DE1112003B - Process for the production of inert calcium oxide - Google Patents

Description

Process for the production of inert calcium oxide when burning from limestone (calcium carbonate) or from hydrated lime is produced by the usual working methods a calcium oxide that is very reactive and has a specific weight of about 1.2 to 1.4. This is especially the case when burning hydrated lime, which provides an extremely quick reacting quicklime.

For various purposes, however, this means high responsiveness and the low specific weight is a disadvantage in use. So reacts z. B. in the carbide production from lime and coal, the moisture of the coal in the mixture storage bunkers with the quick lime under heavy dust accumulation, the is blown out in the carbide furnace. This means both a considerable loss of material as well as an annoying dust emission into the atmosphere. Eliminating this Defects are expensive in terms of equipment and operation.

In certain metallurgical processes, too, the lower is specific Weight disadvantageous, since the lime pieces float on the surface of the melt and difficult to implement with this.

These disadvantages mentioned above can be avoided if the calcium carbonate or hydroxide is sintered at higher temperatures. It becomes a lumpy Calcium oxide obtained, which reacts much more slowly and depending on the sintering has a specific gravity of 2 to 3. The material thus obtained is not more sensitive to moisture, but can be outdoors and for long periods of time be stored in a humid atmosphere without decay.

The following summary shows that the reaction rate according to the degree of sintering of the lime pieces when they are in water are introduced and the temperature increase resulting from the heat of reaction of the water is determined as a function of time.

Temperature rise of water when introducing differently sintered pieces of calcium oxide (175 g CaO in 11 water) Response time temperature rise in ° C Seconds not weak medium strong sintered sintered sintered sintered 30 6 4 0.5 0 60 15 7 0.8 0.2 90 19 10.5 0.9 0.2 120 20 13 1.0 0.3 Continuation of the table Response time temperature rise in ° C Seconds not weak medium strong sintered sintered sintered sintered 150 20.5 15 2.5 0.5 180 21 17 3 0.5 210 21 18.5 4 0.5 240 21 20 5.5 0.5 270 21 20.5 6 0.5 300 21 21 7 0.5 330 21 21 8 0.5 360 21 21 9 0.5 390 21 21 10 0.5 420 21 21 10 0.5 There has been no shortage of efforts to produce sintered lime which can be used for the extraction of calcium carbide and for certain metallurgical purposes. But so far no process has been found that would have been technically useful.

A well-known process is based on limestone (CaCO3), whereby in shaft, Round and rotary kilns are used. With a considerable amount of fuel However, you only get a relatively dense quicklime if the secondary constituents Fee 03, A403 and S'02 are contained in small amounts in limestone. Otherwise Block formation takes place in the furnace, which leads to malfunctions.

It is also known of hydrated lime, which z. B. in the gasification of Calcium carbide is obtained by the so-called dry gasification process, or from calcium oxide in powder form, which occurs after the normal burning of limestone is screened from the pieces and only in small quantities after extinguishing as building or fertilizer lime can be deposited. During further processing, these become powdery After adding water, the starting materials are granulated in rotating drums and then the granules slowly heated to high temperatures on sintering belts or in rotary kilns. Of the high wear of the facilities due to corrosion and the considerable fuel consumption (Depending on the system used, it amounts to 1.3 to 2.5 million kcal per ton of CaO) impair the economy of this process considerably and lead to that in many cases the further processing of the hydrated lime powder is dispensed with.

Another method is to use hydrated lime with only 6 to 7% Briquetting water by pressing and burning the briquettes in shaft furnaces. However, these must not be heated above 1200 ° C, as the impurities in the used lime (a few percent Fe, 0s, Ah 03, Si OZ, etc.), or z. B. the The coal ash produced during carbide production causes it to sinter together into blocks. These sinter masses can, however, be used with the usual discharge devices, such as bar grates or pendulum tables, are not continuously removed from the furnace.

But if you work with such low temperatures that no sintering takes place; then burnt lime, which is very porous inside, easily accrues reacts with water or steam and has only low mechanical strength having.

A process has been found which does not show these shortcomings and in an economical way the extraction of sintered lime in pieces from powdery and / or fine-grained calcium hydroxide, carbonate or oxide. It exists in that the starting materials are briquetted and first at temperatures for some time heated at which no sintering occurs and then with a rapid increase in temperature heated for sintering and the sintered material is continuously removed from the furnace.

With this process a lime is produced which, although extraordinary is inert, is excellently suited for carbide production.

The process is carried out as follows: Firing and sintering takes place in a shaft furnace, which is heated by means of layer or inexpensive mixed fires will. The shaped material to be sintered is placed at the top. The used Coal in hers. Grain size selected so that the sintered material is first used for 1 to 2 Hours at temperatures that are 400 to 600 ° C for calcium hydroxide, for calcium carbonate are 800 to 900 ° C. During this period the water will or split off the carbonic acid. Subsequently, the goods are subject to a rapid rise in temperature heated to 1100 to 1600 ° C depending on the desired degree of sintering. This temperature behavior is achieved by appropriately mixing fine and coarse coal. Possibly the sintering temperature can be lowered by known additives.

It is also possible to use fuel gas or fuel oil and adjust the feed level and set the amount so that the desired temperature profile is reached in the oven will.

In the sintering zone, the material sinters with an even addition of fuel mostly in the form of the fed-in pieces. In addition, blocks are formed which can also include fragments of the bricks.

To ensure that the sintered material is uniform over the entire cross-section of the furnace to be able to discharge, the furnace is below z. B. provided with a scratch discharge. You can also use rotating grids or crushing rollers for the discharge, but will get much more dust and fine grain content. That is not the case with the scraper chain smaller sintered goods between the chain distances without breakage. The discharged Blocks can be crushed to the desired size by known measures.

Contains that for the further processing of the sintered lime to carbide If anthracite or coke used significant amounts of grain size below 3 mm, so can this fine fraction can be used economically for carbide production will. For this purpose it is sieved, expediently to a grain size below 0.5 milled mm and added to the calcium hydroxide before pressing. The one in the The sintering process described above burns only those in the edge areas coal contained in the pellets. The main amount inside the compacts, on the other hand is sintered in and in the subsequent processing comes on carbide as carbon for recovery.

Claims (6)

PATENT CLAIMS: 1. Process for the production of inert Calcium oxide from fine-grained and / or powdered calcium carbonate, calcium hydroxide or calcium oxide, characterized in that the starting materials are briquetted and first heated to temperatures below 1000 ° C for some time, at which no sintering occurs and then the temperature rises rapidly for sintering heated and the sintered material continuously removed from the furnace. 2. Procedure according to Claim 1, characterized in that a sintering temperature of 1100 to 1600 ° C is used. 3. The method according to claim 1 and 2, characterized in that that the sintering is carried out in a shaft furnace. 4. The method according to claim 1 to 3, characterized in that the sintered material is discharged from the shaft furnace takes place by means of scraper chains. 5. The method, in particular according to claim 1, characterized characterized in that coal or coke is added finely to the starting materials and is sintered in. 6. Use of the sintered lime produced according to claims 1 to 5 for the extraction of calcium carbide. Publications considered: German Patent Nos. 387,746, 904,825; Swiss patent specification No. 219 886.