DE102014226486A1 - Apparatus and process for the aftertreatment of combustible constituents containing process exhaust - Google Patents

Abstract

In a process for the aftertreatment of combustible constituents containing process exhaust air, the combustible ingredients in the process exhaust air are reacted in an oxidation catalyst (12). In this case, upstream of the oxidation catalytic converter (12), a content of combustible constituents and / or an oxygen content in the process exhaust air are detected by means of a measuring device (30-34). In addition, by a media addition device (14) upstream of the oxidation catalyst (12) inert media, preferably water or steam added in the process exhaust air such that the content of combustible ingredients in the process exhaust air does not exceed a predetermined first limit and / or the oxygen content in the Process air does not exceed a predetermined second limit.

Description

The present invention relates to a device and a method for the aftertreatment of combustible constituents containing process exhaust air.

In emergency operation of chemical processes or strong heating processes, such as in smelting furnaces, exhaust gases can be produced with highly concentrated combustible ingredients. If such exhaust gases uncontrollably come into contact with oxygen, deflagrations or even explosions can result. Therefore, in conventional plants with chemical or petrochemical processes flare systems are used for the controlled combustion of the exhaust gases.

In general, users of chemical and petrochemical production processes or processes with high heat-up processes are trying to minimize the occurrence of emergency operation when they can not avoid it. Accordingly, emergency relief systems such as torches generally need to be kept in a long-lasting waiting mode for a long period of time, resulting in a high consumption of resources. Torch systems, for example, are associated with high fuel consumption and the production of CO ₂ through the operation of the support flame.

The invention has for its object to provide an improved device and an improved method for the aftertreatment of combustible ingredients containing process exhaust air, which are environmentally friendly. In particular, a reduction of resource consumption, a reduction of energy consumption and / or a reduction of the emission of pollutants to the environment should be made possible.

This object is achieved by the teaching of the independent claims. Particularly preferred embodiments of the invention are the subject of the dependent claims.

The apparatus according to the invention for the aftertreatment of combustible constituents containing process exhaust air has: an oxidation catalyst for converting the combustible ingredients in the process exhaust air; a measuring device for detecting a content of combustible contents and / or an oxygen content in the process exhaust upstream of the oxidation catalyst; a media adding device for adding inert media, preferably water or water vapor, into the process exhaust upstream of the oxidation catalyst; and a control device for controlling the media adding device as a function of the content of combustible ingredients and / or oxygen content in the process exhaust air detected by the measuring device such that the content of combustible ingredients in the process exhaust air does not exceed a predetermined first limit value and / or the oxygen content in the process exhaust air Process air does not exceed a predetermined second limit.

The process according to the invention for the aftertreatment of combustible constituents containing process exhaust air has the following process steps: detecting a content of combustible ingredients and / or an oxygen content in the process exhaust air; Adding inert media, preferably water or steam, into the process exhaust air in such a way that the content of combustible constituents in the process exhaust air does not exceed a predetermined first limit value and / or the oxygen content in the process exhaust air does not exceed a predetermined second limit value; and reacting the combustible ingredients in the process exhaust air in an oxidation catalyst.

According to the invention, the content of combustible ingredients and / or oxygen in a process exhaust air is kept below, preferably well below, a lower explosive limit (LEL) by the addition of inert, non-oxidizable media, preferably water or water vapor. The predetermined first limit for the content of combustible ingredients in the process exhaust air is preferably 50% of the lower explosion limit (LEL) or less, more preferably 25% LEL or less. The LEL depends on the respective ingredients in the process exhaust air and can be taken from the relevant literature or determined by experiments. Due to the temperature dependence of the LEL, a concentration of 25% LEL is generally considered safe. For direct oxidation systems with z. As recuperative or non-recuperative catalytic oxidation with additional safety measures (static or dynamic flame arrestor, detonation disk, multiple concentration measurement, etc.) operation of up to 50% LEL is possible. The predetermined second limit value for the oxygen content in the process exhaust air is preferably 8% by volume, more preferably 5% by volume, even more preferably 3% by volume.

