US2099968A - Gas producer - Google Patents

Description

Nov. 23, 1 37- e. SZIKLA ET AL- GAS PRODUCER Filed April 11, 1954 Wig] Patented Nov. 23, 1937 UNITED STATES ao'sassa GAS PRODUCER Gza 'Szikla and Arthur Rodrick, Budapest, man

Application April 11, 1934, Serial No. 720,138

, In Germany April 18, 1933 10 Claims. (Cl. 48- 16) This invention relates to a process and apparatus for complete or partial gasifying of combustible dust, espec'iallycoaLdust consisting of particles of different sizes for example up to 5 mm.,

5 according to which the distilling and gasifying of the coal dust introduced into the gasifylng cham ber takes place in a rising gas current preferably in the manner set forth for example in our U. 8.

Patent 1,869,949, issued August 2, 1932, in continuous circulation through the gasifying chamber and an adjacent dust collecting chamber, from which latter the incandescent coke dust is re-introduced into the rising gas current of the gaslfying chamber. It will be understood that in order to secure an intensive gasifying of the coked coal dust and to secure the-separation of the slag from the dust, it is necessary to maintain a high temperature in the space in which the gasification takes place. This temperature would be, however, detrimental for the walls of the upper parts of the gasifying chamber as well as of the dust collecting chamber and would produce besides the sintering or caking of the slags.

The object of this invention is to eliminate the drawbacks above referred to in spite of the use of high gasifying temperatures. According to this invention the generator gases produced at a high temperature are cooled to a nondetrimental temperature by means of fresh coal dust, introduced or projected into the upper part of the gasifying chamber, preferably at a pointopposite the passage of the generator gases into the dust collecting chamber, said fresh coal dust being coked at the same time. The gas pro- 5 ducer is therefore provided at the upper part of the gasifying chamber with a substantially horizontally acting projecting device for the introduction of fresh coal dust adapted to produce in the inlet passage of the dust collecting chamber, at 4.0 a certain distance from the top of the gasifylng chamber, a coal dust screen.

Thereby a sufliciently high temperature may be maintained in the gasifying chamber, especially in its lower part, to secure an intensive gas!- 45 fying of the coked incandescent coal particles and to secure a suiiicient fluidity of the slags to allow the particles of molten slags to unite to form comparatively large drops. In consequence the major part of the slag will drop directly within 50 the gasifying chamber and through the bottom opening thereof into the slag collecting space, so that only a comparatively small part of the slag will be transferred into the dust collecting cham ber. The screen of fresh coal protects the top 5501 the gasifying chamber against the radiating heat of the combustion zone as well as against blast flames and cools the generator gases produced in the gasifying chamber before their reaching the dust collecting chamber, so far that the liberated slag particles and those of the coke 5 dust remain in a loose state and do not sinter or fuse to form a cake.

The annexed drawing shows as an example a coal dust gas producer according to the invention.

With reference to the drawing, I is the gaslfying chamber, 2 its bottom and 3 an opening therein for the introduction of -the gasifying air. 4 is a horizontally adjustable slide to regulate the cross sectldnal area of bottom opening 3, H is the l5 opening for introduction of the .fresh.coal dust provided with the projecting device l2. This latter is adapted to project the dust fed through funnel IS in a substantially horizontal. direction across the gasifying chamber, so that the fresh 0 "coalforms a screen l4 extending across the horizontal cross sectional area of the gaslfying chamber into the dust collecting chamber 5. This latter communicates with the gasifying chamber l in the proximity of its top by means of an open- 25 ing 1, located preferably opposite the opening I I.

