Production processes

General 

The maximum annual production capacity in our plant in Emmerich amounts to approx. 40 million bricks and 60,000mof clay boards. Our production is running 5 days a week with 1 shift per day whereas the drying and firing process runs 24/7. We are producing 7 different formats. The colours range from antique-white light-variegated, yellow-bronze-coloured variegated, bronze-coloured variegated flashed, red-brown variegated, red-brown variegated flashed, bronze-coloured variegated, red, red variegated to red flashed. Our total staff in Emmerich consists of 41 persons, thereof 7 employees, 33 workers and 1 apprentice.

Resources

Besides clay as our main resource, we are adding lava, sand and saw dust coming from Germany, the Netherlands and Belgium.

Clay stockpile 

The maximum stocking capacity of our blending bed is approx. 80,000m3. It’s very important for our plant in Emmerich. The main advantage of the circular stock piling is the possibility to balance the natural material differences of the pits. This allows us to build up layers. Every layer has a height of only 30 cm. They are regularly drilled-out at different places in order to analyse these samples. In this way we are able to influence the number of pits (approx. 5-9 different locations) even while building up the stockpile. Hence we are able to consciously control the quality when selecting the resource materials. Important indicators are the percental grit size ratio and the iron-lime ratio. The grit size influences the working properties during the production process whereas the iron-lime ratio defines the colour result during the firing of the body. After setting up the stockpile, it’s moved with the help of a chain dredger in order to mix the different kinds of clay and to balance the moisture. From there, the clay is transported to the processing area with a wheel-type loader.

Processing 

First, we are using a roller mill. The clay is crushed by the pressure of the reversing mills. After the milled raw material had been temporarily stored and fed into different box feeders, it is moved into the circular screen feeder. Here, the working mass is homogenized with the scraper arms and pressed through the screen sheets. After that, the clay is put into a single-shaft mixer where water is added automatically. Additionally, we need sand for the forming frames. It is prepared in a rotary drum dryer with a drum screen.

Forming / Moulding press 

In our plant in Emmerich we use 3 different moulding techniques imitating the traditional procedures of forming bricks by hand. That’s why the label “Soft-mud bricks as made by hand“ has remained until today and established itself on the market. Every moulding press is aligned and optimized for a specific type of brick. The three techniques share a common circular flow of very robust synthetic moulding frames. The possibility to rapidly change the brick format is the main advantage of these loose moulding frames. After each working cycle they are cleaned and sanded in order to avoid that the soft green products stick on the moulding frames. That’s the reason why 5 of 6 sides of a brick are slightly sanded. Another characteristic of this production method is that we’re producing solid bricks or bricks with a frog. These frogs result from indentations of the bed surface of the moulding frame. However, these bricks are not perforated.

Options  

In the following chapter you’ll find a short description of the different types of moulding presses, that we are using:

a) Mould press type Aberson 

This machine consists of a rectangular clay tray, where the prepared mass is moved downwards with the help of 2 slowly turning vertical shafts with paddles. At the bottom there’s a filling device. It has as many small nozzles as there are partitions in the moulding frames. Every nozzle an aperture that is smaller as the respective partition of the moulding frame and its aperture is similar to the section of a “Diaboles”. Furthermore, the filling device has a press assembly. At every cycle it “nods” a little bit downwards in order to increase the pressure a little bit or to balance excess quantities or shortage of quantities. The filled moulding frames are mechanically moved one step forward at every cycle.

b) Aberson's soft mud machine 

The lumps are made and regulated by a special device (so called “cow”). It’s located behind the Einwellenmischer. The volume of the lumps amounts to approx. 25% more than the volume of the moulding frames. By rolling them, sand, saw dust or similar material is put on the outside of these lumps. At the same time it’s rolled in a way that the lump will first hit the bottom of the moulding frame when it’s inserted with a certain speed and not the 4 inner sides. Otherwise the sanded exterior of the chunk would be affected. Because of the energy resulting from insertion and falling, the soft chunk expands itself when hitting the moulding frame and completes the form.

c) Soft mud machine type Hubert 

By means of a vertical press the clay mass is extruded. It’s sanded all around and cut into chunks according to the requirements. Another main characteristic for the Hubert system is the insertion device. This device, consisting of a pair of narrowing conveyor belts, accelerates the inserted chunk. At the same time, the chunk adapts to the correct form and is inserted into a partition of the moulding frame. The steps after filling the moulding frames in different ways is comparable. The excess quantities of the soft mass is taken off and moved back into the single-shaft mixer. After that, a metal plate is put on every moulding frame. Now the moulding frame is turned together with the metal plate in a way that the forming frame can be lifted slowly.

