General methodology for exergy balance in ProSimPlus® process simulator

This paper presents a general methodology for exergy balance in chemical and thermal processes integrated in ProSimPlus® as a well-adopted process simulator for energy efficiency analysis. In this work, as well as using the general expressions for heat and work streams, all of exergy balance is presented within only one software in order to fully automate exergy analysis. In addition, after exergy balance, the essential elements such as source of irreversibility for exergy analysis are presented to help the user for modifications on either process or utility system. The applicability of the proposed methodology in ProSimPlus® is shown through a simple scheme of Natural Gas Liquids (NGL) recovery process and its steam utility system. The methodology does not only provide the user with necessary exergetic criteria to pinpoint the source of exergy losses, it also helps the user to find the way to reduce the exergy losses. These features of the proposed exergy calculator make it preferable for its implementation in ProSimPlus® to define the most realistic and profitable retrofit projects on the existing chemical and thermal plants

Improved Design and Efficiency of the Extractive Distillation Process for Acetone–Methanol with Water

We show how thermodynamic insight can be used to improve the design of a homogeneous extractive distillation process, and we define an extractive efficiency indicator to compare the optimality of different designs. The case study is related to the separation of the acetone–methanol minimum boiling azeotrope with water. The process flow sheet includes both the extractive distillation column and the entrainer regeneration column. Insight from analysis of the ternary residue curve map and isovolatility curves shows that a lower pressure reduces the minimal amount of entrainer needed and increases the relative volatility of acetone–methanol in the extractive column. A 0.6 atm pressure is selected to enable the use of cheap cooling water in the condenser. We optimize the entrainer flow rate, adjusting both column reflux ratios and feed locations, by minimizing the total energy consumption per product unit. The total annualized cost (TAC) is calculated for all processes. Double-digit savings in energy consumption and in TAC are achieved compared to literature values. We then propose a novel efficiency indicator that describes the ability per tray of extractive section to discriminate the desired product between the top and the bottom of the extractive section. Shifting the feed trays’ locations improves the efficiency of the separation, even when less entrainer is used

Process design Optimisation, heat integration, and techno-economic analysis of oil refinery: A case study

This paper outlines a comprehensive analysis of the optimal design and simulation of a crude oil distillation system within a refinery process, including pre-treatment and blending of two crude oils to increase the refinery’s annual profit. This distillation process is currently in operation, and the desired amount of feedstock is obtained from Iraqi Basra light-2015 and Kirkuk-2011 crude oil. To improve the energy efficiency of the utilization rate of crude oil, an atmospheric distillation process unit in this refinery with a capacity of 150,000 barrels per day (bpd) is considered. Aspen HYSYS simulation is used to optimize the distillation unit configuration and its operating performance. This paper also deals with three scenarios by comparing the feedstock compositions to the distillation process and the produced product compositions to minimize utility consumption. A heat integration approach was applied to the 3rd scenario by recycling hot outlet streams to the heat exchangers to increase the temperature of the inlet stream of the distillation column. Results indicated that about £2.29 million per year (Mpy) could be saved from the heat integration systems. Economic analysis and cut yields were carried out for each scenario to investigate the cost-effective and economically viable. Based on the economic analysis, scenario three showed better performance with a comparatively high cumulative cash flow of £31,886 M

Advanced exergetic analysis of preheat train of a crude oil distillation unit

In this investigation, the conventional and advanced exergy analysis is used to obtain information about the conditions of the heat exchangers belonging to a crude oil distillation unit, previously to future studies to establish the most cost-efficient moments for the execution of maintenance activities in the exchangers. Conventional, unavoidable, avoidable, endogenous, and exogenous exergy destruction is calculated and the combinations between these last four terms. Mexogenous analysis is applied to individualize the relationships between the exchangers of the network. The results put the total exergy destruction at over 61.6 MW, being 63% avoidable. Five heat exchangers are considered critical because they concentrate the highest rates of exergy destruction, corresponding to 39% of the total exergy destruction in the network, this categorization allows focusing the improvement works on heat exchangers that will produce a substantial increase in the efficiency of the preheat train. Additionally, to evaluate the performance in a better way, the effect of unavoidable exergy destruction on performance measurement of exchangers through the exergy efficiency is studied, indicating that in some cases removing the unavoidable part can increase the second law efficiency by more than fifteen percentage point

