Optimal Design of Thermal Membrane Distillation Systems for the Treatment of Shale Gas Flowback Water

Shale gas production is associated with the significant consumption of fresh water and discharge of wastewater. The flowback wastewater is tied to the hydraulic fracturing technology used for completing and stimulating the horizontal wells in the very tight formations characterizing the shale formation. Treatment and reuse of these large volumes of wastewater can lead to substantial savings in fresh water usage and reduction of the negative environmental impact thereby enhancing sustainability of the shale gas industry. Such treatment requires selective and cost-effective technology.Thermal membrane distillation (TMD) is an emerging technology that offers several advatanges such as high selectivity in separating water from inorganic solutes and modular nature that can accommodate a wide range of flows. It can also utilize low-level heats that are typically available from shale-gas production and processing.The objective of this work is to develop an optimization approach for the design of TMD systems to treat flowback water. A multi-period formulation is developed to account for the time-based variation in the flowrate and concentration of the flowback water. Modeling equations are used to relate design and operating variables to performance and cost. The optimization formulation also accounts for the period-based changes in the required design and operating variables and reconciles them over the selected periods. Other constraints include quality of the permeate and water-recovery ratio. The optimization formulation and design approach are applied to a case study for the treatment of flowback water for the Marcellus Shale Play. For 75% water recovery, the cost of the permeate is about $2.6/m3. As higher recoveries are sought, the cost per m3 of permeate increases due to capital productivity factors in dealing with the decreasing amount of flowback water over time. The results are reported using a Pareto chart that trades off recovery objectives with cost of treated water

Treatment technologies for cooling water blowdown: A critical review

Cooling water blowdown (CWBD) generated from different industries and district cooling facilities contains high concentrations of various chemicals (e.g., scale and corrosion inhibitors) and pollutants. These contaminants in CWBD streams deem them unsuitable for discharge into surface water and some wastewater treatment plants. The pollutants present in CWBD, their sources, and the corresponding impacts on the ecosystem are discussed. The international and regional (Gulf states) policies and regulations related to contaminated water discharge standards into water bodies are examined. This paper presents a comprehensive review of the existing and emerging water treatment technologies for the treatment of CWBD. The study presents a comparison between the membrane (membrane distillation (MD), reverse osmosis (RO), nanofiltration (NF), and vibratory shear enhanced membrane process (VSEP)) and nonmembrane-based (electrocoagulation (EC), ballasted sand flocculation (BSF), and electrodialysis (ED)) technologies on the basis of performance, cost, and limitations, along with other factors. Results from the literature revealed that EC and VSEP technologies generate high treatment performance (EC~99.54% reduction in terms of silica ions) compared to other processes (membrane UF with reduction of 65% of colloidal silica). However, the high energy demand of these processes (EC~0.18-3.05 kWh/m3 and VSEP~2.1 kWh/m3) limit their large-scale applications unless connected with renewable sources of energy.Funding: This research is funded by Ministry of Municipality and Environment in Qatar, Project MME contract no. P2020/1.Scopu

Process safety and abnormal situation management

This review paper summarizes process safety aspects of abnormal situations and incidents in industrial facilities. Major accidents and their negative impacts on health, safety and environment have shown the importance of enhancing safety culture, understanding causes of abnormal situations and determine effective management strategies. Flaring is a safety industry practice to control and manage processes during normal and abnormal operations. This paper identifies current efforts made by industry and researchers toward better management of abnormal situation for flare reductions. These efforts came about because of current and impending environmental legislation. The paper finds that future strategies developed for ASM must consider safety as well as environmental and economic implications; and it highlights the challenges and future guidelines for safer abnormal situation management.This paper was made possible by NPRP grant No 6-678-2-280 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the author[s].Scopu

Inherently safer design tool (i-SDT): A property-based risk quantification metric for inherently safer design during the early stage of process synthesis

