H2-rich Gas Research Articles

A theoretical study using the multiphase numerical simulation technique for effective use of H2 as blast furnaces fuel

We present a numerical simulation procedure for analyzing hydrogen, oxygen and carbon dioxide gases injections mixed with pulverized coals within the tuyeres of blast furnaces. Effective use of H2 rich gas is highly attractive into the steelmaking blast furnace, considering the possibility of increasing the productivity and decreasing the specific emissions of carbon dioxide becoming the process less intensive in carbon utilization. However, the mixed gas and coal injection is a complex technology since significant changes on the inner temperature and gas flow patterns are expected, beyond to their effects on the chemical reactions and heat exchanges. Focusing on the evaluation of inner furnace status under such complex operation a comprehensive mathematical model has been developed using the multi interaction multiple phase theory. The BF, considered as a multiphase reactor, treats the lump solids (sinter, small coke, pellets, granular coke and iron ores), gas, liquids metal and slag and pulverized coal phases. The governing conservation equations are formulated for momentum, mass, chemical species and energy and simultaneously discretized using the numerical method of finite volumes. We verified the model with a reference operational condition using pulverized coal of 215kg per ton of hot metal (kgthm−1). Thus, combined injections of varying concentrations of gaseous fuels with H2, O2 and CO2 are simulated with 220kgthm−1 and 250kgthm−1 coals injection. Theoretical analysis showed that stable operations conditions could be achieved with productivity increase of 60%. Finally, we demonstrated that the net carbon utilization per ton of hot metal decreased 12%.

Highly efficient MOF-templated Ni catalyst towards CO selective methanation in hydrogen-rich reformate gases

Highly efficient and non-noble metal-based Ni/ZrO2 catalyst templated with Ni/UiO-66 precursor was successfully prepared and applied to CO selective methanation in H2-rich gases. This catalyst showed excellent activity and selectivity in an extremely wide temperature window of 215–350 °C, and it also had high stability with no deactivation during a long-term stability test (120 h). The increased specific surface area, smaller crystallite size (3.5 nm) and higher dispersion (15.3%) of Ni nanoparticles, and the enhanced chemisorption capability for CO might contribute to its excellent performance.

Boosting Cu-Ce interaction in CuxO/CeO2 nanocube catalysts for enhanced catalytic performance of preferential oxidation of CO in H2-rich gases

In this paper, a facile strategy by etching CeO2 spheres pretreated by different concentrations of H2SO4 or NaOH solution with an ionic liquid (IL) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) under hydrothermal condition was developed to achieve CeO2 nanocubes. By depositing CuxO clusters on CeO2 nanocubes via a deposition−precipitation method, CuxO/CeO2 nanocube catalysts loading with different amounts of CuxO clusters were synthesized and the CuxO clusters were highly dispersed onto the surface of CeO2 nanocubes. The Raman spectroscopy, H2-TPR, XPS, and DRIFTS results reveal that there is a strong interaction between CuxO and CeO2. Among these CuxO/CeO2 catalysts, the 10CuCe-2OH-ILs, which was obtained via immersing CeO2 spheres using 2M NaOH, and subsequently being etched by ILs, and then loading ∼10% of copper, exhibits the optimal catalytic performances and stability. The catalytic activity of different catalysts increases in the order of 10CuCe-ILs <10CuCe-1H-ILs <10CuCe-0.1OH-ILs <10CuCe-5OH-ILs <10CuCe-2OH-ILs. The result is in agreement with the order of the surface oxygen vacancy concentration, reducibility and Cu+ content, suggesting that the interaction between CuxO species and surface oxygen vacancies of these CuxO/CeO2 catalysts plays an important role for CO preferential oxidation in H2-rich gases.

