EP0404881B1 - Gas generator for combustion - Google Patents

Abstract

In a firing and drying furnace with fuel gas generators for ceramic mouldings and green bricks, a firing and drying furnace in the form of a tunnel is provided to heat them while facilitating economical gas generation and, in order for the exhaust gases from combustion to meet the statutory purity standards, a secondary air feed pipe is inserted in each feed line (5) carrying producer-gas freed of all residues produced in a gas generator to exhaust gas burners. The suitable producer-gas is fed manually or mechanically with the aid of sensors which respond to the change in the furnace temperature and adjust the quantity of producer-gas supplied. The producer-gas is preferably fed in at low pressure in a regulating region with waste gas burners (3, 4) and controlled by the furnace temperature as described above.

Description

The invention relates to a fuel gas generator according to the preamble of claim 1.

Fuel gas generators of this type are used together with a kiln and a drying oven for ceramic moldings, in particular brick moldings. The kilns for the moldings, which are generally designed as tunnel ovens, are always preceded by drying ovens or dryers in order to remove the water contained in the freshly pressed molded bodies.

The design of the tunnel furnaces and the design of the devices are adapted to the type of energy used to generate the process heat. As a rule, the fire zone of such a tunnel kiln comprises a number of staggered rows of stoves arranged in the stoves' vault, with each row of stoves having a number of staggered holes with burners. Two or more rows of stoves are usually combined into control zones that can be controlled independently of one another.

The operation of such systems, in particular of brick factories, requires an extraordinarily high amount of energy for the drive of the conveying and molding machines and above all for the process heat in ovens and dryers. The possibility of reducing the cost of process heat is often decisive as to whether such a system can still be used to cover costs.

Of crucial importance for the trouble-free operation of the kiln and drying furnace is the delivery of a generator lean gas that meets these technological requirements. Of the main generator-carburetor systems, the mostly preferred countercurrent and cocurrent carburettors, the latter is preferred here for the generation of the lean gas. The generator gas obtained according to the principle of countercurrent gasification can only be used for the subsequent direct combustion, since it contains a high content of difficult liquid pyrolysis products such as tar, phenol and the like, which condense at temperatures below 400 ° C.

In the preferred principle with descending gasification, the drying and pyrolysis zones are formed in the upper part of the reactor. In deviation from the counterflow principle, the air is fed in from above immediately after the pyrolysis zone. The combustion generates the necessary temperatures to split the descending smoldering products from the pyrolysis zone into easily combustible gases. The remaining volatile substances are also gasified from the charcoal. As a result, no tar products get into the subsequent reduction zone.

With regard to the technological peculiarities of these gasification processes, reference is made to "wood gasification", Willy Bierter / Christian Gaegauf, Karlsruhe, 1982, p. 52 ff. A fuel gas generator of the type mentioned at the outset can be found in DE-PS 32 39 624. The fuel gas generator described in this patent has a shaft with essentially cylindrical inner dimensions. The shaft consists of several ring-shaped sheet metal armor with fire-resistant lining, which are separated from one another by disc-like intermediate layers, the lower edge of the shaft being supported on a bracket. The annular bodies formed by the sheet metal armor should be secured against one another by screwing or in some other way. The loading column in the known fuel gas generator rests with its full weight on the wide-area rotating grate, so that it is considerably stressed becomes. The gas is extracted via lateral pipe sockets in the stove ceramic.

The invention has for its object to provide a fuel gas generator of the type mentioned, which enables extremely inexpensive gas generation and whose combustion gases do not only meet the highest applicable requirements for exhaust gas purity (TA-Luft), but fall below them.

This object is achieved by the features specified in the characterizing part of claim 1.

The previously comminuted fuel, eg. B. wood, brought into the feed lock, the upper slider of the lock is open, the lower is closed. The fill level control of the feed chamber of the lock ends this process after the set fill level has been reached. The upper slide then closes the feed lock. If the fill level in the preheating zone falls below the set level, the next level is initiated by the fill level control. The fire in the constriction of the reactor shaft, also known as the firebox, has the task of forming a layer of charcoal. This combustion generates the necessary temperature to split the descending carbonization products from the pyrolysis zone into easily combustible gases. The central supply of the combustion air in the constriction guarantees the temperature necessary for the separation of the gases.

The reduction zone is closed at the bottom by a new design of the firebox. An annular grate element is created by means of the counter cone entering the area of the firebox from below. An annular passage for the ashes is formed, the cross section of which is variable.

The ash produced in very small quantities is collected in the ash room and transported away. Part of this ash can be mixed into the clay for the brick production as a porizing agent.

