JPH01111102A - Natural circulation boiler with forced circulation cooled burner - Google Patents

Abstract

PURPOSE: To correspond to a high heat load and obtain a cooling wall of excellent economic efficiency and high thermal efficiency by a method wherein a cooling section of a surrounding wall near a burner is formed by a heating surface of forced circulation cooling, saturated water of a natural circulation boiler is used for forced circulation, and a steam drum of the natural circulation boiler and a steam drum for cooling water of the forced circulation cooling are used in common. CONSTITUTION: An inner surface of a surrounding wall of a cyclone coal fired furnace 1 is formed by a refractory 10, and a cooling wall 9 is arranged on an outer surface of the refractory 10 for surrounding and cooling it. Saturated boiler water is taken out from a water drum 5 of a natural circulation boiler, and supplied to a forced circulation pump 8 through a downcast pipe 6, and the boiler water of increased pressure enters the cooling wall 9, and cools the back of the refractory 10 caused to reach a high temperature state by the primary air and combustion of pulverized coal blown out from a pulverized coal feeding hole 2. Part of the boiler water having absorbed heat by cooling the refractory 10 is turned into steam to form a mixture of steam, returned to a steam drum 4 of the natural circulation boiler through a riser pipe 7 for water separation, the steam is discharged to the outside, and the saturated water is circulated in the natural circulation boiler as the boiler water.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a cyclone coal combustion furnace or a first combustion chamber equipped with a cyclone furnace or the like for the purpose of removing coal ash in a molten state and burning it with low nitrogen. This relates to a natural circulation boiler.

[Prior Art] Figures 4 to 7 are examples of the prior art. FIG. 4 is a conceptual diagram of a natural circulation boiler equipped with a cyclone coal combustion furnace equipped with a natural circulation cooling wall, and FIG. 5 is a system diagram of the pressure section of FIG. 4. In Figures 4 and 5, 21 is a cyclone coal combustion furnace, 22 is a primary air and pulverized coal inlet, 23 is a natural circulation boiler, 24 is a steam drum, 25 is a water drum, 2
6 is a natural circulation cooling wall of the cyclone coal combustion furnace 21;
7 is the 26th downcomer pipe, and 28 is the 26th riser pipe. - Air and pulverized coal supplied from the pulverized coal inlet 22 are burned in the cyclone coal combustion furnace 21. The peripheral wall of the cyclone coal combustion furnace is formed by a natural circulation cooling wall 26, and the natural circulation cooling wall 26 includes a natural circulation boiler 2.
A downcomer pipe 27 is connected from the water drum 3, and a riser pipe 28 is also connected to the steam drum 24. In the natural circulation boiler 23 equipped with the cyclone coal combustion furnace 21 having this structure, the peripheral wall of the cyclone coal combustion furnace 21 is a natural circulation type cooling wall 26.
In addition to being able to follow a relatively high heat load by being cooled by Circulation boiler 23
It can be said that this method is highly economical because it is absorbed as part of the system. Figures 6 and 7 are examples of other conventional techniques,
Figure 6 is a conceptual diagram of a natural circulation boiler that is the antithesis of an air-cooled cyclone coal-fired furnace, and Figure 7 is a natural circulation boiler that is the antithesis of a cyclone coal-fired furnace that is constructed only of refractories without a cooling device. It is a conceptual diagram. In Figures 6 and 7, 21 is a cyclone coal combustion furnace, 2z is a primary air and pulverized coal inlet, 23 is a natural circulation boiler, 24 is a steam drum, 25 is a water drum, 29 is a cooling blower, and 30 is an air suction The duct 31 is a cooling air layer of the cyclone coal combustion furnace 21, 32 is an air exhaust duct, and 33 is a refractory. In FIG. 6, primary air and pulverized coal supplied from the pulverized coal inlet 22 are burned in a cyclone coal combustion furnace 21. The peripheral wall of the cyclone coal combustion furnace 21 is formed of a refractory material 33 having a small thickness, and a cooling air layer 31 is formed outside the refractory material 33. The combustion gas of pulverized coal burned in the cyclone coal combustion furnace 21 is sent to the natural circulation boiler 23 and heat exchanged with boiler water, but the heat transferred to the peripheral wall of the cyclone coal combustion furnace 21 passes through the refractory 33. It is transmitted to the cooling air layer 31. Air sucked from the air suction duct 30 and pressurized by the cooling blower 29 is fed into the cooling air layer 31 to cool the refractory 33.
After cooling and raising the temperature, it is discharged into the atmosphere from the air exhaust duct 32. The peripheral wall of the cyclone coal combustion furnace having this structure has the advantage that the manufacturing cost of the peripheral wall can be lowered compared to other structures by providing a cooling air layer.

