JPS6233213A - Combustion unit - Google Patents

Abstract

PURPOSE:To accelerate the normal operation of a major combustion unit by a method wherein an air preheater for a start-up is installed at the upstream side of a first-stage catalyst combustion unit, fuel is mixed with the preheating air and passed through a catalyst layer to perform combustion, an amount of mixing air is controlled to mix the fuel with air and passed through a second-stage catalyst layer to perform combustion. CONSTITUTION:Air divided to flow from an air major pipe 1 is heated by a start-up air heater 5 to a temperature higher than an ignition temperature of a catalyst and enters a first-stage fuel mixing unit 6, is mixed with fuel in the first-stage fuel supplying pipe 7, flowed to a first-stage combustion cylinder 9 and then ignited in a first-stage combustion catalyst 8. The combustion generated gas having entered the second-stage catalyst combustion cylinder 12 is mixed with the air in the supplying pipe 11 and an amount of mixed air is adjusted in such a way as its temperature is more than a catalyst combustion temperature and less than a combustion temperature of fuel mixture. Fuel from the second-stage fuel mixing unit 14 is mixed in the mixed gas with the second-stage fuel mixing unit 14, ignited with the second-stage catalyst 15, enters the third-stage catalyst combustion cylinder 16 mixed with the air in the air pipe 1, the fuel in the third-stage fuel supplying pipe 17 is mixed by the third-stage fuel mixing unit 18 and then the fuel is ignited with the third catalyst.

Description

[Detailed Description of the Invention] Conventional catalytic combustors use some means to preheat the entire amount of air flowing into the combustor when preheating the premixed gas to a temperature higher than the ignition temperature for catalytic combustion. In some cases, the heat capacity of the air preheater is large and it takes too much time to preheat the air to a predetermined temperature.

In addition, when trying to obtain preheated air above the ignition temperature of the catalyst by producing high-temperature combustion gas using a conventional burner and mixing it with the combustion air, some unburned material is generated in the Parnall combustion mechanism, and this is heated to the surface of the catalyst. It burns when normal catalytic combustion occurs after adhering to the fuel. When the unburnt substances adhering to the surface of the catalyst are combusted, a localized high temperature is generated, which leads to rapid deterioration of the catalyst, which is inconvenient. This phenomenon is particularly noticeable when combustion operation is frequently intermittent or when combustion is performed under pressure. or.

If a burner is used, it may fail to ignite, so considerable safety considerations must be taken. The catalytic combustor of the present invention has been improved in the above points.

Embodiments of the present invention will be described below based on the drawings.

In Figure 1, 1. is the main air pipe that supplies the entire amount of combustion air. 2. is the air supply pipe for the first stage catalytic combustion,
3. is the first stage catalytic combustor cylinder 9. This is a heat exchanger between the first stage catalytic combustion generated gas and the first stage combustion air provided in the combustion chamber, that is, an air preheater. 4. 6. is the preheated air outlet pipe of the first stage fuel warmer. Start-up air heater 5. is installed. 8. is the first stage combustion catalyst of the first stage catalyst combustion generated gas. 1. The air branched from the main air pipe of 2. is the first stage catalytic combustion air supply pipe. Air preheater 3. through the preheated air outlet pipe 4. Start-up air heater through 5. The fuel is heated to a temperature higher than the ignition temperature of the catalyst in the first stage fuel mixer 6. The fuel enters the first stage combustor tube 9, where it is mixed with the fuel from the first stage fuel supply pipe 7. Flow 9. a first stage combustion catalyst held within8. is combusted and flows to the first stage catalyst combustion air 2. The combustion temperature in this case is 1100℃
6. The first stage combustor combiner at a typical temperature of ~1200°C. The temperature of the preheated air that enters is about 300°C to 450°C.

