Wastewater minimization using aspen water

This thesis lays out the basic principles for analyzing a water using operation and then compares the freshwater and wastewater flowrates for a system with and without reuse. The methods of reuse, recycle and regeneration are discussed to solve the problems of multiple contaminants with multiple constraints. The preliminary mass exchange network is designed and further optimization is carried out by using ASPEN WATER software. Along with network optimizations for minimum water use, minimum network costs which include water costs or discharge costs, can also be determined with help of the software. Minimizing water use as well as the wastewater discharged from a water network are main priorities of the present work. Two industrial case studies are discussed to illustrate the significance of wastewater minimization and the results obtained are compared with that predicted using published method. The first one is a multiple contaminants problem for a starch industry in which water saving was found to be 41% for Demineralised water and 80% for freshwater with water cost savings of about 45% and the second is a analysis of streams in petroleum refining complex in which freshwater savings was around 82%. Key Words: Wastewater minimization, multiple contaminants, ASPEN WATE

Minimizing water and energy consumptions in water and heat exchange networks.

This study presents a mathematical programming formulation for the design of water and heat exchangers networks based on a two-step methodology. First, an MILP (mixed integer linear programming) procedure is used to solve the water and energy allocation problem regarding several objectives. The first step of the design method involves four criteria to be taken into account., ie, fresh water consumption (F1), energy consumption (F2), interconnection number (F3) and number of heat exchangers (F4). The multiobjective optimization Min [F1, F2] is solved by the so-called ɛ-constraint method and leads to several Pareto fronts for fixed numbers of connections and heat exchangers. The second step consists in improving the best results of the first phase with energy integration into the water network. This stage is solved by an MINLP procedure in order to minimize an objective cost function. Two examples reported in the dedicated literature serve as test bench cases to apply the proposed two-step approach. The results show that the simultaneous consideration of the abovementioned objectives is more realistic than the only minimization of fresh water consumption. Indeed, the optimal network does not necessarily correspond to the structure that reaches the fresh water target. For a real paper mill plant, energy consumption decreases of almost 20% as compared with previous studies

Graphical Revamping Of A Crude Distillation Unit Under Two Variable Operational Scenarios - Naphtha Stabilizer And Reformer Operated

Energy costs represent significant parts of the total operating costs of crude refining industries. Energy integration is a typical solution to reduce heating and cooling utilities in crude refining plants through maximizing the target temperature of crude oil streams before entering the furnace. Over the past few decades, a significant progress has been made in energy integration methods including Pinch technology and mathematical programming approaches. Example of these is a graphical technique which plots Thot versus Tcold for energy analysis and revamping studies. The current research employs the Thot - Tcold diagrams in an algorithm to retrofit an existing crude atmospheric distillation unit (CDU) located in north of Egypt (Suez region). This real CDU unit is operated under two different operational modes: (i) without naphtha stabilizer; the process reformer is in operation to reform all naphtha streams without stabilization, and (ii) with naphtha stabilizer; LPG is separated from naphtha stream. The performance of the current HEN is analyzed using the graphical axes of Thot - Tcold diagrams. The graphical method is used to identify exchangers across the Pinch and recognize the potential modifications to improve the energy performance and reduce fuel consumption. Implementing the graphical identified modifications on the existing plant resulted in: (1) stabilizer scenario; energy savings are achieved by 21.1% with additional capital investment of 0.81 MM$and annual energy savings of 0.82 M$, (2) reformer scenario; the energy savings are 0.42 MM$with capital investment of 0.33 M$

Analysis of Cooling Water Systems in a Petroleum Refinery

An important area in process integration is the development of methodologies to minimize water and energy use in industry. More than 20 % of the energy consumption in industry is associated with cooling and heating water. This paper presents analysis and optimization of a re-circulating cooling water system, with the aim to satisfy any supply conditions for the cooling tower. The part of the atmospheric crude oil distillation unit was chosen for analysis and synthesis of cooling water systems by the Kim and Smith design (KSD) method. The load of the cooling tower and the cost related to the cooling water system could be reduced by modifying the configuration of the heat exchanger network. In this paper, the KSD methodology for a developed heat exchanger network is expanded with the principle based on the heuristic algorithmic water sources diagram procedure (WSD) to synthesize the mass exchange network. These procedures are advantageous compared with other methodologies since hand calculation is used, a very useful feature for process engineers. The cooling water network was synthesized, leading to a 40 % reduction in cooling tower load, and consequently, lower operating costs and water consumption

