Energy Efficiency Management in a Steel Plant
Energy Efficiency Management in a Steel Plant
Iron and steel industry is the largest consumer of energy among all industrial sectors. It is an energy intensive industry and the main energy carriers are coal, liquid and gaseous fuels, and electricity. The high energy intensity and the large share of fossil fuels make the energy issue very important for the iron and steel industry. Further, the iron and steel industry is exposed to international competition and energy efficient steel production can be a competitive advantage.
Energy costs represent normally around 20 % to 25 % of the total input cost of the steel plant. Energy use is also a major source of emissions in the iron and steel industry, making energy efficiency improvements an attractive opportunity to reduce both emissions of pollutants and greenhouse gases. Increase in the energy efficiency is an important opportunity to reduce both costs and risks associated with the policies related to the reduction of emissions of pollutants and greenhouse gases. Energy efficiency can thus be an efficient and effective strategy to work towards the so-called ‘triple bottom line’ which focuses on the social, economic, and environmental aspects. Investment in the energy efficiency technologies is a sound strategy in the present day environment for the management of iron and steel plant.
Iron and steel plant processes involve different cycles such as heating, cooling, melting, solidification, and processing. It is a highly energy intensive industry. The reduction of energy consumption in the iron and steel plant is of a special concern. Energy conservation in iron and steel industry is crucial for its competitiveness, sustainability, and minimization of environmental impacts including green house gas emissions and better resource management. The conservation of energy is an important objective for the global steel industry. Energy efficiency technologies and practices meet this challenge and have become increasingly cost-effective in recent years and this has helped at the times when there are high and uncertain energy prices and a very high concern for the environmental issues.
Energy is an important cost factor in the iron and steel industry. Energy efficiency improvement is an important way to reduce these costs and to increase predictable earnings, especially in times of high energy price volatility. There are a variety of opportunities available at individual iron and steel plants for the reduction of energy consumption in a cost-effective manner. There are several energy efficiency practices and energy-efficient technologies available to the iron and steel plants which can be implemented at the component, process, facility, and organizational levels.
In the present day scenario, energy cost cutting and energy efficiency improvements are the most important topics of control for the steel plant management. Since 1960s remarkable achievements have been made by the steel industry in the area of energy conservation and the average energy intensity per ton of steel produced has dropped from 50 GJ/ton (giga joules per ton) in the 1960s to its present level of around 20 GJ/ton. This has been achieved by improving the utilization efficiencies of various forms of energy, by making the steel plant processes more energy efficient, and by the efficient utilization of various materials used in the production of iron and steel.
Since the second half of the twentieth century, iron and steel industry intensified efforts towards conservation of energy as the cost of energy continued to rise. New energy efficient processes such as dry quenching of hot coke, dry cleaning of the gases for the reduction of their dust content, basic oxygen furnace steelmaking, and continuous casting of steels etc. have been invented which have replaced the energy intensive processes like wet quenching of hot coke, wet cleaning of the gases, open hearth steelmaking, and ingot casting along with soaking pits and slabbing / blooming / billet mills etc.
As the pressure for the energy conservation increased, energy conservation efforts moved to system approach in addition to single equipment (such as blast furnace stove, reheating furnace etc.) approach. In the system approach, a complete technological process consisting of a group of equipment is being considered for the energy conservation. Further, under system approach, the reduction in the energy consumption is achieved by controlling the different aspects of the process, such as improvement in the efficiency of the process, reduction in the specific consumption of raw materials and other materials, improvement in the product yields, improvement in the recovery and recycling of the waste energy and waste materials, and reduction in the idle running of the equipments etc.
Further to the system approach, the iron and steel industry continued its energy conservation efforts by studying the processes in minute details, and finding those details which have adverse effects on the consumption of energy. After the identification of these details, methods have been found for the correction of these details for achieving lower energy consumptions. Examples of these are (i) control of the composition of raw materials and other materials in the furnace, (ii) control of moisture of the materials charged in the furnaces, (iii) improving the flow of materials and gases in the furnaces, (iv) replacing costly fuels with cheaper fuels while protecting the process efficiency and product quality, (v) improving the monitoring of the process parameters, (vi) switching over to fully automatic controls from manual and semi-automatic control, and (vii) making the processes more continuous and thus avoiding cooling and then reheating of the intermediate materials.
