JPS6037364B2 - Waste heat boiler that can reduce fluctuations in evaporation amount - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the characteristics of a waste heat boiler that uses a waste gas source with extremely large fluctuations in calorific value, such as a waste heat recovery boiler attached to a steelmaking electric furnace. The present invention relates to a waste heat boiler that is capable of keeping the amount of evaporation of the boiler substantially constant even when heat is generated.

When a general waste heat boiler is applied to a waste gas source whose calorific value fluctuates drastically, the amount of generated steam fluctuates drastically due to the influence of the fluctuating calorific value of the waste gas source.

If the amount of steam generated by the boiler fluctuates drastically, it not only becomes extremely difficult to control the water level in the drum, but also
The negative impact on the steam-using process cannot be ignored.

In order to solve these problems, a number of measures have been developed and put into practice for suppressing fluctuations in the amount of steam generated in this type of waste heat boiler. FIG. 1 and FIG. 2 show typical measures, and both use an accumulator.

That is, the system shown in FIG. 1 is equipped with a high-pressure evaporator 3 in the high-temperature area on the inlet side of the waste gas 2 of the waste heat recovery section 1, and a low-pressure evaporator 4 in the low-temperature area, respectively. The brackish water drum 5 and the low pressure brackish water drum 6 are connected via circulation pipes 7, 8 and 9, 10, and the air chambers of the high pressure air water drum 5 and the air chambers of the low pressure air drum 6 are connected by a pipe 11. It is composed of:

By providing the high-pressure steam/water drum 5 with a sufficient volume, it is operated as an accumulator, and fluctuations in the flow rate of steam to the process 12 side due to fluctuations in the calorific value of the waste gas are detected by the steam flow meter 13. By detecting the detection signal and controlling the opening and closing of the control valve 14 based on the detection signal, steam is replenished from the accumulator 5 and the process 12 is started.
This is to keep the flow rate of steam to the side approximately constant.

In addition, in Fig. 1, 15, 16 are circulation pumps, 17,
18 is a water supply line.

However, the system includes a boiler system with a pressure compatible with the process 12 side and at least several tens of
The steam chamber of the high-pressure side air-water drum 5 is constructed from a combination of two boiler systems having a high pressure of more than 1 kg/kg/kg, and in order to almost completely absorb steam fluctuations, the steam chamber of the high-pressure side air-water drum 5 is It becomes quite large in volume.

In addition, the circulation pump 15 also has a high pressure specification, which has the disadvantage of significantly increasing equipment costs. On the other hand, the system shown in FIG. 2 uses a set of steam generator 19 and steam/water drum 20, and is equipped with a steam accumulator 21 that matches the steam pressure rank on the process 12 side. By providing a volume capable of absorbing fluctuations in steam, the steam flow rate is kept approximately constant.

In this system, if the steam pressure on the process 12 side is low, the volume of the accumulator 21 will inevitably increase, and conversely, if the steam pressure is high, even if the volume can be reduced, the volume of the accumulator 21 will increase. The thickness of the plate must be increased considerably. In any case, the system can almost completely absorb the variation in heat amount and the process 12
In order to suppress fluctuations in the steam on the side, a steam accumulator 21 having an enormous capacity is required, which has a major drawback in that it is difficult to reduce equipment costs. The present invention
The objective is to eliminate the above-mentioned drawbacks in waste heat boilers that use a waste gas source with extremely large fluctuations in heat value, and compared to previous systems, it is possible to significantly reduce equipment costs by making the equipment smaller and simpler. Another object of the present invention is to provide a waste heat boiler system which has extremely stable operation and control characteristics, and which can efficiently absorb fluctuations in heat amount and almost completely prevent fluctuations in the amount of steam generated. It is something. Hereinafter, the details will be explained based on each embodiment of the present invention shown in FIGS. 3 to 5.

FIG. 3 shows a first embodiment of the present invention. In the figure, 22 is a waste heat recovery section of a boiler, and high temperature waste gas A from a waste gas source is supplied from the primary side. .

A heat sink 23 is disposed in the primary side high temperature area into which the waste gas A of the waste heat recovery section 22 flows, and an evaporator 24 is provided in the secondary side low temperature region on the outflow side of the waste gas A. is installed.

