Production Resource Optimisation

Transcription

1 T Rosy Wang, Global Solutions Director for Cement, Schneider Electric, outlines how production resource optimisation can improve efficiency, quality and sustainability. he COO, general manager or plant manager of a cement business faces increasing energy costs, an unsecured supply of fuel and power, volatile volume fluctuations by geographic region, limited capex to expand capacity, increasing sustainability requirements and competitive pressures resulting in a weak operating margin. In response to these growing challenges, solutions have been developed to help win the battle of future competition with maximised business profits and prolonged sustainability. Asset optimisation and corporate governance l Trend 1: volatile volume fluctuations by geographic region (Figure 1). l Trend 2: merger, acquisition, restructuring and market consolidation. l Implications: with the anticipated reduction in construction of new production lines, cement companies will increasingly need technological modifications to master and strengthen existing plant operations and, in emerging markets, to quickly gain a better market share by maximising production of existing facilities. l Possible actions: asset optimisation. Production Resource Optimisation

2 Table 1. KPI impact on revenue from COO perspective KPIs Average Top 20% (as target) The best The worst RF (reliability factor) 93% 98% 99.5% 68% PF (performance factor) 92.5% 98.5% 120% 75% Impact on revenue (top 20% vs average) Annual clinker production of one line (million tpa) Total clinker production in the company (million tpa) Additional clinker if optimised (million tpa) 9.2 Company additional profit 276 (million US$ pa) The number of equivalent clinker lines 6.1 Notes (assumptions) Rated capacity of one clinker line 500 (tpd) Planned overhaul shutdown (days) 15 Margin from clinker production 30 (US$/t) Annual clinker production for one line (15 days for planned overhaul, 0 days for external circumstances) Total clinker lines in the company x (365-15) x RF x PF l RF (reliability) = operation hour / (opening hours - planned shutdown hours - stoppage hours due to circumstances) x 100%. l PF (performance factor) = average kiln output / rated capacity x 100%. l MTBF (mean time between failures) = total operation hours in a year / number of stoppages for incidents. l Clinker volume (yearly production) = rated capacity x 365 x UF x PF or = rated capacity x (365 - planned shutdown days - stoppage hours due to circumstances) x RF x PF. Benchmark For well mastered cement plants, the kiln RF can reach 99.5%; the annual UF can reach 96%; MTBF can reach 30 days, with a longest record of 145 days continous running; PF reaches %. For average plants, the kiln RF is about 90 93% (many companies do not even measure this); the annual UF is around 85%; MTBF stands at 5 days and PF at 92%. For poorly managed plants, the kiln RF averages 68%; the annual UF is <80%; with MTBF of 2 3 days and PF of 75%. Figure 1. World cement production by region. 1 Definitions To begin with, the definitions for plant performance key performance indicators (KPIs) must be consistent. The following are standard KPI definitions: l UF (utilisation factor) = operation hours / opening hours x 100%. KPI impact on revenue and profit The impact of two KPIs from an operations perspective can be seen in Table 1. This shows the statistics for RF and PF in the cement industry, with representative coverage. The average performance delivers RF 93% and PF 92.5%, whilst the top 20% achieved RF 98% and PF 98.5%. The top 20% level is realistic, achievable and should be the company s target. For example, a company with 50 lines, including a US$30/t margin from clinker production, can gain US$276 million pa based on the average company s ability to achieve a top 20% level. The additional production is equivalent to 6.1 new clinker lines. Even in the current economic climate and with the limited availability of Capex, a company can save up to US$6.1 x 200 million (a new line costs about US$200 million), resulting in greater flexibility and competitiveness in an uncertain market. Reprinted from worldcement.com [May 12]

3 Solution 1: KPI reporting and benchmarking An online benchmarking tool can consolidate the KPIs on production, energy consumption and downtime. This tool also allows corporate executives to provide better Figure 2. Online reporting/benchmarking of KPIs. governance by having instant and remote access to an overview of the KPIs across sites, in order to make accurate and quick decisions, including prioritisation of corporate agendas and identification of sites that need additional support (Figure 2). Solution 2: downtime management Visibility of plant operations can help to ensure that a production facility is operating at its peak efficiency by identifying where, how, and why production delays are occurring. By reporting scheduled and unscheduled events, as well as underperforming equipment, a complete analysis of production downtime causes can be obtained. This information is crucial for prioritising maintenance and improving operating procedures. The automatic capture of downtime events helps operators to become more efficient and removes the inaccuracies and inconsistencies of manual systems (Figure 3). Ampla Downtime defines downtime as: l Real downtime the time production has actually stopped. l Virtual downtime the time when production is below the user-defined threshold, but production has not stopped. Example Adelaide Brighton Cement Ltd, Australia, implemented downtime management, the result of which is illustrated in Figure 4. The Adelaide Brighton example demonstrates how a modern IT solution provides a tool for continuous improvement. Not only did the implementation of Ampla reduce downtime stoppages and slow running in the year of implementation, it continued to facilitate y/y continuous improvement. Energy optimisation Energy optimisation covers energy consumption and energy costs. The typical energy cost structure is illustrated in Figure 5. Figure 3. Ampla Production Analyst. Specific energy consumption Many plants initially begin the path to energy efficiency by fixing the basics (for example, retrofits, process optimisation and VSD), which is viewed as a short-term success. After some time, these plants experience performance drifts. Energy management and optimisation cannot be accomplished and sustained through short-term efforts. Figure 4. Adelaide Brighton Cement Ltd, Australia, reduced kiln stoppage with downtime management. 2 Case study A plant in Beijing, China, reduced its power consumption from 121 kw/t to 100 kw/t by following a 3 year intensive improvement programme. However, the positive results that were achieved were not improved upon further. This was due to a variety of factors, the most important being that the plant did

