Louisiana joint venture starts up coke-fueled cogen plant. (Nelson Industrial Steam Co.) (includes related article)

During the mid-1980s, the unpredictability of electric power rates led two refiners and a chemical producer to consider installing their own power-generating facilities.

The outcome was the joint development of a cogenerating plant at Westlake, La.

The plant substantially reduces energy costs and emissions by burning petroleum coke in a state-of-the-art circulating fluidized bed (CFB) steam generator.

The $220-million cogenerating project began in 1988 with the formation of Nelson Industrial Steam Co. (Nisco), a four-partner joint venture consisting of Citgo Petroleum Corp., Conoco Inc., Gulf States Utilities (GSU), and Vista Chemical Co. The purpose of the venture was to develop a cogenerating facility to supply electricity and steam to the partners.

Nisco's two 100-mw CFB reheat steam generators started up smoothly in August of last year. This installation is the first commercial use of an advanced reheat CFB steam generator that combines an innovative heat exchanger with a CFB boiler. This extends the use of efficient CFB technology to large-capacity power generating units.

All four Nisco partners had diverse needs and economic interests, yet each recognized the mutual benefits a partnership could offer. The partnership provided a 200-mw cogenerating plant with two important features: the use of low-cost petroleum coke and the use of GSU's existing power plant at Westlake, which minimized capital costs.

Part of GSU's motivation for entering the project was the weakening of its baseload created by the three companies' collective 200-mw load. GSU sold two older generating units at its Roy S. Nelson generating station, north of Westlake, to Nisco in 1988.

Nisco then embarked on the $220-million construction project to replace the two conventional gas-fired boilers with two Foster Wheeler Energy Corp. (FWEC) coke-fired CFB reheat-steam generators. GSU's existing turbine generators and auxiliary plant-support systems are utilized in place.

Low-cost fuel

Citgo and Conoco supply the 1,800 tons/day of low-cost coke from their refineries in Lake Charles, La. The electricity is sold to GSU, which operates the cogeneration unit.

The use of petroleum coke as a CFB boiler fuel is a perfect solution to the problem of finding a value-added market for coke, a by-product of the refining process. At the same time, coke is an abundant, low-cost fuel, compared to natural gas or coal.

At current prices at the plant site, coke costs approximately $0.20/MMBTU, as compared to $2.00/MMBTU for natural gas. Coal would cost five to eight times as much as coke. GSU had used natural gas before the two CFB boilers were installed.

Coke's low volatile content …