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Globally, the demand for masks has increased due to the COVID-19 pandemic, resulting in 490,201 tons of waste masks disposed of per month. Since masks are used in places with a high risk of virus infection, waste masks retain the risk of virus contamination. In this study, a 1 kg/h lab-scale (diameter: 0.114 m, height: 1 m) bubbling fluidized bed gasifier was used for steam gasification (temperature: 800 °C, steam/carbon (S/C) ratio: 1.5) of waste masks. The use of a downstream reactor with activated carbon (AC) for tar cracking and the enhancement of hydrogen production was examined. Steam gasification with AC produces syngas with H

In the present study, a syngas was produced by preparing coal water mixtures of two different concentrations and gasifying the coal water mixtures. An entrained-flow gasifier of 1 ton/day scale was used and, after undergoing a purification process, the produced syngas was applied to a modified diesel engine for power generation. As the gasification temperature increased, the carbon conversion and the cold gas efficiency were found to increase. In the composition of the produced syngas, the content of H2 remained constant, that of CO increased, and those of CO2 and CH4 decreased. The carbon conversion increased with equivalence ratio. A maximum cold gas efficiency of 66.1% was found at the equivalence ratio of 0.43. N2 was additionally supplied to verify the gasification characteristics depending on the gas feed flow rate. The optimum feed flow rate was verified at different slurry concentrations and equivalence ratio. The produced syngas was supplied to a modified diesel engine and operated depending on the syngas feed flow rate and the engine operation conditions. The brake thermal efficiency of the engine was constant regardless of the syngas feed flow rate. The diesel engine showed high efficiency despite the mixing of the syngas.

Cracking, steam reforming, dry reforming, and combined steam and dry reforming of toluene in model syngas were performed using catalysts to simulate tar removal produced during biomass gasification...

This study aims to optimize the oxy-circulating fluidized bed combustion (oxy-CFBC) process by reducing the amount of flue gas with high-purity carbon dioxide. To achieve this, the stable transition from air mode to oxy mode is tested and validated in a 0.1-MW oxy-CFBC test rig. The results prove that flue gas carbon dioxide separation can achieve 96 vol% (dry) through a stable transition from air mode to oxy mode. Moreover, flue gas production emitted in oxy mode is reduced to one fifth compared to air mode. The proven technologies and oxy-fuel combustion database from this test rig operating experience can be used as empirical operating parameters for the next steps such as demonstration and commercial-scale operation.

To improve the fluidity of a coal water mixture (CWM) having lower viscosity and higher solid concentration, the effects of surfactants (five kinds) and experimental variables such as temperature (5-65 °C), pH (1-11), particle size distribution (PSD) on the viscosity characteristics of two different coals (Shenhua and Kideco Coal) were investigated. Relatively economical surfactants were chosen in this study: sulfonated melamine formaldehyde polymer (SMF-30), naphthalene formaldehyde sulfonate (Sikament-NN), naphthalene sulfonate water reducer (NSWR), naphthalene formaldehyde sulfonate (PC-1000) and poly-carboxylate (PC). The SMF-30, an anionic surfactant, revealed the most significant reduction in viscosity of CWM among the five surfactants since the SMF-30 forms electric double layer on the surface of coal, and the repulsive force of this layer surpasses the aggregation of coal particles. In addition, the viscosity of CWM decreased with increasing pH and temperature, in particular, the increase in OH- on the surface of coals by the addition of NaOH caused the increase in the repulsive force between the negatively charged coal particles. Furthermore, the very fine particles (less than 45 μm) of coals should be removed before making CWMs since it revealed the increase in viscosity of CWMs.

