NO861708L - PYROLYSIS PLANT. - Google Patents

Description

The invention relates to a pyrolysis plant with a carbonization device for carbonization of supplied charge to form a so-called pyrolysis residue and a steam gas, as well as a gas still that is connected to the carbonization device on the gas side and serves to convert the steam gas into a gas distillate that can be used for heating without hesitation.

There are already known pyrolysis plants where waste from households, industry and other industries as well as sewage sludge are subjected to a charring process at 450-500°C under the exclusion of air. In this charring process, there is a volume reduction of the rubbish, resp. the waste, to approx.

10% of its original volume. In addition to the highly carbonaceous pyrolysis residue which can be disposed of without further ado, a steam gas is formed which, due to its share of harmful substances in the known pyrolysis plant, must be cracked in a gas still.

For this purpose, the steam gas is partially burned in a gas still with the addition of small amounts of oxygen and then sucked through a layer of glowing coke. During the partial combustion and the flow through the glowing coke, the molecules in the steam gas's harmful substances are split and the heavy metals bound in the coke in a reduced and water-insoluble form. The distillation gas that flows out of the gas distiller 11a must be cooled and cleaned in a multi-stage washing chain at the known pyrolysis plants before it can be supplied to other consumers. It consists essentially of nitrogen, carbon monoxide, hydrogen

and small proportions of hydrocarbons.

3

Due to its heating value of approx. 5000 kJ per norm m, it can be described as lean gas.

The invention is based on the task of increasing the heating value of the distillation gas as far as possible and at the same time reducing the technical cost for the conversion of the treated waste materials into distillation gas as much as possible.

This task is solved with the features specified in patent claim 1. Favorable designs appear in claims 2-9.

By the fact that the steam gases are no longer partially burned

in the gas still and then drawn through a glowing coke, but directly blown into an iron bath gasifier, the loss in heating value associated with the partial

combustion. The distillation gases that thus flow out of the iron bath gasifier therefore have a significantly higher heating value than those that flow out of the gas still in conventional pyrolysis plants. Furthermore, harmful substance binders can be added to the iron bath, which react with the blown-in steam gas and bind its share of harmful substances to itself. These binders collect in the slag that floats in the iron bath, and can then be removed from this together with the slag. Below this, almost all harmful substances such as sulphur, fluorine and some of the heavy metals are bound to the slag and sluiced out as solids.

In order to prevent freezing of the iron bath, as a favorable further development of the invention, heat energy can be supplied to the molten iron electrically. This can conveniently be done by induction heating.

It is also possible, as a further development of the invention, to add the necessary energy chemically and heat the iron melt either by indirect combustion of a part of the formed distillation gases or by direct supply of ground carbon and oxygen to the iron bath. In yet another favorable design of the invention, the carbon can be supplied to the iron bath as ground coke. However, it would also be possible to use a processed part of the pyrolysis residue from the charring drum for this. In the latter case, the supply of foreign coke can be greatly reduced, possibly even saved entirely.

Further details of the invention will be illustrated by an embodiment shown in the drawing. Fig. 1 shows a previously known pyrolysis plant with a gas still for processing household waste. Fig. 2 shows a pyrolysis plant in accordance with the invention, provided with an iron bath gasifier, and

fig. 3 shows the iron bath carburettor in fig. 2 on average.

From fig. 1 shows the basic structure of a previously known pyrolysis plant 1. In this known pyrolysis plant 1, 2 denotes a waste intake, 3 a deep bunker and 4

a garbage faucet. For shredding the delivered garbage, the garbage crane 4 is assigned a rotary shear 5. To this rotary shear 5

joins a waste transport system 7 which leads to a pre-bunker 6. This opens into a filling chute 8 for a charring drum 10 which rotates about its longitudinal axis 9. The charring drum 10 is then joined on the output side by a dust separator 11 with a downstream residue discharge system 12.

