US1837226A

US1837226A - Manufacture of fuel gas

Info

Publication number: US1837226A
Application number: US640828A
Authority: US
Inventors: Henry O Loebell
Original assignee: HENRY L DOHERTY
Current assignee: HENRY L DOHERTY
Priority date: 1923-05-23
Filing date: 1923-05-23
Publication date: 1931-12-22
Anticipated expiration: 1948-12-22

Description

Dec. 22, 1931. H. o. LOEBELL 1 1,837,226

MANUFACTURE OF FUEL GAS r Filed May 23, 1923 2 Sheets-Sheet 1 Del 2 2il931. H. c LOEBELL 1,337,226

MANUFACTURE OF FUEL GAS Filed May 23, 192:5 2 Sheets-Sheet 2 Patented Dec. 22, 1931 ATENT OFFICE HENRY O. LOEBELL, 01' NEW YORK,

N. Y ASSIGNOB TO HENRY L. DOHERTY, 01 NEW YORK, N. Y.

MANUFACTURE OF FUEL GAS Application filed Kay 23, 1923. Serial No. 640,828.

This invention relates to the manufacture of fuel gas, and more particularlyto a meth- 0d of making gas for industrial purposes by the complete gasification of coal.

The gas which is now being commonly burned for industrial heating purposes is known asa producer gas which has a com-- paratively low calorific value. This gas is manufactured by a process of burning coal wherein inert gases such as nitrogen-of the air used and carbon dioxide formed by combustion of carbon with the air remain in the gas so that 55% to 65% of thejgas is formed of inert constituents. Producer. gas has a limited use for industrial heating purposes, because it has a low flame temperature, a low calorific value and a slow flame propagation. Some heating processes require comparatively high flame temperatures and an attempt has been made to make a blue water gas for this purpose. The. so called blue water gas has a comparatively high flame temperature and a comparatively low percentage of inert constituents, but the cost to manufacture blue water gas isvery high and the yield of the blue water gas from a ton of coal is comparatively small as compared with the amount of producer gas which can be made from a ton of coal.

One object of the present invention is to provide a method of manufacturing an industrial fuel gas which has a comparatively high flame temperature, a rapid flame propagation, and a calorific value which adapts it for practically all industrial heating purposes. p I

Another object of the invention is to provide a method of making industrial gas by which valuable by-products may be recovered and at thesame time a gas will be .produced which is free of contaminating an deleterious constituents.

A further object of the invention is to provide a process of making industrial gas which is efficient, in the conservation of heat and which may be completely controlled to control the character of gas being made.

lVith these and other objects and features in view, the invention consists in-the improved gas making process hereinafter dethereof. The portion of t scribed and specifically defined in the claims.

The various features of the invention are illustrated in the accompanying drawings, in which r Fig. 1 is a view in vertical section with parts in elevationof a gas generator embodyin the preferred form of the invention;

ig. 2 is a top plan viewof the generator shown in Fig. 1;

Fig.. 3 is a vertical sectional view of the waste heat boiler used with the generator, the section being taken on the line 3'-3 of Fig. 2;

Fig. 4 is a horizontal sectional view taken on-the line 4-4 of Fig. 5, illustrating the mechanism for removing coke. from the bottom of the generator; and

Fi 5 is a vertical sectional view taken on the llne 5-5 of Fig. 4 to illustrate the coke discharging mechanism.

The method of making fuel gas embodying the preferred form of the invention may be carried out in the apparatus illustrated in the drawings substantially as follows:

Fuel to'be carbonized, which is preferably a cokin grade of bituminous coal in mixture with co e, isplaced in a hopper 10 and is intermittently lntroduced into the upper part of a generator shaft 12 by means of a pocket the pocket 14 will be filled with coal. At

this timethe valve 18 is closed. Thereupon the valve- 16 will be closed and the valve 18 will be opened to allow the fuel to pass into the top of the generator shaft. The fuel discharging from the pocket 14 passes around a central gas oif-take 20 and is distributed into the top of an upright column of fuel supported in the shaft 12. The upper portion of the fuel column or approximately the portion above the lower end ofthe gas off-take 20, comprises a coal carbonizing zone. The portion ofthe fuel column below the bottom of the ofi-take 20 and extending downwardly a short distance below an offset portion 22 in the shaft 12 constitutes a blast zone in which the fuel is maintained at a comparatively high temperature by artial combustion lie fuel column from the bottom of the blast zone to the bottom of the column is a cooling or quenching zone in which the unburned carbonized fuel and ashes are quenched before being removed from the shaft. The unburned carbonized fuel is continuously discharged from the bottom of the column and continuously moves downwardly through the shaft.