The optionally diluted with inert medium, preferably water, process exhaust air can then be controlled in an oxidation catalyst (to CO ₂ and water vapor) to be implemented. In this way, the risk of deflagration and explosions of the process exhaust air can be reduced. By using the readily available and relatively inexpensive inert medium water, emergency relief systems with high resource and energy consumption such as torches can be dispensed with. By avoiding additional fuel consumption, CO ₂ emissions can also be reduced.

In addition, the process exhaust air can be diluted so much by the addition of inert medium, preferably water (steam), that the oxidation temperature can be lowered, preferably up to the process outlet temperature of the process exhaust air. This can also save resources and energy.

The term process exhaust air is to be understood in this context in particular an exhaust gas and / or an exhaust air of at least one upstream process or an upstream source that includes a load or concentration of impurities. The impurities are at least one combustible component, such as a volatile organic compound (VOC) of the exhaust gas / exhaust air. The process exhaust air may in particular be a solvent-containing process exhaust air which has a loading / concentration of an organic solvent.

The term oxidation catalyst in this context includes any type of device that is capable of oxidation and / or reduction pollutants such as hydrocarbon (HC) and carbon monoxide (CO) in non-toxic substances such as carbon dioxide (CO ₂ ) and water (H ₂ O ) implement. In particular, the term oxidation catalysts encompasses both bulk and monolith catalysts as well as other media which, by the application of catalytic material, perform a catalytic oxidation process, such as catalytically activated filters.

The term media addition device, preferably water addition device, in this context encompasses any type of device which is able to supply an inert medium, preferably water or water vapor, to a process exhaust stream in a controlled or metered manner. As suitable media addition devices preferably injection or injection systems are used, preferably those that lead to an excellent mixing and z. B. have a baffle plate or a nozzle grid.

In this context, the term control device is to be understood as meaning all types of devices which are capable of controlling the media addition device as a function of measured values. The control device preferably has a control, which is connected on the one hand to the measuring device and on the other hand is connected to the media adding device and which can preferably evaluate the measured values of the measuring device. In another embodiment, the control device can also be formed simply by a direct connection of the measuring device or its individual measuring devices to the media adding device.

In a preferred embodiment of the invention, the measuring device has at least one measuring device, which is selected from a first measuring device for detecting the content of combustible ingredients in the process exhaust upstream of the media addition device, a second measuring device for detecting the content of combustible ingredients in the process exhaust downstream Media addition device, and a third measuring device for detecting the oxygen content in the process exhaust air downstream of the media addition device. The third measuring device for detecting the oxygen content preferably has a lambda probe.

In a further preferred embodiment of the invention, downstream of the media addition device, a mixing device, for. As a baffle plate or a static mixer, for mixing the inert medium, preferably water or steam, provided with the process exhaust air. By the mixing device should preferably a homogeneous mixture of process exhaust air and inert medium is achieved, which can meet the first and / or the second limit at all points.

In a further preferred embodiment of the invention, a second temperature measuring device for detecting a temperature of the process exhaust air is provided downstream of the oxidation catalyst. The control device is then preferably designed to also control the media addition device as a function of the temperature of the process exhaust air detected by the second temperature measuring device. In this embodiment, the process exhaust air with inert medium, preferably water (steam), are diluted so that the concentration of the combustible ingredients in the oxidation in the oxidation catalyst produces a maximum increase in temperature of the process exhaust air, a predetermined limit (for example, about 200 ° C. ) does not exceed.

In a still further preferred embodiment of the invention, a heating device for heating the process exhaust air is provided upstream of the oxidation catalyst. The heating device is preferably provided downstream of the media addition device for the inert medium and preferably also downstream of the mixing device. With the help of the heater, the process exhaust air can be brought to the required oxidation temperature if necessary.

In this embodiment, preferably a bypass line for bypassing the heater and a bypass valve device for controlling a flowing through the bypass line portion the process exhaust air provided. Furthermore, a first temperature measuring device for detecting a temperature of the process exhaust air is preferably provided upstream of the oxidation catalyst in this embodiment. The control device is then preferably designed such that it controls the bypass valve device as a function of the temperature of the process exhaust air detected by the first temperature measuring device. The first temperature measuring device is preferably arranged upstream and / or downstream of the heating device. With this embodiment, it can be ensured that the process exhaust air flows into the oxidation catalytic converter with the lowest possible expenditure of energy with a controlled oxidation temperature.

