WO1989004730A1

WO1989004730A1 - Process and device for thermal treatment of contaminated bulk materials

Info

Publication number: WO1989004730A1
Application number: PCT/EP1988/001043
Authority: WO
Inventors: Dieter Stalherm; Horst Dungs; Dieter Hollenhorst; Herbert Taron
Original assignee: Still Otto Gmbh
Priority date: 1987-11-19
Filing date: 1988-11-17
Publication date: 1989-06-01

Abstract

In a process for thermal treatment of contaminated bulk materials in a calcination step in order to dispose of or remove toxic comonents, the gases containing the toxic substances which are evolved during the calcination step are evacuated to atmosphere after a final purification step. The invention also concerns a device for implementing the process. The calcination of contaminated bulk materials is carried out in an indirectly and/or directly heated and in particular continuously operated vertical shaft oven (3).

Description

Method and device for the thermal treatment of contaminated bulk materials

description

The invention relates to a method for the thermal treatment of contaminated bulk goods in an annealing treatment stage for the disposal or removal of toxic constituents, the pollutant-containing gases withdrawn from the annealing treatment stage being released outdoors after a final cleaning and to a device for carrying out the method with the features in the preamble of claim 16.

Contaminated soil and bulk goods are present on many former industrial sites of petrochemicals, mining, in particular coke oven plants and their processing plants, and gas plants. Among these contaminated bulk materials are z. B. to understand with tar, phenolic and oily constituents and heavy hydrocarbons contaminated masses, which may be excavated contaminated soil, dried mud, clay or silt from harbor basins. Thermal processes are particularly suitable for cleaning predominantly organically contaminated floors. Here aromatic, aliphatic and polycyclic / halogenated hydrocarbons are used completely destroyed. Cyan-contaminated floors can also be cleaned.

Processes for the thermal treatment of contaminated earth are known from various publications (e.g. DE-OS 34 47 079), in which the earth is thermally treated in directly or indirectly heated rotary drums with partial combustion of the decomposition products from the earth, and that the resulting production gas is subsequently burned to destroy the toxic constituents. In the case of direct heating in particular, the dust content of the production gas is relatively high, so that problems can arise in the afterburning. In addition, there are limits to the thermal treatment in rotary kilns when increasing the throughput and the treatment temperatures.

The invention has for its object to improve the generic method in relation to the problems mentioned.

To solve this problem, the invention provides that the annealing treatment of the contaminated bulk goods takes place in an indirectly and / or directly heated and in particular continuously operated vertical shaft furnace. Discontinuous operation with known entry and exit systems is also possible. It has been shown that during the thermal treatment in such a vertical shaft furnace, in particular with exclusively indirect heating, the degassing or production gas drawn off contains negligible amounts of dust. This stationary system is particularly economical, particularly with larger throughputs. This applies above all if the gases drawn off during the annealing treatment are afterburned after a possible cooling in the indirect heating stage of the vertical shaft furnace, the combustion temperatures and boiler residence times corresponding to the pollutant requirements of the gases to be burned out. It is possible to dispense with the post-combustion chamber that has been customary up to now and from the indirect one Heating system coming flue gases can, if necessary at all, be subjected to a conventional exhaust gas cleaning with desulfurization and / or denitrification.

The annealing treatment temperature in the vertical shaft furnace can be varied within wide limits, for example between 400 and 1,250 C, according to the temperatures required for the pollutants present. If the bulk material needs to remain in the vertical shaft furnace, it is advantageous if the heat supply to the indirect heating stage is regulated depending on the required final product temperature. That is e.g. B. possible with the known so-called pause heating, with the heating setting taking the different heat requirements being taken into account by taking heating pauses. In addition, it may be expedient to mechanically separate the contaminated bulk goods outside the vertical shaft furnace by comminuting them to a preferred grain size range of 5 to 20 mm and thermally by drying and / or preheating them in a known manner in series, directly in countercurrent pretreated with hot gases heated rotary kilns. The fine dusts which are separated from the gases containing dust removed during the pretreatments by means of dry dedusting can, according to the invention, also be placed in the vertical shaft furnace. To take advantage of the sensible heat of the contaminated bulk goods after the annealing treatment, it is advisable to use the bulk goods preferably indirectly with the production of e.g. B. to cool high-tension steam.