When combustion starts, the air preheater 3. When the temperature of the air coming out of the air rises to 300℃~450℃, start-up air heater 5. operation will be stopped. An electric heater is normally used as the air heater 5° for startup, but an indirect type air heater using combustion gas may also be used. In this case, what is important is to make the first stage combustor as small as possible and the heat capacity of the startup air heater to be as small as possible to shorten the time required for startup as much as possible. The combustion generated gas temperature at the first stage catalytic combustor intake is about 400° C. lower than the combustion temperature. This is because heat is consumed to preheat the combustion air. For example, if the combustion temperature is 1200°C and the air preheating temperature is 400°C, the combustion product gas outlet temperature will be about 850°C.

First stage combustor tube9. to the second stage catalytic combustor cylinder 12.
Supply pipe 1 for the combustion product gas entering the combustion chamber and air for the second stage combustor
1. The amount of mixed air is adjusted so that the temperature is higher than the catalyst ignition temperature and lower than the combustion temperature of the fuel mixture.

The first stage combustion gas is not mixed with the main combustor air, and the second stage
The purpose of using a staged combustor is to make the startup combustor smaller, and the first stage preheats its own air, which lowers the temperature of the outlet gas and reduces the amount of mixed air.I will give an example. It becomes as follows.

When the ignition temperature of the catalyst is 300°C or lower, and the preheated air temperature is 300°C and the catalyst combustion temperature is 1200°C, the combustion amount in the first stage is 1, while the combustion amount in the second stage is 3°3, and the third stage is 15. .7
becomes. On the other hand, if the air supply amount is 1 for the first stage, then the second stage is
The tier is 2.3 and the third tier is 12.1.

Second stage combustor cylinder 12. 10. Combustion gas/air mixer for mixing combustion product gas and air in the combustion chamber. The first stage combustor combiner 14. is installed and the gas is sufficiently mixed. And the second
Stage fuel supply pipe 13. Mix the fuel from the second stage catalyst 15
．． For the third stage catalytic combustor @if 6. Main pipe for air entering 1. It mixes with air from the third stage fuel supply pipe 17.
The fuel from the first stage combustor combiner 18. The mixture is mixed at the 3rd stage catalyst and combusted at the 3rd stage catalyst.

When the combustor is constructed using the method described above, the main combustor can be brought into normal operation in about 10 to 20 minutes for startup. A heat exchanger between the combustion generated gas and the first stage combustion air, that is, an air preheater installed on the downstream side of the first stage combustor.3. As shown in FIG. 2, it is best to fill the outside of the double tube with particles in order to increase the transfer of heat. The higher the heating temperature of the air, the more effective it is to fill the air with particles, increasing the contact area between the air and the particles and increasing the amount of heat transferred to the air. A double outer tube 21. Heat transfer to the tube wall of the first stage combustor tube 9. Refractory material pasted inside 20. Since the surface of is at the temperature of the combustion gas,
The heat radiation from the surface of the refractory material increases and is added to the convective heat transfer from the combustion gas, so the heat receiving area on the combustion gas side can be made considerably smaller. - Heat transfer inside the crab double tube is only through convective heat transfer between the air and the inner surface of the double outer tube. For this purpose, air preheater 3. In order to reduce the size of the combustor and the overall size of the combustor, it is necessary to increase the contact area with air. For this purpose, it is effective to fill the donut ring-shaped area inside the double pipe with full-length or ceramic particles to increase the contact area with air. Heat transfer from the inner surface of the double outer tube to the particles and between the particles is due to heat conduction and radiant heat transfer in the contact area. In particular, the surface area of particles involved in radiant heat transfer is very large, making it possible to downsize the air preheater by 3 degrees.

In FIG. 2, room temperature air entering from the first stage combustion air supply pipe 2° is transferred to the double outer pipe 21. and double inner tube 22. It flows into a donut ring-shaped space formed by In this space there are 23 particles. The air rises through the gaps between the particles, receives heat, passes through the wire mesh 24, and enters the double-pipe inner tube 2.
2. Hot air flows through the inside of the box28. Input preheated air outlet pipe 4
．． going out to 25. 2G is the wire mesh that receives the particles, 2G is the room temperature air inlet surface, and 27. is the lid.

