Mamdouh A. Gadalla

A hierarchical approach for the design improvements of an Organocat biorefinery

Lignocellulosic biomass has emerged as a potentially attractive renewable energy source. Processing technologies of such biomass, particularly its primary separation, still lack economic justification due to intense energy requirements. Establishing an economically viable and energy efficient biorefinery scheme is a significant challenge. In this work, a systematic approach is proposed for improving basic/existing biorefinery designs. This approach is based on enhancing the efficiency of mass and energy utilization through the use of a hierarchical design approach that involves mass and energy integration. The proposed procedure is applied to a novel biorefinery called Organocat to minimize its energy and mass consumption and total annualized cost. An improved heat exchanger network with minimum energy consumption of 4.5 MJ/kgdry biomass is designed. An optimal recycle network with zero fresh water usage and minimum waste discharge is also constructed, making the process more competitive and economically attractive.

Multi-objective optimization of a hydrogen supply chain for vehicle use including economic and financial risk metrics. A case study of Spain

In this paper we present a decision-support tool to address the strategic planning of hydrogen supply chains for vehicle use under uncertainty in the operating costs of the network. Given a superstructure of alternatives that embeds a set of available technologies to produce, store and deliver hydrogen, the objective of our study is to determine the optimal design of the production-distribution network capable of fulfilling a predefined hydrogen demand. The design task is formulated as a multi-scenario mixed-integer linear programming problem (MILP) that decides on the production rates and expansions on capacity over time. The main novelty of the approach presented is that it allows controlling the variability of the economic performance of the hydrogen network at the design step in the space of uncertain parameters. This is accomplished by using a risk metric that is appended to the objective function as an additional criterion to be optimized. An efficient decomposition method is also presented in order to expedite the solution of the underlying mathematical model by exploiting its specific structure. The capabilities of the proposed modeling framework and solution strategy are illustrated through its application to a real case study based on Spain, for which valuable insights are obtained.

Integrated Gasification Combined Cycle (IGCC) process simulation and optimization

Integrated Gasification Combined Cycle (IGCC) technology is increasingly important in the world energy market, where low-cost opportunity feedstocks such as coal, heavy oils and pet coke are among the best alternatives. IGCC technology produces low-cost electricity while meeting strict environmental regulations. To further improve IGCCs efficiency, operating the process at the optimum values, process integration and modifications of the process flow diagrams are typical approaches, where process simulation is used as a tool for implementation. A process simulation model is developed with Aspen Plus® for IGCC system employing Texaco gasifier. The model is applied to conduct sensitivity analyses for key performance parameters and integration options to improve system efficiency and environmental performance. As a result, a significant improvements in process efficiency and environmental performance is attained. Thermal efficiency as high as 45% can be reached and a significant decrease in CO2 and SOx emissions is observed. The CO2 and SOx emission levels reached are 698 kg/MWh and 0.15 kg/MWh, respectively.

An experimental-based energy integrated process for biodiesel production from waste cooking oil using supercritical methanol

Biodiesel has been recognised as one of the effective, green, renewable and sustainable fuels. It is derived from renewable living resources either animal fats or vegetable oils. Biodiesel production in the absence of catalyst using supercritical methanol has recently been receiving significant attention. Non-catalytic transesterification reaction eliminates the difficulties of catalyst preparation and separation processes. Although it has shown high conversion for the reactants with relatively short reaction time in comparison with the conventional catalytic transesterification processes, it has some disadvantages including higher reaction temperature and pressure, large excess of methanol to oil (M:O) molar ratio and higher energy consumption. In an attempt to mitigate these problems, an experimental study followed by process design/integration for biodiesel production from waste cooking oil (WCO) has been performed. A low-quality WCO collected from local restaurants has been selected as a feedstock for the reaction. The experimental phase of the transesterification reaction together with an optimisation procedure resulted in the optimised conditions of M:O molar ratio of 37:1, reaction temperature of 253.5 oC, reaction pressure of 198.5 bar in 14.8 min. The maximum yield was 91%. In addition, kinetics of the reaction has been studied concluding an irreversible pseudo first order reaction with a reaction rate constant of 0.0006 s-1. Moreover, thermodynamics of the reaction has been studied at a temperature range of 240 - 270 oC with resulting frequency factor and activation energy of 4.05 s-1 and 50.5 kJ/mol. A kinetic reactor has been simulated using the experimentally determined kinetic and thermodynamic data. The enthalpy content of the reactor product stream has been used to separate most of the unreacted methanol in an adiabatic flash drum. Finally, a scheme has been developed for an energy integrated process in order to maximise the heat recovery. Energy savings resulted from the developed heat exchanger network (HEN) have been concluded as 32.2 % and 23.8 % for both heating and cooling energies respectively, in comparison with an existing process energy requirements in the literature. The amount of heat exchanged for each unit has been determined in addition to composition, temperature and pressure of the streams. Vacuum distillation column has been designed to separate the unreacted triglycerides from biodiesel in order to fulfil the quality restrictions of the final biodiesel product.

