JP7217928B2 - Heat exchanger and its usage - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat exchanger using superheated steam and a method for using the heat exchanger.

Due to the many heat treatment processes in paper, textile and chemical manufacturing plants, large steam boilers are often installed as a heat source. In addition, even in the case of heating a fluid such as hot air used for drying, it is common to heat the fluid through a heat exchanger (Patent Document 1).

In the case of hot air, it is often used by heating the air to about 150°C, but even if high-pressure steam is flowed into a factory that is far from the boiler, the temperature will drop to about 130°C due to the pressure drop in the piping. There are many. For this reason, there are many cases where surplus steam cannot be used as a heat source even though there is surplus steam.

JP 2013-224810 A

In order to effectively utilize this surplus steam as a heat source, there is a method of reheating the steam whose pressure and temperature have been lowered to the desired temperature to produce superheated steam. When heating to a desired temperature, in order to obtain a temperature higher than the water boiling point at the saturated vapor pressure, the inlet/outlet temperature of the superheated steam must basically be a temperature higher than the water boiling point.

However, in this method, the superheated steam having a temperature higher than the boiling point of water is discharged, and the steam latent heat of the superheated steam is wasted.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above problems, and its main object is to effectively utilize steam latent heat of superheated steam to heat a fluid to be heated.

That is, the heat exchanger according to the present invention is a heat exchanger that heats a fluid with superheated steam, and includes a heat exchange pipe through which a fluid to be heated flows, a downstream portion of the heat exchange pipe, and superheated steam and an upstream container that houses the upstream portion of the heat exchange pipe and is supplied with steam that has passed through the downstream container, the downstream portion of the heat exchange pipe is heated by the sensible heat of the superheated steam supplied to the downstream container, and the heated fluid flowing through the upstream portion of the heat exchange pipe is supplied to the upstream container It is characterized by being heated by the latent heat of water vapor.

In such a case, superheated steam is supplied to the downstream container to heat the fluid to be heated to a desired temperature by the sensible heat of the superheated steam, and steam is supplied from the downstream container to the upstream container. Since the fluid to be heated is heated (preheated) by the latent heat of the steam, the latent heat of the superheated steam can be effectively used to heat the fluid to be heated. The steam supplied to the upstream container may be liquefied by losing its latent heat or may be discharged as steam without liquefying, but the liquefied latent heat is effectively used.

Specifically, the temperature and amount of superheated steam supplied to the downstream container are set so that the heated fluid flowing through the downstream portion of the heat exchange pipe reaches a desired temperature of 100° C. or higher. In addition, it is desirable that the temperature of steam supplied from the downstream container to the upstream container is set to 100° C. or higher.

Here, when the fluid to be heated is air, the maximum temperature that can be heated by the latent heat of water vapor is 100° C., and the sensible heat of water vapor is used to heat the fluid to a temperature higher than that. The latent heat has a large proportion of the energy possessed by the superheated steam. FIG. 2 shows calculated values of the proportion of the latent heat that can be used by the superheated steam according to the present invention. In addition, FIG. 2 shows the latent heat utilization rate (%) in the case of heating air at 20° C. with superheated steam.

In FIG. 2, the portion exceeding 100% indicates that it is impossible to raise the temperature to 100 ° C. with steam latent heat, and control such as increasing the amount of superheated steam to be supplied and adjusting the temperature is necessary. It is shown that.

What can be said from the above calculation results is that the higher the temperature of the superheated steam of the heat source, the higher the latent heat utilization rate. In addition, the temperature of the superheated steam supplied to the upstream vessel should be at least 100° C. and as close to 100° C. as possible to increase the utilization rate of the latent heat. The heat exchanger is designed so that the temperature is 100-110°C.

An inflow temperature detection mechanism for detecting the temperature of the fluid to be heated flowing into the heat exchange pipe, an inflow amount detection mechanism for detecting the amount of the fluid to be heated flowing into the heat exchange pipe, or a heated fluid flowing out from the heat exchange pipe At least one outflow temperature detection mechanism for detecting the temperature of the heating fluid, a superheated steam temperature adjustment mechanism for adjusting the temperature of the superheated steam supplied to the downstream vessel, or an amount of superheated steam supplied to the downstream vessel is adjusted. It is desirable to have at least one superheated steam amount adjusting mechanism and a computing mechanism for calculating an adjustment amount for at least one of the adjusting mechanisms based on the detected value of the at least one detecting mechanism.

