Oxidative catalytic steam gasification of sugarcane bagasse for hydrogen rich syngas production

Reactive Flash Volatilization (RFV) is an emerging thermochemical method to produce tar free hydrogen rich syngas from waste biomass at relatively lower temperature (<900 °C) in a single stage catalytic reactor within a millisecond residence time. Here, we show catalytic RFV of bagasse using Ru, Rh, Pd, or Re promoted Ni/Al₂O₃ catalysts under steam rich and oxygen deficient environment. The optimum reaction conditions were found to be 800 °C, steam to carbon ratio = 1.7 and carbon to oxygen ratio = 0.6. Rh–Ni/Al₂O₃ performed the best, resulting in highest hydrogen concentration in the synthesis gas at 54.8%, with a corresponding yield of 106.4 g-H₂/kg bagasse. A carbon conversion efficiency of 99.96% was achieved using Rh–Ni, followed by Ru–Ni, Pd–Ni, Re–Ni and mono metallic Ni catalyst in that order. Alkali and Alkaline Earth Metal species present in the bagasse ash and char, that deposited on the catalyst, was found to enhance its activity and stability. The hydrogen yield from bagasse was higher than previously reported woody biomass and comparable to the microalgae.     

Exergy analysis of sugarcane bagasse gasification

The gasification technology has been object of study of many researchers, especially those involved in promoting large-scale electricity generation in sugarcane mills. This paper presents a simplified model for the gasification process based on chemical equilibrium considerations. The model consists in the minimization of the Gibbs free energy of the produced gas, constrained by mass and energy balances for the system. Despite the simplicity of the model, its results are reliable in identifying the tendencies of the working parameters of the system. A parametric study has been carried aiming the verification of the influence of many variables inherent to the model, such as: gasification temperature, moisture content, and air temperature, among others. The results were compared with those found in literature and real systems. Following this parametric study, an exergy analysis has been performed in order to evaluate irreversibilities associated to the process, and the influence of temperature, moisture, charcoal production, and thermal losses on them. Finally, a first attempt to integrate a gasifier into a sugarcane mill was performed, which showed the potential benefits regarding the use of such technology.     

Assessment of sugarcane bagasse gasification in supercritical water for hydrogen production

Sugarcane bagasse is one of the major resources of agricultural biomass waste in the world. In this work, supercritical water gasification characteristics of sugarcane bagasse were investigated. The effect of temperature (600–750 °C), concentration (3–12 wt%), residence time (5–20 min) and catalysts (Raney-Ni, K₂CO₃ and Na₂CO₃) on bagasse gasification were studied. A kinetic study on the non-catalytic and Na₂CO₃ catalytic bagasse gasification was conducted to describe the kinetic information of the bagasse gasification reaction. The results showed that a higher reaction temperature, a lower bagasse concentration and a longer residence time could favor the gasification of bagasse, leading to a higher hydrogen yield. Bagasse was nearly completely gasified at 750 °C without using any catalyst and the carbon gasification efficiency could reach up to 96.28%. The addition of employed catalysts remarkably promoted the bagasse gasification reactivity. The maximum hydrogen yield (35.3 mol/kg) was achieved at 650 °C with the Na₂CO₃ loading of 20 wt%. The experimental data fitted well with a homogeneous model based on a Pseudo-first-order reaction hypothesis. The kinetic study showed that Na₂CO₃ catalyst could lower the activation energy E_a of bagasse gasification from 117.88 kJ/mol to 78.25 kJ/mol.     

水蒸气氛围下甘蔗渣热解气化条件的研究

在试验条件下，考察反应温度、升温速率、物料颗粒大小等因素对蔗渣在水蒸气中的热解气化特性的影响。试验结果表明，热解终温越高，物料粒径越小，越有利于产生高质量的热解气。热解终温是热解气化过程主要的决定因素，在先到达热解终温，再通入水蒸气的操作条件下，升温速率的改变对气化效果的影响并不突出。试验在最佳条件(采用粉末物料，在1000℃下进行热解)下，可以得到高热值(10MJ／m^3)合成气和较高的产气率(1．7m^3／kg)。     

Dilute mixed-acid pretreatment of sugarcane bagasse for ethanol production

Integral utilisation of bagasse is a high priority for the diversification of the sugarcane industry. The application of a biorefinery philosophy to bagasse utilisation requires its fractionation into its main components: cellulose, hemicelluloses and lignin. The first stage in that process is the pretreatment, in which a considerable part of hemicelluloses is solubilised, and cellulose is activated towards enzymatic hydrolysis. In this work, a pretreatment method using a mixture of sulfuric and acetic acid is investigated. Two different solid-to-liquid ratios (1.5:10 and 1:10) were used in the pretreatment. Both conditions efficiently hydrolysed the hemicelluloses giving removals above 90%. The extractive components were also effectively solubilised, and lignin was only slightly affected. Cellulose degradation was below 15%, which corresponded to the low crystallinity fraction. The analysis of the morphology of pretreated bagasse confirmed the results obtained in the chemical characterization.     

