US2794706A - Preparation of calcium carbide - Google Patents

Description

PREPARATION OF CALCIUIVI CARBIDE Willem van Loon, Geleen, and Sieds Koopal, Sittard, Netherlands, assignors to Stamicarhon N. V., Heerlen, Netherlands No Drawing. Application December 28, 1053,

Serial No. 400,768

Ciaims priority, application Netheriands December 30, 1952 6 Claims. (Cl. 23-208) The invention relates to the preparation of calcium carbide in shaft furnaces.

In this type of carbide manufacture, charges consisting of a mixture of a solid fuel containing substantial amounts of carbon, such as coke, coal and charcoal, and a calcareous material such as unslaked lime, limestone and dolomite are fed into the top of the furnace, while the heat and high temperature required for the carbide formation are obtained by oxidizing and converting part of the fuel to gaseous materials with the aid of an oxygencontaining blast. The inflammable gases thus formed escape from the top of the furnace, while in the lower section of the furnace a carbide melt is formed which can be discharged continuously or periodically.

The blast used to obtain this result may consist for instance of oxygen enriched air, technical oxygen, pure oxygen or of a mixture of oxygen with either steam or carbon dioxide.

The conversion of solid fuels mainly consisting of carbon by means of an oxygen-containing blast into inflammable gases, in the course of which the ashes of the coal are obtained in the form of a liquid slag, i a well-known process. In this process the composition of the blast is always so selected that the temperature of the combustion zone will be in the range of about 1000 to 1800 C., which will result in exhaust gas temperatures of about 450 to 900 C. being obtained.

However, the temperature of the combustion zone required in the manufacture of calcium carbide is much higher, namely about 2000 to 3000" C. Accordingly, it is to be expected that this very high combustion zone temperature will be accompanied by high exhaust gas temperatures. In order to prevent considerable losses of heat as sensible heat from the gas produced in the combined manufacture of gas and carbide in a shaft furnace it has previously been suggested to make use of regenerators.

OBJECTS It is an object of the present invention to prepare calcium carbide by an improved method of reacting a calcareous material with a solid fuel source of carbon.

It is a further object to prepare calcium carbide in a shaft furnace while at the same time dispensing with the use of regenerators.

It is another object of this invention to prepare calcium carbide by a method having a more favorable heat economy than prior art methods.

A further object of this invention is to obtain a more fluid melt than that obtained in prior art methods of forming calcium carbide in a shaft furnace.

Another object is to obtain a calcium carbide yielding an increased amount of acetylene upon hydrolysis.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific example, while indicating preferred embodiments 2,794,706 Patented June 4, 1957 GENERAL DESCRIPTION These objects are accomplished according to the present invention in the following manner.

Surprisingly we have found that the use of regenerators is entirely superfluous and very low exhaust gas temperatures of to 200 C. can be obtained if the weight ratio between CaO and C in the charge is made betwen 1 to 4 and l to 2 and preferably about 2 to 5, notwithstanding the fact that if a carbide of a predetermined calcium to carbon ratio is desired the processing of highly calcareous charge normally requires higher cornbustion zone temperatures than the processing of a charge with a lower calcium content.

In addition to the advantage of the more favorable heat economy which we found to be incidental to the addition of a relatively large proportion of lime, we have also discovered that during the manufacture of a carbide of a given quality, e. g., carbide containing 62% of CaCz, when the weight ratio betWeen'CaO and C in the charge was greater than 1 to 4, a more fluid melt was obtained than when said ratio was smaller.

Furthermore, it was found that the weight ratio between calcium oxide and carbon in the charge should not be made greater than 1 to 2, because above this limit difficulties are frequently encountered due to the fact that the combustion zone becomes slagged. This slagging cannot be prevented no matter how high the temperature of the combustion is raised.

EXAMPLES A more complete understanding of this invention and the operation thereof may be had by reference to the following examples. Example 1 operates in accordance with the present invention and Example 2, for comparison shows a similar but prior art method of operation.

Example 1 A shaft furnace was fed in accordance with our invention with a charge consisting of a mixture of 80 kg. of coke and 55 kg. of limestone. The coke had an ash content of 10% and the ratio of CaO to C was about 2 to 5. The height of the fuel bed was 4 meters. A blast composed of 77% technical oxygen and 23% steam was employed as this particular gas mixture was found to be particularly elfective in obtaining a good carbide. The initial furnace temperature rose from about 2500 C. to about 2650 C. The temperature of the escaping inflammable gas was C. The carbide obtained yielded 240 liters of acetylene per kilogram when decomposed with water.

Example 2 This example illustrates the results obtained when operating outside the ranges of the present invention.

