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Making cement with 70% lower CO2 emissions

| By Scott Jenkins

A process commercialized by Fortera Corp. (San Jose, Calif.; www.forteraglobal.com) creates a cement product that reduces CO2 emissions by 70% on a ton-for-ton basis, and can be blended with conventional cement or used as a standalone material to make ready-mix concrete. Fortera recently opened a small commercial plant (photo) located in Redding, Calif. at the site of partner and conventional cement producer CalPortland Co.’s (Summerlin, Nev.; www.calportland.com) facility. The Fortera plant, which can produce 15,000 ton/yr of “green” cement, captures CO2 emitted during cement production and permanently sequesters it by mineralizing the CO2 into CaCO3 in the cement mix, explains Fortera CEO Ryan Gilliam.

cement

Source: Fortera

“Fortera’s ReCarb process works within the existing cement-production infrastructure and reduces energy use by using a lower kiln temperature,” Gilliam says. “This creates a path to zero-CO2 cement when renewable energy is used at planned future plants, says Gilliam.

In Fortera’s ReCarb process, limestone is heated in a kiln to make CaO, similar to conventional Portland cement, but the CO2 from the kiln’s fluegas and the CO 2 driven off in the formation of CaO is captured and directed back into the process. Milled CaO is conveyed to a dissolution reactor to dissolve the lime in a proprietary solvent. The dissolved calcium solution is transferred to a multiphase absorber reactor, where waste CO 2 from the plant is introduced to the solution to cause a precipitation reaction that forms a product the company calls reactive calcium carbonate (RCC; tradename ReAct).

The RCC is part of a slurry, from which the liquid is removed with a clarifier, followed by a filter press. The resulting solid cake is dried and broken into powder that can be blended with conventional cement or used alone.

Fortera’s ReAct green cement is ASTM-approved, and exhibits the same strength and durability as ordinary cement, says the company. It will be available this summer for ready-mix suppliers.