BE1028604B1 - Plant and method for reducing the mercury content in the processing of waste for use as a substitute fuel - Google Patents

Abstract

The present invention relates to a plant for the processing of refuse for use as substitute fuel in a combustion device, for example in a plant for the production of cement clinker, the plant having a processing device (10) and a transport device (20) arranged downstream of the processing device (10) in the direction of material flow. has, wherein the transport device (20) has an ejection device, wherein the processing device (10) brings about heat input into the waste, wherein the processing device (10), the transport device (20) or both the processing device (10) and the transport device (20 ) has a suction device (40), characterized in that a partial gas flow (70) is removed from the suction device (40), the partial gas flow (70) being passed through an optical cell (100), the partial gas flow (70) in the optical cell (100) the mercury concentration by means of a detection device b can be determined, the detection device detecting the mercury concentration by means of atomic absorption spectroscopy, an evaluation device being connected to the detection device, the evaluation device being connected to the ejection device, the evaluation device being designed to eject the contaminated waste through the ejection device if a specified concentration of mercury is exceeded .

Description

'BE2020/5637 System and method for reducing the mercury content in the processing of waste for use as a substitute fuel The invention relates to a system and a method for removing mercury-contaminated waste from a material flow for using the waste as a substitute fuel. Garbage is now often used as a substitute fuel. The problem, however, is that the waste can be loaded with mercury. In the event of combustion, this is often emitted with the exhaust air. In addition to the problems of pollution of the environment, there is a particular risk for an operator that limit values can be exceeded here, which could jeopardize his operating license. For example, mercury is found in garbage from dental fillings, fluorescent and energy-saving light bulbs, batteries, cosmetics, electrical and electronic equipment, measuring instruments, catalytic converters, laboratory equipment, preservatives and paints. Thermometers and barometers are only mentioned as examples of measuring instruments. Preservatives and colors are particularly important when disposing of waste wood, where the wood has been impregnated with the appropriate preservatives. Also worth mentioning is the disposal of textiles that may have been contaminated with mercury through dyeing during manufacture. One problem is that these contaminated components hidden in the garbage cannot be found indirectly, so direct easy removal is usually not possible. DE 41 22 113 A1 discloses a method for removing mercury from sewage sludge and using the sewage sludge thus obtained as fuel.

A method and system for improving solid fuel properties is known from EP 2002 179 B1.

JP 2004 359 771 A discloses a method for detoxifying mercury in particular for the production of fuels.

The object of the invention is to avoid the entry of waste contaminated with mercury into an incineration plant by removing contaminated waste in a targeted manner.

This problem is solved by the system with the features specified in claim 1 and by the method with the features specified in claim 7 . Advantageous developments result from the dependent claims, the following description and the drawings.

The system according to the invention is used to process waste for use as a substitute fuel in a combustion device. For example and preferably, the combustion device is part of a plant for the production of cement clinker.

The system has a processing device and a transport device arranged downstream of the processing device in the direction of material flow. The processing device applies heat to the waste.

For example and preferably, the processing device is a comminution unit, for example and in particular a shredder or a cutting mill, particularly preferably a shredder. A shredder is used for mechanical shredding. For this purpose, mechanical energy is introduced into the waste for shredding. Two effects occur here. On the one hand, for example, hollow bodies containing mercury, for example corresponding lamps, are destroyed so that the mercury can escape. On the other hand, the introduction of mechanical energy results in heating, which also converts mercury into the gas phase. Thus, mercury in the gas phase can be detected in the exhaust air from the processing device or in the waste transported out of the processing device.

The transport device has an ejection device. The ejection device is, for example and preferably, a reversible conveyor belt, a belt switch, a scraper or a pusher. In the case of a reversible conveyor belt, this is preferably arranged directly behind the processing device in the direction of the material flow, so that the waste is fed in close to one end of the conveyor belt. For example and in particular, the reversible conveyor belt is thus arranged under the processing device, for example a shredder, or downstream of a shredder in the direction of transport. The waste is transported further to incineration in the normal transport direction, with the waste being transported further along the longer distance of the conveyor belt. In order to carry out an ejection, the running direction of the conveyor belt is reversed, so that the refuse emerging from the processing direction is transported via the short end of the conveyor belt, for example, to a store for later disposal. After the ejection, the conveyor belt is switched back to the usual transport direction.

The processing device, the transport device or both the processing device and the transport device have a suction device. According to the invention, a partial gas flow is taken from the suction. For example and in particular, the pointer flow is taken from the exhaust gas flow via a probe and passed on via a pipe or hose. The mercury concentration in the partial gas flow is determined by means of a detection device.

