The SO(2), NOx Adsorption Process (SNAP) is a dry combined SO(2) and NOx removal process using a regenerable sorbent. The only products from SNAP is nitrogen and sulfur. Removal of SO(2) and NOx from the flue gas is performed in the riser type adsorber. The regenerable sorbent is composed of a high surface area -alumina impregnated with sodium. Regeneration of the sorbent includes heating the sorbent to approximately 600°C and treating it with a reducing gas and steam. The objective of this project is to optimize the SNAP with respect to the performance of the adsorption and regeneration processes.
Investigation of the adsorption chemistry and kinetics in a fixed bed plug flow reactor system using step experiments concluded in a proposed mechanistic model for the simultaneous adsorption of SO(2) and NOx. A window of SOx/NOx ratios is found in which the simultaneous adsorption of SO(2) and NOx is the most effective. This can be explained by the character of the NO adsorption, that, at the same time, is both sequential and competitive with the SO(2) adsorption.
10 different reducing gasses is tested at different temperatures in a laboratory scale fluid bed regenerator. The tests revealed that the regeneration consist of two separate mechanisms leading to SO(2) and H(2)S respectively. Good regeneration performance was obtained using CO and hydrogen/CO mixtures, but these reducing gasses rely heavily on the steam treatment step.
Testing of different methods for production of sodium impregnated sorbents lead to the conclusion that impregnating a bulk alumina with Na-acetate to approximately 5 % Na lead to a sorbent that was fully comparable to commercial available sorbents.
For optimal design and operation of the GSA a 3-D simulation taking the adsorption into account must be performed. The equation for this is defined and programmed. For the simulation of the riser adsorber, an Eulerian-Eulerian approach is taken. The particles are handled as a continuous phase, the solid phase, which interacts with the gas phase through three mechanisms: gas-solid drag plus mass and heat transfer between phases. A dual time stepping method and a finite volume technique are used for the integration in time and space, respectively. The integration scheme is based on point Gauss-Seidel relaxation.