Higher Heating Value Of Syngas Research Articles

Thermodynamic and economic analysis of a hydrogen production process from medical waste by plasma gasification

To reduce the environmental pollution caused by pathogens and radioactive substances carried by medical waste, and alleviate the shortage of non-renewable energy, this work proposes a novel overall process for hydrogen production from medical waste by plasma gasification coupled with ionic liquid-based CO2 capture. The validity of the model is verified by the experimental data. Based on the simulation results, the effects of medical waste types, different gasification agents and carbon conversion rate on the syngas compositions, H2/CO ratio, carbon conversion rate, higher heating value and exergy efficiency are explored. The results show that the rate of hydrogen production from surgical masks is more than twice that of the other two types of medical waste. Steam is the best gasification agent. At this time, the higher heating value of syngas is 26.72 MJ/kg and the exergy efficiency is 78.25%. A comprehensive analysis of the thermodynamic efficiency and technical economy of the overall process shows that the total exergy efficiency is 70.84%. The production cost is 2115.74 USD and the raw material consumption is 2.61 t/t H2. This study can provide a promising theoretical guidance for the resource treatment of medical waste.

Comprehensive parametric study of fixed-bed co-gasification process through Multiple Thermally Thick Particle (MTTP) model

Co-gasification technology provides a promising solution for the energetic valorization of various biomass feedstocks, especially those not directly applicable for gasification owing to their low-calorific values or high ash content, but the complexity of co-gasification technology has put forward challenges to model formulation when using numerical methods to evaluate the performance of the gasifier. In the present work, the Multiple Thermally Thick Particle (MTTP) model is developed and validated for fixed-bed co-gasification process. The sub-phase treatment that extends the conventional Eulerian-Eulerian framework allows calculating the inhomogeneity in the solid phase, and the intra- and inter-particle heat and mass transfer sub-models enable quantitative evaluation of the conversion of different solid fuels with nonnegligible intraparticle gradients. Parametric analyses of moisture content and particle size were performed to evaluate how the degree of difference between each fuel would influence the reaction processes, gasification performances and steady-state operating conditions. Upon changing the moisture content of the fuel mixtures (biomass and MSW) from both 9.0 wt% to 9.0 wt% for MSW and 27.0 wt% for biomass, the maximum temperature difference between the solid particle surfaces of different fuels was nearly 150 K, and the regions of different conversion processes became highly overlapped. When increasing the moisture content of biomass from 9.0 wt% to 27.0 wt% under 1:1 mixing ratio, the cold gas efficiency, volume fraction of H2 and higher heating value of syngas increased from 65.26%, 12.03%, and 6.29 MJ/Nm3 to 68.39%, 15.62%, and 6.44 MJ/Nm3, respectively. Therefore, the quality and efficiency can be improved when increasing the moisture content in a certain range although the overall capacity of the gasifier will decrease. The intraparticle temperature profiles calculated by the MTTP model also revealed that decreasing the particle size from centimeter- to millimeter-level will significantly reduce the temperature difference between the surface and center of the fuel particles, thus accelerating the in-bed reaction rates and increasing the overall capacity of the gasifier. The MTTP model is flexible for various working conditions and solid fuel mixtures, which is a versatile and convenient tool to optimize the complicated co-gasification process.

H2-rich gas production from steam gasification of a winery waste and its blends with industrial wastes. Effect of operating parameters on gas quality and efficiency

A winery waste and its blends with industrial wastes were gasified by steam via a two-step process, employing a fixed bed reactor and a thermal analysis-mass spectrometer unit. Solid materials were characterized in terms of elemental analysis, heating value, internal structure and chemical functional groups, whereas bio-oil, pyrolysis gas and syngas were quantitatively analysed. The effect of temperature, steam-to-biomass ratio and fuel composition on carbon conversion, cold gas efficiency, energy recovery, reaction rate, gas composition and quality were determined and kinetic analysis was performed. When industrial wastes waste wood shavings and refused derived fuel were blended with grape husks and curls at ratios 30:70, upgraded fuels were produced. At 850 °C organic matter was almost completely converted to syngas upon steam gasification. A first-order kinetic model fitted the experimental results successfully, with activation energy values ranging between 54.3 kJ/mol and 143.5 kJ/mol. An increase in steam-to-biomass ratio from 0.5 to 3 resulted in a higher concentration of hydrogen in product gas, while excess steam enhanced hydrogen yield up to 74%. Energy recovery from all fuels was high, cold gas efficiency reached a value of 66% and the higher heating value of syngas ranged between 9.6 and 11.4 MJ/m3.

