JPS5893825A - Quaternary type continuous annealing device - Google Patents

Abstract

PURPOSE:To protect the various devices and apparatus of annealing installations and to utilize the waste gases of combustion to the max. extent by controlling the temp. of hot water and the temp. of the waste gases on the outlet side of a hot water vessel at adequate values and maintaining the pressure balance in a preheating furnace at an adequate value. CONSTITUTION:The waste gases admitted from an annealing furnace 4 into a preheating furnace 3 are sucked with a gas releasing duct 7, and are subjected to heat exchanging in an air recuperator 10 then to heat exchanging with water in a hot water vessel 14. Temp. controlling dampers 15, 16 are disposed to the inlet side of the water heater 14 and a bypass duct 13, and the temp. of the hot water and the temp. of the waste gases are detected with thermocouples 17, 17'. The openings of the dampers 15, 16 are controlled by a temp. indicating controller, whereby the acid condensation of the waste gases is prevented. The waste gases which are reduced of temp. by heat exchanging with water in the vessel 14 are discharged through a gas releasing fan 21 via a pressure regulating damper 18. In the stage of passing through the damper, the pressure in the furnace 3 is controlled by the damper 18, whereby the rate of effective utilization of the waste gases is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion exhaust gas exhaust system for a fire-placed catenary type continuous annealing furnace in which a preheating furnace is installed on the inlet side of the annealing furnace. The combustion air recuperator, water heater, furnace pressure adjustment damper, and exhaust gas exhaust fan are installed in the exhaust duct in order from the preheating furnace side to control the pressure inside the preheating furnaces to a predetermined pressure. It is possible to maintain the pressure balance within the furnace at an appropriate value, improve the effective utilization rate of exhaust gas, and achieve a thorough energy saving effect. In addition, by installing a bypass circuit in the water heater, by installing a temperature control damper on the bypass duct and the water heater inlet side, the hot water temperature and the exhaust gas temperature on the water heater outlet side can be controlled to appropriate values to prevent acid dew condensation in the exhaust gas. This is a catenary-type continuous annealing device that is designed to prevent heat loss and easily protect exhaust ducts, exhaust fans, etc.

Conventionally, for example, the thermal efficiency of a divided catenary type annealing furnace for stainless steel is less than 40% (383,700 to 0a1/l), and even if a monolithic furnace with a preheating furnace is adopted, the furnace thermal efficiency 'KA' is 50% or less. % (306p 900 ””/
l) It was slightly torn. When the combustion air recuperator according to the present invention is installed and the air preheating temperature is 430°C, and it is used at 400°C in front of the burner, the furnace thermal efficiency is 64.
．． 9% (236,500kcal/1) K improvement L,
Furthermore, if a water heater is installed on the downstream side of the -1-Year-L'l''-peller to save energy, for example, if water at 43°C is heated to 70°C at a water flow rate of 14.4♂/h, the water heater NiiQ 38.
As a result of installing this water heater in an annealing furnace that has the ability to heat 34.26T/H stainless steel sheets from 20"C to 1000℃, the furnace has an energy saving effect of 7 x 10" kcal/h. The overall efficiency was 69.7%, achieving significant energy savings.

However, the temperature of the combustion exhaust gas at this time is 740°C on the air recuperator inlet side and 370°C on the air recuperator outlet side, and drops to 360°C on the water heater inlet side and 210°C on the outlet side. It is discharged at 200℃. This exhaust gas used Machito heavy oil as fuel, so depending on the sulfur content in the fuel, the exhaust gas temperature could vary from 180℃ to 180℃ due to changes in operating conditions.
When the temperature drops below 50°C, acid condensation occurs, which oxidizes the exhaust duct, stack, exhaust fan, etc. installed on the downstream side of the water heater, causing problems that shorten its life.

In order to solve this problem, the present invention installs temperature control dampers on the water heater inlet side and the water heater bypass duct, and detects the hot water temperature on the water heater outlet side and the exhaust gas temperature on the water heater outlet side with thermocouples. , the control output is increased if the temperature is indicated, and is decreased if it is a -deviation. In addition, the indicator controller (TICA 130) for exhaust gas temperature on the outlet side of the water heater adjusts the exhaust gas temperature to SV.
The control output is compared with the value, and if the deviation is -, the control output is increased, and if the deviation is ten, the control output is decreased. The low output side of the control outputs of both regulators is selected by low selectors (L, S) and connected to the temperature control damper. By adopting a system consisting of two temperature control dampers and a low selector, the operation of each temperature control damper will not interfere with each other (to prevent the hot water temperature from becoming higher than the SV value), and the water heater output It is possible to control the exhaust gas temperature on the side so that it does not fall below the SV value, eliminates the problem of acid dew condensation in the exhaust gas, and enables energy-saving equipment that makes maximum use of the combustion exhaust gas.

Next, an embodiment of a combustion exhaust gas exhaust system for a catenary type continuous annealing apparatus according to the present invention will be described with reference to FIGS. 1 to 6.

