Automated Kiln Control System

Goal: Reduce the workload and produce more consistent, high

quality filters

The overall piping systemComponents: 50kg tank of liquefied natural gas, ball valves to isolate tanks, hot water bath for converting LNG to gas, high pressure gauge, alarm system to indicate when tank needs to be changed, manual high pressure valve, electronic valve system, low pressure gauges.

Tank and hot water bath

Inside of hot water bathComponents: coil of stainless steel pipe and 3000 watt water heater (below the coil), thermocouple for electronic control of bath water (not shown).

Water bath is kept at about 65 C. Temperature is electronically controlled.

Gas temperature at outlet of water bath is about 45 C – plenty hot enough.

Homemade alarm system to indicate when gas tank needs to be changed.

Manual high pressure regulator and electronic valve.The manual regulator is set so the maximum outlet pressure is 0.05 Mpa – which is the maximum pressure the system needs for firing the kiln to cone 010. The electronic valve then just needs to control the pressure from approximately 0.005 at the start of the burn to 0.05 Mpa at the end.A ball valve is kept slightly open so that even if the electron valve is completely closed the burners will continue to have gas.

Low pressure gauge indicates pressure going to the venturi burners.

The brains of the system is a PYX Series Fuzzy Logic Controller while the heart of the system is a digital electronic valve system

Using information from a thermocouple inside the kiln, the controller and electronic valve work in tandem to control the temperature inside of the kiln.As can be seen the ideal temperature (in green) at this point in the burn was 809 C and the actual temperature read by the the thermocouple in the kiln was 808 C. The system can keep the temperature within 2 C of the program temperature profile. The valve was open 27.1% of full open (at bottom).Other information: 47.4 % is the room humidity and the room temperature was 34.7 C. Temperature on the door of the kiln was 825 C. We use this for comparison to the primary temperature measure near the top, center of the kiln.

One of our 6 venturi burnersThe valves and baffles are always kept fully open.

View of the venturi in use.At 810 C the flame is very blue as it goes into the kiln.

When cones begin to fallThe operator watches for the 010 cone to fall. She then tells the controller the maximum temperature has been reached and controller holds the temperature for a 1 hour soak and then the operator turns off the system by turning off the gas and controller. In Picture: from front to back: Cones 013, 012, 011, 010, 09