CS195260B2 - Method of row briquets caking - Google Patents

Abstract

1384286 Coking briquettes FMC CORP 14 Sept 1972 [15 Sept 1971] 42653/72 Heading C5E A 10 to 36 inch deep bed 24 of green briquettes, made by briquetting coal char with a bituminous binder, is coked on a travelling grate 27 by passing a gas, containing at least 15% oxygen and preheated to 375-450‹ F., through the moving bed at a speed sufficient to prevent the temperature of the briquettes rising to above 575‹ F. The oxygen-containing gas can be air or flue gas. As shown in Fig. 2 the gas 20 is preheated in the combustion chamber 34 and recycled through the moving bed in the various sections of the oven 26 by the blowers 32, 38, 40 and 42, e.g. at 2À4 feet per second.

Description

DARROW WENDELL LINCOLN, DARIEiN (9p. A) (54) Sintering of raw briquettes

The invention relates to a method of sintering raw briquettes by blowing hot sintering gases across the briquette layer on a movable grate.

It is known that better briquettes can be made from roasted coal by briquetting low volatile roasted coal with bituminous binder, followed by drying the raw briquettes in the presence of oxygen at 190-232 ° C in inert gas for 1-2 hours and finally sintering the dried briquettes . Material that can be used as a metallurgical coke, even in blast furnaces, can be made according to U.S. Pat. Nos. 140,241 and 3140,222. According to these patents, the coal is heated by heating to at least 121 ° C and below the forming temperature. tar in the presence of oxygen, which can be added to the non-coal gas or can be present in the coal to form catalyzed coal particles. These particles are then suddenly heated to a tar-forming temperature, in particular to 260 to 482 ° C in a liquefied bed charger or in a series of such devices to remove substantially all of the tar top fraction. The tar-free coke thus produced is then further heated to a higher temperature, in particular to an outlet gas temperature of 760 to 816 ° C, in order to remove non-condensing volatiles and to produce a calcinate containing preferably less than 3% by weight of volatiles but at least one % hydrogen by weight. The calcine is then cooled in an inert atmosphere to a temperature at which it can be further processed in air. The cooled calcinate is then mixed with bituminous binder and formed into briquettes. The binder is preferably made of tar which is solid at ambient temperature. The briquettes are dried in the presence of oxygen.

There is an exothermic reaction between oxygen and a mixture of calcine with tar which causes amalgamation of the calcine and binder. The oxygen-containing gas causes a temperature rise to 260 to 288 ° C inside the briquettes at temperatures of 190 to 232 ° C during oven drying. The dried briquettes are then sintered to reduce the volatile matter content below 3% by weight.

In the laboratory, the briquettes were air dried in a laboratory oven, but the bed height was maintained in a single layer to prevent the temperature from above the ignition point.

As mentioned in the aforementioned patents, the maximum bed height that can be used with air as a drying medium is equal to 127 mm in order to prevent temperature rise and briquette ignition. This height is not large enough to be

195280 achieved good production, so it was necessary to reduce the oxygen concentration in the gas to reduce the reaction rate. This results in a weakening of the bonding formed during drying and thus a lower briquette strength than an optimum strength.

According to U.S. Pat. No. 3,384,557 it has been proposed to dry raw briquettes by heating them by immersion in a liquid bed of heated solids, in particular calcined coke coal particles in the presence of at least 10% oxygen by weight. This method is feasible but requires very careful control.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-mentioned disadvantages and to provide an improved method for sintering raw briquettes. The invention solves the problem by sintering in a layer of raw briquettes having a thickness of 254 mm to 914.4 millimeters, with a hot gas containing from 15 vol.% To 21 vol.% Oxygen, for example hot air, the temperature of which 190-232 ° C, while controlling the rate of hot gas, maintaining the sintering temperature in the range of 260-288 ° C, while the exothermic heat generated in the sintering reaction is controlled in the range of 4.2X10 ⁵ to 8, 4 X 10 ⁵ J / kg / K briquettes, and sintering is performed for one to two hours.

