Hydrothermal biomass gasification

Biomass gasification is a widely used thermochemical process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technology. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modelling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technology into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technological advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technology.

Molecules

Supercritical water gasification has emerged as a promising technology to sustainably convert waste residues into clean gaseous fuels rich in combustible gases such as hydrogen and methane. The composition and yield of gases from hydrothermal gasification depend on process conditions such as temperature, pressure, reaction time, feedstock concentration, and reactor geometry. However, catalysts also play a vital role in enhancing the gasification reactions and selectively altering the composition of gas products. Catalysts can also enhance hydrothermal reforming and cracking of biomass to achieve desired gas yields at moderate temperatures, thereby reducing the energy input of the hydrothermal gasification process. However, due to the complex hydrodynamics of supercritical water, the literature is limited regarding the synthesis, application, and performance of catalysts used in hydrothermal gasification. Hence, this review provides a detailed discussion of different heterogeneous ca...

A review was conducted on the use of thermochemical biomass gasification for producing biofuels, biopower and chemicals. The upstream processes for gasification are similar to other biomass processing methods. However, challenges remain in the gasification and downstream processing for viable commercial applications. The challenges with gasification are to understand the effects of operating conditions on gasification reactions for reliably predicting and optimizing the product compositions, and for obtaining maximal efficiencies. Product gases can be converted to biofuels and chemicals such as Fischer-Tropsch fuels, green gasoline, hydrogen, dimethyl ether, ethanol, methanol, and higher alcohols. Processes and challenges for these conversions are also summarized.

Achieving carbon-negative bioenergy systems from plant materials, 2020

Thermal gasification is a very relevant technological platform to assess in relation to production of carbonnegative bioenergy from plant materials as it offers high feed and product flexibility combined with highenergy efficiency. Many different biomass feedstock and organic secondary resources can be converted into a wide variety of products such as heat, electricity, chemicals, transport fuels and high-value ash and char products. The platform is undergoing fast development, and industry and academia work together to optimize the process performance, increase fuel and product flexibility as well as combine different technologies to increase the efficiency, economic viability and product yield and value. This chapter provides insight on the versatility and potential benefits of biomass gasification and the related biobased products. General key issues of gasification plant designs are discussed, and a series of new concepts and solutions within process integration schemes, polygeneration strategies and biochar uses are described.

Recent Advancements in Biofuels and Bioenergy Utilization, 2018

Biomass and Bioenergy, 2008

Energy & Fuels, 2011

This paper examines the process performance of biomass gasification to methane. Three gasification configurations were studied via process modeling: the (product) recycle, the (secondary) methanation, and the combined (recycle and methanation) mode. The simulations gave insight into the higher heating value efficiency to methane and the process energy demand (hot utility) with varying gasifier temperature (700À800°C) and pressure (1À35 bar). Simulation results show that the overall efficiencies to methane obtained are in the range of 48À66%, of which the combined configuration exhibits the highest overall efficiencies (55À66%). Operation without extra heat input (hot utility) is possible for some cases, but only if the energy requirements for the CO 2 separation unit are lower than 2 MJ/kg of CO 2 via an improved or new CO 2 separation technology.

2019

The gasification process can be considered as one of the greatest conservative techniques in the transformation of biomass because of certain crucial factors such as the consideration of space, reduction of substantial waste volume, flexibility of fuel used, as well as the recovery of energy. The general process of gasification inclines to involve the incomplete burning of the carbon-based part of fossil fuels, which forms an abundant flammable gas in the presence of hydrogen, carbon monoxide and methane or some saturated hydrocarbon gases. When we consider the process of gasification, the parameters deemed to affect its performance, including the type of catalyst used, gasifying agents, biomass ratio and temperatures, as well as the type of raw materials. The primary purpose of this paper is to address the gasification process, including the types of gasifier designs like the fluidized bed, downdrafts, and updrafts. It’s also responsible for addressing the production of tar from th...

Hydrothermal system is an aqueous system where both temperature and pressure are kept above their critical values for water (374 0 C, 22.1MPa respectively). Hydrothermal gasification is a process in which wet biomass such as manure, sewage sludge (Bio-solids), black liquor and other higher moisture containing biomass and wet organic residues are gasified in supercritical water for the production of CH4 and H2. As we know these organic compounds are generally in the form of carbohydrates, proteins, cellulose, glycine, aromatic compounds etc. and each of these compound require a different temperature, pressure and residence time for gasification. But at temperature 600 0 C and pressure 250 bar all compounds are completely gasified by addition of KOH or K2CO3 as catalyst, forming a H2 rich product gas with CO2 as main carbon compounds. Concentrations of CO, CH4 and C2-C4 hydrocarbons are low in product gas. Gasification of biomass at given temperature and pressure (600 0 C and >25Mpa respectively) is called as Supercritical water gasification. The temperature required in this process can be generated by greenhouse effect artificially inside a rectangular glass chamber with minimum establishment cost and almost negligible operational cost. For generation of temperature of about 630 0 C-700 0 C, we need 27.40 kg/m 3 CO2 and 1500W/m 2 of Infrared Red (IR) radiation using IR heaters inside the rectangular glass chamber. By using heat exchangers this temperature is converted to supercritical steam and can be used in digester for gasification of biomass (sludge). Reaction time of digestion of biomass in supercritical water gasification is very small (seconds) as compared to time required (days) in conventional method of digestion in sludge digester. Distributed with permission of authors by GETS 2015 presented at GETS 2015

Chemical Engineering Journal, 2013

Gasification in subcritical (350°C) and supercritical (400°C) water was performed. Glucose and beech sawdust at 15 wt.% were gasified without a catalyst. Micro-autoclaves made of stainless steel and Inconel Ò 625 were compared. Stainless steel showed higher H 2 productions. Inconel Ò 625 enhances CO methanation.