KWS Manufacturing

Screw Feeder for Metering Crushed Limestone at AEP Coal Fired Power Plant in Hallsville, TX

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End User or Owner

AEP SWEPCO Pirkey Power Plant
Hallsville, Texas

General Description of the Application

AEP SWEPCO Pirkey Power Plant, a unit of American Electric Power is a 721 MW coal fired power plant serving East Texas, Louisiana, and Southwest Arkansas. In order to reduce sulfur dioxide emissions produced by burning coal, a sulfur dioxide scrubber system also known as a flue gas desulfurization system removes or “scrubs” sulfur dioxide emissions from the exhaust. The system works by spraying a wet slurry of limestone into a large chamber where the calcium in the limestone reacts with the sulfur dioxide in the flue gas.

Screw Feeder for Metering Crushed Limestone at AEP Coal Fired Power Plant in Hallsville, TX - KWS

Before KWS Screw Feeder Replacement – Spillage from belt feeder caused housekeeping issues.

This reaction enables the sulfur dioxide to be removed before it is released into the atmosphere. As a result, the white plume coming out of the power plant’s stack is water vapor. A by-product of this scrubbing is synthetic gypsum which can be utilized in making wall board for the home and commercial construction industries.

The plant had been using a belt feeder to meter crushed limestone used in the scrubbing process since the plant was put on line in 1985. The open belt feeder presented a housekeeping issue around and below the feeder. Plant personnel asked KWS to review the application and offer a solution to replace the existing belt feeder. KWS provided a screw feeder that exceeded the expectations of the plant.

Design Parameters of Application

  1. Product Type – Crushed Limestone
  2. Material Density – 85 to 90 Lbs. per Cubic Foot
  3. Conveyor System Capacity – 180 Tons per Hour
  4. Duty – 8 to 10 Hours per Day, 7 Days per Week

Advantages Provided by KWS

Screw Feeder for Metering Crushed Limestone at AEP Coal Fired Power Plant in Hallsville, TX - KWS

Before Screw Feeder Replacement – Open belt feeder was a safety concern.

A team of engineers from KWS visited the facility and met the AEP SWEPCO maintenance planner to determine the design parameters for the feeder and the exact needs of the plant. While onsite, the KWS team gathered dimensional information on the existing equipment, determined solutions and recommended a screw feeder which would handle current requirements, give additional capacity for future growth and resolve the housekeeping issues. KWS tested multiple material samples of the crushed limestone to determine accurate bulk densities and flow characteristics. Based on all of the information obtained, KWS was able to perform calculations and design a new screw feeder that was perfect for the application.

Special Features of KWS Design

The new KWS screw feeder fit into the space where the existing belt feeder was located. Based on material testing and design calculations, the new KWS screw feeder was designed to handle an increased capacity of at least 20-percent while accounting for a range of crushed limestone bulk densities due to moisture content. The screw feeder speed was reduced to 20-rpm to allow for complete discharge of crushed limestone onto a larger belt conveyor which fed into the sulfur dioxide scrubber. With the completely enclosed design of the new KWS screw feeder, all of the previous housekeeping issues were eliminated.

Testimonial

"The silo fill time has dropped from over an hour to around 20 minutes. The new system is saving energy as well. Energy savings is a metric which is closely watched by upper management. Finally, the spillage from the belt feeder required a team to clean the area twice a week. The screw has virtually eliminated that need. This KWS screw feeder eliminated one heck of a headache!"

Jason Garrett, Maintenance Planner – AEP SWEPCO Pirkey Power Plant, Hallsville, TX

Screw Feeder for Metering Crushed Limestone at AEP Coal Fired Power Plant in Hallsville, TX - KWS

After KWS Screw Feeder Replacement – Safety-bolted door provides visual inspection during maintenance.

Screw Feeder for Metering Crushed Limestone at AEP Coal Fired Power Plant in Hallsville, TX - KWS

After KWS Screw Feeder Replacement – KWS screw feeder is completely enclosed to eliminate safety and housekeeping concerns.

Limestone

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