Drying systems 

The metal plates carrying the green products are discontinuously and automatically moved by a transfer car to the drying system. Heat is added to start the drying process, where moisture turns into a vapour state and is separated from the solid. In Emmerich approx. 1l of water is evaporated from each brick in that way. The characteristic of the chamber drying system in Emmerich is the periodic loading, unloading and simultaneous drying of all products in the chamber. During that time, the resting products are surrounded by heat. The heat and air streams are constantly adapted and optimized. This can be handled both related to the products and the chambers in order to be able to improve the quality of drying the products and to be more power-saving. The drying procedure takes approx. 3 days. If there’s more time left, we use this time to dry our products slower and thus save energy. There are 10 chambers per moulding press available in order to guarantee an almost continuous flow. The heat supply for the drying system is provided of the waste heat coming from the kiln. If necessary, we can add additional head by means of a natural gas burner. The draught products, the so called “green products”, are moved off the metal plates and set on the jigging system. If necessary, the metal plates are temporarily stored and then transported back to the moulding press.  

Jigging machine 

In order to fire the draught products in a kiln, they need to be piled on the so called kiln cars. These cars have a refractory surface made of fireclay which protects the steel frame and the axes from the high temperature. The jigging systems automatically set up the green products and add them to groups of products. These groups are put on the kiln cars in layers by means of a claw. For every brick type there as optimal jigging pattern.

Firing process / Kiln 

The firing process being the final ceramic-technological activity bonds the fine resource particles by silication irreversibly to a stable body. Besides the colour, the firing process makes the final products water-insoluble, resistant to chemical influences and high pressure-proof (as required for the different Formats). The kilns run 24/7 whereas the areas of moulding and unloading are only covered with one shift 5 days a week. Therefore, there’s a strong need to temporarily store the kiln cars before and after the firing process. The temporary storing as well as the whole firing process are executed in a computerized way. The kilns are fired from above and from the sides by natural gas burners. Combustion air is partly blown in by a air ventilator. As a result of the counter flow principle the combustion air is heated while the fired ware is cooled down and thus brings oxygen into the firezone. The combustion gas, which results from this process, are drawn through the pre-heating zone by means of the controlled flue gas plant. This heats up the product. As the green products are moved through the kiln with the required time, they’re constantly heated and fired at approx. 1100°C (2012° Fahrenheit) in order to become soft-mud bricks. The whole firing process takes about 2-3 days. The flue gas which is drawn out by extraction channels gets into the flue gas cleaning plant with a temperature only a little bit above the dew point and then into the chimney. Our practical experience shows that we can achieve the most efficient results with regards to the energy expenditure, as no supporting firing devices that would need to be heated additionally (fire proof cassettes) are necessary.

Unloading

In order to achieve a better batch, the fired soft-mud bricks are automatically and simultaneously unloaded from two kiln cars in a staircase-shaped way. After that, every brick passes by a sorting area. Finally, the layers of bricks are spread on 8 chain conveyors by a sophisticated temporary storing system and put together again by picking out 3 – 4 single bricks. Then, the newly built layers are separated on two conveyor belts running in parallel. Only from here they are set on transporting pallets. With this we can achieve a very well sorted batch from the whole kiln load. Bricks that had been fired next to each other on the kiln car and thus look similar (which we do not want) will not be sorted next to each other in the batch. Like this we also avoid to have so called clusters of colours on the walls. As our products are transported to our customers over large distances, it’s not possible to loosely package the bricks. In order to prevent the surface of the bricks from damage, paper is automatically put on each layer of bricks. The package is finally shrink-wrapped and made ready for shipment. Then the pallets are transported to our storage area where they are loaded on trucks. After each cycle the surface of the kiln cars is vacuumed. Now the kiln car is available for a new production cycle.