Automated Targeting for Property Integration

Resource conservation is an effective way for reducing operation cost and to maintain business sustainability. Most previous works have been restricted to "chemo-centric" or concentration-based systems where the characterisation of the streams and constraints on the process sinks are described in terms of the concentration of pollutants. However, there are many applications in which stream quality is characterised by physical or chemical properties rather than pollutant concentration. In this work, the automated targeting approach originally developed for the synthesis of composition-based resource conservation network is extended for property-based network. Based on the concept of insight-based targeting approach, the automated targeting technique is formulated as a linear programming (LP) model for which the global optimum is guaranteed. Two literature examples are solved to illustrate the proposed approach

Development of systematic technique for energy and property integration in batch processes

The increasing consumption of energy, generation of waste as well as higher cost of fresh resources and waste treatment systems are the important driving forces for developing efficient, environmentally friendly and economic resource conservation techniques in the process industries. Process integration is being recognized as an useful systematic strategy for resource conservation and waste minimization. Up to date, less research works have been investigated on heat and property integration and these works are only focused on continuous processes.Since the application of batch processes is increasingly popular due to the development of technology-intensive industries such as pharmacy, fine chemistry and foods, it is necessary to consider both heat and property integration in batch processes simultaneously. In this thesis, a new mixed integer nonlinear programming (MINLP) mathematical model is introduced to synthesize a property-based heat integrated resource conservation networks (HIRCNs) for batch processes. A source-HEN-sink superstructure is constructed to embed all possible network configurations. Then, an MINLP model that consists of propertybased resource conservation network (RCN) and heat exchanger network (HEN) models is developed.In the proposed model, the property-based RCN model is formulated based on supertargeting approach while HEN model is formulated via automated targeting method (ATM). The optimization objective is to minimize total annualized cost (TAC) for a batch process system. This includes the operating cost of fresh resources, hot and cold utilities as well as the capital cost of storage tanks. To demonstrate the proposed approach, three case studies were solved. Based on the optimized results, the proposed simultaneous targeting approach for property-based HIRCNs is more effective in term of TAC for HIRCNs than the presented sequential targeting approach

Mathematical modelling of simultaneous water and energy minimisation considering water management hierarchy options

Water and energy are closely interlinked together. The goal to reduce water and energy simultaneously has been a growing research. However, previous studies only consider maximising water reuse and, in some cases, also include water regeneration. This study aims to develop a mathematical model to design water and energy network that further reduces the water consumption, considering the whole water management hierarchy (WMH) schemes. This includes elimination, reduction, reuse, outsourcing and regeneration. Two steps solution is proposed, which involves solving two MINLP models. First, water and energy minimisation network considering WMH schemes and direct heat transfer is designed. The obtained network is then improved by inclusion of indirect heat integration to minimise the objective cost function. Two cases of thermal data extraction are studied for heat integration, Case A extracts individual streams based on supply and targeted temperature, whereas Case B extracts stream after mixer based on mixer temperature and targeted temperature. Streams which temperature load is satisfied in direct heat transfer were excluded for heat integration. The proposed method has been tested with literature case study. The implementation of all possible WMH scheme yields a lower freshwater consumption and wastewater generation. The model selected 35% and 15% of reduction for demand 3 and demand 1 respectively. Case A yields a lower total operating cost but slightly higher investment cost compared to Case B. Case B result in a simpler heat exchanger network, but degradation of the potential energy causes more heating and cooling. Case A is chosen as the optimal network and exhibits 13% reduction of the total cost compared to the literature case study

Improved Targeting Technique and Parsimonious Optimization as Synergistic Combination for Nitrate Hot Spots Identification and Best Management Practices Implementation in a watershed of the Midwestern USA

