A simple approach to improve the robustness of equation-oriented simulators: Multilinear look-up table interpolators

Equation-oriented simulators have some advantages over the modular sequential ones, but improvements are still necessary to deal with nonlinearities, while preserving the robustness of the solver. Linear approximations and/or surrogate models can be used in place of nonlinear models, but the loss of predictive accuracy may be a drawback. An alternative to circumvent this problem is the use of grid-based look-up tables for interpolating responses from rigorous models. This methodology was integrated in an equation-oriented simulator (EMSO). A case study involving the production of bioethanol from sugarcane is used to demonstrate the robustness of this approach. Look-up tables replaced the models of two distillation column trains and of the cellulose hydrolysis reactor. These models were included into the global process and an optimization problem aiming at the maximum production of ethanol was successfully solved by a PSO algorithm varying the solid mass fraction in the hydrolysis reactor.     

Modeling of bioethanol production in unconventional bioreactor assisted by electromagnetic field

The aim of this paper was to estimate fermentation kinetic parameters to develop a mathematical model of the bioethanol production under magnetic field effect. Thus, a non‐structured mathematical model was developed considering three non‐lineal kinetic models typically known as Levenspiel, Aiba, Jerusalimsky, which take into account inhibitory effects of the high product concentration on yeasts. The non‐lineal differential equations system solution was carried out by MatLab software using the Runge–Kutta fourth‐order multivariable method. This method was improved through a replication scheme coupled with Newton–Raphson method modified with a damping Broyden parameter. Experimental data on substrate consumption, biomass formation and ethanol production were collected at magnetic field intensities (H) of 414, 796 and 1216 A/cm during 16 h of fermentation. Consequently, the adjusted model for biomass, consumed substrate and bioethanol produced allowed us to correlate fermentation kinetic parameters with the magnetic field. The best result was observed when Jerusalimsky model modified with a magnetic field parameter was considered, because the RMSD order and R‐square correlation coefficient were around 10^?3 and higher than 0.95, respectively. These results are important to understand the phenomenological behavior of this unconventional bioprocess and be helpful to further sensibility analysis and scale up of the bioethanol production assisted by electromagnetic field. Copyright © 2016 John Wiley & Sons, Ltd.     

Extrusion Pretreatment of Lignocellulosic Biomass: A Review

Bioconversion of lignocellulosic biomass to bioethanol has shown environmental, economic and energetic advantages in comparison to bioethanol produced from sugar or starch. However, the pretreatment process for increasing the enzymatic accessibility and improving the digestibility of cellulose is hindered by many physical-chemical, structural and compositional factors, which make these materials difficult to be used as feedstocks for ethanol production. A wide range of pretreatment methods has been developed to alter or remove structural and compositional impediments to (enzymatic) hydrolysis over the last few decades; however, only a few of them can be used at commercial scale due to economic feasibility. This paper will give an overview of extrusion pretreatment for bioethanol production with a special focus on twin-screw extruders. An economic assessment of this pretreatment is also discussed to determine its feasibility for future industrial cellulosic ethanol plant designs.     

Alkali pretreatment of softwood spruce and hardwood birch by NaOH/thiourea,NaOH/urea,NaOH/urea/thiourea,and NaOH/PEG to improve ethanol and biogas production

Alkali‐dissolution pretreatment of softwood spruce and hardwood birch to improve ethanol and biogas production was investigated. The pretreatments were carried out at different temperatures between ? 15 and 80 °C with NaOH/thiourea (7/5.5 wt%), NaOH/urea (7/12 wt%), NaOH/urea/thiourea (7/8/6.5 wt%), and NaOH/PEG (7/1 wt%) aqueous solutions. The pretreated materials were then subjected to enzymatic hydrolysis for 72 h. The pretreatments by NaOH/thiourea at ? 15 °C improved the hydrolysis yields of spruce from 11.7% to 57% of theoretical yield, and for birch from 23.1% to 83% of theoretical yield. The enzymatic hydrolysis and fermentation of these pretreated materials by NaOH/thiourea with baker's yeast resulted in 54.0% of theoretical yield compared with 10.9% for untreated spruce and 80.9% of theoretical yield compared with 12.9% for untreated birch. Furthermore, anaerobic digestion of pretreated materials resulted in 0.36 L g^?1 VS methane compared with 0.23 L g^?1 VS for untreated birch, and 0.21 L g^?1 VS compared with 0.03 L g^?1 VS for untreated spruce. Copyright © 2012 Society of Chemical Industry     

Ethanol production from wood via concentrated acid hydrolysis,chromatographic separation,and fermentation

BACKGROUND: Production of bioethanol from wood using concentrated acid hydrolysis has received less attention than the dilute acid hydrolysis route. The feasibility of producing lignocellulosic bioethanol from spruce and birch via concentrated acid hydrolysis was studied experimentally. Hydrolysis with sulfuric acid, chromatographic purification of the hydrolysate, and fermentation of the monosaccharides were investigated. RESULTS: Monosaccharide yields of 70% were obtained in the hydrolysis of spruce and birch. Only low amounts of by‐products were formed. With chromatographic purification of the hydrolysate, over 90% of the hydrolysis acid was recovered for recycling, and furfural and HMF were removed completely. Most of the acetic acid was recovered in a separate fraction. The monosaccharide yield in a single pass separation was approximately 70%. In the fermentation, S. cerevisiae produced higher amounts of ethanol and more efficiently than P. stipitis. Chromatographically purified hydrolysates gave higher ethanol productivities and yields than Ca(OH)₂ neutralized hydrolysates. CONCLUSIONS: Chromatographic purification of concentrated acid lignocellulosic hydrolysates has advantages when compared with neutralization with Ca(OH)₂. With chromatography, most of the inhibitory compounds can be removed from the hydrolysates. In addition, due to the recycling of the hydrolysis acid, the economy of the bioethanol manufacturing process is increased considerably. Copyright © 2011 Society of Chemical Industry     

花生壳发酵生产生物乙醇可行性研究

研究以花生壳为原料,采用超临界水一步法获得可发酵糖液,并通过混合菌种将可发酵糖液转化为生物乙醇的工艺方法。不仅使农业废弃物得到综合利用,同时,也获得了良好的经济效益和环境效益。