The heat sink 23 includes a heat storage tank 25 and circulation pipes 26 and 27.
The heat medium B is circulated by a circulation pump 28. The heat medium B is preferably a liquid substance that has a large heat capacity, a high boiling point, and is highly stable with respect to temperature. In the present invention, hot soot oil is used as the heat medium B. In addition, 29 is a thermometer for controlling the hot soot oil B attached to the circulation pipe 26, 30 is a switching valve, and 30a is a bypass line for the hot soot oil.

On the other hand, a brackish water drum 33 is connected to the evaporator 24 via circulation pipes 31 and 32, and canned water C is circulated by a circulation pump 34.

In this embodiment, the canned water C is forcibly circulated by the pump 34, but it goes without saying that a natural circulation method may also be used. The brackish water drum 33 has piping 35, 3
A reboiler 37 is connected to the heat transfer body 37a of the reboiler 37 through hot soot oil circulation pipes 38 and 39 from the heat storage tank 25 to the hot soot oil B from the circulation pump 4. will be sent.

In addition, 41 is a hot soot oil switching valve attached to the circulation pipe 39;
2 is a heat transfer oil bypass pipe, 43 is a control thermometer, 44
is an inert gas boiling device. Further, 45 is a main steam line, through which steam is supplied to the process side 47 through a steam flow meter 46 . Next, the operation of the present invention will be explained.

When there is a load fluctuation on the heat source of waste gas A and the heat load is low and the temperature of heat transfer oil B does not reach the predetermined set temperature, heat transfer oil B is circulated from the switching valve 3 to the bypass line 30a side. It has become so.

Now, due to load fluctuations in the heat source, the heat load is increasing, and hot soot oil B
When the temperature reaches the set temperature or higher, the switching valve 30 is actuated by a signal from the control thermometer 29, and the heat medium oil B is switched and fed to the heat storage tank 25 side. That is, when the amount of heat of the waste gas A is high, the amount of excess heat is stored in the calorific tank 25 via the hot soot oil B. On the other hand, when the steam flow rate to the process 47 side is close to the preset average flow rate, the supply of hot soot oil B to the repoiler 37 is stopped.

Now, when the steam flow rate in the main steam line 45 becomes below the average flow rate, the switching valve 41 is activated by the signal from the steam flow meter 46, and the high temperature soot oil B is transferred from the heat storage tank 25 to the lipofilter 3.
Sent to 7. The steam generated in the reboiler 37 is replenished to the brackish water drum 33, and thereby the main steam line 45
The steam flow rate is always maintained at a value approximately equal to the average evaporation amount of the waste heat boiler. In this embodiment, the amount of steam is controlled by detecting the steam flow rate of the main steam line 45, but the control system may be configured using the pressure of the brackish water drum 33.

The heat transfer oil B is adjusted in such a way that the fluctuation range of the heat amount of the waste gas source is determined in advance, and the total amount and the heat transfer oil B are adjusted so that the heat transfer oil B is not overheated to the transformation point within the fluctuation range. The amount of circulation is determined.

However, in the unlikely event that there is a fluctuation in the amount of heat in the waste gas source that exceeds the expected value, and the temperature of the heat transfer oil B measured by the thermometer 43 on the outlet side of the heat storage tank 25 becomes close to its transformation point temperature, the circulating pump B to circulate the heat medium oil B to the reboiler 37,
The heat transfer oil B is prevented from overheating. FIG. 4 is a system diagram showing the main parts of a second embodiment of the present invention, in which the reboiler 37 is removed and a heat transfer body 37a for hot soot oil B is provided in the water chamber 33a of the brackish water drum 33. It is made up of. That is, it is a system in which the amount of heat in the heat storage tank 25 is transferred to the Naoyabu brackish water drum 33. The control system itself is the same as in the first embodiment, and has the advantage that the main body of the reboiler 37 can be reduced. FIG. 5 is a system diagram showing the main parts of the third embodiment of the present invention, in which a heat exchanger 48 is provided in the heat storage tank 25, and the heat exchanger 48 and the brackish water drum 33 are connected to circulation piping 49, 50. The structure is such that canned water is pumped by a pump 51.

