Abstract SYMPHOS 2011

at a considerable cost and the water recycled. Long term containment of this material also requires considerable
resources, management, and potential environmental risks. In short, there is no overall “good home” for this
material.
The present primary outlets for FSA are fluoridation of drinking water, manufacturing Al-fluorides/Cryolite or
flurosilicates. It only consumes a small fraction of the potential worldwide production volume. But these are low
value added products and generate additional environmental issues. Our proposed technology has a very smart
solution to convert the FSA into the value chain of “renewable green energy” and/ or of semiconductor industry
without environmental discharge/liability issues associated with the phosphoric acid manufacturing plants. The
technology “value adds” to the FSA stream and at the same time removes the environmental issues associated
with it. It converts fluosilicic acid (FSA) to solar/electronic grade polysilicon without any detrimental environmental
aspects.
This high value technology process utilizes fluosilicic acid (FSA). The FSA when mixed with concentrated sulfuric
acid breaks down in to STF, HF and water. The STF is scrubbed with sulfuric acid to remove any residual moisture,
compressed and piped directly to the process for making polysilicon. The HF and water are absorbed by the
concentrated sulfuric acid. This stream is recycled back to the phosphoric acid plant to be utilized in the phosphate
rock reactors. The STF generated is further processed to produce high purity electronic grade silane and polysilicon.
Parts of this process are practiced by many major polysilicon and silane manufacturers. The major steps for
the process are, FSA to STF, STF to SILANE – SILANE purification – SILANE to POLYSILICON, for solar/electronic
applications. Major aspects of the technology will be discussed along with its inherent advantages.
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TAILOR MADE SCREENING TECHNOLOGY FOR DIFFERENT SCREENING TASKS
IN THE PHOSPHATE PROCESSING INDUSTRY
PH-O-07
Oliver Pikhard
Dipl.-Ing. Sigurd Schuetz, Dipl.-Ing. Dietmar Koch, Dipl.-Ing. ,
RHEWUM GMbH, Remscheid/GERMANY
The paper will present an overview of specific requirements of the phosphate industry on screening processes and
technology and in which way they can be met by choosing the right screening technology. The investment costs for
the classification of phosphate products are relatively small compared to the total investment costs. On the other
hand the financial impact of the wrong screen type, mesh or anti-clogging device on the production can be high
compared to the investment costs of a screen. Due to numerous developments in screening machines it becomes
ever more important for the plant operator to decide in favour of the best available technique. The choice of the
right screening technology is influenced by various parameters - some basic facts on screening will be presented as
well as different types of screening machines to demonstrate the way to deciding for the best available technique.