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Answering Pakistan’s Burning Question: How To Ignite Lignite?

Buried 1,000 feet below the parched Thar Desert in Pakistan lies more fuel energy than all the known oil in Iran and Saudi Arabia combined. Just a small fraction of this 175-billion-ton lignite coal reserve is plentiful enough to supply one-fifth of Pakistan’s current energy levels for 50 years. This would significantly bolster the energy supply to Pakistan’s 200 million residents, who per capita have access to roughly just 3 percent of the electricity a typical American consumes. As a local resource, it would also lower hefty bills for imported oil and coal, diminishing Pakistan’s reliance on outside sources for energy.

The problem is that lignite is about as combustible as soggy logs in a fireplace. Composed of more than 50 percent water, as well as other impurities, lignite is known as low-caloric fuel — an ideal description for diet products, but not so much for an electricity resource. That’s partly why Thar’s reserve has gone largely untapped since its accidental discovery in 1992 by geologists searching for drinkable water. Even nine years ago, when the private-public partnership Sindh Engro Coal Mining Company purchased 1 percent of the reserve for mining, one question continued to confound power plant operators: How to ignite lignite?

Last month, an answer arrived. GE Power — which has experience burning a similar form of lignite coal in Europe and the U.S. — will bring its boiler and steam turbine technology to Pakistan. Chinese contractor SEPCOIII announced plans, in June, to use GE Power’s systems as part of its new power plant near Karachi. Known as “Qasim-Lucky,” the plant will generate 660 megawatts of electricity to power 1.3 million Pakistani homes and businesses when Lucky Power begins commercial operations in 2021. “As the first lignite-fueled ultra-supercritical power plant across the Middle East, North Africa and Turkey region, the project will help to set new industry benchmarks in Pakistan,” Qin Xubao, project director at SEPCOIII, said recently.

Ultra-supercritical (USC)” is the operative term here — it describes the titanic pressures GE achieves inside the steam turbine — but first some background. This groundbreaking process begins with GE Power’s mill, known as the Beater Wheel, grinding lignite coal so it’s as fine as baby powder. With more surface area exposed, the tiny particles of coal dry more easily as hot air blows the dust into the combustion chamber. There, even hotter air — temperatures averaging 650 degrees Fahrenheit (340 degrees Celsius) — combusts the pulverized lignite into flue gas.

Above: An “ultra supercritical” steam turbine at the RDK8 power plant in Germany. The water pressure inside reaches 4,000 pounds per square inch, more than what’s exerted when a bullet strikes a solid object. The water, which exists in a “supercritical state,” is heated to 1,112 degrees Fahrenheit (600 degrees Celsius). Top: The boilers of an ultra-supercritical power plant in Neurath, Germany. Images credit: GE Steam Power.

When it comes to combusting lignite, size matters. Every square centimeter of the boiler must fill evenly with gas. Since different fuels burn at different temperatures, GE designs its boilers with Goldilocks dimensions: neither so small that the fuel overheats nor so big that it won’t combust. Just as crucial is the positioning of each component in the boiler. “The way you inject the air into the flame, the way you manage the size of the flame and positioning of the flame, it all impacts how the lignite will react and burn,” explains Sacha Parneix, commercial general manager for GE’s Steam Power business in the Middle East, North Africa and Turkey (MENAT). “We have a lot of design features to make sure that we manage to truly burn this fuel that does not want to completely burn easily.”

Flue gas then travels up to the steam boiler, where its heat transforms water stored in tubes into steam power. The steam’s mechanical energy spins enormous turbines to power electricity generators. It’s also when another kind of engineering magic — GE Power’s steam turbine — kicks in. GE’s ultra-supercritical science puts steam under pressure of roughly 4,000 pounds per square inch — the same impact as a bullet striking a solid object — and heats to 1,112 degrees Fahrenheit  (600 degrees Celsius). The heat and pressure turn steam into a supercritical fluid, a phenomenon where a substance no longer has specific liquid and gas phases but exhibits properties of both at the same time. In this state, the steam can get turbines spinning faster than any other system in operation, more than 20 percent above the world-average net thermal-efficiency rate of coal-fired power plants — a measure of how well the plant converts fuel into heat. That kind of efficiency gobbles up less fuel, reducing both operating expenses and carbon dioxide emissions per kilowatt-hour generated.

Though Lucky Power plans to rely on lignite mined from Thar (with some exports for backup), the plant itself is situated 276 miles (445 kilometers) away in the outskirts of densely populated Karachi. That’s a significant boon to Qasim. “On top of being designed for local Pakistani Thar coal, the project’s location ensures easy connectivity to the national grid and very low transmission and distribution losses in supplying affordable power to the major load center of the city of Karachi,” Parneix says.

All of this further augments GE Power’s work to help Pakistan diversify its power grid. Last May, the company achieved commercial operation for two HA gas turbines for the Bhikki combined-cycle plant in Lahore to power up to 2.4 million homes. GE’s HA gas turbines are planned for operation at two other power plants in Pakistan: Balloki, near Chunian, and Haveli Bahadur Shah, in Jhang. The Haveli Bahadur Shah plant alone is expected to add the electricity capacity needed for another 2.5 million homes. GE also worked with Hawa Energy to launch a 50-megawatt wind farm along the Gharo-Keti Bandar wind corridor in Jhimpir. So far, a quarter of Pakistan’s electricity flows through fuel-agnostic GE-built technologies, supporting Pakistan’s fuel-diversification power-generation strategy.

If things go as planned at Qasim, Thar-mined lignite will get to play a starring role in this story of “How Pakistan Got Its Electric Groove On.”

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