GB2167058A

GB2167058A - Method and apparatus for cooling white cement clinker

Info

Publication number: GB2167058A
Application number: GB08429398A
Authority: GB
Inventors: Erik Molkjaer Jensen
Original assignee: FLSmidth and Co AS
Current assignee: FLSmidth and Co AS
Priority date: 1984-11-21
Filing date: 1984-11-21
Publication date: 1986-05-21
Also published as: JPS61127650A; GB8429398D0; DE3526345A1; DE3526345C2; GB2167058B; FR2573418A1; FR2573418B1

Abstract

In a method of manufacturing clinker for white cement, after the clinker leaves the rotary kiln 1 and is sprayed with reducing agent 17 (e.g. oil) it falls onto an impact plate 4 so as to partly crush the clinker prior to spraying with a cooling agent 18 (e.g. water). In the rotary cooler 5 the clinker is separated into a fine fraction which is finish cooled, and a coarse fraction which is passed quickly through the cooler by means of a helical lifter 7,8 and into a water bath 9 from which it is subsequently removed. <IMAGE>

Description

SPECIFICATION Method and apparatus for cooling white cement clinker The invention relates to a method and apparatus for manufacturing clinker for white cement, which is a cement type substantially identical in chemical and physical properties to conventional Portland cement ("grey cement"), but distinguishable from the latter by its white colour, the method comprising spraying a reducing agent on to the clinker immediately before it leaves a rotary kiln and immediately thereafter quickly cooling the clinker by spraying it with a cooling agent before it is further cooled in a clinker cooler.

A method of the above kind is known from US A-3074705. The reducing agent, e.g. oil, which is sprayed on the clinker at the kiln outlet, is intended for reducing the clinker and preventing oxidation of the surface during an incipient cooling, while the cooling agent, preferably water, which is sprayed on to the clinker immediately thereafter, is intended for cooling the clinker to a temperature below approx. 500"C at which temperature no oxidation and consequently no discolouration of the clinker can take place.

It is a drawback of this known method that, in order to reduce the discolouration, the clinker must be sprayed with adequate water, which gives off an amount of water vapour flowing into the kiln plant and loading it, and which soaks the clinker in such a way that it may affect adversely the quality of the cement manufactured from the clinker.

Further, it has appeared that, during the subsequent drying and finish cooling in a cooler where the cooling is made by air, clinker particles become reoxidized as the surface is reheated by the comparatively large amount of residual heat still present in the clinker and consequently discoloured when exposed directly to air, which affects the whiteness of the finished cement disadvantageously.

To avoid such discolouration particularly of larger clinker particles it is known to let the entire clinker charge fall directly from the kiln clinker outlet down into a water bath for very quick cooling, but such a method requires a complete drying of the entire clinker charge, and soaking the entire clinker charge may still entail the above mentioned unfortunate influence on the quality of the finished cement.

It is an object of the invention to reduce these drawbacks and therefore, according to the invention, after spraying with the reducing agent, the clinker is made to fall down on to an impact plate arrangement at the cooler inlet to crush the clinker partly, before spraying with the cooling agent, the clinker subsequently being separated in the cooler into a fine fraction which is finish cooled and dried by cooler air in that the clinker is passed comparatively slowly through the cooler, and into a coarse fraction which is passed quickly through the cooler for partial cooling and which is finish cooled in a water bath from which the coarse fraction is with drawn, retaining residual heat sufficient for self drying.

By this method the heat from the fine fraction of the clinker is used for complete drying of the fine fraction in the cooler without discolouration thereof, while the larger clinker, i.e. the coarse fraction, is passed so quickly through the cooler that the clinker surface layer is exposed to the air in the cooler for only a short time and thereby to the least possible risk of reoxidation and following discolouration, within the finish cooling in the water bath.

The invention also includes apparatus for carrying out the above method, the apparatus comprising a rotary kiln for burning and sintering cement clinker, a rotary cooler, a first spray device for spraying reducing agent on the clinker at the kiln clinker outlet and a second spray device for spraying cooling agent on the clinker at the cooler inlet, an impact plate arrangement mounted below the clinker outlet of the kiln and in front of the cooler inlet, a dam ring in the cooler inlet, a separator and conveyor in the cooler for separating the clinker into a fine fraction and a coarse fraction and for the quick conveyance of the coarse fraction through the cooler, and a water bath at the cooler outlet for cooling the coarse fraction passed through the cooler by means of the conveyor.

The separator and conveyor may be constituted together by a helical lifter or screw mounted inside the cooler, spaced at a certain distance from the shell of same by means of spacer elements.

The separator/conveyor provides for fast conveyance through the cooler to the water bath of clinker too big to pass through the gap between the circumference of the lifter and the inside of the cooler, while clinker smaller than the gap passes through the cooler in the normal way, i.e. comparatively slowly, being cooled by means of the cooler air down to a temperature where no reoxidation takes place.

