Clay Hollow Block Two Stack Two Baking
We normally adopt ‘two stack two baking
stages’ for the production of hollow blocks, due to the whole process involves
two times brick stack. The 1st stack occurs at robot stacking the wet green block onto the drying rack for
drying. The 2nd stack occurs at robot stacking the dried block onto
the firing kiln cars for baking. We have fully automatic equipment and control
system for the group, loading, transfer, stack operations during the two times
Main technical parameters:
Hollow clay block
Natural gas, heavy oil or coal
600 tons/24h, 70,000 pcs/24h
two-time stack, two time baking
Dry cart number
Firing kiln car number
The keys of Bricmaker hollow brick's two stack two baking automation line:
multi channels tunnel drying kiln and flat roof type tunnel kiln.
1. Multi channels tunnel drying kiln
The application of large multi channels drying kiln and finger type forklift in the block making industry, has received satisfactory feedbacks in China.
Each unit channel is divided into some unit sections from entrance to exit. Each unit section has relatively independent space to maintain the required temperature and humidity. The drying hot air is distributed into each unit sections from the top of the drying kiln. In each unit section, there is one cyclone to blow and cycle the hot air uniformly, to help the moisture in the block steam slowly and uniformly. The cyclone is driven independently and the interval blowing is adjustable according to thermal parameters.
2. Firing tunnel kilns
Compared to traditional external combustion tunnel kilns, this firing kiln has the characteristics of a wider cross-section and a shorter firing cycle. In order to improve the non-uniformity of temperature and air circulation in the kiln, ensure product quality and qualification rate in a shorter firing cycle, we have taken the following measures based on extensive practical experience and calculations:
Adopting a cross flow baking method, that is, during the tunnel kiln roasting process, the air flow through the middle of the billet stack should be increased as much as possible to promote a large amount of gas to flow through the hole of the brick stack, not only around the brick stack, but also to minimize the temperature gradient in each billet stack (each brick), in order to effectively shorten the firing cycle and ensure product quality.
Set up a circulating mixing wind system in the pre tropical and residual tropical zones. By extracting high-temperature flue gas from the front of the preheating zone and then injecting it into the kiln from the middle of the kiln top for stirring, the flow rate of gas passing through the middle of the billet stack is increased, which not only improves the temperature uniformity inside the kiln, but also strengthens the convective heat transfer effect of the preheating zone. The principle of the residual tropical circulation stirring wind system is similar to this.
Add smoke exhaust or heat extraction pipelines in the middle of the kiln roof to increase the ventilation volume in the middle of the stack, improve the heat transfer effect of the entire stack, and achieve the goal of increasing production and quality.
The burner adopts a flow cascade combustion control scheme, which ensures precise control of the controlled variable (furnace temperature) through two main and auxiliary controllers.
Adopting a small pressure difference dispersion firing pressure system, that is, the pressure change in the entire kiln is relatively small, and the high-temperature roasting area is in a slightly positive pressure state to ensure that high-temperature oxidation can fill the entire stack on the vehicle surface, which is conducive to uniform heating and sintering of the stack.
The design of kiln car structure system shall minimize the overall weight of kiln car when selecting materials and designing brick structure on the premise of ensuring the thermal shock resistance and load capacity of kiln car. For example, the supporting platform system (vehicle surface brick plus support brick) is adopted, and the cushion and insulation part are made of light insulation bricks or Aluminum silicate fiber blanket.