What's the real cost of higher efficiency? [electrical energy efficiency]

The problems that California had with electrical energy have only emphasized the need to look at the true cost of high-efficiency energy devices used by cement plants since electrical energy is among the top expenses in producing cement. This article focuses on low-voltage induction motors and lighting systems. Low-voltage induction motors generally account for about 30% of the electrical energy consumed by a cement plant. Lighting systems generally account for about 3-5% of the electrical energy consumed by a cement plant, but it is a fixed load that does not directly contribute to production. Life-cycle cost analysis is used to determine the true costs of this equipment. True equipment cost is defined as the total of the initial capital expenditures plus the operating costs, which include energy and maintenance. Even though the foremost requirement for a piece of equipment is its performance in the production chain, the justification for selecting one piece over another should be based upon the initial capital cost plus operating expenses. A review is given of two selected areas of electrical equipment to test their cost of ownership.     

Optimizing Energy Utilization in Cement Plant Operations

With the increased cost of energy, use of energy in cement plants must be reduced. Various means of reducing energy use in existing plants by changes in plant practices are suggested, with estimates of the magnitude of the major reductions.     

Energy Economics of a Modern Suspension Preheater Plant Compared to a Modern Plant Incorporating Cogeneration

The rising cost of fuel experienced over the past several years has caused the cement industry to look for more energy efficient systems for producing cement. Probably the most popular system has been the suspension preheater, frequently coupled with a roller mill, a flash calciner, or both. While these systems have yielded greatly improved fuel efficiencies, they have also contributed to higher consumption of electrical energy. This, coupled with the rapid rise in cost of electrical energy, has led to a renewed interest in cogeneration, wherein the heat contained in the kiln off-gases is used to produce steam to run turbine generators, thereby increasing the use of lower cost fuel energy while decreasing the use of higher cost purchased electric power energy. The production cost of a suspension preheater is different than for a plant utilizing cogeneration, so the production cost per ton of the two systems is compared, and the differences are used to determine the feasibility of cogeneration for a specific set of conditions. Two cogeneration cases will be examined. One is a plant utilizing generated power from waste heat only, all of which is consumed by the plant. The other is a plant which not only utilizes waste heat power but also produces for sale back to the utility company.     

Cement Plant Cogeneration Opportunities

Rapid escalation of energy costs during the seventies requires a serious investigation of ways to reduce the industrial energy bill which has more than doubled in many states since 1977. Cogeneration offers one way of improving the efficiency of energy utilization for the cement industry. During the forties and fifties, it was common practice in the cement industry to recover the waste heat from kilns to generate electric power. With the advent of central power plants and availability of cheaper power, most of these units were phased out. The energy costs, however, have escalated considerably in the past decade and are now subject to uncertainty with respect to future price and supply. Several engineering studies aimed at evaluating the technical and economic feasibility of cogeneration for cement plants in California were recently conducted. Both steam and organic rankine cycle concepts were considered. The capital requirements and operating and maintenance cost were estimated, and discounted cash flow analyses were performed to determine potential project feasibility. The results of these studies are presented, and cogeneration opportunities are discussed. A discussion of the operating experience at an existing cement plant cogeneration project is also included.     

发电厂电力拖动系统的节能研究

随着厂网分开,发电企业市场化程度的加剧,电厂的发电煤耗、厂用电率已成为发电厂考核的重要指标,直接关系到电厂的经济效益和企业竞争力。现代发电厂的厂用电占发电总量的5％-10％,而电力拖动系统消耗的电量就占到其中的90％以上。分别从电动机供电电能质量、电动机选择及更换、电动机的改造、电动机监控和维护以及电动机运行角度出发,提出了电动机节能措施,最大程度地降低了电厂电力拖动系统的损耗,起到了良好的节能效果。     

The Production of Electrical and Thermal Energy from the Exhaust Gas Heat of Preheater Kilns

It is shown, by means of an example, i.e., a 1600-ton/day four-stage suspension preheater kiln of a cement factory, that the waste heat present in the exhaust gases can be converted into useful electrical and thermal energy. This is possible even though the exhaust gases are heavily loaded with dust. The heat recovery system installed in 1981/1982 in a Swiss cement plant and the respective production line are described in detail. A comprehensive explanation is given concerning the experience of the first operating year, the iqteraction of the new plant with the existing production facilities, and the current measured technical data. The performance limits for economic operation are explained and the decision criteria quoted. Further applications of the successfully tested heat recovery system can be expected wherever beat sources in the form of heavily loaded gases are available.     

