Naphtha Cracking Byproducts To Fuel GE's LM6000 Aeroderivative Gas Turbine
In May of 1999, a GE LM6000 aeroderivative gas turbine will begin commercial operation burning a combination of methane and hydrogen fuel - the byproducts from the naphtha cracking process at Tosoh's petrochemical plant in Yokkaichi, Japan. This is a unique application for the LM6000 because of the fuel it will burn as well as the captive power scheme. Tosoh expects to see a significant increase in the naphtha cracking plant's overall thermal efficiency with the new, efficient naphtha cracking furnace and this new power arrangement.
Japan's Electric Power Market
The Japanese government is currently considering deregulating the country's electric retail business. A final report is expected to be presented to the government by the Special Committee in December of 1998.
For now, captive power generation accounts for a significant portion of Japan's overall electricity business (see Table 1).
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General power utilities (10 companies)
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Wholesale power companies
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Subtotal
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Captive power
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Total
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223,495
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The Japanese government's policy on new thermal power plants has been classified into two categories:
- Short Lead Time Power Plant (SLT Power): Completion of the plant within 10 years.
- Long Lead Time Power Plant (LLT Power): Completion of the plant longer than 10 years.
All SLT Power must be purchased by public tender, and none of Japan's power utilities can compete. All LLT Power including replacement power must also be purchased by public tender. In contrast, tender is open to power utilities as well as independent power producers (IPPs). However no public utilities can construct LLT Power plants unless tender can be obtained through competition with other power utilities and IPP developers.
Tables 2 and 3 provide an overview of IPP tender results and IPP capacity in Japan, respectively.
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1st year (1996)
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2nd year (1997)
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*3rd year (1998)
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*Shikoku Power Utility announced a tender for a 150-MW IPP. All other utilities will not announce tenders for IPPS this year.
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Physical possible capacity
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Actual possible capacity considering fuel and water supply and environmental factors
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Market Forecast
To comply with the Japanese government's commitment to reduce CO2 emissions by 6% until 2010, the central and local governments have imposed very severe environmental regulations on power generating plants. With this in mind, gas turbine combined-cycle power plants using clean-burning fuels will probably account for a majority of future SLT Power projects in this country. Table 4 provides a 10-year forecast of the Japanese power market.
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SLT Power (IPP)
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LLT Power
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Retail Power
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Captive Power (purchased through
negotiated contract)
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The total captive power capacity for the coming 10 years will be maintained or slightly increased. The 8,000 megawatts forecasted in Table 4 will replace existing captive power plants due to life time and environmental issues. It is expected that almost all new captive power plants also will be based on combined-cycle, cogeneration gas turbine technology.
Project Background
Tosoh was established in 1935, and is headquartered in Tokyo, Japan. The worldwide company has 4,600 employees, and approximately 80% of its sales are generated in Japan. Its Petrochemicals Group produces olefin products such as ethylene, propylene and polyolefin products. Other basic groups within the company produce sodium hydroxide and sodium carbonate, and cements such as Portland fly-ash and Portland blast-furnace slag. The company also produces fine chemical products, scientific and diagnostic instruments and systems and specialty materials and electronics products.
Tosoh is expanding its Yokkaichi facility which currently has 13 cracking furnaces with a total production capacity of 400,000 tons of ethylene per year. The expanded plant will feature a unique gas turbine operating in simple cycle mode with the heat recovered from the gas turbine exhaust used for the cracking furnaces.
TEC of Japan and Lummus of the United States are handling the engineering and construction of the naphtha cracking plant expansion and the heat recovery system for the gas turbine exhaust. Mitsui Engineering & Shipbuilding (MES) of Tokyo is responsible for the engineering, procurement and construction of the power generation portion of Tosoh's naphtha cracking plant expansion.
S&S Energy Products, a GE Power Systems business, will supply the LM6000 gas turbine-generator as a subcontractor to MES. The LM6000 will be manufactured by GE Industrial AeroDerivative Gas Turbines (GE-IAD) at its Evendale, OH facility.
Tosoh selected the LM6000 for this project because of its proven performance record in various power generation applications. Currently there are more than 115 LM6000 gas turbines operating throughout the globe.
S&S is no stranger to the Japanese power market. Currently there are two S&S-supplied LM2500 gas turbine-generators operating at two separate power plants in Ibaragi and Takasaki, Japan.
