Valve Selection for slurry duty / H2 Service leak tight closure

[plantprowler]

What are good choices for a valve type for use on a 3" line that introduces a solid+liquid slurry into a reactor. But afterwards the valve must be able to shut off tight against a pressure of approx. 10 barg within the reactor.

Max Temperature is 100 C but the reactor headspace has Hydrogen gas in it. So valve must hold leak tight against H2.

In standard valves e.g. butterfly will the solids interfere with the ability to get a leak tight fit with time?

Solids are relatively hard. Some of the solids are irregularly shaped lumpy granules (approx. 10 mm dia) whereas others are a very fine sub micron sized catalyst powder.

 

[blacksmith37]

Butterfly valves are not a possibility. I would use 2 valves in series, maybe with a bleed. Ball or plug should work in the slurry at moderate temperatures . I would prefer gate type.

 

[plantprowler]

Thanks @blackmith!

Can you explain how you mean by the bleed arrangement you mention?

 

[LittleInch]

You're not asking for much....

Is the valve(s)to be used to start / stop flow?

Hard bits from micron to 10mm will eat most valve types and seals.

Hydrogen is especially difficult to seal against.

You probably need to go for some sort of expanding gate or plug valve as the seal valve with something else used to start / stop the flow, but not required to seal.

Also look up knife valves like this

http://www.dezurik.com/products/pro...-steel-knife-gate-valves-kgnrsb-kgnmsu/56/15/

They seem to have a good reputation for slurries and tight shutoff at relatively low pressures, but you really need to talk turkey with a few suppliers technical reps to understand what they can and can't do.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[blacksmith37]

A bleed is a third valve to vent the volume between the main valves. Large valves (8" +) may have an optional integral bleed valve. It can be also used to measure any pressure between the 2 main valves.

 

[plantprowler]

@Little inch:

Yes, it is a start / stop duty. The actual slurry flow through the line is only during batch-startup; perhaps 1-2 hours every 24 hrs. Rest of the time the valve is just sealing off H2 pressure inside the reactor.

 

[bcd]

Another option. A dual seated floating ball valve. Metal seat on reactor side, polymer seat on opposite side. When material is flowing into the reactor, most abrasive wear is on downstream, metal seat. When valve is shut and pressure is in reactor, ball is pushed into polymer seat and shuts-off tightly. Could be the lowest cost option.

 

[moltenmetal]

"...must hold leak tight against hydrogen..."

All valves leak. And all systems involving valves must manage that leakage, rather than trying to prevent it entirely.

A double block and bleed arrangement which has already been suggested, with the bleeder connected to something which will collect and recycle or vent the hydrogen, would be your best bet. Otherwise, you're going to be doing a lot of maintenance on a single valve in a vain effort to keep it "leak tight"