JPS5928030Y2 - Exhaust heat recovery device for regenerative hot blast stove - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an apparatus for recovering sensible heat from combustion exhaust gas via a heat medium and preheating combustion air and/or fuel gas.

Conventionally, the sensible heat of the combustion exhaust gas of a hot-air stove was dissipated from the atmosphere via the chimney, but in recent years, a portion of this sensible heat has been recovered and used to release the air and/or fuel gas supplied to the combustor of the hot-air stove. There is a trend to reduce the amount of fuel gas used to raise the temperature.

There are various methods for recovering sensible heat from fuel exhaust gas.

FIG. 1 shows a conventional system for preheating combustion air.

Generally, in a hot-blast stove system, the hot-blast stove's combustion chamber I HS'
〜4H8', separately supplying fuel gas and combustion air,
The exhaust gas combusted in the combustor built in the combustion chambers IH8' to 4H8' is put into the heat storage chambers IH8 to 4H8, and heats the heat storage body built in the heat storage chamber.

The exhaust gas then passes through a flue valve 1, a flue 2, a chimney 3, and is released into the atmosphere.

The combustion air is pressurized by the blower 4 and passes through an air pipe 5 and a burner air valve 6, and the fuel gas enters the combustor via a gas pipe 7, a gas cutoff valve 8, and a burner gas valve 9.

In this hot air stove system, a heat exchanger HE1 is installed inside the flue 2 and a heat exchanger HE2 is installed inside the air pipe 5 to recover the sensible heat of the combustion exhaust gas and preheat the combustion air. A closed circuit 11 in which a heat medium can be circulated between the vessels by a heat medium pump 10
will be established.

That is, the heat medium first enters the heat exchanger HE1 in the flue and is heated by the sensible heat of the combustion exhaust gas, and the high temperature heat medium enters the closed circuit 11.
It passes through the heat exchanger HE2 in the air pipe and heats the combustion air.

By heating the combustion air, the temperature of the heat medium is reduced and it passes through the closed circuit 11 again into the heat exchanger HE1 in the flue.

FIG. 2 shows a conventional system based on the same concept, in which a heat exchanger HE3 is installed inside the gas pipe 7 to preheat the fuel gas.

Generally, three to four regenerative hot-blast stoves are installed, and the same hot-blast stove alternately repeats combustion and blowing air.

An example of a typical combustion and air blowing switching schedule in the case of four hot air stoves is shown in Fig. 3.

As can be seen from Figure 3, no matter what time of the year you look at it, two hot air stoves are blowing air at the same time.

In addition, except during the switching (and tightening) period, two hot blast stoves are used at the same time for combustion.

However, since only one hot stove is burning during the switching (and tightening) period, the main flow rates of the fuel gas and combustion air are changed during the switching (and tightening) period, respectively, as shown in Figures 4 and 5.
In the period of 2-unit combustion and tightening), it decreases to the extent that it occurs when two units are burned at the same time.

In the conventional exhaust heat recovery device shown in Fig. 1 or 2, switching (
Because the flow rate of the fluid to be heated (combustion air or fuel gas) decreases dramatically during the period of heat exchanger HE2 (
Or HE3) The temperature drop at the outlet is smaller than when two units are simultaneously combusted, and the exhaust gas returns to the exhaust gas heat exchanger HE1 at a higher temperature.

On the other hand, the temperature level of the combustion exhaust gas does not change much regardless of whether it is one-unit combustion or two-unit combustion, so the difference between the exhaust gas temperature and the heating medium temperature becomes smaller, and the effect is greater than the effect of halving the combustion exhaust gas amount. The amount of exhaust heat recovered by the exhaust gas heat exchanger HE1 tends to decrease.

FIG. 6 shows a variation pattern of the amount of exhaust heat recovered in the exhaust gas heat exchanger HE1 corresponding to the hot stove switching schedule shown in FIG. 3.

As can be seen in FIG. 6, the temperature of the heat medium entering the exhaust gas heat exchanger HE1 tends to be low when two hot stoves are burning simultaneously, and high when one hot stove is burning when switched (and tightened).

On the other hand, the temperature of the heat medium coming out of the exhaust gas heat exchanger HE1 is 2
It tends to be high when multiple units are simultaneously fired, and low when one unit is fired during switching (and tightening).

In other words, since the amount of circulation of the heat medium is constant, the hatched part in Figure 6 shows the amount of waste heat recovered, and the amount of waste heat recovered when two units are combusted simultaneously is greater than when one unit is combusted. I understand that.

