Substantial silica-sand resources are only throughout Malaysia including largely of normal sand deposits and also ex-tin mine tailings. The DMG has estimated the country has several 148. 4 million tonnes regarding silica-sand reserves located in the us of Johor, Perak, Terengganu, Kelantan, Sabah and also Sarawak. Production regarding silica-sand in 2007 improved to 719, 221 tonnes coming from 512, 277 tonnes stated in 2006. They originated in several active mud mining operations inside Johore, Perak and also Sarawak. Most with the silica are found in the manufacturing regarding glass products also to a lesser extent inside the production of ceramics, foundries, glasswool and also water treatment components.
Processing of Silica Mud
Silica Sand—the most frequent ingredient in goblet. Whether the goblet is container goblet, window glass, boro-silicate goblet, fiberglass or h2o glass (sodium silicate), silica sand accocunts for approximately 60-70 percent with the glass batch and so has a significant affect around the glass quality.
Washing is the best and lowest cost way of cleaning silica mud. In some of the very most pure deposits which can be void of weighty minerals, high numbers of clay and silt, no surface staining, washing is sufficient to produce appropriate grade product.
In the act, water is included with the sand which is generally pumped with a cyclone for des. The movement with the slurry passing from the pump and pipeline is sufficient to loosen the tiny amount of fines or clay which can be in the ore physique. Once the minor numbers of fines or clay are already released from the particular silica sand they could be removed via many different methods.
Attrition scrubbing is employed when the clay courts or silts tend to be tightly bound for the silica grains, or clay allergens are similar in proportions to the silica mud grains.
For appropriate attrition scrubbing, it’s important that the sound percentage of slurry be within a selection of 72-75 percent solids. As of this content, there is excellent particle-to-particle contact as well as the viscosity of the particular slurry is low enough allowing the slurry to go freely in the particular attrition-scrubbing tank. If the solids percentages are below 72 percent, there is certainly sufficient water inside the slurry to enable the particles to stay apart preventing the necessary particle-to-particle contact needed to scrub the clay from your surfaces. When the solids are more than 75 percent, the slurry to be able to too viscous as well as the impellers cannot move the slurry. If the slurry does not necessarily adequately move, particle-particle contact just isn’t possible.
In order to be able to process the large percent solids slurry over a consistent basis, the energy transmission system employed is incredibly critical. The greatest solution is any gear driven equipment as shown inside Figure 3. Although v-belt systems have a tendency to work fine if the units are fresh, as they age and so are not properly preserved, slippage occurs as well as the impeller will not rotate with all the resistance caused from the high percent solids. Now, operators tend to incorporate additional water to lessen the percent solids as well as the scrubbing becomes unproductive
Typical scrubbing instances are approximately 5 moments. However, the actual retention time may differ considerably with regards to the amount and form of material which should be liberated. Attrition scrubbing circuits might also include multiple attrition scrubbing period. When there will be significant clay articles, two to a few shorter scrubbing instances with des methods in between works more effectively than one extended scrubbing time. After the clay is liberated, the clay acts being a lubricant between the particular silica grains and so reduces the effectiveness of the scrubbing. Simply by removing the liberated clay slimes, and adding another period of scrubbing, the scrubbing circuit works more effectively.
The number regarding attrition scrubbing cells inside the circuit is furthermore important. Although one cell could have sufficient volume to fulfill the retention moment needed, one cell will result in significant short-circuiting with the feed material. Which is, if the common particle retention moment is 5 moments, there may be particles that may only have maintenance times of 2 minutes among others at 8-10 moments. It is important that no less than two attrition scrubber cells provide to provide the mandatory retention time. Three to four cells are preferred whenever feasible.
By classification with silica mud, des is the method that removes the particular -100 micron substance. These slimes are often clay type nutrients or very fine silica which is detrimental to the particular glass making method. Although there are numerous methods of des, only two are usually widely used on the market: cyclones and hydrosizers It must be noted that several older processing crops may still consist of screw classifiers, but because of the high capital and also maintenance costs they may be not found inside new plants.
Cyclones are low priced and effective inside removing the -100 micron slimes coming from silica sand if the -100 micron material will not exceed 3wt pct. Cyclones are successful in removing a lot of the slimes yet, as the underflow merchandise typically contains 30-40 pct water, some clay slimes be in the underflow merchandise. Typically, cyclones remove 80-90 percent with the –100 micron inside the feed. Multiple cycloning stages will reduce the residual amount of slimes inside the underflow product.
For feeds who have more than 4-5wt pct -100 micron substance, or when there exists a need to eliminate all or area of the -150 micron substance, the best equipment could be the hydrosizer including the FLOATEX ® Thickness Separator shown Number 3.
