DE4337623A1 - Process and apparatus for dewatering and deoiling oil sludges - Google Patents

Abstract

The object underlying the invention is to create a process and an apparatus of the generic type mentioned at the outset with which, using a relatively small amount of equipment resources, oil and water can be economically separated from the residual product then remaining in such a manner that the latter can be landfilled or is reusable, the water can be discharged to the biological system and the oil recovered is reusable. This object is achieved according to the invention by hot flue gases from a burner (4) being passed into the oil sludges introduced into a screenlike dry vessel (2), by release of the free enthalpy of the flue gases most of the water contained in the oil sludges being expelled, together with the oil constituents boiling at the relevant flue gas temperatures, condensed in a condenser (7), this water-oil condensate being passed into a coalescer (14, 16), the water being separated there from the oil and then the end product, before it is landfilled, being subjected to afterburning of the residual oil constituents contained therein. <IMAGE>

Description

The invention relates to a method for Drainage and deoiling of oil sludge and a Device for performing this method.

In the publication "EXTRACTION AS A METHOD FOR CLEANING CONTAMINATED SOIL: POSSIBILITIES, PROBLEMS AND RESEARCH "by W.H. Rulkens, Ph.D., J.W. Assink Hazardous Materials, Control Research Institute, Silver Spring, Md / USA, Management of Uncontrolled Hazardous Waste sites, 1984 will be a number of ways and problems with cleaning oil contaminated Soils suggested. These procedures are based on essentially from washing out by means of a Solvent, being the solvent in addition to water also acetones, ethanols, isopropyl alcohols and hexanes be proposed.

From US-PS 4,098,648 a device for Extraction of bituminous materials from tar sands or tar-containing shale clays known, one Sand suspension in a rotating and with a Wendel equipped container in counterflow one Solvent such as petroleum is exposed. All these previously known methods have the disadvantage afflicted with an effective extraction of the oil-containing contaminants so long no success  is decreed like that in these contaminated Solids contained water around a protective shell forms the core of the contaminants, be it due to the surface tension of the water, due to the Van der Waals forces or other Affinities. Oil-water emulsions are with such Anyway not to separate solvents.

Oil sludges of the type in question here, the in addition to oil-water emulsions, non-rotten biological Containing substances, salts and the like must be disposed of are burned, which costs around DM 600 / t is affected.

Based on this state of the art, the Invention based on the object, a method and a To create a device of the type mentioned at the beginning, with which the oil contained in oil sludge with a relatively little expenditure on equipment economically from the remaining one Residual product can be separated so that the latter landfillable or reusable, the Water can be dispensed into biology and the oil obtained are reusable.

According to the invention, this object is achieved by that in the in a sieve-like drying container introduced oil sludge hot flue gases from a burner be initiated by submitting their free Enthalpy the water contained in the oil sludge for the most part together with those of those concerned Flue gas temperatures boiling oil components driven out, condensed in a capacitor, this  Water-oil condensate passed into a coalescer, there separated the water from the oil and then that dewatered and largely oil-free end product before it is deposited either by the introduction of oxygen or separately a combustion by the contained in residual oil components contained in it. The sieve-like drying container makes it quick Drainage and deoiling using the hot flue gases possible that flow through and around the product. As a result the inert gases that form in the process become a Self-ignition effect, for example through the in avoided the iron sulfides containing oil sludge and the operating temperature can be increased, which in turn associated with a shortening of the procedure is.

To ensure an intensive heat transfer of the flue gases Ensuring the oil sludge is in training the invention of the oil sludge by means of a Worm pump over several within the sieve-like Drying container ring-shaped press nozzles in Strands of mud transferred by rotating knives be broken down into pellets and in this form into the sieve-like drying containers fall. In this way arises within the sieve-like drying container loose pile, which to flow with Flue gases are particularly suitable. Through the Introduction of inert smoke gases in the sieve-like Drying container will self-ignite Product as a result of iron sulfides contained therein prevented. The uncondensed gases are after Leaving the capacitor via a first one Butterfly valve and a first chimney in the free  Atmosphere blown out.

