Energy Efficiency Of Plant Research Articles

Energy efficiency in large industrial plants. Legislative aspects

Energy efficiency in large industries in Latvia has a great potential. To stimulate energy efficiency in industrial sector Latvia has chosen to impose special requirements supplementing the requirements than came from EU Directives. Energy Efficiency Law that came into force in March 2016 impose energy audits or energy management systems to large consumers and large enterprises with aim to introduce at least three energy efficiency improvement measures recommended by the energy management system or energy audit with the highest estimated energy savings or economic return. There has been a public turmoil since Energy Efficiency Law came into force, however latest publications have shown that public opinion has changed to more positive as the number of consumers, who had fulfilled the requirements, grows, and the energy efficiency benefits becomes perceptible.

Optimizing the heat transfer performance of the recovery boiler superheaters using simulated annealing, surrogate modeling, and computational fluid dynamics

The energy efficiency of recovery boiler power plants is largely influenced by the heat transfer to the superheaters. In the design process of such very large-scale applications, one of the key challenges is the a priori geometry optimization by robust numerical approaches. The main objectives of this work are to demonstrate a numerical optimization framework and to optimize the geometry of the superheater region to enhance the heat transfer. The framework is implemented as a surrogate-based optimization method, which combines simulated annealing, local polynomial regression, and computational fluid dynamics. The novelty of this work consists of the following: 1) The optimization framework is designed and introduced. 2) The connection between the geometry and heat transfer is quantified by formulating the optimal design curve. 3) The optimal design for a typical, existing recovery boiler is identified. The results indicate that the uniformity of the flow field is improved, and the heat transfer rate is increased by 5%. 4) The results indicate the importance of minimizing the separation vortices through the geometrical design with a strong linkage to the overall heat transfer rate. 5) The potential of optimization methods in this very large-scale energy production application is demonstrated for the first time.

Comparative energy efficiency of wastewater treatment technologies: a synthetic index approach

Improving the energy efficiency of wastewater treatment plants (WWTPs) provides notable economic and environmental benefits to society. Several studies have benchmarked the energy performance of WWTPs, but they did not take into account for differences in the wastewater treatment technologies they used, thus obscuring their relative efficiencies in removing harmful pollutants. To overcome this shortcoming, this study assessed and compared the energy efficiencies of five wastewater treatment technologies. To do so, the metafrontier approach was used in order to account for the technological differences among plants in removing pollutants. The results evidenced that energy efficiencies for WWTPs using attached-growth processes were higher than for WWTPs using suspended-growth technologies as secondary treatment. Moreover, higher pollutant removal efficiencies associated with biological removal of nutrients compensated for the higher energy requirements of this technology, making these WWTPs more energy efficient in the removal of pollutants. The results of this study provide essential information for improving the sustainability of current WWTPs and can support decision-making in the planning of new wastewater treatment facilities.

Enhanced chiller fault detection using Bayesian network and principal component analysis

Applying the fault detection (FD) techniques to chiller is beneficial to reduce energy use in buildings and to enhance the energy efficiency of refrigeration plants. The purpose of this study is to propose an enhanced chiller FD method with higher accuracies for field applications by combining Bayesian network (BN) and principal component analysis (PCA). The key paths are as follows: first, the data space represented by the normal data is decomposed into two subspaces by the PCA, i.e., principle component (PC) subspace and residual (R) subspace; second, instead of PC subspace, the score matrixes in R subspace are used to develop the BN model. The performance of the proposed method is evaluated by using the experimental data from ASHRAE RP-1043. Test results show that the accuracies are significantly improved by 43% at most (for condenser fouling at Level 1), especially for these faults at slight severity levels.