On the gas side, the dust separator 11 is followed by a gas still 13. This essentially consists of a cylindrical housing 14

which is mounted with a slope of approximately 45°, and on the upper side of which a burner head 15 is mounted. In the middle of the gas still 13 is a grate 16 which covers its entire cross-section and carries a cooking layer 17. At the upper end of the cooking layer there is arranged a coke supply line 18 and at the lower end an ash extraction line 19. To the burner head 15

in addition to the steam gas line 20, a further gas line 21 is also connected which supplies an oxygen-containing gas.

A distillation gas line 22 is connected to the still 13 behind the boiling point 17, in the direction of flow of the gases.

which via a heat exchanger system 23 leads to a combined gas cooling and washing chain 24. The heat exchanger system 23 is equipped with a de-heating steam generator 25, a flue gas heat exchanger 26

and an air preheater 27.

The purified gas that leaves the gas cooling and washing chain 24 is here in the embodiment via a clean gas distributor 28 supplied to the various consumers, i.a. also a combustion chamber 29 which is inserted in front of the charring drum 10. The hot gases that leave the combustion chamber 29 flow through the charring drum 10 and come via a hot gas compressor 30 and a heat exchanger 31 to the chimney 32. The heat exchanger 31, which is inserted in the hot gas line 33 in front of the chimney, through-flow of feed water. The feed water line 34 is connected in series with the de-heating steam generator 25 at the heat exchanger plant 23.

Its fresh steam serves, in a way that is not shown in more detail here, for the internal energy supply of the pyrolysis plant 1. Part of the hot gases can via a recirculation line 35 be led back to the flue gas heat exchanger 26 and mixed with the hot air leaving the air preheater 27, fed to the burner head 15 of the gas still 13. In fig. 1, there is also connected to the gas cooling and washing chain 24 a water treatment plant 36 where harmful substances can be removed from the waste water before it is released into the public pipe system.

During operation of such a previously known pyrolysis plant

1, the waste materials, after being divided in the rotor shaft 5, are led via the pre-bunker 6 to the charring drum 10 rotating about its longitudinal axis 9 and, under constant swirling, heated to 450-500°C by means of the countercurrently conducted hot gases from the combustion chamber 29 at the front the charring drum.

The vapor gases that are produced at this temperature, as well as the remaining solid substance, the so-called pyrolysis residue, are separated from each other in the dust separator 11. As a result of the reduced atmosphere that prevails in the charring drum 10, the heavy metals that enter the charring drum are combined with the waste materials, not oxidized, but bound in undissolved form to the charring coke. In this way, the pyrolysis residue, whose volume is approximately 1/10 of the original waste volume, is immediately suitable for disposal. In contrast, the charring gases contain harmful substances, depending on the composition of the rubbish or of the substances fed in to be charred. These can be largely reduced by the subsequent partial combustion in the burner head 15 of the gas still 13 with sub-stoichiometric oxygen-containing gas and during the subsequent flow through the red-hot coke 17

in the gas still 13 is broken down into a gas distillate which essentially contains nitrogen, carbon monoxide, hydrogen and small amounts of hydrocarbons. This gas distillate is behind the heat exchanger plant 23 in which the operating steam, as well as the oxygen-containing gas mixture to be supplied to the burner head 15 of the gas still 13, is heated in the flue gas heat exchanger 26 and the air preheater 27 and led to the multi-stage gas cooling and washing chain 24. There, carbon dioxide as well as chlorine-containing components washed out. The so-called clean gas that flows out of the gas cooling and washing chain 24 can now be supplied to further consumers without hesitation. A portion of this clean gas is combusted with air in the combustion chamber 29 and used for heating the carbonization drum 10. This exhaust gas from the combustion chamber 29, after passing the hot gas compressor 30, emits its residual heat in the heat exchanger 31 to the feed water for

deheat the steam developer 25, before it is discharged through the chimney 32 to the atmosphere.