影响供电煤耗的主要因素及应对措施

针对降低火电厂供电煤耗、提高电厂的竞争力问题,结合某电厂1号机组实例,分析了发电机组的现状,介绍了该机组在降低供电煤耗方面所采取的技术措施;并对该电厂现存的节煤降耗潜力提出了今后节能降耗工作的重点.     

Development and testing of an energy saving tool – Suitability analysis with case study

The increasing demand for electrical energy, the depletion of fossil fuel based resources and environmental constraints have made it mandatory for the efficient use of electrical energy, energy saving applications and implementing an energy management program. In this paper, a user-friendly tool for tracking and analyzing the electric bills, suggesting the best electricity tariff, controlling the active and reactive power rates, increasing energy efficiency, allowing the consumer to compare the alternatives and avoiding any penalties is presented step by step. The proposed energy saving tool will also help the electrical and more particularly power engineers and consumers in industrial sector to reduce electricity consumption while maintaining the quality of service. The developed tool is applied and tested to determine the optimal design of electrical power system in a university hospital. Test results reveal the performance of the developed tool for an optimization of commercial and industrial plants under different scenarios of power consumption and load demand. The program is written in the Delphi programming environment XE3 to provide enhanced flexibility and runs on Windows.     

考虑能量存取的自备电厂去中心化交易机制探究

传统发电权交易模式下,交易价格需要满足一定的条件才能驱动自备电厂参与新能源消纳,无法充分释放自备电厂的调峰潜力,且在中心化交易系统下,存在运维成本高、交易效率低等问题.为此,文章提出了自备电厂的能量存取服务模式,扩大新能源消纳空间,并采用去中心化交易机制提高交易效率.同时,构建了去中心化的交易撮合模型,以新能源最大化消...     

A Physical Model of Power Electronic Devices Based on Static Voltage Transducers

A physical model of a thyristor ac voltage regulator with microcontroller control operating under an active-inductive load is considered. To increase the level of energy efficiency of existing electric power systems, the arrangement of the control of voltage level of supplied centers both above and below the rated value is an important condition. In existing structures, the transformation ratio generally is a constant, which does not make it possible to take into account the real irregularities of electric energy consumption. Using a transformer in a thyristor voltage regulator makes it possible to solve this problem. It shows that it may be possible to enter a preliminary stage of physical modeling of the considered process by means of creation of a program–technical complex making it possible to simulate the process of transportation of electrical energy from supply centers to consumers.     

Refrigeration generation using expander-generator units

The problems of using the expander–generator unit (EGU) to generate refrigeration, along with electricity were considered. It is shown that, on the level of the temperatures of refrigeration flows using the EGU, one can provide the refrigeration supply of the different consumers: ventilation and air conditioning plants and industrial refrigerators and freezers. The analysis of influence of process parameters on the cooling power of the EGU, which depends on the parameters of the gas expansion process in the expander and temperatures of cooled environment, was carried out. The schematic diagram of refrigeration generation plant based on EGU is presented. The features and advantages of EGU to generate refrigeration compared with thermotransformer of steam compressive and absorption types were shown, namely: there is no need to use the energy generated by burning fuel to operate the EGU; beneficial use of the heat delivered to gas from the flow being cooled in equipment operating on gas; energy production along with refrigeration generation, which makes it possible to create, using EGU, the trigeneration plants without using the energy power equipment. It is shown that the level of the temperatures of refrigeration flows, which can be obtained by using the EGU on existing technological decompression stations of the transported gas, allows providing the refrigeration supply of various consumers. The information that the refrigeration capacity of an expander–generator unit not only depends on the parameters of the process of expansion of gas flowing in the expander (flow rate, temperatures and pressures at the inlet and outlet) but it is also determined by the temperature needed for a consumer and the initial temperature of the flow of the refrigeration–carrier being cooled. The conclusion was made that the expander–generator units can be used to create trigeneration plants both at major power plants and at small energy.     