When mixing fuel with preheated air or a mixture of combustion gas and air, in order to shorten the length of the flow path as much as possible and obtain sufficient mixing, a multi-tube heat exchanger is used as shown in Figure 3. It is preferable to use a porous material, ie, a pipe made of sintered metal, as the pipe corresponding to the heat transfer tube of the vessel, and to allow the fuel gas to permeate into the thick part of the pipe and mix it with the preheated air. This is to avoid creating areas where the fuel concentration is partially high, and if the fuel concentration is high, combustion may start without the aid of a catalyst, which may cause a malfunction in the device.

In FIG. 3, preheating air pipe 29. The preheated air entering from the sintered metal tube 32. Fuel flows through the fuel supply pipe 33. Can plate containing 30. and torso 34. The sintered metal tube 32. After penetrating the thick wall of the fuel air mixture pipe 31. flows to The purpose of using a multi-tube system is to complete the mixing quickly, which shortens the length of the flow path where the mixing is completed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is an explanatory diagram of an air preheater, and FIG. 3 is an explanatory diagram of a second stage fuel mixer. Explanation of the drawing in FIG. 1 1, main air pipe 2, first stage combustion air supply pipe 3, air preheater 4, preheated air outlet pipe 5, air heater 6, first stage fuel mixer 7, 1st stage fuel supply pipe 8, 1st stage combustion catalyst 9, 1st stage combustor cylinder 10, combustion gas/air mixer 11, 2nd stage combustion air supply pipe 12, 2nd stage combustor cylinder 13, 2nd stage fuel supply pipe 14, 2nd stage fuel mixer 15, 2nd stage catalyst 16, 3rd stage combustor tube 17, 3rd stage fuel supply pipe 18, 3rd stage fuel mixer 19, 3rd stage catalyst Explanation of the drawings in Figure 2 20, Refractory material 2. First stage combustion air supply pipe 21
, double outer tube 4. Preheated air outlet pipe 22, double inner pipe
9. Second stage combustor cylinder 23, particles 10. Combustion gas/air mixer 24, wire mesh 11. Second stage combustion air supply pipe 25, particle receiver 4! lq 12. First stage combustor tube 26, room temperature air inlet surface 27, lid 13. 2nd stage fuel supply pipe 28, hot air box 14. Explanation of the drawing of the second stage fuel blender Fig. 3 29. Preheating air main pipe 30, can plate 31, fuel air mixture pipe 32, sintered fully bent pipe 33, fuel supply pipe Applicant: Nippon Chemical Plant Consultant Co., Ltd.

Claims (3)

[Claims] (1) An air preheater for startup is installed upstream of the first stage catalytic combustor, and fuel is mixed in the preheated air, passed through the catalyst layer and combusted, and combustion is generated downstream of the catalyst layer. A heat exchanger between the gas and combustion air is installed to perform heat exchange and heat the combustion air to a temperature higher than the catalytic combustion start temperature.After combustion starts, the startup air heater is stopped and the first stage When mixing air to increase the amount of oxygen-containing gas in the combustion gas, the mixture is kept at a temperature higher than the catalytic combustion start temperature and lower than the ignition temperature when fuel is mixed. A combustor that is characterized by controlling the amount of air, mixing fuel, passing it through a second stage catalyst layer, and combusting it. (2) Claims: In a heat exchanger for combustion gas and air installed on the downstream side of the first stage combustor, particles are deposited in a donut ring-shaped space outside the double pipe that forms the air flow path. The combustor according to claim 1, characterized in that it uses an air preheater filled with air to increase its contact area with air. (3) A plurality of tubes made of porous material are used in the fuel mixer used in the combustor according to claim 1, and the fuel to be mixed is permeated through the thick part of the tube made of porous material and mixed with air. The combustor according to claim 1, characterized in that it uses a fuel mixer for mixing.