JPS63223412A - Method and device for controlled after burner of process exhaust gas containing oxidizable component - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD The present invention relates to a method for the controlled afterburning of process exhaust gases containing oxidizable components.

Here, the gas is pumped through an afterburner device. In this device, the gas is passed through a gas inlet and a heat exchanger to a burner and a combustion chamber, from where it is passed in purified form through a heat exchanger to a gas outlet.

The invention also relates to an apparatus for carrying out the method.

PRIOR ART AND ITS PROBLEMS An afterburner device for oxidizable components in process exhaust gases (exhaust air, carrier gas), such as hydrocarbons, is shown in EP 0 040 690.

Here, the process exhaust gas preheated in a heat exchange tube is sent to a burner whose heat is adjusted in response to the varying amount of oxidizable components and in response to the fluctuating supply of exhaust gas stream at a given time. be done. U.S. Patent No. 2.90
No. 5.523 discloses an exhaust gas treatment method in which slag and combustible waste are catalytically burned together with gaseous components. In order to raise the temperature of process gases that are too cold, this method recirculates a portion of the combustion hot gases and mixes them instead of those normally used for heat exchange, and also increases the temperature of the system's recirculation gases. Start the engine. This recirculation therefore ensures that the light-off level, ie the minimum reference temperature of the catalyst, is maintained. In addition, in this method, unpurified exhaust gas is used to increase the oxygen content when the oxygen content is extremely low or when the content of combustible components is extremely high due to dilution. Air can be pumped into the main stream or bypass flow of the

This serves to protect the catalyst, which should not be heated above 1600°F. Both the recirculation of hot exhaust gas and the feeding of air are different functions in the sense of the technical method, and each achieves a different purpose. Therefore, the recirculation of hot air serves only to maintain the method. In the case of residual heat from the process gas, no recirculation occurs.The air injection only serves dilution purposes and not oxygen addition, so it only serves the purpose of protecting the catalyst from overheating. U.S. Pat.
A method is disclosed that can operate within a temperature range of 43 K).

Sudden temperature changes cause large distortions in the material,
Therefore, it is desirable to keep the temperature extremely constant, as this will accelerate fatigue.

For operation at minimum fuel consumption conditions, the thermal afterburner will remain within the "tolerance range" up to a value just below the predetermined safe shutdown limit until the temperature peak caused by the process change falls again. It is known in practice that the temperature of the combustion chamber can vary. However, in some cases the peak is so high that normal operation must be interrupted to reach the shutdown temperature.

This is known as overtemperature shutdown. This overtemperature and the aforementioned interruptions have a detrimental effect on the durability of the parts, which are subjected to more wear and tear. The problem with the current requirements for linking production and exhaust gas purification is that this usually automatically leads to interruptions in the production process and thus to a significant reduction in productivity.

In addition to the above, there is the fact that in technical applications temperature gauges, such as thermocouples, are placed inside protective sleeves, resulting in delayed, reduced, or even no recording of temperature peaks. be. This is also
It also has a negative impact on the long-term lifespan of the incinerator. Small variations in flow rate, which may occur as an inherent factor during the process, generally have a detrimental effect on combustion chamber temperature. The effect of this variation results in a variation in the uptake of oxidizable components.

''Double temperature fluctuations are unavoidable with current technology if the incinerator operates at its heat capacity and impurity processing limits and measures are not taken to remove excess energy.

However, if the heat input to the system increases significantly faster than the afterburner unit's burners can throttle back to their own heat production, activation of the overtemperature switch will not force a shutdown of the plant. , is absolutely necessary if the plant in question is not equipped with a secondary system for the reduction of the total amount of heat led into the combustion chamber.

As used herein, "total heat" means the enthalpy of the process gas required for processing, including the heat introduced into the oxidizable components and produced by the burner when operating in its minimum control range. Today, as high energy costs force excessive preheating of process exhaust air,
The enclosing of preheated air in the heat exchanger becomes limited.

As already mentioned, this is determined by excessive preheating, but also by the temperature of the exhaust air drawn from the production process. The increased temperature of the extracted air from the production process also increases the preheating temperature, resulting in an overall reduction in the intake capacity of combustible components.

Relative to the overall design capacity, this capacity loss due to temperature increase of the exhaust air is substantial, especially when the device operates at low gas flow conditions. In this case, the constant minimum capacity of the burner consumes a considerable proportion of the capacity of the oxidizable component.

Accordingly, bypass techniques are conventionally utilized to reduce the degree to which the exhaust gases are preheated. The technique uses an example or double-sided bypass principle to redirect a portion of the main exhaust airflow through the heat exchanger.

To partially redirect the flow through such a heat exchanger, all that is required is integrated or internally arranged ducts or piping, control and thermally suitable valves and compensation elements for thermal expansion. and further suitable mixing techniques for remixing the main flow water passing through or bypassing the heat exchanger with the counterflow air. The need for insulation is also increasing.

Regarding bypass (hot side or cold side) as an example, there is an inherent characteristic of bypass technology that for bypass operation the mass of the heat exchanger must constantly find a new level of thermal equilibrium (lJ). In other words, the mass temperature of the heat exchanger is continuously adjusted.

If the heat exchanger is bypassed on the hot gas side, this means that a change in the preheating temperature can only be obtained by changing the thermal balance of the total mass of the heat exchanger, i.e. by means of a very slow reaction process. means to be The latter is therefore unsuitable as a real-time control device.

