DE344478C - Process for the production of plaster of paris - Google Patents

Description

■ " BTTiLiOTiI KKI

BUREAU vü '. " ¹

IMDUÖTRIEELEN t! 6

GERMAN EMPIRE

ISSUED ON NOVEMBER 24, 1921

REICH PATENT OFFICE

PATENT LETTERING

CLASS 80 b GROUP 6

William Malam Brothers in Ruddington, England.

Process for the production of plaster of paris.
Patented in the German Empire from February 15, 192t.

According to the union treaty of June 2nd, icju has priority for this registration registration in Great Britain from i8. Claimed February 1920.

The invention relates to a method for producing plaster of paris, so-called Parisian plaster. Calcium sulfate CCa SO ₄ + 2 H ₂ O), such as from the natural material of old plaster molds, and should enable an uninterrupted work process.

The procedure essentially consists

in that the calcium sulphate under pressure in the presence of practically dry steam deals with which latter is generated in or from the work item when this is in in a closed vessel, at such a high temperature that any condensation occurs of the generated steam is held back.

The subject of the invention is described in more detail with reference to the drawing, namely shows the drawing shows some embodiments of a ge ao for carrying out the method suitable device.

Fig. Ι is a longitudinal section of a retort

Claims (1)

l) between of a kiln by smoke gases or any products of combustion wind heated. Fig. 2 is a similar longitudinal section of a steam-heated furnace. Fig. 3 is a cross-section associated with the latter. In the embodiment of Fig. Ι a horizontal pipe A is built into a flue gas channel α -and is heated by means of a flame or by means of hot gases that are produced by any kind of combustion. The material to be worked is fed in from a hopper B by means of the rotary valve C and discharged from the pipe by the rotary valve C ^1. The plaster of paris to be processed is powdery or granular and is slowly moved through the retort tube by means of a screw conveyor D rotating in it. A safety valve b, through which the generated steam escapes, and a pressure gauge can be provided. In the embodiment according to Fig. 2 and 3, the horizontally arranged container ^ of the kiln is provided with a steam jacket E , which is made sufficiently thick to withstand an internal pressure of about 1.4 to 2.1 kg; this is to prevent condensation of the internal vapor. The material to be worked enters the furnace container from the hopper through a rotary valve C and is removed by the rotary valve C ^1. Inside the furnace space, a number of steam tubes are arranged in the manner of a cage, the tubes being supported by plates g . The latter are provided with headers or connectors and pins so that they can be rotated freely. Outside the group of tubes, several rows of blades d are attached, the blades of which are helically wound and arranged. The tubes G are heated to a high temperature by means of steam from a pressure of 14 to. 21 kg per square centimeter. The work is powdery or granular; as the tubes rotate, it is constantly lifted up by the paddles D and falls down through the grid formed by the tubes G , heating it thoroughly and at the same time slowly moving it from one end to the other of the container. The steam can enter at one end of the tubes and, after flowing through them, leave them at the other end; but it can also be directed back through part of the tubes in one direction and then through the other part of the tubes. H is a steam inlet pipe, K is a steam outlet pipe and h is a safety valve through which the steam generated in the material can be drawn off. "Similar types of device are known for chemical drying processes; baked plaster is suitable. The rotary valves or sluices C, C ^{1 used} for the supply and discharge of the material to be worked are also known in terms of their design; they have the property that one passage is always closed when the other is open, whereby a pressure reduction in the interior of the furnace when filling and discharging the work material is avoided. The plaster of paris is fine-grained or powdery, maintains the state of a practically dry powder during the working process and leaves the pressure chamber or furnace container A in the form of the dry, so-called Parisian plaster powder, which can thus be brought onto the market immediately. As an example of the procedure, consider the following: The ground gypsum is poured continuously into the closed vessel A provided with the screw conveyor and heated therein to a temperature of about 180 to 220 ^° C., a pressure of about 1.8 kg per square centimeter being maintained. Under these conditions, the crystal water is driven out of the gypsum as practically dry steam. Thus, it is frequently dry, powdery or granular gypsum supplied to one end by means of a suitable inlet gate C to the container A at the · and subsequently removed ¹ resistant dry plaster of Paris to the other end by a suitable valve C. Other devices can of course also be used to carry out the method than those described. Patent-A ν claim: j Process for the production of burned, so-called Parisian plaster, characterized in that powdery : or granular calcium sulfate (Ca SO ₄ + 2 H ₂ O) in a closed vessel : under pressure and a temperature of ; 180 to 220 ° C without the addition of moist ! speed or steam is being treated. For this purpose ι sheet of drawings.