Abstract

Introduction

The rotary kiln is the critical equipment in Portland cement clinker production. The duration of shutdowns is determined by the installation of the bricks. And the schedule of the shutdown will be determined by residual thickness of brick lining. 

A promising alternative to overcome these disadvantages is the use of unshaped Magnesia based materials.  This solution involves cost and time saving as well as environmental, health and safety advantages. In addition, the option of relining up to the original brick thickness by gunning, increasing their lifespan becomes an excellent solution.

However, the major challenge for MgO castables is the control of the hydration of magnesia to prevent the spalling and cracking during the curing and drying steps.

The aim of this paper is the development of the Magnesia-Spinel castables as an innovative alternative and/or complement to MgO bricks in rotary clinker kilns. The design allows the application of the castable by gunning and casting, in order to have a versatile product that satisfices all the needs of the clinker producers.

Materials and Methods

Different compositions of Magnesia-Spinel castables have been designed. Different magnesia sources and anti-hydration additives were studied. The evaluation of hydration of the Magnesia and its effects on the castables were carried out by the following techniques: macro-TGA, microscopy, XRD, dilatometry and properties of the samples (230 x 55 x 65 mm). In the second stage, bigger samples (300 x 300 x 300 mm) from the best recipes were casted.

Results

Magnesia-Spinel castables have been developed, without problems of cracking during the curing, drying or heat treatment. Installation methods used were gunning and vibrocasting. The properties of castables are good enough for the application and similar to Magnesia-Spinel bricks.

The control of the Magnesia hydration has been carried out two different ways, such as the selection of raw materials and the design of the microstructure. The chemical compatibility of old bricks and castables has been tested and the integrity of brick coated showed no alteration. The behavior of castable during the process is similar to that of the bricks and no differences in the coating formation have been detected.

New Spinel-Magnesia castables designed are being tested in different clinker production plants, without operating problems up to date. 

Conclusions

An innovative alternative for rotary Clinker kilns has been developed with promising results.

Rebuilt of the old bricks with the Magnesia-Spinel castables is an excellent solution promoting reductions in costs and maintenance shutdown time together with significant environmental, health and safety advantages.