An important special feature of the fuel gas generator according to the invention is the design of the firebox, which also acts as a rust element. It is formed from a conical constriction which narrows from top to bottom and a conical constriction which adjoins this from the bottom up. According to an additional feature, a counter cone can be inserted more or less concentrically into the conical constriction of the firebox, which narrows from bottom to top, thereby producing an annular passage of variable cross-section which forms the grate element. It is provided that the counter cone is arranged at the upper end of a lifting rod which is guided centrally in the reactor shaft and is equipped with a lifting drive, and further that the counter cone is rotatable and its lifting rod is additionally equipped with a rotary drive.

This configuration makes it possible to adapt the grate element formed by the firebox to the nature and grain size of the feed material and to influence the process control. By means of the adjustable counter-cone, the annular passage between the cone and the conical surface of the firebox is changed, whereby the throughput speed can also be controlled.

Another essential feature can be seen in the gas-tight feed lock according to claim 2, which consists of two mutually openable and closable, arranged in the shaft head above and below a loading container, which closes this downwards towards the reactor shaft and upwards to an upstream fuel delivery device , there are sealed flat or rotary valves in their guides. In conjunction with the gas-tight ash chamber lock, which is constructed in a technical and functional manner like the loading lock, it is ensured that the entire reactor shaft, except for the area where the lean gas is drawn off, is absolutely gas-tight.

In order to enable an optimal process course adapted to the respective feed material, the gas generator according to the invention is equipped with a number of measuring, display and control devices.

The supply and loading of the generator with feed must be controlled according to the progress of the process. For this purpose, at least one fill level measuring and display device is arranged in the feed chamber and in the area of the preheating zone in the reactor shaft according to claim 6, by means of which the feed rate of the feed device can be influenced and the feed lock can be controlled via a control device. Above all, two or more level and display devices can be arranged in the reactor shaft to control the fill level in order to detect the upper and lower fill level limit. By means of these measuring devices, the periodic loading and their respective loading quantity as well as the functions of a loading conveyor and the slider of the loading lock required for this can be remotely controlled.

Furthermore, according to the further invention, thermocouples for temperature control in the preheating, the degassing and the oxidation zone are arranged above and in the area of the fire box, the air quantity supply being able to be influenced by changes in cross section of the air openings by means of the measurement results of the thermocouples. Furthermore, it can also be provided that the fan suction power in the to the lean gas discharge line can be influenced by means of measurement results of the thermocouples. In addition, it is also possible to design the control system in such a way that the oxygen content of the reaction air supply can be influenced by means of the measurement results of the thermocouples, depending on the feedstock used and the desired process.

The conception of this gas generator as a whole enables its versatile application and application possibilities in a way that was previously unknown. A wide variety of organic or fossil or inorganic materials can be used in a wide range of grain sizes to produce a lean gas with very good calorific value. What is essential with this generator concept is above all that the combustion of the lean gas generated is particularly environmentally compatible. Measurements by a recognized institute for environmental analysis have shown that the exhaust gas had the following measurements:
Gas chromatographic measurements: oxygen 15.5 vol.% nitrogen 78.3 vol.% methane <0.03 vol.% Carbon dioxide 6.2 vol.% hydrogen <0.01 vol.%

These average values were obtained in normal operation about two hours after the generator was ignited. As a further measurement result it could be determined:
Formaldehyde concentration <0.01 vol.%

With these exhaust gas values, the limit values of the air pollution control regulations (TA Luft) can be undercut.

According to the further invention, the structural features of the fuel gas generator are of great importance, which, according to claim 5, consist in the shaft casing of the generator with the gas-tight generator shaft and the material loading devices being suspended in a frame which consists of frame stands and frame beams connecting them . It is provided that the generator shaft casing are attached to the frame cross members by means of flexible brackets, and further that the frame consisting of the frame stands and the frame cross members is completely surrounded by a frame casing, only the air openings in the area of the Serve foundations for air access.

Of particular advantage is the design that, according to claim 3, an annular space between the frame casing and the shaft casing serves for the reaction supply air supply and is connected to the riser pipe and the air introduction pipe. This ensures that the sucked-in reaction air sweeps along the hot shaft casing and is thereby heated. A further advantageous thermal effect results from the measure according to claim 4. Thereafter, between the shaft casing and the upper and lower part of the reactor shaft there is a vertical gas-tight cylindrical cavity through which the weak gas emerging at the lower end of the reactor shaft draws upwards and into the weak gas manifolds connected to the cavity. This arrangement and design ensures that the lean gas emerging downward in the area of the lower edge of the reactor shaft draws upward in this cylindrical cavity and thereby releases part of its heat to the reactor shaft wall in the upper area of the reactor shaft, ie in the area of the preheating zone Preheating is improved and cooled at the same time.

