JP2001208302A - Condensation type economizer for oxygen burning boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a condensation type economizer which can efficiently recover the sensible heat and latent heat of the exhaust gas from an oxygen burning boiler. SOLUTION: A fin tube 18 through which boiler water is made to flow is arranged in multiple stages nearly perpendicularly to the flowing direction of the exhaust gas from the oxygen burning boiler and most of the front portion of the tube 18 is constituted as a sensible heat transferring region 32 and most of the middle portion of the tube 18 is constituted as a heat transferring region with condensation 34. In addition, most of the rear portion of the tube 18 is constituted as a sensible heat transferring area 36 and the heights of the fins 20 of the tube 18 are made as low as 9-2 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condensing economizer for introducing exhaust gas discharged from an oxyfuel boiler and efficiently recovering latent heat of vapor.

[0002]

2. Description of the Related Art A conventional boiler in which fuel is burned by combustion air has a boiler efficiency of about 86 to 96%, and its heat utilization efficiency is higher than any other heat utilization equipment. In recent years, it has been desired to develop a high-performance boiler with higher thermal efficiency based on a new idea based on energy saving technology.
Conventionally, in order to reduce the amount of exhaust gas by eliminating the nitrogen content in the combustion exhaust gas, and to further increase the boiler efficiency,
BACKGROUND ART A boiler of a type that burns fuel using oxygen instead of combustion air, that is, a so-called oxyfuel boiler is being developed.

[0003] In an oxyfuel boiler, since the flue gas contains almost no nitrogen, the proportion of water vapor and carbon dioxide in the flue gas increases, and the sensible heat and latent heat of the steam in the flue gas are efficiently recovered. Is a major problem in improving boiler efficiency. Further, as described above, since the ratio of carbon dioxide in the exhaust gas is large, there is no need to separate carbon dioxide and nitrogen, and the carbon dioxide-rich exhaust gas can be processed or disposed of as it is, to prevent global warming. Can contribute.

[0004]

In order to recover the sensible heat and latent heat of the exhaust gas from the oxyfuel boiler, attempts have been made to heat the feed water by introducing the exhaust gas into a condensing economizer and exchanging heat. In this case, if a fin tube is used in a heat exchanger such as a condensing type economizer that condenses a large amount of water vapor, the fin efficiency decreases and heat transfer is inhibited due to the bridge phenomenon of condensed drain. A bare tube is used without using a fin tube.
However, in a condensing economizer using a bare tube, it is difficult to increase the heat recovery to a certain value or more. This is because the exhaust gas, which has almost lost water vapor due to condensation in the first stage of the heat exchanger, has a very low flow rate in the second stage, making it difficult to recover heat with a bare tube.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a conventional technique that "when a large amount of condensation occurs, a fin tube is not used in consideration of a decrease in fin efficiency". Oxy-fuel combustion using a fin tube to maximize the heat recovery rate of heat exchangers such as condensing economizers in sensible and latent heat recovery of oxy-combustion boiler exhaust gas by adopting a technical concept completely different from the concept. An object of the present invention is to provide a condensing type economizer for boilers. Also,
An object of the present invention is to provide low fins (low fi fin) in order to achieve both recovery of sensible heat and latent heat of exhaust gas from an oxyfuel boiler.
An object of the present invention is to provide a condensing economizer for an oxyfuel boiler using a fin tube provided with n).

[0006]

In order to achieve the above object, a condensing type economizer for an oxyfuel boiler according to the present invention provides a boiler feed water in a direction substantially perpendicular to a flow direction of an oxyfuel boiler exhaust gas. Are arranged in multiple stages, the front part of the multi-stage fin tube is used as the sensible heat transfer area, the middle part of the multi-stage fin tube is used as the condensation heat transfer area, and the rear part of the multi-stage fin tube is used as the sensible heat transfer area. It is configured as an area.

In this condensing type economizer for an oxyfuel boiler, the fin height of the fin tube is 9 to 2 mm, preferably 8 to 5 mm. The fin tube has a fin height of 9 to 2 mm, preferably 8 to 5 mm, a fin pitch of 5 to 10 mm, preferably 7 to 9 mm, and a fin thickness of 0.5 to 1.5 mm. Is 0.8-1.
2 mm. The tube has, for example, an outer diameter of 25.4.
mm and an inner diameter of 20.2 mm are used. When the fin pitch is less than the lower limit of the above range, condensed water accumulates and a bridge is formed by the condensed water, whereas when the fin pitch exceeds the upper limit of the above range, no bridge is formed but the effect of heat recovery is reduced. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications. FIG. 1 shows a condensing economizer for an oxyfuel boiler according to a first embodiment of the present invention. 10 is a right body, 12 is a left body, 14 is an exhaust gas inlet, 16 is an exhaust gas outlet, 18 is a fin tube (heat transfer tube), 20 is a fin, 22 is a water supply inlet, and 24 is a water supply outlet. The right body 10 and the left body 12 are connected to exhaust gas ducts 26a, 26
The fin tube 18 formed of, for example, a snake tube in the right main body 10 and the fin tube 18 formed of, for example, a snake tube in the left main body 12 are connected via a water supply communication pipe 28. Reference numeral 30 denotes a condensed water discharge valve.

