Making LIMESTONE SLURRY for FGD

The most efficient FGD processes for making Limestone Slurry can be provided by using pulverized limestone vs. the traditional wet ball mill process utilizing crushed limestone.  The wet ball mill process requires a considerable commitment by the power plant to operate a very inefficient process for crushed limestone handling on site and for operating inefficient wet ball mill processes requiring considerable operation cost, maintenance costs and energy costs with less than reliable slurry production.

The VACUCAM®  Ejector Mixer system offers several high capacity processes for efficiently making slurries for flu gas scrubbing. See for Sourcing Pulverized Limestone

The Systems are typically designed for single pass processing of 30%+ solids. The VACUCAM® Ejector Mixer units represent the heart of the process, providing major benefits that cannot be achieved with traditional mechanical mixers. See How It Works

Process Options
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 would be provided for stand-by. 


•    Single Pass Process Direct Into Slurry Storage Tank(s)
A single or a dual mixer can be mounted directly on the top of a slurry storage tank to provide a Single Pass Slurry Process at 30%+ slurry make-up on demand based on maintaining requirements for slurry storage.  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 silo to be elevated with the slurry tank below. See Schematic

•    Single Pass In-Line Process To Remote Slurry Storage
The skidded packaged module is located near the silo discharge, which conveys powder at a maximum delivery rate through an Air-Cone® Hopper bottom.  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 + or – 15% to maintain targeted solids levels. See Schematic

The two single pass processes described above require a water feed at the proper flow rate and pressure to achieve optimum mixer performance.  It is therefore desirable to provide water booster pumps to assure proper flow to the mixer systems.  The skidded system below is an example of a water booster skid with design redundancy.

[no slurry storage tank required]

•    Single Pass Process for Direct PH Control to Scrubber

A similar in-line Single Pass Slurry Process for Direct PH Control can be provided to deliver lime slurry directly to the FGD Scrubber based on a pH feedback loop. A portion of the Scrubber make-up water is diverted to the skidded Vacucam® slurry unit, which delivers lime slurry as required to maintain pH set-point. The pH control loop regulates the speed of the rotary valve on the silo to deliver the required amount of powder to the unit to achieve a slurry solids level to achieve and maintain the pH set-point. See Schematic

Energy Requirements are typically 10–20% of the energy consumed vs. other limestone slurry process options.  Depending on the process option, the slurry process consumes approximately 1–2kwh/dry ton of limestone.  This compares to approximately 10kwh/dry ton of limestone for a typical ball mill process. 

Review Comparisons of Energy Requirements for Typical Mixing Processes

Review Comparisons of $ Cost for Typical Mix Processes vs. Costs for 24TPH CaCO³ Example

• 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

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