At its Tehachapi plant in California, USA, Lehigh Southwest Cement Co was looking for a pregrinding solution to increase cement grinding efficiency and as a result, take advantage of off-peak power savings. From an operational perspective, it was important to minimise peak grinding and downtime of the existing two ball mill systems.
When researching the options, Lehigh Southwest put emphasis on finding a supplier that could understand the unique challenges and provide the cement producer with lower operating and maintenance costs. It was this approach that became key for its relationship with FLSmidth, which was chosen as the EPC partner.
A collaborative working relationship is also an important factor for FLSmidth, according to the company’s Head of Projects and Upgrades, Sathish Krishnamoorthy: “One of the best working relationships we can hope for is when a customer comes to us and shares their challenges. We can then work together to find the best solution.”
Minimal capital investment
As part of their collaboration, Lehigh Southwest and FLSmidth reviewed the existing equipment and site specifications of the Tehachapi plant. Considering the required finish grinding capacity,it was difficult to justify a vertical mill as a solution. Instead, comparing the efficiency gains delivered for minimal capital investment, it became clear that a hydraulic roller press (HRP) would be the most economical choice for a pregrinding function.
Several special project requirements needed to be met. The system’s existing bins were to be used as product cake bins and it needed the flexibility to bypass the roller press circuit.
In addition, specialist expertise was key to navigating design challenges, such as keeping the building height to a minimum. During the engineering phase, the layout was optimised to provide good access and meet all safety standards – all key to Lehigh Southwest implementing the most risk-free, cost-economical solution.
Construction at the site began in August 2016 and the upgraded grinding system was commissioned in May 2017. Within a short time after start-up, it had exceeded the guaranteed process performance parameters, while the goal of minimising downtime was also achieved. As a result of the project, Lehigh Southwest expects to realise a significant reduction in total cost of ownership.
Spare parts planning
Mitigating against any possible failures and minimising potential downtime requires careful spare parts management. The decision was made to order critical spare parts in advance and have them in stock from day one of operation. This, as well as the relative proximity of the FLSmidth support centre facility in Arizona to the Tehachapi plant site, ensured a high level of reassurance, with expertise and supplies being readily available.
Better electrical efficiency
Surrounded by windfarms, Lehigh Southwest is sensitive to its power consumption, so it was particularly important to maximise electric power efficiency with less runtime with the HRP circuit.
Recognising this need, FLSmidth offered a tailored solution that allowed the flexibility to run the plant at optimal times of the day to reduce power consumption and increase savings, while still maintaining production requirements.
The HRP 1.25/ball mill at the Tehachapi plant achieved excellent reliability and energy performance results, the most important of all performance guarantees.
|Table 1: HRP 1.25/ball mill performance guarantees at Lehigh Southwest Cement Co’s Tehachapi plant
|Specific power of total HRP system (kWh/t)
|Reliability factor of HRP system (%)
EPC projects of this type are complex. Avanish Karrahe, product line manager at FLSmidth, explains that every part of the decision-making process needs to be carefully managed to gain the full extent of the efficiencies. But by keeping an open mind and a creative approach to the solutions, Lehigh Southwest and FLSmidth have ensured cost efficiencies are maximised by utilising a maintenance- friendly HRP solution for a non-standard plant layout.
I’m satisfied that we met our responsibilities in delivering to the needs of a customer whose prime focus was on reliability and energy efficiency. We at FLSmidth look forward to working with Lehigh Southwest and the Heidelberg Cement Group in the future.