This study investigates air gasification properties of SRF with high content of residual mixed waste plastic in a 1 kg/h lab scale bubbling fluidized bed gasifier. Gasifier internal diameter is 0.114 m and its height is 1 m. Silica sand particles with a mean diameter of 400 μm is used as the bed material. During the gasification experiments the effect of bed temperature is determined in the range of 600–900 °C and the effect of air-to-fuel equivalence ratio (ER) is investigated in the range of 0.15–0.30. Gas analysis is conducted using a non-dispersive infrared analyzer and gas chromatograph. As the operating temperature and ER increases, the gas yield increases, and tar yield decreases. The yield of CO, CH4, H2, and C2H2 in the gas product increases with temperature, whereas those of CO2, C2–C3 hydrocarbons decreases. The increase in ER decreases the concentrations of CO, CH4, H2, and C2–C3 hydrocarbons and increases the CO2 in the gas product. H2/CO ratio substantially increases with rising temperature and decreases with rising ER. Carbon conversion efficiency (CCE) and cold gas efficiency reach peak at 800 °C and ER of 0.25.

Entrained-flow gasifiers used in commercial integrated gasification combined cycles are usually oxygen-blown. However, oxygen-blown gasification system is expensive to install and operate due to the equipment involved in oxygen purification and supply. To resolve this issue, this study mixed air and oxygen to perform coal gasification. An entrained-flow gasifier of 1 T/D scale was used with the coal water mixture as feedstock. Gasification was carried out at a temperature range of 970–1220 °C, an equivalence ratio of 0.25–0.62, and an air/O 2 ratio of 2.17–9.0. With an increasing gasification temperature, the amount of CO in the syngas increased while CO 2 and CH 4 decreased. Carbon conversion and cold gas efficiency continued to increase with the gasification temperature. In the equivalence ratio test, cold gas efficiency reached 52.1% at around 0.53 before decreasing under a fixed air flow rate of 90 N m 3 /h. By performing gasification with a varying air/O 2 ratio after fixing the flow rate, the influence of the equivalence ratio was examined. In addition, the influence of the flow rate was observed through changes in the air/O 2 ratio of the gasification agent with fixing the equivalence ratio. The maximum carbon conversion and cold gas efficiency were 90.7 and 57.7%, respectively, and the optimal air/O 2 ratio fell in the range of 2.86–3.1.

Biomass combustion in the oxy-fuel circulating fluidized bed is a promising technology to maximize the negative carbon dioxide emission and reduce pollutants emission in power plants. However, biomass ash related behaviors under oxy-combustion with kaolin additives still lack sufficient information. In this study, kaolin was used as an additive to manage ash problems during oxy-biomass combustion in a 0.1 MWth circulating fluidized bed combustion facility. Kaolin was fed at ratios of kaolin/wood pellet (wt./wt.): 0.21 and 0.25 by separately feeding or pre-mixing, respectively. The sampled ashes were characterized using X-ray fluorescence and X-ray diffraction analysis. Additionally, the potassium capture performance, slagging and fouling indices, attrition characteristics, and strength were also evaluated. The results revealed that potassium capture performance was improved by up to 24% at the ratio of kaolin/wood pellet (0.25) and kalsilite (KAlSiO4) within ash increased by adsorption on the metakaolin surface of gaseous potassium. The fouling formation decreased from 0.43 without kaolin to 0.07–0.15 with kaolin. In terms of oxy-fuel operation, SO2 emission was decreased when kaolin used, performing a high CO2 concentration of over 93 vol% and combustion efficiency of over 99%.

The effects of plasma power (1–1.8 kW), oxygen/fuel (0–2.5) and steam/fuel ratios (0–1) on the gasification characteristics of glass fiber-reinforced plastic (GFRP) wastes have been determined in a microwave plasma reactor. GFRP, which is thermosetting plastic composed of glass fibers embedded within a polymer matrix, was used as an experimental sample. While carbon conversion increased with oxygen/fuel ratio, syngas heating value and cold gas efficiency decreased with oxygen supply due to the onset of combustion. With increasing steam/fuel ratio, water-gas shift and ion-reforming reaction favored higher concentration of H2. Increasing the plasma power was found to promote the conversion of carbon dioxide to carbon monoxide. The char surfaces of GFRP that were subjected to variable power and oxygen supplies were analyzed by scanning electron microscopy.

