Search

Biomass renewable energy has become a major target of the Thailand Alternative Energy Development Plan (AEDP) since the country’s economy is largely based on agricultural production. Rice husk (RH) is one of the most common agricultural residues in Thailand. This research aims to investigate yields and properties of biochar produced from copyrolysis of RH and plastic (high-density polyethylene (HDPE)) at different ratios, temperatures, and holding times. For both individual and copyrolysis, the temperature variation generated more pronounced effects than the holding time variation on both biochar yields and properties. For individual pyrolysis of RH, the maximum biochar yield of ∼54 wt % was obtained at 400 °C. A shift in temperature from 400 to 600 °C resulted in RH biochars with higher fixed carbon (FC) and carbon (C) contents by ∼1.11–1.28 and 1.06–1.22 times, respectively, while undetectable changes in higher heating values (HHVs) were noticed. For copyrolysis, obvious negative synergistic effects were observed due to the radical interaction between the rich H content of HDPE and RH biochars, which resulted in lower biochar yields as compared to the theoretical estimation based on individual pyrolysis values. However, the addition of HDPE positively impacted the FC and C contents, especially when 10 and 20 wt % HDPE were added to the feedstock. Besides, higher HDPE blending ratios resulted in biochars with improved HHVs, and >1.5 times improvement in HHV was reported in the biochar with 50 wt % HDPE addition in comparison with RH biochar obtained under the same conditions. In summary, biochars generated in this study have the potential to be utilized as a solid fuel or soil amendment.

Biogas is being produced everyday around the world due to land filling of organic wastes. Reforming of biogas to hydrogen rich gas offers a green source of energy. This work demonstrates reforming biogas into hydrogen rich gas via a non-thermal gliding arc plasma stabilized in a reverse vortex flow with very low and competitive specific energy requirement. Parametric tests determined the individual effects of power input (140-300 W), steam to carbon ratio (0.0–3.0), and equivalence ratio (0.1–0.7) on reformer performance. Factorial tests identified optimal operating condition based on minimizing the specific energy requirement, determined to be 184 kJ/mol H 2 or 1.91 eV/H 2 molecule, significantly below the value for conventional steam reforming of methane, 3.37 eV/H 2 molecule produced. The optimum operating conditions were found at an equivalence ratio of 0.11, a steam to carbon ratio of 0.14, and an input plasma power of 160 W, resulting in methane conversion of 48.8%, hydrogen yield of 23.4%, hydrogen selectivity of 47.8%, and an efficiency of 25.3%. Hydrogen sulfide as a common contaminant in landfill gas has detrimental effects on downstream facilities. The reactor was also evaluated on synthetic biogas containing hydrogen sulfide at low concentration (21 ppm). About 5.7% of the sulfur input to the system was partitioned to the dry outlet reformate stream with the remainder captured as sulfate in a downstream impinger or recovered as a solid of unknown molecular structure deposited on tubing surfaces between the reformer and the impinger. This reforming technology offers potential to be deployed as a lightweight compact portable system for on-site applications such as landfills, and depending on available fuels, in mobile applications such as ships.

There is increasing interest in developing biobased alternative jet fuels to meet rising aviation demand and address environmental concerns. Uncertainty of oil prices, issues of energy security, an...

The effects of processing conditions (closed versus open reactor, pressure, temperature, soaking time, biomass loading, heating rate, and fuel particle size) on product yields and char properties from constant-volume carbonization are reported. Increasing the pretest, inert-gas, system pressure from 0 to 2.17 MPa did not significantly affect product yields or char proximate analysis results. Increasing the reaction time from 30 to 190 min and the temperature in the 300–550 °C range improved fixed-carbon contents and reduced volatile matter while maintaining or slightly increasing the fixed-carbon yields. In contrast to flash carbonization or traditional carbonization observations where larger particles produce beneficial effects, constant-volume carbonization produced equal or higher fixed-carbon contents and yields from smaller biomass particles. This offers possibilities that smaller-sized, lower-grade biomass can be used to produce high, fixed-carbon yield charcoal. Under certain processing conditions, the particulate biomass underwent a transient plastic phase transition that produced a single solid piece of final char. The roles of processing conditions in the formation of this transient plastic phase are also discussed.

Catalytic hydrothermal conversion diesel (CHCD-76), synthesized isoparaffin (SIP-76), and hydroprocessed renewable diesel (HRD-76) have been produced in sufficient quantity and supplied to the U.S. Navy for blending with traditional marine diesel NATO F-76. The present work investigates the storage and oxidation stabilities of DSH-76, CHCD-76, and their blends with F-76. Chemical composition and physicochemical properties of these two biofuels, including viscosity, density, peroxide value, heat of combustion, acid number, and phase behavior, were determined using required ASTM methods. ASTM D4625 and D5304 methods were employed to investigate the long-term storage stability of these two biofuels and theirs blends with F-76. ASTM D5304 method was also modified to investigate the oxidation process of these fuel samples. In addition, ASTM D2274 tests were conducted to investigate oxidation stability of the neat and blended fuel samples. The influence of long-term storage and oxidation on fuel physicochemical properties was investigated based on ASTM methods. SIP-76 and CHCD-76 were found have superior storage and oxidation stability in comparison with petroleum F-76. This is also the first report on storage and oxidation stability of SIP-76 and CHCD-76.

Hydroprocessed renewable diesel (HRD-76) and synthesized isoparaffin (SIP-76) have been produced in sufficient quantity for testing by the US Navy, and demonstrated as compatible replacements or blend stock with marine diesel (NATO F-76). Operational limitations with respect to the lubricity, seal swell and cold-flow properties, however, need to be addressed before using 100% HRD-76 or SIP-76. Aromatics are known to improve seal swell and low-temperature characteristics. In this study, three commercial aromatic fluids (Aromatic 100, 150 and 200) produced from petroleum refining were added to HRD-76 and SIP-76 at various concentrations to investigate their impacts on the properties of the biofuel blend. The composition, hydrogen content and physicochemical properties of these aromatic fluids were determined according to ASTM methods and compared with that of biofuels and F-76. The seal-swell capability of the aromatic fluids and biofuel blends was investigated using nitrile O-rings, while the effects of aromatic fluids on fuel low-temperature quality were evaluated using differential scanning calorimetry. In addition, ASTM D5304 and D2274 tests were conducted to investigate the impacts of adding aromatics to biofuels on long-term storage and oxidative stabilities. Although the composition and characteristics of these three aromatics fluids varied, all were capable of inducing o-ring seal swell and adjusting the density of biofuels without significantly affecting the biofuels’ stabilities. HRD-76 and aromatic fluid blends also exhibited liquid to solid phase transitions at lower temperatures and greater hydrophilicity than neat HRD-76.

