US2702744A - Gasification of powdered fuel and use of a protective gas - Google Patents

Description

Feb. 22, F TOTZEK GASIFICATION OF POWDERED FUEL AND USE OF A PROTECTIVE GAS Filed Aug. 12, 1948 MWW 05% Yw -75 No 0x YGEA/ INVENTOR. fi'/foe/cw 757'ZEK United States Patent GASIFICATION 0F POWDERED FUEL AND USE OF A PROTECTIVE GAS Friedrich Totzek, Essen-Ruhr, Germany, assignor to Koppers Company, Inc., Pittsburgh, Pa., a corporation of Delaware Application August 12, 1948, Serial No. 43,951

6 Claims. (Cl. 48206) The present invention relates in general to improvements in the production of combustible gases that are useful for lighting, heating, chemical reactions, and for other purposes, and is more particularly concerned with the production of such gases from finely-pulverized solid carbonaceous fuels as, for example, pulverized coal, brown coal, lignite and other carbonaceous matter by their reaction with oxygen, or oxygen-enriched air, and with steam or any other fluid oxide, such as carbon dioxide, that can react endothermically with heated carbon to give combustible gas, the solid fuel being in suspension in gaseous media during the course of its reactions.

In a copending application Serial No. 43,950, filed of even date herewith, August 12, 1948, the present inventor has disclosed improved method and means for the gasification of finely-pulverized solid fuel. Briefly described, that improved method comprises continuously introducing the pulverized solid fuel into a flow of oxygen, or oxygen-enriched air under conditions to form a suspension of the former in the latter, the so-formed suspension being then continuously introduced in the form of a jet into a gasification chamber, that is preheated to a temperature that is above the ignition temperature of the suspension, and wherein it is quickly ignited while surrounded by a concurrently flowing envelope containing steam or another fluid oxide, such as carbon dioxide, that can react endothermically with hot carbon to yield, for example, a combustible mixture of carbon monoxide and hydrogen. In the gasification chamber, there thus simultaneously exist a central highly-heated zone, wherein there progresses an exothermic reaction, that is surrounded by an outer zone of lower temperatures in which an endothermic reaction takes place.

In practising this method, dangerous explosions may occur if for any reason delivery of the suspended pulverized coal is interrupted while at the same time the oxygen component of said suspension continues to flow into the gasification chamber because such uncombined oxygen can then flow into subsequent reacting or storage apparatus for combustible gas that has been produced before the supply of pulverized coal was interrupted, and after mixing with such gas can form highly explosive admixtures.

An object of the present invention is therefore to provide simple and effective method and means whereby possible development of the above-described dangerous circumstance can be easily and completely avoided in the event that the supply of pulverized coal normally fed to the gasification chamber is for any reason interrupted for a shorter or longer time.

The invention has for further objects such other operative advantages or results as may be found to obtain in the processes or apparatus hereinafter described or claimed.

In the single drawing there is illustrated a vertical section transversely through apparatus wherein the present process can be practiced, the illustration being a simple apparatus embodying the essentials required for an understanding of the principle of the present invention. It is to be understood, however, that any apparatus embodying such features will be suitable for the practice of fthe1 present improved method of gasification of solid Referring to the drawing, there is shown a reaction chamber 2, which may be circular in cross section having an upper part 3, preferably conical in cross-section. At the top of the chamber 2 there is provided an opening 4 2,702,744 Patented Feb. 22, 1955 ICC into which projects a nozzle 5 forming, between the nozzle and the wall of the opening 4, an annular port 10. The nozzle is equipped with cooling means in the form of a water jacket 5a having an inlet and an outlet for cooling water as shown.

The annular port 10 communicates by plpe 6 W1th either a source of steam or carbon dioxide that are under pressure and are preferably preheated.

Nozzle 5 is connected directly to a mixing apparatus 7 to which oxygen or air enriched with oxygen is fed by i e 8. p 3A conveyor 9 of the worm-screw type feeds finely divided solid carbonaceous fuel contemplated by the present invention to the mixing apparatus 7 from a storage bunker 9a. In mixing apparatus 7, a thorough mixing of the oxygen and solid fuel takes place.

By proper regulation of the temperature and velocity of the mixture of pulverized solid fuel and oxygen, as conventional, to exceed the rate of flame propagation, the suspension is discharged as a jet into the initial tapered reactor chamber 3 without reaction or flash back into the suspension feed pipe 5 from the initial tapered reactor 3.

The annular port 10 for the initial tapered reactor chamber 3 for the gasifier chamber 2 is of such configuration, as shown, that a continuous fiow of endothermal gasifying agent from line 6 is directed to flow, under cocurrent flow with the jet from line 5, only along the upper walls of the initial reactor chamber taper portion 3 for the chamber 2, between the tapering walls and the jet from line 2, and not to penetrate the high temperature zone adjacent thereto where the jet of pulverized coal and oxygen react with one another, i. e. where the jet issues into, and ignites on entering the tapered reactor chamber 3.