Tar formation resulting during lignocellulosic biomass gasification is a major impediment to utilizing biomass energy sources, in that it blocks and fouls the processing equipment; as such, any tar present in the produced syngas much be effectively removed. This study analyzes the ability of commercially available Ni and Ru based CH4 reforming catalysts to effect tar removal and compares deactivation characteristics. Toluene was used as the model biomass tar at concentrations of 30 and 100 g/Nm3. Several additional parameters were also tested, including reaction temperatures (400–800 °C), space velocities (5000–30,000 h−1), and the steam/toluene ratios (2–20). The variation of toluene conversion and product gas composition with reaction conditions was analyzed. Overall, H2 and CO production were favored by the Ru catalyst and generally increased with temperature. Conversion also increased with temperature, with conversions higher than 90% obtained at 800 °C.

Herein, we describe the design and operation of an indirect coal liquefaction plant with integrated coal-water slurry manufacturing, entrained flow gasification, Rectisol, and Fischer–Tropsch processes to produce liquid fuels for vehicles. The above plant contained an entrained flow gasifier (10 t/d test rig) operated using oxygen as a gasifying agent (21 bar, 1100 °C) and could stably produce synthesis gas (37.8 vol% H2, 36.4 vol% CO) at 600 Nm3/h. Due to the importance of impurities in synthetic liquid fuel production, more than 99% of H2S contained in synthesis gas was removed by the Rectisol process employing refrigerated methanol. An iron-based catalyst allowed liquid fuels containing wax, light/heavy oil, and alcohol fractions to be obtained by the Fischer–Tropsch process at a rate of 5 barrel per day, with detailed analysis confirming their compliance with various quality standards and thus their suitability for use as automobile diesel after distillation.

Air gasification of polystyrene was conducted using a two-stage gasifier consisting of a fluidized bed and a tar-cracking reactor filled with active carbon. The aim was to obtain a hydrogen-rich producer gas with a low level of tar. In addition to the possibility of tar removal, the effects of the reaction temperature and equivalence ratio on the producer gas quality were investigated. In this study, it was found that the gasification of polystyrene had different characteristics to the gasification of other plastic, resulting in a high production of char. Active carbon played a crucial role, significantly decreasing the tar content in gas to 11 mg/Nm3. Furthermore, gasification with active carbon produced a gas having a high content of hydrogen (26 vol%). The change in fluidized bed gasifier temperature within the range of 700–900 °C exerted no significant effects on the gas quality. In contrast, a high tar-cracking reactor temperature clearly increased hydrogen and carbon monoxide contents. With an increasing equivalence ratio, oxidation of char was promoted, resulting in a significant increase in gas production and carbon oxides. The current study showed a good possibility for the recycling of polystyrene via gasification, producing a clean and hydrogen-rich gas.

Recently in Korea, the co-firing of biomass in existing pulverized coal power plants has become an important mean to comply with the nation's renewable portfolio standard (RPS). This study investigated boiler efficiency, net plant efficiency, and combustion characteristics from co-firing various biomasses along with two coal blends and the combustion of low rank coals through process simulation based on an existing 500 MWe coal fired power plant using a commercial process simulator (gCCS). Five sources of biomass - wood pellet, empty fruit bunch pellet, palm kernel shell, walnut shell, and torrefied biomass were selected as renewable fuels for co-firing. In addition, hardgrove grindability index tests were conducted for a blend of coal (90%) and each selected biomass (10%) based on thermal share input to investigate the milling power consumption of each blended fuel for a more rigorous simulation. The results show quantitatively that when biomass is co-fired the plant efficiency is decreased due to its lower heating value and more power consumption in mills. The plant efficiency of torrefied biomass co-firing was the highest among all biomass co-firing and combustion of low rank coals due to higher energy density and enhanced grindability of torrefied biomass after torrefaction.