Pongamia seedpods are recognized as a potential feedstock for sustainable aviation fuel production due to the relatively high oil content of the seeds. Pongamia pods are byproduct residues available after seed separation. Pods have high chlorine and potassium content that may be problematic in thermochemical energy conversion systems. Leaching experiments were performed to remove inorganic constituents of pods and thereby reduce the potential for fouling, slagging, and agglomeration. A 23 factorial design determined the impacts of process operating parameters (i.e. rinse water temperature (25 °C vs. 75 °C), rinse duration (10 min vs. 2 h), and particle size (

A novel carbonization process that realizes near-theoretical fixed-carbon yields in ∼3 h is presented. Norwegian spruce and birch sawdusts were carbonized in a hermetically sealed reactor at an initial nitrogen pressure of 0.1 MPa. During a carbonization test, the reactor vessel retained all pyrolytic products inside the hot reaction zone invoking high pressures as the temperature was raised. Given the elevated partial pressures of volatiles and their extended residence times, secondary, heterogeneous, char-forming reactions between the hot solid and the tarry vapors appeared to be promoted. This resulted in charcoals with a remarkably high fixed-carbon yield, noncondensable gases mainly composed of CO2, and negligible amount of free tars. This work presents a reproducibility study on the experimental method and explores the effects of heat-treatment temperature, particle size, mass loading, and immersion time on product distributions and charcoal properties. Proximate and elemental analyses, heating values, and scanning electron microscopy images of charcoal are presented. Higher heat treatment temperatures (from 300 °C to 400 °C), smaller grains (from

Mechanical dewatering and leaching were used to process freshly harvested banagrass ( Pennisetum purpureum X Pennisetum glaucum ) and improve fuel properties relevant to thermochemical conversion. A factorial, 2 3 experiment determined the effects of process operating parameters: particle size (1 mm and 80 mm), rinse water temperature (25 °C and 75 °C), and rinse duration (1 min and 3 min). Characterization of the samples from the process included moisture and ash contents of solid samples, potassium (K) and chlorine (Cl) contents of solid and liquid samples, and chemical oxygen demand, total solids, and total suspended solids of liquid samples. These were used to assess the effectiveness of treatment on reducing K and Cl in the processed material, estimate material/energy losses associated with the processing, and identify further treatment requirements and opportunities for material recovery. The effects of particle size, rinse water temperature, and their interaction indicate that processing with low-grade hot water (75 °C) can improve K and Cl removal by over 10% compared to treatment using ambient temperature water for larger particles (80 mm). The former could result in reduced capital and operating costs for size reduction, as well as reduced material losses during processing.

The present work investigates the properties and oxidation stabilities of biodiesel derived from catfish oil (B100 CFO) generated by the fish processing plants in Vietnam. The composition and physicochemical properties of the B100 CFO were measured, including oxygen content (∼11 wt%), viscosity (4.5306 mm 2 s −1 ), density (0.8772 g cm −3 ), peroxide value (28.13 mg kg −1 ), heat of combustion (39.18 MJ kg −1 ), and acid number (0.12 mg KOH g −1 ). Methyl oleate (46.44 wt%) was the dominant fatty acid methyl ester. B100 CFO was found to have poorer low-temperature quality than most vegetable oil derived biodiesels as determined by its fusion and crystallization properties. Novel modified ASTM D5304 and D2274 tests were employed to study the oxidation process of B100 CFO and the impact of oxidation time on its stability. Under ASTM 5304 test conditions, rapid O 2 consumption by B100 CFO occurred after 8 h, behavior similar to commercial biodiesel stabilized with antioxidant additives. The influence of oxidation condition and time on the B100 CFO physicochemical properties and low-temperature qualities was also investigated according to ASTM methods. Three oxidation stages were identified in B100 CFO based on the peroxide value change during the modified ASTM D5304 and D2274 tests. B100 CFO was also found have superior oxidation stability in comparison with B100 derived from waste cooking oil. This is the first report on oxidation stability of B100 derived from catfish oil.

X-ray fluorescence (XRF) spectroscopy was used to assess the effectiveness of various mild pretreatment methods for improving the fuel quality of banagrass, a tropical grass. Three types of pretreatment were used with increasing levels of severity: (i) S1 involves dewatering (pressing) only, (ii) S2 where the sample is pressed and leached, and (iii) S3 where pressing–leaching–pressing process is used. In addition, the influence of particle size (2 or 60–80 mm), leaching water temperature (25 or 75 °C), and leaching time (1 or 3 min) on the extraction of inorganic elements was examined. The results show that the S3 pretreatment is the most effective and that reducing the particle size has a more significant effect than increasing leaching temperature or time. Using a 2 mm particle size at 75 °C for 3 min produced the greatest effect, removing 50–60 wt % of the Na, ∼65 wt % Mg, ∼90 wt % P, ∼90 wt % K, ∼55 wt % S, and ∼95 wt % Cl. Using dewatering alone (S1) to pretreat the banagrass was the least effective ...

