Molecular hydrogen from organic sources in the deep Songliao Basin,P.R. China

Free hydrogen detected in the Songke-2 well (Songliao Basin, China) has a strong crustal contribution. Here we evaluate whether the source could be the organic matter in Lower Cretaceous coals and shales, and extend our findings regionally. We could establish the rapid growth of aromatic ring systems, forming hydrogen, methane and pyrobitumen, using high resolution mass spectrometry. Molecular hydrogen is generated after late hydrocarbon gas generation is complete, concluding at R_r = 5.0%. The kinetic parameters of molecular hydrogen formation were constructed by subtracting the hydrogen associated with hydrocarbon formation from the total hydrogen, as measured by extensive open system pyrolysis experiments. This new insight was achieved using a CH₄–H₂ stoichiometric balance. Generalised calculations indicate that the yield per unit rock volume closely resembles that of economic shale gas in the Barnett Shale, though storage in organic matrices is unlikely in this depositional setting. While the prolific generation of hydrogen from organic sources appears to be a reality in the Songliao basin, the free H₂ in the Songke-2 mudstream coming from this source must most likely have migrated into the basement rocks mainly from lateral equivalents of the Shahezi rather than from the drilled section itself.     

Study on the evolution of the chemical structure characteristics of high rank coals by simulating the ScCO2-H2O reaction

ABSTRACT

To study the influence of CO₂ on the structure of a coal reservoir during CO₂ geological storage-enhanced coalbed methane recovery (CO₂-ECBM), two high rank coals from the Qinshui basin were exposed to supercritical CO₂ (ScCO₂) and water for 240 h in a laboratory high-pressure supercritical geochemical reactor to simulate the reaction of ScCO₂-H₂O-coal under three burial depths. The changes in the chemical structure of the coals before and after reaction were evaluated by Fourier transform infrared spectroscopy (FTIR). The results show that the ScCO₂-H₂O treatment has a substantial influence on the coal structure, reducing the aromaticity and the degree of aromatic ring condensation, increasing the hydrocarbon-generating potential and improving the maturation level of the coals. The ScCO₂-H₂O system mainly affects the organic functional groups of coals through the chemical reactions: swelling effect, bond dissociation reaction, hydrolysis and substitution reaction. The results of peak fitting show that the ScCO₂-H₂O treatment can significantly reduce the intensities of the bands associated with in-plane -CH₂- vibrations and oxygenated groups (especially C-O groups), but increase the intensities of the aliphatic hydrocarbon and hydroxyl group bands. The changes in the functional group contents after the ScCO₂-H₂O treatment varied between the different rank coals. The effect of temperature and pressure on the functional group contents after reaction is complicated, and it is affected by the macromolecular structures of the raw coals and the sensitivities of the chemical reactions to temperature and pressure. However, there is a critical depth that provides the optimum influence of temperature and pressure on the structure of the organic matter in coal. This paper aims to provide a theoretical foundation for the study of the changes in the coal matrix structure during the long-term storage of CO₂ in coal seams.     

Comparison of staged combustion properties between bituminous coals and a low-rank coal; Fiber-shaped crystallized carbon formation,NOx emission and coal burnout properties at very high temperature

Previously, we developed a new-concept for a drop-tube furnace in order to investigate staged combustion properties for pulverized coals. Two high-temperature electric furnaces were connected in series. Coal was burnt under fuel-rich conditions in the first furnace, then, staged air was supplied at the connection between the two furnaces. In the present study, we investigated influence of burning temperature on NOx emission and combustion efficiency by using the furnace. The influence of the temperature differed between hv-bituminous coals and a sub-bituminous coal. For the hv-bituminous coals, combustion efficiency was improved when burning temperature in the fuel-rich region rose. When combustion efficiency was improved, NOx emission decreased. The NOx reduction reaction in the fuel-rich region was promoted by increasing the burning temperature in this region. On the other hand, NOx emission increased for the sub-bituminous coal when the temperature was higher than 1800 K. Usually, combustion efficiency was increased with burning temperature. However, combustion efficiency lowered for the sub-bituminous coal when burning temperature was higher than 1900 K. We observed the ash obtained by this temperature condition using Scanning Electron Microscope (SEM) and, Transmission Electron Microscope (TEM) and observed fiber shaped carbon. The difference in NOx properties was derived as a difference of hydrocarbon concentration. For low-rank coals (sub-bituminous or lignite), the hydrocarbon formation rate was smaller than that for hv-bituminous coals. When the hydrocarbon contribution to the NOx reduction reaction was large, NOx emission decreased with increasing burning temperature; however, hydrocarbon content in volatile matter was small for low-rank coals.     

