US3008815A - Production of gases of high and low calorific value - Google Patents

Description

Nov. 14, 1961 R. RUMMEL ET AL 3,008,815

PRODUCTION OF GASES OF HIGH AND LOW CALORIFIC VALUE Filed April 21., 1954 2 Sheets-Sheet 1 I F/G.1

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ROMAN RUMMEL, RUDOLF HUTTNER.

@ZQYWA W ATIORNE Y3 Nov. 14, 1961 R. RUMMEL ETAL 3,003,815

PRODUCTION OF GASES OF HIGH AND LOW CALORIFIC VALUE Filed April 21, 1954 2 Sheets-Sheet 2 13 2 wvwv -wvvwvv a I L 6 IIYVENTORS. ROMAN RUMMEL. RUDQLF HUTTNER,

w ATTORN s United States Patent 'Qfiice 3,008,815 Patented Nov. 14,1961

3,008,815 PRODUCTION OF GASES OF HIGH AND LOW CALORIFIC VALUE a Roman Rumme'l, Bruhl, Bezirk, Koln, and Rudolf Hiitt ner, Koln-Raderberg, Germany, assignors to Union Rheinische Braunkohlen Kr'aftstofi Aktiengesellschaft, Wesseling, Bezirk, Koln, Germany, a corporation of Germany Y Filed Apr. 21, 1954, Ser. No. 424,724 Claims priority, application Germany Apr. 25, 1953 4 Claims. (Cl. 48-197) The present'invention relates to a new process for the simultaneous production of gases of high and low calorific value from solid fuels. 7

It' is known toproduce gases of high-calorific value from solid fuels by'low-temperature carbonization or destructive distillation with the aid of solidheat carriers employed in a cyclic process. In this process fine-grained coke is obtainedas by-product which can be used for heating purposes, especially for heating boilers, but can also be gasified to give producer gas by any of the known processes suitable for gasifying fine/grained fuels.

' In accordance with the invention it has been found that gases of high and low calorific value can be produced simultaneously in a convenient and economic manner by combining the aforesaid two processes in such a manner that the coke formed bythe low-temperature carbonization or destructive distillation is gasified by means of air to give producer gases at temperatures higher than the temperature required for heating up the recycled solid heat carrier to the temperature necessary to effectdeview to elevate b'y'means of air the coke leaving the coke oven wherein destructive distillation takes place-and to simultaneously impart the required temperature by partial combustion. I 1

The varied embodiments of this processQhowever, suffer from many disadvantages. The ash introduced along with fresh coal isincreasingly enriched in the circuit of the coke. This necessitates the continuous removal of part of the coke from the circuit. Depending on the ash content of the fuel employed in the production of gases as well as on the concentration of the ash maintained in the circuit of the coke, a substantial percentage of coal is thus withdrawn from the process and obtained as a waste product which can hardlybe utilized." It is possible to remove the'ash from the circuit by leaving in-the producer gets an appropriate amount of flue coke and using the hot producer gas containing dust directly as fuel gas; Apart from the fact; however, that a hot gas containing dust cannot be used for many purposes for instance for undergrate heating of coke ovens, or operating gas turbines, the problem of the ash removal is actually not solved by this method but passed on to the consumer" plant. Moreover, the ash removed by the aforedescribed method leads structive distillation and the recycled solid heat carrier is heated with the producer gases obtained to the temperature required for gasification, for instance to 800 C.- 1100" C., preferably while conveying the heat carrier pneumatically or causing turbulent flow or 'fiuidiz'ation thereof. In contrast to the separate performance of-the two processes, the invention ofiers the possibility of converting all the carbon and hydrogen contained in the fuel into high-grade chemical energy in the form of by-product gas, i.e. gas of high calorific value, also termed rich gas, and producer gas, i.e. gasof low calorific value, also termed lean'or poor gas, since no flue gas isformed in the herein-describedprocess. An additional advantage of the invention is that the new processcan be carried outin-a more simple and cheaper apparatus than that :required to perform the two processes separately. According to the invention, the gasification may be carried out at temperatures which ensure that the sensible heat of the producer gas is sufficientto supply the heat required in the destructive distillation, for instance according-to the process described in U.S. Patent 2,647,045 or in a cyclone gas producer. Y