An evaluation device is connected to the detection device. The evaluation device is also connected to the ejection device. The evaluation device is designed to eject the contaminated waste through the ejection device when a predetermined concentration of mercury is exceeded. In this case, the decision about ejection can be made not only on the basis of the mercury concentration, but also on the basis of the mercury concentration over time. In this case, a conclusion about the type of contamination can be drawn from the concentration and the course of the concentration. For example, breaking a lamp containing mercury can cause a brief but very sharp increase in the mercury concentration in the exhaust air. The crime, for example, of a mercury

clinical thermometer would release large amounts of liquid mercury in particular and therefore cause a smaller increase in the mercury concentration. In the case of waste wood with a mercury-containing impregnation, the increase in the mercury concentration would be lowest, but over a longer period due to the large spatial extent. In another embodiment of the invention, it is conducted through an optical cell. In the optical cell, the mercury concentration in the part of the stream is determined by means of a detection device, the detection device detecting the mercury concentration by means of atomic absorption spectroscopy. The use of atomic absorption spectroscopy is preferred, since this also works relatively trouble-free in the matrix and with very high sensitivity. Furthermore, since only one element, in this case mercury, is to be detected, atomic absorption spectroscopy is preferable to atomic emission spectroscopy for this application. Cold vapor atomic absorption spectroscopy is particularly preferred, and it is usually possible to dispense with the addition of a reducing agent since the mercury is already expelled from the processing device in its elemental form. The measurement is preferably carried out in a temperature window of 50°C to 100°C.

Optionally, a so-called gold trap can be connected upstream of the cold vapor atomic absorption spectroscopy. The precisely defined volume of the sample gas is passed through a gold trap. Here, the metallic mercury combines with the gold. After a collection phase, the gold trap is heated up electrically. As a result, the mercury is released again and conveyed through the optical cell (cuvette) with an inert carrier gas stream. In an alternative embodiment, the detection device is based on energy dispersive X-ray spectroscopy (EDX). For this purpose, an electron beam is directed into the partial flow and the emitted X-ray radiation is recorded. In an alternative embodiment, the detection device is a mass spectrometer.

> BE2020/5637 In an alternative embodiment, the detection device is a gas chromatograph. In a further embodiment of the invention, the partial gas flow between the suction device and the optical cell can be heated. The advantage of this embodiment is that precipitation of water can be avoided. In particular, the target temperature can be tracked according to the ambient conditions and temperature in the shredding unit, for example the shredder.

In a further embodiment of the invention, the partial gas flow is removed by means of a diaphragm pump. The diaphragm pump is particularly preferably arranged behind the optical cell in the partial gas flow. A diaphragm pump is preferred because it requires particularly little maintenance and does not have any major interaction with the partial gas flow.

In a further embodiment of the invention, the partial gas flow has a filter device between the suction device and the optical cell. A filter can be used to remove dust, for example. This avoids scattering of the measuring beam in the optical cell and its contamination. The filter device preferably has a blockage detection system, for example a first pressure sensor arranged in front of the filter and a second pressure sensor arranged behind the filter. The degree of contamination of the filter can be deduced from the pressure difference.

In a further sprawling invention, the detection device has a low-pressure mercury lamp as the light source. A beam splitter, for example a semi-transparent mirror, is particularly preferably arranged between the low-pressure mercury lamp and the optical cell. A portion of the beam is directed to a reference detector, which continuously records the intensity of the low-pressure mercury lamp. The mercury concentration can thus be determined reliably and with time stability.

In a further aspect, the invention relates to a method for discharging waste contaminated with mercury from a plant according to the invention, the method having the following steps: a) processing waste in a processing device, b) sucking off the air above the waste processed in step a). Garbage, c) continuous removal of a partial gas flow from the air extracted in step b), d) passing the partial gas flow through an optical cell, e) recording the mercury concentration of the partial gas flow in the optical cell, f) evaluating the mercury concentration measured in step e), g) decision based on the evaluation in step f) whether the waste is incinerated or ejected by means of the ejecting device, h) injecting the waste for incineration or ejecting the waste according to the decision made in step g).

In a further embodiment of the invention, the partial gas flow is returned to the sucked-off air after it has been detected in step e). This is particularly advantageous if the extracted air is subjected to further cleaning steps before it is released to the environment.

In a further embodiment of the invention, the decision in step g) is made based both on the level of the mercury concentration detected in step e) and on the basis of the duration of an increased mercury concentration. This makes it possible to specify different threshold values in order to be able to reliably detect the different types of contamination, again circumscribed.

In a further embodiment of the invention, the detection device and the optical cell are thermally stabilized.

The system according to the invention is explained in more detail below with reference to an exemplary embodiment illustrated in the drawings.

Fig. 1 plant

Fig. 2 mercury detector In Fig. 1 an exemplary system is shown highly schematically.