After an advantageous development of Invention is achieved when a certain Maximum flue gas temperature in the supply line to Condenser the burner producing the hot flue gases turned off, the first fireplace by switching the first Butterfly valve closed and a blower turned on which the water and some oil containing smoke gases in a cycle again and again through the sieve-like drying container and through the Condenser conducts, causing the cooling in the latter Flue gases permanently in a sieve-like drying container heated again through the product and charge yourself with water and possibly with oil and deliver this in turn to the capacitor. Through this Circular mode of operation of the inert flue gases in front of their Entry into the sieve-like drying container none or does not contain any significant amounts of water vapor achieves a better evaporation effect in the pile and hence the drainage and deoiling process from this Accelerated aggregate to the end product. At the same time through this recycle mode of the flue gases through the Cooler, the residual product to a temperature cooled down and its discharge despite the still in contained minor oil components in the oxygen-containing atmosphere without the risk of Autoignition ensured. This procedure is regarding his energy use and his apparatus expenditure extremely economical, because now for the first time also significant quantities Oil, namely about 250 l / t can be recovered, which only use about 50 liters of oil  Generation of hot flue gases, a few m³ of cooling water as well as the operating current for pumps and blowers as well Face landfill costs. This is the Disposal of oily sludges for the first time not with a loss of approx. DM 600 / t, but still at a profit.

It is advantageous when one reaches one Temperature sensor in the supply line to the Condenser set minimum flue gas temperature, from this temperature sensor via a control device the fan is switched off, the first butterfly valve of the first chimney opened and the burner again switched on. This will make the Operating temperature for drainage and oil removal increased until the flue gas maximum temperature is reached again is reached and the temperature sensor again Burner switches off, the first chimney by switching a first butterfly valve closes and the blower switches on. This process is repeated as long as until the desired degree of drainage and de-oiling is reached.

When the desired drainage or Degree of oil removal, the burner is switched off first butterfly valve closed and by the Suction blower cooled, inert on the condenser Flue gases, e.g. B. essentially in the form of N₂ and CO₂, through the drained and largely deoiled Product passed until its temperature is below the autoignition temperature. To the drainage and deoiling as well as cooling of the Residual product to a temperature below the  Autoignition temperature becomes the bottom of the sieve-like drying container opened and the contents in filled a container for further use. The Residual product can also be afterburned undergo, which is also advantageous can be carried out that is still called Residual product in the sieve-like drying container air is fed and after self-ignition over the iron sulfides contained in it a combustion of the residual oil contained therein is triggered. This will the burned residual product can be landfilled.

In terms of device, that of the invention underlying task essentially thereby solved that the sieve-like drying container from a closed outer container and one inside concentric and at a distance from its inner wall arranged sieve container, wherein in the Space between the sieve container and the inner wall of the A heating plate to the sieve container directional baffle guides for the hot flue gases are arranged as well as near the upper area of the sieve container shows the degree of filling Level sensor and below the sieve container in the Outer container a hydraulically swiveling Bottom cover is attached. Be through the heating plate the hot smoke gases from the burner into the gap between the heating plate and the inner wall of the outer container led to the bottom of the sieve container to pass through from there the baffle guide in counterflow to the product flow through. The sieve container can also be used better contact of the flue gases with the Oil slurries also contain indentations.  

To achieve one of flue gases intensely as well flowable with low flow losses Pile of the oil sludge is above the Sieve container inside the outer container an over a feed line with a screw pump for the Oil slurry connected nozzle ring and below that Outlet openings of the nozzles a rotating knife for Cut the strands pressed out of the nozzles arranged in pellets.

Furthermore, the space between the heating plate and the inner wall of the outer container via a Inlet line with the burner as well as via one at the outlet line arranged on the opposite side and a connecting line to the capacitor and then via a chimney pipe with the first chimney in Flow connection.

To when the maximum flue gas temperature is reached on the one hand to save energy and on the other hand nevertheless those in the heating surfaces and others heated areas within the sieve-like Enthalpy contained in the drying container for further Drainage and deoiling of the product in one exploiting the closed cycle is the Flue gas outlet line from the condenser via a Bypass line and a second butterfly valve with one Blower connected, the pressure line with the Inlet pipe for the flue gases in the sieve-like Drying container is connected. This allows the Flue gases when their maximum temperature is reached below The burner is switched off permanently when the burner is closed  first chimney in the bypass line over the switched on fans in a closed circuit again and again through the heated sieve-like Drying container and from there to condense the in contained water and oil components over the Condenser and from there again into the sieve-like drying containers are returned.

