Benchmarking energy utilization in cement manufacturing processes in Nigeria and estimation of savings opportunities

Nigeria is a leading producer of cement in Africa. Because cement production is energy intensive, with significant adverse impacts on the environment, an apparent need exists to assess the Nigerian cement industry to identify energy use mitigation options. The potentials for reducing energy use in typical Nigerian cement manufacturing plants, through the implementation of available energy efficiency measures, were assessed in this study, alongside the attendant costs of implementing those measures. To achieve these, using numerous globally available energy efficiency technologies and measures, energy conservation supply curves were constructed for three Nigerian cement manufacturing plants which operate on wet, semi-wet, and dry cement manufacturing processes, respectively. Comparisons with global best and Chinese benchmark plants with respect to thermal and electrical energy consumption were also made. The comparisons showed that, with respect to the global benchmark plants, thermal energy savings of between 19.83 and 52%, and electrical energy savings of between 35.23 and 43.10%, were possible. With respect to the Chinese benchmarks, thermal energy savings of 10.74–47.32%, and electrical energy savings of 20.95–30.17%, could be achieved. The plants considered performed significantly less than either of the benchmarks in terms of both thermal and electrical energy usage. The energy conservation supply curves for the plants showed that implementing the cost-effective energy efficiency measures could lead to energy savings of about 235,038, 237,913 and 374,055 GJ/year, for the wet, semi-wet, and dry cement manufacturing plants, respectively. Furthermore, technically feasible efficiency measures could yield energy savings of about 250,272, 259,795 and 395,447 GJ/year, respectively. Achieving these savings will improve profitability in the Nigerian cement industry and make the unused energies available for utilization in other sectors of the Nigerian economy.     

Desalination by distillation and by reverse osmosis — trends towards the future

As the requirement for fresh water increases worldwide, there is a need for more and more plants that are able to treat non-conventional water sources. Sea water has become an important source of fresh water in many arid regions. This feature provides an overview of recent process improvements in sea water desalination using reverse osmosis, multi-stage flash, multi-effect distillation and electrodialysis. Areas discussed include the use of alternative energy sources (wind energy, solar energy and nuclear energy) for reverse osmosis or distillation processes, and the impact of the different desalination process on the environment. Also covered are the implementation of hybrid processes in sea water desalination, and the pretreatment of desalination plants by pressure-driven membrane processes.     

Sustainable multi-period electricity planning for Iskandar Malaysia

This paper presents the current situation and projected planning of the electricity generation sector for Iskandar Malaysia by implementing a model to optimise the cost, utilise the usage of available renewable energy sources, and achieve carbon dioxide reduction targets. This Mixed Integer Linear Programming model was developed with the main objective of minimising the total cost of electricity generation, taking into consideration energy demand, reserve margin, electricity generation, peak and base generation, resource availability, and CO₂ emission. Data for the year 2013 were forecasted until 2025 to illustrate the analysis for this study, and are represented via four scenarios. This optimal model is capable of balancing types of fuel and switching coal plants to natural gas power plants. It also enhances the use of renewable energy (RE) to meet CO₂ emission targets. The model is further integrated with several other considerations related to energy systems, such as suitability of power plants as peak or base plants, RE resource availability, intermittency of solar power, losses during transmission, fuel selection for biomass, decision to retrofit existing coal power plant to NG power plant, and construction lead time of power plants. The results for this study determined that the optimal scenario is Scenario 3 (CS3). This research proves that Iskandar Malaysia can reduce CO₂ emission by 2025 via utilisation of RE. This model is generic and can be applied to any case study, which would be useful for assisting government policy-making.     

Optimum values of energy converter efficiency

Analytical expressions for optimum values of the thermodynamic and thermal efficiency of heat converters to other kinds of energy have been obtained with the use of the methods of nonlinear equilibrium thermodynamics. Their comparison with the data of industrial power plants has been made.     