Robustness enhancement for chiller sequencing control under uncertainty

Chiller sequencing control is an important technique for achieving energy efficiency of multi-chiller plants while not sacrificing indoor thermal comfort. Available typical controls, such as bypass flow-based control and direct power-based (P-based) control, uses individual indicator to switch chillers on or off. However, these controls suffer from various uncertainties in operation and may lead to insufficient cooling supply, unstable operation, or energy waste. A simple but practical way to enhance the robustness of chiller sequencing control is to explore and make use of the complementarity of different load indicators. Hence, this paper presents three methods to enhance the robustness of chiller sequencing control by hybridizing the use of different load indicators. Numerical studies are used to analyze the robustness of the enhanced controls under different levels of uncertainty.

Thermodynamic, Economic and Environmental Evaluation of an Improved Ventilation Air Methane-Based Hot Air Power Cycle Integrated with a De-Carbonization Oxy-Coal Combustion Power Plant

Efficient utilization of ventilation air methane (VAM) as well as improving the energy efficiency of de-carbonization oxy-coal combustion power plants are intensively studied for achieving energy savings and greenhouse gas (GHG) emission control. Here, an improved VAM-coal hybrid power generation system, which integrates a VAM-based hot air power cycle with a de-carbonization oxy-coal combustion circulating fluid bed (CFB) power plant was proposed. In the proposed system, part of the boiler flue gas was bypassed to feed the VAM auto-oxidation, and the whole VAM oxidation heat was efficiently utilized to drive a hot air power cycle. Meanwhile, the turbine exhaust air was utilized to heat the feed/condensed water within the regenerative heating trains in a cascade way, which was in turn beneficial to de-carbonization oxy-coal combustion plant. The mass and energy balance of the proposed system were determined using the simulation process. The thermodynamic benefits, economic viability and the environmental impacts were discussed. Results showed that energy efficiency of the proposed system reached 27.1% with the energy saving ratio at 0.9%. The cost of electricity (COE) was $118.15/MWh with the specific CO2 emission as low as 17.46 kg CO2/MWh.

Improved Configurations For Liquefied Natural Gas Cycles

The most important challenge in a natural gas liquefaction plant is to improve the plant energy efficiency. A process topology should be implemented, which results in a considerable reduction of energy consumption as the natural gas liquefaction process consumes a large amount of energy. In particular, system design focusing on configuring cold part cycle is an attractive option. In this study, various energy recovery-oriented process configurations and the potential improvements of energy savings for small- & midscale liquefied natural gas plants were proposed and compared with almost exclusively commercial trademarks processes. These improved simulation based investigations were validated under the variation in feed gas pressure, mixed refrigerant cooling reference temperature and the pinch temperature of cryogenic plate fin heat exchanger. The simulation results exhibited considerable reduction of specific total energy consumption. Therefore, the proposed liquefaction cycles have a simple topology, hence lower capital cost and compacter plant layout, which is compatible for power-efficient, offshore, floating liquefied natural gas liquefaction plants.

Modular life cycle assessment of municipal solid waste management

Life cycle assessment (LCA) is commonly applied to examine the environmental performance of waste management systems. The system boundaries are, however, often limited to either one tonne of material or to specific waste treatments and are, therefore, lacking a systems perspective. Here, a framework is proposed to assess complete waste management systems based on actual waste flows, assessed with a detailed material flow analysis (MFA) in a modular MFA/LCA approach. The transformation of the MFA into a product-process-matrix facilitates a direct link between MFA and LCA, therefore allowing for the assessment of variations in flows. To allow for an up-to-date and geographically specific assessment, 190 LCA modules were set up based on primary industrial data and the ecoinvent database. The LCA modules show where there have been improvements in different recycling processes over the past years (e.g. for paper recycling) and highlight that, from an environmental perspective, closed-loop recycling is not always preferable to open-loop recycling. In a case study, the Swiss municipal solid waste management system, of which there is already a detailed MFA, was modeled using the new LCA modules and applying the modular MFA/LCA approach. Five different mass flow distribution scenarios for the Swiss municipal solid waste management system were assessed to show the environmental impact of political measures and to test the sensitivity of the results to key parameters. The results of the case study highlight the importance of the dominant fractions in the overall environmental impacts assessment; while the metal fraction has the highest impact on a per kilogram basis, paper, cardboard, glass and mixed municipal solid waste were found to dominate the environmental impacts of the Swiss waste management system due to their mass. The scenarios also highlight the importance of the energy efficiency of municipal solid waste incineration plants and the credits from material substitution as key variables. In countries with advanced waste management systems such as Switzerland, there is limited improvement potential with further increases in recycling rates. In these cases, the focus of political measures should be laid on (i) the utilization of secondary materials in applications where they replace high-impact primary production, and (ii) an increased recovery of energy in waste-to-energy plants.

