Disposal of waste materials containing hydrocarbons e.g., sludge of roller scale uses a dryer with indirect heating to extract volatile components and cleaning of the exhaust gas to separate dust from it

The invention relates to a device and a method for treating a waste material containing hydrocarbons, in particular a mill scale sludge and / or grinding sludge, the waste material being heated in a dryer while moving by indirect heat supply and thereby removing hydrocarbons and other volatile components, in particular H₂O, being freed.

Waste materials contaminated with hydrocarbons (organic compounds), in particular solids and sludge, arise on the one hand in many production processes, e.g. as grinding sludge or mill scale, on the other hand also when hydrocarbons are accidentally released into the environment, such as oil-contaminated soil.

Waste contaminated with hydrocarbons poses a considerable problem for the environment, since there is no efficient and at the same time inexpensive method for processing these waste materials.

Various methods for treating hydrocarbon contaminated waste are known in the art.

EP0373577A1 teaches a two-stage process and a device for processing sewage or industrial sludge containing organic components. As part of the conversion process taught, the sludge is mechanically pre-dewatered, conveyed into the interior of an indirectly heated continuous conveyor and there exposed to heating while the volatile components are expelled at the same time. In a subsequent, second stage, there is a dwell at the conversion temperature to expel the remaining volatile components from the solid product. In practice, this procedure turns out to be comparatively inefficient, since the sludge must be heated to a relatively high temperature in order to expel the hydrocarbons by the device and procedure shown. An economical operation of such a system can therefore not be achieved.

DE19715839A1 teaches a method and a device for cleaning oil- and water-containing mill scale sludge, the sludge being subjected to a two-stage treatment. In a first step, water is volatilized by heating the sludge. In a second step, the dried sludge is subjected to a vacuum treatment at an elevated temperature to volatilize the hydrocarbons. Practice shows that the system is relatively inefficient, since the generation of the vacuum required to volatilize the hydrocarbons is associated with high construction and operating costs.

Two-stage processes are characterized by a higher expenditure on equipment and control and regulation technology.

AT400579B teaches a one-step process for the recovery of organic-chemical impurities, such as oil or fat, and possibly moist and metal-containing material, such as scale or shavings, the material being heated indirectly in a reducing atmosphere to above the boiling point of the highest-boiling fraction of the organic contamination is heated, and is flushed with non-oxidizing carrier gas to avoid condensation. This process proves to be uneconomical in practice, since the material has to be heated to a temperature above the boiling point of the highest-boiling organic impurities.

The present invention is therefore based on the object of overcoming the disadvantages of the prior art and of developing a simple and economical method according to the preamble of claim 1, as well as a suitable device for carrying out said method according to the preamble of claim 14.

This object is achieved according to the method according to the invention according to the characterizing part of claim 1 and according to the device according to the invention according to the characterizing part of claim 14.

With the degradation of the hydrocarbons by chemical and / or radiation technology aids, which break down the hydrocarbons with a high molecular weight into hydrocarbons with a lower molecular weight, in particular by means of selective oxidation, the waste can be effectively cleaned of hydrocarbons even at low temperatures.

In order to achieve high temperatures, especially in larger systems, indirect heating, for example through the vessel wall of a dryer, is therefore not economical

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Reasons for, as with indirect heating, in contrast to direct firing by a flame and hot gas, the heating takes place solely through thermal conduction. The operating temperature in the dryer is reached correspondingly slowly.

If the process temperature in the dryer is therefore kept low, a significant time saving can be booked, especially when starting up the cold dryer.

By using chemical and / or radiation technology aids to break down the hydrocarbons, which results in a lowering of the mean volatilization temperature of the hydrocarbons, the cleaning process is significantly accelerated.

The result is the increased economic efficiency of the process compared to the prior art, on the one hand through a lower heating energy requirement and on the other hand, due to the shorter treatment time and the lower maximum operating temperature, through smaller, more cost-effective apparatus.

The waste material is heated while it is moving in order to ensure rapid and even heating.

The movement of the solids and / or sludge in the vessel can take place by moving the vessel, for example by rotating the vessel, and / or by moving a device in the vessel, for example by rotating a tool.

According to various embodiments of the invention, it is possible to operate the method at atmospheric pressure, at positive or negative pressure. The overpressure area saves the fan having to suck in the exhaust gases. For this purpose, a gas-tight design of the material supply and removal is advantageous.

