Steam Gasification System Research Articles

Quasi-equilibrium thermodynamic model with empirical equations for air–steam biomass gasification in fluidized-beds

Gasification is one of the most promising technologies for converting biomass into a fuel. This study presents a simple and practical biomass gasification model based on thermodynamic equilibrium to find effective operating conditions of the air–steam gasification system in fluidized-beds. The carbon conversion fraction empirically obtained was involved in a global gasification reaction. Two empirical equations as the non-equilibrium factor expressing the deviation from equilibrium were derived as the function of the equivalence ratio (ER) from 43 experimental data sets of various operating conditions and different feedstocks. One energy balance was also solved for determining the gasification temperature (T). After the producer gas composition with respect to ER and steam to biomass ratio (SBR) was obtained from the air–steam biomass gasification (ASBG) model, process performances such as lower heating value, heat efficiency, net heat efficiency, and H2/CO molar ratio were evaluated. An effective operating area was suggested from the contour plot of the process performances with respect to ER and SBR in the auto-thermal gasification temperature from 700 to 830°C.

Integrated catalytic adsorption (ICA) steam gasification system for enhanced hydrogen production using palm kernel shell

This paper investigates the integrated catalytic adsorption (ICA) steam gasification of palm kernel shell for hydrogen rich gas production using pilot scale fluidized bed gasifier under atmospheric condition. The effect of temperature (600–750 °C) and steam to biomass ratio (1.5–2.5 wt/wt) on hydrogen (H2) yield, product gas composition, gas yield, char yield, gasification and carbon conversion efficiency, and lower heating values are studied. The results show that H2 hydrogen composition of 82.11 vol% is achieved at temperature of 675 °C, and negligible carbon dioxide (CO2) composition is observed at 600 °C and 675 °C at a constant steam to biomass ratio of 2.0 wt/wt. In addition, maximum H2 yield of 150 g/kg biomass is observed at 750 °C and at steam to biomass ratio of 2.0 wt/wt. A good heating value of product gas which is 14.37 MJ/Nm3 is obtained at 600 °C and steam to biomass ratio of 2.0 wt/wt. Temperature and steam to biomass ratio both enhanced H2 yield but temperature is the most influential factor. Utilization of adsorbent and catalyst produced higher H2 composition, yield and gas heating values as demonstrated by biomass catalytic steam gasification and steam gasification with in situ CO2 adsorbent.

過熱水蒸気式ガス化システムを用いた各種バイオマスガス発電系のエネルギ使用量およびCO2排出量のライフサイクル評価（―地域規模，ガス化プラント規模，各種バイオマスガスによる影響度解析―）

過熱水蒸気式ガス化システムを用いた各種バイオマスガス発電系のエネルギ使用量およびCO2排出量のライフサイクル評価（―地域規模，ガス化プラント規模，各種バイオマスガスによる影響度解析―）

Biomass heat pipe reformer—design and performance of an indirectly heated steam gasifier

Indirectly heated dual fluidized bed (DFB) gasifiers are a promising option for the production of syngas, in particular in the small- and medium-scale range. The application of so-called heat pipes solves the key challenge of indirectly heated gasifiers—the heat transfer into the gasifier's reformer part. Performance, technical challenges, and solutions for the so-called biomass heat pipe reformer are discussed, and the development of the last 10 years is summarized. An equation for the heat pipe reformer's cold gas efficiency is presented. The equation applies for any dual fluidized bed gasifier and indicates that the efficiency of the combustion process dominates the cold gas efficiency of any directly or indirectly heated allothermal steam gasification system.

