US1639391A - Process of distilling and gasifying solid carbonaceous fuel - Google Patents

Description

. l I 1,639,391 1927' e: w. WALLACE PROCESS OF DISTILLING AND GASIFYING SOLID CARBONACEOUS FUEL Filed Jan.l5, 192s Patented Aug. 16, 1927. I

unrra sire-res PATENT errier.

GEORGE W. WALLACE, .OF SAN FRANCISCO, CALIE ORNIA.

rnoonss or msrrnmue AND GASIFYING SOLID cnnnonaonons FUEL.

Application filed January 13, 1926. Serial .No. 81,119. g

bonization and then gasifying the residue to make producer gas, the carbonization and the main gas production being spatially separated but consecutive operations, carbonization being effected in a relatively stationary zone established and maintained at an intermediate point in a relatively short, pervious, moving body or column of fuel with one end (the feed end) relatively cold and the other end (the delivery end) relatively hot, the desired temperature conditions within the column being maintained with the aid of hot producer gas coming from the gasification operation and being stabilized by supplying enough air to form a flame impinging on and heating the delivery end and establishing gas producer conditions in the mass of fuel delivered therebeyond, the flame gases and the gaseous and vaporous products of distillation formed in carbonization.being taken forward in the column against the line of movement of the solid materials therein and gasification of the hot material delivered from said face being effected by a draft current containing air, this draft current usually also containing products of combustion or steam. or both; the gases produced in carbonization and in gasification being if desired separately collected either completely or partially; all as more fully hereinafter set forth and as claimed. 7

The distillation and the gasifioat-ion of coal are old arts but it has heretofore proved diiiicult to combine low temperature carbonization or' distillation of coal with eflicient gasification. Low temperature carbonization is desirable as giving the best yield of the best grad byproducts; oils, tars and gases. Both. updraft producers and downdraft producers fail to accomplish this combination. With an updraft producer tars and other liquid products of carbonization condense and trickle down towards the heat to undergo secondary decomposition. As an incident to this it is extremely dillicult to keep the fire-bed open in an updraft producer without resort to poking. In the downdraft producer, gases and vapors are taken. away from the hot zone but there are insuperable difiiculties in running such a producer continuously; these difficulties arising partly in the .feed of fuel and partly from the accumulation of ash.

It is the purpose of the present invention to provide a simple and economical method whereby coal may be distilled to obtain the products of low temperature carbonization and the hot carbonized material be gasified.

by a draft current while still hot; the two actions being consecutiveand taking place 1n the same apparatus but being spatially separated so that each can be conducted under thebest conditions and be independently controlled. In most types of producers all the gas produced in the gasifying zone necessarily passes through preheating zones;

making temperature conditions in the latter uncontrollable, and particularly where carbonization occurs. This is not necessary in the present invention, means being provided whereby, some, much, or most of the producer gas can be by-passed. Except with fuels quite oor in fixed, carbon, such as some oil sha es, there is an excess of producer gas to be by-passed.

While the producer gas formed in the usual operation is at an average temperature and is in sufficient volume to afford all the heat necessary in carbonization, yet the temperature fluctuates and the volume is generally or usually greater than is needed. Theicarbonization operation can not be individually controlled and performed under the best conditions; that is under conditions affording the bust yield of the best products. Nor can the quite dissimilar fixcd gases formed in the two operations be separately collected. It is the object of the present invention to obviate these disadvantages. while retaining the advantages of updraft gas production; and to this end I do most of my gasification on carbonized fuel in a chamber other than that in which carbonization takes place. effecting merely enough gasification in the carbonization chamber to stabilize heating conditions therein.

In the present invention, 1 establish and maintain a relatively short moving, pervious column of the material to be distilled with one end, the feed end, relatively 0001 (often not above 212 F.) and the other end, the discharge end, at a very high tomperature. in the material at the discharge end is introduced a current of hot producer gas coming from the gasificationstep. Vifhile the average temperature of this gas is suiticient and a suiiicient volume can be passed through the fuel, to maintain the temperature gradients I desire within said column, in practice ll find it better not to rely wholly upon this source of heat and to supplement it by flame heat. This has the advantage of stabilizing temperature conditions within the carbonizing chamber and making it independent of gasifier conditions and the further advantage of discharging carbonized materials into the producer at a very-high-temperature, usually around 2000"; which much facilitates the producer operation. To torm the flame T supply some air to the producer gas just before it enters the carbonizing chamber, forming a dame impinging on the delivery end. This forms H t) andC O from H, and CO in the gas with developmentof high temperature locally. The amount of air being relatively small, the flame is of reducing nature; i. e., not all the producer gas entering the carbonizing chamber is burnt. Just beyond the face howeverthe CO and H 0 are again reduced to CO and H, by the carbon with a drop in. temperature; the temperature coming back to a normal producer gas temperature, say 1500- 1600" F. The increase in temperature caused by the air addition and flame formation is temporary only; but the addition subserves the two purposes'of superheating the discharged material and producing a fixed temperature in the column which is independent of producer conditions. While the particular temperature developed at this point in the column may vary somewhat with conditions (volume of air, composition of'gas, speed of feed, etc.) in any given operationthe temperature developed is constant enough to permit ready establishment and maintenance of a practically stationary, uniformly operating carbonizing zone within the column. The hot gases passing forward meet and heat the materials and are cooled thereby, establishing the desired temperature gradient with a carbonizing zone at a point intermediate the two ends.

