JPS6315086A - Method of operating scrap preheating facility by furnace exhaust gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is used in the field of manufacturing screws using scrap (scrap iron) as a raw material, and in particular, it is used to preheat the scrap using the exhaust gas of the furnace during operation. related to how to operate the equipment.

[Prior Art] When scrap is preheated, oil and fat adhering to the scrap and mixed plastics, chemical fibers, rubber, etc. are combusted, generating gas that causes odor pollution. Therefore, in conventional scrap preheating equipment, the gas after preheating the scrap is returned to the main exhaust line of the furnace and mixed with the high temperature furnace exhaust gas to thermally decompose and dilute the odor gas.

Conventionally, when preheating scrap with such equipment, only the temperature of the gas after merging is monitored, and this gas temperature is maintained at a predetermined high temperature (for example, 7').

The mixing ratio of the amount of preheating gas and the dilution gas m was adjusted by adjusting the rotation speed of a damper or a suction fan so that the temperature was 0° C.) or higher.

[Problems to be Solved by the Invention] However, the temperature of the exhaust gas from a furnace that uses scrap as raw material fluctuates widely, from 100 to 1200°C, and as mentioned above, it is necessary to maintain the temperature of the exhaust gas after merging at a predetermined high temperature or higher. In this operating method, the time during which the exhaust gas can be introduced into the preheating chamber and the flow rate of the preheating exhaust gas are greatly restricted, and therefore the scrap cannot be sufficiently preheated. That is, in the conventional operating method, if the temperature of the waste waste from the furnace is, for example, 700° C. or less, preheating operation cannot be performed, and no waste heat can be recovered. Therefore, the conventional operation method has a low waste heat recovery rate and high temperature preheating of scrap is impossible.
I don't expect much energy saving effect from preheating.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and includes a main exhaust line that leads the waste gas from the furnace to the atmosphere diffuser, and a main exhaust line that leads the waste gas from the furnace to the atmosphere diffuser. Scrap preheating equipment using furnace exhaust gas, which is equipped with a preheating gas line that leads to the preheating chamber and makes the exhaust gas after scrap preheating join the main exhaust line, and a preheating gas flow rate adjustment device that adjusts the amount of furnace exhaust gas that is guided to the scrap preheating chamber. characterized in that the preheating gas flow rate is adjusted so that the difference between the temperature of the exhaust gas from the furnace and the temperature of the gas after the scrap preheating and the exhaust gas flowing through the main exhaust line are joined is constant. It is said that

[Function] According to the above operating method, when the temperature of the exhaust gas from the furnace is high, the amount of odor generated is large, and the temperature of the exhaust gas after the merger is increased to increase the thermal decomposition capacity. do. In addition, when the temperature of the furnace exhaust gas is low, the amount of odor generated is also relatively small, so the temperature of the exhaust gas after merging is lowered and the operation is performed at a lower thermal decomposition capacity to improve the efficiency of exhaust heat recovery in the low temperature range. Try to improve. Therefore, it is possible to efficiently preheat scrap by effectively utilizing the furnace exhaust gas in a wide range from high temperature to low temperature range without causing odor pollution.

[Example] An embodiment of the present invention will be described below with reference to FIG.

This figure shows a system diagram of a facility for preheating scrap using furnace exhaust gas suitable for carrying out the present invention, and what is indicated by the symbol l is a scrap melting furnace. In this furnace I,
A main exhaust line 2 that guides exhaust gas inside the furnace to the outside of the furnace is connected. This main exhaust line 2 is connected via a dust collector 3 and a dust collection fan 4 to a chimney 5 installed as an atmospheric dissipator, so that the exhaust gas from the furnace 1 is released into the atmosphere from this chimney 5. It has become.

The main exhaust line 2 is provided with a preheating gas line 6 that branches off near the furnace 1 and joins the main exhaust line 2 again before the dust collector 3. And this preheating gas line 6
A scrap preheating chamber 7 is installed in the middle. The scrap preheating chamber 7 is used to store scrap (scrap iron) before being melted, and the scrap is introduced into the preheating chamber 7 from the preheating gas line 6 and is preheated by exhaust gas.

Dampers 8.9 for opening and closing the preheating gas line 6 are provided on the inlet and outlet sides of the preheating gas line 6 with respect to the scrubber knob preheating chamber 7.

Further, a damper IO for controlling the flow rate of exhaust gas is provided between the branch and confluence points of the main exhaust line 2 and the preheating gas line 6.

The reference numeral T1 is a thermometer that measures the temperature of the exhaust gas flowing in the main exhaust line 2 just before the branch point of the preheating gas line 6, that is, the temperature of the exhaust gas from the furnace I. Moreover, what is indicated by the reference numeral T2 is a thermometer that measures the temperature of the exhaust gas flowing downstream of the confluence of the preheating gas line 6 in the main exhaust line 2.

