A Pilot-Process for Calcium Hydroxide Production from Iron Slag by Low-Temperature Precipitation
The production of Ca(OH)2 via limestone thermal decomposition is an energy intensive process resulting in significant CO2 emissions. However, if produced in a manner that eludes limestone calcination, Ca(OH)2 could be a “CO2-negative” material. Herein, we demonstrate the operation of a continuous, low-temperature (< 100 °C), aqueous-phase pilot-process to produce Ca(OH)2 using calcium extracted from alkaline industrial wastes. The three-step process encompasses unit operations including: calcium leaching from steel slag, leachate concentration by reverse osmosis, and Ca(OH)2 precipitation by temperature swing. This process presents several advantages compared to the traditional route. First, it advances the recycling of waste from the steel industry. Second, it operates significantly below the temperature used in conventional lime production (900 °C) as it bypasses limestone calcination, responsible for ~65% of the CO2 emissions from the current process. Thus, the new process has a lower CO2 footprint and enables the use of industrial waste heat. Mass and energy balances revealed that increasing the calcium concentration of the feed solution and the precipitation temperature, decrease the energy demands of the reverse osmosis step, thereby reducing the process’s overall CO2 footprint. The pilot system operated continuously and produced nearly 1 kg per day of Ca(OH)2 with a purity greater than 95 wt.%. The ability to produce size-controlled particulates was demonstrated by adjusting the residence time in the precipitation reactor. Importantly, the process achieved full water reutilization. The outcomes offer new insights and understanding relevant to developing and up-scaling low-CO2 processes for cement, lime, and portlandite
Year of publication: |
[2022]
|
---|---|
Authors: | Vallejo Castaño, Sara ; Callagon La Plante, Erika ; Collin, Marie ; Sant, Gaurav ; Pilon, Laurent |
Publisher: |
[S.l.] : SSRN |
Subject: | Produktivität | Productivity |
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