The present invention relates to a device that increases the amount of waste heat recovered in accordance with the operating characteristics of a hot air stove, and the system is shown in FIG.

This system has a closed circuit 11 in which a heat exchanger HE2 is installed in the air pipe 5, a heat exchanger HE3 is installed in the gas pipe 7, and a heat medium is simultaneously circulated between the heat exchanger HE1 installed in the flue 2. will be established.

Further, valves 12 and 13 capable of adjusting the flow rate of the heat medium are provided at the branch portion of the heat exchanger HE2 and the heat exchanger HE3 in this circuit.

FIG. 9 shows a case where combustion air is heated in an embodiment of the present invention.

During normal operation, the flow rate regulating valve 12 is fully open and the valve 13 is fully closed, and the heated heat medium passes through the exhaust gas heat exchanger HE1 and reaches a high temperature through the valve 1.
2, enters the combustion air heat exchanger HE2, radiates heat, and returns to the heat exchanger HE1 again.

A thermometer with a transmitter 14 for measuring the combustion air temperature and a temperature indicating regulator 15 are installed downstream of the heat exchanger HE2 in the combustion air pipe, and a predetermined combustion air temperature is set in advance, and the set temperature is set. If the temperature becomes higher, the flow rate adjustment valve 12 is throttled down and the flow rate adjustment valve 13 is opened at the same time, thereby making part of the heat medium available for heating the fuel gas.

By employing such a device, even if there is a thermal fluctuation during operation of the hot air stove, the sensible heat of the exhaust gas of the hot air stove can be effectively utilized.

In particular, as mentioned above, the heat fluctuations when switching hot stoves are extremely large, and when this device is adopted, the exhaust gas heat exchanger HE
The fluctuation pattern of the amount of waste heat recovery in No. 1 is as shown in FIG. 7, and the amount of waste heat recovery increases significantly.

In this embodiment, the combustion air is heated to a constant temperature and the fuel gas is heated intermittently, but it goes without saying that the fuel gas is heated to a constant temperature and the combustion air is intermittently heated. is also possible.

Either fuel gas or combustion air is heated intermittently, but as the number of hot blast stoves increases, the proportion of switching time in the hot blast stove switching cycle increases, so fuel gas calories are saved. The weight loss will be significant.

[Brief explanation of the drawing]

Figure 1 shows a hot blast furnace exhaust heat recovery device when preheating combustion air with a conventional system, and Figure 2 shows a hot blast stove exhaust heat recovery device when preheating fuel gas with a conventional system. Figure 3 is a diagram showing a typical switching schedule for combustion and air blowing in a hot air stove, Figure 4 is a diagram showing a fuel gas flow rate fluctuation pattern in the fuel gas main pipe corresponding to the switching schedule in Figure 3, Figure 5 is a diagram showing the combustion air flow rate fluctuation pattern in the combustion air main pipe corresponding to the switching schedule in Figure 3, and Figure 6 is a diagram showing the combustion air flow rate fluctuation pattern in the combustion air main pipe corresponding to the switching schedule in Figure 3.
Figure 7 shows the fluctuation pattern of the amount of waste heat recovery corresponding to the switching schedule shown in Figure 3 for the exhaust heat recovery device of the present invention. FIG. 8 is a diagram showing a hot-blast stove exhaust heat recovery device according to the present invention, and FIG. 9 is a diagram showing an embodiment of the hot-blast stove exhaust heat recovery device according to the present invention. 1... flue valve, 2... flue, 3...
... Chimney, 4 ... Air blower, 5 ... Air pipe, 6 ... Burner air valve, 7 ... Gas pipe, 8 ... ... Gas cutoff valve, 9 ... Burner gas valve, 10 ... Heat medium pump, 11 ...
...Closed circuit J12.13...Flow rate adjustment valve, 1
4...Thermometer, 15...Temperature indicator controller, HEl, HE2. HE3...Heat exchanger.

Claims (1)

[Scope of utility model registration request] A combustion exhaust gas pipe (flue) is used in an exhaust heat recovery device that uses the sensible heat of the combustion exhaust gas of a regenerative hot blast stove using a heat medium to preheat the burning air or fuel gas supplied to the combustor of the hot blast stove.
The heat exchanger installed in the combustion air system and the heat exchangers installed in the combustion air pipe and the fuel gas pipe are connected by a common heat medium circulation pipe, and the combustion air system heat exchanger and the fuel gas An exhaust heat recovery device for a regenerative hot blast stove, characterized in that a flow control valve is incorporated in each of the heat medium inlet pipe and outlet pipe of a system heat exchanger.