Gas Lower Heating Value Research Articles

Production of high calorific value hydrogen-rich combustible gas by supercritical water gasification of straw assisted by machine learning

This article reveals the basic laws of straw supercritical water gasification (SCWG) and provides basic experimental data for the effective utilization of straw. The paper studied the impact of three operational conditions on the production of high-calorific value hydrogen-rich combustible gases through SCWG of straw within a quartz tube reactor. The findings reveal that elevated reaction temperatures, extended residence times, and reduced feedstock concentrations favor the SCWG of straw. When combustible gas contains carbon dioxide, the maximum low heating value (LHV) of the gas is 21 MJ/Nm3. Upon removing carbon dioxide, the LHV of the gas reached 38 MJ/Nm3. Subsequently, a machine learning (ML) model was developed to forecast gas yield and LHV during the SCWG process. The results demonstrate that the model exhibits robust generalization capabilities. ML can be extensively applied to forecast biomass SCWG processes across various operational conditions.

Simulation of waste tire gasification in bubbling fluidized bed by Aspen: Contribution ratio analysis

Waste tire gasification in a bubbling fluidized bed is a promising thermochemical conversion technology that not only utilize waste tire but also produce energy. To reveal the gasification performance of waste tire in a bubbling fluidized bed, two Aspen models were developed to simulate the effect of gasification agent types (such as air, steam, carbon dioxide and their mixtures), considering chemical reactions that reached thermodynamic equilibrium (CRTM) or were controlled by kinetics (CRK). The simulated gas compositions (H2, CO, CO2 and CH4) and lower heating value (LHV) were compared with experimental data under various operating conditions. The results showed that CRK model exhibited much better performance than the CRTM model. These two models were further utilized to analyze the effect of gasification agent type on gas composition and LHV. The contribution ratios of different chemical reactions were detailed analyzed, such as hydrogen combustion, carbon monoxide combustion, methane combustion, carbon combustion, steam gasification, water gas shift reaction and carbon dioxide gasification. The established Aspen model for waste tire gasification in a bubbling fluidized bed could be served as a guideline for selecting operation conditions to achieve high hydrogen composition, carbon conversion, and gas yield.

Predicting the NOx emissions of low heat value gas rich-quench-lean combustor via three integrated learning algorithms with Bayesian optimization

Predicting the NOx emissions of low heat value gas rich-quench-lean combustor via three integrated learning algorithms with Bayesian optimization

Solid recovered fuel gasification in sliding bed reactor

This study examines a solid recovered fuel gasification process in the context of a regional, clean energy supply from an affordable source. The examination of this approach was performed under various equivalence ratios and load regimes. A unique cross/updraft gasification reactor with a fixed (sliding) bed over the circular grate with tangential gasification media intake was utilised. This technology is a perspective in waste-to-energy and waste-to-materials production. The investigated parameters included producer gas quality and purity, overall conversion efficiency and char material yield. It was found that a low material load is very beneficial in terms of gas purity and conversion efficiency, reaching up to 93%. Also, the formation of tar compounds was measured as low as 0.7 g/m3. However, when the equivalence ratio parameter was 0.14, the gas's lower heating value was only 2.4 MJ/m3. Also, a lower heating value equal to 5.0 MJ/m3 was reached in a low-efficiency regime (48%) when the fuel load was more significant (48.5 kg/h), and the equivalence ratio was only 0.04. The low tar content suggests a very clean process. Also, the material valorisation in the form of char is beneficial as this carbon-rich material no longer has a waste character and can be utilised in many fields.

Experimental study on combustion and thermal characteristics of impinging premixed flames for low heating value gas (LHVG) fuels

The combustion and thermal characteristics of impinging premixed flames for low heating value gases (LHVGs) composed of methane, propane, and nitrogen are experimentally investigated. For the experiment, a combustor with an impingement plate is used to study the flame stability regions based on flame shapes and visualize OH radical distribution. The OH radical distribution is observed via OH* chemiluminescence and OH planar laser-induced fluorescence (OH-PLIF). Thermal characteristics are investigated by measuring the temperature distribution of the plate and the heat transfer rate into the cooling water. The results show that the flame stability region narrows as the heating value of the fuels decreases. Also, as the equivalence ratio increases (i.e., »1), the flame stability region is expanded. The OH radical intensity of LHVGs is observed to be lower than that of methane. The OH-PLIF images show where OH radicals are more distributed in the flame. The temperature distribution of the plate is determined by the flame shape according to the heating value, and the heat transfer rate into the water has a linear tendency to the fuel's thermal power. Based on these findings, LHVGs can be utilized without system improvement within the flame stability range in the impinging flame system.

