Editing Gasification (section)

===Counter-current fixed bed ("up draft") gasifier===
A fixed bed of carbonaceous fuel (e.g. coal or biomass) through which the "gasification agent" (steam, oxygen and/or air) flows in counter-current configuration.<ref>Thanapal SS, Annamalai K, Sweeten J, Gordillo G, (2011), “Fixed bed gasification of dairy biomass with enriched air mixture”. Appl Energy, doi:10.1016/j.apenergy.2011.11.072</ref> The ash is either removed in the dry condition or as a [[slag]]. The slagging gasifiers have a lower ratio of steam to carbon,<ref>{{Cite conference|title=Development Status of BGL-Gasification|url=http://www.iec.tu-freiberg.de/conference/conference_05/pdf/21_Picard.pdf|last1=Kamka|first1=Frank|last2=Jochmann|first2=Andreas|date=June 2005|conference=International Freiberg Conference on IGCC & {{ill|XTL fuel|lt=XtL|de|XtL-Kraftstoff}} Technologies|others=speaker Lutz Picard|access-date=2011-03-19|url-status=dead|archive-url=https://web.archive.org/web/20110719095948/http://www.iec.tu-freiberg.de/conference/conference_05/pdf/21_Picard.pdf|archive-date=2011-07-19}}</ref> achieving temperatures higher than the ash fusion temperature. The nature of the gasifier means that the fuel must have high mechanical strength and must ideally be non-caking so that it will form a permeable bed, although recent developments have reduced these restrictions to some extent.{{Citation needed|date=June 2014}} The throughput for this type of gasifier is relatively low. [[Thermal efficiency]] is high as the temperatures in the gas exit are relatively low. However, this means that tar and methane production is significant at typical operation temperatures, so product gas must be extensively cleaned before use. The tar can be recycled to the reactor.

In the gasification of fine, undensified biomass such as [[rice husks|rice hulls]], it is necessary to blow air into the reactor by means of a fan. This creates very high gasification temperature, as high as 1000 C. Above the gasification zone, a bed of fine and hot char is formed, and as the gas is blow forced through this bed, most complex hydrocarbons are broken down into simple components of hydrogen and carbon monoxide.<ref>{{cite journal |last1=Khan |first1=Muhammad Mueed |last2=Amjad |first2=Abdul Basit |title=Hydrogen production from municipal waste and low grade lignite blend |journal=Results in Engineering |volume=24 |pages=103495 |year=2024 |doi=10.1016/j.rineng.2024.103495 |doi-access=free }}</ref>