KR100519747B1 - Sequential catalytic combustion system and its method - Google Patents

Abstract

The present invention relates to a sequential catalytic combustion system and a method thereof, and an object thereof is to implement a heat generating device that replaces a general flame burner by applying catalytic combustion. Second, it should be independent of the conditions of the mixed gas and maximize the advantages of catalytic combustion by eliminating the flame combustion during initial start-up and the steady state combustion in the preheating process of the mixed gas and solving the system itself. Eliminates the problems of durability, high temperature product generation, and mixed gas explosions.The catalyst combustion reaction is independent of the mixed gas conditions, so that it can handle large flow rates and maintain stability even under rapid temperature or equivalence ratio changes. It is to provide a combustion system and method.

The configuration of the present invention is characterized by a system and method for inducing a sequential catalytic combustion reaction by combining a catalytic combustor unit comprising a catalytic combustion unit and a heat exchanger to transfer a part of the heat generated in the catalytic combustion to a preheating process of the mixed gas.

Description

Sequential catalytic combustion system and its method

The present invention relates to a sequential catalytic combustion system and a method thereof, and in particular, by combining a catalytic combustor unit composed of a catalytic combustion unit and a heat exchanger, the catalytic combustion is sequentially performed by transferring a part of heat generated in the catalytic combustion to a preheating process of a mixed gas. It relates to a system and a method for inducing a reaction.

Catalytic combustion refers to the combustion of mixed gas at the catalyst surface. Compared with general flame combustion, catalytic combustion has the characteristics of surface combustion and lean combustion.

This allows full combustion, regardless of the nature of the combustor, given a sufficient catalyst surface area for a given gas mixture, and relatively relatively by burning directly on ultra-lean gases (approximately equivalent to 0.2 equivalents in LPG) that cannot be combusted in normal flame combustion. It means having a very low adiabatic flame temperature (general flame temperature around 1400 ℃, catalytic combustion around 500 ℃).

The low temperature combustion characteristics are free of high temperature combustion products such as NOx and furthermore advantageous in terms of durability of the device.

Despite these advantages, catalytic combustion is limited in certain conditions.

This is because the conventional catalytic combustor is less applicable in terms of efficiency and stability to the general combustion conditions than the flame combustor.

Therefore, to develop a combustor that maximizes the advantages of catalytic combustion, three technical problems must be overcome.

The first is the durability of the catalyst, which has secured a certain level of economics and applicability through recent active material development. Therefore, it is left out here.

Second is the mixed gas preheating problem. Catalytic combustion has a specific catalytic combustion start temperature according to the type of fuel gas, and the reaction starts only at that temperature (see FIG. 8).

Therefore, in order to start catalytic combustion, the mixed gas needs to be preheated above the catalytic combustion initiation temperature. At this time, preheating using flame combustion is generally used as the most economical and effective method.

However, in the case of a large-capacity treatment facility, the use of preheating flame combustion increases proportionally, thus causing problems such as supply of additional fossil fuel, deterioration of durability of the apparatus, explosion risk, and high temperature product generation.

These problems are developed to a level that offsets the advantages of the application of catalytic combustion as the large capacity.

In order to solve this problem, there has been an EHC approach to heat the surface of the catalyst by heating the catalyst support above the initiation temperature of the catalyst combustion, but in this case, there is a disadvantage in that disconnection due to the high temperature in the catalyst support occurs frequently during combustion. Application is restricted.

Another solution is to use a catalyst fin tube (see FIG. 6). This method carries a catalyst on the side of the catalyst fin tube shell and flows a mixed gas to the fin tube side.

At this time, catalytic combustion occurs on the shell side, and a part of the heat generation preheats the mixed gas on the tube side, and simultaneously generates heat and preheating.

However, this method also has a high preheating load using flame combustion, and in particular, it is very difficult to maintain thermal equilibrium at the catalyst surface. Next, there is a heat exchange type catalytic combustion device (see FIG. 7).

It consists of a catalytic combustion part and a high temperature heat exchanger, and a part of the catalyst calorific value preheats the mixed gas flowing inside the high temperature heat exchanger. Therefore, once catalytic combustion reaches a steady state, it is not necessary to preheat through flame combustion through its own preheating process. It is easy to control because it is independent of the mixed gas compared to the fin tube method, but also requires preheating using flame combustion during the initial operation, which is a big disadvantage in the large flow rate treatment.

