Simulated Producer Gas Research Articles

Hydrogen-Rich Syngas Production via Dry and Steam Reforming of Methane in Simulated Producer Gas over ZSM-5-Supported Trimetallic Catalysts

This study investigated the production of hydrogen-rich syngas from renewable sources using durable and efficient catalysts. Specifically, the research focused on steam methane reforming (SRM) and dry methane reforming (DRM) of simulated producer gas from biomass steam gasification in a fluidized bed reactor. The catalysts tested are ZSM-5-supported nickel-iron-cobalt-based trimetallic catalysts in different ratios, which were prepared via the wet impregnation method. Synthesized catalysts were characterized using XRD, BET, H2-TPR, and SEM techniques. The results of the SRM with the simulated producer gas showed that the 20%Ni-20%Fe-10%Co/ZSM-5 trimetallic catalyst, at a gas hourly space velocity (GHSV) of 12 L·h−1·g−1 and reaction temperature of 800 °C, achieved the highest CH4 conversion (74.8%) and highest H2 yield (65.59%) with CO2 conversion (36.05%). Comparing the performance of the SRM and DRM of the simulated producer gas with the 20%Ni-20%Fe-10%Co/ZSM5 at a GHSV of 36 L·h−1·g−1 and 800 °C, they achieved a CH4 conversion of 67.18% and 64.43%, a CO2 conversion of 43.01% and 52.1%, and a H2 yield of 55.49% and 42.02%, respectively. This trimetallic catalyst demonstrated effective inhibition of carbon formation and sintering, with only 2.6 wt.% carbon deposition observed from the thermo-gravimetric analysis of the used catalyst from the SRM of the simulated producer gas, thus promoting the potential of the ZSM-5-supported trimetallic catalysts in methane reforming.

Catalytic reforming of model biomass-derived producer gas

This work includes a complete study of the reaction of reforming a simulated producer gas stream comparing a Ni-based catalyst with another one promoted with potassium to enhance the resistance to coke formation. Although coke deposition is unavoidable in the presence of tars in the stream, the analysis of different reaction parameters revealed that operating at 750 °C, weight hourly space velocity (WHSV) of 60 L−1 g−1 h−1 and 10–20 vol% of steam is possible to minimize the accumulation of carbon deposits. Moreover, it was demonstrated that the addition of potassium helps to mitigate carbon formation, but a high concentration of steam leads to nickel sintering and/or partial oxidation of metallic nickel. On this basis, it was successfully evidenced that the Ni-K catalyst is an excellent candidate for obtaining clean syngas from producer gas reforming.

Benzene conversion using a partial combustion approach in a packed bed reactor

This study investigates the partial combustion technique for tar conversion using a modified experimental set up comprising a packed bed reactor with bed-inside probe for air supply. Simulated producer gas (SPG) and benzene were selected as a real producer gas alternative and model tar component respectively. The benzene conversion was investigated under different experimental conditions such as reactor temperature (650–900 °C), packed bed height (0–12 cm), residence time (1.2–1.9 s), air fuel ratio (0.2 and 0.3) and SPG composition. The results showed insignificant effect of temperature over benzene conversion while air fuel ratio of 0.3 caused high benzene conversion than at 0.2. Absence of packed bed lead high benzene conversion of 90% to polyaromatic hydrocarbons (PAHs) compared to similar low PAHs free benzene conversion of 32% achieved at both packed heights. In SPG composition effect, H2 and CH4 had a substantial inverse effect on benzene conversion. An increase in H2 concentration from 12 to 24 vol% increased the benzene conversion from 26 to 45% while an increase in CH4 concentration from 7 to 14 vol% reduced the benzene conversion from 28 to 4%. However, other SPG components had insignificant impacts on benzene conversion.