Process simulation and optimization of groundnut shell biomass air gasification for hydrogen-enriched syngas production

In this study, a detailed steady-state equilibrium simulation model was designed using ASPEN Plus software to analyze and assess the efficiency of the groundnut shell biomass air gasification process. The developed model includes three general stages: biomass drying, pyrolysis, and gasification. The predicted results are quite similar to those found in the literature, which is consistent with simulation results being validated against experimental data. The effect of different operating parameters, like the gasification temperature, gasification pressure, and the equivalence ratio (ER), on the syngas composition and H₂/CO ratio is investigated using sensitivity analysis. The findings of the sensitivity analysis revealed that raising the temperature preferred H₂ and CO production, whereas increasing the pressure has favored CO₂ and CH₄ production. Increasing the ER value also boosted CO and CO₂ yield. Moreover, in an effort to optimize the amount of H₂ generated within the process, the sensitivity analysis was used to evaluate the simultaneous effect of operational parameters on the molar fraction of H₂. To maximize H₂ as a desired product, the following operating parameters were achieved: gasification temperature of 894 °C, gasification pressure of 1 bar, and ER of 0.05, resulting in an H₂ molar fraction of 0.64.     

Sustainable fermentation approach for biogenic hydrogen productivity from delignified sugarcane bagasse

Improper lignocellulosic wastes management causes severe environmental pollution and health damage. Conversion of such wastes particularly sugarcane bagasse (SCB) onto bioenergy is a sustainable approach due to a continuous depletion of conventional biofuels. The delignification of SCB is necessary to proceed for bio-genic H₂ productivity by anaerobic bacteria. The effect of autoclaving, pre-acidification/autoclaving and pre-alkalization/autoclaving of SCB on glucose recovery and subsequently H₂ productivity by dark fermentation was comprehensively investigated. Pre-acidified SCB with 1% H₂SO₄ (v/v) provided H₂ productivity of 8.5 ± 0.14 L/kg SCB and maximum H₂ production rate (R_m) of 105.9 ± 8.3 mL/h. Those values were dropped to 2.7 ± 0.13 L/kg SCB and 58.3 ± 12.9 mL/h for fermentation of delignified SCB with 2% H₂SO₄. This was linked to high levels of total phenolic compounds (1775.3 ± 212 mg/L) in the feedstock. Better H₂ productivity of 13.9 ± 0.58 L/kg SCB and R_m of 133.9 ± 3.6 mL/h was achieved from fermentation of pre-alkalized SCB with 1%KOH (v/v). 256.8 ± 9.8 U/100 mL of α-amylase, 165.7 ± 7.6 U/100 mL of xylanase, 232.8 ± 6.1 U/100 mL of CM-Cellulase, 176.5 ± 5.0 U/100 mL of polyglacturanase and 0.702 ± 0.013 mg M B. reduced/min. of hydrogenase enzyme was accounted for the batches supplied with delignified SCB by KOH. The Clostridium and Bacillus spp. was dominance and prevalence resulting a higher H₂ productivity and yield. A novel strain of Archea and alpha proteobacterium were also identified and detected.     

Screening and optimization of pretreatments in the preparation of sugarcane bagasse feedstock for biohydrogen production and process optimization

