JPS5810670B2 - Atmosphere heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiant tube type atmosphere heating furnace.

More specifically, in a radiant tube type furnace, brazing,
This is an atmospheric heating furnace used for heat treatments such as gas nitrocarburizing, carburizing, annealing, and standardization, and it collects and refines the N2 contained in the burnup gas of the heating burner using fuel at a predetermined air-fuel ratio. It is used as part of the furnace atmosphere gas,
This article relates to an atmosphere heating furnace that saves resources and makes effective use of gas.

When performing heat treatments such as brazing, gas nitrocarburizing, gas carburizing, annealing, and standardization on iron-based parts, a heat source for heating the iron-based parts to the treatment temperature and oxidation of the workpiece during heating are required. , a protective atmosphere gas to prevent decarburization, or a carrier gas when performing gas carburizing or gas nitrocarburizing.

Therefore, electric power and various fuels are required as heating sources, and at the same time, simple gases or various converted gases are required as protective atmosphere gases.

A list of heating sources, ie, heating energy, and protective atmosphere gas used in this heat treatment is as follows.

Using electricity as a heating source for the above heat treatment,
Efficiency loss during energy conversion is significant, and heat treatment using gas heating only recovers part of the heat from the waste gas, but most of it is released into the atmosphere. Currently, metamorphosed gas is used in production.

In addition to fuel gas, endothermic converted gas requires additional electricity in the manufacturing process, and exothermic gas wastes thermal energy generated in the manufacturing process.

The present inventors have devised the present invention in order to improve the above-mentioned energy loss of conventional atmosphere heating furnaces.

An object of the present invention is to burn fuel, which is a mixture of air and fuel gas at a predetermined ratio, in a heating burner in a radiant tube type atmosphere heating furnace, and to reduce the amount of N contained in the combustion waste gas.
To provide an atmosphere heating furnace which purifies and recovers 2, effectively utilizes energy, saves energy, and is advantageous in terms of saving resources.

Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a vertical side view of the atmosphere heating furnace, and FIG. 2 shows a front view thereof.

The furnace 1 includes a furnace body 3 made of a refractory material surrounded by a frame 2, and on a floor member 4 of the furnace body 3, a rail 5 for placing and transporting a workpiece W is provided.

Recesses 6, 6 are provided on the left and right sides of the floor member 4, into which the U-shaped bent portions 7a of the radiant tubes 7.7 face, and the radiant tubes 7.7 are arranged in pairs on the left and right sides of the furnace body 3. In the illustrated example, a plurality of them are provided vertically in the front-rear direction.

As is known, the radiant tube 7.7 is made of a cylindrical body made of refractory material or heat-resistant special metal, which is bent into a U shape, and both ends 7b and 7c are connected to the furnace body 3 and the ceiling 3a, 2a of the frame 2. 7c is used as a discharge port.

On the other hand, 7b is an inlet portion, and heating burners 8 are installed in this portion, and a mixture of air and fuel gas is supplied to the burners 7 via a pipe 9.

Radiant tube 7... fuel exhaust gas outlet lower c.
... are connected and merged by a pipe body 10, and the pipe bodies 10 are branched outside the furnace, and one branch path 10a is connected to the flue, and the other branch path 10b is connected to the flue.
This is extended, a compressor 11 is interposed in the conduit 10b, and a cooler 12 is connected downstream of the compressor 11 so that N20 can be removed.

An adsorption tower 13 for the purpose of removing CO2 is connected downstream of this cooler 12, and a tank 14 is connected downstream of this,
Tank 14 is connected to conduit 15 and end 15 of conduit 15
A is connected to and faces the processing chamber S of the furnace 1, and a flow meter 16 for controlling the flow rate of N2 is interposed in the pipe line 15.

A furnace air sensor 17 faces the ceiling of the furnace 1, and the sensor 17 transmits information to the gas analyzer 18. A hydrocarbon gas supply port 19 is provided on the ceiling of the furnace 1, and a conduit 20 for this is provided. is connected to a gas source via a control valve 21.

Then, it is controlled by the analyzer 18 of the control valve 21, and is opened and closed as necessary to supply gas into the chamber S.

In the above, a mixture of hydrocarbon gas such as propane gas and air is used as the fuel to be supplied to the burner 8, and this is combusted, and the combustion gas is passed through the radiant tube, and the radiant heat of this is used to heat-treated.

Then, atmospheric gas according to the process is introduced into the chamber S,
For example, in gas nitrocarburizing treatment, a mixture of 0 endothermic modified gas and ammonia gas (NH3), a mixture of 0 exothermic modified gas, methanol decomposition gas, and ammonia gas (NH3), etc. are used as the processing gas in the furnace. .

The combustion waste gas passes through the radiant tube 7 and enters the pipe body 10.
The passage in the pipe body 10 is suctioned by the compressor 11, and the waste gas is discharged through the flue and led to the cooler 12 through the branch pipe 10b, where it is converted into N20
will be removed.

Then, CO2 is removed in the adsorption tower of the next stage, and the gas is purified into a gas containing N2 as its main component.The gas is stored in a tank 14, the flow is controlled by a flow meter 16, and the required amount is controlled through a pipe 15. It is put into the furnace S through the supply port 15a.

That is, the combustion waste gas is recovered and purified, and only N2 is introduced into the furnace chamber S.

By the way, a mixture of fuel gas and air is supplied to the burner 8 from the fuel gas supply device 22 and the air supply device 23 while the flow rate is controlled, and is used for combustion as a mixture. However, in the present invention, the mixture of fuel gas and air is The air-fuel ratio is set slightly lower than the stoichiometric air-fuel ratio to minimize or eliminate residual oxygen in the exhaust gas.

The relationship between the refined components of waste gas, air, and fuel in the air-fuel ratio when propane gas is used as the fuel gas is shown below.

In this way, with the above air-fuel ratio, 02 can be ignored because it is possible to keep the oxygen potential low by adding hydrocarbon gas into the furnace according to the signal sent from the furnace air sensor installed in the furnace. N2 occupies most of the amount, which is then injected into the furnace to be used as a protective atmosphere gas or processing gas.

Although gas nitrocarburizing has been taken as an example above, it goes without saying that it can also be used in furnace brazing, gas carburizing, annealing, standard treatments, and by collecting and purifying N2 from waste gas and introducing it as an atmosphere.

As described above, according to the present invention, N2 is recovered and purified from the waste gas produced by burning fuel with a constant air-fuel ratio in a combustion burner, and this is used as the atmosphere in the furnace and as a processing gas.
Waste gas, which in the past was only partially used for the purpose of heat recovery, can be effectively used as an atmosphere and processing gas, and in the end, it is the same as refining N2 gas by burning fuel, which saves thermal energy. While being taken out, this is used as a heating source for the object to be treated, and at the same time, the N2 gas is purified, making it possible to promote effective use of energy and save resources, which has enormous practical effects.

The above requires only the installation of radiant tube waste gas piping and accessory equipment, making it possible to provide an energy-saving and resource-saving atmosphere heating furnace relatively easily, and effectively reducing total operating costs. can.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional front view of the furnace, and FIG. 2 is a longitudinal sectional side view thereof. In the drawing, 1 is a furnace, 7 is a radiant tube, 10 to 16
is a N2 recovery, purification and supply system.

Claims (1)

[Claims] 1. In a radiant tube type atmosphere heating furnace, a device is installed to recover and purify N2 contained in the burnup gas of the heating burner of the radiant tube, and this device and the inside of the furnace where N2 is used as a protective atmosphere gas in the furnace are installed. An atmosphere heating furnace characterized in that these are connected in communication through a N2 supply pipe.