Benzene Conversion Using a Partial Combustion Approach in a Packed Bed Reactor

This study investigates the partial combustion technique for tar conversion using a modified experimental set up comprising a packed bed reactor with bed-inside probe for air supply. Simulated producer gas (SPG) and benzene were selected as a real producer gas alternative and model tar component respectively. The benzene conversion was investigated under different experimental conditions such as reactor temperature (650 – 900 °C), packed bed height (0 – 12 cm), residence time (1.2 – 1.9 s), air fuel ratio (0.2 and 0.3) and SPG composition. The results showed insignificant effect of temperature over benzene conversion while air fuel ratio of 0.3 caused high benzene conversion than at 0.2. Absence of packed bed lead high benzene conversion of 90% to polyaromatic hydrocarbons (PAHs) compared to similar low PAHs free benzene conversion of 32 % achieved at both packed heights. In SPG composition effect, H2 and CH4 had a substantial inverse effect on benzene conversion. An increase in H2 concentration from 12 to 24 Vol% increased the benzene conversion from 26 to 45% while an increase in CH4 concentration from 7 to 14 Vol% reduced the benzene conversion from 28 to 4%. However, other SPG components had insignificant impacts on benzene conversion.

Simulation-based investigation of tar formation in after-treatment systems for biomass gasification

Even though biomass gasification remains a promising technology regarding de-centralized sustainable energy supply, its main limitations, namely the issues of unsteady operation, tar formation in after-treatment systems, and consequential high maintenance requirements, have never been fully overcome. In order to tackle the latter two deficiencies and to increase the understanding of thermodynamic and thermokinetic producer gas phase phenomena within the after-treatment zones, a numerical system dynamic model has been created. Thereby, naphthalene has been chosen to represent the behavior of tars. The model has been validated against a wide variety of measured and simulated producer gas compositions. This work particularly focuses on the investigation and minimization of tar formation within after-treatment systems at low pressures and decreasing temperatures. Model-based analysis has led to a range of recommended measures, which could reduce the formation tendency and thus the condensation of tars in those zones. These recommendations are (i) to decrease gas residence time within pipes and producer gas purification devices, (ii) to increase temperatures in low-pressure zones, (iii) to increase hydrogen to carbon ratio, and (iv) to increase oxygen to carbon ratio in the producer gas. Furthermore, the numerical model has been included in the cloud-computing platform KaleidoSim. Thus, a wider range of process parameter combinations could be investigated in reasonable time. Consequentially, a simulation-based sensitivity analysis of producer gas composition with respect to process parameter changes was conducted and the validity basis of the above recommendations was enlarged.

Sewage Sludge-Derived Producer Gas Valorization with the Use of Atmospheric Microwave Plasma

Atmospheric microwave plasma was applied to the processing of the partially cleaned producer gas obtained from sewage sludge gasification. The plasma processing resulted in residual tar compounds conversion and changes in the gas composition. During the tests with a different gas flow rates and microwave power inputs, liquid and gaseous samples were collected to evaluate the plasma reactor’s performance. The conversion efficiency ranged from 19 to 100% and it depended on the specific energy input (SEI), gas flow rate, initial tar concentration, and the nature of the tars compounds. Generally, it was shown that the conversion rate increased with the SEI and that the aliphatic, cyclic and substituted compounds were converted much easier than benzene. Moreover, applying plasma led to the production of heavier aromatics (i.e. naphthalene, indene, acenaphthylene) but the rise in their concentration was significantly smaller than the amount of converted compounds. The gas composition changes revealed in the increase of H2 and CO concentration that was an effect of hydrocarbons and CO2 conversion. Additionally, it was indicated that the microwave plasma reactor’s performance was noticeably worse than in the case of the laboratory test with a simulated producer gas. This was mainly attributed to differences in the reactors’ geometry, lower hydrogen concentration and the presence of inorganic deposit on the reactor’s walls that might have inhibited microwaves transfer. In general, the microwave plasma technology seems promising in the context of cleaning and upgrading the producer gas, however, further optimization research is necessary to make it more reliable and less energy consuming.Graphic

A semi-empirical approach towards predicting producer gas composition in biomass gasification

