Economic and environmental strategies for process design

This paper first addresses the definition of various objectives involved in eco-efficient processes, taking simultaneously into account ecological and economic considerations. The environmental aspect at the preliminary design phase of chemical processes is quantified by using a set of metrics or indicators following the guidelines of sustainability concepts proposed by . The resulting multiobjective problem is solved by a genetic algorithm following an improved variant of the so-called NSGA II algorithm. A key point for evaluating environmental burdens is the use of the package ARIANE™, a decision support tool dedicated to the management of plants utilities (steam, electricity, hot water, etc.) and pollutants (CO2, SO2, NO, etc.), implemented here both to compute the primary energy requirements of the process and to quantify its pollutant emissions. The well-known benchmark process for hydrodealkylation (HDA) of toluene to produce benzene, revisited here in a multiobjective optimization way, is used to illustrate the approach for finding eco-friendly and cost-effective designs. Preliminary biobjective studies are carried out for eliminating redundant environmental objectives. The trade-off between economic and environmental objectives is illustrated through Pareto curves. In order to aid decision making among the various alternatives that can be generated after this step, a synthetic evaluation method, based on the so-called Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) (), has been first used. Another simple procedure named FUCA has also been implemented and shown its efficiency vs. TOPSIS. Two scenarios are studied; in the former, the goal is to find the best trade-off between economic and ecological aspects while the latter case aims at defining the best compromise between economic and more strict environmental impact

Economic and environmental impacts of the energy source for the utility production system in the HDA process

The well-known benchmark process for hydrodealkylation of toluene (HDA) to produce benzene is revisited in a multi-objective approach for identifying environmentally friendly and cost-effective operation solutions. The paper begins with the presentation of the numerical tools used in this work, i.e., a multi-objective genetic algorithm and a Multiple Choice Decision Making procedure. Then, two studies related to the energy source involved in the utility production system (UPS), either fuel oil or natural gas, of the HDA process are carried out. In each case, a multi-objective optimization problem based on the minimization of the total annual cost of the process and of five environmental burdens, that are Global Warming Potential, Acidification Potential, Photochemical Ozone Creation Potential, Human Toxicity Potential and Eutrophication Potential, is solved and the best solution is identified by use of Multiple Choice Decision Making procedures. An assessment of the respective contribution of the HDA process and the UPS towards environmental impacts on the one hand, and of the environmental impacts generated by the main equipment items of the HDA process on the other hand is then performed to compare both solutions. This ‘‘gate-to-gate’’ environmental study is then enlarged by implementing a ‘‘cradle-togate’’ Life Cycle Assessment (LCA), for accounting of emission inventory and extraction. The use of a natural gas turbine, less economically efficient, turns out to be a more attractive alternative to meet the societal expectations concerning environment preservation and sustainable development

Comparison of two methods in multi-criteria decision-making: application in transmission rod material selection

Transmission rod is an indispensable part in diesel and gasoline engines. Its job is to convert rotation into translational motion or vice versa. The transmission rod material selection plays a very important role, affecting its working function and durability. This study was conducted to compare two Multi Criteria Decision Making (MCDM) methods in transmission rod material selection. They are PIV (Proximity Indexed Value) method, and FUCA (Faire Un Choi Adéquat) method. Seven types of steel commonly used in transmission rods were reviewed for ranking, inclusive of: 20 steel, 40 steel, 45 steel, 18Cr2Ni4WA steel, 30 CrMoA steel, 45Mn2 steel and 40CrNi steel. Nine parameters were used as criteria to evaluate each steel including minimum yield strength, ultimate tensile strength, minimum elongation ratio, contraction ratio, modulus of elasticity, mean coefficient of thermal expansion, thermal conductivity, specific thermal capacity, and density. The weights of the criteria were calculated using three methods inclusive of MEAN weight method, Entropy weight method and MEREC weight method (Method based on the Removal Effects of Criteria). Each MCDM method was combined with the three weight methods mentioned above to rank the alternatives. The obtained results show that when using both PIV and FUCA methods to rank the alternatives, the best and worst alternatives are found regardless of the weight of the criteria. The best alternative determined using the PIV method is also the best alternative determined using the FUCA method. It means that the two PIV and FUCA methods have been shown to be equally effective. Among the seven transmission rod materials reviewed, 20 steel was identified as the best, and 40CrNi steel was identified as the wors

Biodiesel Production from Waste Vegetable Oils: Combining Process Modelling, Multiobjective Optimization and Life Cycle Assessment (LCA)

