washing & classifying | mclanahan
Sand, aggregate and minerals must be washed in order to meet many required specifications for various projects. Washing and classifying equipment provides producers with the ability to remove excess water and deleterious materials such as clay, silt, shale, coal, soft stone, roots, twigs and other debris from the rock.
McLanahan manufactures a wide range of washing and classifying equipment, meaning the company is able to select an option that will ensure each customer has the best process engineered solution for their washing and classifying application.
McLanahans washing equipment can help producers meet specifications by removing the deleterious material that can harm final products. This equipment employs rotating paddles and screw shafts to scour and abrade the material, as well as a rising current of water to aid in the liberation of clays, crusher dust, silt and other fine material. The agitation of the equipment results in particle-on-particle attrition that also helps to remove deleterious material.
Classifying equipment from McLanahan can help producers to separate even the smallest material to create products of various mesh sizes. This allows producers to do more with a single deposit, potentially increasing their profitability. Besides classification, McLanahans classifying equipment can also aid in the removal of lightweight deleterious material.
Flat-Bottom Classifiers/Lites-Out I Hydrocyclones I Hydrosizers I Rotary Trommels I Sand Classifying Tanks I Sand Washing Plants I Screw Washers I Slurry Pumps I Thickeners I Ultra Fines Recovery Plants
If not washed, construction material containing deleterious materials can cause cracking in structural projects and prevent drainage in transportation projects. Similarly in the coal industry, unwashed coal can decrease its quality and efficiency and, therefore, its price.
Washing is becoming increasingly important as producers find themselves progressing farther into their reserves and extracting material with greater amounts of deleterious materials, or facing stricter specifications for their construction aggregate. Washing and classifying equipment helps producers meet these strict specifications and do more with their deposit.
Another function of washing and classifying equipment is particle sizing. Classifying equipment is ideal for separating material that is too small to be sized on traditional screening equipment. Using classifying equipment, producers can remove excess material, retain finer particles and create multiple products from a single feed. In this way, producers are able to make the most of their deposit by creating additional salable products at one time.
There are many options when it comes to choosing the right washing and classifying equipment for your application. Some material only requires rinsing on a screen to remove the undesirables, while other material requires a more vigorous washing process to liberate the clay and other debris.Certain equipment is best for washing coarse materials, while other equipment is ideal for washing and classifying fine materials. In order to process material for a variety of markets, producers can employ a combination of washing and classifying equipment to meet their needs.
grit classifier basics: what is a grit classifier? - jms
Grit Classifiers or also known as a grit screw, grit separator or grit classifier are used at wastewater plants at the headworks (front end of the plant) to help separate the grit from organics and water.Grit removal needs to be done at the headworks of plants to help reduce wear to upstream pumps and mechanical equipment. Grit can also cause pipe blockage and reduce the effective volume of the treatment basins. Grit classifiers usually consist of a hopper positioned on top of an inclined screw conveyor. Typically grit classifiers are made of stainless steel housing and have a high strength abrasion resistant fights on the screw because of the abrasive application.
All types of grit classifiers typically receive a grit slurry from an air lift pump or a grit pump(s). Most classifiers receive a grit slurry that is 1-3% solids mixture.The hopper of a traditional grit classifier is designed for the shortest retention time to allow heavier grit to settle, but not the lighter organic material. The organic material is carried out of the hopper with the grit free overflow and is returned to the plants process. As the grit is carried up the incline and passes the water line elevation, by rotating a very slow RPM screw conveyor, it allows time for the water to drain back into the hopper. The screw conveyor conveys the grit out of the system and usually into a dumpster to then be hauled to a landfill.
Grit classifiers can range from 12 to 24 in diameter (12 is the most popular size). Grit classifiers are sized by hydraulic flow of gallons per minute (GPM) and solid conveyance for the screw conveyor. Influent flow drives the size of the hopper and whether a hydrocyclone should be considered.
When receiving flows less than approximately 250 GPM a hydro-cyclone is not necessary, but when flow exceeds 300 GPM or so the use of hydrocyclones is often considered. Hydrocyclones separate the water from the grit, sending over 90% of the flow back into the plants process grit free. The grit slurry, less than 10% of the flow, goes to the grit classifier hopper. Adding a hydrocyclone to a system allows the hopper of the grit classifier to be smaller for a system that will have a higher influent flow to achieve the same retention time and efficiency.
