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Wacker Chemie Polysilicon Plant, United States of America

Key Data

German chemicals manufacturer Wacker Chemie is building a new polysilicon plant in the state of Tennessee, US. The plant will manufacture hyperpure polycrystalline silicon to tap the anticipated growth in demand from the solar and semiconductor industries.

The new plant will be built in a 550-acre (220ha) site in Bradley County in Cleveland. The facility will be a fully integrated site that will produce 15,000mt of polysilicon a year. Wacker will invest about €1.1bn ($1.5bn) in the project that is expected to create about 650 jobs.

The construction is scheduled for completion by the end of 2013. First production is expected in early 2014.

Tennessee polysilicon plant background

Wacker initially planned to build a 10,000mt plant with an investment of $1bn, but later increased the capacity in anticipation of higher-than-expected growth.

The company purchased the land in February 2010 for approximately $20m as it had mid-term plans by that time to build the project. The company officially announced its intention to build the plant in December 2010.

The site was chosen for several benefits including the presence of suitable transportation infrastructure, water and electricity. Power supply in the location is reliable and economical and the company can source chlorine over-the-fence from the nearby OLIN Corporation plant.

"The Wacker Chemie plant will manufacture hyperpure polycrystalline silicon."

Owners / financing

The plant will be 100% owned by Wacker Chemie. The company already has credit lines available for more than $1bn and has secured prepayments to the same amount.

The federal, state and county authorities have provided several incentive packages, including tax credits and infrastructure grants.

Contractors and construction

Construction will begin with earthmoving works to control perimeter erosion. Demolition and offsite drainage works will follow. Construction work is divided into packages and contracts will be awarded accordingly. The contract for package 1A has been awarded to a local construction firm Wright Brothers.

Silicon feedstock

The feedstock for production of polysilicon is silicon. Wacker will procure silicon metal from various global suppliers. Solar cells and photovoltaic devices require silicon of very high purity, that is, hyperpure silicon. In order to achieve such high purity, the silicon to be used is produced from a compound called trichlorosilane (TCS).

Trichlorosilane is a chemical compound that contains elements of silicon, hydrogen and chlorine. When heated to a high temperature, the compound decomposes into individual elements, producing silicon.

Silicon is first granulated through grinding to produce hyperpure silicon. Hydrogen chloride gas is combined with the granules inside a reactor to form trichlorosilane liquid. The liquid is distilled to remove impurities such as boron, phosphorous or carbon. The purified liquid is then heated at 1,000°C in a reactor to undergo the Siemens process. Silicon atoms are condensed on silicon rods inside the reactor chamber. Hyperpure polysilicon is obtained by crushing the rods.

Process technology

The facility will integrate the production of feedstock trichlorosilane, the polysilicon deposition reactors, the recycling plant and the processing plant.

"Wacker will procure silicon metal from various global suppliers."

It will employ closed-loop operation, which involves recycling of silane and other wastes to produce byproducts that can be used for other chemical processes.

Closed loop operation has several advantages. It reduces wastage and loss of process chemicals and yields more quantity of silicon into hyperpure polysilicon.

The plant will employ Wacker TCS technology. The technology has several benefits such as lower energy consumption, and improved reactor yield and throughput. It also uses fewer raw materials and improves environmental sustainability.

Market growth

The global market for polyvinyl products is estimated to register a compounded average annual growth rate of 42% during 2007-2014. Wacker sees a strong demand for polysilicon from solar cell (photovoltaic) manufacturers and electronics industries.

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