Torrefaction can be used to reduce the oxygen content of biomass and improve the feedstock properties for thermochemical conversion. Pongamia (Millettia pinnata), a leguminous, oil-seed bearing tree, is a potential resource for sustainable aviation fuel production due to the high oil content of its seeds. The present work investigates thermochemical pretreatment of pongamia processing residues, i.e. pods. Torrefaction tests were performed with both a fixed bed reactor and a macro thermogravimetric analyzer (TGA) under nitrogen atmospheres. The effects of process conditions on feedstock properties relevant to thermochemical conversion technologies, proximate and ultimate composition, heating value, and Hardgrove grindability index (HGI), were measured. The chemical structure, reactivity, and changes in elemental composition of the torrefied materials were also investigated. The mass and energy yields decreased 43% and 25%, respectively, from the mildest (165 °C) to the most severe (281 °C) torrefaction conditions, while the energy densification index increased from 1.15 to 1.68. The HGIs of pods torrefied at temperatures >215 °C were found to equal or exceed the HGI of a reference bituminous coal sample. A LECO model TGA801 macro-TGA with a sample loading capacity of ~95 g was also used to torrefy pongamia pods. Products from the LECO and the fixed bed reactor were comparable, and the macro-TGA was demonstrated to be a useful fast screening tool to study effects of process parameters.

The efficacy of C4 grasses as feedstocks for liquid fuel production and their climate mitigation potential remain unresolved in the tropics. To identify highly convertible C4 grasses, we measured final fuels and postprocess biomass produced in two laboratory-scale conversion pathways across 12 species and varieties within the Poaceae (grass) family. Total mass, carbon, and energy in final fuels and postprocess biomass were assessed based on field mass and area-based production. Two lignocellulosic processes were investigated: (1) anaerobic digestion (AD) to methane and (2) hot water pretreatment and enzymatic hydrolysis (HWP-EH) to ethanol. We found AD converted lignocellulose to methane more efficiently in terms of carbon and energy compared to ethanol production using HWP-EH, although improvements to and the optimization of each process could change these contrasts. The resulting data provide design limitations for agricultural production and biorefinery systems that regulate these systems as net carbon sources or sinks to the atmosphere. Median carbon recovery in final fuels and postprocess biomass from the studied C4 grasses were ~5 Mg C ha−1 year−1 for both methane and ethanol, while median energy recovery was ~200 MJ ha−1 year−1 for ethanol and ~275 MJ ha−1 year−1 for methane. The highest carbon and energy recovery from lignocellulose was achieved during methane production from a sugarcane hybrid called energycane, with ~10 Mg C ha−1 year−1 and ~450 MJ ha−1 year−1 of carbon and energy recovered, respectively, from fuels and post-process biomass combined. Carbon and energy recovery during ethanol production was also highest for energycane, with ~9 Mg C ha−1 year−1 and ~350 MJ ha−1 year−1 of carbon and energy recovered in fuels and postprocess biomass combined. Although several process streams remain unresolved, agricultural production and conversion of C4 grasses must operate within these carbon and energy limitations for biofuel and bioenergy production to be an atmospheric carbon sink.

Mitigation of climate change via increased plant productivity and soil carbon (C) sequestration during land use change can be a powerful driver of the net greenhouse gas emissions of a sustainable production system. Yet the net climate change mitigation of managed forests is affected by both tradeoffs between C sequestration and non-renewable C emissions and assessment methodology. As a case study, we measured ecosystem stocks to determine the potential C implications of converting pasture to managed eucalyptus forest and compared them with the eucalyptus production system's non-renewable C emissions. The forest border was chosen as the system boundary and operations spanned from forest establishment activities to harvested wood placed at the forest perimeter. Eucalyptus biomass C was 57.2 ± 4.2 Mg C ha−1 and soil C stock (to ∼1 m depth) was approximately an order of magnitude greater. By the prevalent method for bulk density-based determination of C stock, conversion of pasture to eucalyptus fore...

The present work investigates the storage and oxidation stabilities of 100% biodiesel (B100) derived from waste cooking oil. Physical properties and chemical composition of B100, including viscosity, density, peroxide value, heat of combustion, acid number, and phase behavior, were measured. The analysis showed that this B100 contains over 60% unsaturated esters. The long-term storage stability was studied based on ASTM D4625 which simulates up to two years storage by holding samples at 43 °C. Modified ASTM D5304 and D2274 tests were conducted to investigate oxidation processes of B100. An extended ASTM D2274 method was also employed to investigate the influence of oxidation time on stability. The influence of long-term storage and oxidation reactions on physicochemical properties and phase behavior was investigated using ASTM methods. The existence of three stages of B100 oxidation was identified based on the property changes after the modified ASTM D5304 and D2274 tests.

Supported micron-sized molybdenum disulfide (MoS2) has been extensively studied for catalytic synthesis of Higher Alcohols Synthesis (HAS) from synthesis gas (syngas). However, the process is associated with low space–time–yield (STY) and poor selectivity under high temperature (300–325 °C) and high pressure (10–20 MPa) operation, making it unattractive for commercial application. Nano-sized MoS2 catalyst particles improve selectivity to alcohols but the yields are low possibly due to catalyst aggregation and mass transfer limitations. This study describes the use of oil-in-polyethylene glycol (PEG) microemulsion-based encapsulation of hydrophobic catalyst nanoparticles (MoS2) to prevent aggregation, increase surface area and increase mass transfer across the two phases. In this study, nano-sized MoS2 was first synthesized by sonolysis of hexacarbonyl molybdenum and yellow sulfur in hexadecane in

Tropical biomass feedstock candidates, banagrass ( Pennisetum purpureum × Pennisetum glaucum ), guinea grass ( Panicum maximum ), energy cane ( Saccharum spontaneum ), and sugar cane ( Saccharum officinarum L.) (as reference) were harvested and processed using pressing and leaching techniques to improve fuel properties for thermochemical conversion. Test results are reported that summarize the impacts of treatment methods on fuel properties and provide detailed data on mass and element partitioning between process streams to inform system design. The processed fuels had lower ash contents, improved heating values, higher ash deformation temperatures, and higher volatile matter to fixed carbon ratios than the parent materials. The liquid streams generated by the process were characterized for chemical oxygen demand, sugar content, total solids, total suspended solids, and major and trace elements. At least 20% of the initial fuel dry matter was partitioned to the byproduct liquid streams as total solids under the combined influences of leaching and mechanical processing. Analytical results support the land application of liquids as a nutrient recycling option. Element partitioning between solid and liquid process streams was determined and material and element mass balances were performed. Chemical equilibrium calculations based on the elemental composition of the parent materials and processed fuels and steam gasification conditions predicted substantial reductions in concentrations of K, Cl, S, Na, and Mg in the product gas.