Origin and Properties of Oltu Gemstone Coal

Abstract

This study focuses on the origin and properties of the Oltu gemstone or Oltustone. The Oltu gemstone known as ‘Black Amber’ is dull-bright black color, and is very low ash, high volatile matter, total sulfur and calorific value. Very high volatile matter content on a dry-ash free basis (66.52%) and non-agglomerating character imply that its coal rank is very low. The Oltu gemstone includes abundant organic (amorphous) matter and trace amounts of quartz and pyrite. Petrographic study indicated that pyrite and quartz generally finely disseminated the organic matter. Major and trace element data have low concentrations. The trace element concentrations fall within the range values for the most world coals, except for Bi that exceeds range values (0.1–0.5 μg/g) in most world coals. Petrographic observations on the polished briquette have shown that the gemstone was made of xylite including mainly textinite and corpohuminite, minor amounts of resinite and liptodetrinite. Mean values of random reflectance (%Rr) measurements on the textinite and corpohuminite are 0.23 and 0.30%Rr, respectively. These values indicate very low coal rank, in agreement with the volatile matter.     

The correlations of chemical property,alkali metal distribution,and fouling evaluation of Zhundong coal

The utilization of Zhundong coal has encountered severe ash-related problems principally due to its high-alkali feature. However, the evaluation of fouling tendency and correlations of chemical properties of Zhundong coals based on a large database has been seldom performed. The present work aimed to reveal the correlations of chemical properties, distributions of alkali and alkaline earth metals (AAEMs) and iron, and the fouling propensity of Zhundong high-alkali coals based on datasets of >250 samples. The fuel ratio of the majority (∼95%) of Zhundong coals lay in the range of 1.0–2.45. A quantified correlation between fuel ratio and volatile matter content was obtained. The ash composition of Zhundong coal gathered in a small area of the ternary diagram of Fe₂O₃-alkali metal-alkaline earth metal oxide components. The principal sodium of water-soluble form in Zhundong coals varied notably from 45% to 95%, more than half of the potassium was insoluble form, the majority (∼90%) of alkaline earth metals were in forms of ammonium acetate-soluble and HCl-soluble, and ∼67% of iron was HCl-soluble form. The quantitative correlations based on plentiful datasets could improve the comprehension of correlations among the coal chemical properties, fouling behaviors and its reaction activity.     

Movable injection point–based syngas production in the context of underground coal gasification

Underground coal gasification (UCG) has been proven as a viable technology for the generation of high calorific value syngas using deep mine coal seams. The use of multiple injection points/movable injection point method could be an alternate technique for efficient gasification of high ash Indian coals. In this context, the present study is focused on evaluating the heating value of syngas using a variety of gasifying agents such as pure O₂, air, humidified O₂, and CO₂-O₂ dual-stage gasification under movable injection method for high ash coals. It is found that the use of movable injection point method had significantly increased the heating value of the product gas, compared with the fixed point injection method. For high and low ash coal under pure O₂ gasification, the calorific value of syngas obtained using movable injection point is 123.2 and 153.9 kJ/mol, which are 33.5% and 24.3% higher than the syngas calorific value obtained using fixed injection point, respectively. Further, the air as a gasification agent for high ash coals had increased the gross calorific value of the syngas by 24%, using this technology. The results of high ash coal gasification using humidified oxygen at optimum conditions (0.027-kg moisture/kg dry O₂) and CO₂-O₂ gas had enhanced the syngas calorific value by 12.6% and 5%, respectively. Humidified O₂ and CO₂-O₂ gasifying agents produced a high-quality syngas with the calorific value of 190 kJ/mol, among the gasifying agents used. The experimental results had shown that the movable injection point method is found to be a better alternative for the generation of calorific value-enriched syngas using high ash-based Indian coals.     

