Heat integration modeling of hydrogen production from date seeds via steam gasification

The purpose of the current study is to identify the potential of energy-efficient hydrogen (H₂) production from date seeds as biomass via steam gasification process along with heat integration in Gulf countries. A reaction kinetics model has been established for steam gasification with in-situ carbon dioxide (CO₂) capture of date seeds using MATLAB software. The kinetics of reactions involved in the gasification process was calculated using the optimization parameters fitting approach. The heat integration model has been developed via mixed integer nonlinear programming (MINLP) in MATLAB. In the parametric study, temperature and steam/biomass ratio considered their impact on syngas composition and energy recovery. Results showed that both variables have a strong positive effect on H₂ production and depicted maximum production of 68 mol% at a temperature of 750 °C with steam/biomass ratio of 1.2. Methane (CH₄) and CO₂ production were low in the product gas, which showed the activity of water gas shift reaction, methanation reaction, and carbonation reaction. Utilization of waste heat via process heat integration within the system reduced system's external heat load. More than 70% of energy recovered, which could be utilized for gasification and steam production. Energy analysis and process heat integration proved a prospective approach for energy-efficient and sustainable hydrogen production from date seeds.     

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.     

Existing large steam power plant upgraded for hydrogen production

This paper presents and discusses the results of a complete thermoeconomic analysis of an integrated power plant for co-production of electricity and hydrogen via pyrolysis and gasification processes fed by various coals and mixture of coal and biomass, applied to an existing large steam power plant (ENEL Brindisi power plant – 660 MW_e). Two different technologies for the syngas production section are considered: pyrolysis process and direct pressurized gasification. Moreover, the proximity of a hydrogen production and purification plants to an existing steam power plant favors the inter-exchange of energy streams, mainly in the form of hot water and steam, which reduces the costs of auxiliary equipment. The high quality of the hydrogen would guarantee its usability for distributed generation and for public transport. The results were obtained using WTEMP thermoeconomic software, developed by the Thermochemical Power Group of the University of Genoa, and this project has been carried out within the framework of the FISR National project “Integrated systems for hydrogen production and utilization in distributed power generation”.     

Parametric analysis and assessment of a coal gasification plant for hydrogen production

The purpose of this paper is to conduct a parametric study to show the best steam to carbon ratio that produces the maximum system performance of an integrated gasifier for hydrogen production. The study focuses on the energy and exergetic efficiency of the system and hydrogen production. The work is completed using computer simulation models in Engineering Equation Solver software package. This software is used for its extensive thermodynamic properties library. An equilibrium based model is used to determine the performance of the system. The data is presented in graphs which show the chemical composition in molar fractions of the syngas, the overall energy and exergy efficiency of the system, and the hydrogen production rates. A study of these parameters is conducted by varying the steam to carbon ratio entering the gasifier and the ambient temperature. It is observed that the higher the steam to carbon ratio that is achieved the more hydrogen and more power the plant is able to produce. Because of this, the exergy and energy efficiency of the system increases as the steam to carbon ratio increases as well. It is also observed that the system favors a lower ambient temperature for maximum exergy efficiency and hydrogen production.     

Comparative assessment of various gasification fuels with waste tires for hydrogen production

In this paper, waste tires are comparatively studied and assessed as a feedstock relative to coal and coconut char. An Integrated Gasification Combined Cycle (IGCC) is developed by using the Aspen Plus to assess the suggested gasification feedstocks based on their carbon dioxide emissions and hydrogen production to feed rate ratios. Note that many tires are disposed of every year in North America and are stockpiled in the masses in landfills, which cause various environmental implications. In the present study, it is found that waste tires as a feedstock for gasification are a viable solution to this ever-rising problem. The hydrogen production to feed rate ratio is found to be 0.158 which is very competitive with high-quality coals and coconut char. The net power production from the combined cycle when tires are used as the feedstock for the gasifier is found to be 11.1kW. The optimal hydrogen production to feed rate ratio is also achieved at the maximum net power production rate. The energy and exergy efficiencies of the overall system are found to be 55.01% and 52.31% when the waste tires are used as a feedstock.     