This work evaluated the effects of individual alkaline, sodium carbonate (Na₂CO₃ denoted as; NaC), sodium sulfide (Na₂SO₃ denoted as; NaS) and combination of NaC + NaS pretreatment for the saccharification of sugarcane bagasse (SCB). The effects of different pretreatments on chemical composition and structural complexity of SCB in relation with its saccharification were investigated. For enzymatic hydrolysis of pretreated SCB we have utilized the produced crude enzymes by Streptomyces sp. MDS to make the process more cost effective. A enzyme dose of 30 filter paperase (FPU) produced a maximum reducing sugar (RS) 592 mg/g with 80.2% hydrolysis yield from NaC + NaS pretreated SCB under optimized conditions. The resulted enzymatic hydrolysates of each pretreated SCB were applied for hydrogen production using Clostridium beijerinckii KCTC1785. NaC + NaS pretreated SCB hydrolysates exhibited maximum H₂ production relative to other pretreatment methods. Effects of temperature, initial pH of culture media and increasing NaC + NaS pretreated SCB enzymatic hydrolysates concentration (2.5–15 g/L) on bioH₂ production were investigated. Under the optimized conditions, the cumulative H₂ production, H₂ production rate, and H₂ yield were 1485 mL/L, 61.87 mL/L/h and 1.24 mmol H₂/mol of RS (0.733 mmol H₂/g of SCB), respectively. The efficient conversion of the SCB hydrolysate to H₂ without detoxification proves the viability of process for cost-effective hydrogen production.     

Hydrogen and syngas production from biomass gasification for fuel cell application

Gasification process is being developed to produce a clean and efficient gas flue from fuels such as coal, biomass, and solid/liquid wastes for power generation. In this work, a biomass gasification kinetic model that can predict reaction temperature, gasification performance, and gas composition has been developed for a circulating fluidized bed (CFB). Experimental data from a CFB power plant have been used to validate the model. It is confirmed that the addition of steam is important for increasing the hydrogen concentration and syngas caloric value. Based on the predicted results, an optimal condition is suggested for air and steam gasification in the CFB gasifier.     

A novel use for sugarcane bagasse hemicellulosic fraction: Xylitol enzymatic production

The excess of sugarcane bagasse (SCB) from the sugar-alcohol industry is considered a by-product with great potential for many bioproducts production. This work had as objective to verify the performance of sugarcane bagasse hemicellulosic hydrolysate (SCBHH) as source of sugars for enzymatic or in vitro xylitol production. For this purpose, xylitol enzymatic production was evaluated using different concentrations of treated SCBHH in the commercial reaction media. The weak acid hydrolysis of SCB provided a hydrolysate with 18 g L⁻¹ and 6 g L⁻¹ of xylose and glucose, respectively. Considering the reactions, changes at xylose-xylitol conversion efficiency and volumetric productivity in xylitol were not observed for the control experiment and using 20 and 40% v.v⁻¹ of SCBHH in the reaction media. The conversion efficiency achieved 100% in all the experiments tested. The results showed that treated SCBHH is suitable as xylose and glucose source for the enzymatic xylitol production and that this process has potential as an alternative for traditional xylitol production ways.     

Production of hydrogen-rich syngas from absorption-enhanced steam gasification of biomass with conch shell-based absorbents

In this study, steam gasification of pine sawdust is conducted in a fixed-bed reactor in the temperature range 650–700 °C with calcined conch shell (CS) serving as a starting absorbent. The CS is further subjected to hydration (HCS) and calcination (CHCS) to prepare a modified absorbent. It is found that the hydration-calcination treatment of CS causes smaller CaO crystal grains with a larger BET surface area and more porous surface. As a consequence, CHCS exhibits higher catalytic activity for tar reforming, faster reaction rate for CO₂ absorption and better performance for H₂ selectivity than CS. Elevating the temperature contributes to tar reduction but results in lower H₂ content and higher CO₂ content, while an increase in Ca/C leads to higher H₂ content. And the H₂ content can reach approximately 76% with the use of CHCS when temperature and Ca/C ratio are 650 °C and 2, respectively.     

Biohydrogen production from sugarcane bagasse hydrolysate by elephant dung: Effects of initial pH and substrate concentration

Pre-heated elephant dung was used as inoculum to produce hydrogen from sugarcane bagasse (SCB) hydrolysate. SCB was hydrolyzed by H₂SO₄ or NaOH at various concentrations (0.25-5% volume) and reaction time of 60 min at 121 °C, 1.5 kg/cm² in the autoclave. The optimal condition for the pretreatment was obtained when SCB was hydrolyzed by H₂SO₄ at 1% volume which yielded 11.28 g/L of total sugar (1.46 g glucose/L; 9.10 g xylose/L; 0.72 g arabinose/L). The maximum hydrogen yield of 0.84 mol H₂/mol total sugar and the hydrogen production rate of 109.55 mL H₂/L day were obtained at the initial pH 6.5 and initial total sugar concentration 10 g/L. Hydrogen-producing bacterium (Clostridium pasteurianum) and non hydrogen-producing bacterium (Flavobacterium sp.) were dominating species in the elephant dung and in hydrogen fermentation broth. Sporolactobacillus sp. was found to be responsible for a low hydrogen yield obtained.     

