Increase In Gas Yield Research Articles

Validation of a new set-up for continuous catalytic fast pyrolysis of biomass coupled with vapour phase upgrading

A fully controlled, continuously operated mini-plant has been designed and constructed based on auger reactor technology. Three types of biomass fast pyrolysis experiments were performed in this set-up, viz. non-catalytic, in situ catalytic fast pyrolysis and ex situ upgrading of non-catalytic fast pyrolysis vapours by means of a downstream, moving-bed catalytic reactor. Pine wood was selected as the reference biomass feedstock. The mini-plant enables variation of the catalyst loading and contact times while producing larger samples suitable for full characterization in continuous operation. Due to short catalyst residence times and the fact that the biomass fed to the reactor is always brought into contact with fresh catalyst (in case of in situ catalysis) or the pyrolysis vapours always contact with fresh catalyst in the moving bed catalytic reactor (in case of ex situ catalysis), catalyst deactivation and coking are prevented ensuring improved experimental repeatability in catalytic pyrolysis experiments. The performance of the system was verified by in- and ex situ application of a single type of heterogeneous ZSM-5 based acidic catalyst while the non-catalytic results were taken as reference. Catalytic fast pyrolysis results in more effective oxygen removal from the bio-oil in the form of water, and resulting in lower yields of the organic fraction. Moreover catalytic decarbonylation reactions gave rise to increased gas yields. With in- and ex situ catalysis, increases in the char yields were observed as well as coke deposition on the catalyst surface. GC×GC-FID and GC×GC-TOF-MS analysis of the produced bio-oils showed that the use of in- and ex situ catalysis causes conversion of high molecular weight compounds to lower ones. Disappearance of detectable sugars and aldehydes, a decrease of the yield of acids, formation of phenols, and favoured aromatics production were the other catalytic effects observed.

Characteristics of Gases From Co-Pyrolysis of Sawdust and Tires

The composition and characteristics of permanent gases that evolve during co-pyrolysis of sawdust and waste tires were observed. Gas composition was determined by gas chromatography, whereas gas characteristics were studied by pyrolysis–Fourier transform infrared (Py-FTIR) spectroscopy. Results show that as co-pyrolysis temperature and the proportion of sawdust in the mixture of biomass and waste tires increase, the gas yield increases, but the relationship between the addition of sawdust and gas yield is nonlinear. A synthetic effect exists among the co-pyrolysis gases. When the mass ratio of sawdust to tires is 1:2, and pyrolysis temperature is 600°C at a flow rate of 90 ml min−1, gas yield reaches 30.3 wt%. The mass fraction accounted for by ignited gases (such as CO, H2, CH4, C3H8, C3H6, and C2H4) is nearly 46% with a gross calorific value (GCV) of 17.9 MJ Nm−3, indicating that the gases may act as fuel gas. As a desulfurizer, ZnO removes 92% of H2S in the gaseous products. The content of H2S is below 10 × 10−9 g g−1 when ZnO is used during co-pyrolysis. Py-FTIR analysis shows that gases containing saturated C–H bonds (such as CH4 and C3H8) evolve first, followed by CO2, CO, and water vapor, and finally, vinyl-containing gases such as C3H6. It confirms that gases produced by co-pyrolysis of biomass and tires are completely utilized as resources while they are disposed. This has a great significance for sustainable supply of energy.

High-yield hydrogen production from glucose by supercritical water gasification without added catalyst

Continuous supercritical water gasification of glucose is investigated with a recently developed updraft gasification apparatus under various conditions: temperatures of 600–767 °C, residence times of 15–60 s, glucose concentrations of 1.8–15 wt% and without added a catalyst. The experimental gas yields are compared with predicted values at equilibrium that are estimated via Gibbs free energy minimization. Total gas yields and hydrogen gas yield increase with temperature. At 740 °C and 1.8 wt%, hydrogen gas yields become very high (10.5–11.2 mol/mol glucose). The hydrogen gas yields do not vary significantly with different residence times. The hydrogen gas yield decreases to 5.7 mol/mol glucose at 15 wt%, a value very close to the predicted value (6.3 mol/mol glucose). Only acetic acid is detected in the liquid effluents at temperatures above 740 °C, while 42 products are detected at 600 °C. The highest hydrogen gas yield obtained in this study is 11.5 mol/mol glucose at 25 MPa, 767 °C, and 1.8 wt%, for 60 s; this value is very close to the theoretical equilibrium hydrogen yield of 11.9 mol/mol glucose. Under these conditions, the carbon efficiency is very high (91%) and total organic carbon (TOC) in the liquid product is very low (23 ppm), indicating that glucose is almost completely converted to gaseous products. Comparison with other work under similar operating conditions shows that the current reactor is capable of attaining higher hydrogen gas yields at temperatures above 650 °C. Possible explanations for the higher hydrogen gas yields are presented.