Process configuration of Liquid-nitrogen Energy Storage System (LESS) for maximum turnaround efficiency

Diverse power generation sector requires energy storage due to penetration of variable renewable energy sources and use of CO₂ capture plants with fossil fuel based power plants. Cryogenic energy storage being large-scale, decoupled system with capability of producing large power in the range of MWs is one of the options. The drawback of these systems is low turnaround efficiencies due to liquefaction processes being highly energy intensive. In this paper, the scopes of improving the turnaround efficiency of such a plant based on liquid Nitrogen were identified and some of them were addressed. A method using multiple stages of reheat and expansion was proposed for improved turnaround efficiency from 22% to 47% using four such stages in the cycle. The novelty here is the application of reheating in a cryogenic system and utilization of waste heat for that purpose. Based on the study, process conditions for a laboratory-scale setup were determined and presented here.     

Energy production from biomass and its relevance to urban planning and compatibility assessment: two applicative cases in Italy

While the demand for energy in Italy continues to increase, the European Union Directive 2009/28/EC has set a goal of obtaining 20 % of all energy from renewable sources by 2020. It is required both for efficient energy utilization and the development of renewable energy plants, including biomass. In this context, we consider the use of residues from forest maintenance, residues from livestock, the use of energy crops, the recovery of food waste, and the residuals from agro-industrial activities. At the same time, it is necessary to consider the consequent environmental impact. In this study, we applied these considerations to two specific areas in Italy, with different characteristics using the tool of environmental balance. This approach presents a substantial innovation for performing a quantitative analysis of the environmental impact. The specific-considered cases can also indicate a general methodology, useful for energy production compatibility planning.     

致力项目开发点燃发展引擎——多种核能与核技术新项目开发概要

作为中国核工程开发海外市场的旗舰,中原对外工程有限公司将项目开发作为发展引擎,在百万千瓦级核电项目开发、研究性核反应堆项目开发、多功能医院中子照射器开发研究及多用途模块式小型反应堆项目开发工作中不懈努力,为和平利用核能、核技术做出贡献.     

基于再生水源热泵的城市污水处理厂冷热联供系统

城市污水处理厂高耗能限制其运转及发展,基于能耗分析提出了污水处理厂资源能源综合利用技术路线。再生水源热泵回收污水厂外排水低温余热,将其提升后满足污泥高温消化等需热工艺;被吸取热量后低温水用于建筑制冷,形成再生水源热泵冷热联供系统。研究了冷热联供系统工况,以系统联合负荷收益性能系数为指标,提出夏季工况下联供系统最优制冷量即热泵蒸发侧吸热量,分析了蒸发温度对制冷效率影响。整体能流分析表明,再生水源热泵冷热联供系统可降低城市污水厂污泥厌氧消化处理工艺和建筑制冷供暖能耗,夏季和冬季工况节能率分别可达30%、40%。     

The potential of biomass supply for energetic utilization in a small Italian region: Basilicata

The European Union Directive 2009/28/EC (European Parliament and of the Council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing directives 2001/77/EC and 2003/30/EC, Directive 2009/28/EC) establishes a common framework for the use of energy from renewable sources in order to reduce both greenhouse gas emissions and reliance on fossil fuels from foreign markets; more specifically the EU has the ambitious goal of reaching a 20 % share of energy from renewable sources in the overall energy mix by 2020. These objectives could drive policies that offer substantial economic subsidies for the use of renewable energy, both in Italy and in many other European countries. For all these reasons, biomass (one of the major sources of renewable energy) plants are getting a lot of attention in Italy, but it is necessary to determine whether using of this type of energy is environmentally beneficial and economically feasible. In this study, we evaluate the energy and so the environmental aspects by considering both current and potential biomass supplies available for energy utilization in a small region in the South of Italy: Basilicata, as well as the consequences of this energy conversion at both the local and the global scale.     