The paper provides a comparison of five distinct models, often used in thermodynamic equilibrium modeling that allows the study of feedstock effect on gasification process. The five models were thus formulated and solved using MATLAB software. The results were compared with published experimental data. The model based on equilibrium constant derived using methane formation reaction and water gas shift reaction showed comparatively better performance. Once the model was selected, the response surface analysis was employed to predict the parameters, such as reactor temperature and feedstock moisture content, for a maximum heating value of the producer gas. Simulations were performed for 50 different biomass feedstocks and simplified correlations were developed from simulated producer gas composition using multiple linear regression. These correlations may be suited for the quick comparison of different feedstocks in gasification process.

The Effects of Temperature and Gas Species on Ammonia Removal in the Simulated Producer Gas of Biomass Gasification by H2-Reduced Titanomagnetite

In this study, catalytic removal of NH3 in simulated producer gas from biomass gasification has been experimentally investigated using H2-reduced titanomagnetite (Fe2.9Ti0.1O4) in a lab-scale fluidized bed reactor at temperatures of 500 and 750 °C, respectively. Effects of gaseous species and their combination on the NH3 removal were examined by using seven gas mixtures: (1) Simulated producer gas (H2, CO, CO2, and CH4); (2) H2 in Ar; (3) CO in Ar; (4) CO2 in Ar; (5) CH4 in Ar; (6) H2, CO, and Ar; and (7) H2, CO, CO2, and Ar. In these test gases, the NH3 concentration was 2300 ± 200 ppmv. The experimental results show that temperature has a significant effect on NH3 decomposition in all of the tested gases, and the reduced titanomagnetite had a much higher activity at 750 °C than at 500 °C. In the simulated producer gas, the NH3 decompositions were 28.4 and 94.7% at 500 and 750 °C, respectively. Side reactions including the reverse water–gas shift reaction, the (reverse) Boudouard reaction, the (reverse) ...

High performance Ni-Fe-Mg catalyst for tar removal in producer gas

A Ni-Fe-Mg material, supported on a ceramic substrate, suitable for application in a gasifier or reforming reactor was evaluated as a catalyst for tar decomposition via steam reforming. Experiments were conducted in a laboratory-scale fixed-bed reactor using simulated producer gas containing toluene and ethylene as tar surrogates. The catalyst was prepared by wet-impregnation and characterized by analytical techniques to include: BET, XRD, TPR, and SEM. The elemental composition of Ni, Fe, and MgO was optimized for maximum activity and stability. The optimized catalyst composition contained Ni, Fe, and MgO in the ratio 45:21:34 by weight. The observed catalyst activity was superior in comparison to other alkaline earth metal promoters: CaO, SrO, and BaO as well as a reference catalyst, Ni-K-MgO, in the temperature range between 600 and 800 °C. Time on stream with the optimized composition showed sustained tar (toluene + ethylene) conversion of near 100% at 750 °C for at least 48 h, indicating no coke formation. The coke formation affinity of Ni was reduced by the presence of the FeNi3 alloy. The enhanced performance with MgO is attributed to the strong adsorption of H2O forming Mg(OH)2 species facilitated on the oxide ion vacancy site of MgO acting as oxygen exchange site.

Investigation of ammonia removal from the simulated producer gas of biomass gasification by H2-reduced titanomagnetite