Anaerobic waste activated sludge co-digestion with olive mill wastewater

Co-digestion of waste activated sludge (WAS) with agro-industrial organic wastewaters is a technology that is increasingly being applied in order to produce increased gas yield from the biomass. In this study, the effect of olive mill wastewater (OMW) on the performance of a cascade of two anaerobic continuous stirred tank (CSTR) reactors treating thickened WAS at mesophilic conditions was investigated. The objectives of this work were (a) to evaluate the use of OMW as a co-substrate to improve biogas production, (b) to determine the optimum hydraulic retention time that provides an optimised biodegradation rate or methane production, and (c) to study the system stability after OMW addition in sewage sludge. The biogas production rate at steady state conditions reached 0.73, 0.63, 0.56 and 0.46 l(biogas)/l(reactor)/d for hydraulic retention times (HRTs) of 12.3, 14, 16.4 and 19.7 d. The average removal of soluble chemical oxygen demand (sCOD) ranged between 64 and 72% for organic loading rates between 0.49 and 0.75 g sCOD/l/d. Reduction in the volatile suspended solids ranged between 27 and 30%. In terms of biogas selectivity, values of 0.6 l(biogas)/g tCOD removed and 1.1 l(biogas)/g TVS removed were measured.

Two stage pyrolysis-catalytic gasification of waste tyres: Influence of process parameters

The pyrolysis-catalytic steam gasification of waste tyres has been investigated using a two-stage fixed bed reactor. The catalyst used was Ni/Al2O3. The influence of the process parameters, catalyst:waste tyre ratio, gasification temperature and water injection rate on hydrogen production were investigated. The results indicated that the potential H2 production (conversion of the hydrogen in the tyre to hydrogen gas) was 7.19wt.% when the catalyst:waste tyres ratio was 0.5 (g/g), which increased to 20.0wt.% at the catalyst:waste tyres ratio of 2.0 (g/g). Increasing the gasification temperature from 600 to 900°C was shown to increase gas yield from 14.3wt.% to 56.8wt.% and the potential H2 production increased from 3.2 to 13.1wt.%. The steam flow rate, in terms of the amount of water injected, had a small but significant influence on the potential H2 production. The characteristics of the carbon deposited on the reacted catalysts were examined by temperature-programmed oxidation (TPO) and scanning electron microscopy (SEM) and were shown to consist of be monoatomic carbon and filamentous carbon. The amount of carbon deposited on the catalyst was reduced with an increase in the amount of catalyst used and the water content. However, the highest amount of coke deposited on the catalyst was 20.8wt.% for the gasification temperature of 700°C.

Fast pyrolysis in a novel wire-mesh reactor: Design and initial results

Pyrolysis is known to occur by decomposition processes followed by vapour phase reactions. The goal of this research is to develop a novel device to study the initial decomposition processes. For this, a novel wire-mesh reactor was constructed. A small sample (<0.1g) was clamped between two meshes that were heated fast (up to 10000°C/s, ΔTmesh ±35°C) by an electrical current. The mesh/feedstock was placed inside a vacumized (P<0.3mbar), liquid nitrogen cooled vessel (Twall<−80°C). These two last features were proven to result in a low vapour life time (<15–25ms versus ∼2s in typical pyrolysis). The vapour residence time and temperature could be increased by increasing the pressure inside the reactor and by removing of the liquid nitrogen cooling. Reproducible results concerning yields (mass balance closures 90–110wt%) and analysis were obtained (oil by SEC and NMR, gas by GC, char by FTIR). The yields and oil composition were changing with loading from 0.05g to 0.1g, despite the small sample amounts. Compared to more “conventional” pyrolysis processes, high oil yields (84wt%), very low char yields (5wt%) and low gas yields (8wt%) were obtained. Using a high speed camera, movies were made and together with accompanying pressure profiles, it was possible to estimate the conversion rate. At 500°C the conversion process was finished within 0.8s which is faster than previously reported in the literature. Especially an increase in gas yield (+14wt%, mainly CO) was observed in absence of cooling (Pvac/No Cooling), while both the gas (+4wt%) and char yield (+3wt%) increased under atmospheric pressure (Patm/Cooling), all at the expense of oil yield. Compared to more “conventional” pyrolysis oil, the oil did contain: (i) heavier molecules and (ii) a sugar fraction.