Integrated gasification and Cu-Cl cycle for trigeneration of hydrogen, steam and electricity

This paper develops and analyzes an integrated process model of an Integrated Gasification Combined Cycle (IGCC) and a thermochemical copper-chlorine (Cu-Cl) cycle for trigeneration of hydrogen, steam and electricity. The process model is developed with Aspen HYSYS software. By using oxygen instead of air for the gasification process, where oxygen is provided by the integrated Cu-Cl cycle, it is found that the hydrogen content of produced syngas increases by about 20%, due to improvement of the gasification combustion efficiency and reduction of syngas NO_x emissions. Moreover, about 60% of external heat required for the integrated Cu-Cl cycle can be provided by the IGCC plant, with minor modifications of the steam cycle, and a slight decrease of IGCC overall efficiency. Integration of gasification and thermochemical hydrogen production can provide significant improvements in the overall hydrogen, steam and electricity output, when compared against the processes each operating separately and independently of each other.     

Exergoeconomic analysis of a hybrid system based on steam biomass gasification products for hydrogen production

In this paper, a conceptual hybrid biomass gasification system is developed to produce hydrogen and is exergoeconomically analyzed. The system is based on steam biomass gasification with the lumped solid oxide fuel cell (SOFC) and solid oxide electrolyser cell (SOEC) subsystem as the core components. The gasifier gasifies sawdust in a steam medium and operates at a temperature range of 1023-1423 K and near atmospheric pressure. The analysis is conducted for a specific steam biomass ratio of 0.8 kmol-steam/kmol-biomass. The gasification process is assumed to be self-thermally standing. The pressurized SOFC and SOEC are of planar types and operate at 1000 K and 1.2 bar. The system can produce multi-outputs, such as hydrogen (with a production capacity range of 21.8-25.2 kgh⁻¹), power and heat. The internal hydrogen consumption in the lumped SOFC-SOEC subsystem increases from 8.1 to 8.6 kg/h. The SOFC performs an efficiency of 50.3% and utilizes the hydrogen produced from the steam that decomposes in the SOEC. The exergoeconomic analysis is performed to investigate and describe the exergetic and economic interactions between the system components through calculations of the unit exergy cost of the process streams. It obtains a set of cost balance equations belonging to an exergy flow with material streams to and from the components which constitute the system. Solving the developed cost balance equations provides the cost values of the exergy streams. For the gasification temperature range and the electricity cost of 0.1046 $/kWh considered, the unit exergy cost of hydrogen ranges from 0.258 to 0.211 $/kWh.     

High hydrogen content syngas for biofuels production from biomass air gasification: Experimental evaluation of a char-catalyzed steam reforming unit

This work investigates the performance of a reformer reactor for the upgrading of syngas and char derived from a pilot-scale air gasifier. The proposed setup represents a circular approach for the production of hydrogen-rich syngas from air gasification. Specifically, the reforming-unit was operated under a range of temperatures (from 700 °C to 850 °C) and steam flow rates and for each the improvement in producer gas composition and reducing species yield is evaluated. The results highlight that an increase in hydrogen concentration is obtained at higher temperature, moving from 16.2% to 21.3%, without using steam, and to 45.6%, with steam injection on the char-bed, while CO concentration did not follow a monotonic behavior. Moreover, the gas quality index, defined as a ratio between reducing species and inert species, delivered the highest values at the highest temperatures and steam flow rates. These results provide a guide for future gas quality optimization studies.     

Thermal conversion efficiency of producing hydrogen enriched syngas from biomass steam gasification

This paper presents the results from an experimental study on the energy conversion efficiency of producing hydrogen enriched syngas through uncatalyzed steam biomass gasification. Wood pellets were gasified using a 100 kW_th fluidized bed gasifier at temperatures up to 850 °C. The syngas hydrogen concentration and cold gas efficiency were found to increase with both bed temperature and steam to biomass weight ratio, reaching a maximum of 51% and 124% respectively. The overall energy conversion to syngas (based on heating value) also increased with bed temperature but was inversely proportional to the steam to biomass ratio. The maximum energy conversion to syngas was found to be 68%. The conversion of energy to hydrogen (by heating value) increased with gasifier temperature and gas residence time, but was found to be independent of the S/B ratio. The maximum conversion of all energy sources to hydrogen was found to be 25%.     

