Triple Mass-Flow Screw Feeders and Conveyors Phosphate Ore

General Description

The Ma’aden Phosphate Company (MPC) is a large phosphate mining business in the Middle East. MPC mines the large phosphate deposit at Al Jalamid in the North of Saudi Arabia and utilizes local natural gas and sulfur resources to manufacture Diammonium Phosphate (DAP) at their processing facilities. DAP is a very common fertilizer and is used to boost crop production so the world can better feed its population. The raw phosphates are sedimentary rocks, formed from the remains of long-dead organisms. The wet phosphate is ground and conveyed to a large storage hopper via belt conveyor. The pant-leg storage hopper discharges to two mass-flow screw feeders that meter the product into two large rotary dryers. The dried product is conveyed out of the dryer discharges with screw conveyors. The original screw feeders and conveyors were improperly designed and causing constant interruptions to the operations at the plant.

Design Parameters

KWS Advantages

FEECO International, a manufacturer of rotary dryers, sizing and processing equipment provided the rotary dryers for the project. MPC contacted FEECO for retrofits to their dryers but was also seeking help to improve the operation of their screw feeders and conveyors. FEECO and KWS have worked as a partnership on many previous projects and have a very comfortable working relationship because both companies offer professional engineering services and quality workmanship. The original screw feeder and conveyor manufacturer failed to understand the bulk material characteristics and harsh operating conditions. The phosphate ore packs and is very difficult to meter and convey. The original screw feeders and conveyors were designed incorrectly. As a result, MPC had constant problems with over-amping motors, plugged conveyors and bridging/rat-holing in the hopper. KWS reviewed the existing design and made recommendations to improve operation. Down-time in a plant this size is extremely costly. The design and manufacture of mass-flow screw feeders requires engineering knowledge and manufacturing aptitude. KWS has designed and manufactured thousands of mass-flow screw feeders successfully. Screw flight design and tight tolerances are very important to achieve true mass-flow from a hopper. MPC needed their plant making capacity as quickly as possible. The new project was to be designed, manufactured and delivered on an expedited schedule. KWS was up to the challenge.

Special Features

KWS designed and manufactured triple mass-flow screw feeders to match the existing hopper at the plant. Each mass-flow screw was mounted on an oversized heavy-duty center pipe to reduce deflection under load and provide very high torque carrying capabilities. KWS understands difficult applications and designs heavy-duty systems to meet demanding operating conditions. Each mass-flow screw was equipped with individual low-speed, high torque gear reducers to meter the phosphate ore under packed, upset conditions. The gear reducers were too large to put all three side-by-side on the screw feeders. KWS designed special gear reducer mounts and located the gear reducers on opposite ends so there would be plenty of room for maintenance. The screw conveyors handling the dried product after the rotary dryers were designed to account for the heavily loaded conditions with increased horsepower and heavier construction. KWS also supplied abrasion resistant AR400 flights and removable liners to provide long life and reduce wear due to the abrasive product.