Case studies - Discharge of difficult to manage products

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Case study 1 - Redesign of 4800m3 concrete silo cluster. Retrofit the discharge system to suit multiple products.

Products:

• Soybean Meal, Maize Gluten, Tapioca Starch and other feed materials.

Requirements:

• Conversion of existing concrete silo cluster with six cells of 800m3 capacity to handle various products for feed.
• The ability to accurately control the discharge from the silos for weighing requirements.
• Tight space constraints for installation of equipment.
• Retain as much of the existing conveying system as possible.

Considerations:

• Flow problems associated with common raw materials for animal feed, such as soybean meal, maize gluten, tapioca etc.
• The range of different products being stored and suitability of a discharge system.
• The need for complete flow control of all products.
• Use as much as possible of the existing silo and conveying system configuration.
• Space constraints to maneuver in and installation of new equipment.

The solution:

• Bulk solids flow properties testing of all the products being handled.
• Redesign of the hopper, with a large enough diameter to prevent silo bridging. The existing hopper was retained and cut open to a diameter of 4.0m.
• To accommodate space restrictions and accessibility, the dischargers were supplied in two halves.
• A controlled rate of mass flow was achieved by using a SILETTA® UBL. By using the Siletta discharger, the existing hopper walls were retained even though they were shallow in angle.
• The benefits also allowed the existing hopper discharge point to mount in its original position.

Results:

• Accurate discharge difficult products.
• Short redesign time and cost effective.

Case study 2 - 100m3 Biomass Fuel feed system.

Products:

• Milled palm nut shells, milled straw and other wastes.

Requirement:

• Enormous quantities of waste from agricultural products, to be used as secondary fuel feed for the cement kiln.

Considerations:

• The properties of these milled products exhibit different flow characteristics from extremely cohesive to free flowing and flooding, with all variations between these extremes.

Requirements:

• Enormous quantities of waste from agricultural products, to be used as secondary fuel for the cement kiln.

Considerations:

• The properties of these milled products exhibit different flow characteristics from extremely cohesive to free flowing and flooding, with all variations between these extremes.

The solution:

• By testing flow characteristics of all the products, the critical arching dimension for the most cohesive products calculated to be greater than 2 m.
• For the self fluidizing products, allowances for deaeration were required. A new separate silo was installed for deaeration purposes.
• The main silo was converted to Ideal Flow. A SILETTA®- UBL was supplied, with the diameter equal o the silo diameter.
• For proportioning, an Ideal Flow Silo of 2m3 and a SILETTA® of 1.2m diameter were designed. To allow deaeration, 90 % of the content had to be used as a buffer, to prevent flooding.

Results:

• Successful discharge and mass flow control of all products. This installation saves fuel and this enabled reduction in the quantity of oil to be imported, which is very important for developing countries.

Case study 3 - Proportioning of Fibreglass.

Products:

• Chopped Fibreglass.

Requirements:

• The product which was of various sizing of different lengths to be proportioned in to a water stream for production of fiberglass tissues.
• A second to second accuracy and repeatability required to be better than 1%.

Considerations:

• Difficulties in discharging and achieving batch weights within specification - 1%.

The solution:

• In order to prevent bridging and rat holing, an IDEAL FLOW SILO was used. For proportioning, a specially designed SILETTA® for fiberglass was chosen. As the fibrous materials don't flow uniformly, a special proportioning program was developed.

Results:

• A simple solution was realized, easy to maintain and with an accuracy of 0.5%.

Case study 4 - Tioxide transfer to pneumatic conveying line.

Products:

• Tioxide at 50 degrees celcius.

Requirements:

• Replace a mechanical handling system prone to flushing and irregular feed to the pneumatic conveying system.
• Discharge product from four silos into pneumatic conveying lines.

Considerations:

• Tioxide is a very fine powder and is self fluidising.

The solution:

• Flow properties of the product were tested. As the material easily fluidised, a Siletta ST unit with close fitting louvers was selected and installed.

Results:

• Flushing and flow problems were eliminated, uniform feed and plant reliability attained.