Pre-design Optimization of Crude Oil Distillation Flowsheet

Several first principle models of crude oil distillation units were developed in Aspen Plus{TM} for purposes of pre-design optimization of flowsheet structure and apparatus design and choice of the optimal variant of distillation to provide the process flexibility in respect to flowrate of crude oil and oil quality. The developed models consider air temperature and type of crude oil. The two-column flowsheet of crude oil distillation is adopted as basic. The sum of the capital investments and operation costs per year was estimated for the basic flowsheet. Stepwise increasing of crude oil flowrate is used to determine "weak points" of the flowsheet and estimate maximum oil flowrate. Parametrical optimization was performed for each step. The alternative upgrading flowsheets were developed to increase operation effectiveness in a wide range of crude oil flowrates. The optimization criterion was developed to evaluate the relative efficiency of the alternative distillation unit flowsheets. The optimization criterion was a ratio of average annual revenue from the sale of petroleum products to the total costs (capital investments and operational costs) with restrictions on the product quality. The way of re-equipment of the column internals was chosen as a preferable variant

Energy Evaluation of the Use of an Absorption Heat Pump in Water Distillation Process

It is impossible to transform the whole energy into useful work. It is impossible to increase the processes of cultivation of foods without water. It is impossible to separate all ions and minerals from water. Most of the real processes are thermodynamically irreversible. Calculations may indicate the fraction of efficiency of a thermal process. All the above mentioned facts have led to some proposals of cycles that exchange energy in order to produce a useful effect for the society. The key sustainable related parts are: to obtain water free of minerals or ions by distillation process. In this chapter, thermodynamic cycles will be explained for distillation using thermodynamic cycles of thermal machines called absorption heat pumps (AHPs). Distillation process offers to the AHPs an opportunity to diminish the consumptions of fossil fuels. The AHPs are able to work with 2% of mechanical energy to carry out a sustainable distillation process. Most of the energy of an absorption heat pump operation is thermal energy. The operation of the AHPs are defined with the coefficient of performance (COP); the variations of this parameter are shown as function of the different scenarios to obtain sustainable distilled water

Solar-driven thermo-hydraulic process for reverse osmosis desalination

International audienceExisting distillation-based desalination processes are highly thermal energy consuming. Reverse osmosis (RO) technique is more efficient than thermal-based processes but it remains a solution that still induces high operating and maintenance costs. In this paper, an innovative thermally powered RO-based desalination process is presented. This new RO thermo-hydraulic process enables the pressurization of the salty water beyond its osmotic pressure to allow the permeation water through a semi-permeable membrane, thanks to a piston or an elastic bladder that is set in motion in a reservoir by a working fluid following a thermodynamic engine cycle similar to an Organic Rankine Cycle. The evaporator is heated by low grade heat (70 to 80°C) such the one delivered by plate solar collectors, while the condenser is cooled by the concentrated salty water. In order to enable a continuous drinkable water production, this process needs to implement two reservoirs, alternatively connected either to a high pressure evaporator or to a low pressure condenser. Such installation, designed here for brackish water desalination (5 g/liter), should enable an average daily production of 300 liters of drinkable water per m² of solar collectors with a production cost below 4€/m 3. That technology seems to be relevant for small scale (5 to 10 m 3 /day) the daily water needs of people living in remote areas, in accordance to the location and the solar resource. A modeling of the whole process, considering a quasi-steady state approach has been developed in order to study its dynamic behavior, optimize its design and maximize its performances. This paper presents the preliminary results relative to the performance of such solar-driven desalination process