Experimental research on hydrogen-rich syngas yield by catalytic biomass air-gasification over Ni/olivine as in-situ tar destruction catalyst

This research focuses on investigating the air-gasification process of pine sawdust using a fluidized bed unit with Ni/olivine as an in-situ tar destruction catalyst. The goal is to eliminate tar production and obtain high-quality synthesis gas. Consequently, the effects of reaction conditions and catalyst properties on the producer gas composition, the lower heating value (LHV) of the yielded synthesis gas (syngas), char conversion efficiency (CCE), and cold gas efficiency (GE) are comprehensively explored. The conclusions indicate that higher temperatures favor the H2 and CO production and result in an evident decrease of CH4 and C2H4, which is responsible for the increasing gas LHV. The tar capture efficiency (TCE) increases by increasing the equivalence ratio (ER); however, a reverse trend obtains for gas LHV because of a significant decline in the combustible gas contents. The results also reveal that when using Ni/olivine as the bed material, GE reaches an optimum value of 72.4% at equivalence ratio (ER) of 0.21 and then lowers down with a further increase in ER to 0.39 due to the enhanced char combustion reaction. The tar yield (1.3–6.8 g/Nm3) significantly decreases with temperature, whereas H2 concentration (14.1–29.8 vol %), CCE (51.3–89.1%), GE (44.8–86.1%) and gas LHV (5.13–7.19 MJ/Nm3) promote at high temperature. Compared to raw-olivine, the lower heating value (LHV) of the producer gas slightly increases under the same conditions (T = 800 °C and ER = 0.21) when the bed material is Ni/olivine. The conclusions obtained help to provide reliable theoretical guidance for operating condition optimization of biomass catalytic air-gasification with Ni/olivine as bed material in a fluidized bed reactor.

Predicting NOx Distribution in a Micro Rich–Quench–Lean Combustor Using a Variational Autoencoder

Micro gas turbines are widely used in distributed power generation systems. However, the combustion of gas turbine combustors produces a large amount of nitrogen oxides (NOx), which pollute the environment and endanger human life. To reduce environmental pollution, low-emission combustors have been developed. In recent years, there has been an increasing focus on the use of low-heat-value gas fuels, and it is necessary to study the NOx emissions from low heat value gas fuel combustors. Data-driven deep learning methods have been used in many fields in recent years. In this study, a variational autoencoder was introduced for the prediction of NOx production inside the combustor. The combustor used was a micro rich-quench-lean combustor designed by the research group using coal bed gas as a fuel. The internal NO distribution contour was obtained as the dataset using simulation methods, with a size of 60 images. The model architecture parameters were obtained through hyperparameter exploration using the grid search method. The model accurately predicted the distribution of NO inside the combustor. The method can be applied in the prediction of a wider range of parameters and offers a new way of designing combustors for the power industry.

Modelling and performance analysis of power system in gas engine-driven heat pump

The gas engine-driven heat pump (GHP) is an energy-saving and environmentally friendly technology. In previous studies, there were few dynamic quantitative analyses of gas engines’ exergy efficiency (ηex,e) and waste heat recovery (Qrec), which are essential but not easy to achieve. This paper establishes the multivariate regression equations of related physical quantities according to the manufacturer or experimental data. Based on the above, the effect of the engine’s two-dimensional (2-D) factors on thermal efficiency (ηe), ηex,e, and Qrec are analyzed, respectively. Since the scroll compressor manufacturer could not provide data and selection software, a general modelling method was proposed based on experimental data and gain the quantitative analysis of mechanical (ηm) and exergy efficiency, which is also less in previous studies but essential. In addition, the primary performance of GHP is also analyzed through the coupled model of the power system. The main results show that: ηe and Qrec are positively correlated with the engine’s load, while ηex,e is the contrary. Using a higher low heating value (LHV) gas can increase ηe and Qrec by 3.38 % and 1.12 kW, respectively, compared with a lower one. The ηex,sc and ηm of the compressor are positively correlated with the heat pump load, varying in 55.51–77.12 % and 68.20–97.52 %, respectively. In summary, the power system model established in this paper can supplement the lack of quantitative analysis of main parameters in the previous GHP, and the modelling method of the compressor is also generally applicable to other heat pump systems.

