Maximising process efficiencies
Howden’s control philosophy for Turbo blowers is a result of many years of process experience combined with the most efficient turbo blower technology.
One of the most efficient control methods that Howden successfully applies to our turbo technologies is the Most Open Valve (MOV) principle. This can be applied to the Sulphur Recovery Unit to control the O2 levels in the Claus Burner directly from the output of the Turbo Blower with minimum energy consumption.
Controlling both the blower and the downstream valves using the MOV principle, the blower output is optimised to meet the required O2 level in the process.
The MOV control loop works by maximising the valve opening (within the control range of the valve), which minimises the pressure (head) losses in the system. This reduction in the required system pressure allows the blower discharge pressure to be reduced correspondingly, with no loss of flow which reduces the energy consumption and the cost of running the process.
Howden has demonstrated in practice that by applying these principles up to 25% power saving over conventional header pressure control systems can be gained.
In the case of the Sulphur Recovery Unit by considering both the blower and downstream valves as an integrated system rather than as separate, independent systems, we can improve the overall system energy efficiency. In the SRU process Howden Blowers are typically operating at several hundred kilowatts up to several megawatts in the largest SRUs and are normally running 24/7 so the wasted energy is significant.
In addition, the incorporation of the Tail Gas trim signal into this integrated system could allow the trim valve to be removed from the process all together with the blower guide vanes and main flow control valve working together to provide efficient flow regulation. This would further reduce pressure losses but would also introduce significant CAPEX savings by removing the trim valve, and it’s associated pipework, supports, foundations etc and their design costs as well as help to reduce the cost of the blower package itself and it’s auxiliaries.