Modelling and analysis of energy footprint of manufacturing systems

Increasing the energy efficiency of manufacturing plants will reduce the production costs and environmental impact. In order to analyse and improve the energy efficiency of manufacturing plants, however, we need models to evaluate the energy footprints of the plants. A key challenge of estimating plant-level footprints is that systemic methods of connecting information on the product, machine and plant levels are not available. Thus, we propose methods to parameterise product-level elements and to model machine-level factors based on those elements. From the machine-level models, the proposed approach performs simulation experiments and provides the energy footprints in closed-form equations for the plant level. We also suggest that the resulting model can be combined with probabilistic techniques to benchmark the energy efficiency of plants at the industry level. In a case study, we demonstrate how to apply the proposed methods to estimate the energy footprint of a hypothetical plant. The procedures introduced here enable manufacturers to evaluate the energy consumption of their facilities at early stages of manufacturing, and provide tools to assess the energy efficiency of their plant by comparison with peers.     

Neutron measurements at nuclear power reactors [55]

Staff from the Pacific Northwest National Laboratory (operated by Battelle Memorial Institute), have performed neutron measurements at a number of commercial nuclear power plants in the United States. Neutron radiation fields at light water reactor (LWR) power plants are typically characterized by low-energy distributions due to the presence of large amounts of scattering material such as water and concrete. These low-energy distributions make it difficult to accurately monitor personnel exposures, since most survey meters and dosimeters are calibrated to higher-energy fields such as those produced by bare or D₂O-moderated ²⁵²Cf sources. Commercial plants typically use thermoluminescent dosimeters in an albedo configuration for personnel dosimetry and survey meters based on a thermal-neutron detector inside a cylindrical or spherical moderator for dose rate assessment, so their methods of routine monitoring are highly dependent on the energy of the neutron fields.Battelle has participated in neutron assessments at a number of LWR facilities to characterize neutron radiation fields and to evaluate the responses of plant dosimeters and survey instruments. In these studies, the tissue equivalent proportional counter was used for measuring neutron dose and dose equivalent rates, and multisphere spectrometers were used to measure energy distributions. The use of these instruments in LWR work locations is usually difficult because of extreme environmental conditions such as high temperatures.These studies have confirmed the presence of low-energy neutron fields in most work locations. The studies have also found that albedo dosimeters used at power plants typically overrespond significantly when using a calibration based on californium exposures. Survey instruments also respond highly in typical LWR environments.     

Development and integration of new processes consuming carbon dioxide in multi-plant chemical production complexes

Fourteen new energy-efficient and environmentally acceptable catalytic processes have been identified that can use excess high-purity carbon dioxide as a raw material available in a chemical production complex. The complex in the lower Mississippi River Corridor was used to show how these new plants could be integrated into this existing infrastructure using the chemical complex analysis system. Eighty-six published articles of laboratory and pilot plant experiments were reviewed that describe new methods and catalysts to use carbon dioxide for producing commercially important products. A methodology for selecting the new energy-efficient processes was developed based on process operating conditions, energy requirements, catalysts, product demand and revenue, market penetration and economic, environmental and sustainable costs. Based on the methodology for selecting new processes, 20 were identified as candidates for new energy efficient and environmentally acceptable plants. These processes were simulated using HYSYS, and a value-added economic analysis was evaluated for each process. From these, 14 of the most promising were integrated in a superstructure that included plants in the existing chemical production complex in the lower Mississippi River corridor (base case). The optimum configuration of plants was determined based on the triple bottom line that includes sales, economic, environmental and sustainable costs using the chemical complex analysis system. From 18 new processes in the superstructure, the optimum structure had seven new processes including acetic acid, graphite, formic acid, methylamines, propylene and synthesis gas production. With the additional plants in the optimal structure the triple bottom line increased from $343 million per year to $506 million per year and energy use increased from 2,150 TJ/year to 5,791 TJ/year. Multicriteria optimization has been used with Monte Carlo simulation to determine the sensitivity of prices, costs, and sustainability credits/cost to the optimal structure of a chemical production complex. In essence, for each Pareto optimal solution, there is a cumulative probability distribution function that is the probability as a function of the triple bottom line. This information provides a quantitative assessment of the optimum profit versus sustainable credits/cost, and the risk (probability) that the triple bottom line will meet expectations. The capabilities of the chemical complex analysis system have been demonstrated, and this methodology could be applied to other chemical complexes in the world for reduced emissions and energy savings. The system was developed by industry–university collaboration, and the program with users manual and tutorial can be downloaded at no cost from the LSU Mineral Processing Research Institutes website .     