Simulation of biomethanol production from green syngas through sustainable process design

Methanol is considered an alternative energy source due to its various applicability and high octane. As a fuel, it releases low emissions, and shows high performance and low risk of flammability. Egypt faces a high population growth rate, which implies an increase in the agricultural production. At present, the agriculture waste materials are burned leading to major environmental problems besides the loss of potential resources. This work builds a design methodology for producing biomethanol fuel from green syngas. The design methodology is based on rigorous model using the Aspen HYSYS® simulation software, and takes into account both economics and environment. As a case study, the design methodology is applied to design a plant that converts rice straw in Egypt into methanol. The raw materials for this process are selected from the major regions in Egypt producing rice straw with a total capacity of 1.6 million tons per year. These local regions are Kafr el Sheikh, Dakahlia and Sharkia governorates, located in northern part to Cairo. The methanol produced from the process is estimated to be around 156 thousand metric tons per annum. The process equipment capital costs are estimated to be 498 million dollars with total energy costs of 17 million dollars per annum. On the other hand, an annual revenue of 537 million dollars is obtained. The simulation model obtained in this study can be applied to any syngas coming from other gasification processes with different biomass feedstock. In addition, the model provides a robust basis for further studies of process integration leading to innovative and sustainable solutions to climatic and energy problems.

New Environmentally-Conscious Design Approach and Evaluation Tool for Chemical Processes

Abstract This work develops a set of assessment tools for the environmental evaluation of chemical processes and proposes an approach that integrates environmental perceptions into design. A new environmental indicator based on the materials flows between the process and environment is developed. The Material Balance Environmental Index (MBEI) includes toxicities and their environmental implications. Global and categorized environmental indices are computed following three levels of aggregation, and several categories of environmental concerns. Furthermore, a ternary diagram is proposed to graphically show the environmental performance and the individual contribution of the different categories ( i.e. ecosystem quality, natural resources and human health) in the total impact. The methodology is tested using the formaldehyde process as case study, where data are obtained from rigorous process simulation validated with industrial data.

Environmental Design of IGCC through Pinch Analysis, Process Integration and Parameters Analysis

Abstract Environmental consciousness and energy prices are both leading to revolutionary calls for energy alternatives, and cleaner power production technologies, and further to the efficient use of sources (e.g. coal, natural gas). Integrated gasification combined cycles (IGCC) are such technologies that can meet todays power generation needs, through the combination of high environmental performance, competitive cost-of-electricity and broad fuel flexibility. In this work, systems of IGCC are modeled to provide a robust basis for studies on energy efficiency and environmental improvement. Sensitivity analyses are performed to screen a number of process parameters and operation conditions, which lead to efficient processes. Pinch analysis principles are applied to base cases such that design is better understood and improvement modifications to design are generated for best energy and environment performances. The overall performance of the system is evaluated and improved through constructing composite curves for better heat integration and energy efficiency. From both studies of sensitivity analyses and pinch analysis, emissions levels of CO 2 , SO 2 and NO x are reduced and environmental performance is improved. Economic evaluations of modifications and improvement solutions are keys for a final decision of the optimal solutions. Moreover, further steps of detailed design of heat integration opportunities are essential to adopt a practical and feasible configuration.

