Recovering Steam Leaks, Boiler Improvements Yield Benefits
Improving boiler feedwater heating, recovering steam leak-off and reducing ester still heat use are among the ways the Eastman Chemical Co.’s Kingsport, Tenn., plant has won multiple Significant Improvement in Manufacturing Awards from the American Chemistry Council (ACC). In 2011, Eastman’s winning projects included five at the Kingsport site.
Recovery of Steam Leak-Off. Six Sigma techniques were used to recover 15 psi steam leak-off from shaft seals on turbo-generators in a powerhouse. New construction and use of an abandoned recovery system resulted in an annual energy savings of 44,391 MMBTU and an annual reduction in greenhouse gas emissions of 4,661 tons annually.
Improvements in Boiler Feedwater Exchange. The stage heaters at a powerhouse were operating at reduced efficiency due to material wear in the heat exchangers, resulting in the boiler feedwater bypassing the heaters. A monitoring program compared temperatures of the feedwater exiting the stage heater with an entitlement value, which returned the heaters to optimum efficiency and resulted in an increase in the feedwater’s temperature. As a result, the heat input required during steam generation was decreased and topping power from the generators was increased. These changes led to annual energy savings of 180,456 MMBTU and an annual greenhouse gas emissions reduction of 17,330 tons.
Improvements in Distillation Columns. Two changes - adding a new distillation column and replacing an existing column with a new more efficient design - led to lower reflux rates, tighter control and greater energy efficiency while maintaining production. The new column was started up when the existing column was shut down to replace sieve trays with distillation trays and optimize tray spacing for greater efficiency. The changes resulted in annual energy savings of 44,150 MMBTU and an annual greenhouse gas emissions reduction of 4,635 tons.
Reduced Ester Still Heat Use. An ester still had been heated with 600 psig steam modulated through a valve to a lower pressure. Experiments with the still revealed that the column could be heated from an existing 100 psig steam header with decreased energy use and increased control. The heater was repiped to take the steam from the header and drain it to a lower pressure condensate header, resulting in annual energy savings of 81,000 MMBTUs and an 8,500-ton reduction in greenhouse gas emissions.
Reduction of Natural Gas Use in Three Heat Transfer Material Furnaces. The furnaces provide heat for dimethyl terephthalate production. A new control strategy now automatically shifts the load from less efficient furnaces to more efficient ones, so the overall heat duty required is provided at maximum efficiency. When compared to 2008, natural gas consumption was reduced by 80 scf per MMBTU of heat delivered to the process, with a savings of 35,393 kscf in 2010, or 6.3 percent of total gas used. This converts to an annual savings of 36,455 MMBTUs and 1,922 tons of greenhouse gas.
Improved Steam Turbine Discharge. At Eastman’s Longview, Texas, site, the company was recognized with an ACC award for improving steam-turbine discharge. The company added an additional steam line to maintain a constant 175 psig steam-discharge pressure, which resulted in lower 1,500 psig steam demand, an annual savings of 34,000 MMBTUs and 2,250 tons of greenhouse gas emissions.
This is the 18th consecutive year that Eastman has earned the energy awards, receiving six of the 48 awards presented to 17 ACC member companies.