Towards achieving Zero Liquid Discharge in process industry

Fresh water is invaluable in supporting life on Earth. It is scarce, cheap, and exploited. A number of initiatives have been taken to reduce the consumption of fresh water, particularly in agricultural and residential situations. In industry, much focus has been placed on pollution control and wastewater minimisation, however attention to source protection and water minimisation is nominal. The ultimate goal of any water management program is achieving Zero Liquid Discharge (ZLD). This research argues that with a current focus on pollution control and wastewater minimisation, ZLD is not attainable. Protection of water sources has recently been identified as the most critical issue preventing sustainability of industrial water management. It is also given the least attention. This thesis argues that incorporating water auditing and water conservation programs into industrial water management programs is a crucial step towards achieving water source protection and ultimately in achieving zero liquid discharge. A water audit of key water using operations at the BP Refinery in Kwinana has been undertaken to test this hypothesis. The BP Oil Refinery in Kwinana is an example of an industry which has received much attention for its excellent practice in water management. BP has almost halved its total water consumption from 7ML/day in 1996 to 4ML/day in 2007. It has developed employee awareness-raising programs, on-site recycling and reuse of wastewater and is now in the final stages of using recycled domestic wastewater as a key water source, expected to minimise fresh water consumption even further. Despite this, detailed analysis of the major water uses at the refinery show a number of poor management practices and severe wastages of water. In assessing the whole of refinery water use in Chapter 2, we see that poor record keeping and meter reading is commonplace. Major leaks are left unattended and information about major water-loss incidents is often unavailable. In Chapters 3-5 we look more closely at specific water using operations within the refinery. The refinery steam system is one of the largest fresh water users on site and has been commended for its steam trap survey program and the development of condensate return infrastructure, increasing the percentage of condensate returned from 32% in 1998 to a condensate return target of 50% in 2007. Despite this, major losses still occur in the steam system and turnaround time for fixing major leaks can take years. Simple measures can improve the condensate return rate from 50%-75% quite easily, but there are few incentives for the refinery to invest in such a program which offers diminishing returns. The use of water in process units is enormous, particularly the use of scheme water in the Residue Cracking Unit. A number of available tools and techniques, particularly water pinch and water optimisation tools, are widely recognised to reduce water use on such units but have not been investigated at BP. Many water losses on process units occur because of poor operator management and a focus on increasing efficiency of feed throughput which offers the refinery the greatest financial return. Another inefficient water user in the process category is the Waste Management Area Land Farm. The land farm is irrigated to keep the moisture content of waste high. The exceptionally large volumes of water used in this area can be easily reduced, however costs are considered too high. Finally we assess other uses of water at the refinery. Other uses include commercial and domestic uses, safety showers and the staff carwash. Because of the extraordinary volumes of water used in the refining process, these other uses are considered comparatively insignificant. Practically no water efficiency measures have been taken at this level, and enormous wastages of high quality water are witnessed through our case study of the staff carwash. The carwash is an enormous water waste which uses scheme water once before it is discharged to the sewer. Each of these case studies shows major inefficiencies in current water management at a number of levels at the BP Refinery in Kwinana. It is important not to forget that this refinery has been recognised for its excellence as a leader in water management not only in the Kwinana Industrial Area but also in the global oil refining industry. This reflects the inherent flaws in water management throughout industry. Chapter 6 assesses management implications associated with reducing water use on site and applies these principles and concepts to industry in general. The most significant barriers to closing industrial water loops were found to be neglect of protection of water sources and larger focus on pollution prevention and wastewater minimisation; misconceptions about the true value of water; and poor regulatory drivers to reduce water use. A paradigm shift in industrial water management to incorporate a more holistic approach is required if water scarcity is to be seriously addressed by industry

Assessment Lagging Performance Indicators of Cooling Tower Water Wastage at Refinery (Parco) & Possible Upgradations to Eco Design for Water Conservation

