FLOCCULANT PLANT & MIXING SYSTEMS
Flocculant plants are used in water treatment, heavy industrial and mining - basically wherever the separation of material from solution is required. When designed correctly, these plants will provide constant supply of flocculant in solution to the thickeners, with the polymer chains undamaged and correctly uncoiled for highly efficient separation performance.
Options and features typically found in a flocculant plant in would be:
Dry flocculant storage; (small hopper, bulk bag breaker or silo with dust collectors and level instruments),
Dry powder screw feeder
Heated feed cone and venturi,
Suitably sized pneumatic blower and pipework,
Wetting head assembly with control instruments and valves,
Mixing tank with agitator and storage tanks (including level sensors)
Transfer and dosing pumps, if requested
Fully programmed field mounted control panel, if requested,
Compliance to Australian standards
Guarding to Australian Standards AS4024
BHT FLOCCULANT MIXING PLANT
Flocculant plants are typically used to agglomerate particles in solution to aid in settling and separation in thickeners. Flocculants are specifically designed and selected by flocculant manufacturers (SNF, BASF, etc) to suit the customer process demands.
BHT flocculant plants are designed and manufactured to ensure long life and reliable service in the harshest of operating environments. Clear access and easy maintenance of the flocculant plants are key to BHT design to ensure optimal 'up time' of the plants and the highest possible safety for operators and maintenance personnel.
By working with BHT for the supply of your next flocculant plant you will enjoy the following benefits;
A tailored solution, engineered to suit customer specific site requirements,
Compliance to customer engineering and manufacturing specifications,
A consultative design process utilising the latest industry standards and guidelines for process control, Australian Standards and BHT proprietary design systems,
Provision of 3D models to allow convenient integration into overall plant layouts to ensure accurate interface and tie-in with piping.
Operator ergonomic considerations when handling the dry flocculant and equipment for maintenance.
Flocculant Mixing and Feeding Design
Dry Flocculant Storage
The delivery method of dry flocculant, whether by 25kg bag, bulk bag, and flocculation tankers, determines the selection of the dry storage vessel, whether it is a small bin, bag breaker, or silo, respectively. The delivery method is usually governed by the consumption rate and how remote the site is relative to supplier of flocculant.
Bins filled by 25kg bags are manually loaded by operators either by simply dropping the bag on a spike within the hopper or to be vacuumed emptied.
Non-reusable bulk bags, whether 750 or 1000kg capacity, are lifted by an overhead monorail and split by a large spike within the bag breaker hopper. Reusable bulk bags are positioned above specially designed bulk bag hoppers which allow the operator to safely untie the drawstring on the underside of the bulk bag and empty the contents.
Silos are used to receive flocculant in bulk from pneumatically unloaded tankers are are equipped with dust collectors, level instruments and bin activators to aid in the loading, storage, and unloading.
Dry Flocculant Feed System
The dry feed system is critical in correctly dosing the dry flocculant into the wetting head. If transferred at too high a rate for the wetting head to pre-wet , the flocculant will clump together and impede mixing. If transferred too slow there will not be sufficient time for the flocculant to be added before the tank fills. The dry feed system comprises of a screw feeder, heated cone, venturi, pneumatic blower, and pneumatic piping.
The screw feeder is designed to be fixed speed to be matched to the wetting head capacity. Additional flocculant is easily added to the system by extending the operating time of the screw feeder.
The heated cone, situated after the screw feeder, shall funnel the flocculant into the venturi and pneumatic air stream, but with the amount of air entering the pneumatic system there is a possibility for condensation to occur on the heated cone internal surface. Thus BHT supply a proprietary heated cone that is thermostatically controlled to ensure constant temperature on the cone surface when the pneumatic blower is and is not working.
Selection of the pneumatic blower is essential to ensure that the flocculant is delivered to the wetting head and does not block the pneumatic piping due to insufficient conveying air. There are two styles of lean phase pneumatic blowing used on the flocculant plants; a ring blower and rootes blower. Each is selected based on the throughput of flocculant being delivered and the amount of back pressure caused by the piping route. For small systems, a ring blower is an economical option, but with larger systems a rootes type blower is installed to maintain continuous high pressures and flows.
Selection of the wetting head and corresponding instruments are crucial to the correct operation of the flocculant plant to ensure adequate wetting of the flocculant at the desired mix tank fill rate. Depending on water flow requirements, a "rapid fill" line may be added to the wetting head assembly which allows higher tank fill rates in larger systems. Alternatively a dual wetting head arrangement can be installed.
The wetting head comprises of a ring of sprays located around the pneumatic discharge nozzle of the dry flocculant. These sprays provide water droplets of sufficient size and amount to wet the dry flocculant particles before entering the mixing tank. The distribution pot which houses the sprays, evenly feeds each spray and has a tapping point for a pressure gauge to ensure the sprays are working at design pressure.
Pressure and flow instruments are usually required on the water feed line to ensure that sufficient water is supplied to the wetting head for correct pre-wetting of the powder. If the pressure or flow are detected to be too low, the flocculant plant will pause in its operation and alert the operators with an alarm.