Further, a method for using a heat exchanger according to the present invention includes a heat exchange pipe through which a fluid to be heated flows, a downstream container that houses a downstream portion of the heat exchange pipe and is supplied with superheated steam, A method of using a heat exchanger comprising an upstream container that houses an upstream portion of a heat exchange pipe and is supplied with steam that has passed through the downstream container, wherein superheated steam is supplied to the downstream container. The temperature and amount of is set so that the heated fluid flowing in the downstream portion of the heat exchange pipe reaches a desired temperature of 100 ° C. or higher, and is supplied from the downstream container to the upstream container The temperature of steam is set to 100° C. or higher.

According to the present invention configured in this manner, the fluid to be heated can be heated by effectively utilizing the steam latent heat of the superheated steam.

It is a figure which shows typically the structure of the heat exchanger which concerns on one Embodiment of this invention. It is a figure which shows the latent-heat utilization rate in the case of heating 20 degreeC air with superheated steam.

An embodiment of a heat exchanger according to the present invention will be described below with reference to the drawings.

<1. Device configuration>
The heat exchanger 100 according to this embodiment heats a fluid such as air using superheated steam as a heat source. In addition, as the superheated steam used in the heat exchanger 100, it is assumed that the surplus steam in a factory having a large boiler is reheated by the superheated steam generator. It may be superheated steam that has already been used, or may be superheated steam that is obtained by reheating the used superheated steam.

Specifically, as shown in FIG. 1, the heat exchanger 100 accommodates a heat exchange pipe 2 through which a fluid to be heated flows, a downstream portion 2a of the heat exchange pipe 2, and a downstream side to which superheated steam is supplied. It is provided with a container 3 and an upstream container 4 that accommodates the upstream portion 2b of the heat exchange pipe 2 and is supplied with steam that has passed through the downstream container 3 .

The heat exchange pipe 2 has an introduction port P1 through which the fluid to be heated is introduced, and an outlet port P2 through which the fluid to be heated is introduced. Further, the heat exchange pipe 2 forms a meandering flow path in each of the vessels 3 and 4 in order to increase the heat exchange area. Austenitic stainless steel, Inconel alloy, or the like can be used as the material of the heat exchange pipe.

The downstream container 3 has one space 3S that accommodates the downstream portion 2a of the heat exchange pipe 2, and has a supply port P3 to which superheated steam is supplied and a drain port P4 to discharge drain. are doing. Ideally, the downstream container 3 does not need the drain port P4, but it is provided because there are cases where the drain may actually come out.

The upstream container 4 has one space 4S that accommodates the upstream portion 2b of the heat exchange pipe 2, and includes a supply port P5 to which steam that has passed through the downstream container 3 is supplied, and steam or drain. and an ejection port P6 for ejection.

In this embodiment, the downstream container 3 and the upstream container 4 are configured by partitioning one container with a partition wall 5 . A connection path 51 that connects the downstream container 3 and the upstream container 4 is provided in the partition wall 5 , and the connection path 51 serves as the supply port P<b>5 for the upstream container 4 . As materials for the downstream side container 3 and the upstream side container 4, austenitic stainless steel, Inconel alloy, or the like can be used.

In this heat exchanger 100, the heated fluid flowing through the downstream portion 2a of the heat exchange pipe 2 is heated by the sensible heat of the superheated steam supplied to the downstream container 3, and the upstream portion of the heat exchange pipe 2 is heated. The heated fluid flowing through 2b is configured to be heated by the latent heat of steam supplied to the upstream container 4 .

Specifically, the temperature Θs and the amount Qs of the superheated steam supplied to the downstream container 3 are set so that the heated fluid flowing through the downstream portion 2a of the heat exchange pipe 2 reaches a desired temperature of 100° C. or higher. It is set so that the temperature Θsc of steam supplied from the downstream container 3 to the upstream container 4 is 100° C. or higher.

<2. Design method>
Here, a method for designing the heat exchanger 100 of this embodiment will be described.

First, the maximum temperature Θsm of superheated steam supplied to the heat exchanger 100 from a superheated steam treatment device or a superheated steam supply device (not shown) is determined from the viewpoint of durability and manufacturing cost.
Next, when the superheated steam to be supplied has the maximum temperature Θsm and the air (heated fluid) of about 90° C. has the maximum inflow Qam, A superheated steam amount Qsm is set.
Subsequently, the heat exchange area S1 of the heat exchange pipe 2 of the downstream container 3 is set so that the temperature Θsc of steam flowing from the downstream container 3 into the upstream container 4 is about 100 to 110°C.
The heat exchange pipe 2 of the upstream vessel 4 is provided with a heat exchange area S2 required for heating the fluid to be heated at an inflow temperature Θa (for example, 20°C) to 95 to 100°C with steam of 100°C.

