From line freezer to high-tech IQF solutions
The new systems are so-called IQF (Individually Quick Frozen) freezers. In this process, products are frozen individually and rapidly on a conveyor belt. Whereas traditional tunnel freezers blow air over the product and injection air freezers operate at high pressure, the DI freezer opts for a clever middle ground. It uses much lower pressure and dual airflow.
“The technology behind the DI freezer is based on dual airflow”, explains Engineering Manager Richard Veenstra. “Cold air is directed over the product from both above and below. In addition, products are also blown on both the head and tail ends. This ensures highly efficient heat transfer and a uniform freezing process.”
Customers see the benefits reflected in their energy bills. “The energy consumption of DI freezers is significantly lower. This is partly due to how the fans operate, and partly due to the use of nozzle technology and lower air pressure. As a result, energy savings of up to 20 per cent are possible compared with conventional systems”, says Project Manager Chris Muller.
Faster freezing = better product quality
The strength of the DI freezer lies in its rapid freezing process. This has an immediate positive impact on product quality. For example, there is less dehydration and therefore less weight loss. Ice crystals remain small, keeping the cell structure intact. Salts and minerals are less likely to migrate to the centre of the product. The fish emerges with better colour and appearance.
“For our client, who works with breaded fish products, this is essential”, says Chris. “After being coated in chilli sauce and breadcrumbs, the fish is first flash-frozen in the first freezer (approximately 140 seconds). The products are then fully frozen in a second freezer, which is connected in series (approximately 400 seconds).”
A notable feature is the configuration of two DI freezers in series. Instead of a single long freezer, Equans opted for two shorter units. This delivers a surprising capacity advantage. “In the first freezer, only the outer layer of the fish is frozen, which helps it retain its shape. The products can then be stacked in the second freezer without sticking together. This significantly increases the effective capacity. In this setup, 1 + 1 actually equals 3”, says Chris.
Freezer with a compact and hygienic design
Whereas the company’s old freezer line was 40 metres long, a system measuring approximately 14 metres is now sufficient. That saves a considerable amount of floor space. The freezers were supplied fully prefabricated and manufactured in-house by Equans.
The DI freezer also sets a new standard in terms of hygiene and maintenance. “The insulated, fully welded stainless steel casing can be opened completely via an electric lifting system”, explains Chris. “This makes all components easily accessible. We therefore focused entirely on this aspect during the design phase. The freezer has sloping surfaces, which ensures that dirt accumulates as little as possible.” The large evaporator surface, in turn, ensures a longer service life.
The DI freezers run on ammonia (NH₃), a natural refrigerant. The systems are also suitable for CO₂, offering flexibility for future applications. The choice of ammonia was dictated by the existing refrigeration system at the Urk site. Although the freezers operate within the limitations of this refrigeration system, there is still potential for growth. “At lower temperatures, the freezer can operate even more compactly and powerfully,” says Chris.
Although only the freezers were supplied to this customer, they are integrated with the existing refrigeration system. According to Chris, the added value lies in the control system: “We coordinate the freezers and the refrigeration system so that capacity, energy consumption and product flow remain in constant balance. This coordination prevents peak loads and ensures a more stable process with fewer faults and more predictable energy consumption. When the refrigeration plant (cooling system) is also designed and supplied by Equans, this integration can be taken a step further. The customer then benefits from a single, cohesive system with a single point of contact in the event of faults or maintenance.”
From prototype to future-proof freezer
The DI freezer is the result of years of development. Following a prototype and an initial installation at a client’s site in Belgium, the systems at the Urk-based fish processor are now in their third and fourth generations. The design has been fully optimised in line with the latest standards in hygiene, maintenance and performance. This has resulted in a more robust construction, improved accessibility for maintenance and a more hygienic design featuring smart drainage and hinged sections.
With its advanced freezing technology, Equans is responding to a changing market. Although fish processing in Urk is under pressure from external factors such as quotas, wind turbines and the ban on pulse fishing, international demand for high-quality freezing technology is growing. “The DI freezer offers a scalable, energy-efficient and high-quality solution for this”, says Chris. “A system that will serve companies well for years to come and delivers on all fronts.”
