Frequently asked questions

See below details of some of the frequently asked questions relating to our range of washing plant installations for the full range of minerals including:

sand and gravel
crushed rock
iron ore washing
construction and demolition waste recycling
Lignite removal
Air classification

Question 1 -
My settling ponds need to be cleared quite often and I think I may be losing some fine sand with my wash-water. Have you a solution to this?

This is a very common situation particularly where dewatering / bucket wheels are being used. Our Evowash sand washing system eliminates unnecessary fines loss. The custom specified hydrocyclone accurately separates silt from your sand. This maximises your commercial sand output and can dramatically reduce the volume of solids passing to your lagoon.

Question 2 -
If I recover extra fine particles to my sand won't it be too fine for my customers?

CDE plant is specified according to your individual materials and requirements. We will recover all possible fines within your preferred output specification. Our Dual Sands Plant lets you divert any excess fines to your building or asphalt sand, maintaining the concrete (or main sand) specification. Furthermore we often find that sand from a dewatering wheel can carry a surprising level of sub 75 micron particles even though >150µm particles may pass to the pond; because the separation point is approximate and difficult to control. The CDE Evowash sand washing system guarantees that silt goes to your pond while sand goes to your weighbridge. We believe that's how it should be.

Question 3 -
I currently dry-screen and know that my material would benefit from washing but I have very little water available on site. Is there any way round this?

Yes. We find that water shortage is a problem for many quarries, even in a country as wet as Ireland! We can offer you a turnkey system with a closed water circuit. In such a case water requirement for 100tph feed may be as low as 15m3/hr. See our AQuaCycle High-Rate Thickeners and GHT Filter Presses for more information.

Question 4 -
I have some very heavily clay bound material that I would like to wash, have you a suitable process?

CDE have considerable experience with difficult feed stocks. The Rotomax Log Washer and Aggmax attrition system can handle very plastic material; see our installation for the Lagan Group's Duleek Quarry in Ireland which can be found in the sand washing case studies section of this site. Please tell us about your material and we will advise you on the best process.

Question 5 -
Can my quarry dust be washed to create concrete specification sand?

Probably. “Average” Quarry Dust shows 85% passing 5mm and 14% passing 75µm. We can process this to offer 100% passing 5mm and 4% passing 75µm. Depending on your 150-600µm fractions this should provide a suitable concrete sand substitute. Email us a sieve analysis of your raw dust and we can tell you the anticipated sand grade and how much water would be needed.

Question 6 -
Isn't a dewatering screen's size the bottom line when it comes to sand moisture content?

Not at all, just as an engine's power is not merely a function of its cylinder capacity. If this was the case CDE would have the largest dewatering screens on the market; we don't. There are numerous factors to consider including structural design, screening media, amplitude and speed. We have extensively researched and tested our dewatering screens and believe them to be the most advanced currently available.

Question 7 -
Other companies offer sand plants with ‘cyclones, why are CDE's any different?

Versatility quality and performance. We select the correct ‘cyclone size and type from a wide range of models to suit your application. This guarantees efficiency and silt cut-point accuracy. Water can only leave our plant via the ‘cyclone i.e. there is no weir on our sump. This eliminates the risk of quality fines loss to your settling pond. Moreover some alternative systems actually incorporate “density separators” which look like, but behave quite differently from, true hydrocyclones as used by CDE. Durability is also a key factor; all CDE ‘cyclones are fully rubber lined. It's also important to note that a CDE plant is much more than just a ‘cyclone; our systems integrate the best dewatering screens, pumps and ‘cyclones in single efficient and compact units to offer you the highest possible performance and reliability.

Question 8 -
I'm concerned about using chemicals in my water treatment process. Are there any risks to my products or the environment?

Modern polyelectrolyte / flocculant agents are safe and easy to handle, especially in powder form. It is essential that you use the correct dose for your application. If excess flocc. is used this can carryover in the clean water and be recycled to the rinsing screen where it may effect the classification process. We have developed our own Automated Dosing Systems to eliminate this risk. Providing that you use the agents in the correct manner there is no adverse environmental impact. The flocculants we recommend are widely used by government and council water treatment facilities and the food industry.

Question 9 -
I process sand from a number of different sites and have difficulty maintaining my output specifications. Is there a solution?

CDE have the developed the Multi-Sands Plant for this very problem. This system offers you two or more in-spec products from varied feed stock. It is also the ideal process set-up where specialist grades such as golf or filter sand are required. This is based on our Evowash sand washing technology but incorporates our unique Counter Flow Classification Unit in order to enable the efficient production of many grades of sand from one feed stream.

Question 10 -
I only require a single sand output at the moment but might like to upgrade to dual sands production in the future; is this possible / practical with your system?

Absolutely. Because our system is highly modular it is possible to modify and upgrade most plants should your material, tonnage or output requirements change.

Question 11 -
I'm not familiar with hydrocyclones as used in most of your washing plants. How much maintenance and servicing is required?

All CDE ‘cyclones are fully rubber lined using ouw own unique process to ensure maximum wear resistance. Wear is very low compared with other systems. Even the pipe-work and connections are of the highest specification and quality and are built to last. The design of our Evowash single , dual and Multi-Sands Plants means that no moving parts are submerged in the sand slurry, greatly reducing potential wear. The modular format of these plants makes routine servicing very straightforward with minimum down-time; if you currently operate an Evowash sand washing plant you will be surprised at how little you actually have do to keep a CDE unit in optimum condition.

Question 12 -
Can I reduce my lagoon space by using CDE equipment?

Yes; how far do you want to go? The CDE Evowash sand washing plant will guarantee you don't lose any valuable fine sand to your pond while our Aquacycle High-Rate Thickeners will reduce waste volumes by ~14 times. Our GHT Filter Press completely eliminate the need for settling ponds.

Question 13 -
How does your system add value to low grade iron ore?

CDE systems are designed around your material according to your project needs but an iron ore upgradation system will typically include heavy attrition, screening and density separation. Many ores show poorest Fe value in the size fraction below 75 microns and this is also where the Al2O3 and SiO2 values are highest. By efficiently removing this fraction we are able to improve the overall Fe but often more importantly for our clients, reduce Al2O3 and SiO2 contamination thus improving downstream steel making processes.

Question 14 -
How does CDE iron ore washing differ from ore beneficiation?

Speaking literally any system which increases the grade of an iron ore feed can be termed as beneficiation but we realise that most of the industry understands beneficiation to imply large scale circuits including grinding and very fine particle recovery. Most CDE iron ore systems achieve excellent grade improvement and contaminant reduction without the need for fine crushing or grinding i.e. via advanced attrition, washing, and density separation. Our systems are also generally better suited to operators who have variable feed materials or need a greater level of flexibility than full scale beneficiation circuits allow. Where crushing, grinding and or magnetic separation are required we can offer customised circuits to meet this need.

FAQ's