Catalyst characterization and activity of Zr or Mn containing Ru/Q10 were investigated for Fischer–Tropsch synthesis in a stirred slurry tank reactor. The addition of Zr or Mn in Ru/Q10 enhanced CO conversion, C 5 + selectivity and space time yield at 503 K, 5.0 MPa and 1800 h − 1 , and the catalyst activity was highly stable during the reaction. The addition of Zr or Mn can inhibit the oxidation of Ru species and it can maintain the active reduced Ru atoms on the catalyst surface. Ru/Q10 showed lower activity compared to Zr or Mn containing catalysts and it was deactivated due to the oxidation of active and reduced Ru species. Catalyst characterization results of BET, BJH, XRD, TPR, H 2 chemisorption, TEM, EDS and XPS were studied, and it suggests that a small amount of Zr or Mn addition can increase the surface atomic concentration of Ru due to the inhibition of the oxidation of the Ru species. ZrO 2 in Ru/Zr/Q10 and MnO in Ru/Mn/Q10 were formed on the catalyst surface, and it can be related to the maintenance of the Ru species in a reduced state, resulting to enhanced catalyst activity and stability.

This paper focuses on reforming dodecane and hydroprocessed renewable diesel to hydrogen rich gas in a non-thermal gliding-arc plasma stabilized in a reverse vortex flow reformer. The liquid fuels were directly injected into the reaction chamber using an ultrasonic nozzle and entrained in the reverse vortex flow before passing through the plasma. Initial parametric tests were used to investigate the individual effects of varying power input, steam to carbon ratio, and equivalence ratio on reformer performance. Subsequent factorial tests varied these parameters to identify optimal specific energy requirements. Optimal reforming conditions for dodecane, a model diesel compound, resulted in specific energy requirements of 134.1 ± 1.1 kJ mol−1 H2 produced, a H2 yield of 65.0 ± 0.02%, and an efficiency of 37.0 ± 0.02%. Optimal conditions for hydroprocessed renewable diesel resulted in a specific energy requirement of 176.1 ± 3.8 kJ mol−1 H2 produced, a H2 yield of 64.2 ± 1.7%, and an efficiency of 35.0 ± 1.0% at 95% confidence intervals. Physical operating boundaries due to arc extinction were identified.

The present work investigates the effects of biodiesel contamination on conventional and renewable marine diesels, i.e., NATO F-76 and HRD-76. The physical properties and chemical composition of F-76, HRD-76, and biodiesel were measured, including viscosity, density, peroxide value, heat of combustion, and acid number. Long-term (ASTM D4625) and accelerated (ASTM D5304) test methods were used to investigate the influence of biodiesel contamination on storage stability of HRD-76, F-76, and their blends. The impact of biodiesel contamination on oxidation stability of neat and blended fuels was also studied by conducting test ASTM D2274. In addition, the influence of biodiesel contamination on physicochemical properties after stressing the fuel was investigated according to the ASTM methods. The presence of biodiesel at contaminant levels did not have significant effects on the fuel properties or storage and oxidation stability of neat and blended HRD-76 or F-76. Properties of contaminated samples were deter...

The effects of pore size on Ru/SiO 2 catalyst performance were investigated for Fischer–Tropsch synthesis under the conditions of 503 K, 20 bar and 1800 h − 1 . Ru/SiO 2 with 10 nm pore size catalyst showed higher catalytic activity than Ru/SiO 2 catalysts with 3, 6 and 30 nm pore sizes. The 10 nm pore size, Ru/SiO 2 catalyst exhibited uniform pore diameter, an increased surface concentration of active Ru metals, and the increased dispersion of Ru on the surface compared to the other pore diameters. Deactivation was clearly observed for all Ru/SiO 2 catalysts during the reaction. The addition of small amounts of Zr and Mn (1:30, Zr or Mn:Si) improved catalytic activity and stability for Fischer–Tropsch synthesis. The deactivation rate of Ru/Zr/Q10 was about 21% at 51 h time on stream and this rate was much lower than Ru/Q10 (57%). Ru/Mn/Q10 showed higher catalytic activity than Ru/Q10 and Ru/Zr/Q10, and its deactivation rate was much lower ~ 9% after 51 h time on stream. The small amount of Mn added to the Ru/SiO 2 increased the concentration of active Ru metals and enhanced their dispersion on the support surface.

In this study, the physical properties and chemical composition of hydroprocessed renewable diesel derived from algae (HRD-76) were measured. Analysis of HRD-76 showed that the main components are C15–C18 n-alkanes and branched monomethyl hexadecanes and heptadecanes. Approximately 50% of HRD-76 is n- and iso-C17. Long-term (ASTM D4625) and accelerated (ASTM D5304) tests were conducted to investigate the storage stability of HRD-76, F-76, and their blends and the effects of long-term storage on the fuel properties. In addition, the ASTM D2274 method was used to test the oxidation stabilities of the neat and blended fuels. HRD-76 has better storage and oxidation stabilities than F-76, and the post-test changes in the fuel properties are influenced by the F-76 fraction in the fuel blend. Extended ASTM D2274 tests were also conducted to investigate the influence of long-term oxidation on the physicochemical properties of the fuel.

Two types of biomass fuel were gasified in a steam atmosphere using a bench-scale fluidized bed reactor. Filter char, bed material and the product gas stream were sampled and analyzed for a total of 21 elements including Al, Ca, Fe, K, Mg, Na and Si defined as major elements (ME), and Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, P, Sr, Pb, Ti, V, and Zn defined as trace elements (TE). The effects of the sampling system and gasification system on the measurement were determined. Mass balances for ME and TE are reported for individual elements and overall. It was found that most ash particles or metal elements can be captured by a silicon carbide candle filter that removes small particles from the gas phase, but some of volatile elements pass through the filter and are present in the gas stream.

