Bench scale evaluation of the solid-liquid separation steps in the formate process based seed reprocessing option

Coal-Fired Open-Cycle Magnetohydrodynamics (MHD) power generation system requires the use of a sulfur-free potassium salt as a seed material. This potassium seed when added to the coal before combustion serves the two-fold purpose of increasing plasma conductivity in the MHD channel and removing environmentally offensive sulfur compounds from the flue gas by forming K₂SO₄. Most of the seed material (over 85%) is collected in the form of potassium sulfate in the downstream particulate collection devices, with the remaining potassium being tied up as potassium aluminosilicates in the radiant furnace slag. Because of the high cost of fresh seed and limited commercial use of K₂SO₄, the disposal of spent seed is not economically feasible. Thus, a seed reprocessing scheme must be developed to collect and regenerate the spent seed.

In this work, the Formate Process-Based Seed Reprocessing Option is considered. A complete solid-liquid separation (SLS) system to recover the soluble potassium sulfate from spent seed is developed. Additionally, a SLS system to remove the insoluble gypsum formed in the Formate reactor is developed. Preliminary economics of the proposed solid-liquid separation system are completed and related to the overall cost of the Formate Process.