Hydrocarbon Fractions Obtained from Recycling of Waste Materials

Pyrolysis of contaminated waste plastics was carried out in a laboratory scale batch reactor at 450 °C under nitrogen atmosphere. Raw materials were original high density polyethylene (HDPE) and waste motor oil flasks from industrial sector. Volatile products were passed through a fixed catalyst bed with temperature of 350 °C. In the experiments Y-zeolite, β-zeolite, HZSM-5, Co/Mo and Ni/Mo catalysts were used. Three product fractions were obtained: gas, liquid and heavy oil. Catalysts had mainly effect on the gas and liquid yields, the amount of the residue did not show significant differences in the case of the same raw material. By pyrolysis of contaminated raw material higher volatile product yield could be observed compared to pyrolysis of the original raw material. Catalysts increased gas yields and had influence on the composition of products. Most significant effect could be observed in the case of Y-zeolite and β-zeolite catalysts. Contaminant level of liquid products could be decreased in case of thermo-catalytic pyrolysis, which is a key property for further application of the pyrolysis products.

Meat and bone meal and coal co-gasification: Environmental advantages

Meat and bone meal (MBM) is currently an important waste product found all over the world. Actually, part of this residue's energy power is lost in land fills. Co-gasification of MBM and coal in a fluidised bed reactor, using air as a fluidising agent, has been studied as a possible alternative for the management of this material. The research studied the influence of the operational conditions (temperature, equivalence ratio and MBM percentage fed) on the product gas composition and on the gas lower heating value. The operational conditions analysed were temperature (800–900 °C), equivalence ratio (0.25–0.35) and the MBM percentage added to coal (0–1 wt.%). The results obtained were analysed according to the Design of Experiments (DOE) statistical tool. Experimental results obtained showed that co-gasification of coal with a low percentage of MBM are possible in a fluidised bed reactor. 9 (vol.%) of carbon monoxide and 6 (vol.%) of hydrogen are obtained in the produced flue gas. A gas with a heating value, between 2100 and 3500 kJ/(STP)m 3, has been quantified. The addition of (up to) 1 wt.% of MBM to the coal gasification does not affect the CO and H 2 gas production, however, the gas yield increases and the lower heating value decreases with this addition.

Gas formation regularities at the consecutive and simultaneous impact of ionizing radiations and heat on Turkish lignites

The regularities of formation of gases H2, CO and hydrocarbons C1–C4 at the consecutive and simultaneous influence of ionizing radiations and heat on Turkish lignites of Karaman–Ermenek deposit was researched. It is shown that at the consecutive influence of radiation and heat the gas yield depends extremely on the preliminary irradiation dose. The simultaneous influence of these factors on lignite leads to the gas yield increase which is connected with acceleration of the active radiolytic particles’ diffusion and breaking off reactions with their participation. Under the influence of the accelerated electron beam lignite decomposes with the relatively high radiation-chemical yields than under the influence of gamma radiation which is connected with acceleration of the diffusion processes due to the irradiated sample’s heating.

Noncatalytic gasification of isooctane in supercritical water: A Strategy for high-yield hydrogen production

