Using Spraycasting to Optimize Equipment Lifetime & Operation Campaigns
by Thomas Höjer, Boiler & Incinerator Marketing Manager at Calderys.
In the world of refractories, a faster installation to minimize the downtime while enhancing product performance is a requirement. We’ve been working on developing this ideal solution since 1998. Today, Spraycasting (or Wet Shotcreting) is one of the fastest growing technologies for working and back-up linings. Spraycasting is the process of pneumatically projecting refractory pumpables, at high velocity, on all types of surfaces. Spraycast products combine the technical qualities of a cast material with the speed of a gunning installation method (e.g. CALDE® SPRAYCAST line). The application of moulds is avoided, giving spraycast (a.k.a. wet shotcrete or wet gunning) installation the advantages of cost, time and labor savings.
The results show more profitable installations as the end-customer extends his operation campaign.
The distinct feature of Spraycasting is that in most situations, it is possible to achieve an installation rate which is 3–10 times faster (300–1000 Kg/man/hr for a dense product) compared to the traditional cast methods (dry gunning applications and brick installation techniques) while still achieving a performance which is similar to or above that of a low cement castable. The added advantages are: very little rebound/wastage (less than 5%), no dust, 100% water control, optimal mixing, no moulds required, and most importantly, the same products can be used as castables as well as pumping materials. The versatility of the technique and the products makes it the fastest and the safest refractory installation method for almost all industries including Iron & Steel, Aluminium, Petrochemicals, Power, Incinerators, Cement and many more. Let’s look at some of the industry applications for Shotcrete Installations.
Spraycasting in Rotary Kiln
The below Maintenance work of the Kiln at one of our customer’s sites, producing around 200 KT of titanium slag per year & 110 KT of high purity pig iron.
After the wrecking, marking, welding, and installation of CALDE® joints, it took 3–5 days to install 633 Tons of CALDE® Spraycast, with two running Spraycast machines & eight installers. This was done at an average of 1 Ton/man/hour. Had this been done traditionally by moulding & hand casting, it would have taken 2–3 months of time including setting of the castable.
Spraycasting in Blast Furnace, Reheat Furnace & Torpedo
Spraycasting is becoming one of the most popular technologies for Blast furnace, reheating furnace and Torpedo repairs and maintenance due to the advantages of faster installation, lower rebound during installation and better life of the lining. The latter majorly depends upon the material selected, thickness of the installed lining, surface conditions (extent of scab present in the BF before wet shotcreting) and operating conditions.
This picture shows Spraycasting being done in the combustion chamber upper parts. 800 kg of Spraycasting material in the hopper consumed in 10 minutes. On an average ~3500kg/hour = ~25 m2.
The Spraycast products can, after mixing, be pumped with a double piston pump or similar, to the place of installation at high elevation. The material is sprayed in place through a spraying nozzle by adding compressed air and liquid add-mix. The add-mix stabilizes the material and thus prevents the product from slumping from the roof or wall, still allowing hand trimming if desired. It also enhances the setting rate. The wet spraycast product setting procedure takes place after this. It usually requires two teams, a nozzle team and a machine crew, for execution.
The process has a complex sequence of material handling, mixing and pumping to ensure the lining is properly installed. Knowing how to stop and start also requires a fairly high level of competency. Cleaning the equipment and conveying system has a direct impact on how well the next installation will go. Therefore, it becomes inevitable to have an experienced and well trained execution team at the site.
The Spraycast technology combines the best features of several different installation techniques allowing the shortest possible downtime of the customer’s equipment and increasing their campaign lengths. To reduce the total customer equipment down-time even further a sol-gel bond spraycast product can be chosen to be a double-win as the customer equipment production can start even sooner.
Would you like to discover this technique for your equipment? Contact us.