Review of Current Technologies for Particulate Mitigation in Biomass and Mixed Waste Gasification

The growing global energy demand and environmental concerns have accelerated the transition toward sustainable waste-to-energy technologies such as gasification. The gasification of biomass, municipal solid waste (MSW), and refuse-derived fuels (RDF) provides a versatile pathway for syngas production. However, the presence of impurities, most notably particulate matter (PM), presents substantial operational and environmental hurdles that constrain its direct utilization in high-value energy and chemical synthesis. PM in the generated syngas originates from a complex mixture of unconverted carbonaceous residues, mineral ash, and condensed inorganic vapors, exhibits significant heterogeneity, dictated primarily by the initial feedstock composition and the specific thermodynamic profile of the reactor design. This review provides a comprehensive analysis of PM removal technologies for producer gas purification, categorized by operating temperature into cold, warm, and hot gas cleaning systems. Wet scrubbing systems including spray scrubbers, venturi scrubbers, cyclones, and wet electrostatic precipitators effectively remove coarse PM (>5 μm, up to 99% efficiency) but suffer from energy losses and wastewater generation. Mid- to high-temperature systems such as fabric filters, sand filters, and granular bed filters achieve >99% efficiency for PM >0.5 μm but face clogging and pressure drop limitations. Hot gas cleaning technologies, including ceramic candle filters and multilayer granular beds, maintain syngas enthalpy and achieve >99.9% efficiency for submicron PM. Hybrid electrostatic systems integrating agglomerators, electrostatic precipitators (ESPs), bag filters, and sorbent injection further enhance the removal of ultrafine PM (<1 μm) and acid gas (HCl, SO2). This review identifies existing limitations and highlights emerging research directions for optimizing PM removal efficiency and improving overall gasification system sustainability.