According to the invention, it is proposed to prevent temperature rise not by retarding the reaction, but by allowing the reaction to run at an optimum rate, creating a gas stream fast enough to remove reaction heat from the deep bed sufficiently to keep the briquette temperature below their flash point.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail with reference to the drawing, in which FIG. Drying of raw briquettes consists of an oxygen-induced reaction between the calcined particles and the oxygenated binder. The reaction is induced by heating the raw briquettes to a temperature of about 204 ° C. When the reaction is initiated, it emits heat so that the temperature of the briquettes increases. It is important that the temperature of the briquettes does not exceed 288 to 302 ° C, because at higher temperatures the briquettes would catch fire.

When working with shallow layers, the briquette temperature never rises too much due to heat loss. The temperature rises when the layer is increased to 152.4 mm and above. In deeper beds, the reaction has proven to be slowed by reducing the oxygen content of the gas flowing through the bed.

? The amount of gas required for this purpose varies, of course, with its temperature, composition and reaction rate, and with the amount of heat that must be removed. The temperature must be high enough to initiate the reaction within a reasonable time. A large batch of raw briquettes, warm 82 to 93 ° C, ignites in the air. However, in order to achieve an adequate reaction time, the gas must be heated to about 190 ° C. The temperature of the gas should not be so high that it does not act as an effective heat sink, therefore its temperature should not exceed 232 ° C. The preferred range is 210 + 9.5 ° C, allowing operation without too high a gas velocity.

Heated air or gas containing air mixed with flue gas or other inert diluent may be used. However, the oxygen content of the gas must be sufficiently high that the gas leaving the drying oven contains at least 15% by volume of oxygen.

A typical embodiment of the invention is illustrated in the drawing. The molten tar and calcine are fed to the mixer 10 where they are mixed. The mixture 12 is fed to the briquetting machine and the briquettes 16 with the conveyor 18 are fed to the grate sieve 20, which removes fine particles and feeds the briquettes 16 to the inlet 22 which creates the desired layer 24 of briquettes 16 on the movable grate 27. briquettes 16 onto a second conveyor 28 that carries the dried briquettes 16 into the sintering furnace 26.

At startup, heat is supplied to achieve a gas inlet temperature of 190 to 232 ° C and to cause an exothermic sintering reaction. When the sintering furnace 26 is heated, the heat input is reduced. The speed of the current required to maintain the temperature is dependent on the height of the layer 24, the oxygen concentration and the inlet temperature. The required rate can be calculated from reaction heat and other temperature data.

The oxygen-containing gas 30 is fed to the sintering furnace 26 through a blower 32. It is preheated in the combustion chamber 34 by mixing with a small amount of fuel gas 36 and recycled through the sintering section 26 using a number of other blowers 38, 40, 42. The auxiliary heaters 44 and 46. These auxiliary heaters 44, 46 and the combustion chamber 34 are not needed after starting the process because the reaction heat of the briquettes 16 ensures that the desired temperature is maintained while maintaining the oxygen content at about 15 vol%. The fan 48 sucks off the gas from the inlet compartment and feeds the front fractions into the furnace.

In industrial operation, air and fuel gas with 18.5% oxygen by volume gave good briquettes in layers 610 mm high at a gas flow rate of 7.3 m / s and a drying time of 2 hours.

The method of the invention may of course be varied without departing from the spirit of the invention.

SUBJECT

Claims (1)

Method for sintering raw briquettes by blowing hot sintering gases across a layer of briquettes on a movable grate, characterized in that the sintering is carried out in a raw briquette layer having a thickness of 254 to 914.4 millimeters with hot gas containing 15 to 21 vol% oxygen, e.g. whose temperature is maintained at 190-232 ° C while controlling the hot gas velocity, maintaining the sintering temperature at 260-288 ° C, while the exothermic heat generated in the sintering reaction is controlled at 4, 2 X 105 to 8.4 X 10 ⁵ J / kg / K, and sintering is performed for one to two hours. 1 sheet of drawings Severografl, Urod 7, Moet