Gasification Of Lignocellulosic Biomass Research Articles

Techno-economic analysis of ammonia production via integrated biomass gasification

Ammonia (NH3) can be produced by synthesis of nitrogen and hydrogen in the Haber–Bosch process, where the economic challenge is the hydrogen production. Currently, substantial amounts of greenhouse gases are emitted from the ammonia industry since the hydrogen production is almost exclusively based on fossil feedstocks. Hydrogen produced via gasification of lignocellulosic biomass is a more environmentally friendly alternative, but the economic performance is critical. The main objective of this work was to perform a techno-economic evaluation of ammonia production via integrated biomass gasification in an existing pulp and paper mill. The results were compared with a stand-alone production case to find potential technical and economic benefits deriving from the integration. The biomass gasifier and the subsequent NH3 production were modelled using the commercial software Aspen Plus. A process integration model based on Mixed Integer Linear Programming (MILP) was used to analyze the effects on the overall energy system of the pulp mill. Important modelling constraints were to maintain the pulp production and the steam balance of the mill. The results showed that the process economics and energy performance are favourable for the integrated case compared to stand-alone production. The main conclusion was however that a rather high NH3 selling price is required to make both production cases economically feasible.

Environmental and exergetic evaluation of hydrogen production via lignocellulosic biomass gasification

Abstract Gasification is a promising pathway for the conversion of biomass into energy products. In particular, the syngas generated through biomass gasification is of great interest for hydrogen production. Based on an overview of technological options, a base-case system for hydrogen production via biomass gasification is defined, and its environmental and thermodynamic performance is evaluated through a life cycle assessment and an exergetic analysis. The case study involves poplar gasification in a low-pressure char indirect gasifier, catalytic tar destruction, cold wet gas cleaning, syngas conversion and hydrogen purification. The calculated exergetic efficiency of the plant is 48%, a value comparable to that of conventional coal gasification technologies for hydrogen production. The total exergy loss of the plant (mainly associated with the flue gas streams) is found to be 4.6% of the fuel exergy provided to the overall plant, while 47% of the overall fuel exergy vanishes as exergy destruction within the individual components of the plant. The life cycle assessment of the system covers from poplar cultivation to hydrogen purification. Seven impact potentials are considered: cumulative energy demand, global warming, ozone layer depletion, photochemical oxidant formation, land competition, acidification and eutrophication. The life-cycle energy balance of the system suggests a relatively promising energy performance. Poplar cultivation and harvesting, biomass pre-treatment and syngas cleaning are identified as the subsystems with the largest contributions to the environmental impacts. Measures to enhance the environmental and energy performance of the system should focus on minimizing the poplar feedstock demand, improving the logistical planning for biomass supply, reducing the natural gas demand of the steam reforming subsystem, and optimizing the electricity demand of the gas cleaning subsystem. Lower consumption levels of fertilizers and diesel for poplar cultivation and harvesting should also be achieved.

A Theoretical Study of Two Novel Concept Systems for Maximum Thermal-Chemical Conversion of Biomass to Hydrogen

Two concept systems that are based on the thermochemical process of high-temperature steam gasification of lignocellulosic biomass and municipal solid waste are introduced. The primary objectives of the concept systems are 1) to develop the best scientific, engineering, and technology solutions for converting lignocellulosic biomass, as well as agricultural, forest and municipal waste to clean energy (pure hydrogen fuel), and 2) to minimize water consumption and detrimental impacts of energy production on the environment (air pollution and global warming). The production of superheated steam is by hydrogen combustion using recycled hydrogen produced in the first concept system while in the second concept system concentrated solar energy is used for the steam production. A membrane reactor that performs the hydrogen separation and water gas shift reaction is involved in both systems for producing more pure hydrogen and CO2 sequestration. Based on obtaining the maximum hydrogen production rate the hydrogen recycled ratio is around 20% for the hydrogen combustion steam heating system. Combined with pure hydrogen production, both high temperature steam gasification systems potentially possess more than 80% in first law overall system thermodynamic efficiencies.