With' most organic materials decomposition or carbonization is an exothermic action. Once the materials are brought to the reaction temperature, say about 800 F., charring sets in with development of heat. The exact ten'iperature reached depends upon the materials and upon the consumption of heat in radiation, in heating up accompanying mineral matters, etc. Sometimes this exothermic action is masked by heat losses. Sometimes, however, it is suilicient to keep the carbonization going. The amount of hot gas and oi air which are delivered to and pass through the column of c iuel s more exothermic ess necessity rather warm.v Giten the temperature "re--- mains below but approaches 212 F. because of condensation of moisture. Tarry matter and oils boiling at temperatures above 212 l3. are also here condensed as far as the volume of gases will permit. At the other end the temperature is that of hot flame gases say 1800-2800 E; this temperature however dropping at once as thegases pass J into the carbonized material, by reason of endothermic producer gas-reactions; reduction of CO and H 0. Somewhere intermediate the two ends a zone of 'carbonization is instituted and maintained and with a fixed feed of material the zone remains practically stationary, moving but little to either side. The gases and vapors produced in carbonization' pass through the incoming material heating it up and drying it and some vapors are themselves condensed to a large extent. However because of the "dilution by the flame gases, ordinarily a considerable amount of valuable oily products goes on beyond and must be recovered by cooling and scrubbing the efliuent gas. The scrubbed gas is rich from a B. t. u. standpoint and containshydrocarbons and also some producer gas; that used as a draft currentand that produced by the action of the air.

The hot materials passing beyond the action of the flame are in condition and at a temperature to undergo. ready 'gasification with the production of producer gas by the action of a suitable draft current. Such a draft current is passed through an accumulating column of materials coming from the .carbonizing zone with the production of the usual types of producer gas, viz, m xtures of CO and N. with more or less CO and H. The amount of gas obtained of course varies with the materials treated. With bituminous coal containing but little ash, large volumes of gas are obtained in both the carboniz'ng zone and the producer zone while on the other hand with some oil shales the carbonized material delivered to the proassess:

' ducer may carry only 2 or 3 per cent of fixed.

carbon, and give a correspondingly low yield of gas in the producer section. Ordinarily however there is an excess of gas over and above that required in the carbonizing zone and this excess may be diverted and collected to be mixed with gas coming from the scrubbers or to be separately used as circumstances may dictate. lhe two types of gas gas is produced with temperatures restrained by the presence of endothermics. And in any event conditions in the carbonizing column are more easily and accurately controlled when flame heating is used.

In my usual practice with most fuels, the operation is continuous and a single piece of apparatus is used; but the two actions are se arated in point of space.

ill the present invention granular materials are supplied to a reacting chamber having theform of a short'conduit as successive small charges or by a continuous feeding device thereby establishing and maintaining a moving pervious column with the feed end, as stated, often not above 212 F. Through this moving column are passed hot burning gases in countercurrent with production of hot discharged material and of a short zone wherein normal producer actions (reduction of CO and H 0) occur and a normal producer gas temperature is reestablished. As the materials move forward against the hot gases they become dried and preheated and at some rather definite temperature, say around 800 F. carbonization sets in with a comparatively sudden evolution of gases and vapors. These. gases and vapors are carried backward through the cooler material by the heating gases. llhe moving material quickly carbonizes and passes forward toward the discharge end. In practice, while the zone of carbonization, which is relatively short, may shift backwards and forwards a little, it remains practically stationary. When-the carbonized material reaches the zone of hi her temperature towards the discharge on itbecomes sufficiently heated to reduce the C0, and H 9 in the flame gases to CO and H 'lVith the feed end cool, or relatively so, there is a sharp decline in the temperature gradient from the carboniziug zone toward it; or, in other wordsthcre is quick cooling of the produced vapors and liquid with avoidance of injurious changes.

