Stavola Contracting was founded in 1948 as a family-run business. Today, Stavola Companies remain a family-owned and operated business, consisting of four major divisions: Asphalt and Recycling Materials, Construction Materials, Contracting and Real Estate, all located in New Jersey. Stavola Companies’ production facilities include two quarries, 10 asphalt plants, 3 recycling centers, and gravel mining operations which has let Stavola expand their production to over 6 million tons of construction products annually.
Their Bound Brook location, traditionally a dry screening and crushing plant produced a high quantity of ¼ minus (screenings) and although a saleable material, it had a lower market value compared to the other products and demand would vary depending on local or industry requirements. Over the years as the market fluctuated, Stavola accumulated a huge quantity of this screenings material which, overtime had become contaminated with larger rock and also weathered — producing higher levels of silt leaving an inconsistent grade product.
Stavola investigated the testing of this material using air separation and high frequency screening techniques but these failed to produce a clean consistent product and were deemed unsuccessful. Research showed that by washing this dust, a clean spec-consistent grade manufactured sand could be produced which could successfully be incorporated into specialty asphalt mixes.
“The turnkey solution Emerald Equipment Systems offered was the natural choice for the Bound Brook Project. Emerald’s specialized equipment exceeds our project requirements producing a consistently washed high grade material and eliminating the requirement for costly settling ponds,” said Stavola.
The project scope involved a washplant that would accept the feed from the current crushing plant and also have the capability to accept feed from the legacy screenings stockpile. As their project demands changed, they would have the capability of producing a dry unwashed ¼ minus from the crushing plant and also produce clean manufactured C-33 or asphalt spec sand with chips from the washplant. Water onsite was available through two sources: limited withdrawal from a ground line and also from an inconsistent pond system, which was mainly used for truck washing and dust control around the quarry. The solution was to install a closed loop water and silt management system.
The project was required to deliver a minimum of 200-300tph of sand along with any stone products, recycle all the water in the system and process 40-60tph of silt. The feed material was of a basalt type stone with 70-80 percent fines and a high varying silt rate. The project called for a sand product: specifically, a manufactured concrete C-33 spec with less than 3 percent silt.
The modular designed washplant consisted of the following:
- 25 yd3 hopper with tipping grid accepting feed from a loader and overland conveyor
- 100 ft. feed conveyor with rap around walkway
- 20 ft. x 8 ft. dual shaft incline rinser
- Finesmaster dual product sand plant and 100 ft. powered radial wrap around walkway stockpile conveyors.
As the feed material was very abrasive, the rinser (wet screen) was fitted with polyurethane modular screen mats allowing individual 1 ft. x1 ft. panels to be removed quickly and replaced as needed or if a different specification was required. All chutes and catchbox systems were lined to enhance and increase the wear life of the components.
The modular water and silt management plant contained a stainless steel silo for water clarification and sludge separation, a 1.3 x 1.3m with extensible 200-plate filter press and a modular flocculant dosing station with homogenizer tank.
The complex characteristics of the freshly crushed basalt material and the legacy material, required an additional coagulant compound to aid settlement in the separation process to achieve a balanced filter cycle to wash plant run time. With the addition of the DOSON system this was easily achieved using the automatic testing and dosing adjustment function. A dual mud /water clarification sensor was fitted to the silo at multiple locations where the water clarity and mud thickness was measured.
The press was equipped with coreblow and cloth wash functions to minimize downtime, extend wear life and reduce labor costs. The core blow flushes out all the residual material built up between the plates, the cloth wash cleans both outer and inner cloths along with plates.
The double stage high pressure filter pump fills the chambers with mud and filters until all water has been expelled with only dry cakes remaining between the plates. The cloth wash also utilizes this pump to thrust water though each plate chamber and flush the system ensuring seamless stage filtering.
The press is also equipped with a TT2 opening system, which reduces the opening and closing time of the plates by opening in multiple plate packs versus single plates. The HD shaker system operates after each cycle to remove any residual mud buildup on the plates.
“The turnkey wash plant coupled with the water and silt management plant recovers over 90 percent more water than other washing processes,” said Mike Tormey of Emerald. “The customer realizes huge financial savings by eliminating sludge ponds completely with the addition of the plate filter press which reduces handling and cleanout costs.”
Stavola continued, “The high production plant allows us to process both the legacy pile of screenings and the current #10 product from the crushing plant generating higher revenue streams and freeing up value footprint area.”