biowaste to sewage sludge. The latest development of the intermediate pyrolysis technology is Fraunhofer UMSICHT´s Thermo-Catalytic Reforming process (TCR®). It is a novel process for the production of char, gas, and bio-oils with improved properties. One significant innovation of TCR® is the integrated downstream catalytic reforming step. This multi-patented technology enables the high quality of the final products carbonisate, syngas, and oil. The robustness of the process permits the utilization of various biogenic feedstocks. The yield of the products depends on the chemical properties of the feedstocks, whereas the quality and characteristics of the products are due the robustness of the process, largely independent of the feedstocks. With the focus on the TCR® oil there is one unique selling point: The oil is thermally stable and therefore distillable. This is the basis for other thermal upgrading processes like e.g. hydro-treatment. Furthermore, the thermal stability of the TCR® oil is a basic prerequisite for usage in the fossil petrol processing industry. This includes, among other applications, combined heat and power (CHP) plants. Additional unique properties are the low water content, the low total acid number, and the high heating value. The high quality of the crude TCR®-oil can be further improved to EN fuel quality by distillation and hydrodeoxygenation (HDO). For hydrodeoxygenation sulfonated NiMo catalyst at temperatures of around 370 °C and a pressures in the range of 140 bar and with LHSV of 0.3 per hour were applied. The resulting products showed full properties of standard hydrocarbon fuels. A separation into diesel and petrol fraction by rectification demonstrated, that both fractions met the fossil fuel standards (EN 228 and EN 590). Through hydrotreating the hydrogen content was increased and the oxygen, sulphur and nitrogen content was significant lowered or respectively removed in an efficient way with a yield over 85 %. Please click Additional Files below to see the full abstract

Thermal stability of sewage sludge pyrolysis oil

The stability of the oil phase obtained from intermediate pyrolysis process was used for this investigation. The analysis was based on standard methods of determining kinematic viscosity, gas - chromatography / mass - spectrometry for compositional changes, FT-IR for functional group, Karl Fischer titration for water content and bomb calorimeter for higher heaating values. The methods were used to determine changes that occurred during ageing. The temperatures used for thermal testing were 60 °C and 80 °C for the periods of 72 and 168 h. Methanol and biodiesel were used as solvents for the analysis. The bio-oil samples contained 10 % methanol, 10 % Biodiesel, 20 % Biodiesel and unstabilised pyrolysis oil. The tests carried out at 80 °C showed drastic changes compared to those at 60 °C. The bio-oil samples containing 20 % biodiesel proved to be more stable than those with 10 % methanol. The unstabilised pyrolysis oil showed the greatest changes in viscosity, composition change and highest increase in water content. The measurement of kinematic viscosity and gas chromatograph mass spectrometry were found to be more reliable for predicting the ageing process