• Energy Research

The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing the oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil on biodiesel led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol.

Abstract Distillation of close-boiling mixtures, such as propylene–propane and ethyl benzene–styrene systems, is an energy intensive process. Vapor recompression techniques and heat pumping-assisted columns have been adopted for such applications for their high potential of energy savings. In direct vapor recompression columns, the vapors leaving the top of the column are compressed, and in the reboiler of the same column, these vapors are condensed to provide heat for vapor generation. Internal heat integrated distillation columns or iHIDiCs are new developments employing the same concept of vapor recompression. These new column configurations can have significantly lower energy demands than common vapor recompression units. In iHIDiCs, rectifying section is operated at a higher pressure (i.e. higher temperature) than in stripping, and therefore its heat can be used to generate vapor in stripping section. So far, design of these column configurations is performed based on engineering experience, simulation or experimental studies on given cases, including dynamic control simulations. Within previous and most recent research efforts on iHIDiCs, there exist no generalized design methods or systematic approaches for design of these internal integrated distillation columns. The present paper presents a systematic design procedure for iHIDiCs. A design hierarchy for iHIDiCs is developed, which includes two phases of design, thermodynamic and hydraulics. This design procedure is applied using commercial simulation-based design methods. In thermodynamic design, temperature profiles for column sections are used as a design tool to guide designers. On the other hand, hydraulic capacities of stages for heat exchange are analyzed to determine the maximum physical space area available for heat exchange. Hence, feasibility regions for both heat integration and hydraulic design are identified.

This paper demonstrates the usability of pinch analysis as a tool for conceptual design of internally heat integrated distillations columns (HIDiCs). Incorporated appropriately into the overall design procedure, pinch analysis enables a fast approach to an optimum thermal performance, while bringing new insights and improving the understanding of the nature of HIDiC designs. As illustrated by using a state of the art propylene splitter as the base case, this approach emerged into an essential tool for the identification of economically interesting configurations for HIDiC applications.

Heat exchanger network pinch sets the limitations of heat recovery for existing network topologies. Improving the heat recovery within a pinched-network is independent of the areas of individual exchangers present in the network, rather the topology of the network must be altered. Such a change in the topology can be very capital intensive and in many cases seems not easy to implement. This research aims to overcome the Network Pinch through proposing process operation changes, avoiding network topology alterations; hence, debottlenecks the heat-integrated systems towards further energy savings beyond the maximum heat recovery limitations. A new graphical representation is recently proposed to simulate existing preheat trains/networks with all energy equipment. The recent graphical representation is employed in this work to identify the pinching matches that limit heat recovery. Therefore, such graphs are key tools to identify potential process changes by which the Network Pinch is overcome. New graphs are constructed involving hot stream temperatures against cold stream temperatures. Existing exchangers are described by straight lines, with slopes related to flows of process streams and heat capacities. Exchanger matches touching the line where hot outlet stream temperature equals cold inlet stream temperature are pinching matches; this condition corresponds to absolute maximum heat recovery (ΔT = 0). Potential process changes within a distillation unit are identified to relax the Network Pinch and further heat recovery is maximised. The slope of such an exchanger match is decreased or the location of the pinching match is altered keeping the same slope. These changes are translated into process changes within the crude oil distillation unit. Accordingly, the process changes are determined based on which match is pinched besides its location within the network. An illustrative example shows that process changes overcome the Network Pinch and energy recovery is increased by 14% beyond the maximum level achieved for the existing process conditions. Capital investments imposed are minor compared with substantial energy cost savings.

Gasification processes convert carbon-containing material into syngas through chemical reactions in the presence of gasifying agents such as air, oxygen, and steam. Syngas mixtures produced from such processes consist mainly of carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), and methane (CH4); this gas can be directly utilised as a fuel to produce electricity or steam. Besides, it is regarded as a basic feedstock within the petrochemical and conventional refining industries, producing various useful products like methanol, hydrogen, ammonia, and acetic acid. In this work, a rigorous process model is developed to simulate the co-gasification of coal-biomass blends through an entrained flow gasifier. The proposed model is tested originally for American coal. The model validation is made against literature data and results show good agreement with these practical data, providing a robust basis for integration and retrofitting applications. Effects of critical parameters, comprising gasification temperature, steam/O2 ratio, and feedstock variability on the syngas composition and gasifier efficiency are studied. The developed model is further applied in a project to revamp an existing Egyptian natural gas-based power plant, replacing its standard fuel with coal-rice straw blends. The revamping project integrates the existing plant with a gasification unit burning a blend of coal and rice straw to replace the conventional fuel used. The feedstock used constitutes a dry Egyptian coal and a coal-rice straw blend (10 wt% rice straw), gathered locally. Different blending scenarios are investigated and the best performance is achieved with coal to rice straw ratio of 90:10 on weight basis, attaining 85.7% cold gas efficiency and significant economic savings. Results showed that the total annualised cost of the revamped process decreased by 52.7% compared with a newly built integrated gasification combined cycle (IGCC) unit. (Less)