Performance of a water gas shift pilot plant processing product gas from an industrial scale biomass steam gasification plant

In this paper, the performance of a commercial Fe/Cr based catalyst for the water gas shift reaction was investigated. The catalyst was used in a water gas shift pilot plant which processed real product gas from a commercial biomass steam gasification plant with two different qualities: extracted before and extracted after scrubbing with a rapeseed methyl ester gas scrubber. The performance of the WGS pilot plant regarding these two different gas qualities was investigated. For this reason, extensive chemical analyses were carried out. CO, CO₂, CH₄, N₂, O₂, C₂H₆, C₂H₄, and C₂H₂ and H₂S, COS, and C₄H₄ S were measured. In addition, GCMS tar and NH₃ analyses were performed. Furthermore, the catalyst's activity was observed by measuring the temperature profiles along the reactors of the water gas shift pilot plant. During the 200 h of operation with both product gas qualities, no catalyst deactivation could be observed. A CO conversion up to 93% as well as a GCMS tar reduction (about 28%) along the water gas shift pilot plant was obtained. Furthermore, a specific H₂ production of 63 g H₂ per kg biomass (dry and ash free) was reached with both product gas qualities. No significant performance difference could be observed.     

Hydrogen production from steam gasification of tableted biomass in molten eutectic carbonates

The steam gasification of tableted biomass for H₂ production in molten salts was investigated under different conditions. The results showed that the ternary molten carbonates (32 wt% Li₂CO₃, 33 wt% Na₂CO₃ and 35 wt% K₂CO₃) acted as heat medium and catalyst in the gasification process. The use of molten salts could significantly increase total gas and H₂ production and simultaneously decrease the concentrations of CO and CH₄ in the product gas, and also decrease the yield of condensable tar. The increase in gasification temperature and mass ratio of steam to biomass (S/B) was beneficial for H₂ production process. However, excessive steam contributed slightly to the increase in H₂ production and largely increased the energy consumption. The optimal S/B ratio was found to be 1.0. The feedstock after tabletting could completely immersed in molten salts, which improved the contact between biomass and molten salts and thus favored the biomass gasification for H₂ production. When biomass particle size was 0.25 g/piece, the yield of H₂ reached 807.53 mL/g biomass.     

High efficient production of hydrogen from crude bio-oil via an integrative process between gasification and current-enhanced catalytic steam reforming

High efficient production of hydrogen from the crude bio-oil was performed in the gasification-reforming dual beds. A recently developed electrochemical catalytic reforming method was applied in the downstream reforming bed using NiCuZnAl catalyst. Production of hydrogen from the crude bio-oil through both the single gasification and integrative gasification-reforming processes was investigated. The maximum hydrogen yield of 81.4% with carbon conversion of 87.6% was obtained through the integrative process. Hydrogen is a major product (∼73 vol%) together with by-products of CO₂ (∼26 vol%) as well as very low content of CO (<1%) and a trace amount of CH₄ through the integrative route. In particular, the deactivation of the catalyst was significantly depressed by using the integrative gasification-reforming method, comparing to the direct reforming of the crude bio-oil. The mechanism and evaluation for the downstream electrochemical catalytic reforming were also discussed. The integrative process with higher hydrogen yield and carbon conversion, potentially, would be a useful route to produce hydrogen from the crude bio-oil.     

Low temperature steam gasification to produce hydrogen rich gas from kitchen food waste: Influence of steam flow rate and temperature

Large amount of food waste is generated from Indian kitchens and disposing off such a large amount possesses a great challenge in terms of environmental degradation and viable food waste processing technology. In this work, steam gasification was tested as an alternative viable technology to process the kitchen food waste. Preliminary study was carried out at low temperature on steam gasification in a fixed bed reactor to study the influence of steam flow rate (SFR) and temperature on the syngas yield, syngas composition, hydrogen yield. Performance parameters such as carbon conversion efficiency (CCE), and apparent thermal efficiency (ATE) are also calculated. Steam flow rates are varied from 0.125 mL/min to 0.75 mL/min and the temperatures are varied from 700 °C to 800 °C. The highest hydrogen yield is obtained at 0.5 mL/min SFR and 800 °C temperature and its highest value is 1.2 m³/kg. The highest value of performance parameters, CCE and ATE are found to be 63% and 1.8.     