A preheating operation control device 11 into which the measured values are input is connected to these temperature meters T Iq T 2 .

This control device 11 controls each of the dampers 8.9 to indicate a temperature lower than the thermometer T or thermometer T+ with a constant difference.
．． 10 is controlled to open and close as follows. In other words, ■The temperature of T decreases, so the temperatures of T and T2,
If the difference becomes larger than the set value, the flow rate control damper IO provided in the main exhaust line 2 is adjusted in the direction of opening to reduce the flow rate of the exhaust gas flowing into the preheating chamber 7, thereby reducing the temperature rise of T. Measure.

■If the temperature of T2 rises and the temperature difference between T1 and T2 becomes smaller than the set value, adjust the flow rate control damper 10 in the closing direction to increase the flow rate of exhaust gas flowing into the preheating chamber 7, Measure the temperature drop of T.

■If the temperature T1 of the exhaust gas from the furnace, which is the heat source for preheating, increases or decreases, the temperature of T2 will increase or decrease accordingly, but the flow to the preheating chamber 7 can be adjusted in the same way by adjusting the opening degree of the flow rate control damper 10. The exhaust gas flow rate is increased or decreased to control the temperature difference to a set value.

■If the temperature of T1 or T2 falls below the preheating operation lower limit temperature, dampers 8 and 9 on the back of the scrap preheating chamber 7 are installed to prevent odor pollution due to a decrease in odor thermal decomposition ability. Close and interrupt preheating.

The set value of the temperature difference between the above thermometers T1 and T, and the set value of the lower limit temperature of the preheating operation are determined by the degree of mixing of odor components, the flow rate of exhaust gas from the furnace I, the height of the chimney, etc. This is determined by the degree of dilution and diffusion effect, etc.

As described above, according to this embodiment, the temperature of the exhaust gas from the furnace 1 and the temperature of the exhaust gas after the exhaust gas after scrap preheating and the exhaust gas flowing through the main exhaust gas line 2 are combined are determined by the respective thermometers TI and T2. is measured, and the control device 11 controls the opening and closing of the flow rate control damper 10 so as to indicate a temperature that is lower than the thermometer T or thermometer T1 by a certain difference. Therefore, depending on the temperature of the exhaust gas from the furnace l,
The exhaust gas from the scrap preheating chamber 7 containing odor components is sufficiently thermally decomposed or diluted by the exhaust gas flowing through the main exhaust gas line 2, thereby making it possible to efficiently preheat the scrap without causing odor pollution. Become.

FIG. 2 is a diagram showing an embodiment of the pond of the present invention.

In this embodiment, instead of the above-described embodiments, the branch point and the confluence point of the secondary hot gas line 20 are placed in opposite positions, and no damper is provided on the main exhaust line 2 side.

Note that this line 20 is downstream of the preheating gas line 20.
A suction fan 21 is provided to create a flow of exhaust gas. This suction fan 21 is connected to the control device 11.

In this embodiment as well, each thermometer T
The control device 11 controls the flow rate of the exhaust gas flowing into the preheating chamber 7 by adjusting the rotation speed of the suction fan 2I so that the difference between the measured values indicated by 1 and T becomes constant as described above, and the odor components are combined. It is reasonably thermally decomposed and diluted by the exhaust gas at the point.

Furthermore, since this confluence point is close to the furnace 1, the exhaust gas there remains at a high temperature with no heat loss.

Therefore, there is an advantage that the ability to thermally decompose odor components is even higher.

[Effects of the Invention] As explained above, according to the method of operating the scrap preheating equipment using furnace exhaust gas of the present invention, the temperature of the exhaust gas from the furnace, the exhaust gas after scrap preheating, and the exhaust gas flowing through the main exhaust line are combined. Since the flow rate of the preheated gas is adjusted so that the difference between the temperature and the temperature of the subsequent gas is constant, the thermal energy of the exhaust gas from the high temperature range to the low temperature range can be efficiently recovered without causing odor pollution. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of one embodiment of equipment suitable for implementing the present invention, and FIG. 2 is a system diagram of another embodiment. ■・・・Scrap melting furnace (furnace), 2・・・・・・
Main exhaust line, 5...Chimney (atmospheric radiator), 6
．． 20... Preheating gas line, 7... Scrap preheating chamber, 8.9.10... Damper, 11...
・Control device, T1, T, ... thermometer.

Claims (1)

[Claims] A main exhaust line that leads furnace exhaust gas to an atmospheric diffuser, a preheating gas line that leads the furnace exhaust gas to a scrap preheating chamber and joins the exhaust gas after scrap preheating to the main exhaust line, and a furnace exhaust gas that leads to the scrap preheating chamber. In the scrap preheating equipment using furnace exhaust gas, which is equipped with a preheating gas flow rate adjustment device that adjusts the amount of so that the difference between
A method for operating a scrap preheating facility using furnace exhaust gas, the method comprising adjusting the flow rate of the preheating gas.