The condensate side of the Condenser a coalescer and this a separation container subordinate, the upper area for the removal of the Oil with an oil pipe with its lower area connected to a sewage pipe. That from the Oil obtained from coalescing can be used for combustion and can also be used for other purposes. Part of it will advantageous to operate the burner after its Start-up phase used. The water can be in biology are given. The maximum flue gas temperature and the Flue gas minimum temperature are determined by one in the Supply line arranged to the capacitor Temperature sensor controlled. This switches on Reaching the adjustable on it Rabchgas maximum temperature via a control device the burner, the first butterfly valve closes first chimney and turns on the fan. At The flue gas switches when the minimum flue gas temperature is reached Temperature sensor via this control device Blower off, the first butterfly valve opens to the first Fireplace and turns on the burner again. Through the alternately switching the burner on and off Connection with the circuit management described above the flue gases can be economical for as long Drainage and deoiling of the product operated  be until the desired drainage and Degree of de-oiling is reached. Then the bottom flap of the outer container opened and the residual product of it be used for further use.

However, it is also possible to post-burn to be carried out inside the outer container. To this Purpose is with the first butterfly valve open and at open second butterfly valve in the bypass line atmospheric outside air through the first chimney burner switched off via the suction line from the fan sucked in and via its pressure line into the Inlet line of the sieve-like drying container promoted. Here is a third butterfly valve for second fireplace opened, over which the then resulting combustion gases are derived. By Access to the atmospheric outside air is due to the iron sulfides contained in the residual product Auto ignition triggered.

An embodiment for performing the The inventive method is based on a Device shown in the figure.

The device 1 according to the invention essentially consists of a sieve-like drying container 2 , into which hot flue gases from a burner 4 are introduced via an inlet line 3 and leave a sieve-like drying container 2 via a discharge line 5, a feed line 6 to a condenser 7 . The uncondensed flue gases pass from the condenser 7 into the free atmosphere via an outlet line 8 , a first butterfly valve 9 and a first chimney 10 .

The condenser 7 is acted upon by a cooling water supply line 11 by the cooling water, which leaves it via the cooling water outlet line 12 .

The water-oil mixture condensed out in the condenser 7 passes via a connecting line 13 to a coalescer 14 , which is followed by a separating container 16 via a further connecting line 15 . The oil that settles in the upper region 16 a of the separation container 16 is fed to an oil container 18 via an oil discharge line 17 , whereas the water that settles in the lower region 16 b can be released into the biology via a waste water line 19 , since its residual oil content is below 20 ppm is.

In addition, the device 1 according to the invention includes a bypass line 20 , which is connected via a second shut-off valve 23 to a blower 21 , the pressure line 22 of which leads to the inlet line 3 of the sieve-like drying container 2 . The outlet line 5 from the sieve-like drying container 2 is connected not only to the feed line 6 , but also to a second chimney 26 via a flue gas line 24 and a third butterfly valve 25 . The burner 4 obtains its oil supply from an oil tank 27 , which can also be connected to the oil container 18 via a connecting line 28 and an oil pump 29 .

Below the sieve-like drying container 2 there is a container 30 for receiving the dewatered and de-oiled residual product, which is then either fed to a separate post-combustion or, in the post-combustion to be described later, gets into it in the sieve-like drying container 2 in a landfill-ready state.

In addition, the screen-like drying container 2 is connected via a screw pump 31 and an oil sludge line 32 to a ring 33 of press nozzles 34 arranged in the top part in the screen-like drying container 2 , under which a rotating knife 35 is arranged. From this knife 35 , the strands pressed out of the nozzles 34 can be cut into pellets and then fall into the sieve-like drying container 2 .

This sieve-like drying container 2 consists of a closed outer container 36 and a sieve container 38 arranged therein concentrically at a distance 37 , whereby in the space between the sieve container 38 and the inner wall 36 a of the outer container 36 a heating plate 39 with baffle guides 40 directed towards the sieve container 38 for the hot flue gases is arranged. Also located in the upper part 38 a of a 38 Siebbehälters the filling and freeness indicating level sensor 41, the measuring, for example, two, the conductivity of the filled product electrodes. This conductivity essentially depends on the water content. Below the sieve container 38 , a hydraulically pivotable bottom cover 42 is attached in the outer container 36 . This bottom cover 42 is arranged so that, on the one hand, a concentric extraction of the sieve container 38 from the outer container 36 is ensured before the upper region 38 a of the sieve container 38 by pivoting in the direction of the double arrow 43 to the opening 30 a of the container 30 by means of a hydraulic piston Cylinder unit 44 is pivoted.

