Optimizing Cement Kiln Operation is the Most Cost-Effective Way to Reduce Emissions

There is a delicate balance between combustion and efficiency and NO_x generation, accurate measurement and quick response needs to be combined with optimization software.

Yokogawa process analyzers are already used to measure O₂ and CO at the upper end of a kiln or at the outlet of a flash furnace, where high-temperature, dust-laden gases flow. An in situ Zirconia oxygen analyzer provides a number of unique benefits Yokogawa analyzers are installed at the outlet of an ESP to monitor dust concentrations and optimize efficiency. They are installed in the stack to measure NO_x, SO₂, and O₂. With new regulations requiring scrubbers for removal of acid gases, the instruments can also be used to control reagent feed.

Yokogawa has many decades of experience in the cement industry Blue Circle Southern Cement (BCSC) is a leading Australian cement producer with manufacturing operations in the most populated eastern states. It operates a 1 million ton dry process kiln and a 500,000 ton wet process kiln at Berrima, a 550,000-ton dry process kiln on extensive raw material reserves at Waurn Ponds near Geelong in Victoria, and a 300,000 ton off-white cement kiln at Maldon.

At the Maldon Plant, Yokogawa's CENTUM XL distributed control system (DCS) had been introduced in 1990 and migrated to CENTUM CS 3000 in 2001. BCSC was satisfied with the performance of these systems, which have greatly exceeded their expectations by running problem free and experiencing zero lost production time . In addition, at the Berrima Plant, BCSC had introduced CENTUM XL and migrated it to CENTUM CS 3000. The customer was thus well familiar with Yokogawa's products and services, which became a factor in their subsequent decision to select Yokogawa's Exaquantum and Exaplog solution-based package software at these plants. The key features of these two packages are as follows:

Exaquantum Plant Information Management System

• For current and historical data viewing and storage

• Easy to use long-term data management

Exaplog Event Analysis Package

• For quantitative analysis of problems in the DCS event log

• Analysis of DCS historical logs using  When, Where, What (''3W'') filters

Cement plants in Japan are major purchasers of Yokogawa systems. DENKA’s selection of Exapilot in 2007 considered the following points:

1. The ease of integrating Exapilot with the Yokogawa CENTUM CS 3000 DCS used at the plant, which allows procedural overviews from Exapilot to be displayed on the CENTUM system’s graphic display

2. Exapilot enables both the automation and visualization of operational procedures

3. Exapilot is easy to configure and configuration changes can be done without high level programming knowledge

4. Exapilot is separate from the DCS so it is easy for operators to try a variety of procedures while a process is operating in order to find the best procedure.

The startup procedure for a vertical raw material mill is visualized in an Exapilot flowchart, and certain of the sub-procedures are automated. Operator workload is decreased and the mill operates smoothly and steadily without excessive vibration thanks to a reexamination of many settings, so maintenance work does not need to be carried out as frequently.

Important procedures during the startup of the finishing mill that have a direct bearing on product quality can be configured in Exapilot. No procedures are missed, operator workload is reduced, and mill startup can be completed in 20 percent less time. This is especially advantageous because the plant is operated at night to take advantage of cheaper electricity rates and workers on the night shift often have to perform the startup and shutdown procedures.

A variety of procedures can be standardized to optimize an operation. To aid in the visualization of an operation, comments can be entered next to an Exapilot flowchart, transforming it into an instruction manual. The visualization of all operational procedures in flowcharts facilitates the review and improvement of all the know-how of the Omi cement plant’s most skilled operators. This enables the plant to continue to make further improvements in the automation of its operations and of course facilitates the transfer of important technical know-how.