Dynamic modeling and control of a hot-gas desulfurization process with a transport desulfurizer

In a previous paper, a dynamic mathematical model of bubbling fluidized-bed reactors in a hot-gas desulfurization process was developed and several co ntrol structures were evaluated. This paper extends this work in three area s: (1) a dynamic model of a transport-type reactor is developed for the des ulfurizer, (2) the hydraulics of the solid flows in the system are more rig orously modeled, and (3) the use of the regenerator feed temperature to con trol the regenerator temperature is explored. Process designs are studied w ith two different cross-unit solids circulation rates. The impact of altern ative process configurations on both steady-state economics (capital invest ment) and dynamic controllability is explored. The control structure used f or the bubbling-bed desulfurizer process is shown to provide effective cont rol for the transport desulfurizer process. Although solids circulation bet ween units depends strongly on pressure differentials between the desulfuri zer and regenerator, effective control of solids flow rates can be achieved if standpipes are designed with sufficient height. The temperature of the feed gas to the regenerator provides an effective manipulated variable for the control of the regenerator temperature.