Catalytic removal of NH3 by both unprocessed and H2-reduced titanomagnetites (Fe2.9Ti0.1O4) from two gases has been experimentally investigated in a lab-scale fluidised bed reactor. The test gases include Ar gas as control and simulated producer gas from biomass steam gasification (H2, CO, CO2 and CH4). In the test gases, the NH3 concentration was 2300 ± 100 ppmv and the operation temperatures were varied from 500 to 850 °C.The experimental results show that in the control Ar gas, the H2-reduced titanomagnetite had much higher activity than the unprocessed titanomagnetite to decompose NH3 at all of the temperatures tested, and the efficiency of NH3 removal increased with reaction temperature. The NH3 decomposition by the reduced titanomagnetite was 97.8% at 500 °C, 99.7% at 600 °C, and 100% at 750 and 850 °C, in comparison with corresponding values of 31.6%, 34.0%, 83.9% and 93.2% for the unprocessed titanomagnetite. Therefore, the H2-reduced titanomagnetite was then employed to remove NH3 in the simulated producer gas in which the NH3 decomposition was 28.4 ± 3.4%, 94.7 ± 2.8% and 98.4 ± 0.4%, respectively, at 500, 750 and 850 °C. In NH3 decomposition in the simulated gas, side reactions have been identified and analysed which played different roles at different temperatures and also affected the gas composition. At 500 °C, the carbon formation from the Boudouard reaction significantly suppressed the activity of the reduced titanomagnetite for NH3 decomposition.

Investigation of hydrogen sulphide removal from simulated producer gas of biomass gasification by titanomagnetite

This work investigated removal of H2S from simulated producer gas by using iron-based sand, named titanomagnetite (Fe2.9Ti0.1O4), in a fluidised bed quartz reactor. The aims of this study were to determine the effectiveness of titanomagnetite and the most effective operation temperatures, and to examine the effect of steam and CO in the producer gas. In the experiments, H2S concentration in the gases was controlled at 240 ± 20 ppmv and the test gases were, respectively, (1) Ar gas, (2) simulated producer gas from biomass steam gasification (CO, CO2, CH4 and H2), (3) mixture of Ar and steam, and 4) mixture of Ar and CO. Unprocessed and H2-reduced titanomagnetites were used as sorbents and operation temperatures were varied from 350 to 750 °C. Results from the experiments show that both of the unprocessed and the H2-reduced titanomagnetites were effective to remove H2S in Ar gas at 600 °C. However, at the same temperature, the H2S removal efficiency was reduced in the simulated gas for which the unprocessed titanomagnetite was more effective than the H2-reduced titanomagnetite. For the unprocessed titanomagnetite, the temperature range for most effective H2S removal was found to be 400–450 °C. It was also observed that both steam and CO in the gas mixture reduced the removal efficiency significantly although steam in the gas had more significant impacts.

Plasma-assisted Toluene Destruction in Simulated Producer Gas

Toluene is chosen as a model tar compound and destroyed by a rotating gliding arc (RGA) discharge in simulated producer gas. A maximum toluene destruction efficiency of 95.6% is achieved. Meanwhile, the concentration of the useful components of synthesis gas (CO and H2) is significantly enhanced compared to the initial producer gas, indicating that the RGA plasma has great potential for further and simultaneous application in tar cracking and producer gas upgrading.

Effect of water addition in a microwave assisted thermal cracking of biomass tar models

Producer gas from biomass gasification is plagued by the presence of tar which causes pipe blockages. Thermal and catalytic treatments in a microwave reactor have been shown to be effective methods in removing tar from producer gas. A question arises as to the possibility of enhancing the removal mechanism by adding water into the reactor. Toluene and naphthalene were used as tar models in the present study with N2 as the carrier gas followed by the use of simulated producer gas. Thermal treatment with various amount of water was added at temperatures in the range of 800–1200°C. The tar removal efficiency obtained 95.83% at the optimum temperature of 1200°C for naphthalene in for toluene 96.32% at 1050°C at water to tar ratio (W/T) of 0.3. This study shows that the removal of tar by microwave irradiation with water addition is a significant and effective method in tar cracking.