Power Requirements
Tosoh currently uses the byproduct gas of the naphtha cracking process for the naphtha cracking furnaces. With the new power plant, the byproduct gas will be used to fuel the LM6000 gas turbine-generator set to produce 41 megawatts of electricity. The electrical power generated by the gas turbine will be used at the Yokkaichi facility. The exhaust heat from the gas turbine will be recovered to supply heat to both the new naphtha cracking furnace and the existing furnaces. Total plant capacity will increase 25% to 500,000 tons of ethylene per year.
Tosoh expects the Yokkaichi facility's overall thermal efficiency to improve greatly with the new naphtha cracking furnace and the captive power arrangement.
The LM6000
The LM6000 shares 90% commonality with GE's CF6-80C2 aircraft engine, and is a unique aeroderivative in that its low-pressure turbine can be directly coupled to its load without using a separate power turbine. This concept improves the simple-cycle efficiency, and reduces the gas turbine's cost and unit size.
The LM6000 low pressure rotor consists of a five-stage low pressure compressor and a five-stage low pressure turbine connected by means of a mid-shaft, which extends through the center of the engine. The high pressure rotor consists of a 14-stage high pressure compressor and a direct-coupled, two-stage high pressure turbine. Table 5 lists the LM6000's 60-hertz performance specifications.
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The LM6000 is designed to operate at an output shaft speed of 3600 rpm for electrical power generation. The high pressure rotor speed varies from ~6000 rpm to 10,600 rpm over the operating power range from idle to full power. A reduction gearbox reduces shaft speed from 3600 rpm to 3000 rpm in 50 hertz applications. The gas turbine is equipped with three systems which control airflow to achieve the desired performance characteristics.
Variable inlet guide vanes in front of the low pressure compressor modulate airflow entering the flowpath. Variable bleed valves between the low and high pressure compressors allow some airflow to be dumped at low power conditions. Six stages of variable stator vanes on the high pressure compressor stage maintain high efficiency over the power range.
LM6000 Package
S&S uses standardized package designs to shorten the manufacturing schedule. This enables S&S to have a power plant operational shortly after the signing of a contract. All packages are factory assembled and tested at full load prior to shipment from the company's Houston, TX headquarters. These tests use the contract control panel and auxiliary systems to minimize field start-up and debugging time. This demonstration of power output and heat rate significantly reduces performance risks for the owner and operator.
Each S&S gas turbine package features a UBC Zone 4 earthquake-qualified structural design, durable electrical systems and all stainless steel fluid systems and reservoirs. The Brush generator is designed to accommodate full gas turbine power output over the full ambient air temperature range. The generator is sized larger than the turbine output to accommodate future ratings increases. The gas turbine is controlled by Woodword Governor's NetCon 5000 controls.
LM6000 Enhancement
GE recently announced an enhancement to the already-popular LM6000 ideal for customers that want more power: A new spray intercooling system which is expected to increase this aeroderivative gas turbine's power output by at least 9%. Known as the LM6000 SPRINT™ (SPRay INTercooling), this product enhancement also will reduce simple- and combined-cycle life cycle costs. Benefits of the SPRINT system include:
- 9% power boost at ISO conditions;
- 17% increase in power on hot days (greater than 800F) with some efficiency improvement; and
- elimination of inlet chillers for most installations.
SPRINT Description
The SPRINT cooling lowers the high-pressure compressor inlet temperature, which in turn effectively lowers the compressor discharge temperature. The system consists of an interstage mist injection system which cools the low pressure booster discharge air. Water is injected into the airflow path through a series of 24 air-assisted spray injection nozzles located in the engine front frame. Air for the system is supplied from the engine's 8th stage customer bleed extraction port.
By using the SPRINT spray intercooling system, the compressor pressure ratio can be increased and additional air can be directed through the compressor to increase the gas turbine's output characteristics (see the attached SPRINT system schematic.)
In addition to being offered for production LM6000 PC units, the SPRINT system will be available for those LM6000 PA models that have already been retrofitted using an LM6000 uprate kit.
Conclusion
Industrial captive power is on the rise in Japan, and numerous opportunities are present for environmentally-friendly gas turbine-based power plants. S&S is uniquely positioned to offer reliable packaged power systems to meet the country's increasing demand. S&S expects to deliver the LM6000 gas turbine-generator set to Tosoh's Yokkaichi site in late 1998.
Mr. Kazunobu Ogiso is President of S&S Technical Services Japan, Ltd. He is headquartered in Tokyo.
Mr. Terrence Sharp is Marketing Manager, Japan and Korea, for GE Industrial AeroDerivative Gas Turbines. He is also headquartered in Tokyo.