Effective energy management practices are needed for achieving results towards energy efficiency and energy conservation in the iron and steel plant. Energy management practices provide several opportunities in the iron and steel plant which include (i) decrease of the energy intensity per ton of crude steel, (ii) adoption of the good practices for utilization of energy sources more effectively, (iii) use of good practices for the recovery of heat and gas energy wherever practical, (iv) enable the plant management to develop plans for reduction of the energy intensity of the plant, and (v) enable the plant management to carry out prioritization of those investments which have very high impact on the energy efficiency. Improved energy efficiency can also result in other benefits which outweigh the energy cost savings. These include (i) decreased business uncertainties and reduced exposure to fluctuating energy costs, (ii) increased product quality and switch to higher added value market segments, (iii) increased productivity, and (iv) reduced environmental compliance cost.
Strategic energy management programmes
A sound energy management programme is needed to create a foundation for positive change and to provide guidance for managing energy throughout the plant. Hence, continuous improvements to energy efficiency typically only can occur when a strong organizational commitment exists. Energy management programmes help to ensure that energy efficiency improvements do not just happen on a one-time basis, but rather are continuously identified and implemented in a process of continuous improvement.
Understanding how energy is used and managed is essential to manage the energy during the production. Changing how energy is managed by implementing a plant wide energy management programme is one of the most successful and cost-effective ways to bring about energy efficiency improvements. Ideally, such a programme includes facility, operation, environmental, health, safety, and personnel management. Fig 1 shows the major elements in a strategic energy management programme.
Fig 1 Major elements in a strategic energy management programme.
In the iron and steel plants without a clear programme in place, opportunities for improvement can be known, but are not promoted or implemented because of organizational barriers, even when energy has a considerable cost. These barriers can include (i) a lack of communication among different departments of the plant, (ii) a poor understanding of how to create support for an energy efficiency project, (iii) limited finances, (iv) poor accountability for measures, or (v) organizational inertia to changes from the status quo.
A successful programme in energy management begins with a strong organizational commitment to continuous improvement of energy efficiency. This involves assigning oversight and management duties to a very senior executive, establishing an energy policy, and creating a cross functional energy team. Steps and procedures are then put in place to assess performance through regular reviews of energy data, technical assessments, and benchmarking. From this assessment, the steel plant is able to develop a base-line of energy use and set goals for improvement. Such performance goals help to shape the development and implementation of an action plan.
An important aspect for ensuring the success of the action plan is involving personnel throughout the organization. Personnel at all levels are to be aware of energy use and goals for efficiency. Employees are to be trained in general approaches to energy efficiency in day-to-day practices.
Evaluating of the performance involves the regular review of both energy use data and the activities carried out as part of the action plan. Information gathered during the formal review process helps in setting new performance goals and action plans and in revealing best practices.
Establishing a strong communications programme and seeking recognition for accomplishments are critical steps to build support and momentum for future activities.
The establishment of an energy team is an important step toward solidifying a commitment towards continuous energy efficiency improvement. The energy team is mainly to be responsible for planning, implementing, bench-marking, monitoring, and evaluating the steel plant energy management programme, but it can also include providing training, communicating results, and providing employee recognition.
In forming an energy team, it is necessary to establish the organizational structure, designate team members, and specify roles and responsibilities. Senior management needs to perceive energy management as part of the plant’s core operational activities, and hence ideally the energy team leader is to be someone at the higher level who is empowered with the support of senior-level management. The energy team is also to include members from each key operational area within the plant and be as multi-disciplinary as possible to ensure a diversity of perspectives. It is crucial to ensure adequate funding for the energy team’s activities, preferably as a line item in the normal budget cycle as opposed to a special project.
Prior to the launch of the energy team, a series of team strategy meetings are required to be held for considering the key initiatives to be pursued as well as potential pilot projects which can be show cased at the programme’s kickoff. The energy team is to then perform facility audits with key plant personnel at each facility to identify opportunities for energy efficiency improvements. As part of the facility audits, the energy team is also to look for best practice technologies to help highlight success stories and identify areas for inter-department knowledge transfer.
A key function of the energy team is to develop mechanisms and tools for tracking and communicating progress and for transferring the knowledge gained through facility audits across an organization. Examples of such mechanisms and data tools include best practice databases, facility bench-marking tools, intranet sites, performance tracking scorecards, and case studies of successful projects.
For sustaining the energy team and build momentum for continuous improvement, it is important that progress results and lessons learned are communicated regularly to the management, executives, and the employees and that a recognition and rewards programme is put in place.
The success of energy efficiency assessments or audits to reduce energy use has been proven in a large number of cases. Embedding audits in an energy management system helps to guarantee successful implementation of audit results.