A novel process simulation model for hydrogen production via reforming of biomass gasification tar

Process modeling and simulation are very important for new designs and estimation of operating variables. This study describes a new process for the production of hydrogen from lignocellulosic biomass gasification tars. The main focus of this research is to increase hydrogen production and improve the overall energy efficiency of the process. In this study, Aspen HYSYS software was used for simulation. The integration structure presented in this research includes sections like tar reforming and ash separation (Ash), combined heat and power cycle (CHP), hydrogen sulfide removal unit (HRU), water-gas shift (WGS) reactor, and gas compression as well as hydrogen separation from a mixture of gases in pressure swing adsorption (PSA). It was found that the addition of CHP cycle and the use of the plug flow reactor (PFR) model, firstly, increased the overall energy efficiency of the process by 63% compared to 29.2% of the base process. Secondly it increased the amount of hydrogen production by 0.518 kmol (H2)/kmol Tar as compared with 0.475 of the base process. Process analysis also demonstrated that the integrated process of hydrogen production from biomass gasification tars is carbon neutral.     

Waste biomass to liquids: Low temperature conversion of sugarcane bagasse to bio-oil. The effect of combined hydrolysis treatments

This article describes the influence of different sugarcane bagasse hydrolysis pretreatments on modifications to biomass feedstock and the characteristics of the resultant pyrolysis products. Sugarcane bagasse was pretreated with acid, alkaline or sequential acid/alkaline solutions and pretreated samples were then subjected to a low temperature conversion (LTC) process under He or O₂/He atmospheres at 350-450 °C. Both pretreated samples and sugarcane bagasse in natura were analyzed by determination of their chemical composition and by thermogravimetric, FTIR and SEM analyses. The gases yielded during LTC were monitored on-line by quadrupole mass spectrometry, and the liquid fractions obtained were characterized by FTIR and ¹H and ¹³C NMR. Irrespective of the sugarcane bagasse pretreatment applied, the main bio-oil component obtained was levoglucosan. However, the LTC yield of bio-oil depended on the hydrolysis treatment of the biomass and decreased in the presence of O₂. The acid hydrolysis pretreatment increased the LTC bio-oil yield notably.     

Hydrogen-rich syngas production from municipal solid waste gasification through the application of central composite design: An optimization study

This study aims to investigate the influence and interaction of experimental parameters on the production of optimum H₂ and other gases (CO, CO₂, and CH₄) from gasification of municipal solid waste (MSW). Response surface method in assistance with the central composite design was employed to design the fifteen experiments to find the effect of three independent variables (i.e., temperature, equivalence ratio and residence time) on the yields of gases, char and tar. The optimum H₂ production of 41.36 mol % (15.963 mol kg-MSW⁻¹) was achieved at the conditions of 757.65 °C, 0.241, and 22.26 min for temperature, ER, and residence time respectively. In terms of syngas properties, the lower heating value and molar ratio (H₂/CO) ranged between 9.33 and 12.48 MJ/Nm³ and 0.45–0.93. The predicted model of statistical analysis indicated a good fit with experimental data. The gasification of MSW utilizing air as a gasifying agent was found to be an effective approach to recover the qualitative and quantitate products (H₂ and total gas yield) from the MSW.     

Techno-economic evaluation of strategies based on two steps organosolv pretreatment and enzymatic hydrolysis of sugarcane bagasse for ethanol production

Several strategies based on a two steps organosolv pretreatment followed by enzymatic hydrolysis of sugarcane bagasse (SCB) were evaluated with the objective of selecting operational conditions suitable to promote an efficient and low cost production of ethanol. Initially, the influence of six variables used for the organosolv pretreatment was studied. The variables included the time of the first organosolv pretreatment step, the use of 45% ethanol as pulping solution, solid-to-liquid ratio of the ethanol solution used during the first pretreatment step, time of second organosolv pretreatment, concentration of ethanol and concentration of NaOH solution used in the second pretreatment step. Further assays of enzymatic hydrolysis were carried out to promote additional reduction in the costs of the process and improve the results of cellulose conversion to glucose. Eliminating the milling step of the pretreated SCB, using a commercial tensoactive (composed of esters and several surfactants), and recycling 50% of the slurry obtained during the second step of organosolv pretreatment as reaction medium proved to be feasible for use during the enzymatic hydrolysis. Fermentation of the glucose medium produced under the selected pretreatment conditions to ethanol by Saccharomyces cerevisiae occurred with 81% efficiency and a cost of 102.88 $/hL of ethanol.     

