Hydrogen-rich Gas Production Research Articles

Investigation of biochars derived from waste lignocellulosic biomass and insulation electric cables: A comprehensive TGA and Macro-TGA analysis

This study investigates the thermochemical decomposition and gasification performance of biochars produced from blends of waste lignocellulosic biomass and waste insulation electrical cables at varying temperatures. Characterization tests revealed changes, particularly in ash content (27.5 %–34 %) and elemental composition, with nitrogen content increasing notably in biochar samples compared to the original feedstock. Van Krevelen diagrams demonstrated a reduction in O/C and H/C ratios with increasing production temperature, resembling fossil fuels more closely. The thermogravimetric and the derived thermogravimetric profiles illustrated distinct degradation stages influenced by heating rates and production temperature. Macro-TGA tests provided insights into biomass residue behavior under gasification conditions, indicating higher reaction rates at elevated temperatures. Syngas analysis highlighted the impact of temperature and equivalence ratio on syngas composition, with higher temperatures favoring hydrogen-rich gas production. The observed trends in cold gas efficiency (42.61 %–50.40 %) and carbon conversion efficiency (45.83 %–50.40 %) underscore the significance of temperature control in maximizing gasification performance. Biochars produced at higher temperatures demonstrated superior gasification performance, suggesting potential for optimizing biochar production processes to enhance energy recovery and waste valorization.

On-site hydrogen-rich gas production from diesel: A comprehensive study on catalyst development with nickel and diverse metal oxides (MgO, La2O3, CeO2, SiO2) supported on alumina

The study aimed to investigate the impact of nickel-incorporating diverse metal oxides (MgO, La2O3, CeO2, SiO2) supported on alumina on the Diesel steam reforming reaction. Catalytic activity tests were performed within a reaction period of 6 h at 800°C and atmospheric pressure. The amount of catalyst is 30 gr in each experiment corresponding to a LHSV value of 0.2 hr−1. The tests proved that the performances of Ni-containing La2O3 and CeO2-supported catalysts were highly stable and active in steam reforming of Diesel, giving complete conversion. The incorporation of CeO2 (20 % wt) into Al2O3 support resulted in a significant reduction in the amount of coke formation from 0.85 % to 0.26 %. In order to investigate catalyst stability, time-on stream tests extending to 6 days, totaling 36 hours were performed using 5Ni@10La2O3-Al2O3. As a result of the long-term stability test, no deactivation has been observed under the test conditions despite very few amounts of carbon (1.33 wt%) formed. When comparing the short-term and long-term tests, similar syn-gas production results were observed, along with approximately the same amount of carbon formation.

Synthesis of bentonite-supported Ni, La, and Ca catalysts for hydrogen production through steam reforming of acetic acid

In this study, the production of hydrogen-rich gas through the steam reforming of acetic acid using bentonite-supported catalysts was investigated. Bentonite was treated by washing and calcination. Bentonite-supported Ni, Ca, La, Ni–La, and Ni–Ca catalysts with different active metal loadings of 10 and 30 wt% were synthesized using the wet impregnation method. The catalysts were characterized using XRD, XRF, SEM, EDS, BET, FT-IR, NH3-TPD, and Raman. The activity tests of the catalysts were carried out in a continuous flow tubular reactor at various temperatures (500, 600, 700, and 800 °C). Product gas composition was determined by gas chromatography (μ-GC). The effect of bentonite treatment, active metal type, and bimetallic combinations (Ni/Bent, Ni/Bent*, La/Bent, Ca/Bent, Ni–La/Bent, and Ni–Ca/Bent) were studied. The highest hydrogen yield obtained without a catalyst was 8.61% at 700 °C. This yield increased to 74.5% at 600 °C with 30 wt% Ni–La/Bentonite, and to 42.6% with 30 wt% Ni/Bentonite catalysts, respectively. The experimental results show that bentonite has a suitable catalytic activity on its own and is a promising support material for the steam reforming of acetic acid.

