William Jerald, CalPortland.
The manufacturing of portland cement is an energy intensive operation, requiring large amounts of electricity and pyroprocess fuels for kiln operations. The business of operating a cement plant requires a sharp focus on the cost of energy consumption. CalPortland is a building materials company that operates three cement plants in the US, with two plants located in California and one in Arizona. CalPortland cement plant operations have been in production since 1891, and the experience of running these plants has helped set the foundation of the company that exists today. Part of the growth experience was embracing the systematic process of corporate energy management.
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ENERGY STAR certification
In 2003, CalPortland was approached by the US Environmental Protection Agency’s (EPA) ENERGY STAR® programme, recruiting it to become an ENERGY STAR partner. The ENERGY STAR partnership provides a variety of tools for assisting with the building and operation of an effective energy-management programme. This programme is officiated by the building of a proper structure, as defined by the ENERGY STAR assessment matrix, defining a management structure, tracking and monitoring energy, and recognising energy-management achievements.
ENERGY STAR provides a variety of methods for recognising achievements in energy management. The ENERGY STAR partnership recognises corporate energy-management programmes by annually awarding ENERGY STAR Partner of the Year awards to businesses and organisations that have energy programmes that follow each phase of the ENERGY STAR assessment matrix and show extraordinary effort in the management of energy. CalPortland has won the ENERGY STAR Partner of the Year award for fourteen consecutive years. The award compares the CalPortland energy-management programme against other well-known nationally recognised companies.
The ENERGY STAR programme recognises individual facility achievements by providing certifications for many types of facilities, including office buildings, cement plants, automotive manufacturing, pharmaceutical, integrated steel plants, and many others. The certification process uses an Energy Performance Indicator (EPI), which is an economic modelling tool developed by Dr Gayle Boyd of Duke University.
The EPI uses energy and production data from all the cement plants in the US and creates a scoring system ranking a cement plant from 0 to 100. A plant achieving 100 is the highest ranked and most efficient of the cement plants in the US. When a plant scores above 75 it is eligible for ENERGY STAR plant certification. This ENERGY STAR plant certification is an important recognition and comes with a congratulatory letter to the CEO of the certified company, a certificate of achievement, and the ability to promote the certification with signs, flags, banners, and with press releases to local and national media entities.
Each year, CalPortland enters production and energy data into the EPI to determine its ENERGY STAR certification. It then applies for certification for those plants that exceed the 75-point mark. Four CalPortland cement plants have earned ENERGY STAR certification over the years. The CalPortland Colton cement plant was ENERGY STAR certified from 2006 to 2010, after which the Colton plant was retired due to the economic impact of the recent recession. In Arizona, the Rillito cement plant’s operations have produced six years of ENERGY STAR certification from 2012 to 2017. The Mojave cement plant in California was certified in 2006 and 2007, and then again in 2016. Most recently, the newly acquired Oro Grande cement plant achieved its first ENERGY STAR certification in 2017.
The Rillito cement plant
The Rillito cement plant first achieved the ENERGY STAR certification in 2012. A key factor in establishing an efficient plant is simply minimising energy consumption per unit of product produced. For a cement plant, the mmbtu per tonne is the key performance indicator used for monitoring the plant performance. The Rillito cement plant is focused on the reliability of its equipment, which minimises kiln downtime, reducing fuel and electrical consumption during idle production. The Rillito cement plant maintenance department closely monitors equipment status using predictive analysis, including monthly vibration analysis monitoring of critical process components.
The US Department of Energy’s Better Plants Program has provided efficiency improvement measures to the Rillito cement plant, such as the In-Plant Training (INPLT) programme. The Rillito plant performed a compressed air study and a process fan study using INPLT programme Both studies identified multiple energy-efficiency opportunities and gave the plant guidance on what pieces of equipment would give maximum savings for the plant’s capital investment.