Gasification of lignite in a dual fluidized bed gasifier — Influence of bed material particle size and the amount of steam

The dual fluidized bed steam gasification system, developed by the Institute of Chemical Engineering at Vienna University of Technology, was originally developed for the utilization of woody biomass as feedstock, but during practical operation of the industrial sized plants of this system it turned out that fuel flexibility is the key issue for economic breakthrough. Therefore, gasification tests were carried out with lignite at different operating conditions at the dual fluidized bed pilot plant at Vienna University of Technology. Tests were performed with an input fuel power of 90kWth. Olivine was used as bed material and the applied particle size was 370 and 510μm. The steam-to-carbon ratio was varied between 1.3 and 2.1kgH2O/kgcarbon. In addition to standard online measurements of the permanent gas components of the product gas, impurities like NH3, H2S and tar were also measured. It turned out that a lower amount of steam for fluidization caused a better performance of the gasification reactor in terms of product gas yield, carbon conversion and water conversion. The high catalytic activity of the lignite ash was also a reason for the high product gas quality producing low amounts of condensable hydrocarbons, like tar.

Thermodynamic analysis of the hydrogen peroxide decomposition parameters

This paper discusses the estimation of the decomposition parameters of the liquid–gas-steam system, which is produced by the hydrogen peroxide decomposition at isobar conditions. The thermodynamic analysis calculates the two critical concentrations, which mark the phase transitions of the system depending on the initial pressure and hydrogen peroxide concentration.

Cost modeling approach and economic analysis of biomass gasification integrated solid oxide fuel cell systems

This paper presents a cost modeling approach and the economic feasibility for selected plant configurations operating under three modes: air gasification, mixed air-steam gasification, and steam gasification combined cycle solid oxide fuel cell (SOFC) systems. In this study, three cases of biomass gasification integrated SOFC without combined cycle (base case 1) are compared with biomass gasification integrated SOFC-gas turbine (GT) with heat recovery steam generator (HRSG) hybrid configuration (case 2) and biomass gasification integrated SOFC-steam turbine (ST) cycle (case 3) for biomass feed stock. The plant design cases of integrated biomass gasification processes, SOFC, and combined cycles are investigated primarily employing aspen plus™ flow sheeting models. Based on the mass and energy balance results of the system simulations, the economic model calculates the size and cost estimates for the plant configuration equipments. Detailed purchase cost estimations for each piece of equipments and the corresponding total bare module cost were established based on the bare module factor, and the total direct permanent investment were established. The calculated direct permanent investment was used for economic feasibility analysis of the cogeneration plant configuration. The economic feasibility decision parameters, such as purchase cost estimations, total specific plant cost per kW, the financial net present value (FNPV), internal rate of return, and benefit to cost ratio for the system configurations were compared for three design cases. The results shows that the cost of the steam gasification system is shown to be highest compared to the mixed air steam gasification system and air gasification system due to the higher hydrogen production. Other than the SOFC and gasification costs, a significant cost towards the heat exchangers is about 15% to 20% of the total equipment purchase cost. The specific plant cost for the air gasification varied from the 16 600 US$/kW to 19 200 US$/kWe. For the case of biomass gasification-integrated SOFC-GT configuration, the major cost portions are shared by the SOFC, HRSG, and gasifier. The HRSG equipment shared a cost portion of 25% to 30% for all the operating modes. The cost is decreased with a similar trend as that of steam, mixed air-steam and air gasification systems. For the case of biomass gasification integrated with SOFC-ST configuration, the total equipment purchase cost decreases at a rate of 15% to 20% for both mixed air steam and air gasification system. Plant specific cost for the steam gasification mode varied from 15 200 to 17 200 US $/kW which is significantly very high.

Hydrogen from biomass: large-scale hydrogen production based on a dual fluidized bed steam gasification system

Hydrogen is used as an important feedstock for the chemical industry. Common production technologies for the production of hydrogen from fossil fuels today cause relevant CO2 emissions. Hydrogen from renewable energy sources is discussed as an alternative option to replace traditional feedstock and can therefore be part of a low-carbon energy system. This paper describes the results of a simulation of a concept for the production of hydrogen with biomass as feedstock. The described investigations include a possible process design, the process simulation using the software IPSEpro, a description of the operation characteristics, and a profitability analysis of the applied hydrogen production concept. The simulation result shows that 61 MW of hydrogen can be produced from 100 MW wood chips and 6 MW of electricity. As a result, hydrogen production costs of 54 €/MWh can be estimated. For the investigated concept, the wood chip price is the most important factor for the hydrogen production cost followed by investment costs for the plant and the realized plant operation time per year.