Third, there is a dependency problem on the mixed gas of catalytic combustion. Catalytic combustion maximizes the contact of the mixed gas to the catalyst surface by surface combustion, which means that the catalytic combustion reacts very sensitively to the physical and chemical conditions of the mixed gas. That is, it generally has a response speed of several seconds depending on the conditions of the temperature of the mixed gas, flow velocity distribution, equivalent ratio, and the like. The greater the flow rate of the mixed gas, the greater the variability of the condition, the more the difficulty of the combustion control is proportional. Therefore, it is required to maintain stable catalytic combustion against the rapid change of condition of the mixed gas according to the application to the large-capacity industrial equipment. In addition, the start-up time must be short before the reaction is extinguished and ignited again, and the control of the catalyst surface temperature should be low and easy to control.

The above-mentioned points are factors limiting the scope of application despite the advantages of catalytic combustion, and solving these problems is the most important issue.

An object of the present invention for solving the above problems is to implement a heat generating device to replace the general flame burner by applying catalytic combustion.

To this end, first, the burden of preheating the mixed gas should be minimized. Second, the condition of the mixed gas should be independent, and the combustion of the mixed gas should be eliminated during initial start-up and steady-state combustion. By maximizing the advantages of catalytic combustion, it eliminates the durability problems caused by flame combustion, the generation of high temperature products, the explosion of mixed gas, etc., and the catalytic combustion reaction is independent of the mixed gas conditions so that large flow rate treatment is possible. In addition, the present invention provides a catalytic combustion system and method which maintains stability even in a sudden change in temperature or equivalent ratio.

The present invention, which achieves the above object and accomplishes the problem for eliminating the conventional drawback, in the catalytic combustion apparatus, includes a flow controller positioned in an upstream region of the catalyst support to induce a uniform flow rate distribution, and a catalyst is supported. A catalyst burner comprising a catalyst carrying support and a heat insulating layer sequentially connected to prevent heat loss from the catalyst surface; A catalytic heat exchanger is installed in contact with the catalytic combustion unit and consists of a heat exchange unit consisting of a high-temperature fin tube to transfer a portion of the heat generated by the catalytic combustion to the mixed gas to perform a preheating process. The fin tube is arranged in a structure orthogonal to the direction in which the gas burned in the catalytic combustion section flows, and the heat exchange unit of one unit and the catalytic combustion unit of the other unit communicate with each other so as to independently preheat and burn simultaneously. It is done.

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The unit consisting of the catalytic heat exchanger is connected in parallel to four units, the first unit is composed of a trigger unit in which the combustion reaction is initiated by the mixed gas preheater, and then the adjacent units connected in parallel are sequentially serialized by the initial combustion of the trigger unit. And is configured to combust to commence catalytic combustion.

In addition, after each unit is composed of one catalytic combustion system, it is configured in parallel with a plurality of catalytic combustion systems, and one catalytic combustion system is configured as a trigger system.

In addition, the catalytic combustion method of the present invention,

In the initial operation mode, the catalyst is composed of a plurality of units composed of a catalytic combustion unit and a heat exchanger in parallel, and then, in the initial driving mode, the catalytic combustion is performed using one of the plurality of units as a trigger unit, and the neighboring units are sequentially heated and preheated. To do that,

In the steady state mode, each of the plurality of units is characterized by a combustion method consisting of a parallel combustion step of simultaneously dividing and processing the total mixed gas flow rate.

The above will be described in more detail below.

A system that maximizes the advantages of catalytic combustion is suitable for parallel combustion, which consists of a number of individual units.

Individual units each employ a catalytic combustion heat exchanger which simultaneously performs catalytic combustion reaction and mixed gas preheating.

The catalytic combustion heat exchanger continuously transfers a portion of the heat generated from the catalytic combustion to the preheating process of the mixed gas through the high temperature heat exchanger, and thus, the burden of preheating the mixed gas during the initial start-up is largely solved by itself.