Catalytic Reforming of Volatiles from Biomass Pyrolysis for Hydrogen-Rich Gas Production over Limonite Ore

The feasibility of using natural limonite ore for catalytic cracking of biomass pyrolysis volatiles was investigated to study the effects of the catalyst-treated method, temperature, space velocity, and atmosphere on carbon conversion and gas yields. Limonite ore has a certain catalytic activity in the cracking of tarry material, and the activity could be significantly enhanced after reduction with H2. When reduced limonite was used, the gas yield increased to the maximum value of 41.6 mmol/g and the yield of carbon in water-soluble tar decreased to a negligible value (0.7%) by increasing the reforming temperature from 400 to 650 °C. The reforming activity of reduced limonite is comparable to the commercial Ni/Al2O3 catalyst. Steam can inhibit carbon deposition on limonite and give a H2-rich gas (H2 content of 70.4 vol %) in a high yield of 74.1 mmol/g at 700 °C. A lower space velocity improves carbon conversion and gas production. The study revealed the possibility of using limonite as an alternative and...

H2-rich gases production from Catalytic Decomposition of Biogas: Viability of the process associated to the co-production of carbon nanofibers

The exploitation of biogas for different applications such as the production of hydrogen, syngas or bio-methane appears as an interesting option to valorise this renewable source. However, these processes are energetically penalized and have to offer an extra added value to become economically attractive. In this context, the Catalytic Decomposition of Biogas (CDB) has been recently proposed as a potential alternative to be considered for biogas valorization. In this process, syngas (H2 and CO) and valuable carbon nanofibers (CNFs) are simultaneously generated. The know-how obtained in previous studies allowed us to select the optimum experimental conditions to simulate the implementation of a CDB continuous process using a fluidized bed reactor. The process consisted in a cyclic operation, by which after the completion of the each run, carbonaceous material produced (containing ca. 6% of catalysts) was withdrawn from the reactor, and the required amount of fresh catalyst to keep catalyst inventory constant was added to the reactor. Characterization of carbonaceous material carried out by several techniques revealed the prevalence of fishbone-like CNF with very interesting textural and structural properties. Mass and energy balances carried out pointed out that the viability of the CDB process depends on the co-production of valuable CNFs that can be used in different applications.

Durability of catalytic performance of the chlorine-doped catalyst Ni(Clx)/ZrO2 for selective methanation of CO in H2-rich gas

Chlorine-doped catalysts Ni(Clx)/ZrO2 (x=0.0–0.6) were prepared for selective methanation of CO in H2-rich gas (CO-SMET). Effects of chlorine ions were studied by means of X-ray diffraction (XRD), temperature programmed reduction (TPR) and adsorption measurements. It is found that chlorine ions could promote Ni crystallite growth and suppress CO2 adsorption. As a result, a deep removal of CO to below 10ppm was achieved with a high selectivity of more than 50% in a wide reaction temperature range. And, at the reaction temperature of 220°C, the selectivity of CO methanation kept at 100% with CO outlet concentration below 10ppm in the 100h durability test over the catalyst Ni(Cl0.1)/ZrO2. However, the selectivity decreased with reaction time at the higher reaction temperatures of 240°C and 280°C. Both X-ray fluorescence spectroscopy (XRF) analysis and ion chromatography analysis proved that chlorine ions evolved in the catalytic reaction, which then allowed for more CO2 to be adsorbed on the catalyst and hydrogenated into methane. This finally resulted in the decrease of the selectivity of CO methanation.

CunTM: Promising catalysts for preferential oxidation of CO in H2-rich gas

Preferential oxidation of CO (PROX) is an important reaction for removing CO to a parts-per-million level from the hydrogen-rich stream. Recent experimental results show single-atom alloys (SAAs) of Cu surfaces doped by transition-metal (TM) of group VIII (TM=Ni, Pd, Pt) exhibit excellent catalytic performance toward hydrogenation and a variety of oxidation reactions including PROX of CO. To unravel mechanism, we performed DFT calculations to investigate. CunPt exhibited higher activity for both H2 dissociation and the PROX when compared with CunNi and CunPd. Especially, Cu6Pt emerges as the best surface for both H2 dissociation and the PROX. The investigation on catalytic mechanism, we first found the element step is the formation of hydroxyl and atomic oxygen simultaneously. This work provides insight into the Cu-TM SAA catalysts, which may give helpful information for design of Cu-based catalysts for industrially important PROX.