To be successful in a obtaining a uniform grind that is necessary to achieve a high percentage of recovery it is necessary to control the degree of fineness that the ore is reduced to. This is done by separating the fine material from the course and regrinding the coarse until it is fine enough for efficient mineral extraction.
To be able to obtain the necessary control over the amount of grinding required, a method of effective classification and separation by size must be available. For maximum effectiveness it should take place after every stage of grinding.
The types of equipment that are used to accomplish this are called CLASSIFIERS. There are three basic kinds used. The first two, the RAKE classifier and the SPIRAL or screw classifier work on the same principal, and are not often used any more. These two types were popular for many years. It wasnt until the development of the CYCLONE type classifier that their popularity faded. You may still find a few though, in the older mills and the mills that require a classification of the larger ore sizes that the cyclones are not very good at sizing.
Both the rake and spiral classifiers take advantage of the natural settling characteristics of ore. Any time that slurry is allowed to flow over a surface the tendency of the ore is to graduate itself into layers of different sized material. The larger sizes will be on the bottom, these are also the ones that are the slowest moving. As you come closer to the surface, the material will become smaller and faster until the very finest and the easiest to wash away is on top.
To understand how these two classifiers make use of this settling action, a description of them is required. First, to have the classification happen, the slurry must be able to flow. This means the classifiers must be inclined. The working portion of these two classifiers are the RAKES or SPIRAL/screw which are placed into the flow of ore. To separate the course material from the fine, the rakes and spiral make use of the same theory, but differ in its application. The theory is, as the slurry flows down the inclined bed of the classifier it will separate into different sizing. The larger ore that is on the bottom will not be flowing as fast as the light ore on top.
To separate the two, the rakes and the spiral will pull the all of the slurry back up the incline, then, let it go to flow back down towards the underflow or in this case the fine ore discharge point. The smaller, faster ore will be able to travel a longer distance than the large particles before the rakes or spiral will pull the ground material back towards the coarse ore discharge. If the Classifier is able to pull the course ore backwards further than it can travel forwards, then eventually the bigger particles will be pulled all the way to the top of the incline where they will be discharged. The smaller faster pieces of ground rock will end up at the bottom of the incline to be discharged as fine material that is ready for the next stage of processing.
This type of classifier will do away with the necessity of pumps. The length of the incline that is needed is long and steep enough to have the material lifted to the feed end of the mill. The flow of the finer ore will run down hill to the next piece of equipment.
The concentrator that used this type of classification was built on the side of a hill to make use of gravity to get the material from one stage of production to the next. It was because of this that this type of concentrator was referred to as a GRAVITY FLOW/MILL. I used the past tense in this paragraph because this design of mill is no longer in use.
I want to know what is the range of the % Solids content in overflow from screw/spiral classifier in Hematite Iron ore washing for efficient operation of classifier. I also want to know what is Auto dilution in thickener. Does Auto dilution has any effect on Pumping capacity of clarified water from thickener.
Each operation is different, but the good news is that you can simply determine the solids % wt. in the SOF, try 2 -3 times daily over one week, get a profile. If below 5% wt., you may not need auto dilution, also depending on ore and grind size. This is almost a clarifier regime, often workable without rakes in certain units. Above 5% in general start looking at auto-dilution before adding the flocculant do this off-line. Make sure that the thickener underflow (TUF) discharge comes out continuously, otherwise you may need to play with the lifters, if you have them. The UF solids % wt. must be correlated with the yield stress.look for 30 Pa high-end cut off value for lean operation. When the ore or grind size changes, you need to repeat the evaluation.
My take on these classifiers is that the clear water added to the classifier feed determines the size of the largest heaviest particle going to the overflow. This is the criteria that you should be working to achieve. As you probably have more than one classifier reporting to the thickener you will need to perform the solids percent in each overflow. As you add water to the classifier feed, the separation efficiency increases. You should be raising or lowering the discharge weir to attain the desired size cut. Only if the thickener becomes overloaded should you add water. Pumping excess water adds cost and wear to pump trains.
Pulp density of the Overflow defines % of solids in thickener. This solids% depends also up on quality of recycle water used in spiral processto know quantum of solids..you have to give feed quantity and underflow quantity.
