High Humidity, Sinking Pellets: A Beira Aquafeed Plant Holds Water Stability and Cooler Control with a Hongyang SZLH508 Ring Die Line

On the coast of central Mozambique, where relative humidity can sit above 70% for weeks at a time, a commercial aquafeed plant outside Beira was losing margin to two faults that never show up on a quotation sheet. Its sinking tilapia pellets looked sound as they left the die but disintegrated too fast in pond water, and they left the cooler warm enough to sweat inside a 50 kg bag before reaching the farm gate. Both faults traced back to the same two stages of the line, conditioning and cooling, and both were being amplified by Sofala Province’s ambient conditions.

The plant produces 2.0-4.0 mm sinking pellets for Nile tilapia, with a smaller campaign share of shrimp feed. In 2025 it replaced an ageing pellet mill with a Hongyang SZLH508 ring die pellet mill (508 mm die inner diameter, 160 kW main motor, 120 mm effective die width, 186 rpm die speed) and paired it with an SKLN counterflow cooler rated 10 t/h. The purchase was less a capacity upgrade than a control upgrade: the plant needed a line that could hold a fixed thermal and moisture window on a wet coast every shift, not a line that ran well on a dry afternoon and drifted by the weekend.

Twelve months on, batch QC places two-hour water stability of the 3 mm tilapia pellet above 70%, against below 50% on the old line; pellet durability has risen by several points; and cooled pellet temperature sits within 3-5 degrees C of ambient, the figure Hongyang specifies for the SKLN counterflow design. Throughput on unchanged formulations holds in a 6-9 t/h band for 3 mm sinking pellets. The plant’s own explanation is not motor size but rhythm: the cooler no longer sets the pace of the shift.

The customer is a privately held aquafeed producer operating a single-line plant on the northern approach to Beira. Founded in 2019 on the back of the Sofala pond boom, it built its business on one promise to tilapia growers: a pellet that survives the trip to the pond and the first hour in it. Its raw material basket is typical of the region – imported fishmeal and soybean meal, local rice bran, cassava by-product and maize.

The plant’s technical manager put the requirement plainly: not more tonnes, but the same tonne every day, at a moisture level the warehouse could live with.

Hongyang’s engineering team proposed a full replacement of the pelleting and cooling stages. The core machine is the SZLH508 ring die pellet mill.

The counterflow principle is critical: Air meets pellets in the opposite direction. Surface cracking from sudden chilling is avoided, and the final moisture gradient across the pellet is flatter—preventing sweating in the bag.

Installation took eleven days, including civil work. Hongyang’s commissioning engineer worked with the plant’s own team through a five-day run-in that was a moisture audit of the whole line.

• • Die Specification: Adjusted to a 3.0 mm hole with a deeper taper to reduce fines.
• • Thermal Growth: Roller-to-die clearance was re-checked hot to account for 32 degrees C ambient conditions.
• • Humidity Adaptation: Cooler’s bed height and fan damper curve re-mapped for 85% relative humidity.

Operational Results

• Pellet durability index improved by several points; fines significantly reduced.
• Final moisture held in a stable band, eliminating bag condensation risks.
• Successful campaign shrimp feed production without specialized die changes.
• Lower specific energy consumption due to improved line synchronization.

For Mozambique, every tonne of high-quality feed produced domestically shifts the protein supply equation. As national standards are drafted, plants that can document moisture and stability windows will lead the market.

For Hongyang, the Beira project proves that equipment must be tuned to the site. The 508 mm die and 160 kW motor provide the power, but the conditioner programme and cooler balance provide the quality. The equipment was bought once; the settings are reviewed every campaign.

References

1. World Bank, World Development Indicators, “Aquaculture production (metric tons)” – Mozambique (series ER.FSH.AQUA.MT), 2021-2023.
2. Ministry of Economy and Finance, Mozambique, budget execution reports 2023 and 2024.
3. FAO, Committee on Fisheries, Sub-Committee on Aquaculture (COFI:AQ XII), 2023.
4. Malabo Montpellier Panel, “FISH-FRIENDLY” report, 2024.
5. Norges Vel / CEPAQ end-of-term review, 2024.
6. PRODAPE programme data for Sofala Province, 2023.
7. Muhala et al. (2021) and World Bank (2024) – aquafeed cost analysis.
8. Hongyang Feed Machinery product and case documentation at ringdies.com – SZLH508 ring die pellet mill and SKLN counterflow cooler series.