Energy Recovery from Solid Waste Materials via a Two-step Gasification Process by Steam

Different biomass waste materials were gasified by steam up to 850 °C, employing a fixed bed reactor and a thermal analysis-mass spectrometer unit. Raw fuels and biochars were characterized, while bio-oil, pyrolysis gas and syngas were quantitatively analyzed. Gasification efficiency and energy potential of all solid, liquid and gaseous products were determined. The higher heating value of biochar particles, bio-oil and pyrolysis gas ranged between 16-28 MJ/kg, 21.4-33.4 MJ/kg and 10.2-13.5 MJ/m3, respectively. Organic matter was almost completely converted to syngas and lower quantities of CO2, CH4 and hydrocarbons upon steam gasification, with H2 yield reaching values up to 60%. The higher heating value of syngas produced varied between 9.8 MJ/m3and 11.4 MJ/m3.

H2-rich syngas production from air gasification of date palm waste: an experimental and modeling investigation

The energy generation from renewable sources is in prime focus not only oil-importing countries as well as oil-exporting countries. This study aims to probe the energy generation (syngas) from Saudi Arabian date palm fronds through air gasification in a downdraft fixed-bed system. In addition, an equilibrium process simulation model was developed using Aspen Plus, and predicted results were compared with experimental results. Furthermore, the mass and energy flows of the system were also analyzed. In parametric study, the impact of temperature (600–900 °C), particle size (2–6 mm), and air flowrate (1–4 l/min) were investigated on syngas composition and gasification performance parameters higher heating value, gas yield, carbon conversion efficiency, and cold gas efficiency. The results indicate that H2 concentration was enhanced with the rise of temperature and particle size from 12.12 to 26 vol.% and 26.02 to 26.89 vol.% respectively. The enrichment of H2 concentration was due to the activation of endothermic reaction and methane-reforming reaction as CH4 was dropped up to 12.6 vol% with increased temperature. The higher heating value of syngas, carbon conversion efficiency, and cold gas efficiency have shown an increasing profile with increased temperature and air flowrate. The gas concentration profile obtained from the simulation model found good agreement with the experimental results. The energy analysis shows that the process is highly energy consuming, and most of the energy waste is in the form of condensate that could be potentially utilized. This study will be helpful for researchers and commercial enterprises to produce syngas from Saudi Arabian date palm fronds.

Predicting the higher heating value of syngas pyrolyzed from sewage sludge using an artificial neural network.

Sludge pyrolysis is a complex process including complicated reaction chemistry, phase transition, and transportation phenomena. To better evaluate the use of syngas, the monitoring and prediction of a higher heating value (HHV) is necessary. This study developed an artificial neural network (ANN) model to predict the HHV of syngas, with the process variables (i.e., sludge type, catalyst type, catalyst amount, pyrolysis temperature, and moisture content) as the inputs. In the first step, through optimizing various sets of parameters, a three-layer network including 8 input neurons, 15 hidden neurons, and 1 output neuron was established. Then, in the second step, an ANN model has been successfully used to predict the HHV of syngas, with a fitting correlation coefficient of 0.97 and a root mean square error (MSE) value of 14.62. The relative influence of input variables showed that the pyrolysis temperature and moisture content were the determining factors that affected the HHV of syngas. The results of optimization experiments showed that when temperature was 895°C and the moisture content was 45.63wt%, the highest HHV can be obtained as 438.22kcal/m3-N. Moreover, the ANN model showed a higher prediction accuracy than other models like multiple linear regression and principal component regression. The model developed in this work may be used to predict the HHV of syngas using conventional operational parameters measured from in situ experiments, thus further providing predictive information for the use of syngas as energy and fuel.

