Pre-cast, pre-fired solutions for critical areas
Pre-cast, pre-fired solutions for critical areas

Pre-cast, pre-fired solutions for critical areas

Unplanned refractory shutdown not only reduces production, impacts profitability but also increases refractory cost. A few critical areas of a cement plant like tip casting (nose ring) and cooler beam (bull nose) are very sensitive, say
Dr Saumen Sinha, Alok Nagar, Rajeev Kumar Laharia, R Chokkar and Satwinder Kalsi.

All cement manufactures always showcase efforts to achieve ideal kiln operational condition, i.e., one shutdown in a year. Targeting for more refractory life in the critical areas of cement plant enables to meet the objective. Refractory relining is time taking, hence maximising the refractory performance in any areas would provide financial benefits along with mental/operational satisfaction.

Most of the cement plants use substantial volume of refractory during shutdown, which calls for huge workforce deployment during installation. Safety concerns over the temporary manpower engaged during shutdown are of paramount importance today.

Refractory shutdown destabilises cement kiln operation, so avoiding production interruption is one of the major targets for cement manufacturers today. There are many instances where unproductive hours were greater than the actual shutdown duration. Unplanned refractory shutdown not only reduces production, impacts profitability but also increases refractory cost. A few critical areas of a cement plant like tip casting (nose ring) and cooler beam (bull nose) are very sensitive.

Tip casting (TC) is exposed to the:

  • very high clinker abrasion,
  • thermal shock due to unstable coating, and
  • severe mechanical stress due to kiln rotation, first tyre migration and bolting system of metal blocks.
  • Normally bricks are being used in TC and they are matched with performance of burning zone bricks lining performance. This is an ideal condition. Over a period of time, due to outlet shell ovality/well mouth there arises difference in hole positions and various issues of tip casting metal blocks resulting in misalignment of the outlet ring. This results in reduction of tip casting refractory performance. Position of metal retainer ring and its design also plays an important role in the performance of bricks used in tip casting.

    To overcome this situation, most of the cement plants started using various grades of castable (monilithic lining). The dismantling of castable and relining it with new castable takes approximately two to three days more than that it takes for brick lining. Utmost precaution during castable installation and controlled dryout of refractories are prime requirements for castable lining performance. Matching the performance of castable lining in tip casting with other area of kiln lining is always a challenge for cement kilns and normally extends the downtime.

    Moreover, damage of small portion of brick lining or failure of castable lining, in a few tip-casting panels, leads to total shutdown of the plant and wastage of minimum four to five days with an additional cost of Rs 15 to Rs 20 lakh (only refractory cost/stoppage).

    The cooler beam (bull nose) is exposed to:

  • Very high clinker dust abrasion
  • High temperature
  • Heat accumulation and more height of clinker bed (for heat recovery) damage refractory in Cooler Bull nose. Shape of bull nose and its position etc. are also responsible for its poor performance.

    Assured solution - Calde ready shapes BN (Calde RDS BN)
    N G Johnson (Northern) of United Kingdom was pioneer in providing refractory ready shape solutions for cement plant critical areas. Acquisition of N G Johnson by Calderys has provided access to this advance technology for TC, BN and damper.

    At present, these blocks are being manufactured at Calderys Nagpur Works, Maharashtra. Calderys Provides tailor-made pre-cast- pre-fired solutions for:

  • Tip casting (nose ring)- Calderys RDS TC
  • Cooler bull nose beam - Calde RDS BN
  • Hoisting damper - Calde RDS DP
  • For more demanding applications, such as where abrasion resistance, chemical resistance and higher temperature strength is desirable, Calderys Ready Shapes can be used. It has the best resistance to acid and alkali attack and also possesses a much higher thermal conductivity, meaning that heat up and cool down more quickly to save energy costs. These blocks are being manufactured with very high grade special castable and state-of-the-art manufacturing techniques to ensure superior and reliable performance.

    Benefits:

  • Safe and reliable installation
  • Installation time reduced by 50 per cent
  • Castable hardening/dry out time is not required
  • Easy repair, option of changing only damage portion
  • Reduce specific cost
  • For TC, separate steel casting blocks not required
  • The performance of various grades of castables installed in some of the cement plants at cooler bull nose, kiln tip castings are indicated below.

    User list (TC Block)

  • Ambuja Cement, Bhatapara (being installed in February 2020)
  • Prism Johnson Limited, India, Satna Works (yet to be installed)
  • Hanson UK Heidelberg Cement Group - Ketton Works > 18 months
  • Hanson UK Heidelberg Cement Group - Padeswood Works > 18 months
  • Hanson UK Heidelberg Cement Group - Ribblesdale Works >18 months
  • CRB (formerly Lafarge) - Dunbar Cement Plant > 18 months
  • Conclusion
    It is evident from the present user that use of ready shapes provides immense benefits and improved performance (almost double the existing performance). These shapes are easy to use within least possible time. Manufacturing of Calde Ready Shape blocks in controlled condition with state of the art technology would ensure its superior performance. These blocks would help in reduction of unplanned shutdown and also to control the cost of refractory as it is already established in overseas.

    References
    -National Cement and Building materials, Publication
    -Survey of Cement Industry & Directory

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