During the ozone season, from May through September, the AMS optimizer predicts NOx emission rates. This estimate is based on fuels being burned to ensure that emission limits aren’t violated. The documented NOx savings can even be traded at the end of the NOx season. (The EPA’s Clean Air Act Amendments of 1990 set a goal of reducing NOx by 2-million tons from 1980 levels; one of the provisions of that act establishes NOxtrading.) For the optimizer to operate effectively, instrumentation throughout the power generation and steam distribution systems must be highly reliable. The optimizer monitors instruments. When suspect measurements are received, the data validation capabilities within the optimizer are configured to reject suspect readings and substitute the last good readings or default to expected values. The system also alerts operators of an instrument fault. Accurate, well-calibrated instrumentation is a key to success in controlling any process, especially steam and power generation. For example, if the measurement of produced electricity was in error by only +2 MW, imported electricity would be 2-MW higher than the optimum. The error in projected costs, the added cost, could be more than $350,000 per year. This is a powerful incentive for maintaining a vigilant instrumentation PM program.
Earlier this year, Eastman received the American Chemistry Council’s Exceptional Merit award for “significant improvements in manufacturing at a plant site” based on the utilities optimization system. This recognition from our peers in the chemical industry acknowledges our efforts to conserve energy.
In turn, we appreciate Emerson’s contribution to this award. Their technology and expertise were instrumental in helping us meet our energy cost reduction goal. Emerson provided a low-risk solution that has generated high returns. An audit was conducted comparing past operation against new operation with the optimizer. The architecture for the optimizer is presented in Figure 3.
Figure 3. The chart above shows the approach
This audit verified the savings estimated when the project began — a payback of less than six months! To help define the true benefit of the new system, savings were broken down further. The online optimizer was responsible for 90% of the savings; a further 10% was accrued from the offline systems. These systems monitored less critical components. Periodically, stored data are downloaded from these independent monitors. With AMS Optimizer, we have a robust and reliable system allowing us to accurately sustain economic decisions that will continue to generate savings for years to come. Lessons learned from operating the optimization system may help to improve the process and lead to further improvements in controls and real-time cost savings.
C. Lemuel Mixon is a technical associate in Utilities Distribution services with Eastman Chemical Co., Kingsport, Tenn.; e-mail him at clmixon@ eastman.com.