US1995540A - Method of aerating slurries - Google Patents

Description

106. COMPOSITIONS,

Cross Reference COATING 0H PLASTIC.

- March 26, 1935. A. H. HARRISON METHOD OF AERATING SLURRIES. 7

Filed' July 5, 1932 -'IC I I ARTHUR HUGO HARRISON Patented Mar. 26, 1935 l 1. 95. .uNITED' PATENT "OF Pics METHOD or AERATING'SLURRIES v v I Arthur Hugo Harrison, Gold Pines, Ontario, Canada, assignor to Carbonated Lime Processes Limited and harden upon hydration, and equall'y'wellto materials, which have not in themselves this setting capacity but which require some further processing step to bind .the aerated mass into permanent form, such, for example, as lime and clay, which may be hardened by carbonation and burning respectively.

. Various methods of aerating cementitious materials have been proposed, among which may be mentioned the chemical release of a gas in the slurry, whipping air into the slurry, and mixing the premade foam therein. Some of these methods have been widely used in the production of porous building materials from plaster of Paris, cement and the like. In view of the greater insulation capacity of cellular materials these methods have made it possible to produce greatly improved building materials.

The object of the present invention is to provide an improved and simple method of aeration in making such cellular materials.

The invention will now be described with reference to the accompanying drawing which illustrates di 1 n tically the operation of the method and in which,

Figure 1 is a longitudinal sectional view of the apparatus and Figure 2 a cross sectional view on line 22 of Figure 1.

It has been found that air can be most successfully incorporated in a slum by suitable agitation, beating or mixing in a closed space and that the density of the aerated product can be determined by the pressure maintained in the closed space during the agitation or As the air is whipped into the slurry the latter expands to occupy space originally filled with the air and when released from the chamber the aerated slurry expands as determined by the pressure maintained in the chamber. When the pressure in the closed space is varied the density of the aerated slurry and of the hardened or finished product made therefrom varies and adjustment of this pressure provides a ready means of regulating the density of the finished product.

In the drawing, 1 represents a chamber providing the closed space within which the aeration of the slurry is effected. 2 is a rotatable shaft carrying radial arms 3 on which are mounted a plurality of bars or paddles 4, the.

whole constituting the means for uniformly incorporating the air into the slurry. The shaft 2 is mounted in any suitable bearings and is caused to rotate at the desired rate by a. motor or any suitable means, not shown. Helically set Application July 5, 1932. Serial No. 620,845

1 Claim. (oral-:12.)

vanes or other means 5of any desiredtype are provided for causing the slurry to travel through the agitating zone at a rate such that the required amount of air will beincorporated in the slurry during the passage of the slurry through :5 the agitating zone. The agitating arms 4 are preferably shorter than the chamber 1 so as to provide a feeding zone 6 and a discharge zone '7. Slurry is fed into the zone 6 by means of a pipe or the like 8 discharging near the bottom of the 10 chamber. Air under a predetermined constant pressure is admitted at 9. The aerated slurry under the influence of the pressure in the chamber is discharged at 10. A pressure relief valve 1-J,may be provided.

In operation a slurry, comprising a mixture of water and eme laster of Paris lime cla Mme, and conaunn g any suitable BuBBleforming agent, is fed in I the chaber and air elling paddle arms 4 air.is drawn or whipped into,.eslu where'it s retame in e form' 0 "n es y' the bubble-forming agent. The period of agitation and the rate at 'which the shaft 2 travels will influence the amount of air incorporated in the slurry, but in practice these factors are preferably fixed at the most conj venient point and the extent of aeration gov- I erned by the pressure maintained in the chamber. Increase in pressure increases the amount 3 of air occluded in the slurry and, of course, when i the aerated slurry is discharged from the cham- X ber the mass expands with the freedom from super-atmospheric pressure.

The following specific examples are given to illustrate the effect of variation in the pressure within the chamber. In these cases the shaft of the agitating device was rotated at 270 R. P. M. and the period of agitation was two minutes.

1. A slurryof Portland cement was aerated 50 as above describe un er 0 owing conditions of pressure and the product weighed after being allowed to set for 10 days.

Weight-lbs.

per cu. ft. 55 Agitation at atmospheric pressure Agitation at 30 lbs. pressure 37 Agitation at 50 lbs. pressure 25' 2. A slurry of plaster of Paris aerated under 50 2 days gave the following results.

Weight-lbs. per cu. ft. Agitation at atmospheric pressure.v 68 Agitation at 12 lbs. pressure '82 Agitation at 24 lbs. pressure 51 Agitation at 60 lbs. pressure 23 3. A lime slurry aerated as described gave the following results.

Weight-lbs. per cu.1't. Slurry before agitation 77.8

4. A slurry oiLqalgaerated under varying pressures gave the o lowing results.

Agitation at 50 lbs. pressure 33. 4 Agitation at 83 lbs. pressure 17.5

These examples illustrate the fact that the density of the product may be maintained at the desired point by control of the air pressure employed during aeration. The rate at which the agitator revolves and the time of agitation are mentioned merely as illustrative of what has been done in this respect in practice and are subject to wide variation.

W the character herein us re we u and there are many available. Rosin u. lu r tioned as examples 0 some that may be used alone or in combination.

It will be apparent that aerated slurries of non-cementitious material, such as lime, clay and the like, require further processing to put them 2E3 agltated under atmospheric pres- 5 in the form in which they will be used in pracg 'gg 'a' gg'g gggg a t 'ce and such processes are now available in the Agitation at 30 pressure ":jiwrt. The aerated lime slurry may be hardened Agitation at 40 lbs. pressure QB Sa carbona'mon the may by I claim: 7

In the production of cellular building materials the method of aerating a slurry which comprises admitting slurry containing a bubble-forming agent to a closed space to but partially fill said space, admitting air to fill said space and to provide therein a predetermined pressure greater than atmospheric, maintaining said predetermined pressure constant and agitating the slurry to cause at least a portion of said air to be incorporated therein. I

ARTHUR HUGO HARRISON.

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