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Common bricks from the Czech Republic

Heluz – Europe’s most modern common brick factory in Hevlin

At the beginning of March 2009 the Heluz brick factory in the Czech town of Hevlin on the Austrian border was officially commissioned. The foundation stone for the new brick factory was laid in October 2007. The planning and implementation of this new highly-modern common brick plant lay with KELLER ICS; the preparation equipment was supplied by Rieter-Werke in Constance. The new production facility increased the total production of the company by 40 %.

The project

A complete new production plant for the manufacture of highly porous common bricks with an output of 800 t/d of fired goods was built on the existing factory site. Different sizes with a bulk density of up to 0.6 kg/dm³ can be manufactured in the factory. Grinding of the complete product range is possible. The basic raw materials for the manufacture of common bricks are clay from the existing quarry, which is mixed with saw dust and papermaking sludge as aeration agents. The use of Styrofoam as an additive is also possible. The necessary raw material testing was carried out in Keller HCW’s in-house ceramic laboratory in Ibbenbüren- Laggenbeck.

For the design of the factory by Keller HCW GmbH, important criteria adapted for local conditions were determined jointly with the owner:

  • Optimum utilization of the production hall
  • Gentle handling of the products
  • Assurance of quality and quantity
  • High availability of the plant
  • Reduced spare part requirements
  • Efficient use of energy for the operation of machinery, dryer and kiln

Project data

The output of the new common brick factory is up to 800 tonnes of fired goods per day with a bulk density of 0.8 kg/dm³. Products with a bulk density of up to 0.6 kg/dm³ can be manufactured in the new plant by the increased use of aeration agents.

Working times:
Preparation plant
50 weeks/year
7 days/week
2 shifts/day
7 hours/shift (effective)

Shaping plant and machinery
50 weeks/year
7 days/week
3 shifts/day
7 hours/shift (effective)

Output for the reference size:
16.089.150 common bricks/year
321.783 common bricks/week
45.969 common bricks/day
2.189 common bricks/hour

Reference size:

For the plant start up the reference size 380 mm x 247 mm x 238 mm with a perforation of 59 % and the two bulk densities 0.6 kg/dm³ und 0.8 kg/dm³ was agreed.

Common bricks, partition wall bricks and acoustic bricks can be manufactured as additional products.

Production

Material preparation

The raw clay material is fed into 2 box feeders by frontend loaders, then removed by steel slat conveyors and fed to the preparation plant via a belt system. Papermaking sludge from a third box feeder as well as preprepared saw dust from a silo are added to the clay material as aeration agents. Metal parts contained in the raw material are removed before entering the grinding pan by means of a metal detector with a reversible conveyor.

In the grinding pan, which has central material feed and closed plates on the inside runners, the material is pre-crushed, moved to the outside grinding tracks with perforated plates by means of scrapers where it is crushed again and finally pressed through the perforations onto the collector plates. These are running in opposite direction under the grinding pan and then they feed on to the next grinding level via a belt. The water addition at the grinding pan is controlled via a moisture control and measuring system so that continuous material humidity is achieved. In the following roller mill, which has a grinding gap of 2 mm, the crushing of the material is continued. A material distributor directly before the roller mill arranges for an even material distribution over the mills to avoid uneven wear. Automatic lathes are used for the turning of the roller shells. The final grinding size of 0.8 mm is achieved by the following high-capacity fine roller mill with monocradle technology. The preparation machinery is connected to a de-dusting plant. The collected dust is added back into the mix from the dust filter to the material flow on the belt. The ready prepared material is fed to the aging plant or alternatively directly to the shaping plant via a belt system.

In the aging plant the material is intermediately stored in six storage bins to mature so that a continuous plasticity of the material can be reached during the shaping process. The material is fed by a computer controlled belt system to achieve a homogenous mixing of the material in the bin. The working material is removed from the aging plant and fed to the shaping plant by a computer controlled automatic longitudinal excavator. The shaping plant starts with the box feeder which serves as a material buffer between the preparation andshaping  plant. Via a belt system, which allows the discharge of the material into a prepared container, the material is fed to a third roller mill where any dried out material is crushed. A further metal detector is installed in front of the shaping machinery to eliminate metal parts, thereby avoiding unnecessary wear of the machinery. In the circular screen feeder the material is again mixed thoroughly, the final humidity is achieved and the material is pressed through screen sheets and fed to the extruder group. Humidity is controlled by an automatic humidity measuring and control system by measuring the pressure head pressure and the power supply at the extruder worm.

