Tunnel Kiln for Clay Solid Brick and Hollow Block Making

Ibrick Tunnel kiln for clay solid brick and hollow block making 

The Production Line is with Yearly Output of 30 Million Clay Sintering Bricks
Working SystemProductive 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 Process and Baking in the Tunnel Kiln Process.
Main equipment has box feeder, primary roller crusher, fine pulverizing grinder, double shaft mixer, reversible belt conveyor, multi-buckets excavator, mixing and extruder, double stage vacuum extruding machine, tunnel dryer, tunnel kiln.

Technological Description
For this production line, raw material is clay, finished products is your brick. Big quantity raw material is required to be treated.
In raw materials 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. Raw material will be sent to primary roller crusher and fine pulverizing grinder in turn. Coal powder will be added here and mixing with water.
In order to increase the warehouse capacity and improve the ageing effect, the inclined-shaft type ageing warehouse is adopted. Thus the raw material is being distributed on the top by movable belt conveyor, aged raw material will be unloaded from side edge by multi bucket excavator.
General process is adopting semi-stiff plastic extruding process for brick molding, tunnel dryer for drying and tunnel kiln for firing.
This is advanced and practical technology, which can meet the production requirement.

Raw material preparation
Before raw material being sent into raw material stock, masses of impurity and some organic parts will be eliminated by man power. In raw material stock, clay will be sent to box feeder by loader, and being sent to roller crusher and fine pulverizing grinder.  Crushed clay with grain smaller than 3mm, and will be sent to double shaft mixer, water added and mixed, here the material moisture content reach to 13-14%. Thus the raw material is being sent to aging room by warehouse reversible belt conveyor.

Raw material aging process
Material will be aged in the aging room, thus, water inside will be diffused and evenly divided, the grains will be further dissolved, tempered and plasticized  so that the shaping performance will be greatly improved.
Aged material will be unloaded on belt conveyor by multi-bucket excavator, then being sent to box feeder in molding process. Box feeder with big stock capacity, which can guarantee the mixer extruder and extruding machine's feeding requirement, stabilize the green brick adobe moisture content and molding process. Meanwhile, this gives buffering time for multi-bucket excavator to change the working position.  This also water down the synchronization requirement for former process. The aged material moisture content will reduce 1%.

Molding process
Aged clay material first will be sent to mixing extruder for water replenishing and mixing, then the double stage vacuum extruder will squeeze material to clean-surface and solid-inside columns, which will be cut into the required adobes by cutter.
Extruding machine is the key equipment among the whole production line, its performance are required as follows:
1) They can meet the need of different specification and hole shapes of the brick
2) The vacuum degree is -0.092Mpa, the extruding pressure is 1.5-2.0Mpa.
3) The hourly output per set is more than 8000pcs bricks.
 
Drying and firing
Drying and firing will adopt twice setting & firing process. Drying chamber adopts new type tunnel dryer with inner width of 2.4meter. Whole production line adopts 7 lines of double-rail tunnel dryers. The heating source is residual/waste heat from the tunnel kiln.

The smoking air feeding temperature and air volume will be adjusted through the air-adjustment-system, so as to ensure the drying quality of green bricks. Well-dried green bricks will be unloaded from drying cart and re-stacking on the kiln cart manually.

Tunnel kiln adopt large section with inner width of 4.6meter, it is designed as a flat ceiling structure with refractory bricks. Considering bricks can not have black center and patterns, the firing fuel source is major by inner-mixing-coal, outer-casting-coal as replenish, the heat should meet the firing technology requirement. This kiln is suitable for firing products with 1600-2600KJ/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.

Thermal Engineering Equipment
Determination of thermal engineering equipment for drying and firing
According to raw material and technology process, the thermal engineering equipment for drying and firing process adopts 1 group of small section tunnel dryer & 1 piece of big section tunnel kiln.

The feature of this design is low investment, flexible production, make good use of the waste heat from tunnel kiln, make full use of the tunnel kiln advantage. At the same time, it can reduce the consumption of energy. In addition, the small tunnel dryer and kiln with high heat use efficiency, big capacity, advanced technology, thus enabling the investor to lower their production cost, to improve the product quality and to enhance their economic efficiency.