Gasification of dried sewage sludge was performed in a newly developed three-stage gasifier consisting of an auger as well as fluidized and fixed bed reactors to produce a producer gas with low-levels of contaminants. The auger reactor was designed to generate tar in advance, thereby enhancing the tar destruction in the fluidized bed gasifier and fixed-bed reactor. In the study, the effects of each reactor temperature and activated carbon as an impurity absorbent were mainly investigated. The reaction temperatures of the auger and fixed bed reactors were shown to have a strong influence on the tar removal, while that of the fluidized bed reactor mainly affected the producer gas composition. The three-stage gasifier clearly decreased the tar content in producer gas and condensed tar and increased the H 2 production. In an experiment performed with activated carbon at the auger reactor temperature of ∼710 °C and the fluidized bed and fixed bed reactor temperatures of ∼830 °C, the tar and H 2 contents in producer gas were only 22 mg/Nm 3 and ∼29 vol%, respectively. Activated carbon clearly reduced the NH 3 and H 2 S contents in producer gas. The minimum NH 3 and H 2 S contents were 324 and 346 ppmv, respectively.

Nanostructured silicon (Si) is useful in many applications and has typically been synthesized by bottom-up colloid-based solution processes or top-down gas phase reactions at high temperatures. These methods, however, suffer from toxic precursors, low yields, and impractical processing conditions (i.e., high pressure). The magnesiothermic reduction of silicon oxide (SiO2) has also been introduced as an alternative method. Here, we demonstrate the reduction of SiO2 by a simple milling process using a lab-scale planetary-ball mill and industry-scale attrition-mill. Moreover, an ignition point where the reduction begins was consistently observed for the milling processes, which could be used to accurately monitor and control the reaction. The complete conversion of rice husk SiO2 to high purity Si was demonstrated, taking advantage of the rice husk’s uniform nanoporosity and global availability, using a 5L-scale attrition-mill. The resulting porous Si showed excellent performance as a Li-ion battery anode, r...

Technology for converting biomass such as rice husk into a useable energy sources are key to address energy consumption issues. The effects of temperature (600–900 °C), equivalence ratio (ER, 0.15–0.3), and addition of catalyst on the gasification characteristics of rice husk were investigated in a bubbling fluidized bed reactor with an inside diameter of 0.067 m and a height of 1.55 m. As the reaction temperature and ER were increased, the concentrations of CO and CO 2 in the product gas decreased. Slight increases in CH 4 and H 2 concentrations were also observed with increasing temperature. Throughout the temperature range of interest, an increase in ER resulted in decrement of both the higher heating value of the product gas and the cold gas efficiency. Furthermore, the effect of operating condition and addition of bed material were determined in a bubbling fluidized bed reactor. An increase in reaction temperature and ER decreased the tar content. The addition of calcined dolomite and olivine in the bed material reduced the amount of tar during rice husk gasification in a bubbling fluidized bed reactor. These results have the potential to be applied to the conversion of biomass into a useable energy source.

Summary Because of its fuel flexibility and high efficiency, pressurized oxy-fuel combustion has recently emerged as a promising approach for efficient carbon capture and storage. One of the important options to design the pressurized oxy-combustion is to determine method of coal (or other solid fuels) feeding: dry feeding or wet (coal slurry) feeding as well as grade of coals. The main aim of this research is to investigate effects of coal characteristics including wet or dry feeding on the performance of thermal power plant based on the pressurized oxy-combustion with CO2 capture versus atmospheric oxy-combustion. A commercial process simulation tool (gCCS: the general carbon capture and storage) was used to simulate and analyze an advanced ultra-supercritical(A-USC) coal power plant under pressurized and atmospheric oxy-fuel conditions. The design concept is based on using pure oxygen as an oxidant in a pressurized system to maximize the heat recovery through process integration and to reduce the efficiency penalty because of compression and purification units. The results indicate that the pressurized case efficiency at 30 bars was greater than the atmospheric oxy-fuel combustion (base line case) by 6.02% when using lignite coal firing. Similarly, efficiency improvements in the case of subbituminous and bituminous coals were around 3% and 2.61%, respectively. The purity of CO2 increased from 53.4% to 94% after compression and purification. In addition, the study observed the effects of coal-water slurry using bituminous coal under atmospheric conditions, determining that the net plant efficiency decreased by 3.7% when the water content in the slurry increased from 11.12% to 54%. Copyright © 2016 John Wiley & Sons, Ltd.