In the heat exchanger 100 designed as described above, when the rated maximum inflow Qam and maximum outflow temperature Θm are used, the latent heat utilization rate is maximized when the amount of superheated steam is Qsm and the maximum temperature Θsm of the superheated steam. Become. By the way, the control of the outflow temperature Θ flowing out from the heat exchange pipe 2 first sets the maximum temperature Θsm and the amount Qsm of the superheated steam supplied so that the output air has the maximum amount Qam and the maximum temperature Θm. Then, it is conceivable to perform precise control by adjusting the temperature Θs of the superheated steam.

Then, the heat exchanger 100 of the present embodiment determines the required superheating at the maximum superheated steam temperature Θsm from the outflow temperature (control set value) Θ, the inflow temperature Θa of the heated fluid, and the inflow amount Qa of the heated fluid. It has a computing mechanism 6 that computes the amount of water vapor Qs. With this calculation function, it is possible to set the necessary superheated steam amount Qs under the operating conditions even when the operating conditions are changed, and control can be performed to maximize the latent heat utilization rate in the heat exchanger 100. .

Therefore, the heat exchanger 100 includes an inflow temperature detection mechanism 7 that detects the inflow temperature Θa, an inflow amount detection mechanism 8 that detects the inflow amount Qa, and an outflow temperature detection mechanism 9 that detects the outflow temperature Θ of the heated fluid. and The heat exchanger 100 also includes a superheated steam amount adjustment mechanism 10 that adjusts the amount of superheated steam Qs supplied to the downstream container 3 . Then, the calculation mechanism 6 calculates the adjustment amount in the superheated steam amount adjustment mechanism 10 based on the detection values of the detection mechanisms 7 to 9, and controls the required superheated steam amount Qs. In addition, the heat exchanger 100 has a superheated steam temperature adjustment mechanism that adjusts the superheated steam temperature Θs supplied to the downstream vessel 3, and the calculation mechanism 6 is based on the detection values of the detection mechanisms 7 to 9. Then, the adjustment amount in the superheated steam temperature adjusting mechanism may be calculated to control the required superheated steam temperature Θs.

<3. Specific example>
A specific example is as follows.
When the heat exchanger 100 is operated with an inflow Qa, an inflow temperature of 20°C, an outflow temperature of 300°C, a superheated steam amount Qsm, and a superheated steam temperature of 600°C, the maximum latent heat utilization rate is 22.8%. (See Figure 2).

Here, considering the case of operating with the outflow temperature changed to 150 ° C., first, with the superheated steam at 600 ° C. and the heat exchange area S1, the amount of superheated steam Qsn that can be made to 150 ° C. from the air with the inflow Qa of 90 ° C. Calculate and set. At this time, the maximum latent heat utilization rate is 91.1%. Fine adjustment of the outflow temperature Θ is performed by controlling the superheated steam temperature Θs. If some of the operating conditions are fixed or set stepwise, the detection mechanism for that part may not be necessary.

<4. Heat calculation of heat exchanger 100>
The specific heat of air A and the specific heat of superheated steam S in the following calculations actually vary slightly depending on the temperature, but are assumed to be the same here for simplification.
1. Thermal calculation in downstream vessel 3

(1) Outflow temperature Θ: 150°C
Inflow temperature Θa: 90°C
Air heating heat quantity: (150-90) x A x Qa ₁₅₀ ≈ 60 x A x Qa ₁₅₀
A: air specific heat, Qa ₁₅₀ : air volume

(2) Outflow temperature Θ: 300°C
Inflow temperature Θa: 90°C
Air heating heat quantity: (300-90) x A x Qa ₃₀₀ ≈ 210 x A x Qa ₃₀₀
A: air specific heat, Qa ₃₀₀ : air volume

(3) When the superheated steam temperature is 600° C., the outlet temperature from the downstream side vessel 3 to the upstream side vessel 4 is 110° C., and the superheated steam amount Qs is constant, the heating amount of the superheated steam is about (600−110)×S×Qs. becomes. where S is the superheated steam specific heat.

At this time, the relationship between the amounts of air heated to 150° C. and 300° C. is about Qa ₃₀₀ =(60/210)Qa ₁₅₀ .

Therefore, if the same amount of superheated steam with the same temperature of 600°C is input to the heat exchanger 100 designed with Qa ₁₅₀ , and the amount of air is changed to 60/210, the output air of 300°C can be obtained. and the outlet temperature can be 110°C. Since the amount of heat exchange is the same, if the heat exchange area S1 is secured at 150° C. where the temperature difference is small, 300° C. will be sufficient.

