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At the time the decision was made, the company had eight dryers nearly ready to ship but lacked burners. One of the requirements placed on the burners was that they perform equally well with natural gas, fuel oil, or propane. Another requirement was that they meet increasingly stringent regulations for emissions of NOx, CO and noise.

Astec's only previous experience was a single pre-mix burner built in 1993. This burner was designed using a traditional approach which involved building a series of prototypes, measuring their performance, and gradually iterating toward an acceptable design.

Using this approach, it typically takes six to 12 months to meet design objectives. This is because of the considerable time required to build and test each prototype and because physical testing provides only limited diagnostic information. Just about the only information that can be gained on the flow within the burner comes from drawing conclusions based on the shape and color of the flame, and from measuring the combustion emissions.

Simulation used from the beginning

Fortunately, Astec had previously established a CFD capability that made it possible to simulate the design of a burner ' or any other fluid flow problem ' and determine flow velocity, pressures and chemical species concentrations anywhere within the solution domain.

Astec engineers developed an initial premix burner concept design consisting of a centrifugal blower, fuel train and gas injection orifices, fuel and air mixing chamber, and a nose where combustion takes place. The advantage of a premix design is that air and fuel are mixed prior to entering the burner body, which results in a more intimate mixture and tends to lower emissions.