We investigate fluidization characteristics of the mixture of rice husk, silica sand and rice husk ash as a preliminary study for valuable utilization of rice husk ash obtained from gasification of rice husk in a fluidized bed reactor. As experiment valuables, the blending ratio of rice husk and sand (rice husk: sand) is selected as 5:95, 10:90, 20:80 and 30:70 on a volume base. Rice husk ash was added with 6 vol% of rice husk for each experiment and air velocity to the reactor was 0~0.63 m/s. In both rice husk/sand and rice husk/sand/ash mixture, the minimum fluidization velocity (Umf) is observed as 0.19~0.21 m/s at feeding of 0~10 vol.% of rice husk and 0.30 m/s at feeding of 20 vol.% of rice husk. With increasing the amount of rice husk up to 30 vol.%, can not measure due to segregation behavior. The mixing index for each experiment is determined using mixing index equation proposed by Brereton and Grace. The mixing index of the mixture of rice husk/sand and rice husk/sand/ash was 0.8~1 and 0.88~1, respectively. The optimum fluidization condition was found for the good mixing and separation of rice husk ash.

Implementation of circulating fluidized bed (CFB) boilers in the energy sector has witnessed a steady increase owing to their afforded advantages of operational flexibility in terms of compliance with several low-grade fuels and in-situ DeSOx and DeNOx capabilities. In recent years, the rise in global warming and development of intermittent power-generation technologies have stressed the need for development of techniques to afford high-efficiency low-emission (HELE) power-generation, effective carbon capture and storage, and flexible operation of thermal power plants. To meet these demands, the Future Energy Plant Convergence Research Center (FEP CRC) has investigated oxy-combustion technologies for CFB boilers that use low-grade fuels with calorific values

Oxy-combustion with a circulating fluidized bed (Oxy-CFBC) can facilitate the separation of high CO2 concentration and reduce emissions by biomass co-firing. This study investigated Oxy-CFBC characteristics such as temperature, solid hold-up, flue gas concentrations including CO2, pollutant emissions (SO2, NO, and CO), combustion efficiency and ash properties (slagging, fouling index) with increasing input oxygen levels (21–29 vol%), and biomass co-firing ratios (50, 70, and 100 wt% with domestic wood pellet). The possibility of bio-energy carbon capture and storage for negative CO2 emission was also evaluated using a 0.1 MWth Oxy-CFBC test-rig. The results show that combustion stably achieved with at least 90 vol% CO2 in the flue gas. Compared to air-firing, oxy-firing (with 24 vol% oxygen) reduced pollutant emissions to 29.4% NO, 31.9% SO2 and 18.5% CO. Increasing the biomass co-firing from 50 to 100 wt% decreased the NO, SO2 and CO content from 19.2 mg/MJ to 16.1 mg/MJ, 92.8 mg/MJ to 25.0 mg/MJ, and 7.5 mg/MJ to 5.5 mg/MJ, respectively. In contrast to blends of sub-bituminous coal and lignite, negative CO2 emission (approximately −647 g/kWth) was predicted for oxy-combustion only biomass.