In a further embodiment of the invention, the heating device has a heat exchanger to which a heat of reaction of the oxidation catalyst is supplied. By using the heat of reaction of the oxidation catalyst for heating the process exhaust air to the oxidation temperature of the energy consumption of the system according to the invention can be reduced.

The heat of reaction of the oxidation catalyst can alternatively or additionally also be used as a secondary energy source, for example for generating water vapor, electricity, hot water, etc. and / or for preheating the inert medium to be added to the process exhaust air.

The above and other advantages, features and applications of the invention will become more apparent from the following description of an embodiment with reference to the accompanying drawings. In it shows the only one 1 a schematic representation of the structure of a device for the aftertreatment of process exhaust air according to an embodiment of the invention.

1 shows a system for post-treatment of process exhaust air containing combustible ingredients, according to an embodiment of the present invention.

The process exhaust air is sent via a process exhaust line 10 an oxidation catalyst 12 fed. In this oxidation catalyst 12 For example, volatile organic compounds (VOC) from process exhaust air such as hydrocarbons (HC) and carbon monoxide (CO) are converted into non-toxic substances such as carbon dioxide (CO ₂ ) and water (H ₂ O). The oxidation temperature of the process exhaust air required for this reaction is, for example, about 300.degree. In this case, the oxidation catalyst 12 Ideally heated and maintained by the enthalpy contained in the process exhaust air to the required operating temperature.

Before the process exhaust air the oxidation catalyst 12 flows through it, it is through a water addition device 14 as an example of a media addition device provided according to the invention, a mixing device 16 and a heater 18 directed. By the injection of water or steam by means of the water addition device 14 the content of combustible ingredients and / or the oxygen content is prevented from exceeding predetermined limits. In particular, the content of combustible ingredients is regulated below a predetermined first limit of, for example, about 25% of the lower explosive limit (LEL) and / or the oxygen content in the process exhaust air is controlled below a predetermined second limit of, for example, about 3% by volume.

For this control is downstream of the process outlet and upstream of the water addition device 14 first a first measuring device 30 for continuously detecting the content of combustible ingredients in the process exhaust air. In addition, downstream of the mixing device 16 a second measuring device 32 for continuous recording of the content of combustible substances and a third measuring device (eg lambda probe) 34 provided for continuously detecting the oxygen content in the process exhaust air. The three measuring devices 30 . 32 . 34 together form the measuring device of the invention. With the water addition device 14 Water (steam) is injected into the process exhaust air until the content of combustible ingredients has fallen below 25% LEL and / or the oxygen content has fallen below 3% by volume.

The diluted with water (steam) process exhaust stream is passed through the heater 18 to the operating temperature of the oxidation catalyst 12 heated to about 300 ° C, if necessary. The heater 18 has for this purpose, for example, a heat exchanger to which the heat of reaction of the oxidation catalyst 12 is supplied. In this embodiment, the resource and power consumption of the heater 18 kept low.

When flowing through the oxidation catalyst 12 the flammable ingredients in the process exhaust air are converted to CO ₂ and water. The outlet temperature of the process exhaust air from the oxidation catalyst 12 is preferably at most about 500 ° C.

As in 1 shown, is also a bypass line 20 provided the heater 18 bypasses. If the process exhaust already (approximately) the operating temperature of the oxidation catalyst 12 of about 300 ° C, is an additional heating of the process exhaust upstream of the Oxidation catalyst is not required and the process exhaust air can therefore through the bypass line 20 at the heater 18 be led past. Depending on the temperature of the process exhaust air, it is desirable only a part of the process exhaust air to the heater 18 to pass by. For this purpose, a bypass valve device is upstream of the heater 22 intended. This bypass valve device 22 has, for example, a bypass valve in the bypass line 20 and / or a bypass valve in the process exhaust line 10 on or has a two-way bypass valve.

For controlling the temperature of the process exhaust air upstream of the oxidation catalyst 12 is upstream of the oxidation catalyst 12 at least a first temperature measuring device 36 downstream and / or upstream of the heater 18 intended.