According to a particular embodiment of the invention, the hydrocarbons are broken down at temperatures below 450.degree. C., in particular 400.degree.

According to a particular embodiment of the invention, the indirect heat is supplied via the vessel wall and / or via heated moving parts and / or by means of radiation, such as, for example, via microwaves.

Since, according to the method according to the invention, no heating gas is introduced into the vessel and the volume of the gases to be sucked off is very small, the outlay for the necessary treatment of the sucked off gas is minimized.

The independent regulation of heating power and composition of the gas atmosphere in the dryer, which is possible through indirect heating, is also advantageous.

According to a further particular embodiment of the method according to the invention, oxygen, in particular oxygen-inert gas mixtures or oxygen-enriched air, and / or solid and / or liquid and / or gaseous peroxide / hyperoxide, preferably hydrogen peroxide, and / or ozone and / or a catalyst is used as chemical auxiliary used to decompose the hydrocarbons.

The volatilization of the moisture contained in the waste materials supports the volatilization of hydrocarbons that are volatile in steam. In particular, the addition of oxygen-containing oxidizing agents creates oxygen-containing groups in the hydrocarbon molecules, as a result of which the water-repellent (hydrophobic) properties of the hydrocarbons are reduced. This has an advantageous effect on the water vapor volatility of the hydrocarbons, so that the volatilization of the hydrocarbons is accelerated further.

According to preferred embodiments of the invention, oxygen or oxygen-enriched air is used as the oxidizing agent for the selective oxidation. However, other oxygen-containing gas mixtures or substances can also be used. If the waste material also contains easily oxidizable substances, such as metallic magnesium, it may be necessary, depending on the grain size, to set an oxygen content below 20.8% in order to limit the oxidation kinetics. In this case, radiation is advantageously used to support the breakdown of hydrocarbons.

According to a further embodiment of the invention, peroxides / hyperoxides in gaseous and / or liquid and / or solid form, preferably hydrogen peroxide and / or ozone, are used exclusively or additionally as oxidizing agents.

The use of catalysts also leads to an acceleration of the degradation reactions

AT 409 226 B on the hydrocarbons. Depending on its composition, the catalyst can be introduced as a fine material and then remain in the de-oiled material or be introduced into the vessel in the form of larger pieces, the pieces then being separated from the de-oiled material and reinserted. Before re-use, a treatment to increase the activity of the catalyst is also possible, depending on the type of catalyst.

The decomposition of the hydrocarbons, for example through exothermic oxidation, generates additional heat that is effective directly on the waste material and thus heats the waste material from the inside out. This improves the heating and thorough heating of the input material and accelerates the process.

The addition of oxidizing agents leads to an oxidative partial degradation of the hydrocarbons, which in turn leads to a lowering of the volatilization temperature and therefore to a more rapid volatilization of the hydrocarbons.

According to a particularly preferred embodiment of the method according to the invention, high-energy radiation, in particular in the form of UV radiation, is introduced into the dryer as a radiation aid to decompose the hydrocarbons.

This accelerates the degradation reaction.

The decomposition of the hydrocarbons, for example the cleavage of the chemical bond by means of high-energy radiation, generates additional heat that is directly effective on the waste material and thus heats the waste material from the inside (in the dryer). This improves the heating and thorough heating of the input material and accelerates the process.

According to a further embodiment of the method according to the invention, a maximum temperature of 350 ° C., in particular 300 ° C., based on the heating medium, is set in the dryer.

According to further special embodiments of the method according to the invention, the dryer is operated at a pressure-dependent internal temperature of 40 ° C to 350 ° C or 300 ° C or up to 450 ° C, preferably 400 ° C, in particular in the range of 80 ° C to 250 ° C, particularly preferably 120 ° C to 200 ° C (at 1 atm).

It cannot be ruled out that briefly, in particular locally, the input material is heated above the process temperature.

According to an additional feature of the method according to the invention, the waste material is mechanically dewatered and / or chemically and / or thermally predried before the treatment.

The pre-dewatering or pre-drying already removes a large proportion of the water from the mill scale sludge, which significantly reduces the throughput or treatment times in the vessel for removing the hydrocarbons.

According to a further embodiment of the invention, at least part of the H₂O content of the waste material can be bound by adding quicklime, the amount of quicklime added preferably corresponding to or below the stoichiometric ratio of the lime slaking reaction.

