Economic Design of Low Pressure Air Piping Systems

With the aid of marginal economic optimization theory and headloss approximation equations for low pressure air systems, an economic design technique is presented for wastewater treatment plant diffused air piping, in specific, and all low pressure gas systems, in general. Basically the approach is to identify major tradeoffs, categorize them as either benefits or costs, and then optimize by expending cost increments until the accrued incremental benefit approximately equals the last cost increment. The discrete nature of commercially available pipe sizes greatly simplifies the optimization process. Sensitivity of the technique to a number of parameters, e.g., interest rate, project life, power cost, is investigated and an example problem is solved. Economic velocities are shown to be defective as a design tool for air piping.