US1795829A - Process of enriching a lean combustible gas - Google Patents

Description

March 10, 1931. v H. A. BRASSERT ET AL 1,795,329

' PROCESS OF ENRICHING A LEAN COMBUSTIBLE GAS Filed Dec. 31, 1923 atented HERMAN A. BRASSERT, OE CHICAGO, ILLINOIS, AND CHARLES W. ANDREWS, OF DULUTH, MINNESOTA, ASSIGNORS TO'H. A. BRASSERT & COMPANY, .OF CHICAGO,

ILLINOIS, A CORPORATION OF ILLINOIS PROCESS OF ENRICHING A LEAN COMBUSTIIBLE GAS Application filed December 31, 1923. Serial No. 683,641.

gas which is harmless to the brick of furnace structure. It permits of increasing or decreasing the heat value of the gas to suit the demand and has the advantage of a low cost of manufacture so that the cost of pro- 15 duction ranges along with producer gas. We

can increase the upper range of the B. t. u. value of the gas to such a degree that a high enough flame temperature can be realized without regeneration of the gas.

One of the applications of our gas is the coke oven industry. With the exception of a few specially designed coke ovens which are fired with producer gas, all of the by-product coke ovens in this country are heated with 5 a portion of their own gas. This coke oven gas has a very high heating value, generally close to 550 B. t; u. per cubic foot and consequcntly has a far greater commercial value for distribution in municipalities to be used 30 for cooking and other domestic purposes or as a heating agent in small industries, than it has for heating the coke ovens. For heating large industrial or metallurgical furnaces, the value of a gas is measured by the 5 amount of coal it replaces, and economy,

therefore, demands the production of gases of lower values than coke oven gas. On the other hand, most coke ovens are not so designed that lean gases, such as producer gas to can be used. Our process provides a gas of a B. t. 11. content between producer gas and coke oven gas. Further the alkali'content of the gases have been effectually removed, which it is not possible to accomplish by the washing, for instance, of blast furnace gas,

except by the most elaborate and expensive means. I

Another field Where our process applies is the steel industry and particularly open hearth furnaces. Open hearths are now heated with producer gas unless, tar, oil, na-

tural gas or coke oven gas are available.

The producer gas is sometimes brought over from the producers hot and dirty, resulting in considerable expense and loss of production through clogging of the regenerators. In order to save as much as possible of the sensible heat of the producer gas, the gas producers are located immediately behind the open hearths. Usually the steel heating furnaces all carry their own producers with the result that steel plants have a large number of scattered gas producer plants resulting in meiiicient production. This arrangement sub ects the consuming furnaces to many local variations, resulting from the quality of coal, labor conditions and other conditions which are diflicult to control with so many isolated units.

The substitutes for producer gas, such as oil and tar are more expensive, natural gas is rapidly giving out and coke oven gas is too light a gas to be used economically by itself. It has a tendency 'to rise to the top and burn high above the bath, more rapidly destroying the roof and failing to impart the heat or combustion to the steel in an efficient man- .ner.

Producer gas contains not often more than 130 B. t. u. per cubic foot and in many cases less without its sensible heat. It varies in quality according to the composition of the coal and the producer practice. This gas is in many cases too lean to permit of maximum production of steel in an open hearth furnace, such as may be obtained with oil and tar.

Our process overcomes all of these difiiculties. It produces a heavier gas which is clean and of a higher B. t. u. value. The use of this gas will eliminate the many scattered producer plants in steel works and will consolidate the manufacture of gas in one central installation which will furnish gas to the producer which is similar to a water gas generator. Coal or coke or a mixture of both are charged at the top and ashes are withdrawn from the bottom. In themiddle section of the apparatus a blast of air, which is preferably preheated, is applied and at the bottom gases of a low B. t. u. value are admitted, together with additional air, if desired. The process can be worked either intermittently or continuously. If worked intermittently, the blast applied in the middle of the generator is alternated so that the gases of combustion are withdrawn and used to alternatingly heat regenerating stoves, the heat of which is applied to the incoming blast or incoming low B. t. u. gas or both. WVhen making gas, the blast in the middle section is shut off in the intermittent process and a gas of a low B. t-. u. value, such asproducer gas or blast furnace gas, or stack gases are admitted through the bottom with or without additional air according to the composition of the gas which is desired and also depending on the quality of the gas which is used.

The blast furnace. or other gases are admitted preferably hot these use their original sensible heat. In ascending through the hot ashes and coke which have been preheated during the blasting, they are heated by the countercurrent principle and in turn cool off the descending coke and ashes, thus recovering the amount of heat which otherwise would be lost at the bottom. The hot ashes in the lower portion of the generator are at a high temperature, which temperature however, is maintained below the fusing point of the ash. In order to make this recovery o'f heat as complete as possible, in the intermittent process the products of combustion from the blast period may be carried down and out through the same head through which the gases or air, or both, are admitted at the bottom of the producer.

