Serpentinite Carbonation Process Routes using Ammonium Sulfate and Integration in Industry

Abstract

Vast resources of serpenitinite rock available worldwide are capable of binding CO2 amounts that diminish the capacity of methods based on geological storage of CO2. R&D has been ongoing in Finland for many years on developing large‐scale application of process routes for serpentinite carbonation. Several routes have been assessed in the laboratory, in all cases using ammonium salts to extract magnesium from rock followed by carbonation either in a gas/solid reactor at elevated temperatures and pressures or in an aqueous solution at ambient conditions. The choice for either route is motivated by the CO2‐producing source, (waste) heat availability, the magnesium (hydro‐)carbonate product aimed at, and a preference for energy efficiency or simplicity. Rocks from several locations have been analysed. A special issue is the recovery of the ammonium flux salt, typically from an aqueous solution. As for application, several industry sectors are considered, such as a (natural gas fired) power plant, a lime kiln, or iron‐ and steelmaking, applying mineral carbonation (MC) to blast furnace top gas. The analysis includes life cycle assessment (LCA). Finally, the use of magnesium (hydro‐)carbonates for heat storage is addressed.

Metals Production, CO2 Mineralization and LCA

“…Pressures, temperatures, and Mg(OH) 2 feed vs. gas feed were optimized for maximum CO 2 as well as combined CO 2 + CO conversion efficiencies while minimizing production of reactive MgO and energy input requirements. LCA studies that include the production of Mg(OH) 2 as part of serpentinite carbonation for treatment of flue gases from a power plant or a lime kiln are given elsewhere [14,17].…”

“…Mineral sequestration offers a large-scale CCS option for Finland and many other countries, where the underground storage of CO2 is not possible [10]. While a significant volume of the literature using ÅA routes for CO2containing exhaust gases from heat and power production exists, metal production or mineral processing [11][12][13][14][15][16][17][18] a special opportunity arises for the processing of a BF top gas with Mg(OH)2 that can be obtaineded from thevast(more than needed) natural resources of magnesium silicate rock Figure 2 summarizes the slag2PCC concept that may operate on CO 2 -containing gas directly (if the target PCC quality allows for it) without a need for a separate CO 2 capture step. This opportunity is one of the main strengths of CO 2 mineralization as a CO 2 capture and storage (CCS) technology, since the capture step gives a very significant energy penalty (see [10]).…”

“…Mineral sequestration offers a large-scale CCS option for Finland and many other countries, where the underground storage of CO 2 is not possible [10]. While a significant volume of the literature using ÅA routes for CO 2 -containing exhaust gases from heat and power production exists, metal production or mineral processing [11][12][13][14][15][16][17][18] a special opportunity arises for the processing of a BF top gas with Mg(OH) 2 that can be obtaineded Metals 2020, 10, 342 3 of 16 from thevast(more than needed) natural resources of magnesium silicate rock available worldwide [19]. BF top gas, containing CO 2 as well as CO in more or less equal amounts of approximately 20 vol.%, can be processed by sequential mineralization of CO 2 followed by conversion of CO into CO 2 and H 2 via the CO/water shift reaction [20]:…”

Hydration of Magnesium Carbonate in a Thermal Energy Storage Process and Its Heating Application Design

“…As mentioned earlier, nesquehonite (NQ) is a product of a CCSM process and precipitated in a solution containing MgSO 4 into which ammonia and CO 2 are absorbed [8][9][10][11]. At temperatures above 50 • C hydromagnesite (HM) and ammonium sulphate are formed according to reaction (R3) and below 50 • C NQ and ammonium sulphate are formed [8,20,21].…”

“…Samples were kept for 1 week, 2 weeks and 2 months under atmospheric conditions for comparison with the original sample. The risk of emitting 1 out of 5 CO 2 from NQ resulting in HM (not reversible) can be monitored by scanning electron microscopy (SEM) [9,20,21]. As mentioned earlier, according to Hill et al NQ forms HM if stored under 1% of CO 2 at 25 • C, and under 0.1% of CO 2 at 10 • C although, the rate of this process seems to be unknown [7].…”