Enhancement of hydrogen-rich gas production by acetic acid steam reforming: characterization of Ni–Co modified biochar-based catalysts

Abstract The development of cost-effective and highly efficient biochar-based catalysts is essential for the catalytic steam reforming process of bio-oil. In this study, pickling peanut shell biochar was used to prepare biochar-supported Ni/Co monometallic catalyst and biochar-supported nickel-Co bimetallic catalyst through the impregnation method. The catalytic effect of these catalysts on acetic acid (a bio-oil model compound) steam reforming was investigated. It was found that Co could enhance the dispersion of metal particles. The catalyst exhibited the best catalytic effect and significantly improved resistance to carbon deposition with a loading of 8 wt% and a Ni-to-Co ratio of 6:2. At the temperature of 600 °C and the S/C ratio of 3, the selectivity of H2 reached 84.48 %, and the conversion of acetic acid reached 95.49 %. A synergistic effect was observed between Ni and Co, leading to increased metal dispersion, enhanced reducibility, and a higher number of active centers. Co facilitates water dissociation and promotes the oxidation of C–H and mobile O, resulting in a faster decarbonization rate. The effective utilization of biochar-based catalysts and the rational utilization of bio-oil contribute to the timely achievement of carbon emission reduction targets.

Cascade Proportional-Integral Control Design and Affordable Instrumentation System for Enhanced Performance of Electrolytic Dry Cells.

In this paper, we present a cost-effective system for monitoring and controlling alkaline electrolyzers, intending to improve hydrogen gas production on a laboratory scale. Our work includes two main innovations. Firstly, we suggest an approach to calibrate a standard air flow meter to accurately measure the flow of hydrogen-rich gas from electrolyzers, improving measurement accuracy while keeping costs low. Secondly, we introduce a unique cascade control method to manage hydrogen-rich gas production in the electrolyzer, ensuring precise control over gas flow rates. By combining affordable, energy-efficient devices with a PI control system, we achieve efficient gas production through electrolysis, replacing manual control approaches. Experimental results confirm the effectiveness of our cascade control method, demonstrating stable operation with minimal errors. These results provide a foundation for further research into control strategies to enhance the performance of electrolytic cells.

Production of high calorific value hydrogen-rich combustible gas by supercritical water gasification of straw assisted by machine learning

This article reveals the basic laws of straw supercritical water gasification (SCWG) and provides basic experimental data for the effective utilization of straw. The paper studied the impact of three operational conditions on the production of high-calorific value hydrogen-rich combustible gases through SCWG of straw within a quartz tube reactor. The findings reveal that elevated reaction temperatures, extended residence times, and reduced feedstock concentrations favor the SCWG of straw. When combustible gas contains carbon dioxide, the maximum low heating value (LHV) of the gas is 21 MJ/Nm3. Upon removing carbon dioxide, the LHV of the gas reached 38 MJ/Nm3. Subsequently, a machine learning (ML) model was developed to forecast gas yield and LHV during the SCWG process. The results demonstrate that the model exhibits robust generalization capabilities. ML can be extensively applied to forecast biomass SCWG processes across various operational conditions.

Enhanced production of hydrogen-rich gas from municipal sewage sludge gasification using a CaO-RM composite catalyst

Hydrogen-rich gas, characterized by high yield and purity, can be effectively generated through the steam gasification of sewage sludge (SS), offering substantial benefits for organic solid waste treatment and resource conservation. This study evaluated the gasification performance in a horizontal moving-bed reactor employing a wet-mixed CaO-red mud (CaO-RM) composite catalyst. The effects of CaO loading rate (CaO/RM), catalyst-to-SS ratio (CaO-RM/SS), and reaction temperature on the syngas yield, lower heating value (LHV), carbon conversion ratio, H2 to CO (H2/CO) ratio, and H2 yield were investigated. Results indicated that red mud loaded with a calcium-based catalyst significantly enhanced syngas production, particularly for hydrogen generation, during SS gasification. A maximum hydrogen molar fraction of 50.84% and a yield of 7.07 mol/kg were achieved with a CaO/RM of 40% and a CaO-RM/SS of 30% at 750 °C. With the reaction temperature increase from 700 to 900 °C, the catalytic performance for secondary tar cracking and steam reforming was further enhanced. The total syngas yield, H2 yield, hydrogen molar fraction, LHV of syngas, and carbon conversion rate peaked at 0.79 m³/kg, 19.30 mol/kg, 54.41%, 10,249.48 kJ/kg, and 65.67%, respectively, at 900 °C.