In FIG. 7, secondary air and pulverized coal supplied from the pulverized coal inlet 22 are combusted in a cyclone coal combustion furnace 21, and the combustion gas is cooled by exchanging heat with boiler water in a natural circulation boiler 23. It is then emitted into the atmosphere.

The peripheral wall of the cyclone coal combustion furnace is composed only of refractories 33, and the generated combustion gas is sent to the natural circulation boiler 23 in a high temperature state, so the thermal efficiency during heat exchange in the natural circulation boiler is good. It has the advantage of

[Problems to be Solved by the Invention] However, the above conventional combustion furnace has the following problems. First of all, a natural circulation boiler that is the antithesis of a cyclone coal combustion furnace with a natural circulation cooling wall shown in Figures 4 and 5 has a stable flow in the evaporation tube because the cooling wall on the peripheral wall of the cyclone coal combustion furnace is of a natural circulation type. Due to restrictions on the heat load on the heat transfer surface in order to maintain performance and prevent burnout of the heat transfer surface, the combustion furnace becomes large, which is economically disadvantageous, and parts with complex shapes must be manufactured due to circulation constraints. I had the inconvenience of not being able to do that. Next, the combustion furnace with the cooling air layer shown in Figure 6 requires not only equipment costs such as a cooling blower and air duct, but also operating power for the blower, and the temperature rise due to cooling the combustion furnace. Discharging air into the atmosphere causes heat loss, which is economically disadvantageous, and also has the disadvantage that the permissible heat load of the combustion chamber is low due to the heat resistance of the refractory.

In addition, the combustion furnace formed only of refractories shown in Fig. 7 is
Since there is no cooling material on the inner circumferential wall of the combustion furnace, the temperature of the combustion chamber becomes high, and the permissible heat load of the combustion chamber is low due to the heat resistance of the refractory.

[Means for Solving the Problems] Means for solving the above problems are as set forth in the claims, in which, in a natural circulation boiler, the cooling part of the peripheral wall near the burner is replaced with a heat transfer surface of forced circulation cooling. A natural circulation boiler with a forced circulation cooling burner, which uses saturated water from a natural circulation boiler as the forced circulation water, and shares the steam drum of the natural circulation boiler with the steam drum for cooling water on the heat transfer surface of forced circulation cooling. It is.

[Function] In a natural circulation boiler, the peripheral wall of the combustion chamber near the burner is formed of a refractory material and a cooling wall that cools the refractory material. Boiler water in a saturated state from a natural circulation boiler is taken out, the pressure is raised by a forced circulation pump, and the pressure is sent to the cooling wall near the burner, which cools the surrounding wall near the burner, which has reached a high temperature due to the combustion of the fuel spouted from the burner. . The boiler water, which cools the peripheral wall and absorbs heat, partly becomes steam and becomes a steam-water mixture, is returned to the steam drum of the natural circulation boiler.

Boiler water for cooling the peripheral wall near the burner is pressurized and pumped by a forced circulation pump, so it is possible to manufacture the peripheral wall near the burner even if it has a very complicated shape, and it also reduces the heat load on the heat transfer surface. By dividing the cooling wall or taking structural considerations accordingly, it is possible to provide a cooling wall that can be handled most efficiently and economically under any conditions. Furthermore, by using saturated water from a natural circulation boiler as cooling water and returning the generated steam to the steam drum of the natural circulation boiler, it becomes possible to efficiently utilize the amount of heat absorbed by the cooling wall.

[Example] An embodiment of the present invention will be described below based on the drawings.