Further, when the steady state is reached, the preheating of the continuous mixed gas excluding flame combustion is possible by controlling the equivalence ratio of the mixed gas.

However, honeycomb type catalytic heat exchangers are stable for low flow mixed gas treatment, but have some disadvantages for high volume mixed gas treatment.

The larger the volume of the mixed gas, the more difficult it is to maintain uniformity of the mixed gas flow rate and equivalence ratio distribution upstream of the catalyst honeycomb, and the burden on preheating the mixed gas to initiate initial catalytic combustion increases.

Once the mixed gas non-uniformity occurs, control stability at the catalyst surface is low and blow off occurs frequently.

Therefore, a different approach is required to apply to industrial flue gas treatments (500,000 kcal / hr or more) that are not really small (100,000 kcal / hr or less) but mainly to large volume treatments.

As mentioned above, batch processing of a large volume of mixed gas in one combustor has many problems, so it is ideal that a large volume of mixed gas is processed by a system configured in parallel with multiple combustor units.

In addition, a system that maximizes the advantages of catalytic combustion is suitable for a series combustion method in which a catalytic reaction is sequentially induced and a chain reaction is induced in each combustor unit during initial driving.

In order to minimize the preheating process of a large amount of mixed gas, it is advisable to adhere to the proven technical method (preheating by using the catalytic combustion calorific value in the steady state operation) when the steady state is reached, and to minimize the preheating burden during the initial operation. Focus.

The system thus consists of a number of units consisting of catalytic heat exchangers.

As a conventional method, preheating a large amount of mixed gas to one combustor has a number of problems (previously, the total flow rate / number of system configuration units).

After the start of the catalytic combustion reaction of the combustor unit which acts as a trigger during the initial operation, the heat generated at this time is used to induce combustion to the entire unit sequentially (see FIG. 3).

The use of such Domino chain reactions allows for unlimited expansion of the catalytic combustion capacity regardless of the initial mixed gas preheating problem.

The system of the present invention can theoretically be implemented in two units, but in practice it is based on a combination of four units for mixed gas flow control (see Figure 1).

Based on this basic system, a combination of multiple systems is possible, which means unlimited mixed gas processing capacity. In other words, unlike the conventional method of having to design the flow control for all conditions on a case-by-case basis according to the processing capacity, the processing capacity can be covered by simply adding or subtracting the unit.

In the initial operation, the reaction starts in series combustion and in steady state operation, the reaction is maintained in parallel combustion.

The preheating of the trigger unit during initial operation and the use of catalytic combustion in the steady state are realized so that flame combustion can be completely eliminated even in the preheating of a large amount of mixed gas.

Hereinafter, the configuration and the operation of the embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is an exemplary view showing a schematic configuration of a sequential catalytic combustion system according to the present invention, Figure 2 is a detailed view of a catalytic heat exchanger unit constituting a sequential catalytic combustion system according to the present invention, Figure 3 Reaction sequence and configuration diagram of the sequential catalytic combustion system, Figure 4 is an embodiment showing a three-dimensional catalytic heat exchanger unit constituting the sequential catalytic combustion system according to the present invention, Figure 5 is a heat exchange unit of the unit Although shown in detail, the components of the sequential catalytic combustion system of the present invention are as follows.

One system consists of a total of four units 1, 2, 3, 4 (see FIG. 1). Each unit constituting the system is a catalytic heat exchanger consisting of a combustion section 6 and a heat exchanger 7.

Combustion portion 6 constituting the catalytic heat exchanger is composed of a catalyst support (9), a flow controller (8) and a heat insulating layer (10) carrying a catalyst.

The catalyst support 9 uses a ceramic honeycomb in a volume calculated according to the capacity. Ceramic honeycomb usually uses 200 cell / inch ² and supports a certain amount of suitable catalyst depending on the type of processing gas. Generally, platinum catalyst is used to treat LPG and Toluene.

The flow controller 8 is located upstream of the catalyst support 9 in order to induce a uniform flow rate distribution due to the characteristics of surface combustion, and a ceramic honeycomb of 100 to 150 cells / inch ² is used. The flow controller 8 suppresses the occurrence of hot spots due to the nonuniformity of the flow rate and the equivalent ratio, and obtains the combustion stabilization effect due to the heat storage.