A comparative study on biodiesel production from waste cooking oils obtained from different sources using supercritical methanol

Biodiesel has been considered as a reasonable replacement fuel for petroleum diesel. It has many advantages over petroleum diesel including its biodegradability and non-toxicity. In addition, it provides free aromatics and sulphur combustion and it is a greener fuel with lower carbon monoxide and hydrocarbons emissions. However, biodiesel has lower heating value and it is relatively more expensive than petroleum diesel. In an attempt to reduce the cost of biodiesel, waste cooking oil (WCO) has been considered as a competitive feedstock. It also provides more sustainability for the produced biodiesel as it is a result of transformation of waste to greener source of energy. The main concern for using WCO as a feedstock for biodiesel production is the presence of high concentration of free fatty acids (FFA), which result in saponification reaction while using the conventional alkaline catalysed process. Saponification lowers the biodiesel yield by preventing the separation of biodiesel from the product. In this study, a non-catalytic method for biodiesel production from WCO using supercritical methanol has been investigated. Two different feedstocks with different FFA concentration have been examined. Response surface methodology (RSM) using Box Behnken Design (BBD) and Central Composite Design (CCD) has been employed to analyse the effect of different reaction variables including methanol to oil (M:O) molar ratio, temperature, pressure and time on biodiesel yield. Numerical optimisation has been applied to determine the optimum conditions for maximum production of biodiesel for each feedstock. It has been concluded that the feedstock with higher FFA concentration produce higher biodiesel yield within the same reaction conditions. This result indicates the significance of using supercritical methanol technique for feedstocks with high FFA concentration as it enhances both esterification of FFA and transesterification of triglycerides (TG) to fatty acids methyl esters (FAME).A possible solution is studied to solve the global solid waste, air pollution, and energy crisis issues. Rice straw is an abundant biomass that is often disposed of by open-field burning. The carbohydrates and sugars in rice straw can be acid hydrolysed to produce furans which are the building blocks of a fuel known as ethoxymethyl furfural, which has an energy density similar to gasoline. A model was created to represent the concentration of the different components present in the reactor with respect to residence time.

Optimising biodiesel production from high acid value waste cooking oil using supercritical methanol

In this study, biodiesel production from a typical Egyptian waste cooking oil (WCO) with high acid value content (18 mg KOH/g oil) has been analysed by studying the main factors affecting biodiesel and glycerol yields. Response Surface Methodology (RSM) via Central Composite Design (CCD) has been used to analyse the effect of four independent variables, i.e. methanol to oil (M:O) molar ratio, temperature, pressure and time on the reaction responses. A quadratic model for each response has been concluded representing the interrelationships between reaction variables and reaction responses. In addition, the predicted models’ adequacy has been evaluated through Analysis of Variance (ANOVA) method. Numerical optimisation technique has been applied to conclude the optimum reaction conditions for maximum production of biodiesel resulting in 98% and 2.05% for biodiesel and glycerol yields at M:O molar ratio, temperature, pressure and time of 25:1, 265oC, 110 bar and 20 minutes, respectively. Experimental validation has been analysed for the predicted optimum conditions resulting in 98.82% biodiesel yield with 0.83% relative error.

Modelling of Coal-biomass Blends Gasification and Power Plant Revamp Alternatives in Egypt’s Natural Gas Sector

Recently, there has been a growing research interest in the co-gasification of biomass with coal to produce syngas and electricity in a sustainable manner. Co-gasification technology do not only decrease potentially the exploitation of a significant amount of conventional coal resources, and thus lower greenhouse gases (GHG) emissions, but also boost the overall gasification process efficiency. In the present work, a rigorous simulation model of an entrained flow gasifier is developed using the Aspen Plus® software environment. The proposed simulation model is tested for an American coal and the model validation is performed in good agreement with practical data. The feedstocks used in the proposed gasifier model are dry Egyptian coal and a blend of an Egyptian coal and rice straw that is gathered locally. The proposed gasifier model mainly consists of three reactors. The first one is a yield reactor where the coal pyrolysis occurs, the second reactor is a stoichiometric reactor where the gasification reactions arise, and the third reactor is a Gibbs reactor where the water-gas and steam-methane reforming reactions take place. The influence of using a feed mixture of 90 % coal and 10 % rice straw on the gasifier efficiency is investigated. The developed model provides a robust basis for revamping of an existing Egyptian natural gas-based power plant to replace its standard fuel with a coal-rice straw blend, in case of low natural gas supply. The model is further employed to assess different revamping scenarios and alternatives within the natural gas power plant. For a dry blend of (90 % Egyptian coal and 10 % rice straw), the cold gas efficiency is estimated as 85.7 %, while for dry Egyptian it is calculated as 79.61 %. The revamped Egyptian natural gas power plant decreases the total annualized cost (TAC) by 52.7 % with respect to a new constructed integrated gasification combined cycle (IGCC) plant. Besides, the payback period decreases to 1.24 y rather than 12 y in case of the construction of a new IGCC power plant. (Less)