Figures 1 and 2 are system diagrams of a natural circulation boiler equipped with a cyclone coal combustion furnace equipped with forced circulation type cooling walls based on the present invention. Figure 1 is the overall system diagram, and Figure 2 is the system diagram of the Figure a-a
The arrow view and FIG. 3 are developed system diagrams of the cyclone coal combustion furnace cooling wall used in the embodiments of FIGS. 1 and 2. 1st
- In Figure 3, 1 is a cyclone coal combustion furnace, 2 is a primary air and pulverized coal inlet, 3 is a combustion chamber of a natural circulation boiler,
4 is a steam drum, 5 is a water drum, 6 is a downcomer pipe, 7 is a riser pipe, 8 is a forced circulation pump, 9 is a cyclone coal combustion furnace 1
The cooling wall 10 forming each part of the peripheral wall is a refractory material. The inner surface of the peripheral wall of the cyclone coal combustion furnace 1 is formed of a refractory 10, and the outer surface of the refractory 10 is surrounded by a cooling wall 9 to cool the refractory 10. Natural circulation boiler water drum 5
Saturated boiler water is taken out from the tank and sent to the forced circulation pump 8 via the downcomer pipe 6. The boiler water pressurized by the forced circulation pump 8 enters the cooling wall 9 and cools the refractory 10, which has reached a high temperature due to the combustion of secondary air and pulverized coal ejected from the pulverized coal inlet 2, from the back side. Refractory 1
0 is supported by a large number of studs welded to the cooling wall 9, and these studs prevent the refractory 10 from falling off due to sudden heat loads.
This improves heat transfer between the cooling wall 9 and the cooling wall 9, and prevents the refractory 10 from being damaged. Part of the boiler water that has absorbed heat by cooling the refractory 10 turns into steam, which is returned to the steam drum 4 of the natural circulation boiler via the riser pipe 7 as a steam-water mixture, where it is separated into steam and water. The steam is sent outside and the saturated water is circulated within the natural circulation boiler as boiler water.

[Effects of the Invention] As is clear from the above embodiments, the present invention cools the burner or the peripheral wall near the fuel injection hole in a natural circulation boiler using forced circulation cooling water, and uses saturated water from the natural circulation boiler as the forced circulation cooling water. By using the steam drum of a natural circulation boiler and the air-water drum of the cooling water that cools the surrounding wall of the burner or combustion injection hole to become a steam-water mixture, it is possible to reduce the complexity of burners or fuel injection holes with complex shapes. In addition to making it possible to cool the refractories on the peripheral wall, by dividing the cooling wall according to the heat load of each part and selecting and supplying the optimal amount of cooling water, it is possible to cope with high heat loads and achieve economic efficiency with good thermal efficiency. This has the effect of making it possible to obtain a cooling wall with excellent cooling properties.

[Brief explanation of the drawing]

Figures 1 and 2 are system diagrams of a natural circulation boiler equipped with a cyclone coal combustion furnace equipped with forced circulation type cooling walls based on the present invention. Figure 1 is the overall system diagram, and Figure 2 is the system diagram of the Figure a-a
The arrow view and FIG. 3 are developed system diagrams of the cyclone coal combustion furnace cooling wall used in the embodiments of FIGS. 1 and 2. 4 to 7 are examples of prior art. DESCRIPTION OF SYMBOLS 1...Cyclone coal combustion furnace, 2...Secondary air and pulverized coal inlet, 3...Combustion chamber of natural circulation boiler, 4...Steam drum, 5...Water drum, 6
...Down pipe, 7...Rising pipe, 8...
Forced circulation pump, 9... Cooling wall, 10... Refractory, 21... Cyclone coal combustion furnace, 22... Secondary air and pulverized coal inlet hole, 23... Natural circulation boiler, 24 ...Steam drum, 25...
Water drum, 26... Cooling wall, 27... Downpipe, 28... Rising pipe, 29... Cooling blower, 30... Air suction duct, 31... Cooling air layer, 32... ...Air discharge duct, 33...Refractory. Applicant Kawasaki Heavy Industries, Ltd.

Claims (1)

[Claims] In a natural circulation boiler, the cooling section on the peripheral wall near the burner is formed by the heat transfer surface of the forced circulation cooling, and the saturated water of the natural circulation boiler is used as the forced circulation water, and the steam drum of the natural circulation boiler and the forced circulation cooling are used as the forced circulation water. A natural circulation boiler with a forced circulation cooling burner, characterized in that it shares a steam drum for cooling water on the heat transfer surface.