Fatma El Zahraa Ashour

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.

The simulation of existing crude oil distillation processes is distinctive and difficult owing to its complex nature and interactions, including variable feedstocks, highly integrated processes, tight cuts specifications, and environmental limitations. This study introduces a systematic simulation-based algorithm for retrofitting an existing crude distillation column. The algorithm accounts for all details of the associated heat recovery system. Both distillation unit and HEN (heat exchanger network) are addressed simultaneously in the simulation. The proposed procedure is applied to simulate an existing CDU (crude distillation unit) processing 100,000 bbl/d crude oil of an Arabian origin. The rigorous simulation model achieved can fully describe the existing plant performance, and for this it is thus validated with the actual data for column operation parameters, cuts flow and specification, and for all details of heat exchanger network. The results are found in a good agreement with the actual data. The model is then applied for optimisation and revamping projects to minimise the energy consumption and the amount of CO2 emissions from the refinery. The advantage of the simulation model is its relevance to refining industries in performing any future revamping studies, modification tests, product changes, and capacity enhancement.

CO2 removal process by Amine absorption can be improved by adding an activator such as piperazine (a secondary amine) to the aqueous Methyl Diethanol Amine (MDEA) solution. The shuttle mechanism and the effect of Piperazine on CO2 removal process have been studied and simulated through licensed simulation software, Unisim. The simulation was used to simulate amine absorption process for CO2 removal and to study the effect of the process variables on CO2 removal efficiency. An actual Process Flow Diagram (PFD) was built to simulate the absorption process based on an actual feed gas stream from Egyptian natural gas plant raw gas. The natural gas stream contained 10% CO2 and is treated to reduce the CO2 content to less than 1% by mole. CO2 removal efficiency was investigated by changing process parameters, namely absorption process pressure and temperature, amine concentration and lean amine circulation rate. Piperazine addition, either on account of water or MDEA, increases the absorption efficiency but to a certain limit, when the reaction is no longer mass transfer limited. Temperature decrease improves absorption efficiency, unlike the common behavior of pure aqueous MDEA. Also, decreasing column pressure contributes in reducing CO2 partial pressure in the feed gas and consequently decreases reaction rate with amine. Increasing circulation rate was found to increase the absorption efficiency till reaching the equilibrium.

ORC (organic Rankine cycle) is a promising technology for conversion of heat into useful work. This study utilizes the ORC in an existing gas treatment plant in Egypt, as a case study, to recover the waste heat and convert it into electricity. A simulation model using Aspen HYSYS v7.1 has been built up for the case study. Two different cycles, the basic and the regenerative cycles, have been studied. Various working fluids have been investigated using different parameters such as net work produced, efficiency, volumetric flow rate and the irreversibility. To be more confident about the best working fluid, a capital cost and profitability analysis has been performed for the most two promising working fluids. The simulation has shown that regenerative cycle using either benzene or cyclohexane is the most promising choice. However, the capital cost and profitability study has shown that benzene is more suitable as working fluid than cyclohexane. Finally, an optimization study on the parameters indicates that the turbo expander inlet pressure of 4.1 MPa and temperature of 290 °C–300 °C are the most appropriate working conditions.

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.

Crude 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.