In this work, an Inherently Safer Design Tool (i-SDT) is presented for early stage process synthesis to characterize and track the risk associated with different life-cycle phases of industrial processes. It also helps to develop characteristic equations for different safety parameters (i.e., flammability, explosiveness, toxicity, etc.) under various operating conditions. This property-based inherent safety quantification metric is a tailor made semi-quantitative safety analysis tool which provides safety assessment in a continuous manner to overcome the subjective nature of the existing available safety metrics. The core of this design and safety assessment tool is probabilistic risk quantification using accident and incident investigation (with over 600 incidents and within 27 years of time span), a property integration model and an exponential curve fitting method. The proposed safety metric has the flexibility to operate by identifying the major accident-prone units/sections of a process, as well as the major safety and operating parameters. The final output of this i-SDT tool is a cluster safety parameter score (CSP) which provides insights regarding the investigated unit/section or process for carrying out inherent safer design using a very limited amount of process information. The developed i-SDT tool was applied to compare different technologies of Ammonia processes in order to assess the safer option in terms of risks associated with the accident-prone unit/section and to highlight the areas of safety improvement in any existing process using the inherent safer design principles. In the future, this metric can can be embedded into a techno-economic framework to perform the cost and safety analysis simultaneously using available materials, design and accident information. - 2018 Elsevier LtdThis paper was made possible by NPRP grant No 6-678-2-280 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the author[s]. The author thanks Ahmed AlNouss for his contribution in developing the necessary simulation models for the presented Ammonia case study.Scopu

Managing Uncertain Industrial Flares during Abnormal Process Operations using an Integrated Optimization and Monte Carlo Simulation Approach

In this work, an integrated optimization framework with Monte Carlo (MC) simulation techniques is suggested for the systematic synthesis of energy alternative tools, such as cogeneration (COGEN) systems, which can effectively manage industrial flares with uncertain occurrence patterns. The optimization model that was previously developed is now extended to incorporate the risk associated with the uncertain nature of the flaring events that are probabilistically characterized based on empirically meaningful historical samples. The model aims at minimizing the total annualized cost including fixed and operating costs of the system, the value of by- and co-products (i.e., power, excess heat), and regulatory taxes/credits associated with Green House Gases (GHGs). A base case ethylene production plant is presented to illustrate the applicability of the proposed approach and highlight trade-offs between different performance objectives (economic, environmental and energy-related). The results show that some of the examined factors (i.e., CO2 tax savings) can be severely affected by small variations in flaring profiles, whereas others are only slightly affected by such variability (i.e., power vs. heat generation curves, fixed and operating costs). Therefore, the uncertain nature of flaring events may be of high importance in process performance and should be inevitably considered during abnormal situation management. 1 2017 Elsevier B.V.Scopu

Dynamic simulation and optimization targeting emission source reduction during an ethylene plant start-up operations

Chemical plant flare minimization has been practiced not only during regular operating conditions but also abnormal operations such as start-ups, shutdowns, and process upsets. This paper focuses on introducing a generic approach by using dynamic simulation for emission and greenhouse gas reductions, which is demonstrated by a case study of a front-end de-ethanizer ethylene plant start-up. The new merits presented in this work include investigating different approaches of using intermediate storage units to accumulate and recycle off-specification streams from the recovery section, ultimately targeting flareless start-up for the entire ethylene plant. Large-scale dynamic simulations, emission characterizations, operation scheduling, and solution evaluation are carried out systematically to achieve the goal of flare minimization. It shows that the proposed optimization procedure contributes a great deal in evaluating new strategies and predicting process dynamic behaviors. It also helps achieve precise timing to control the recycle loop; hence, flaring can be minimized while the start-up time is shortened.This work was supported in part by Qatar National Research Fund ( NPRP 5-351-2-136 ) as well as Texas Air Research Center and Center for Advances in Water and Air Quality both headquartered at Lamar University .Scopu

Integrated Data (i-Data), Mining and Utilization Approach for Effective Flare Management Strategies

Upset emissions occur during plant startup, shutdown, maintenance, malfunction, and flaring incidents. A wide range of these upsets cannot be managed by standalone control systems; plant personnel intervention is necessary sometimes. The methods needed to assist plant personnel to control and prevent abnormal process operations are gathered under abnormal situation management. Abnormal operations that lead to flare have significant economic, environmental, and safety impacts. Flaring is necessary for managing process upsets, however, it leads to the emission of greenhouse gases (GHG) and volatile organic compounds (VOCs), causing negative social impacts and local transient air pollution. In addition, excessive flaring results in energy and raw material losses. These are valuable commodities that must be sustained. Therefore, flare minimization during normal and abnormal operational situations has great environmental, industrial, and societal benefits. It is not possible to quantify the impacts without understanding the properties and magnitude of these upsets. Such analysis requires extensive amount of historical data. There are large sets of design, operational, and flaring data readily available; however, the challenge when it comes to flare mitigation is in using them effectively and in a timely manner. In this Article, a systematic approach to collect, analyze and utilize historical flaring data based on current industrial practices is presented. An ethylene base case study along with its historical process and flaring incidents data is used to demonstrate the significance of using and integrating data within developed flare management strategies. In the presented case, design and historical process data are used to assess the environmental impacts of abnormal incidents and to identify underlying causes and indicators that lead to process upset, that is, abnormal situations. The data sets are utilized within an optimization algorithm to identify design alternatives to mitigate process incidents and reduce its root causes. The paper highlights the challenges that are faced by environmental agencies in terms of data utilization and documentation. (Figure Presented).This paper was made possible by NPRP grant No 5-351-2-136 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Green hydrogen for industrial sector decarbonization: Costs and impacts on hydrogen economy in qatar

