I have experience with metering molten sulfur and would like to up grade my pump to something jacketed. I found a 40K usd$ unit which is kind of expensive for a pump that meters .1-1.5 liter per minute and is not fully jacketed.

So anybody out there that has experience with metering small quantities of molten sulfur?

anybody know of any companies that offer some nice jacketed metering pumps?

We had similar issues with pumping molten iodine (MP=115C)..
Most of the pumps (including ceramic piston metering pumps with heat tracing, PTFE diaphragm pumps in a "hot box"  thermostatically controlled to 130 C--I can give you references if you are interested) would end up either leaking at the seals or freezing.  

One idea that we came across but were never fully able to implement (project ended) was having a feed tank and metering high temp (130C), pressurized liquid H2O into the tank.  Exactly the same amount of I2 (or sulfur in your case) would be displaced into the process, assuming that there was no vapor left in the tank.  This takes some design work (obviously) to make sure that there is adequate pressure relief in case the sulfur solidifies, etc., but it should be doable.

Possible holes that need to be investigated:
1) Make sure that the densities are significantly different so that you don't get an emulsion of the phases
2) I think that the equilibrium lies toward elemental sulfur and water, but make sure that you won't form H2SO3 or other compounds in significant quantities (sulfur chem definitely seems complicated)
3) Obviously, this could cause trouble if trace amounts of water will be an issue.  We were desperate to find a way to get the I2 flowing, though, and this was one of the few promising, possibly repeatable ways within our budget that we could find.

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