Prilling process

Besides the shove Stesge Process) there are two other modern commercially important processes — the Prilling Process and the Crystallization Process (See inclosed flowsheets)... 

In the Prilling Process, such as practiced by the Lion Oil Co (Division of Monsanto Chemical Co, El Dorado, Arkansas), the production centers around a prilling tower, where a coned soln of AN forms into small droplets which flow downward against a stream of air. The resulting slightly moist prills are screened, dried and cooled by air Slid sgmn screened... 

FLOW DIAGRAM FOR THE PRODUCTION OF AMMONIUM NITRATE BY THE PRILLING PROCESS (LION OIL CO)... 

A laboratory scale prilling process is simply melting ADN in an immiscible liquid. Stirring above the melting point causes shearing forces to produce droplets, which are quenched to hard spheres upon cooling of the mixture. This process is also an opportunity to dissolve stabilizers in the ADN while molten. 

Sasol in South Africa produces a porous, prilled ammonium nitrate (PPAN) that finds its widest application in a mix with fuel oil. This mixture is used as an explosive and is commonly known as ANFO (Ammonium Nitrate Fuel Oil). Standard PPAN contains randomly distributed closed pores of an uncontrolled variable size and quantity. Sasol also makes EXPAN by using a patented process where polymeric microspheres are entrained uniformly in individual prills. Surfactants are added prior to the prilling process to ensure that the microspheres are evenly distributed in the prill. The addition of these microspheres (or encapsulated gas bubbles) reduces and controls prill density to desired levels. This improves the sensitivity and performance of the explosive while retaining the desirable properties of the standard prills (mechanical strength, oil absorption and free-flowability)106. 

Figure 11.. Block diagram for urea granulation and prilling processes. (Reproduced by permission of European Fertilizer Manufacturers Association)...

The crystal density of AN is about 1.72 g/cc, and the particle density of explosive-grade AN prills ranges from 1.40 to 1.45 g/cc depending upon the manufacturing process. This difference in crystal and particle density reveals the volume of pores or voids created by the specialized prilling process. The porosity of AN prills is the property desired in the manufacture of ANFO, since this determines how much FO can be absorbed. This intimate mixture of AN with FO is critical in the... 

Because of the high conversions in the synthesis, the recycle section of the plant is very small. An evaporation stage with vacuum condensation system produces urea melt with the required concentration either for the Stamicarbon fluidized-bed granulation or for prilling. Process water produced in the plant is treated in a desorbtion/hydrolyzer section. This section produces an effluent, which is suitable for use as boiler feedwater. 

Table 8.18. Ammonium Nitrate Prilling Process Requirements F roduct Ammonium nitrate Capacity 1,400 tpd Capacity utilization 90% Annual production 415,800 tpy Process Hgh-density prilling Investment cost - battery limits, US 28 million - storage, US 7 million Working capital, US 3.6 million...

AZF in Mazingarbe, France, with a capacity of 500 tpd. tilizer plants use the high-density prilling process. ... 

The company also offers a proprietary low-emission prilling process with a closed circuit for prill tower cooling air. An original method for flow of cooling air through the system (without fans) is used in that process. 

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