Garbage is transported into a processing device 10 via a conveyor belt 30 .

The processing device is a shredder, for example.

A suction device 40 is arranged above the processing device 10 .

The suction device 40 can also be part of the housing of the processing device 10 .

A transport device 20 is arranged below the processing device 10, which in the example shown is designed as a conveyor belt, which is designed to be realizable.

In normal operation, the transport device 20 conveys the waste shredded by the processing device 10 further into a combustion device, for example the rotary kiln or the calciner of a plant for the production of cement clinker.

By reversing the direction of transport of the transport device 20, the waste can also be transported in plant 60.

According to the invention, this is done precisely when the waste is contaminated with mercury.

The contamination with mercury is detected by means of a mercury detector 50 which removes a partial gas flow 70 from the suction device 40 .

FIG. 2 shows the mercury detector 50 from FIG. 1. The partial gas flow 70 is first cleaned by a filter 150 and then enters the optical cell 100.

A membrane pump 160 is arranged behind the optical cell 100 .

The partial gas flow 70 (not shown here) is then fed back into the main gas flow of the suction device 40.

A low-pressure mercury lamp 110 shines through the optical cell 100, and the transmitted light is detected by a detector 130.

A beam splitter 120 is arranged in front of the optical cell 100 and directs a small portion of the excitation radiation from the low-pressure mercury lamp 110 to a reference detector 140 .

In this way, in particular, aging effects of the low-pressure mercury lamp 110 can be easily corrected.

An evaluation unit, not shown in the figures, evaluates the detected mercury concentration and decides whether the transport device 20 should transport mercury-contaminated waste into the storage facility 60 by reversing the transport direction.

Reference sign

10 processing device

20 transport device

30 conveyor belt

40 suction 50 mercury detector

60 camp

70 partial gas flow

100 optic cell

110 low pressure mercury lamp 120 beam splitter

130 detector

140 reference detector

150 filters

160 diaphragm pump

Claims (11)

patent claims 1. Plant for the processing of waste for use as substitute fuel in a combustion device, for example in a plant for the production of cement clinker, the plant having a processing device (10) and a transport device (20) arranged downstream of the processing device (10) in the direction of material flow, wherein the transport device (20) has an ejection device, the processing device (10) bringing about heat input into the refuse, the processing device (10), the transport device (20) or both the processing device (10) and the transport device (20) having a suction device (40), characterized in that a partial gas flow (70) is removed from the suction device (40), the mercury concentration being determined by means of a detection device in the partial gas flow (70), an evaluation device being connected to the detection device, the evaluation device being connected to the discharge device chtung is connected, wherein the evaluation device is designed to eject the contaminated waste through the ejection device when a predetermined concentration of mercury is exceeded. 2. Plant according to claim 1, characterized in that the partial gas flow (70) is passed through an optical cell (100), wherein the partial gas flow (70) in the optical cell (100) can be determined by means of the detection device, the mercury concentration, the detection device The mercury concentration was recorded using atomic absorption spectroscopy. 3. Installation according to one of the preceding claims, characterized in that the processing device (10) is a comminution unit, preferably a shredder or a cutting mill. 4. Installation according to one of the preceding claims, characterized in that the ejection device is a reversible conveyor belt, a belt switch, a scraper or a slide. 5. Plant according to one of the preceding claims, characterized in that the partial gas flow (70) between the suction device (40) and the optical cell (100) can be heated. 6. Plant according to one of the preceding claims, characterized in that the partial gas flow (70) is removed by means of a diaphragm pump (160). 7. Plant according to one of the preceding claims, characterized in that the partial gas flow (70) between the suction device (40) and the optical cell (100) has a filter device. 8. A method for discharging waste contaminated with mercury from a plant according to one of the preceding claims, the method comprising the following steps: a) processing waste in a processing device (10), b) sucking off the air above the in step a) processed waste, c) continuous removal of a partial gas flow (70) from the air extracted in step b), d) passing the partial gas flow (70) through an optical cell (100), e) detecting the mercury concentration of the partial gas flow (70) in the optical cell (100), f) evaluation of the mercury concentration measured in step e), g) decision based on the evaluation in step f), whether the waste is to be incinerated or is discharged using the ejection device, h) injecting the waste to incineration or Rejecting the waste according to the decision made in step g). 9. The method according to claim 7, characterized in that the partial gas flow (70) is returned to the extracted air after detection in step e). 10. The method according to any one of claims 7 to 8, characterized in that the decision in step g) is made both on the basis of the level of the mercury concentration detected in step e) and on the basis of the duration of an increased mercury concentration. 11. The method according to any one of claims 7 to 9, characterized in that the detection device and the optical cell (100) are thermally stabilized.