"Blackbox" cooling solution to enhance Yara's growth goals

 

Summer 2016


Yara is the leading provider of sustainable crop nutrition solutions, supporting farmer profitability through knowledge, optimal quality and productivity. It has a leading position in nitrogen applications, and has become a total solutions provider in the market for emission control solutions. The Porsgrunn location, about 140 km southwest of Oslo produces NPK and CN fertilizers.

NPK fertilizers are primarily composed of three main elements: Nitrogen (N), Phosphorus (P), and Potassium (K), each essential in plant nutrition. Nitrogen helps plants grow quickly, increases the production of seed and fruit, and betters the quality of leaf and forage crops. Nitrogen is also a component of chlorophyll, the substance that gives plants their green color, and also aids in photosynthesis. Phosphorus, also a key player in the photosynthesis process, supports the formation of oils, sugars, and starches. Additionally, phosphorus encourages the growth of roots, and promotes blooming. Potassium, assists in photosynthesis, fruit quality, the building of protein, and the reduction of disease. The production capacity of the plant is stated in Table 1.

PORSGRUNN
The company started the so called Bamboo project a couple of years ago. Bamboo is a fast growing plant, which makes it the perfect synonym for the fast-growth plans of Yara. As part of this program the plant-management has decided to increase the production capacity. One of the bottlenecks is the cooling capacity of the plant during the summer period.

STANDARD OPTIONS VS "BLACKBOX OPTION"
As standard solutions could not achieve the required output temperature (i.e. as low as possible without having freezing problems) Bronswerk was requested to prepare three customized options in order to realize the preferred air conditions. The main difference between the three options could be found in the degree of compliance with the specifications. All of the three solutions would have the same thermal performance, however the "blackbox" option, which was chosen by Yara, would be the fastest and most economical solution within the project requirements. This option was called the black box option because the solution was the focal point, and no stone was left unturned in finding this solution. Bronswerk allocated all possible resources to conduct extensive research resulting in a suitable (customized) solution. The difficulty in finding this solution lay in increasing the production performance while meeting the demands and staying in compliance with the restrictions of Yara. The result was an air-conditioning unit different from standard solutions in terms of temperatures and allowable pressure drops (see figure 1). These kinds of challenges are perfectly suitable for Bronswerk: debottlenecking and revamping existing installations to improve the capacity within the actual plot size limits keeping the original equipment in tact as much as possible! These were exactly the reasons why Yara allowed Bronswerk to make their process more sustainable.

PROCESS OPTIMIZATION AND SOLUTION
The proposed solution was especially designed to meet the critical design demands (to cool back washed ambient air of a temperature of 13° Celsius (100% RH) to a temperature of 2° Celsius (100% RH) First, the unit needed to be able to cool down to 2° Celsius without the risk of ice formation. Bear in mind that standard units are only able to cool down to 7° Celsius before ice formation starts. Secondly, the unit needed to be able to withdraw 2 m3/hour of moist from the air for the air cooling to be efficient. The natural working fluid used for this process was R717 (ammonia). In order to use this medium to cool down the air and to extract the moist, an in-between circuit was designed, consisting of a compressor, heat exchangers and ducted bundles as shown in figure 1. There were only a few concerns. Firstly, because of applying two bundles in an existing channel the resulting pressure drop of the installation had to be compensated in some way. For this reason Bronswerk provided the new set up with a new fan, eliminating any kind of pressure loss in the process. Furthermore, the system will be not in operation throughout the whole year. This will mainly occur during winter times when the air has less humid. For this reason a by-pass system was applied enabling Yara to shut off the unit thereby preventing unnecessary usage. Last but not least, droplets needed to be separated from the cooled down air. Therefore two demisters were applied on both sides of the bundles to extract the water from the air.

THE PROJECT STATUS
At this moment Bronswerk is finalizing the remaining activities for this project which will be in full operation at the end of 2016. First major results are being expected in spring 2017 but the forecasts are very positive. The research, combined with a suitable process solution, engineering and hardware supply, make this project one of a kind and underline both Yara's and Bronswerk's ambition to be a role model within the industry when it comes to process optimization and sustainability.

 

Table 1: Production volumes Yara Porsgrunn site

Production volumes  
Ammonia 500,000 tons
Nitric acid 1,350,000 tons
NPK 2,000,000 tons
CN (as solids) 810,000 tons

Contact details:
For more information or to find out what this can mean for your system, send an email to Femke@bronswerk.com