If only the cold gas side is bypassed, the control speed is considered instantaneous, so the more the flow rate decreases in the heat exchanger, the less air bath is preheated and the greater the bypass take-off. As the temperature increases, the preheating becomes larger. This property causes extreme pre-combustion of the combustible components within the heat exchanger. This therefore constitutes a heat exchanger that is largely unsuitable for the combustion of oxidizable components, all with negative effects.

In addition to this, the temperature level of the heat exchanger as a whole
and this does not fall rapidly due to its generally large mass.

Although cold bypass represents a potential solution to single-sided bypass of heat exchangers, it still comes with significant limitations and negative consequences. That is, thorough mixing of cold, unpreheated bypass flow with extremely hot, preheated air is required.

This is necessitated by the fact that a temperature difference of 15 within the combustion chamber for the flow cross-section can mean poor combustion and high CO levels. As a result, it is necessary to simultaneously increase the combustion chamber temperature by 15 degrees.

At the high temperature levels at which modern branzes operate under low burner minimum duties and extremely high final cleanup demands, this additional 15 poses considerable technical difficulties.

Good mixing and combustion chamber technology is required to avoid high CO and NOx levels and obtain the required high standards of combustion. In order to meet more rapid reactive production processes and to meet safety requirements as well as requirements for wide adaptability and high durability, the immediate application of incineration technology is limited to heat exchange technology. This is a level that can be observed in the energy control system that bypasses both sides of the device. Single side (
Compared to the cold side) bypass, the double-sided bypass system is
There is a considerable difference in the concentration of oxidized components. Therefore, double-sided bypass is often questioned as a suitable technology when larger capacity variations are involved and higher demands are made on the quality of the process technology. This is especially the case when the combustible components have low ignition temperatures, ie mineral oils and benzine.

(Fr This is because the high temperature region leads to weakening of the desteel and rapid scale formation.

High CO emissions must be avoided as much as possible.

High CO production, however, is closely related to bypass technology. The higher the concentration of oxidizable components, the longer the out-exchange inactivity time, resulting in more CO generation. Therefore, bypass operation further strengthens this J: connection.

Bypass techniques are generally technically complex and expensive;
It also requires a high degree of control and management.

In the case of double-sided bypass of the heat exchanger, the flow rates must be as equal as possible at any point in the control and the control devices must always operate in parallel.

Bypass systems are also complex in construction and detailing, and cumbersome to assemble and commission. Furthermore, a considerable degree of maintenance is required during operation.

Also, in the device shown in European Patent No. 0040690,
The heat exchange tubes are inserted into a cylinder which is curved inwardly on the hot side of the device, ie in the region of the burner, and which concentrically surrounds the burner. Such a structure has the advantage that, when used in various processes, the individual tubes may expand differently depending on temperature without causing damage such as crack formation. However, in this case, the welding of the inwardly curved tubes to the barrel is extremely complicated in manufacturing technology due to the small distance between the tubes. Since the cylindrical body itself requires a fairly large wall thickness, it is not possible to adjust the expansion of the heat exchange tube according to the temperature situation, and therefore the welding heat applied during welding may cause the cylindrical body to shrink or warp. Therefore, in some cases, excessive stress may be applied to the curved portion of the pipe.

Moreover, the entire length of the heat exchange tube does not serve as a heat exchanger. The reason for this is that the high temperature exhaust gas does not act directly on the curved end, but is deflected or flows in the opposite direction, and as a result does not have any effect on the above portion. Furthermore, scale formation is unavoidable at the curved portion of the tube. This is because the curved portion is on the hottest side of the device. If the tube is subject to particularly high expansion velocity changes in this region, this scale formation can lead to a loss of tube wall thickness. Moreover, such special expansion rate changes are also observed during normal processing steps.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method in which fluctuations in the concentration of oxidizable components during the process and increases beyond a certain volume of oxidizable components do not lead to undesirable consequences as mentioned above. There is something to do.

In other words, the combustion chamber temperature does not increase as a result of improper mixing, temperature peaks reaching the shutdown limit are avoided, high temperature shutdown becomes practically impossible, and the entire technological system linked to the production process Increases the flexibility of the combustion system as an integral part of the system, avoids the problems of bypass systems and their associated direct and indirect costs, and increases impurity concentrations to a greater extent than would be expected with a single-sided bypass system. is constantly being processed, no expensive mixing techniques are required, no additional equipment is required to the afterburner system, and no insulation and its thermal compensation means are required.

” With respect to a series of methods, the above objects are achieved by the present invention as follows. That is, the present invention adds process exhaust gas to a mixture of purified process exhaust gas and fresh air. The latter process exhaust gas is sent in the desired amount to the afterburner. This is to maintain the concentration of oxidizable components of the gas mixture at a regulated level. In other words, when the concentration of combustible components increases, the purified process exhaust gas, together with fresh air, is added at the moment when the burner reaches its minimum control range, and the range adjusted to increase said concentration. , the amount is added. Such additions are made precisely to the extent necessary to maintain the temperature within the combustion chamber according to the desired apparent value. The burner itself remains within minimal control during this process and does not intervene in the process. The establishment of the mixed air temperature is accomplished by a second control cycle, which determines the amount of warm purified exhaust gas or cool fresh air to be added. The quantity required for this control corresponds to the deviation between the actual temperature of the exhaust gas and the desired apparent temperature. In other words, the manual temperature of the mixture of untreated gas, purified exhaust gas and fresh air to be sent to the afterburner device is maintained at an adjustable level. Furthermore, it is proposed in the invention that an appropriate amount of mixed air consisting of some purified exhaust gas and fresh air is added to the process gas. The gas has a very high concentration of combustible components before being fed to the afterburner device. It is also proposed that this air mixture input corresponds, by dilution, to the exact amount required to maintain a constant combustion chamber temperature within a minimum control range. That is, while the burner is constantly operating in the minimum range, the combustion chamber temperature is kept under control and at the same time the combustible component concentration in the exhaust gas is virtually constant.