Energy monitoring of process systems: time-series segmentation-based targeting models

Energy monitoring systems calculate actual energy use, estimate energy needs at normal operation, track energy metrics, and highlight issues related to energy efficiency of process plants. Analysis of key energy indicators (KEIs) allows the comparison of process efficiency at different operating regimes. Based on the extracted knowledge realistic targets of KEIs can be determined. The performance of data-driven targeting models depends on how effective the operating regimes are characterized. Till now this modeling task is performed manually based on heuristic and subjective evaluation of the operation. A goal-oriented time-series segmentation technique has been developed to automate the selection of proper data used for the identification of targeting models. With the proposed novel segmentation algorithm targeting-models for different operating regions can be automatically determined. The concept of the resulted energy monitoring system is demonstrated at Heavy Naphtha Hydrotreater and CCR Reforming Units of MOL Hungarian Oil and Gas Company.     

Production of green energy from co-digestion: perspectives for the Province of Cuneo, energetic balance and environmental sustainability

In Italy and many European countries, energy production from biomass is encouraged by strong economic subsidies so that biomass energy plants are getting large diffusion. Nevertheless, it is necessary to define the environmental compatibility taking into account global parameters as well as environmental impacts at regional and local scales coming from new polluting emissions. The environmental balances regarding new energy plants are of primary importance within very polluted areas such as Northern Italy where air quality limits are systematically exceeded, in particular for PM₁₀, NO₂, and ozone. The paper analyzes the renewable energy scenario relating to manure anaerobic digestion and biogas production for the Province of Cuneo, N–W Italy, and the environmental sustainability of the possible choices. The study is focused on energy producibility, heat and power, nitrogen oxides and ammonia emissions, GHG (greenhouse gases) balances dealing also with indirect releases of CH₄ and N₂O, as well as emissions due to energy crops production. The most important conclusion that can be drawn is that the production of renewable energy from anaerobic digestion could cover up to 13 % of the Province electricity consumption, but sustainability in terms of CO₂ emissions can be reached only through an overriding use of agricultural waste products (manure and by-products instead of energy crops) and cogeneration of thermal energy at disposal; the application of the best available techniques to waste gas cleaning, energy recovery, and digestate chemical–physical treatments allows positive emissive balances.     

Energy Planning for Puerto Rico: A Systems Modeling Approach

This study presents various models for energy planning for the year 2000 in Puerto Rico. Puerto Rico depends on imported oil for 99% of its energy needs. The island has many promising energy sources such as biomass (sugar cane bagasse), photovoltaics (solar energy), ocean thermal energy conversion (OTEC), and wind power systems (WPS). These energy sources present some trade-offs in costs, pollution level, and fuel importation, which are studied. Uncertainty in future demand is taken into account. Integer variables representing the possible electricity generation plants are defined. The best compromise solution using the global criterion method for multiple objectives is presented. The proven alternatives such as coal-steam plants, nuclear plants, and biomass steam plants could have political constraints. New technologies such as photovoltaics, OTEC, and WPS possess many uncertainties. Should the cost of these alternatives be less than the electricity generated using oil, a combination of these energy sources would represent the best alternatives to solve Puerto Rico's electricity needs.     

