Mathematical modelling of heat transfer in dedusting plants and comparison to off-gas measurements at electric arc furnaces

A mathematical simulation tool is presented in order to model enthalpy flow rates of off-gas and heat transfer of cooling systems at dedusting plants in electric steel making sites. The flexibility of the simulation tool is based on a user-defined series of modular units that describe elementary units of industrial dedusting systems, e.g. water-cooled hot gas duct, air injector, drop-out box, mixing chamber, post-combustion chamber, filter, etc. Results of simulation were checked with measurements at industrial electric steel making plants in order to validate the models for turbulence, heat transfer and chemical reaction kinetics. Comparison between computed and measured gas temperature and composition yield excellent agreement. The simulation tool is used to calculate off-gas temperature and volume flow rate, where off-gas measurements are very difficult to apply due to high gas temperatures and high dust load. Heat transfer from the off-gas to the cooling system was calculated in detail for a pressurised hot water EAF cooling system in order to investigate the impact of the cooling system and the dedusting plant operation on the energy sinks of the electric arc furnace. It is shown that optimum efficiency of post-combustion of EAF off-gas in the water-cooled hot gas duct requires continuous off-gas analysis. Common operation parameters of EAF dedusting systems do not consider the non-steady-state of the EAF off-gas emission efficiently.     

Energy conservation in home furnaces

This paper considers the economic attractiveness of improving the design of new furnaces and modifying existing furnaces to raise their efficiency. Engineering field studies and laboratory tests have shown that even new furnaces waste a substantial portion of the energy in the heating oil or natural gas that they burn. It is concluded that improving the efficiency of new and existing furnaces is not only technically feasible but highly economical. Fuel use reductions of 10–15% are achievable by measures that will pay for themselves in a few years. These design improvements have been understood in principle for years, but have not been put to use because consumers are unable to verify efficiency claims and will therefore not pay a higher price for higher efficiency. Several policies are proposed that would create incentives which would lead to the adoption of more efficient designs. Such policies are necessary if we are to utilize the technological capabilities that are available.     

Energy efficiency and the influence of gas burners to the energy related carbon dioxide emissions of electric arc furnaces in steel industry

Determining the complete energy balance of an electric arc furnace (EAF) provides an appropriate method to examine energy efficiency and identify energy saving potentials. However, the EAF energy balance is complex due to the combined input of electrical energy and chemical energy resulting from natural gas (NG) combustion and oxidation reactions in the steel melt. In addition, furnace off-gas measurements and slag analysis are necessary to reliably determine energy sinks. In this paper 70 energy balances and energy efficiencies from multiple EAFs are presented, including data calculated from plant measurements and compiled from the literature. Potential errors that can be incorporated in these calculations are also highlighted. The total energy requirement of these modern EAFs analysed ranged from 510 to 880 kWh/t, with energy efficiency values (η = ΔH_Steel/E_Total) of between 40% and 75%. Furthermore, the focus was placed on the total energy related CO₂ emissions of EAF processes comprising NG combustion and electrical energy input. By assessing multiple EAF energy balances, a significant correlation between the total energy requirement and energy related specific CO₂ emissions was not evident. Whilst the specific consumption of NG in the EAF only had a minor impact on the EAF energy efficiency, it decreased the specific electrical energy requirement and increased EAF productivity where transformer power was restricted. The analysis also demonstrated that complementing and substituting electrical energy with NG was beneficial in reducing the total energy related CO₂ emissions when a certain level of substitution efficiency was achieved. Therefore, the appropriate use of NG burners in modern EAFs can result in an increased EAF energy intensity, whilst the total energy related CO₂ emissions remain constant or are even decreased.     

Energy conservation in 210 MW coal-fired thermal power plants

This paper reports the results of energy analysis of two 210 MW coal-fired thermal power stations located a good distance apart. A new and simple method for evaluation of thermal efficiency has been presented. Measures for improvement in plant performance in the coal, air, water and steam circuits as well as auxiliary power and secondary oil have been depicted, based on the analysis and existing field conditions.     