Note that 51 is a control valve whose opening/closing is controlled according to the measured value of the steam flow meter or the temperature value of the heat medium oil B in the heat storage tank 25. In this embodiment, the repoiler 37 can be omitted as described above, and equipment costs can be significantly reduced. As mentioned above, the present invention is characterized by the use of hot soot oil, which has the characteristics of large heat capacity, high boiling point, and high thermal stability, in a normal pressure liquid phase, and is different from the conventional one. Compared to other technologies, it has many superior features as described below.

'1} Since all heat transfer guns are normal pressure systems,
It is possible to design the entire system at a low pressure, and the discharge pressure of the hot soot oil circulation pumps 28, 40 is sufficient to compensate for the flow resistance of the system, so that equipment costs can be significantly reduced.

Furthermore, since the entire system is a low-pressure system, it is highly safe and the system is extremely easy to control.

[21] Hot soot oil has extremely high thermal stability, and even if its temperature is raised to about 300 oo, which corresponds to a pressure of approximately 90 k9/G in terms of steam pressure, no deterioration occurs.

{3} Assuming that the fluctuation in the heat value of the waste gas source is the same, the volume of the heat storage tank required to absorb the fluctuation is approximately 110 to 12
decreases to 0.

For example, the range of heat fluctuation is 1.0×l pkcal/2 kcal/h
According to an example of a plant experiment in which the hot soot oil system according to the present invention absorbs the fluctuation and maintains the amount of steam generated at a substantially constant value close to the average value, it takes about 4.
A heat storage tank at 0 is sufficient.

On the other hand, according to the conventional steam accumulator system, in order to maintain the amount of steam generated close to the average value,
An accumulator having a volume of approximately 800 mm is required, and the present invention allows for significant downsizing of equipment and a significant reduction in equipment costs.

As mentioned above, the present invention has excellent operating characteristics and is extremely compact.
Although it is an inexpensive facility, it has excellent practical utility in that it can efficiently store and absorb heat fluctuations in the waste gas source and easily maintain the amount of steam generated at a preset constant value.

[Brief explanation of the drawing]

FIGS. 1 and 2 are system diagrams showing conventional measures for maintaining the amount of steam generated in a waste heat recovery boiler at a constant value. FIG. 3 is a system schematic diagram showing the first embodiment of the present invention.
FIG. 4 is a system schematic diagram showing a second embodiment of the present invention. FIG. 5 is a system schematic diagram showing a third embodiment of the present invention. A... High temperature waste gas, B... Heat medium (hot soot oil),
C... Canned water, 22... Waste heat recovery section, 2
3... Heat sink, 24... Evaporator, 25...
・・Heat storage tank, 26, 27, 38, 39, 49, 50
...Circulation piping, 28,40...Circulation pump, 3
0...Switching valve, 33a...Brackish water drum water chamber, 33...Brackish water drum, 37a...
Heat medium oil heat transfer body, 37...Reboiler, 45...
...Main steam line, 46...Steam flow meter,
47... Process side, 48... Heat exchanger.
Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A heat sink 23 is provided in the primary high temperature region of the waste heat recovery section 22, and an evaporator 24 is provided in the secondary high temperature region, and the heat sink 23 and the heat storage tank are provided. 25 are connected by circulation pipes 26 and 27 to circulate the heat medium oil B, so that when the heat load of the waste gas source increases, heat is stored in the heat storage tank 25 via the heat medium oil B, and the evaporation is generated. The vessel 24 and the brackish water drum 33 are connected via circulation pipes 31 and 32, and the brackish water drum 3
3 to the process 47 side, and when the generated steam is insufficient, steam is generated using the high temperature heat transfer oil B in the heat storage tank 25 as a heat source, and the steam flow rate is kept approximately constant. A waste heat boiler that can reduce fluctuations in 2. A reboiler 37 using high-temperature heat transfer oil B as a heat source is provided,
A waste heat boiler capable of reducing fluctuations in evaporation amount according to claim 1, wherein the steam generated in the reboiler 37 is supplied to the brackish water drum 33. 3. A waste heat boiler capable of reducing fluctuations in evaporation amount as set forth in claim 1, wherein a heat transfer body 37a using high-temperature heat transfer oil B as a heat source is disposed in the water chamber 33a of the brackish water drum 33. . 4. Fluctuation in evaporation amount according to claim 1, in which a heat exchanger 48 is disposed within the heat storage tank 25, and the heat exchanger 48 and the brackish water drum 33 are connected by circulation pipes 49, 50. A waste heat boiler that can reduce waste heat.