Influence of calcium promoter on catalytic pyrolysis characteristics of iron-loaded brown coal in a fixed bed reactor

The Fe–Ca catalysts in catalytic pyrolysis of brown coals were studied to investigate the catalytic activity of the Fe–Ca in a fixed-bed reactor. Experimental results showed the maximum yields of the light aromatic hydrocarbons (LAHs) were 5.90 wt% (0.88 wt% of benzene, toluene and xylene ‘BTX’, 4.10 wt% of phenol and cresol ‘PC’ and 0.92 wt% of naphthalene) when the 1.5% Ca was added into 5% Fe-loaded brown coal. The yields of water and gas significantly reduced, the tar yield gradually increased with increasing heating rate. The characterization results indicated that when calcium promoter was impregnated with iron, Ca₂Fe₂O₅, CaO, Fe₂O₃ and α-Fe were formed on the surface of the coal char, Ca₂Fe₂O₅ and α-Fe decomposed polyaromatic tar, CaO and Fe₂O₃ accelerated water gas shift reaction to enhance the H₂ yield, the Fe₂O₃ and Ca₂Fe₂O₅ could be reduced to α-Fe by volatiles (C, CO and H₂) under high temperature catalytic pyrolysis. The synergistic effects between iron and calcium improved brown coal pyrolysis and the volatiles such as free radical fragments were further pyrolyzed, indicating that Fe–Ca catalysts inhibited α-Fe deactivation by tar and carbon deposition, thus promoting brown coal pyrolysis and formation of CO_x, H₂ and LAHs.     

Solar water heating potential in South Africa in dynamic energy market conditions

This paper is an attempt to determine the potential for solar water heating (SWH) in South Africa and the prospects for its implementation between 2010 and 2030. It outlines the energy market conditions, the energy requirements related to residential and commercial water heating in the country and the solar water heating market dynamics and challenges. It was estimated that 98% of the potential is in the residential sector and the rest in the commercial sector. The total thermal demand for 20 years for water heating was estimated to 2.2 EJ. A ‘Moderate SWH implementation’ will provide 0.83 EJ of clean energy until 2030 and estimated cost savings of 231 billion rand. For an ‘Accelerated SWH implementation’ these figures are 1.3 EJ and 369 billion rand. The estimated accumulated reduction of CO₂ emissions due to SWH can be as high as 297 Mt. The increased affordability of residential hot water due to SWH is an important social factor and solar water heating has a strong social effect.     

Study of devolatilization during chemical looping combustion of large coal and biomass particles

Chemical Looping Combustion (CLC) is one of the emerging technologies for carbon capture, with less energy penalty. The present way of using pulverized coals in a fluidized bed (FB)-CLC have limitations like loss of unconverted char and gaseous combustibles, which could be mitigated by use of coarser fuel particles. Devolatilization time is a critical input for the effective design of FB-CLC systems, primarily when large fuel particles are used. The present study investigates the devolatilization time and the char yield of three coals of two shapes, namely, two high ash Indian coals and a low ash Indonesian coal and a wood (Casuarina equisetifolia) in the size range of +8–25 mm, at different fuel reactor temperatures (800–950 °C) of a hematite based CLC unit. The devolatilization times of single fuel particles during CLC are determined using a visual method called ‘Color Indistinction Method’. Indonesian coal has the longest devolatilization time among the fuels, and biomass has the least. Increasing the bed temperature enhances the rate of volatile release, whereas this effect is less pronounced in larger particles. Devolatilization of Indonesian coal is found to be strongly influenced by the changes in operating conditions. With the decrease in sphericity, a maximum of 56% reduction in devolatilization time is observed for the +20–25 mm slender particles of Indonesian coals when compared to the near-round particles. The maximum average char yields at the end of the devolatilization phase for coal and biomass are about 55–76% and 16% respectively. Char yield in coal particles increases with an increase in particle size, whereas biomass particles show relatively consistent yield across all experimental conditions. Increase in bed temperature reduces the char yields of coal up to 12% and in biomass up to 30%. High volatile Indian coal is the most influenced fuel by the changes in fuels shape. A correlation for determining devolatilization time under CLC environment is presented, and it successfully fits most of the experimental values within ±20% deviation for coals (R² = 0.95) and within ±15% deviation for biomass (R² = 0.97).     