In order to provide eflicient cooling of the rising gases and eliective protection of the top of the gasifying chamber against high temperatures, as well as to prevent the formation of slag accu- 30 mulatlons at the top by upwardly projected slag particles, the projecting device I! or the orifice II is located in such a manner in the upper part of the gaslfylng chamber, that the screen I formed by the projected, coal particles, partly or completely occupies the upper space 22. The gas generated with a high temperature rises in shaft I and enters space 22 while penetrating the coal screen I. Thereby a heat exchange takes place under very favorable conditions, caus- 40 mg the cooling of the gas and the solidifying of the slag particles. It will be understood that this cooling of the gases by the introduction of fresh, cool coal is not detrimental to the overall thermal efficiency of the gas producer. It will be understood that the thermic and pyrometric eifect or eff ciency of the total combustion is not affected at all, but the cooling effect of the fresh coal lowers the temperature of the generated gases, while the heat withdrawn from the gases is utilized for the coking of the freshcoal. The intermediary cooling of the producer gases by the introduction of fresh coal has no effect on the ultimate temperature attained in the upper reglon of combustion chamber 19, by the subsefeeding dry coke dust into the producer, the composition and temperature of the combustible gas p oduced would be the same with or without intermediary cooling. In using a coal rich in gases, the composition of the gas produced with intermediary coolingwill be different from that obtained without cooling and will be more desirable, as the fresh coal isdistilled in the absence of oxygen, that is to say, outside of the combus-.

tion zone of the gasifying shaft.

The intermediary cooling has therefore no drawback whatever, but has the great advantage of allowing high temperatures in the gasifying chamber, which secure the separation of the slags in liquid state.

According to this process incandescent coke will be gasified in the gasifying chamber at high temperatures and the high temperature of the gases produced will be decreased usefullyby utilizing the heat of said gases for the drying, distilling, coking and heating of the fresh coal to the temperature of incandescence.

If a rotating wheel is used for the introduction of the coal dust, the shape, or more or less horizontal position of the coal dust screen ll, may be synchronized with the operating requirements of the gas producer, either by changing the point of impact of the coal dust on the wheel, or by changing the speed of said wheel.

The dust collecting chamber and the gasifying chamber communicate in the proximity of their respective bottoms by means ofa channel 8, through which the coke dust is returned from the dust collecting, chamber into the gasifying chamber. An inclined choke surface 9 is provided at the gasifying-chamber end of channel 8 and opposite thereto, at the dust collecting chamber end of channel 8, a reciprocating plunger l0, or a plurality thereof, are provided to push the coke dust collected in chamber 5 into channel 8. Owing to the resistance of the choke surface 9, the pushing of the coal dust is counteracted by a substantial pressure, so that the coke dust will be strongly compressed in channel 8. This will prevent the gas in the proximity of the bottom of the gasifying chamber,- the pressure of which exceeds the gas pressure in the dust collecting chamber, from blowing back'the coke dust and this arrangement also prevents the streaming of air from the gasifying chamber immediately into the dust collecting chamber through channel 8.

The water cooled scraper i6 above the plungers l0 removes the coke dust from the upper face of the plungers.

It is essential that the slide I controlling the width of the bottom opening 3 may be located at the side of the bottom opening adjacent to the return channel 8, because here the coke dust accumulation is constantly maintained by the stufling action of the plun ers l0 and is kept in motion towards the wor ng edge of slide l,

whereby any accumulation of slag in the gap between slide 4 and bottom plate 2 is prevented.

The operation is as follows:

The coal dust projected through aperture li into the gasifying chamber enters the rising hot gas stream and will be coked. As the producer gases coming into contact with the coal dust do not contain oxygen, the gases of distillation do not undergo any combustion, but enrich the producer gases with hydrocarbons which when burnt in chamber ill will produce a radiating flame. The dropping incandescent coke dust will be gasified in the shaft I. By suitably adapting the air admission to the quantity of coal fed, a temperature can be obtained at which the slag melts and drops from the circulation through bottom opening 3. The top 6 of the gasifying chamber is protected against the high temperature of this latter by the direct screening eifect of coal dust screen it. But the fresh coal dust has be sides a cooling effect on the rising producer gas by heating the coal and evaporating of its moisture. The, distillation of the fresh coal and the decomposition of steam, if such be present consume heat, while no new heat is generated, be.- cause in this part of the, chamber no more free oxygen is present, so that no combustion can take place. The introduced fresh coal dust, after having been subjected to a distillation and being in incandescent state, either enters the dust collecting chamber 5 or drops through quiescent zones in the proximity of the walls of the gasifying chamber towards its bottom. The gases cooled in the above describedlmanner enter the dust collecting chamber 5 with a temperature substantially lower than thetemperature of the "producer gases, and at. which the slag granulates.

