High quality sand from a 50 year old waste product

• 
• 27th August 2008
• Quarrying
 

A new CDE sand washing plant in Estonia is producing high quality building materials from what had previously been a waste product.

The plant was purchased to process material that was simply being stockpiled as waste as a result of the high clay content. This same material is now being sold on the Estonian building materials market as high quality, fully certified sand and aggregates.

The plant has recently been commissioned for Paekivitoodete Tehase (Limestone Products) and is located in Estonia's capital, Talinn. "The plant is actually visible as you fly in to Talinn airport" says CDE's Eoin Heron who was responsible for delivering the project. The urban location of the site required that CDE's proposal contained a detailed environmental impact statement as required by the planners. This dealt with issues such as noise pollution and site conditions likely to have an effect on the residents in close proximity to the site.

Limestone Products

CDE compiled a detailed report for the planners in Estonia and all the information provided met with the planners approval. As such permission was granted to the customer to install this new washing plant. Paekivitoodete Tehase (Limestone Products) is Estonia's leading producer of crushed limestone products and they operate several sites in the Talinn area. The new CDE plant is installed at their Vao quarry, which has been in operation for 50 years. The materials produced by Limestone Products are used extensively on the construction market in Estonia, and this market has been undergoing considerable development in recent years, which has been good for business.

A Technological First

Since the company was founded it has developed a reputation for innovation, and this is something that they are very proud of. "We are seen as leaders in Estonia in relation to bringing new technologies and processes to the market" explains company Chairman, Vladimir Libman. "The introduction of this CDE washing plant is yet another example of how we approach business. These technologies have never been used before in Estonia and we are delighted to say that we are the first to use them."

The pride of the not only the Chairman, but the company as a whole, was visible for all to see at an event at the site in June 2008 celebrating the opening of the plant. This gala event was attended by many local dignitaries, environmental bodies and industry representatives, as well as the British Ambassador to Estonia, Peter Carter. There were also representatives from CDE and Baltem, CDE's distributor for the region, present at the event at the invitation of Mr Libman. This is the first project that CDE have won in the region through their association with Baltem, who also represent the company in the neighbouring countries of Latvia and Lithuanuia.

"We are delighted to be working with Baltem in the region" says Eoin Heron. "Through their representation of Komatsu in Estonia, they have established a reputation for a company that delivers on their promises and takes the establishment of good customer relationships very seriously, This matched the expectations that we have of all our dealers and we are very pleased to be working with them, not only on this project but a number of other significant projects in the region."

Commercial products from waste

The CDE washing plant has been brought in specifically to deal with material which has been stockpiled as waste since the quarry began production some 50 years ago. This material is a by-product of the crushing processes in the quarry and up until now, Limestone Products have not been able to find a system capable of processing it in a way that will produce commercially viable products in a cost effective manner.

As is the nature of the company, rather than giving up on their search, and merely dumping this waste material they continued to look for a solution. Their persistence eventually paid off when they made contact with CDE at the UK's bi-annual quarry show, Hillhead, in June 2007.

"The problem that Mr Libman had was that the material they were stockpiling was very dirty with high clay content" explains Eoin Heron, CDE's European Sales Manager. "We were able to show them that we had a considerable amount of experience in working with difficult materials such as that which they were having a problem with."

After several site visits to show Mr LIbman and his colleagues some sites in the UK and Ireland where similar problems had been encountered and much deliberation between the customer and CDE's technical design team at their head office in Cookstown, the deal was eventually done for a 150 tons per hour CDE washing plant for material from 40mm down.

Project Outline

The washing plant begins with a 20t feed hopper, which in turn feeds the latest addition to the CDE product set, the AtroFeed. This unit is designed to provide the necessary attrition to clay bound materials. The concept involves using a very high pressure jet of water, which at the point of impact with the feed material provides enough attrition to remove the clay. Following this stage, material is fed to a double deck rinsing screen from CDE's ProGrade range and the +16mm material and 5-16mm material is stockpiled. The -5mm material is sent to a heavily customised dual sands plant from CDE's EvoWash range. Here, the 2-5mm grit is rinsed again and dewatered and the 0-2mm material is pumped to the 2^nd screen. The washed sand (-63 micron to 2mm) is stockpiled while the waste water and -63 micron material is sent to a CDE AquaCycle T08 thickener. This forces the sludge to settle and this is then pumped to settling ponds. The clean water is recycled back to the washing system, dramatically reducing the requirement for fresh water to feed the system.

Efficient cleaning

This project marks the first commercial use of CDE's AtroFeed and this is something that both CDE and the customer are very proud of. "For the specific requirements of this project the AtroFeed was the ideal product" says CDE's Eoin Heron. "Given the clay bound nature of the feed material and the individual characteristics of this project it was the perfect application."