The heat insulating layer 10 maintains thermal equilibrium by preventing heat loss from the catalyst surface.

The heat exchanger 7 constituting the catalytic heat exchanger transfers a part of the heat generated from the catalytic combustion to the mixed gas to perform a preheating process (see FIG. 5).

The heat exchange part 7 is composed of a high-temperature fin tube 11, a hot combustion gas passes through the shell side 111 of the fin tube, and a mixed gas passes through the tube side surface 112.

Design factors related to the number and arrangement of fin tubes 11 are taken into account the mixed gas flow rate, temperature, equivalence ratio, adiabatic flame temperature, catalytic combustion start temperature, combustion gas discharge temperature, combustion gas flow rate, heat loss, etc. Influenced thermal equilibrium calculations.

The heat transfer coefficient, which is a particularly important design factor, is proportional to the flow rate and therefore dependent on the mixed and combusted gases.

In practice, for example, with a 20% design margin based on LPG, a general purpose fuel gas, it aims to preheat the mixed gas up to about 250 ° C and has a flue gas flow rate of 15 to 30 m / s.

In general, a two or three pass fin tube 11 bank arrangement is applied to the heat exchange between the combustion gas and the mixed gas at the same flow rate at room temperature.

One unit (1, 2, 3, 4) of the system has a calorific value of at least 20,000 kcal / hr on an LPG basis.

This is experimentally derived value considering space velocity, equivalence ratio, heat transfer coefficient, and durability of catalyst honeycomb.

The sequential catalytic combustion system thus has a calorific value of at least 80,000 kcal / hr (= 20,000 kcal / hr * 4).

In the case of reducing the heat generation amount of the individual units 1, 2, 3, 4, the application of the high temperature fin tube 11 to the heat exchanger 7 of the units 1, 2, 3, 4 is not suitable.

A compact heat exchanger with superior heat exchange efficiency can be used under low flow rate and low heat transfer coefficients, but this is susceptible to high temperatures and is likely to lead to leakage.

On the other hand, when the individual units 1, 2, 3, 4 and the heat generation amount are extended, the heat exchanger 7 has no problem, but the combustion unit 6 is composed of a multi-stage combustion type or a matrix type.

In this case, it is expected that each unit 1, 2, 3, 4 consists of a high load catalytic combustion section 6 and a heat exchanger section 7.

It is possible to increase the throughput of the system to 200,000 kcal / hr or more by high-loading the catalytic combustion section 6 of the units 1, 2, 3, 4.

The method of high enrichment includes integration of the catalyst support 9, multi-stage combustion and control of the equivalence ratio of the mixed gas.

One of the important reasons for setting the sequential catalytic combustion system as the four basic building blocks (1, 2, 3, 4) is the convenience of flow control of the mixed gas.

In the conventional catalytic combustion system, the flow path is curved when the mixed gas preheated in the heat exchange unit 7 flows into the catalytic combustion unit 6 (see FIG. 7).

The larger the capacity, the wider the area of the catalyst combustion section 6 is perpendicular to the flow because the catalyst support 9 is combined in a matrix form.

Due to the surface combustion characteristics, the mixed gas must have a uniform flow rate distribution so that the matrix of the catalyst support 9 has a uniform combustion reaction.

However, it is very difficult to realize a uniform flow velocity in a wide plane in a curved channel. In addition, increasing the flow rate for higher loads will increase the flow distribution distortion. The curved flow path has a large surface area and not only a large heat loss, but also a large pressure loss due to the installation of a damper or a porous plate.

However, in the sequential catalytic combustion system, the flow paths of the four units 1, 2, 3, and 4 are all formed in a straight line, thereby eliminating the above disadvantages.

The configuration of the device is compact, resulting in less heat loss and less space for the device for the same capacity.

The trigger unit 1 which initiates the combustion reaction of the sequential system consists of a catalytic heat exchanger and an additional mixed gas preheater 5.