The fast pyrolysis behaviour of pretreated banagrass was examined at four temperatures (between 400 and 600 C) and four residence times (between ~1.2 and 12 s). The pretreatment used water washing/leaching to reduce the inorganic content of the banagrass. Yields of bio-oil, permanent gases and char were determined at each reaction condition and compared to previously published results from untreated banagrass. Comparing the bio-oil yields from the untreated and pretreated banagrass shows that the yields were greater from the pretreated banagrass by 4 to 11 wt% (absolute) at all reaction conditions. The effect of pretreatment (i.e. reducing the amount of ash, and alkali and alkali earth metals) on pyrolysis products is: 1) to increase the dry bio-oil yield, 2) to decrease the amount of undetected material, 3) to produce a slight increase in CO yield or no change, 4) to slightly decrease CO2 yield or no change, and 5) to produce a more stable bio-oil (less aging). Char yield and total gas yield were unaffected by feedstock pretreatment. Four other tropical biomass species were also pyrolyzed under one condition (450°C and 1.4 s residence time) for comparison to the banagrass results. The samples include two hardwoods: leucaena and eucalyptus, and two grasses: sugarcane bagasse and energy-cane. A sample of pretreated energy-cane was also pyrolyzed. Of the materials tested, the best feedstocks for fast pyrolysis were sugarcane bagasse, pretreated energy cane and eucalyptus based on the yields of 'dry bio-oil', CO and CO2. On the same basis, the least productive feedstocks are untreated banagrass followed by pretreated banagrass and leucaena.

This paper focuses on the reforming of methane into hydrogen rich gas by means of gliding arc plasma stabilized in a reverse vortex flow. Parametric tests utilizing a 42 mm diameter reactor investigated the effects of electrode gap distance, reaction chamber exit diameter, steam input, methane input (fuel to oxygen ratio), and power input. Over the range of conditions tested, reactor performance was most sensitive to methane input. Decreasing the diameter of the reaction chamber exit impeded the performance of the reformer. A set of factorial tests determined the optimal operating conditions of the system to be at flow rates of 2 slpm nitrogen, 0.56 slpm oxygen, 1.25 slpm methane, an electrode gap distance of 34.5 mm, an outlet diameter of 12.65 mm, and a power input of 260 W. At these conditions the system yielded 83.3% hydrogen selectivity, 79.8% methane conversion and efficiency of 43.5%. Physical operating boundaries of the system defined by soot production and arc extinction were identified.

Permanent gas species, tar compounds, sulfur compounds, and ammonia produced from a bench-scale (∼1 kg/h) fluidized-bed biomass gasifier were analyzed. Two commercial Ni-based catalysts and one commercial ZnO sorbent were evaluated under varied conditions by quantifying contaminants from the reactor inlet and outlet with specific sampling and analysis methods. The Ni catalysts targeted tar destruction and ammonia reduction, and the ZnO sorbent was selected for sulfur compound removal. Tar components were identified by gas chromatography−mass spectrometry (GC−MS) and quantified by GC−flame ionization detector (FID). A total of 13 compounds (≥C6) were identified in raw product gas, principally “lighter tar” species with an average concentration of 15.5 g m−3 (dry gas basis). For tar species that were not detected by GC, a gravimetric method was used to quantify the portion of “heavier tar” (5.3 g m−3 dry gas basis). These data are raw gas tar concentrations for the gasifier-operating conditions used for the...

Previously a lab scale catalytic autothermal reformer (ATR) capable of operating at pressures from 6 to 50 bar was constructed and tested. The objective of the experimental program was to maximize H2 production per mole of O2 supplied (H2(out)/O2(in)). In this companion paper a 1-D, heterogeneous, numerical model is developed and tested for simulating the high pressure ATR. The effects of molar steam to carbon (S/C) and oxygen to carbon (O2/C) ratios are studied and optimal operating conditions are identified for three system operating pressures; 6, 28 and 50 bar. Experimental optimal conditions and model results are compared and found to be in close agreement. The optimal conditions, however, predicted by the model at pressures of 28 and 50 bar have higher S/C ratios and produce higher H2(out)/O2(in) yields than the experimentally determined optimums. A sensitivity analysis consisting of 9 model parameters is also performed. The model is most sensitive to the activation energy of the two steam reforming reactions used in the model and the operating parameter O2/C.

The adsorption capacity of activated carbon for the natural gas contaminant dimethylsulfide (DMS) was improved by impregnating it with FeCl3 introduced in solution to affect surface modification. A DMS adsorption mechanism and roles of impregnated FeCl3 on the capacity enhancement were proposed based on experimental tests results. Samples of activated carbon and activated carbon impregnated with FeCl3 were tested as DMS sorbents. Samples loaded with DMS were subsequently extracted with n-octane and the resulting solvents were analyzed for sulfur species using a gas chromatograph equipped with a sulfur chemiluminescence detector. No other sulfur compounds were detected in the liquid samples other than DMS. DMS, dimethyl disulfide, and carbonyl sulfide were recovered from identical DMS-adsorbed samples of activated carbon impregnated with FeCl3 subjected to temperature programmed desorption (TPD) in a nitrogen gas stream. Only DMS was recovered from the activated carbon samples. The TPD patterns indicate different kinetics of DMS desorption related to the carbon phase and the new active sites created by the FeCl3 impregnation. The new active sites improved DMS adsorption capacity and likely had stronger affinity with DMS molecule. As a reference, similar tests were investigated using methyl mercaptan (MM) as an adsorbate on the carbon sorbents. A different adsorption mechanism was found and discussed from these experimental results. Regeneration of the used carbon sorbents by thermal desorption was also explored.

An assessment of ethanol production potential from dedicated energy crops was conducted for the State of Hawaii considering lands, crop species, and conversion technologies. Evaluation of the spatial distributions of soil types, zoning, and annual rainfall was conducted using geographic information system data. Saccharum officinarum (sugarcane), Pennisetum purpureum (banagrass), Leucaena leucocephala, and Eucalyptus grandis were selected as potential feedstocks for sugar-based and lignocellulosic ethanol production. The analysis shows that only one cropping scenario applied to all available agriculturally zoned lands in the state would be capable of producing enough ethanol to meet the state's current motor gasoline consumption on an energy equivalent basis. State goals of displacing 20% (volume) of highway fuels by 2020 could be met by 14 of the 16 cropping and land use combinations. This indicates that the State of Hawaii could promote energy diversification through its choice of land leases. Distribution of suitable lands among islands is not consistent with motor fuel demand, suggesting that provisions must be made to support development of adequate storage and harbor facilities to enable movement of fuel between points of production and use. Comparison of possible production volumes with economic plant sizes indicates that sufficient feedstocks could be available on Maui, Hawaii, Oahu, and Kauai to realize economies of scale in production facilities. This study should be refined in the future to adequately address issues of environmental preservation, water consumption, and land use to provide additional guidance for policy and economic decision making.

