DE974655C - Method and device for degassing fine-grain or dust-like fuels - Google Patents

Description

Method and device for degassing fine-grained or dusty Fuels It is known to use pulverulent fuels in externally heated retorts to be heated in the absence of air in order to generate the fuels with degassing gas, To coke tar and coke. The fuels can rest in the retorts, but they can also be mechanical or by their own gravity or by a carrier gas moved in or through the retort. It is also known to be powdery To heat and coke fuels directly with hot gases, be it in the Float or in a bed stirred up by the hot gas.

All of these known processes have certain deficiencies dormant storage of the pulverulent fuels to be treated in too little specific Performance, with moving goods in the strong entrainment of dust into the withdrawing material Degassing material and also in the dilution of the degassing gas by the carrier gas lie. Other known methods achieve high-temperature gases by the fact that they the heat required to heat the fuel from hot heat transfer media bring in. So were through several treatment rooms one below the other guided inert coarse-grained or lumpy shaped heat carriers, which in the top Treatment room were heated with fire gases, coke or coal were added. The mixture got into a water gas generator in which steam was blown through the mixture, to be cooled with air in a subsequent room. From the chilled The fine was sieved off and the coarse was reused as a heat transfer medium brought back to the uppermost treatment room.

Another water gas generation process used as fuel Coarse coke that migrated down a gas generator shaft. With the for the water gas generation required Water vapor was through the Coarse coke blown fine-grained heat transfer medium from an inert Material and small amounts of fine-grain fuel passed. Above the pillar of coarse-grained coke, the heat transfer media then formed one like a fluidized bed moving layer from which they are led down into a furnace. The fuel, which was finely distributed in the heat transfer media, was released into this by air blown in burned. As a result, the heat transfer media were heated up so that they could be used when they were reintroduced in the water gas generator in these the heat required for gas generation brought in. For the degassing of fine-grained material, however, these processes are used not suitable because fine-grained fuel settles on the surface of the hot coarse-grained heat carrier sets, causing disruptions in the further movement of the Mixture of heat transfer media and material to be degassed enter, which is an orderly Would make degassing processes impossible. In addition, in contrast to Gasification, when degassing coke or coke-like residues, for their processing the known gasification processes working with heat carriers do not provide any clues can give.

Methods are also known in which solid heat carriers transfer the heat for degassing. So coarse-grained or lumpy solid heat carriers followed their heating mixed with the fine-grain fuel in a separate room and the mixture is passed through a rotating drum serving as a degassing space. That Process was used for degassing baking coal for the production of mainly fine coke. After the coke had been separated off, the heat transfer media were raised and heated and returned to the degassing (Adolf Thau, "Die Schwelung von Braun- und Steinkohle", Halle 1927, p. 685 ff.).

Another known method is to use coke as a heat transfer medium used. This coke was heated in a grate furnace and then in a degassing room introduced, with a bunker filled with hot coke and the bunker discharge device should prevent the passage of gas from the degassing room into the furnace, but this could only be unsuccessful. When entering the degassing room the fuel to be degassed is mixed with the hot coke. The degassing gases that escaping from the free surface of the degassing space were considered to be heat-producing Gas used, while that introduced into the degassing space and that newly formed in it Coke discharged below and brought to the grate furnace for reuse became. Most of the fuel ash was carried away with the hot gases from the grate furnace (German patent 549 554).

It is also known to use a two-stage degassing of fuels Carry out the help of heat carriers. The hot heat transfer media got into one Manhole. The fuels to be processed were added to them. The temperature the heat transfer medium was chosen so that the fuel is degassed at low temperatures revealed. The resulting gases were drawn off separately, and the Fuel on its way through the shaft into a high temperature distillation zone one, in which hot water gas that was generated in a deeper zone of the shaft, was passed through the mixture of fuel and heat transfer medium. Below the zone In which the water gas was generated, a combustion zone was provided in the Air was introduced and which served to provide all of the necessary for the procedure Generate heat. Below the combustion zone, the hot one was moving downwards Gut'by blown water vapor on for its reuse as a heat transfer medium brought to appropriate temperature in the cryogenic distillation zone while the heated steam was used to generate water gas.

