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Refractory Curing
Ensuring Optimum Refractory Performance
Importance of Refractory Curing
It is fundamentally crucial that proper dry out of refractories should be undertaken as water is the common solvent for mixing of rams, castable and cement used for installation. This water, which is hydraulically bonded through chemical interactions, between various refractories after installation needs to be driven out from the lining or else can cause a severe crack by trapping steam in the lining which shall ultimately give way to the entire castable lining. To ensure optimum refractory performance it is imperative that all moisture is removed thoroughly and uniformly during the course of heat-up and prior to the plant being subjected to on-stream production.
Common Problems and Failures
The performance of any lining in a furnace is considered to be reasonable when similar service lives are achieved on a regular basis. Premature lining failure may be defined as one that does not achieve normal or average performance and service life. Furnaces and vessels do not consume the refractory with corrosive liquid metal, slag, abrasion, impact, etc., which are common in metallurgical furnaces. Refractory lining problems and failures are mainly due to thermo-mechanical stresses, erosion, and chemical attack. The most common refractory problems experienced are:
- Hot spots (higher casing temperature)
- Excessive cracking
- Spalling of lining (thermal, mechanical, structural)
- Erosion and thinning of lining
- Chemical attack/corrosion from process gases (such as hydrogen, carbon monoxide, sulphur dioxide, alkalise), flue gases (sulphur, sodium, vanadium), steam, etc.
- Acid-gas dew-point corrosion of refractory and metallic parts
- Partial melting and degradation of lining
- Excessive shrinkage and development of gaps
- Anchor failure and detachment of lining from wall
- Failure of metal liner over refractory
- Explosive spalling during dry out
- Mechanical damages.
Service Life
No guarantee whatsoever on the service life of refractory can be given without a controlled dry out method done by a competent company with the correct equipment and experience. The dry-out must be done by using high velocity gas or diesel burners and must be documented and given to the client after the dry-out is complete. The client must receive a signed chart certificate from the responsible technician after the completion of the dry out, this is proof and will serve as a guarantee.
It is of utmost importance that the dry out is done in a controlled manner. The dry out operation must follow a heating curve that is relevant and accurate to the type of material and the thickness 0f the lining used in the furnace. The service life of the refractory is directly affected by the way the dry out is being conducted. If the dry out is not done properly the life service will be shortened drastically. The financial impact will be significant as this will interfere with production and ultimately a premature shutdown and rebuild of the furnace.
African Heating Gas Division (Pty) Ltd, will ensure that the client receives a professional and reliable service to ensure you get the maximum production from your furnace/kiln/boiler, etc.