Expanding on this, Mr Libman explains "We are very pleased with the results being achieved by CDE's new technology and we are delighted to be able to say that we were the first company in the world to run this equipment on our site."

The AtroFeed provides a high level of attrition to the feed material, where this is necessary to remove a high percentage of clay. The material is delivered to the AtroFeed directly from the hopper and from here it is transferred to the screening station. One of the many advantages here is that the need for a transfer conveyor from the hopper to the screening station is eliminated. The feed material, mixed with the water from the high pressure jet is piped to the screen, thus reducing the space required for an installation such as this.

The washing process

The rinsing screen supplied to this project is a ProGrade R2M108 (1.8m x 6m) double deck screen. At this stage the material is washed and sized into +16mm material, and 5mm - 16mm material. This material is then discharged into concrete bays beneath the screen.

The washing of the -5m material on this project required a substantial amount of customisation of the CDE equipment as a result of the nature of the feed material, as Eoin Heron explains. "With the amount of clay that we had in this feed, it was clear that at the sand washing stage, further washing would be required. The result of this is a second washing screen for all the -5mm material. This essentially ensured that we were able to get the material clean enough to be commercially viable."

At the first stage of this sand washing process, all the -5mm material is sent to a dewatering screen where the 2-5mm material is rinsed again and dewatered. Following this it is stockpiled. The -2mm material is fed through CDE's hydrocyclones to another screen. The hydroclone technology used by CDE on their EvoWash sand plants is widely accepted to be the most efficient way of removing the unwanted -63 micron material.

Customisation to add value

"We use high quality components throughout our sand plant range" explains Eoin. "This includes not only the hydrocyclones but many other industry leading components such as Warman pumps and polyurethane screen decks. Our sand plants are designed to give the customer the maximum amount of product on the ground. We know that this is what really adds value to their business."

According to CDE it is the high level of customisation in this plant that has allowed Limestone Products to process this waste material into commercially viable products. "The evidence that an off the shelf product would not have been able to process this material comes in the fact that this material has been here for 50 years" states CDE's Sales Director, Enda Ivanoff. "Only through a system built specifically to deal with the individual characteristics of this project, where we able to solve the problem for Mr Libman."

Reducing Environmental Impact

Another key element of this project from very early on was the environmental considerations that the planners were demanding. This required a degree of water treatment and recycling on the plant to minimise the environmental impact of the operation. This is an area where CDE have gained significant experience in recent years and have supplied many international projects with systems including complete closed circuit water treatment including their AquaCycle thickeners and filter presses.

Following the sand washing phase of this project the waste water and -63 micron material is sent to an AquaCycle T08 thickener. On entering the thickener the waste sludge is treated with a small amount of flocculent which is prepared in the fully automated polyelectrolyte dosing station which forces the silts and clays to settle to the bottom of the tank. The rakes fitted at the bottom of the tank move the thickened sludge to the centre of the tank, near to the discharge point. The rakes also send signals back to the PLC control panel about the amount of resistance they are encountering, and the sludge pump automatically starts and stops as required. The thickened sludge is then pumped to the settling ponds on site.

Meanwhile the clean water overflows the top of the thickener tank and is recycled back to the washing plant. This dramatically reduces the amount of water used in the washing process, reducing not only the environmental impact of the plant but the running costs also.

A Unique Project

There are several elements of this project which make it stand out from the crowd. Firstly, the fact that the material being processed has been stockpiled as waste for some 50 years suggests that Paekivitoodete Tehase are nothing if not persistent and are a company willing to go that extra mile in the search for new innovations in processing technology.

Secondly, the system offered by CDE to turn this waste material into commercially viable products shows the value in the treatment of each project as an individual entity, which requires its own unique solution. "This project, more than any other, provides support to our often stated belief that providing off the shelf products is simply not an efficient way to deliver systems to this industry" states Enda Ivanoff. "Each project has its own individual characteristics in relation to feed material and output requirements that necessitate an individual approach."

This was a project of many firsts. The first time anyone has been able to process this feed material effectively. The first time CDE's new AtroFeed system has been incorporated into any commercial project. The first full plant installation that CDE have completed in the region. Given the success being reported by the customer, there is no doubt that more will follow in the months and years to come.

At the official opening of the plant in June 2008, Limestone Products Chairman, Vladimir Libman commented "Our company has developed a reputation for innovation which has been the foundation of our success in recent years. The introduction of CDE's technologies to Estonia is the latest example of our commitment to the development of our business through the adoption of the best systems available to us."

There are many more CDE case studies available in the downloads section of their web site at www.cdeglobal.com/downloads, where you will also find several previous project installation videos. For further information on this or any other CDE project, please contact the company on info@cdeglobal.com or by telephone on +44 28 8676 7900.

Associated Links

• Hub-4 Profile of CDE Ireland Ltd
• CDE Ireland Ltd Company Website