In the vacuum double shaft mixer the material is mixed again, de-aerated in the vacuum chamber and fed to the worm extruder. At the outlet of the mixing chamber the mass of the mixer is shredded into small pieces by rotating knives and a tooth comb to ensure a fast and thorough aeration. In the circular screen feeder and the double shaft mixer, steam, generated by a separate steam generator, is added. In the worm extruder the compacted material is fed via the pressing cylinder and pressure head to the die where the first shaping step (length and width of the brick) is achieved. The brick height is defined in the following cutter system.

Machinery – Wet side

The extruded clay column is fed to the cutting device via a transfer plate. A measuring belt determines the exact clay column speed for the  precise control of the cutting device. Because of the high preparation water content and the very fine perforation there is the risk of product deformation caused by the transport of the cut product. To overcome this problem a punching device is installed in front of the cutting device. In the cutter one brick per working cycle is cut from the clay column and then transferred to a frequency-controlled belt creating a defined distancebetween the cut products.  Cutting of the products is effected with waste which is re-fed to the shaping plant via a waste transport system.

Three 4-axis industrial robots gently grip 4 products each on the cut face and load one prepared pallet each. A transport carriage transports the loaded pallets into the area of the dryer car loading while a belt conveyor simultaneously transports three empty pallets into the area of the pallet loading. The loading of the prepared dryer car with loaded pallets, as well as the preparation of empty pallets on the belt conveyor, is achieved by a driving gear mounted on a craneway. In case of size changes a further driving gear stores the required pallets in a pallet storage, depositing or alternatively retrieving them.

Tunnel dryer plant

The dryer plant is designed as a tunnel dryer with two separately controlled tunnels and wet storages installed in front of them. Each tunnel is equipped with an exit sluice to maintain the drying climate. The circulation required for drying is effected for each tunnel and each circulation circuit via three axial fans installed  in an intermediate ceiling. The drying air is blown between the products and then circulated by means of slot nozzles installed in the intermediate ceiling. The required heat energy comes primarily from the kiln.  Additionally required energy is generated via an auxiliary burner and fed to the dryer via radial fans. Corresponding to the drying characteristics, the tunnel dryer is separated into 10 climate zones. The saturated wet air is discharged out of the dryer via axial fans installed in wet air stacks. The control of the supply air and waste air flows is effected via electrically driven control valves installed in the ducts or air channels, or via the rotary speed of the wet air fans respectively. Measuring devices for pressure, moisture and temperature arrange for an air and temperature control in the tunnel dryer exactly adapted to the respective situation (e. g. with size changes). The automatic control of the dryer is effected by a freely programmable process computer. Consumption and status data can be called up at any time.  Size depending drying curves are retraced fully-automatically, synchronized with the actual value and adjusted if required.

Dry side and setting machine

Unloading of the pallets loaded with the dried products is effected sequentially to the wet side via a driving gear with gripper. A carriage transports the loaded pallets into the unloading position; the transport of the empty pallets into the takeoff position is effected  simultaneously by means of a liftable and lowerable conveyor. In the take-off position the empty pallets are taken-up by the driving gear  and deposited on the stillage of an empty dryer car. The return transport of the empty and stacked pallets to the wet side is effected by the dryer cars. A driving gear with a corresponding gripper unloads the pallet and deposits the dried products on belt conveyors. A fixed storage table is installed for the size depending intermediate storage of products. The products are grouped and fed to the setting robots via a two-row belt conveying system and a stopper. The combination of turning device and turnover star allows the bricks to be turned onto the cut face. Two industrial robots grip the products which are taken off the conveyor by lifting plates and they are arranged on the tunnel kiln car in a blade setting pattern. For an easier gas release of the bricks during the firing process, the individual layers are set with the teeth on top of each other whereas for the setting of intermediate wall bricks separate fully-automatic exchangeable robot gripping tools are used.