The adoption of oxy-combustion in a circulating fluidized bed (CFB) producing ultra-supercritical (USC) steam has been investigated to increase energy efficiency and reduce CO2 emissions of coal-fired power plants. This paper presents a techno-economic analysis for 500 MWe USC-CFB power plants with air- and oxy-combustion in the presence of CO2 capture. An amine absorber unit (AAU) and a CO2 processing unit (CPU) were used to capture CO2 in the air- and oxy-combustion power plants, respectively. The air-combustion power plant without CO2 capture (Case 1) showed the highest net electricity efficiency (46%), whereas the introduction of an AAU in the air-combustion power plant (Case 2) reduced the net efficiency to 36%. The net efficiency (39%) of the oxy-combustion power plant with CPU (Case 3) was higher than that of Case 2 owing to the recycling of hot flue gas. The levelized cost of electricity (LCOE) of Case 3 (59 $/MWh) was lower than that of Case 2 (64 $/MWh), which demonstrated that oxy-combustion was advantageous compared to air-combustion in a scenario with CO2 capture. The sensitivity analyses of the electricity price and CO2 credit showed economic situations where Cases 2 and 3 would be profitable.

Hydrothermal treatment is a promising option for pretreatment drying of organic waste, due to its low energy consumption and contribution to increasing fuel energy density. In this study, the characteristics of hydrothermally treated sewage sludge were investigated, and pyrolysis and steam gasification were performed with the sludge before and after hydrothermal treatment. The overall composition of product gases from treated sludge was similar to that obtained from steam gasification of wood chips, particularly under high-temperature conditions. In addition, the increase in lignin content of sewage sludge following hydrothermal treatment could help enhance methane yield in product gas during pyrolysis and steam gasification. The findings suggest that hydrothermal treatment is an appropriate method for improving sewage sludge for use as an alternative to biomass and fossil fuels.

Air gasification of mixed plastic waste was conducted in a two-stage gasifier. The effects of the combination of olivine as the fluidized bed material and activated carbon with or without other additives for tar cracking, as well as a Ni-plated distributor, the use of steam as a gasifying agent, and the calcination of olivine on the producer gas compositions and tar production, were also investigated. The maximum H 2 concentration (27.3 vol%) was obtained with 900 g of activated carbon in the tar-cracking zone, and through the use of calcined olivine as the bed material. In the experiments, the maximum tar removal efficiency calculated using a base case reached 98.2%. The LHVs of the producer gases were in the range of 6.1–9.0 MJ/Nm 3 . The increase in the activated carbon amount led to an enhanced H 2 production, as well as a decrease in tar production. The Ni-plated distributor was found to be effective for tar removal. In the application of dolomite in the tar-cracking zone and the use of steam as a fluidizing medium resulted in a high rate of HCl removal. The minimum HCl concentration in the producer gases was under 1 ppm.

Air gasification of dried sewage sludge (DSS) was performed with olivine as the bed material and coal-based activated carbon as the tar-cracking additive in a two-stage gasifier to produce a hydrogen-rich producer gas with low tar content. Additionally, to investigate the possible regeneration of coal-based activated carbon, two different activating agents (carbon dioxide and steam) were applied. Finally, to reduce ammonia and tar contents, the performance of a Ni-coated distributor was examined. In the experiments, gasification at a steam to fuel ratio (STF) of 1.11 achieved a tar removal efficiency of 98% and a maximum hydrogen content of 34 vol.%. Furthermore, the activated carbon used for the gasification was less deactivated, compared to those used in the experiments without any reforming agent. When a Ni-coated distributor was applied, the ammonia content in the producer gas was significantly reduced to 11 ppm.

A fraction of mixed plastic waste was gasified using olivine as a bed material and activated carbon as a tar-cracking additive in a two-stage gasifier. The effects of the amount of activated carbon, the use of an activated carbon filter, and the removal of an EP (electrostatic precipitator) from the process on the gas composition and tar amount generated were investigated. The effects of the ER (equivalence ratio), the type of distributor, the use of steam and the use of a wire mesh basket for activated carbon on the coke removal were also examined. As a result, H 2 concentrations of around 30 vol% were obtained with 1500 g of activated carbon. The tar removal efficiency was maximized at about 98% with the application of 1500 g of activated carbon and steam. The LHVs (lower heating values) of the producer gases obtained with the two additives at ERs of about 0.31 were in the range of 5.3–6.2 MJ/Nm 3 .