”-The following various advantages are clearly obtained. That is, the burner temperature is always controlled to an apparent desired level, which level cannot be exceeded under the same conditions. Also, the heat exchanger always maintains the same temperature level regardless of impurity concentration and degree of excess energy control. Also, the dead time of the medium to be superheated in the heat exchanger is reduced to the extent that overpower control is reduced.

Also, CO generation decreases rather than increases. Also, the preheat temperature is kept constant rather than fluctuating.

In addition, the heat exchange acts as a pre-combustion region (the tendency is small.
Temperature equilibrium is kept constant. Additional benefits provided by the technology include constant idle operation, standby until warm, lower cost start-up of the entire system and shorter start-up times, as well as higher temperature peaks and higher temperatures across the board. The durability of the device is improved by clearly eliminating fluctuations, C.
Reduced carbon diffusion into the steel due to reduced O levels and therefore long-term retention of steel properties, elimination of repeated shocks caused by switching from process air to cold air, extremely rapid response to process changes similar to burners reduction in CO levels due to reduction in natural generation, as well as the avoidance of control responses to excessive exhaust temperatures as well as high combustion chamber temperatures when the concentration of combustible components is already too high for burner control. This makes it possible to reduce NOx levels.

According to the invention, the oxidizable component concentration is such that when the minimum zone of the burner is reached, the amount of heat obtained by the combustion of the oxidizable component maintains the combustion chamber temperature exactly at its desired apparent level and that Constantly adjusted to allow no fall or rise.

The following characteristics are also relevant to the solution proposed by the invention. That is, the outlet temperature of the purified and recooled exhaust gas obtained from the afterburner device is constant. Conventional bypass systems experience fluctuations of up to 150K (=270F). −
The process control proposed by Rikki operates at an almost constant temperature. This constant temperature provides advantages not only for the unit itself, but also for all devices connected to it. That is, while all connection devices are generally designed and constructed for low standard temperature levels.

This applies to all equipment, including chimneys.

A fundamental further characteristic of this system is its suitability, which allows it to be adapted without risk for safe operation for heat exchangers preheating to very high temperatures.

In the case of devices with bypass, the limits of their preheating capacity (up to 550°C, 1022°
F (described in the literature), but the proposed system of the present invention far falls short of that limit. Preheating is 6
It can be run up to 50°C, 1202°F, and as mentioned above, this is virtually constant.

The measure for mixing air into the raw process gas is that the combustible components exceed the maximum capacity possible with minimum burner control.

The parameters of the air determine the mixture of warm and cold air that should be added to the system. That is, the process air temperature level. If this temperature also exceeds the apparent value and requires mixed air, fresh air is first added and then, when the apparent temperature is reached, warm air is supplied.

However, if the temperature is unacceptably low, then first only warm air is added as needed. That is, the system is maintained at a normal temperature level at all times and locations.

The bypass unit, on the other hand, is subject to very large fluctuations due to a) the medium and b) the device. The system of the present invention eliminates repetitive stress on each component. Everything stays warm or hot. The operation then achieves an ideal mode of operation, ie one that keeps the operation of all components constant over long periods of time.

On the other hand, some of the dual characteristics can also be achieved by: That is, when the process air flow stubs, i.e., during process-related and machine-related shutdowns, a small fraction of the mixed warm air adjusted to the normal process air temperature is removed. The quantity continues to operate in the most economical manner, so that all temperature levels of normal process operation are maintained completely evenly in each part of the plant, ensuring preparation for subsequent continuation of operation with the process gas.

A device for controlled afterburning of oxidizable constituents contained in a process exhaust gas, preferably connected to a process exhaust gas inlet and a heat exchanger having a tube bundle preferably arranged concentrically around a combustion chamber. a burner with a high-velocity mixing chamber, a main combustion chamber and a process exhaust gas outlet, wherein connection means are provided between the device and the process exhaust gas inlet, via which the purified exhaust gas can be A controlled amount of air is mixed with air and passed into the mainstream. This connecting means is preferably provided between the process exhaust gas outlet and the inlet.

A simple design method that does not require any operation inside the device or the installation of a butterfly valve type mechanism,
In order to maintain the oxidizable component proportion at a constant level and to modify the temperature of the process gas, it is possible to add the required amount of purified process exhaust gas and/or exhaust air to the untreated process exhaust gas.

Therefore, the incinerator may be configured as follows.

That is, connecting means are provided between the process exhaust gas outlet and the inlet, by means of which fresh air is mixed with the purified exhaust gas in the desired amount and brought into circulation or backflow.

The air mixture thus created is added to the process exhaust gas downstream of the suction side of the process exhaust gas fan.

Warm air is channeled to the outside using simple design techniques. The supply of both warm and cold air is regulated by independent controls such as tambours or valves.

The amounts of cooled and warmed air, respectively, are determined by a quality controller that monitors the temperature of the process mixture air delivered to the afterburner device.

The total amount of air required is determined by a temperature controller corresponding to a constant combustion chamber temperature.

Another object of the present invention is to provide a device which can reliably protect a heat exchanger against expansion due to temperature and its fluctuations, as well as against ↑n deviation of the surface portion, by means of a simple construction.