A novel gas separation integrated membrane bioreactor to evaluate the impact of self-generated biogas recycling on continuous hydrogen fermentation

A Gas Separation Membrane Bioreactor (GSMBR) by integrating membrane technology with a continuous biohydrogen fermenter was designed. The feasibility of this novel configuration for the improvement of hydrogen production capacity was tested by stripping the fermentation liquor with CO2- and H2-enriched gases, obtained directly from the bioreactor headspace. The results indicated that sparging the bioreactor with the CO2-concentrated fraction of the membrane separation unit (consisting of two PDMS modules) enhanced the steady-state H2 productivity (8.9–9.2 L H2/L-d) compared to the membrane-less control CSTR to be characterized with 6.96–7.35 L H2/L-d values. On the other hand, purging with the H2-rich gas strongly depressed the achievable productivity (2.7–3.03 L H2/L-d). Microbial community structure and soluble metabolic products were monitored to assess the GSMBR behavior. The study demonstrated that stripping the bioH2 fermenter with its own, self-generated atmosphere after adjusting its composition (to higher CO2-content) can be a promising way to intensify dark fermentative H2 evolution.

Effect of crystallite size on the performance and phase transformation of Co3O4/Al2O3 catalysts during CO-PrOx - an in situ study.

The preferential oxidation of carbon monoxide has been identified as an effective route to remove trace amounts of CO (approx. 0.5-1.0 vol%) in the H2-rich reformate gas stream after the low-temperature water-gas shift. Instead of noble metal-based catalysts, Co3O4-based catalysts were investigated in this study as cheaper and more readily available alternatives. This study aimed at investigating the effect of crystallite size on the mass- and surface area-specific CO oxidation activity as well as on the reduction behaviour of Co3O4. Model Co3O4 catalysts with average crystallite sizes between 3 and 15 nm were synthesised using the reverse micelle technique. Results from the catalytic tests revealed that decreasing the size of the Co3O4 crystallites increased the mass-specific CO oxidation activity in the 50-200 °C temperature range. On the other hand, the surface area-specific CO oxidation activity displayed a volcano-type behaviour where crystallites with an average size of 8.5 nm were the most active within the same temperature range. In situ characterisation in the magnetometer revealed that the Co3O4 crystallites are partially reduced to metallic Co above 225 °C with crystallites larger than 7.5 nm showing higher degrees of reduction under the H2-rich environment of CO-PrOx. In situ PXRD experiments further showed the presence of CoO concurrently with metallic fcc Co in all the catalysts during the CO-PrOx runs. In all experiments, the formation of fcc Co coincided with the formation of CH4. Upon decreasing the reaction temperature below 250 °C under the reaction gas, both in situ techniques revealed that the fcc Co previously formed is partially re-oxidised to CoO.

Design of an integrated biomass gasification and proton exchange membrane fuel cell system under self-sustainable conditions: Process modification and heat-exchanger network synthesis

The design and analysis of an integrated biomass gasification and PEMFC system to generate heat and power demand for residential applications are presented in this study. Two biomass gasification configurations using sawdust as a feedstock are considered: air–steam biomass gasification (AS-BG-PEMFC) and steam-only biomass gasification (SO-BG-PEMFC). The biomass processing consists of a biomass gasification which is used to produce H2-rich gas (syngas), followed by high- and low-temperature shift reactors and a preferential oxidation reactor. Pinch analysis is performed to evaluate and design a heat-exchanger network in the two biomass gasification systems. The remaining useful heat is recovered and employed for a reactant preparation step and for a heating utility system in a household. The simulation results indicate that the SO-BG-PEMFC generates syngas with a greater H2 content than the AS-BG-PEMFC, resulting in higher fuel processor and electric efficiencies. However, the AS-BG-PEMFC provides a higher thermal efficiency because a high-temperature gaseous product is obtained, and more energy is thereby recovered to the system. The total heat and power efficiencies of the AS-BG-PEMFC and the SO-BG-PEMFC are 83% and 70%, respectively. The Sankey diagram of energy flows reveals that the performance improvement depends entirely on the utilization of useful energy in the exhaust gas.

