DE521712C - Process for the production of cement, which contains gypsum mixed in - Google Patents

Description

GERMAN EMPIRE

ISSUED ON
MARCH 26, 1931

REICH PATENT OFFICE

PATENT LETTERING

CLASS 80 b GROUP p54315 vijSob

Patented in the German Empire on January 4, 1927

It is known that plaster of paris is added to Portland cement in order to influence the setting time of the cement as desired, the plaster of paris usually being added in the form of raw plaster of paris (CaSO ₄ , 2H ₂ O) and in amounts between 2 and 5% of the cement weight if it is pure Portland cement, but the addition of gypsum can be increased up to 25% if one is dealing with cement containing slag.

By heating the raw plaster to a ^{temperature between 125 0} and 180 ⁰ C, it is known that 1 ¹ I ₂ molecules of water are expelled from the plaster, and this form of plaster is known as burnt plaster and is characterized by the fact that it sets quickly , ie hardens when water is added. When the burning

If the temperature is increased above 180 ^° C., the plaster of paris also gives off the remainder of its water of crystallization and assumes a state that is referred to as burned to death, in which state the plaster of paris does not set at all or only very slowly when water is added.

Experience has now shown that the usual method of adding raw plaster of paris to Portland cement, namely the addition of gypsum to clinker and the grinding of this Mixture in a mill does not give a uniform product, so that the one obtained in this way Cement setting time fluctuates considerably and cement which under the same conditions often vary widely in their setting times, which is a serious disadvantage.

A detailed study of these relationships has led to the realization that this Disadvantage is mainly due to the thermal conditions, which in rule of the mill and which have the consequence that the plaster of paris is sometimes called raw plaster and sometimes present as plaster of paris in the finished cement, from which the various The setting time of the cement in different parts of a cement mass leaving the mill results.

The setting time of an ordinary, finely ground fresh Portland cement mixed with plaster of paris is very much longer (often 500 ° / ₀ ) when the plaster of paris is contained in the cement as raw plaster of paris than when the plaster of paris in the cement is in the form of burnt Plaster of paris is present. If the plaster of paris is burned to death, the setting time is lengthened compared to burnt plaster, depending on the temperature up to which the plaster of paris was heated, so that under certain circumstances the setting time is only about 10% shorter than the setting time of cement, the raw Contains plaster of paris.

This information applies both to the time that is calculated from the addition of

Water to cement until the start of setting, as well as for the further time that It is calculated until it has completely set, and they do not only apply to Portland cement with the addition of gypsum, but also essentially for cement, the blast furnace slag or the like. Was added.

The experiments carried out have also shown that the condition of the plaster of paris is a

ίο great influence on the marriage of the Cement exerts required energy. If z. B. plaster of paris is added, then is about 60% more time to grind the cement required than when raw plaster of paris or severely overheated plaster of paris was added.

The present invention is based on the knowledge obtained from these experiments with cement to which various types of gypsum have been added. The main feature the invention is that plaster of paris to cement in such form and under is added such that the plaster of paris will not be in the finished cement mix is contained in the form of plaster of paris, or in other words, there will be action taken, thereby ensuring that the plaster of paris in the cement is either in the form of raw plaster of paris or dead-burned Plaster of paris is included.

This result can be achieved in a number of ways. In particular like the following possibilities are mentioned:

I. The mill in which the clinker and raw gypsum are ground are during the grinding process appropriately cooled, e.g. B. by sprinkling the mill with water to prevent the raw plaster of paris from being heated to a temperature which begins the transformation into plaster of paris.

II. The cooling can also be effected in such a way that one is water in drops or in atomized state into the interior of the mill, and in such an amount that the heat absorbed by the evaporation is sufficient to preclude the occurrence of the transition temperature of the gypsum.

III. The clinkers are cooled, e.g. B. by artificially cooled air, on a suitable low temperature before going into the mill for the purpose of common grinding be introduced with added plaster of paris.

IV. The grinding media, which under the influence of the grinding process in the.

Mill have become hot, are led out of the mill and in a suitable place Cooled way and then reintroduced into the mill. Cooling down can too take place in a special chamber, which is in the mill body itself in the extension the grinding chamber is provided. In this way, the grinding media are cooled so far that the mixture of clinker, raw plaster of paris and grinding media does not reach the tempera

; ment begins in plaster of paris.

V. The raw plaster of paris is finely ground by itself and is then finely ground to the one Cement added, which was previously cooled so far that the plaster of paris with the mixture cannot be converted into the fired state with the cement.

