6500×2300×2000mm Gas fired Car Bottom Furnace
Bogie Hearth Annealing 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 car bottom furnace body steel structure is made from 12-18#
U steel and 4-14mm 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. The furnace door edge is made of 14mm
heat-resistant
steel casting material in several pieces.
2.2 lining
The lining material is 1260 type 1000℃ high purity refractory fiber
compacted block. 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 car bottom furnace manufacturer 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 10
pieces
of wheels. Each wheel diameter is 300mm.
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 trolley type heat treatment furnace is driven by motor reducer
gear
driving mechanism. The moving speed of the bogie is 6-8m/min.
2.4 Sealing System
Sealing between the furnace door and the furnace body is through
the
electric push-rod. Sealing between the bogie and the real wall is
through
the spring mechanism. When the bogie moves inside the hearth, the
bogie
contacts tightly with the rear wall to prevent heat loss.
Bogie side sealing method
2.5 furnace door
The bogie hearth furnace for quenching 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
bottom part
is made of 20mm RQTSi5 heat resistant casting material. The furnace
door
has the feature of simple, practical, reliable and convenient
maintenance.
The furnace door is fixed on the bogie.
The soft contact sealing structure is arranged between furnace door
and
furnace lining. The fiber sealing block around the furnace door
protrudes
out of the furnace door inner lining. The furnace door frame is
equipped
with thick steel plate. When the furnace door is closed, the
electric push
rod is used to compress the furnace door. In this way, the sealing
fiber
block fully contact with the steel plate for sealing. When the
furnace door
is opened and closed, the gap between the furnace door and the
steel plate
of the furnace door frame is 100mm to ensure the stable movement of
the
furnace door.
2.6 burning system
The burning system is comprised of AGS 125HB 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 bogie hearth furnace for annealing 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
cold 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 stress relieving car bottom furnace has a complete fault
detection, alarm,
diagnosis, and safety protection system. On the control cabinet
there is an alarm lamp.
3.Main Technical Parameters
| No. | Item | Technical Parameters |
| 1 | Fuel | Natural gas |
| 2 | fuel gases calorific value Gas pressure before furnace | 8600kcaL/Nm3 0.05-0.1Mpa |
| 3 | Rated temperature | 1000℃ |
| 4 | Normal used temperature | 650℃-700℃ |
| 5 | Heating zone | 6 zones |
| 6 | Surface temperature of furnace body | ≤50℃+ room temperature |
| 7 | | ≤55℃+ room temperature |
| 8 | Loading capacity | 20 ton/furnace |
| 9 | Temperature measurement accuracy | ±2℃ |
| 10 | Burner gas consumption | 138Nm3/h |
| 11 | Gas pipe total requirement | 193Nm3/h |
| 12 | Air consumption | 3328Nm3/h |
| 13 | Power of bogie motor | 7.5KW, 1 set |
| 14 | Power of combustion fan | Approx 11KW |
| 15 | Temperature uniformity | ≤±10℃ |
| 16 | Effective working size | 6500×2300×2000mm(L×W×H) (excludes the base support) |
| 17 | Hearth size | 6900×2600×2600mm(L×W×H) (includes the base support) |
| 18 | Quantity and model of burner | 6pcs, 320KW/hour, AGS 125HB burner |
| 19 | Temperature control method | PID regulation + PLC touch screen control (Siemens), manual control |
| 20 | Max temperature rise speed | 180℃/h at full capacity |
| 21 | Temperature record | K type thermal couple |
| 22 | Bogie move speed | 6-8m/min |
| 23 | Furnace lining | high quality heat-resistant fiber |
| 24 | Furnace door opening method | Electric up and down, speed 6-8m/min |
| 25 | Furnace door sealing method | Sealed by 4 sets electric push-rod |
| 26 | Bogie power supply | Coil of cable |
| 27 | Bogie driving power | motor reducer gear driving mechanism |
| 28 | Furnace door sealing method | Sealed by 4 sets electric push-rod |
| 29 | Sealing method between furnace side and bogie | Sealed by 4 sets electric push-rod |
| 30 | Sealing method between furnace back and bogie | Sealed by a spring compacted fiber block |
| 31 | Consumption index | Heat efficiency at full load η≥40% |