For almost all hydrosizers, the basic principles of operations are usually similar, but several have better handle systems or h2o distribution. Figure 4 under shows a cut away with the hydrosizer.
The hydrosizer can be a hindered settling create. Therefore, it utilizes an ongoing of water, introduced throughout the bottom of the particular hydrosizer, to expand sand slurry in to a state of teeter. On this teetered state, the sand grains can classify themselves so your coarse grains report to the bottom where they are going to stay relatively close together with high h2o velocities flowing among them. The finer particle will probably be dispersed to the bigger levels where they are going to stay in a lot more open suspension and so, the water pace between them will probably be low.
The hydrosizers have a pressure-sensing device inserted in to the teeter zone to offer an indication with the specific gravity. For almost any pre-set upward existing of water, the precise gravity is indicative with the average particle size with the sand above the particular sensing position, and therefore enable you to provide a variable signal to work a valve to regulate the discharge with the coarse material in the bottom of the hydrosizer.
The hydrosizer features a greater separation efficiency when comparing a cyclone. That is due, in portion, to the function of operation as well as the addition of “clean” water added inside the teeter zone. The internet result is fewer fines inside the sand and an even more consistent level of the fines. If the sand is usually to be dried, the fines are removed ahead of drying. Since the fines have an overabundance surface area, fuel savings inside the dryer operation may be significant. In inclusion, with less fines there is certainly less dust, which lowers worker experience of silica dust and also reduces maintenance around the dust collection method.
Capital cost every ton varies together with feed rates nevertheless the range is typically $1000-2000/ton/hr with all the lower cost being for your higher feed costs.
Sizing for glass sand is incredibly critical in order to make high quality goblet product. Sizing has to be discussed in a couple of different areas. One is the opportunity to size the ore with near 0. 5 mm one other is to stop oversize grains (+1mm) from entering the item.
Sizing to supply a sand product which is less than 0. 5 mm is normally conducted with any screen or hydrosizer. The particular allowable material previously mentioned 0. 5 mm continues to be greatly reduced within the last few 10-15 years. It absolutely was not uncommon inside the 1980’s for the particular glass producers allowing 5wt percent +0. 5 mm inside the specifications for goblet sands, Today, they may be pushing the reduce to 0 pct on +0. 5 mm together with specification now getting proposed with limits around the 0. 4 mm display screen.
The lower level of coarser grains permits the glass makers to operated reduced furnace temperatures and observe after high production ranges. The lower furnace temperature not merely saves in gas costs, but, as a result of lower furnace temperature ranges, additional savings are usually realized with more time furnace life.
The other dimensions aspect is how much oversize grains. These include measured as +1 mm grains and so are limited to some grains per kg. These grains generally are too large to melt inside the furnace and cause defects inside the glass. Like the particular refractory minerals reviewed above, a few grains per kg brings about 1000’s of defects each day, and can substantially impact the goblet production cost.
High frequency screens furnished by companies like Derrick or Rotex are often used to help make the 0. 5 mm divorce. The latest improvements are high capacity screens that will size 250 tph together with one screen. The particular high capacity monitors employ several display screen decks within a single machine unit. The device employees a nourish distribution system in which evenly feeds almost all screen decks at the same time. Figure 6 shows a photograph of the screen created by Derrick for this kind of application.
Screens are generally sized to generate a good either undersize or perhaps oversize product. Which is, if the goal is undertake a product that is completely -0. 5 mm, the underflow with the screen will satisfy this goal. Nonetheless, the oversize with the screen will consist of some -0. 5 mm. A normal size distribution with the products and nourish are shown under in Table 1.
|Table 1 Typical Screen Size Distribution|
|Size (micron)||Feed (wt%)||Oversize (wt%)||Lndersize(wt%)|
Inside plants that integrate drying, screening is frequently accomplished after drying because the screening operates better when dry. Nonetheless, if high proportions of +0. 5 mm material were inside the ore body, then wet screening could be preferred to eliminate the maximum amount of oversize as possible ahead of drying. This approach will save you the drying cost and permits higher production costs of final product from your dryer. Typical capital cost to get a screens ranges coming from $1000-2000/ton/hr.
As well as screening, the 0. 5 mm separation can be accomplished with a hydrosizer including the FLOATEX ® Density Separator that is previously discussed. These units offer you some advantages over screens considering that the capacities for the identical footprint are more than for screens. They offer a lot more flexibility in dimensions since a cut size may be changed with change for the sensor set point when compared to the necessary screen material changing in monitors. A typical dimensions separation is demonstrated in Table a couple of below.
|Table 2 Typical FLOATEX® Density Separator Size Distribution|
|Size (micron)||Feed (wt %)||Underflow (wt %)||Overflow(wt %)|