Tunnel kiln plant

The kiln plant, fired with natural gas, consists of a heating- up zone, firing zone and cooling zone and is designed as a tunnel kiln. In the preheater the residual moisture is driven from the dried products and they are prepared for the heating-up and firing process. Furthermore, the preheater serves as an inlet sluice to maintain a continuous pressure profile in the kiln. In the heating-up zone highvelocity burners with ignition and flame control are installed in the tunnel kiln walls or in the kiln ceiling. These burners are equipped with a central combustion air supply and in combination with the flue gases they heat-up the kiln car load. Furthermore, in the heating-up zone the tunnel kiln is equipped with a laterally installed flue gas circulation system. This serves for the better burnout of the aeration agents and the temperature distribution. The heating of the tunnel kiln is mainly effected via the kiln ceiling by feeding natural gas as fuel to the tunnel kiln via a top burner plant consisting of a certain number of injector burners. In the firing zone burners are combined in groups over two firing lanes. The top burner plant is designed with a common air and gas supply system. All burner groups are equipped with a valve train at their inlet allowing the burner groups to be switchedoff during the pushing process or in case of faults. For cooling purposes fresh air is forced into the tunnel kiln by pressurised air fans and fed to the hot bricks. A part of the hot air is drawn off and fed to the dryer. The residual air flows through the firing and heating-up zones. The hot flue gases flow from the firing zone through the kiln load  towards the kilninlet, heating up the products on the kiln car. The cooled flue gases and the low temperature carbonization gases are taken off at the kiln inlet zone and  are fed to a regenerative thermal post-combustion system. The gases, contaminated with harmful substances, flow into the heat exchanger chambers which are filled with a ceramic material and thereby heated up. This causes the ignition of the volatile organic matters. In the firing chamber the mixture ignites and is discharged via the next heat exchanger. This causes the flue gases to cool down and releases the heat back into the ceramic heat exchanger. The cooled and cleaned air is fed via a stack to atmosphere. The entire kiln plant is equipped with automatic measuring, control and regulating systems and a process computerused for process control. Corresponding switching devices are installed for thecontrol of security-related functions. Faults are reported acoustically and can belisted and logged via the  computer. The current fault message is displayed at the switch cabinet.

Unloading – packaging

The fired bricks are removed from the tunnel kiln cars by 2 industrial robots and set onto two belt conveyors. A two-row belt conveyor system transports the fired bricks to the grinding station. Bricks, which are positioned on their cutting surface, are suitably arranged for the  grinding machines by a combination of a turning device and a turnover star. The separation of the two incoming brick rows is effected by a transfer device followed by a belt conveyor. The two brick rows are fed into a single twostep grinding machine, each via an angular transfer device and chain conveyor system, where they are ground to size plane-parallely. A feeding system arranges for the automatic centring of the bricks and transfer to the transport system of the grinding machine. The low-wear transport system guarantees the precise guiding of the bricks passing through and  compensates for any uneven thickness of the bricks. The adjustment of the individual grinding heads via servo-drives guarantees an exact holding point and an exact readjustment.

This is further improved by using a specially developed measuring system. After the grinding process, the accrued brick dust is taken off and fed to two independent de-dusting plants. The surrounding area is protected from noise and dust emission by two separate acoustic hoods; the access to the grinding machine for service operation is fully maintained. After the grinding process the bricks, free from brick dust, are put onto the cutting surface and grouped to dispatch pack layers. An industrial robot stacks the  brick layers onto pallets. The stacks of empty dispatch pallets are loaded onto a magazine conveyor, separated by a transfer device, fed to the loading position via a chain conveyor system and then adjusted. The packed dispatch pallets are transported through the packaging plant via chain conveyors. A film hood is put over the dispatch packs by means of an automatic film hood machine, shrunk and then transferred to the magazine chain conveyor. There they are removed by a forklift and transported into storage.

Control system

The control of all machine and plant components as well as the preparation and shaping plant is effected by a switch and control centre with PLC SIMATIC S7, designed and produced by Keller HCW. Coordinated components and standard interfaces give a smooth operation. The use of visualization systems increases the operation reliability. At the same time these systems minimize downtime in case of faults. Another advantage regarding reliability is the worldwide teleservice of the Keller HCW plants. In case of faults, specific analyses of the reasons for machine or operating faults can be done quickly. The availability of automation and process guidance systems are essentially improved. If necessary, the service specialist can directly influence the control of the plant. Teleservice permits the remote visualization and control of the plant, programming of the process control computer and the programmable logic control (PLC), specific analysis of operating and fault messages as well as file transfer, software updates and documentation.


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