Continuous supercritical water gasification of isooctane, a model gasoline compound, is investigated using an updraft gasification system. A new reactor material, Haynes® 230® alloy, is employed to run gasification reactions at high temperature and pressure (763 ± 2 °C; 25 MPa). A large-volume reactor is used (170 mL) to enable the gasification to be run at a long residence time, up to 120 s. Various gasification experiments are performed by changing the residence time (60–120 s), the isooctane concentration (6.3–14.7 wt%), and the oxidant concentration (equivalent oxidant ratio 0–0.3). The total gas yield and the hydrogen gas yield increase with increasing residence time. At 106 s and an isooctane concentration of 6.3 wt%, a very high hydrogen gas yield of 12.4 mol/mol isooctane, which is 50% of the theoretical maximum hydrogen gas yield and 92% of the equilibrium hydrogen gas yield under the given conditions, is achieved. Under these conditions, supercritical water partial oxidation does not increase the hydrogen gas yield significantly. The produced gases are hydrogen (68 mol%), carbon dioxide (20 mol%), methane (9.8 mol%), carbon monoxide (1.3 mol%), and ethane (0.9 mol%). The carbon gasification efficiency is in the range 75–91%, depending on the oxidant concentration. A comparison of supercritical water gasification with other conventional methods, including steam reforming, autothermal reforming, and partial oxidation, is also presented.

Liquefactions of peat in supercritical water with a novel iron catalyst

Raw iron ore has been investigated for use as a catalyst in direct liquefaction of peat into bio-crude by supercritical water treatment. The liquefaction treatments were conducted at temperatures from 350 °C to 500 °C for a residence time from 10 min to 4 h. The supercritical water treatment of peat with the iron ore generally resulted in 19–40 wt% yield of heavy oil (HO) that has a higher heating value (HHV) of 30–37 MJ/kg. An increase in the operating temperature generally increased gas yield and decreased oil and char yields, while a maximum HO formation was observed at around 400 °C. At 400 °C for a residence time of 2 h, the addition of the raw iron ore in the operation produced HO at a very high yield of about 40 wt%, nearly doubling that of the treatment without catalyst. An increase of water-to-peat ratio led to enhanced formation of HO products, accompanied by a decrease in gas or char yield. The optimal reaction time appeared to be 2 h for the maximum HO production, and a longer residence time than 2 h generally led to a decrease in HO yield but an increase in gas yield. Compared with the raw iron ore, its H 2-reduced form and two synthesized iron-based catalysts (FeOOH and Fe 2O 3) all showed a lower activity for HO production. Some conventional biomass liquefaction catalysts (i.e., KOH, FeCl 3 and FeSO 4) showed negligible or even negative effects on the HO yield, while these catalysts were found very active for promoting the gas yields and hydrogen formation.

Comprehensive study of the influence of total pressure on products yields in fluidized bed gasification of wood sawdust

Wood sawdust gasification experiments were performed in a steam fluidized bed at 800 °C between 2 and 10 bar. An evolution of gas yields with time was measured during the tests, and especially an increase of hydrogen and carbon dioxide yields. This test duration effect was ascribed to char build-up in the bed. As tests proceed, the contribution of char steam gasification to gas yield increases, and the catalytic effect of char on hydrocarbons and tar conversion and on water–gas shift reaction is enhanced. As total pressure increases from 2 to 10 bar, hydrogen, carbon dioxide and methane yields increase by 16%, 53% and 38% respectively, whereas carbon monoxide yield decreases by 33%. The changes in gaseous yields with pressure can be partly explained by the influence of pressure on gas phase reactions (acceleration of water–gas shift kinetics and change in hydrocarbon reactions). The increase of methane yield with pressure is rather suggested to be linked to a change in secondary pyrolysis reactions scheme under high pressure.

Gasification Characteristics of Coal/Biomass Blend in a Dual Circulating Fluidized Bed Reactor

The effects of reaction temperature (750−900 °C), steam/fuel ratio (0.5−0.8), and biomass ratio (0, 0.25, 0.5, 0.75, 1) on the gasification characteristics have been determined in a dual circulating fluidized bed reactor (combustor, 0.04 m × 0.11 m × 4.5 m high; gasifier, 0.04 m × 0.285 m × 2.13 m high). Indonesian Tinto sub-bituminous coal and Quercus acutissima sawdust were used as the coal and biomass, respectively. The product gas yield, carbon conversion, and cold gas efficiency from gasification of biomass are higher than those of coal with increasing temperature and steam/fuel ratio. After pyrolysis, surface area, pore volume, and micropores of coal/biomass blend char increase. The maximum increase in gas yield can be obtained with a biomass ratio of 0.5 at the given reaction temperature. Calorific values of the product gas are 9.89−11.15 MJ/m3 with the coal, 12.10−13.19 MJ/m3 with the biomass, and 13.77−14.39 MJ/m3 with the coal/biomass blends at 800 °C. The synergistic effects on the basis of cal...

