Dry Flow Meter System Delivers
Material returned directly to the mix process from the Baghouse causes extreme fluctuations. Ez-Flo Dust Return System not only eliminates the sag and surge feeding it also allows the user to reject excess material easily.
Positively Unique! This system has so many pluses. The benefits vary depending upon what the job requires. Job 1) When a certain amount of dust is to be returned to the process and the balance is to be rejected. Job 2) When all the dust is to be returned, but the varying return baghouse rate to the drum mixer requires even flow rate. Job 3) When mineral filler is required to help make up the minus 200 the baghouse dust is not providing, such as SMA jobs where total minus 200 control is imperative. The features that make this system so versatile and so different from other auger/bin systems are numerous. Surge bin discharge is normally controlled by vane feeders which are expensive, heavy, and take up a lot of vertical space. The vertical space is necessary to make it as voluminous as possible so as to absorb all sags and surges, yet have steep cone angles to keep material from bridging, and not too high as to make it necessary to feed the Bin with augers, yet short enough not to erect the bin with a crane.
Butterfly valves require very little maintenance compared to a rotary valve (vane feeder) and take up only 6" of vertical height. Flow control with a butterfly valve can be much smoother than the shovels full of material being added one shovel full at a time with a vane feeder, especially when a large vane feeder is rotating slowly. Therefore a modulating (variable position) butterfly valve was used to control the flow of material passing through. Some people feel bridging problems in an automatic system is best handled using a vane feed over a vane feeder. We say bridging is a problem with either system and that the problem needs correcting whether a rotary valve or a butterfly valve is used.
The Control System pictured to the right not only adjusts the position of the valve, it also will fire a burst of air into the material when bridging starts to develop. So as a means to continuously weigh the dust, an Ez-Flo (26" tall) flow scale with temperature protection was mounted on the down stream side. The Scale reported the flow rate to the Controller and the Controller regulates the flow by adjusting butterfly valve. This allows great closed loop control since the Butterfly Valve feeds the Flow Scale with no intermittent conveying device between them like an auger. Placing the Surge Bin on load cells and weighing the depleting weight is not possible since the Surge Bin always has material feeding it making it impossible to determine the depletion rate. When rejecting material, ingeniously the filling of the surge bin first and regulating the bin’s output and the balance of the dust to be rejected is carried over to the second discharge port on the Surge Bin Feed Auger. When using the system to take the sags and surges out of the dust flow; many systems fail because the operator sets the speed to keep the bin empty. He does this so as not to be bothered to adjust it now and then or he does not understand the importance to adjust it. This totally defeats the purpose of this equipment in this application. The control system gently reminds the operator audibly when the discharge flow is set too high or too low. A slight adjustment in speed allows the Bin Level to correct itself. If the correction allows the bin level to pass through the Mid-Level Point, the operator is reminded again that a set point change is required. Some high spec jobs require close control while adding minus 200 (such as fly ash) to the mix. The ideal situation is to have one scale weigh the Dust and the Flyash and control it accordingly. The Mid level and Low Level Bindicators could be used to stop and start the discharge of flyash into the surge bin as controlled. Control of the flow of material can be tricky. The lower flow rates occasionally desired may be so low as to cause bridging when the valve is near closed, causing surging as the controller tries to meet the demand of the set point required. A combination of strategic aeration pad placement, air pressure regulation and automatic air jet bursts helps this situation significantly.
Watch Dust Control Video https://www.youtube.com/watch?v=cZMFz5urHfM
When thinking...Solids Impact Flow Meter, Solids Flow Meter, Continuous Weigh, Mass Flow Scale, Bin Depletion Scale, Dry Flow Meter, Belt Scale, Mass Flow Scale, Impact Flow Meter, Weigh Depletion Pod…Think Ez-flo.