The sequential ignition method through the trigger unit 1 of the system of the present invention compensates for the weaknesses of the existing catalytic combustor. The unit for initiating the combustion reaction of the sequential system is described as the trigger unit 1. 1, the mixed gas preheater 5 is physically connected to the unit 3 (4). Therefore, the fuel gas preheated in the mixed gas preheater passes through the heat exchange part of the unit 3 (4) and reaches the inlet of the catalytic combustion part of the trigger unit 1 to start the combustion reaction. That is, the heat exchange part of the unit 3 (4) is only a passage through which the fuel gas passes without any reaction, and the catalytic combustion part of the trigger unit 1 is substantially connected and the combustion reaction is started. Therefore, the actual combustion mechanism can be seen that the mixed gas preheater is connected to the catalytic combustion section of the trigger unit (1).

Conventional combustors rely solely on flame combustion for mixed gas preheating until catalytic combustion reaches a steady state, requiring up to 50% of the total heat generated at 100% of the mixed gas flow rate.

For example, up to 500,000 kcal / hr of flame combustion is required for initial combustion for catalytic combustion of 1,000,000 kcal / hr.

Since the burden of flame combustion preheating is determined by the initial temperature of the mixed gas used, the application of catalytic combustion is the most decisive reason to be limited to the treatment of high temperature and low heat mixed gas treatment.

In addition, the preheating method using flame combustion, which is the most economical method for preheating large flow gas mixtures, had to be selected, resulting in the durability of the device, the need for additional flame burner equipment, the difficulty of flow control, and the use of catalytic combustion with explosion risk. This has the weakness of offsetting.

However, the trigger unit 1 of the sequential system first preheats only the flow rate of 25% of the total mixed gas. This flow rate is easier to control than flame combustion and a clean electric heater can be used.

In actual operation, it is expected that the preheating burden can be further reduced by increasing the combustion temperature by controlling the equivalence ratio for flow rates below 25%.

Once catalytic combustion is started in the trigger unit 1, the preheated mixed gas which has passed through the high temperature heat exchanger of the trigger unit 1 is injected into the next unit 2.

When the catalytic combustion reaction is started by the preheated mixed gas, the same principle is also sequentially started in the next unit (3).

When the catalytic combustion reaction of the four units 1, 2, 3, 4 in this order reaches a steady state, the mixed gas preheater 5 of the trigger unit 1 plays a role.

As described above, the sequential catalytic combustion system is a series processing method in which the units 1, 2, 3, and 4 are ignited in sequence during initial operation, but when the steady state is entered, four units 1, 2, 3, and 4 are operated. It is switched to a parallel process that burns at the same time.

9 illustrates a system that can expand the processing capacity by connecting a plurality of sequential catalytic combustion systems, which will be described below.

On the basis of a sequential catalytic combustion system composed of four units (1, 2, 3, 4), each unit (1, 2, 3, 4) serves as a trigger unit of another system to which it is connected.

That is, this system, in which all four units 1, 2, 3, and 4 trigger other systems, will be referred to as a trigger system 13.

The combustion gas passing through the trigger system is double burned in the trigger unit 1 of the connected system.

Once the trigger unit 1 of the connected system responds, the remaining three units 2, 3, 4 also react sequentially.

At this time, the combustion gas generated in the trigger system is assisted by an electric heater and at the same time injects fuel gas such as LPG into the mixed gas to ignite another trigger unit 1.

At steady state, all systems preheat themselves and burn on their own with only the calorific value of catalytic combustion.

With such a mechanism, the processing capacity can be infinitely expanded through the combination of the sequential catalytic combustion system 12.

In addition, when the combination is three-dimensional, the device can be compact, and heat loss can be reduced.

In terms of the initial driving time, the sequential system is expected to shorten the running time rather than the existing system that heats the entire flow rate due to the characteristics of the catalytic combustion which is the response speed as the surface combustion.

This difference becomes more noticeable in the initial run time as the flow rate increases.

In short, the present invention provides a system that induces catalytic combustion sequentially by direct preheating of only 25% or less of the total flow rate, thereby implementing 100% preheating and 100% combustion with catalytic combustion.

The present invention overcomes the preheating and flow control weaknesses of existing catalytic combustion systems and maximizes the advantages of catalytic combustion.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

In the present invention as described above, the sequential catalytic combustion system is not only completely independent from flame combustion, but also has an effect of replacing a conventional flame combustion combustor.