In order to produce a clean producer gas, the air gasification of dried sewage sludge was conducted in a two-stage gasifier that consisted of a bubbling fluidized bed and a tar-cracking zone. The kind and amount of bed materials, the kind of additives in the upper-reactor, and the moisture content in the sewage sludge were selected as operating variables in order to investigate their effects on the development of the producer gas characteristics. In our experiments, the gasification of a dried sewage sludge sample containing 30 wt.% of moisture with a combination of calcined dolomite as the bed material and activated carbon in the tar-cracking zone removed the most tar and produced the highest hydrogen concentration. The total tar removal efficiency and the H2 content in the producer gas from the sample noted above reached 88.4% and 32.1 vol.%, respectively. The LHVs of all the producer gases were high with values above 7 MJ Nm−3.

In this experiment, air gasification was conducted with a fraction of mixed plastic wastes using a two-stage gasifier. Calcined dolomite as a bed material and activated carbon as a tar-cracking additive were simultaneously used for the production of a producer gas containing low tar and high hydrogen. The effects of the bed material, equivalence ratio (ER), amount of activated carbon, and temperatures in two reaction zones (the upper- and lower-reactor) on the composition of producer gas and amount of tar generated were investigated. When the amount of activated carbon increased from 0 to 900 g using calcined dolomite as the bed material, the concentrations of H 2 and CO in the producer gas increased sharply from 14.9 to 26.1 vol% and from 9.4 to 16.8 vol%, respectively. When 900 g of activated carbon was applied, the total tar amount was about 96% less than that obtained with only silica sand as the bed material. The maximum Lower Heating Value (LHV) of the producer gas was about 13.4 MJ/Nm 3 .

Air gasification of dried sewage sludge was conducted in a two-stage gasifier. In the experiments, natural occurring materials, such as natural zeolite, olivine and dolomite, as well as biomass-based and coal-based activated carbons, were applied to the upper reactor of a two-stage gasifier, while sand and calcined dolomite were used as the fluidized bed material in the lower reactor. The reusability of the spent coal-based activated carbon and spent calcined dolomite was also investigated. The combination of calcined dolomite as the bed material and coal-based activated carbon in the upper reactor produced the highest H2 (28 vol.%) and CO (21 vol.%) contents. Furthermore, total amount of tar generated with the combination was 91% less than that generated with no additive in the upper reactor and sand in the lower reactor. The H2 content and tar removal efficiencies in the experiments with the spent activated carbons and spent calcined dolomites were shown to be better than those without additives in the upper reactor.

Nanostructured silicon (Si) is useful in many applications and has typically been synthesized by bottom-up colloid-based solution processes or top-down gas phase reactions at high temperatures. These methods, however, suffer from toxic precursors, low yields, and impractical processing conditions (i.e., high pressure). The magnesiothermic reduction of silicon oxide (SiO

Gasification experiments with railroad wood ties treated with creosote were conducted in a two-stage gasifier to produce a high caloric producer gas with low tar content. In the experiments, sand and dolomite as the bed material were compared, and the effects of temperature in a range from 666 to 818 °C and equivalence ratio from 0.19 to 0.52 were also investigated. Additionally, the effectiveness of additives (biomass-based activated carbon, coal-based activated carbon and dolomite) and their combination on the removal of tar were examined. As a result, the combination of dolomite as the bed material and coal-based activated carbon in the tar cracking zone gave the best performance with respect to tar removal. With this combination, the total amount of tar was reduced by 91.9%, compared to that obtained by using only sand as the bed material in the gasifier. Furthermore, the tar content in the producer gas was below 0.1 g/N m 3 . Coal-based activated carbon also improved the production of hydrogen up to about 29 vol.%. The LHVs of most producer gases in these experiments were above 7 MJ/N m 3 .