In order to achieve the above object of the present invention, in the present invention, the heat exchange tube is bent outward at its cold end. This has the advantage that the circumferential area of the tube end is significantly expanded compared to an inwardly curved tube shape, which facilitates welding and enables automation of the welding operation. The mutual separation distance between the welded ends is extremely large, and therefore, compared to the known technology, the covering portion that receives the welded ends does not require a separate component such as a cylinder, and the present invention The configuration utilizes the inner wall of the outer annular chamber as a mounting surface, through which a carrier gas having an oxidizable component is supplied from the inlet boat to the heat exchange tube. There is. The risk of shrinkage and warping when welding tubes is eliminated due to the large spacing, so the wall thickness can be reduced and the
The overall bow property in the compensation area is enhanced. Since it is possible to provide a surface of the desired size for the outwardly curved heat exchange tubes, this allows the number of adjacent tube rows to be increased as the number of outer tube rows increases. 00406
90, which increases the turbulence of the flow around the tubes and reduces the number of chambers for cross-flow to be arranged in the heat exchange area. Can be done. Additionally, this allows for a simpler structure and lower manufacturing costs.

Yet another major advantage is that the tube walls can be made thinner, since no extra wall thickness is required to compensate for wear due to scale formation. Since this extra wall thickness is eliminated, the overall elasticity of the tube bend is significantly increased. This also reduces costs and allows the use of low-alloy or non-alloy tubes in the curved portions of the tube.

Furthermore, the device of the present invention is applicable even under severe environmental conditions. For example, there are large amounts of combustible components,
In the case of high gas tap temperatures in conjunction with significant preheating, the environment is such that it causes strong precombustion of some of the combustible materials. In this case, in the present invention, although the high temperature is exhibited in the high temperature region of the heat exchange tube,
It is compensated and averaged by the outwardly directed curved tube section.

Therefore, in the device according to the invention, the extremely high preheating and the always associated precombustion do not cause serious damage. That is, the heat transfer body, in its high-temperature part, is and can serve as a pre-combustion chamber.

A further advantage of the invention is that the hot section of the heat exchanger strongly acts as a first-stage combustion chamber, and this feature is particularly advantageous at low flow rates and with higher loads of combustible material. Occurs in some cases.

For example, the level of permissible stress is several times higher than in the 700°C region.

A particular advantage is that pre-combustion of a portion of the combustible material takes place safely in the tubes of the heat exchanger.

Another advantage of the curved tube end configuration on the cold side of the device is that there is little wear on the curved tube section because the flow velocity of the medium flowing through the tube is low there.

In the boundary region between laminar flow and turbulent flow, one pipe or one
When one group of tubes is exposed to laminar (or turbulent) flow, other tubes adjacent to it or other groups of tubes are exposed to turbulent (or laminar) flow. This undesirable characteristic becomes a problem when the combustion device has a large flow range. The resulting non-negligible longitudinal expansion differences require particularly high elasticity of the individual tubes. This situation is particularly problematic when there is a drastic change from laminar to turbulent flow or vice versa. That is, the expansion difference occurs in response to the magnitude of the speed change, and in particular, the compensating member must accommodate this large speed change. However, a curved pipe section with scale may not be able to meet the above requirements very well since there is a risk of losing the protective scale.

In the configuration of the invention, the gas flowing outside the heat exchange tube can be supplied via the curved tube section. This places the curved tube section in a temperature range of approximately 250 DEG C. to 300 DEG C., and the risk of damage, either overall or between individual tubes, is largely eliminated due to rapid and large temperature changes. Also, scale formation is prevented and wall pressure loss no longer occurs.

According to a further development of the invention, the carrier gas is supplied from the gas inlet to the curved end of the heat exchange tube via an outer annular chamber arranged in the region of the outer wall of the substantially cylindrical device. Supplied. In this configuration, the annular chamber extends to the gas outlet. This arrangement has the advantage that the inner wall of the annular chamber acts as a heat exchange surface, and the outer wall also serves a somewhat similar function. It is thus not only necessary to preheat the supplied fluid, but also to ensure, inter alia, that any condensate present is sufficiently vaporized when it enters the heat exchange tube through the gas inlet. Moreover, the preheating performed in the annular chamber does not simplify the structure of the tube-type heat exchanger and reduce the manufacturing cost.

By supplying the heat exchanger tubes with a chilled carrier gas containing oxidizable components in an annular chamber adjacent to the outer shroud, costly external insulation measures are not required and a horizontal configuration is possible. In this case, a heat-resistant footrest configuration is not required.

Further, in the configuration of the present invention, the annular chamber projects between the gas man [] and the gas outlet.

Furthermore, the invention provides that the gas inlet has a first annular chamber communicating with it and is arranged in the area of the burner, the first annular chamber coaxially surrounding the burner.

Furthermore, its advantages are significant, for example, in the preheating of gases, the vaporization of condensates, longitudinal heat compensation, the construction and installation of tubes such as risk-free precombustion or heat exchange.

Further advantages, features, and specific configurations of the present invention will be apparent from the following embodiments described with reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a conventional excess energy control system in which the basic components of an afterburner device are schematically illustrated. Untreated process gas is extracted by extraction fan 12
and is conveyed to the afterburner via the process gas inlet 14. The untreated process gas is then passed through heat exchanger 1
6 into a combustion chamber 18, in which the oxidizable components, which have not yet been partially combusted in the heat exchanger unit, are combusted. The combustion chamber 18 can extend from the burner 20 via a high-velocity pipe, not shown in this figure.
The fuel intake is regulated by a control valve 22. The purified exhaust gas from the chamber 18 is passed through the heat exchanger 16 to preheat the untreated process gas by heat recovery means.