Numerical Evaluation of Biochar Production Performance of Downdraft Gasifier by Thermodynamic Model

A theoretical evaluation of the biochar production process using a biomass gasifier has been carried out herein. Being distinguished from the previous research trend examining the use of a biomass gasifier, which has been focused on energy efficiency, the present study tries to figure out the effect of biochar production rate on the overall process performance because biochar itself has now been given a spotlight as the main product. Biochar can be utilized for agricultural and industrial purposes, along with the benefit of climate change mitigation. A thermodynamic model based on chemical equilibrium analysis is utilized to demonstrate the effect of biochar production rate on the producer gas characteristics such as gas composition, LHV (lower heating value) and cold gas efficiency. Three gasifier models using chemical equilibrium model are reconstructed to simulate biochar-producing gasifiers, and seven kinds of biomass are considered as feed material. Depending on the assumptions applied to the models as well as the biomass types, the results of the simulation show a large variance, whereas the biochar yield rate increases. Through regression analysis with a generalized reduced gradient optimization method, simplified equations to estimate the cold gas efficiency (CGE) and LHV of producer gas of the biochar production process were derived as having six parameters of biomass LHV, fractions of ash, carbon and water, reduction zone temperature, and biochar yield rate. The correlation factors between the thermodynamic model and the regression model are 96.54% and 98.73% for the LHV of producer gas and CGE, respectively. These equations can supply the pre-estimation of the theoretical maximum performance of a planning biochar plant.

Agricultural Crop Residue Based Biomass in India: Potential Assessment, Methodology and Key Issues

Concerns of climate change, depletion of fossil fuels and energy crisis have motivated the world to explore the alternative sources of energy. Renewable sources such as biomass, solar, wind and small hydro are the best alternatives to meet the increasing energy demand. In the present paper, bio energy potential of 12 agricultural crops cultivated in India has been estimated based on gross crop residue (GCR), surplus crop residue (SCR) and crop residue ratio (CRR). Crop statistics and model of GCR and SCR reveal that India produces 1043.24 million tonnes gross crop residue annually, out of which reasonable amount is consumed as cattle feeding, animal bedding, organic fertilizer, fuel for heating and cooking. Additionally, 356.7 MT biomass is available as surplus crop residue on annual basis that can directly be used for power production. The potential assessment of available surplus crop residue has been estimated as 53,767 MWe per year. Different biomass gasifier technologies are studied and compared based on ash melting temperature, fuel specifications, maximum fuel moisture content, gas lower heating value, and admissible power production. Various key issues (technical, economical, social and environmental) have also been discussed to cover the use of crop residue biomass for power generation.

Effect of hydrogen addition on flame stability and structure for low heating value coaxial nonpremixed flames

ABSTRACT An investigation of effect of hydrogen addition on flame stability and structure i.e. combustion characteristics of low heating value gases (LHVGs) that consist of methane, propane, nitrogen is carried out experimentally and numerically. For the experiment, a coaxial non-premixed jet-type combustor and Planar Laser Induced Fluorescence (PLIF) system are used to evaluate the flame stability limit and flame shapes and visualize OH radical distribution, respectively. For the numerical analysis of hydrogen added LHVGs, the calculation using the FLUENT software with decreased GRI 3.0 mechanism is performed to study the 2D flame temperature distribution and radial flame structure. As a result, the flame length of LHVGs reduces as hydrogen is added. CH* and OH* radicals visualized by chemiluminescence system are distributed closer to the nozzle as hydrogen is added to LHVGs. OH-PLIF images show that OH intensity of LHVG 6000 is higher with hydrogen addition. The flame stability of LHVGs is improved with hydrogen addition. As for the numerical result, the reduction of flame length and width of LHVG 6000 are predicted with adding the hydrogen.

Urea assisted pyrolysis of corn cob residue for the production of functional bio-oil

Corn cob (CC) biomass nitrogen-enriched pyrolysis was carried out in a fixed bed with urea atmosphere at 300–600 °C, and formation mechanism of N-containing species was explored in depth. Results showed that urea assist pyrolysis greatly increased bio-oil and gas yields. H2 yield increased sharply to (19.3 vol%) and became the main composition at higher temperature, while CH4 and CO yield deceased, and the lower heating value of gas reached. For bio-oil, the content of phenols (main compositions) and N-containing species increased significantly, and the maximums reached 47.6% and 23.7%, respectively. While that of acetic acid, O-containing species (aldehydes/ketones/furans/esters) and aromatics decreased largely accordingly. For biochar, nitrogen content increased. The introduction of ammonia source can achieve the transformation of carbonyl compounds to nitrogen containing compounds. Possible reaction pathways of biomass N-enriched pyrolysis were proposed based on products evolution. In conclusion, biomass N-enriched pyrolysis could obtain high-valued N-containing chemical species and functional bio-char.