In such a previously known pyrolysis plant 1, the added waste substances such as garbage, sewage sludge and industrial waste are converted into a pyrolysis residue whose volume is approximately 1/10 of the original substances, and which can be disposed of without hesitation. In addition, on the detour around the gas still 13, a gas distillate is produced which can be used for heating purposes or energy utilization. In addition to the added waste materials, coke is also needed for the gas still 13

and water for the gas cooling and washing chain 24. This water must be freed from harmful substances via a water treatment plant 36 before it can be discharged into the public canal network. The residual coke that has passed through the gas still 13, which has largely burned out, can also be disposed of without hesitation.

In contrast to the known pyrolysis plant 1 shows

fig. 2 a pyrolysis plant 40 in accordance with the invention. This pyrolysis plant also has a garbage intake 41 with a deep bunker 42 and a garbage crane 43 as well as a rotary shear 44 which is fed by the garbage crane and serves to divide the supplied garbage, as well as a garbage transport system 46 that leads to a front bunker 45. And here too there is connected to the pre-bunker 45 a charring drum 48 which rotates about its longitudinal axis 47. To this drum there is the same as in the embodiment in fig. 1 connected a dust separator 49 with a downstream pyrolysis residue discharge system 50 to separate the pyrolysis residues from the steam gas. In contrast to the embodiment in fig. 1, however, there is an iron bath gasifier 52 connected after the dust separator 49 on its gas side under intermediate connection of a vapor gas compressor 51. This iron bath gasifier is in turn followed on the gas side by a heat exchanger system 53.

In the design example, this again contains a de-heating steam developer 54, a flue gas heat exchanger 55 and an air preheater 56. In contrast to the design in fig. 1, the cooled distillation gas that flows out of this heat exchanger system, while saving a washing chain, can be supplied to the consumers directly via a distillation gas compressor 58 connected to the distillation gas line 57. In the embodiment, however, a dust separator 83 is inserted in front of the distillation gas compressor whose dust extraction is connected via a transport line 84 the dust separator 49.

In the pyrolysis plant 40 according to the invention remains

part of the distillation gas burned in a combustion chamber 59

and supplied the hot flue gases via a hot gas line 60 to the charring drum 48. The hot gas line from the charring drum 48 also leads here, before the exit to a chimney 61, to a heat exchanger 62 through which the feed water for the deheating steam developer 54 is led in countercurrent. As can be seen from fig. 2, the vapor gas line 63 opens into a fuel line 64 for the carbon-containing substances such as e.g. finely ground coke (grain size less than 1 mm $) or pyrolysis residues as well as a further line 65 for an oxygen-containing gas mixture out into the bottom of the iron bath gasifier 52. In front of this place, the line 65 opens into a flue gas recirculation line 66

which is led through the heat exchanger 55, and a fresh air line 68 which is led through the air preheater 56 and is equipped with an air compressor 67. In these, for setting the oxygen content of the gas mixture, a throttle valve 69, 70 is built in.

During operation of the pyrolysis plant 40 according to the invention, household or industrial waste or clarification sludge - including old car tires - which is delivered to the garbage intake 41 in fig. 2, divided in the rotor shaft 44 and via the waste transport system 46 supplied to the charring drum 48 which rotates about its longitudinal axis 47. In the dust separator 49 which follows the charring drum, the steam gas is separated from the charring residues and by the steam gas compressor 51 blown into the iron melt 71

at the iron bath carburettor 52 via the steam gas line 63. Via the fuel line 64 which opens into the iron smelter 71, ground coke is supplied there, which may have been mixed with a harmful substance binder in the form of ground limestone or burnt lime, and if necessary may also have been mixed pyrolysis residue. In addition, combustion air or oxygen is drawn in via the air compressor 67 in front of the air preheater 56, which is heated up in the air preheater and blown into the iron melt 71 via the line 65. In this way, an oxidation of the carbon takes place in the iron melt

in the coke and in the pyrolysis residue. The resulting heat

free, covers the heat losses of the iron bath carburettor 52. The temperature of the iron bath can be set using the amount of introduced carbon and oxygen, possibly also of oxygen from the air. The harmful substance binder - especially limestone - which is added together with the pyrolysis residue or the coke, floats as slag on the iron bath and is from time to time sucked away together with the harmful substances via a slag extraction pipe 72.

