JPH109780A - Control method of outlet gas temperature in rotary regenerative heat exchanger - Google Patents

Abstract

[PROBLEMS] To control the temperature of the gas on the inlet side of an electrostatic precipitator by simply adjusting the gas temperature on the outlet side with a device used in a conventional process, in particular, a rotary regenerative heat exchanger. Provides a way to adjust to the desired range. A regenerative rotary engine comprising a rotor (2a), a heat transfer element (2b) incorporated in the rotor (2a), and a sector plate (2c) for separating a flow of a high-temperature fluid and a flow of a low-temperature fluid flowing in the rotor (2a). In the heat exchanger 2, by displacing the sector plate 2c,
A part of the low-temperature fluid flows to the high-temperature fluid side to adjust the outlet gas temperature of the high-temperature fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily adjusting a gas temperature at an outlet side of a rotary regenerative heat exchanger used as a heat exchanger.

[0002]

2. Description of the Related Art After exhaust gas from a boiler is subjected to dust collection by an electric dust collector or other dust collecting device, the exhaust gas is finally discharged into the atmosphere through necessary processes. This is usually done in the case of large boilers.

[0003] Before supplying the boiler exhaust gas to the above-mentioned electric dust collector or other dust collecting device, the heat of the exhaust gas may be recovered and heat-exchanged by a heat exchanger in order to transfer the heat to the fresh air for the boiler. It is usually done.

[0004] By the way, depending on the fuel used in the boiler, a considerable amount of SO ₃ is present in the boiler exhaust gas.
In order to neutralize this, an NH ³ injection step may be provided between the heat exchange step and the dust collection step.

[0005] By injecting NH ₃ into the electrostatic precipitator inlet side gas, neutralization reaction with SO ₃ in NH ³ and gas progresses. The reaction product of this neutralization reaction is mainly NH ⁴
HSO ₄ and (NH ⁴ ) ₂ SO ⁴ .

[0006]

Although these reaction products are initially thought to be gaseous, they can easily become solids due to their low vapor pressure. And, as the molar ratio of NH ^{3 to} SO ₃ increases, the amount of (NH ₄ ) ² SO ₄ generated increases.

[0007] Of NH ⁴ HSO ₄ and (NH ⁴ ) ₂ SO ⁴ , NH ₄ HSO ⁴ has a melting point of 147 ° C., and is very easily absorbed by moisture and easily deliquescent. For this reason, a sticky adhered substance is formed in the apparatus (for example, in the electric precipitator), so that handling is not easy.

On the other hand, since (NH ₄ ) ² SO ₄ has stable properties, of the reaction products of the above-mentioned neutralization reaction,
It is preferable to maintain (NH ⁴ ) ₂ SO ⁴ as high as possible.

However, even this stable (NH ₄ ) ² SO ₄ has the property of decomposing when the temperature is increased. Its decomposition produces NH ³ and NH ₄ HSO ⁴ . This decomposition has been observed to begin at temperatures above 160 ° C.

Accordingly, it is important to prevent the decomposition of (NH ₄₎ ² SO _4, the NH ⁴ HSO ₄ with difficulties produce handling. For that purpose, it is necessary to maintain the temperature of the gas on the inlet side of the electrostatic precipitator so as not to exceed 160 ° C.

On the other hand, NH ₃ generated by the decomposition of (NH ⁴ ) ₂ SO ⁴ passes through the electrostatic precipitator and stays in the outlet gas as it is. If this gas is released into the atmosphere as final exhaust gas, it may cause environmental pollution. From this viewpoint, it is necessary to maintain the temperature of the gas on the inlet side of the electrostatic precipitator in a range not exceeding 160 ° C.
Furthermore, it is necessary to maintain the supply gas temperature in a predetermined range in order to make the electric precipitator function stably.

As described above, the demand for preventing the melting of NH ⁴ HSO ₄ , preventing the decomposition of (NH ⁴ ) ₂ SO ⁴ , and stabilizing the function of the electrostatic precipitator has led to the demand for the electric precipitator. It is desirable to maintain the temperature of the exhaust gas on the inlet side in the range of 130C to 140C.

From such a viewpoint, it is conceivable to provide a special duct device for supplying fresh air for cooling into the gas on the inlet side of the electrostatic precipitator.

An object of the present invention is to provide an apparatus used in a conventional process, particularly a rotary regenerative heat exchanger, to easily control the outlet gas temperature without providing such a special apparatus. An object of the present invention is to provide a method for adjusting the temperature of the gas on the inlet side of the electrostatic precipitator to a desired range by adjusting the temperature.