Energy conservation by using energy efficient electric motors

This paper deals with energy conservation by installing energy-efficient (EE) motors instead of standard efficiency motors. This transition become a necessity as a direct result of limitation in energy sources and escalating energy prices. As electric motors use about three quarters of the total electric energy in Bahrain, attempts to conserve the energy consumed by electric motors recently received intensive research efforts. Therefore, the energy efficiencies of energy efficient motors are compared with those of standard efficiency motors ranging from 5 to 300 HP. To provide more clarification in this regard, full design details of 200 HP standard-efficiency and energy-efficient motors are compared. Pay back periods when replacing standard-efficiency motors with energy-efficient motors, with reference to Bahrain's market, have been discussed. Finally the energy-conservation capability of EE motors in the petrochemical industry has been discussed.     

Energy conservation and emission reduction policies for the electric power industry in China

Because of China's increasingly limited energy supplies and serious environmental pollution, much attention has been paid to conserving energy and reducing emissions to help the country's economy achieve sustainable development. As the electric power industry is the largest consumer of coal resources in China and also emits high levels of air pollutants each year, the Chinese government has enacted many technical and economic policies for energy conservation and emission reduction in the last few years. These policies are summarized in this paper, along with relevant laws and medium- and long-term plans, all of which address ideas such as adjusting the power generation mix, promoting demand-side management, introducing energy-efficient scheduling, and installing desulfurization units. The paper also assesses the results of these policies by analyzing several key indicators of energy consumption and emissions. The analysis shows that although some progress has been made in conserving energy and reducing emissions, substantial work is still required for China to catch up with developed countries. Some suggestions for future work are provided.     

我国电弧炉不还原快速炼钢的现状及建议

本文简介了目前国内电弧炉炼钢工艺的进展情况及电弧炉还原期工艺的变革。在分析我国电弧炉不还原快速炼钢法(以下简称NR法)的工艺原理、特征、产品质量、工艺效果和经济效益的基础上,肯定了该法是一种多、快、好、省的炼钢法,提出了在我国普通电炉钢厂大力推广NR法的建议,指出了目前存在的问题及今后的设想。     

偏心底出钢电弧炉的炉型特点及砌炉技术

阐述偏心底出钢电弧炉的结构特点,炉衬蚀损机理,相应的筑炉工艺,提出进一步提高炉龄的措施。     

Implementing China’s national energy conservation policies at state-owned electric power generation plants

China’s 11th Five-Year Guideline identified energy conservation as one of the country’s fundamental policies and established a mandatory target: 20% reduction in national average energy intensity by 2010. Despite the various policies, laws, and administrative reforms to support energy conservation, China fell behind schedule for meeting its conservation targets in 2006 and 2007. Using a combination of available literature and an interview-based case study, this paper examines the implementation of energy conservation and investigates impediments to achieving China’s conservation goal in the electric power generation sector. Three key impediments are detailed: (1) municipal governments’ incentives to overlook conservation-related central directives primarily because of budget pressures linked to financial decentralization, (2) procedural obstacles in the form of time required to obtain project approvals for high-efficiency power generation units, and (3) financial obstacles making it difficult for power generation enterprises to raise capital for energy conservation projects. An interview-based case study of a state-owned coal-fired electric power generation company demonstrates the influence of the aforementioned obstacles. While procedural obstacles are notable, they can be managed. However, electricity pricing reforms and/or stronger subsidy programs will be needed to address the financial obstacles facing Chinese power generation companies.     

Energy conservation in traffic

This paper discusses the energy that is being wasted in the transport section in Amman due to three main factors: namely, the time delay at the major traffic light intersections, the warming up periods of vehicles, and the drag force acting on heavy vehicles. It was found that the fuel which is being used due to the first and second factors contribute 2.2 and 3.0% to the total annual fuel cost in Jordan. Finally, recommendations and suggestions are given to cut down the fuel consumption in Amman due to the above mentioned factors.     

Energy and materials conservation

The impetus for energy conservation is far less than that for the more efficient use of feedstock materials in industry. Pertinent background statistics for the UK since 1970 are presented in this article. At present energy prices are artificially low.     

电弧炉煤氧喷吹助熔工艺及应用

本文介绍了炼钢电弧炉采用的煤氧喷吹系统及工艺,阐述了该技术在电炉炼钢生产中的节电效果,同时提出需要进一步改进技术和提高的方向。     

Modelling of electric energy consumption in the AC electric arc furnace

In this paper, the variation of electric energy consumption in the AC electric arc furnace (EAF) with various production parameters is studied using a developed computer program. The energy equation is modelled using the first law of thermodynamics. The effects of temperature of liquid steel, stack gas, scrap pre‐heated and cooling water and duration at which the EAF cover is open on electric energy consumption are investigated. The calculated electric energy values are compared with the actual electric energy used in the EAF and values received from literature. They are in a good agreement. Copyright © 2002 John Wiley & Sons, Ltd.     