A major advantage of this pyrolysis plant 40 lies in

that the technical expense, thanks to the use of an iron bath gasifier 52 instead of a gas still 13, is significantly reduced, since the distillation gases leaving the iron bath gasifier are already free of harmful substances and can be incinerated without hesitation. Thus, the system makes the subsequent connection of a washing chain 24 unnecessary. With the savings in the washing chain, however, the necessary water treatment plant 36 is also saved. But this new pyrolysis plant offers advantages not only in terms of construction costs, but also in terms of operating costs. Thus, less coke is needed to maintain the temperature of the iron bath than where coke is otherwise consumed in the coke storage of a conventional gas still 13

with comparable performance. Furthermore, the carbonization residues can go a long way in replacing the coke needed to maintain the temperature of the iron bath. Thereby, in most cases it becomes unnecessary to deposit charring residues or residual coke. Instead, a relatively small amount of slag is obtained. Fig. 3 shows

an iron bath carburettor 73 which is somewhat modified in relation to the embodiment in fig. 2. Here, too, a vapor gas line 74 is connected to the iron bath carburettor at the bottom. It leads through the chamotte lining 75 into the iron melt 76. Next to the vapor gas line 74, a line 77 opens in the same way for the supply of harmful substance binder and possibly also of pyrolysis residues. In the upper hood of the iron bath carburettor 73 is a distillation gas outlet 78 with a flanged distillation gas line 79. In a side wall of the iron bath carburettor 73 there is a drain 80 arranged just above the surface of the molten iron 76

for the slag 81 which floats on the iron bath and contains the harmful substances. The iron bath carburettor's lower section, which accommodates

the iron melt 76, is enclosed by a winding 82 for induction heating.

In contrast to the design example in fig. 2, the temperature losses in the iron melt 76 are not compensated by the addition of coke and oxidizing agents, but via induction heating.

This means that there is no need to bring in any oxygen

in the iron smelter. Only in the case of the addition of pyrolysis residues can a negligible amount of oxygen be blown into the iron bath to reduce the quantities that must be deposited. The main advantage of this measure lies in the saving of energy by utilizing the chemical energy released by the oxidation of the pyrolysis residue's carbon. The heat that is then produced in addition by oxidation of the pyrolysis residues also leads to savings in electrical heating energy.

Claims (10)

1. Pyrolysis plant with a carbonization device for carbonization of supplied charge to form a pyrolysis residue and a steam gas, as well as with a gas still that is connected to the carbonization device on its gas side and serves to convert the steam gas into a distillation gas that can be used for firing without hesitation, characterized by that the gas distiller is an iron bath gasifier (52, 73) which is supplied with energy for temperature setting, and into whose liquid molten iron (71, 76) steam gas is blown in and harmful substances and binders are introduced. 2. Pyrolysis plant as specified in claim 1, characterized in that the iron melt (76) is supplied with heating energy electrically (82). 3. Pyrolysis plant as specified in claim 2, characterized in that the iron melt (76) is supplied with heat by induction heating (82). 4. Pyrolysis plant as specified in claim 1, characterized in that the iron melt (71) is supplied with energy chemically (64, 65). 5. Pyrolysis plant as specified in claim 4, characterized in that the iron melt is heated by burning part of the formed distillation gas. 6. Pyrolysis plant as stated in claim 5, characterized by an indirect heating of the iron bath. 7. Pyrolysis plant as specified in claim 4, characterized in that the iron melt (71) is supplied with carbon and oxygen or air. 8. Pyrolysis plant as specified in claim 7, characterized in that the iron melt (71) is supplied with ground coke. 9. Pyrolysis plant as specified in claim 7, characterized in that the iron melt (71) is fed with carbonization residues. 10. Pyrolysis plant as specified in claim 1, characterized in that contaminated foreign gases can be introduced for thermal destruction or chemical binding of harmful substances brought into the iron melt.