The objective of this work is to propose an integrated and generic framework for eco- design that generalizes, automates and optimizes the evaluation of the environmental criteria at earlier design stage. The approach consists of three main stages. The first two steps correspond to process inventory analysis based on mass and energy balances and impact assessment phases of LCA methodology. The third stage of the methodology is based on the interaction of the previous steps with process simulation for environmental impact assessment and cost estimation through a computational framework. Then, the use of multi-objective optimization with a multicriteria choice decision making allows to select optimal solutions. The methodology is illustrated through the acid-catalyzed biodiesel production process

Utilization of Char from Biomass Gasification in Catalytic Applications

Utilization of biomass as an energy source is likely to increase in the near future. One way to recover energy from biomass is via gasification, which enables the production of electricity, heat, chemicals, or fuels such as synthetic natural gas or gasoline. The desired product from gasification is synthesis gas, which is a mixture of CO and H2; however by-products such as tar and char are formed. The tars must be decomposed or removed, as they can cause clogging in downstream equipment. Tars are most commonly decomposed catalytically or thermally. However, thermal decomposition requires high temperatures, and catalyst deactivation takes place during catalytic decomposition. This thesis focuses on the utilization of char as a catalyst for tar decomposition. Char has a surface area that is higher than many typical catalysts, and contains catalytic minerals and metals which are well dispersed on the surface. Using char in this application would eliminate the need for purchasing expensive catalysts, and deactivation would not be a concern since deactivated char could be easily replaced by fresh char which is produced inside the gasifier. In addition, it provides a useful application for the char, which would otherwise be considered to be a low value product. In this work, poplar wood was gasified in a fluidized bed reactor under steam and CO2 at 550, 750, and 920C for different periods of time. The char was recovered from the fluidized bed, and its properties were studied. The BET surface area of the char ranged from 429-687 m^2 g^-1 and increased with increasing gasification temperature or time. In addition, micropores were observed in char that was made in CO2, but not in char that was made in steam. Gasification was also done in an ESEM under air, steam, and CO2. ESEM results showed sintering of the metals and minerals on the char surface during gasification in air and steam, but sintering was not observed during gasification with CO2. This showed that the properties of char depend on the gasification conditions. Catalytic activity of the char was demonstrated for decomposition of methane, propane, and toluene, which is a major component of gasification tar. The light off temperature for methane decomposition using a char catalyst was 100C lower than the light off temperature when a commercial Pt/Al2CO3 catalyst was used. Higher surface area char had higher catalytic activity. However, microporous char had lower catalytic activity than non-microporous char with a similar surface area, indicating that diffusion limitations occur in the micropores, reducing access to these catalytic sites. Deactivation was observed during catalytic cracking of CH4. A 20% reduction in surface area and 33% reduction in mesopore volume were observed when comparing the used char catalyst to the fresh sample. This indicates that deactivation occurs via pore blocking. Kinetic analysis of the data showed a steeper deactivation function for mesoporous char that was made in H2O compared to microporous char that was made in CO2. A steeper deactivation function is indicative of a higher number of catalyst sites per pore, since once a pore becomes blocked all of the catalytic sites within the pore will become inaccessible. Therefore, char made in steam, which is mesoporous, has more accessible catalyst sites per pore. The char morphology influences its catalytic activity, which increases with increasing accessible surface area. The accessible surface area of the char depends on both the surface area and the porosity of the char. Carbon based materials such as chars have been used in low temperature catalytic applications. In these applications, the catalytic activity is attributed to the presence of oxygen groups on the surface. Therefore, in this thesis the role of oxygen groups in the catalytic activity of the char for high temperature applications was investigated. Temperature programmed desorption (TPD) was used to identify the types of oxygen groups on the char surface and both acidic (lactone, carboxylic) and basic (pyrone, quinone) groups were identified. There were no significant differences in the concentration and type of surface oxygen groups amongst the different char samples. In order to understand the role that these compounds play in the catalytic activity of the char, oxygen was added to the surface of a char sample via nitric acid treatment and its catalytic performance was compared to the raw char. However, when the sample was heated in nitrogen to the reaction temperature (850C) prior to utilization for methane decomposition, the oxygen groups desorbed, and the catalytic activity of the oxygenated char was the same as the raw char. Therefore, the char has catalytic activity even when the acidic surface oxygen groups have been removed. The role of metals in the catalytic activity of the char was studied. Metals were removed via acid washing, and the catalytic activity of the acid washed char was compared to the untreated char. The catalytic activity of the acid washed char was 19% lower than the untreated char, which demonstrated that the presence of metals increases the catalytic activity of the char. The metals were found to be dispersed on the surface of the char. When the char was heated to 1000C, and was then used to catalyze the decomposition of CH4, the catalytic activity of the char was lower than the untreated sample. Therefore, the gasification process preserves the high dispersion of inorganic elements in the char, which improves the catalytic performance of the char. Char is often considered to be a by-product of gasification processes. However, this work has shown that char is a valuable product that has the potential to be used in catalytic applications. It has a surface area which is higher than many commercial catalysts, and contains metals and minerals which are catalytically active and are well dispersed on the char surface