To accomplish this bathing or flushing of the walls of the reactor one or more annular channels 11 are provided in the lower part of the apparatus 2 which communicate by means of a continuous slit 11a, as shown, which is formed to direct such medium only along the walls of said space. Of course, by diffusion the so-introduced medium will migrate, especially in the lower part of the reaction space, into its central portions but uninterrupted flushing of the walls themselves by a film of steam, or the like, is one of the primary objects to be achieved.

The useful gas produced by the reaction is removed from the reaction chamber 2 through outlet 12 provided in the lower part of the gasifier apparatus and at such rate that the suspended ashy constituents have no opportunity to assume the temperature of the reaction chamher or the produced gas, and below the melting point of the ash of the fuel.

The produced gas can be delivered by line 12 to means for removing dust, cooling, scrubbing, purification or other processing, all as described in my aforesaid copending application.

According to the present invention any suitable combustlble gas, and preferably part of the combustible gas that is produced in the process itself, is continuously returned from storage 14 by line 15, to the gasification system into which it is introduced at such place and in such manner, as at 16, that it does not efiectively disturb the aforesaid zones of reaction nor the movement of the coal particles in them, i. e. the employed combustible gas is preferably introduced or re-introduced into the gas1fication system adjacent the gas-outlet to the gasification chamber. The so-introduced or returned protective gas should be at such elevated temperature that the resultant gaseous mixture adjacent the outlet of the gasification chamber is above the ignition point of the mixture with oxygen. The employed protective gas can be preheated, if necessary, by burning a small portion thereof with oxygen and mixing the hot combustionproducts with the remainder as shown at 17.

This protective gas should for safety reasons be introduced or recycled to the gasification system at such rate that it can completely react chemically with substantially all of the oxygen, employed to form the suspension of powdered fuel, at the rate such oxygen is introduced into the gasification system in the event the supply of solid fuel component should fail. Ordinarily, to obtain positive protection against all eventualities the rate of introduction of protective gas into he gasification system should be at most about twice the rate by volume at which oxygen is introduced thereinto.

In the following claims the term oxygen includes pure oxygen, oxygen-enriched air and gases or vapors con taining a higher concentration of oxygen than is contained in normal air.

The invention as hereinabove set forth is embodied in particular form and manner but may be variously embodied within the scope of the claims hereinafter made.

I claim:

1. Process of continuously gasifying finely-divided carbonaceous fuel with free oxygen-containing gas and a fluid oxide capable of reacting endothermically with said fuel comprising uniformly suspending said fuel in a suflicient amount of free oxygen-containing gas to burn a suflicient portion, but not all, of said fuel to raise the remaining portion of said fuel to temperatures above those minimum temperatures favoring the reaction of said fuel with said fluid oxide to form carbon monoxide, thereafter, injecting said suspension in the form of a jet into an inlet end of a reaction chamber at ignition temperatures in a direction axial to said chamber, whereby said jet is ignited as it issues into said chamber and said portion of said fuel is rapidly burned by said free oxygen-containing gas while flowing through a primary combustion zone within said chamber, the heat evolved by said burning within said combustion zone rapidly and simultaneously heating said remaining portion of said fuel in said combustion zone to above said temperatures favoring the formation of carbon monoxide, peripherally enveloping said jet and said combustion zone with an annular stream of said fluid oxide flowing cocurrently with said jet and said fuel and gas in said combustion zone in a direction along, outside of, and around the outer peripheries of said jet and said combustion zone, said stream of fluid oxide forming a continuous enveloping layer of said fluid oxide between said jet and said combustion zone and the walls of said chamber, thereby permitting the temperature of said remaining portion of said fuel in said combustion zone to rise rapidly to above said temperatures favoring the formation of carbon monoxide by said rapid burning in said combustion zone without any substantial interference from endothermic reactions in said combustion zone between said fluid oxide in said annular stream and said fuel, while simultaneously insulating the walls of said chamber from the heat of combustion in said combustion zone and preventing hot solid particles within said combustion zone from contacting said walls of said chamber and preheating said fluid oxide by said heat to temperatures favoring the reaction of the same with said remaining portion of said fuel to form carbon monoxide, thereafter, combining the hot reaction products of said remaining portion of said fuel flowing from said combustion zone with said preheated fluid oxide from said envelope of fluid oxide to endothermically react said heated remainder of said fuel with said preheated fluid oxide, and finally introducing combustible gas at a point adjacent to the product gas outlet of said chamber to consume unconsumed oxygen to prevent subsequent formation of explosive mixture in the event the powdered fuel injection is stopped, said point adjacent to the product gas outlet being located so that introduction of the combusctlible gas will not interfere with the envelope of fluid 0x1 e.