[0015]

According to the present invention, there is provided a method for adjusting an outlet gas temperature in a rotary regenerative heat exchanger, comprising the steps of:
Displacement of the sector plate in a rotary regenerative heat exchanger including a heat transfer element built in the rotor and a sector plate for separating a flow of a high-temperature fluid and a flow of a low-temperature fluid flowing in the rotor. Thus, a part of the low temperature fluid is caused to flow toward the high temperature fluid side to adjust the outlet gas temperature of the high temperature fluid.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a boiler, the exhaust gas of which is sent to a rotary regenerative heat exchanger 2. In the rotary regenerative heat exchanger 2, the exhaust gas as the high-temperature side gas heats the heat transfer element 2b loaded in the rotor 2a.

The exhaust gas whose temperature has been lowered by heating the heat transfer element 2b is sent to the electrostatic precipitator 3, where dust and the like in the exhaust gas are removed and discharged into the atmosphere from a chimney (not shown) or the like. You.

On the other hand, reference numeral 4 denotes a pushing fan, which sends outside air, that is, fresh air for a boiler, to the rotary regeneration type heat exchanger 2. The fresh air sent to the rotary regeneration heat exchanger 2 is:
The temperature is increased by being heated by the stored heat transfer element 2b and supplied to the boiler 1 as combustion air.

In FIG. 1 and FIG. 2, reference numeral 2c denotes a sector plate which controls the flow of exhaust gas as a high-temperature fluid flowing into the rotor 2a and combustion air as a low-temperature fluid flowing out of the rotor 2a. Has the function of separating.

The sector plate 2c is displaced by a driving device 5 such as an electric motor, and as shown by a virtual arrow in FIG. 2, a part of the combustion air enters the exhaust gas and the temperature of the exhaust gas is reduced. Lower it. That is, the temperature of the exhaust gas is adjusted by adjusting the amount of displacement of the sector plate 2c. Reference numeral 6 denotes an outlet gas temperature detector for operating the driving device 5 via a control device 7.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a pressure balance of a fluid flowing through a system composed of a rotary regenerative heat exchanger 2, a boiler 1 and an electrostatic precipitator 3 will be described. The pressure of the fresh air supplied to the rotary regenerative heat exchanger 2 is 880 mmAq, and a pressure drop of 140 mmAq occurs while passing through the low temperature side of the rotary regenerative heat exchanger 2. On the cold fluid outlet side, the fluid pressure drops to 740 mmAq. 500 in boiler 1
Since there is a pressure drop of about mmAq, the fluid pressure on the high-temperature fluid inlet side of the rotary regenerative heat exchanger 2 is 240 mmAq
Becomes

Further, since a pressure drop of 190 mmAq occurs during the passage on the high-temperature side of the rotary regenerative heat exchanger 2, the pressure of the fluid at the high-temperature fluid outlet side of the rotary regenerative heat exchanger 2 drops to 50 mmAq.

As a result, by displacing the sector plate 2c to increase the gap between the sector plate 2c and the rotor 2a, fresh air flows from the low-temperature fluid side of the rotary regenerative heat exchanger 2 to the high-temperature fluid side.

FIG. 3 is a graph showing the relationship between the displacement of the sector plate 2c and the exhaust gas temperature drop. The exhaust gas temperature drop (° C.) increases as the displacement (mm) of the sector plate 2c increases. Can be read.

[0025]

[Effect of the Invention] 1) by displacing the sector plate, by adjusting the outlet gas temperature of the high temperature fluid flowing part of the low temperature fluid to the high temperature fluid side, NH ₄ HSO ⁴ in generating effectively It became possible to suppress. 2) By displacing the sector plate and flowing a part of the low-temperature fluid to the high-temperature fluid side and adjusting the gas temperature on the outlet side of the high-temperature fluid, it is possible to reduce the NH ₃ concentration and prevent environmental pollution. It becomes possible. 3) By displacing the sector plate and flowing a part of the low-temperature fluid to the high-temperature fluid side and adjusting the outlet-side gas temperature of the high-temperature fluid, the supply gas temperature is maintained within a predetermined range. It has become possible to stabilize the operation of the dust container.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a boiler air preheating system.

FIG. 2 is an explanatory diagram of exhaust gas temperature adjustment by displacement of a sector plate.

FIG. 3 is a graph showing a relationship between a displacement amount of a sector plate and a decrease in exhaust gas temperature.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 boiler 2 regenerative heat exchanger 2 a rotor 2 b heat transfer element 2 c sector plate 3 electric precipitator 4 push-in fan 5 drive 6 temperature detector 7 controller

Claims (1)

[Claims] 1. A rotary regenerative heat exchanger comprising a rotor, a heat transfer element incorporated in the rotor, and a sector plate for separating a flow of a high-temperature fluid and a flow of a low-temperature fluid flowing in the rotor. And adjusting the outlet gas temperature of the high temperature fluid by displacing a portion of the low temperature fluid to the high temperature fluid side by displacing the sector plate.