4 Figure 5. Energy cost structure in cement manufacturing. Figure 6. Plant EE story need for continuous improvement. Figure 7. Plant power consumption on air compressors. Figure 8. EOS dashboard view for energy KPIs. not have a real-time energy management system to aid continuous improvement (Figure 6). Figure 7 shows the air compressor power consumption/t for cement grinding. The average is 2.5 kwh/t, with fluctuations ranging from 1.5 kwh/t (the best this plant achieved) to 7 kwh/t. If the plant maintained its best power consumption level on a daily basis, it could save 1 kwh/t with the same facility through optimisation. For this 1 million tpa cement plant, the savings could be 1 million kwh pa and US$ pa. The solution air compressor system optimisation consists of VSD and smart control, can avoid idle running and maintain stable pressure of the system. Solution: online energy optimisation system (EOS) An EOS can provide online production and energy KPIs with the dashboard views for different profiles in the cement plants and different levels in a company (Figure 8). The plant is able to carry out production and energy analysis in addition to real-time benchmarking, which can be done by region, plant, workshop or crew. This system enables operators to react faster and management to make decisions earlier to avoid big energy losses. Today, with an EOS, the kiln coach can focus more on analysis and other duties rather than generating statistics, since key reports, including shift, daily and monthly, can be automated. The operators get more eyes to optimise kiln operation with real-time feedback through the Operator Tool Box. Process efficiency and optimisation solutions Figure 9 indicates process parameters in clinker making; a ±10% difference in the process parameters can be observed from plant to plant. Therefore, the heat consumption can vary greatly even with the same process depending on process mastery. These fluctuations can indicate opportunities for optimisation. From the central control room (CCR), one can easily observe the two key parameters: The temperature of preheater exhaust gas (T of C1). The temperature of cooler exhaust air (T of cooler exhaust). The energy efficiency level of a plant can be quickly evaluated with these two parameters. The following are some benchmark examples: l For a 4-stage preheater plant, the T of C1 exhaust can be C, whilst for a 5-stage preheater plant, the T of C1 exhaust can be C. l For a typical plant with a 5000 tpd line, at a fuel cost of US$3.6/GJ, if the C1 T reduces by 10 C, the specific heat consumption can be reduced by 0.7%. This results in an annual saving of approximately US$ l If the cooler exhaust T reduces by 10 C, the specific heat consumption can be reduced by 0.4%, which amounts to an annual saving of approximately US$ Reprinted from worldcement.com [May 12]

5 Process efficiency assessment energy step Today, a systematic methodology is available to assess process efficiencies. Energy Step contains the necessary measurements and in-depth diagnostics on all major energy consumption areas. Through this solution, root causes for high heat consumption and high power consumption can be analysed and a prioritised improvement project list, including investment and payback, can be provided. Case study Lunan Cement in China, containing two 2500 tpd kilns with 4-stage preheater, had a high heat consumption. Through a kiln audit and a diagnostic with simulation for combustion, Figure 9. Clinkering process. The process parameters vary greatly, allowing plenty of room for optimisation. a root cause was found uncompleted combustion of fuel in the calciner due to temperatures that were too low. The modification was designed and conducted during kiln shutdown, resulting in the waste gas temperature at preheater outlet (C1) being reduced from 400 C to 360 C. 3 The plant can save tpa in standard coal, a savings value of about US$1.5 million pa. Energy cost Situation and trends Electricity demand and price are increasing by 7.5% pa y/y. Thermal energy prices increase by 14% pa globally. In countries where alternative fuel (AF) is not yet commonly used, the thermal energy price has increased by 20% pa, whereas in developing countries where AF is commonly used, the mixed thermal energy price is less dependent on coal markets (Figure 10). Many cement companies are suffering profit loss due to energy cost increases. Conch, the largest cement producer in China, claimed that pressure from rising electricity prices remains (6.31% more than the previous year), the price of coal is soaring and energy costs are 68.6% of total costs, even with waste heat recovery (WHR) contribution. The margin for cement businesses is reducing while the price of cement has increased. 4 Solution 1: turn waste heat to green energy WHR WHR can make the most use of the heat from waste gas from the preheater and cooler, to generate electricity of kwh/t clinker without additional coal. This depends on the process and process mastery of the plant. The payback period is usually within three years. It mainly depends on the country location and its electricity supply rate. If the rate is >US$80/MWh or US$90/MWh, it will be profitable to build WHR. WHR is a matured technology; approximately 1000 WHR systems have been installed around the world. WHR not only reduces energy costs, it also improves a plant s carbon footprint. Solution 2: energy procurement services and solutions One can gain an overview of energy usage at the site, regional and enterprise level and optimise energy procurement through the following means: Third party market intelligence to drive decisions. Leveraging competition in deregulated markets and rate structures in regulated markets. Managing energy sourcing as a strategic component of energy spend. Matching sourcing activities to the risk profile of the organisation. Increasing visibility across an enterprise to usage and best practices via dashboard views. Figure 10. The energy price revolution for cement plants. This can result in a reduced energy cost (US$/MWh) of up to 10%, as well as a more reliable energy supply.

