EXAIR Adjustable Air Amplifiers Helps Clear the Smoke

Smoky Foundry
Smoky Foundry

An overseas customer had a problem with their coal blasting furnace. As the workers would open a 1.2 meter by 1.2 meter door to shovel in coal, the foundry would fill with smoke.  This was a hazard and a nuisance for the crew.  They saw articles about how EXAIR Air Amplifiers were used in smaller ovens for exhausting hot flue gases, and they wondered if the EXAIR Air Amplifiers could be used for something much larger.

He sent me an email with some additional details about their furnace system. They had a fan that was mounted in the stack that had a capacity of 50 m^3/min.  This was fed into a filtration collection system to remove the residue byproducts.  The temperature inside the furnace was approximately 450 deg. C.  From this information, I could calculate the required velocity to keep the smoke inside the furnace.

Smoke starting to migrate out of the opening
Smoke starting to migrate out of the opening

In sizing this application, I determined that I could use an equation from Heskestad and Spaulding. This equation was developed to find the minimum velocity required to keep smoke from egressing into corridors during fires.  In this case, we were keeping the smoke from egressing into the foundry.  The formula looks like this:

V = 0.64 * Sqrt(g * H * (T – To)/T)      Equation 1

V – Velocity (m/s)

g – Gravitational acceleration (9.8 m/s^2)

H – Height of Opening (meters)

T – Avg. Fire Temperature (Kelvin)

To – Avg. Space Temperature (Kelvin)

In this equation, we are mainly fighting the forces of the temperature difference from inside the hot furnace area to the outside cooler area.  The outside area was near 40 Deg. C, and this gave me the temperature difference.  In converting these temperatures to the absolute temperature, Kelvin.  I calculated the fire temperature, T, to be 450 Deg. C + 273 = 723 Kelvins; and the space temperature, To, to be 40 Deg. C + 273 = 313 Kelvin.

In placing the given information into Equation 1, the minimum velocity could be found.

V = 0.64 * Sqrt(9.8 m/s^2 * 1.2m * (723K – 313K)/ 723K)

V = 1.65 m/s

 

If the velocity could be maintained at this mark of 1.65 m/s, then the smoke could not egress into the plant.  They had a stack fan that was flowing 50 m^3/min, or 0.83 m^3/sec.  We can determine the velocity that the stack fan was producing by calculating the flow over an area:

V = Q/A      Equation 2

V – Velocity (m/s)

Q – Flow (m^3/sec)

A – Area (m^2)

 

With a door opening of 1.2m by 1.2m, or 1.44m^2, the velocity can be calculated by placing the known values into Equation 2:

V = (0.83 m^3/s) / (1.44m^2)

V = 0.58 m/s

Now we can see why they were getting smoke pluming from the coal furnace into their facility. They required a minimum of 1.65 m/s, and the stack fan was only drawing 0.58 m/s.  If we take the difference, we can determine how much additional velocity will be required to keep the smoke within the furnace: 1.65 m/s – 0.58 m/s = 1.07 m/s.

 

To determine how much air flow would be needed to create a velocity of 1.07 m/s through the door opening, I just had to rearrange Equation 2 to determine the flow, Q.

Q = V * A = 1.07 m/s * 1.44 m^2 = 1.54 m^3/s

To better correlate the flow data, I converted 1.54 m^3/s to 92.4 m^3/min of air flow.

EXAIR's Adjustable Air Amplifier
EXAIR’s Adjustable Air Amplifier

EXAIR Air Amplifiers are designed to have large amplification ratios (the ratio between the amount of ambient air being moved compared to the amount of compressed air used).  This makes them perfect as an efficient air mover.  Being that this was a furnace application, the High Temperature Stainless Steel Adjustable Air Amplifier was required.  This Air Amplifier has a temperature rating of 374 deg. C, and it can be easily mounted at a safe distance to meet this temperature requirement.  The largest unit that we stock is the model 6034, a 4 inch (10cm) Stainless Steel Adjustable Air Amplifier.  It has a 24:1 amplification ratio that can create an outlet flow of 34 m^3/min.  (It would only need 1.42 m^3/min of compressed air at 5.5 bar to create this outlet flow).  For this customer to reach the 92.4 m^3/min to keep the smoke from escaping, he would need to install three units (3 * 34 m^3/min = 102 m^3/min).  He mounted the Stainless Steel Adjustable Air Amplifiers to some extraction wyes in their stack and added solenoids to them.  So, when the crew opened the door to load the coal, the Air Amplifiers would operate to keep the exhaust smoke from filling the room.  The company and operators were very satisfied as it made the environment clear to see and safe to work.