1000MW 燃煤机组中压厂用电压等级选择与节能降耗

电厂发出电能的同时要消耗大量电能,而中压电动机是电厂主要的能耗大户,中压厂用电压等级选择是否合理,将直接影响中压电动机的效率和电厂的电能消耗。因此,为实现节能降耗,对中压厂用电压等级选择进行研究是非常必要的。对于1000MW燃煤机组,6kV一级和10kV一级两个厂用中压系统方案都有应用实例。针对JL电厂2×1000MW燃煤机组工程的实际情况,在技术性能都能满足相关规程要求的前提下,通过对中压电动机的运行效率进行定性分析和定量计算,结果表明:6kV方案相比10kV方案中压电动机的运行效率较高,可以节省大量电能且初期投资接近,故在本工程中6kV方案优于10kV方案。     

Considerations of Ground Fault Protection as Influenced by the Occupational Safety and Health Act and the Mining Enforcement and Safety Administration

The first step in recognizing the necessity of low voltage ground fault protection was taken by the 1971 National Electrical Code (NEC), Section 230-95. With the passage of the Occupational Safety and Health Act (OSHA) of 1970, more emphasis has been placed on adherence to the code. Since the establishment of OSHA, questions have been raised as to the jurisdiction between the Occupational Safety and Health Administration and the Mining Enforcement and Safety Administration (MESA). This has resulted in both agencies considering and deciding on design standards for cement plant electrical systems. Indications are that in the future, MESA standards will also recognize the necessity of adequate ground fault protection. Since the introduction of ground fault protection in the codes, there have been arguments for and against the methods of applying ground fault protection. It is for this reason that the present code requirements are minimal. In order to provide the electrical service reliability required by modern cement plants, more extensive protection is required. The intent of this paper is to evaluate the new requirements of ground fault protection. It also examines how we, as engineers concerned with electrical power systems in cement plants, approach the problems of providing safe reliable electrical systems which meet applicable code requirements and which also function satisfactorily in relation to plant operation.     

降低燃煤电厂厂用电率技术分析翟德双

降低机组厂用电率是燃煤电厂节能减排的重要内容之一,也是提高发电企业经济效益的有效手段。本文根据当前燃煤电厂电力和煤炭市场形势,以及节能减排要求,分析发电机组各辅机及系统的实际运行情况,找出影响厂用电的各项因素,总结普遍存在的不足之处,挖掘厂用电节电空间,提出了降低厂用电率的优化运行调整措施,强化设备检修维护对策,以及有效的技术改造措施。     

变频调速技术在电厂节能改造中的应用

随着电力系统商业化运营的逐步实施,发电厂的节能降耗日显重要,减少厂用电量以降低生产成本为各电厂所重视,这使得交流变频调速技术在发电厂的应用逐步增多。为此．在介绍变频器调速原理的基础上,以某柴油机发电厂变频调速节能改造为例,探讨了发电企业变频调速节能改造的意义,同时针对现有系统存在的弊端,提出了改造措施,改造后实际运行表明,节电率约达40％,节电效果明显。     

高压变频器在高温风机中的节能应用

针对水泥厂10kV高温风机工频运行采用风门调节中的高耗能问题,通过采用10kV高压变频器,实现变频调速及远程控制。介绍了该高压变频器的特点及其显著的节能效果。     

Short-term optimization of the new Avče pumping plant and three existing hydro power plants on the Soča river in Slovenia

