Catalytic cracking of tar in biomass pyrolysis gas in the presence of calcined dolomite

Pyrolysis-A tool in the wastewater solids handling portfolio, not a silver bullet: Benefits, drawbacks, and future directions

Pyrolysis is the process whereby carbonaceous materials, such as biosolids, are heated between 400°C and 900°C in the absence of oxygen. Three main products are generated: a solid product called biochar, a py-liquid that consists of aqueous phase and non-aqueous phase liquid, and py-gas. The biochar holds value as a beneficial soil amendment and sequesters carbon. The py-liquid is potentially hazardous and needs to be dealt with (including potentially reducing it on-site via catalysis or thermal oxidation). Py-gas can be used on-site for energy recovery. Pyrolysis has gained recent interest due to concern over per- and polyfluoroalkyl substances (PFAS) in biosolids. Although pyrolysis can remove PFAS from biosolids, it has been shown to produce PFAS that reside in py-liquid, and the fate in py-gas remains a knowledge gap. More research is needed to help close the PFAS and fluorine mass balance through pyrolysis influent and effluent products because pyrolysis alone does not destroy all PFAS. The moisture content of biosolids substantially affects the energy balance for pyrolysis. Utilities that already produce a dried biosolids product are in a better position to install pyrolysis. Pyrolysis has both defined benefits (solids reduction, PFAS removal from biosolids, and biochar production) as well as remaining questions (the fate of PFAS in py-gas and py-liquid, mass balance on nutrients, and py-liquid handling options) that will be answered through more pilot and full-scale demonstrations. Regulations and local policies (such as carbon sequestration credits) could affect pyrolysis implementation. Pyrolysis should be considered as an option in the biosolids stabilization toolbox with application being based on individual circumstances of a utility (e.g., energy, moisture content of biosolids, PFAS). PRACTITIONER POINTS: Pyrolysis has known benefits but limited full-scale operational data. Pyrolysis removes PFAS from biochar, but PFAS fate in gas phase is unknown. Moisture content of influent feed solids affects energy balance of pyrolysis. Policy on PFAS, carbon sequestration, or renewable energy could impact pyrolysis.

Debrominated high quality oil production by the two-step catalytic pyrolysis of phenolic printed circuit boards (PPCB) using natural clays and HY

The two-step catalytic pyrolysis (CP) of a phenolic-printed circuit board (PPCB) over in-situ natural clays (dolomite, bentonite, and olivine) and ex-situ HY(30, SiO₂/Al₂O₃: 30) was investigated by tandem micro reactor-gas chromatography/mass spectrometry. The non-catalytic pyrolysis (NCP) of PPCB produced oxygenated, phosphorous, and brominated compounds due to the presence of paper, tetrabromo bisphenol A (TBBA), phosphorous flame retardants, and phenol resin in the PPCB. Among the natural clays, dolomite showed the highest debromination and aromatics formation efficiency during the in-situ CP of PPCB followed by bentonite and olivine owing to the different catalyst properties. Two-step CP of PPCB over in-situ natural clays and ex-situ HY(30) achieved higher efficiency on the formation of higher quality oil (mono-phenol and aromatic hydrocarbons) with a lower Br content than the one-step CP of PPCB. Among the two-step catalysts, the combination of in-situ dolomite and ex-situ HY(30) provided the highest quality oil production due to the high acidity and sufficiently large pore size of dolomite. Two-step CP of PPCB over in-situ dolomite and ex-situ HY(30) also revealed a longer lifetime than the one-step CP of PPCB over ex-situ HY(30), not only for the formation of aromatic hydrocarbons and mono-phenols, but also for debromination.

Application of biomass pyrolytic polygeneration by a moving bed: Characteristics of products and energy efficiency analysis

In order to overcome the shortcoming of batch production in the retort and improve the quality of three-state products, a moving bed as pyrolysis furnace and torrefaction pretreatment were both used in a demonstration of biomass pyrolytic polygeneration. The bench and demonstration scale experiments were both investigated in this work. The results show that when the pyrolysis temperature between 550 °C and 750 °C, it can not only maintain the relative stability of the tri-state products yield, but also guarantee the quality. When the demonstration ran at this temperature, it can continuously deal with biomass for about 7E+03 kg/h, and reach 5.42E+07 kg/yr, which can be converted into 1.12E+07 Nm³ of bio-gas, 3.78E+06 kg of tar, 7.63E+06 kg of vinegar and 1.14E+07 kg of biochar. The lower heating value of bio-gas and biochar were respectively 12.5 MJ/m³ and 30.5 MJ/kg, which showed the great potential as gas and solid fuel.