The inventive method is by means of Device according to the invention as described above carried out as follows:

After inserting the sieve container 38 into the outer container 36 , with the bottom 42 closed, that of the screw pump 31 is supplied to the nozzle ring 33 , 34 via the oil sludge line 32 and oil sludge is pressed out of the nozzles 34 in the direction of the sieve container 38 . The extruded oil sludge strands are cut into pellets by the rotating knife 35 . These pellets form a relatively loose mass in the sieve container 38 . After the filling of the sieve container 38 up to the upper region 38 a is indicated via the level sensor 41 , the burner 4 is switched on. This sucks in via the oil line 27 a from the oil tank 27 oil, which burned in it and then the resulting hot flue gases from z. B. 1000 ° C via the inlet line 3 in the intermediate space 45 and in the direction of arrow 46 to the bottom 38 b of the sieve container 38 . From there, the hot flue gases flow both in the serpentine lines 47 resulting from the baffle guides 40 along the outer region of the sieve container 38 and as a result of the loose accumulation of the pile in the form of pellets through its inner region. The hot flue gases are charged with water and oil gases in this flow path through the oil sludge product and leave the sieve-like container 2 via the outlet line 5 . When the third butterfly valve 25 is closed and the second chimney 26 is closed, they reach the condenser 7 via the feed line 6 . In the condenser 7 , the water and oil vapors are condensed out and reach the coalescer 14 via the line 13 and from there via the connecting line 15 to the separation container 16 , in which they settle in the manner already described and are withdrawn therefrom. The rest of the flue gases subjected to condensation in this way reach the free atmosphere via the outlet line 8 when the second butterfly valve 23 is closed, via the open butterfly valve 9 and the first chimney 10 .

A temperature sensor 48 is arranged in the feed line 6 to the condenser 7 and transmits its temperature values to a computer-controlled control device 49 . When the maximum flue gas temperature in the supply line 6 to the condenser 7 is reached , the controller 49 switches the burner 4 off via servomotors (not shown) and closes the first shut-off valve 9 to the first chimney 10 . At the same time, he opens the second butterfly valve 23 of the bypass line 20 and switches the blower 21 on. As a result, when the third shut-off valve 25 is closed, the flue gases cooled on the condenser 7 are sucked in by the blower 21 via the bypass line 20 and pressed via the pressure line 22 into the inlet line 3 to the sieve-like drying container 2 . From there they reach the intermediate space 45 , in which they are heated again by the hot inner wall 36 a of the outer container 36 and by the heating plate 39 . Since the water content in them is zero, they continue to take water vapors and oil vapors on their way through the heated product in the sieve container 38 due to their low partial pressure of water and reach the condenser 7 again via the outlet line 5 and the feed line 6 . The charged water and oil components are condensed out on this and the discharged flue gases are then passed again via the blower 21 into the sieve-like drying container 2 . The process is repeated until the temperature sensor 38 indicates the minimum flue gas temperature. When the minimum flue gas temperature is reached, the temperature sensor 48 switches off the blower 21 via the control device 49 and opens the first shut-off valve 9 to the first chimney 10 . The second butterfly valve 23 to the bypass line 20 is closed and the burner 4 is switched on again. When the maximum flue gas temperature in the feed line 6 to the condenser 7 is reached again, the burner 4 is switched off again by the temperature sensor 48 via the control device 49 , the first butterfly valve 9 to the first chimney 10 is closed and the second butterfly valve 23 to the bypass line 20 is opened, and the fan 21 switched on again. This process is alternately repeated until the desired degree of dewatering and de-oiling of the product in the sieve container 38 is reached, which is measured by the electrodes 41 of the level sensor measuring the electrical conductivity of the product and is likewise communicated to the control device 49 or other control devices. The level sensor 41 thus fulfills a double function.

Then, according to a first alternative, the bottom cover 42 of the outer container 36 is opened in the direction of the double arrow 43 and the residual product contained in the sieve container 38 is transferred into the container 30 . This residual product can still contain oil components that still have to be incinerated in order to be able to landfill. This afterburning can take place in different forms.

It is also possible to carry out this post-combustion within the outer container 36 . In this case, all shut-off flaps 9 , 23 , 25 and thus the first and second chimneys 10 , 26 are opened with the outer container 36 closed, and at the same time the fan 21 is switched on when the burner 4 is switched off. As a result, fresh air is drawn in from the outside atmosphere via the first chimney 10 and the bypass line 20 from the blower 21 and blown into the space 45 between the inner wall 36 a of the outer container 36 and the heating plate 39 via the pressure line 22 and the inlet line 3 . From there, the atmospheric outside air gets from below into the still hot residual product, which as a result ignites the iron sulfides it contains through the supply of oxygen. The combustion gases are then discharged into the outside atmosphere via the outlet line 5 and the third opened butterfly valve 25 and the second chimney 26 . After the afterburning has ended, the bottom 42 of the outer container 36 is opened and the residual product which has already been afterburned is fed via the container 30 to a landfill.