Ceria supported nickel catalysts for CO removal from H2-rich gas

AbstractCO in H2-rich gas must be removed to meet various requirements in industrial applications. Four methods, i.e., the precipitation method using aqueous ammonia, the complexing method using urea, the complexing method using citric acid and the precipitation method using ammonium carbonate, were adopted to prepare samples NiO/CeO2 as catalyst precursors for removal of CO from H2-rich gas via selective methanation reaction. The sample NiO/CeO2 prepared by the precipitation method using aqueous ammonia as precipitant exhibited the highest catalytic activity both for CO methanation and for CO2 methanation after reduction prior to the catalytic reaction. Chlorine ion was then doped to suppress CO2 conversion. Effect of chlorine doping was investigated. Over the optimal catalyst 40%Ni(Cl0.2)/CeO2, CO in the H2-rich gas was removed to below 10 ppm with selectivity of 60% or higher at reaction temperatures 230–250 °C in the test period of 75 h.

Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition.

Hydrogen is often described as the fuel of the future, especially for application in hydrogen powered fuel-cell vehicles (HFCV’s). However, its widespread implementation in this role has been thwarted by the lack of a lightweight, safe, on-board hydrogen storage material. Here we show that benign, readily-available hydrocarbon wax is capable of rapidly releasing large amounts of hydrogen through microwave-assisted catalytic decomposition. This discovery offers a new material and system for safe and efficient hydrogen storage and could facilitate its application in a HFCV. Importantly, hydrogen storage materials made of wax can be manufactured through completely sustainable processes utilizing biomass or other renewable feedstocks.

Effect of metal ions on the steam gasification performance of demineralized Shengli lignite char

Lignite is considered to be a promising coal to obtain H2 or H2-rich synthesis gas. In order to investigate which metal ions promote its high H2 production, Shengli lignite after partial demineralization followed by addition metal ions were mainly studied. The steam gasification reaction with temperature programmed was tested by using fixed-bed reactor. XRD, Raman, XPS and FTIR were used to do the research on microcrystalline structure changes of the Shengli lignite. The results proved that the gasification reactivity of HCl treatment samples were poor. The addition of alkali metal and alkaline earth metal had a distinguished catalytic effect on the steam gasification. Nevertheless, transition metal had a slight catalysis. The metal ions added into the acid treatment lignite decreased initiating gasification temperatures, increased H2 cumulative yield and H2/CO ratio in the syngas from the steam gasification, especially for Ca, K and Na. The XRD and Raman results revealed that the addition of alkali metal and alkaline earth metal made the char structure disorderly, and hindered chemical structure of coal changes towards graphitization. The XPS results indicated that the content of CO increased significantly after adding metal ions, which could contribute to opening the loop of aromatic nucleus. The reaction mechanisms about how metal ions catalyzed low-rank coals in steam gasification were proposed.

Parametric study of pyrolysis and steam gasification of rice straw in presence of K2CO3

A parametric study of pyrolysis and steam gasification of rice straw (RS) was performed to investigate the effect of the presence of K2CO3 on the behavior of gas evolution, gas component distribution, pyrolysis/gasification reactivity, the quality and volume of synthetic gas. During pyrolysis, with the increase in K2CO3 content in RS (i) the instantaneous CO2 concentration was increased while CO concentration was relatively stable; (ii) the yield of CO2 and H2 increased on the cost of CH4. During steam gasification of RS, with the increase in K2CO3 content in RS (i) the instantaneous concentration of CO2 and H2 increased while instantaneous concentration of CO and CH4 decreased; (ii) the yield of CO2 and H2 production and total yield increased; and (iii) yield of CO and CH4 production followed the order: 9% K2CO3 RS<6% K2CO3 RS<raw RS<3% K2CO3 RS<water-leached RS. Water-leached RS showed the highest pyrolysis reactivity, while stream gasification reactivity was proportional to K2CO3 content in RS. The results of this study reveal that the presence of K2CO3 during pyrolysis and steam gasification of RS effectively improves production of H2 rich gas.

