MICROGRAVITY RESEARCH IN SUPPORT OF TECHNOLOGIES FOR THE HUMAN EXPLORATION AND DEVELOPMENT OF SPACE AND PLANETARY BODIES by National Research Council

Author:National Research Council
Language: eng
Format: epub
Tags: Space and Aeronautics : Space Exploration and Development
Publisher: NATIONAL ACADEMY PRESS
Published: 2000-07-02T16:00:00+00:00

Production of Portland Cement

The central process in the production of portland cement is the heating of a mixture of sources of calcium carbonate and silica in a kiln at 1400 to 1600 °C. In this temperature range, calcium silicates are formed. The raw materials are processed before burning to obtain a feed that is thoroughly pulverized and homogeneous, which ensures a product that is uniform in composition. Failure to do this would result in cement with irregular properties and performance. Similarly, the control of the burning process is critical. This heat treatment, taking place in a rotary kiln, is called clinkering. It consists of a number of steps, as shown in Figure III.F.1. The inclination of the kiln, together with its rotation of 60 to 200 rph, causes the feed to move slowly along the length of the kiln. Material may remain in the kiln between 20 min and 2.5 h depending on the type of kiln and the specific production method. The material emerging from the kiln is called clinker. It is conveyed to ball mills, where it is finely ground with a small amount of gypsum and then stored until needed.

FIGURE III.F.1 Schematic outline of conditions and reactions in a typical cement rotary kiln (dry process). SOURCE: Mindess and Young (1981).

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