Strip 1 includes sealing roll 2 and support roll 5
After passing through the preheating furnace 3 and forming a catenary, it enters the annealing furnace 4. Strip 1 in annealing furnace 4
A burner 6 is installed to heat the strip 1 to a predetermined temperature, and the exhaust gas combusted by the burner 6 flows into the preheating furnace 3 side where the furnace pressure is low, and the strip 1 is heated to a temperature of 200°C to 380°C depending on the combustion exhaust gas.
After being preheated, the exhaust gas is sucked into the exhaust duct 7 and passes through the air recuperator 10. In the air recuperator 10, air is blown to the air recuperator 10 by a combustion air blower 11 in order to preheat the combustion air.
The air is preheated to 50°C to 550°C and the pressure regulating valve 12
After the pressure is controlled by , it is supplied to the burner 6 for the annealing furnace 4 . The air recuperator protection system consists of a thermocouple 9' on the outlet side of the air recuperator that keeps the air at a certain temperature, as shown in Figure 3.
Detect the exhaust gas temperature on the inlet side of the recuperator with thermocouple 9.
Temperature indicating controllers are provided for each controller, and the one with the lower control output signal of both controllers is the low selector (L, S).
is selected and connected to the temperature control valve 8 for protecting the recuperator, and when either the recuperator inlet exhaust gas temperature or the recuperator outlet air temperature reaches the set value, the temperature control valve 8
opens to suck in the atmosphere and protect the air recuperator (you can also use a blower to blow in air without sucking in the atmosphere). For example, in the embodiment of the present invention, the temperature on the exhaust gas outlet side is set at 850° C. in view of the construction cost of the recuperator, and the temperature on the outlet side of the air is set at 550° C. due to the pollution limit (NOx value limit).

Next, the exhaust gas that has been heat exchanged in the air recuperator further enters the water heater 14 and is heat exchanged with water. However, since the continuous annealing furnace of the present invention is a multipurpose heat treatment equipment that processes various heat patterns, it is simply If a method of controlling only the hot water temperature is adopted, the temperature on the exhaust gas outlet side will drop too much, causing the problem described above (
Acid dew condensation was occurring, causing oxidation problems in subsequent equipment.

Therefore, a temperature control damper 15 is installed on the inlet side of the water heater 140, a temperature control damper 16 is installed in the bypass duct 13, the hot water temperature is detected with a thermocouple 17, and the exhaust gas temperature is detected with 17'. Temperature indicating regulators (TICA 131, TICA 130) that increase or decrease the control output as described above
'), when the control output is connected to the temperature control dampers 15 and 16 via the low selector (L, S), the respective dampers 15 and 16 are opened, and the relationship between the S output becomes as shown in Fig. 6. While controlling the hot water temperature, it is possible to prevent acid dew condensation in the exhaust gas. In addition, as a water heater protection system, water is supplied from a cold water tank n to the water heater 14 by a water supply pump 24,
Hot water is sent by the pressure pump 5 to the hot water scrubber and the water washing spray device after pickling, but when the water supply to the water heater 14 stops, a water flow meter n issues an alarm and the temperature control damper 15
The water heater is protected by creating a sequence in which the damper 16 is fully closed and the damper 16 is fully opened.

Next, when the exhaust gas whose temperature has been lowered by heat exchange with water in the water heater passes through the regular damper 18, the pressure inside the preheating furnace is controlled by the damper 18. As shown in Fig. 2, the control flow includes feedback control by detecting the pressure in the preheating furnaces and using a pressure indicating regulator (CPICA 150), as well as feedforward control using the flow rate of fuel burned in the annealing furnace 4. A special valve compensation function has been added to ensure high control range ability, and the pressure detection position of the preheating furnace can be switched using the stock valve 26, improving furnace pressure controllability. There is.

The exhaust gas that has passed through the regular damper 18 is discharged outdoors by the exhaust fan 21.As shown in FIG. The exhaust gas temperature is controlled to a predetermined value of 300°C or less.

As described above, in the present invention, an ultra-energy-saving catenary-type continuous annealing apparatus that protects each device and equipment of the annealing equipment without causing any loss and makes maximum use of combustion exhaust gas has been obtained.

[Brief explanation of drawings]

Figure 1 is the layout of the exhaust gas exhaust system of the catenary type continuous annealing apparatus of the present invention, Figure 2 is the furnace pressure control flow diagram, and Figure 3 is the furnace pressure control flow diagram.
The figure shows the air recuperator protection flow diagram, Figure 4 is the water heater control flow diagram, Figure 5 is the exhaust fan protection flow diagram, and Figure 6 is the opening degree and low selector of the ill temperature control damper on the water heater side. It is a relationship diagram of output. 1... Strip 2... Seal roll 3... Preheating furnace 4... Annealing furnace 5... Support roll 6... Burner 7... Exhaust gas exhaust duct 8... Air recuperator protection Temperature control valve 9.9'
... Temperature control valve thermocouple 10 as above ... Air recuperator 11 ... Combustion air blower 12 ... Combustion air normal control valve 13 ... Bypass duct 14 ... Water heater 15 ...・Temperature adjustment damper 16 in front of water heater...temperature adjustment tuna damper 17.17' for bypass
・・Thermocouple for water heater control 18 ・Furnace pressure adjustment damper 19 ・Temperature control valve for exhaust fan protection ・Thermocouple for temperature control valve 21 ・Exhaust fan 22 ・Cold water Tank...Water flow meter...Water supply pump for water heater 5...Hot water pressure pump 26...Stop valve. n...Hot water tank patent applicant Representative patent attorney Tomoyuki Yabuki (and one other person)

Claims (1)

[Claims] In a direct-fired catenary type continuous annealing furnace in which a preheating furnace 3 is disposed on the inlet side of the annealing furnace 40, an exhaust duct 7 is disposed on the inlet side of the preheating furnace 30, and a Combustion air recuperator 10, water heater 14, exhaust 7 in order
At the same time, a bypass exhaust duct 13 is installed in the exhaust duct 7' that connects the combustion air recuperator 10 and the water heater 14, and the bypass exhaust duct 1
Temperature control dampers 16 and 15 are installed in the exhaust duct 7' on the side of the water heater 14 and the water heater 14, respectively, and the pressure of the preheating furnace is installed in the exhaust duct that connects the water heater 14, the bypass exhaust duct 13, and the exhaust fan 21. A catenary-type continuous annealing apparatus characterized in that an adjustment damper 18 is provided.