Application of ‘C.A.R.B. financial methodology’ analysis for alternative energy technologies into UK housing

Current energy trends in UK housing are reviewed and then assessed by introducing the ‘CARB financial analysis’ methodology. CARB is an acronym for ‘Carbon Abatement’, as it evaluates the potential carbon-dioxide reduction from different technologies; ‘Relative’, as all the technologies examined are dependant on various primary sources; and ‘Balance’, as the cost of surplus CO₂ is quantified. According to conventional financial analysis, most of the technologies examined have the potential to provide positive returns on the investments especially for those with an environmentally conscious agenda. Further reduction of up to 30% of most installed alternative energy systems cost is required to compete with an investment in, e.g., a UK pension scheme. Using the ‘CARB financial analysis’ the cost of reducing CO₂ has been quantified, and compared with the potential cost of climate change impact. Conventional installed solar technologies are not financially attractive both with a pay back period calculations and ‘CARB financial analysis’ under current market costs and governmental subsidy regimes. Heat recovery technologies could be sensible investments, both in financial and environmental terms under particular assumptions; especially if the investment budget is small. The use of cogeneration technologies provides a financial advantage in the attempt to minimise the cost of climate change impact, as pay back period of such investment could be less than 7 yr, and the cost of CO₂ saved could be two to seven times less than the global damage cost of carbon emissions.     

Evaluation of technical improvements of photovoltaic systems through life cycle assessment methodology

Since solar energy systems feed on a ‘clean’ energy source, they do not produce polluting emissions during their operation. However, they carry the environmental weight of other phases in their life cycle. In order to analyze the energy and environmental profile of these systems, it is necessary to expand the system boundaries, taking into account also the ‘hidden impacts’ related to production, transportation and system disposal at the end of its technical life. Here, the life cycle assessment methodology is applied to derive a complete and extended energy and environmental profile of photovoltaic systems. As reference case, a conventional multi-crystalline building integrated system is selected, retrofitted on a tilted roof, located in Rome (Italy) and connected to the national electricity grid. Then improved configurations of the reference system are assessed, focusing on building integration issues and the operational phase (considering an experimental hybrid photovoltaic system with heat recovery). Environmental ‘pay back times’ of the assessed systems are then calculated for CO₂ equivalent emissions and embodied energy. All the analyzed configurations are characterized by environmental pay back times one order of magnitude lower than their expected life time (3–4 years vs. 15–30 years). Thanks to a wider exploitation of photovoltaic potential during its ‘zero emission operation’, these results are further lowered by photovoltaic hybrid systems (environmental pay back times, depending on heat recovery configuration, go down to 40–50% of the values calculated for the reference case).     

JP-8 catalytic cracking for compact fuel processors

In processing heavier hydrocarbons such as military logistic fuels (JP-4, JP-5, JP-8, and JP-100), kerosene, gasoline, and diesel to produce hydrogen for fuel cell use, several issues arise. First, these fuels have high sulfur content, which can poison and deactivate components of the reforming process and the fuel cell stack; second, these fuels may contain non-volatile residue (NVR), up to 1.5 vol.%, which could potentially accumulate in a fuel processor; and third is the high coking potential of heavy hydrocarbons. Catalytic cracking of a distillate fuel prior to reforming can resolve these issues. Cracking using an appropriate catalyst can convert the various heavy organosulfur species in the fuel to lighter sulfur species such as hydrogen sulfide (H₂S), facilitating subsequent sulfur adsorption on zinc oxide (ZnO). Cracking followed by separation of light cracked gas from heavies effectively eliminates non-volatile aromatic species. Catalytic cracking can also convert heavier hydrocarbons to lights (C₁–C₃) at high conversion, which reduces the potential for coke formation in the reforming process. In this study, two types of catalysts were compared for JP-8 cracking performance: commercially-available zeolite materials similar to catalysts formulated for fluidized catalytic cracking (FCC) processes, and a novel manganese/alumina catalyst, which was previously reported to provide high selectivity to lights and low coke yield. Experiments were designed to test each catalyst’s effectiveness under the high space velocity conditions necessary for use in compact, lightweight fuel processor systems. Cracking conversion results, as well as sulfur and hydrocarbon distributions in the light cracked gas, are presented for the two catalysts to provide a performance comparison.     