Technological parameters for Drying and Firing
Output index
The production scale which this project determines is to produce 30 million pieces per year of sintering common bricks. Given 10% of the aggregate wastes of the drying and baking, the annual actual production output will reach 33 million pieces.

Setting form and dryer & kiln cart specification
Dryer cart setting form
Wet green bricks are being put on the ductile cast iron drying cart manually. 4x11 pieces per layer, total 5 layers. 220pcs bricks per cart. Considering the clay with high plasticity data in your area, also with bigger size, so, we place the bricks on the simple steel bracket after first three layers being stacked on the base of the drying cart. Drying shrinkage is about 5%.
Drying cart size: 1100×1100×250mm (L. x W x H)
Drying car quantity: 1400 pcs (dryer inside contain: 840 pcs , stock cart quantity in entrance & exit ends: 150+110pcs, unloading area: 110pcs, cart returning line: 160pcs, inspection and repair area: 30pcs. )

Kiln cart setting form
Dry green brick are being put on the kiln cart manually, 4 x 11 bricks per layer.
3 stacks in vertical direction, 4 stacks in transverse direction. 12layers in 127mm side, 528 bricks per stack, 6336 bricks per kiln cart. Firing shrinkage is about 5%.
Kiln cart size: 4350×4660×840mm (Lx W x H), this dimension include the lining brick height.
Kiln cart quantity: 60 pcs (33 pcs of the carts contained inside the kiln)
 
Drying chamber System & Construction
This design adopts small section drying chamber with flattop. It is with brick & concrete structure, with precast-concretetop plate, partition wall with thickness of 240mm, side wall with thickness of 490mm, top layer and insulating layer with thickness of 500mm.
The heat source of drying chamber is the waste heat from tunnel kiln, which will be supplied to each drying chambers through air channel by heat-supply blower from the chamber bottom. The drying chamber set up air-feeding system, moist-releasing system and testing system. Bottom layer bricks are ending-up setting method, so that to improve the drying efficiency and quality.

Tunnel kiln system and structure

System
The tunnel kiln has complete system of smoke discharging, cooling, waste heat releasing,  pressure balancing under the kiln car, running and detecting system. Baking curve inside of the kiln will be more reasonable, production system more coordination through the adjustment of those system.
At the entrance side, there is a preparatory room, and a cut-off door between the preparatory room and the kiln pre-heating zone. There are entrance and exit doors at both ends of the tunnel kiln. Thus it effectively avoid entering the cold air and ensure the baking system inside not be influenced by outside.
 
Structure
Foundation: Tunnel kiln is with strip foundation. From bottom to up by order is lime soil, rubble, reinforced concrete girder (railway girder)/ board (under kiln wall)

Wall: Red brick is laid for the pre-heating zone and cooling zone where the temperature is below 200oC. The rest is adopt combined wall. The fireclay bricks will be laid on the baking zone and inner wall of insulting zone. 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 sides, 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 firebrick wall support the main beam's weight. Refractory fibrofelt, rock wool felt, rock wool board are put on the refractory hander plate, which compose complex insulation layer. 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 insulativity and structure's durability.

Coal casting hole: It is with function such as following, replenish heat, debugging, observation, replenish oxygen or cooling under negative pressure, releasing heat under positive pressure etc. This is widely used for tunnel kiln process with inner fuel technology, which can not be cut down or cancelled.

Sand seal: Sand seal slot is being put in the kiln cart skirt board, which insulate the high temperature from outside, thus to avoid cold air sucked into kiln under negative pressure which will lower the kiln temperature, and to avoid high temperature gas go to kiln cart underside under positive pressure which will destroy the kiln cart steel structure or deform the railway.

Afterheat system
Products direct heat and afterheat system are being put on top of the tunnel kiln, temperature curve in 450-200 oC range. Extractive afterheat occupies 80% of the total required heat for drying, heat source clean and no pollution. Through heat exchanger, except whole factory workshop heating, the rest high temperature gas is being sent into drying chamber. Direct heat is being extracted quickly and effectively, this will shorten the kiln length so that to lower the kiln construction investment.

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Ibrick Tunnel kiln for clay solid brick and hollow block making 
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