The shaft furnace was fed with a mixture of 80 kg. of the same coke and 25 kg. of the same limestone as in Example 1. The ratio of CaO to C was about 1 to 5. The fuel bed had a height of 4 meters. The blast used was a mixture of 65% technical oxygen and 35% steam as those proportions were found best for obtaining a good carbide using the ratio of coke to limestone of this example. The gases escaping from the shaft furnace had a temperature of 280 C. The carbide obtained yielded 220 liters of acetylene per kilogram when decomposed with water under identical conditions with those employed in Example 1.

CONCLUSION The present invention provides a process for the manufacture of calcium carbide in a shaft furnace by starting from a mixture 'of "a solid fuel, mainly consisting of carbon, and a calcareous addition inwhichprocess part of the fuel present is converted to gases by an oxygencontaining gas in order to'provid'e the amount of heat and the high temperaturerequired forthe formation of calcium carbide, and an inflammable gas escapes through the top of the furnace, while in the lower section of the furnace molten carbide is collected which can be discharged either continuously or periodically; the process according to the invention being characterized by the fact that the weight ratio of calcium oxide and carbon in the charges to be supplied to the furnace is higher than 1 to 4 and lower than 1 to 2.

A comparison of Example 1 with Example 2 shows that by operating in accordance 'with the present invention it is possible to prepare calcium carbide in a shaft furnace in which the gases escaping from the furnace have a considerably lower temperature than the gases obtained when using a lesser amount of calcium oxide while at the same time the process of the present invention results in a carbide having a greater yield of acetylene per unit weight of the carbide.

We claim:

1. A process of preparing calcium carbide in a furnace from a mixture of a solid fuel comprising carbon, and a calcareous material, said process comprising converting part of said fuel to gases with an oxygen-containing blast in order to provide the heat and high temperature required for the carbide formation, permitting the inflammable gas to escape through the top of the furnace, while in the lower section of the furnace molten carbide produced by the reaction of the remainder of said fuel and calcareous material is collected, the weight ratio between the calcium oxide and carbon in the calcareous material and fuel mixture fed into the furnace being greater than about 1 to 4 and lower than about 1 to 2.

2. The process of claim 1, wherein the solid fuel is a member of the group consisting of coke, coal and charcoal. a

3. The process of claim 1, wherein the calcareous material is a member of the group consisting of unslaked lime, limestone and dolomite.

4. The process of claim 1, wherein the solid fuel is a member of the group consisting of coke, coal and charcoal, and the calcareous material is a member of the group consisting of unslaked lime, limestone and dolomite.

5. A process of preparing calcium carbide in a furnace from a mixture of a solid fuel selected from the group consisting of coke, coal and charcoal and a calcareous material selected from the group consisting of unslaked lime, limestone and dolomite, said process comprising converting part of said fuel to gases with an oxygen-containing blast at a temperature of about 2000 to 3000 C., permitting the inflammable gas to escape at a-temp'erature of about to 200 C. through the top of the furnace, while in the lower section of the furnace molten carbide produced by the reaction of the remainder of said fuel and calcareous material is collected, the said ratio be tween the calcium oxide and carbon in the calcareous material and fuel mixture fed through the furnace being greater than about 1 to 4 and lower than about 1 to 2.

6. The process of claim 5, wherein the fuel is converted to gases at a temperature of about 2500 C. and the inflammable gas escapes at a temperature of about 180 C. and the ratio of calcium oxide to carbon is about 2 to 5.

References Cited in the file of this patent UNITED STATES PATENTS 1,374,317 Norton Apr. '12, 1921 1,507,740 Kirby Sept. 9, 1924 1,872,202 Williams Aug. 16, 1932 2,380,008 Abrams July 10, 1945 FOREIGN PATENTS 501,376 Canada Apr. 13, 1954

Claims (1)

1. 5. A PROCESS OF PREPARING CALCIUM CARBIDE IN A FURNACE FROM A MIXTURE OF A SOLID FUEL SELECTED FROM THE GROUP CONSISTING OF COKE, COAL AND CHARCOAL AND A CALCAREOUS MATERIAL SELECTED FROM THE GROUP CONISTING OF UNSLAKED LIME, LIMESTONE AND DOLOMITE, SAID PROCESS COMPRISING CONVERTING PART OF SAID FUEL TO GASES WITH AN OXYGEN-CONTAINING BLAST AT A TEMPERATURE OF ABOUT 200 TO 300*C., PERMITTING THE INFLAMMABLE GAS TO ESCAPE AT A TEMPERATURE OF ABOUT 80 TO 200*C. THROUGH THE TOP OF THE FURNACE, WHILE IN THE LOWER SECTION OF THE FURNACE MOLTEN CARBIDE PRODUCED BY THE REACTION OF THE REMAINDER OF SAID FUEL AND CALCAROUS MATERIAL IS COLLECTED, THE SAID RATIO BETWEEN THE CALCIUM OXIDE AND CARBON IN TEH CALCAREOUS MATERIAL AND FUEL MIXTURE FED THROUGH THE FURNACE BEING GREATER THAN ABOUT 1 TO 4 AND LOWER THAN ABOUT 1 TO 2.