Recent interest in fuel cells has led to the conceptual design of an ocean floor, fuel cell-based, power generating station fueled by methane from natural gas seeps or from the controlled decomposition of methane hydrates. Because the dissolved oxygen concentration in deep ocean water is too low to provide adequate supplies to a fuel processor and fuel cell, oxygen must be stored onboard the generating station. A lab scale catalytic autothermal reformer capable of operating at pressures of 6–50 bar was constructed and tested. The objective of the experimental program was to maximize H2 production per mole of O2 supplied (H2(out)/O2(in)). Optimization, using oxygen-to-carbon (O2/C) and water-to-carbon (S/C) ratios as independent variables, was conducted at three pressures using bottled O2. Surface response methodology was employed using a 22 factorial design. Optimal points were validated using H2O2 as both a stored oxidizer and steam source. The optimal experimental conditions for maximizing the moles of H2(out)/O2(in) occurred at a S/C ratio of 3.00–3.35 and an O2/C ratio of 0.44–0.48. When using H2O2 as the oxidizer, the moles of H2(out)/O2(in) increased ≤14%. An equilibrium model was also used to compare experimental and theoretical results.

Synthetic natural gas (SNG), which is produced from petroleum and distributed via pipeline in Honolulu by The Gas Company, was analyzed using a gas chromatograph equipped with a sulfur chemiluminescence detector (GC/SCD). Hydrogen sulfide (H 2 S), methyl mercaptan (MM), ethyl mercaptan (EM), dimethylsulfide (DMS), dimethyl disulfide (DMDS), tetrahydrothiophene (THT), ethyl disulfide (EDS), and one unidentified compound (UN1) were detected. Among these sulfur compounds, THT is added as an odorant and was present in the highest concentration. A commercial activated carbon (Calgon OLC plus 12X30) was modified by oxidation and impregnation methods and the resulting materials were evaluated for their ability to adsorb sulfur compounds present in SNG. The evaluation results indicate that all of the modification methods can improve the retention of individual sulfur compounds or the total sulfur capacity compared with the untreated virgin carbon. It is also found that activated carbons impregnated with metal impurities have different selectivity for sulfur compounds. Cu and Zn loaded carbons had the highest capacity for H 2 S removal, Fe loaded carbon was more efficient for DMS removal (the most difficult S compound to remove), and carbon oxidized by HNO 3 was the best for THT removal. Based on these findings, a composite sorbent consisting of Cu loaded and Fe loaded carbons was designed and tested. The test results indicate that the composite sorbent had improved performance in the removal of individual sulfur compound. A linear programming model was used to design a composite sorbent optimized to minimize the required sorbent mass based on a 1-kW scale fuel cell system service target. Validation tests showed that the optimized sorbent required less of the individual modified carbon components than when they were individually used for the same sulfur removal target.

Excessive emissions of fossil CO2 are known to be a primary cause of global climate change. Emissions from the iron and steel-making industries account for 5−6% of global fossil CO2 emissions. Biocarbon (i.e., charcoal) could be used to replace the coal currently employed to smelt iron ore and thereby reduce fossil CO2 emissions. In Brazil, Eucalyptus wood charcoal is used to smelt iron ore, but there is interest in the use of charcoal produced from other biomass feedstocks. Banagrass, a variety of elephantgrass (Pennisetum purpureum, Schum.), which produces near-record amounts of biomass, is a promising biomass candidate for charcoal production in Brazil and elsewhere. In this paper we describe results of charcoal production from banagrass of different ages and states of demineralization. Mature banagrass provides the highest yields of biocarbon. In addition to its maturity, the structure of the feedstock strongly influences the fixed-carbon yield. Our results indicate that banagrass may be preferred to ...

A commercial activated carbon (Calgon OLC plus 12X30) was modified by oxidation and impregnation methods. The capacities of the resulting sorbents to adsorb tetrahydrothiophene (THT) were evaluated by conducting breakthrough tests. Carbon modified by oxidation with 50% HNO 3 solution followed by impregnation with 1.05 mmol FeCl 3 per gram sorbent displayed the greatest improvement in THT capacity, increasing from 0.9 mg S per gram of the parent activated carbon to 6.4 mg S per gram of the modified carbon sorbent. Effects of modification on surface physical and chemical properties were investigated using nitrogen sorption, scanning electron microscopy (SEM), and the pH detector. The results indicate that improving THT adsorption capacity is related to the surface acidity/basicity of carbon sorbents, i.e. increasing the acidic groups on the carbon surface improves THT capacity. The surface chemical properties play a more important role than physical properties (such as pore structure) in enhancing the sulfu...

A series of tests were performed to investigate reforming of reagent-grade propane-1,2,3-triol, (C3H8O3) commonly called glycerin, to produce a H2 rich gas. Effects of the operating parameters, oxygen to carbon ratio, steam to carbon ratio, and temperature, were determined using a factorial experimental design. A mathematical model defining the effect of the three parameters was derived and used to improve the hydrogen yield. From the range of experimental conditions, it was concluded that the oxygen to carbon ratio, as well as the interaction between oxygen to carbon ratio and temperature had the most important effects on H2 yield. A 4.5 mol quantity of hydrogen was produced per mole of glycerin at experimental conditions of oxygen to carbon ratio of 0, steam to carbon ratio of 2.2, and temperature of 804 °C. This is 65% of the maximum theoretical H2 yield, and 90% of the H2 yield predicted by thermochemical equilibrium. A 1.4 mol quantity of CO was also produced per mole of glycerin, presenting the pote...

