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Technical Article

Handling Limestone


As featured in International Cement Review
by Austin Anderson

Many products used as building blocks for the materials used in everyday life may not be obvious at first glance. Among these commonly-used, hidden materials is limestone. From the roads people drive on to the cosmetic products used each morning and the buildings they spend their days in, limestone is all around us.

Limestone, also known as calcium carbonate (CaCO3), is an essential and multifaceted mineral formed from calcium salts. Most commonly-used in infrastructure and the construction industry, limestone is an essential mineral and is used in a variety of ways, including as:

  • conditioner to neutralise acidic soils
  • base aggregate for road construction
  • cement and mortar ingredient
  • reagent for flue gas desulphurisation in the control of air emissions
  • suppressant for methane explosions in coal mines
  • means to remove impurities from blastfurnaces in iron production
  • a calcium supplement for livestock and poultry
  • a calcium source for cereals and breads
  • a filler and pigment for toothpaste, paper, plastics, paint and tiles, among other end products.

Globally, more than 100Mta of limestone are mined with a 10th of all sedimentary rocks being limestone. More than half of the world’s limestone is produced by China, followed by the USA and India.

Vortex and the limestone industry
Vortex has developed an expertise with handling abrasive materials such as limestone through an extensive and close working relationship with the industry. Through years of experience, Vortex has identified the key wear points of material handling components, reinforced those areas with abrasion-resistant materials and added features to reduce the time it takes to perform maintenance on these components.

When handling abrasive materials such as limestone, abrasion and wear become major concerns. Slide gates and diverters that incorporate protective liners made of abrasion-resistant steels, polymers, chromium carbide, ceramics, and even strategically-placed ‘rock boxes’ to minimise abrasion and allow equipment to last longer in harsh environments.

Another concern when handling limestone and other minerals is material leakage through the valve and into the atmosphere. These emissions can be detrimental to the health of workers and nearby ecosystems. Vortex products provide a positive seal to prevent these scenarios.

Figure 1

Case study: Titan Lined Diverter for handling dolomitic limestone rock
A limestone supplier in the southeastern US contacted Vortex to assist in a project handling dolomitic limestone rock (4-5in in size). Dolomitic limestone is formed when groundwater containing magnesium comes into contact with limestone. The calcium within the limestone is converted into magnesium.

The size and weight of the Titan Lined Diverter (TLD) is 1219 x 406mm (48 x 16in and 2358kg (5200lb), respectively. It is designed for use in gravity flow applications handling abrasive materials such as dolomitic limestone rock. Material from one source can be diverted to either of two or three destinations. The TLD offers replaceable wear liners for added abrasion resistance and removable access panels for internal inspection, cleaning or maintenance.

The hydraulically-actuated TLD shown in Figure 1 features a 2692 x 406mm (106 x 16in) transition that feeds material to a 1219 x 406mm (48 x 16in) diverter inlet and two 914 x 406mm (36 x 16in) outlets. Material contact areas (three sides) contain replaceable abrasion-resistant steel liners (400 BHN). An ‘A-style’ AR blade covers and protects the blade shaft from wear and abrasion.

Two inspection ports are mounted on the inlet transition and the diverter internals are accessible through a removable cover on the actuator side.

The diverter will be mounted, tilted at a 37˚ slope (actuator side up), to become part of a chute. Lifting lugs have been added to assist with the installation.

Figure 2

Case study: Rod/Pin Gate assists limestone supplier
Vortex’s engineering department provides customers with non-catalogue products designed specifically for their unique applications. A limestone supplier sourced the Vortex Rod/Pin Gate (R/PG) to handle dolomitic limestone rock.

Vortex application engineers match the right valve to the application parameters. Material characteristics, environment and valve requirements all must be considered to properly modify the valve to fit the application.

The size and weight of the R/PG is 711mm (28in) and 453kg (1000lb), respectively.

This type of gate uses individual metal rods to control material flow. Driving more rods into the opening shuts down the desired flow of material through the gate. Removing rods increases material flow. For certain applications, rods can be arranged to trap oversized material for later removal.

Since these gates are being used with vibratory feeders, hitch pins are being utilised to keep the rods in place. The vertical tubes on either side of the pins provide holders for the hitch pins.

Gates of this type are typically used for handling larger-sized, heavy material. The large rods are more resistant to wear. Rod size, in this case 51mm (2in) rods with 13mm (½in ) separation, is dictated by the process procedure.

Figure 3

Case study: Titan Slide Gate assists Malaysian cement manufacturer
A Malaysian cement manufacturer contacted Vortex Global to assist in the handling of limestone powder. These gates are electrically actuated but can also be manually operated if need be.

The size and weight of the Titan Slide Gate (TSG) is 300mm (12in) and 43kg (94lb), respectively. It is designed to meet the most demanding applications when handling heavy-duty abrasive materials. The TSG handles dry material in gravity flow applications where positive material shut-off and dust-tight sealing is required. This slide gate is available in a wide variety of configurations with rectangular sizes and customer specific hole patterns.

These application specific TSGs were manufactured with stainless steel blades and electric actuators.

The gates are mounted beneath product silos. The 400V/3PH/50Hz actuators are equipped with 4-20mA inputs and outlets that offer infinite positioning of the blade for precise material flow control.

Additionally, the actuators contain a hand wheel for manual operation if there is a loss of power.

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