VI. The plaster of paris is burned to death either before it is mixed with the cement or while it is in mixture with the cement. The gypsum can be burned to death before it is mixed with the cement in a kiln which is heated by combustion gases taken from a cement kiln and the temperature of which is high enough to cause the gypsum to burn to death. Another method would be to add the heat of the still hot clinker directly or indirectly to the raw gypsum, e.g. Example, in that it passes the raw gypsum by a clinker cooler in which the clinker is cooled and are usually introduced at a temperature of about 1000 ⁰ C. The raw plaster of paris can either pass through the cooler in a mixture with the clinkers, or it can also be kept separated from the clinkers by a heat-transferring wall.

This procedure can be used no matter whether the clinker cooler is an independent structure or whether it is z. B. is formed by an extension of the rotary kiln in which the cement is burned. In the latter case, the raw plaster of paris into the end section of the furnace used for cooling the clinker on a suitable one Place behind the flames heating the furnace, and this can be done mechanically happen, e.g. with the help of a pipe with a transport screw or by means of Compressed air or otherwise.

By adding only part of the plaster of paris in a dead-burned state while the remainder is added in the usual state and in the usual way, leaves a setting time can be achieved that lies between the setting time, which results if either all of the plaster of paris is burned to death, or if no part of the added one at all Plaster of paris is burned to death.

In the drawings, various devices are shown, which for the Implementation of the invention are suitable.

Fig. Ι and 2 illustrate in longitudinal section or in a cross section according to the

Line H-II of Fig. Ι a machine to finish with previously finely ground raw plaster mix ground cement.

Figures 3 and 4 are longitudinal sections of two different forms of devices in order to Burning plaster of paris to death with the help of heat contained in cement clinker.

In the device shown in FIGS. 1 and 2, 1 denotes a mixing drum which runs on hollow pins 2 and is provided with suitable lifting strips 3 on its inner wall. The feed of the material to the mixing drum takes place at the left end of the same through the pin 2, in which a screw conveyor 4 is seated. The mixing drum is emptied through the hollow pin 2 at the right end of the drum. The finely ground raw gypsum is fed to the feed connection at the left end of the drum through a pipe 5 with a screw conveyor 6 working in it. At the same time, the completely ground cement is also fed through a pipe 7 with a screw conveyor 8, the two pipes 5 and 7 opening to a common chamber 9, from the bottom of which the two substances pass through an inclined filling pipe to the hollow pin 2 at the left end of the drum. The cement supply pipe 7 is enclosed by a water jacket 11 through which cooling water flows. In this way the cement is cooled to the extent that it does not convert the raw plaster of paris to plaster of paris during the mixing operation in the machine.

The arrangement shown in Fig. 3 is used to raw plaster with the help of heat Burning to death clinker bricks leaving a cement kiln. The cement kiln is a rotary kiln 12, under which a rotatable cooling drum 13 is arranged, which the clinker is obtained from a chamber 14 through a chute 15 leading into the cooling drum 13 opens. The raw gypsum is also fed to the gutter 15, from one Silo 16 by means of a feed table 17.

The device shown in Fig. 4 is similar to that shown in Fig. 3. In this However, the raw plaster is not mixed with the clinker, but from the trap Silo 16 passed through the feed table 17 into a pipe 18 with a screw conveyor, which Tube is enclosed by the cooling drum 13. In the pipe 18, the raw plaster of paris is burned to death Gypsum converted, in which state it emerges from the pipe and through a pipe branch 19 into a collecting container got.

Claims (6)

Patent claims: 1. Process for the production of cement, which contains gypsum mixed in, characterized in that the gypsum is added to the cement either in the dead-burned state or under temperature conditions, that it is burned to death in the end product, or that the admixture of gypsum with cement is in the process of raw plaster of paris or a mixture of raw plaster of paris and dead-burned plaster of paris takes place under such conditions, that when mixing or grinding together, the temperature never rises to the firing temperature, for the purpose of keeping the end product free of gypsum in the calcined state. 2. The method according to claim 1, characterized in that the cooling of the mixture components by sprinkling the outer mill wall or by evaporation from into the mill interior In the form of drops or in the form of a spray of water introduced. 3. The method according to claim 1, characterized in that the grinding media at times separated from the grist and by suitable means either outside the mill or in a special, The chamber lying in the extension of the mill can be cooled and then fed back into the mill. 4. The method according to claim 1, characterized in that the dead burning of the raw gypsum is made by the heat of clinker emerging from a cement kiln, e.g. B. by passing through of the raw gypsum through the clinker cooler either as a mixture with the clinkers or separately from them a heat transferring wall. 5. Installation of rotary kilns for burning cement for induction the dead-burning of plaster of paris according to claim 4, consisting of a feed pipe for raw plaster of paris, which is either after the point of the rotary kiln where the clinker emerges, or which one opens into the clinker cooling drum. 6. Installation of rotary kilns for burning cement for induction the dead-burning of gypsum according to claim 4, characterized in that a conveyor system is installed in the clinker cooling drum is installed, which allows the raw plaster of paris to move through the cooling drum separately from the clinker. 1 sheet of drawings