Equipment Sizing and Gas Flow Rate
The flow rate of synthesis gas when using air as an oxidant is approximately twice that of the equivalent oxygen-blown gasifier. This has consequences both for equipment sizing and for the gas-cleaning technologies.
An air-blown gasifier must either be twice the size of an oxygen-blown one, or two are required. Whether the design is refractory-lined (e. g., Texaco) or fitted with a cooling wall (e. g., Shell or Noell), the gasifier is an expensive piece of equipment. The same goes for the syngas cooler and other downstream equipment such as filters and gas-cleaning equipment.
Besides the effect on equipment, one also needs to look at the emissions. To achieve the same absolute sulfur emissions, the sulfur slip from the SRU for an air-blown unit must be half that of an oxygen-blown gasifier since there is twice as much gas. This will certainly require additional expenditure in the AGR unit.