Gas cleaning, gas conditioning and tar abatement by means of a catalytic filter candle in a biomass fluidized-bed gasifier

A bench-scale fluidized-bed biomass gasification plant, operating at atmospheric pressure and temperature within the range 800–820 °C, has been used to test an innovative gas cleaning device: a catalytic filter candle fitted into the bed freeboard. This housing of the gas conditioning system within the gasifier itself results in a very compact unit and greatly reduced thermal losses. Long term (22 h) tests were performed on the gasifier both with and without the catalytic candle filter, under otherwise identical conditions. Analysis of the product gas for the two cases showed the catalytic filtration to give rise to notable improvements in both gas quality and gas yield: an increase in hydrogen yield of 130% and an overall increase in gas yield of 69% – with corresponding decreases in methane and tar content of 20% and 79%, respectively. HPLC/UV analysis was used to characterize the tar compounds.

Syngas production from pyrolysis of municipal solid waste (MSW) with dolomite as downstream catalysts

Syngas production from pyrolysis of municipal solid waste (MSW) with calcined dolomite as catalysts, has been investigated in a bench-scale downstream fixed-bed reactor over the temperature range of 750–900 °C. The influence of weight hourly space velocity (WHSV) and reactor temperature on product yields and gas composition were studied. Syngas production from pyrolysis of MSW varied in the range of 47–67 mol%. The results indicated that the presence of calcined dolomite influenced greatly the product yields and gas composition in pyrolysis process, and revealed significant catalytic performance on increasing gas yield and decreasing oil yield and char yield compared to non-catalytic process. A higher temperature resulted in a higher conversion of MSW into syngas production with a significant increase of H 2 and CO contents. Meanwhile, syngas from MSW pyrolysis is highly desirable as feedstock for Fischer–Tropsch synthesis for the production of transportation fuels, also can be directly used as a MHV fuel with lower heating value of ∼13.87 MJ/N m 3.

Biogas production from anaerobic co-digestion of agroindustrial wastewaters under mesophilic conditions in a two-stage process

Abstract Co-digestion of organic wastes is a technology that is increasingly being applied for simultaneous treatment of several solid and liquid organic wastes, in which the content of nutrients can thereby be balanced, and the negative effect of toxic compounds on the digestion process may be decreased giving an increased gas yield from the biomass. Moreover, co-digestion may contribute to a more efficient use of anaerobic digestion (AD) reactors and cost-sharing by processing multiple waste streams in a single facility. In this study, efficient biodegradation of a mixture containing olive mill wastewater (OMW), liquid cow manure (LCM) and cheese whey (CW) using a two-stage anaerobic process was examined. Two continuously stirred tank reactors (CSTRs) were used under mesophilic conditions (35°C) in order to enhance acidogenesis and methanogenesis. The overall process was designed with a hydraulic retention time (HRT) of 19 days. The acidogenic reactor was initially fed with an influent mixture composed of 55% OMW, 40% CW and 5% LCM. After the 87th day of operation, the mixture was changed to 90% of CW and 10% of LCM based on the actual availability of wastes produced by the respective agroindustries. The average removal of dissolved chemical oxygen demand (COD) was 75.5% and 85.2% for the two examined scenarios at OLR of 5.5 ± 0.36 and 4.5 ± 0.30 g total COD/Lreactor/d, while the methane production rate at the steady state reached 1.35 ± 0.11 and 1.33 ± 0.15 L CH 4 /Lreactor/day respectively.

Hygienic effects and gas production of plastic bio-digesters under tropical conditions

Plastic plug-flow bio-digesters have been promoted as a good option for improved treatment of manure and wastewater in developing countries although minimal information has been published on their hygienic status. This bench-scale study replicates bio-digester conditions to evaluate the reduction of pathogen and indicator microorganisms at three different hydraulic retention times (HRT) in the anaerobic treatment of pig manures at 30 degrees C for 50 days. Results showed that physicochemical values differed between HRTs. Gas production efficiency was better for longer HRTS. The accumulated sludge at the reactor's base increased with longer HRT. Phages and bacteria examined were reduced, but none was completely eliminated. Log10 reduction of bacteria ranged from 0.54 to 2.47. Phages ranged from 1.60 to 3.42. The reduction of organisms at HRT = 30 days was about one log10 unit higher than HRT = 15 days and about two log10 units higher than HRT = 3 days. The results indicate that the reduction of tested organisms increases with HRT. However the hygienic quality of the liquid effluent does not meet required quality values for surface and irrigation water. Longer HRTs are recommended to increase gas yield and achieve higher pathogen reduction. More barriers should be applied while handling bio-digester outputs to minimise risks to environmental and human health.

