Röben invests in the future
The flexible plant sets new standards in brick production
With the famous push on the “red button”, Rhineland-Palatinate’s Minister President Kurt Beck and Röben’s Managing Director Wilhelm-Renke Röben, officially opened the new Röben clinker brick factory in Bannberscheid near Montabaur (Westerwald) on February 16. “It is a proud achievement that we, as a family business, can invest in a project of this dimension” said Kurt Beck in acknowledging the commitment of the Röben Tonbaustoffe GmbH. “This investment sets an example“, Beck says “showing that the excellent raw materials in the Westerwald, the capability of the people and the long tradition in the ceramic sector can lead to investments even in these times. And it has become clear that the Westerwald is a safe location for the production of bricks – I am glad about it“.
The new plant was supplied by Keller HCW from Ibbenbüren. With this investment, the factory in Bannberscheid, where Röben has been manufacturing clinker bricks for the German and European market since 1970, becomes one of the most modern clinker brick factory in Europe. The plant was constructed in the existing hall by Röben Tonbaustoffe and KELLER ICS within a period of only nine months. The plant is capable of producing three different sizes with three different materials at the same time. Highest flexibility and highest quality are the characteristic features of the plant.The product range is wide ranging: facing bricks, ceramic clinker bricks, pavers and clinker facing strips with the typical product characteristics such as long-life cycle, frost resistance as well as a variety of surface finishes and colours. The capacity of the plant is 18 million ceramic clinker bricks and 20 million clinker facing strips per year.
The machinery for the manufacture of products
The different products can be manufactured on three parallel production lines. In the product production lines 1 and 2 facing bricks, specials and angular facing strips are manufactured. With a separate surface processing plant for each extruder line, the wet clay column is provided with different surface structures or sanded as required. Four sided chamfering of the clay column is also possible by means of the ‘Stargate’ chamfering device at the KELLER cutter. Depending on the size, up to five products can be cut simultaneously with the lateral cut universal cutter. When changing size, different cutting thicknesses are adjustable. The product distance and the number of the products on the pallets vary depending on the size. Loaded pallets are transferred in prepared chamber dryer cars via different transport and gripping devices.
On product production line 3 flat extruded facing strips, split tiles and specials are manufactured. On this production line two robots are used for loading the pallets and this allows for a variety of product processing before the pallets are loaded. The loaded and arranged pallets are then, as on the other production lines, loaded into the prepared chamber dryer cars. The dryer cars are then taken automatically into the pre-selected drying chamber.
The chamber dryer consists of 16 units (individual chambers). An extension by four chambers is possible at any time. Each of the chambers has an inlet and outlet door. This allows for a feeding on the principle of first-in / first-out. The suspended doors of the chamber currently in use are moved by means of a fully-automated unhinging device. The individual chambers work separately, so that for each product individual drying curves can be retraced. This guarantees a flexible production of different sizes and clay mixtures. Depending on the product, the drying time varies between 44–72 hours.
Stationary jet walls installed on both sides of the dryer cars are used for the air circulation. The jet walls, which are provided with horizontal slots in connection with a reversible airflow, allow for an even ventilation of the products over the entire setting height and setting depth. Waste heat from the tunnel kiln is used for drying. To accomplish this, the hot air is fed into a hot air distribution pipeline above the drying chambers by means of a hot air fan. This pipeline is connected with the individual drying chambers via automatic air regulation flaps. The drying chambers are additionally equipped with secondary circuits, which in connection with internal air channels, arrange for an even energy distribution over the chamber depth. In the initial phase of drying, natural gas burners, integrated in the secondary circuits, allow for a particularly careful heating of the product and a high humidity. The discharge of the wet air is effected via individual stacks installed in each drying chamber. A precise control of the drying climate is achieved by the use of humidity and temperature measuring devices. The control of the dryer is effected in an energy- optimized way by the use of the proven K-Matik process control system.
The pallets loaded with dried products are unloaded from the dryer car in layers and then fed to the unloading plant via different transport devices. A robot removes the products from the pallets and deposits them on the feeding device to the kiln car setting machine. The empty pallets are then taken to pallet storage or back to the loading plant. Depending on the product and the setting pattern, the products are turned, inverted, sanded, engobed or glazed by means of respective devices. The product is fed in different ways to the kiln car loading position by means of various conveying, gripping and adjusting devices. Above the kiln car, two robots with layer grippers take-up the prepared product layers and deposit them, depending on the setting pattern, on the kiln car deck. The flexibility with which the plant has been designed by the KELLER Engineers is emphasized again by the fact that, if required, mixed settings such as facing bricks and facing strips can be set at the same time. A tunnel kiln car cleaning plant is installed to clean the tunnel kiln cars. It cleans the tunnel kiln cars before they enter the setting machine again.