Fine-grained fuel is already used for the purpose of degassing by means of fine-grained fuel solid heat transfer medium has been heated directly. Here, fine oil shale was heated with fine slate residue is blown into a retort by means of steam and passed through there this held in agitated bulk. The one heated in a separate room fine slate residue provides the heat for degassing. This took place in one special room in which the hot slate residue is conveyed by means of pneumatic conveying arrived (E.V. Murphree, "Gas, Coal, Oil Shale," The Oil and Gas Journal of 8.4. 1948, p. 69).

These known degassing processes had special facilities in the form of furnaces or gasification rooms required for the heat transfer medium to bring to the desired temperature. Also made the promotion, in particular hot heat carrier, difficulties causing high mechanical wear Conveyor and also caused significant costs, especially if it was the degassing of baking fuels required for such gasification processes come first and foremost. Because this involved the circulation of very considerable amounts of heat transfer medium required in order to prevent disturbances caused by baking symptoms as far as possible.

The method according to the invention works with fine-grained or dusty solid heat carriers, uses their favorable heat transfer when degassing fine-grained Or dusty fuels or the like. And leads to a degassing gas that largely dust-free, without the aforementioned disadvantages of the known processes must be accepted.

According to the invention, the degassing of fine-grained or dust-like Fuel with the fine-grained or dusty degassing residues in the circuit as a heat transfer medium, which after heating with the material in a closed bed down a degassing chamber while the generated gas is on upper Part of this space is withdrawn and whereupon the heat transfer medium with the degassing residue withdrawn from the lower part of the degassing chamber and pneumatically by means of air in a collecting space are promoted, carried out so that the serving as a heat transfer medium Degassing residue of about 0.1 to 1 mm grain size during pneumatic conveyance Partially burned in a vertical conveyor line and thus back to 60o is heated up to 120o ° C and that the conveying gas together with the finest portion the heat transfer medium is discharged from the collecting tank, whereupon three to twenty times as much, expediently nine to twelve times the amount of the heated heat transfer medium, based on the fuel to be degassed is introduced into the degassing space. The vertical Conveyor line has compared to known pneumatic conveyor lines, in which, however not a simultaneous Rufheiz the heat carrier takes place, the advantage that with the required high flow velocities and those occurring during call heating high temperatures, corrosion and erosion of the conveyor line largely avoided will.

Depending on the switched on temperature conditions and the occurring The reaction rates here lead to a different reaction rate Ratio of carbon dioxide to carbon oxide in the reaction gases of the conveying air.

The collecting tank in which the heat transfer medium after its call heating of the reaction gases of the conveying air are separated, advantageously consists of one Coarse separator, e.g. B. in the form of a calming chamber or a simple cyclone, so that the finest fractions are only separated to a limited extent and removed from the heat transfer circuit be discharged with the reaction gases.

The grain size of the circulating heat transfer medium is advantageously between about o, 1 and i, o min diameter. If the grain size is finer than 0.1 mm, the separation is from the conveyed gases is usually more difficult and requires fine separators with higher Gas velocity and thus due to the required pressure loss with a high expenditure of energy work. On the other hand, the floating speed increases with the grain diameter on, so that the speeds of the pneumatic conveying and thus the Energy expenditure and wear increase with the grain diameter and significantly larger diameter than i, o mm the cost of the process in uneconomical Way can rise. The introduced fuel also expediently has a maximum grain size of i, o mm. But it can also be a little coarser. because of the degassing process a shrinkage or reduction in the specific weight of the grain occurs. The advantageous grain size of the fuel is easy to achieve by sieving, or, when delivering coarse grain, can be easily produced by simply chopping it up and does not require increased grinding effort, as is often the case with normal dust firing or dust gasification occurs because of the conveyance after a very finely ground dust.

The circulation of the heat transfer medium is regulated so that the degassing space of the space for heating and pneumatic conveying on the one hand and the collecting and separator, on the other hand, by pouring the mixture of fuel and heat transfer medium is shut off. This is z. B. achieved that below of the degassing chamber there is a throttle device which is adjustable The amount of the mixture of heat transfer medium and residue emerges from the degassing chamber leaves. This regulates the amount of the circulating heat transfer medium at the same time. Especially if it is ensured that the mixture of heat carrier and fuel is introduced into the degassing space in a closed bed, causes the throttling also that there is a closed column in the degassing space. The amount of this Gutsäule is determined, for example, by an overflow, by the excess Heat transfer medium is discharged before the supply of the new fuel to be gasified. When passing through the degassing space, the heat transfer medium has around the degassing residue increased. After the call heating and pneumatic conveying, the fine-grained portion becomes partly separated. The heated heat transfer medium then forms together with the fresh abandoned fuel the bed, and the excess flows through the overflow away. There is no excess left because the proportion of fine dust that escapes is greater than access to degassing residues, it will be useful for safe maintenance a closed bed, additional heat transfer medium is introduced into the circuit. This can be done, for example, together with the fuel to be degassed. the Closed column of goods from the throttle device to the overflow prevents gas flow between the gas space of the degassing space on the one hand and the delivery space or separation space on the other hand. The pressure in the degassing space is advantageously constant Depending on the pressure in the pneumatic conveying or in the separator for the circulating heat carrier from the reaction gases of the promotion, where appropriate a suitable overpressure is maintained in the separation space opposite the discharge space will.