Energy and process control systems and monitoring
Energy reduction can be achieved through active monitoring of energy consumption and an intelligent energy management system. A systems approach to energy efficiency management in and outside the production facilities (layout, energy producer, supplier, and user) is required in the steel plant.
The use of control systems can play an important role in energy management and in reducing the use of energy. Control systems can reduce the time needed to perform complex tasks, improve frequently product quality and consistency, optimize process operations leading to reduced down-time, reduced maintenance costs, reduced processing time, and increased resource and energy efficiency, as well as improved emissions control. The control systems are hence frequently not solely designed for energy efficiency. This is especially true in the iron and steel plant, where increases in productivity most frequently directly improve energy efficiency. A variety of process control systems is designed for most, if not all, process steps in iron and steel plant. Some of the examples are combustion control systems of coke oven batteries, automation of the hot blast stove, blast furnace control systems, post-combustion control in electric arc furnace, and control of reheating furnace.
Improvements in control systems are driven by improvements in process monitoring, process modelling, and process optimization. Increasingly, advanced control systems are under continuous development and large potentials to exploit their benefits hence exist even though some steel plants can already have modern process control systems in place. As process control systems rely on information from many stages of the processes, an important area is the development of sensors. Further, apart from input in control systems, monitored data can also be used to assess the validity of new process models or to improve knowledge of a process.
Model based controls
A model allows assessing the influence of certain practices and process parameters. This can be supported by running simulations. Modelling, hence, helps to improve the understanding of a process, which facilitates the design of control systems, operations, and applications which lead to energy savings. This is particularly true for models of, or that incorporate, energy usage. Models also support process planning and can hence help to make processes leaner and to avoid peaks in the need of a specific input.
Models can have different levels of detail. Two specific advanced detailed types of modelling which recently have found their way to steel plant processes are computational fluid dynamics (CFD) and finite element method (FEM). The use of these types of models can improve the understanding of flow processes and thus allow improvement of metallurgical processes at the steel plant.
Process simulation is another area which helps in energy conservation. It allows calculating the process performance and the energetic / exergetic efficiency of the process and to provide a guide to the calibration of the process parameters which best fit the individual units of the plant.
Expanding the system boundary of a model to include more aspects of the process or by considering more installations / plants has the potential to further increase energy efficiency.
In optimizing process efficiency, it is to be clear which parameter is to be optimized, such as productivity, energy use, carbon di-oxide emissions, process stability, steel cleanliness etc. In some cases, a combination of required parameters is to be optimized. Boundary conditions can exist such as the minimum quality of a product.
The extent to which process efficiency can be improved by process control depends on the potential to influence the process (e.g. installation of oxy-fuel lances in an electric arc furnace) and the data of the process which are available (e.g. composition of furnace flue gas). The optimization procedure can make use of both simulations and data from processes or experiments. Sometimes, archived production data can be a valuable resource to improve the process efficiency. Some optimization procedures apply algorithms to find an optimum. Other optimization procedures are model-based or just consist of testing a range of control procedures to find an optimum.
New energy management systems which use artificial intelligence, fuzzy logic (neural networks), or rule-based systems mimic the ‘best’ controller, using monitoring data and learning from previous experiences. Neural network based control systems have successfully been used in the several processes of the steel plant (e.g. electric arc furnace, rolling mills, and sintering plant etc.).
Process knowledge based systems incorporate scientific and process information applying a reasoning process and rules in the management strategy. Although these systems have been used in design and diagnostics, they are hardly used in the steel plant processes.
Energy management efforts, which aim to reduce energy use, are a must as well as a key element for a steel plant’s energy management programme. Twin approach for energy management in a steel plant is desirable and necessary. Energy management programme can be system based through the implementation of ISO 50001-2018 standard as well as it can be a technical approach based on real time information obtained from process monitoring and control systems and on production plans received from production planning systems. While the first approach is a management approach which stream-lines all the systems connected with energy use and energy conservation, the second approach provides information on actual and planned energy indicators of production, distribution, and consumption on real time basis to energy operators for decision making and controlling.
System approach for energy management
System based energy management enables a steel plant to establish the systems and processes necessary to improve energy performance, including energy efficiency, its use and its consumption. Implementation of systems is intended to lead to reductions in energy consumption and in turn leads to reduce greenhouse gas emissions and other related environmental impacts. The energy cost also gets reduced through systematic management of energy. Successful implementation of systems depends on commitment from all levels and functions of the management of the steel plant, and especially the top management.