. The newprocess has special advantages when the 'coke formed in the destructive distillation is used as solid heat carrier. Apart from coke, other heat carriers customary' in the art may be employed according. to the invention forinstance pellets of clay or metal. The utilization of the'own coke as heat carrier andan an paratus for carrying out such process was described in principle by Bube (Thau, Kohlenschwelung, 1938, page 131). This proposal was taken up more'recently by a number of authors who adapted the processusing the own coke as heat carrier to the present state of technology by resorting to new apparatus for instance means utilizing fiuidization or pneumatic conveyance, further-' more cyclones and mixing nozzles,'which'were'devised to carry out similar processes. All these proposals have in' method suifers from the disadvantage that the air em to a disagreeable rigid coupling between the gas producer and the plant consuming producer gas. The two kinds of plants must be erected side by side and the failure-or breakdown of a gas producer unit likewise affects the appertaining consumer unit, =for ,instance' a boiler. Thus, it is necessary-touincrease the number of spare units, which increases thecapital invested. Apart from the:'difiiculties involved in removing ash frorn'the cyoliccurrent the above described prior art ployed to pneumatically elevate and heat the recycled coke must not be preheated to a' high temperature in order to avoid slagging joccurring atthe inlet, which would cause intolerable. stoppages of operation. Hence it follows that the greater-part of the reaction heat .can-

not be-led-back to the process by means of theair stream but can be recovered only as waste heat. The calorific value of the producer gas is thusdiminished. The necessity of confining the preheating of air to relatively low temperatures does not allow of making up, increasing or renewing therecycled coke by gasifying freshcoal, or of varying the amount and-heating power of the producer gas within certain limits. 1 g 1 I g The present inventionprovid'es a process that is void of the above described;.-drawbacks. In the new process, part of the recycled coke, which corresponds to the approziimate amountof coke freshly'fo'rmed in the lowtemperature 'carbonization (or destructive distillation), is gasified atfhigh temperature to give producer gas, the

. temperature.'applied beingfor' instance so high that the temperature is obtained'by preheating the air employed in the 'gasification toja high temperature for instance by means of the hot producer gas'after heating up the recycled coke. The proportion of the recycled coke to be gasified can be reduced temporarily and the amount of the: recycled cokemadeiup or increased by simultaneously this manner the amount and the heating power of the pro ducer gas can as well be controlled and varied. This allows of invalidating, at least partially, the rigid interdependence in the production of producer gases and byproduct gases. As regards the dimensions of the gas producer unit due consideration should of course be given to the practicability of gasifying other fuels simultaneously with the recycled coke, in accordance with the conditions prevailing in every given case. If, for any reason, the proportion of other :fuels to be gasified simultaneously is relatively high, only part of the producer gas obtained is required to heat up the recycled solid heat carrier while the remainder can be led off directly for waste-heat utilization, for instance for preheating air.

The invention will now further be described with reference to the accompanying diagrammatic drawings which illustrate by way of example two embodiments by which the invention can be carried into effect.

