Tunnel Kiln for Clay Bricks Firing

Ibrick new technical clay brick tunnel kiln 

tunnel kiln for clay bricks firing 


Productive Technology
The Production Line with Daily Output of 250000pcs Clay Sintering Bricks Technology 
Sintering bricks are produced by using clays as raw materials and adopting two-time setting and baking processes, that is Semi-stiff plastic extruding process; drying in the tunnel drying chamber using single layer process and baking in the tunnel kiln with natural gas.
Main equipments are plate feeder, primary roller crusher, fine pulverizing grinder, double shaft mixer, reversible belt conveyor, multi-buckets excavator, mixing and extruder, double stage vacuum extruding machine, automatic loading and unloading system, tunnel drying chamber, robot hand, tunnel kiln, de-hacking machine.
 
Technical point
Considering Bangladesh raw material's character according to our long period experience, any project must meet follow technical requirement:
a,The material should fully mix when processing, thus to ensure the molding of the green brick and drying uniformity. 
b,The clay material should be fine treated, the biggest particles should be less than 2mm or so. 
c,Molding moisture content must controls under 18%, strictly control the section before critical point when drying and drying cycle is not less than 36 hours. 

Raw material crushing and aging
In the raw material warehouse, loaders will supply raw materials to plate feeders. At the upper part of materials warehouse there are metallic fences so as to prevent masses of raw limestone and sandstone from damaging the equipment. Meanwhile, masses of impurity and some organic parts will be eliminated by man power.
Clay(After de-ironing by the suspension type magnetic separator on the belt conveyor ) will be sent to roll crusher for crushing by plate feeder, and being sent to the high speed fine pulverizing roller by belt conveyor, and then will be sent to the double shaft mixer, water added and mixed uniformly here. The grains will be then dissolved, tempered and plasticized through 72 hours aging so that the shaping performance will be greatly improved, which will greatly improve the formability of the brick.
 
Molding
The double stage vacuum extruder will squeeze material to clean-surface and solid-inside columns, which will be cut into the required adobes by automatic segment cutter and automatic cutter, and then will be loaded on the drying car by automatic up-loading system and transported to drying chamber by machines.



Drying and firing
Drying and firing will adopt two times stacking=firing process. Drying chamber adopts 2 groups (each group with 5pcs) of tunnel dryer with inner width of 4.66meters. The heating source is cooling heat of the dried-products and high temperature smoke heat from the tunnel kiln. The smoking air feeding temperature and air volume will be adjusted through the drying air-adjustment-system, so as to ensure the drying quality of green bricks. Well-dried green bricks will be unloaded from drying cart by undercarriage system and re-stacking on the transfer belt in the molding section automatically, then the well-dried bricks will be stacked on the kiln cart and sent to front end of tunnel kiln by ferry car.  
Tunnel kiln adopt 2 set of large section with inner width of 6.9meter, it is designed as a flat ceiling structure. It is adopt external firing and baking process with the main heat source of natural gas(80%) and assist heat of coal dust mixed into raw material(20%), this kiln is suitable for firing products with 1300-1500KJ/Kg.
Tunnel kiln has smoke-releasing system, recycling system, waste-heat recovery system, cooling system and pressure balancing system. This kiln has following features: large section, high yield, small section temperature difference, good heat preservation effect. Meanwhile, the kiln auto-control system is equipped to ensure the baking heat parameters are stable, so the firing quality is guaranteed.
The products are Discharged from the kiln car by de-hacking machine and taken to the products yard by folk lift trucks.

Process mechanical equipment selection
Raw material processing
Brick making  raw material processing have a direct relation about the good or bad of molding performance and quality of products, so it is not only requires the advanced performance of the equipment itself but also for reliable running when use the equipment.
 
Molding
Extruding machines is the key equipment among the whole production line, its performance can meet the requirement as follows:
a,They can meet the need of different specification and hole shapes of the brick
b,The vacuum degree is -0.092Mpa, the extruding pressure is 2.5Mpa
c,The hourly output per set is more than 15000 pcs of bricks
 
Key technology index
1).Clay material water content                                                   ≤8%  
2).Feeding material granularity size for primary crushing         ≤210mm
3).The material granularity size after fine pulverizing               ≤2mm 
4). Molding moisture content                                                    ≤16~18%
5). Extruding pressure                                                                2.3~2.5MPa 
6). Vacuum degree                                                                      ≤-0.092MPa  
7). Drying yield                                                                          95%
8). Firing yield                                                                            96%
9). Drying period                                                                       40hr
10). Firing cycle                                                                          53hr
 
Tunnel kiln system
The technology choose flat celling tunnel kiln. The tunnel kiln has complete system of 
smoke discharging, cooling, heat releasing, pressure balancing under the kiln car, running and test system. Baking curve inside of the kiln will be more reasonable through the adjustment of those system.
There are entrance and exit doors at both ends of the tunnel kiln. At the entrance side, there is a preparatory room, and a cut-off door between the preparatory room and the kiln joint zone. Thus it effectively avoid entering the cold air and ensure the baking system of the kiln.
 
Tunnel kiln structure
Red brick is laid for the pre-heating zone and cooling zone where the temperature is below 200ºC. The rest part, baking zone and the innermost wall of insulating zone are adopt clay refractory brick. The clay insulting bricks will be used for laying the insulting area. Meanwhile, refractory fabric felt (for the relative part of temperature curve above 600 Celsius) or rock wool felt will be used for stuffing and red bricks will be laid on the external wall.
Kiln roof structure: One kiln car space remained in low temperature zone on both side, which adopt cast-in concrete top slab. For other position, clay material plate, hanger plate through davit hang under H type steel beam by cast product. Both sides wall body support the main beam's weight. High aluminum cotton ,refractory fibro felt, rock wool felt, rock wool board are put on the refractory hander plate, which compose complex insulation layer. The crack between the top plate will be impacted by high aluminum fiber .High temperature binder is being filled up to the gap between the boards, and is being painted on the upside of the insulating layer, thus to ensure the material's insensitivity and structure's durability.



Working System 
Ibrick new technical clay brick tunnel kiln 

tunnel kiln for clay bricks firing 
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