In accordance with environmental protection regulations, the heating exhaust gases from the thermal treatment stages of a final chemical and / or physical flue gas cleaning, e.g. B. Desulfurization and denitrification.

To solve the problem according to the invention, it is also proposed that the annealing treatment of the contaminated bulk goods be carried out in one or more rotary Pipe furnaces in direct heat exchange with hot gases, preferably flue gases, take place and only the fine dust separated after dry dust removal is heated in an indirectly heated vertical shaft furnace at least to the treatment temperatures of the other bulk materials and then, if necessary, added to them.

Here, the hot fine dusts drawn off on the feed side of the contaminated bulk goods are not subjected to intermediate cooling after the dry dedusting, but instead are fed directly to an indirectly heated oven for further heating and are heated there to the treatment temperature of the other bulk goods. In the case of indirect heating, the fine dusts are in particular not associated with additional flue gases. Only the relatively low volume flows of expelled pollutants are subtracted, which can be easily combusted with the other heating or flue gases. Indirect heating is preferably carried out in a vertical shaft furnace through which the bulk goods are moved continuously from top to bottom. In the lower area of the shaft furnace, they can then already be subjected to indirect intermediate cooling. As a result, the temperatures at the discharge devices can be kept relatively low even at high treatment temperatures, so that materials which are not too expensive do not have to be used.

The heat of the exhaust gases, which generally occur at well over 1,000 ° C after the afterburning, can be used directly and / or indirectly first for indirect heating of the shaft furnace and then for preheating the combustion media in the annealing treatment devices and / or afterburning. With indirect preheating of the combustion media for indirect heating, the flue gases generated can be disposed of directly in a chimney.

The invention also relates to a device for carrying out the method described, which is based on the Written device goes out and is characterized in that an indirectly heated shaft furnace is connected to the dust on the dust side and that the shaft furnace is connected via a conveying device for the dust to a mixer maintained after the annealing treatment device. A cooling device for the cleaned bulk goods can be connected to the mixer with a return device for the cooled bulk goods to the mixer. In particular at very high treatment temperatures of the bulk goods, this partial return of the already cooled bulk goods to the mixer can considerably lower the entry temperature into the final cooling drum. The cooling drum can thus also be constructed in a simpler and more cost-effective manner.

The invention is explained in more detail, for example, with the aid of the attached FIGS. 1 and 2.

According to FIG. 1, the continuous bulk material feed (1) takes place in a vertical shaft furnace (2) using suitable filling systems. With an hourly throughput of 5 t / h, the composition of the bulk material is as follows:

Earth dry 4,400 kg

Temperature 20 ° C average grain size D '10 mm.

The bulk material is continuously heated by the indirectly heated

Vertical shaft furnace with a shaft volume of approx. 25 to 30

3 m transported. The vertical shaft furnace (2) is followed by a preferably two-stage indirect cooling at the bottom after a possibly interposed shut-off stage, the water supplied via the pump (20) being preheated in the colder stage (4). In the upper, hotter cooling stage (3), high-tension steam is collected in the steam drum (21) and drawn off via the line (24). On the pump (22) at Natural circulation via the bypass (23) can be dispensed with. 4,400 kg of cleaned dry earth leave the system at a temperature of approx. 50 ° C at the lower outlet (5).

At the upper end of the vertical shaft furnace (2), carbonization gas laden with pollutants is drawn off via the line (6), which after indirect cooling (7) is fed into the indirect heating stage (9) with the aid of the blower (8). There it is burned with the addition of additional heating gas (G) and combustion air (L) supplied at different levels. The extracted flue gas (11) is used in regenerators or recuperators for preheating the combustion air and at a temperature of approximately 350 ° C. after any flue gas desulfurization (12) and denitrification (13) required with the blower (14) the fireplace (15) completely cleaned in the atmosphere. To cool the carbonization gas in the indirect cooler (7), cooling water can be circulated via an indirect heat exchanger (17) with a pump (16), the heat exchanger (17) in turn connected to an open cooling water circuit with a cooling water pump (18) and cooling tower (19) is connected.