Research on Catalytic Reaction of Cotton Straw Pyrolysis Based on Model Compounds

The study starts from the clean conversion of desulfurized ash and biomass resources, based on correlation analysis and Langmuir-Hinshelwood model, studies the components of cotton stalk pyrolysis products and describes the mechanism and effects of desulfurized ash as a catalyst in the pyrolysis process. Regression analysis, support vector machine, and other methods are used to predict the yield or output of pyrolysis products, which is of great significance for the efficient utilization and sustainable development of cotton stalks. The study found that desulfurized ash significantly promoted the thermal decomposition of cotton stalks, increased the pyrolysis gas yield and lower heating value, increased the production of hydrogen-rich gas in the pyrolysis gas, and reduced the production of carbon oxides. Through the study of model compounds, it was found that desulfurized ash has different catalytic effects on the process of cellulose and lignin components in cotton stalks generating pyrolysis gas.

Co-production of porous N-doped biochar and hydrogen-rich gas production from simultaneous pyrolysis-activation-nitrogen doping of biomass: Synergistic mechanism of KOH and NH3

In this study, a method of simultaneous activation and nitrogen doping during biomass fast pyrolysis for co-production of porous N-doped biochar and H2-rich gas production was proposed. The effect of temperature on chemical interaction mechanism of KOH and NH3 was investigated at 500–800 °C. Results showed that KOH and NH3 had a synergistic effect on pore development and nitrogen doping, and the specific surface area and nitrogen content reached maximum values of 2008.37 m2/g and 5.05 wt%, respectively. It may be due to that NH3 entered pores generating by KOH activation for further activation, and at the same time, excessive NH3 could convert new O-containing groups to N-containing groups for more effective nitrogen doping. What's more, the H2 concentration and yield were up to 56.67 vol% and 517.95 mL/g, respectively. It indicates that the synchronization method of fast pyrolysis-activation-nitrogen doping is a promising approach, which is of great significance for the high-value utilization of biomass.

Experimental and feasibility study of bio-waste valorization through pyrolysis for energy and materials production in the concept of circular economy

The pyrolysis and co-pyrolysis characteristics of large abundant bio-wastes, namely date pits (DP), peanut shells (PS), coffee grounds (CG), and tea waste (TW) were investigated in detail. The TG/DTG and pyrolysis procedures were used to examine the thermal pyrolysis behavior of these agro-wastes and their blends (50%CG/50%DP, 50%CG/50%PS, 50%DP/50%PS, 50%TW/50% DP,50%TW/50%PS and 50%CG/50% TW by weight). The characterization of these feedstock has shown their suitability for energy and material valorization. Experiments were carried out in a batch pyrolysis at a medium heating rate of 10 °C/min. The goal was to identify the best combination aiming to produce either char or hydrogen-rich gas, which can contribute to the development of the circular bio-economy. It was demonstrated that pyrolysis favored the liquid product, fluctuating from 34.31% (TW) to 50.92% (DP), while the co-pyrolysis greatly increased the gaseous product, which ranged between 42.02% (TW-DP) and 55.17% (PS-TW). The blending of CG and PS resulted in heightened reactivity, leading to an enhanced generation of H2 (34.44%). The optimal mixture was found to be CG-TW, showcasing superior performance in terms of gas quality (38.39% H2) and yield (53.74%). This outcome underscores the potential of CG and TW as a synergistic blend for efficient hydrogen-rich gas production. The FTIR findings revealed that the recovered biochars have the potential to serve as solid fuels, biofertilizers, or carbon materials. Additionally, they could be used as eco-friendly precursors for chemical and related industries. By analyzing various waste mixtures and their respective pyrolysis properties, this research aims to contribute to the development of sustainable waste management practices as well as efficient energy and material production methods.

Modelling and Simulation of Co-Gasification of Chlorella Vulgaris and High-density Polyethylene Using Aspen Plus

A technical innovation that holds promise for producing renewable fuel and decreasing waste disposal is the production of syngas from the co-gasification of waste materials and biomass. In this present study, a new simulation model for co-gasifying high-density polyethylene (HDPE) and microalgae using Aspen plus V10 was built. Several operating parameters, including operating temperature, air equivalence ratio (ER), biomass blending ratio, steam-to-biomass ratio (S/B), and air/steam ratio, were investigated for their influence on the yield and composition of H2, CO, CO2, and CH4. Results indicated that these operating parameters had significant impacts on the gaseous products. High gasifier temperatures (1000°C) for the co-gasification process favored the formation of H2 and CO and increased their yields. Also, the yield of H2 significantly decreased when the value of the equivalence ratio was increased. According to simulation results, increasing the steam-to-biomass ratio favored the synthesis of H2 and CO up to a point. In addition, waste plastic (HDPE) in the feedstock should be kept at a minimum to favor the production of hydrogen-rich gas. The findings show that the model results agree with previous experimental studies. This research study has proven the air-steam co-gasification of microalgae and HDPE as a suitable process for the production of syngas rich in hydrogen.