Підвищення енергоефективності виготовлення залізорудних котунів на фабриках огрудкування

Production of iron ore pellets requires considerable energy, since the energy costs of pellets is over 20 %, which is an important issue for pelletizing plants. The aim of the article is to substantiate and develop a systematic approach to manage energy resources pelletizing plant with increased energy efficiency in the production of iron ore pellets. On the basis of strategic energy indicators, functionals are assigned to manage the energy resources in general for the pelletizing plant and, on their basis, functionals are formed for the energy consumption of aggregates and mechanisms in the sections: the composition of bentonite and limestone, grinding, pelletizing, burning, sorting and dispatch of pellets, taking into account the adjustment functions dispatcher and actual consumption of energy resources by each site object. Using a system approach to manage the energy efficiency of the pelletizing plant, it has been possible to develop a flowchart of an automated energy efficiency management system based on the use of functionals that determine: the volumes of consumption of energy resources of the pelletizing plant and individual sections, specific energy costs by mechanisms and aggregates of sites for certain types of work, output by production sites. The introduction of an automated system for managing the plant's energy resources, based on a systematic approach, will increase energy efficiency, which will help reduce energy costs, improve the quality of pellets, increase profitability, and strengthen the financial standing of the factory of justification. Key words: pelletizing factory, pellets, energy consumption, energy efficiency, system management, automated control system

A novel energy assessment of urban wastewater treatment plants

Wastewater treatment is a high energy consuming process, and its energy demand is considerably increasing due to the introduction of more restrictive standards on the quality of water effluents, that require advanced technologies for pollutant removal. Energy audits are carried out in order to improve energy efficiency of wastewater treatment plants, by introducing some measures, such as adjustments of the treatment scheme, or optimization of existing operational units. At the same time, energy recovery from wastewater treatment and its by-products is being implemented in order to reduce economic costs and environmental impact of the process. In order to assess the benefits resulting from implementation of these interventions, procedures for evaluation of energy performance of wastewater treatment plants are being developed.In this work, a novel method is proposed for assessing energy performance of wastewater treatment plants by coupling simple energy performance indicators with specific pollution removal efficiencies. This procedure is applied to a large database of wastewater treatment plants, in order to define some classes of energy performance depending on removal efficiency. The method is also used to analyse some Italian plants, representative of different design and management conditions. As a result, only 8.2% of around 300 plants presents the highest class of performance, considering the energy consumption related to the organic matter removal.

Effects of Oxy-Fuel Combustion on Performance of Heat Recovery Steam Generators

The performance of steam power plants, utilizing recovered waste heat from air-fuel and oxy-fuel combustion, are compared. Temperature profiles in the heat recovery steam generator (HRSG), steam production rate, net-work output and energy efficiency are simulated for different conditions. Investigations are made into the effect of varying pinch point on HRSG performance, net-work and energy efficiency for power generation utilizing oxy-fuel combustion. It is found that with increased pinch point there is an associated decrease in HRSG and steam plant efficiencies. Exhaust gas composition influences the energy efficiency of the power plant. When air-fuel and oxy-fuel combustion are compared there is a reduced amount of nitrogen in the oxidant stream in the latter case. When comparing air-fuel and oxy-fuel combustion, a considerable deviation in HRSG and steam power plant performance is exhibited, with oxy-fuel combustion offering benefits in system efficiency and plant output. The exhaust gas composition at the HRSG inlet contributes significantly the performance characteristics of the system. Raising the HRSG inlet temperature also increases power generation and system efficiency. The results provide insights into the use of oxy-fuel combustion for systems utilizing HRSG for power generation while demonstrating the influence of gas composition, pinch point, and exhaust gas temperature on system performance, and suggest that oxy-fuel combustion can help enhance the contribution to sustainable development of some energy systems.