Energy conservation in Chinese housing

In the People's Republic of China (PR China), even though climatic conditions are severe, energy use in buildings has traditionally been insignificant by Western standards. The recent increases in household energy consumption have left two options: increase household energy use at the expense of industrial and environmental gains, or develop policies to conserve or restrict household energy consumption. This paper explores the problems in introducing low-cost energy conservation practices in Henan Province, PR China. The paper describes both the practical problems encountered in the introduction of new building materials and designs and also the institutional barriers that inhibit the development of an energy conservation delivery system. A major theme of this paper is that conventional Western solutions for energy conservation often come up against significant unexpected barriers in developing nations, rendering these solutions ineffective. For instance, the high cost and/or unavailability of materials in many countries require building redesign solutions that do not utilize insulation, vapour barriers, and modern heating and cooling plants. Similarly, the particular political and economic organization of a country may mean that coordination of a regional or national conservation programme will require an approach quite different from the public or private development programmes in Western developed countries.     

Energy conservation policies in Jordan

Jordan imports almost all the energy required for its social and economic development. During the period 1974–1984, energy consumption grew at an average rate of about 14%/year, due mainly to growth in the national economy; but exacerbated by inefficient use of energy. To alleviate the burden of the energy bill on the economy, the Ministry of Energy has adopted a policy aimed at securing sufficient energy supplies at minimum cost to the economy. This policy has focused on improving the efficiency of energy-use and encouraging energy conservation in order to reduce the effect of oil imports on foreign reserves, reduce the impact of emissions of toxic gases on the environment, and the cost of additional investment in production facilities. The energy conservation programme was put into application in early 1985. The energy income elasticity during the period 1985–1988 has dropped from (1.4) to (1), which indicates a substantial improvement in overall energy utilization.     

建筑节能技术探讨

由于建筑物的设计中有不合理之处,导致建筑物的空调负荷偏大,使建筑物增加了一部分不必要的能耗。建筑物里的空调系统设计方案也存在很多缺陷,使能耗过大。本文从建筑物和空调系统两方面进行分析,分别对建筑物及空调系统的节能技术措施进行了探讨。其主要节能技术措施有:使建筑物的规划设计科学、增强围护结构的隔热保温性能、使空调系统设计更科学合理、提高空调系统的管理意识。     

Energy conservation in the UK

This study starts with an analysis of past energy ‘conservation’ by relating energy use to output in the period 1900–1980. The results of a survey in manufacturing industries and local authority services are then presented, aimed at assessing the conservation effort since 1973 and that planned for the near future; the emphasis is on the measures and their results that can be realistically expected. Obstacles to conservation are analysed on the basis of the sample survey. Among the other consuming sectors transport and household use are discussed in some detail,with the conclusion that energy requirements in the UK are unlikely to exceed the 1979 level during the decade to 1990.     

Energy conservation, expectations and uncertainty

This paper investigates consumers' decisions about a (single and lumpy) conservation project accounting for uncertainty and expectations (rational versus myopic). Rational expectations take into account that the profitability of individual conservation measures will affect fuel prices (here set by cartelized supply). Ignorance of this interdependence between conservation and price leads to premature investments. The interplay between demand and supply creates an incentive for a consumer cartel to initiate conservation strategically, which advances conservation compared with rational consumers but not always ahead of individually myopic decisions.     

Software development for energy analysis and heat recovery from boilers and furnaces

Microcomputer software has been developed for engineers and consultants in industry to analyze the performance of boilers and furnaces and to estimate the potential for heat recovery through heat exchanger design and economic optimization. The module is designed for useful application in small and medium scale industries which consume large amounts of conventional or alternative fuels, specifically in developing countries. An attempt has been made to render the package user-friendly, practical, flexible, easy to maintain and expandable to take into consideration the specific requirements of the users.

The package consists of a library of fuel data, a library of projects and a study section which carries out combustion analysis, basic heat exchanger design with the user's data options and an optimization of design configuration leading to the minimum heat exchanger cost.