If you have an application where smoke and fumes are a nuisance, you can contact an Application Engineer at EXAIR to see if an Air Amplifier would work in your application.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Super Air Knife Eliminates Alumina Dust Carryover on Conveyor

EXAIR Super Air Knives are quite often used on belt-style conveyors to blow off and clean the conveyor of any residual product that may try to stick to the belt and fall off at points along the travel where the product can pile up and create a real mess.

Our most recent version of this application was for a conveyor moving alumina dust in a foundry. Our Australian distributor, Compressed Air Australia, worked with the end user to apply this solution.

Mounting an Aluminum Super Air Knife across the width of the conveyor on the underside, just down-stream of the head pulley, the customer was able to completely eliminate the dust accumulation under the belt.

Before Super Air Knife Installation:                          After Super Air Knife Installation:

Alumina dust 1Alumina dust 2

The Super Air Knife with Plumbing Kit, installed below the conveyor belt:

Alumina dust 3

By installing the Super Air Knife, the customer was able to keep production running on the conveyor. Before, they had to stop periodically so the operators could clean up the dust. Dealing with the dust is a safety hazard for the operators for a variety of reasons including inhalation and personal safety risk working around moving parts. The solution allowed production to remain up and moving for longer periods. It also allowed workers to be safer in the environment and also concentrate their manpower and time on other activities as they no longer had to worry about cleaning up this material.

The compact nature of the Super Air Knife with the Plumbing Kit allowed the customer to tuck the unit right up where it was needed most. Notice how the Super Air Knife is blowing almost parallel to the belt. This is key in any Air Knife installation to allow for the longest contact time possible between the airflow and the target. This counter-flow arrangement is how the best performance is achieved with the Super Air Knife.

Neal Raker, Application Engineer
nealraker@exair.com

Vortex Tubes Keep Load Cells in Steel Mill Cool

ladle car

Our Australian distributor, Compressed Air Australia has a customer in the foundry business that produces large building components. Recently, they ran into a problem with their load cells overheating. Load cells are positioned underneath what is called the ladle car so that the contents of the ladle that rides on top can be weighed.

load cell

The contents of the ladle are obviously very hot and radiate heat in all directions. This can cause the compartments in the floor where the load cells are contained to become very hot as well. This caused errors in readings that were being produced by the load cells. It was determined that some form of cooling was going to be necessary. However, due to very tight configuration of the load cell compartments, choices were limited.

The customer had heard about vortex tubes, made an internet search and found EXAIR Vortex Tubes. With the guidance of our distributor, we were able to determine that a model HT3230 (High Temp. Vortex Tube) connected at each load cell compartment, purging the enclosed space, dropped the temperature from 200°C down to a much cooler 80°C that was requested by the customer.

The customer was able to address their over-heating problem adequately and the load cells are working properly.

Neal Raker, Application Engineer
nealraker@exair.com

Super Air Knives Used To Deflect Fumes and Smoke from Furnace

One of our overseas distributors had an interesting application in a foundry. Their customer has a large furnace that opens at various times for a variety of reasons. When the furnace doors open, smoke and fumes come rolling out of the furnace. The customer has a large vent hood type system to aid in removal of these fumes and smoke. Unfortunately the vent does not capture all the smoke when released. So, the customer devised a plan to mount (4) model 110042SS 42” Stainless Steel Super Air knives onto large masts to get them up high enough to create a “ceiling” of air that would deflect the smoke into the vent hood for removal. Following are a couple of photos of the set up.

SAK2 sak1

Below is a photo of the control cabinet housing the filter and regulator equipment.

SAK3

Previously, the customer had nothing in place to assist the vent hood. Now they do and are quite happy with the result.  There were some small system adjustments that needed to be made, but once fully operational, the Super Air Knifes performed well to help reduce the overall pollution seen within the area.

Neal Raker, Application Engineer
nealraker@exair.com