The gas is made by several distinct reactions which take place between the fuel and the air and steam used for making the gas. The first reaction is an exothermic reaction which takes place when air is used to burn carbon of the fuel, according to the following equation:

C+O +3.78 N

CO 3.78 N, 14600 B. T. U.

A second reaction takes place between the carbon of thev fuel bed and the carbon dioxide which is formed by the combustion of air, in accordance with the following equation, which is endothermic:

A third reaction takes place between carbon of the fuel bed and steam which is introduced at the fuel bed, the'reaction being endothermic, as follows:

A fourth reaction is that which takes place when the volatile material, principally hydrocarbons, is distilled from the coal by the passage of hot gases through the fuel column.

In the present process the air and steam used in making gas are preheated and then introduced into the blast zone of the fuel column to carry on reactions outlined above. The mixture of air and steam is heated in a pair of preheaters which are so arranged that one preheater is used for preheating the mixture, while the other preheater is being heated by burning gas therein. When one preheater has been cooled to the minimum working temperature which is desirable, by passing steam and air through it, the circulation of the steam and air mixture is stopped and then started in the other preheater which was be ing heatedduring the time when the first preheater was used for heating the mixture of steam and air. To accomplish this air is introduced into. one of the preheaters 24 through a pipe 26, and steam is supplied to the pipe 26 through a pipe 28. The steam and air mixture enters the top of an exhaust section 30 of the preheater, passes downward- 1y through a checker brick filling in the sectlon 30, then through an openin 32 into the bottom of the main section of the preheater 24, and thence passes upwardly through a checker brick filling in the main section. In passing through the two'sections of the preeater the steam and air mixture becomes highly heated and it then flows through 3.

blast neck 34 into a passage 36 surrounding.

above, and the hot gas formed passes upwardly through the off-take in contact with a series of superheating tubes 38, wherein water vapor or steam to be used for the gas making operation is superheated before it is introduced through the pipes 28 into sections 30 of preheaters 24. After passing through the off-take'20 the gas flows through outlets 40, Figs. 1 and 2, to a conduit 42 which conducts it to inlet flues 44 of

waste heat boilers

46 and 48. In the waste heat boilers the hot gas passes upwardly through a series of tubes 50, Fig. 3, to a passage 52 at the top of the boiler, then downwardly through tubes 54 to an outlet flue 56, whence the gas passes through a conduit 58 to a cooler of suitable construction, whereby the gas may be cooled and be ready to pass to the place of consumption or to the usual holder (not shown).

In normal operation of the gas generator the hot gas carried off through the off-take 20 is used to heat the boilers 46. and 48 simultaneously. If, however, one of the boilers needs to be-cleaned or if one of the boilers gets out of order, all of the gas may be passed through one of the boilers at a time. To accomplish this a valve 60, Fig. 1, is mounted in the inlet fiue44 in a position to be moved into a, valve seat 62 positioned at the bottom of the conduit 42. The valve is mounted upon a rod 64 which moves through a stuffing box 66 positioned in the floor of the flue 44. To reciprocate the rod-64 through the stuffing box a chain 68 is attached to the floor of the fine 44 and passes over pulleys 72 and 74, down to an operating platform.

When the preheater 24, for example, shown at the left of Fig. 1, is used for preheating the air and steam mixture, the preheater 24, shown at the right, is being heated by burning gas therein. At this time the preheater 24 at the right of Fig. 1 is cut off from the shaft 12 by means of a valve 76, and a portion of the 'gas from the conduit 58 is conducted through a pipe 78 and valve 80 into the top of the main section of the preheater. At the same time air is introduced through an inlet 82, and the mixture of burning gas and air passes downwardly through the main section of the preheater, then up wardly through the exhaust section 30 of the preheater, and exhausts through an outlet 84. A cover 86 on the outlet 84 is open during the heating operation of the preheater, and the air and

steam inlet pipes

26 and 28 are closed respectively by suitable valves 85 and 87 (Fig. 1).

The central off-take 20 is supported on the top of the shaft 12 by the outlet pipe 40 and also by a series of braces 88 whlchare attached to the frame 90 of the generator.

The inner lining of the off-take consists of the superheating tubes 38 which are connected between an inlet manifold 92 at the top, Figs. 1 and 2, a distributing manifold 94 at the bottom, and an outlet manifold 96 at the top. The steam to be superheated is introduced into the inlet manifold 92 by means of a pipe 95 which connects with a steam header 97, mounted between the

waste heat boilers

46 and 48.

