Alcoa is piloting a scrubber technology that it says halves water use and requires 30 percent less energy, compared to traditional wet scrubbers, and reduces scrubber installation costs and operating costs by about one-third for aluminum smelters and refineries.
The company says its In-Duct Scrubber, under construction as part of a commercial-scale demonstration project at the company’s baked anode and calcined coke facility (pictured) in Lake Charles, La., will remove up to 90 percent of sulfur dioxide, particulate matter and hydrogen fluoride emissions at the plant. Alcoa expects commissioning and on-site testing of the project to be complete in August 2014.
Alcoa plans to commercialize its technology after completing the demonstration project.
Conventional scrubbers, suitable primarily for large power plants, are 100- to 150-foot tall towers requiring significant capital to construct and energy to operate. These traditional systems pump a limestone or sodium-based solution to the top of the tower and spray the solution onto flue gas, which is propelled from the bottom to the top of the building.
Alcoa’s In-Duct Scrubber was designed to reduce sulfur dioxide and particulate matter emissions generated from aluminum smelters as well as small to intermediate industrial boilers ranging from 50 MW to 120 MW. The scrubber moves flue gas from the smelter or boiler into a horizontal chamber and sprays a sodium-based solution onto the gas stream in the same direction as the gas flow. The sodium-based solution reacts with the sulfur dioxide in the flue gas to turn it into water and sodium sulfate. When mixed with lime, sodium sulfate produces a gypsum byproduct, which can be used to make various beneficial products such as wallboard and additives for cement making.
Alcoa’s high-velocity, horizontal scrubbing process allows up to three times more gas to be treated than in an equivalent conventional scrubber space, the company says. The technology treats upwards of 90 percent of sulfur dioxide in less than one-fifth of a second compared to traditional wet scrubbers, which could take 10 to 15 seconds.
The technology also is modular in design and requires less physical space allowing flexibility in how these systems are constructed.
Late last month Alcoa and the Saudi Arabian Mining Company (Ma’aden) completed an engineered wetlands wastewater management system in Saudi Arabia that the companies say will reduce water demand by about 2 million gallons per day and save more than $7 million annually that would otherwise be used to purchase fresh water.
The companies say the system at the Ma’aden-Alcoa joint venture project site is the first of its kind.
Photo Credit: Alcoa