Introduction:
Pneumatic conveying has become a dependable transfer method in material handling processes, employing air as the medium to transfer bulk materials through pipelines from source to destination. The efficacy of this process hinges on the interplay between material characteristics and the solids-to-air ratio. A meticulously designed pneumatic conveying system offers a streamlined and cost-effective solution for transporting powders and granular materials within industrial settings.
Vacuum conveying systems represent a specialized facet of pneumatic conveying, relying on suction to transport powders from a pickup point to various process equipment, including silos, hoppers, and mixers. Dilute phase conveying, a prevalent technique in the food industry, involves entraining material in an air stream, making it adaptable for conveying a myriad of products irrespective of size, shape, or density.
Efficient processing within the spice industry is of extreme importance, especially when dealing with highly volatile oil spices. This article delves into the challenges associated with traditional handling methods and introduces vacuum conveying as a potential remedy to enhance processing efficiency.
Challenges in Traditional Handling Methods
Traditional methods of handling volatile oil spices often fall short in meeting industry demands. Limitations and drawbacks associated with these methods, such as degradation of product quality and manual intervention, underscore the necessity for innovative approaches. This section emphasizes the pressing need for solutions that can overcome the challenges inherent in traditional spice handling.
Advantages of Pneumatic Conveying Systems:
- Cost-effectiveness in both installation and operation.
- Minimal product degradation during the transfer process, contingent upon the specific characteristics of the product.
- Limited exposure of the product to the external environment, ensuring product integrity.
- Environmental friendliness and ease of maintenance.
- Capability for transporting materials over relatively longer distances.
- Suitable for managing multiple sources and destinations efficiently.
- Flexibility in terms of rerouting and system expansion.
- High system reliability due to a reduced number of moving parts.
- Customization options based on the unique requirements of the customer.
Challenge:
A prominent global food company recently faced challenges in conveying highly volatile oil spices during the formulation of their multi-spice mixture. The issues prompted the company to seek an effective and automated material handling solution to minimize material waste and reduce manual intervention.
Solution:
In response to the challenges posed by conveying highly volatile oil spices, the food company engaged Aishin to devise an innovative material handling solution. Aishin proposed the utilization of a vacuum conveying system specifically designed for the transfer of extremely volatile spices such as cumin and coriander. The key components of this vacuum transfer system included:
Suction Gun and Hose: Employed for material pickup through polypropylene bags.
Boxer: A highly efficient compact pneumatic conveyer facilitating the transfer of material from a retaining hopper to a filling hopper, equipped with a single pleated filter unit.
Cyclone Hopper: A receiving hopper designed with a single maintenance hole and an inclined material inlet for improved cyclonic action.
Rotary Air Lock Valve (RALV): Essential in preventing backflow of material in a pressurized system, the RALV had a housing vane clearance of 0.3 mm for quick cleaning.
ASN Fluidizer (Air Sweep Nozzles): Functioning as an anti-bridging and rat-hole disruption equipment, these compressed air-actuated nozzles ensured seamless material flow.
Blower and Exhaust: A centrifugal type blower with specific specifications for vacuum rating, drive, and ingress rating.
Results and the stages involved:
The vacuum conveying system’s design was meticulously tailored to parameters such as material bulk density, physical characteristics of the product, and process equipment requirements. The system successfully conveyed cumin and coriander powders, both with a high content of volatile oil, simulating actual process conditions.
To mimic the actual product characteristics during vacuum transfer, the cumin and coriander powders were heated from ambient conditions (33°C, 78% RH) to 48°C in the Gansons Nauta mixer to enable the release of volatile oils. The powders were then fed through the suction gun into the cyclone hopper, with suction times and cycles optimized for efficient material transfer.
The calculated pickup throughout for cumin and coriander, based on the inlet duct diameter, were found to be 1,250 kg/hr and 750 kg/hr, respectively. Leaks in the cyclone hopper, attributed to improper maintenance hole positioning, were addressed through silicone sealant.
During the discharge phase, it was observed that in the absence of air sweep nozzles (ASN), the Rotary Air Lock Valve encountered difficulties in discharging the material due to heavy bridging. However, when the Air Sweep Nozzle was operational (with a 5-second time lag in each consecutive purge), the entire material was efficiently discharged through the RALV, leaving no residue on the hopper walls.
The discharge throughput with Air Sweep Nozzle operational reached 2,720 kg/hr for cumin and 2,580 kg/hr for coriander, showcasing the system’s effectiveness in handling highly volatile oil spices. This case study not only highlights the successful implementation of a vacuum conveying system but also emphasizes the importance of tailored solutions in overcoming specific material handling challenges within the food industry.