Controlling SO2 emissions during start-up of multi-bed sulphuric acid converters

The catalytic converter in sulphuric acid plant is normally designed to work high conversions to avoid recycle, and the associated integrated heat recovery system makes the process relatively tightly constrained. Because of this, considerable care is needed during start-up in order to avoid excessive emissions which would fail to satisfy criteria set by the factory inspectorate.

For a fast, clean start-up it is necessary to have a detailed appreciation of the reactor dynamics; the simulation developed here demonstrates how this can be done. In particular, it is possible to explore the level of detail necessary to enable operational policies for start-up to be explored. It is shown that, by suitable programming of the flow rates in the system, appropriate to the initial bed temperatures, clean fast start-ups are possible which avoid excessive stack gas emissions of sulphur dioxide.