The oils and tars sufler from any prolonged action of heat even at the temperature at which they are produced.

in the accompanying-illustration l have shown, more or less diagrammatically, certain apparatus useful in the performance of the described process. The view isin central vertical section, certain "minor parts being shown in elevation.

In this showing, element 1 is a tubular reaction chamber of any convenient material, such as masonry or metal; this chamber having the form of a relatively short conduit of appropriate cross section. Usually 1 form it as a cylindrical or oval brick lined iron chamber. At one end, 2, material is forced. into. it'by the action of any convenient stoking means. I have shown a cylinder 3 containing plunger 4 actuated by. drive means 5 for charging. With the feed shown, the

advancing column ofmaterial fills the entire cross section of the reaction chamber. Raw material enters throughchute 6. At this end of the apparatus is drain 7, for condensed liquids, and outlet 8 leading to condensing and suction means (not shown) for removing vapors andgases. Ordinarily it is desirable to use scrubbing means (not shown) in connection with the condensing means where it is important, as it usuallyis, to remove light oils. Water or steam pipe 9 is provided in the event that cooling of the feed end by this means is desirable. However, with most coals there is suflicient moisture present or formed in combustion to provide all the cooling necessary. The material may be previously wetted down. Generally however this is not necessary; and sometimes, as with lignite, peat and wood, preliminary drying to a greater or less extent, is desirable. Within the reaction chamber the moving column of material may be regarded as passing through three zones A, B and C; A being the drying and preheating zone, B the carbonizing zone. while C is the high temperature zone. Hot carbonized material passing through zone C is-discharged in a supcrhcatcd condition at open end 10 in which it forms. as shown, an angle-of-repose face. Against this face is projected flame from element 11. This; element 11 may be an air pipe or it may be a gas pipe with air induced through damper means 12. The materials coming from the end face of the column on the reaction chamber drop into chamber 13 forming a column or bed of hot fuel, the bed resting on grate means 14. Through this bed is forced in updraft, a gasifying draft current from pipe. 15 which may be supplied with air, products of combustion or steam or mixtures of the same coming from pipes 16, 17 and 18. The particular character of draft current used depends on the material, and to some extent on the richness of gas wanted. V fhere the carbonized materials are coke or charcoal, that is, are rich in carbon, 1 generally employ liberal proportions of endothermics. Steam in addition to its endothermic action and its value increasing the B. t. u. and quantity of the gas, has a shielding; action on ammonia and in Working with coke rich in nitrogen, Where the production of ammonia is a desideratum, there may be enough Water vapor introduced into the draft current to give a gas of the type 0' that "formed in Monti producers. Gas produced with the aid of the draft current and not needed for passage throughthc reaction chamber goes 'to a place of storage or (not shown) through outlet 19.' it is usually mixed afterward With the gases from the reaction chamber Where gas is Wanted of higher B. t. u. than that of producer gas- Ash accumulation 2O below'the grate may be moistened by Water from pipe 21; cooling the ash and i'urnislu ing Water vapor for the draft current.

siderable proportion of the endothermic water introduced at 21 and vaporized in v u f qucuchin the hot ashes may rorm a conused. Ash is removed from the accumulanets and gas.

low 7 l/Vhile other types of ash removal may be same considerations apply tion by star wheel 22 continuously or from time to time. Since the gasification chamher is supplied with hot carbon, the use of an endot'hern'iic in the draft current is particularly desirable as giving more gas and keeping the temperature of the lire-bed bethe clinkering or sintering point.

employed, the rotary grate shown is convenient and with the lire-bed temperature controlled by endothermics, as it should be, is practical.

'lhe material treated in the present invention may be any vegetable material suclras bark. Wood. straw, sawdust, etc. from which it is desirable to obtain carbonization prod- In this event acid resistant metals or materials should be used at the cool end of the reaction chamber and in the condensing and gas collecting means. @r the material employed ma be any bituminous coal. lignite, oil sha eor 'brown coal. The present invention is particularly useful in handling ligmites ot'high Water content since the heat of vaporization of Water in the rear part of zone A is balanced out by condensation toward the feed end. The

to peat.

ll regard my invention as applicable in the dual treatment of any material capable of giving valuable products by low tempera 'ture carbonization and producer gas high temperature gasification. do not herein claim the apparatus illustrated, that forming; matter in another and copendirigz application Serial No. 81,148, tiled "l /lay l8, 1.925.