Catalytic ethanolysis and gasification of kraft lignin into aromatic alcohols and H2-rich gas over Rh supported on La2O3/CeO2–ZrO2

Efficient catalytic ethanolysis and gasification of kraft lignin were conducted over a versatile supported catalyst Rh/La2O3/CeO2–ZrO2 to give high-value aromatic alcohols and H2-rich gas. The removal of phenolic hydroxyl group was the most prevalent reaction, and importantly, almost no phenols, undesired char and saturating the aromatic ring were detected. Meanwhile, the feedstock and solvent both played key roles in H2 generation that contributed to the hydrodeoxygenation of liquid components and made the whole catalytic process out of H2 supply. Reusability tests of catalyst indicated that the crystalline phase transition and agglomeration of support, the loss of noble metal Rh and carbon deposition were the possible reasons for its deactivation in supercritical ethanol. Comparing with water, methanol and isopropanol system, ethanol was the only effective solvent for the depolymerization process.

Hydrogen production by steam reforming of DME over Ni-based catalysts modified with vanadium

Dimethyl ether steam reforming (DME-SR) for hydrogen production has been studied over VNi/Al2O3 catalysts as part of an investigation aimed at the development of effective technology based on second generation of biofuels. Methanol steam reforming (MeOH-SR) was investigated as a step of the DME-SR process. High activity in the MeOH-SR was observed and two different mechanism depending on temperature and influenced by the vanadium content (0.5, 1 and 3%) was evidenced: direct methanol decomposition to CO and H2 was observed at low temperature and low vanadium content and methanol steam reforming reaction occurs majorly to give an almost stoichiometric H2/CO2 ratio at moderate to high temperature (400 °C) over 3VNi. DME conversion is complete at 500 °C over VNi catalysts in DME-SR, as a two steps reaction: DME hydrolysis and MeOH-SR giving an H2 rich gas reformate generated with a H2 selectivity c.a. 60–70% over 0.5VNi and 3VNi, values maintained during 4.5 h of activity in the same reaction conditions with no signs of deactivation or significant coke formation over catalyst surface.

Pressure swing adsorption for coproduction of power and ultrapure H2 in an IGCC plant with CO2 capture

The coproduction of power and ultrapure H2 within an Integrated Gasification Combined Cycle (IGCC) plant implementing CO2 capture offers advantages in terms of flexible operation while retaining good efficiency. The common design includes an absorption unit for removing CO2 from a high pressure syngas followed by a Pressure Swing Adsorption (PSA) unit for purifying a part of the resulting H2-rich gas stream. A drawback of this design consists in the necessity for compression of the PSA tail gas in order to recover the energy available in the residual H2 content. This paper presents two novel configurations for power and H2 coproduction with CO2 capture, entirely based on PSA technology. The first relies on two PSA trains in series (Two-train PSA), while the other is able to carry out CO2 separation and H2 purification within a single PSA train (One-train PSA). The two systems were defined and simulated through a composite model of the whole plant. The process simulation results showed that both the configurations proposed are able to shift between the two energy products without compromising the performance of the plant. The load of the plant could be decreased by increasing the ultrapure H2 throughput, while maintaining a constant feed of coal to the gasifier. The Two-train PSA configuration achieved higher performance in terms of energy efficiency and H2 purity. The One-train PSA configuration returned slightly lower but still good performance, while its design includes a single separation stage instead of two. Additionally, both configurations enable the avoidance of PSA tail gas compression giving an advantage against the absorption-based design. A comparative analysis with results taken from the literature seems to confirm this assertion.