2. The process of claim 1, in which the free oxygencontaining gas is oxygen-enriched air.

3. The process of claim 1, in which the free oxygencontaining gas is substantially pure oxygen.

4. A process for producing combustible gas comprising carbon monoxide, which process comprises: introducing pulverized coal suspended in a gaseous medium comprising free oxygen as a jet into a chamber maintained at at least the ignition temperature of said coal, the oxygen and coal being in such proportions that only part of the coal is exothermically reacted with the oxygen and the remainder of the coal is heated to a high temperature for its subsequent endothermic reaction, introducing an endothermic gasifying agent into said chamber coaxially of the jet with discharge of the endothermic agent into the chamber in relation to the jet so as to form between the walls of the chamber and the jet a cocurrently-flowing peripherally-enveloping annular stream surrounding said jet of pulverized coal suspended in oxygen as the jet issues into and ignites on entering the chamber and partially burns, thereafter allowing the endothermic gasifving agent to commingle with the hot products resulting from the combustion step to react therewith, removing the product gas from the chamber, and introducing combustible gas at a point adjacent the product gas outlet from the chamber to consume unconsumed oxygen to prevent subsequent formation of an explosive mixture if the pulverized coal injection is stopped while the oxygen continues to flow into the chamber, said point adjacent to the product gas outlet being so located that the introduction of the combustible gas will not interfere with the envelope of endothermic gasifying agent.

5. The process of claim 4, in which the endothermic gasifying agent comprises steam.

The process of claim 4 in which the endothermic gasifying agent comprises carbon dioxide.

References Cited in the file of this patent FOREIGN PATENTS 413,130 Great Britain Aug. 4, 1933 532,341 Great Britain Jan. 22, 1941 274,479 Switzerland June 16, 1951 OTHER REFERENCES Atwell, Koppers Powdered Coal Gasification Process, published September 2, 1947, PB 85165 FIAT Final Report 1303, pages 13, 14, 16.

Industrial and Engineering Chemistry, vol. 40, pages 567-570, April 1948.

Haslam et al., Fuels and Their Combustion, 1926, page 450.

Claims (1)

1. PROCESS OF CONTINUOUSLY GASIFYING FINELY-DIVIDED CARBONACEOUS FUEL WITH FREE OXYGEN-CONTAINING GAS AND A FLUID OXIDE CAPABLE OF REACTING ENDOTHERMICALLY WITH SAID FUEL COMPRISING UNIFORMLY SUSPENDING SAID FUEL IN A SUFFICIENT AMOUNT OF FREE OXYGEN-CONTAINING GAS TO BURN A SUFFICIENT PORTION, BUT NOT ALL, OF SAID FUEL TO RAISE THE REMAINING PORTION OF SAID FUEL TO TEMPERATURES ABOVE THOSE MINIMUM TEMPERATURES FAVORING THE REACTION OF SAID FUEL WITH SAID FLUID OXIDE TO FORM CARBON MONOXIDE, THEREAFTER, INJECTING SAID SUSPENSION IN THE FORM OF A JET INTO AN INLET END OF A REACTION CHAMBER AT IGNITION TEMPPERATURE IN A DIRECTION AXIAL TO SAID CHAMBER, WHEREBY SAID JET IS IGNITED AS IT ISSUES INTO SAID CHAMBER AND SAID PORTION OF SAID FUEL IS RAPIDLY BURNED BY SAID FREE OXYGEN CONTAINING GAS WHILE FLOWING THROUGH A PRIMARY COMBUSTION ZONE WITHIN SAID CHAMBER, THE HEAT EVOLVED BY SAID BURNING WITHIN SAID COMBUSTION ZONE RAPIDLY AND SIMULTANEOUSLY HEATING AND REMAINING PORTION OF SAID FUEL IN SAID COMBUSTION ZONE TO ABOVE SAID TEMPERATURES FAVORING THE FORMATION OF CARBON MONOXIDE, PERIPHERALLY ENVELOPING SAID JET AND SAID COMBUSTION ZONE WITH AN ANNULAR STREAM OF SAID FLUID OXIDE FLOWING COCURRENTLY WITH SAID JET AND SAID FUEL AND GAS IN SAID COMBUSTION ZONE IN A DIRECTION ALONG, OUTSIDE OF, AND AROUND THE OUTER PERIPHERIES OF SAID JET AND SAID COMBUSTION ZONE, SAID STREAM OF FLUID OXIDE FORMING A CONTINUOUS ENVELOPING LAYER OF SAID FLUID OXIDE BETWEEN SAID JET AND SAID COMBUSTION ZONE AND THE WALLS OF SAID CHAMBER, THEREBY PERMITTING THE TEMPERATURE OF SAID REMAINING PORTION OF SAID FUEL IN SAID COMBUSTION ZONE TO RAISE RAPIDLY TO ABOVE SAID TEMPRATURES FAVORING THE FORMATION OF CARBON MONOXIDE BY SAID RAPID BURNING IN SAID COMBUSTION ZONE WITHOUT ANY SUBSTANTIAL INTERFERENCE FROM ENDOTHERMIC

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