Using Field Data for Energy Efficiency Based on Maintenance and Operational Optimisation. A Step towards PHM in Process Plants

Energy saving is an important issue for any industrial sector; in particular, for the process industry, it can help to minimize both energy costs and environmental impact. Maintenance optimization and operational procedures can offer margins to increase energy efficiency in process plants, even if they are seldom explicitly taken into account in the predictive models guiding the energy saving policies. To ensure that the plant achieves the desired performance, maintenance operations and maintenance results should be monitored, and the connection between the inputs and the outcomes of the maintenance process, in terms of total contribution to manufacturing performance, should be explicit. In this study, a model for the energy efficiency analysis was developed, based on cost and benefits balance. It is aimed at supporting the decision making in terms of technical and operational solutions for energy efficiency, through the optimization of maintenance interventions and operational procedures. A case study is here described: the effects on energy efficiency of technical and operational optimization measures for bituminous materials production process equipment. The idea of the Conservation Supply Curve (CSC) was used to capture both the cost effectiveness of the measures and the energy efficiency effectiveness. The optimization was thus based on the energy consumption data registered on-site: data collection and modelling of the relevant data were used as a base to implement a prognostic and health management (PHM) policy in the company. Based on the results from the analysis, efficiency measures for the industrial case study were proposed, also in relation to maintenance optimization and operating procedures. In the end, the impacts of the implementation of energy saving measures on the performance of the system, in terms of technical and economic feasibility, were demonstrated. The results showed that maintenance optimization could help in reaching an energy costs recovery equal to the 10% of the total costs for an electric motor system.

Effects of Storage Conditions, Total Solids Content and Silage Additives on Fermentation Profiles and Methane Preservation of Cattle Manure Before Anaerobic Digestion

The impacts of storage conditions, total solids content and silage additives were investigated at laboratory scale for cattle manure during up to 120 days. Wheat straw was used as co-substrate in the study of the effects of total solids content. Glucose and starch were used as model molecules of sugar-rich co-substrates. Single-handedly cattle manure lost 37% of its original methane potential after 120 days of anaerobic storage. This was essentially caused by the low total solids content and by the absence of water soluble carbohydrates in the feedstock. Wheat straw addition decreased moisture content and enabled cattle manure stabilization for a pH of 6.0. In contrast, extensive heterofermentative lactic acid bacteria fermentation occurred during co-ensiling with glucose and the pH quickly dropped to values below 4.0. Starch was used as substrate for fermentation but its hydrolysis limited bacterial activity and acidification. Finally, all the three co-substrates led to minimal methane potential losses after 120 days of storage. Co-ensiling will improve the energy efficiency of agricultural biogas plants that use stored cattle manure as feedstock.