An investigation of the use of chemical equilibrium calculations to predict experimental measurements of the trace species K, Na, and Cl in a gasifier product stream was completed. The method applied two sequential equilibrium calculations. The first calculation used fuel and air data as input and was performed at the gasifier temperature (∼800 °C). A second calculation used the results of the first calculation as input and was performed at the temperature of the hot gas filter (∼700 °C). Equilibrium calculations based only on the fuel composition and air input data predicted potassium, sodium, and chlorine concentrations that were greater than measured experimental values. The equilibrium concentration of potassium, which is the alkali metal of particular interest in this study, was an order of magnitude larger than the experimental results (153 ppmw vs 28 ppmw). Including the mass of bed material used in the experiments as input to the equilibrium calculation reduced the predicted potassium concentratio...

Autothermal reforming of LPG was studied in a fixed-bed reactor by varying controlled parameters, such as reforming temperature, steam-to-carbon ratio (S/C), oxygen-to-carbon ratio (O/C) and catalyst. The conditions tested were two nickel-based catalysts, at 680–820 °C, with S/C of 0.30–1.9 and O/C of 0.64–1.4. In addition to controlled variables, it was found vapor composition of LPG withdrawn were not constant at different levels of tank exhaustion. The fuel vapor contained more heavy components and odorant—ethyl mercaptan as the bottle approached empty. Multivariate data analysis method, projections to latent structures (PLS), provided quantitative analysis of the effects of temperature, S/C, O/C, fuel composition and catalyst activity on reformate gas composition. Temperature, S/C and O/C were found to be the most important parameters for fuel conversion and avoiding carbon deposition. Sulfur poisoning by odorant was the main cause of catalyst deactivation. Composition of hydrocarbons in LPG vapor was shown to affect the autothermal reforming process, but the influence was less significant. Under test conditions, reformate gas composition generally approached equilibrium. The kinetically controlled methane reduction was well predicted by a PLS regression model.

This project had two main goals. The first goal was to evaluate several high yielding tropical perennial grasses as feedstock for biofuel production, and to characterize the feedstock for compatible biofuel production systems. The second goal was to assess the integration of renewable energy systems for Hawaii. The project focused on high-yield grasses (napiergrass, energycane, sweet sorghum, and sugarcane). Field plots were established to evaluate the effects of elevation (30, 300 and 900 meters above sea level) and irrigation (50%, 75% and 100% of sugarcane plantation practice) on energy crop yields and input. The test plots were extensive monitored including: hydrologic studies to measure crop water use and losses through seepage and evapotranspiration; changes in soil carbon stock; greenhouse gas flux (CO2, CH4, and N2O) from the soil surface; and root morphology, biomass, and turnover. Results showed significant effects of environment on crop yields. In general, crop yields decrease as the elevation increased, being more pronounced for sweet sorghum and energycane than napiergrass. Also energy crop yields were higher with increased irrigation levels, being most pronounced with energycane and less so with sweet sorghum. Daylight length greatly affected sweet sorghum growth and yields. One of the energy crops (napiergrass) wasmore » harvested at different ages (2, 4, 6, and 8 months) to assess the changes in feedstock characteristics with age and potential to generate co-products. Although there was greater potential for co-products from younger feedstock, the increased production was not sufficient to offset the additional cost of harvesting multiple times per year. The feedstocks were also characterized to assess their compatibility with biochemical and thermochemical conversion processes. The project objectives are being continued through additional support from the Office of Naval Research, and the Biomass Research and Development Initiative. Renewable energy assessments included: biomass feedstocks currently being produced by Hawaiian Commercial & Sugar Co., and possibilities of producing methane from agricultural and livestock wastes and the potential of photovoltaic systems for irrigation pumping at HC&S. Finally, the impact of a micro-hydroelectric system on a small-farm economics and the local community was assessed.« less

Cofiring tests were conducted in a boiler at the Hawaiian Commercial & Sugar factory at Puunene, Hawaii. Three tests were conducted; a baseline test firing coal and fuel oil (Test 1) and two cofiring tests utilizing coal, fuel oil, and biomass. In the latter two tests, bagasse (Test 2) and a blend of bagasse and fiber cane (Test 3) were used as the biomass fuel. Biomass accounted for 62% and 50% of the total energy inputs for Tests 2 and 3, respectively. All three tests were conducted in a spreader stoker-type boiler operating at a steam flow rate of 46.5 tonne h −1 at 63.2 bar and 400 °C. Fuel properties, boiler efficiency, solids removed in the pollution control devices, and stack emissions of criteria pollutants were monitored during the test campaign and results are reported herein. In addition, a laser induced breakdown spectroscopy probe and a deposition probe were installed near the superheaters to characterize fire-side ash behavior under each of the test conditions.

