8000×3500×2300mm Gas fired Bogie Hearth Furnace
1.Application
The gas fired bogie hearth furnace is mainly used for heat
treatment
of metal parts.
2.Structural Introduction
2.1 furnace body
The bogie hearth furnace body steel structure is made from 12#
-18#U
steel and steel plates. The side pillar and back pillars are made
from sectional
steel, and are reinforced with sectional steel bracings. The
external wall of the
furnace is painted with 2 layers of primers, and 2 layers of
coating paint. The
key part of the furnace is painted with heat resistant paint.
2.2 lining
The bogie hearth furnace manufacturer lining adopts 1360 high
aluminum refractory
fiber folding block with long-term service temperature of 1100℃.
The total thickness
of furnace lining is 320mm. This refractory lining structure has
the advantages of low
heat conductivity, strong anti-shock capacity, and anti-erosion.
Aluminum silicate fiber
compression block with thickness of 300mm is designed as the high
temperature
refractory layer.
2.3 bogie
The bogie hearth furnace price is comprised of heat preservation
material, bogie frame
and moving mechanism. The refractory layer is divided into 3
sub-layers, i.e., 1st top
high-alumina brick layer, and 2nd and 3rd layer with both light
clay bricks.
The bogie framework is made of 20# U-steel and 20# I-steel. The
edges of the bogie
are made of 20mm I-steel. The bogie is equipped with 10pieces of
wheels. Each wheel
diameter is 350mm.
The heat preservation material is divided into 3 layers, the top
layer being high-alumina
bricks, and 2nd and 3rd layer being both light clay bricks.
The bogie is driven by motor reducer gear driving mechanism. The
moving speed of the
bogie is 6-8m/min.
2.4 Sealing System
The sealing between the door and the body of the furnace and the
trolley is more critical.
The sealing between the furnace door and the furnace body uses the
electric push rod.
This makes the whole door tightly sealed up, so as to ensure that
the heat inside the furnace
does not leak from the door
2.5 furnace door
The bogie hearth furnace design door is comprised of all-fiber
lining and steel structure shell.
The door is built with silicate aluminum compressed fiber blocks
same as that for the furnace
body. The shell is a welding structure from sectional steel and
steel plates. The furnace door
has the feature of simple, practical, reliable and convenient
maintenance. The furnace door
is fixed on the bogie.
Soft hard contact sealing structure is set between the furnace door
and the furnace lining.
When the furnace door is closed, the electric push rod mechanism is
used to compress the
furnace door to make the sealing fiber block contact with the
furnace mouth. When the
furnace door is opened, pull the electric push rod pressing
mechanism to separate the furnace
door from the furnace mouth frame steel plate with a clearance of
100 mm, so as to ensure
that the furnace door does not scratch or touch with the furnace
lining and trolley during the
lifting process. And ensure smooth movement when opening and
closing.
2.6 burning system
The burning system is comprised of Krom high speed burners,
proportional combustion control
system, gas valve, solenoid valve, burner control box, etc. The
burner has the functions of
automatic ignition, flame detection, and flame out alarm. The
burner controller receives the
control signal of the temperature controller and controls the
large/small fire status of the burner
based on the heat load requirement so that adjustment of the
temperature is realized.
A) The burner has adjustment function and the adjustment rate is
1:10 and the air efficient
is 1-5. The burner could meet the temperature uniformity of the
heat treatment process and
effectively control the air-gas ratio so that the fuel consumption
is reduced.
B) When the furnace is working, the burning system could
automatically cut off the electrical
gas valve and general safety valve in the case of power failure
detected by the alarm system.
When the power supply is resumed, the worker needs to open the
safety valve and restart the
ignition program after purging function is confirmed.
The burner is set with a proportional control unit which enables
alternative burning of large
and small fire, fire out alarm, and re-ignition. The burner control
box has both manual and
self-run modes available. The worker could operate in front of the
furnace or in the control
cabinet.
C) The pipe before the burner is equipped with solenoid valve, and
manual gas adjustment
valve. The valve system could realize an ideal gas/air supply ratio
so that the air excess
efficient is lower than 1.1.
2.6.1 air system
The air piping system is comprised of high pressure centrifugal
fan, automatic regulation valve,
pressure gauge and pipes. The air volume is to match the gas
volume, and the air excess rate
is lower than 1.20.
2.6.2 gas supply system
The general gas supply pipe is equipped with a pressure regulation
device (equipped with a
filter), a low pressure switch and a pressure gauge. For the sake
of safety there is one fast
cut-off valve on the general gas pipe.
2.6.3 discharge system
The car bottom furnace supplier takes direct fume discharge method.
The fume is directly
vented out through the flue pipe to the atmosphere. The fume
conducts heat exchange with
the heat exchange before emission to the atmosphere.