Integrated Water Resources Management Modelling For The Oldman River Basin Using System Dynamics Approach

Limited freshwater supply is the most important challenge in water resources management, particularly in arid and semi-arid basins. However, other variations in a basin, including climate change, population growth, and economic development intensify this threat to water security. The Oldman River Basin (OMRB), located in southern Alberta, Canada, is a semi-arid basin and encompasses several water challenges, including uncertain water supply as well as increasing, uncertain water demands (consumptive irrigation, municipal, and industrial demands, and non-consumptive hydropower generation, and environmental demands). Reservoirs, of which the Oldman River Reservoir is the largest in the basin, are responsible for meeting most of demands, and, protecting the basin’s economy. The OMRB has also faced extreme natural events, floods and droughts, in the past, which reservoir management plays a critical role to adapt to. The complexity of the climate, hydrology, and water resource system and water governance escalates the challenges in the basin. These factors are highly interconnected and establish dynamic, non-linear behavior, which requires an integrated, feedback-based tool to investigate. Integrated water resources (IWRM) modelling using system dynamics (SD) is such an approach to tackle the different water challenges and understand their non-linear, dynamic pattern. In this research study the Sustainability-oriented Water Allocation, Management, and Planning (SWAMPOM) model for the Oldman River Basin is developed. SWAMPOM comprises a water allocation model, dynamic irrigation demand, instream flow needs (IFN), and economic evaluation sub-models. The water allocation model allocates water to all the above-mentioned demands at a weekly time step from 1928 to 2001, and under different water availability scenarios. Meeting irrigation demands relies on the crop water requirement (CWR), which is calculated under different climatic conditions by the dynamic irrigation demand sub-model. This sub-model estimates the weekly irrigation demand for main crops planted in the basin. SWAMPOM also computes environmental demands or instream flow need (IFN) for the Oldman River, and allocates water to rivers to meet IFN under different policy scenarios and uncertain water supply. Finally, the major water-related economic benefit in the basin, earned by agriculture and hydropower generation, is computed by the economic evaluation sub-model. The results show that SWAMPOM could reasonably satisfy the demands at a weekly time step and provide an adequate estimation of the crop water requirement under different hydrometeorological conditions. Based on the SWAMPOM’s results, the average annual irrigation demand is 306 mm over the historical time period from 1928 to 2001 in the main irrigation districts. The average weekly instream flow need of the Oldman River is calculated to be approximately 20.5 m3/s, which can be met in more than 97% of weeks in the historical time period. Average annual water-related economic benefit was computed to be 192.5 M$in the OMRB. It decreased to 82.8 M$ in very dry years, and increased up to 328.6 M$ in very wet years. This research also developed different sets of Oldman Reservoir’s operation zones, resulting in trade-offs between the optimal economic benefit, water allocated to the ecosystem, minimum floodwater and minimum flood frequency. This helps decision makers to decide how much water should be stored in the reservoir to meet a specific objective while not sacrificing others. A multi-objective performance assessment, Pareto curve approach, is applied to identify the optimal trade-offs between the four objective functions (OFs), and 18 different optimal, or close to optimal sets of operating zones are provided. The decision regarding the operating zones depends on decision makers’ preference for higher economic benefit, water allocated to IFN, or flood security. However, the set of operating zones with minimum floodwater causes 11 less flood events; the operating zones with maximum economic benefits result in 4.1% more financial gain; and the zones with maximum water allocated to IFN lead to 10.1% more ecosystem protection in the whole 74 years, compared to current zones

Sustainable design of biorefinery processes: existing practices and new methodology

Nowadays, eco-designing products is increasingly practiced. The next challenge for sustain- ability is to optimize production processes. Biorefi neries are particularly concerned with this improve- ment, because they use renewable resources. To identify the contribution of transformation processes to the overall environmental impacts, Life Cycle Assessment (LCA) appears as the adequate method. A literature review highlights that LCA is mainly performed on biorefi neries to compare biomass feed- stocks between them and to a fossil reference. Another part of environmental LCA compares the impacts of different processing routes. Nevertheless, these evaluations concern already designed pro- cesses. Generally, processes are considered as a unique operation in assessments. However, some criteria like operating can notably modify environmental burdens. The eco-design of biorefi nery pro- cesses can be guided by coupling process simulation to LCA. This method has been emerging in the chemical sector in recent years. Consequently, this paper proposes a new methodological approach to assessing the complete sustainability of biorefi nery processes, since its fi rst design stages. In addi- tion to coupling process simulation and environmental LCA, the other pillars of sustainability will be assessed. Indeed, Life Cycle Costing and Social Life Cycle Assessment can be performed to obtain an integrated methodological framework. The simultaneous optimization of the environmental, economic, and social performances of the process can lead to antagonist ways of improving. Consequently, compromises should be realized. Thereby, the multi-objective optimization can be accomplished by a metaheuristic method supported by a decision-making tool. Finally, the main limits of this method and some perspectives and ways for improving are discussed