The amount of conveying air determines the heat that your heat transfer medium supplied by reaction of the conveying air with the carbon in the residue will. The air required for the combustion is not sufficient for the promotion of the heat transfer medium to be carried out, then it is advisable to use others, not in the reaction participating gases added, e.g. B. combustion gases or nitrogen. Should the heat transfer medium drawn off at the overflow does not contain any residues with significant carbon contents contain, the conveying air can also contain water vapor, if necessary Mix in carbon dioxide or both. This does not affect the call heating more consumed Carbon of the residue to carbon oxide and hydrogen implemented. This is particularly beneficial when you have the conveying gases after leaving the pneumatic conveying and the separation of the circulating heat transfer medium. These can, for example, be fed directly to a downstream steam boiler. Second air is blown into the steam boiler to remove the combustible parts of the To burn off reaction gases and the fine dust carried along.

This embodiment of the method has the advantage that the supplied Fuel to be degassed completely in concentrated degassing gas, in lean gas and fine dust is transferred in a highly heated form. The procedure can be thus advantageous with dust firing, e.g. B. in steam boilers, combine, re-concentrated Degassing gas, e.g. B. for town gas purposes, and to produce liquid hydrocarbons and the remaining coke in lean gas and dust of the finest form at high temperature to convert in this open-minded way with great advantage for the combustion can be used in steam boilers. However, the process can also be carried out with large Success z. B. in connection with roasting and sintering furnaces or other metallurgical Procedures are used. The exploitation of the tangible and chemically bound Heat from the conveying gases and the fine dust carried along is also expedient in a steam boiler or the like, if the carbon of the degassing residue is not is completely gasified, but part of it as a granular residue on the overflow pipe is deducted.

In the event that the fine dust in the combustion of the reaction gases in your downstream steam boiler or in other facilities, since he possibly z. B. is prone to deposits and causes severe wear the gases also through fine separators, e.g. B. in the form of highly effective multiclones, are largely dedusted. The fine dedusting makes it possible to use higher gas velocities to be used in a steam boiler or, for example, in a gas turbine. The departed one fine dust is then added to the heat transfer circuit or other uses, z. B. a separate steam boiler, a sintering belt od. Like., Fed to the to utilize the carbon contained in it.

The degassing can be done either at high, medium or low Temperatures are carried out. This depends mainly on the desired Nature of the degassing products. Used at a high degassing temperature from Z. B. worked zooo ° C, the tar released from the degassing material is largely decomposed and converted into gas and the volatile constituents of the material to be degassed largely expelled. Only a small amount of coke remains as a residue. If you degassed, however, at a low temperature of z. B. 600 ° C, the dated remains Degassed tar largely preserved and goes with the degassing gas out of the degassing space. The amount of degassing gas is less than that of high-temperature degassing, but generally has a higher calorific value; also the amount of residue is greater, as part of the volatile constituents remains in the coke.

In the event that the most complete recovery possible of the in the fuel contained tar is desired, especially when using low degassing temperatures and avoiding decomposition can be achieved, discharging small amounts Steam or even gas in the degassing space can be advantageous in order to get through the flushing effect to achieve faster removal of the tar vapors and thus tar decomposition to prevent if possible. Care must be taken that the whirling up of the Dust is avoided as possible.

From a thermal economic point of view, it is advantageous to use the air for the pneumatic Promotion of the circulating heat carrier and / or the freshly supplied fuel to be heated beforehand. It is advantageous to use the heat of the hot exhaust gas or the reaction gases after the deposition of the circulating heat carrier for the To use heating of the air and / or the fuel, the fuel being predried and also, if necessary, its ability to be baked beforehand by means of a thermal treatment can be eliminated.