The compressed air study used a specialist to perform a review of the compressed air supply and demand system, train the facility on compressed air energy matters, and provide a comprehensive report on the study findings. The process fan study was similar, as a fan specialist assisted the process engineering group with the reviewing of the installed fans and their fan curves. This involved taking into account the current process condition fan measurements and evaluating the performance of the fans, while looking for energy-efficiency opportunities.
Each year, the Rillito plant continues to operate at a very efficient level, funding capital projects to further improve its efficiency. Installing an expert control system, allowing advanced controls to minimise control transients, assisted the process. A feed control bin was installed to properly meter in-baghouse dust, which allowed a more consistent raw feed supply, minimising kiln fuel adjustments to prevent fuel waste.
Most recently, a US$9 million investment was made to the clinker cooler. The entire 1972 vintage cooler was removed and replaced, and all fans where modified from direct drive damper controlled fans to high-efficiency variable frequency drives. The cooler modification has reduced operational downtime, increased thermal recovery from the clinker (allowing cooler consistent clinker sizing), and returned the hot gases back to the kiln process (requiring less fuel for heating). The combination of good maintenance practices to maintain high reliability, as well as the multiple energy-efficiency improvements, has kept the Rillito cement plant ENERGY STAR certified for 6 years from 2012 − 2017.
The Oro Grande cement plant
In October 2015, CalPortland acquired the Oro Grande cement plant from Martin Marietta. The Oro Grande cement plant is a facility near Victorville, California, and has been in operation since 1909. In 2006, the plant was modernised by installing a new raw material stacker reclaimer, a new hydraulic roll press raw mill, a modern five-stage dual string preheater tower, and a two-pier kiln. The kiln feeds a clinker storage dome and one 11 500 hp. ball mill for finish grinding.
When the Oro Grande cement plant was acquired, the CalPortland energy-management team began work on evaluating the plant’s energy intensity and working with the CalPortland process engineers to identify areas of improvement. An important aspect of energy management is tracking energy consumption. The energy-management team leveraged the existing modern energy-monitoring system and improved the collection, accounting, and documentation of energy usage.
Efforts are being made to increase the kiln uptime by improving the maintenance practices of the plant. The Oro Grande cement plant has an extremely large compressed air footprint, so the CalPortland team quickly evaluated the compressed air systems and developed a plan to improve the compressed air system performance. The process control system’s control loops were scrutinised and time has been spent on adjusting the loop settings and tuning. Continuing the focus on process control, CalPortland added two process engineers to the plant staff to bring the process engineering to CalPortland standards.
The increased focus on energy allowed the Oro Grande cement plant to earn its first ENERGY STAR certification in 2017. CalPortland’s goal for the plant is to continue to improve efficiency. Capital project improvements for this year include upgrades to the secondary crushing system that will improve the energy intensity of the crushing system, as well as providing a more consistent raw mix sizing distribution, which will improve the energy efficiency of the hydraulic roll press raw mill. The raw mill has undergone multiple process control and maintenance improvements to increase the uptime and production of the system.
The Oro Grande cement plant has a clinker storage dome and is finish mill limited. With only one finish mill onsite, the plant runs out of clinker storage space and the kiln must be shut down many times during the year for inventory control. CalPortland began engineering a second finish mill in 2017 and broke ground on mill expansion in 2018, with expectations that the mill will be operational by 2019. The second finish mill will allow the Oro Grande cement plant kiln to become much more efficient with minimal kiln idle time. These multiple energy-efficiency efforts will help the plant maintain its ENERGY STAR certification going forward.
CalPortland spends over US$100 million on energy annually. The company’s energy programme keeps a focus on energy cost reduction. The CalPortland/ENERGY STAR partnership provides the company with tools and guidance on how to create and maintain a successful energy-management programme.
About the author: William Jerald is Chief Energy Engineer at CalPortland.
This article first appeared in the May 2018 issue of World Cement. Interested in reading more like this? Sign up for a FREE TRIAL subscription here.
Read the article online at: https://www.worldcement.com/special-reports/23042018/be-an-energy-star/