Auburn’s award-winning TRIBO technology has also successfully been adapted to serve various roles in process applications. With its ability to non-intrusively monitor particle flows in a multitude of airflow environments, triboelectric particle monitoring technology has proved the most adaptable and reliable for solving several process engineering challenges. These include Flow/No Flow and More Flow/Less Flow detectors as well as particle velocity monitoring.
Auburn Systems’ Triboelectric dust detectors are known for their wide use in monitoring PM 2.5 emissions from pollution control devices such as dust collectors. So, how is it that they can also be used to monitor particle velocity? By taking data from two TRIBO units placed in line Auburn is able to determine particle velocity with great accuracy using a patented cross correlation technique developed by Auburn Systems. These units offer improved reliability and accuracy compared to older mechanical devices for dense flow and microwave and pitot tube detectors used for dilute phase conveying. Many Auburn units have been running without replacement for over 30+ years! With Auburn’s help many facilities have been able to overcome unique process engineering challenges.
For example, one cereal manufacturing plant used Auburn particle velocity monitors to solve a difficult conveying issue. During the manufacturing process the finished breakfast cereal is fragile and needed to be protected from damage in the conveying system. Using Auburn’s TRIBO particle velocity monitoring systems operators monitor the velocity of the product being conveyed vertically in an air classification system. The purpose is to convey the product at a minimum velocity to prevent damage without causing backups and other conveying difficulties. The non intrusive sensor is placed flush on the duct wall.
Another example is monitoring velocity in order to compensate for product buildup within a conveying system. Another food manufacturer uses Auburn triboelectric detectors to monitor the velocity of marshmallow bits throughout its production process. The marshmallow product builds up over time and eventually the equipment has to be shut down for cleaning. Before reaching that point the partial buildup causes the velocity to drop off, which further speeds up the build up process. To extend time between shutdowns a triboelectric system monitors the velocity within the conveying system and then increases the fan speed to maintain adequate velocity and keep the product moving.
Particle velocity also plays a key role in the function of dust collection systems. The dust particles must travel above a certain velocity to remain entrained or carried by the airstream. This is called the minimum conveying velocity and varies from product to product (usually between 3500 - 4500 ft/m). If the air velocity in the system ever drops below this minimum conveying velocity the dust particles will begin to settle and dropout of the airstream. This is important for proper dust collector operation, preventing health and safety hazards, and minimizing emissions. Let’s consider each and how conveying velocity can affect each one.
These dust accumulations lead to blockages which choke the system, reducing suction and preventing it from adequately venting any dust source(s) to which it is connected. This can cause damage at sources, increasing airborne dust levels and creating an unsafe working environment while also increasing emissions. Even more seriously, in applications involving combustible dusts any accumulation within the ductwork can provide a fertile starting location for a combustible dust fire or explosion, with the potential to destroy entire facilities and regularly cause millions of dollars in damages and often take the lives of workers.
Auburn’s TRIBO series makes use of a simple and durable probe design that is superior to conventional mechanical or optical flow detectors. For this reason, TRIBO Flow/No Flow detection systems prove reliable for many process applications such as:
• Powder injection
• Pneumatic conveying
• Screw conveyor flow, etc.
The conveying or transporting of dry particulate for manufacturing processes requires a reliable means to verify flow/no-flow (blockage). Auburn loss-of-flow detectors, which are closely related to the dust emission bag rupture detectors (onset of particulate flow) are in use for a wide variety of flow applications in a number of industries. Typical examples include: monitoring for blockages or for no-flow detection in pneumatic conveying/material handling systems, to monitor screw feeders and/or fan operation; monitoring the velocity of particles to reduce product breakage for cereal manufacturers; monitoring pulverized coal injection to boilers to balance the flow evenly from the multiple nozzles (in beta tests) and more.
A particularly challenging application where triboelectric systems provide the only reliable solution is solid fuel injection measurement for energy efficiency. Controlling a modern boiler, furnace or kiln at, or near, maximum efficiency is an extraordinarily complex problem. Numerous parameters need to be monitored and controlled. Moreover, when the fuel is pulverized coal, the monitoring of fuel feeding rate and consistency remains a challenge.
Traditional instruments cannot monitor the gas-solid two phase flow in real time with enough accuracy, robustness and cost-benefit ratios. Inefficient fuel feed monitoring further complicates the ability to optimize boiler/furnace performance. Excess fuel flow is ultimately wasteful, and unnecessary additional air flow will dissipate valuable generated heat, and both cases will produce excessive emission.
Also, in very recent developments, large scale power utilities are required to reduce or eliminate SO2 and mercury emissions and must verify the flow of 1) lime and 2) activated carbon injection into the exhaust gas flow stream, agents injected to react with those pollutants, and subsequently collected by fabric filter collectors for disposal. These applications, a hybrid of a process control/compliance application are particularly appropriate for triboelectric technology.
In these applications more comprehensive control technology will save energy and reduce pollution.The use of Auburn Systems’ TRIBO More Flow/Less Flow products has helped many industries facilities overcome these challenges and others to reap significant operational benefits as well as cost savings over other methods.