Influence of TiO2/electrode interface on electron transport properties in back contact dye-sensitized solar cells

The influence of the TiO₂/electrode interface was investigated on electron transport properties at the interface and in TiO₂ porous film in back contact dye-sensitized solar cells. Analysis of dye-sensitized solar cells (DSCs) with Ti and TCO indicated that electron transport properties at TiO₂/Ti and TiO₂/TCO interfaces are similar despite the former's lack of a ‘built-in potential’. The dependence of short circuit current density on TiO₂ thickness indicated that TiO₂ electron transport is not affected by ‘built-in potential’ or electrode structure. Electron transport thus appears similar in back contact dye-sensitized solar cells and DSCs. A back contact dye-sensitized solar cell fabricated with a Ti electrode and optimum TiO₂ porous film showed a conversion efficiency of 7.8% with a metal mask under an air mass of 1.5 sunlight.     

New sustainable bioconversion concept of date by-products (Phoenix dactylifera L.) to biohydrogen,biogas and date-syrup

The dates production is usually accompanied by considerable loss of fruit byproducts. The chemical analysis showed that ‘Deglet Nour’ discarded flesh is rich in soluble sugars (79.8% ± 0.8%) and fibers (12.3% ± 0.4%). A processing approach was implemented to permit the production of biohydrogen from the flesh and biogas from the crude fiber fraction after soluble sugars extraction. This approach showed interesting results since the obtained biochemical hydrogen potential and the maximum methane yield were 292 mL H₂/gVS _initial and 235 mL CH₄/gVS _fibers respectively. Parallelly, the “hot water” soluble sugar fraction (date syrup) was of interest for agro-alimentary applications and showed a high sucrose, glucose and fructose content of 33.5%, 11.8% and 13.17% respectively. This study presents a proof of concept allowing an efficient sustainable energetic conversion of the date by-products biomass to biohydrogen via dark fermentation or to soluble sugars fraction and biogas via a biorefinery approach.     

Modeling the behavior of selenium in Pulverized-Coal Combustion systems

The behavior of Se during coal combustion is different from other trace metals because of the high degree of vaporization and high vapor pressures of the oxide (SeO₂) in coal flue gas. In a coal-fired boiler, these gaseous oxides are absorbed on the fly ash surface in the convective section by a chemical reaction. The composition of the fly ash (and of the parent coal) as well as the time-temperature history in the boiler therefore influences the formation of selenium compounds on the surface of the fly ash. A model was created for interactions between selenium and fly ash post-combustion. The reaction mechanism assumed that iron reacts with selenium at temperatures above 1200 °C and that calcium reacts with selenium at temperatures less than 800 °C. The model also included competing reactions of SO₂ with calcium and iron in the ash. Predicted selenium distributions in fly ash (concentration versus particle size) were compared against measurements from pilot-scale experiments for combustion of six coals, four bituminous and two low-rank coals. The model predicted the selenium distribution in the fly ash from the pilot-scale experiments reasonably well for six coals of different compositions.     

Potential of green ammonia production in India

The threat of climate change is forcing the world to decarbonize all economic sectors. Ammonia primarily used for fertilizer production and a potential, ‘hydrogen carrier’ currently accounts for ~27% of global hydrogen consumption and ~1% of global greenhouse gas emissions. In this analysis, we assess the techno-economic potential of ammonia production using onshore wind, open-field photovoltaic and batteries for both domestic usage and export scenarios in India, which is currently one of the world's largest producer and importer of ammonia. Our results reveal that India's potential can comfortably satisfy global ammonia demand with lowest ammonia costs of 723 EUR/t_NH3 and 765 EUR/t_NH3 for the domestic and export scenario, respectively. To compete with conventional ammonia production a carbon tax of 224–335 €/t_CO2 would be required. Finally, costs of shipping liquid hydrogen and the ‘hydrogen carrier’ ammonia are similar here giving other economic, environmental and safety factors higher relevance.     

