Technical Products and Services Inc. MANA Technical Products and Services Inc.
Your Single Source of Fluid Handling Products Since 1981

145 State Highway 94, Blairstown, NJ 07825  Ph: 908-362-9981  F: 908-362-5631

 

Blow off : Cement and Mining Industries

 

 

sonic-air-systems-blower-air-knife-cement-blow-offA recent installation at a major Eastern U.S. cement plant has proven to be an innovative solution for cleaning their finishing mill feed belt thereby eliminating persistent and costly powder recovery and dust control issues resulting in a less than 6 month payback based on labor reduction, environmental safety and recovery of previously discarded clinker powder. 

 

The standard cement industry process is that after clinker is cooled, it is then conveyed to a silo where additional compounds such as gypsum and limestone are added.  The completed formulation is then transferred on a 40 inch wide  open flat conveyor feed belt to the finishing mill for final grinding.  During the empty conveyor belt’s return trip to the silo a significant amount of residual clinker powder and dust is generated throughout the entire area as it becomes dislodged from the surface of the belt, including the small cracks in the conveyor belt. Powder continuously falls from the belt across the entire return conveyor route back to the silo, with heavier powder concentrations quickly building up near the finishing mill and under drive rolls which vibrate these powders from the belt. 

 

sonic-air-systems-blower-air-knife-clinker-blow-off
Clinker being transferred

sonic-air-systems-blower-air-knife-clinker-blow-off
Clinker is dumped

into a finishing mill

sonic-air-systems-blower-air-knife-clinker-blow-off
Clinker Dust falling

from the conveyor belt

sonic-air-systems-blower-air-knife-clinker-blow-off
Surface of a clinker conveyor belt

sonic-air-systems-blower-air-knife-clinker-blow-off
Clinker dust under a conveyor
sonic-air-systems-blower-air-knife-clinker-blow-off
Drive roller dislodging clinker dust
sonic-air-systems-blower-air-knife-clinker-blow-off
Air Knife Attached
to Scraper Bar
sonic-air-systems-blower-air-knife-clinker-blow-off
Air Knife Blowing
Dust From Cracks
A large percentage of this material is so fine that it easily becomes airborne dust, resulting in a coating on all of the surrounding instrumentation, motors and other rotating equipment.

 

Clinker transfer belts are made of special materials to withstand the clinker temperature and weight although eventually they develop small surface cracks.  During the trip from the silo to the finishing mill, fine clinker, gypsum and limestone powders settle into these cracks where they remain even after the clinker is transferred to the finishing mill. Once the belt becomes inverted, after the head pulley, the generation of excess powder and dust can be so problematic to the personnel, equipment and inventory costs that most plants must institute daily manual clean-up and recovery programs. This non-value added process can last as long as two hours per day and consist of shoveling the powder into wheelbarrows for transfer to the finishing mill and then sweeping the area clean of the residual dust. In addition to trying to maintain a clean working environment, this material represents saleable product, so its’ recovery and transfer to the finishing mill is considered a priority. These daily clean-ups result in a significant portion of the powder, in dust form, being discarded after sweeping the area.

 

The Maintenance Manager at this particular cement plant had heard of testing performed at their sister plant that proved  a High Velocity Air Knife installed inside the discharge chute between the scraper bar and chute exit prevented powder and dust from carrying forward from that point. It was decided that testing would be performed at this plant because there were some operational differences.  The local representative for Sonic Air Systems loaned their 7½ HP demo blower to the customer for testing and participated in analyzing the performance. Sonic is a manufacturer of high efficiency blowers and air knife systems located in Brea California.  They are known for pioneering innovative blower and air knife designs for any application or environment.

 

During these new tests a number of variables were adjusted in order to determine the optimum blow off effectiveness. These variable included the air knife angle of attack, spray height, the air knife aperture (slot width) and the exit air velocity in order to obtain sufficient belt cleaning. The result was a clean belt with the lowest power demand from the demo blower. This data, along with the digital pictures and videos, were provided to Sonic Air Systems for additional analysis.  Video clips of the dramatic test results are below.

 
 
 

Sonic Air Systems provided a detailed proposal that included a belt cleaning performance guarantee that consisted of a single air knife oriented across the width of the conveyor belt, located between the scraper bar and exit of the chute.  The high velocity air clears the cracks of dust which remains contained within the chute for transfer to the finishing mill with the rest of the clinker.  This system is specifically designed to provide a high impact laminar air flow across the entire conveyor belt with a minimum amount of air flow so that it would not upset the operation of the existing dust collection system.

 

Use of the available existing compressed air was considered, however the blower system costs only $3 per day to operate whereas using compressed air would have cost over $50 per day.  This significant energy savings is due to the ultra efficiency of the blower design, as it consumes about 6% of the horsepower required by an air compressor which would require 15 times the horsepower of the Sonic system.  It was clear that implementing the blower system was the most cost effective solution for this application.

 

The compact blower system has sealed bearings, integral belt drive and a cartridge air filter on the inlet of the blower, so there is very little maintenance. The average annual preventative maintenance cost of this blower/air knife system over a five year period is less than $500 annually and would consist of cleaning or replacing the intake filters as needed, drive belt once each year and blower bearings at 18,000 hour intervals. All of these items are each easily replaced within 15 minutes and do not require special skills, tools or training.

 

 

 

 

The customer has operated their system continuously since May and they advised that it has resulted in the following advantages:

 

• Labor reduction = $6,240 annual savings.

• Less gypsum, lime and fine clinker is lost during the conveying process = $TBD in recovered product.

• A significantly cleaner work environment which is expected to prolong the life of instrumentation, rotating equipment and the conveyor   belt itself. Again, the savings is expected to be sizeable but will take 6-12 months to define.

 

Due to the short term R.O.I. resulting from these process improvements (within 6 months), the customer is evaluating other opportunities to upgrade several additional conveyors used to transfer clinker, coke and coal.

 

Blower Specifications

• 305 MPH, (5HP)

• 16 Groove flanged pulley

• 316SS acoustical (protective) enclosure

• Dual inlet filter/silencers

• Hard anodized aluminum XE Sonic Air Knife