2.6.4 Furnace pressure control system
The pressure on the working table in the furnace is kept at (+15
Pa), which is very beneficial
to the uniformity of temperature and the thermal efficiency of the
furnace. When the pressure
in the furnace is too high, the hot air in the furnace will escape
from the furnace mouth and other
unsealed places, resulting in the heat loss caused by the escape of
the flue gas; because the
high temperature flue gas in the furnace escapes to the outside of
the furnace, it will affect the
door, the side seal and burner of the furnace directly, which is
related to the overall service life
of the furnace; when the pressure in the furnace is too low, a
large number of cold air outside
the furnace will be absorbed into the furnace, as well. The heat
loss of off-furnace flue gas is
increased. The low pressure of the furnace causes the diffusion of
cold air outside the furnace
into the furnace, and secondary combustion is formed due to the
entry of oxygen-containing
old air, which has adverse effects on the uniformity of furnace
temperature, oxidation of workpiece
and thermal efficiency of the furnace. Therefore, effective
technical measures must be taken to
control the furnace pressure with full automatic control. Our
method is to control the furnace
pressure effectively by using a system consisting of pressure
taking device, pressure transmitter,
intelligent instrument and so on. The furnace pressure is
controlled in the optimum state (the
surface of the trolley is in a slightly positive pressure). At this
time, the exhaust gas is in a dynamic
equilibrium state, which can not only ensure that the furnace gas
does not overflow, but also
ensure that the cold air outside the furnace is not sucked into the
furnace, so as to save energy
and maximize the efficiency of the furnace.
2.6.5 Heat exchange and flue system
A flue is set at the back of the furnace, and it is carried out
with the heat exchanger (according
to the national standard GB3486-83). The flue leads to the outside
of the factory building. The
cold air is exchanged with the heat exchanger to preheat the
combustion-supporting air before
entering the burner, so as to improve the heat efficiency of the
furnace.
Heat exchangers and flue gas exhaust pipes are insulated by
internal insulation (using fiber
castables) to ensure the service life of heat exchangers and flues.
2.6.6 fault detection and alarm system
The wholesale car bottm furnace has a complete fault detection,
alarm, diagnosis, and safety
protection system. On the control cabinet there is an alarm lamp.
2.7 control system
control system has the following parts: Ⅰ. Burning control system;
Ⅱ. Electrical power control
system; Ⅲ.temperature control system .
Measures taken for burning control system:
K type thermal couple gets mV signal and sends it to temperature
PID controller (SHIMADEN
brand). The temperature controller calculates the signal and
outputs 4-20mADC control signal
to the electrical actuator. The actuator further sends a signal to
the burner controller after
calculation.
The burner controller is mainly responsible for ignition and flame
detection. When the terminal
receives the ignition signal, the burner controller carries out
flame simulation and self testing stage.
If during this simulation and self-test stage the burner couldn’t
detect the flame signal. The burner
controller would open the gas solenoid valve and convert the
voltage 220VAC to 5KV for ignition
(ignition time about 3S). If the burner detects the flame signal in
the safe time period (about 8S),
the yellow indication light of the burner would be on (ignition
successful). If the burner couldn’t
detect the flame signal, the red light would be on (ignition
failed). The burner controller is locked
and the gas solenoid valve is cut off.
B) electrical power control system: The electrical power control
system mainly controls ON/OFF
of the fan, and IN/OUT of the bogie.
C) temperature control and record system
The system has the functions of temperature setup, control and
digital display. And also there is an
audible and visual alarm at over-temperature situations.
Temperature control zone arrangement
A:temperature control system
The furnace is equipped with 4 thermal couple and an intelligent
temperature controller. The furnace
is controlled by 4 zones.
B: instrument temperature control
The temperature controller allows setup of heating time, holding
time, and cooling time. It has
self-tuning and self-adjustment function, and displays SV and PV.
3.Main Technical Parameters
| No. | Item | Technical Parameters |
| 1 | Fuel | Natural gas |
| 2 | fuel gases calorific value Gas pressure before furnace | 8600kcal/Nm3 20-70Kpa |
| 3 | Rated temperature | 1100℃ |
| 4 | Normal used temperature | 450-850℃ |
| 5 | Furnace body surface temperature | ≤45℃+room temperature |
| 6 | Max temperature rise speed | 0-150℃/h |
| 7 | Heating zone | 4 zones |
| 8 | Temperature measurement accuracy | ≤±1℃ |
| 9 | Full power gas consumption | 235m3/h |
| 10 | Gas pipe line demand | 270Nm3/h |
| 11 | Air consumption | 3328m3/h |
| 12 | Temperature uniformity | ≤±10℃ |
| 13 | Effective working size | 8000*3500*2300mm |
| 14 | Furnace hearth size | 8400*3900*2800mm ( including the height of support iron) |
| 15 | bogie max loading capacity | ≤45000kg |
| 16 | Quantity and model of burner | 8pcs, AGS 125HB, 320kw/h |
| 17 | Temperature control method | Intelligence temperature controller, touch screen, pulse
combustion, Siemens PLC and manual control; remote control of
furnace door lifting and bogie moving. |
| 18 | Temperature record | K type thermal couple |
| 19 | Furnace lining | heat resistant all fiber structure |
| 20 | Power supply | 380V, 3phase, 50Hz |
| 21 | Furnace door opening method | By electric hoist, Speed 6-8m/min |
| 22 | Bogie walking speed | 6-8m/min |
| 23 | Bogie motor power | 5.5KW*2sets |
| 24 | Combustion fan power | 11kw |
| 25 | Consumption index | Heat efficiency at full load η≥40% |
| 26 | Furnace door surface temperature | ≤50℃+room temperature |
