JPS599833B2 - Waste heat recovery equipment that prevents corrosion caused by sulfur oxides - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat repellent recovery device such as a boiler, and more specifically, a heat transfer surface of a heat exchanger that absorbs sulfur oxides SO in combustion exhaust gas.
This invention relates to a heat repellent recovery device that prevents corrosion caused by x.

In boilers, industrial furnaces, and incinerators that use sulfur-containing fuel oil such as C heavy oil as fuel, or incinerators that may emit sulfur oxides (SOx), the feed water heat exchanger, etc. may be corroded by the sulfur oxides (SOx) in the combustion exhaust gas. Problems have been pointed out for some time.

In other words, the surface temperature of the heat transfer coil of a typical feed water heat exchanger is slightly higher than the normal feed water temperature, so even if the temperature of the combustion exhaust gas flowing in the flue is the dew point temperature of sulfur oxide SOx (the temperature of the fuel Although it varies depending on the sulfur content, even if the temperature is higher than 140℃ (generally around 140℃), when this combustion exhaust gas comes into contact with the surface of the heat transfer coil, the temperature decreases and the sulfur oxide SOx contained in it condenses on this surface. It is believed that the sulfur oxide SO = converted into sulfuric acid corrodes the surface of the heat transfer coil.

In order to solve this corrosion problem, an exhaust heat recovery device that utilizes the constant temperature characteristics of a heat pipe that maintains a temperature close to that of the heat receiving side has been proposed, for example, in Japanese Utility Model Publication No. 18641/1983. However, when the above-mentioned device is installed in a boiler etc. that is subject to load fluctuations, the combustion exhaust gas temperature T
Since the surface temperature Tm of the heat transfer coil on the heat absorption side of the heat pipe also changes in proportion to When the temperature drops below the dew point (])ew point), corrosion occurs on the surface of the heat transfer coil similar to the one mentioned above, causing clogging of the ζ coil and damaging the heat pipe's resistance to heat. (In addition, the symbol T in the figure
gi is the gas inlet temperature, Tgo is the gas outlet temperature, Two is the feed water outlet temperature, and Twi is the water inlet temperature).

Further, there still remains the problem that the temperature of the combustion exhaust gas decreases too much due to the endothermic action when passing through the exhaust heat recovery device, causing the inside of the rear flue or chimney to be corroded by sulfur oxide SOx.

In view of such problems, the present invention maintains the surface temperature of the endothermic side of the heat pipe at or above the dew point temperature of sulfur oxide SOx, regardless of load fluctuations in the boiler, thereby preventing corrosion. In addition to preventing sulfur oxides, S
The purpose of this study is to propose a new waste heat recovery device that can be protected from corrosion caused by Ox.

Therefore, the details of the present invention will be explained below based on the drawings.

FIG. 2 is a schematic diagram showing an example of boiler equipment equipped with a heat repellent recovery device, which is an embodiment of the present invention. As is clear from the detailed diagram shown in FIG. 3, this heat repellent recovery device 1 has a heat receiving section 11 that receives thermal energy of combustion exhaust gas, and a heat receiving section 11 for heating water supplied to a boiler 2. and a feed water heating section 12,
A large number of heat pipes 14 are firmly fixed to a thick plate 15 made of a corrosion-resistant metal such as stainless steel that partitions these two parts, each having a heat absorption part and a heat radiation part in the heat receiving part 11 and the water supply heating part 12, respectively. has been done.

Reference numerals 13 and 13 denote two partition walls that partition the inside of the feed water heating section 12 in a direction perpendicular to the combustion exhaust gas flow path.
Three independent water chambers 12a formed by 3 and 13
At jl2b and 12C, each group of heat pipes 14, which are similarly divided into three groups, is located.

Furthermore, three water pipes 6a, 6b, 6c extending from a balance tank 5 (FIG. 2), which will be described later, are connected to these water chambers 12a, 12b, and 12C.
Above 12bt12c, there are three overflow pipes 7.
a, 7b, and 7c extend toward the balance tank 5.

5 is a balance tank for supplying water to the boiler 2 via the water supply pump P2, and a circulation pump P1 and a flow rate adjustment valve 1 are provided between this tank 5 and the three water pipes 6a) 6b76C. They are connected by a water pipe 6.