This method is not only very economical in terms of its energy consumption and expenditure on equipment, but can also be used profitably by recovering the light oil components. Furthermore, this process ensures that the residues are deoiled to less than 2%, so that the latter can be landfilled. Depending on the setting of the maximum flue gas temperature to the minimum flue gas temperature, the process can be run in the sieve-like drying container 2 with a shorter or longer operating time per batch. Due to the closed-loop procedure, the enthalpies contained in the residual product and in the heated surfaces in the outer container 36 and in the heating plate 39 are used economically for further dewatering and deoiling of the residual product.

Reference list

1 device
2 drying containers
3 Inlet line
4 burners
5 , 8 outlet line
6 supply line
7 capacitor
9 first butterfly valve
10 first fireplace
11 cold water supply line
12 Cooling water outlet line
13 , 15 , 28 connecting lines
14 coalescers
16 separation containers
16 a upper area of the separation container 16
16 b lower region of the separating container 16
17 Oil drain line
18 oil containers
19 sewage pipe
20 bypass line
21 blowers
22 Blower pressure line 21
23 second butterfly valve
24 flue gas pipe
25 third butterfly valve
26 second fireplace
27 oil tank
27 a Oil line
29 oil pump
30 containers
30 a opening of the container 30
31 worm pump
32 Oil sludge line
33 wreath
34 press nozzles
35 knives
36 outer container
36 a inner wall of the outer container 36
37 distance
38 sieve containers
38 a upper area of the sieve container 38
38 b bottom of the sieve container 38
39 heating plate
40 baffle guides
41 level sensor
42 bottom cover
43 double arrow
44 piston-cylinder unit
45 space
46 arrow
47 serpentine line
48 temperature sensors
49 control device

Claims (19)