Suitable valves

98 and 100 are placed in the header 97 to control the flow of steam from the boilers. The steam flows from the inlet header 92 downwardly through tubes 38 to the header 94 and then upwardly through tubes to the header 96 and out through a pipe 102, which preferably is connected with the pipes 28 that enter the preheaters 24. Water is introduced into the waste heat boilers'through inlet pipes 104. The waste heat boilers will abstract the larger portion of the heat from the fuel gas and this heat will normally produce asuflicient amount of steam to take care ,of the requirements of the gas making operation. However, the waste heat boilers may be supplemented with other steam boilers in making up the .required amount of steam, so that one of the waste heat boilers may be shut down for any desired purpose.

By the time the fuel has moved downwardly through the carbonizing zone and reached ,the blast zone there is substantially no volatile material therein and therefore the gas which passes upwardly through the.

offtake 20 contains substantially no tar, ammonia. or other products which, are usually formed in coal gas. Accordingly, the gas which leaves the waste heat boilers does not require any special purification.

The volatile material of the coal and other valuable by-products such as tars, oils and ammonia are removed from the coal by low temperature carbonization. To accomplish this, a small portion of the hot producer gas being made inthe blast zone is led upwardly around the off-take 20 through the carbonizing zone ofthe fuel column to slowly distill off the by-products. This small amount of 1 gas containing the by-products passescinto an' outlet 106 at the top of the shaft, and flows through a conduit 108 which conducts it to the usual purification and treating equipment (not shown). In this equipment the valuable by-products are removed and the purified gas may then be mixed with the gas passing through the outlet pipe 58. By this means substantially all of. the valuable byproducts of the coal may be continuously removed and the coal converted into a coke or carbonized fuel which-is very well suited for a blue water gas reaction. The gas containing the by-products is comparatively small in volume, compared with the entire'gas output of the producer, and therefore the by-products may be recovered by treating a comparatively small amount of gas.

Although-the temperatures usedin the blast zone for making gas are comparatively high, these temperatures are not sufliciently high to slag or clinker the fuel, and therefore a comparatively large amount of the unburned fuel passes down to the bottom of the fuel column. This fuel is principally coke or carbonized fuel and must be quenched to prevent destruction of the bottom of the shaft 12. To this end the unburned carbonized fuel and ash is supported in the bottom of the shaft upon a series of hoppers 110, Figs. 1, 4, and 5. The hoppers are preferably. made of a steel construction and are protected by refractory masonary lining. The hoppers,-seven in number, consist of six peripheral hoppers, and a central hopper. An opening 112 is formed in the ing through these openings flows upon a series of movable platforms 116, which are spaced from, but directly under the openings; The platforms 116 are arranged to be given a reciprocating motion by means of water operated engines 118 to discharge the carbonized fuel from the platforms into .a hopper 120 immediately below the hopper 110. To cool the carbonized fuel passing down to the hopper 110 a water or steam pipe 122 is positioned below the hopper and has an outlet 124 extending into each of the open-' ing's 112 and 114 by which water or steam may be directed into the carbonized fuel to quench and cool it. The water or steam introduced into the hot carbonized fuel passes upwardly through the fuel column in the form of'vapor, thus acting to effectively cool the carbonized fuel in its upward passage. By the time the steam reaches the blast zone it is highly preheated and enters into reaction with the carbonized fuel of the fuel column, so that it isutilized in making gas in the same way that the steam entering the fuel column through the preheater is used.

The carbonized fuel discharged from the hopper 110 to the hopper 120 passes through a series of outlets 126 on the bottom of the hopper 120 and is collected in a'chamber 128 at the bottom of the shaft. Periodically a door 130' at the bottom of the chamber 128 is opened and the carbonized fuel accumulated therein may be drawn out. At the time the a moved into position to cover the outlets 126 by means of operating shafts 134. that extend to the outside of the shaft 12. When the door 130 is closed the doors 132 are ened to permit the carbonized fuel to pass rom the hopper 120 to the chamber 128 and thus the carbonized fuel and ashes may be withdrawn from the bottom of the shaft without allowing gas to escape. To assist in moving the m carbonized fuel through the hopper 120 a series of pokers 136 pass through the chamher 128 and the hopper 120, by which the carbonized fuel may be barred and broken up whileit is passing down to the openings 126 of the hopper 120.

An important feature of the present invention consists in giving a high degree of preheat to the mixture of air and steam bemg used for making gas whereby the inert material from the combustion of air may be retained in the gas while making a gas of comparatively high calorific value and high flame propagation. By preheating the steam and air the gas can be made with a lower percentage of air in proportion to the amount of steam used, and thus cut down the amount of inerts in the gas. This may be demonstrated as follows:

In the exothermic reaction between carbon and air when both the carbon and the. air

start cold, the following reaction takes place:

' CD 3.7 8N 14600 B. T. U.

