Northern Indiana Public Service Company (NIPSCO) from Merrillville, Indiana, supplies energy to over 821,000 natural gas and 468,000 electricity customers. One of the company's primary goals is to improve air quality: Since 1990, NIPSCO has invested over 350 million dollars and succeeded in reducing emissions by 70%. The same year, NIPSCO began complying with the "Clean Air Act" – strict flue gas standards.
The ambitious target: the emissions of the new plant in Chesterton, Indiana needed to follow the flue gas standards, even for sulfur gas emissions (SOx). The customer had other challenging requirements: minimum investments, economic operation, no power generation interruptions, low lifecycle costs and high profitability. That’s difficult enough itself but then the design engineers of Pure Air Products, a contracting company, found further technical barriers. The engineers knew SEEPEX pumps could handle these obstacles and recommended involving our experts.
When generating power from fossil fuels like black coal, lignite and crude oil, large quantities of sulfur dioxide are released. The flue gas desulfurization plant removes sulfur compounds from flue gas emitted by power plants. This generally occurs via lime scrubbing, which is then oxidized to form gypsum.
This process has special requirements:
- Transporting high-density gypsum sludge to the drainage or centrifuge tanks.
- Conveying filtrate mash from the centrifuge to the waste water treatment plant, where it is further processed into cake.
A real challenge: gypsum sludge and mash are both extremely abrasive and have incalculable densities. And then there's the 24/7 continuous operation. But that's no problem for our pumps!
SEEPEX supplied various pumps: a BN 70-6L pump in block design for the gypsum sludge and three pumps each from the NS 17-6L and 26-6L ranges with a free bare shaft for the filtrate mash. The pump casings are coated internally and all rotating parts are made of stainless steel, while the 6L rotor and stator geometry offers increased volumetric and mechanical efficiency. To increase the stator’s service life, the pumps are equipped with retensioning devices.
The SEEPEX pumps operate 24/7 trouble-free and virtually maintenance-free even with the variable solid content. The requirements initially given by NIPSCO were completely fulfilled.