Wacker Chemie Silicone Production Facility, Saxony, Germany


The facility has an annual capacity of 120,000mt of siloxane

Wacker Chemie's silicone production facility is located in Nünchritz in Saxony, Germany. The facility has an annual capacity of 120,000mt of siloxane. Wacker has been operating at the site since November 1998 after it acquired the facility from Hüls AG. Since then, Wacker has invested more than €550m to upgrade the facility.

The Nünchritz facility manufactures about 200 of Wacker's portfolio of 3,500 products using crude silicon, methanol and hydrogen chloride as raw materials. The products produced by the facility include pyrogenic silica, siliconates, chlorosilanes, silicone fluids and antifoam agents. It also produces silicone emulsions, silicates and silicone rubber and the requisite precursors. About 930 people are employed at the Nünchritz facility.

Expansion of Wacker Chemie's facility

"The Nünchritz facility manufactures about 200 of Wacker's portfolio of 3,500 products using crude silicon."

In 2008, Wacker announced that it was planning to build a new polysilicon production plant with a nominal capacity of 10,000mt/y. Initial production at the plant commenced in October 2011.

The plant was officially put into production in April 2012. The plant is expected to reach its full production capacity of 15,000mt/y by the end of 2012.

The company invested about €900m for the project. Construction of the new plant generated more than 500 jobs.

Expansion of the plant was undertaken to keep up with the double-digit annual growth in polysilicon demand from the solar industry and the increasing demand from the electronics industry.

The project was financed by state incentives, self-financing, prepayments and a loan from the European Investment Bank (EIB). In May 2009, EIB approved a €400m long-term loan to finance the construction of the plant.

Saxony plant details and history

The Nünchritz site has been through expropriation, disassembly and reconstruction since the 1900s. After the site was acquired by Wacker from Huls, the company modernised and expanded the site by setting up production facilities and infrastructure. Wacker built a number of new plants for manufacturing silicones and their precursors and also expanded existing facilities.

"The project was financed by state incentives, self-financing, prepayments and a loan from the European Investment Bank (EIB)."

A monomer plant that had an initial capacity of 30,000mt/y of siloxane was commissioned by Wacker in 2001. In 2005, the company completed the first stage of expansion of the monomer plant. The second stage of expansion of the monomer plant was completed in 2006. The expansion increased the capacity of the plant to 100,000mt/y of siloxane. In 2007, capacity of the plant was further expanded to 120,000mt/y.

Wacker built an alkoxy / BS15 plant in 2001, which consists of two sub-systems, each with related stores and a central tank farm for feed materials and final products. The plant features state-of-the-art Siemens PCS 7 process control systems.

In 2002, Wacker completed the construction of an emulsion plant for GMP production, a chloromethane plant, an H siloxane plant, an HDK/SHK plant and a Silester plant. The H siloxane plant was expanded further in 2004. The company expanded cartridge filling in 2002 and again in 2005 at the facility.

Closed-loop production process at Nünchritz

"Expansion of the plant was undertaken to keep up with the double-digit annual growth in polysilicon demand from the solar industry."

The Nünchritz facility features a closed-loop production process. Müller-Rochow synthesis is the first step of the production process, in which crude silicon is first ground into small particles of about 1mm in size. The particles are transferred into a fluidised-bed reactor operating at 300°C.

Chloromethane is injected into the reactor from the bottom, where it reacts with the crude silicon. The reaction with chloromethane transforms silicon into a heavy mass containing a mixture of different methylchlorosilanes. The mixture is repeatedly evaporated and condensed in distillation towers to obtain a pure form of the main raw material for production of silicones - dimethyldichlorosilane.

The dimethyldichlorosilane produced from the distillation towers goes through hydrolysis. The process produces high-molecular chlorine-free compounds containing various silicon atoms. During hydrolysis water reacts with dimethyldichlorosilane and yields chains of siloxanes, which contain one oxygen atom between two silicon atoms. Linear siloxane chains or polydimethylsiloxanes are only used to make silicone. The remaining silanes are used to produce pyrogenic silica by hydrolysing them at more than 1,000°C.

The hydrolysis process generates huge quantities of hydrogen chloride gas. The hydrogen chloride is used for two purposes. Some of the hydrogen chloride is sent to the plant's hydrogen chloride loop where it reacts with methanol. The reaction with methanol produces chloromethane which is used during Müller-Rochow synthesis.

The remaining hydrogen chloride is reacted with silicon to produce a crude silane mixture. This mixture is purified by repeatedly evaporating and condensing in distillation towers. The end products from this process include tetrachlorosilane. Some of these silanes fuse with alcohol to form silicate esters. Silicate esters are clear liquids that can be used in paints and coatings.

Technology installed at the silicone production plant

The €550m invested by Wacker into the facility also included installation of the latest and most efficient technologies for minimising air emissions, liquid effluent and solid waste discharges. The technologies installed at the Nünchritz site have helped the company reduce specific steam consumption by 80% and specific electricity consumption by 60%.

The factory contributes less than one percent of the region's total air pollution, well under the allowable limits prescribed by the law.

The facility's electricity needs are met by an integrated power station, which was converted to natural gas in 2006. Steam generation at the power station has helped the company save 75,000t of carbon dioxide annually. The company has also incorporated individual energy measures, including a coupled heat system for distillation and a heat recovery system for residue incineration.


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