If, however, the air is preheated to 2000 F.

C+2H O=CO +2H 17400 B. T. U.

4 If however, the steam is preheated to 2000 F. and the carbon isheated to 1500 F., a gain of approximately 4125 B. U. may be made.

The endothermicreaction between carbon and carbondioxide, assuming that both are cold, is substantially as follows C+ CO2=2CO5900 B. T. U.

If, however, the CO is preheated to 2000 F.

and the carbon is preheated to 1500 F. a gain of substantially 2725 B. T. U. may be effected. Assuming that the above reactions take place when the constituents are cold, as out lined above, a thermal heat balance may be obtained when the endothermic reaction between carbon and water vapor and the carbon and carbon dioxide constitutes 45% of the reaction, and the exothermic reaction between 5 carbon and air constitutes 54.5% of the reaction. With such a combustion the analysis of the gas would be, in percentages by volume:

C0 =252 I-I =22.8 N =52.0 B. T. U. value of gas per cubic foot=7 5 However, when assuming that the reactions take place, when the steam and air are heated to2000 F. and the carbon is heated to 1500 F. a thermal heat balance will take place when 39% of the constituents enter into exothermic reactions, and 61% of the constituents enter into an endothermic reaction. Using the heat balance for the preheated materials, a gas formed by the combustion will analyze in percentages by volume:

(lO =27.2 H =33.1 N =39.7 B. T. U. value of gas per cubic foot=108 In other words, by preheating the steam, air and carbon. the nitrogen content is reduced from 52 to 39.7%, the inerts are reduced from 77.2 to 66.9% and the calorific values increased from 74.5 to 108 B. T. U. per cubic foot. In the present process the degree of preheat depends strictly upon the nature of the coal which is being treated, and, preferably, will vary from 1200 F. to 2200 F. By preheating, a gas having a calorific value of from 200 to 225 B. T. U. per cubic foot may be produced which has most of the advantageous features of Water gas. The products of combustion of this gas will have a calorific value ranging from -90 B. T. U. per cubic foot even when no preheat is imparted to the blast air.

A typical analysis of a gas made by the present process is substantially as follows:

oo.=7%; N =40%; C0='24%; H =25%; CH =4% In accordance with the character of the coal being treated a gas may be made which will have a total amount of inerts of from 45 to 52 per cent. Furthermore, by the low temperature carbonization applicant is able to gain a substantial amount in volume of methane produced and also gains considerably in the amount of carbon monoxide and hydrogen produced which aid to increase the flame temperature and the flame propagation of the gas. The gas formed in carbonizing the coal above the blast zone has a comparatively high heat value, and when this gas is blended with the gas taken ofi through the off-take 20, a gas is produced which when burned has a flame temperature ranging from 3000 F. 3200 F. and which is therefore suitable for practically all industrial heating purposes.

With the process outlined above, it will be seen that the manufacture of gas may be thoroughly controlled, and that the process will give a very good heat balance because the fuel is introduced and removed from the generator substantially cold, and the residual umn through a generator, continuously introducing a blast mixture of steam-and air into a mid-portion of the column to maintain gasmaking temperatures therein, passing a portion of the gas-formed upwardly through the fuel above the mid-zone to carbonize the fuel by heat transfer therewith and separately removing this enriched producer gas from the top of the generator, removing the major portion of the gas from the generator at a posi- I ducer gas, comprlsmg continuously passing tion directly adjacent the mid-portion of the column, introducing water only into the lower portion of the column below themid-zone to cool and quench the fuel, and passing steam thus generated upwardly through the fuel into the blast zone. v

2. A method of making high quality producer gas, comprising continuously introducing a blast mixture of air and steam into the mid-portion of a fuel column'to maintain gas-making temperatures therein, continuously exhausting the major portion of the producer gas formed from the central portion of the fuel column at a position immediately adjacent the blast zone, passing another portion of the producer gas formed through the fuel in the upper portion of the column to dist-i1 said fuel and enrich said gas -with its volatile components, continuously introducing a cool stream of water 1nto the lower portion of the column below the blast zoneand passing the steam thus formed upwardly in heat transferring relationship through the fuel, and preheating the blast mixture by burning the centrally exhausted producer gas in heat interchanging relationship with the steamand air entering the fuel column.