The reaction of the quicklime generates heat, which significantly accelerates the heating of the waste material. Furthermore, the addition of the lime proves to be particularly advantageous for the further processing of the waste material, for example in a sintering plant or in an agglomeration process. In particular in the case of agglomeration (e.g. granulation, briquetting), the use of an additional binder can be dispensed with at least partially in this way. Experience has shown that agglomeration without additional binders is possible with an addition of more than 5% by weight of CaO. Finally, as is already known to the person skilled in the art from the prior art, the agglomerates can be hardened with CO₂ (Limestone formation).

According to a further additional feature of the method according to the invention, the temperature of the waste material and / or the composition of the extracted gases is measured in the dryer. According to a further feature of the method according to the invention, a control and / or regulation of the process parameters of the treatment in the dryer, for example the movement intensity in the dryer and / or the heating power in the dryer and / or the quantitative use of chemical and / or radiation technology aids, is based on the determined measured variables to break down the hydrocarbons.

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For efficient control of the process, it is advantageous to measure the temperature in the vessel, preferably the temperature of the waste material, and / or the temperature and / or the composition of the extracted gases (one or more of: carbon monoxide content, carbon dioxide content, hydrogen content, oxygen content, hydrocarbon content) . The measured variables determined support the control and / or regulation of the process parameters, in particular the heating energy supply and / or the oxidizing agent supply and / or the movement intensity, which can be suitably changed in the course of the process.

By evaluating the measured variables, conclusions can be drawn about the progress of the reaction in the process. In this way, a product can be manufactured that has a consistent composition and meets the high quality standards of the iron and steel industry. In particular when the end product of the process according to the invention is used in a sintering plant and / or charging into a blast furnace, the end product may only have a limited content of hydrocarbons. Even when recycling contaminated soil, strict requirements regarding the maximum content of hydrocarbons must be observed.

The temperature on the vessel is preferably measured with thermocouples, which are guided into the working area of ​​the vessel in a protective jacket tube.

According to a particular embodiment of the method according to the invention, a control variable is determined by comparing the hydrocarbon content of the waste material before and after the treatment in the drying vessel, for example by analyzing the gas composition, and taking into account the temperature and / or the intensity of movement of the input material in the dryer, the quantitative use of chemical and / or radiation technology aids to break down the hydrocarbons is regulated.

According to a particular embodiment of the method according to the invention, the extracted gases are passed into a, preferably thermally insulated and / or indirectly heated, dedusting device, in particular a hot gas cyclone, for dedusting, preferably via heated lines.

For the treatment of the extracted gases, the person skilled in the art can choose from various exhaust gas cleaning processes, depending on the type of hydrocarbons. However, it is advantageous to guide the extracted gases into a, preferably thermally insulated and / or indirectly heated, dedusting device in order to separate dust particles entrained from the vessel. The heating of the lines which are used to transport the extracted gases is advisable and is provided in accordance with a further advantageous embodiment of the method according to the invention and the device according to the invention.

The dedusting device is preferably operated at a temperature which is at least as high as the temperature in the vessel. This prevents the volatile components, in particular the preferably higher-boiling hydrocarbons, from precipitating on cold surfaces.

According to a further embodiment of the method according to the invention, the exhaust gases, preferably pre-dedusted, are cooled in a cooler, preferably a condenser, and optionally then filtered in an activated carbon filter and / or biofilter.

According to a further embodiment of the method according to the invention, the exhaust gases, preferably pre-dedusted, are thermally or catalytically post-burned.

According to a particular embodiment of the method according to the invention, the energy from the thermal or catalytic post-combustion is used to heat the dryer, for example to heat a thermal oil, and / or other devices to carry out the method.

The hydrocarbons are preferably completely broken down by combustion in a thermal or catalytic post-combustion. The energy of this combustion is advantageously used, for example to heat the heating medium which is required to heat the vessel.

The invention proves to be particularly advantageous in the treatment of mill scale slurries and grinding slurries, and is documented in the most detailed manner in this regard. However, the statements on this special medium are only exemplary in nature and in no way limit the application of the subject matter of the invention to the treatment of sludges

AT 409 226 Β in general or mill scale slurries in particular.

The method according to the invention and the device according to the invention can also be used for treating other waste materials containing hydrocarbons, in particular those containing solid particles, preferably in the metalworking industry, such as those obtained, for example, in the production or processing of aluminum, titanium or copper. Furthermore, hydrocarbon-containing solids and / or sludge from the non-metal-processing industry, in particular grinding sludge, can also be treated according to the inventive method.