Life cycle assessment of hydrogen production from biomass gasification systems

In this study, a Life Cycle Assessment (LCA) of biomass-based hydrogen production is performed for a period from biomass production to the use of the produced hydrogen in Proton Exchange Membrane (PEM) fuel cell vehicles. The system considered is divided into three subsections as pre-treatment of biomass, hydrogen production plant and usage of hydrogen produced. Two different gasification systems, a Downdraft Gasifier (DG) and a Circulating Fluidized Bed Gasifier (CFBG), are considered and analyzed for hydrogen production using actual data taken from the literature. Fossil energy consumption rate and Green House Gas Emissions (GHG) are defined and indicated first. Next, the LCA results of DG and CFBG systems are compared for 1 MJ/s hydrogen production to compare with each other as well as with other hydrogen production systems. While the fossil energy consumption rate and emissions are calculated as 0.088 MJ/s and 6.27 CO₂ eqv. g/s in the DG system, they are 0.175 MJ/s and 17.13 CO₂ eqv. g/s in the CFBG system, respectively. The Coefficient of Hydrogen Production Performance (CHPP) (newly defined as a ratio of energy content of hydrogen produced from the system to the total energy content of fossil fuels used) of the CFBG and DG systems are then determined to be 5.71 and 11.36, respectively. Thus, the effects of some parameters, such as energy efficiency, ratio of cost of hydrogen, on natural gas and capital investments efficiency are investigated. Finally, the costs of GHG emissions reduction are calculated to be 0.0172 and 0.24 $/g for the DG and CFBG systems, respectively.     

Potassium catalytic hydrogen production in sorption enhanced gasification of biomass with steam

Sorption enhanced gasification (SEG) of biomass with steam was investigated in a fixed-bed reactor to elucidate the effects of temperature, catalyst type and loading on hydrogen production. K₂CO₃, CH₃COOK and KCl were chosen as potassium catalyst precursors to improve carbon conversion efficiency in gasification process. It was indicated that from 600 °C to 700 °C, the addition of K₂CO₃ or CH₃COOK catalyzed the gasification for hydrogen production, and hydrogen yield and carbon conversion increased with increasing catalyst loadings of K₂CO₃ or CH₃COOK. However, the hydrogen yield and carbon conversion decreased as the amount of KCl was increased due to inhibition of KCl on gasification. The maximum carbon conversion efficiency (88.0%) was obtained at 700 °C corresponding to hydrogen yield of 73.0 vol.% when K₂CO₃ of 20 wt.% K loading was used. In particular, discrepant catalytic performance was observed between K₂CO₃ and CH₃COOK at different temperatures and the corresponding mechanism was also discussed.     

An investigation into steam gasification of biomass for hydrogen enriched gas production in presence of CaO

Biomass steam gasification could be an attractive option for sustainable hydrogen production. Biomass, regarded as carbon neutral emitter, could be claimed as carbon negative emitter if carbon dioxide produced is captured and not allowed to emit to the environment during the process. Thus here an experimental study is carried out to find out the potential of hydrogen production from steam gasification of biomass in presence of sorbent CaO and effect of different operating parameters (steam to biomass ratio, temperature, and CaO/biomass ratio). Product gas with hydrogen concentration up to 54.43% is obtained at steam/biomass = 0.83, CaO/biomass = 2 and T = 670 °C. A drop of 93.33% in carbon dioxide concentration was found at CaO/biomass = 2 as compared to the gasification without CaO. Mathematical model based on Gibbs free energy minimization has been developed and is compared with the experimental results.     

