CH658449A5 - Process and apparatus for the thermal treatment of aqueous sludges containing combustible substances - Google Patents

Description

The invention relates to a process for the thermal treatment of aqueous sludges which contain combustible substances, in which the sludges are subjected to oxidation in an oven at elevated pressure and at elevated temperature, the gas being produced from the sludge during the oxidation -Vapor mixture thickened the sludge to be oxidized by indirect heat exchange, and a device for carrying out the process.

In addition to combustion, oxidation is also to be understood to mean carbonization or gasification.

In a process known from DE-PS 27 53 537 for the thermal treatment of aqueous sludges, a thin-film evaporator is heated with a gas-steam mixture from a pressure-resistant furnace, whereby sewage sludge in particular is thickened to such an extent that it is fed into the furnace and burned without additional fuel can be. The disadvantage is that the heat transfer from the gas-steam mixture to the heating wall of the evaporator chamber of the thin-film evaporator is not high enough, so that the evaporator must be dimensioned larger to improve the efficiency. Another disadvantage is that the gas-vapor mixture flowing into the thin-film evaporator is not cleaned, but still contains dirt and pollutants.

The object of the invention is therefore to avoid these disadvantages and to provide a method of the type mentioned, in which the entire heat of the gas-steam mixture can be better introduced into the evaporator chamber of the thin-film evaporator, so that the dimensions can be reduced, at the same time Dirt and pollutants are to be removed from the gas-steam mixture.

According to the invention, this is achieved in a method of the type mentioned at the outset by bringing the gas / steam mixture into direct contact with a heat transfer medium, the usable heat of the gas / steam mixture being transferred to the heat transfer medium and by thickening the sludge with the aid of the heated heat transfer medium is carried out.

Advantageously, the heat transfer medium is the condensate formed during the condensation of the steam from the gas-steam mixture, through which the gas-steam mixture is passed and which thereby absorbs useful heat which it emits to the evaporator chamber of a thin-film evaporator. In this way, dirt

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and removes pollutants from the gas vapor mixture; there is also a better heat transfer from the boiler room to the evaporator room of the thin-film evaporator. The dirt and pollutants are continuously removed.

In the area of influence of the thin-film evaporator or the mixing condenser, a heat exchanger can be arranged, which feeds excess heat that is not required for the evaporation of the sludge into a district heating network or to other heat consumers.

An alternative embodiment of the method according to the invention is characterized in that the gas-steam mixture is brought into indirect contact with a heat transfer medium via a heat exchanger, the usable heat of the gas-steam mixture being transferred into the heat transfer medium, and in that the thickening of the sludge with the help of the heated heat transfer medium is carried out. This heat transfer medium can have a higher boiling point than water.

Heating the sludge to be thickened by means of a water or heat transfer bath advantageously causes gentle thickening, i.e. there is no local overheating, which can lead to the burning of a sensitive, protein-rich sludge.

The invention is explained in more detail with reference to a schematically illustrated embodiment in the drawings. Show it:

1 is a thin film evaporator, the boiler room is filled with condensed water,

Fig. 2 shows a thin film evaporator with an external mixing condenser.

2 denotes a thin-film evaporator, the heating chamber 11 of which has a circumferential nozzle base 16. This heating chamber 11 is filled with condensed water up to a certain height, through which hot gas-steam mixture is passed from a pressure-resistant furnace 3 via a filter 10. Droplet separators 17 are arranged above the water surface of the boiler room 11. The arrangement works as follows:

A gas-steam mixture is introduced from the pressure-resistant furnace 3 via filter 10 and flows via a nozzle base 16 into the condensation water (water bath) which is located in the heating chamber 11 and acts as a heat transfer medium. The vapor of the gas-vapor mixture condenses and gives off its sensible heat and heat of condensation; the gas contains only sensible heat, which is given off to the condensed water. The condensation constantly creates new condensed water, which is, however, continuously removed via a heat exchanger 14 and a relaxation machine 15, so that the boiler room 11 is not overfilled. That in the evaporator chamber 11 'of the thin-film evaporator 2 during the thickening

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The steam resulting from the sludge is also utilized and the thickened sludge is fed into the furnace 3 by means of a pump.

The mud, e.g. an industrial sludge,

if necessary, flammable substances are added in sufficient quantities so that the combustion process maintains itself.

In Figure 2, a mixing condenser 1 is provided, in which the gas-steam mixture coming from the pressure-resistant furnace 3 is introduced via filters 10 and nozzle bottoms 16. The vapor of the gas-vapor mixture condenses, while the cooled, cleaned gas is drawn off via a filter 12 and an exhaust gas turbine 13. The sensible heat of the gas as well as the sensible heat and condensation heat of the steam heat the condensation water serving as the heat transfer medium, which is pumped out of the mixing condenser 1 via a pump 4 into the heating chamber 11 of the thin-film evaporator 2. There it gives off its heat to the evaporator chamber 11 ′ or the sludge in the evaporator chamber of the thin-film evaporator 2. The constant condensation of steam creates excess condensed water, which is drawn off via heat exchanger 14 and expansion machine 15. The cooled condensed water is fed out of the heating chamber 11 via a return line 5 back into the mixing condenser 1, where it is warmed up again and conveyed back via pump 4 into the heating chamber 11 of the thin-film evaporator.

