Systematic design of separation process for bioethanol production from corn stover

Separation process is very crucial in bioethanol production as it consumes the highest energy in the process. Unlike other works, this research systematically designed a suitable separation process for bioethanol production from corn stover by using thermodynamic insight. Two separation processes, i.e., extractive distillation (case 2) and pervaporation (case 3), were developed and compared with conventional molecular sieve (case 1). Process design and simulation were done by using Aspen Plus program. The process evaluation was done not only in terms of energy consumption and process economics but also in terms of environmental impacts. It was revealed that pervaporation is the best process in all aspects. Its energy consumption and carbon footprint are 60.8 and 68.34% lower than case 1, respectively. Its capital and production costs are also the lowest, 37.0 and 9.88% lower than case 1.

Optimization of biogas supply networks considering multiple objectives and auction trading prices of electricity

This contribution presents an hourly-based optimization of a biogas supply network to generate electricity, heat and organic fertilizer while considering multiple objectives and auction trading prices of electricity. The optimization model is formulated as a mixed-integer linear programming (MILP) utilizing a four-layer biogas supply chain. The model accounts for biogas plants based on two capacity levels of methane to produce on average 1 ± 0.1 MW and 5 ± 0.2 MW electricity. Three objectives are put forward: i) maximization of economic profit, ii) maximization of economic profit while considering cost/benefits from greenhouse gas (GHG) emissions (economic+GHG profit) and iii) maximization of sustainability profit. The results show that the economic profit accrued on hourly-based auction trading prices is negative (loss), hence, four additional scenarios are put forward: i) a scenario whereby carbon prices are steadily increased to the prevalent eco-costs/eco-benefits of global warming; ii) a scenario whereby all the electricity auction trading prices are multiplied by certain factors to find the profitability breakeven factor, iii) a scenario whereby shorter time periods are applied, and investment cost of biogas storage is reduced showing a relationship between cost, volume of biogas stored and the variations in electricity production and (iv) a scenario whereby the capacity of the biogas plant is varied from 1 MW and 5 MW as it affects economics of the process. The models are applied to an illustrative case study of agricultural biogas plants in Slovenia where a maximum of three biogas plants could be selected. The results hence present the effects of the simultaneous relationship of economic profit, economic+GHG profit and sustainability profit on the supply and its benefit to decision-making.

Process intensification technologies for CO2 capture and conversion – a review

With the concentration of CO2 in the atmosphere increasing beyond sustainable limits, much research is currently focused on developing solutions to mitigate this problem. Possible strategies involve sequestering the emitted CO2 for long-term storage deep underground, and conversion of CO2 into value-added products. Conventional processes for each of these solutions often have high-capital costs associated and kinetic limitations in different process steps. Additionally, CO2 is thermodynamically a very stable molecule and difficult to activate. Despite such challenges, a number of methods for CO2 capture and conversion have been investigated including absorption, photocatalysis, electrochemical and thermochemical methods. Conventional technologies employed in these processes often suffer from low selectivity and conversion, and lack energy efficiency. Therefore, suitable process intensification techniques based on equipment, material and process development strategies can play a key role at enabling the deployment of these processes. In this review paper, the cutting-edge intensification technologies being applied in CO2 capture and conversion are reported and discussed, with the main focus on the chemical conversion methods.

Economic feasibility of gasoline production from lignocellulosic wastes in Hong Kong

In this study, the conceptual process flowsheet was developed and the economic feasibility of woody biomass conversion to biofuel as feedstock was analysed by considering several promising experimental processes for lignin depolymerization, such as hydrodeoxygenation and hydrogenolysis, along with lignocellulosic biomass fractionation processes. The engineering simulation process toward the commercial production of bio-gasoline from lignocellulosic biomass using SuperPro Designer® was modeled. The compatibility of the end products with the current gasoline specifications was evaluated and various blending options were investigated to meet the octane number and Reid vapor pressure requirement of the product. The economic potential of the simulated engineering process was then evaluated from an economic perspective. The operating costs and capital investment of three scenario using three different catalytic systems were estimated and discussed to assess of the potential of commercializing of woody biomass valorization process. The main potential market segments were identified, including the process by-products such as xylose and cellulose pulp. From the economic evaluation study, it was found that selling the biomass fractionation products alone does have a greater profit than valorization of lignin to produce bio-gasoline, with net present value of RMB 22,653,000 and RMB 177,000, respectively at the same return on investment if the plant is set up in Hong Kong. It was also found that catalysts play a pivotal role in determination of the profitability in the valorization process, not only because of the price of the catalyst, but also the product distributions obtained with various types of it. To obtain the same gross profit, the sale price of bio-gasoline has to be set higher with platinum catalysts than with ruthenium catalysts (nearly 10 folds). Thus, catalyst development and process improvement are crucial in the establishment of bio-based circular economy.