The % solids in classifier overflow may vary in wide range, its all depends on your ore characterisation and operating variables. For the same operation we used to get 15-18% solids as my ore contains too much fines & this is not end process in our case.Try to concentrate on end products. Do not let go valuables in your final tailings.
spiral classifiers | screw classifiers | dove
DOVE Spiral Classifier, also referred to as Screw Classifier, or Spiral Mineral Separator, is highly efficient classifier designed for closed circuit wet classification and separation of the Slimes (Fines) from a sandy sized (Coarse) material. It is well suited for classification, where a two product size-split is required. Due to inherent operational qualities, DOVE Spiral Classifier is ideally suited Sizing applications, Washing Applications, and Dewatering sand or crushed material from Hydro cyclone, or lower screen residues.
DOVE Coarse and Fine Spiral Classifiers are supplied in various capacities, tub lengths, screw sizes and technical specifications. We supply total of 16 models, where 10 models are configured with single screw and 6 models with dual screw.
Spiral Screw classifier is a type of common mechanical classifier, consists primarily of an inclined tub and a transport screw for the coarse material. The fine material residue is at the lower end of the tub and the coarse material residue is at the upper end. The principle of the operation and separation of solid grains is based on the law of gravity and concept that the solid particles are different in size and specific gravity, therefore the settling speed in the water is different. Fine ore particles float in the water and overflow, and respectively coarse ore particles settles to the bottom. As a guide line, a unit with longer length classifier will dewater the same material to a higher degree, and likewise a unit with a greater diameter of screw revolving the identical speed will produce higher capacity. In the application of dewatering fine material, the screw speed is reduced to allow proper classification and dewatering.
DOVE laboratory will assay your ore samples rapidly and analyze your raw materials and recommend the most efficient processing plant according to the ore specifications, minerals composition, and ore assay results, and your project size and the geologic and topographic conditions of your mine.
screw grit classifier
Screw Grit Classifiers (SGC) from Napier Reid offer a solution to removing, washing, and dewatering grit and sand, in addition to protecting downstream mechanical equipment and improving the performance and reliability of drainage systems.
As the grit and other heavy materials are transported up the inclined plane, the specially designed conveyor tumbles and washes the grit in order to remove the organics from it. The washed organics are returned to the effluent connection by an organic return connection.
Once the grit and heavier material is elevated above the classifiers water level, the solids are further dewatered by transferring them to a convenient discharge height. The grit falls through the grit discharge chute into a grit collection box or into a screw conveyor for disposal.
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screw classifiers and improving sand washing efficiency
The use of wet processing technology for sand production is an established process across the world as it allows you to increase the efficiency of concrete production by giving you a sand product with greatly reduced volumes of material in the minus 200 mesh range.
This gives you unrivalled control over your silt cut point - the specification of your cyclone set up is determined after extensive material testing to determine the proportion of minus 200 mesh material to be removed.
The minus 200 mesh material exits the overflow at the top of the cyclone with the waste water and this is sent to your settling ponds. The sand fraction exits the cyclone at the bottom, ready for dewatering and stockpiling.
Once your sand slurry with the minus 200 mesh material removed is discharged from your hydrocyclones it should be delivered to a dewatering screen which is sized according to your specific capacity requirements.
grit classifier | fluidyne corp
The Hydro-Grit Classifier is designed for the separation, dewatering and removal of settleable inorganic material typically at the inlet/headworks of a municipal or industrial wastewater treatment plant.
The grit classifier consists of a sloping bottom tank and a screw conveyor. The grit settled at the bottom of the tank is collected, lifted by the screw conveyor and then drained and discharged. The screw diameter and consequently the grit classifier model varies according to the volume of grit to be dewatered.
The Hydro-Grit Classifier can either be a stand-alone unit or it can work in conjunction with the Hydro-Grit Grit Vortex Separator, which separates grit from the entire influent flow entering the plant. The concentrated grit from the Grit Vortex Separator is airlifted or pumped to the classifier for further separation, dewatering and removal.
The Hydro-Grit Classifier incorporates lamella plate sedimentation for separating the grit and other inorganic solids, and a shaftless screw conveyor for dewatering and removal of the settled material.