A Study on the Pyrolysis Behavior and Product Evolution of Typical Wood Biomass to Hydrogen-Rich Gas Catalyzed by the Ni-Fe/HZSM-5 Catalyst

The thermo-chemical conversion of biomass wastes is a practical approach for the value-added reclamation of bioenergy in large quantities, and pyrolysis plays a core role in this process. In this work, poplar (PR) and cedar (CR) were used as staple wood biomasses to investigate the apparent kinetics of TG/DTG at different heating rates. Secondly, miscellaneous wood chips (MWC), in which PR and CR were mixed in equal proportion, were subjected to comprehensive investigations on their pyrolysis behavior and product evolution in a fixed bed reactor with pyrolysis temperature, catalyst, and the flow rate H2O steam as influencing factors. The results demonstrated that both PR and CR underwent three consecutive pyrolysis stages, the TG/DTG curves shifted to higher temperatures, and the peak temperature intervals also enhanced as the heating rate increased. The kinetic compensation effect expression and apparent reaction kinetic model of CR and PR pyrolysis were obtained based on the law of mass action and the Arrhenius equation; the reaction kinetic parameter averages of Ea and A of its were almost the same, which were about 72.38 kJ/mol and 72.36 kJ/mol and 1147.11 min−1 and 1144.39 min−1, respectively. The high temperature was beneficial for the promotion of the pyrolysis of biomass, increased pyrolysis gas yield, and reduced tar yield. This process was strengthened in the presence of the catalyst, thus significantly increasing the yield of hydrogen-rich gas to 117.9 mL/g-biomass. It was observed that H2O steam was the most effective activator for providing a hydrogen source for the whole reaction process, promoted the reaction to proceed in the opposite direction of H2O steam participation, and was beneficial to the production of H2 and other hydrocarbons. In particular, when the flow rate of H2O steam was 1 mL/min, the gas yield and hydrogen conversion were 76.94% and 15.90%, and the H2/CO was 2.07. The yields of H2, CO, and CO2 in the gas formation were significantly increased to 107.35 mL/g-biomass, 53.70 mL/g-biomass, and 99.31 mL/g-biomass, respectively. Therefore, H2 was the most dominant species among gas products, followed by C-O bond-containing species, which provides a method for the production of hydrogen-rich gas and also provides ideas for compensating or partially replacing the fossil raw material for hydrogen production.

Oriented pyrolysis of biomass for hydrogen-rich gas and biochar production: An energy, environment, and economic assessment based on life cycle assessment method

This study aimed to analyze a technology of hydrogen-rich gas from full-component oriented pyrolysis (FCOP) of biomass using energy, economic, and environmental life cycle assessment. Firstly, the study taked corn straw (CS) as the research object, the yield of hydrogen-rich gas and char produced by the oriented pyrolysis method are 78.26% and 20.35%, and the yield of biochar produced by activating char with phosphoric acid is 40%. Secondly, the system boundary of FCOP of biomass to produce hydrogen-rich gas and biochar was creatively designed, establishing the energy, environmental, and economic analysis comprehensive model. Various energy, economic, and environmental indicators were computed to facilitate process optimization for hydrogen-rich gas co-production biochar and explored the feasibility of the process. The results show that the stage of hydrogen-rich gas prepared by FCOP of biomass is an important factor affecting energy output and input, and has the highest standard pollutant emissions (92.11%). This process has low carbon emissions and GHG emissions, showing good sustainability and application prospects, which has important guiding significance for realizing cleaner production and solving the energy crisis. Thirdly, taking the large-scale system of producing hydrogen-rich gas co-production biochar, which processes 40,000 t of CS per year, as an example, the economic benefit analysis results were obtained, that is, IRR, NPV, and Pm are 22%, 6.33 million yuan, and 7.3 years, respectively. Meanwhile, the key factors, including the initial investment, expenses of biomass and catalyst, and the sale income of hydrogen and biochar, which are the main factors affecting the economic efficiency of technology, and uncertainties were identified through sensitivity analysis. Finally, we put forward in the background of ecological civilization, the research focus and thinking for the development of hydrogen production technology from pyrolysis/gasification of biomass were proposed. The results obtained can be valuable in practical applications to enhance the sustainability and viability of hydrogen production in biomass conversion and utilization activities. The applied energy, economic, and environmental methodologies appear to be reliable and comprehensive tools for assessing the whole-life sustainability and viability of biofuel.

