Pneumatic conveyor for spices

The benefits of innovation

Adopting an innovation policy, industries can achieve significant benefits, which have positive consequences on the income statement, production and work quality. In thi case, implementing a pneumatic conveying system, dedicated to treatment of large quantities of spices, has completely transformed the company. After building a pilot plant in-house and using it continuously for a few months, the results were so positive that the owners decided to adopt the same system on all production lines.

The system implementation required quite an effort, both in the design phase and in the on-site tests that were essential to optimise the whole process. Our technicians were also able to solve some handling problems due to the heterogeneity of the product and their quantities. Our commitment and the quality of what we achieved, together with the customer’s satisfaction, make us very proud of this project.


The company

Our customer is an Italian company that buys, processes and packages spices and aromatic herbs of different nature and consistency. They are mainly intended for buyers in the business segment, who sell them to retailers, as the well-known Cannamela in all Italian supermarkets, or they can use these spices in other productions, such as food, liqueurs or perfumes. The human intervention in the production was very consistent, both in handling the processed product and in packaging, also because, as mentioned, the spices are the most diverse. They ranged from bay leaves or dill seeds to cinnamon bark, turmeric rhizome or wormwood twigs. Workers were also forced to wear heavy protective masks for the respiratory tract and eyes, necessary because of the dust clouds rising from the machinery. The presence of this dust and large bags stacked with processed and unprocessed spices also necessitated extensive and periodic cleaning. In order to maintain proper cleanliness and avoid the proliferation of insects, an external company was paid on a monthly basis to lift everything off the ground and thoroughly clean all surfaces. In addition to the cost, production also had to be stopped at this rate.

The required pneumatic conveying system had to be integrated with the company’s existing machinery. In the traditional process, the raw spices were manually loaded onto a conveyor belt which, at reduced speed, took them to a grinder, a shredding machine, and then deposited them on a vibrating sieve with perforated mesh using a bucket conveyor. Here, the ground products are divided into three pieces through increasingly fine meshes, at the highest level the small pieces of leaves, twigs and peelings remain, at the lowest level the powders. At the end of the sieve the three selections fell by gravity into as many containers. The two finer pieces were still taken by hand to the dosing stations, where, again with human input, they were packed according to demand. The larger spices, on the other hand, were reloaded by workers at the beginning of the route to be broken up again.

Pneumatic conveying for spices

Connecting a pneumatic conveying system to existing equipment would have brought considerable benefits, some immediately obvious, others important, but not always perceivable at first glance. Human labour in both spice transport and packaging would be eliminated, replaced by a simple check of the system. In other words, the product will be transported in closed pipelines, resulting in greater speed, better hygiene, no spillage and virtually no risk of injury to workers. No heavy containers to be moved by hand or with pallet trucks, everything will be transported in overhead pipes or fixed to the walls, thus also freeing up space in the hall. At the packaging station, the electronic automatic weighing system will allow the quantity of spices to be precisely dosed into the bags. There will be no more wastage and all packs will contain exactly the same amount of product.

The most challenging section of the pneumatic conveying system we have created is at the end of the sieve table, where the chopped and selected product is taken in three different formats. The powdered spice is simply dropped into a stainless steel hopper and pneumatically sucked from there to the larger dosing hoppers. The particle size and flow characteristics of the less fine spice, together with the larger quantity coming out of the sieve, do not allow the use of a gripping solution as for the powder. This is why we opted for direct suction through a steel funnel conveyor and subsequent pneumatic conveying to the second weighing and packaging station. Similarly, the third gripping point required an even different solution before conveying the spice from the larger pieces to the cycle’s starting tank for reinsertion. In this third case we are dealing with leaf fragments, twig bits and bark shreds in even larger quantities. Larger elements require more air flow in the conveying pipes and involve the risk of clogging due to their tendency to compact tightly. This is why a vibrating channel is the optimal choice, designed to keep the spices in a smooth flow before suction.

To increase the safety of the entire pneumatic spice transport system, two level indicators have been installed in the holding hoppers of the first and third intakes. This is a mechanism based on a very slowly rotating paddle placed almost at the top of the container. If one of these paddles blocks, the system knows that a blockage has almost filled the corresponding hopper. The electronic system would then trigger an alarm and switch off the corresponding suction line, thus protecting pumps and machinery. Why wasn’t the same thing done at the second spice intake? Because with direct suction there is no parking of the product, as happens in the collection basins, which as it arrives is immediately sucked up and taken away.


Avoiding system downtime

It is a real challenge to use a pneumatic conveying system to handle different spices, broken up into heterogeneous elements a few millimetres in size. In fact, dropping a product of this nature into a hopper will sooner or later lead to a blockage of the suction inlet, regardless of its diameter and section. The spice begins to slow down, sliding on the internal surface of the hopper, and little by little it will compact and get stuck, piece by piece, starting from the edges. Over time, a sort of dome will be created to prevent the product coming from above to be sucked in.

Having ruled out other possibilities, the use of a vibrating channel was the solution to avoid blockage, because the oscillation prevents the pieces from getting stuck together. This component has been designed for pneumatic conveying and dosing of irregularly shaped granular products and particularly fragile products that could be damaged by augers or spirals. In addition to spices, typical examples are cereal flakes, fibre, crisps and puffed rice. It consists of a hopper with a more or less horizontal channel at the outlet. The whole thing is made to vibrate by electromagnets, inducing a jerking motion which, as well as making the material jump slightly, also makes it advance. They are also equipped with a control logic that makes it possible to regulate both the material flow and the vibration frequency. They are widely used in the pharmaceutical industry, the chemical industry, the food industry and inside packaging machines. At the end of the channel we installed the suction duct for the pneumatic conveying.

Study and tests were necessary to understand how to balance correctly the channel vibration frequency and flow rate, depending on the spice type falling into the channel. In an initial theoretical design phase, these quantities were calculated by rough margins. This was followed by several sets of tests on the pilot plant built at the customer’s premises. This phase was very time-consuming because the pneumatic conveying system would have had to process very different spices, ground into large-grained and totally inhomogeneous fragments. A lack of accuracy would have led to the system blocking even with the vibrating channel, especially considering that the plant would have had to be in operation almost twenty-four hours a day.


Improvements made

The final pilot plant proved its value, running perfectly for months without a hitch. This, combined with the considerable benefits achieved by the company, has led the management to extend the pneumatic conveying technology to all spice processing lines. At Apply, we are very proud of this project, that we consider to be our flagship. The time and energy spent by our design engineers and fitters has brought the following results for our customer.

  • Increased production
  • Faster product handling
  • No product waste
  • No product contamination from external agents
  • Packages with weight accurate to the gram
  • Less space occupied by machinery on the farm
  • No dispersion of residues into the environment
  • Reduced working hours of dedicated staff
  • Reduced risks for operators