The purified exhaust gas is then discharged via duct 24. Duct 14. Bypass 26.28 can be used in combustion chamber 18 if there are wide variations in the process gas related to the concentration of the component to be oxidized occurring in bypass 26.28.
It acts to moderate the temperature rise inside. This is obtained by partially bypassing the heat exchanger 16,
Therefore, the level of residual heat is reduced as long as necessary to increase (fluctuation) the concentration of combustible components. During this time, burner 22
operates with minimal control as long as the temperature of the combustible components continues to be absorbed.

In this process, bypass 26 is designed for cold gas flow and bypass 28 is designed for hot gas flow. Both bypasses 26°28 are valves 34.1
or a device IO attached to a control mechanism such as 36.1
It has a circulation duct 30 or 32 in or around it to regulate or deactivate the bypass. This configuration of the bypass 26 is such that the cold process gas in the duct 14 and the burner chamber are open to the combustion chamber 18 in FIG. ). The bypass 28 configuration provides communication between the combustion chamber 18 and the exhaust gas outlet 24 . Since the bypass simply increases its flow rate as long as the residual volume flowing through the heat exchanger 16 experiences greater resistance than the volume flowing through the bypass, the control capacity is determined by the second controller's control over the main flow. Unless you throttle back to continuously increase the amount carried by the bypass, it will quickly become a problem. The reference numbers for these devices are 34.2 and 36.2.

The equipment installed downstream of the device 10 for utilizing the residual heat contained in the purified exhaust gas is shown in FIG. 1 in the form of a warm water/heat exchanger. The device comprises a heat exchanger 65, a bypass control device in the form of butterfly valves 63.1 and 632 for increasing and decreasing the heat to be exchanged, a bypass duct 62 and a merging duct 64, as well as consumption points 67 and 66. It consists of a closed circuit water system 61.

Now, upon exiting the heat exchanger 65 or partially or completely bypassing it, the further cooled exhaust air flows towards the chimney.

All components of the device 10, including the exhaust gas duct (33), must be designed to withstand the maximum temperatures that occur.

A method of controlling afterburning of oxidizable components in process exhaust gas (exhaust air, carrier gas) according to the present invention is illustrated in FIG. Here, parts corresponding to those shown in FIG. 1 are given the same reference numbers.

The untreated process gas is passed to heat exchanger 16 and from there enters combustion chamber 18 via feed line 14 . In this line 14 is a process exhaust gas fan 38 equipped with quantitative flow control means (shown here as a rotational speed change).
is installed. After residual heat in the heat exchanger 16,
The still untreated process gas is passed to the vicinity of the burner 20 and from there reaches the actual main combustion chamber 18 via a high speed vibrator, not shown here. burner 20
The required amount of fuel is supplied at a predetermined timing by a control valve. The purified gas is then passed from the combustion chamber 18 through the hot gas side of the heat exchanger 16 to the outlet 24.
sent to. If the concentration of the untreated exhaust gas exceeds the control capacity of the burner, according to the invention the concentration is corrected by adding already purified exhaust gas and mixing with fresh air. This allows only stray gases with a certain proportion of oxidizable components (eg, solvent) to be delivered to the device 10. This allows the burner 20 to operate within a certain minimum control range (basic duty). Since the particular proportion of the components to be combusted is kept constant, the temperature within the device 10 is ensured to be constant, so that the components, especially the tubes of the heat exchanger 16, do not undergo any expansion, tension, etc. It is not affected by fluctuations in . This increases the service life of the heat exchanger.

As mentioned above, the control functions in this process are 1.
It depends on the temperature indicated in the combustion chamber 18 (actual temperature) by two thermocouples. It is a temperature controller 49,
It is compared with the apparent temperature at 1. Depending on the deviation between the actual temperature and the apparent temperature, fuel supply is made via the valve 22. That is, burner 20 first operates towards its minimum duty. This is the minimum switch 22. Displayed by ■. In order to maintain the temperature in the combustion chamber 18 at an apparent value, the control valve 46.1
．． ．． 46.2 is activated to add fresh air and/or purified process exhaust gas to the untreated process exhaust gas flowing in the duct 14.

The exhaust air, cooled and purified in the heat exchanger 16, is taken off at the exhaust gas outlet 24 (highlighted by the connection point 42) and from there passes through a line 44 to an integrated circuit, which can be accompanied by a mixing characteristic. Sent to point 47.

The amount of purified air required at a given time is determined by the control valve 4.
6.1. An appropriate amount of fresh air is passed to mixing point 47 via a control or valve 462. The partial vacuum in line 48 causes both suctions, now in the form of mixed air.

Line 48 goes to process outlet air duct 14)
The partial vacuum or suction pressure is maintained constant within this duct 14.

The mixture of process exhaust air and added air is then fed into the heat exchanger 16 by means of a suction fan via line 14.1.

The preheating temperature and combustion chamber temperature do not change. The burner fires within the minimum control range. That is, the control device shown here guarantees that as soon as the burner reaches its minimum control range, it remains completely constant, which means that the combustible component level decreases, the feeding operation ends, and the burner enters control action. will be maintained until it is taken again.