The ascending gases of low B. t. u. value contain CO and H 0. These are decomposed by contact with the hot carbon forming CO, H and CH thereby increasing the B. t. u. value of the gas. The coke at this hottest zone or point of highest temperature will be at a temperature of at least two thousand degrees Fahrenheit. The gases, after passing through the hottest zone at the center of the producer, continue in their upward flow and give off their heat gradually to the descending fuel masses and thereby Carbonize the coal, which has been charged at the top.. The volatile matter of the coal is taken up with the gases and further enriches them. The

composition of the gas resulting from this processcan be varied by charging a percentage of coke or coke breezewith the coal. It will be lowest if only coke or coke breeze are charged and highest if only coal is charged. It can also be varied by the composition of the gas which is admitted at the bottom and by control of the amount of air which is admitted for blasting relativeio the amount of air ad mitted at the bottom.

If the process is operated as a continuous one, the air is blasted in through the middle section and through the bottom continuously and the products of combustion from the burning of coke with this air pass upward with the gases admitted at the bottom, thereby lowering the B. t. u. content of the gases, as compared to the intermittent process. The continuous process, however, has the advantage of greater simplicity and can also be controlled in regard to the quality of the resulting gas by varying the coal and coke charge. In this case the regenerators for heating the blast gases, if it is desired to heat them, have to be fired with fuel from outside sources or with a part of the finished gas, or with part of the raw gas as admitted at the bottom,

The finished gas will have a greater degree of purification than the raw gases admitted at the bottom, particularly if the same are blast furnace gases. The blast furnace gases besides iron ore, contain carbon and lime dust, and some alkalies, principally potassium and sodium oxide. These are Very destructive to the brick in coke ovens and other furnace structures on account of the great affinity of these alkalies for the silica in the brick. We have found that by passing them through the highly heated coke, coke ashes or other suitable materials which have a chemical affinity for the impurities, the alkalies combine with the acid elements and are thus absorbed and eliminated. Among such suitable materials would be crushed quartz, or other acid materials which may be either mixed with the coke in the unit or exposed to the gases separately.

The gases leaving the top of the producer carry a large amount of sensible heat. This is recovered by passing them preferably through a waste heat boiler. They can also be used in the continuous process for heating a recuperator used for heating the blast. After the sensible heat has beenabstracted from the gases, they can be further cooled and washed for the recovery of tar, ammonia, light oils and for other purposes.

It is an object of the present invention to provide a new and improved method'for the production and enrichment of gases and the control of the thermal content of the gases produced or enriched.

It is a further object to provide a method of this character in which the gases are cleaned and impurities removed during the process.

Other and further objects will appearas the description proceeds.

We have illustrated in the accompanying drawings one form of apparatus adapted for carrying out our process.

In the drawings z- Figure 1 is a plan view, partially in section, of the apparatus; and

Figure 2 is a vertical section taken on line 22 of Figure 1.

The gas unit 11 is shown as provided with a lower portion 12, which may be water cooled, and with a brick-work upper portion 13.

The lower portion 12 is connected to the base pan 14 by the enclosing plates 15. The pan 14 is adapted to contain cooling water and the ashes from the bottom of the unit are thrust outwardly of the base by means of the rotating member 16. The upper portion of the unit carries the fuel charging passage 17 controlled by valve 18 and also carries the stirrer 19 which is rotated by the mechanism 20. The upper portion is further provided with the passage 21 through which the gases pass from the unit. I The passage 22 opens centrally of the bottom of the unit and this passage is shielded by the mushroom head 23. This head is hollow and the passage 24 leads to the interior of the head. The passage 25 controlled by valve 57 enters the bottom of the passage 22 and is adapted to introduce the gases to be purified and enriched. The cross passages 26 and 27 join the vertical passage 22 and their junctions with the latter passage are controlled by valves 28 and 29. The passage 26 leads to the hot blast stove 30 and the passage31 controlled by valve 32 leads to the lower end of the brick-work in the stove. Similarly, the passage 27 leads to stove 33, the brick-work of WlllCll is in communication with passage 34 controlled by valve 35.

The bustle pipe 36 is connected to a plurality of tuyeres 37 which are directed into the unit 11 at a point intermediate its height.

The bustle pipe 36 is connected to stove 30 by means of passage 38 controlled by valve 39. The bustle pipe is also connected to the stove 33 by passage 40 controlled by valve 41.

