Converting Waste Gas into Clean Energy: Solar is leading efforts of worldwide sustainable power generation

Each year, China produces over 300 million tons of coke, nearly 60 percent of the global supply for one of the most important ingredients for steel making. Coke is created from distilling coal, or "coking," a process that releases a hydrocarbon-rich gas containing approximately 60 percent hydrogen and 23 percent methane. Traditionally, about half of this runoff gas is reused in the coking batteries while the other half is used as a raw material for chemical processing, fuel, or is simply flared.

Coke oven gas, a by-product in the manufacturing of coke - an ingredient vital to steel production - can be highly toxic when vented into the atmosphere. China, the biggest producer of coke, has turned to Caterpillar's subsidiary, Solar Turbines Inc., to find a sustainable solution to this issue. Solar's highly efficient gas turbines are converting this harmful gas into clean, usable electricity and steam. Compared to conventional systems, a fifteen megawatt Solar turbine running on coke oven gas can reduce carbon dioxide emissions by 94,000 tons per year - the equivalent of planting over 21,000 acres of trees.

In 2004, Solar Turbines recognized that coke oven gas (COG) had the potential to be cleaned and transformed for power generation, specifically to create electricity and steam in a combined heat and power (CHP) plant. In 2006, the Shandong Jinneng Coal Gasification Co. Ltd., a coking plant in China, commissioned a Taurus™ 60 gas turbine generator set and heat recovery steam generator for a combined heat and power system, which would harness the COG for thermal uses and reduce their energy costs. Solar was the first in the industry to successfully apply COG in gas turbines.

At the time, the plant had an annual coke production of 600,000 tons and the coke batteries produced about 865,000 standard cubic feet of COG per hour. The CHP system, provided by Solar, helped to provide 5,341 kilowatts of power and 13 metric tons of saturated steam per hour. In total, the CHP plant saved the customer nearly $4 million in the first year of operation. The application was so successful that the plant earned back its entire investment in energy savings and purchased three additional Taurus 60 turbines the following year. As capacity grew, the customer went on to purchase four Titan™ 130 turbines for the same plant.

In January 2008, The U.S Environmental Protection Agency (EPA) recognized the Shandong Jinneng Coal Gasification Company with a CHP Partnership International Award for their coke oven gas-firing system.

The system was rated at 68 percent efficiency and was determined to use approximately 26 percent less fuel than the equivalent of separate heat and power sources. By recovering the coke oven gas and using it for fuel, the operation of one Taurus 60 COG CHP system reduces CO2 emissions by 40,000 tons per year, equivalent to eliminating the annual emissions from approximately 6,600 cars, or off-setting the damaging effects of these emissions by planting 8,200 acres of forest. Cost savings and an additional energy source make gas turbines an attractive option for our customers, but the environmental benefits are paramount.

Solar has sold 30 units in China for COG application, 10 Taurus 60 turbines and 20 Titan 130 turbines, seven of which were booked in January 2011. Currently, 10 COG units are in commercial operation and have logged more than 130,000 operating hours. A team of engineers is continuously working to improve technology to prevent hot corrosion of the turbines. By including coatings for the turbine blades at the first two stages of operation, filtrating the air inlets and purging the liquid fuel forward, the engineering team has made the turbines more durable in harsh operating environments.

Looking ahead, the future appears to be bright for gas turbine applications in coking plants. In addition to the environmental and economic benefits, COG has tremendous potential to serve as a resource for China's rapidly growing economy and increasing energy demand. In 2010, China produced 388 million tons of coke. If the coke oven gas was harnessed for clean energy, it would produce 10 gigawatts of electricity and 24,000 tons per hour of steam - the equivalent amount of energy produced with 35 million tons of coal. And while China is the world's largest coke producer, additional market opportunities exist in other countries including Poland, Germany, Turkey, Belgium, Russia and the Ukraine. In addition to natural gas and landfill gas, COG represents yet another way that Solar is at the cutting edge of sustainable power generation worldwide.

Products from Solar Turbines play an important role in the development of oil, natural gas and power generation projects around the world. Solar Turbines' products include gas turbine engines (rated from 1590 to 30,000 horsepower), gas compressors, and gas turbine-powered compressor sets, mechanical-drive packages and generator sets (ranging from 1.1 to 22.4 megawatts).