Referring first to FIG. 1, fresh coal to be gasified (which has a grain size below 2 mm.) is blown into the degasifier 2 (i.e. the space. wherein the destructive distillation or low-temperature carbonization takes place) by means of a carrier gas, for instance a partial stream of the lay-product gas. The degasifier 2 contains a preheated coarse-grained solid heat carrier which moves slowly from the top toward the bottom. The coal blown into the degasifier 2 is destructively distilled during its upward motion through the interspaces of the coarse-grained heat carrier. The mixture of the by-product gas and coke thus produced passes through the pipe 3 to the cyclone 4 wherein the coke is separated from the gas. The gas is drawn off through the pipe 5 to be used for any desired purpose. The coke passes through the pipe 6 and is blown into the gasifier or gas producer 3 through the pipe 15 with the aid of cold air. After heating to high temperature the greater part ofthe air used for gasification is led into the gas producer '8- through the pipe 7. The gas producer 8 may be designed as the gasifier described in 'U.S. Patent 2,647,045. The ash flows off through the pipe 9 as liquid slag while the hot producer gas passes through the pipe 10 into the heater 11 wherein it gives up part of its heat to the solid heat carrier. From the heater 11 the gas streams through the pipe 12 into the air preheater 13 and thence through the pipe 14 to be used for any desired purpose. The preheated air is led into the gas producer 8 through the pipe 7 as described above. The heat carrier heated up in the heater 11 flows into the degasifier 2, transfers therein part of its heat to the coal to be destructively distilled and is conveyed back to the heater 11 with the aid of the bucket elevator'16.

In FIG. 2, brown coal which is predried to a Water content of 2% is conveyed to the degasifier 2 through pipe 1. At the inlet 23 of the degasifier 2 the brown coal is mixed at a proportion of 1:4.5, with hot (1000 C.) recycled coke coming from the container 21. The coal is destructively distilled in contact with the live coal. The thus obtained gas of high calorific value (by-product gas) is led off through the pipe 3. The mixture of recycled coke and freshly formed coke leaves the degasifier 2 through the bottom at a temperature of about 800", C. About 95% of the mixture passes through the pipe 4 to the conveying and heating tube 11, the remainder through the pipe 5 to the pipe 6 and is blown into the gas producer 8 with the aid of cold air. It is within the scope of the invention to gasify simultaneously fresh coal' (water content'2%), which is admitted through the pipe 20. The liquid slag'fiows off through the pipe 9 and the hot (about 1650 C.) producer gas passes to the heating tube 11 through the pipe 10. In the heating tube 11 the recycled .coke is conveyed pneumatically to the cyclone 21 and simultaneously brought to the required initial temperature of 1000? C. At this temperature the recycled coke which is separated in the cyclone .21 returns to the degasifier 2. The producer gas flows through the pipe 12 to the air preheater 13 and gives otf therein its sensible heat (down to about 300 C.) and passes then into a second separator 15 through the pipe 14. The fines of the recycled coke are separated in the separator 15 and blown into the gas producer 8 through the pipes 19 and 17 by means of cold air. The producer gas passes through the pipe 18 intoa container to be finally cooled as usual and is then led into a storage tank. (The container and the storage tank are not shown in the drawing.) The air used in the gasification process is heated to about 700 C. in the air preheater 13 and led into the gas producer 8. The recycled coke and fresh coal are normally introduced into the gas producer 8 in quantities and at a proportion ensuring that the heat required in the destructive distillation is used up and the unavoidable losses of recycled coke are compensated. If, for any reason, an additional amount of fresh coal is to be gasified, an appropriate part of the hot producer gas can be led directly into the air preheater 13 through the by-pass pipe 22 and the pipe 12.

The process of the invention permits of obtaining from 1000 kg. of brown coal of 2% water content, 305 Nm. of by-product gas which yields 223 Nm. of a gas of a gross (upper) calorific value of about 5180 kcal./Nm. after washing out the carbon dioxide to 2% In addition, about 2500 Nm. of producer gas with a gross calorific value of about 1255 -kcal./Nm. are simultaneously obtained. The term Nm. is an abbreviation of normal cubic meter and means m5 at 0 C. and 760 C. mm.

mercury pressure.

