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30 / March 2021 powderbulk.com ESTIMATING PRESSURE DROP FOR A DILUTE-PHASE PNEUMATIC CONVEYING SYSTEM Dilute-phase pneumatic conveying systems are fairly simple as they're made up of four components to move material and air through a pipeline: the air mover, solids feeder, pipeline, and separator. While each component plays a part, the air mover carries a lot of the system's responsibilities in transporting the material. Choosing the correct air mover for your system involves many considerations. This article focuses on estimating the pneumatic conveying line's total pressure drop, which is vital to selecting a suitable air mover for your system and application. Eric Maynard, Jenike & Johanson and safety equipment are also commonly integrated with the pneumatic conveying system. A key element you must consider for pneumatic conveying design is the air mover, which may be a compressor, centrifugal fan, or positive-displacement (PD) blower. If you don't select the proper air mover for your planned pneumatic conveying system, then the airflow — and hence velocity — may be compromised and could allow for buildup, line plugging, and erratic system performance at best. The system pressure drop, or pressure loss, during air and solids transport through the entire conveying line is critical to estimate as this will help you select a suitable air mover. The following worked example is focused on system pressure drop estimation and doesn't focus on trouble- shooting common pneumatic conveying problems 1 like abrasive wear, particle attrition, rate limits, buildup, or plugging. Additionally, a suitable minimum conveying velocity determination isn't covered in the worked example but can typically be found through pilot lab testing and scaling of the results or through the use of reliable historical performance data, such as with dilute-phase conveying of cement or flour. Worked example For this example, consider the design of a positive- pressure dilute-phase pneumatic conveying system that must transport powder at 10,000 lb/h using ambi- ent air. Based on a preliminary layout, the pipeline and equipment arrangement is shown in Figure 1. Assume two 90-degree elbows are used with a radius- to- diameter (r-to-d) ratio of 4, the conveying line's terminal point is at atmospheric pressure, and no leak- age occurs with the rotary valve. P neumatic conveying is an important and practical form of bulk solids transport that has appli- cations in almost every industry. The range of materials that can be transported is extensive. Powders and granular materials of nearly every type can be con- veyed, including finished products like sludge pellets (from a municipal wastewater treatment plant for exam- ple), candy, and pressed metal parts as well as stringy materials, such as chopped fiber and metal turnings. A pneumatic conveying system consists of four basic components: the air (or gas) mover, solids feeder, pipeline, and separator. While these components' placements may vary depending on whether the sys- tem is operating in a vacuum or pressure conveying mode, their basic functions remain the same. The air mover provides the proper airflow rate required for material transport at the right velocity and pressure. The solids feeder introduces the solid par- ticles at a controlled rate into the pipeline where they are mixed with the conveying air. Positive-pressure systems require devices to feed material from atmos- pheric pressure into a pressurized pipeline, while vacuum systems need to minimize air leakage into the pipeline as this can create conveying problems. The pipeline consists of straight sections, both horizontal and vertical, connected together with bends. In the sep- arator, the solids are decelerated and recovered from the airstream in which they have been transported and then stored in a silo or fed into another piece of equipment or process. The air is typically released into the atmosphere. In closed-loop systems, the inert gas is recirculated after being cleaned and often cooled to limit a gradual increase in operating temperature, which happens due to the pressurization cycle reusing the same gas over and over. Controls, instrumentation,