Can a wastewater treatment plant be a powerplant? A case study

Today wastewater treatment plants are evaluated not only in terms of their treatment efficiency but also concerning their energy efficiency. Increasing energy efficiency can be realized either through operational optimisation or by realising an already existing potential for energy generation on-site. The main source of energy at a municipal wastewater treatment plant is the biogas produced in the anaerobic sludge digester. Studies indicate excess digester capacities of about 20% in Germany available for co-fermentation of organic substrates other than sewage sludge. This paper presents an example of a municipal wastewater treatment plant going towards an energy self-sufficient operation and even a surplus energy production as the result of an increasing co-fermentation of sludge from grease skimming tanks. In 2005 on average 113% of the electricity consumed for plant operation was generated on-site in gas engines. Co-fermentation of about 30% (related to the total dry residue input) of grease interceptor sludge in the presented case does not only effect a 4-times increased gas yield, but also an intensified 20% higher anaerobic degradation of the organic matter of the sewage sludge and thus having a positive influence not only on the energy and financial balance but also on the anaerobic sludge stabilisation with respect to the degradation degree of the organic fraction.

Effect of Experimental Conditions on Gas Quality and Solids Produced by Sewage Sludge Cogasification. 1. Sewage Sludge Mixed with Coal

Cogasification of sewage sludge mixed with coal showed that the amount of sewage sludge supplied to the gasifier, depending on its availability, could vary without affecting the gasifier performance; however, it had an influence on the syngas composition. The use of sewage sludge during coal gasification gave rise to an increasing gas yield and energy conversion, mainly because the gas produced had a greater hydrocarbon content. H2S, HCl, and especially NH3 were also found to increase, due to higher contents of nitrogen in the sewage sludge compared with coal. The rise of both the temperature and the air flow rate resulted in the production of more gas and a lowering of hydrocarbon, char, and tar contents. A decrease in NH3 content was also observed, as the increase of these parameters promoted the destruction of this compound. The rise in the equivalent ratio also led to lower contents of H2S and HCl, probably due to the partial oxidation of these compounds; however, the total amount of these elements released to the gas phase was not considerably affected. On the other hand, H2S formation was favored by the rise in temperature up to 850 °C, while the HCl concentration was not significantly affected. Heavy metals supplied with the fuel were mostly retained in solid residues, with Pb and Hg being the most volatile at 850 °C. However, the leachability of these metals was found to be below the analytical detection levels, and only small quantities of SO42- and Cl- were released.

Studies on Gasification of Coir Pith

Coir pith is considered as an undesirable waste of coir industries. It is difficult to burn coir pith in normal atmospheric conditions. It decomposes slowly, taking 8-10 years for complete decomposition due to higher lignin content of 37 to 45%. Being dust, it is easily blown by wind. When ignited, it does not burn completely and emits continuous smoke for several days polluting the environment. Therefore, the study was conducted to produce combustible gas from coir pith through fluidized bed gasification process. A fluidized bed gasifier was developed. Coir pith of0.511 mm mean particle size was used as feed material. Thermogravimetric studies were also conducted to determine the combustion behaviour of coir pith. Thermograms obtained for raw coir pith revealed distinct stages of thermal degradation and the ignition temperature was found to be 550°C. Minimum fluidizing velocity of 0.1 m/s was adopted for sand bed. A general trend of increasing gas yield with increasing air factor and slightly decreasing trend of calorific value were noticed. The average gas composition was found to be 2.3 to 6.5%, 9.1 to 16.2% and 6.4 to 20.5% for CH4, Hz, and CO, respectively. The combustible gas was well burnt in a low calorific burner, which will fulfill the thermal needs, or the combustible gas can be used in the dual fuel engine to produce mechanical power or electricity. The average calorific value of the gas was found to be 4.23 MJ/m3