Thermal Flow Meters for Pulp & Paper Applications

Thermal Flow Meters for Pulp & Paper Applications
Trees used in paper-making go through processing in a de-barker and a chipper, where they reduce to approximately one-inch wood chips. The wood chips are pressure cooked in a digester and become pulp, refined, turned into slush, and screened. Screening drains away liquid, and the resulting pulp is then pressed and dried into the paper. Several steps within the pulp and paper-making process create emissions that must be monitored and reported.

Creating paper pulp relies on a careful balance of low-velocity air flows among the various processes. For example, the recovery boiler following the digester modulates to follow the digester load changes. Additionally, a recovery boiler uses the black liquor's chemical reaction to generate heat for the boiler. It has three airflow systems requiring tight control to create stable air flows.

Kurz Instruments provides a good application note explaining the areas where thermal flow meter uses appear in the pulp and paper production process. You can download the application note below.

DOWNLOAD THE THERMAL FLOW METERS FOR PULP & PAPER APPLICATION NOTE HERE

For more information on instrumentation for pulp and paper mills in New England, contact PSI Controls (Piping Specialties, Inc.). Call them at 800-223-1468 or visit their website at https://psi-team.com.

Ball Valves Used for Black Liquor in Pulping Kraft Process

Black liquor valves

Many toxic, corrosive, and reactive chemicals are used in pulp and paper mills in chemical pulping. This incredibly hostile environment requires well-engineered automatic valve systems and durable valve actuators, spring units, and positioners. 

Suppose you understand how paper is made and what chemicals are usually used in the atmosphere. In that case, you can instantly understand why special consideration is required for valve and actuator selection.

In the early stage of paper production, digesters combine high heat and a heavy alkaline liquid called "white liquor" to convert wood chips into a pulp during separation from wood chips. White liquor (mainly sodium hydroxide and sodium sulfide), process water, heat, and pressure are used to separate wood chips into lignin and cellulose fibers. The white liquor breaks down the lignin (the substance that binds the wood fiber together) in wood chips. The resulting combination of water and spent white liquor produces "black liquor." This liquid pulp residue mixture made up of lignin and hemicellulose, and inorganic compounds such as sodium hydroxide and sodium sulfide is toxic. Another by-product of this process is Hydrogen Sulfide, a toxic, corrosive, and flammable gas. 

Effects on Ball Valves

In piping and ball valves, managing these process chemicals and by-products is difficult. Pipe diameters range from 2"-10", but the most common sizes are 4", 6" and 8." Usually, these processes are ANSI / ASME Class 150 and ANSI / ASME Class 300, the most common end connection being 150 # and 300 #. Process temperatures are usually high, between 250 ° F and 350 ° F. The valve body and end connection materials are generally 316 stainless steel, but you'll also find carbon steel requested. Applications can include manual lever, gear operators, pneumatic actuators, and electrical actuators in valve assemblies.

The most concerning issue is the sticky molasses-like liquor builds upon the ball valve face and contaminates the back seat spaces, inducing strong internal clearance forces, resulting in valve lock-up over long static periods. A superior ball valve seat design from A-T Controls addresses the viscous material problem.  

A-T Controls developed a solution for this extreme pulp and paper service and black liquor service with notable improvements to their FMS series. This valve incorporates a "scraper seat" feature that eliminates the molasses-like residue baked on the ball's face and eliminates valve lock-up. The addition of Aflas ® o-rings seal the seat cavity from media build-up, and a Venturi hole in the ball is also provided.

Typical black liquor ball valve from A-T Controls:

  • Series: A-T Controls FMS
  • Sizes: ½" -8"
  • Rating: ANSI/ASME Class 150/Class 300 with 150# and 300# flanges, API 607.
  • Ball and Seats: Tungsten Carbide coated metal scraper seats (Aflas® o-rings and Venturi Ball for black liquor service.) 

Please consult a Piping Specialties Applications Engineer for material selection for your black liquor application. This information is a guideline, and customers are solely responsible for construction materials, preparation of the valves for service, and lubricants being compatible with their black liquor application.

For a free consultation, call Piping Specialties at 800-223-1468 or visit their website at https://psi-team.com.

Radar Level Measurement: Comparison of 24 GHz and 80 GHz

Radar level transmitters are among the most accurate technology choices for process level and storage tank applications for continuous level measurement under demanding conditions.  These transmitters utilize Frequency Modulated Continuous Wave (FMCW) technology that offers superior signal processing capabilities and more reliable measurement than other techniques. The state-of-the-art signal processing capabilities of these transmitters, along with their frequency range, helps to ensure optimum application coverage.

24 GHz radar transmitters cover a broad range of applications, including liquids & solids. 

80 GHz radar transmitters are especially beneficial for level measurements in narrow tanks with internal obstructions due to their small beam angle.

This video, courtesy of AMETEK Drexelbrook, demonstrates many of the other differences between 24 GHz and 80 GHz models of radar level transmitters.

For more information on radar level transmitters in New England, contact PSI Controls (Piping Specialties, Inc.). Call them at 800-223-1468 or visit their website at https://psi-team.com.