Isolation of Thermophilic Acetogens and Transformation of Them with the <i>pyrF</i> and <i>kan</i><sup><i>r</i></sup> Genes

The application of microbial catalysts to syngas from the gasification of lignocellulosic biomass is gaining interest. Acetogens, a group of anaerobic bacteria, can grow autotrophically on gaseous substrates such as hydrogen and carbon dioxide or syngas and produce acetate via the acetyl-CoA pathway. Here, we report the isolation from a soil sample of two thermophilic acetogen strains, Y72 and Y73, that are closely related to Moorella sp. HUC22-1 and M. thermoacetica ATCC39073. The optimal growth temperature and pH for the strains were 60 °C and 6.0-6.5. Uracil auxotrophy was induced in them by replacing the orotate monophosphate decarboxylase gene (pyrF) with the kanamycin resistant marker (kan(r)). The transformants were isolated by supplementation of the basal medium with 300 mg/L of kanamycin. The transformation efficiency of strains Y72 and Y73 was 20-fold higher than that of strain ATCC39073. Hence these strains are considered possible hosts for thermophilic syngas fermentation.

H2 processes with CO2 mitigation: Thermo-economic modeling and process integration

Within the challenge of greenhouse gas reduction, hydrogen is regarded as a promising decarbonized energy vector. The hydrogen production by natural gas reforming and lignocellulosic biomass gasification are systematically analyzed by developing thermo-economic models. Taking into account thermodynamic, economic and environmental factors, process options with CO2 mitigation are compared and optimized by combining flowsheeting with process integration, economic analysis and life cycle assessment in a multi-objective optimization framework. The systems performance is improved by introducing process integration maximizing the heat recovery and valorizing the waste heat. Energy efficiencies up to 80% and production costs of 12.5–42 $/GJH2 are computed for natural gas H2 processes compared to 60% and 29–61 $/GJH2 for biomass processes. Compared to processes without CO2 mitigation, the CO2 avoidance costs are in the range of 14–306 $/tCO2,avoided. The study shows that the thermo-chemical H2 production has to be analyzed as a polygeneration unit producing hydrogen, captured CO2, heat and electricity.

Thermogravimetric Pyrolysis and Gasification of Lignocellulosic Biomass and Kinetic Summative Law for Parallel Reactions with Cellulose, Xylan, and Lignin

Pyrolysis and gasification of lignocellulosic (woody) biomass and its main components, cellulose, xylan, and lignin, were studied using a combined thermogravimetry and gas chromatography experimental setup at a heating rate of 10 °C min–1 in the temperature range of 140–900 °C using air and/or steam gasifying agents (100% air, 50% air/50% steam, 25% air/75% steam, and 70% steam/30% argon). Simulated biomass composed of a mixture of cellulose, xylan, and lignin at 50:25:25 wt % was also investigated. A three-parallel-reaction kinetic model was formulated on the basis of the weighted sum of reaction rates for the individual components and experimentally validated in terms of reaction rates, carbon conversions, and product gas yields for lignocellulosic and simulated biomass.

Deactivation of a Ni-Based Reforming Catalyst During the Upgrading of the Producer Gas, from Simulated to Real Conditions

The deactivation of a nickel reforming catalyst during the upgrading of the producer gas obtained by gasification of lignocellulosic biomass was studied. The research involved several steps: the selective deactivation of the catalyst in a laboratory scale; the streaming of the catalyst with the producer gas of a downdraft and an oxygen/steam circulating fluidized bed (CFB) gasifier; and tests in a reformer placed in a slipstream of the CFB gasifier. The information obtained allowed to elucidate the catalyst deactivation mechanisms taking place during the reforming of the producer gas: physical deactivation by deposition of fine ashes, aerosol particulate or carbon; poisoning by H2S and HCl present in the gas phase and thermal sintering because of the high operation temperatures required to avoid the chemical deactivation. These physical and chemical effects depended on the composition of the biomass fuel.

