Thermaflow vs. Carbon Stick

COMPARISON OF THERMAFLOW HEATING SYSTEM TO CARBON STICK HEATERS

Carbon sticks have been in the hot dip galvanizing industry for over 30 years. They are made of carbon, utilize submerged combustion, and with the exception of the bottom cap, hold up very well in the corrosive environment. The thermaflow heaters are constructed of carbon as well, and this again is because carbon is inert to acid and preflux, handles extremely high temperatures, and is quite simply the best choice for the application. Thermaflow heaters also utilize submerged combustion because it is the most efficient means of heat transfer available for acid and preflux tank heating. This is where the similarities end the uniqueness of the Thermaflow heating system begins.

Both use carbon:

Carbon sticks – The carbon stick is designed to allow air and gas to travel downward from the top to a chamber in the bottom, where the mixture is ignited and allowed to exhaust through holes located in a removable bottom cap with flame actually penetrating into the liquid. The velocities of the gases erode the holes and require replacement of the bottom cap periodically (sometimes often).

Thermaflow heater – The design of the heater allows for combustion to take place in a burner located at the top of a carbon tube. The carbon is utilized as a firing tube, precisely machined to allow for combustion to be completed before allowing the products of combustion to be exhausted into the liquid. The combination of tube length and the diameter of the exhaust outlet minimize erosion. After 18 months of service, there is no visible wear on the carbon tube.

Both utilize submerged combustion:

Carbon Sticks – The carbon stick has air and gas brought in at the top of the stick through a piping tee, and the two gases mix together on the way down to the bottom. The ratio of air and gas is not precise, as the operator makes adjustments in mixture mostly by what ever seems to make it stay ignited, or more simply put, guessing. Once a flame has been established, the stick is lowered into the tank, where the flame forces its way into the liquid. This contact of flame to liquid allows for a portion of the flame to be quenched, causing incomplete combustion of some of the gas. The combination of poor mixture and unburned fuel take away from the efficiency of submerged combustion.

Thermaflow heater – The Thermaflow heater utilizes a proprietary design (there is a patent pending) which has a burner mounted at the end of a carbon tube. The burner is equipped with both air and gas orifice plates with pressure ports to measure exact flow of gases. These flows are then adjusted to precise levels based on empirical data on the burner, which allow for proper air/gas ratios. In addition, the carbon tube is machined to a size that will allow the complete combustion of fuel before it is exhausted into liquid. This combination of proper mixture and complete combustion allows only the Thermaflow heater to achieve efficiencies of more than 90%.

Both have combustion blowers:

Carbon sticks – The air requirements for carbon sticks requires that a pressure of at least 6-psi be supplied. This high pressure is most commonly supplied by a rotary lobe type of blower with a positive displacement, which means that the rpm of the blower be timed for the volume of air output desired. If, for instance, the blower is sized for three carbon sticks and you want to shut down to two, you either change pulley sizes or vent the excess air to the atmosphere to keep from damaging the blower. Also, this type of blower has a reservoir of oil that lubricates the moving parts that requires periodic changing and disposal. The life expectancy of the blower depends on how well it is maintained and is usually 2-3 years. The high volume/pressure requirements also require an electric motor with high horsepower.

Thermaflow heaters – The air requirements for Thermaflow heaters is very much the same as what is used in most industrial furnaces today. Designed for reliability as well as efficiency, the air supply is provided by a centrifugal type blower. The air pressure is well below 2 psi, and once the system has been installed, the number of heaters you are running can be changed without making any changes to the blower. The only maintenance required is to lubricate a shaft bearing every six months with a shot of grease and there is no oil to change or dispose of. The typical life of this type blower is usually in excess of 10 years. Since the pressure requirement is so much less, the electric motor size is usually 1/3 to ½ the size of that for carbon sticks.

Ignition:

Carbon sticks – Carbon sticks require manual ignition. This is accomplished by raising the stick out of the tank, placing a torch into one of the holes in the bottom cap, and then lowering the stick back into the tank. This task requires experience, as it is sometimes difficult to get the air/gas mixture right, and is time consuming for a hoist to handle the stick during ignition.

Thermaflow heaters – Thermaflow heaters are equipped with an ignitor, which only requires the turning of a switch to ignite. The heater never has to be touched. The ignitor switch illuminates once the heater is on.

Flame monitoring:

Carbon sticks – There is no flame monitoring on the carbon sticks. The only way to know when they are out is by having personnel make a visual check.

Thermaflow heaters – Thermaflow heaters have flame monitoring which is incorporated into the flame safeguard system. The unit is designed with gas solenoid valves that are operated by a flame relay, which will turn the gas off in the event of flame failure, air or gas pressure getting out of acceptable range, or electrical failure. An alarm output is provided for monitoring. Although the thermaflow heaters are extremely reliable, proper monitoring will let you know in the event of a flame failure.

Protective housing:

Carbon sticks – Carbon sticks are supported from the top and hang exposed in the tank.

Thermaflow heaters – Thermaflow heater design completely encapsulates the carbon tube with high-density polypropylene to protect it from damage caused by mishandled work being processed in the tank. This housing is designed in such a way as to promote a suction from the bottom which causes a flow of liquid to travel up through the heater and out an opening in the top. This flow allows the Thermaflow heater to direct and mix the exhausting gases to achieve maximum thermal efficiency.

BTU output:

Carbon Sticks – The BTU output is estimated to be between 350,000 to 400,000. There is no adjustment; therefore it may be difficult to achieve proper temperatures.

Thermaflow heaters – Thermaflow heaters have a BTU output range from as little as 5,000 to over 500,000 per heater. This means that you will be able to achieve ideal operating temperatures in any size tank, and in most instances with only one heater.

Build-up of crystals:

Carbon sticks – Carbon sticks have a tendency to allow build-up of crystals at the exhaust holes in the bottom cap, which causes the flame to become unstable.

Thermaflow heaters – Build-up has not proven to be a problem for the thermaflow heater. The design of the heater utilizes a much larger, single exhaust hole, which does not allow any of the flame to come into contact with the liquid, which promotes crystallization.

Thermaflow Heating System has a patent. Plastic Welding & Fabrication, LTD. Owns the sole license agreement to manufacture and distribute.