The pipe reactor, or cross pipe reactor, is an acid-base reaction vessel, initially developed to produce ammoniated phosphate fertilizer. Pipe reactors are now beginning to gain popularity again for the energy saving potential they can offer to granulation operations. Though not required in any system, in the right environment, the addition of a pipe reactor to a fertilizer granulation system can prove invaluable.
Pipe reactors can be designed into a new system, or retrofitted into an existing system, with the option to replace the pre-neutralizing stage. In the case of an existing system, the addition of a pipe reactor is a simple integration, basically “plugging right in.” The original tanks used for the pre-neutralizing stage can function as feed tanks for the pipe reactor. The precise liquid control system is a critical design consideration in any pipe reactor retrofit.
Pipe Reactor Basics
In a traditional fertilizer granulation approach, ammonia is typically sparged into a tank of phosphoric acid. This pre-neutralizes the feed before granulation in a rotary drum. One downside of this neutralization reaction is the inability to capture and utilize the very large heats of reaction present in the neutralization stage. In contrast, a pipe reactor can accomplish this neutralization in a controlled reactor where containment and utilization of the acid-base heat of reaction is possible.
The pipe reactor discharges the hot melt directly into the rotary granulator. The pipe reactor accepts phosphoric or sulfuric acid in one side of the pipe, and gaseous or liquid ammonia is sparged into the reaction chamber. The result, either ammoniated phosphate or sulfate, is a hot “melt” of superheated product. Precise fluid control is critical in metering the required reactants.
The melt is sprayed onto the bed of recycle material within the rotary granulator. The contained heat of the reaction from the pipe reactor contributes to the heat requirement for moisture removal from the granulated material. This reduces the dryer fuel requirement for the plant. The addition of a pipe reactor can significantly reduce the amount of energy required to dry the material and lead to large fuel savings for the plant.
For novel organic-based fertilizer production, pipe reactors offer additional benefits. In addition to removing odor, pipe reactors offer customizable nutrient fortification. Feedstock rates can be adjusted to control nutrient grade.
A pipe reactor granulation process has unique challenges to successful operation. Although with the right design and operation, the pipe reactor can deliver significant value by reducing plant energy costs and improved fertilizer production.
FEECO custom engineers and manufactures pipe reactors for traditional and new fertilizer production processes. FEECO can build entire granulation systems, or retrofit a pipe reactor to fit into your existing operation. For more information on FEECO’s granulation capabilities, contact us today!