The fresh to be added, to be degassed. Fuel becomes appropriate mixed evenly and intimately with the heated heat transfer medium. this happens advantageous in a device, which from the heated heat carrier in a thin stream and is flowed through at a correspondingly greater speed, while at the same time in The fresh fuel is fed into the electricity in an even and steady manner will. By applying three to twenty times, preferably nine to twelve times Weight amount of heat transfer medium compared to the amount of fresh fuel the individual fuel grain is well coated and quickly heated up. As a result of emaciation of the fuel with the circulating heat carrier, the movement at the inlet into the Degassing space and the rapid heating, there is no major caking and also not for cake formation with baking fuels, so that all fuels can be processed regardless of their baking capacity. Any caking less individual grains with each other does no harm and is predominantly used in the pneumatic Delivery line destroyed.

The process according to the invention is advantageously carried out in one apparatus carried out, in the case of a degassing space and with this through a preferably connected narrow shaft for the supply of the heated heat transfer medium the separation room for this is located. The conveyor line for pneumatic conveying is preferably placed in the interior of the device, so that it opens the degassing space, the supply channel for the mixture of heat transfer medium and to be degassed fuel and runs through the separation space for the heat transfer medium. However, it is also possible to arrange the conveying line outside the degassing temperature.

In the figure, a device suitable for the new method is shown as an example and schematically. i represents a vertical, angular or round shaft in which the degassing is carried out. 2 is the pneumatic conveying line in which the heat transfer medium is conveyed up while being heated at the same time. 3 is the coarse separator for separating the heated heat carrier from the gases, which is shown here in the form of a calming chamber. 16 shows the sheet metal jacket surrounding the device, 18 the refractory lining. The separator 3 is located above the degassing space i and is connected to i by a narrow channel 4, in which the heated heat transfer medium has a temperature of about 600 to 1200 ° C , e.g. B. iooo ° C, depending on the requirements, sinks steadily in the room i. The channel q. is shown as an annular space around the conveying path 2, which extends axially through the degassing space i. The channel .4 can also be designed as a closed channel independent of the conveyor line 2.

The fresh fuel is steadily in from a storage container 5 fed into the channel 4., the feed device in the example shown consists of a ring 6 provided with blades and the blades the fuel Press through holes or slits 7 into the channel 4.. The fuel sinks in the mixture with the hot heat transfer medium quickly downwards into the degassing room and gives under Heating from its volatile constituents, which rise in the gas collecting chamber 8 and at 9 from the degassing room z. B. in the cooling, condensation and cleaning equipment known design. The degassed fuel mixed with the cooled fuel Heat transfer medium with a temperature of about .Ioo to iooo ° C, z. B. 700 ° C, depending on the chosen conditions, slowly sinks down in room i and passes over a Throttle device io, which regulates the circulating amount of heat transfer medium, on the side into the lower part of the conveyor line 2. From below the conveyor line 2 Air introduced via line i i, which is advantageously in a superheater 12 a temperature of about zoo to 1000 ° C, e.g. B. 500 ° C, is heated. The heat exchange can here z. B. with the hot degassing gas or the hot combustion gases the conveying air or with any external heat source. The supplied conveying air pulls the heat carrier up in the conveying path 2 and reacts with the carbon carried in the heat transfer medium to form carbonic acid and carbon oxide with appropriate heat generation, so that the heat carrier on the desired temperature between about 600 and 1200 'C, z. B. to iooo ° C, heated will. In the separator 3, the coarser grain size of the heat transfer medium is made up of the reaction gases deposited and returned to the degassing chamber i, so that the cycle of the circulating heat transfer medium closes. The reaction gases flow, still laden with the finer grain of dust, at 13 from the separator 3 and become a steam boiler 1q. supplied in which the reaction gases and dust with the admixture of air (from line 15) are burned completely.