Thermochemical Conversion of Napier Grass for Production of Renewable Syngas

Fuel resource diversification is a global effort to deviate from non-renewable fossil fuels. Biomass has been identified as an alternative solid biofuel source due to its desirable properties and carbon neutrality. As reported in the literature, biomass can positively contribute towards combating climate change while providing alleviation for energy security issue. As part of efforts to diversify biomass resources, this work intends to explore the potential of Napier grass, one type of energy crop, for the production of renewable syngas via gasification. This energy crop is originally from Africa, which is highly productive with low cost (40 tonnes per year per hectare). Limited studies were conducted to analyze the potential of such an energy crop as a fuel source, which is the subject of this work. In order to analyze the full potential of such energy crop, the physical and chemical characteristics of this biomass was first analyzed. To determine the productivity of syngas from this biomass, fluidized bed gasifier was used in this work. The effects of gasification process parameters (i.e., equivalence ratio and temperature) on product yield and producer gas compositions were examined. Besides, the effects of equivalence ratio towards higher heating value of syngas and carbon conversion efficiency were analyzed. Based on the ultimate analysis results, the molecular formula of Napier gas was CH1.56O0.81N0.0043. Meanwhile, the higher heating value of such biomass was determined as 16.73 MJ/kg, which was comparable to other biomasses. It is noted that in this work, the volatile matter was determined as 85.52% and this promoted gasification process remarkably. The dynamics of the reactions involved were observed as a significant variation in product yield and biogas components were recorded at varying equivalence ratio and gasifier operating temperature.

Effect of particle size and temperature on gasification performance of coconut and palm kernel shells in downdraft fixed-bed reactor

Gasification of coconut shell (CS) and palm kernel shell (PKS) is conducted in a batch type downdraft fixed-bed reactor to evaluate the effect of particle size (1–3 mm, 4–7 mm, and 8–11 mm) and temperature (700, 800, and 900 °C) on gas composition and gasification performance. The response surface methodology integrated variance-optimal design is used to identify the optimum condition for gasification. Gas composition, which is measured using the biomass particle size of 1–11 mm at 700–900 °C, are 8.20–14.6 vol% (H2), 13.0–17.4 vol% (CO), 14.7–16.7 vol% (CO2), and 2.82–4.23 vol% (CH4) for CS and 7.01–13.3 vol% (H2), 13.3–17.8 vol% (CO), 14.9–17.1 vol% (CO2), and 2.39–3.90 vol% (CH4) for PKS. At similar conditions, the syngas higher heating value, dry gas yield, carbon conversion efficiency, and cold gas efficiency are 4.01–5.39 MJ/Nm3, 1.50–1.95 Nm3/kg, 52.2–75.9%, and 30.9–56.4% for CS, respectively, and 3.82–5.09 MJ/Nm3, 1.48–1.92 Nm3/kg, 59.0–81.5%, and 33.0–57.1% for PKS, respectively. Results reveal that temperature has a greater role than particle size in influencing the gasification reaction rate.

Gasifying agents type at lower temperature effect on bubbling fluidised bed gasification for low rank coal

Oxygen and steam as gasifying agents are preferred for gasification process compared to air due to the production of higher heating value of syngas and lower contents of diluents. Lower operating temperature is required for low rank coal (LRC) gasification process. This is because, carbon conversion will occur faster with high reactivity of LRC. Ash agglomeration formation is also prevented at lower operating temperature. Hydrodynamics of bubbling fluidisation and gasification process are expected to be affected with different gasifying agents and operating temperature. Computational fluid dynamics (CFD) method was used to select suitable superficial velocity for bubbling fluidised bed (BFB) simulation and explore the effects of different gasifying agents at a lower operating temperature. The model was validated with theoretical values and superficial velocities of three to four times the minimum velocity (3~4Umf) were selected due to its best uniform bubbling fluidisation. Different gasifying agents will produce different bubbling patterns which relates to the density and viscosity of the gasifying agents. Many and faster moving bubbles were produced when using oxygen and air at 1,073 K while no changes is detected when using steam. This concludes that air and oxygen as gasifying agents give higher effect to the bubbling hydrodynamics compared to selection of steam as gasifying agent.