The method according to the invention and the device according to the invention are also suitable for cleaning oil-contaminated floors.

The inventive separation of the hydrocarbons from the solid and / or sludge, in particular from the mill scale sludge, allows the end product of the process to be used in sintering plants or other facilities for which a low hydrocarbon content is required.

If an oxidizing agent is used, the metallic components contained in the waste material are partially oxidized, with the exothermic oxidation taking place to a limited extent, the temperature in the interior of the dryer increasing rapidly and without additional heating, thus saving considerable heating costs. Last but not least, as already mentioned, the oxidation of the hydrocarbons also contributes to the further heating of the mill scale sludge.

If an oxidizing agent is used as a chemical aid to decompose the hydrocarbons, the conversion of the hydrocarbons is essentially complete from a temperature that depends on the respective input material (for mill scale slurries this is around 180 - 200 ° C (1 atm)) Exothermic reactions, in particular the oxidation of wüstite to haematite and / or to magnetite, a sharp rise in temperature takes place.

If, in addition to the hydrocarbons, the waste material contains other substances that react exothermically with the oxidizing agent, for example wustite or other metallic components, it is advantageous, in particular for the targeted limitation of the product temperature, to have a controllable supply of inert gases, preferably beyond the regulation of the oxidizing agent supply to be provided. With this procedure, the regulation of the temperature as well as the oxidation of the waste material in the treatment chamber can be accelerated considerably.

According to an advantageous embodiment of the invention, the process, in particular the temperature of the waste material in the treatment chamber, can be controlled by regulating the indirect heating, for example also in the sense of cooling the heating medium (cooling medium).

The process is operated continuously or as a batch process.

The following non-limiting process data from experiments using O₂ as oxidizing agents vary depending on the type of mill scale and the rolling oils used.

Process management: batch operation

Amount of feed material: 11 Oil content of the mill scale before and after treatment:

Before treatment: 1-5% by weight

After treatment: <0.1-0.3% by weight

Water content of the mill scale before and after treatment:

Before treatment: 10-40% by weight

After treatment: <0.1% by weight

Treatment temperature: start at RT; End at 250-350 ° C

Treatment time: 30-60 min

Oxygen: 20-30 vol%

Vessel size: 1.5 m³

Vessel type: indirectly heated jacketed mixer (heated with thermal oil)

Movement intensity: 30-100 revolutions per minute

The invention is further characterized by a device for carrying out the method according to the invention according to claim 14.

According to various embodiments of the invention, the dryer is provided as a heated rotary tube or heated screw conveyor or as a heated mixer.

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According to further embodiments of the invention, the dryer according to the invention also fulfills the function of a mixer and / or granulator, for example in the form of a mixer with a horizontal or vertical shaft. In another embodiment, the vessel is designed as a rotary tube or a mixing screw.

According to an additional feature of the device according to the invention, a conveying means for supplying oxygen and / or peroxide / hyperoxide and / or ozone into the treatment chamber of the dryer is provided as a device for breaking down the hydrocarbons.

According to a further preferred embodiment, a radiation source for irradiating the waste material in the treatment chamber of the dryer, in particular with UV radiation, is provided as the device for breaking down the hydrocarbons.

According to a further preferred embodiment, a line for supplying carrier gas, in particular inert gas, is provided on the dryer.

According to a further preferred embodiment, a device for moving the waste material is provided in the dryer and / or the treatment room itself is designed to be rotatable.

According to a further preferred embodiment, a heat-insulated and / or, preferably indirectly, heatable dedusting device is provided for dedusting the gases sucked out of the treatment chamber, which optionally via a number of heat-insulated and / or additionally heatable lines on the one hand with the dryer and on the other hand with other devices for treating the gases extracted from the dryer.

The dedusting device can be designed, for example, as a cyclone or as a filter. Dedusting by means of an electrostatic precipitator, as known to the person skilled in the art from the prior art, can also be considered. According to a preferred embodiment of the device according to the invention, the dedusting device can connect directly to the vessel and can preferably be heated together with the vessel.

In another embodiment, a washer is provided as the dedusting device.

According to a further preferred embodiment, a cooler, preferably a condenser, and optionally an activated carbon filter and / or biofilter for cleaning the extracted gases is provided after the dryer, optionally after the dedusting device.

The condenser, as known from the prior art, expands the exhaust gas and / or cools it down and / or separates higher-boiling components of the gas, in particular hydrocarbons. An activated carbon filter can be installed after the condenser for further cleaning of the exhaust gases.

