Pneumatic conveying rises to materials handling challenges

Paul Boughton
Following a change in US law, one of the world's largest producers of folding cartons and coated boxboard packaging had the opportunity to earn a significant tax credit. This led the company to rely even more on energy provided by a bio-mass by-product of their process.

Black liquor is the by-product used to fuel the on-site power plant that creates as much as 66 per cent of the electric energy used by the mill. To prepare the black liquor for the power plant, salt-cake needed to be hauled in by rail, transferred to a storage silo, and metered into a wet mix tank.

The company selected United States Systems (USS) to design and manufacture the complete salt cake conveying, storage, and mixing system. Project objectives necessitated an efficient system with the ability to unload an entire railcar in less than one operator shift. USS met the design challenges by engineering a continuous flow airlock system to meet project specifications.

A concern expressed by the salt cake supplier was that moisture from the 93°C liquid in the mix tank would rise through the rotary valve and make its way into the silo cone. Moist salt cake will not flow properly. USS engineered the system to minimise the migration of moisture into the spout by utilising a slide gate to isolate and seal the moisture from the airlock. However, when the gate is open and the salt cake is being added to the wet tank, moisture might still migrate upwards.

To solve that potential problem, engineers at USS devised a way to purge the zone below the airlock with compressed air while the gate is open.

The compressed air causes a net downflow of air and minimises the moisture migration upward into the spout. The solution proved successful and they are now unloading up to 2700kg/h of salt cake to the wet mix tank. USS technicians provided the start-up assistance to get the salt cake moving quickly and trained personnel in operation and safety.

For another USS project, a large warehouse management firm needed a total system solution to capture material and convey it into an overhead silo for bulk bag filling. The company required a dependable pneumatic conveyor system that could run without unscheduled downtime and meet the high material transfer rate of 14 500kg/h. The machine also needed to run automatically to save time and cost. The firm asked USS to design and manufacture a large version of a small ultra-portable diesel-driven system they already own that was built by USS decades ago.

USS listened to the customer and appreciated its positive experience with the system and explored alternative solutions. Although USS builds diesel-driven systems, the energy costs and safety issues involved in the constant refuelling of a diesel-driven system made it an undesirable solution in this case, where the solution needed to be portable but not 'ultraportable'.

The problem was two-fold: to design a system to keep energy costs down and one that could be transported elsewhere if needed.

After careful consideration of these unusual design requirements, USS proposed a custom-engineered total system solution: an electric-powered, skid-mounted USS Venturi 30 pneumatic conveyor system including blower package and controls.

Other design requirements resulted in the inclusion of NEMA 4 rainproof control panels that allow the operator the flexibility to run the conveyor in either automatic or manual modes.

Meanwhile, Clyde Process Solutions (CPS), another global provider of pneumatic conveying and air filtration solutions for process industries, has won four contracts in recent months. The first, worth £1.7 million, is with a leading global supplier of cereals, snacks and processed foods.

CPS will supply this customer with an ingredient handling system at one of its largest production facilities located in the north central region of the US. CPS will utilise its pneumatic conveying technology to handle all the ingredients used in the manufacture of their new cereal product (Fig. 1).

This new deal strengthens CPS's position in the food industry, particularly the US market, and follows on from two earlier contracts won from Asian steel producers. Worth £900 000, the first contract involves supplying one steel producer based in China with a pneumatic conveying system that will transport quicklime within its production facility. Quicklime, more commonly known as lime, is used by the steel industry as a raw material to purify steel. The CPS pneumatic conveying system will transport quicklime over a distance of one mile, which the company directors believe is a world leading distance for this raw material using pneumatic conveying technology. The order value of this contract is £0.9 million.

The second part of this order, worth £1m, will see the company supply a steel producer based in Taiwan with a pneumatic injection system that will inject pulverised coal into its blast furnace. Coal is used as the prime fuel within a blast furnace that reacts with predominately hot air and iron ore to produce iron, which is then refined to create steel.

Commenting on the orders, CPS chief executive Alex Stewart said: "We are pleased to maintain the sales conversion momentum we have built in recent weeks. Both contracts have been secured from existing customers, which is testament to the strong performance of our technologies once deployed within our customers' production processes. Furthermore, our pedigree in providing pioneering solutions is enhanced through the contract secured in transporting quicklime over one mile, which represents an industry first."

CPS's fourth contract is with one of Eastern Europe's leading cement producers and is worth £1.1m. CPS will supply this plant with a pneumatic conveying system that will be utilised to transport fly ash within its cement producing facility. Fly ash is a waste material produced predominately from the power generation industry when burning coal. Fly ash is commonly used as an alternative material and fuel across a wide range of process industries. The cement industry utilises fly ash as an alternative material to mineral in the production of finished cement.As such, says the company, the cement industry represents a significant opportunity for the group with this order providing a basis for future growth

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