Metodologias para projeto de processos químicos na solução de problemas ambientais

Nas últimas décadas, discussões sobre sustentabilidade têm colaborado para muitas iniciativas de proteção ambiental. Avanços sobre normas ambientais e compromissos internacionais têm sido propostos para controlar os impactos ambientais locais e globais. A indústria química tem papel relevante neste cenário. Emissões industriais são descartadas rotineiramente em compartimentos ambientais e, quando essas emissões ultrapassam limites de capacidade de suporte de ecossistemas, danos ambientais são identificados. Esses problemas são enfrentados com o projeto ambientalmente consciente de processos químicos, o qual compreende três elementos-chave: (1) métricas para avaliação ambiental, (2) técnicas de prevenção da poluição e (3) métodos para consideração da variável ambiental no projeto. Um vasto conjunto de métricas para avaliação ambiental é identificado na literatura. Diferentes propriedades e fundamentos são encontrados nessas várias métricas, o que torna complexo o emprego na análise de processos. Nesta tese, são analisadas em detalhe as propriedades dos índices Waste Reduction Algorithm (WAR), Standard Chemical Exergy (SCE) e Sustainable Process Index (SPI). Um novo índice chamado Environmental Potential of Emissions (EPE) foi desenvolvido para agregar as propriedades de WAR e SCE, relevantes para a avaliação de desempenho ambiental de processos químicos. Esta tese aborda metodologias que empregam o projeto ambientalmente consciente de processos químicos para solução de dois problemas correntes na indústria, a compensação ambiental e a seleção de tecnologias sustentáveis. As metodologias desenvolvidas integram técnicas de prevenção da poluição a problemas de otimização definidos a partir de critérios econômicos e ambientais. Os critérios ambientais são introduzidos por meio de um modelo proposto para permitir a comparação entre o potencial de impacto ambiental do processo e metas estabelecidas. A aplicação dos métodos desenvolvidos nesta tese revela a efetividade de projetos de integração de processos para reduzir impactos e compensar danos ambientais derivados de processos industriais em operação. A seleção de tecnologias para novos projetos sustentáveis é abordada por método alternativo baseado na avaliação do tempo de retorno para efetivação dos benefícios ambientais alcançados por processos benignos do ponto de vista ambiental. Os resultados desse trabalho são obtidos a partir de estudos de caso baseados em processos químicos típicos.In the last decades, discussions about sustainability have collaborated for many environmental protection initiatives. Advances on environmental regulations and international commitments have been proposed for control of local and global environmental impacts. The chemical industry has an important role in this scenario. Industrial emissions are often discarded on environmental compartments and damages are identified when these emissions exceed the supportability of ecosystems. These problems are faced by the environmentally conscious design of chemical processes which has three key elements: (1) metrics for environmental assessment, (2) pollution prevention techniques and (3) methods to consider the environmental variable in the project. A broad set of environmental assessment metrics can be found in the literature. Different properties and fundamentals are found in these several metrics making complex the analysis of processes. In this thesis, the properties of the indices Waste Reduction Algorithm (WAR), Standard Chemical Exergy (SCE) and Sustainable Process Index (SPI) are detailed. A new index called Environmental Potential of Emissions (EPE) was developed to aggregate the WAR and SCE properties that have an important role for the environmental performance assessment of chemical processes. This work addresses methodologies for the use of the environmentally conscious design of chemical processes to solve two actual problems of the industry, the environmental compensation and the selection of sustainable technologies. The developed methodologies integrate the pollution prevention techniques to optimization problems defined from economic and environmental criteria. The environmental criteria are introduced through a proposed model to enable comparison between the environmental impact potential of the process and goals. The application of the methods developed in this thesis reveals the effectiveness of the process integration design to reduce impacts and to compensate environmental damages from the operation of industrial processes. The selection of technologies for new sustainable designs is addressed by alternative method based on the evaluation of the return time for realization of environmental benefits achieved by benign processes of environmental point of view. The results of this work are achieved from case studies based on typical chemical processes