As shown in Figure 1, the passage for the outgoing gases leads to a Y, the branch 42 of which, controlled by valve 43, leads to the waste heat boiler 44. The waste heat boiler 44 is connected by passage 45 controlled by valve 46 with the passage 47 which leads to any suitable gas yielding or holding apparatus. The branch 48, controlled by valve 49, leads to the recuperator 50 which is connected by passage 51, controlled by valve 52,

to the passage 47. Air to be heated is intro-' duced into the recuperator 50 by passage 53, controlled by valve 54, and may be led from the recuperator to the bustle pipe 36 through passage 55, controlled by valve 56. l v

In the operation of the apparatus shown, according to our method, if the intermittent method is used, valve 32 controlling passage 31 is opened, as are 35,39 and 29. Valves 28, 41, 43, 49, 52, 56 and 57 are all closed. The incoming air passes through passage 31 and through the heated stove 30. It then goes through passage 38 to'the bustle pipe 36 and passes through the tuyres in the midst of the charge. This air causes combustion in the gas unit and the products of combustion pass downwardly through passage 22 .and through passage 27 to the stove 33 which absorbs heat from the gases. The waste gas passes out through passage 35.

When the fuel in the unit has been sufliciently heated, the valves 29 and 39 are closed and the valve 57 opened. The gas to be enriched may enter through passage 25 and pass from under the head 23 up through the fuel in the unit. The gas absorbs some of the heat from the fuel and the CO and H 0 are decomposed by contact with the hot carbon forming CO, H and CH A controlled amount of comparatively cool air may be introduced at this time through the head 23, the air entering through passage 24 and serving to cool the head. Also, if desired, some heated air from the stove 33 may be mixed with the gas entering under the head, by opening valve 29 any desired amount. Further air may be introduced at this time through the tuyeres from the bustle pipe 36, by opening the valve 41 and allowing the air to enter from the stove 33, which was heat ed during the previous blast period. During this portion of the process, the fuel will preferably be agitated by rotating the stirrer 19.

In cases where it is desired to clean the gas preliminary to passing it through the unit, it may be admitted through passages 25a or 25?) controlled by'valves 57a and 57?). It will then be heated in the checkerwork beneath the perforated arches 58 or 59 in the stoves 30 and 33 and will pass up through the masses of material, 6001' 61, such as has been described as suitable for removing the alkali content, such for example as crushed quartz, coke, ash, etc. This material is maintained during the process at a suitable temperature for the reaction.

The gas in passing up through the fuel ash and fuel will also be relieved of its impurities, or of its remaining impurities as the case may be, the sodium and potassium compounds uniting with the silicia in the ash. The gas will be enriched in the upper portion of the unit by the volatiles which it will sweep out from the raw fuel charge therein. The enriched and purified gases pass from the unit through passage 21 and give up a large portion of their heat in the waste heat boiler 44. Gases are carried through passage 47 to any desired point of storage or use.

It will be understood that fuel will be introduced during the process, by opening the valve 18 controlling passage 17. As has been breeze, or any desired mixture or proportion of these fuels. When the content of the unit has become cooled below a temperature adapted for eflicient operation, the passage of I gas is stopped by closing valve 57 and the air and gas pass up through the unit and the purified and enriched gas passes through passage 21 and thence through passage as, valve 49 being open, ,to the recuperator 50. In the recuperator the gases give up much of their sensible heat and the cool gases are carried through passage 51, valve 52 being open, to the gas main 47. The gas may be introduced through the stoves, if it is desired to operate upon it as described in connection with the intermittent process.

Air is introduced into the recuperator through passage 53, valve 5A being open, and is heated therein. This heated air is carried through passage 55, valve 56 being open, to the bustle pipe 36. This heated air passes from thebustle pipe into the unit through the tuyeres 37, as before. If it is desired to mix some of the heated air with the gas as it enters under the mushroom head 23, the valves 39 and 28 may be slightly opened and valve 32 closed. Some of theair from the bustle pipe will then pass through the vertical passage in the stove 30 and through passage 26 to the passage 22 Where it will mingle with the gas enteringthe bottom of the unit.

It Will be seen that our method may be carried out in a number of ways and the amount of enrichment of the gas may be closely controlled. Thiscontrol is accomplished by the nature of the fuel introduced and also by the amountot blast through the tuyeres. A further control consists in the introduction, if desired, of any preferred amount of heated air with the gas as it enters under the mushroom head. The stirrer is particularly desirable when raw fuel, such as bituminous coal is charged into the top of the unit. The stirrer prevents caking and assures free and uniform passage of the gases.

By the method described, a gas containingapproximately 17 5 B. t. u. per cubic foot can be obtained. If it is desired to further increase the thermal value of the gas this can be accomplished by enrichment with oil in the usual method.

Another method of increasing thethermal value'of the gas is by the addition of a controlled amount of steam to the incoming blast furnace gas. In this way blue water gas is formed; at the same time the gas is enriched during the modifying of the composition of meaeee the gas. In this method the thermal value can be raised to over 200 B. t. u.

live have illustrated one form of apparatus adapted to carry out our improved method and have described certain manners of carrying it out as illustrative thereof, but we contemplate such changes and modifications claim.

We claim: 7 v The process of enriching a combustible gas,

as come within the scope of the appended which consists in passing the gas together Signed at Chicago, Illinois, this 28th day of December, 1923.

' HERMAN A. BRASSERT.

CHARLES W. ANDREWS.

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