This study focuses on the development of a strategic framework for the design of a hydrogen supply chain network (HSCN) mainly investigating the potential of industrial decarbonization and multi-sectors integration (i.e., transportation, energy, shipping) via green hydrogen economy. The problem was formulated as a mixed integer linear programming (MILP) and solved in GAMS/ IBM ILOG CPLEX 30.3.0 solver. The applicability of the developed model was demonstrated using a base case Eco-industrial city consisting of 10 diverse industrial portfolios targeting decarbonization by 5%. The solution was able to find the optimal HSCN from the probable superstructure along with the optimal sizing of green hydrogen production (453.03 MM kg/y), optimal water sources, optimal sinks and the optimal amount of byproducts generation. Furthermore, the multi-purpose model can accomplish detailed techno-economic-environmental analysis for variable scenarios (e.g., variation in decarbonization target, liquid hydrogen demand, hydrogen production cost, earnings from byproducts) based on net present value. 2020 Elsevier LtdThis paper was made possible by NPRP grant No 10-0205-170347 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the author[s].Scopu

Managing abnormal operation through process integration and cogeneration systems

Flaring is a common industrial practice that leads to substantial greenhouse gas emissions, health problems, and economic losses. When the causes, magnitudes, and frequency of flaring are properly understood and incorporated into the design and operation of the industrial plants, significant reduction in flaring can be achieved. In this paper, a process integration approach is presented to retrofit the process design to account for flaring and to consider the use of process cogeneration to mitigate flaring while gaining economic and environmental benefits. It is based on simultaneous design and operational optimization where key flaring sources, causes, and consequences of process upsets are identified then included in the energy profile of the process to design a combined heat and power system with special emphasis on discontinuous sources due to process upset. Environmental and economic benefits are weighed against the cost of process retrofitting. A base case study for an ethylene process is used to illustrate the applicability of the proposed approach and to evaluate the process performance under varying abnormal situation scenarios.NPRP grant #5-351-2-136 from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Integration of Energy and Wastewater Treatment Alternatives with Process Facilities to Manage Industrial Flares during Normal and Abnormal Operations: Multiobjective Extendible Optimization Framework

This work reports an extendible multiobjective optimization framework to find the optimal configuration of energy utilization and wastewater treatment facility of the process. It incorporates two sustainable energy integration alternative tools, i.e., a cogeneration (COGEN) unit and thermal membrane distillation (TMD), as available add-ons to the process during normal operation and for abnormal situation management. The objective of the framework is to reduce the environmental footprint of abnormal flares by enumerating and assessing possible process configurations in order to manage flares from uncertain sources and to utilize unused energy resources for wastewater treatment. The core of this optimization framework is developed using a genetic algorithm and its objective function is aimed at minimizing the total annualized cost which accounts for the fixed and operating costs of the system, the value of produced coproducts (i.e., power, wastewater treatment savings, income from permeate), and taxes/credits associated with greenhouse gases. An ethylene process plant is used to demonstrate the applicability of the developed framework. The results of different alternative configurations demonstrate the economic, energetic, and/or environmental trade-offs of integrating TMD and the COGEN unit with the process plant both for flare mitigation and during normal operation. It was seen that the total annualized cost (TAC) dropped around 35% and the payback period reduced from 7.01 to 4.61 years when an integrated process plant (ethylene plant), utility unit (COGEN), and wastewater treatment facility (TMD) was considered instead of separate divisions. Moreover, utility savings were achieved up to 8% and annual incomes from coproducts were increased around 20% for the integrated ethylene plant, COGEN, and TMD unit. Besides, prolific recycling opportunities of unused flare streams and treated wastewater were identified to make some valuable products from waste streams.Scopu