Utility Consumption Research Articles

Process simulation of integrated palm oil mill, refinery and oleochemical processes

Processes involved in the palm oil industry can be categorized into three main operations; upstream operation (planting and milling), midstream operation (physical/chemical refining), and downstream operation (palm-based oleochemical processing). For the last few years, some industrial key players have emphasized a change from stand-alone operations towards an integrated manufacturing facility. This has become the basis idea for integration of palm-based production processes. It includes material integration, shared energy and utility resources and waste-to-feed utilization. Integrated process however, involves a complex network; thus, the process has to be simulated to analyze its feasibility in terms of process throughput and material, energy and utility consumption. Hence, this paper addresses the basis to simulate the integrated palm oil process using process simulator Aspen Plus V8.6 for its dynamic capabilities in adjusting process variables to meet the required capacity for a target product. This study is critical in providing a basis and overview of the typical processes in palm oil industry and the possible interrelations associated with the proposed integrated facility for palm oil-based production.

OPTIMIZATION OF ENERGY UTILITIES CONSUMPTION IN THE AQUEOUS SODIUM HYDROXIDE SOLUTION EVAPORATION

The paper proposes the retrofit design of a three-unit evaporator for evaporating of aqueous sodium hydroxide solution in order to increase its concentration. The retrofit assumes the creation of a heat exchange equipment network that has to implement heat recovery of the process streams of the evaporator. The design was carried out with the pinch-analysis methods. The treshhold problem (demand for hot utilities only) was identified by shifting the composite curves and the treshhold temperature difference 11,7 °С was found. Problem definition, like a pinch problem, was made with the choice of minimum temperature difference DTmin = 12 °С in heat exchange equipment. The design of the heat exchangers network that realizes the minimum consumption of external utilities and maximum energy recovery was created, and the network optimization with energy relaxation was carried out. Modern plate heat exchangers as heat exchange equipment were chosen and calculated. The economic evaluation of the design was conducted. The payback period will be about two months.

Vapor recompression with interreboiler in a ternary dividing wall column: Improving energy efficiency and savings, and economic performance

This work deals with a ternary dividing wall column (DWC) for improving its energetic and economic potential through thermal intensification route. In this light, a vapor recompression heat pump system in conjunction with an interreboiler (IR) is proposed to configure externally with the classical DWC scheme that allows heat transfer through the dividing wall. Formulating a variable manipulation policy at dynamic state, it is investigated that the vapor recompressed DWC with inter and bottom reboiler (VRDWCIBR) shows a better performance than the VRDWC with either bottom reboiler or interreboiler(s). For a ternary hydrocarbon system, the VRDWCIBR secures the best performance, providing a 81.05% savings in utility consumption (which is double to that of DWC) with a thermodynamic efficiency of 55.60% and a payback time of 2.82 years. The proposed heat integration arrangement can be retrofitted with a little modification in the classical DWC column.

Heat transfer enhancement to decrease the energy consumption of a Light Naphtha Isomerization unit by means of heat exchanger network retrofitting

The Light Naphtha Isomerization (LNI) process increases the quality of gasoline, and the Pinch Design Method (PDM) is a novel method in the field of heat transfer that implements the design of Heat Exchanger Network (HEN) to improve energy efficiency. In this research, the HEN of an LNI unit was retrofitted using PDM to determine the best design to decrease hot and cold utility consumption. Stream selection and data extraction were necessary for PDM, and graphical tools in the form of Composite Curves (CC) and a Grand Composite Curve (GCC) were presented to calculate the minimum and actual hot and cold targets. The base-case results showed minimum hot and cold targets of 37 and 42 MW for ΔTmin = 10 °C, respectively and an energy pocket above the pinch in the interval of between 120 and 180 °C. The pocket enhanced heat recovery because of the large driving forces, decreasing MP steam consumption. Scenarios were suggested for the retrofitting of the LNI unit to enhance heat transfer to decrease energy consumption. In particular, the heat pump intensified heat transfer from the Cooling Water cold utility at 29.5 °C to the MP Steam hot utility at 150 °C.

Multi-objective Operational Optimization of a Hydrotreating Process Based on Hydrogenation Reaction Kinetics

Utility consumptions in hydrotreating (HDT) units are rapidly increasing because more heavy and sour crude oil are being processed to satisfy the increasing market demand of clean fuels, which then cause the direct and indirect emissions of CO2 and SO2. The environmental impacts of utilities should be considered when optimizing an HDT unit. A multi-objective optimization is proposed to reduce the operating cost and environmental impacts of utilities and products based on hydrogenation reaction kinetics. A cracked diesel HDT unit is adopted to illustrate the proposed model which is solved by e-constrains method to obtain the Pareto fronts and three scenarios: minimum operating cost, minimum environmental impacts, and the best compromise. For all scenarios, increasing temperature and decreasing pressure can reduce both the operating cost and environmental impacts. The decreasing of sulfur content in product is at the expense of consuming more utilities. It is not always favorable when the sulfur content of ...

