A specialized area of pneumatic conveying concerns solid material injection. This involves the delivery of solids into a process at a controllable, accurate and variable rate. Another requirement of solids injection is that the material entry to the process must be smooth and unpulsed. This means that the mode of conveying is dilute phase. However, do to high pressure drops required during conveying, and high process operating pressures, the method of introducing the solids into the conveying line is by high pressure vessel.

The types of processes that benefit from solids injection are varied. These include combustion processes (e.g., gasifiers, fluid bed combustors), chemical processes (e.g., chemical reactors, kettles), metallurgical processes (electric arc furnace, cupola, AOD furnace) and many more.

Process pressures can vary from high vacuum to high positive pressures (up to 600psig), and injection rates can be as small as 1 lb./minute, or as high as 2000 lbs./minute. Delivery into the process may be continuous (24 hours/day), or fixed batches.

Macawber provides a sophisticated solids injection system called the Controlveyor®. The Controlveyor® system uses an accurate metering feeder that is internally fitted to a pressure vessel. The feeder is equipped with a variable speed drive to provide a turn down range of up to 20:1 from maximum. Standard injection rate accuracy is + 3% by volume. Accuracies of + 1% by weight can be provided by the addition of load cells and sophisticated control systems. The Controlveyor® is available is both continuous and batch arrangements.