IJssel Technology opts for cone with Kalcret

A test project in the red-hot cone of a shaft furnace. IJssel Technology (IJT) is an engineering company specializing in improvement of industrial production processes. One of IJT’s projects is the maintenance of the shaft furnace of Nedmag Industries in Veendam. At the end of the production process, magnesium oxide at a temperature of 550º C exits the furnace into the furnace cone and then through a product cooler into the storage bunker. To protect the furnace’s taper from wear, IJT wanted to try a new lining: Kalcret. We speak to the person responsible for this project, Albert C. Antema.

“Certainly, Nedmag makes a raw material for the refractory brick industry: dead burned magnesium or magne-sium oxide. The raw materials for this are magnesium brine, which is extracted locally from the Groningen soil, and a magnesium-containing lime, so-called dolime from Belgium. These raw materials are used to make magnesium hydroxide in a chemical process. This magnesium hydroxide is dewatered and then dried in a calcining kiln, where it comes out as magnesium oxide. It is then pressed into briquettes. These look like pigeon eggs. These briquettes are sintered in a shaft furnace at 2000° C in a continuous process. To remove it from the furnace, a water-cooled pull and push bar slides the product from a table into the cone. Similar to those machines at the carnival that push coins off the table. That last part of the process is what we’re talking about here.”

“The hot, freshly sintered magnesium oxide bricks (looks like gravel) fall into the cone. Due to the drop height from the table of the hot wear product, that cone wears out very quickly. Until now, we have combated the wear with abrasion-resistant sheets of the material Vautid. Applied like “roof tiles.” The big disadvantage of this is that those plates are welded to the structure and will eventually warp and therefore wear out anyway. Sometimes a “roof tile” breaks loose and blocks the outlet of the cone. We also had to replace some every six months. A very tedious job, because you work in a cone that tapers to 500x700mm, you have no headroom because the table is above your head. You have absolutely no room for maneuver. We wanted to try it with a material that is easier to apply. And cannot come loose. Like wear-resistant cement concrete: Kalcret.”

“We looked at the specifications first. Kalcret is wear resistant and can withstand temperatures up to 1200º C so that shouldn’t be a problem. Furthermore, it is easier to apply and also easier to repair if necessary. Of course it was not just our decision, but together with the installation manager of Nedmag it was decided to try it with one of the two kilns.”

“Our own people first removed all the old “roof tiles” and also cleaned the cone. That was still quite a job because those plates hung roof tile by roof in welded hooks. When we finished, the cone wall turned out to look a lot worse than we had thought. So we first asked Wivé to come and take another look. With the question, “Can you still do this for the price quoted?” That turned out to be the case. The work was performed under Wivé’s supervision by Kalenborn. They first assembled a reinforcement of expanded metal – a kind of flexible grid with diamond-shaped openings. That was welded to the cone wall and Kalcret was applied on top of it, with the trowel, just pushing it through well and smoothing it out flat.

“Well, now just wait and see how it holds up. I do hope that for the first two years we won’t have to work on it at all. Then it will also be economically interesting. This furnace will go back into production soon and the next stop is scheduled for six months from now. Then we will see how it holds up and whether we need to repair anything. If necessary, we will grind out a piece and press in new material. That doesn’t seem to be that complicated. We’ll see.”

“Sure. Although chances are that that Kalcret clad cone will last longer here than I will. After all, I’m retiring next year.”