Hydroprocessing of Fischer–Tropsch biowaxes to second-generation biofuels

Upgrading of Fischer–Tropsch (FT) biowaxes to second-generation biofuels via hydroprocessing is the final step for increasing the fuel amount of the overall biomass conversion route: gasification of lignocellulosic biomass, FT synthesis, and hydroprocessing. The typical FT product portfolio consists of high molecular weight paraffinic waxes as the main product and FT fuels in the diesel and naphtha boiling range. OMV's objective and contribution to the project focus on achieving coprocessing of FT biowaxes with fossil feedstock using existing hydrotreating plants of crude oil refineries. Various test runs have been examined with a conventional refining catalyst under mild conditions (380–390°C, 5.8 MPa; WHSV, 0.7–1.3 h−1) in a pilot plant. Pure FT biowax is converted to gases, fuels, and an oil/waxy residue in a fixed-bed reactor with a porous catalyst layer technology. The presence of hydrogen in the reaction chamber reduces the fast deactivation of the catalyst caused by the formation of a coke layer around the catalyst particle surface and saturates cracked hydrocarbon fragments. Another approach is the creation of synthetic biodiesel components with excellent fuel properties for premium fuel application. Basically, premium diesel fuel differs from standard diesel quality by cetane number and cold flow properties. Hydroprocessed synthetic biodiesel (HPFT diesel) has compared to conventional diesel advantages in many aspects. Depending on the catalyst selected, premium diesel quality can be obtained by shifting cold flow operability properties of HPFT fuels to a range capable even under extreme cold conditions. In addition, a high-quality kerosene fraction is obtained to create bio jet fuels with an extremely deep freezing point, as low as −80°C. The isomerization degree, as well as the carbon number distribution of high paraffinic profile, and the branching degree have a major impact on the cold flow properties and cetane number. FT diesel has, compared to HPFT diesel, a slightly higher derived cetane number (DCN > 83) and a cloud point of −9°C, whereas HPFT diesel reaches values as low as −60°C. Although the HPFT naphtha obtained consists of high amounts of isoparaffins, the RON/ MON values are comparable to fossil straight-run naphtha. The reason is that the branching degree of isoparaffins from the naphtha fraction is not sufficiently high enough to reach the typical octane number values of gasoline products delivered at filling stations. Assuming the goal of launching a premium biodiesel or biokerosene fuel to the market, these hydroprocessed synthetic biofuels from FT biowaxes are ideal blending components.

Laminar burning behaviour of biomass gasification-derived producer gas

In the currently reported work, a mixture of H 2, CO and N 2 (21:24:55 vol%) has been considered as representative of the producer gas coming from gasification of lignocellulosic biomass. Laminar burning velocities have been determined, with simultaneous study of the effects of flame stretch rate and instabilities. Experimentally determined laminar burning velocities derived from schlieren flame images, over a range of equivalence ratios, have been compared with those determined using the CHEMKIN code. Good agreement obtained for 1 bar flames, but significant differences were observed for high pressure cellular flames. Markstein numbers were also derived from the experimental data and corresponding Lewis numbers were calculated. Hydrogen thermo-diffusive effects tended to destabilise lean flames, while the CO content resulted in laminar burning velocity peaking at very high equivalence ratios. The peak burning rate of producer gas proved faster than those of conventional fuels, such as isooctane and methane.

Establishing the optimal sizes of different kinds of biorefineries

AbstractThis paper explores the factors that influence the optimal size of biorefineries and the resulting unit cost of biofuels produced by them. Technologies examined include dry grind corn to ethanol, lignocellulosic ethanol via enzymatic hydrolysis, gasification and upgrading to hydrogen, methanol, and Fischer Tropsch liquids, gasification of lignocellulosic biomass to mixed alcohols, and fast pyrolysis of lignocellulosic biomass to bio‐oil. On the basis of gallons of gasoline equivalent (gge) capacity, optimally sized gasification‐to‐biofuels plants were found to be 50–100% larger than biochemical cellulosic ethanol plants. Biorefineries converting lignocellulosic biomass into transportation fuels were found to be optimally sized in the range of 240–486 million gge per year compared to 79 million gge per year for a grain ethanol plant. Among the biofuel options, ethanol, whether produced biochemically or thermochemically, is the most expensive to produce. Lignocellulosic biorefineries will require 4.7–7.8 million tons of biomass annually compared to 1.2 million tons of corn grain for a grain ethanol plant. Factors that could reduce the optimal size of lignocellulosic biorefineries are discussed. © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd

Prediction of the Autoignition Delay Time of Producer Gas from Biomass Gasification

The greenhouse effect and the increasing demand for energy have encouraged the use of alternative fuels, with agricultural and forestry biomass waste being two of the main renewable sources that European and Spanish policies have been promoting during the last several years. In this article, theoretical results for the chemical autoignition delay time of producer gas obtained from the gasification of lignocellulosic biomass are presented. These results, together with those obtained in a previous work related to the laminar flame speed of the gas, are of great interest both for understanding the chemical kinetic mechanisms that control the fuel oxidation process and for the development of combustion models that provide significant information to be used as a tool for the optimization and design of internal combustion engines. The CHEMKIN software, in conjunction with the GRI-Mech chemical reaction mechanism, has been used to compute the autoignition delay time for different producer gas compositions, diffe...