In addition, downstream of the oxidation catalyst 12 a second temperature measuring device 38 intended. If the outlet temperature of the process exhaust air from the oxidation catalyst 12 exceeds a limit temperature of, for example, about 500 ° C, the process exhaust air can be injected via the water addition device more water.

The heat of reaction of the oxidation in the oxidation catalyst 12 can, as in 1 shown, for heating the process exhaust air in the heater 18 be used. Alternatively or additionally, this heat of reaction can also be used as a secondary energy source, for example for generating water vapor, electricity, hot water, etc.

Thus, the clean gas flow to the heat exchanger 18 optionally a heat exchanger 24 be supplied, in which he with the process exhaust air via the water addition device 14 water to be injected is in heat exchange. In this case, the clean gas flow is further cooled and the einzudüsende water is preheated. In addition, the water contained in the clean gas stream by condensation in the heat exchanger 24 be recovered. The condensate 26 can then be returned to the process.

As in 1 indicated, are the measuring equipment 30 . 32 . 34 and the temperature measuring devices 36 . 38 wired or wireless (eg by radio) with a controller 40 connected. This control 40 is also wired or wireless (eg, by radio) with the water adding device 14 and the bypass valve device 22 connected. Depending on the type of heater 18 is the controller 40 also connected with this. The control 40 is configured to the water addition device 14 , the bypass valve device 22 and possibly the heater 18 depending on the measured values of the various measuring devices 30 - 38 head for.

Alternatively, the control device of the invention may also be provided by a direct connection (wired or wireless) of the various measuring devices 30 - 38 with the components to be controlled 14 . 18 . 22 be formed.

• – die Vermeidung oder Reduzierung der Gefahr von Verpuffungen und Explosionen;
• – die Kontrolle der Explosionsfähigkeit der Prozessabluft durch Minimierung oder Reduzierung des Gehalts von brennbaren Inhaltsstoffen und/oder von Sauerstoff mittels des leicht verfügbaren und vergleichsweise kostengünstigen Inertmediums Wasser;
• – die Absenkung der Oxidationstemperatur auf zum Beispiel etwa 300°C und damit die Annäherung an die Prozessaustrittstemperatur;
• – die Vermeidung eines zusätzlichen Brennstoffverbrauchs (z. B. für Fackelsysteme);
• – die Vermeidung einer zusätzlichen Erzeugung von CO₂ durch die Verbrennung zusätzlicher Brennstoffe;
• – die Nutzung der Reaktionswärme zur Aufrechterhaltung der notwendigen Betriebstemperatur des Oxidationskatalysators;
• – die Möglichkeit der Nutzung der Reaktionswärme zur Erzeugung von Dampf, Heißwasser, Strom, etc.; und
• – die Anpassung der Ein- und Austrittstemperaturen der Prozessabluft in den bzw. aus dem Oxidationskatalysator durch die Inertverdünnung mit Wasser oder Wasserdampf.

The advantages that can be achieved with the system of the invention described above include, for example:

• - the prevention or reduction of the risk of deflagration and explosions;
• - the control of the explosive capacity of the process exhaust air by minimizing or reducing the content of combustible ingredients and / or oxygen by means of the readily available and relatively inexpensive inert medium water;
• - The lowering of the oxidation temperature to, for example, about 300 ° C and thus the approach to the process outlet temperature;
• - the avoidance of additional fuel consumption (eg for flare systems);
• - the avoidance of additional production of CO ₂ through the combustion of additional fuels;
• - the use of the heat of reaction to maintain the necessary operating temperature of the oxidation catalyst;
• The possibility of using the heat of reaction to produce steam, hot water, electricity, etc .; and
• - The adaptation of the inlet and outlet temperatures of the process exhaust air into and out of the oxidation catalyst by the inert dilution with water or water vapor.