In both embodiments, it is advantageous that the gas scrubbing in the condensed water makes the filter 12, predominantly an electrostatic filter, smaller or can be dispensed with entirely.

The choice of material for the thin-film evaporator and / or mixing condenser can be favorably influenced by adding chemicals for dirt precipitation and / or binding of pollutants.

Instead of a thin-film evaporator, other forms of evaporator design, such as tube bundle evaporators, hollow screw evaporators or others, can also be provided.

Due to the external arrangement of the mixing condenser, better gas scrubbing is possible due to the larger apparatus dimensions.

If the excess amount of condensate is not able to remove the pollutants and pollutants to a sufficient extent, a separate wash water cleaning circuit can be provided. This applies to the thin film evaporator as well as to the mixing condenser and the heat exchanger.

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2 sheets of drawings

Claims (9)

658 449 PATENT CLAIMS 1. A process for the thermal treatment of aqueous sludges which contain combustible substances, in which the sludges are subjected to oxidation in an oven at elevated pressure and at elevated temperature, by means of indirect means of the gas / vapor mixture generated from the sludge during the oxidation Heat exchange thickens the sludge to be oxidized, characterized in that the gas-steam mixture is brought into direct contact with a heat transfer medium, the usable heat of the gas-steam mixture being transferred to the heat transfer medium, and that the thickening of the sludge is carried out with the aid of the heated heat transfer medium becomes. 2. The method according to claim 1, characterized in that the condensed water of the gas-steam mixture is used as the heat transfer medium, with which the heating chamber of a thin-film evaporator is filled, that the gas-steam mixture is passed through the condensation water located in the heating chamber, the steam of the Gas-steam mixture condenses, that the cooled gas is drawn off, and that condensed water constantly loaded with dirt and pollutants is drawn off from the boiler room in an amount which corresponds to the amount of the condensed-out steam. 3. The method according to claim 1, characterized in that the condensed water of the gas-steam mixture is used as the heat transfer medium, through which the gas-steam mixture is passed in a special heat exchanger designed as a mixing condenser, the steam condensing and the cooled, cleaned gas being drawn off is that the heated condensed water is directed into the heating chamber of the thin-film evaporator and releases its heat to the sludge in the evaporating chamber, that cooled condensed water is returned to the mixing condenser for reheating, and at the same time an amount of condensed water laden with contaminants and pollutants is drawn off, which Corresponds to the amount of condensed water from the steam. 4. The method according to any one of claims 2 or 3, characterized in that an additional heat exchanger is arranged in the area of influence of the heat exchanger designed as a mixing condenser and / or the thin-film evaporator, by means of which excess heat can be transferred from the gas-steam mixture into a connected district heating network or other heat consumers is. 5. A process for the thermal treatment of aqueous sludges which contain combustible substances, in which the sludges are subjected to oxidation in an oven at elevated pressure and at elevated temperature, by means of indirect means of the gas / vapor mixture generated from the sludge during the oxidation Heat exchange thickens the sludge to be oxidized, characterized in that the gas-steam mixture is brought into indirect contact with the heat transfer medium via a heat exchanger, the usable heat of the gas-steam mixture being transferred into the heat transfer medium, and that the thickening of the sludge with the aid of the heated heat transfer medium is performed. 6. The method according to claim 5, characterized in that water or a substance is used as the heat transfer medium, the boiling point of which is above that of water, for example a heat transfer oil, with which the heating chamber of the thin-film evaporator is filled, that the gas-steam mixture by a heat exchanger is conducted, the vapor of the gas-vapor mixture condenses, the cooled, purified gas is withdrawn, and that condensed water is continuously withdrawn from the heat exchanger in an amount which corresponds to the amount of the condensed-out steam. 7. The method according to any one of claims 2 to 6, characterized in that the waste heat of the excess, from the boiler room of the thin-film evaporator and / or from the heat exchanger flowing condensate is made usable in further heat exchangers and is optionally fed for further use. 8. An apparatus for performing the method according to claim 1 or 2, characterized by a thin-film evaporator (2), the heating chamber (11) is filled with condensed water and has a nozzle base (16) through which the gas-steam mixture can be introduced into the condensed water. 9. Apparatus for carrying out the method according to claim 1 or 3, characterized by a heat exchanger designed as a mixing condenser (1) which is filled with condensed water and has a nozzle base (16) through which the gas-steam mixture can be introduced into the condensed water.