The exhaust gas from the oxyfuel boiler is introduced from the exhaust gas inlet 14 into the right main body 10 and is provided with a multi-stage fin tube 18 disposed substantially horizontally in a direction substantially perpendicular to the flow of the exhaust gas.
The sensible heat is recovered in a sensible heat recovery area (exhaust gas inlet area) 32 substantially at the preceding stage. Next, the steam in the exhaust gas is condensed in the condensation heat transfer region (downstream region of the exhaust gas inlet region) 34 in the middle stage of the multi-stage fin tube, the latent heat is recovered, and the sensible heat of the non-condensed exhaust gas (mainly carbon dioxide) is reduced. Collected. Thereafter, the sensible heat of the exhaust gas is recovered in a sensible heat transfer area (exhaust gas outlet area) 36 at the subsequent stage of the multi-stage fin tube. FIG.
Describes the case where the main body is divided into two right and left, but it is also possible to combine the main body into one,
Further, the left and right main bodies may be further divided into a plurality of upper and lower stages.

Next, an experimental example will be described. In the condensing type economizer shown in FIG. 1, the right body is divided into two upper and lower stages, and the left body is divided into two upper and lower stages.
8-stage fin tube (coil tube with spiral fins)
And a total of 72 stages of fin tubes were provided. The material of the fin tube is SUS316LTB, outer diameter 25.4m
m, inner diameter 20.2mm, fin material is SUS316L,
The fin height was 8 mm, the fin pitch was 8.7 mm, and the fin thickness was 1.0 mm. 122 ° C. oxyfuel boiler exhaust gas is introduced from the exhaust gas inlet and heat is recovered, and 18 hours from the exhaust gas outlet.
Exhaust gas at ℃ was discharged. The inlet feedwater temperature was 16 ° C and the outlet feedwater temperature was 79 ° C. The total pressure loss is 28
mmH ₂ O.

[0011]

As described above, the present invention has the following effects. (1) Since a fin tube is used by adopting a technical idea completely different from the conventional technical idea of not using a fin tube in consideration of a decrease in fin efficiency when a large amount of condensation occurs, a fin tube is used. The sensible heat and latent heat of the oxyfuel boiler exhaust gas can be efficiently recovered, and the heat recovery rate of the entire condensing economizer can be maximized. (2) Low fin (low f)
By using (in), sensible heat and latent heat can be recovered more efficiently. By combining this condensing type economizer with an oxyfuel boiler, it is possible to increase the boiler efficiency to as high as about 105%.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a condensing economizer for an oxyfuel boiler according to a first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Right main body 12 Left main body 14 Exhaust gas inlet 16 Exhaust gas outlet 18 Fin tube (heat transfer tube) 20 Fin 22 Water supply inlet 24 Water supply outlet 26a, 26b, 26c Exhaust gas duct 28 Water supply connection pipe 30 Condensate discharge valve

Continuing on the front page (72) Inventor Masayuki Koyama 1000 Aochi-cho, Kusatsu-shi, Shiga Prefecture Inside the Shiga Plant of Kawaju Cold Engineering Co., Ltd. (72) Inventor Masahiro Kube 2-1-6 Ecchujima, Koto-ku, Tokyo

Claims (3)

[Claims] 1. A fin tube through which boiler feedwater flows is provided in multiple stages so as to be substantially perpendicular to the flow direction of the oxyfuel boiler exhaust gas, and a substantially front stage of the multi-stage fin tubes is used as a sensible heat transfer region. A condensing economizer for an oxyfuel boiler, characterized in that a substantially middle stage of the multi-stage fin tube is a condensing heat transfer region and a substantially rear stage of the multi-stage fin tube is a sensible heat transfer region. 2. The fin tube has a fin height of 9 to 2 mm.
The condensing economizer for an oxyfuel boiler according to claim 1, wherein 3. The fin tube has a fin height of 9 to 2 m.
m, fin pitch 5-10mm, fin thickness 0.5-
The condensing economizer for an oxyfuel boiler according to claim 1, which is 1.5 mm.