Assessing the energy intensity of alternative chemical and cryogenic natural gas purification processes in LNG production

The production of Liquefied Natural Gas (LNG) from natural gas reservoirs with high content of acidic compounds is expected to be a strategic and crucial issue for the development of the natural gas market in future decades. Therefore, the identification of alternative suitable processes for the synergistic natural gas purification and LNG production, when the amount of CO2 in the raw gas feed is high, and their comparative thermodynamic assessment, is necessary to foster a cleaner and efficient production of LNG.In this paper, the energy intensity of the classical chemical absorption units using aqueous solutions of Methyldiethanolamine (MDEA) and the novel Dual Pressure Low-Temperature Distillation process (DPD) operating in different national contexts is assessed by means of the Net Equivalent Methane analysis and the Energy Life Cycle Assessment. These methods return respectively the equivalent methane and the embodied non-renewable energy invoked by the two alternative processes in one operating year. In general, the primary energy required by the construction phases of both the systems results negligible compared to the operation phase, and most of the latter is due to the consumption of energy utilities, which is strongly dependent by the considered national context. According to the results obtained by means of both the methodologies, the DPD process is generally less energy intensive compared to MDEA: the DPD process results to be an efficient and promising technique to perform the synergistic natural gas purification and LNG production.

Integration of thermo-vapor compressors with phenol and ammonia recovery process for coal gasification wastewater treatment system

Current phenol and ammonia treatment process consumes a large amount of hot utilities to recover crude phenol and aqua ammonia, which includes 0.5 MPag steam (2.68 MW), 1.0 MPag steam (10.17 MW), and 2.5 MPag steam (1.97 MW) based on the benchmark treatment capacity of 100 t/h. This paper fixates on the further improvement of energy efficiency by process integration and innovation. A novel integrated process is proposed in this paper to abate utilities consumption. Two scenarios have been analyzed following the Grand Composite Curve. The results show that one of the new integrated processes performs better energy saving efficiency. It requires 53.7% (7.96 MWsteam) less hot utility consumption and 57.5% (6.86 MWcw) less cooling water consumption at the expense of 68.7% (662 kWelec) more electricity use, as suggested in simulation results. The estimated cost savings relevant to the improved process is 1.095 million US$/y, and the emission reduction is 5237 t CO2 e/y.

Analysis of Heat Cascade Through Process Components to Reduce the Energy Consumption in Industrial Systems

Energy savings result in economic and environmental benefits. Site-wide energy analysis of industrial systems considers all plant components, such as unit operations, heat exchangers, boilers, and turbines. This article presents the analysis of heat cascade through these components to reduce the overall energy consumption. As a consequence of the two first principles of thermodynamics, heat from hot utilities transferred to a process is gradually cascaded to the environment through process operations and exchangers. The enthalpy rate curves shift to ambient temperature through operations and exchangers; the difference between the outlet and inlet enthalpy rate curves of a system is equal to the flow rate of cascaded heat as a function of temperature. Reducing the energy consumption implies decreasing the flow rate of cascaded heat through process operations or exchangers in the entire temperature interval between the hot utility and the environment. Herein, the heat cascade is first analyzed to identify process operation modifications in order to reduce the utility consumption. Second, the heat cascade through a plant, including a boiler, a turbine, process operations, and exchangers, is represented on a single diagram for site-wide energy analysis. Third, the heat cascade through several processes is analyzed to integrate an industrial site. The proposed method provides benefits in comparison to foreground/background analysis and total site analysis, which are two commonly used approaches to identify energy-saving opportunities for industrial symbiosis. Analysis of heat cascade through individual operations and heat exchangers is simple and powerful, and its concepts can be used in software to identify energy-saving projects.