LIST OF REFERENCE NUMBERS

10

Process exhaust air duct

12

oxidation catalyst

14

Medium addition device for inert media, preferably water (vapor)

16

mixing device

18

heater

20

bypass line

22

Bypass valve means

24

Heat exchanger (preheater, condenser)

26

condensate

30

first measuring device

32

second measuring device

34

third measuring device

36

first temperature measuring device

38

second temperature measuring device

40

control device

Claims (15)

Apparatus for aftertreatment of process exhaust air containing combustible constituents, comprising: an oxidation catalyst ( 12 ) for converting the combustible ingredients in the process exhaust air; a measuring device ( 30 - 34 ) for detecting a content of combustible ingredients and / or an oxygen content in the process exhaust air upstream of the oxidation catalyst ( 12 ); a media addition device ( 14 ) for adding inert media into the process exhaust air upstream of the oxidation catalyst ( 12 ); and a control device ( 40 ) for controlling the media adding device ( 14 ) as a function of the measurement device ( 30 - 34 ) detected content of combustible ingredients and / or oxygen content in the process exhaust air such that the content of combustible ingredients in the process exhaust air does not exceed a predetermined first limit and / or the oxygen content in the process exhaust does not exceed a predetermined second limit. Device according to claim 1, characterized in that the measuring device ( 30 - 34 ) has at least one measuring device which is selected from a first measuring device ( 30 ) for detecting the content of combustible ingredients in the process exhaust upstream of the media adding device ( 14 ), a second measuring device ( 32 ) for detecting the content of combustible ingredients in the process exhaust downstream of the media addition device ( 14 ) and a third measuring device ( 34 ) for detecting the oxygen content in the process exhaust air downstream of the media addition device ( 14 ). Device according to one of the preceding claims, characterized in that downstream of the media adding device ( 14 ) a mixing device ( 16 ) is provided for mixing the inert medium with the process exhaust air. Device according to one of the preceding claims, characterized in that downstream of the oxidation catalyst ( 12 ) a second temperature measuring device ( 38 ) is provided for detecting a temperature of the process exhaust air and the control device ( 40 ) is preferably configured to allow the media adding device ( 14 ) in response to the detected by the second temperature measuring device temperature of the process exhaust air. Device according to one of the preceding claims, characterized in that upstream of the oxidation catalyst ( 12 ) a heating device ( 18 ) is provided for heating the process exhaust air. Apparatus according to claim 5, characterized in that a bypass line ( 20 ) for bypassing the heater ( 18 ) and a bypass valve device ( 22 ) for controlling a through the bypass line ( 20 ) flowing portion of the process exhaust air are provided. Apparatus according to claim 6, characterized in that upstream of the oxidation catalyst ( 12 ) is provided a first temperature measuring device for detecting a temperature of the process exhaust air and the control device ( 40 ) is preferably configured, the bypass valve device ( 22 ) in response to the detected by the first temperature measuring device temperature of the process exhaust air. Device according to one of claims 5 to 7, characterized in that the heating device ( 18 ) has a heat exchanger to which a heat of reaction of the oxidation catalyst ( 12 ) is supplied. Device according to one of the preceding claims, characterized in that downstream of the oxidation catalyst ( 12 ) a heat exchanger ( 24 ) is provided for heating the inert media to be added into the process exhaust air through the process exhaust air. A process for the aftertreatment of combustible constituents containing process exhaust air, comprising the process steps: detecting a content of combustible ingredients and / or an oxygen content in the process exhaust air; Adding inert media to the process exhaust such that the content of combustible ingredients in the process exhaust does not exceed a predetermined first limit and / or the oxygen content in the process exhaust does not exceed a predetermined second threshold; and reacting the combustible ingredients in the process exhaust air in an oxidation catalyst ( 12 ). A method according to claim 10, characterized in that the content of combustible ingredients in the process exhaust air before and / or after adding inert medium is detected in the process exhaust air and / or detects the oxygen content in the process exhaust air after adding inert medium in the process exhaust air becomes. A method according to claim 10 or 11, characterized in that a temperature of the process exhaust downstream of the oxidation catalyst is detected and the addition of inert media in the process exhaust air is preferably carried out in dependence on the detected temperature of the process exhaust air. Method according to one of claims 10 to 12, characterized in that the process exhaust air upstream of the oxidation catalyst ( 12 ) is heated. A method according to claim 13, characterized in that the process exhaust air by means of a heat of reaction of the oxidation catalyst ( 12 ) is heated. Method according to one of claims 10 to 14, characterized in that a heat energy of the process exhaust air downstream of the oxidation catalyst ( 12 ) is used for heating the inert media to be added into the process exhaust air.

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