For wet flue gas desulfurization projects with a limestone powder requirement of approximately 3–15 tonnes per hour, a compact dry grinding line can provide a reliable and practical reagent supply. This production range is commonly suitable for industrial boilers, captive power plants, smaller thermal units, retrofit desulfurization projects, and centralized limestone preparation for several medium-size absorption systems.

An MTW European Mill from Liming Heavy Industry can be integrated with crushing, controlled feeding, powder classification, dust collection, finished-powder storage, and slurry preparation equipment. The result is a complete limestone powder preparation line that delivers stable output for continuous wet FGD operation.

Recommended Process Flow

Raw limestone receiving → Crushing → Buffer storage → Controlled feeding → MTW European Mill → Classification → Pulse dust collection → Finished-powder silo → Slurry preparation → FGD absorber

The process begins with limestone receiving and preliminary inspection. High-calcium limestone is transferred to the crushing section, where the material is reduced to a suitable feed size for the mill. After crushing, the material enters a buffer bin to maintain a steady supply to the grinding system.

A controlled feeder delivers crushed limestone to the MTW European Mill at a stable rate. Inside the mill, limestone is ground and classified continuously. Qualified fine powder is collected by the pulse dust collector and conveyed into the finished-powder silo. Coarse particles are returned automatically for further grinding until they meet the specified fineness.

Why the MTW European Mill Fits This Capacity Range

Small-to-medium FGD projects require more than a mill with an appropriate hourly output. They need stable powder fineness, manageable equipment investment, reliable operation, and convenient integration with slurry preparation equipment. The MTW European Mill is suitable for this type of production line because it provides controlled grinding and internal classification in a compact arrangement.

Typical Equipment Configuration

A 3–15 TPH FGD limestone powder line is normally designed as a coordinated system. The main equipment arrangement can include:

• Limestone receiving hopper and grizzly screen.

• Jaw crusher, impact crusher, or hammer crusher for feed-size reduction.

• Belt conveyor and magnetic separator for material transfer and tramp-metal protection.

• Raw limestone storage bin with level indication.

• Vibrating feeder, belt feeder, or weigh feeder for stable mill feeding.

• MTW European Mill from Liming Heavy Industry.

• Internal classifier and main air system.

• Pulse bag filter and rotary discharge valve.

• Bucket elevator, screw conveyor, or pneumatic conveying equipment.

• Finished limestone powder silo with level switches and vent filter.

• Powder dosing feeder for slurry preparation.

• Slurry preparation tank with process-water supply and agitator.

• Slurry storage tank, density meter, and duty-and-standby slurry pumps.

• Electrical cabinet, PLC control system, and field instrumentation.

The final equipment list should be selected according to raw limestone size, moisture, hardness, required product fineness, available installation area, and the required operating reserve for the FGD unit.

Finished Powder and Slurry Preparation

For wet limestone FGD, the purpose of the grinding plant is to prepare a powder that can dissolve efficiently after mixing with water. The finished limestone powder is normally stored in a sealed silo before it is fed into a slurry preparation tank.

A dosing device transfers limestone powder from the silo into process water under continuous agitation. The agitator keeps the solids suspended and helps produce a stable slurry concentration. The prepared slurry is then pumped to the absorber reaction tank according to the operating demand of the desulfurization system.

The overall chemical reaction can be represented as:

CaCO₃ + SO₂ + ½O₂ + 2H₂O → CaSO₄·2H₂O + CO₂

Consistent powder fineness is important because oversized limestone particles dissolve more slowly. Excessive coarse particles may increase residual limestone in the gypsum slurry and reduce effective reagent utilization. At the same time, grinding much finer than required can increase energy consumption. The best operating target is the fineness that matches the actual FGD absorber design and limestone reactivity.

Capacity Planning for a 3–15 TPH Line

The selected output should be based on maximum limestone demand rather than average daily consumption. The design calculation should consider boiler load, coal sulfur content, required SO₂ removal efficiency, limestone CaCO₃ content, operating Ca/S ratio, and grinding-system availability.

For example, if the wet FGD absorber consumes 8 TPH of limestone powder at maximum load, the grinding line should not be designed at exactly 8 TPH. The project should include production margin for changes in limestone quality, temporary high-sulfur fuel conditions, wear of grinding components, and planned maintenance. Finished-powder storage should also provide sufficient inventory for continued slurry preparation during short mill interruptions.

Finished-Powder Storage

The finished-powder silo is an essential part of a small-to-medium FGD grinding line. It decouples grinding production from slurry consumption and provides an operating reserve during short maintenance stops or temporary upstream material interruptions.

The minimum usable silo capacity can be estimated using:

Usable powder storage capacity = Maximum limestone consumption × Required backup time

For a line supplying 8 TPH of limestone powder, a 12-hour operating reserve requires:

8 TPH × 12 hours = 96 tonnes of usable powder storage

The actual silo should be larger than the calculated usable capacity because the design must allow for low-level dead stock, freeboard, powder bulk-density variation, and safe high-level operating limits.

Operating Priorities

Stable operation depends on maintaining coordinated control of crushing, feeding, grinding, storage, and slurry preparation. The following points should receive continuous attention:

• Keep the crushed limestone feed size stable and prevent oversized stone from entering the mill.

• Maintain a consistent feed rate through a controlled feeder rather than manual gate adjustment.

• Check raw limestone CaCO₃ content, moisture, hardness, and silica content regularly.

• Control finished-powder fineness through classifier adjustment and routine sieve or particle-size testing.

• Monitor mill current, airflow, pressure, vibration, and bag-filter differential pressure.

• Keep the finished-powder silo dry and ensure smooth discharge to the dosing system.

• Maintain stable slurry density through coordinated powder dosing, process-water flow, and tank agitation.

• Provide adequate powder inventory before planned mill maintenance.

• Use duty-and-standby slurry pumps where uninterrupted FGD reagent supply is required.

A Practical FGD Powder Solution

For limestone powder demand between 3 and 15 TPH, an MTW European Mill-based system provides a practical balance of output, fineness control, equipment integration, and operating flexibility. With suitable crushing, controlled feeding, pulse dust collection, sealed powder storage, and stable slurry preparation, the line can supply a wet FGD absorber with consistent limestone reagent.

The final configuration should always be matched to the actual limestone test data and maximum SO₂ removal demand. A correctly sized MTW European Mill line helps maintain continuous powder production, stable slurry quality, and reliable operation across the complete FGD reagent preparation process.