A Novel Divided-Wall Heat Integrated Distillation Column: Thermodynamic and Economic Feasibility

This work introduces a new divided-wall thermally integrated column that aims to enhance the thermodynamic reversibility of distillation operation. Dividing the cylindrical shell into two equal semicylinders by a vertical wall, they are proposed to operate under a diabatic condition under the framework of traditional heat integrated distillation column (HIDiC) scheme. This leads to transfer of the heat from the high- to low-pressure side through that wall, thereby reducing the utility consumption. In this way, this novel divided-wall HIDiC configuration attempts to utilize the internal energy source and thus improves its thermodynamic efficiency and economic performance. Simulating a binary wide-boiling system, it is observed that the proposed scheme secures a 42.30% savings in energy consumption with a payback period of 3.45 yr. Although the traditional HIDiC shows a better performance in terms of energy savings (50.80%) and payback time (3.31 yr), the proposed HIDiC is more practically relevant from the design and operational perspective.

Enrichment of syngas-converting mixed microbial consortia for ethanol production and thermodynamics-based design of enrichment strategies

BackgroundThe production of ethanol through the biochemical conversion of syngas, a mixture of H2, CO and CO2, has been typically studied using pure cultures. However, mixed microbial consortia may offer a series of benefits such as higher resilience and adaptive capacity, and non-sterile operation, all of which contribute to reducing the utility consumption when compared to pure culture-based processes. This work focuses on the study of strategies for the enrichment of mixed microbial consortia with high ethanologenic potential, investigating the effect of the operational conditions (pH and yeast extract addition) on both the ethanol yield and evolution of the microbial community along the enrichment process. The pH was selected as the main driver of the enrichment as it was expected to be a crucial parameter for the selection of carboxydotrophic bacteria with high ethanologenic potential. Additionally, a thermodynamic analysis of the network of biochemical reactions carried out by syngas-converting microbial consortia was performed and the potential of using thermodynamics as a basis for the selection of operational parameters favoring a specific microbial activity was evaluated.ResultsAll enriched consortia were dominated by the genus Clostridium with variable microbial diversity and species composition as a function of the enrichment conditions. The ethanologenic potential of the enriched consortia was observed to increase as the initial pH was lowered, achieving an ethanol yield of 59.2 ± 0.2% of the theoretical maximum in the enrichment at pH 5. On the other hand, yeast extract addition did not affect the ethanol yield, but triggered the production of medium-chain fatty acids and alcohols. The thermodynamic analysis of the occurring biochemical reactions allowed a qualitative prediction of the activity of microbial consortia, thus enabling a more rational design of the enrichment strategies targeting specific activities. Using this approach, an improvement of 22.5% over the maximum ethanol yield previously obtained was achieved, reaching an ethanol yield of 72.4 ± 2.1% of the theoretical maximum by increasing the initial acetate concentration in the fermentation broth.ConclusionsThis study demonstrated high product selectivity towards ethanol using mixed microbial consortia. The thermodynamic analysis carried out proved to be a valuable tool for interpreting the metabolic network of microbial consortia-driven processes and designing microbial-enrichment strategies targeting specific biotransformations.

Performance analysis of a heat integrated column with heat pumping

In this work, a heat pump system in the form of vapor recompression (VRC) is introduced in the dividing wall column (DWC) to further improve its thermal efficiency performance. It is a fact that the temperature difference is reasonably large between the top and bottom of a DWC, which typically produces at least a single side product. This may lead to a very large compression ratio (CR), with which, the operation of VRC in the DWC becomes quite complicated and may not be economically so attractive. To improve this situation, the vapor recompression mechanism is further proposed between the side stream and reboiler drum of the DWC column. Utilizing the latent heat of a vapor stream from an intermediate tray in liquid reboiling of the stripper, this side vapor recompressed DWC (SVR-DWC) configuration can reduce the utility consumption and thus improves its energetic and economic potential substantially. This proposed thermally integrated scheme is finally illustrated by a ternary system.

Innovative Path-Breaking “Cold Process” to Manufacture Sulphonating Agents and Sulphur-Based Chemicals

Manufacture of Sulphuric acid and Sulphonating agents underwent revolutionary change as a result of the inventive contact process using Vanadium Pentoxide catalyst in the 1950’s. The “Single-Contact Single-Absorption” process was widely used until the1970’s. The conversion efficiency of SO2 to SO3 was restricted to 96.5% resulting in stack emissions of 16 to 20 Kgs of Sulphur dioxide per ton of acid produced. Global warming and environmental concern prompted further improvement by introducing DCDA, Double-Contact Double-Absorption process. In the DCDA process the product SO3 was absorbed by introduction of Inter-Pass Absorption Tower (IPAT) keeping V2 O5 contact process unchanged. Thus, the overall conversion efficiency was raised to 99.5-99.7 %, thereby reducing Sulphur dioxide emissions to below 4 Kgs per ton of acid produced. This is today taken as an International Standard as recommended by Environmental Protection Agency of USA. Even so, at the current production level of over 150 million tons of Sulphuric acid per annum, this results into over one million tons of acid rain per year! This acid rain has serious impact on flora and fauna as well as aquatic life. The path-breaking “Cold Process” invented by Navdeep Enviro and Technical Service Pvt. Ltd, Mumbai (India), and for which a patent has been applied at the International Patent Agency in Geneva, is designed to produce Sulphuric acid and Sulphonating agents with zero emission of Sulphur dioxide, which totally eliminates acid rain. This paper outlines the techno economic features of the process, giving cost effectiveness of reduced plant area, lower maintenance costs, and higher cogeneration of steam with lower utility consumption.

