Wet scrubbers remove sulfur dioxide from industrial flue gas by passing the gas through a slurry spray. Because the design of wet scrubbers depends upon the fuel being burned and the amount of sulfur in the fuel, B&W must custom design each scrubber they sell. When designing a scrubber the engineer has to balance a number of competing factors including its geometry, gas flow velocity, sulfur dioxide removal rate, slurry droplet carry-over rate and the pressure drop.

Previously, engineers constructed 1/8-scale models, at a price of $50,000 to $80,000 each, to evaluate the performance of a design. To reduce engineering costs, B&W decided to augment the physical model testing of wet scrubbers with computational fluid dynamics (CFD) analysis software to simulate scrubber performance. The CFD software, CFX from AEA Technology, is capable of two-phase modeling. This was very important to B&W because their wet scrubbers must deal with gas and liquids.

B&W engineers spent four years modeling (both numerically and physically) a base design. This allowed B&W to calibrate the digital model data, such as pressure drop, liquid fractions in the absorber, Amount of carryover and gas, etc.

Now, modifying the base model to match new design parameters takes approximately one week. By running the model in CFX for one week, engineers are able to observe the scrubber's performance under six different operating conditions.

One person can now do a job which previously required three people to perform, thereby giving B&W considerable savings one each design.