A study of treatment methods to improve the fuel characteristics of sugarcane variety B52298 was conducted. Two parent materials, whole cane (WC) and stripped cane (SC), were included in the study. The whole cane material was subjected to three treatments: (1) no treatment, WC-U; (2) a single milling, WC-M; and (3) an initial milling followed by leaching and a secondary milling, WC-MLM. Treatments (1) through (3) are in order of increasing severity. The stripped cane material was subjected to treatment (3) and designated as SC-MLM. Regardless of parent material, milling produced moisture contents of ∼50% wet basis and fiber bulk densities of ∼97 kg m−3 in the treated fuels and produced a shift in particle distributions toward smaller sizes. Geometric mean diameters (by weight) of the WC-U, WC-M, WC-MLM, and SC-MLM materials were 2.3, 1.8, 1.3, and 1.3 mm, respectively. Ash generated from the fuel was reduced by roughly 1% (absolute) for each milling operation, resulting in reductions of ∼2% for the WC-MLM and SC-MLM treatments. Ash reduction was primarily due to the removal of K, Cl, and S by the treatment operations. Ash removal, in addition to reductions in the O content of the treated fuels, contributed to an increase in the energy content of the fuels from ∼17.6 MJ kg−1 in the parent materials to 18.4 and 19.2 MJ kg−1 for the WC-MLM and SC-MLM treatments, respectively. K, Cl, S, and N concentrations were all reduced in the fuel by the treatments. K comprised ∼1.3% of the parent materials and Cl accounted for 0.65% and 0.83% of dry matter for the whole cane and stripped cane parent materials, respectively. Reductions in K concentration relative to the parent materials for the WC-M, WC-MLM, and SC-MLM treatments were 50%, 86%, and 91%, respectively. Cl was reduced 62% by the WC-M treatment relative to the unprocessed whole cane, and removal was essentially complete for the two leached treatments. Sulfur in the two parent materials accounted for ∼0.22% of plant dry matter. Compared to the parent materials, the WC-M, WC-MLM, and SC-MLM treatments removed 36%, 82%, and 86% of the S, respectively. Nitrogen concentrations in the stripped cane and whole cane parent materials were 0.48% and 0.37%, respectively. Nitrogen reduction by the WC-M, WC-MLM, and SC-MLM treatments was 12%, 27%, and 57%, respectively. Ash deformation temperatures (oxidizing atmosphere) increased in the treated fuels compared to parent materials. Ash from the WC-MLM treatment did not attain the initial stage of deformation at the maximum test temperature, 1482 °C. Ash of the WC-M and SC-MLM treatments became fluid at ∼1350 °C. Experimentally determined fluid temperatures for the more severely treated fuels compared well with values predicted by a ternary phase diagram for the SiO2–K2O–CaO system. Slagging and fouling indices were computed for each of the fuel treatments. Values for WC-U and WC-M exceeded a benchmark of 0.34 kg (K2O+Na2O) GJ−1 and would be expected to cause ash deposition in boiler use. Values for the WC-MLM and SC-MLM treatments were 0.13 and 0.08 kg (K2O+Na2O) GJ−1, respectively, and are good candidates for boiler fuels. Concomitant reductions in S and Cl for these two fuels further reduce the likelihood of ash deposition, as well as improve environmental performance by reducing criteria and acid gas pollutant emissions. Mass balances for K and Cl were conducted for the treatment operations. Closure for the balances ranged from 112% to 122% over all treatments, and was viewed as validating the consistency of the results.

A bench-scale gasifier system composed of a fluidized-bed gasifier, high-temperature ceramic filter, and fixed-bed solid sorbent reactor was used to study the removal of alkali from a hot product gas stream. During a test conducted with an empty solid sorbent reactor, dry gas-phase concentrations of 28 ppmw K, 11 ppmw Na, and 1309 ppmw Cl were measured. Four subsequent tests utilized 2.4−3.4-mm-diameter particles of activated bauxite or emathlite in the solid sorbent reactor. Over these four tests, K concentrations ranged from 0.03 to 0.07 ppmw, and Na concentrations ranged from 0.2 and 0.9 ppmw at the exit of the solid sorbent reactor. Chlorine concentrations at the exit of the reactor were essentially unaffected. Hot-water leaching tests indicated that alkali capture by activated bauxite and emathlite was through physical adsorption and chemisorption, respectively.

Gasification of four biomass feedstocks (leucaena, sawdust, bagasse, and banagrass) with significantly different fuel-bound nitrogen (FBN) content was investigated to determine the effects of operational parameters and nitrogen content of biomass on the partitioning of FBN among nitrogenous gas species. Experiments were performed using a bench-scale, indirectly heated, fluidized-bed gasifier. Data were obtained over a range of temperatures and equivalence ratios representative of commercial biomass gasification processes. An assay of all major nitrogenous components in the gasification products was performed for the first time, providing a clear accounting of the evolution of FBN. Important findings of this research include the following: (1) NH3 and N2 are the dominant species evolved from fuel nitrogen during biomass gasification; >90% of FBN in feedstock is converted to NH3 and N2; (2) relative levels of NH3 and N2 are determined by thermochemical reactions in the gasifier; these reactions are affecte...

Leaching of inorganic materials has recently been shown to substantially improve the combustion properties of biomass fuels, especially straw but including other herbaceous and woody fuels. Leaching with water removes large fractions of alkali metals (typically >80% of potassium and sodium) and chlorine (>90%). Smaller fractions of sulfur and phosphorus are also removed. Alkali metals are heavily involved in ash fouling and slagging in combustion and thermal gasification systems. Chlorine is a facilitator of alkali volatilization, and contributes to corrosion and air pollution. The presence of these elements has reduced or eliminated the use of certain biomass fuels in many combustion applications, even where such use might provide significant environmental benefits. Leaching could mitigate the undesirable effects of biomass ash in thermal systems. Reported here for the first time are comparative studies of volatile inorganic species evolving from leached and unleached biomass fuels during thermal convers...

Thermodynamic cycle analyses of biomass gasifier-based electric power stations at two scales, nominally 5 and 20 MWe (net electric power output), were performed to assess process performance and viability. Various configurations (Rankine, simple, steam-injected gas turbine, and combined cycles) of a 5 MW stand-alone power station were modeled and a 20 MW biomass-based integrated gasifier combined-cycle cogeneration facility at a sugar factory was simulated. Information gained from these analyses will be applied to determine whether biomass gasification-based electricity production is practicable in Hawaii and other sugar producing locales.

An experimental study of hydrogen production from biomass was conducted using a benchscale fluidized bed gasifier. Parametric experiments were performed to determine the effects of reactor temperature, equivalence ratio, and steam to biomass ratio. Experimental measurements of gas composition and yield were used to calculate the hydrogen yield potential, the capacity of the gas stream for hydrogen production by shifting carbon monoxide and steam reforming higher hydrocarbons. Over the ranges of experimental conditions examined, hydrogen yield potential proved to be most sensitive to equivalence ratio, varying from 62 g H2 kg−1 of dry, ash-free biomass at an equivalence ratio of 0.37, to 128 g H2 kg−1 of dry, ash-free biomass at an equivalence ratio of 0.0. Of the conditions tested, the highest hydrogen yield potential, 128 g H2 kg−1 of dry, ash-free biomass, was achieved at a reactor temperature of 850 °C, equivalence ratio of 0.0, and a steam to biomass ratio of 1.7. This is 78% of the theoretical maximum yield of 165 g H2 kg−1 of dry, ash-free biomass for this feedstock.