The innvestigation of the process streams integration in the multi­effect evaporation plant for the concentration of sorghum syrup

The study on the integration of heat streams of the evaporation station for sorghum syrup concentrating is presented. The relevance of the research is is why the research, aimed at reducing the consumption of external energy and enhancing operating efficiency, is relevant and has practical value. The main purpose of the work is to create a scientifically substantiated design with enhanced economic indicators of operation, ensuring saving in consumption of hot utility (steam) and cooling water. The problem was solved using the pinch-analysis. Heat streams, requiring heating and cooling, were identified, and the alternative project based on the selection of the value of minimum temperature difference DT min ., was created. This value was calculated and substantiated based on the data on thermal streams. The stream of condensate of return steam, the heat excess of which had not been used so far, was added to the system. For the alternative project, the layout of heat exchange equipment was proposed, calculation of plate heat exchangers was performed. The designed network of heat exchangers made it possible to decrease the annual steam consumption by 18 %. Cost-effectiveness analysis was conducted by comparing the indicators for two of the projects of the syrup preheating department for the evaporation station. The proposed alternative project saves power consumption of cooling water by 35.9 kW, of heating vapor steam – by 60.5 kW. At the interest rate of profit tax of 18 %, implementation of the alternative project will pay off in 4 months. As a result, net annual gain of an enterprise is planned to increase by 16 %, at virtually the same payback period of the projects. Application of the methods of heat streams integration made it possible to develop an effective project of sorghum syrup preheating before evaporation and ensure saving of external utilities.

The influence of national holiday structure on domestic tourism expenditure

This study attempted to examine the influence of national holiday structure on the domestic tourism expenditure in the context of China. Using a multiprovincial survey data set from China National Tourism Administration, we developed a utility–consumption model to empirically analyze the consumption effects of Weekend Getaway, Paid Leave, National Day Golden Week Holiday, and National Festivals and Memorial Days (NFMDs). Results show that while the consumption effects of the first three types of holiday are significant and robust, the effect of NFMDs on tourism consumption is not statistically significant. This suggests that the first three types of holiday in China may function more effectively than NFMDs in promoting willingness to travel and tourist consumption. Policy recommendations and implications are discussed based on the study results.

Green initiatives and their competitive advantage for the hotel industry in developing countries

The purpose of this study is to identify the organisational capabilities that complement the adoption of a proactive environmental strategy, and the specific benefits that can arise from such a strategy. The study focuses on developing countries that depend heavily on the tourism industry, but where environmental problems challenge the future of this industry. The study proposes that learning orientation, innovativeness, and quality management positively affect the adoption of proactive environmental strategies. Based on empirical data from hotels in Thailand, PLS-SEM was applied to explore these relationships. The results confirm the hypotheses but also show that the green strategy positively affects environmental performance and organisational competitive advantage. More specifically, green strategies lead directly to positive environmental performance in terms of the consumption of utilities, waste management, and environmental risk management, leading to cost competitiveness and competitive advantage through differentiation.

A Process Systems Framework for Rapid Generation of Life Cycle Inventories for Pollution Control and Sustainability Evaluation.

Life Cycle Assessment (LCA) is a tool that aids in sustainable decision-making among product and process alternatives. When implementing LCA, the efficient and accurate modeling of chemical processes for Life Cycle Inventory (LCI) generation is still challenging. Challenges include a lack of systematic design and simulation tools and approaches to develop chemical process models for obtaining and analyzing more realistic LCI results. In this contribution, a novel process systems framework is proposed for estimating LCI results when implementing pollution control technologies. This framework involves the development and incorporation of pollution control unit (PCU) modules into process simulation and generation of LCI data associated with the PCUs for use in a sustainability evaluation. Different pollution control modules are designed for rapid LCI estimation and applied to obtain emissions, utility consumption, material, and land footprint results related to waste streams of a process simulation. Then, the LCI results are analyzed with the objectives of minimizing the environmental impact and utility consumption. The proposed framework is illustrated via a biomass/coal gasification process for syngas production with the end goal of acetic acid manufacturing. Results associated with this case study show that the developed framework can provide guidelines for sustainable decision-making based on generated LCI results.