Water is, as mentioned, the preferred cooling agent used at the inlet of the cooler, and to remove the thus generated water vapour the cooler may in known way be provided with a suction pipe, the inlet opening of which is directed down towards the clinker layer at the cooler inlet.

Apparatus according to the invention will now be described, reference being made to the accompanying diagrammatic drawing which shows a longitudinal section through the cooler end of a rotary kiln plant.

The clinker outlet end 1 of a rotary kiln has the usual burner 2, and is encased by an outlet housing 3, having at its bottom an inclined impact plate arrangement 4.

An underlying rotary cooler 5 for cooling the material threated in the kiln has, at its inlet end, a dam ring 6 and, along its entire length, a helical lifter 7 mounted so as to be spaced at a distance from the inside of the cooler shell 5 by spacer elements 8.

At the cooler outlet end is a water bath 9 with a conveyor 10 for discharging the cooled coarse fraction of the clinker from the water bath down on to a conveyor 12.

Further, in the cooler shell 5 at the cooler outlet end is a gate arrangement 11 for moving the cooled fine fraction of clinker directly down on the conveyor 12, which thus transports away the total of the finish cooled clinker.

The cooler 5 may further have a pipe 13 for supplying cooling agent to the cooler inlet and a suction pipe 14 with its inlet opening 15 directed downwards to suck away water vapour at the cooler inlet. Reducing agent for the clinker is fed into the kiln clinker outlet through a pipe 16.

The apparatus operates in the following way: When the hot clinker having a temperature exceeding 1100 C leaves the kiln, reducing oil is sprayed thereon as indicated at 17, without flame formation.

From the kiln outlet the clinker falls down through the stationary housing 3 and hits the impact plate 4 to be partly crushed and guided towards the cooler inlet in which it is cooled by water, as indicated at 18.

The clinker passes the dam ring 6, which equalizes and controls the stream of clinker past the water spraying zone 18, and flows into the cooler 5 proper to be separated by means of the screw arrangement 7, 8 into a fine fraction and a coarse fraction. The fine fraction passes between the screw 7 and the inside of the cooler shett 5, and is cooled below 500"C by the cooler air and hence passes out through the grate 11 directly down on to the conveyor 12.The coarse fraction with particle dimensions larger than the gap determined by the distance elements 8 cannot pass through the gap between the circumference of the screw 7 and the inside of the cooler shell 5 and therefore, due to the coarse pitch of the screw, is conveyed quickly by the latter through the cooler and out into the water bath 9, in which it is cooled down to a temperature below 500"C.

By this quick conveying through the cooler 5 the surfaces of the large clinker particles do not reoxidize to any significant extent before the finish cooling in the water bath 9. The fine fraction of the clinker, which passes more slowly through the cooler 5, is also cooled sufficiently fast in the cooler 5 to avoid reoxidizing.

The water vapour generated from spraying at 18 is sucked away through the inlet opening 15 of the suction pipe 14 and consequently does not load the kiln.

The fine fraction, which has passed through the cooler 5, is discharged at the end of same through the grate arrangement 11 and down on to the conveyor 12. The coarse fraction is removed from the water bath 9 by means of the conveyor 10 at such a velocity that the clinker still contains residual heat sufficient for self-drying, after which it is also discharged onto the conveyor 12.

Claims

1. A method of manufacturing clinker for white cement, comprising spraying a reducing agent onto the clinker when it leaves a rotary kiln and thereafter quickly cooling the clinker by spraying a cooling agent thereon before it is further cooled in a clinker cooler, characterized in that after spraying with the reducing agent, the clinker is made to fall down on to an impact plate arrangement at the cooler inlet to crush the clinker partly, before spraying with the cooling agent, the clinker subsequently being separated in the cooler into a fine fraction which is finish cooled and dried by cooler air in that the clinker is passed comparatively slowly through the cooler, and into a coarse fraction which is passed quickly through the cooler for partial cooling and which is finish cooled in a water bath from which the coarse fraction is withdrawn, retaining residual heat sufficient for selfdrying.

2. Apparatus for carrying out the method according to claim 1, the apparatus comprising a rotary kiln for burning and sintering cement clinker, a rotary cooler, a first spray device for spraying reducing agent on the clinker at the kiln clinker outlet and a second spray device for spraying cooling agent on the clinker at the cooler inlet, an impact plate arrangement mounted below the clinker outlet of the kiln and in front of the cooler inlet, a dam ring in the cooler inlet, a separator and conveyor in the cooler for separating the clinker into a fine fraction and a coarse fraction and for the quick conveyance of the coarse fraction through the cooler, and a water bath at the cooler outlet for cooling the coarse fraction passed through the cooler by means of the conveyor.

3. Apparatus according to claim 2, characterized in, that a combined separatoriconveyor is constituted by a helical lifter or screw mounted inside the cooler, spaced at a certain distance from the shell of same by means of spacer elements.

4. A method of manufacturing clinker for white cement, substantially as described with reference to the accompanying drawing.

5. Apparatus for use in a method of manufacturing clinker for white cement, substantially as described with reference to the accompanying drawing.