ПРОМІЖНЕ ОХОЛОДЖЕННЯ ЦИКЛОВОГО ПОВІТРЯ В ГАЗОТУРБІННИХ УСТАНОВКАХ АЕРОТЕРМОПРЕСОРАМИ

Existing technologies to improve the fuel and energy efficiency of gas turbine plants due to intercooling of the cycle air are analyzed. One of the promising ways for increasing the efficiency of such technologies is using thermogasdynamic compression in the heat recovery processes of secondary energy resources. A feature of this process is the pressure rate increase due to the instant evaporation of a finely dispersed liquid is injected into the air stream which accelerated to the speed of sound. When the pressure of the boiling liquid is increased, the power consumption for compressing the working fluid (cyclic air) is reduced, the efficiency is increased and the consumption of the fuel and energy resources of the gas turbine plant is reduced.The advantages of cooling technology with an aerothermopressor are outlined in the article. The aerothermopressor is a multifunctional jet apparatus, whose work consists in injecting water into the stream of cyclic air when it is compressed in the gas turbine plant compressor. If this apparatus is used for cooling of cycle air, it will be compensate for aerodynamic losses along the air path and it will reduce compression work in the compressor, increase the consumption of the working fluid and, as a result, increase the gas turbine plant power. The basic schemes of the aerothermopressor installation between the stages of low and high pressure compressors are considered. Theoretical thermodynamic cycles of such gas turbine plants are presented and the advantage of using a contact cooler for intercooling of the cyclic air in comparison with surface air coolers for intercooling is defined in this paper.The proposed cooling technology makes it possible using low-potential heat of secondary energy resources of gas turbine plants (heat of cyclic air), the utilization of which by traditional methods is problematic because the temperature of waste heat sources is low.The tasks are determined, the solution of which will ensure the possibility of rational organization of cooling processes in the aerothermopressor, which in turn will allow achieving optimal parameters for increasing the efficiency of the gas turbine plant and reducing the specific fuel consumption in relation to the variable climatic conditions of operation

Process integration and design for maximizing energy efficiency of a coal-fired power plant integrated with amine-based CO2 capture process

System-wide integration of post-combustion CO2 capture process into a coal-fired power plant is an effective and practical strategy to improve cost-effectiveness for capturing CO2 emissions from the power sector. Considerable reduction of the net energy efficiency of a power plant by 20–40% is inevitable due to energy requirements for the CO2 capture and power requirement for the CO2 compression. Hence, this study focuses on minimizing the net efficiency penalty through integrated design of coal-fired power plant with CO2 capture process in a holistic and systematic manner. In order to analyze the techno-economic impact of integrated process on the net power plant efficiency, overall process models are developed in a commercial simulator Aspen Plus®, in which a 550 MWnet supercritical coal-fired power plant is simulated and validated. A pilot-scale post-combustion CO2 capture process based on MEA, together with CO2 compression, is modeled and scaled-up to meet the commercial-scale capacity. Simulation-assisted optimization is performed to enhance the overall performance of capture-integrated power generation through fully exploiting system interactions and examining relevant economic trade-offs. A case study is carried out to evaluate the effect of several heat integration options and demonstrate a considerable benefit for reducing the net efficiency penalty.

Thermodynamic assessment of SNG and power polygeneration with the goal of zero CO2 emission

The current coal-to-SNG (synthetic natural gas) projects are facing two main issues, addressing on insufficient energy utilization and large amount of carbon emissions. For this reason, we proposed a coal-based SNG and power cogeneration process, at the ability to achieve high-efficiency and achieve zero-energy-penalty separation of CO2, by incorporation with chemical looping combustion (CLC). The main objective of this paper is to estimate thermodynamic performances under the effects of key parameters in order to pre-examine whether the proposed process is thermodynamically viable. At optimal condition (oxygen to carbon ratio (O/C) = 0.4, steam to carbon ratio (S/C) = 0.8 and recycling ratio of unreacted gas (Ru) = 3), the overall plant energy efficiency, exergy efficiency and energy saving ratio are 58.84%, 56.59% and 10.82%, respectively. The proposed process is compared with several traditional systems that aims to further demonstrate the superiority of such process design in terms of thermodynamic and preliminarily economic assessment. A sensitivity analysis is also included to examine the effects of different coal feedstocks and oxygen carriers of CLC on system performances.