Basic Study on Hydrogen-Rich Gas Production by High Temperature Steam Gasification of Solid Wastes

In this paper, basic studies on the high temperature steam gasification system which is named as HyPR-MEET system were carried out using the Japanese cedar and pure polyethylene (PE) particles as feedstocks. First, the characteristic of steam gasification is investigated. With each feedstock, the hydrogen concentration increases as the gasification temperature rises, but the increase rate of the hydrogen concentration decreases over the temperature of 1073K for Japanese cedar and 1173K for PE. The increase of the steam/carbon molar ratio also increases the hydrogen concentration. Second, the effectiveness of the Ru/Al2O3 catalyst for steam reforming of tar components is investigated. With use of this catalyst, tar components can be reformed at the temperature of 973K, while the temperature of 1173K is required without use of any catalysts. Furthermore, light hydrocarbon gases are also reformed with this catalyst, and the hydrogen concentration in the reformed gas can reach the value of 55% for Japanese cedar, and of 68% for PE.

Model development and validation: Co-combustion of residual char, gases and volatile fuels in the fast fluidized combustion chamber of a dual fluidized bed biomass gasifier

A one-dimensional steady state model has been developed for the combustion reactor of a dual fluidized bed biomass steam gasification system. The combustion reactor is operated as fast fluidized bed (riser) with staged air introduction (bottom, primary and secondary air). The main fuel i.e., residual biomass char (from the gasifier), is introduced together with the circulating bed material at the bottom of the riser. The riser is divided into two zones: bottom zone (modelled according to modified two phase theory) and upper zone (modelled with core-annulus approach). The model consists of sub-model for bed hydrodynamic, conversion and conservation. Biomass char is assumed to be a homogeneous matrix of C, H and O and is modelled as partially volatile fuel. The exit gas composition and the temperature profile predicted by the model are in good agreement with the measured value.

Modelling and simulation of the biomass fired dual fluidized bed gasifier at Guessing/Austria

l steady state model of the gasification reactor of a dual fluidized bed biomass steam gasification system has been developed. The gasification reactor is operated in bubbling regime. The model distinguishes two zones: dense zone and freeboard zone. The dense zone is the bubbling bed and is modelled with modified two phase theory while freeboard is modelled as a plug flow reactor. The main fuel is biomass (wood) and is introduced into the dense zone. Biomass is modelled as a homogeneous matrix of C, H, and O. The solids within the dense zone are considered to be well mixed while the gases are in plug flow regime. Energy balance is solved globally in each zone. Results show that the wood is only partly converted in the gasifier. The gas composition profile and temperature profile predicted by the model is in good agreement with the values measured at 8 MW (fuel power) plant in Guessing/Austria.

Basic Study on Hydrogen-rich Gas Production by High Temperature Steam Gasification of Solid Wastes

In this paper, the basic studies on the high temperature steam gasification system which is named as HyPR-MEET system are carried out using the Japanese cedar and pure polythylene (PE) particles as feedstocks. First, the characteristic of steam gasification is investigated. With each feedstock, the hydrogen concentration increases as the gasification temperature rises, but the increasing rate of hydrogen concentration decreases over the temperature of 1 073 K for Japanese cedar and 1 173 K for PE. The increase of the steam/carbon molar ratio also increases the hydrogen concentration. Second, the effectiveness of the Ru/Al2O3 catalyst for steam reforming of tar components is investigated. With use of this catalyst, tar components can be reformed at the temperature of 973 K, while the temperature of 1 173 K is required without use of any catalysts. Furthermore, light hydrocarbon gases are also reformed with this catalyst, and the hydrogen concentration in the reformed gas can reach the value of 55 vol% for Japanese cedar, and of 68 vol% for PE.

OS3-6 廃棄物の高温水蒸気ガス化システムに関する研究開発(OS3 バイオマス・新燃料・環境技術,循環型社会における動力エネルギー技術)

OS3-6 廃棄物の高温水蒸気ガス化システムに関する研究開発(OS3 バイオマス・新燃料・環境技術,循環型社会における動力エネルギー技術)