According to FIG. 2, the contaminated bulk goods are fed in via (31) at the head of the first rotary drum furnace (33). At the opposite end is the direct burner (34), to which gas (G) and air (L) are supplied. In countercurrent to the flue gases, the bulk goods are transported lengthways through the rotary drum (33) and are dried and heated in direct heat exchange. As a rule, the treatment end temperature of the bulk goods is 600 to 800 ° C., the heating taking place in a drum and the subsequent drum being dispensed with. In this case, the outlet temperature of the flue gases from the rotary drum (33) near the feed point of the bulk goods is approx. 300 to 350 ° C. However, if the contaminated bulk goods have to be heated to 1200 C for certain reasons, two rotary kilns (33) are connected in series. In this case The temperature of the flue gases emerging from the two rotary drums (33) in the mixture rises to approx. 500 to 600 C. With this direct heating in the rotary tube furnaces, depending on the fineness of the bulk goods, up to 30% by weight, based on the amount of fine dust discharged with the flue gases. This fine dust is in the dry dedusting (25), the z. B. consists of a bag filter system or multi-cyclones, separated and then brought in an indirectly heated shaft furnace (28) to the treatment temperature of the other bulk materials. The flue gases enter the afterburning chamber (26), where they are treated and treated by the direct burner (27) at temperatures of 1000 to 1300 ° C. The exhaust gas is led via line (36) to the final cleaning (not shown) and possibly to heat recovery before it reaches the atmosphere via the chimney.

The fine dust separated in the dedusting station with the help of bag filters or multicyclones, which due to the circumstances have only been subjected to a treatment temperature of 300 to 350 C or 500 to 600 C, are heated to a temperature of 600 to 800 ° C in the indirectly heated shaft furnace or heated up to 1200 C in the alternative with the two rotary kilns. The pollutants expelled from the fine dust here, together with the flue gases from the rotary kilns, reach the exhaust gas combustion system (26). The flue gases resulting from the indirect heating of the shaft furnace from the heating walls (30) are sucked off in a pressure-controlled manner via a flue gas blower (39) and passed via line (37) to the chimney (not shown). The size of the flue gas pressure in the heating cables is regulated so that it is practically identical to the gas pressure inside the shaft furnace (28) (+/- 1 mbar). The lower part of the shaft furnace (28) is equipped with an indirect cooling device (29), the filter dust heated to 600 to 800 ° C or alternatively to 1200 ° C being cooled to below 600 ° C with the aid of cooling water (35) . The cooled filter dust is sam with the thermally treated bulk goods from the rotary drum furnaces (33) into the mixer (32) and then cooled in the cooling drum (40) likewise with the aid of cooling water (35). A bulk material cooled to approx. 50 ° C. is then drawn off at (38). In the event that the earth in the rotary drum furnaces (33) has to be heated to above 600 ° C (e.g. to 1200 ° C), a part of the bulk material, which has already been cooled to 50 ° C, is conveyed via the return conveyor (41 ) transported to the mixer (32), a mixing temperature of below 600 ° C. being set when entering the cooling drum (40).

Reference list

(1) Bulk infeed

(2) vertical shaft furnace (3), (4) cooling stage

(5) cleaned bulk goods

(6) dusty gas

(7) indirect cooler

(8) blower

(9) indirect heating level

(10) blower

(11) flue gas

(12) Flue gas desulfurization

(13) Denitrification

(14) blower

(15) fireplace

(16) pump

(17) heat exchanger

(18) Cooling water pump

(19) cooling tower

(20), (22) cooling water pump

(21) steam drum

(23) Bypass

(24) steam

(25) Bag filter system or multi-cyclone

(26) Post combustion chamber

(27) direct burner

(28) indirectly heated shaft furnace

(29) Cooling device

(30) heating walls

(31) Bulk goods deliveries

(32) mixer

(33) rotary drum furnaces

(34) direct burners

(35) Cooling water

(36) Exhaust gas for gas cleaning

(37) Exhaust gas to the fireplace

(38) cleaned bulk goods

Claims

1. A process for the thermal treatment of contaminated bulk materials in an annealing treatment stage for the disposal or removal of toxic constituents, the pollutant-containing gases withdrawn from the annealing treatment stage being released into the open after a final cleaning, characterized in that the annealing treatment of the contaminated bulk materials is carried out indirectly and / or directly heated and in particular continuously operated vertical shaft furnace.

