DE1471571B1 - Continuous process for calcining coke - Google Patents

Description

The invention relates to a method for the continuous degassing of coal in a shaft furnace, according to which the coal is heated directly by flammable gases conducted in cocurrent, and coke and Gas can be withdrawn separately, according to patent 1258 386, in which the coal is fed to a combustion zone together with air in an unheated state, the combustion zone as a result of the oxygen consumption of the gas supplied with the coal limited to a narrow expansion range and in the degassing zone following the combustion zone by the temperature of the now oxygen-free Gases complete degassing of the coal is achieved.

In addition to this already proposed method is from the Belgian patent 538 642 in one two-stage process for the gasification of coal or complete implementation of up to the slag Coal to volatile hydrocarbons only known to use a purge gas, which under the ao Conditions of the known method with the coal practically does not react, in particular because of the in the known method for this too low temperatures and the complete lack of a Combustion zone within the chamber containing the coal according to that already proposed Procedure.

Also with other similar known methods, for example according to the German patent specification 406 409, only the flushing gas principle is used, in which essentially no direct reaction with the use of coal.

Another known process (US Pat. No. 2,998,354) requires very expensive equipment and uses e.g. B. oxygen in excess, so that a high combustion of carbon entry.

In contrast, it is the object of the invention, the method already proposed according to the main patent in terms of its economy and applicability for calcining coke, in particular Petroleum coke, to improve significantly, also by taking advantage of its constructive and procedural Simplicity, for example, its continuous and on the principle of direct current of gas and coke to one another.

The method according to the invention is characterized in that in one method the initially defined type for the purpose of calcining coke instead of coal containing volatile constituents Coke, especially petroleum coke, is used and that the oxygen-containing gas is air in such Amount is supplied that to cover the heat of the process 2 to 25 percent by weight, in particular 5 to 10 percent by weight of the coke is burned.

An additional advantage is achieved if there is an additional fuel in the combustion zone, z. B. non-coking hydrocarbons introduced will.

With the method according to the invention, on the one hand, it is possible when calcining coke to achieve even lower carbon burn-up and, on the other hand, when using coke with higher Fraction of volatile constituents these partly valuable constituents despite the use of a combustion zone to win at least a large part according to the method already proposed, the combustion zone also being adjustable via the excess of oxygen-containing gas is. The method according to the invention is therefore particularly suitable for economical calcination of Suitable for petroleum coke and otherwise produces a calcined coke of good and uniform quality.

In contrast to known processes, the temperature remains within the coke column until it enters of the coke into the combustion zone is initially low and increases due to the direct current principle only suddenly increases sharply within the combustion zone in order to remain high afterwards, so that the unreacted volatile constituents cannot be precipitated again, but neither can can be further burned.

The method according to the invention is carried out, for example, as follows: Comminuted Coke is fed into a feed hopper and a lock designed as a conveyor star wheel Chamber introduced, wherein the closure prevents a substantial loss of pressure in the chamber. The chamber runs out into a conical bottom section, at the end of which a device for Discharge of the calcined coke from the chamber provided without significant pressure loss in the chamber is.

After the coke has entered the chamber, the coke builds up and moves aground gravity down through the chamber. If desired, the introduced coke can with A hot inert gas, usually exhaust gas, can be preheated. The oxidant is about the whole width of the coke column introduced into the chamber distributed.

The coke continues downward to an immediately below the oxidant input zone located combustion zone. The combustion zone tends to move upwards in the chamber move, however, is done by controlling the volume of coke and the amount of oxygen-containing gas practically held in a fixed position.

Virtually all of the oxidizing agent available is consumed at the front of the combustion zone, increasing the depth of that zone is limited to a few centimeters, which is a great deal compared to the entire treatment area represents low volume.

The area below the combustion zone contains coke, although its temperature is above its ignition temperature, which, however, no longer burns due to the lack of an oxidizing agent will. The calcining time can be varied by changing the depth of the chamber as well as the feed rate the coke and the oxidant flow rate can be controlled. The preheating is supported temperature control and the extraction of flammable gas and volatile substances from the Oven.