Gate-to-Gate Energy Consumption in Chemical Batch Plants: Statistical Models Based on Reaction Synthesis Type

Energy consumption in the chemical industry is an important operating cost and environmental impact factor and reducing it is also explicitly mentioned as one of the key principles of green chemistry. Energy consumption has thus been included in diverse process design and evaluation tools as a key metric. However, measurements of energy consumption at the process equipment level are scarce, especially in fine chemical production typically performed in multiproduct and multipurpose batch plants. In this work, we present a shortcut approach based on statistical models, such as probability density functions (PDF) and classification trees, for estimating steam consumption which typically represents the highest energy utility consumption in batch plants. The output of these models is in the form of intervals derived from PDF interquartile ranges and as classes derived from the classification trees, respectively. The validation results (i.e., goodness of fit, cross validation, and case studies) show that the mo...

Improving energy efficiency in a complex natural gas refinery using combined pinch and advanced exergy analyses

A real-life case study of a Heat Exchanger Network (HEN) in a complex natural gas refinery was considered, using the pinch technology concept combined with advanced exergy analysis (so-called CPEA). This could be done by supertargeting, a tradeoff between capital and operational costs, applied to the five divided zones in the plant, based on the concept of zonal targeting method. It was shown that the potential of improvement on both the utility consumption and the heat recovery were about 36.09% and 42.65% respectively, so there was a huge potential of the energy saving relative to the existing network. Meanwhile, a new approach to the advanced exergy analysis of HENs has been proposed by considering ΔTmin = 0 °C in the well-developed Carnot factor-Enthalpy diagram of balanced exergy composite curves. Considering unavoidable exergy loss in the retrofitted network, it was shown that the CPEA method led to the exergetic efficiency of 88.27%, which shows more than 78% improvement compared with 49.45% of the existing network. So from practical points, the CPEA method represents a new attempt to develop a systematic framework to optimize complex HENs in energy systems, by using an integrated set of pinch and advanced exergy analyses, in order to reduce the energy consumption most efficiently, while strongly promoting cleaner production alternatives.

Optimization model for the design and feasibility analysis of membrane-based gas separation systems for CO2 enhanced coal bed methane (CO2-ECBM) applications

The purpose of this study is the development of an optimization model to design a coal bed methane (CBM) gas separation system using a multi stage membrane process. The proposed model is formulated using a nonlinear programming (NLP) technique and includes maximizing the total profit as the objective function, along with several constraints to fulfill the design specification under various scenarios. Using the proposed model, we can (i) identify the optimal system configuration and operation strategies such as the required membrane area, the number of stages, recycle strategies, and utility consumption; and (ii) analyze the cost contribution and major cost drivers that have effects on the system configuration and economics. We also investigate the sensitivity of major parameters, including the composition of the raw CBM feed and CH4 market price on the process configurations and operation strategies that affect the overall economics of the CBM production system.

Tackling increased CO2 concentration in feeds for existing acid gas removal units: A simulation study based on a customized CO2 kinetics model

ABSTRACTA Middle East-based amine sweetening unit, with an overall capacity of about 2.2 BSCFD of gas, is among the world’s largest process plants and currently processes sour gas with 10 mol% of hydrogen sulfide (H2S) and carbon dioxide (CO2) put together. Current expectation is that acid gas contents in the feed may increase beyond the design limit of the plant. The present work is an effort to quantify the effects of the feed gas CO2 increase on the plant and to proffer solutions to handle these effects efficiently. We revised the kinetics of amine-based CO2 absorption correlation of an existing model using real-data-driven parameters re-estimation. Evolutionary technique that employs particle swarm optimization algorithm is used for this purpose. The new CO2 kinetic model is inserted in a first-principle process simulator, ProMax® V4.0, in order to analyze various solutions necessary to mitigate the operational challenges due to increased feed CO2. The process plant with present design and operating conditions is determined to handle up to 8.45 mol% CO2 contents in the sour gas feed. Further results revealed that methyldiethanolamine, diethanolamine, and dimethyl ether propylene glycol (DEPG) could not handle this high feed CO2 challenge, even at maximum (design) steam and solvent usage. However, diglycolamine exclusively renders the solution as it treats high CO2 feed gas efficiently with allowable utility consumption, while satisfying the constraints imposed by product gas specifications.