The fact that excessive concentrations of combustible components are reduced and maintained at a certain low level and how this is done has been fully explained. An explanation was also given of how the burner operates with minimal flame conditions. Next, the role of temperature control regarding the present invention will be explained.

Practical experience shows that the higher the combustible component concentration, the higher the temperature of the process exhaust air.

Often, high process temperatures are necessary to separate components, such as separating solvents from inks and paints.

Moreover, when the temperature of the process exhaust gas is high, the preheating temperature also becomes high. This means that the higher air preheating temperature reduces the temperature difference between the constant high incineration temperature in the combustion chamber and the air preheating temperature. However, although the burner consumes a proportion of this, even when it throttles back to its minimum control range, a smaller amount is left for heat exchange of oxidizable components in the process exhaust air. It is. This means that the higher the process air temperature, the higher the preheat in the heat exchanger and the lower the acceptable concentration of oxidizable components in the exhaust air (which constitutes the second fuel source). do.

According to the invention, the device, by its temperature control,
Eliminate this phenomenon.

When the plant reaches the "first capacity limit J" through the minimum setting of the burners, the temperature controller 15.1
The above apparent value is determined by the thermal lightning couple 15 downstream from the suction fan 38.
By comparison with the actual value measured by , it is determined how much cold air should be added and at what point warm air should be added simultaneously. In this way, the preheat temperature is also returned to its normal temperature and the throughput capacity of combustible components is increased. Therefore,
The entire unit returns within a certain parameter range.

However, in the rare case where the concentration of oxidizable components is associated with a temperature lower than the desired exhaust air temperature, this can be done automatically by increasing the exhaust air temperature primarily by adding hot air. Modification controlled. This also prevents condensate formation in the inlet area of the incinerator and incinerator.

In other words, the control device described above counteracts the tendency towards condensation when the concentration of condensable components is high and the risk of condensate formation is particularly high, such as at low temperatures.

All operating modes operating with normal cold air also operate with warm air according to the invention.

This means staying warm during idle link operation, warming up still cold equipment, and starting.

In the former case, this indicates an economical mode of operation with a very low volume flow of warm air. The warm air temperature corresponds exactly to the apparent process gas temperature. Temperature control means 15.1 set the correct mixing temperature.

All components of the afterburner device maintain normal temperature levels as a result of the warm idle link operating mode. A warm air starting operation provides a faster and more economical starting operation than a cold air starting operation. Furthermore, the area between the suction fan 38 and the heat exchanger 16 is continuously heated until a certain level is reached when the unit is ready for operation. At this level, the risk of condensation in the hazardous area is eliminated when switching to process operation.

Extensive technical testing of the process has revealed various unexpected properties, including: Therefore, this is something that deserves special attention. These are listed below.

a) Due to the warm-up idle-link operating mode, a distinctly improved thermodynamic state prevails throughout the afterburner device even at minimum flow rates. As a result, the minimum air flow rate required to cause a shutdown operation could be reduced by 35%. Correspondingly, the costs for stopping operations have decreased. This is further complemented by the cost savings generally obtained by the warm-up mode of operation, which is an inherent feature of this type of operation.

b) The method responds in seconds and ranks at least as well as burner control and is far superior to bypass systems. This also allows the introduction of ultra-high speed thermocouples.

C) During idle linking, ie in warm-up operating mode, the temperature remains constant at the outlet of the afterburner device. This not only has already proven beneficial results for downstream peripheral equipment (e.g. equipment for hot water heat exchangers), but also for so-called "cold-hot surface J-actuated heat exchangers". The surrounding equipment is cooled considerably when the incinerator is operated with cold air and reaches the condensation zone. To avoid this, excessive heat recovery should not be allowed. In the present invention this is avoided. Heat recovery is increased considerably without risk, and the process becomes more economical overall.

d) Pressure fluctuations caused by continuous processing do not affect the amount of heated air flowing back, since temperature control takes precedence.

e) The risk of fire is fundamentally eliminated by eliminating all risks of condensation in the inlet area of the afterburner device.

f) Modern production technologies already today provide "high-speed cleaning systems", as in the case of rotating machines in the printing industry.
Contains. Large amounts of solvent are thus introduced into the exhaust gas stream in seconds or in a very short period of time. Therefore, the concentration of combustible components rises rapidly. The process according to the invention reacts quickly to this peak and protects the afterburner device from overtemperature.

FIG. 3 shows the basic structure of the afterburner device. Here, the system of the invention is realized. The afterburner device 50, which is arranged horizontally in the figure, has cylindrical outer casings 52.1 and 522, which are connected by a closed end 54.56. A burner 60 is located at the closed end 56 concentrically with the main axis 58 of the case 52 and opens into a high speed mixing tube 62. This tube 62 is connected to a main combustion chamber 64 connected by an outer closed end 54 .

However, the configuration in which the high speed mixing tube 62 protrudes into the main combustion chamber 64 as shown is not an essential requirement.

An annular chamber 66 is formed concentrically with the high speed mixing tube 62 and opens into a chamber 68 in which a heat exchange tube 70 is disposed concentrically with the longitudinal axis 58. The heat exchange tube 70 opens into an outer annular tube 72, the chamber 72 of which is placed outside the outer wall 52 and transitions into the man lower 4. An annular chamber 76 connected to the exit lower 8 is also provided.

One end 8 of the heat exchange tube 70 near the output lower 8
0 are bent outwards, ie in the direction of the case 52, so that they open in an almost perpendicular position to the case 82 of the outer annular chamber 72. heat exchange tube 70
The other end 84 opens into a tube plate 86 . This tube plate 86 defines a pre-combustion chamber 88 surrounding the burner 60 in the chamber 6.
Separated from 8.

