Keep Your Preheaters and Coolers Absolutely Clean and Flowing
Turbo-Flow™ is an automatic high pressure pulsing solution that keeps riser duct and cyclone walls clean. Recently introduced by Flow Industries Ltd, the developer of Silo-Flow™ - a leading solution for the toughest silo/bin/hopper clogging problems (see also in ICR September 2009). Flow’s patentedTurbo-Flow™ technology uses air pressure of up to 3000psi / 200bar. It was field tested successfully and is being implemented by the world’s leading cement manufacturers. The system can be also used efficiently in clinker cooler applications to avoid snow-man formation.
The most effective solution thus far is by manually using high pressure water-jets. This laborious and dangerous job is carried out by specially trained and dressed workers. The high pressure water (typically up to 10,000 psi / 600-700 bar) may cause both mechanical and thermal damage to the refractory lining. The workers must wear protective gear and are exposed to various hazards. Air cannons (~100 psi / 7 bar) are frequently installed in large numbers throughout the preheater’s riser and cyclones floorsand on the cooler walls. A typical preheater tower may have between 30-150 air cannons. The low pressure air canons present a partial solution with questionable effectiveness and an operational and maintenance headache.
The Turbo-Flow™ system consists of several interconnected components: 1)Turbo-Flow™ Device (TFD)
(including air and water injection systems) 2)Control Panel for both air and water supplies 3)High Pressure (HP) Compressor
(capable of 3000 psi / 200 bar) 4)Air tanks (air storage buffer)
The Turbo-Flow™ system creates repeated high-impact combined air-water spray that covers a wall area of 5-9 sqm. Once the air and water supply are switched on, the TFD pulses automatically at a rate of one pulse every 3-4 seconds. Typically the system is activated for 30-90 seconds every 30-90 minutes. The frequency and pressure depend on the severity of the buildup and whether full buildup cleaning or only maintenance is required.
The TFD is mounted on any existing or specifically built 6” (for TFD-6 model) or 4” (for TFD-4 model) pipe and flange. For best results its internal pipe connects to heavy duty nozzle that is built into the refractory and points towards the adjacent perpendicular wall. The nozzle may be the same as used today with low-pressure air-cannons, although larger, heavier duty nozzles may prove more durable.
A Field TestFig. 2 illustrates the Turbo-flow™ test apparatus including the 6” pipe, steel reinforcements and nozzle. The test period lasted 1.5 months. Two weeks of base lining the data, then two and a half weeks of TFD activation and monitoring, then dismantling the TFD unit for lab inspection and another ten days to monitor after effects was conducted at Nesher Cement (a 5-MTA integrated plant at Ramle, Israel) during March and April 2011. The test objective was to monitor daily changes in the wall temperatures supplemented by visual inspection through the wall’s peek-holes. These would serve as a proxy to the amount of buildup on the internal wall, as the temperature would be inversely proportional to the amount of buildup. The more buildup, the more the wall would be insulated and the lower the external temperatures would be. The affected wall was divided into a virtual grid of sixteen inspection segments. Most of the segments had peek-holes, some of them used for the water-jet cleaning apparatus.
Typically each pulse will consume 1-1.5 liters of water and 200-300 liters of air. The air-water spray has a dual action. The first is the sheer impact of the combined air-water mass that hits the wall at high force generated by the high pressure air stored in the TFD and its high-speed release. The secondary action is that of the water droplets “exploding” into gas on impact with the extreme temperature inside the vessel. This additional energy is released right at the target zone and magnifies the impact. Both actions are less extreme than water-jets, but they are delivered repeatedly and effectively.
During the TFD activation period, it was mistakenly shut off twice, once over a weekend and once overnight. Also the kiln and preheater had a couple of irregular days when the buildup increased unexpectedly but then returned to “normal” rate.
Test results showed that the TFD made a very significant difference. At the affected area the internal wall was kept completely clean of almost any buildup. This was evidenced by the significantly higher temperatures on the wall across from the TFD, and from the peek-holes inspections at areas 9-12. Internal air-pressure data used for online buildup monitoring, had a full inverse correlation to the temperature readings, i.e., the higher the temperature the lower the air pressure readings were from the relevant segment. Perhaps most importantly, the water-jet crew that typically cleans this wall 1-2 times per day (!) has not performed ANY cleaning on any segment during the TFD operation, except once after the weekend mistaken shut-off.
The complete raw data from the test shows a clear trend for higher temperatures and clean wall in the segments across from the TFD unit, in particular segments 9-12 but also 13-16. The latter normally tend to be cleaner than the rest of the wall. Nevertheless, peek-hole inspection showed an even cleaner surface than usual. For more information and complete test report please contact: info@flow-industries.com.
Fig. 1: A TFD-6 unit mounted on the corner of a riser duct wall
Fig. 2: Schematic illustrating top view of the riser duct section and Turbo-Flow™ installation
Fig. 3: April 14th temperature readouts and
peek-holes inspection data
overlaid on the virtual grid
(not all segments have peek-holes)
Fig. 4: The clean riser wall segments 9-16 showing all
peek-holes open during inspection 17/4/11.
Fig. 5: Graph of temperatures recorded on the segments across from the TFD over time
Fig. 6: Difference in average segment temperatures between when the TFD unit was working and not.
Note that the most significant difference
is in segments 9-12,
however, most other segments were positively affected.
