JPH0631696B2 - Combined gas preheater - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite gas preheater such as an air heater for a boiler and a fuel gas heating device used for recovering exhaust heat from dust-containing gas such as coal-fired boiler exhaust gas.

[Conventional technology]

 FIG. 4 is a side view of a gas preheating device showing a conventional example.

Conventionally, a gas preheater in which a plurality of heat exchangers 01 and 02 are arranged with a partition wall and heat is transferred by circulating a heat transfer medium 03 between the heat exchangers 01 and 02 is a high temperature exhaust gas 04, etc. It is used to avoid mixing of the heated gas and the heated gas 05, or leakage of gas from one duct 06 to the other duct 07. In the gas preheater 08, water is used as the heat transfer medium 03, one of the heat exchangers 01 and 02 is used as the evaporator 09, and the other is used as the condenser 010, which is a natural circulation utilizing the density difference between steam and water. A method of circulating a heat transfer medium is generally adopted. However, in the above method, the saturation pressure of water, which is the heat transfer medium 03, increases as the temperature range in which heat is exchanged increases, so the density difference between water and steam decreases, and the natural circulation force decreases. Therefore, in the gas preheater 08 that uses water as the heat transfer medium 03, there is a practical upper limit temperature level, and it is difficult to set the temperature of the heated gas 05 to 350 ° C. or higher.

Further, the conventional gas preheater employs a vertical arrangement of heat transfer tubes which is advantageous in natural circulation. The heat transfer tube is usually composed of a circular finned tube, but if dust such as ash is contained in the exhaust gas, it is easy for dust to accumulate on the fin surface and it is difficult to sufficiently wash it with water. It is a heat transfer tube arrangement.

[Problems to be solved by the invention]

Depending on the coal type of the coal-fired fuel, the air preheating temperature is about 35
Even when 0 ° C or higher was required, when only water was used as the heat transfer medium, natural circulation was not established, and the exhaust gas temperature of about 400 ° C could not be effectively exchanged. Also,
The dust contained in the exhaust gas adheres to the heat transfer surfaces such as fins of the heat transfer tubes forming the heat exchanger to block the heat transfer surfaces, resulting in a decrease in heat transfer efficiency.

[Means for solving problems]

According to the present invention, the hot exhaust gas flows downward from one side of one of the two vertical ducts that are adjacent to each other across the partition wall, and the heated gas flows from the lower side of the duct to the upper side, and the heated gas flows between the ducts. A composite of a vertical flow system in which heat is transferred by a heat transfer medium circulating in a heat exchanger provided penetrating the partition wall to perform heat exchange between the high-temperature exhaust gas and the heated gas. In the gas preheater, a single pipe heat pipe heat exchanger using an organic heat medium as a heat transfer medium is used in the high temperature part, and a separate heat pipe heat exchanger in which water naturally circulates in the middle and low temperature parts. The composite gas preheater is characterized in that the heat transfer tubes are arranged substantially horizontally and attached.

〔Example〕

An embodiment of a gas vertical flow type hybrid heat pipe type air preheater according to the present invention will be conceptually shown in FIGS. In the air preheater 1 of the present embodiment, the high temperature part is composed of a single tube heat pipe type heat exchanger 2 using an organic heat medium, and the middle and low temperature part is a separate heat pipe type heat exchanger in which water naturally circulates. It is composed of three. Therefore, the high-temperature boiler exhaust gas 4 flows downward from the upper part, and becomes a low-temperature exhaust gas 5 by heat exchange, and is discharged to a desulfurization device (not shown) or a smoke exhaust device (not shown). On the other hand, the air 6 sent from the forced draft fan (not shown) flows upward from the lower part and becomes high temperature preheated air 7 by heat exchange and is sent to the boiler combustion chamber (not shown). Each heat pipe heat transfer tube is arranged substantially horizontally so as not to hinder the circulation of the heat medium.

The separated heat pipe heat exchanger 3 needs to be divided into a plurality of modules according to the temperature levels of the exhaust gas 5 and the air 6. Further, in order to secure the natural circulation force, it is necessary to place the evaporator portion 3a on the exhaust gas 5 side at a position lower than the condensation portion 3b on the air side. On the other hand, in the single-tube heat pipe type heat exchanger 2, the operating point (heat medium pressure and temperature) of the heat pipe is automatically determined according to the temperature levels of the exhaust gas G and the air 6. FIG. 3 is an example of a temperature diagram showing the operating state of the entire hybrid heat pipe type air preheater. In this example, the exhaust gas temperature from 400 ° C to 350 ° C is set as the usage range of the single-pipe heat pipe 2, and 350 ° C.
To 140 ° C. is the range of use of the separate type heat pipe 3, and the range of the separate type is further divided into 6 modules according to the temperature level.

〔The invention's effect〕

The gas preheater consists of a single-pipe heat pipe heat exchanger using an organic heat medium as the heat transfer medium in the high temperature section, and a separate heat pipe heat exchanger in which water circulates naturally in the middle and lower sections. In the complex-type gas preheater of the type, in the duct in which each of the heat exchangers is laminated in multiple stages, the high-temperature exhaust gas and the heated gas are completely partitioned by the partition wall, so the preheating temperature of the heated gas is efficiently It can be 350 ℃ or higher if necessary.

Further, since the plurality of heat transfer tubes constituting each heat exchanger are horizontally arranged, it is easy to blow suit and wash with water as a measure to prevent clogging of the heat transfer surface of the heat transfer section due to dust-containing gas and as a measure against duct adhesion. It is possible to adopt the heat transfer surface arrangement.

[Brief description of drawings]

FIG. 1 is a side view conceptually showing one embodiment of a gas vertical flow type composite air preheater according to the present invention, and FIG. 2 is a side view taken along the line AA in FIG. FIG. 4 is an example of a temperature diagram showing an operating state of the entire hybrid type heat pipe type air preheater, and FIG. 4 is a side view of an apparatus showing a conventional example. DESCRIPTION OF SYMBOLS 1 ... Composite type gas preheater, 2 ... Single tube heat pipe type heat exchanger, 3 ... Separation type heat pipe type heat exchanger, 4 ... High temperature boiler exhaust gas, 5 ... Low temperature exhaust gas, 6 ... For heating Air, 3a ... Evaporator part on exhaust gas side, 3b ... Condensing part on air side.

Claims (1)

[Claims] 1. A hot exhaust gas flows downward from one side of one of two vertical ducts adjacent to each other across a partition wall, and a gas to be heated flows from the lower side of the other duct to an upward direction. In a vertical gas flow system in which heat is transferred by a heat transfer medium circulating in a heat exchanger that is provided penetrating the partition wall in between to perform heat exchange between the high-temperature exhaust gas and the heated gas. In the combined gas preheater, a single pipe heat pipe heat exchanger using an organic heat medium as a heat transfer medium is used in the high temperature part, and a separate heat pipe type heat exchanger in which water naturally circulates in the middle and low temperature parts. A composite gas preheater, characterized in that the respective heat transfer tubes are arranged substantially horizontally and mounted.