About 20% of energy in manufacturing is connected to refrigeration, heating water, the purpose of this research is to save environment by conserving water losses and these has to be replenished. Monitor rate of evaporation make up and blow down water superiority to authorize that the up-gradated structure is acting as predicted. Increasingly the most forward thinking using highly treated recycled water, side filtration, and option of ozone treatment, changing behavior of blow-down and replacing water saving equipment’s or modifying to reduce energy in addition water needs, which save budgets in addition recover water management in the future. This will address the problems found through an environmental review of current and future cooling systems, the technological, economic and environmental implications, with possible technical and non-technical solutions. Considering the current water crisis around the world, it is essential to expand the functions of these wet refrigeration towers to decrease their water consumption with maintaining their performance, therefore it has a great potential to recycle water evaporation. Which has not considered so far? This retrofit research using possible up-gradations at different research study, Reference [22] at existing facility regarding environment improvements (sustainability & water conservation) to perform a realistic evaluation of this idea. Experimental data measured and dynamic Eco approaches performed to evaluate the water saving potential. The result shows that water losses at one unit control from maximum (440) to minimum 108level to promote environment sustainability

Optimization with Integrated Offline Parametric Optimization of Detailed Process Model of an Interceptor Unit for Water Network Synthesis and Retrofit Design

Petroleum refineries is a prime example of industrial plants that demand high quantities of water for process consumption and generate volumes of highly contaminated industrial eflluents and wastewaters. Scarcity of freshwater resources and increasingly stringent environmental regulations on industrial effluents have motivated refineries to develop water reuse technologies for sustainability of plant operations. The technology concept can be characterized into three (3) strategies: reuse, regeneration, and recycle (W3R). The major contribution of this work is to consider the design of alternative refinery water network structures that incorporate the detailed design of wastewater treatment technology (or interceptor) in an optimization-based modeling framework as an offline parameter optimization problem. For this purpose, a source-interceptor -sink superstructure representation is adopted that embeds many feasibly possible alternative water network configurations. A mixed-integer nonlinear programming (MINLP) optimization model is formulated based on the superstructure with the objective of minimizing freshwater import, wastewater generation, piping interconnections, and the total cost of installing and operating the treatment technology. The parametric optimization problem comprising of material balances and the detailed phenomena model for interceptor, specifically for a single-stage hollow fiber reverse osmosis (HFRO) membrane module, is incorporated in the overall MINLP framework. The modeling approach is developed in conjunction with its implementation into general algebraic modeling system (GAMS), using data of a real operating refinery situation. The model is solved iteratively by branch and reduce optimization navigator (BARON), resulting in freshwater consumption requirements to be 296.2 m3 /h at the optimal refinery water network structure and operating conditions, which accounts for nearly 61% of water recovery compared to current operating requirements (before the integration and retrofit initiatives based on W3R)

Waste water minimization using pinch analysis

This thesis lays out the basic principles for analyzing a water using operation and then compares the freshwater and wastewater flowrates for the system with and without reuse. First, the system is defined as a mass transfer problem in which the contaminant is transferred from a contaminant rich process stream to a water stream. Next, the system is analyzed treating each water-using operation separately. Finally, the minimum freshwater requirement for the integrated system is determined by maximum water reuse subject to constraints such as minimum driving force for mass transfer. For this analysis, the concentration composite curve, the concentration interval diagram and the freshwater pinch are introduced. The methods of regeneration reuse and recycle are also discussed. The approach for single contaminant problem is extended to multiple contaminants problem with multiple constraints. The preliminary mass exchange network is designed on the basis of concentration interval diagram and further simplification is achieved by loop breaking. The basic concepts of each method are formulated into a mathematical code to obtain computer-aided solution to a problem. Two industrial case studies are discussed to illustrate the significance of wastewater minimization and the results obtained are compared with that predicted using analytical method. The first one is a SO2 extraction problem from four process streams and the second is a petroleum refinery complex problem. An average reduction of about 20% in the freshwater requirement is achieved with water reuse while a reduction of about 60 % is achieved by regeneration reuse. There is also a reduction in the number of units in the mass exchange network by four units with water reuse