(4) When the air volume is changed to 0.5 Qa ₁₅₀ for the above operation with an outflow temperature of 150 ° C and an air volume of Qa of ₁₅₀ , the required superheated steam volume to achieve an outlet temperature of 110 ° C at a superheated steam temperature of 600 ° C is It becomes about 0.5Qs.

Since the amount of heat exchange is _halved , the heat exchange area S1 is sufficient. 110°C.
(5) Assuming that the air amount is constant (Qa ₁₅₀ =Qa ₃₀₀ ), the superheated steam temperature is 600° C., and the outlet temperature is 110° C., the superheated steam amount Qs ₁₅₀ ≈(60/210)Qs ₃₀₀ .

Therefore, if the same amount and temperature of superheated steam of 600 ° C is input to the heat exchanger 100 designed with Qa ₃₀₀ , and the amount of superheated steam is changed to 60/210, the output air of 150 ° C can be obtained. and the exit temperature can be 110°C. Since the output air at 300°C has a larger heat quantity than the output air at 150°C, 150°C is sufficient if the heat exchange area S1 for the output air at 300°C is secured.

2. Calculation of heat in the upstream vessel 4 As shown in the latent heat utilization rate in FIG. It is clear that air at 20°C can be heated to 90°C (calculated 100°C).

3. Overall heat flow In the upstream vessel 4, the heat exchanger temperature near the air inlet side becomes low, so a large amount of latent heat of saturated steam begins to be received from near the inlet side. When the heat exchange area is sufficient, heat exchange is performed in the entire heat exchanger of the upstream container 4, and the temperature of the air rises to around 100°C (calculated to 90°C).

On the other hand, since the downstream container 3 also has a sufficient heat exchange area, by supplying the amount of superheated steam that can obtain the amount of heat at a temperature from 600 ° C. to 110 ° C. in order to raise the temperature to the set outflow temperature, An outlet temperature of 110° C. for the superheated steam can be ensured.

<5. Effect of the present embodiment>
According to the heat exchanger 100 configured in this way, the superheated steam is supplied to the downstream container 3, and the sensible heat of the superheated steam heats the fluid to be heated to a desired temperature. 4 is supplied with steam to heat (preheat) the fluid to be heated by the latent heat of the steam, the latent heat of the superheated steam can be effectively used to heat the fluid to be heated.

<6. Modified Embodiment of the Present Invention>
It should be noted that the present invention is not limited to the above embodiments.

For example, although the downstream side container 3 and the upstream side container 4 are integrally constructed in the above-described embodiment, they may be constructed from separate containers.

In addition, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.

Reference Signs List 100 Heat exchanger 2 Heat exchange pipe 2a Downstream portion 2b Upstream portion 3 Downstream container 4 Upstream container 6 Operation mechanism 7 ... Inflow temperature detection mechanism 8 ... Inflow detection mechanism 9 ... Outflow temperature detection mechanism 10 ... Superheated steam amount adjustment mechanism

Claims (2)

A heat exchanger that heats a fluid with superheated steam,
a heat exchange pipe through which a fluid to be heated flows;
a downstream container that houses the downstream portion of the heat exchange pipe and is supplied with superheated steam;
an upstream container that houses the upstream portion of the heat exchange pipe and is supplied with steam that has passed through the downstream container ;
an inflow temperature detection mechanism for detecting the temperature of the fluid to be heated flowing into the heat exchange pipe;
an inflow detection mechanism for detecting the amount of heated fluid flowing into the heat exchange pipe;
an outflow temperature detection mechanism for detecting the temperature of the heated fluid flowing out of the heat exchange pipe;
At least one of a superheated steam temperature adjustment mechanism for adjusting the temperature of superheated steam supplied to the downstream container, or a superheated steam amount adjustment mechanism for adjusting the amount of superheated steam supplied to the downstream container;
a calculation mechanism for calculating an adjustment amount in at least one of the adjustment mechanisms based on the detected values of the inflow temperature detection mechanism, the inflow amount detection mechanism, and the outflow temperature detection mechanism ;
The heated fluid flowing through the downstream portion of the heat exchange pipe is heated by the sensible heat of the superheated steam supplied to the downstream container,
A heat exchanger, wherein the fluid to be heated flowing through the upstream portion of the heat exchange pipe is heated by latent heat of steam supplied to the upstream vessel. A method of using the heat exchanger according to claim 1 ,
The temperature and amount of superheated steam supplied to the downstream vessel are set so that the heated fluid flowing in the downstream portion of the heat exchange pipe reaches a desired temperature of 100 ° C. or higher, and the downstream side A method of using a heat exchanger, wherein the temperature of steam supplied from a container to the upstream container is set to 100° C. or higher.

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