简单地说, 增稠剂 专注于沉淀的固体, and clarifiers focus on the clear overflow liquor — the name given to a solution free of suspended solids.
澄清器
A clarifier will typically treat a low-density slurry of less than 5% weight per weight solids with a focus on producing a clear liquid with suspended solids of less than 100 parts per million (ppm). 达到这些高度的清晰度, the upcurrent flow (rise rate) needs to be low to prevent entrainment of fine particles.
澄清器 are characterized by having larger diameter, shallow tanks with a more lightweight rake and drive system.
如何确定澄清器的尺寸
A starting point for sizing clarifiers for most sand and mineral processing applications is to take the volumetric overflow divided by settling area, 通常缩写为m/hr或gpm/ft2.
虽然这提供了一个指导方针, testwork is highly recommended to confirm the required rise rate to meet the target clarity. Testwork is comprised of a matrix of different throughput rates, 化学剂量和剪切条件. 对于任何给定的流, the tank area or diameter required is determined by the designated rise rate, the chemical dosage regime and the specific design of the equipment.
澄清剂是如何工作的
The clarification process uses gravity but is often enhanced with chemical treatment. To achieve high levels of clarity, both a flocculant and coagulant may be required.
The coagulant can be added initially to neutralize the surface charge on particles and allows them to stick together, 形成团块. The flocculant can be afterward to pull all the coagulated clumps together to form flocs.
A complication may arise for very low-density feed slurries (those less than 1% solids) where the particles are too dispersed to be easily collected by the flocculant or coagulant. 在这些情况下, an improved solids-contact mechanism may be required where careful control of shear conditions is needed. These mechanisms ensure sufficient energy to create large (and faster settling) colloids but not high enough shear to break apart the loosely bound flocs.
One commonly employed technique for improved solids contact is known as High Density Sludge (“HDS”). This technique involves recycling a portion of the underflow to a pre-contact tank to mix with the incoming feed to reduce the sludge volume and increase the density
Another technique is to settle the solids on steeply inclined laminar plates. 用这种技术, the solids fall faster by sliding down the plate surface rather than in a free-settling mode. 原则上, 这是个好主意, but the requirements to build a plate stack that can structurally manage a high solids loading restricts this nifty idea to smaller, 轻质固体应用.
Should the process specification require a suspended solids level significantly lower than 100ppm – perhaps discharge to public waterways, a sedimentation process alone may not be a cost-effective solution. Combining it with a security filter may be an option. Think of a security filter like a swimming pool filter — the clarifier overflow passes through a medium such sand or other more exotic material. However, as with the swimming pool filter, you have to periodically backwash to clean the media.
增稠剂
A thickener, in contrast, is designed to do just that – thicken!
While a part of this process by definition releases the liquid, 溢流液的质量是次要的. 悬浮物的净度可达1,000ppm在某些情况下是可以容忍的, though a typical specification is less than 300ppm.
像澄清器, 增稠剂 can use flocculants to clump smaller particles together, allowing them to settle faster than they would on their own without the use of the flocculating agent. A rake mechanism in the 增稠剂 helps guide the settling solids to the center of the tank for discharge via centrifugal underflow pump.
取决于增稠剂的种类, the underflow will range in density from a free-flowing mud to a paste.
增稠剂 are characterized by having higher side walls, 更陡峭的地面斜坡和更坚固的机构.
如何给增稠剂上浆
以获得最高的底流密度, features such a tank geometry and rake design will be more critical. 底流密度, 在某种程度上, is proportional to the mud residence time (how long the particles remain the tank) and the compression effects of the column of settled muc so driven by the side-wall height.
澄清剂或增稠剂?
It can be tempting to try to do both the thickening and clarifying functions to maximum benefit in one go. 虽然这在技术上是可行的, you’d need a really large diameter (for low rise rate and good clarity), yet tall tank with higher side walls and a robust drive and rake mechanism.
正如你所期望的那样, 这将带来巨大的成本溢价, and it may be difficult to convince the money men it is a sound proposition.
The trick is to figure out what is really important for your application, 增稠或澄清, 并设计适合的设备.