2. The method of claim 1, d a d u r c h g e k e n n ¬ z e i c h n e t that the gases withdrawn from the bulk material during the annealing treatment are afterburned in the indirect heating stage of the vertical shaft furnace after a possible cooling and dry dedusting.

3. The method according to claim 1 or 2, dadurchge ¬ indicates that the annealing treatment of the entire contaminated bulk goods in the vertical shaft furnace at a product end temperature adapted to the requirements temperature of 400 to 1,250 ° C.

4. The method of claim 3, d a d u r c h g e k e n n ¬ z e i c h n e t that the heat supply to the indirect heating stage is regulated depending on the required product temperature when the bulk material needs to remain in the vertical shaft furnace.

5. The method according to at least one of claims 1 to 4, that the contaminated bulk goods are subjected to mechanical pretreatment by comminution to a preferred particle size range of 5 to 20 mm.

6. The method according to at least one of claims 1 to 5, that the contaminated bulk goods are subjected to a thermal pretreatment by drying and / or preheating outside the vertical shaft furnace.

7. The method according to claim 6, that the pretreatment is carried out in one or more rotary kilns connected in series, preferably heated directly in countercurrent with hot gases, in a rotary kiln.

8. The method according to claim 5 to 7, so that the dust-containing exhaust gases removed during the pretreatment are subjected to a dry dedusting and the separated fine dusts are placed in the vertical shaft furnace.

9. The method according to at least one of claims 1 to 8, characterized in that the cleaned bulk goods after the annealing treatment, preferably indirectly, are cooled. 10. The method according to at least one of claims 1 to 9, characterized in that the heating exhaust gases of the thermal treatment stages are subjected to a final chemical and / or physical Rauch¬ gas cleaning.

11. Process for the thermal treatment of contaminated bulk goods in a glow treatment stage for the disposal or removal of toxic constituents, the pollutant-containing gases withdrawn from the glow treatment stage being released outdoors after a final cleaning, characterized in that the glow treatment of the contaminated bulk goods in one or Several rotary tube furnaces connected in series in direct heat exchange with hot gases, preferably smoke gases, are carried out and only the fine dust separated after dry dedusting is heated in an indirectly heated vertical shaft furnace to at least the treatment temperatures of the other bulk materials and then, if necessary, these be added.

12. The method according to claim 11, so that the fine dust is mixed with the other cleaned bulk goods after the indirect heating after a, preferably indirect, intermediate cooling.

13. The method according to any one of claims 7 or 8, d a ¬ d u r c h g e k e n n z e i c h n e t that the pollutants expelled from the fine dust in indirect heating are burned together with the other heating or flue gases.

14. The method according to claim 13, characterized in that the exhaust gases from the afterburning are used directly and / or indirectly for indirect heating. is. Method according to at least one of claims 1 to 14, characterized in that the waste gases from indirect heating are used to preheat the combustion media in the glow treatment device and / or afterburning.

16. Device for performing the method according to one of claims 11 to 15, with

an annealing treatment device which has one or more rotary tube furnaces (33),

- a dry dedusting (25),

- An afterburning chamber (26) connected to the dry dedusting on the gas side

- A device for final cleaning of the exhaust gases until discharge into the open, characterized in that an indirectly heated shaft furnace (28) is connected to the dry dust (25) on the dust side and that the shaft furnace (28) is connected to the glow treatment device via a conveying device for the dust Mixer (32) is connected.

17. The apparatus of claim 16, so that the mixer (32) is followed by a cooling device (40) for the cleaned bulk goods with a return device (41) for the cooled bulk material to the mixer (32).

18. The apparatus of claim 17, so that the shaft furnace (28) is provided in the lower part with a cooling device (29) for indirect cooling of the fine dust.