PMC-Paprican air content probe and control system has been designed specifically for use in the pulp and paper industry. It can also be used effectively in other applications where the measurement or control of air content is important, such as water/waste and mining industries.
PMC provides an effective solution to identify and control problems before they start. The System utilises high accuracy, durable ceramic sensors that are ideally suited for measuring levels and pressures in paper slurry applications. Other applications include controlling the defoamer in recycling and brownstock washing, and verifying the signal from a consistency meter.
The System provides real-time measurement of entrained or injected gas content in a pre-determined zone of an aqueous suspension. Two PMC flush-mounted pressure sensors are placed in direct contact with process liquid. The sensors are typically fixed laterally on one or more pipes that are firmly held in place on a plate or in flanges mounted on the top or side of a tank, vessel or flotation cell. The change in pressure between them provides an accurate measurement of dispersed gas content.
Numerous functional gases are used in pulp and paper manufacturing for processes such as pulp-bleaching liquor-oxidation, pulp and water acidification, ink flotation, and effluent treatment. Unwanted air in these systems can seriously impair pumping, washing, and papermaking operations. Online monitoring of air content allows for better understanding of aeration in the decontamination and de-inking of wastepaper pulp.
Continuous monitoring of air content in the paper slurry helps to control the air bubble size in recycled pulp suspensions.
Dispersed gas creates surface foam in white water, which eventually releases hydrophobic contaminants when the bubbles burst at the surface. This phenomenon contributes to formation of deposits, web breaks, dirt spots and holes in paper. In pulp washing, air bubbles in pulp mats reduce drainage rate and generate foam in the drop leg. The addition of defoamer is essential for coalescing air bubbles in the pulp suspension or in the surface foam. Moreover, presence of air causes some on-line sensors such as microwave consistency meters to malfunction. Conversely, dispersed air may be beneficial when introduced on purpose in a suspension, by aspiration or sparging systems. For example, dispersed air flotation is a key step for decontamination of recycled pulps, where both the amount and size of air bubbles directly affects the rate at which ink particles and other contaminants are removed from the suspension.
The probe can be mounted temporarily or permanently in both non-agitated and agitated vessels, over a broad range of temperatures, in corrosive and abrasive media. It can be easily made portable for monitoring and troubleshooting air content in various site locations.