1. A process for the dewatering and deoiling of oil sludge, characterized in that hot flue gases from a burner ( 4 ) are introduced into the oil sludge introduced into a sieve-like drying container ( 2 ), by releasing their free enthalpy the water contained in the oil sludge mostly together with the the oil components boiling the flue gas temperatures concerned, condensed in a condenser ( 7 ), this water-oil condensate passed into a coalescer ( 14 , 16 ), where the water is separated from the oil and then the dehydrated and largely oil-free end product is either passed through before being deposited the introduction of oxygen or separately is subjected to combustion by the residual oil components contained in it. 2. The method according to claim 1, characterized in that the oil sludge by means of a screw pump ( 31 ) over several above the sieve-like drying container ( 2 ) annularly arranged press nozzles ( 34 ) is converted into sludge strands which are broken down into pellets by rotating knives ( 35 ) and fall into the sieve-like drying container ( 2 ) in this form. 3. The method according to claim 1 or 2, characterized in that a self-ignition suppressing inert gas atmosphere is created by the introduction of inert flue gases into the sieve-like drying container ( 2 ). 4. The method according to any one of claims 1 to 3, characterized in that the uncondensed gases are blown into the free atmosphere after leaving the condenser ( 7 ) via a first butterfly valve ( 9 ) and a first chimney ( 10 ). 5. The method according to any one of claims 1 to 4, characterized in that when a certain maximum flue gas temperature is reached in the feed line ( 6 ) to the condenser ( 7 ) the hot flue gas generating burner ( 4 ) is switched off, the first chimney ( 10 ) by switching the first butterfly valve ( 9 ) closed and a fan ( 21 ) is switched on, which conducts the water and some oil-containing flue gases in a cycle through the sieve-like drying container ( 2 ) and through the condenser ( 7 ), whereby the in the latter (7) cooled flue gases in the sieve-like drying container ( 2 ) are continuously heated and passed through the product, which are charged with water and possibly with oil and released in turn in the condenser ( 7 ). 6. The method according to claim 5, characterized in that when a temperature sensor ( 48 ) in the feed line ( 6 ) to the condenser ( 7 ) is set to the minimum flue gas temperature, from this temperature sensor ( 48 ) via a control device ( 49 ) the blower ( 21 ) switched off, the first shut-off valve ( 9 ) of the first chimney ( 10 ) is opened and the burner ( 4 ) is switched on again. 7. The method according to any one of claims 1 to 6, characterized in that when the desired degree of dewatering or de-oiling the burner ( 4 ) is switched off, the first butterfly valve ( 9 ) is closed and the suction fan ( 21 ) on the condenser ( 7 ) cooled, inert flue gases, e.g. B. in the form of N₂ and CO₂, are passed through the drained and largely de-oiled product until its temperature is below the auto-ignition temperature. 8. The method according to any one of claims 1 to 7, characterized in that after the dewatering and de-oiling and cooling of the residual product to a temperature below the self-ignition temperature, the bottom ( 42 ) of the sieve-like drying container ( 2 ) is opened and the contents in a container ( 30 ) is filled for further disposal. 9. The method according to any one of claims 1 to 8, characterized in that the residual product is subjected to post-combustion.   10. The method according to claim 9, characterized characterized that the Afterburning of the still hot residual product an air supply to burn the contained in it Residual oil is carried out. 11. A device for carrying out the method according to claims 1 to 10, characterized in that the sieve-like drying container ( 2 ) from a closed outer container ( 36 ) and a sieve container ( 38 ) arranged concentrically therein and at a distance from its inner wall ( 36 a) there is, in the space between the sieve container ( 38 ) and the inner wall ( 36 a) of the outer container ( 36 ), a heating plate ( 39 ) with baffle guides ( 40 ) directed towards the sieve container ( 38 ) for the hot flue gases and in the vicinity of the In the upper area of the sieve container ( 38 ) there is a level sensor ( 41 ) indicating the degree of filling, and below the sieve container ( 38 ) in the outer container ( 36 ) there is a hydraulically swiveling bottom cover ( 42 ). 12. The apparatus according to claim 11, characterized in that above the sieve container ( 38 ) within the outer container ( 36 ) via a feed line ( 32 ) with a screw pump ( 31 ) for the oil sludge nozzle ring ( 33 ) and below the outlet openings of the nozzles ( 34 ) a rotating knife ( 35 ) for cutting the strands pressed out of the nozzles ( 34 ) is arranged in pellets. 13. The apparatus of claim 11 or 12, characterized in that the space ( 45 ) between the heating plate ( 39 ) and the inner wall ( 36 a) of the outer container ( 36 ) via an inlet line ( 3 ) with the burner ( 4 ) and an outlet line ( 5 ) arranged on the opposite side and a feed line ( 6 ) with the condenser ( 7 ) and then via a chimney line ( 8 ) with the first chimney ( 10 ). 14. Device according to one of claims 11 to 13, characterized in that the flue gas outlet line (S) from the condenser ( 7 ) via a bypass line ( 20 ) and a second butterfly valve ( 23 ) is connected to a blower ( 21 ), the Pressure line ( 22 ) is connected to the inlet line ( 3 ) of the flue gases in the sieve-like drying container ( 2 ). 15. The device according to one of claims 11 to 14, characterized in that the outlet line ( 5 ) from the outer container ( 36 ) via a third butterfly valve ( 25 ) is connected to a second chimney ( 26 ). 16. Device according to one of claims 11 to 15, characterized in that the condensate side of the condenser ( 7 ) is followed by a coalescer ( 14 ) and this a separating container ( 16 ), the upper region ( 16 a) for discharging the oil with an oil line ( 17 ) and its lower area ( 16 b) is connected to a sewage pipe ( 19 ). 17. Device according to one of claims 11 to 16, characterized in that a temperature sensor ( 48 ) is arranged in the supply line ( 6 ) to the condenser ( 7 ), which when the maximum flue gas temperature which can be set on it is reached, via a control device ( 49 ) The burner ( 4 ) switches off, the first shut-off valve ( 9 ) of the first chimney ( 10 ) closes and the fan ( 21 ) switches on. 18. The apparatus according to claim 17, characterized in that the temperature sensor ( 48 ) switches off the blower ( 21 ) on reaching the adjustable flue gas minimum temperature via the control device ( 49 ), the first butterfly valve ( 9 ) to the first chimney ( 10 ) opens and the burner ( 4 ) switches on again. 19. The device according to one of claims 11 to 18, characterized in that for the post-combustion of the residual product with the first shut-off valve ( 9 ) of the first chimney ( 10 ) and with the second shut-off valve ( 23 ) open in the bypass line ( 20 ) atmospheric outside air from the fan ( 21 ) can be sucked in and conveyed via its pressure line ( 22 ) into the inlet line ( 3 ) into the sieve-like drying container ( 2 ), the third butterfly valve ( 25 ) being opened to the second chimney ( 26 ).