Mixing Abrasive Fly Ash and Water

General Description

A biomass-to-energy power generation facility located in the north east was having continuous problems with an existing screw conveyor used to mix fly ash with up to 10% water content. Water is typically added to fly ash for stabilization and to eliminate dust problems. The fly ash is then sent to disposal or used as an additive for concrete. Drive shafts and screws were breaking and flights were not standing up to the abrasive material. The existing unit required constant maintenance and caused the plant considerable downtime. KWS provided a mill-duty pugmill as the solution. A pugmill is a twin counter-rotating paddle mixer that provides very aggressive mixing.

Design Parameters

KWS Advantages

KWS understood the requirements for adding moisture to fly ash. Aggressive mixing is required in order to create a homogenous mixture. Rotational speed of the pugmill is critical for proper operation. KWS relied on their extensive experience in conveying and mixing to provide the proper solution. We also provided single source responsibility for the Customer from design to support.

Special Features

KWS designed paddles made of chromium carbide plate to reduce abrasion. The paddles were adjustable so the Customer could vary the degree of mixing based on fly ash consistency. We also made the paddles replaceable so maintenance and downtime were kept to a minimum. Each screw was driven independently by a high-torque drive unit to handle any type of upset condition. The drive shafts were oversized as an added factor of safety. The heavy-duty bearings were located outboard of the housing to protect them from contamination and premature failure. KWS also provided a spray system for adding water to the fly ash.