P-graph approach to criticality analysis in integrated bioenergy systems

The use of integrated bioenergy systems (IBS) is a prospective solution to address the emergent global demand for clean energy. The sustainability of IBS compared to stand-alone biomass processing facilities is achieved through integration of process units or component plants via their bioenergy products, by-products, wastes, and common utilities. However, such increased component interdependency makes the resulting integrated energy system vulnerable to capacity disruptions. IBS in particular are vulnerable to climate change-induced events (e.g., drought) that reduce the availability of biomass feedstocks in bioenergy production. Cascading failure due to such supply-side disruptive event is an inherent risk in IBS and may pose a barrier to the commercial-scale adoption of such systems. A previous study developed a risk-based criticality index to quantify the effect of a component’s disruption within integrated energy systems. This index is used to rank the component’s relative risk in the network based on the ripple effects of its disruption. In this work, a novel P-graph approach is proposed as an alternative methodology for criticality analysis of component units or plants in an IBS. This risk-based metric can be used for developing risk management polices to protect critical facilities, thereby increasing the robustness of IBS against disruptions. Two case studies on determining the criticality index of process units in an integrated biorefinery and component plants in a bioenergy park are used to demonstrate the effectiveness of this method.     

Retrofit of steam power plants in a steel mill

This article presents a systematic methodology for the analysis and design of steam power plants in a typical steel mill. Therein most of the steam is produced by applying synthesis gas, a side-product from the coke processing plants. This offers the opportunity of energy integration with vicinal companies using fuel oil or natural gas for generating steam. Components of this work include the energy reallocation and the retrofitted design of steam systems. In this study, the current strategy of energy utilization for existing sites in a steel mill is first assessed. In this regard, the energy policy is adjusted in order to enhance the performance and reduce the costs of the steam power plants. Thereafter, the retrofit is taken into account to evaluate the potential energy for the integration. The problems are formulated as a mixed integer nonlinear program based on a superstructure approach. The results of an industrial case study show that the energy integration among plants is benefit, which provides incentive to promote the cooperation of neighboring companies in an eco-industrial park.     

The use of non-azeotropic refrigerant mixtures in heat pumps for energy saving

In the past non-azeotropic binary refrigerants were frequently proposed for use in refrigeration plants on account of their favourable qualities regarding energy economy, capacity control and bridging of wide temperature ranges. Up to now, however, they did not succeed in industrial use, because these aspects were not prevalent for the exclusive methods of refrigeration by the conventional compression refrigeration cycles. It is demonstrated that non-azeotropic refrigerant mixtures provide considerable advantages for heat pump application in this direction.The possibilities of different refrigerant mixtures and their composition for use in heat pump cycles are especially regarded.First results of measurements concerning the application of those mixtures are given and discussed.     

Methodology for thermal design of novel combined refrigeration/power binary fluid systems

Refrigeration cogeneration systems which generate power alongside with cooling improve energy utilization significantly, because such systems offer a more reasonable arrangement of energy and exergy “flows” within the system, which results in lower fuel consumption as compared to the separate generation of power and cooling or heating. This paper proposes several novel systems of that type, based on ammonia–water working fluid. Importantly, general principles for integration of refrigeration and power systems to produce better energy and exergy efficiencies are summarized, based primarily on the reduction of exergy destruction. The proposed plants analyzed here operate in a fully-integrated combined cycle mode with ammonia–water Rankine cycle(s) and an ammonia refrigeration cycle, interconnected by absorption, separation and heat transfer processes. It was found that the cogeneration systems have good performance, with energy and exergy efficiencies of 28% and 55–60%, respectively, for the base-case studied (at maximum heat input temperature of 450 °C). That efficiency is, by itself, excellent for cogeneration cycles using heat sources at these temperatures, with the exergy efficiency comparable to that of nuclear power plants. When using exhaust heat from topping gas turbine power plants, the total plant energy efficiency can rise to the remarkable value of about 57%. The hardware proposed for use is conventional and commercially available; no hardware additional to that needed in conventional power and absorption cycles is needed.     

冷库能耗分析及节能措施探讨

通过对郑州市部分冷藏企业冷库的调研,分析了造成冷库能耗的各种因素,并对冷库采取的节能措施进行分析探讨,旨在帮助冷藏企业进一步降低生产成本、提高经济效益。