The burner 60 is extended by a burner front portion 90, the Wi portion 90 of which is essentially conical and has a plurality of holes 92 drilled around its periphery. This burner 60 has the shape of a bell mouth that expands along the direction of the high speed tube 62. The high speed tube 62 together with the burner front 90 [Coanda nozzle (
Coanda, jet) J (in areas 98 and 94) at its pendulum entrance cone. This is a concentric link around the burner and constitutes the part that supplies air to the burner or removes air from the burner.

The connecting part 100 or outlet lower 8 is connected to a mixing device. The mixing device is not shown, but corresponds to the mixing device 46, 47 shown in FIG.

The process gas to be combusted by the device according to the invention is sent via the inlet lower 4 to the annular chamber 72 and via the heat exchange tube 70, the burner front 90, the Coanda nozzle 96 and the high velocity tube 62 to the main combustion chamber. 64. The purified gas then reaches the inner annular chamber 66 and the chamber 68 surrounding the heat exchange tubes 70, where it flows over its entire length in a transverse counterflow. In this case, a swirling flow of gas is generated in the chamber 68 as shown by the arrow, thereby exchanging heat in these surrounding areas.Then, the gas flows through the annular chamber 76 to the outlet lower 8. be discharged.

The inner wall 82 of the outer annular chamber 72 is connected to the inner annular chamber 66.
This configuration allows the gas supplied to the heat exchange tube 70 via the input lower 4 to be preheated. can. by this,
Any condensation that may occur can be vaporized to ensure that no buildup within the heat exchange tubes 70 occurs. The heat exchange tube 70
In the region of the curved end 80 of the temperature is at most about 250°
C to 300 C, the temperatures are negligible with respect to the stresses in the heat exchange/pre-combustion tubes and there is no risk of scale formation. Therefore, the loss of wall thickness can also be eliminated,
Due to the high elasticity and strength, fatigue of the curved end 80 can be avoided. The ends 80 serve to compensate for different longitudinal expansions of the heat exchange tubes 70 caused by temperature changes or non-uniform flow. Since the gas temperature in the region of the curved end 80 can be reliably set low, the flow velocity is also low (therefore, there is less risk that the inner wall of the tube in the curved tube section will be abraded by the mixed powder).

Even when the amount of combustible components increases, burner 60
In order to ensure that the pump operates in a minimum control range (basic duty), the purified gas is conveyed via connection 100 to a mixing device designated 46.47 in FIG. Here some fresh air is added to obtain the desired mixing temperature. The warm air mixture thus obtained flows via line 48 to line 14, as shown in FIG. A certain degree of mixing is achieved, so that a constant concentration of oxidizable components is maintained, a constant combustion chamber temperature is maintained, and the required or desired temperature is obtained before the afterburner device.

Since the concentration is constant, temperature fluctuations are largely eliminated or occur only to a small extent in individual areas of the plant, in particular in the area of the heat exchange tubes 70. As a result, large and problematic variations in thermal expansion are also eliminated.

Any undesirable negative effects resulting from high pre-combustion levels are also avoided. In order to maintain the concentration of oxidizable components at a good level, according to the invention, no connection 100 is placed in the device IO, through which the purified exhaust gas is taken off to be mixed with the untreated process gas. Mixing as proposed can be done without complicating the structure of the device 10. The device 50 according to the invention is therefore easy to maintain and reliable in operation.

Tables 1 to 3 below explain once again that the afterburner device operated according to the invention automatically creates optimal conditions for thermal combustion and therefore for the device itself. .

The thermal afterburner plant discussed here has a heat exchange efficiency of 76% and up to 15. This is from OOOma3/h. Although the apparent exhaust gas temperature in the example is 160°C, it actually deviates from this. Combustion chamber temperature is 7
It is kept at a constant temperature of 60°C. The plant shown here is equipped with a special burner that obtains the oxygen necessary for combustion from the exhaust gas (second air burner: comparator). Minimum capacity (lower limit of control range)
is 678 W h / h.

The plant receives supplies from various independent sources. Depending on the sources and their number, the flow rate, exhaust gas temperature and in particular the amount and concentration of oxidizable components in the exhaust gas vary. The oxidizable component is mineral oil. Tests were conducted under three different operating conditions and the results are shown in the following table.

Table 1. Targets and capacities of afterburner devices without surplus energy control.

Djm'n I 2 3 Exhaust gas flow rate (V)mo”/h 3.5005.000
8.500 oxidizable components g/m. ” 8
7. + 3KWh/h 330.6421.6
302.4 Before the blower (7) C' 20
4 190 160 Exhaust gas temperature in combustion chamber (711G' 760 750 760 Required temperature (t4) Planned residual heat temperature (t,] C06281i2:l
[+16 K 132 13 of combustion process
7 Residual value of 144 tank (tl K at minimum flame 45 31.5 1
8.5 burner consumption +1) Incineration of oxidizable components K 87 105.512
Residual value for 5.5 (tl Incineration of oxidizable components KWh/h 131 226.
Free heat capacity in V for 9458.8 KWh/h to be removed 199.6194.
6 None Surplus Heat Explanation" 1. In operating state 1.2, there is a considerable amount of surplus heat generated from the oxidizable components with respect to the amount of waste waste V. This is because, in both cases, the control function according to the invention comes into play once the burner reaches the lower limit of its control range (minimum control range, basic duty) so as to create room for increasing the amount of oxidizable constituents. It means to do. In both cases, the apparent exhaust gas eddy current (here 160″
C) has increased significantly, so the system intervenes to correct this.

