Flow control for polysilicon

During the process, raw material, intermediate products and byproducts include Si powder, Cl2, H2, HCl, SiHCl3, SiH2Cl2 and SiCl4, therefore valve’s design must be able to deal with these medium, especially the highly abrasive Si powder.

The chemical compounds are extremely dangerous. H2 and SiHCl3 are easily combustible, HCl is dangerous and extremely corrosive, SiHCl4 is a highly toxic substance that poses environmental hazards, which makes it necessary to recover these substances, and bring them back into the production process. Handling these chemicals, including the safe and environmentally sound disposal as well as emission control at the same time is not easy. All these chemicals should be captured and recovered to decrease raw material consumption and increase the whole process efficiency.

SiHCl3 production is a complex reaction equilibrium system, different products and by-products form in the fluid bed reactor. Reaction condition should be controlled precisely to maximize SiHCl3 yield.

Health, safety, environment

Valve leaking poses both an environmental and safety issue due to risk of fire, toxicity and volatility of gases. Emergency shutdown and on/off valves must be able to perform their action in a process or equipment failure. 

Top-class products at maximum yield

The market calls for clean products and high quality. It is important that the process is stable, flexible and under control. Proper valve performance in fluid bed reactor, CVD reactor and recovery system improves the accuracy of throughput control and adversely affects to the plant performance and also the downstream processes. 

Maintenance costs

Valves play an extremely important role in successful polysilicon producing performance. Poorly performing valves in the process must be serviced because they will have a direct impact on the efficiency of the process. 

Plant run-time

Silicon plants are looking for longer plant run-times since downtime means production losses and is a remarkable cost including maintenance costs. This requires reliable equipment.

We are all tuned up to answer these challenges through our polysilicon application experience and product offering for control, safety and automated on/off duty that ensure high valve performance. Neles valves have proven performance history and are designed for efficient and reliable process operation.

Safety

We are the only single source emergency shutdown valve supplier who has the experience and knowledge to combine intelligence with most reliable valves and actuators. Technology selections like rotary stem operation and inherently fire safe design ensure that latest emission and fire safety standards can be applied. Reliable valves with first intelligent, SIL3 approved safety valve controller and partial stroke testing system Neles ValvGuard™ will ensure that plant emergency shutdown valves will always perform properly when needed.

Efficiency

Throughput losses and poor control performance will be avoided with high performance rotary valves. Flow through the process unit may be changed as the need arises with rangeability of 150:1 and further with full bore ball valves. Our advanced intelligent digital valve controllers for control, on-off and ESD applications ensure high positioning accuracy and fast response. Correct valve selection and sizing with our Nelprof™-program we can assure the best valve performance and process control.

Availability

Simple rotary designs, same face-to-face dimensions, and global service network and inventory management will help you to optimize your maintenance activities. Rotary valves have been in service for several years without requiring maintenance and show no sign 
of leakage. The proven performance of Neles valves with long lasting metal seat tightness and shut-off capabilities makes them an ideal solution for on-off, control and critical catalyst handling applications.

Reliability

Valve performance trend data collected by our smart valve controllers and analyzed by open FDT/DTM technology based configuration and condition monitoring software, makes it possible to predict and respond to maintenance requirements and reduce unscheduled downtime. This gives full transparency to the valve performance in process control.