•Six diverse biomass fuels are evaluated as an alternative renewable energy source for the UK.•Thermal degradation of biomasses by using variable inert to oxidising environments.•Pyrolytic, ...combustion and kinetic analyses with the help of TGA, DTG and DSC.•High rates of thermal decomposition are noted in oxidising atmosphere.•The reaction order 0.5 modelled fitted well for all biomass fuels.
This study investigates the thermal and kinetic analysis of six diverse biomass fuels, in order to provide valuable information for power and energy generation. Pyrolytic, combustion and kinetic analyses of barley straw, miscanthus, waste wood, wheat straw, short rotation coppicing (SRC) willow and wood pellet were examined by non-isothermal thermogravimetry analyser (TGA), differential thermogravimetric (DTG) and differential scanning calorimetry (DSC) techniques. Biomass fuels were thermally degraded under N2, air, CO2 and the selected oxy-fuel (30% O2/70% CO2) reaction environments. The thermal degradation under inert N2 and CO2 atmospheres showed an almost identical rate of weight loss (R), reactivity (RM × 103) and activation energy (Ea) profiles. Similar profiles for R, RM and Ea were observed for the environments under air (21% O2/79% N2) and the oxy-fuel combustion. Results indicated that the thermal decomposition rate for biomass fuels in an oxidising condition was faster than in an inert atmosphere, favourable effect on thermal degradation of biomass fuels was observed when oxygen content increased from 21 to 30%. Higher activation energies with lower reactivity were observed for the biomass fuels that have low cellulosic contents as compared to the other fuels. Regression analysis confirmed that the reaction order 0.5 modelled fitted well for all biomass samples. All these findings will provide valuable information and promote the advancement of future researches in this field.
•Revised equation of regeneration heat is proposed to include process related factors.•Key parameters (e.g. heat of adsorption) experimentally determined.•Parametric analysis made on both physical ...properties and process related parameters.•Calculated regeneration heat for PEI/silica sorbent based system is 2.46GJ/tCO2.•Working capacity, moisture adsorption and heat recovery are most influential factors.
The thermal energy required for regeneration of CO2-rich adsorbents or absorbents is usually regarded as the most important criterion to evaluate different materials and processes for application in commercial-scale CO2 capture systems. It is expected that the regeneration heat can be greatly reduced by replacing the mature aqueous monoethanolamine (MEA) technology with amine-based solid adsorbents capturing systems, due to the much lower heat capacity of solid adsorbents comparing to aqueous MEA and the avoidance of evaporating a large amount of water in the regenerator. Comparing to the MEA technology, the regeneration heat for solid adsorbent based systems has not received adequate attention especially on the impacts of process related parameters. Further, the methodologies used in previous investigations to calculate the regeneration heat may have deficiencies in defining the working capacities, adopting proper heat recovery strategies and/or evaluating the effect of moisture co-adsorption. In this study, an energy equation to calculate the regeneration heat has been revised and proposed to systematically evaluate the most important parameters affecting the regeneration heat, including the physical properties of the adsorbents and process related variables including the heat of adsorption, specific heat capacity, working capacity, moisture adsorption of the polyethyleneimine (PEI)/silica adsorbent, the swing temperature difference and the degree of heat recovery. Based on the parametric analysis, the calculated regeneration heat for the PEI/silica adsorbent based system is found to be around 2.46GJ/tCO2, which is much lower than the value of 3.9GJ/tCO2 for a typical aqueous MEA system and is also lower than 3.3GJ/tCO2 for an advanced MEA system. Sensitivity analysis of all the parameters has also been conducted and the results have shown that working capacity, moisture adsorption and heat recovery ratios are the most influential factors. With more proficiency and development in the energy efficient process designs, the advantages of a solid adsorbent based capturing system over typical MEA systems will be justified.
