(647a) The Novel Cal-C Process for Single-Stage Removal of CO2, SOx and NOx – Experimental Studies and Process Analysis and Integration

A multiple-gas cleanup process is
proposed for the removal of CO₂, SO_x and NO_x
from coal combustion flue gas. This cleanup occurs at high temperatures
(500-650 °C) in a single-stage gas-solid fluidized-bed reactor. This process ?
named Cal-C process ? utilizes limestone-derived calcium sorbent and
inexpensive coal char, and consists of the three-step calcium looping developed
at OSU with the addition of char to the carbonator. The calcium sorbent is
re-circulated through the system in a closed loop after regeneration and
reactivation, while fresh addition of char is warranted due to complete
consumption.

The process has been verified
experimentally using a lab-scale fluidized-bed reactor setup and the
simultaneous removal of all the species of interest has been established. Based
on previous studies, lignite coal chars are known to be suitable for this
application. In this work, experiments are performed to quantify the
consumption of char on the basis of selectivity of char toward NO. Different
parameters such as calcium to char loading, O₂ concentration and NO
concentration are studied for their effect on this selectivity. Further, the
fate of gaseous species such as CO and H₂, which are likely to be
produced in-situ, is investigated and possible process conditions are
identified for minimizing unwanted byproducts. Different process configurations
with respect to the entry of char in the process loop are also analyzed
experimentally. Thermogravimetric analysis of the hydration (reactivation) reaction
is also conducted to study the effect of presence of char on the hydration
kinetics. Using ASPEN simulations, the process analysis is conducted and different
process configurations are evaluated with respect to the opportunities for heat
recovery, minimization of excess char requirement, etc.