Above the feed device 6-7 for the fuel is on channel q. or on the separator 3, an overflow line 16 is arranged through which the excess heat transfer medium, e.g. B. coke is withdrawn from the circuit. To ensure proper operation, it is necessary that at least small amounts are constantly withdrawn from the overflow line 16, which is expediently checked. The removal of heat transfer medium at the overflow ensures the constant filling of the channel q. with heat transfer medium or fuel, which is necessary to obtain a reliable gas barrier between the degassing chamber i and the separator 3 in connection with a corresponding pressure control in the degassing chamber i and the separator 3 in mutual dependence. If the fuel does not form any excess coke that can be drawn off from the overflow line 16, then, in order to be able to control the presence of the closed bed, heat transfer medium is advantageously additionally fed to the circuit. The heat transfer medium withdrawn from the overflow line 16 can then be fed back into the circuit, for example together with the fuel to be degassed. 1 9 illustrates a i arranged in the lower part of the Entgasungsraumes rust, which through the line: 2o steam can be supplied to flush the space so that the flash gas laden with the Teerdämpfen moves more quickly from the room.

Large exit areas for the gasification gas from the layer i can for example be created by the fact that blinds. Sieves or grids or the like. as boundary walls of the downward migrating mixture of fuel and heat carriers be used. The degassing gas can then be particularly dust-free in one Collect gas space and be discharged.

The method and apparatus according to the invention are particular for the production of gas with a high calorific value, e.g. B. for town gas purposes, or for the subsequent extraction of individual gaseous hydrocarbons from the gas or for the extraction of tar in connection with the production of energy, to which with the reaction gases and the fine gases formed with the conveying air are particularly advantageous Dust used in high temperature is suitable. The simplicity of the The process is based on the construction and rapid operational readiness of the device to be used with particular advantage for covering peak demand. For cover of particular peaks in gas and energy demand that occur at different times, can in addition to a setting of the operating conditions adapted to the required requirements expedient the tar accruing can be used. By redirecting the tar in the degassing space and decomposition of the same can increase the gas yield «-Earth, or by burning the tar, for example in a steam boiler, increase the energy consumption.

The device is of a closed design and can also be used at higher Pressures are operated if this is desired in special cases, e.g. B. for the better Utilization of hot conveying gases occurring under overpressure, for example in Gas turbines, or to generate a degassing gas under positive pressure, which is the cleaning and facilitates the forwarding.

Claims (6)

PATENT CLAIMS: i. Process for degassing fine-grained or dusty Fuels with circulating fine-grained or dust-like heat carriers, after heating with the fuel in a closed bed through a degassing space are led downwards, while the gas generated is withdrawn from the upper part of this space whereupon the heat transfer medium with the degassing residue from the lower part of the degassing chamber withdrawn and pneumatically conveyed by means of air into a collecting space, thereby characterized in that the degassing residue serving as a heat transfer medium from o, i to i in grain size during pneumatic conveying into a @ - vertical @ 2 conveyor l. ',)). `corner Partly burned by the conveying air and thus back to 60o to 120o ° C is heated and that the conveying gas together with the finest proportion of the heat transfer medium is discharged from the collecting container, whereupon three to twenty times, preferably nine to twelve times the amount of the heated heat transfer medium, based on the amount to be degassed Fuel is introduced into the degassing space. 2. The method according to claim i, characterized in that excess heat transfer medium accumulating in the separator Discharged from the circuit above the point of addition for the fresh fuel will. 3. The method according to claims i and 2. characterized in that the Conveying air through heat exchange with the hot degassing gases and / or with the hot conveying gases is heated. 4 .. The method according to claims i to 3, characterized characterized in that the conveying air is combustion gases, nitrogen, carbonic acid or Water vapor can be added. 5. The method according to claims i to 4, characterized characterized in that the closure of the degassing space against the space of the promotion and heating of the heat transfer medium and the space in which the heat transfer medium from the reaction gases the conveying air is separated, is effected by columns of heat transfer media. 6. Device for carrying out the method according to claims i to 5, characterized by a degassing space (i), a vertical pneumatic conveying line (2) and a higher than the degassing space separating space (3), which is through a narrow channel (4) with is connected to the degassing chamber. Considered publications: German Patent Specifications Nos. 549 554, 56-1870, 568 315; French patents 11r. 632,466, 9-16,957; British Patent Nos 305 1o6, 589,516. U.S. Patents 11r. 1 698 3d.5, 1 977 68.a, 2 399 450, 2 405 395, 2.4232 501, 2 432 873, 2 .a.62 8 9 i; Gas-Journal, 1947, p.617; The Oil and Gas Journal, April 4, 1948, pp. 69 and 70; Thau, "Kohlenschwelung", 1938, pp. 86 to 88 and 131 to 133; Handbook of the chem.-techn. Apparate, Vol. 4, 1941, pp. 1644 to 1647.