Techno-economic feasibility assessment of sorption enhanced gasification of municipal solid waste for hydrogen production

Waste-to-fuel coupled with carbon capture and storage is forecasted to be an effective way to mitigate the greenhouse gas emissions, reduce the waste sent to landfill and, simultaneously, reduce the dependence of fossil fuels. This study evaluated the techno-economic feasibility of sorption enhanced gasification, which involves in-situ CO₂ capture, and benchmarked it with the conventional steam gasification of municipal solid waste for H₂ production. The impact of a gate fee and tax levied on the fossil CO₂ emissions in economic feasibility was assessed. The results showed that the hydrogen production was enhanced in sorption enhanced gasification, that achieved an optimum H₂ production efficiency of 48.7% (T = 650 °C and SBR = 1.8). This was 1.0% points higher than that of the conventional steam gasification (T = 900 °C and SBR = 1.2). However, the total efficiency, which accounts for H₂ production and net power output, for sorption enhanced gasification was estimated to be 49.3% (T = 650 °C and SBR = 1.8). This was 4.4% points lower than the figure estimated for the conventional gasification (T = 900 °C and SBR = 1.2). The economic performance assessment showed that the sorption enhanced gasification will result in a significantly higher levelised cost of hydrogen (5.0 €/kg) compared to that estimated for conventional steam gasification (2.7 €/kg). The levelised cost of hydrogen can be reduced to 4.5 €/kg on an introduction of the gate fee of 40.0 €/t_MSW. The cost of CO₂ avoided was estimated to be 114.9 €/tCO₂ (no gate fee and tax levied). However, this value can be reduced to 90.1 €/tCO₂ with the introduction of an emission allowance price of 39.6 €/tCO₂. Despite better environmental performance, the capital cost of sorption enhanced gasification needs to be reduced for this technology to become competitive with mature gasification technologies.     

A study of combined biomass gasification and electrolysis for hydrogen production

An integrated system for the production of hydrogen by gasification of biomass and electrolysis of water has been designed and cost estimated. The electrolyser provides part of the hydrogen product as well as the oxygen required for the oxygen blown gasifier. The production cost was estimated to 39 SEK/kg H₂ at an annual production rate of 15?000 ton, assuming 10% interest rate and an economic lifetime of 15 years. Employing gasification only to produce the same amount of hydrogen, leads to a cost figure of 37 SEK/kg H₂, and for an electrolyser only a production cost of 41 SEK/kg H₂. The distribution of capital and operating cost is quite different for the three options and a sensitivity analyses was performed for all of these. However, the lowest cost hydrogen produced with either method is at least twice as expensive as hydrogen from natural gas steam reforming.     

Evaluation of greenhouse residues gasification performance in hydrogen production

In this study, a modeling study was carried out to investigate the potential of hydrogen production from greenhouse tomato and pepper residues blending in different rates (0%, 25%, 50%, 75% and 100%) by air-steam gasification. The numerical model developed for the gasification system assumes that all carbon in the mixture is gasified. Air to fuel rate and steam to fuel rates are 0.05 due to high content of O₂ in biomass residues. The gasifier temperature is 877 °C (1150 K) for developed model. According to the result of this study, increasing tomato residues blending rate increases hydrogen content of syngas. It is mainly caused by the content of O₂ in tomato residues being higher than content of O₂ in pepper residues. This study shows that the O₂ content of greenhouse residues is an important factor in syngas production, especially in H₂ production.     

Thermodynamic analysis of hydrogen production from biomass gasification

An investigation is reported of the thermodynamic performance of the gasification process followed by the steam-methane reforming (SMR) and shift reactions for producing hydrogen from oil palm shell, one of the most common biomass resources. Energy and exergy efficiencies are determined for each component in this system. A process simulation tool is used for assessing the indirectly heated Battelle Columbus Laboratory (BCL) gasifier, which is included with the decomposition reactor to produce syngas for producing hydrogen. A simplified model is presented here for biomass gasification based on chemical equilibrium considerations, with the Gibbs free energy minimization approach. The gasifier with the decomposition reactor is observed to be one of the most critical components of a biomass gasification system, and is modeled to control the produced syngas yield. Also various thermodynamic efficiencies, namely energy, exergy and cold gas efficiencies are evaluated which may be useful for the design, optimization and modification of hydrogen production and other related processes.