Optimizing product flow and powder injection rates
Controlling injection rates of dry powders plays a crucial role in many industrial processes. The ability to monitor and control the injection rates can mean the difference between quality product and profitability versus….well, let’s just say lots of headaches.
Importance of Controlling Powder Injection Rates
Think of any number of different applications that incorporate injection of dry bulk solids or powders and it becomes evident that carefully controlling the rate of injection can have a dramatic impact. For example, coal injection rates need to be consistent and responsive to operator commands. Failure to control these accurately can result in overheating of the furnace, increase emissions or low output.
Continuing with coal, lets move to carbon black/sorbent injection for mercury control. If the injection rate is not consistent then capture efficiency will also vary possibly resulting in failing a stack test, which in turn could result in large fines and even shutdown until compliance is achieved.
In other facilities injection rates play a crucial role in many manufacturing processes. Interrupted flow or injection rates could severely affect the final quality of products like ferrous and non ferrous refining and smelting.
For these reasons we can see that careful control of injection rates should be a priority among plant operators. But what options are available for flow rate control?
Mechanical Flow Measurement Devices
Within bulk conveying applications numerous different types exist. By far, the most common are mechanical devices. These devices essentially are mechanical components that move as product flows by/through/over them (think watermill in a river turned by passing water). The rotation is then calculated by the device controller to provide a measurement of product flow.
While a relatively simple solution for many cases, mechanical detectors have several distinct drawbacks. First, they are subject to extensive wear and tear, especially if the product itself can cause abrasion. Diligent preventative maintenance and repair are required to keep them from failing. Second, mechanical devices require the product to flow through them, some designed to require ALL product to flow through them. This creates a problem when any kind of issue occurs as it can cause blockages or even halt production until the mechanism is repaired.
Using Triboelectric Technology for Monitoring Injection
In recent years, many have turned to using triboelectric detectors for flow monitoring in injection systems. This is because of the unique advantages that these systems provide over other monitoring methods. Using the triboelectric effect Auburn Systems has created several flow monitoring systems. These include a Flow/No Flow application as well as a More Flow/Less Flow application.
In both systems, an electrically isolated probe is inserted into the conveying duct (either purposely intrusive or a non-intrusive ring design). As the material passes through the duct and past the sensor a triboelectric signal is generated that is then transmitted to the controls in pico amps, and it then either triggers a simple relay alarm signal or passes on the pico amp signal to a PLC or other control system. When used for simple Flow/No Flow monitoring, the relay signal is usually set to trigger when the signal drops below a certain level, indicating very conclusively that flow has ceased. In dilute phase systems using the sensor for More Flow/Less Flow monitoring, the unit can either trigger an alarm once the signal (And thus flow) has changed by a given percentage or can pass the reading on to the control room where it can be monitored.
In particular, using the More Flow/Less Flow monitoring for injection rates can be useful for plants looking for tighter control over dry powder injection rates in their processes. It offers a relative indication in real time on whether the flow is increasing or decreasing they can carefully make adjustments to the flow rate.
Careful monitoring of dry product injection rates is essential for the many processes that employ them. Take time to investigate why so many have decided to employ triboelectric flow monitoring over other methods and see for yourself the benefits!