Application of Powder-Flow Coolers in Catalyst Production

As processable crude oils become poorer in quality and environmental standards continue to tighten, higher demands are being placed on fuel quality. Ultra-deep hydrodesulfurization has become a major focus in diesel hydrotreating. In producing desulfurization catalysts, lowering the catalyst temperature to facilitate handling and packaging is a key step. Therefore, selecting and designing a catalyst cooler within the process package is crucial to ensuring reliable operation of the catalyst production line.

Overview of the Catalyst Cooler Process and Performance Requirements

The finished catalyst is activated in an activation furnace, where temperatures reach about 375–400 ℃. Catalyst is then lifted by a discharge bucket elevator to the powder flow cooler feed inlet. The hot catalyst enters from the top of the powder flow cooler and is cooled to 60℃. After cooling, the catalyst is screened then sent to the finished-product silo for storage and packaging.

Selection of the Catalyst Cooler

Catalysts are generally classified by physical form as either powder or granules. Traditional cooling options include rotary drum coolers and fluidized-bed coolers. In most catalyst production lines, cooling is accomplished with a rotary drum cooler or a fluidized-bed cooler, using air cooling before packaging. However, whether a rotary drum cooler or a fluidized-bed cooler is used, the heat transfer is gas–solid with direct contact between the cooling media and the catalyst, which often leads to poor product quality, high airflow demand, high energy consumption, and large footprint, as well as heavy dust-removal loads for the exhaust gas. Compared with air-cooling technologies such as conventional fluidized-bed and rotary drum coolers, powder-flow coolers offer the following advantages:

(a) Use circulating water for cooling, cutting energy use by 90%;

(b) Does not use gas as the coolant, resulting in near-zero dust emissions;

(c) Lower installation cost, with no need for gas-handling equipment, such as refrigeration dehumidifiers, blowers, large-diameter air ducts, induced-draft fans, dust collectors, scrubber towers, and emission-control units;

(d) Simple design with no moving parts; operates as static equipment, keeping maintenance costs low;

(e) Compact structure and small footprint, easy to integrate in to existing plant systems, and equally suitable for retrofit projects.

Powder-flow cooling technology effectively integrates uniform mass flow conveying principles for particulate materials, plate-type heat-transfer technology, and advanced powder heat-transfer simulation software. The powder-flow cooler’s heat-transfer plate assembly consists of a set of vertical heat-transfer plates. As cooling water flows through channels inside the plates, heat is removed by conduction to cool the catalyst particles between the plates. The catalyst particles pass evenly and in a controlled manner from top to bottom by gravity.

The mass flow conveying principle was identified by Jenike and Johansen in the 1960s. They developed a theory describing the characteristics of solid particles and predicted their flow behavior, enabling bins and silos to be designed for free discharge while avoiding dead zones and bridging. Typical mass flow storage includes a vertical silo and a discharge cone. When a small amount of material flows through a mass flow bin, the entire inventory in the bin moves as a whole.

The mass flow conveying principle is central to the design of a powder flow cooler. To achieve uniform cooling, the material must pass through the cooler’s entire cross-section at an even rate. To establish mass flow, a discharge device that delivers uniform flow must be installed at the bottom of the heat exchanger. Stable, even flow at the bottom allows the material to move uniformly across the full cross-section of the cooler.

The catalyst powder flow cooler consists of four sections: the feed hopper, heat-transfer plate assembly, discharge device, and control system. Catalyst particles enter the feed hopper from the top of the unit, then are evenly distributed into the channels between the heat-transfer plates. The particles descend slowly between vertically arranged parallel plates, with an appropriate residence time to achieve the optimum outlet temperature. This slow, controlled movement effectively prevents product abrasion and breakdown, fundamentally preserving particle integrity. Temperature is uniform and controllable, maintaining optimal product quality, eliminating caking and agglomeration, and avoiding changes in product properties.

Powder-flow coolers are mainly used in: catalysts, fertilizers, soda ash, chemical products, polymers, sugar production, and dried-sludge processing. Since the early 1990s, powder-flow coolers built a strong reputation in the catalyst sector and were gradually adopted for FCC catalysts, CCR catalysts, activated-carbon catalysts, and other catalyst applications.

At a catalyst plant of a Chinese petrochemical company, a powder-flow cooler has been used on the finished-product line. Key parameters are as follows: the material is a 1.6–2.5 mm elongated shape; throughput is 800 kg/h; catalyst temperature is reduced from 375°C to 70°C. Since commissioning and startup in 2005, no major components have been replaced. No scaling has occurred inside the heat-transfer plates, and there has been no need for acid cleaning. The unit has now operated safely and steadily for more than 20 years.

Conclusion

In catalyst production, many manufacturers use outdated technology and cannot sustain continuous operation. Production often relies on manual, batch-by-batch procedures, resulting in inconsistent catalyst performance, higher production costs, poor working conditions, and emissions such as dust and wastewater that do not meet environmental requirements. Therefore, when building new projects or carrying out expansions and upgrades, most catalyst plants must address the following: reducing or eliminating gas and dust emissions, improving product quality, meeting capacity and space needs for scale-up, and lowering operating and maintenance costs. Powder-flow coolers can effectively remove these production bottlenecks, reduce unit production costs, and meet green, environmentally compliant emission requirements.