There are two main types of slurry ice technologies on the market. We believe buyers need to be aware of pros and cons of each type of system in order to make an informed decision. So, in this article we are going to review different types of slurry ice making technology and explain the differences in the context of an actual project.
Crushed Ice Water Slurry Technology
This is the case of systems where regular flake, shell, or block ice is produced and crushed into small pieces, and then mixed with water in different proportions. The advantage of this system is that it does not need to have a high salt content to generate crystals, since it uses regular ice. However, in order to maintain fluidity and pumpability of the slurry, it still requires to add salt.
The disadvantage of these systems is that they use conventional ice making technology with all its drawbacks, including low energy efficiency, exposure to the ambient and contamination, difficulty of handling ice chunks and inefficient storage systems. These systems also have an ice crusher, which adds to the energy consumption and contamination risk to the ice. This type of slurry ice does not provide the same cooling characteristics as Deepchill® as crushed ice pieces are non-uniform and easily separate from water.
Deepchill® generators use a scrape surface heat exchanger and create crystals in agitation inside the fluid resulting in microscopic spherical crystals suspended in water. The main advantage of this system is that these generators are extremely efficient and are fully closed to contaminants. Deepchill® systems are versatile and can produce slurry ice from freshwater or seawater, and they can also work with low salinity waters.
The Deepchill® system has a unique storage design where it allows passive storage of Deepchill® (without mixing). This design also allows users to produce and store Deepchill® with very high concentrations of up to 70%.
It is noteworthy to mention that Deepchill® ice fraction is accurately measured using colorimeter method that measures actual cooling capacity. However, in the industry ice fraction is estimated using a coffee press (mesh plunger) to separate the liquid and solid fractions of slurry. This method is not accurate as water still remains in the lower section causing to falsely increase the ice volume.
How Does the Performance of Fake Slurry Ice Compare to Deepchill® Slurry?
|Deepchill® slurry||Crushed ice water slurry|
|Cooling capacity||Microscopic crystals have the highest cooling rate.||Crushed ice and water mix has a much lower cooling rate, as a small increase in size of crystals can lead to a 15% reduction in cooling rate.|
|Slurry ice behaviour when applied on product||Microscopic crystals are very hard to separate, so Deepchill® stays homogenous much longer and provides a uniform cooling through the entire tank or container.||Crushed ice pieces have a tendency to quickly separate and float to the top, so cooling will not be uniform throughout a container, resulting in inconsistent product quality.|
|Mixing storage tank||Uses a helix mix tank that can provide true 40-60% ice concentration with higher cooling capacity. Deepchill® storage tanks are compact and more efficient.||Typically use mixers that can only store and mix up to 30% ice concentration. This makes the storage tank sizes larger and less efficient.|
|Passive storage silo||Highly efficient silos allow high volume storage of Deepchill® without mixing and enable handling of peak demands.||Do not have this technology.|
What Does it Mean in the Context of a Project?
In the example of a farmed shrimp cooling and preservation project, there were a number of challenges:
Challenge #1: Salinity of water was as high as 4-5%. When making slurry ice using conventional methods, it would concentrate and create a salinity over 6-7%. This would result in low temperature slurry that would freeze the product. With such a high salt concentration, it could also affect the flavour of the product.
Challenge #2: Slurry had to be pumped into tubs and brought to the farm, and because it was a stationary tub, using crushed ice water would mean large crystals to separate, resulting in a layer of crystals at the top and brine at the bottom. This would not provide uniform or fast cooling.
Challenge #3: It was hard to maintain a constant low temperature for shrimp in warm weather temperatures, causing product to rapidly deteriorate.
Application of crushed ice water slurry in this Case:
– As crushers cannot produce fine enough crystals, the ice pieces will separate during transportation of slurry to the site, resulting in non-uniform cooling.
– As there is no large storage of slurry ice, ice crushing and mixing with water becomes a bottleneck in the process.
– The crushed ice mix will not provide a high cooling rate needed to quickly chill shrimp in warm weather conditions.
Application of Deepchill® in this case
– Deepchill® provides an extremely high cooling rate that can superchill and maintain the shrimp at sub zero temperature even when ambient temperature is hot.
– The ability to store large volumes of Deepchill® at very high density as high as 70% without any need of agitation enables users to operate 24 hours a day 7 days a week and discharge Deepchill® in a short period of time.
– Deepchill® fractions are easily adjustable and can provide very high fraction for harvesting in warmer temperatures.
– Deepchill® is very homogeneous with fine crystals, so it does not separate during transportation to and from the farm.