Gasifying agents type at lower temperature effect on bubbling fluidised bed gasification for low rank coal

Oxygen and steam as gasifying agents are preferred for gasification process compared to air due to the production of higher heating value of syngas and lower contents of diluents. Lower operating temperature is required for low rank coal (LRC) gasification process. This is because, carbon conversion will occur faster with high reactivity of LRC. Ash agglomeration formation is also prevented at lower operating temperature. Hydrodynamics of bubbling fluidisation and gasification process are expected to be affected with different gasifying agents and operating temperature. Computational fluid dynamics (CFD) method was used to select suitable superficial velocity for bubbling fluidised bed (BFB) simulation and explore the effects of different gasifying agents at a lower operating temperature. The model was validated with theoretical values and superficial velocities of three to four times the minimum velocity (3~4Umf) were selected due to its best uniform bubbling fluidisation. Different gasifying agents will produce different bubbling patterns which relates to the density and viscosity of the gasifying agents. Many and faster moving bubbles were produced when using oxygen and air at 1,073 K while no changes is detected when using steam. This concludes that air and oxygen as gasifying agents give higher effect to the bubbling hydrodynamics compared to selection of steam as gasifying agent.

Influence of Solids Circulation Flux on Coal Gasification Process in a Pressurized High-density Circulating Fluidized Bed

The coal gasification behaviors in the pressurized high-density circulating fluidized bed under various solids circulation fluxes were studied with the CFD method, which combines the two-fluid model and coal gasification reactions represented by the chemical percolation devolatilization and the MGAS models. The numerical method was validated with two experimental cases, and detailed distributions of gas species and temperature in the riser were illustrated to understand the gasification process. To fully understand the influence of solids circulation flux on the gasification behavior, a series of cases were simulated with the solids flux varying gradually from 260 to 1010 kg/m2s, and the composition and quality of syngas were compared between various cases. The higher heating value of syngas firstly increased and then decreased with the increase of solids flux, and it reached the highest value around 480 kg/m2s. The influence of solids flux on gasification process was further analyzed through the contours of temperature, solids concentration, and gas composition in the riser.

Effect of limestone catalyst on co-gasification of coconut fronds and wood chips

Biomass energy via gasification is an attractive substitute of fossil fuels. The distribution of biomass on the earth is scattered, so transportation and collection of biomass complicates the supply of biomass especially when the gasification rely on one type of biomass. Therefore, cogasification of different biomass is proposed as a potential solution for interruption-free gasification. Beside, unwanted by-products such as tar that cause blockage in downstream equipment can be minimized through the use of catalyst in gasification to accelerate tar reforming process. In this study, catalytic co-gasification of blended feedstock of 70% wood chips and 30% coconut fronds was carried out in a downdraft gasifier using limestone as primary catalyst. The effects of catalyst loading (0%, 30%, 50%, and 70% w/w) on syngas composition, gas yield, carbon conversion efficiency and heating value of syngas were investigated. The results showed that at 50% biomass to catalyst ratio, maximum H2 content of 11.39%, CO of 17.88%, carbon conversion efficiency of 69.49%, gas yield of 1.68 Nm3/kg and higher heating value of syngas 5.11 MJ/Nm3 were achieved. Higher catalyst loading (70%) blocked the air passage, which caused poor gasification. No more than 50% catalyst suggested for stable co-gasification operation.

Downdraft Co-gasification of Oil Palm Frond with Other Oil Palm Residues: Effects of Blending Ratio

As the largest amount of biomass residues produced from the palm oil industry, the oil palm frond (OPF) is a promising solid fuel resource for gasification. However, the difficulty in processing OPF into solid fuel may affect the solid fuel production rate and consequently the gasifier operation. To ensure a continuous gasifier operation unaffected by the shortage of OPF fuel, empty fruit bunch (EFB), palm mesocarp fiber (PMF) and palm kernel shell (PKS) were introduced as a pairing fuel with OPF for co-gasification. The potentials of the fuel mixes and the effects of the fuel blending ratio on syngas higher heating value, specific syngas yield, carbon conversion efficiency and cold gas efficiency were studied. The experiments concluded that all fuel mixes of all blending ratios satisfied all the syngas quality indicator requirements and that all the tested fuel mixes can be utilized for downdraft co-gasification to produce results similar to the downdraft gasification of 100% OPF.