3. A method of making high quality producer gas, comprising continuously blasting a preheated combustion supporting gas, pref- V erably a mixture of steam and air, Into the mid-portion of a column of fuel to maintain gas-making temperature therein, continuously removing the major portion of the gas formed from the fuel column adjacent the blast zone, passing another portion of the gas upwardly through the fuel of the column above the blast zone to carbonize said fuel,

removing the last mentioned enriched portion of gas from the generator separately from the major portion of the gas, and controlling the preheat imparted to the blast mixtureto produce an enriched gas having a gross calorific value of 200 B. T. U, per cubic foot or higher. r

4. A method of making high quality producer gas, comprising continuously passing fuel in acolumn through a generator, continuously introducing a blast mixture of steam and air directly into the mid-portion bonize said fuel by direct heat transfer therewith, removing the last mentioned enriched vportion of gas from the generator separately from the major portion of gas formed in the blast zone, and cooling and quenching any unburned carbonized fuel and ash in the column below the blast zone with water vapor.

5. A method of making high quality profuel in a column through a generator, continuously introducing a blast mixture of steam and air into the mid-portion of the fuel column to maintain gas-making temperatures therein, passing part of the gas formed upwardly through the fuel above the blast zone to carbonize said fuel by diriact heat transfer therewith, preheating said blast mixture to a a degree such that an enriched producer gas having a gross calorific value of 200 B. T. U. per cubic foot or higher is produced, and continuously removing said enriched gas from the upper part of the generator.

6. A method of making high quality p ro.-

ducer gas, comprising Econtinuously passing fuel in a column through a generator, continuously introducing a blast mixture of steam and air directly into the mid-portion of the column to maintain gas-making temperatures therein, preheating said blast mixture to a temperature above 1200 F. before tity of air introduced will maintain the amount of inerts in the gas produced below 52%. Y

7. A method of making producer gas of high calorific value, comprising continuously passing fuel in a column through a genenator, continuously introducing a blast mixture of air and steam peripherally into the mid-portion of the fuel column to maintain gas-making temperatures therein, preheat-, ing said blastmixture before admitting it into the fuel column, removing a part of the gas formed directly from the blast zone of the fuel column,,and passing another portion of the gas formed upwardly through the fuel above the blast zone to carbonize said fuel and to enrich said portion of gas with volatile products distilled therefrom, introducing introducing it into the fuel column, continu- 6 enriched producer water into the fuel residue in the lower porrect heat transfer'therewith, passing steam thus formed into the heated blast zone to generate gas, and continuously removing the gas from the upper portion of the fuel column.

8., A methodof making high quality pro-- ducer gas, comprising continuously passing fuel in a column through a shaft generator, continuously introducing a blast mixture of air and steam into the mid-portion of the column around its periphery and forcing the mixture through the fuel column to maintain gas-making temperatures therein, exhausting part of the gas formed from the fuel column at a point in its longitudinal axis directly adjacent the blast zone, passing another portion of the gas formed in contact with the fuel in the upper portion of the column to carbonize said fuel and enrich said gas with volatile components distilled therefrom, continuously introducing water into the lower portion of the column to cool and quench the fuel residue therein, and to serve as a medium for returning the sensible heat of the fuel and ash passing the blast zone to the midportion of the fuel column.

9. Amethod of making high quality producer gas, which comprises, continuously introducing a, combustion supporting gas, preferably a mixture of steam and air, directly 7 into the mid-portion of a column of fuel to form a blast zone, and forcing said mixture through thefuel column to maintain gasass'aaae moving from the generator the said portion of gas, separately removing another portion of the gas formed from the fuel column at a pointin the vertical axis thereof adjacent the blast zone, and regenerating and utilizing the potential heat ofwthe last-named portion of gas for generating steam and preheating air for subsequent use in the process.

In testimony whereof I afiix my signature.

HENRY O. LOBELL.

making temperatures therein, exhausting a portion of gas formed from the fuel at a point in the central portion of the column adjacent the blast zone, passing another portion of the gas formed upwardly in heat transferring relationship through the fuel above the blast zone to distil said fuel and enrich said gas portion with its volatile components, regenerating and utilizing in the process they potential heat of the centrally exhausted gas and the sensible heat of the fuel residue and ash in the lower portion of the fuel column, the heat thus regenerated from the centrally exhausted gas being utilized to preheat the air and to generate and superheat the steam of the air-steam mixture used in gas making.

' the upper 1200 F. before it enters the column, passing of steam and air mixture to a temperature above a. portion of the gas formed upwardly through art of the fuel column in direct contact wit the fuel therein to preheat and carbonize the fuel and enrich-the gas, and re-