Estimation of the Laminar Flame Speed of Producer Gas from Biomass Gasification

Because of the importance that the energy use of agricultural and forestry wastes has acquired over the last years, results for the laminar flame speed of producer gas coming from the gasification of lignocellulosic biomass are presented in this work. These results have great interest for the development of combustion models that provide significant information to be used as a tool for the optimization and design of specific internal combustion engines. The CHEMKIN software, together with the GRI-Mech chemical reaction mechanism, has been used to compute the laminar flame speed for different producer gas compositions, different values of pressure and temperature, and different producer gas/air equivalence ratios. The results have been compared with those obtained in an experimental combustion bomb, as well as with the laminar flame speed obtained for conventional fuels, showing that the flame speed of the producer gas is less than that of isooctane but greater than that of methane. A sensitivity analysis ...

Economics of a coordinated biorefinery feedstock harvest system: lignocellulosic biomass harvest cost

Abstract A potential advantage of lignocellulosic biomass gasification–fermentation technology is that a variety of feedstocks, including agricultural residues, native grasses, introduced perennials, and dedicated energy crops may be gasified by the same facility. Since harvest windows differ across species, gasification–fermentation technology would enable the use of specialized harvest and collection machinery throughout many months and reduce the fixed costs of harvest machinery per unit of feedstock. This study was conducted to determine the cost to harvest lignocellulosic biomass for use as biorefinery feedstock, and to determine the potential economies of size that might result from a coordinated structure. An agricultural machinery cost computer program was used to determine which specific type of machines would result in the lowest costs at intensive levels of use. A machinery complement estimator was used to design a coordinated set of machines and estimate costs for owning and operating the machines. The designed coordinated harvest unit includes ten laborers, nine tractors, three mowers, three rakes, three balers, and one bale transporter. The cost for mowing, raking, baling, gathering, and stacking in-field was estimated to be from $11.26 to $14.01 Mg −1 depending upon biomass yield. A biorefinery with an annual feedstock requirement of 910 Gg yr −1 would require approximately 18 harvest units and an average machinery investment of $11 million. Additional research is necessary to determine the cost to procure material from the landowner, the cost to store, storage losses, and the cost to transport feedstock from in-field stacks to a biorefinery.

Egypt: timescale slips for Eatco project

This work investigates and compares the thermodynamic performance of alternative platform chemicals for the production of light olefins (i.e., ethylene, propylene, and mixed butylenes) via gasification of lignocellulosic biomass (forest residues). Two concepts based on the same general process layout are considered: (i) via methanol synthesis and methanol-to-olefins (MTO) synthesis; (ii) via direct dimethyl ether (DME) synthesis and DME-to-olefins (DTO) synthesis. The work is based on process models established in Aspen Plus to obtain mass and energy balances. Heat recovery targets for integration of a steam network for combined heat and power production are investigated using pinch analysis tools. The different process alternatives are compared in terms of energy efficiency (ηen). Additionally, to identify key process differences, the cold gas efficiency (ηcg,i) and carbon conversion (Cconv,i) from biomass feedstock to various intermediate products along the process value chain are compared. The results show that light olefins could be produced with an energy efficiency of approximately 52–54% (higher heating value (HHV) basis) using methanol and DME as platform chemicals. The two investigated concepts had similar cold gas efficiency along the process value chain and overall electricity balance. Accordingly, no significant thermodynamic difference could be identified for the two investigated cases. One interesting feature that is identified is that the same amount of the renewable carbon in the feedstock is lost, mainly as CO2, regardless of whether the methanol or DME route is adopted. The difference is where in the process value chain most of the CO2 is formed and removed.

Scale-up of downdraft moving bed gasifiers (25–300 kg/h) — Design, experimental aspects and results

Two installations with different biomass processing capacities (25–50 and 200–300 kg/h) were designed and constructed for air gasification of lignocellulosic biomass. This paper describes both installations as well as the experimental procedure. The influence of operating conditions on the amount and quality of products was determined. The results obtained from processing forestry waste are analysed. Values above 90% for mass conversion efficiency and over 70% for cold gas efficiency were reached.