New NPK pilot plant up & running

Oslo -Yara’s Innovation and R&D department has been quite busy lately. In an effort to continuously improve Yara’s operations and processes, Yara’s research center in Porsgrunn, Norway, has successfully initiated a new NPK pilot plant. It’s designed to improve operations significantly while providing more flexibility.

“Mother liquor”

"The NPK pilot has been in continuous operation since start-up," Sten Bjørneboe, responsible for Yara’s plant operations, says. "Although there are still some teething problems left to deal with -- which is to be expected with such a complex pilot plant -- it is already working very well, and we are really satisfied with its flexibility."

The new facility is actually a kind of "mini-plant" for NPK production, based upon the so-called nitrophosphate process that Yara utilizes to produce finished fertilizers in its facilities at Porsgrunn and further north in Glomfjord, Norway.

"The nitrophosphate process consists of a number of process steps," Kari-Anne Leth-Olsen, head of Yara’s P/NPK department, explains. "First: Digestion, where phosphate rock is dissolved in nitric acid to create 'digestion liquor.' Second, there’s Crystallization, where this liquor is cooled, creating calcium nitrate, which is then separated out.

"The phosphorous-containing liquor, which is called ‘mother liquor,’ is brought to the next step. Ammonia is added in step three, Neutralization. During this step, what we call ‘NP liquor’ is created," she adds.

Replacing old hardware

"The new pilot plant gives us the possibility to produce NP liquor from nitric acid, phosphate rock and ammonia, and represents a big improvement over the previous NPK pilot plant," Rob Louwe, a Yara R&D employee who was responsible for the building of the pilot plant, explains. "Although some improvements were made over the years, a lot of (the plant’s) hardware dated back to the ‘50s and ‘60s. Operating the old plant was almost entirely manual."

The new facility uses mostly brand new equipment, much of which can be operated from a new steering and control system. A new cooling system for the crystallization phase has been included. It uses a novel refrigerant liquid that can cool the mother liquor down to at least -20°C. A dedicated two-step gas-scrubbing system is also included to comply with emissions regulations.

"We have already started to see the benefit of having such a flexible pilot plant in our innovation projects," Kari-Anne says. "This investment will help us test and solve some of our challenges of improving existing processes and also evaluate the effect of using new raw materials in our plants."

"We hope that Yara's NPK plants will benefit from using this pilot facility to evaluate new process parameters and also for troubleshooting and raw materials investigations."