Feeding the world: the many benefits of plunger and centrifugal pumps in fertilizer manufacturing — The demand for fertilizers is booming as the global population reaches new heights. But there's a catch to it: Handling of raw materials that are demanding at best and highly aggressive at worst. No wonder, that one should take special care when selecting a pump for such production processes. There are in fact some pump designs that go the extra mile...
According to a recent report from the United Nations, the global population surpassed 7.6 billion people in May 2018 and will total more than eight billion by 2024. That’s a lot of mouths that need to be fed. And the number of people that will require nourishment continues to climb at an undeniably steady rate. This population growth is the most obvious reason that the fertilizer industry will remain one of the globe’s most significant sectors. As reported by the International Fertilizer Association (IFA), there are a number of other factors that will also contribute to amplified demand for fertilizer: A decrease in the amount of available agricultural land, which will increase the importance of optimized yields on the remaining land; evolving dietary requirements in both established and emerging countries and markets; stricter government regulation of quality requirements for fruits and vegetables; and growth in the use of different crops as the basis for alternative fuels.
These factors will demand that the manufacture of fertilizers remain an important link in the global food-supply chain, which will, by extension, also raise the importance of the industrial equipment that is used to facilitate its production. For our discussion, we will focus on the part that pumps play in fertilizer production and how two specific types — API plunger and ISO centrifugal — can play a critical role in ensuring the reliability, safety and efficiency of the fertilizer-manufacturing process.
Fertilizer Production: A Challenging Process
As mentioned, it stands to reason that, as food demand grows, so will the demand for fertilizers. Therefore, as the production volume increases, the risks inherent in its production will also multiply.
Whether the fertilizer being produced is of the “straight” variety, which generally consist of single ingredients like ammonium nitrate, ammonium sulfate or potassium chloride (potash); the “combined” type, such as monoammonium phosphate and di-ammonium phosphate; or a “compound” configuration, with NPK fertilizers (a mixture of various levels of nitrogen, phosphorus and potassium compounds) being the most typical in this category, the manufacturer must create a production system that can successfully handle potentially dangerous or hazardous raw materials and finished compounds.
Each of these types of fertilizers has a different manufacturing process, but what they all have in common is that they require the handling of raw materials that can damage the various components in the production system. For pumps, the main danger is that the materials handled can be highly abrasive and/or corrosive. Also, when these materials need to be transferred from one stage of the process to another they can take various forms, including solutions and suspensions or slurries.
In addition to the challenges of handling abrasive/corrosive materials, along with liquids of varying degrees of viscosity and solids levels, the manufacture of fertilizer requires a specific combination of chemical reactions. In many cases, ammonia (NH3) is mixed with water and introduced to the production process, such as for the neutralization of phosphoric acid (H3PO4). Ensuring that the ammonia water is successfully administered in the production process is the job of the process pump.
Another challenge for the fertilizer manufacturer is controlling the amount of fugitive emissions during the production process. This is critical because regulatory bodies pay more and more attention to the levels of emissions that reach the atmosphere during industrial manufacturing. Ammonia emissions generally can occur during the ammoniation process. The amount of emissions will depend on the pH level of the liquid and its viscosity.
Again though, the job of ensuring that emission levels do not exceed established standards is the responsibility of the pump. An overriding challenge for fertilizer manufacturers is choosing the right pump for the various operations in the production chain.
If an incorrect style is chosen, the results can be tragic: Even explosions can occur. The leading causes of pump explosions include insufficient flow through the pump and improper system design and maintenance. Therefore, every precaution must be taken before selecting the pumps for use in the manufacturing of fertilizers.
The Criteria for Pump Selection in Fertilizer Production
While external gear, progressive cavity, screw and radial/axial piston pumps have gained some acceptance for use in the various liquid-transfer processes common in fertilizer production, plunger pumps can be a better choice, especially when used for the injection of ammonia water in the ammoniation process. With a plunger pump, the length of the plunger is longer than its stroke. They should not be confused with piston pumps, which are designed as a style of pump where the length of the piston is shorter than its stroke.
Additionally, plunger pumps are defined as reciprocating positive displacement (PD) pumps that possess one or multiple inline plungers, are configured horizontally and powered by an electric motor or an engine. They can be single-acting (suction occurs as the plunger ascends and discharge takes place as the plunger is depressed) or double-acting, in which the suction and discharge stages take place simultaneously on opposite sides of the plunger.
Plunger pumps are capable of creating incredibly high suction pressure, in some cases up to 3000 bar (43,000 psi), but the flow rates are directly proportional to the pump speed, not the pressure. Conversely, the discharge pressure is not speed-dependent, but relies solely on the design of the discharge piping. These operational capabilities allow plunger pumps to realize pumping efficiencies of up to 90 %. Also, component wear is minimized because the pump’s packing is situated in the sleeve surrounding the plunger, not on the plunger itself, resulting in uniform and long-life packing wear.
Other wear parts include gaskets, rings, bushings, check valves and springs, but if proper maintenance procedures are observed, it is not uncommon for plunger pumps to operate for 20 years without requiring any maintenance, other than the periodic replacement of the wear parts. Plunger pumps also have a small footprint, which makes them ideal for installations where available operating space is at a premium. Their design and method of operation makes them perfect for handling almost any type of fluid, even those that are corrosive or hazardous, which puts them in the sweet spot for use in fertilizer-manufacturing processes.
These Pumps Keep Fertilizer Production Flowing
Global population growth will continue to drive the need for reliable sources of high-quality food. Fertilizer will continue to play a critical role in ensuring that agricultural food products satisfy demanding levels of production, quality and consumability. By extension, the pumps that are used in the production of fertilizers will need to keep performing in a way that guarantees reliability, efficiency and safety.
The many features and benefits that API plunger pumps and ISO centrifugal pumps offer, can play a significant role in meeting the nourishment needs of the world’s constantly expanding population, in the most efficient and safest manner possible.
* * The author is Market & Product Manager for Finder Pompe, Auxerre/France.