Reliance Industries, India’s largest business enterprise, operates a $3 billion, 17-plant industrial complex near Surat, the country’s eighth largest city. The Reliance Hazira complex consists of a naphtha cracker and 16 other plants producing polymers, fiber intermediates, polyester and petrochemicals.
As part of the facility’s first phase, Reliance built a cogeneration plant to provide the other plants with electricity and steam. The cogeneration plant has nine GE Frame 6 turbines each with a 125 ton per hour (TPH) heat recovery steam generator, and two 40 MW steam turbines. There is also a 95 TPH natural circulation forced drought auxiliary boiler. The generators and boilers together provide 350MW of power and 1220 TPH of steam, by burning a variety of fuels including natural gas, cracker gas, C9, naphtha and high sulfur diesel. Between the heat recovery systems and the use of inlet fogging, the plant achieves an overall effective fuel utilization rate of 70%.
“With the gas turbine cogeneration system installed, it is possible to recover a substantial percentage of the exhaust heat and this achieves considerable savings in fuel,” Said the plant’s Sr. General Manager. “This system also results in reduced emissions and has minimal impact on the environment.”
Raising Winter Output
Under normal operating conditions, the cogen plant allows the Hazira complex to operate independently of the grid (the Gujarat Electricity Board), but in case of emergency it can connect to the grid. The complex normally demands about 280MW, below the plants 350MW total capacity. The load is shared by the gas and steam turbines, but the preference is to use the gas turbines as much as possible.
“The efficiency of the gas turbines is greater than the steam turbines,”says the Plant Manager. “Hence, if we load the gas turbines more than the steam turbines, it gives a cost benefit in unit generation.”
To further increase the GT output, Reliance started looking into inlet cooling methods to provide a power boost. They decided on trying a MeeFog system since it had a proven design with a low capital cost and could provide long-term reliability with less maintenance than other technologies. They installed the first system on one of the Frame 6 units. Based on the successful pilot, Reliance added MeeFog units onto four more of the GTs the following year.
Unlike many power plants which use fogging to meet peak summertime loads, the Hazira foggers operate on the opposite schedule. The foggers are shut down in the summer monsoon season and then brought back online during the relatively cooler (80°+ instead of 100°+), drier months.
“Our site is near the coast and the humidity level is very high for 7 to 8 months out of the year, the rest of the months we are running the fogging skids.”
They set the MeeFog units to bring the compressor inlet temperature down to about five degrees above the dry bulb temperature. When the foggers are operating, Reliance reported that they are able to boost the GT output by 8% to 10%, which reduces the need to use the boilers, resulting in higher fuel efficiency and lower emissions.