These construction measures improve the thermal efficiency and therefore not only the heat balance, but also a better carbonization and degassing of the feed material, with the result that an energy-rich lean gas and a lower residue content is produced.

Further features and advantages of the invention result from the exemplary embodiment shown in the drawing and explained in more detail below.

Fig. 1

einen vertikalen Längsschnitt durch einen Brenngaserzeuger;

Fig. 2

einen Teilschnitt gem. Fig. 1.

Show it

Fig. 1

a vertical longitudinal section through a fuel gas generator;

Fig. 2

a partial section acc. Fig. 1.

The fuel gas generator 41 is designed as a gas generator and is suspended in a frame, which in the exemplary embodiment consists of four frame stands 42 which are connected to one another at their upper end by frame cross members 45. A bracket 46 is attached to the frame cross members 45, in which the cylindrical shaft casing 47 of the gas generator is fastened, the larger part of the shaft casing hanging downward in the frame 42, while a shorter piece of the shaft casing holds the frame cross members 45 towering above. This ensures that the shaft casing can move up and down without constraint.

The shaft casing 47 is closed at the bottom by a base plate 48 and at the top by a head plate 49, both of which are annular.

The shaft head 50 is placed on the upper head plate 49 and is closed at the top by a gas-tight loading lock; This consists of a flat slide 52, 53 arranged below and above a loading chamber 51, which are sealed in their guides. Above the upper flat slide 53, a feed feeder 54, not shown, is provided. The material falls into the loading chamber 51 when the upper flat slide 53 is open. This is equipped with a fill level measuring and display device 89. In this way, the feed supply 54 can be influenced and the feed lock controlled via a control device (not shown). After closing the upper flat slide 53, the lower flat slide 52 is opened and the material falls into the generator shaft 55, 57 located underneath. The upper shaft part 55 is connected to the upper top plate 49 in a hanging manner, provided with an inner lining and serves as a preheating and degassing zone 56 for the filled material. In the area of this zone, a fill level measuring device 88 is arranged, which can also be combined with a temperature sensor. As a result, the course of the process, in particular the throughput rate and also the process temperature, can be monitored and, if necessary, influenced.

Below the preheating and degassing zone is a lower shaft part 57, which is equipped with a highly refractory lining 58 and has a fire box 65. This is formed from a conical constriction 59 which narrows from top to bottom and a conical constriction 60 which adjoins this from bottom to top. The oxidation and reduction zones 70 are formed in this area.

A cylindrical cavity 66 extends between the shaft casing 47 and the upper and lower shaft parts 55 and 57 of smaller outside diameter, which extends from the lower edge of the lower shaft part 57 to the head plate 49. In this cavity 66, the lean gas produced and drawn down at 64 pulls upwards and heats the material present in the preheating zone 56, after which it passes through the lean gas collecting pipes 67 and the ring line 68 into the lean gas discharge line 77.

The reaction air or an inert gas is fed into the reactor shaft 55, 57 through an air inlet pipe 63, which runs centrally in the vertical axis A of the reactor 41 and extends down to the starting area of the firebox 65 and is connected to the riser pipe 62. The reaction air is sucked into the area of the openings 44, which are left free in the frame casing 43 surrounding the frame stand 42 in the area of the foundation. Between this casing 43 and the cylindrical manhole casing 47, an annular space 61 is created, through which the sucked-in air rises, heats up and enters the riser 62.

It is essential for the process control in the generator that the counter-cone 71, which can be inserted into the fire box 65 from below, sits concentrically to the vertical axis at the upper end of a lifting rod 72, which is sealed and can be raised and lowered in a vertical guide 73. The lower part of the vertical guide 73 is designed in a manner not shown as a hydraulic lifting cylinder. The hydraulic drive consists of the motor 84, the hydraulic pump 82 and the expansion tank 83. Furthermore, a rotary drive with a motor 78 is arranged such that it acts directly on the lifting rod 72.

The counter cone 71 can be adjusted so that the conical ring-shaped passage 69 is larger or smaller. The combination of firebox 65 with counter cone 71 acts as an adjustable grate element which can be adapted to the nature, in particular the grain size, of the feed material. The ash parts fall through the passage 69 and reach the ash chamber 76 located above the ash chamber lock 91, 92, 93, where it accumulates on the upper flat slide 92. The ash chamber 76 has an inclined surface 74 which is penetrated by the vertical guide 73 of the lifting rod 72 and is sealed off from it by the stuffing box 75. Furthermore, this inclined surface is steep enough and coated in such a way that ash bridges do not occur.

