Successful long-term contract sand processing is delivered by Duo Mineral Processing for Hanson’s Masters Quarry

22 February 2018

Owned and operated by Hanson UK, Masters Quarry is situated on the Puddletown Road near the Dorset town of Wareham.

Masters Quarry was previously worked by Hanson and Holme Sand and Ballast as a single unit between 1987 and 2012 and comprised of four extraction areas, Hyde and Hines and Masters North and South with Hanson operations being mothballed in September 2012.

Masters (or Hyde as it was originally known) is situated in an area classified as lowland heathland and is internationally recognised as an important habitat for smooth snakes and sand lizards; Both animals and their habitat are protected – European Protected Species (EPS).

The land was not classified as important until the late 1990’s. Prior to this time the quarry worked the underlying sand, removing the heathland in the process. When Hanson UK received notification that the land was to be designated as a cSAC (candidate Special Area of Conservation) in addition to the SSSi and SPA designations, extraction was transferred from the Masters North and South areas to the freehold land at Hyde Pit, which, having already been stripped prior to the notification of the designation, allowed the quarry to continue working at outputs levels of circa 300kt.

Planning modification orders preventing the extraction of minerals from undisturbed Heathland were then formally issued in November 2006, sterilising approximately 9Mt of reserve. Most of the minerals affected by the modification orders however were located within Masters North and South, therefore the mineral asset was not affected, although the orders significantly reduced the minerals available for future extraction.

Simon Parkes – QM takes up the story, “Although never worked as a stand-alone quarry, Hanson planned to re-open Masters Quarry in April 2016 with a fresh team and I was appointed as QM to take the project forward.

We had a lot of problems with the EPS, as in this area we have every species of reptile in the UK, therefore we had a responsibility to survey and ascertain the number of reptiles, which considering there had been no activity since 2012 the numbers were considerable. Following surveying, applying for a licence, erecting a reptile fence, capturing and moving animals to a receptor area, this was eventually achieved to the satisfaction of all parties.”

Having cleared the site a ramp down to the quarry floor had to be constructed. As nothing previously existed this had to be created from the ground up. Work commenced in October 2016 and a ramp was constructed from the highway level of 53m AOD, to the plant site level of 37m AOD with the first 50m paved. All the infrastructure work including the plant pad was completed by Hanson Contracting using a variety of asphalt, concrete and roller compacted concrete (a first for Hanson in this area).

A successful tender:
Having completed many successful projects with Duo, Hanson awarded the mineral processing contract to the Duo Minerals Processing Division.

The processing contract is based on a cost per ton with the plant easily capable of 300,000 tonnes/annum.

Simon commented, “Through previous contact at other sites I already had a working relationship with Duo therefore it was an easy transition to work alongside them again.”

As the English and Welsh dealer for Terex Washing Systems (TWS) Duo can offer innovative wash plants and water management solutions. This demonstrates TWS commitment to providing outstanding products, customer support and expertise in the field to meet customers’ individual needs.

The Sand & Gravel Processing Plant:
The material to be processed is predominantly sand with small quantities of gravel on the surface and underlying seams of clay to varying depths. Considering previous processing issues Duo based their plant design around the latest TWS technology incorporating the successful Terex® Aggresand™ 206, and as there were quantities of lignite on-site a single TAK was also included in the specification to remove this element from the fines fraction.

The TEREX® AggreSand™ 206 modular wash plant is pre-wired and pre-plumbed and is an easily installed modular concept that facilitates quick installation; a combination that is very appealing in terms of access, serviceability and modularity.

The all electric plant at Masters includes a rinsing screen, sand plant, lignite removal plant, stockpilers and all associated pipework and electrics on one modular chassis, with a sizing screen completing the specification.

Simon commented, “It’s a very neat compact plant incorporating an in-line system which TWS & Duo have had major success with in the market, where the TWS modular concept has been well received. Its ideal for the operation at Masters and we have confidence in the operation delivering our expected production rates.”

Currently operating at 150tph the plant features two ‘side by side’ remote control tipping grids. These are both fed from one ramp by a loading shovel. A dryer courser deposit extracted from Hines Quarry and then delivered to Hyde is then fed onto one grid with the second receiving on-site material. Manual blending can then take place with the material fed up the primary conveyor.

Material is then fed onto a 20 x 6 triple deck rinsing screen, working at 18◦ angle this utilizes individually controlled spray bars on each deck. The 2-bearing screen is fitted with polyurethane modular media on all decks with the top deck acting as a protection deck removing any oversize (mainly clay balls) which are then fed via an on-board conveyor to stockpile. A middle deck feeds any 6-10mm gravel and smaller clay balls by on-board conveyor also to stockpile.

The split bottom deck, 2mm and 5mm provides the feed to produce the required two sands. All chute-work on the AggreSand™ 206 employ the now well tested dead-box system which results in ‘rock on rock’ set-up which is proving to give excellent wear properties.

The Masters AggreSand™ 206 is a high capacity 150tph sand plant with a high-energy 4.3m x 1.8m dewatering screen and consists of one 200/150 pump for coarse sand and a 200/150 pump for soft sand. A 625mm cyclone for coarse sand and one 500mm cyclone for fine sand produce two clean in-specification sands. A specially designed rubber-lined underflow box allows blending to take place so that an acceptable coarse and fine sand ratio can be achieved. These sands are then delivered to separate radial conveyors and stockpiled.

Lignite plant:
The plant at Masters incorporates a TAK Lignite Hydro Classifier which has been supplied through Duo’s Spanish partner AMP. This is a specialised sand classification tool which classifies the sand according to the weight of the particles. With the lignite being a third of the weight of sand it singles out the lighter grains of lignite and floats them out over the top leaving the sand grains behind. Essentially, it’s a unit that is designed for classification of glass sands which have very tight tolerances, therefore by moving the set point in the classifier vessel either up, or down you can adjust to a very refined measure of how much bottom end you have in the sand.

At Masters the sand is screened through the main washing screen of the AggreSand™ 206 and then fed to the main sand sump and then up into the TAK via the hydro cyclone. This then concentrates the flow ensuring a flow of about 65% solids is established (which means that within that vessel, the upstream current – to classify the sands and float off the lighter particles).

At the front-end the sand screen feeds the sand through into a sump which pumps it up into the hydro cyclone which is mounted above the TAK. The hydro cyclone then removes the ultra-fine particles, taking them from the top and then feeds a concentration of sand into the TAK. When the sand settles in the TAK a clean water upstream current is introduced from the bottom and then by moving the set point, up or down you can then control precisely what the grading is at the bottom end of the sand and how much you float off.

Cutting Edge Control System:
The control system for this specific AggreSand™ wash plant is stored in a centralized cabin on the site which is one of the options offered by Duo through TWS on all AggreSand™ installations, alternatively the panel can be mounted onto the machine, all of which are pre-wired. This option exemplifies the flexibility of TWS and Duo and the AggreSand™ concept to suit individual customer needs or preferences.

John Bracken – Duo Sales Director, summarised, “Duo and Hanson have a very good working relationship on numerous projects. A lot of thought has gone into this plant and it has been designed in such a way that a logwasher can be incorporated when more gravel bound material is excavated in the future. Additionally, should the market demand it a second TAK can also be added to the plant.”