In the following years a new pumping plant Av?e is going to join the existing cascade of three small-regulating-basin hydro power plants (HPPs) on the So?a river in Slovenia. The pumping plant operation will have to be synchronous to the operation of existing plants and vice versa since all four plants depend upon the same inflow and since they all belong to the same generation company that buys and sells electricity to a day-ahead electricity market. The So?a river has torrent alpine characteristics so there are doubts about the operation of the system in frequent dry seasons. As shown in this article, such questions can be effectively solved by first presenting the hydro system of four HPPs under study as a directed graph and then as a mixed integer linear program (MILP): a set of equations and inequations modeling technical issues of HPPs and a target function (the day-ahead market price) modeling the electricity market. A small and simple MILP model called Flores has been used for this study. The MILP approach requires only to specify the problem since the solution is found by using available commercial computer solvers. It can be applied on-line and it can be augmented to include also the transmission constraints, ancillary services, etc.     

Synchronous and slip-ring induction motors drive cement mills

In the process of selecting a suitable motor for a cement mill, there are several issues to consider that, for the purpose of analysis, can be grouped into two distinct categories. The first category is the technical analysis, which is based on engineering considerations that evaluate the merits of either a synchronous or a slip-ring induction motor installation. The second category is the economical analysis, which follows closely the results of the technical evaluation with emphasis on the original investment cost and the cost of operating and maintaining the equipment over its useful lifespan-estimated as 30 years. Among the technical issues, the first should be identifying the torque requirements and initial power system limitations. The choice of motor design will largely depend on these requirements. The other issues relate to electrical energy savings. With the cement mill being the largest single power consumer in the plant, the choice of motor and drive will directly influence these savings, which can be significant. Several cement mill installations in operation today are discussed     

CHP Plants in Russia: the Necessity for Technological Renovation

The role of combined heat and power (CHP) plants in the electric power industry of Russia is shown. The operational efficiency analysis of public service CHP plants and the fuel, power, and age structure of the existing CHP plants are carried out. Their main problems, such as underuse of generating equipment, excessive production in the condensing mode, high degree of equipment wear, and technological heterogeneity, are identified. The necessity of technological renovation of the CHP plants is shown. The energy efficiency of the combined production of electric and thermal energy by the existing CHP plants is compared to modern technologies for their separate gas and coal production. It is shown that the thermal capacity of the CHP plants in Russia exceeds the required capacity by almost two times. Estimates of the CHP plant thermal capacity necessary to cover the current heat loads are obtained for Russian regions. Main directions of the CHP plants' renewal based on the use of competitive domestic equipment and operation according to the heat load schedule are determined. Systemic impacts achieved by technological renewal are determined for gas-fired CHP plants with allowance for the climatic and load features of the Russian regions. It is shown that the technological renewal of gas-fired CHP plants will allow saving up to 16% of today’s fuel consumption, reducing the total CHP thermal capacity by 47.5% with the same volume and heat supply mode. The operation of a CHP plant according to the heat load schedule leads to a reduction in the electric capacity of the CHP plant by 20% with an increase in electricity generation by 11%. As a result, the consumption of the installed electric and thermal capacity of the CHP plant increases dramatically as does the fuel efficiency and the annual loading balance of external gas-fired condensing power plants. The needs for GTPs and CCGTs required for the technological renovation of the CHP plants is assessed. The necessity for developing competitive domestic medium and high power GTPs is considered.     

计及低频采样用电量信号的电器运行情况识别方法

电器运行情况识别是负荷分解的一个重要研究方面。为克服低频采样下功率信号信息量低的问题,将用电量信号引入用于电器运行情况识别。首先基于用电量信号,估计采样点间有功功率曲线走势,重构负荷总有功功率信号。再结合人们用电习惯确立电器设备运行应满足的约束条件,利用整数规划法对重构的总有功功率信号进行电器运行情况识别。数值模拟结果表明,与不考虑用电量信号的算法相比,所提算法能在一定程度上复原电器设备在采样间隔内的投切动作,对于电器运行情况识别准确率更高。