That is, in the present invention, conventional catalytic combustion can be burned even under very rare mixed gas conditions (LPG equivalent equivalence ratio 0.2 to 0.3, general flame combustion is an extreme value of 0.5) where general flame combustion cannot exist, and high-efficiency combustion compared to general flame combustion. (Approximately 100% complete combustion), clean combustion (high-temperature products such as NOx, no incomplete combustion products such as CO) despite the advantages of limited application to solve the problem of the mixed gas preheating and flow control It is possible to realize the system that maximizes the advantages of the system, and it is possible to compete not only in the field of high-temperature low-heat waste gas treatment, which is superior to conventional catalytic combustion, but also in the heat generation device field that generates heat sources of various capacity under 1000 ℃. It is a useful invention having an industrial invention that is expected to use.

1 is an embodiment showing a schematic configuration of a sequential catalytic combustion system according to the present invention,

2 is a detailed view of a catalytic heat exchanger unit constituting a sequential catalytic combustion system according to the present invention,

3 is a reaction sequence and configuration diagram of a sequential catalytic combustion system,

4 is an exemplary view showing in three dimensions the catalytic heat exchanger unit constituting the sequential catalytic combustion system according to the present invention,

5 is a detailed view of the heat exchanger of the unit,

6 is an exemplary view showing a state of a conventional fin tube type catalytic combustor,

7 is an exemplary view showing a state of a conventional honeycomb type catalytic combustor,

8 is a table showing the catalyst combustion start temperature according to the fuel gas type of the mixed gas,

FIG. 9 is an exemplary view showing an expansion of a processing capacity by connecting a plurality of sequential catalytic combustion systems.

<Description of the symbols for the main parts of the drawings>

(1): Trigger unit (2): Unit 1

(3): unit 2 (4): unit 3

(5): mixed gas preheater (6): catalytic combustion section

(7): heat exchanger (8): flow controller

(9): catalyst support support 10: heat insulating layer

(11): high temperature fin tube (12): sequential catalytic combustion system

(13): trigger system 111: shell side of the high temperature fin tube

112: tube side of the high temperature fin tube

Claims (4)

In the catalytic combustion device, In order to induce a uniform flow rate distribution, the flow controller 8 located in the upstream region of the catalyst support, the catalyst supporting support 9 on which the catalyst is supported, and the heat insulating layer 10 for preventing heat loss from the catalyst surface are sequentially A catalytic combustion section 6 connected; A catalytic heat exchanger is installed in contact with the catalytic combustion unit, a heat exchanger (7) consisting of a high temperature fin tube (11) to perform a preheating process by transferring a portion of the heat generated by the catalyst combustion to the mixed gas. Thus, the high temperature fin tube of the heat exchange unit 7 in the unit is arranged in a structure orthogonal to the direction in which the gas burned in the catalytic combustion unit flows, and the heat exchange unit of one unit and the catalyst combustion unit 6 of the other unit communicate with each other. Sequential catalytic combustion system, characterized in that configured to implement the preheating and combustion at the same time independently. The method of claim 1, The unit consisting of the catalytic heat exchanger is connected in parallel to four units, the first unit is composed of a trigger unit (1) in which the combustion reaction is initiated by the mixed gas preheater (5) and then adjacent to each unit (2, 3, And 4) sequentially burned in series by the initial combustion of the trigger unit (1) to start catalytic combustion. The method according to claim 1 or 2, Each unit (1, 2, 3, 4) is composed of one catalytic combustion system 12, and then again configured in parallel with a plurality of catalytic combustion systems, one of the catalytic combustion system to the trigger system (13) Sequential catalytic combustion system characterized in that the configuration. In the catalytic combustion method, After having a system according to any one of claims 1 to 2, wherein a plurality of units comprising a catalytic combustion unit and a heat exchange unit are combined in parallel, the catalyst is burned in the initial operation mode using one of the plurality of units as a trigger unit, and then Sequentially heating and preheating the unit to perform series combustion; In the steady state mode, each of the plurality of units are composed of a parallel combustion step of simultaneously dividing the total mixed gas flow rate processing method characterized in that the combustion method.