Silicon Manufacturer Reduces Reactor Turnaround Frequency

Challenge

A high-purity silicon material manufacturer was looking for a solution to ensure a positive shutoff of gas flows. The company produces 500 tons of high-purity silane gas, 1,000 tons of electronic grade polysilicon, and 18,000 tons of granular polysilicon annually.  They commercially manufacture solargrade-silicon using silane-based fluidized bed reactor (FBR) technology.  In this type of reactor, a fluid (gas or liquid) is passed through a solid granular material at high enough velocities to suspend the solid and cause it to behave as though it were a fluid. The reactors require severe service valves to isolate hydrogen and silane gas flow at very high temperatures. The gas streams have entrained silicon dust, which is incredibly abrasive. The customer required positive shutoff of these gas flows.

Solution

Valin worked with Metso (Neles) engineering and the Metso service center to develop a loaded seat valve providing bidirectional sealing. The bidirectional sealing and vent port in the body cavity allows the customer to use one valve as a double block and bleed valve. The metal-seated valves maintain positive shutoff for process safety. Valin also provided multi-cell cartridge heaters, controls, and a high-temperature sintered metal filtration system to remove silicon dust from the recycled hydrogen. Along with product specification, Valin’s team provided design, engineering and consulting expertise.

Customer Benefits

The customer runs each reactor in a continuous campaign.  After each campaign, a reactor turnaround is required (which costs the company around $200K). A turnaround is a scheduled event wherein an entire process unit is taken off stream for an extended period for revamp and/or renewal. If a valve begins to leak during a campaign, the campaign must be aborted prematurely, and the company must schedule a turnaround regardless of the current campaign duration. Valin's solution has successfully prevented aborted campaigns saving the company hundreds of thousands of dollars.

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