Modeling and Parametric Study for Maximizing Heating Value of Gasification Syngas

There are a number of experimental and theoretical studies on the energy conversion of oil palm derivative biomass. Moreover, the potential of this abundant biomass residue for renewable energy in major producing countries in Southeast Asia has been well documented. In this study, the results of an equilibrium model of downdraft gasification of oil palm fronds (OPF), developed using the Aspen Plus chemical process simulator software, and its validation are presented. In addition, an optimization of the major output parameter of importance (i.e., the higher heating value of syngas) with respect to the main operating parameters (i.e., temperature, equivalence ratio (ER), and moisture content) was performed. The response surface method (RSM) was used to determine the mathematical relationship between the response of interest, which was the heating value of syngas, and the operating conditions. This method was used to further determine the conditions that would lead to optimum higher heating values of syngas. Optimum values identified by RSM were: oxidation zone temperature of 1000 °C, moisture content in the range of 4%, and an equivalence ratio of 0.35. These optimum operating conditions and the corresponding higher heating value of syngas were found to correspond with the experimental results.

SIMULASI PENGARUH UKURAN PARTIKEL DAN EQUIVALENCE RATIO DALAM PROSES GASIFIKASI TANDAN KOSONG KELAPA SAWIT

In this study, a simulation for gasification process of oil palm empty fruit bunches waste (OPEFB) using a fixed bed gasifier (throat downdraft) by varying the particle size of OPEFB and equivalence ratio (ER) was investigated. The rate of fuel consumption was 10 kg/h with air as the oxidizing medium and 1 hour process time for 1 batch. Simulation was performed with two-dimensional approach (2D) using Computational Fluid Dynamics (CFD) ANSYS FLUENT 14 software. Simulation results show that ideal amount of equivalence ratio (ER) for gasification process of OPEFB pellets with diameter (φ) of 6 mm and 8 mm is 0.1 ≤ ER ≤ 0.2. ER variation affects the higher heating value of syngas (HHV), the carbon efficiency (ηC), gasification efficiency and temperature distribution in the gasification reactor. Variations in particle size did not have a significant effect in the gasification process.Keywords: CFD, OPEFB gasification, particle size, equivalence ratio

Integration of biomass/steam gasification with heat recovery from hot slags: Thermodynamic characteristics

Herein the thermodynamics of an emerging strategy, biomass/steam gasification integrated with heat recovery from hot slags, were systematically investigated following the principle of minimum Gibbs free energy to simultaneously deal with the issues of biomass disposal in agricultural sector and heat recovery in steel industry. Not only the syngas yields but also the influence of slags were identified including blast furnace slags (BFS) and steel slags (SS). The results demonstrated that, from viewpoint of maximization of H2 production and higher heating value (HHV) of syngas, the optimum gasification temperatures for biomass and sludge were 1000 °C and 1100 °C, respectively. Compared to BFS, SS remarkably increased the H2 production and syngas HHV at lower temperatures; while for polluted gas releases including NH3, NO and NO2, BFS showed more prominent influence. The present results thus provided significant clues for syngas yield optimization and pollution mitigation toward application of this novel route.

Mathematical modeling of extra-heavy oil gasification at different fuel water contents

In this study, a kinetic model for extra-heavy oil gasification has been developed. It is a zero dimensional, steady state model based on global reaction kinetics and is capable of predicting performance parameters of the process. Effects of parameters, including fuel water content and equivalence ratio on tar yield, gasification temperature and performance parameters such as syngas higher heating value (HHV), carbon conversion efficiency (CCE), cold gas efficiency (CGE) have been discussed. The results indicate that the higher equivalence ratio is more favorable for carbon conversion and tar cracking; however, it lowered gas caloric value and cold gas efficiency. It is also found that the higher carbon conversion and lower tar yield are possible at higher fuel water content. The model is validated by experimental and thermodynamic data and found relatively to be in good agreement.

Gasification performance of coals using high temperature air

MEET ( Multi-staged Enthalpy Extraction Technology) system is a new coal/wastes-fired power generation system. In order to establish the MEET system technology, a demonstration plant of commercial scale, MEET-II, was installed. The capacity of the MEET-II is 2 t/day of coal of 4 t/day of RDF. MEET-II consists of a pebble bed slagging-gasifier, a high temperature air generator, and a high temperature air combustion boiler. Gasification with high temperature air results in higher heating value of syngas. Cleaned-up syngas is used as a fuel for the boiler as well as for preheating air up to 1000 °C. Combustion and gasification tests at the MEET-II were conducted using pulverized coal as a fuel. Combustion experiments demonstrated almost complete char combustion with a short residence time, and gasification experiments demonstrated targeted calorific value of syngas, 1000 kcal/m N 3.