Predicting the Nox Emissions of Low Heat Value Gas Rql Combustor Via Three Integrated Learning Algorithms with Bayesian Optimization

Predicting the Nox Emissions of Low Heat Value Gas Rql Combustor Via Three Integrated Learning Algorithms with Bayesian Optimization

Effects of Gasification Temperature and Equivalence Ratio on Gasification Performance and Tar Generation of Air Fluidized Bed Gasification Using Raw and Torrefied Empty Fruit Bunch

This paper presents gasification performance study and tar generation at different gasification temperature and equivalence ratio using air fluidized bed gasification process. Empty fruit bunch (EFB) is selected as feedstock where two types of EFB were used which are raw EFB and EFB undergo torrefaction process as pretreatment. Experimental results show the synthesis gas yield, lower heating value (LHV), cold gas efficiency (CGE) and tar generation are steadily increased for both feedstock when gasification temperature is increased from 700 to 900°C. When ER is increased from 0.26 to 0.33 at fixed gasification temperature of 900°C, all gasification performances except LHV show an increment trend. Torrefied EFB shows superior performance in terms of producing more synthesis gas and better LHV compared to raw EFB. However, tar generated from torrefied EFB is higher than raw EFB. Based on tar component analysis, it has been found that 7 tar components are detected where all of tar components are classified as tertiary polycyclic aromatic hydrocarbons (PAHs) group for both feedstocks. Based on tar analysis, naphthalene is the most produced tar components obtained from gasification of raw and torrefied EFB.

Techno-economic analysis of producing low heating value underground coal gasification gas in Indonesia

Indonesia is currently reviewing the use of underground coal gasification (UCG) technology to utilize deep-seated coal. UCG may exploit the coal deposit that is not feasible for open-pit mines due to its great depths. In this study, the UCG plant in two coal mines, the Kideco Jaya Agung (KJA) and the Indominco (IMM) coal mines, will be compared their economics in producing low heating value gas with a capacity of 170,000 MJ/hour. The UCG plants implement the linking vertical well (LVW) technique combined with reverses combustion linking (RCL). The discounted cash flow (DCF) method is used for financial analysis to determine the minimum selling price of UCG low heating value gas. The study aims to understand the economic feasibility of applying UCG technology to Indonesia’s different characteristics of coal deposits. The results show the minimum prices of the low heating value UCG gas of KJA and IMM UCG plants are USD 3/MMBTU and USD 3.57/MMBTU, respectively. The operating cost of the IMM UCG is higher than that of the KJA UCG plant due to its thinner and deeper coal seams.

Evaluation on energetic and economic benefits of the coupling anaerobic digestion and gasification from agricultural wastes

The sustainability of the anaerobic digestion (AD) plant was closely related to the disposal of digestate and enhancement of energy recovery. Aiming to promote this, coupling AD and digestate gasification (AD-gasification) was proposed and evaluated for a large-scale AD plant. Firstly, characterization of the solid digestate was measured. Secondly, air gasification of the solid digestate was performed. Finally, two scenarios aiming at enhancing energy recovery as electricity or gas were investigated.Superior C content (50.14 wt%), H/C (1.57) and O/C (0.62) molar ratios and lower heating value (LHV) of solid digestate (18.01 MJ/kg) made it propitious to gasification. Air gasification of digestate at 800 °C with ER = 0.26 resulted in the optimal LHV of producer gas (6.35 MJ/Nm3) and cold gas efficiency (CGE, 66.99%). In the biomass-to-electricity scenario, the excess of heat from the CHP system in the AD plant was sufficient to dry the solid digestate. Compared with the stand-alone AD plant, the total electricity from the coupling system increased about 11%. In the biomass-to-gas scenario, the gas income increased by 14% when the initial solid digestate was naturally air-dried to a water content of 50%. This research would provide technical guidance for the sustainability of the AD industry.