According to a further preferred embodiment, a thermal or catalytic post-combustion device for treating the extracted gases is provided after the dryer, if necessary after the dedusting device.

The post-combustion device is advantageously coupled to the heating device of the vessel so that the energy released during post-combustion is used.

According to a particular embodiment of the device according to the invention, a flame arrester device, in particular in the form of an immersion quench, is provided after the dryer, if necessary after the dedusting device.

According to a further particular embodiment of the device according to the invention, freely movable bodies, in particular beater bars, are provided in the dryer, which reduce any caking of waste materials on the dryer and the formation of agglomerates.

According to a further preferred embodiment, one or more probes and / or sensors are attached to the gas discharge line for discharging the gases produced in the treatment chamber and / or to the dryer, whereby the temperature and / or composition of the extracted gas and / or the temperature in the vessel can be determined, and the device for indirect heating of the dryer and / or the devices for moving the waste material in the treatment chamber are designed to be controllable.

The sensors and / or probes are particularly preferably used to determine the carbon monoxide content and / or the carbon dioxide content and / or the hydrogen content and / or the oxygen content and / or the hydrocarbon content and / or the temperature in the vessel.

According to a feature of the device according to the invention, the means for supplying the

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Oxidizing agent attached to the vessel control devices, with which the oxidizing agent supply can be regulated.

According to one feature of the device according to the invention, control devices are attached to the means for heating the vessel, with which the energy supplied for heating the vessel can be regulated.

According to a feature of the device according to the invention, control devices are attached to the means for moving the solid matter and / or sludge, with which the movement intensity can be controlled.

According to a preferred embodiment, the solids and / or sludge are introduced into the dryer via an intermediate bunker with a corresponding metering device.

The method according to the invention and the device according to the invention are explained in more detail below with the aid of non-restrictive drawings.

FIGS. 1 and 2 show non-limiting schematic embodiments of devices for carrying out the method according to the invention.

According to FIG. 1, a device for carrying out the method according to the invention is shown, a vessel 1 being charged with preferably pre-dewatered mill scale sludge via a conveying line 2. The mill scale sludge has already been pre-dewatered by mechanical treatment and has a low water content and a high content of hydrocarbons. The vessel 1 is equipped with a device 3 for moving the mill scale sludge introduced into the container for treatment.

Oxidizing agent is fed to the vessel 1 via a number of lines 4. In addition to the oxidizing agent, inert gases, preferably nitrogen, can be introduced into the dryer. 1 shows a quasi-continuous process, the mill scale sludge being conveyed through the vessel and finally transported away through a line 5 for further use. The exhaust gases produced in the vessel are introduced into a heat-insulated and heated gas dedusting device 7 via a heated line 6, the gas being separated from dust which is discharged via a line 8. The gas is conveyed further via a heated line 9 into a condenser 10, expanded and cooled in this condenser, and the condensed liquid is discharged via a drain 11. A number of cooling lines 12, 13 are provided for cooling the condenser.

Finally, the gas reaches an activated carbon filter, for example, and is freed from further impurities, for example residual hydrocarbons.

The vessel in FIG. 1 is preferably heated indirectly, with a heating medium 14 flowing through the jacket of the vessel. A number of valves and sensors or probes are provided on the various lines for transporting the, in particular gaseous, media, through which the flow rate, the composition or other measured variables are recorded or controlled. In this case, sensors for recording the concentration 15 and flow meters / valves 16 for controlling the flow rate are attached to the line 4 for supplying the oxidizing agent. A sensor 17 for determining the temperature of the heating medium is attached to the line for supplying the heating medium 14 and to the line 18 for discharging the heating medium. The pressure drop in the exhaust gas is determined by a sensor 19 on the gas dedusting device. Finally, after the condenser, a probe 21 for determining the carbon monoxide, carbon dioxide and oxygen content is provided on a line 20 for discharging the residual gas.

The process temperature is recorded by temperature measuring sensors 22 and represents a guide value for the process control.

FIG. 2 shows a further preferred, non-limiting, embodiment of a device for carrying out the method according to the invention, the method operating in batches (batch operation).

The device differs from the embodiment shown in FIG. 1 in that the exhaust gas is thermally post-burned after the filter in an afterburning chamber 24 with a burner 26. The energy of the exhaust gas is used to heat the vessel 1 by means of a heat exchanger 25.