Carbon Capture and Storage (CCS) uses a combination of technologies to capture, transport and store carbon dioxide (CO2) emissions from large point sources such as coal or natural gas-fired power ...plants. Capturing CO2 from ambient air has been considered as a carbon-negative technology to mitigate anthropogenic CO2 emissions in the air. The performance of a mesoporous silica-supported polyethyleneimine (PEI)–silica adsorbent for CO2 capture from ambient air has been evaluated in a laboratory-scale Bubbling Fluidized Bed (BFB) reactor. The air capture tests lasted for between 4 and 14 days using 1kg of the PEI–silica adsorbent in the BFB reactor. Despite the low CO2 concentration in ambient air, nearly 100% CO2 capture efficiency has been achieved with a relatively short gas–solid contact time of 7.5s. The equilibrium CO2 adsorption capacity for air capture was found to be as high as 7.3wt%, which is amongst the highest values reported to date. A conceptual design is completed to evaluate the technological and economic feasibility of using PEI–silica adsorbent to capture CO2 from ambient air at a large scale of capturing 1Mt-CO2 per year. The proposed novel “PEI-CFB air capture system” mainly comprises a Circulating Fluidized Bed (CFB) adsorber and a BFB desorber with a CO2 capture capacity of 40t-CO2/day. Large pressure drop is required to drive the air through the CFB adsorber and also to suspend and circulate the solid adsorbents within the loop, resulting in higher electricity demand than other reported air capture systems. However, the Temperature Swing Adsorption (TSA) technology adopted for the regeneration strategy in the separate BFB desorber has resulted in much smaller thermal energy requirement. The total energy required is 6.6GJ/t-CO2 which is comparable to other reference air capture systems. By projecting a future scenario where decarbonization of large point energy sources has been largely implemented by integration of CCS technologies, the operating cost under this scenario is estimated to be $108/t-CO2 captured and $152/t-CO2 avoided with an avoided fraction of 0.71. Further research on the proposed 40t-CO2/day ‘PEI-CFB Air Capture System’ is still needed which should include the evaluation of the capital costs and the experimental investigation of air capture using a laboratory-scale CFB system with the PEI–silica adsorbent.
•PEI–silica adsorbent capturing CO2 from ambient air evaluated in a BFB reactor.•The equilibrium CO2 adsorption capacity for air capture as high as 7.3wt%.•40t-CO2/day CFB air capture system using PEI–silica adsorbent proposed.•The energy penalty for the proposed air capture system estimated to be 6.6GJ/t-CO2.•The operating cost of the air capture system estimated to be $152/t-CO2 avoided.
Alcohol-containing polymer networks synthesized by Friedel–Crafts alkylation have surface areas of up to 1015 m2/g. Both racemic and chiral microporous binaphthol (BINOL) networks can be produced by ...a simple, one-step route. The BINOL networks show higher CO2 capture capacities than their naphthol counterparts under idealized, dry conditions. In the presence of water vapor, however, these BINOL networks adsorb less CO2 than more hydrophobic analogues, suggesting that idealized measurements may give a poor indication of performance under more realistic carbon capture conditions.
Exploration for shale gas occurs in onshore basins, with two approaches used to predict the maximum gas in place (GIP) in the absence of production data. The first estimates adsorbed plus free gas ...held within pore space, and the second measures gas yields from laboratory pyrolysis experiments on core samples. Here we show the use of sequential high-pressure water pyrolysis (HPWP) to replicate petroleum generation and expulsion in uplifted onshore basins. Compared to anhydrous pyrolysis where oil expulsion is limited, gas yields are much lower, and the gas at high maturity is dry, consistent with actual shales. Gas yields from HPWP of UK Bowland Shales are comparable with those from degassed cores, with the ca. 1% porosity sufficient to accommodate the gas generated. Extrapolating our findings to the whole Bowland Shale, the maximum GIP equate to potentially economically recoverable reserves of less than 10 years of current UK gas consumption.
Starches were isolated and characterised from 10 potato cultivars grown under the same conditions (with a commercial starch for reference). The chemical composition revealed some differences amongst ...the starches with protein ranging from 0.30% to 0.34%, amylose 25.2% to 29.1% and phosphorus 52.6–66.2
mg 100
g
−1. High performance size-exclusion chromatography (HPSEC) fractionation of isoamylase debranched amylopectin showed that the amylopectin molecules were less branched and consisted of more B1, but less A-chains, than cereal starches. Gelatinisation onset (
T
o), peak (
T
p) and conclusion (
T
c) temperatures of the native potato starches ranged from 58.7 to 62.5
°C, 62.5 to 66.1
°C and 68.7 to 72.3
°C, respectively, whilst the gelatinisation enthalpies ranged from 15.1 to 18.4
J
g
−1. The gelatinisation temperatures of the starches increased in common with the amounts of short and intermediate sized amylopectin chains. The
13C magic angle spinning nuclear magnetic resonance (
13C CP-MAS NMR) and wide angle X-ray diffraction (XRD) data (30.6%
±
0.22% crystallinity on average) showed little variance amongst the samples. Particle sizing results, however, revealed more variance (20.6–30.9
μm mean diameter). Overall, these data reveal the subtleties of cultivar specific variation against a background of constant environmental conditions.