The flammable volatile components are sucked out of the chamber and, for example, by partial condensation separated from the condensable hydrocarbons in a condenser. If so desired some of the non-condensable gases can be returned to the chamber for preheating purposes will. Insulating the chamber prevents significant heat loss.

The inventive method is suitable for

However, calcining coke is particularly useful for calcining petroleum cokes. In particular the process is suitable for calcining the flame-retardant types of petroleum coke with high Share of fugitives. The volatile flammable constituents can thus be used in an economical manner recovered if the coke contains more than about 15 weight percent volatiles.

The oxidizing agent used in the process according to the invention is preferably oxygen or a Mixture of oxygen with inert gases. Examples of these mixtures are air or a mixture of oxygen and superheated steam. The oxidizing agent can before its use in the invention Process can be preheated to any temperature.

The amount of oxidizing agent used in a particular process is of the nature of this Oxidant and the type of coke to be calcined, from the desired temperature of the combustion zone and on the desired volatile, combustible content of the end product. The amount of oxidizing agent required for a special process can be determined on the basis of empirical values can be determined, but in general corresponds to the one introduced into a chamber Amount of oxidizing agents necessary for complete combustion of only about 2 to 25 percent by weight of the coke to be calcined required. It is preferable to use as much oxidizing agent as that about 5 to 10 percent by weight, based on the coke, of the total charge are covered.

The preheating temperature as well as the coke and oxidant throughput should be set in such a way that that immediately below the combustion zone a temperature of about 540 to 1400 ° C and preferably from about 815 to 1360 ° C is maintained. The highest temperatures occur at the Front of the combustion zone, where most of the oxygen is consumed. When moving down of the calcined coke away from the combustion front occurs a continuous slower Temperature drop.

example

In a series of experiments, a coke which had been crushed to a grain size <0.833 mm was used to fill an insulated tubular furnace with an inside diameter of about 76 mm and a length of about 1220 mm. The coke had a density of about 1.59 and a volatile combustible content of about 5.40 percent by weight. The air was introduced at the top of the sealed tube while the gas outlet was controlled so that a pressure of about 0.7 kgf / cm ² prevailed at the top of the tube. The pressure drop across the tube was typically about 0.42 kgf / cm ² . The coke was ignited from the bottom or bottom of the tube by means of an electric heater or igniter. Additional heat was supplied to the area of the combustion front in the tube with the help of externally attached resistance heating coils. The temperature of the heating coils was usually around 200 to 375 ° C.

The following table shows various operating conditions and results. The yield relates only to the remaining coke; there are no volatile hydrocarbon products in it contain.

attempt
No. Final salary of
volatile, flammable
Fabrics
(%) yield
(Yo) Air flow
m '/ h · m ^s at ° C speed
the flame front
(m / h) temperature
the flame front
(° C) 1
2
3 1.94
3.01
4.81 86.7
91.5
97.8 230
117
40 0.45
0.30
0.15 749
704
538

As shown in the example, the temperature in the combustion zone can be increased, whereby the non-condensable or condensable fuels contained in the exhaust gases can be returned to the combustion zone in the preheating step. Optionally, the Coke can also be moistened with a non-coking hydrocarbon fuel before leaving is placed in the furnace. For this purpose, the coke particles can, for example, with kerosene or Naphtha can be wetted and placed in the furnace.

Claims (2)

Patent claims: 1. Process for the continuous degassing of coal, in a shaft furnace, according to which the coal is heated directly by flammable gases conducted in cocurrent, and coke and gas are separated are deducted, according to Patent 1,258,386, characterized by that for the purpose of KaI-zinierens of coke instead of coal, coke still containing volatile constituents, in particular Petroleum coke is used and that air is supplied in such an amount as the oxygen-containing gas is that for the heat coverage of the process 2 to 25 percent by weight, in particular 5 to 10 percent by weight, of the coke to be burned. 2. The method according to claim 1, characterized in that an additional in the combustion zone Fuel, e.g. B. non-coking hydrocarbons are introduced.