6 Quality mastery Figure 11. Quality Management Information System. What is good quality? Good quality entails the strength to meet customer needs and reduce energy consumption in a sustainable manner. This includes: l The uniformity of cement (for example, the standard deviation of strength). The lower the deviation, the better the uniformity. The higher the confidence when a concrete maker designs his concrete, the less cement he has to use per m 3 of concrete and the lower his concrete cost. l The fineness and workabilities. If the cement is ground too fine with high Blaine (specific surface area m 2 /kg), this not only consumes more energy for finish grinding but may also lead to poor workability of cement when making concrete. By visiting several ready mix stations, it was observed that concrete customers value the uniformity of cement as a key quality indicator. They are willing to pay higher prices for cement with better uniformity and workability, which will make their control easier and costs lower. Figure 12. Cement industry projected CO 2 emissions. 6 How to achieve good quality? Quality is determined by process, quality, and operation management. Kiln and cement mill operators play important roles in quality optimisation. Optimising daily operations can improve clinker and cement uniformity. Today, tools are available to assist with this: l Quality Management Information System (Figure 11). l Advanced Process Control. 5 This can significantly help to stabilise quality, especially when multifuels are used in the kiln. Sustainable development Cement, especially clinker manufacturing, is a carbon-intensive transformation process: l 1 t of clinker production generates t CO 2. 6 This depends on: MJ/t, kwh/t and loss from (CaCO 3 + MgCO 3 ). l 1 t of cement production generates t CO 2. This depends on: C/K ratio and kwh/t for finish grinding. Figure 13. CO 2 online reporting, benchmarking and breakdown. The cement industry has been challenged to reduce CO 2 emissions/t of cement. However, total emissions are increasing due to growing total cement demand worldwide. Figure 12 shows projected CO 2 emissions (in million t). CSI drafted the CO 2 protocol on cement and therefore only CSI members have been reporting their CO 2 emissions annually and manually. Today, the tool for online reporting and Reprinted from worldcement.com [May 12]

7 benchmarking for CO 2 emissions in the cement process is available to report on the following: l Total CO 2 emissions (tpd, tpm and tpa). l Unit emission t CO 2 /t clinker, t CO 2 /t cement (by type of cement). l The breakdown for direct CO 2 from fuel combustion, CaCO 3 decomposition and indirect CO 2 from electricity consumption. With this tool, cement companies can have better visibility with immediate emissions data. As a result, actions can be taken quickly to reduce GHG emissions and carbon tax if applicable (Figure 13). Conclusion Production resource optimisation covers asset and equipment efficiency, energy and quality optimisation and sustainability. l By improving equipment efficiency (RF, PF, MTBF), a company can increase revenue/profit and market share in a growing market without huge investment in new production lines, as well as being more flexible with less risk to cope with market changes. Online benchmarking helps corporations to consolidate and enhance existing plant operations. l Energy cost is 40 70% of production cost, with increases each year. Online energy management systems, energy audits and process optimisation can help reduce energy consumption/t. Energy trading services can help cement plants to pay less US$/MWh. WHR can generate power from waste process heat and reduce power use from the grid, thereby reducing energy bills and CO 2 footprint. l Quality optimisation impacts upon energy consumption and customer satisfaction. Uniformity is a very important quality indicator and can be achieved with quality management information systems and advanced process control. l Cement manufacturing is a carbon-intensive process. Online CO 2 reporting helps cement companies have better visibility and reduce their CO 2 footprint. All of the above can be achieved through people. Fostering an optimisation culture within the company and having a good system for continuous improvement can help with future competition, while remaining sustainable. References 1. Key facts and figures, Cembureau (2011). 2. Aurora, V., Adelaide Brighton Cement Ltd Presentation (2011). 3. Wang Zhirong, R., Simulation of RSP Preheater/Precalciner System, 4 th International Cement Conference, Beijing (1998), p Conch Cement Energy Cost, Digital Cement (2008). 5. Stettler, D. Controlling the Burn, ICR, March (2010), p Wang, R., Low Carbon Low Energy-Solutions from Schneider Electric, Beijing International Cement Summit (2010). 7. CSI-GNR (Get the Number Right) Report (2011).