Energy Recovery via Thermal Gasification from Waste Insulation Electrical Cables (WIEC)

The recovery of noble metals from electrical wires and cables results in waste materials such as polyvinyl chloride (PVC) and polyethylene (PE), that is, waste insulation electrical cables (WIEC), which have been processed by gasification for energy recovery. This study focused on the effect of blending the ratio of WIEC on the gasification feedstock composition and the lower heating value (LHV) of produced syngas, through controlled tests and tests under different loads on the generator. The controlled gasification experiments were carried out at blending ratios between pine biomass and WIEC of 90:10, 80:20, and 70:30 and with pine biomass only (100%). For the loads gasification, the experiments were carried out at a blending ratio of 80:20. The controlled experimental results presented that the highest hydrogen content, approximated 17.7 vol.%, was observed at a blending ratio of 70:30 between pine biomass and WIEC and the highest LHV of syngas was observed at a blending ratio of 90:10, with 5.7 MJ/Nm3. For the load gasification experiments, the results showed that the highest hydrogen content was obtained with a load of 15 kW in the generator, approximately 18.48 vol.% of hydrogen content, and the highest LHV of synthesis gas was observed during the 5 kW test, with 5.22 MJ/Nm3. Overall, the new processing of waste insulation electrical cables using a downdraft gasification reactor demonstrates great promise for high quality syngas production.

Hydrogen gas yield and trace pollutant emission evaluation in automotive shredder residue (ASR) gasification using prepared oyster shell catalyst

This work examines the hydrogen gas yield and trace pollutants partitioning in automobile shredder residue (ASR) catalytic gasification by fixed bed and fluidized bed gasifier with controlling at equilibrium ratio (ER) 0.2, temperature 900 °C, and 5%–15% prepared catalyst addition. Oyster shell (OS) is a valuable resource due to its higher calcium content that it could prepare as a catalyst for enhancing the hydrogen production in ASR gasification. In the case of the fixed bed gasifier experiments, the highest lower heating value (LHV) and syngas production were found at 900 °C and 10% OS catalyst addition. The maximum H2 and CO composition were 6.57% and 5.97%, respectively. The LHV of syngas was approximately 4.43 MJ/Nm3. The fluidized bed gasifier could provide a good ASR decomposition and heat transfer behavior. The syngas yield results indicated the maximum H2 and CO composition were 12.12% and 10.59%, respectively. It was obviously showed that the syngas production and energy conversion efficiency were enhanced by applying fluidized bed gasifier. The maximum produced gas LHV was 10.77 MJ/Nm3 as well as the cold gas efficiency (CGE) of produced gas was 71.62%. On the other hand, the volatile sulfur and chlorine speciation formed in ASR gasification were mainly partitioned in the solid and/or liquid phase. It implied that tested OS catalysts could inhibit the volatile sulfur and chlorine speciation emission in the produced gas as well as enhance the produced gas quality. In summary, this research could provide basic insight into enhanced syngas production and quality in ASR catalytic gasification using the prepared OS catalyst.

Conversion of diesel locomotive engines to operation on natural gas motor fuel

This research paper contains the results of analysis of a range of variation of the lower heating value of gas during the process of conversion of diesel locomotive engines to operation on natural gas as motor fuel. It was demonstrated in this paper that the range of variation of the lower heating value at the various fields considered in it varied within the limits to 32.4%. A proposal was made to take into consideration the so-termed lower heating value of diesel fuel and natural gas when running diesel locomotive engines on liquid-gas fuel complementary to atmospheric conditions.

Optimization of oil palm empty fruit bunch gasification temperature and steam to biomass ratio using response surface methodology

An experimental work of empty fruit bunch gasification was conducted by using the bubbling fluidized bed to study the effect of the gasification temperature and steam biomass ratio (SBR) on the synthesis gas yield, Lower Heating Value (LHV) and Cold Gas Efficiency (CGE). Response Surface Methodology (RSM) was used to design the gasification experiment from the temperature range of 800 – 1000°C and SBR range of 0.5 – 1.5. Thirteen number of runs were generated based on Central Composite Design (CCD) with five replicated center points. Three regression models for predicting synthesis gas yield, LHV and CGE were developed and Analysis of Variance (ANOVA) was performed in this study. From ANOVA, the most influencing factor was gasification temperature which obtained higher F-value compared to SBR. The numerical optimization was also conducted in order to obtain the optimum condition to maximize the synthesis gas yield, LHV and CGE. From numerical optimization, gasification temperature of 800 °C and SBR of 1.14 were determined as the optimum condition which contributes to the maximum synthesis gas yield, LHV and CGE which are 1.25 Nm3/kg, 10.49 MJ/Nm3 and 90.72% respectively. The percentage error between the predicted and actual value of response variables was calculated and the error obtained lesser than 1%. Thus, it confirmed that the models obtained can be used to optimize the gasification of the empty fruit bunch.