Cost-effective Modular Coal Preparation Plants
The new concept in designing modular coal preparation plants offer the advantages of gradual build up on beneficiation capacity, writes Sunil Yadav.
As coal mining projects have long gestation period of around seven to eight years for underground mines and four to five years for open cast mines to reach peak production, a new concept in designing modular coal preparation plants offer the advantages of gradual build-up on beneficiation capacity. This keeps up with the increased production and thereby obviates the necessity of blocking capital investment at the outset hence saving on capital cost. Read on to know how.

Construction of modular plant

All structural steel models in the modules are in accordance with the current standards of the steel construction related to the design and fabrication of structural steel for buildings. Structural steel connections are designed for field bolted assembly. Each module has wide flange floor members with T Cord upper members which fit together as modules are stacked. All necessary bracing is included on each module prior to shipment. This results in a rigid frame to withstand with equipment in place. When assembled together, the modules produce a very stable structure.

Pre-engineered size of modules

The framework of all modules is pre-engineered and standardised to the same size. The size of a module is 11'-0" wide by 12'-0" high by 30'-0" or 40'-0" long.

Interconnection of modules

Each module is manufactured with high quality workmanship including jigs and fixtures to ensure that all connections will match when lifted into place during field erection. Most connections are by hi-tensile steel bolts with all the holes drilled in the shop prior to shipment. Splice plates are used on all column connections.

Foundation requirements

Foundation works consists of establishing construction lines and levels from customer's benchmarks, furnishing and installing concrete, forms, reinforce?ment steel and anchor bolts.

The actual foundation can be piers or a slab to support the structural modules and depends on the site conditions. Since the spans are not that great and there is a minimum of eight columns per module distributing the load, normally permits slab foundations to be utilised.

Electric powering of modular plant

Each module is pre-wired with wiring in rigid galvanised steel conduit except the conduit is used for field connections between the modules. Each module has a junction box and once the modules are stacked in place, the flex conduit is simply connected from the upper module to the junction box of the next lower module. The pre-wiring includes all electrical devices within the module such as motors, stop jog switches, lighting and electrical outlets.

Preparation equipment utilised

The basis for the selection of all preparation equipment within a modular coal preparation plant is the same as would be used in a conventional coal preparation plant. The customers' raw coal size analysis and washability data are reviewed by coal preparation engineers to determine the most efficient and economic method of cleaning to meet the particular quality requirements. Then the various modules are assembled to develop the circuits determined to be the most efficient and economical by the coal preparation engineers.

All the equipment utilised in the modular plants is the same type and high quality has been used in conventionally structured coal preparation plants for years. Even though the modules are standardised, variations in modules stacking obtain different circuits and combinations of circuits to create a functional plant that gives the flexibility necessary to produce an efficient plant design. A 7'-0" space is even left between the stacks of modules to accommodate such things as a stair system, machinery well, piping etc. A small elevator could even be included.

Logistics and transportation of modules

All modules are designed for rail truck transportation with lifting lugs provided on each module. After a few years of operation, if it becomes necessary to move a plant, it could be disconnected at the modular connections and transported and re-assembled at the new site.

Field erection and commissioning

Once the foundation work is completed, the field erection of modular plants primarily consists of lifting each module from the truck or rail car and placing it in the proper position. After a module is lifted into position, all that remains to be done is the connections to anchor the bolts and other modules, connecting flexible electrical connections between junction boxes, piping connections, and adding the necessary chutes, hoppers and sluices to complete the circuits.

Metso modular coal preparation plants

Metso modular coal preparation plants are a step above the conventional coal preparation plants. The main advantage of modular plants is that they are pre-engineered and have a shorter completion time than conventional preparation plants. This time saving results in lower capital costs. In addition, modular plants offer the efficiency and reliability available in most custom-built plants, but has the added benefit of being easy to disassemble and move to a new location. Finally, modular plants may be designed to allow the addition of future modules to expand the plant only when production increases warrant.

Metso modular plants employ conventional coal washing equipment. Many standard circuits are available including heavy medium washing (both vessel and cyclone), jigs, and water-only cyclones.

Cost saving through modularity

Modular coal preparation plants are a means of giving the customer a compact modular design, with the most of the pluses of a customer designed plant, faster and at less cost. Metso can offer the total system from concept to commissioning as well as operation and maintenance services for the whole life of the modular coal preparation plant. Hence it is customer satisfaction guaranteed under one umbrella.

ADVANTAGES

Shorter completion time hence lower overall capital cost.
  • Lowest payback period.
  • Cost reduction due to pre-engineered plant.
  • Majority of assembly work to be done in Metso workshop under expert supervision.
  • Field receiving, storage and fit-up problems at site to be eliminated.
  • Ease of disassembly and shifting the plant to another coal mine location.
  • Add on features of module to enhance capacity of modular plant.
WHAT METSO OFFERS  
  • Sieve bends.
  • Raw coal de-sliming screens.
  • Clean coal D&R screens.
  • Refuge coal D&R screens.
  • Heavy media cyclones (Multotech).
  • Classifying cyclones (Multotech).
  • Lo-flo bath
  • Low intensity magnetic separators.
  • Slurry pumps.
  • Centrifuges
  • All chutes. Tankage and launders.