Clarification Principles In Separation

Clarification Principles In Separation,  removing suspended solids from liquids is necessary in many processes. Plants generally use clarifiers for this. Clarifiers are settling tanks and, thus, often also are called settlers. In addition, the devices sometimes serve for thickening — in these cases, they are termed thickeners.

Clarifiers usually feature a built-in mechanism for continuous removal of the solids deposited by sedimentation. Concentrated impurities discharged from the bottom of the tank are known as sludge while the particles that float to the surface of the liquid are called scum. Most commonly, a clarifier comes in a circular design but rectangular and other configurations also are available.

Usually, before a fluid goes to a clarifier, it undergoes coagulation and flocculation processes. These cause finely suspended particles to clump together to form larger and denser particles that settle more quickly and stably — easing the separation, improving efficiency and, thus, conserving energy. Such treatment also promotes the settling of colloids. In addition, isolating particle components first using these processes may reduce the volume of downstream treatment operations like filtration.

After coagulation, flocculation by large mechanical paddles allows coagulates to form denser particles or flocs that settle more easily. The stream then goes to the clarifier where the separation of clarified liquid from the solids and flocculated coagulate occurs by permitting the heavier and larger particles to settle to the bottom. Particles from a layer of sludge requiring regular removal and disposal. Clarifiers usually incorporate mechanical solids-removal devices that move as slowly as practical to minimize re-suspension of settled solids. The clarified liquid often is pumped to filters to eliminate any residual particles; filtered liquid then flows to the next process.

Tanks are sized to give liquid an optimal residence time. Economy favours using small tanks but if the liquid flow rate through the tank is too high, most particles won’t have sufficient time to settle. Considerable attention is focused on reducing liquid inlet and outlet velocities to minimize turbulence and promote effective settling throughout available tank volume. Baffles prevent fluid velocities at the tank entrance from extending into the tank; overflow weirs uniformly distribute flow from liquid leaving the tank over a wide area of the surface to minimize resuspension of settling particles.

Design and Operation of Clarification

Control of liquid flow into a clarifier is important. Reducing the velocity increases the hydraulic retention time inside the clarifier for sedimentation and helps to avoid excessive turbulence and mixing, thereby promoting the effective settling of suspended particles. The inlet flow also should be distributed evenly across the entire cross-section of the settling zone inside the clarifier; as a very rough indication, the settling zone’s volume often is around 30–40% of total capacity of a clarifier.

During the Clarification Principles Separation, the sludge formed from the settled particles at the bottom of the clarifier, if left for an extended period, may become gluey and viscous, creating difficulties in its removal. Using gas (or other means) to free the sludge can cause the re-suspension of particles and the release of dissolved materials throughout the liquid, reducing the effectiveness of the clarifier. This sludge should be drained properly from the bottom of the tank — usually this involves using specially designed positive-displacement pumps.

Two dominant forces act upon the solid particles in clarifiers: gravity and particle interactions. Too high a flow can lead to turbulence, hydraulic instability and potential flow short-circuiting. Improvements and modifications made during the last few decades, particularly for improving the separation process, have enhanced clarifier performance. For instance, installation of specially designed perforated baffle walls (based on advanced hydrodynamic simulations) promotes flow uniformity.

The clarifier mechanism is designed for constant operation, the flow usually enters the center draft tube through a horizontal influent pipe extending from the tank sidewall.

Enduramaxx’s Clarification Tanks are used for the continuous mechanised removal of suspended solids or solid particles from a liquid. Clarification Principles Separation are also involved with Conical Clarification Tanks or Clarification Cone Bottom Tanks are available in a range of sizes. Enduramaxx Polymer Mixing Tanks manual preparation systems for powder polymers which provides an economical and effective solution for effluent treatment in process and industrial applications.  Polymer Mixers, also known as agitators, are an essential part of industrial process engineering – from the smallest plant room to a clean-in-place system for an entire factory. Therefore the Enduramaxx range of electric chemical mixers is a great complement to any chemical dosing system. Mixers for these polymer mixing vessels are designed as a low-speed mixer, for Water Treatment with viscous fluids, with options of Single or Three Phase Motors available with stainless steel shafts.   Coagulation Treatment MixersFlocculation Treatment Mixers are part of the primary wastewater treatment.

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