V5a, V (3b is an automatic water supply valve provided in the first and second water pipes Sat6b that supplies water into the two water chambers 12a j 12b located on the combustion exhaust gas outlet side, and The operation is controlled by the output signal of the combustion exhaust gas temperature detection sensor S (Fig. 2) arranged near the outlet, and when the combustion exhaust gas outlet temperature Tgo reaches a preset temperature, for example, 180°C or less, First, the first automatic water supply valve V5a operates to stop the water supply into the first water chamber 12a,
If the combustion exhaust gas outlet temperature Tgo further decreases, the second automatic water supply valve v6b operates to stop the water supply into the second water chamber 12b.

satsb is a drain pipe branched from the first and second water supply pipes 5a and 6b, and is for discharging the water in the first and second water chambers 12a and 12b, and each of these pipes 8a,
8b is provided with automatic drainage valves 8a and V8b which open in conjunction with the first and second automatic water supply valves V5a and v6b.

In addition, the reference numeral 9 in FIG. 1 indicates a water supply tank for replenishing water into the balance tank 5, and P3 indicates a supplementary water/pump that operates according to the water level in the balance tank 5, and illustration is omitted. However, a drain inlet port is provided below the third water chamber 12c to introduce the condensed steam from the boiler 2 through the load side circuit, and the water in the feed water heating section 12 is heated by the high temperature drain. A preheating structure is adopted.

Next, the operation of the above-described device will be explained.

Under normal operating conditions in which the boiler 2 is operated at close to its rated output, the combustion exhaust gas temperature Tg is sufficiently high;
Circulation pump P, by. The water in the balance tank 5 is sent to the three water chambers 12a, 12b,
1 2 c.

Therefore, all the heat pipes 14 provided in this heat repellent recovery device 1 maintain sufficient contact with the water supplied into each water chamber 12a, 12b, 12C, and absorb the combustion exhaust gas received by the heat receiving section 11. Heat the feed water to the maximum extent possible.

In this state, even if the surface temperature Tm of the heat transfer coil on the heat absorption side of the heat pipe 14 decreases due to the heat exchange action described above, the flue gas temperature Tg is sufficiently high, so the flowing yellow oxide SOx condenses on the coil surface. There is no such thing (Part 4)
figure).

Next, when the load of the boiler 2 is reduced to, for example, 80% or less, the combustion exhaust gas temperature Tg is also reduced accordingly, and on the exit side of the heat receiving section 11, this gas temperature Tgo is set to, for example, 180°C. The temperature drops below the set temperature (
Figure 4).

This state is immediately detected by the combustion exhaust gas temperature detection sensor S, and this detection output closes the automatic water supply valve V5a of the first water pipe 6a, and at the same time closes the automatic water drain valve Via of the discharge pipe 8a branched from this pipe 6a. The valve is opened, and the flow rate adjustment valve v1 is further throttled to reduce the water supply amount to /3.

As a result, the water in the balance tank 5 is supplied only to the second and third water chambers 12bj12C, and the water in the first water chamber 12a located on the combustion exhaust gas outlet side is discharged.

Therefore, the heat pipe 1 located inside this water chamber 12a
The fourth group is in an empty state, and as shown in FIG. 4, its gas side surface temperature Tma rises to near the combustion exhaust gas outlet side temperature Tgo, and condensation of sulfur oxide SOx on this surface is avoided.

On the other hand, since the heat pipes 14 group in the first water chamber 12a are cut off from contact with water, the total effective heat transfer area of all the heat pipes 2 and 14 arranged in the heat repellent recovery device 1 increases. As the amount of heat absorbed decreases, the combustion exhaust gas outlet temperature Tgo stops decreasing, and even if the temperature in the combustion exhaust gas duct 4 and the chimney 3 decreases to some extent, these wall surfaces It is not corroded by sulfur oxide SOx.

If the load on the boiler 2 is further reduced at night, etc., the combustion exhaust gas outlet temperature T will decrease despite the above-mentioned operation.
go begins to decline again.

This state is detected again by the combustion exhaust gas temperature detection sensor S, and this detection output closes the automatic water supply valve V6b of the second water supply pipe 6b, and at the same time opens the automatic drain valve V8b of the drain pipe 8b to drain the water into the second water chamber. Drain the water in 12b.