Hydrothermal carbonisation (HTC) is an attractive biomass pre-treatment as it produces a coal-like fuel, can easily process wet biomass and wastes, and lowers the risk of slagging and fouling in ...pulverised fuel (PF) combustion boilers. One of the major factors in determining the suitability of a fuel as a coal replacement for PF combustion is matching the char reactivity and volatile matter content to that of coals, as these significantly affect heat release and flame stability. The char reactivity of wood and olive cake biocoals and their respective drop tube furnace chars have been studied using thermogravimetric analysis in comparison to other biomass fuels and high-volatile bituminous coal. It was found that HTC reduces the reactivity of biomass, and in the case of HTC of wood pellets the resulting biocoal has a char reactivity similar to that of high-volatile bituminous coal. Proximate analysis, X-ray fluorescence analysis, and textural characterisation were used to show that this effect is caused primarily by removal of catalytic alkali and alkaline earth metals. Subsequent torrefaction of the wood biocoals was performed to tailor their volatile matter content to match that of sub-bituminous and high volatile bituminous coals without major impact on char reactivity.
•Hydrothermal carbonisation reduces the char reactivity of biomass.•Char reactivity of wood biocoal is similar to that of bituminous coal.•Reduced biocoal reactivity is primarily due to alkali/alkaline earth metal removal.•Torrefaction of biocoal produces a coal-like fuel in composition and reactivity.
The Neoproterozoic era (1,000-542 Myr ago) was an era of climatic extremes and biological evolutionary developments culminating in the emergence of animals (Metazoa) and new ecosystems. Here we show ...that abundant sedimentary 24-isopropylcholestanes, the hydrocarbon remains of C(30) sterols produced by marine demosponges, record the presence of Metazoa in the geological record before the end of the Marinoan glaciation ( approximately 635 Myr ago). These sterane biomarkers are abundant in all formations of the Huqf Supergroup, South Oman Salt Basin, and, based on a new high-precision geochronology, constitute a continuous 100-Myr-long chemical fossil record of demosponges through the terminal Neoproterozoic and into the Early Cambrian epoch. The demosponge steranes occur in strata that underlie the Marinoan cap carbonate (>635 Myr ago). They currently represent the oldest evidence for animals in the fossil record, and are evidence for animals pre-dating the termination of the Marinoan glaciation. This suggests that shallow shelf waters in some late Cryogenian ocean basins (>635 Myr ago) contained dissolved oxygen in concentrations sufficient to support basal metazoan life at least 100 Myr before the rapid diversification of bilaterians during the Cambrian explosion. Biomarker analysis has yet to reveal any convincing evidence for ancient sponges pre-dating the first globally extensive Neoproterozoic glacial episode (the Sturtian, approximately 713 Myr ago in Oman).
•Feeding compositions could change the dominance between carbon formation and elimination.•The property of carbon residues can be altered by varying the feeding CH4/CO2 ratio.•Coating carbon covering ...Ni particles under CH4-rich conditions leads to deactivation.•Some active Ni NPs survived under CH4-rich condition during DRM.
A previously developed mesoporous Ni–CaO–ZrO2 catalyst (NCZ) was submitted to dry reforming of methane (DRM), and the influence of feeding compositions on the properties of accumulated carbon was comprehensively studied. To this end, the used catalysts (NCZ-x) were characterized with a particular focus on the carbon residuals, using X-ray diffraction, N2 adsorption, transmission electron microscope, scanning electron microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy, etc. The results indicate that by varying the composition of the feeding gas, the morphology and chemical inertness of the accumulated carbon changed considerably, and the deactivation of the NCZ catalyst under CH4-rich conditions can be associated with the formation of coating carbon species that leads to the coverage of highly active Ni nano particles (NPs).
Although biomass co-firing is now well established in pulverised fuel (PF) combustion under conventional air-fired conditions, there is little information available on how biomass will behave in ...oxy-fuel firing. Using thermogravimetric analysis (TGA) and a drop tube furnace (DTF), this study examines the impact of co-firing biomass and coal under oxy-fuel conditions compared to normal air firing, with the emphasis on the potential catalytic effect of biomass-contained alkali and alkaline metals on coal char burnout. Individual chars and their blends prepared from sawdust, pinewood and a South African coal in a DTF and normal tube furnace under slow-heating conditions have been used in TGA char burnout tests. The results demonstrate that the coal/biomass char blends burned off significantly faster than predicted under both oxy-fuel and air-firing conditions, and this synergistic catalytic effect was found to be considerably more pronounced in oxy-fuel conditions. In particular, the DTF biomass/coal char blends from devolatilisation in CO2 burn off approximately two times faster than those prepared in nitrogen. To further examine the catalytic effect, the raw sawdust sample was first extracted with 5M hydrochloric (HCl) acid to remove its contained alkali and alkaline metals before the char preparation and subsequent char burnout tests. It was found that the removal of the alkali and alkaline metals led to almost complete loss of the catalytic effect as observed with the untreated sawdust derived char samples. The results indicate that biomass having relatively high contents of alkali and alkaline metals can serve as effective combustion catalysts to improve coal combustion efficiency.
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