Microwave pyrolysis of oil palm fiber (OPF) for hydrogen production: Parametric investigation

The microwave assisted pyrolysis of oil palm fiber (OPF) for production of hydrogen rich gas was experimentally investigated by considering different reaction parameters. Five different OPF sample sizes (i.e., lengths less than 1mm, 1–3mm, 4–6mm, 7–9mm and 10–12mm), microwave power ranging from 400W to 900W, reaction temperatures ranging from 450°C to 700°C and N2 flow rates ranging 200–1200cm3min−1 were tested. The hydrogen and the total gas yield from all process parameters have been reported. The microwave assisted pyrolysis was carried out by using a microwave reactor which has a capacity of providing 2450±25MHz microwave frequency. It has been found that the use of a smaller OPF particle sizes, a higher microwave power, a higher reaction temperature and a higher N2 flow rates significantly yields more H2 rich gas. The char produced at the maximum hydrogen yield process parameter was considered for TGA and SEM analyses and the results shows a potential use for the soil fertilization.

Selective methanation of CO over Ni/Al2O3 catalyst: Effects of preparation method and Ru addition

Four methods were adopted to prepare samples 20%NiO/Al2O3 with calcination fixed at 500 °C, which were then reduced into 20%Ni/Al2O3 and used as catalysts for reaction of selective methanation of CO in H2-rich gas (CO-SMET). XRD and TPR measurements indicate that nickel aluminates were formed in the calcined samples and their formation was influenced by preparation methods. Higher temperatures were required to reduce the calcined samples more efficiently and to achieve a higher catalytic activity for CO-SMET. Among the four methods, the precipitation method using ammonium carbonate as precipitant produced the highest catalytic activity both for CO methanation and for CO2 methanation after reduction at 800 °C for 2 h. The calcined sample 20%NiO/Al2O3 prepared with the method was therefore used as support and impregnated with Ru3+ solution. Ru addition promoted reduction of Ni2+ ions in the calcined sample even at the low temperatures of 400 °C and 500 °C. The catalyst 1%Ru–20%Ni/Al2O3 reduced at 500 °C thus had a superior performance, removing CO to ca. 30 ppm with a selectivity as high as 75% at reaction temperature of 220 °C.

Pre-combustion packed bed chemical looping (PCCL) technology for efficient H2-rich gas production processes

A novel reactor system is presented and investigated for the production of a hydrogen rich gas stream for power or ammonia production, based on pre-combustion chemical looping (PCCL) technology using dynamically operated packed bed reactors. In this process, the oxygen carrier (OC) is alternately oxidized with a gas mixture of air and steam to produce a H2/N2 product gas stream combining oxidation by air and water-splitting, and subsequently reduced with syngas producing a concentrated CO2 stream. The process is carried out at elevated pressure, but at intermediate temperature (in the range of 600–900°C), which allows circumventing the extremely high temperatures required in chemical-looping combustion. In addition, the N2/H2 gas stream can be produced at the required composition for ammonia production, rendering this process also competitive with the conventional ammonia production. A preliminary experimental study has been carried out in a 2kWth packed bed reactor using an iron-based oxygen carrier. The influence of the operating temperature and the initial solid composition during the oxidation cycle on the H2-rich gas yield has been investigated. The complete reduction to pure iron reduces the reactivity of the material due to sintering, whereas a controlled reduction to wüstite (FeO) allows to maintain a higher stability of the material, although the oxygen capacity is decreased.A preliminary thermodynamic assessment of the integrated PCCL plant for power production with natural gas has been carried out reaching an electrical efficiency of 49–51.5% (depending on the plant arrangement) with a carbon capture rate above 95%. The main parameter affecting the plant performance was found to be the steam requirement during the oxidation cycle. The comparison with benchmark technologies has confirmed the potential of the PCCL system.