“White Gold” for the whole world Hot, hotter, natural gas: porcelain manufacturer KAHLA fires quality products at 1,400 degrees Celsius
As a versatile form of energy, natural gas plays a key role in industrial production. In particular complex manufacturing processes which require an exact amount of heat are barely possible without natural gas, for natural gas delivers constant heat in precisely the volume needed – and thus guarantees the quality of the products.
The making of porcelain not only requires great expertise; it also requires great volumes of natural gas. The porcelain manufacturer KAHLA from Thuringia has been making high-end tableware from hard porcelain, which is very stable and durable, since 1844 in the blazing heat of the kilns. The plates, cups and pots go through the furnace at least twice during the manufacturing process and are fired at temperatures of 900 to 1,400 degrees Celsius.
Sustainability strategy safeguards production in Thuringia
Since these high temperatures make production an energy-intensive process, natural gas has an important role to play. “Natural gas is the most efficient energy source for this purpose,” says Christin Biedermann, who is the “pro Eco” manager in charge of the sustainability strategy “KAHLA pro Eco” launched in 2009.
The porcelain manufacturer is certified according to ISO 14001 and invested early in innovative technologies such as photovoltaics and energy-efficient kilns. “These have been important steps in helping us to continuously save energy, reduce CO2 emissions substantially and safeguard production as well as jobs long-term,” Biedermann explains.
More than 14 tons of raw materials daily
The work performed by hand still plays an important role in modern porcelain production - this is evident in the foundry, for example. The porcelain body is produced here before it goes to the kiln. The porcelain paste is mixed together from kaolin, feldspar and quartz. Water is added and the paste is cast in a plaster mould. More than 14 tons of the raw materials are processed across all the manufacturing divisions per day, and they are sourced 100% in Germany. Werner Mücke, who works in the foundry, has just finished filling the last moulds when a timer goes off behind him: it is time to empty the moulds that have already been filled. With a few skilled hand movements, he pours the remaining paste from the plaster mould into a collecting basin so that it can be used later. “In contrast to the other stages of production, there are no buttons to be pressed here. In the foundry, true craftsmanship by hand is required. It requires experience to press the raw products out of the mould without damaging them,” says Mücke, who has been working at KAHLA for 47 years.
Every day 14 tons of raw materials are processed
The raw materials are sourced 100 percent in Germany
Handwork still plays an important role
Precise heat input thanks to natural gas
Once the porcelain has fully dried, the so-called “bisque-firing” stage follows, in which the porcelain wares are fired at 900 degrees Celsius to remove all the water. The natural gas flows directly to the kiln through pipes, where it is burned right in the kiln chamber. Various firing zones are formed this way in the kiln, and in these firing zones there are various precisely defined temperatures. This precise provision of heat is the big advantage of natural gas. For porcelain production it is crucial that the right temperature is available in a certain place in the furnace at the right time. The firing curve stipulated must be maintained during the entire process. Even small temperature fluctuations can destroy the porcelain wares in the kiln.
The natural gas feed is regulated directly via a valve controller in the combustion chambers. A technician monitors the settings and can intervene immediately if there are any problems. “The rough material is fired at 900°C, and the temperature has to be exactly right,” Biedermann explains. The articles are now ready for the glazing. Plates and cups are glazed automatically; more complex porcelain wares are done by hand. KAHLA’s traditional blue underglaze decoration is created at this stage of the production process. The pattern is stamped onto the fired articles by hand and then dipped in the glaze bath. This creates a particularly long-lasting product, for decorated porcelain is created this way after being fired just twice.
1. As soon as the porcelain items have been removed from the cast they are put on shelves to dry.
2. The pots and saucers already start sweating from the heat outside the furnace. The 900 degree Celsius bisque-firing removes all the water from the porcelain. Only then is it ready for glazing.
3. The natural gas travels through the yellow pipes to the combustion chambers of the new central kiln and provides temperatures of up to 1,400 degrees Celsius. The natural gas supply is regulated from outside by a slider.
The kiln produces 40 percent fewer CO2 emissions compared to its two predecessors.
4. State-of-the-art machines are the basis of the efficient production operations at KAHLA. The plates are picked up by the arm of this machine and polished fully automatically by robot.
5. Applying the traditional blue and white floral design as an underglaze requires the highest concentration and a steady hand.
40 percent CO2 reduction
To ensure the glazing is inseparable from the porcelain, the porcelain wares run through another firing process. In the glost-firing stage, lasting approx. five hours, the articles are heated to up to 1,400 degrees Celsius. This firing takes place in the modern central kiln installed in 2011. With a useable chamber 56 meters in length and 54 centimeters high, it is the central element of the factory in Kahla. The kiln can fire both cups and hollow and flatware together continuously and has 25 percent more capacity than its two predecessors together.
The purchase of this kiln was a key element of the “KAHLA pro Eco” strategy, for it consumes a good 40 percent less natural gas and therefore also reduces CO2 by 40 percent. “The investment has paid off. We can now manufacture more efficiently and in a more environmentally friendly manner. Furthermore, to be even more sustainable in future, we are planning to use the waste heat from the kiln this year for the heating too,” Biedermann says.
Up to 45,000 porcelain items can be produced at the plant a day.
Exports all over the world
A high-quality product “Made in Germany”, the Thuringian porcelain is exported to over 60 countries. Over a third of the tableware is used in hotels, restaurants and restaurants.