I tore down the gasifier today, and found that I had a fair bit of moisture in my filter. I was not happy with the performance of the copper loop- so decided I would try a new idea that I had been thinking about. Basically, I wanted to make a small water line that dripped water down into a steam vessel that had a nice big outlet. The outlet and body is made from 1/2" iron pipe, and on the bottom is a roughly 1" stub of 3/4" round stock with some little fins welded on. I read that steam expands 1700:1 compared to the water volume, so this way I figure there will be much less back pressure trying to push the water back up into the hopper.
It mounts in the center, too, and the thought is that the charcoal will be able to slip past it down to the reaction zone.
I stuffed a thermocouple up into the steam vent that goes maybe halfway into the iron pipe.
I got good results, although I am still dialing in how to run it, I think. There needs to be some way for air to get in just below the needle valve, or else the drops can sort of bunch up in the clear tube.
A quick video of it in action.
It ran pretty well, putting out around 600 watts with the heater once it got up to temperature. It took about 20 minutes from start up for the temperature of the steam to exceed 100C. Once up and running, I was getting about 160C steam, and no water was making it down to my nozzle. The upper thermocouple stayed at about 500C. It was cold and windy today, and I realized I really should have some insulation on my steam pipe.
Also, I measured the water drip rate afterwards, and was putting in about 2.75ml/min. Runtime was good today, I shut down at about 48min, when the outlet temp had risen to 77C.