The contamination of rivers with nitrate from agricultural diffuse sources is not just a risk for ecosystems and their services, but also a health risk for water users. The Great Lakes (USA and Canada) are suffering from eutrophication problems. The Midwest is one of the richest farming land and one of the most productive areas on the planet. Thus, agriculture is one of the biggest drivers of local economies, accounting for billions of dollars of exports and thousands of jobs. The Midwest encompasses the Corn Belt region, a specialised system in corn production. Many of its agricultural basins drain into the Great Lakes. Corn requires a heavy amount of fertilizer to keep the best-yielding varieties. Some of the soils also require artificial drainage due to their low permeability, and to enable agriculture. The Cedar Creek watershed (CCW) in northeastern Indiana in the Corn Belt region is used as a case study area in this dissertation. Intensive agriculture in the CCW is characterised mainly by corn and soybean production. Tile drains are used, ejecting nitrate directly into the water. To find hotspots of nitrate is, then, crucial to avoid water quality deterioration. Identification of critical source areas of nitrate (CSAs) impairing waters is challenging. There are, mainly, two methodologies to identify hotspots of nitrate for the implementation of Best Management Practices (BMP): the targeting technique and the optimization approach. The targeting technique tends to identify hotspots based on loads of nitrate, omitting geomorphological watershed characteristics, costs for BMP implementation, and their spatial interactions. On the other hand, the parsimonious strategy does contemplate the trade-off of the economic and environmental contribution but requires sophisticated computational resources and it is more data-intense. This research presents a new framework based on the synergistic combination of both methodologies for the identification of CSAs in agricultural watersheds. Changes in watershed response due to alternative BMP applications were assessed using the model Soil and Water Assessment Tool (SWAT). Outputs in SWAT (nitrate export rates and nitrate concentration at the subbasin level) were used to evaluate the changes in water quality for the CCW. The newly developed targeting technique (HosNIT) considers SWAT outputs and intrinsic watershed parameters such as stream order, crop distance to the draining stream, and downstream nitrate enrichment/dilution effects within the river network. HosNIT establishes a workflow, based on a threshold system for the parameters considered, in order to spatially identify priority areas from where nitrate is reaching water. The more precise hotspots of nitrate are identified, the more improved the allocation of limited resources for conservation practices will be. HosNIT allows for a more spatially accurate CSAs identification, which enables a parsimonious optimization for BMP implementation. This parsimonious strategy will test BMP’s performance based on the environmental contribution and cost at the hotspots determined by HosNIT. The optimised solution for the CCW comes from the environmental contribution (decrease percentage of nitrate concentration at outlets) per dollar spent. For this case study means a year average of 3.7% of nitrate reduction with the optimised selection of scenarios for the studied period

Algebraic approaches to resource conservation via process integration

The primary objective of this dissertation is to introduce several algebraic procedures to the targeting of material recycle networks. The problem involves the allocation of process streams and fresh sources to process units (sinks) with the objective of minimizing fresh purchase and waste discharge. In the case of composition-limited sinks, allocation to process sinks is governed by feasibility constraints on flowrates and compositions. A systematic non-iterative algebraic approach is developed to identify rigorous targets for minimum usage of fresh resources, maximum recycle of process resources and minimum discharge of waste. These targets are identified a priori and without commitment to the detailed design of the recycle/reuse network. The approach is valid for both pure and impure fresh resources. The devised procedures also identifies the location of the material recycle pinch point and addresses its significance in managing process sources, fresh usage, and waste discharge. The dissertation also addresses the targeting of material-recycle networks when the constraints on the process units are described through flowrates and properties. This property-integration problem is solvedusing a non-iterative cascade-based algebraic procedure. Finally, for more complex cases with multiple fresh sources and with interception networks, a mathematical-programming approach is developed. Because of the nonlinear non-convex characteristics of the problem, the mathematical model is reformulated to enable the global solution of the problem. Several case studies are solved to illustrate the ease, rigor, and applicability of the developed targeting technique

Synthesis of heat integrated resource conservation networks

Huge amount of energy and fresh resources (i.e. water, chemicals, solvents) are consumed by process industries to achieve the desired product throughput and quality. The current drive toward sustainability and business competitiveness has driven the process industries to effectively use these resources. Thus, resource conservation activities have become the centre of attention as compared to conventional end-of-pipe waste treatment system. Process integration has been commonly used as an effective tool for resource conservation and waste reduction. One of the most established areas of process integration is concentration- and property-based resource conservation networks (RCNs). Most works in RCNs synthesis do not consider temperature as part of process constraints. However, in many cases, temperature is an important design parameter. Thus, simultaneous consideration of mass/property and heat recovery should be addressed. Earlier works in this area have been mainly focusing on heat integrated water networks (HIWNs).However, these methods cannot be applied for property-based RCNs, as they are limited to “chemo-centric” system. Clearly, a more generic approach is needed for the synthesis of concentration- and property-based heat integrated resource conservation networks (HIRCNs). This thesis presents novel and generic methodologies for the synthesis of concentration- and property-based HIRCNs with variable operating parameters (i.e. flowrates, temperatures and properties). Firstly, a new generic overall methodology for concentration- and property-based HIRCNs is established. Next, a general framework for synthesis of HIRCNs with and without heat of mixing is presented. Based on this framework, new methodology for the synthesis of HIRCNs with and without heat of mixing are established respectively. Moreover, a revised floating pinch method is developed for utilities targeting in heat exchanger networks (HENs) with varying temperature range, and it is incorporated in the new methodologies for the synthesis of HIRCNs with and without heat of mixing. Various case studies are solved to illustrate the developed methodologies