AbstractCrude oil atmospheric distillation systems are an energy intensive processes; it was evaluated that the energy requirement for such plants is equivalent to a 2% of the total crude oil processed [1]. An existing crude oil atmospheric unit is very expensive to modify due its complex configuration and interactions, and existing constraints of structure, limited space area, matches, bottlenecked equipments, etc. Thus, a few new crude distillation units are built and projects for revamping existing equipments are rather common. Revamping an existing plant is a difficult task, more complex than a new process design; many parameters must be considered and sometimes it is not possible to quantify all of them.This paper presents a new methodology based on rigorous simulation and optimisation framework that addresses both the distillation column and the heat exchanger network simultaneously to maximise the use of existing equipments. The methodology considers process changes and structural modifications together with the interactions between the existing distillation process and heat recovery system. The new method includes multiple objective functions such as energy savings, emissions reduction, capacity enhancement, and profit improvement.An actual atmospheric plant for MIDOR, an Egyptian refinery, has been considered for applications of the new optimisation methodology. Several retrofit solutions have been obtained, ranging from zero-modifications and simple additional exchanger areas to additional units or equipments.

Egypt is an importer of energy, yet 5.7 MMSCM (200 MMSCF) of natural gas is flared every day and causes a negative environmental impact. Recovery of such significant amount is crucial and accordingly there are three alternative solutions to recover these gases, namely LPG/condensate extraction, recycling, or power generation. These alternatives were studied technically, financially, and economically, and results indicate that investors’ orientation and vision play a vital role in decision making especially when production sharing agreement is applied. The conflict of interest among investors was tackled and applied on a case study from different perspectives. Results indicate that the added value itself differs from one investor to another. In the case studied, international oil companies “IOCs” prefer recycling to achieve reasonable net present value “NPV” up to $40 million. National oil companies “NOCs” prefer generating power to achieve maximum net value added “NVA” up to $58 million, to maximize the environmental and social added value. The least feasible option is extracting LPG/condensate from the flared gas although Egypt is LPG importer. The conflict of interest and current oil prices are the reasons behind postponing such projects. So, Egyptian government should impose policies to reduce flared gas emissions and maximize benefits through these projects and this can be done by compromising with “IOCs” to ensure maximum financial/social benefits.

Biodiesel production using supercritical methanol in the absence of catalyst has been analysed by studying the main factors affecting biodiesel yield. A quadratic polynomial model has been developed using Response Surface Methodology (RSM). Box-Behnken Design (BBD) has been used to evaluate the influence of four independent variables i.e. methanol to oil (M:O) molar ratio, temperature, pressure and time on biodiesel yield. The optimum biodiesel yield is 91% at M:O molar ratio, temperature, pressure and reaction time of 37:1, 253.5oC, 198.5 bar and 14.8 minutes, respectively. Overall reaction kinetics has been studied at optimum conditions concluding a pseudo first order reaction with reaction rate constant of 0.0006 s-1. Moreover, thermodynamics of the reaction has been analysed in the temperature range between 240 and 280oC concluding frequency factor and activation energy of 4.05 s-1 and 50.5 kJ/mol, respectively. A kinetic reactor has been simulated on HYSYS using the obtained kinetic data resulting in 91.7% conversion of triglycerides (TG) with 0.2% relative error from the experimental results.

Abstract The aim of this work is to develop and optimize an integrated process for natural gas plant in Egypt instead of flaring these gases and losing their revenues. The natural gas is sour wet feed gas containing mercury and some of volatile organic compounds with a capacity of around 21 million cubic feet per day. These impurities require sophisticated gas treatment processes that can handle and control the pollutants to acceptable limits. The design of new gas plant will be performed through firstly, the design methodology and cascade configuration of gas plant units based on feed gas composition. Secondly, integrated development and optimization of gas treatment process model is achieved using Aspen HYSYS simulation program. Thirdly, modeling of natural gas liquids extraction unit and fractionation train is conducted based on the required marketable products specifications. Finally, Aspen process economic analyzer program is used to calculate the expected capital expenditures of the plant. Optimizing the plant configuration accounts for best selection of treatment units and processing equipment, including mercury removal unit, sulfur recovery unit, BTEX recovery unit, etc. The preliminary capital expenditures of the gas conditioning and processing plant will be around 48 MUSD.