As shown have single carbonization chamber supplying the gasifieation chamber but a plurality operating in parallel may be so used. ln increasing capacity it is in general better to do it by increasing the size of the gasification chamber and increasing the number of carbonizing chambers feed-- ing it; that a battery of reaction chambers. maybe arranged in rows either side by side or one above another, to discharge into'a single producer chamber, thereby furnishing a sufficient quantity of hot carbonized material to give any desired capacity for the producer. Because of the character of the material discharged by. the carbonizing chamber operation of large sizeproducer gas units is practicable. Ordinarily the flow of gases through the carbonizing chamher is induced that is is produced by a suction device at some point, and proper valve arrangements at this point facilitate materially the establishment of the uniform and regulable carbonization ll Want. In using a plurality of carbonizing chambers feeding a sing e producer chamber, admission of airto the several carbonizing chambers is through a corresponding numberof ports properly arranged for even distribution oi tlame and producer gas to each of the reaction chambers. Hoiveven-With individual control of the suction in each chamber irregularities in this respect are not serious. Any desired disposition may be made of the producer gas which is not used in the carbonizingr chamber to utilize its sensible heat and fuel value. Gas leaves the producer chamber in the present invention at a high temperature. "Where such a place of use is a boiler plant, the distilling and gasiiying plant may be made a part of the boiler setting.

What l claimisr- 1. In the low temperature distillation and carbonization and gasilication of solid fuel containing volatile matter. the process which comprises establishing and maintaining a substantially horizontal moving column of material to be carbonized. impinging aflame of burning gases on one end of said column, passing" said burning: gases through the material in countercurrent, maintaining the resaaar end a flame of burning gas with a movement of flame gases through the column in countercurrent to the solid material therein, dropping hot carbonized material from the flame-impinged discharge face into a Vertical accun'iulation, gasifying said vertical accumulation by an updraft current passed therethrough and collecting gases coming from said moving column and from said accumulation.

3. In the distillation and carbonization' and gasiti-eation of solid fuel containing volatile matter with the formation of valuable byproducts, the process which comprises carbonizing a substantially horizontal body of fuel by impingement on one end thereof of a flame of burning gases, simultaneously establishing and maintaining a moving column of the material to be carbonized, maintaining the feed end at relatively low temperature and the discharge end at a high temperature with an intermediate zone where carbonizing conditions occur, temperatures at the hot end being maintained by directing a flame of burning gases thereinto, thereby setting up and maintaining a zone of pre-heat at the discharge endand also a zone of reduction where the flame gases react with incandescent carbon and are changed from combustion gases to combustible gases, dropping the hot carbonized material from the flame impinged discharge face of the column into a vertical accumulation within a gasification chamber, gasifying the carbon residue by passing a suitable draft current and discharging the ash from the gasification chamber, and collecting and recovering the gaseous, volatile and liquid by-products resulting in the carbonizing and gasifying zone.

5. In the distillation and carbonization and gasification of solid fuels containing volatile matter, the-process which comprises establishing and maintaining a positively moving substantially horizontal column of material to be carbonized, adding freshmaterial to one end, directing a flame of burning gases through the material from the opmaterial, thereby setting up and maintaining a relatively stationary mid-zone of carbonization and distillation in the column, the temperature within the body decreasing from a maximum adjacent the point of entry of burning gases to a minimumadjacent the end at which fresh material isintroduced, with an intermediate mid-zone temperature depending on the reaction maintained in the mid-zone, dropping the hot carbonized material from the flame end of the column into a gasiflcation chamber, gasifying the carbonized material by passing a draft current therethrough, using gases thus formed to maintain the flame and the zone of carboniz-ation, discharging the ash from the gasification chamber, and collectin and recovering the gaseous volatilerand liquid byproducts formed in the carbonizing and gasifying zones.

- 6. In the utilization of solid fuel containing volatile matter, the process which comprises establishing and maintaining a short, moving, substantially horizontal pervious column of fuel having a feed end at a relatively low temperature and a discharge end at a relatively higher temperature; said relatively higher temperature being substantially that of a flame of burning gases, with an lntermediate carbonization zone between the feed end and the discharge end, the

temperature of the carbonization zone being determined by the heat evolved by the reactions therein and the temperature gradient from the discharge end to the feed end; supplying the discharge end with a draft of flaming producer gas to maintain flame temperature thereon, conducting the flame gases through the column whereby a short producer zone is created near the dischargeend, so discharging the hot material as to form a bed and passing a draft current therethrough to form producer gas, hot producer gas therefrom being used to furnish said flame. v

In testimony whereof, I aflixed my signature.

'GEORGE w. WALLACE.

have hereunto

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