The ash chamber lock consists of the upper ash chamber flat slide 92 and the lower ash room flat slide 93, between which the ash chamber 91 can be closed airtight upwards and downwards. The ash is emptied periodically - like the material loading - always one The amount of ash drained from the ash chamber 76 into the ash chamber 91 and from there by opening and closing the lower flat ash slide valve 93 into the collection and transport container 94.

A sensor 87 is arranged in the ash chamber, which reports a certain fill level and initiates the sluicing of this amount of ash. After a larger ash element has been passed through and accumulated in the transport container 94, the latter is removed and exchanged for an empty container.

Claims (6)

1. A fuel gas generator for generating lean gas by gasification of organic solids in lump form, such as wood, peat, fossil fuels, or inorganic substances, in a reactor shaft which is provided with a refractory lining and which, for the purpose of supporting the downwardly travelling charge column and its reaction products formed by de-gasification, is narrowed in the central zone by walls, which form coaxial truncated cones, to form a firebox having a diameter of about two-thirds to one-quarter of the shaft inside diameter, and having a fuel charging means in the form of a gas-tight charging lock, and having a central reaction air supply in the shaft head on the vertical axis of the reactor shaft, and, in layers, a pre-heating zone, degasification zone, oxidation zone and reduction zone and, disposed in the region of the latter, lean gas discharge apertures with at least one lean gas discharge line connected thereto, further comprising a circular or annular grate element closing the bottom of the reduction zone and with an ash chamber therebeneath, and having an ash discharge means in the form of a gas-tight ash space lock, characterised in that the circular or annular grate element projects into the downwardly widening truncated cone (60) in the form of a coaxial companion cone (71) axially slidable in its vertical position and together with the truncated cone (60) forms an annular conical gap of variable cross-section as a passage (69), the companion cone (71) being mounted on a raisable, lowerable and rotatable reciprocating rod (72) provided with a reciprocating drive (81; 82; 83; 84) and a rotary drive (78), in such manner that the whole performs the function of the grate with the ash discharge means and lean gas discharge, the lean gas not leaving the reactor shaft (55, 57) until it has flowed through the grate element (60, 69, 71).
2. A fuel gas generator according to Claim 1, characterised in that the gas-tight charging lock (51, 52, 53) consists of two flat slide valves (52, 53) which are disposed in the shaft head (50) above and beneath a charging container (51) and which close the same off at the bottom from the reactor shaft (55) and at the top from a preceding fuel conveying device (54), and the gas-tight ash space lock (91, 92, 93) which closes off an ash space (91) and is controlled by a level measuring and indicating device (87) in the ash chamber (76) also consists of two flat slide valves (92, 93), which flat slide valves are sealed in their guides and can be alternately opened and closed.
3. A fuel gas generator according to Claim 1, characterised in that an annular space (61) is provided coaxially to the reactor shaft (55, 57) between an outer jacket (43) and an intermediate jacket (47), and serves for the supply and pre-heating of the reaction air and is connected to a riser pipe (62) and a central air introduction pipe (63).
4. A fuel gas generator according to Claim 1, characterised in that a gas-tight annular space (66) is provided between an intermediate jacket (47) and the outer wall of the reactor shaft (55, 57) and coaxially to the latter and serves for guidance, cooling and heat yield to the charge, of the lean gas leaving at the bottom end of the bottom reactor shaft (57) and its introduction into the connected lean gas collecting pipe (67).
5. A fuel gas generator according to Claim 1, characterised in that the intermediate jacket (47) of the generator (41) together with the gas-tight reactor shaft (55, 57) and the material charging devices is suspended by flexible mountings (46) from frame crossmembers (45), the latter bearing on vertical radially disposed frame uprights (42), and in that the frame thus formed is completely surrounded by an outer jacket (43), only the apertures (44) which serve for the access of air being left free in the foundation zone.
6. A fuel gas generator according to Claim 1, characterised in that at least one level measuring and indicating device (89; 88) is disposed respectively in the charging chamber (51) and in the region of the pre-heating zone (56) in the reactor shaft (55), whereby, by means of a controller, the delivery capacity of the charging device (54) is influenced and the charging lock (52, 53) controlled, and in that thermocouples are disposed above and in the region of the firebox (65) for temperature monitoring in the pre-heating, degasification and oxidation zones, the measurements of the thermocouples controlling and regulating the supply of reaction air by cross-sectional change of the apertures (44) and the oxygen component of the supplied reaction air or of the inert gas and the fan throughflow in the suction line (77) of the lean gas discharge.

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