Use of lower grade coals in IGCC plants with carbon capture for the co-production of hydrogen and electricity

This paper investigates the potential use of lower grade coals in an IGCC-CCS plant that generates electricity and produces hydrogen simultaneously with carbon dioxide capture and storage. The paper underlines one of the main advantages of gasification technology, namely the possibility to process lower grade coals, which are more widely available than the high-grade coals normally used in European power plants. Based on a proposed plant concept that generates about 400 MW net electricity with a flexible output of 0–50 MW_th hydrogen and a carbon capture rate of at least 90%, the paper develops fuel selection criteria for coal fluxing and blending of various types of coal for optimizing plant performance e.g. oxygen consumption, hydrogen production potential, specific syngas energy production per tonne of oxygen consumed, etc. These performance indicators were calculated for a number of case studies through process flow simulations. The main conclusion is that blending of coal types of higher and lower grade is more beneficial in terms of operation and cost performance than fluxing high-grade coals.     

A model for determining the global solar radiation for Makurdi,Nigeria

An empirical model for determining the monthly average daily global solar radiation on a horizontal surface for Makurdi, Nigeria (Latitude 7°7′N and Longitude 8°6′E) was developed using the Angstrom–Page equation. The solar radiation (W/m²), hours of bright sunshine and cloudiness were measured hourly from 0600 H to 1800 H daily for 18 months. The constants ‘a’ and ‘b’ of the Angstrom linear type equation were determined by plotting the clearness index (H/H_o) against the possible sunshine hours (n_s/N) to obtain the line of best fit. The constant ‘a’ was obtained from the intercept of the line on the y-axis while the constant ‘b’ was obtained from the slope of the line. The developed model for determining the global horizontal solar radiation at the location was H = H_o [0.17 + 0.68(n/N)] with a coefficient of correlation of 0.78. The mean bias error and root mean square error that were used to test the performance of the constants were 0.17% and 1.22% respectively. The measured solar radiation was compared with the solar radiation predicted by the model and no significant difference was found between them using F-LSD at P ≤ 0.05.     

Mechanism study of nitric oxide reduction by light gases from typical Chinese coals

Coal devolatilization plays an important role in NO formation and reduction. In this study, the coal pyrolysis experiment was performed in an entrained flow reactor to obtain the light gas release characteristics. Six typical Chinese coals with volatile content ranged from 8.8% to 38.3% were studied. The pyrolysis temperature was in the range from 600 to 1200 °C. A significant rank dependence of HCN, CO and C₂H₂/C₂H₄/C₂H₆ was observed and their release for high volatile coals was higher than that for low volatile coals. The HCN–N/NH₃–N ratio ranged from 0.00 to 0.66 for anthracite coals and ranged from 1.63 to 3.90 for high volatile coals. Based on the experimental results, the effect of coal pyrolysis gas on NO reduction in a plug flow reactor at reducing atmosphere was kinetically calculated. The optimal excess air ratio(α_opt) corresponding to the maximum NO removal efficiency decreased with an increase in reduction temperature. For the light gas from the HL coal pyrolyzed at 800 °C, the α_opt decreased from 0.73 to 0.17 when the reduction temperature increased from 927 to 1327 °C. The rate of production analysis indicated that NO removal efficiency was determined by 3 competing reaction paths: NO reduction, NO formation and oxygen consumption by combustible species.     

Combustion,performances, and emissions characteristics of Hermetia illucens larvae oil in a direct injection compression ignition engine

Hermetia illucens larvae oil (HILO) is among biofuel feedstock from insects that has high potential to reduce dependency on petroleum resources. The present paper is motivated by the need to critically examine the effect of HILO mixed with diesel fuel (DF) on combustion, engine performance, and emission characteristics of a single cylinder direct injection (DI) compression ignition (CI) engine. The experiment was performed at a constant speed of 1500 rpm under various engine loads. The results revealed that the in-cylinder pressure, heat release rate (HRR), and the ignition delay (ID) were reduced by an average of 3.32%, 12.89%, and 4.36%, respectively. The brake specific fuel consumption (BSFC) and exhaust gas temperature (EGT) increased considerably at all engine loads. The brake thermal efficiency (BTE) was discovered to be lower by 11.47% compared to DF. The finding also shows that carbon monoxide (CO), carbon dioxide (CO₂), and unburned hydrocarbon (UHC) emissions increased with the addition of HILO. The nitrogen oxides (NO_x) emission reduced by 19.80% compared to DF at all the engine loads. Overall, this study concluded the potential of HILO in CI engine as a promising renewable and environmentally friendly resource for the better earth.