Energy management system standard ISO 50001-2018 specifies the energy management system requirements, upon which a steel plant can develop and implement an energy policy, and establish objectives, targets, and action plans which take into account legal requirements and information related to significant energy use. It specifies requirements for establishing, implementing, maintaining, and improving an energy management system, whose purpose is to enable the steel plant to follow a systematic approach in achieving continual improvement of energy performance, including energy efficiency, energy use, and energy consumption. This standard also specifies requirements applicable to energy use and consumption, including measurement, documentation and reporting, design and procurement practices for equipment, systems, processes and personnel that contribute to energy performance. The standard applies to all variables affecting energy performance which can be monitored and influenced by the steel plant. However the standard does not prescribe specific performance criteria with respect to energy.
Energy management is the practice by which the iron and steel industry works strategically with energy issues, and an energy management system is a tool to be used by the steel plant management in order to implement energy management. Requirements for energy management systems are specified in the International Standard ISO 50001. The ISO 50001 follows the Plan-Do-Check-Act (PDCA) process for the continual improvement process and incorporates energy management into everyday organizational practices. Successful energy management is required to be strategically handled, and one key element in this regards is to have an organized and on-going programme of energy saving projects. The PDCA cycle in Fig 2 illustrates the process of successful energy management system.
Fig 2 PDCA cycle for energy management system
In the context of energy management, the PDCA approach can be outlined as follows.
- Plan – It consists of conducting the energy review and establishing the baseline energy performance indicators, objectives, targets and action plans necessary to deliver results which will improve energy performance in accordance with the energy policy of the organization.
- Do – It constitutes the implementation of the energy management action plans.
- Check – It consists of monitoring and measuring the processes and the key characteristics of operations which determine energy performance against the energy policy and objectives, and report the results.
- Act – It constitutes taking actions for continually improving the energy performance of the organization.
The process of successful energy management in a steel plant consists of several steps. These steps are described below.
Energy policy – the energy policy and vision of the organization are the foundation for priorities and decision-making with regard to energy issues.
Preparation of energy plan – An energy review is conducted and targets, objectives, and action plans are established to meet legal requirements and the energy policy of the organization.
Implementation and operation – The action plans are implemented and this involves, for example, procurement, operational control, communication, documentation, training, and awareness.
Checking and correction – These activities involve actions such as energy monitoring and energy performance analysis, reporting of results, evaluation of compliance with legal requirements, and the energy policy of the organization, besides corrective and preventive actions.
Management review – During the management review the opportunities to improve energy performance are identified and the top management revises the energy policy of the organization, goals, and targets based on information and data extracted from the checking process. The review ensures continual improvements in energy performance and the energy management system.
A well structured energy management is a reliable instrument to improve the energy performance of the steel plant. Further, successful energy management needs a strategic approach which includes (i) an initial energy audit, (ii) senior management support, (iii) monitoring of energy use, (iv) recognition that management is as important as technology, and (v) an organized and on-going programme of energy-saving projects. There are four main components which are important for an effective energy management system. These components are (i) analysis of historical data, (ii) energy audits, (iii) engineering analysis and investment proposals based on feasibility studies, and (iv) personnel training and information.
The energy policy of the steel plant organization is required to give the energy manager the authority to be part of business planning, the purchasing of production and measuring equipment, energy reporting, and training of employees. Planning is very important for any energy management programme, and to develop a successful plan the people assigned to implement the plan are required to participate in the planning process.
A successful energy management system frequently relies on one ambitious person who makes things happen. However, in order to have productive and permanent energy management, it is important to develop an organizational structure which involves all the employees. Employees are a great untapped resource in energy management programmes, and their ideas for improved energy efficiency are to be sought. A good practice is that the energy managers devote 20 % of their working time to talking to the employees. Human resource helps in sustainable and enhanced energy performance through improved opportunities for learning, knowledge sharing, flexibility, commitment, creativity, and teamwork.
The awareness that human resources are important has increased in recent times. A Danish energy management model which previously focused mainly on technical monitoring and measuring but now also includes information exchanges, communication, internal and external audits, and employee engagement. The energy manager is required to have support from an energy team with representatives from finance and accounts, purchase, production, and maintenance and each of the operation department. The purpose of this team is to bring new ideas and to supplement skills which the energy manager lacks.
Compliance with legal requirements is required to be evaluated, and energy management practices are to be continuously evaluated and corrected. This needs monitoring and measuring energy use through sub-metering and recurring internal energy audits. The reporting requirements are to be kept as simple as possible (e.g., visualizing energy utilization in a continuous graph and comparing it to the set norm). However, data and key performance indicators (KPIs) do not frequently allow for effective energy performance evaluation and decision support. In addition, steel plant can industry experience problems in finding software suitable for visualising key energy efficiency performance indicators and simulation tools which can integrate energy efficiency performance.