MANAGEMENT OF GAS-AIR ENERGY INSTALLATION OF INDUSTRIAL ENTERPRISE

Purpose. The goal of the work is to substantiate the issue of effective use of kinetic energy of gas-air flows used by the technological installation for generating electric power, which will allow developing a new control algorithm and creating new software for controlling the gas-air power plant. To test the adequacy of the developed control algorithms and software, to develop a laboratory gas-air power plant.Methodology. To investigate the distribution of air-gas mass in process plants used industrial plant simulation method performed in software SolidWorks Flow Simulation. The method of simulation allowed to develop a new control algorithm and create new software taking into account the basic technical requirements for the management of the gas-air power plant. To test the efficiency of the developed algorithms and control software for the gas-air power plant, a physical modeling method was used on a developed laboratory installation connected via a USB interface with a computer and has a virtual model of the SCADA system presented in the LabVIEW environment.Findings. Based on the modeling of gas-air flows on the developed mathematical model, the optimal ratios of pipeline sizes are rationally determined, the gas-air mixture costs necessary for the most efficient operation of the gas-air power plant, that is, in the working zone of the gas-air path, the generator screw contacts the most significant flows, providing the maximum effect rotation. The obtained results of research of gas-air flows of technological installations of an industrial enterprise in the software environment of SolidWorks Flow Simulation and on their basis the basic technical requirements for the management of a gas-air power plant are developed. An optimal control algorithm has been developed that enabled it to be introduced into the control scheme of a gas-air power plant with a microprocessor or a specialized microcontroller.Originality. New possibilities for further improvement of the known basic mathematical models of the kinetics of gas-air flows have been found and variants of adaptation in the field of gas dynamics have been proposed for estimating the expenditure of gas-air flows during the operation of a fan installation on a pipeline. The structural scheme and algorithms for controlling the gas-air power plant are developed, which includes a fan, a generator, a pipeline and a control unit based on the use of the Arduino Uno microcontroller. The algorithm of the subroutine for connecting the gas-air power plant with the SCADA system.Practical value. The proposed method of generating electric power by a gas-air power plant with a microprocessor control system, as shown by calculations confirmed by experimental studies on a laboratory installation, allows to reduce up to 20% of the amount of spent electricity by a process unit and can be used in industrial conditions. The introduction of gas-air power plants with a microprocessor system and a SCADA system will improve the energy efficiency of process plants.

Study on Energy Efficiency of Several Different Roof Plants in Wuhan

Study on Energy Efficiency of Several Different Roof Plants in Wuhan

Bio-DME production based on conventional and CO2-enhanced gasification of biomass: A comparative study on exergy and environmental impacts

In this study, a novel single-step synthesis of dimethyl ether (DME) based on CO2-enhanced biomass gasification was proposed and simulated using ASPEN Plus™ modelling. The exergetic and environmental evaluation was performed in comparison with a conventional system. It was found that the fuel energy efficiency, plant energy efficiency and plant exergetic efficiency of the CO2-enhanced system were better than those of the conventional system. The novel process produced 0.59 kg of DME per kg of gumwood with an overall plant energy efficiency of 65%, which were 28% and 5% higher than those of conventional systems, respectively. The overall exergetic efficiency of the CO2-enhanced system was also 7% higher. Exergetic analysis of each individual process unit in both the CO2-enhanced system and conventional systems showed that the largest loss occurred at gasification unit. However, the use of CO2 as gasifying agent resulted in a reduced loss at gasifier by 15%, indicating another advantage of the proposed system. In addition, the life cycle assessment (LCA) analysis showed that the use of CO2 as gasifying agent could also result in less environmental impacts compared with conventional systems, which subsequently made the CO2-enhanced system a promising option for a more environmental friendly synthesis of bio-DME.

Co-production of Hydrogen and Copper from Copper Waste Using a Thermochemical Cu–Cl Cycle

A novel hybrid Cu–Cl thermochemical cycle is developed and assessed for the co-production of hydrogen and copper using copper waste. An experiment is also conducted to establish the high-temperature electrolytic step as a proof of concept. A detailed parametric study is conducted to assess the effects of such parameters as process step temperature and energy efficiency of the electrical power plant that provides electricity to the cycle on the energy and exergy efficiencies of the overall cycle. The values of the energy and exergy efficiencies of the cycle are 31.8 and 69.7%, respectively. The maximum specific exergy destruction occurs in the electrolytic step. The results show that the proposed cycle performs better in terms of energy and exergy efficiencies compared to similar four-step Cu–Cl cycles. Using the proposed cycle, a new avenue may be open for copper waste to be more advantageously managed, potentially enhancing the sustainability of the relevant processes through improved environmental prote...