Development of a Process for Aqueous Mineral Carbonation on Municipal Solid Waste Incinerator Bottom Ash with Recovery of Useful Chemicals

Abstract

We propose a cost-effective aqueous mineral carbonation process for municipal solid waste incinerator (MSWI) with using CO2 captured from MSWI flue gas. In this process, sodium bicarbonate (NaHCO3) and potassium chloride (KCl) are recovered. The former can be used as a neutralizing agent for acid gas treatment in the MSWI, which can contribute to reducing the operating cost of MSWI and also reducing the cost of the CO2 fixation to the bottom ash. First, the basis of a new mineral carbonation process was designed, and the system continuity was investigated by equilibrium simulations with data from salt crystallization tests. Then, the carbonation/extraction tests on bottom ash were performed. In the result, the amount of CO2 fixed to ash is 0.12 tonnes CO2 per tonne of the ash, the dissolved rates of Na, K and Cl were 48, 27 and 95%, respectively. Though this process can sequester relatively small amount of CO2, which is 2,880 tonnes CO2 per year for the MSWI of the size of 230 thousand tonnes of waste per year, the cost of the process was calculated to be US$ 58 (JPY 4,600) per tonne CO2 avoided, while the produced useful chemical, NaHCO3, might compensate the cost of the MSWI operations.