Biomass screening for syngas production by flash photopyrolysis.

A few seconds flash photopyrolysis is used as efficient screening tool for the investigation of selected biomass in producing syngas, hydrogen and biochar. This innovative approach allowed rapid pyrolysis of the biomass, which was followed by a precise gas analysis and quantification, using Mass Spectrometry (MS). The analysis of the gas composition from three distinct biomass wastes in this study provides new insights into their thermochemical characteristics, expanding thus our knowledge of the potential of the selected biomass resources for the production of carbon, syngas, and/or hydrogen-rich gas production. This enhanced characterization revealed the potential of biomass transformation in contributing to innovative green energy sustainable solutions.

Hydrogen-rich gas production via supercritical water gasification (SCWG) of oily sludge over waste tire-derived activated carbon impregnated with Ni: Characterization and optimization of activated carbon production

In this study, the production of activated carbon (AC) through the chemical activation of waste tire (WT) using H3PO4 and KOH for H2 production by SCWG of oily sludge (OS) donated by Persian Gulf Star Oil Company was investigated. H3PO4 was the best activating agent based on some pretests results, and then the synthesis of AC was optimized using Response Surface Methodology. Based on BET surface area of synthesized ACs, thirty combinations of the four variables namely; activation temperature (350–550 °C); activation time (1–4 h); H3PO4 to WT ratio (1–3 w.w−1); and H3PO4 concentration (20–40 wt%) were optimized. CHNS, TGA, FE-SEM, and EDS-mapping analyses were used to characterize the AC and catalyst synthesized in optimum condition (activation temperature: 450 °C; activation time: 2.5 h; H3PO4 to WT ratio: 2 w.w−1; and H3PO4 concentration: 40 wt%), which presented a surface area of 170 m2 g−1. Finally, Ni was impregnated on the optimized AC with different loadings (5–15 wt%) to evaluate its performance in H2 production by SCWG of OS. Although H2 yield in catalytic experiments was higher than that observed in non-catalytic experiment, results showed that the maximum H2 selectivity was 66% in SCWG of OS using AC impregnated with 10 wt% Ni.

Mathematical modelling and optimization of producing hydrogen-rich gas in COREX melter gasifier

The integration of dome injection technology and coal gasification technology can enhance space utilization and generate high-quality reducing gas in the dome of COREX melter gasifier, making it a promising process for hydrogen-rich gas production. In this study, a comprehensive 3-D mathematical model is utilized to depict the inner characteristics with dome coal injection, including flow filed, thermal state, gas composition and particle behavior in the dome of COREX melter gasifier. The results indicate that the flow field in the dome can be categorized into jet flow region, impinging flow region and plug flow region. The gasification performance exhibited significant improvement, particularly the hydrogen production capability, which increased by 2150 Nm3/h. The proportion of C(s) consumed by combustion decreased to 37.32 %, while that of gasification increased to 62.68 %. Without oxygen compensation, the optimal coal injection ratio is determined to be 204.5 kg/t. As the oxygen flow rate through the oxygen burners increases from 1478 Nm3/h to 4478 Nm3/h, the dome temperature rises, advancing the devolatilization process of coal particles and improving combustion efficiency. When CO2 is used as the alternative carrier gas, the proportion of CO in the export gas increases by 0.03 % and that of CO2 increases by 1.11 %. However, when H2O is used as the alternative carrier gas, the proportion of H2 in the export gas increases by 0.35 % and that of H2O increases by 0.89 %.

Thermogravimetric and thermovolumetric study of municipal solid waste (MSW) and wood biomass for hydrogen-rich gas production: a case study of Tashkent region.