As a result, the heat pipes 14 group in the second water chamber 12b also become empty, raising their surface temperature Tmb to near the combustion exhaust gas outlet temperature Tgo, and reducing the amount of heat absorbed by all the heat pipes 141 to / 3 to prevent the combustion exhaust gas outlet temperature Tgo from falling (Figure 4).

Note that if the combustion exhaust gas outlet temperature is about 200° C., a normal heat pipe will not be affected even if it is in an empty state.

Furthermore, since the closer the heat pipe 14 is to the combustion exhaust gas outlet side, the lower its surface temperature Tm is, if the heat pipes 14 are emptied sequentially starting from the gas outlet side as in the above embodiment, sulfur oxides will be deposited on their surfaces. Condensation of SOx can be prevented, but if the set temperature is sufficiently high, the order of the heat pipes to be emptied, that is, the positional relationship of the ice chambers to be drained, does not matter.

Furthermore, in the embodiment described above, the interior of the feed water heating unit 12 is divided into three water chambers 12a, 12b, and 12C to control the total amount of heat absorption, but the amount of heat absorption can be controlled with higher precision. For this purpose, the number of ice compartments may be increased, or to simplify the apparatus, the number of ice compartments may be two, and only one of the ice compartments may be provided with a water supply/drainage control means.

As described above, according to the present invention, the inside of the fluid flow path in which the heat pipe group is located is divided by a partition wall having a surface perpendicular to the combustion exhaust gas flow path and parallel to the heat pipe, and a plurality of partitioned Since at least one of the melt chambers is equipped with a water supply and drainage means that is controlled according to the combustion exhaust gas temperature, the total amount of heat absorbed by the heat pipes can be easily adjusted by letting some of the heat pipe groups dry. To avoid corrosion of the heat pipe surface or flue by sulfur oxides by always maintaining the combustion exhaust gas outlet temperature above the dew point temperature of sulfur oxides regardless of load fluctuations of the boiler etc. Not only that, but when used in a boiler or the like, it becomes possible to equally heat the amount of liquid corresponding to the load.

Moreover, since the partition wall in the liquid flow path is parallel to the heat pipe, an independent ice chamber can be formed regardless of expansion, contraction, etc. of the heat pipe, making the device extremely easy to manufacture.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between boiler load, combustion exhaust gas temperature, heat pipe gas side surface temperature, and feed water heating temperature;
Fig. 2 is a schematic diagram of boiler equipment equipped with a heat repellent recovery device which is an embodiment of the present invention, Fig. 3 is a perspective view showing the main parts of the same device, and Fig. 4 is a state controlled by the same device. It is a figure showing the temperature relationship of each part. 1... Heat repellent recovery device, 11... Heat receiving section, 12... Water supply heating section, 12a, 12b, 12
C...Water chamber, 6a, 6b, 6c...Water pipe, ? a, 7b, 7c...overflow pipe, aa, ab...discharge pipe, P...
...Pump, S...Sensor for detecting combustion exhaust gas temperature, V6a, V5b...-Automatic water supply valve, V8a, vBb...Automatic drain valve.

Claims (1)

[Claims] 1. In a heat repellent recovery device using heat pipes as heat transfer means between combustion exhaust gas and a liquid to be heated, the liquid flow path in which the heat pipe group is located is perpendicular to the combustion exhaust gas flow path and The dew point of the sulfur oxide in the combustion gas is divided by at least one partition wall having a surface parallel to the heat pipe, and at least one of the plurality of liquid chambers partitioned by the partition wall is A liquid supply/drainage means is provided that is controlled by a combustion exhaust gas temperature detection means that outputs an output at at least one set temperature based on the temperature, and the heat pipe in the at least one liquid chamber is connected to the heat pipe in accordance with the combustion exhaust gas temperature. Corrosion caused by sulfur oxides characterized by maintaining the surface temperature of the heat pipe and the combustion exhaust gas outlet temperature above the dew point temperature of the sulfur oxides by bringing the heat pipe into contact or non-contact with the liquid. A heat repellent recovery device that prevents 2. Claims in which at least one liquid chamber located on the combustion exhaust gas outlet side among the plurality of liquid chambers partitioned by the partition wall is provided with liquid supply/drainage means controlled by the combustion exhaust gas temperature detection means. 2. A heat repellent recovery device for preventing corrosion caused by sulfur oxides according to item 1.