In operating state 3, the concentration of oxidizable components in the exhaust gas is lower than the capacity of the unit allows for this flow rate. The burner thus precisely controls the amount of energy lost without the control of the present invention by adjusting the amount of fuel.

Table 2: Processing of tasks by the system according to the invention for operating state 1.2.3 in Table 1.

Dim 'n I 2 3 (46, I]
Beniyu's m. 3/h 960 950 --
- Warm air recycling (I=I addition m.”/h 1.97 via 46,2+
01. ! 150 --- cold air t=+o cv new total flow Mk m. 3/h 6.4307.
9008.500 Newly revised exhaust gas temperature C016016
0160 Residual heat record C' 616 61
6 616 Combustion chamber temperature (:l' 760
760 760 Fuel consumption KWtl/h
67.8 67.8224.2 Iron crystallinity
C' 309 3099 310 If the thermal afterburner is done by a bypass system known in the current state of the art, the output temperatures for operating conditions], 2.3 will be 442°C, 399°C and 310°C, respectively. Will.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the principle of an afterburner method for process gases containing oxidizable components Z with a bypass for energy control, and FIG. 2 shows an afterburner according to the invention corresponding to FIG. FIG. 3 is a schematic diagram of an afterburner device for carrying out the method according to the invention. 16...Heat exchanger 18...Combustion chamber 20...Burner 24...Exhaust gas outlet 50...Afterburner device 60...Burner 62...High speed mixing tube 70...Heat exchange tube 72・・・Annular room Ii Mitsu・Tsubo 2', -I 勺τ Aj

Claims (16)

[Claims] (1) A method for controllable thermal afterburning of a process exhaust gas containing oxidizable components, the process exhaust gas being routed through an afterburner device and comprising a gas inlet, a heat exchanger, a burner, a combustion chamber and the like. The process exhaust gas to be sent to the afterburner device is conveyed to the gas outlet via a heat exchanger in a purified state from , mixed with fresh air to a desired extent with purified process exhaust gas. (2) The inlet temperature of the mixed gas consisting of untreated process exhaust gas, purified process exhaust gas and fresh air and fed into the afterburner device is maintained at an adjustable level. Method. 3. The method of claim 1, wherein the burner is operated in a minimum control range. 4. The method of claim 1, wherein the purified process exhaust gas is added to the untreated process exhaust gas after passing through a heat exchanger. (5) A device for controlled afterburning of process exhaust gases containing oxidizable components, comprising a gas inlet, a burner preferably with a high-speed mixing tube, a combustion chamber, and a combustion chamber concentric with the high-speed mixing tube. An apparatus for implementing the method according to claim 1, comprising a heat exchanger with attached heat exchange tubes and a gas outlet, in particular an apparatus (10, 50) and a gas inlet (14, 48, 74). A connection means (102, 44) is provided between the apparatus (102, 44), and the purified process gas is passed through the connection means (102, 44) to the apparatus (102, 44).
0.50) to a desired extent. (6) The heat exchange tube (70) is bent outward at the cold end (80) and the purified process exhaust gas can flow around the heat exchange tube. Device. (7) The duct (14) conveying the untreated process exhaust gas to the afterburner device (10) is equipped with a suction fan (38), on the suction side of which a partial vacuum can be created, via which it is purified. 6. Apparatus according to claim 5, characterized in that the processed process exhaust gas and fresh air can be added to the untreated process exhaust gas to any desired extent. (8) The temperature of the purified process exhaust gas and/or the fresh air to be added to the raw process exhaust gas is controlled by a control device such as a butterfly valve (46.1; 46.2), the control variable being 8. Device according to claim 7, characterized in that it is determined by the temperature indicated on the pressure side of the suction fan (38) of a gas mixture consisting of treated exhaust gas and purified exhaust gas and/or fresh air. (9) The concentration of oxidizable components in the process exhaust gas to be thermally incinerated in the combustion chamber (18; 64; 94) depends on the temperature in the combustion chamber when the burner (60) operates in the minimum control range. Claim 5 characterized in that it is correspondingly controlled.
The device described. (10) An apparatus for combusting oxidizable components in a carrier gas, comprising a gas inlet, a gas outlet, a burner, a high-speed mixing chamber connected to the burner, and a heat exchanger, the apparatus comprising: The exchanger has a plurality of tubes arranged around the high-speed mixing chamber and through which the gas to be purified flows in a transversal counterflow manner with respect to the purified gas, the tubes being connected at one end to In the curved heat exchange tube, the heat exchange tube is bent outward at its cold end. 11. The apparatus of claim 10, wherein the gas flowing outside the heat exchange tube can be guided through the curved tube section and the bent end. (12) The carrier gas is supplied from the carrier gas inlet to the region of the outer case of the substantially cylindrical device.
11. The device of claim 10, wherein the device is fed to the curved end of the heat exchange tube via an outer annular chamber provided therealong. 13. The apparatus of claim 12, wherein the annular chamber extends between the carrier gas inlet and the carrier gas outlet. (14) The carrier gas inlet is connected to the first annular chamber and arranged in the region of the burner.
The device described. 15. The apparatus of claim 14, wherein the first annular chamber coaxially surrounds the burner. 16. The apparatus of claim 12, wherein the inner wall of the outer annular chamber forms a heat exchange surface for preheating the carrier gas supplied to the apparatus.