The incandescent coke dust accumulating in the dust collecting chamber is loose and rolls from the dust bank'l8 towards the return channel 8. The coking of incompletely coked coal particles is completed on the dust bank IS. The producer gases, substantially freed from suspended coke dust, are conducted to their final destination, where they are burnt, for example, under a boiler in combustion chamber i9 with secondary air admitted through channels 20.

The temperature stages of the gas can easily be calculated on the basis of an analysis-of the coal supposing a heat exchange. The temperature of the gas produced in the'gasifying shaft from incandescent coal is calculated to be about 1480" C. for all kinds of coal, if complete conversion to carbon dioxide be assumed.

By using brown coal with lower heating value of 5300 cal., 38% coke content, 14% moisture and 8.5% ash, for example, the temperature resulting from the introduction of fresh coal dust can be calculated to 970 C. without considering the decomposition of water vapours.

The temperature difference reached practically is smaller, owing to the incomplete exchange of heat. In a continuously working plant the temperature measured in the gasifying shaft was' perature is suillcient to realize practically the advantages of the process according to the invention. The rate of heat *exchange and the temperature decrease reached thereby can be controlled by the degree of fineness of the coal dust,

by the dimensions of the gasifying shaft and of the dust collecting'chamber as well as by the construction of the projecting device for the fresh c'oal dust.

The heat exchange between the gas'and the coal may often be sufllcient and the cooling ofthe gas can be increased by the following means:

a. Increase of the time of dropping of the coal particles by retarding their fall by means of baflle plates inserted in the path of travel of the gases adapted to accumulate the dropping coal particles and allow them to trickle again into the gas current. In the drawing, for example, three alternating baiiles 25, 26 and 21, form a cascade the coal particles and the gases. The lowest baflle 21 is arranged in such a manner as to direct the falling dust in front of the stuffing plungers' I0 while the gas current is diverted and accelerated in such a manner as to promote the separation of dust and gas.

b. By water cooling. This may be eifected either by moistening the fresh coal or by introducing finely dispersed water at suitable places, for instance, at the entrance to the dust'collecting chamber through opening 28 directly into the gases.

0. By cooling'by means of a cooling the example shown in the drawing the top of the gasifying chamber is formed by tubes 29. This construction is advantageous for the reason that rid. In

it allows the top to be inclined in a favourable considerable, while if the gas is strongly cooled by the coal, it will give off less heat towards the,

grid.

d. The heat exchange may be further increased and the temperature of the gasifying chamber enhanced by inclining the upper end 24 of the partition 23 between the gasifying chamber and the dust collecting chamber towards the former so as to narrow upwards the upper end of the shaft 1. Thereby" the loss of heat of the gasifying shaft by radiation towards the coal dust screen i4 and the grid 29, if any, is restricted, so that the temperature insaid shaft will rise.

In certain cases it may be desirable to lower the range of temperatures of the whole process. For this purpose suitable quantities of burnt gases, and/or steam are mixed with the primary air introduced through the bottom aperture 3. The carbon dioxide of the combustion gases or the steam will be decomposed under heat absorption in the shaft by the incandescent coke, whereby the temperature'of the producer gas is lowered.

even before it reaches the coal dust screen. The admission of steam produces gases of lower temperature, since part of the coke is gasifled by the steam to produce a correspondingly smaller volume of gases than would be obtained by using air, of which four-fifths is inert nitrogen. This smaller volume of gases will be cooled to a greater degree by the introduction of a given quantity of fresh coal.