We claim:

l. A process for gasifying carbonaceous fuel which comprises passing gravity-fed, heat-carrying particles downwardly through a first gasification zone, injecting a carbonaceous fuel into the gravity-fed path of said heatc'arrying particles within said first gasification zone, said heat-carrying particles transmitting sufiicient heat to the fuel to convert said fuel to coke and a high calorie gas,

passing said high calorie gas, in countercurrent to saidv gravity-fed heat-carrying, particles, out of said first gasifi cation zone while passing at least a portion of said coke through a second gasification zone where sufiicient heat is transmitted to said coke by a pro-heated gas to produce a low calorie gas, passing said low calorie gas through additional gravity-fed heat-carrying particles in a heating zone wherein heat from said low calorie gas is transmitted to said heat-carrying particles prior to their passage through said first gasification zone, and then passing said low calorie ga through a gas heating means to provide the pro-heated gas used in said second gasification zone.

2. The process of claim 1 wherein all of said low calorie gas is contacted with said heat-carrying particles.

3. A process for lga'sifying carbonaceous fuel which comprises passing heat-carrying particles by gravity-feed from a pre-heating zone through a first gasification zone, injecting carbonaceous fuel into said first gasification zone in substantial countercurrent to said heat-carrying particles, said heat carrying particles acting to transmit sufficient heat to said fuel to convert said fuelto coke and a high calorie gas, passing said coke and high calorie gas out of said first gasification zone into a separating zone where the high calorie gas is separated from the coke and removed from the system, passing said coke from said separating zone to a second gasification zone where a heated gas is inserted to transmit heat to said coke to form a low calorie gas, passing said low calorie gas into said pro-heating zone to transmit heat to said heat-carrying particles, and then passing said low calorie gas through a gas heating means forpre-heating the gas inserted into said second gasification zone.

4. The process of claim 1 wherein only a portion of said lowacalorie gas contacted with said heat carrying particles While the remaining portion of said low-calorie gas is withdrawn from the system.

References Qited in 1116 file of this patent UNITED STATES PATENTS 6 Riblett June 17, 1952 Roetheli Dec. 30, 1952 Reichl et a1. Oct. 6, 1953 Mayland Nov. 3, 1953 Garbo et a1 Apr. 6, 1954 Welinsky May 4, 1954 Danulat et a1 Feb. 8, 1955 Nelson et a1. Jan. 3, 1956

Claims (1)

1. A PROCESS FOR GASIFYING CARBONACEOUS FUEL WHICH COMPRISES PASSING GRAVITY-FED, HEAT-CARRYING PARTICLES DOWNWARDLY THROUGH A FIRST GASIFICATION ZONE, INJECTING A CARBONACEOUS FUEL INTO THE GRAVITY-FED PATH OF SAID HEATCARRYING PARTICLES WITHIN SAID FIRST GASIFICATION ZONE, SAID HEAT-CARRYING PARTICLES TRANSMITTING SUFFICIEIENT HEAT TO THE FUEL TO CONVERT SAID FUEL TO COKE AND A HIGH CALORIE GAS, PASSING SAID HIGH CALORIE GAS, IN COUNTERCURRENT TO SAID GRAVITY-FED HEAT-CARRYING PARTICLES, OUT OF SAID FIRST GASIFICATION ZONE WHILE PASSING AT LEAST A PORTION OF SAID COKE THROUGH A SECOND GASIFICATION ZONE WHERE SUFFICIENT HEAT IS TRANSMITTED TO SAID COKE BY A PRE-HEATED GAS TO PRODUCE A LOW CALORIE GAS, PASSING SAID LOW CALORIE GAS THROUGH ADDITIONAL GRAVITY-FED HEAT-CARRYING PARTICLES IN A HEATING ZONE WHEREIN HEAT FROM SAID LOW CALORIE GAS IS TRANSMITTED TO SAID HEAT-CARRYING PARTICLES PRIOR TO THEIR PASSAGE THROUGH SAID FIRST GASIFICATION ZONE, AND THEN PASSING SAID LOW CALORIE GAS THROUGH A GAS HEATING MEANS TO PROVIDE THE PRE-HEATED GAS USED IN SAID SECOND GASIFICATION ZONE.

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