Fe and CaO promoted Ni catalyst on gasifier bed material for tar removal from producer gas

A new Ni-based mixed oxide material (Ni-Fe-CaO) for catalyzing Carbo HSP gasifier bed material was prepared and characterized by XRD, TPR, TEM, and SEM techniques. The catalyst performance for tar removal from a simulated producer gas mixture via steam reforming was tested in a laboratory-scale fixed-bed reactor between 700 and 800°C, using toluene and ethylene as tar surrogates. Ni–Fe–CaO catalysts had significantly higher activity and deactivation resistance for toluene removal compared to either Ni–Fe or Ni catalysts. Keeping CaO loading similar in the catalysts, the Ni:Fe ratio was varied and the optimum tar conversion and highest COx selectivity were obtained with ratios of 3:1 and 2:1. The turn over frequency (TOF) on Ni in the Ni–Fe–CaO mixed oxides were higher compared to pure Ni or Ni–CaO combinations and increased with lowering Ni/Fe ratio. High tar removal activity (80% vs 68%) and COx selectivity (96% vs 98%) at 750°C were obtained for 1.6% (Ni45Fe15Ca40)/Carbo HSP and 1.6% (Ni40Fe20Ca40)/Carbo HSP compositions, respectively. Deactivation occurred mainly due to sintering of the 1.6% (Ni45Fe15Ca40) composition reducing conversion efficiency by 17% (from 99.7% to 83%) after 48h in time-on-stream at 800°C. After regeneration with a O2/H2 sequence, the conversion was reduced from 98% to 80% after 24h in time-on-stream. Similarly, 1.6% (Ni40Fe20Ca40) composition shows a stable conversion of ∼80% at the end of 50h, which was much superior compared to the 1% (Ni65Fe35)/Carbo HSP catalyst. The individual role of Fe and CaO in promoting Ni for improving catalytic activity and stability in Ni-Fe-CaO was investigated

Improved catalytic performance of CaO and CeO2 promoted Ni catalyst on gasifier bed material for tar removal from producer gas

A new catalytic material containing the mixture of Ni, CaO and CeO2 for catalyzing commercial gasifier bed material (Carbo HSP) was synthesized and characterized by XRD, TPR/TPO, TPD and SEM techniques. The catalyst performance for tar removal in simulated producer gas mixture via steam reforming was tested in a lab-scale fix-bed reactor at atmospheric pressure and over a temperature range from 600 to 800°C. The combination of Ni-CaO-CeO2 had significantly higher activity for toluene removal as compared to Ni, Ni-CaO or Ni-CeO2 systems. At 700°C, the optimum composition 2.5wt.% (Ni20Ca60Ce20) displayed 68% and 52% conversions for C7H8 and C2H4 respectively, leading to the highest CO2 selectivity. This catalyst composition shows only 7% (from 100% to 93%) deactivation in activity after 48h in time-on-stream at 800°C. After regeneration with an O2/H2 sequence, the conversion recovers to 100% and decreased only to 95% after 48h in time-on-stream. Ni activity and stability are enhanced from the individual roles of CaO and CeO2. The CeO2 can act as redox component that provides for a higher H2O dissociation leading to carbon oxidation and the CaO can enhance the basicity of the catalyst as well as provide for a higher dispersion of Ni metal. The catalytic steam reforming of tars also results in a higher H2-to-CO ratio.

Tar and CO2 removal from simulated producer gas with activated carbon and charcoal

Steam gasification of biomass produces gases such as CO, CO2, H2, CH4, H2O, C2–C5 hydrocarbons, tars (aromatic hydrocarbons), NH3, HCN, and H2S, which are commonly known as producer gas. To produce liquid fuel, CO2 and tars have to be removed from the producer gas. The CO2 can be converted into a useful product such as CO using the reverse Boudouard reaction (CO2+C↔2CO). Tars can be removed in the presence of carbon by adsorption. Using simulated producer gas flow, reactor studies (200°C–950°C) of the reverse Boudouard reaction and the adsorption of toluene and ethylene, tar surrogates, were conducted with different commercially activated carbon and mesquite charcoal. The study showed that the reverse Boudouard reaction is limited by kinetics. The concentration of CO from the reverse Boudouard reaction approaches equilibrium with increase in temperature and residence time. The adsorption of the tar surrogate toluene in the presence of carbon at lower temperature of 200°C–300°C is a useful removal mechanism.