Tunnel kiln plant
Core piece of the plant is the top fired tunnel kiln which has a total length of 172 m including inlet and outlet sluice. It is designed for a maximum temperature of 1320 °C. The firing time is about 55 hours. Firing is effected with natural gas. A holding room and a preheater, both arranged on the storage track next to the kiln, effectively avoid reabsorption and allow for an optimum heat-up and final drying of the product before entering the kiln. Due to the wide variety of products in the factory in connection with the different clay mixes, which require adaptations of more than 150 K in the maturing temperature, the demands on temperature equalisation and on short transitions when changing product groups was very high. These pre-settings were achieved by means of an optimally adjusted process engineering and control system. In the heat-up zone the tunnel kiln is equipped with a flue gas circulation system integrated in the kiln walls. By using this system a good temperature equalisation is achieved in the heat-up zone. Furthermore, due to an intensification of the heat exchange between the product and flue gas, the circulation leads to reduced flue gas losses. Further on in the heat-up zone high-speed side burners with ignition and flame control are installed in the tunnel kiln walls. These burners allow for an even temperature increase through a sequencer. The following top burner plant consists of 23 injector burner groups which are equipped with pulse control to achieve an optimum temperature equalisation. Each burner is individually controlled on the gas side via a solenoid valve. The pulse control is done electrically via software modules in the Simatic. The parameters are assigned to the product-specific firing programmes and can be managed and adjusted via the process control system. Hot air from the cooling zone of the kiln is used as combustion air. This also contributes to the low energy consumption of the kiln.
To obtain the different shades, many products have to be manufactured by reduced firing. Extremely flexible reduction burner groups are used for this purpose. There is the possibility of feeding the reducing gas via the firing gap as well as directly onto the packs. As required, either pure gas or a sub-stoichiometric gas-air mixture can be injected. Each burner lance can be controlled individually via the reduction programme. The cooling zone starts with a strong rapid cooling system which is divided into 3 separately controlled groups. Furthermore, above the quartz inversion point the cooling zone is equipped with an efficient high-temperature offtake. It is lined on the inside with ceramic fibre and is therefore not fitted with a direct fresh air intake. A lateral circulation system has also been integrated in the cooling zone for energy reasons. A temperature- controlled low temperature offtake and a pressure-controlled contravec fan complete the cooling zone. In comparison to the old production plant, the energy costs of the tunnel kiln can be reduced by about 25 %. This was made possible by the high-quality insulation of the tunnel kiln, the utilization of a special undercar cooling system as well as the utilization of the circulation systems and an optimized heat compound. The tunnel kiln is controlled on the basis of the latest Simatic technology. The K-Matik process control system is also used for visualization and process control, which in reference to the variety of products is of vital importance.
Unloading – pack forming
The high flexibility of the plant can also be seen in the area of kiln car unloading and packaging. Clinker bricks and facing strips are unloaded, sorted and packed by separate plants. After passing through the tunnel kiln, the products are taken to the unloading position. Unloading grippers take-up the stacked products and deposit them on the respective conveying devices. Facing strips and split facing tiles are unloaded parallel to the brick unloading plant. With the belt conveyors, the separated facing strips are taken to the manual sorting station and to the manual packaging station. Facing bricks or pavers are deposited in packs onto a bar chain conveyor by means of the unloading gripper. Two robots, as well as further gripping and transport devices, separate the packs for the following sorting line. A transfer gripper takes a set number of brick rows and deposits them on the feeding table. From that point, they are grouped into square packs by means of an adjusting device. A robot stacks the brick rows on pallets. Intermediate paper layers can also be inserted by the robot by means of a specially designed combined gripper and suction device.
The control of all machine and plant components is effected by a switch and control centre with PLC SIMATIC S7, designed and produced by Keller HCW. 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 used in Keller HCW plants. In case of faults, diagnosis of the reasons behind machine or operating faults can be done quickly. The availability of automation and process guidance systems is 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.