In every energy management programme, it is important to have support from the senior management. Moreover, the energy manager and the energy committee are required to revise the energy policy and recommend updating when necessary. If climate change issues are administrated by an energy manager or an environmental manager then the steel plant has more climate friendly practices. Further, if there is a hierarchical proximity between the energy manager and the top management, then the steel plant has a more energy and climate friendly management. However, if the top management is in charge of the energy and the climate related issues then the reverse is true.
The energy management system enables the steel plant to achieve its policy commitments, take action as needed to improve its energy performance, and demonstrate the conformity of the system to the requirements of the standard. The standard applies to the activities under the control of the steel plant, and application of the standard can be tailored to fit the specific requirements of the plant, including the complexity of the system, degree of documentation, and resources.
The system approach for energy management contributes (i) to more efficient use of available energy sources, (ii) to enhanced competitiveness, and (iii) to reducing greenhouse gas emissions and other related environmental impacts. The system approach does not establish absolute requirements for energy performance beyond the commitments in the energy policy of the organization and its obligation to comply with applicable legal requirements and other requirements.
Energy management system helps plant operators to monitor and optimize the energy flows. It helps the management to analyze and compare results against plans. It detects avoidable energy losses and generates consumption forecasts and minimizes peak loads.
Technical approach based energy management
The technical approach based energy management in the steel plant has several benefits consisting of (i) optimization of all the purchases and consumptions of all fuel types and energy inputs, (ii) creation of an efficient system for comprehensive management of all major energy flows within the steel plant, (iii) optimization of the use of by-product fuel gases within the steel plant, (iv) making possible the effective use of media pressure energy, sensible and physical heat of metallurgical gases and fumes, (v) reducing energy intensity per ton of crude steel, (v) reducing carbon di-oxide and other emissions, and (vi) operating as an effective system for the comprehensive management of energy flow.
The technical approach based energy management normally consists of an energy management information system (EMIS) which provides relevant real time information regarding energy performance to the key individuals and departments. This enables detection of energy related opportunities and anomalies and contributes to the energy performance and operational improvements.
Functions of EMIS includes display of real time operational information, monitoring consumption and any affecting factors, data acquisition and aggregation from disparate data sources, online energy balance, monitoring of sustainability of KPIs, alerts for sudden changes in use patterns, analysis of the data, usage and cost analysis, , bench-marking with best periods, target performance and best practices and predicting of trends. EMIS also carries out forecasting and planning based on near real time reporting. EMIS plays a key role in strategy and continuous improvement process. It provides real time visibility of energy data which facilitates decision making.
For an effective EMIS, steel plants have an energy management centre equipped with a supervisory control and data acquisition (SCADA) system which gathers all plant site energy information and manages the load dispatch. Energy information to SCADA system is provided by remote PLCs (programmable logic controllers) and field instruments. Energy management optimization tools are used for high performance energy process data management and for the recording of time series – both historic and forecasts- of measured and calculated data. For this real time process data is collected from various data acquisition systems through interfaces and stored in the database as time histories.
The EMIS is not a simple energy management department or a single computer data acquisition system, but rather the entity for energy management and control system. EMIS is equipped with a variety of the digital monitoring instruments and mainframe computers, presenting fuel gases (coke oven gas, blast furnace gas, and converter gas etc.), steam, electricity, utility gases (oxygen, nitrogen, argon, and compressed air etc.), water (fresh water, circulating water, soft water, demineralised water and the external drainage etc.), and other information on the same platform. It not only has the functions of energy flow rate monitoring, energy supply and demand display, and energy forecasting, but also can auto generate an optimal scheduling strategy to achieve a steady supply and efficient utilization according to the change of production.
With the implementation of the EMIS in the steel plants, the majority of energy related decision making is done on-line, and only a small number of off-line decisions are taken. This has helped in the operational optimization.
EMIS provides several benefits to the steel plant with respect to the energy performance of the steel plant. These benefits include (i) accurate measurement and recording of energy consumption which helps to make timely and intelligent decisions, (ii) ability to better handle any abnormal operation caused by process upsets or unplanned equipment outage, (iii) ability to correlate energy consumption of process units to its measured output, and with benchmarks using data from the histories and this allows to set targets for energy efficiency improvements, and periodic review of the targets, and (iv) plant wide access to the energy supply and consumption of the entire site through a centralized server, enabling monitoring of individual energy networks, and individual process units in real time.