Energy Management in a Steel Plant
Energy Management in a Steel Plant
Iron and steel industry is the largest consumer of energy among all industrial sectors. Energy conservation in steel industry is crucial for its competitiveness, sustainability and minimization of environmental impacts including green house gas emissions and better resource management. As per World Steel Association, energy costs represent around 20 % to 25 % of the total input of steel plants. Energy cost cutting and energy efficiency improvements are the most important topics of control for the steel plant management. Energy management provides the following opportunities in a steel plant.
- It provides opportunities to decrease the energy intensity per ton of crude steel
- It provides opportunities to adopt best or good practices for utilization of energy sources more effectively
- It provides opportunities for using best or good practices for recovery of heat and gas energy wherever practical.
- It enables the plants to develop plans for reduction of plant’s energy intensity
- It makes plant to carry out prioritization of those investments which have biggest impact on the energy efficiency.
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 implementation of ISO 50001-2011 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 streamlines 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 50001-2011 specifies the energy management system (EnMS) 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 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 that can be monitored and influenced by the steel plant. However the standard does not prescribe specific performance criteria with respect to energy.
An EnMS 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. ISO 50001 – 2011 standard is based on the Plan – Do – Check – Act (PDCA) continual improvement process and incorporates energy management into everyday organizational practices, as given in Fig 1. In the context of energy management, the PDCA approach can be outlined as follows
- Plan – To conduct the energy review and establish the baseline, energy performance indicators, objectives, targets and action plans necessary to deliver results that will improve energy performance in accordance with the steel plant’s energy policy.
- Do – To implement the energy management action plans.
- Check – To monitor and measure processes and the key characteristics of operations that determine energy performance against the energy policy and objectives, and report the results.
- Act – To take actions to continually improve energy performance.
Fig 1 PDCA cycle for energy management
The system approach for energy management contributes to more efficient use of available energy sources, to enhanced competitiveness and to reducing greenhouse gas emissions and other related environmental impacts. It does not establish absolute requirements for energy performance beyond the commitments in the energy policy of the steel plant 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 usually consists of an energy management information system (EMIS) which provides relevant information to key individuals and departments. This enables detection of energy related opportunities and anomalies and contributes to energy performance and operational improvements. Functions of EMIS includes near real time operation, monitoring consumption and any affecting factors, data acquisition and aggregation from disparate data sources, online energy balance, monitoring of sustainability KPIs, alerts for sudden changes in use patterns, analysis of the data, usage and cost analysis, , benchmarking 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 that gathers all plant site energy information and manages the load dispatch. Energy information to SCADA system is provided by remote PLCs 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.
Following benefits are available from the EMIS system.
- Accurate measurement and recording of energy consumption, that helps to make timely and intelligent decisions.
- Ability to better handle any abnormal operation caused by process upsets or unplanned equipment outage.
- Ability to correlate energy consumption of process units to its measured output, and with benchmarks using data from the histories. This allows to set targets for energy efficiency improvements, and periodic review of the targets
- 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.
The technical approach based energy management has the following advantages.
- It optimizes purchase and consumption of all fuel types and energy inputs
- It creates an efficient system for comprehensive management of all major energy flows within the steel plant.
- It optimizes the use of byproduct fuel gases within the steel plant.
- It makes possible the effective use of media pressure energy, sensible and physical heat of metallurgical gases and fumes.
- It reduces energy intensity per ton of crude steel.
- It reduces CO2 and other emissions.
- It operates as an effective system for the comprehensive management of energy flow.