Making Limestone Slurry for FGD
The Vacucam® Slurry Systems are capable of making limestone slurries with 30+% solids on a single pass. The VACUCAM® Ejector Mixer represent the heart of the process, providing major benefits that cannot be achieved with traditional mechanical mixers.
Three process options are available to meet any plant capacity and provide the most efficient use of plant logistics. All processes provide for dry material storage and conditioned feed to the slurry process. With high capacity slurry making, high quality slurry of 30%+ solids can be delivered to one or multiple scrubbers. A single system can produce ample slurry into storage tank(s) and a second unit can be provided for stand-by.
Option 1: Single Pass Process Direct Into Slurry Storage Tank(s)
A single or a dual VACUCAM® mixer assembly is mounted to discharge directly into the top of a slurry storage tank. The mixer assembly conveys conditioned limestone powder from a surge hopper located below the silo discharge, slurries the powder with water on a single pass to 30%+ solids and discharges the slurry into the slurry storage tank. Slurry make-up is on demand based on slurry storage requirements. The mixers can be operated as a single unit, or as a dual unit depending on slurry make-up demand. This process configuration requires the slurry storage tank to be located directly below the silo.
Option 2: Single Pass In-Line Process to Remote Slurry Storage
The skidded packaged Vacucam® in-line slurry module is located near the silo discharge. The module conveys conditioned limestone powder from a surge hopper located below the silo discharge and slurries the powder with water on a single pass to 30%+ solids. The finished slurry is continuously pumped from the in-line slurry tank to one or more slurry storage tanks. A level transmitter on the in-line tank controls the VFD on the transfer pump. The process can be supplied as a single pass steady state process by measuring the finished slurry density discharging from the mixer. The water delivery rate to the mixer can be adjusted by ± 15% to maintain targeted solids levels.
Option 3: Single Pass Process for Direct pH Control to Scrubber
This process is designed to deliver limestone slurry directly to the FGD Scrubber based on a pH feedback loop. A fixed portion of the scrubber make-up water is diverted to the skidded VACUCAM® in-line slurry unit. The unit conveys conditioned limestone powder from a surge hopper located below the silo, slurries the powder with the scrubber make-up water and delivers the slurry to the scrubber as required to maintain pH set-point. The pH control loop regulates the speed of the rotary valve on the silo to deliver limestone powder to the unit at the rate required to maintain the pH set-point. Slurry solids level will vary depending on the amount of limestone required to maintain pH.
Utilizing the VACUCAM® Ejector Mixer Slurry Process for producing limestone slurries offers major benefits for FGD in Power Plants that cannot be achieved with other processes.
- Optimize Slurry Quality and Scrubbing Efficiency
- Lower Initial Capital Costs
- Lower Installation Costs
- Less Real Estate Required for Installation
- Lower Operating Cost in Terms of Manpower, Maintenance and Overall Operating Costs
- Greatly Reduce Power Consumption Per Ton of Finished Slurry – Approximately 1–2kwh/ton of Dry Limestone
- Reduced Slurry Storage Required
- Much Greater Operation Flexibility
- Instant start and Stop of slurry Process
- Immediate Slurry Capacity as Required
- Total System Automation
- Simple Wash Down of Slurry Process