GEK Wiki / Temperature Instrumentation
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Temperature Instrumentation

Page history last edited by Wendy 13 years, 4 months ago

 

Thermocouples

 

Type K thermocouples are acceptable for all locations in the gasifier. Most thermocouple readers are designed to read Type K (including the GCU). Other types require a reader designed and calibrated for that type. Metal sheaths 1/8" or 1/16" in diameter work well (1/16" is very flexible and can passed between sealed flanges if necessary).

 

 

Important Thermocouple Locations

  • Top of Reduction: Mounted to the top of the reduction cone, at the edge (TC needs to exit the top of the reactor).  Use a 1/4" ss tube welded to the lip of the reduction cone to protect the TC.  The tube should protrude into the flow area about 3/8" of an inch.  Plug the tube with a ss weld at the end.

     

  • Bottom of Reduction: Inserted through the manometer port, between the air lines, 1" in from the bottom edge of the reduction code (must be removed when removing reactor)

     

  • Combustion: Mounted 1" directly in front of the air nozzles. I have added another 2.5" mild steel sacrificial sheath around the thermocouple to protect it from oxidation in the combustion zone (this sheath burns out quickly, use stainless if possible). We are retrying the alumina sheath shown in the pyrolysis assembly photo below (white). There are different ways this could be mounted. Mine comes down with the pyrolysis profile thermocouples from the top lid and goes into a small ring welded to an air nozzle offset by thin rod to keep it centered. Consider the impact placement will have on fuel flow and design to minimize this effect.

 

These are key. Other thermocouple locations are described at the bottom of this page.  See the pictures below for how these are installed (plus one other odd one to measure the side of nozzle temps, which you don't need)

 

Here's a thread from the forum with some more install info: http://www.gekgasifier.com/forums/showthread.php?p=707#post707

 

 

 

Pyrolysis/Combustion Profile Assembly

 

The pyrolysis profile assembly is designed to measure the vertical temperature profile through the bed of biomass above the combustion zone. The combustion thermocouple (1/8" sheathed) is installed in front of an air nozzle (1" in front, same elevation). A series of 1/16" sheathed thermocouples are installed at 1", 2", 3", 4", 6", and 8" above the tip of the combustion thermocouple. A thin (1/16") stainless tube is brough to combustion level to measure pressure at combusiton. A piece of alumina tubing is shown above to protect the combustion thermocouple at high temperatures. The thermocouples and tube were seperated by threading a series short two hole alumina rod lengths in a helical pattern around the central combustion thermocouple resume help. The seperation provided by this should limit thermal conduction between thermocouples. The assembly was held together by wrapping stainless wire around it.

 

 

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