Efficient sugar production from sugarcane bagasse by microwave assisted acid and alkali pretreatment

Sugarcane bagasse represents one of the best potential feedstocks for the production of second generation bioethanol. The most efficient method to produce fermentable sugars is by enzymatic hydrolysis, assisted by thermochemical pretreatments. Previous research was focused on conventional heating pretreatment and the pretreated biomass residue characteristics. In this work, microwave energy is applied to facilitate sodium hydroxide (NaOH) and sulphuric acid (H₂SO₄) pretreatments on sugarcane bagasse and the efficiency of sugar production was evaluated on the soluble sugars released during pretreatment. The results show that microwave assisted pretreatment was more efficient than conventional heating pretreatment and it gave rise to 4 times higher reducing sugar release by using 5.7 times less pretreatment time. It is highlighted that enrichment of xylose and glucose can be tuned by changing pretreatment media (NaOH/H₂SO₄) and holding time. SEM study shows significant delignification effect of NaOH pretreatment, suggesting a possible improved enzymatic hydrolysis process. However, severe acid conditions should be avoided (long holding time or high acid concentration) under microwave heating conditions. It led to biomass carbonization, reducing sugar production and forming ‘humins’. Overall, in comparison with conventional pretreatment, microwave assisted pretreatment removed significant amount of hemicellulose and lignin and led to high amount of sugar production during pretreatment process, suggesting microwave heating pretreatment is an effective and efficient pretreatment method.     

Numerical and experimental investigation of hydrogen-rich syngas production via biomass gasification

In this work, the relation between hydrogen-rich syngas production and the gasification parameters such as equivalence ratio (ER), gasification temperature and biomass moisture content were studied. Stoichiometric equilibrium model that developed during this study was used to investigate the optimum hydrogen output generated from woody biomass in a fixed bed downdraft gasifier by considering the thermodynamic equilibrium limit. The mathematical model, based on thermodynamic equilibrium is necessary to understand complicated gasification process that will contribute to obtain maximum attainable hydrogen production. The effects of different oxidizing agents on the hydrogen concentration in the product gas as well as the effect of various air-biomass, oxygen-biomass and steam-biomass ratios were investigated. For validation, the results obtained from the mathematical model were compared with the experimental data obtained from the gasifier that uses air as gasification medium. The validated mathematical model was used to represent the gasifier that uses both oxygen and air-steam mixture as the gasification medium and the theoretical results were obtained for both cases. The theoretical results clearly show that the gasification process specially ones that use the air-steam mixture as the gasification medium can be used for hydrogen production.     

Hydrogen production from steam gasification of biomass: Influence of process parameters on hydrogen yield – A review

Steam gasification is considered one of the most effective and efficient techniques of generating hydrogen from biomass. Of all the thermochemical processes, steam gasification offers the highest stoichiometric yield of hydrogen. There are several factors which influence the yield of hydrogen in steam gasification. Some of the prominent factors are: biomass type, biomass feed particle size, reaction temperature, steam to biomass ratio, addition of catalyst, sorbent to biomass ratio. This review article focuses on the hydrogen production from biomass via steam gasification and the influence of process parameters on hydrogen yield.     

Hydrogen and syngas production from sewage sludge via steam gasification

High temperature steam gasification is an attractive alternative technology which can allow one to obtain high percentage of hydrogen in the syngas from low-grade fuels. Gasification is considered a clean technology for energy conversion without environmental impact using biomass and solid wastes as feedstock. Sewage sludge is considered a renewable fuel because it is sustainable and has good potential for energy recovery. In this investigation, sewage sludge samples were gasified at various temperatures to determine the evolutionary behavior of syngas characteristics and other properties of the syngas produced. The syngas characteristics were evaluated in terms of syngas yield, hydrogen production, syngas chemical analysis, and efficiency of energy conversion. In addition to gasification experiments, pyrolysis experiments were conducted for evaluating the performance of gasification over pyrolysis. The increase in reactor temperature resulted in increased generation of hydrogen. Hydrogen yield at 1000 °C was found to be 0.076 g_gas g_sample⁻¹. Steam as the gasifying agent increased the hydrogen yield three times as compared to air gasification. Sewage sludge gasification results were compared with other samples, such as, paper, food wastes and plastics. The time duration for sewage sludge gasification was longer as compared to other samples. On the other hand sewage sludge yielded more hydrogen than that from paper and food wastes.