The process of gasifying takes place in the conditions of equilibrium, if the quantity of introduced primary air is suflicient to gasify the total quantity of introduced coal. Suppose that the efiieiency of cooling and the proportion of air and coal are the same, the cooling of the producer gas by the coal (and not by the additional cooling of water injection or cooling grid and the like) will be the same at different loads, because the same unity of fresh coal corresponds to the unity of gas, independently from the load.

Hence the temperature of the cooled gas current is the means to control the process, by influencing the quantity of primary air admitted in dependence upon said temperature. Accordingly, if the temperature of the gas current in chamber 5 is too high, the admission of primary air is restricted, whereby the quantity of gas produced is decreased and is cooled to a greater degree by the fresh coal. On the other hand, by increasing the quantity of primary air, more gas of high temperature is produced if the temperature of the gas current in 5 is too low. This greater volume of gas will be cooled to a lesser degree by the same quantity of fresh coal. This regulation can be effected automatically by means of a temperature measuring instrument (not shown) influenced by the temperature of the gas current in chamber 5.

What we claim is:

1. In a gas producer for gasifying and distilling combustible dust, especially coal dust, a gasifying chamber with a bottom opening for admission of air and removal of slags, a regulating means controlling said opening. a dust collecting chamber communicating with the gasifying chamber at its upper part and receiving hot gases and coke dust from said gasifying chamber, a coke dust return channel directly connecting the .bottom portions of said chambers and ending at the bottom of the gasifying chamber whereby continuous circulation of coke dust through said gasifying chamber and said dust collecting chamber is permitted, and a device provided at the upper part of the gasifying chamber for introducing fresh coal dust in the shape of a screen across the cross sectional area of at least one of said chambers whereby the producer gases generated in said gasifying chamber are cooled to a temperature lower than. the melting temperature of the slag.

2. A gas producer according to claim 1, in which the device for introducing the fresh coal dust is arranged in such a' manner that the coal dust screen divides the gasifying chamber into two superposed parts, the upper of which is at least partly occupied by the coal dust screen.

3. A gas producer according to claim 1, in which the device for introducing the coal dust is located opposite to the opening leading into the dust collecting chamber.

4. A gas producer according to claim 1, in which a choke surface is provided at the gasifying chamber end of the dust return channel, reciprocating plungers being arranged in the dust collecting chamber opposite to said choke surface adapted to stuif the coke dust accumulated at the bottom of the dust return channel into said channel.

5. A gas producer according to claim .1, in which the regulating means controlling the width of the bottom opening of the gasifying chamber is located at the return channel side of said bottom opening. V I

-6. A gas producer according to claim 1, in

which baiile plates receiving the dropping coal.

particles are provided in the dust collecting chamber to interrupt the fall of said particles and to form a multiple cascade of coal dust.

7. A gas producer according to claim 1, in which a. water injecting tube. is arranged in the upper part ofat least one of saidchambers.

8. A gas producer according to claim 1, in which cooling tubes are arranged at the top of the gasifying chamber.

9. A gas producer according to claim 1, in which a partition is provided between the gasitying and dust collecting chambers, said partition being inclined at its upper part so as to narrow upwardly the cross sectional area of the gasifying chamber.. a

10. In a gas producer of the character deing for admission of air and removal oislags, a dust collecting chamber, said chambers communieating with one another at the top and bottom,

the communication at the bottom being above said air admission opening and normally being closed by collected dust, mechanical means for advancing dust from said dust collecting chamber to said gasifying chamber through said communication, and means for introducing fresh coal dust into the upper part 01 said gasifying chamber in the shape of a screen which extends across the cross-sectional area 01 the gasifying chamber, whereby the producer gases generated in said gasifying chamber are cooled to a temperature non-detrimental to the walls of the upper part of said gaslfying chamber. v

GEZA SZIKLA.

ARTHUR ROZINEK.

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