Air gasification was conducted with fractions of construction woody wastes in a two-stage gasifier, consisting of a fluidized bed zone and a tar cracking zone. The aim of this work is to investigate the influence of reaction conditions and additives on the composition of producer gas and tar content in producer gas. A producer gas obtained with activated carbon of 540 g at an ER of 0.26 was mainly composed of H2 (25 vol.%), CO (22 vol.%) and CH4 (5 vol.%). Regarding tar removal efficiency, activated carbon was better than olivine. The tar removal rate with virgin activated carbon reached up to 80%. The reuse of spent activated carbon caused an efficiency loss in tar removal to some extent. Overall, it seems that the strong need for intensive downstream tar removal measurements can be removed with the use of a two-stage gasifier and the application of activated carbon.

Air gasification was conducted with a fraction of mixed plastic wastes in a newly developed two-stage gasifier. In this work, the influence of the reaction parameters, such as equivalence ratio, upper-reactor temperature and feed size, on the producer gas composition and tar removal were investigated. In addition, the effects of activated carbon and dolomite were also examined. At an equivalence ratio of 0.21, a very clean producer gas was obtained with a LHV of 13.44 MJ/Nm 3 . Activated carbon had a better tar removal efficiency than dolomite. The amount of additive had significant effects on the tar removal efficiency and hydrogen production. When 640 g of activated carbon was applied, the total tar production was about 2.5 times less and H 2 production two times higher than without activated carbon.

Experiments were carried out with a woody waste fraction using a two-stage gasifier consisting of a fluidized bed zone and a tar cracking zone that was filled with activated carbon. In the experiments, the effects of experimental conditions such as the temperature and the equivalence ratio were investigated. In addition, the results of the experiments with virgin activated carbon, without activated carbon, and with spent activated carbon were compared. The producer gases that were obtained in the experiments were analyzed using GCs (FID and TCD) and a GC–MS system. The producer gas obtained with the application of activated carbon at an ER of 0.2 had high H2 content (16 vol.%, N2-free), and its lower heating value was above 10 MJ/Nm 3 . In addition, the total amount of the tar captured by the scrubbers and the electrostatic precipitator was reduced sixfold when activated carbon was applied.

The production of sewage sludge in South Korea is continually increasing. Until now, much of the sewage sludge in the country has been disposed of by dumping it into the ocean, which the London Convention wants stopped. Therefore, new sewage sludge treatment methods should be sought. Sewage sludge can be energetically utilized through gasification, which produces combustible gases such as H2, CO, and CH4. During the gasification of a biomass, however, a large amount of tar is also formed. In this paper we report the results of the experiments that were conducted on the air gasification of dried sewage sludge in a newly developed two-stage gasifier. In such experiments, activated carbon was applied to reduce the tar components of the producer gas. The total amount of tar that was reduced was 6-fold when activated carbon was used in the upper reactor of the gasifier. The effects of the reaction conditions, such as the reaction temperature and the equivalence ratio, on the gas composition were also investiga...

0 20 40 60 80 100 Sand 2500g/No additive (Previous results ref. [14]) CD 1500g/No additive (Run1) CD 1500g+DSS ash 200g/No additive (Run2) CD 1500g+DSS ash 500g/No additive (Run3) CD 2000g/No additive (Run4) CD 1500g/CD 600g (Run5) CD 1500g/AC 600g (Run6) CD 1500g/AC 600g/15 wt.% moisture content (Run7) CD 1500g/AC 600g/22 wt.% moisture content (Run8) CD 1500g/AC 600g/30 wt.% moisture content/Sample 2 after ADP (Run9) CD 1500g/AC 600g/30 wt.% moisture content/Sample 3 before ADP (Run10) Total tar amount (g/kg DSS) Tar removal efficiency (%)