Application of municipal solid and wood waste, as dominant sources of biomass, could be a promising alternative for producing energy from renewables via thermochemical gasification technology. In this paper, a study of thermogravimetric analysis (TGA) and excurrent gas composition produced by the municipal solid waste (MSW) and wood biomass gasification is presented. Thermogravimetric and heat flow curves for waste samples were performed at the temperature interval of 20-890 °C with a heating rate of 10 °C min-1 under a nitrogen atmosphere. According to thermal analysis data, differential scanning calorimetry (DSC) curves, the degradation stages of waste samples was determined, which correspond to the mono- or bimodal evolution of volatile compounds and the degradation of the resulting carbon residue. The gasification experiments were conducted in a high-pressure quartz reactor at temperatures of 850, 900, and 950 °C, using steam (0.3 g/min) and argon (2 dm3/min) as the gasifying agents. To ascertain the syngas composition, gas chromatography was employed in conjunction with a thermal conductivity detector. Both types of biomass showed remarkably similar syngas compositions. The highest concentration of hydrogen-rich gases was recorded at 950 °C for wood biomass, with 42.9 vol% and 25.2 vol% for hydrogen (H2) and carbon monoxide (CO), and for MSW, with an average 44.2 vol% and 18 vol% for H2 and CO. Higher temperatures improved the syngas composition by promoting endothermic gasification reactions, increasing hydrogen yield while decreasing tar and solid yields. This research helped to comprehend the evolution of the gasification process and the relationship between increased H2 and CO production as the gasification temperature increased.

La-doped Ni/ZrO2 catalyst for the production of H2-rich gas by upgrading vapors coming from pyrolysis of biomass and co-pyrolysis of biomass with plastic

The main goal of this work was to develop efficient catalysts for the production of hydrogen-rich gas by upgrading vapors coming from the pyrolysis of biomass and co-pyrolysis of biomass with plastic. A series of nickel catalysts supported on zirconia modified by lanthanum was synthesized. The role of La and its optimal concentration have been studied. The activity of prepared materials was determined with the use of cellulose, poplar, and a mixture of poplar and low-density polyethylene. The analysis of the physicochemical properties of investigated catalysts showed that introducing lanthanum into the zirconia structure resulted in an increase in surface area, pore size, and pore volume. La contributed to the stabilization of tetragonal zirconia. Moreover, its incorporation into the ZrO2 structure led to the formation of stronger interactions between the active phase and support. This facilitated formation of smaller NiO crystallites on the surface of modified materials. It is worth noting that La doped catalysts were more resistant against coke deposition and their deactivation rate was lower than that noticed for parent Ni/ZrO2. It was demonstrated that the addition of polymer (LDPE) to biomass (poplar) resulted in a significant increase in the efficiency of hydrogen production. The highest hydrogen yield was obtained in the presence of the catalyst containing 8% of La.

Valorization of microalgae oil via steam reforming for hydrogen-rich gas production over Ni/CeO2-ZrO2

This study investigated the steam reforming of microalgae oil in the existence of Ni/CeO2-ZrO2 catalyst to assess its potential for hydrogen production. For this purpose, the catalyst was synthesized by the impregnation-co-precipitation method and characterized using various techniques. Catalytic microalgae steam reforming was performed in a continuous flow quartz fixed bed reactor and the effects of reaction temperature, weight hourly space velocity, and steam to microalgae volume ratio on conversion and hydrogen selectivity were evaluated. The findings revealed that microalgae oil, especially with a high oleic acid content, showed promise as a feedstock for hydrogen production via steam reforming. Suitable conditions were identified as a reaction temperature of 850 °C, weight hourly space velocity of 29 h−1, and steam to microalgae oil volume ratio of 12:1, resulting in 99.79 % hydrogen selectivity and 100 % microalgae oil conversion. Furthermore, a characterization of the spent catalyst was conducted, and a coke deposition of 19.17 mgcarbon/gcat.h was observed following 15 h of reaction.

Experimental Research on the Production of Hydrogen-Rich Synthesis Gas via the Air-Gasification of Olive Pomace: A Comparison between an Updraft Bubbling Bed and a Downdraft Fixed Bed

Experimental Research on the Production of Hydrogen-Rich Synthesis Gas via the Air-Gasification of Olive Pomace: A Comparison between an Updraft Bubbling Bed and a Downdraft Fixed Bed