An asphalt drum mixing plant is a parallel flow continuous plant used to manufacture asphalt, macadam and other forms of coated road stone, sometimes collectively known as blacktop, hot mix or asphalt concrete.
The manufacture of hot mix requires the combination of several aggregates, sands and fillers, in the correct proportions, heated, and finally coated with a binder, usually bitumen based or, in some cases, tar.
The temperature of the finished product after transport to the final destination must be high enough to be practical. Temperatures between 120 and 170 °C are common.
The drum mix plant is a modern one having all the essential features of latest generation hot mix plant to obtain quality hot mix designed for road construction works as well as road repair and maintenance works undertaken to improve road surfaces. The proposed plant is simple to manufacture, operate and maintain with fully indigenous sophisticated and effective controls for efficient process control. The proposed plant will meet all the engineering specifications in construction and factors of safety provided as per the norms.
Four aggregate bins, individual variable drives underneath each bin with precision gates.
The drum mix plant has a system of cold aggregate feeder hopper bins that store and control the flow of sand and gravel to ensure correct aggregate gradation in the asphalt mix.
Single deck vibratory screen is provided at the discharge end of the gathering conveyor to enable rejection of any oversize material above the permissible limit before loaded on the slinger conveyor and to the drier.
Slinger conveyor is used for the transfer of aggregates to the drum unit. A slinger conveyor will be fitted with the load cell. This load cell will weigh the aggregates collectively.
The equipment will monitor the total weight put into the drum and indicate this in tonnes per hour with a cumulative read out and totaliser.
The rotating drum is fitted with flights that dry the mix in the first half of the drum. Once the material moves to the second half of the drum, it is mixed with bitumen and filler material.
“The exterior of the THERMO DRUM shall be insulated with ceramic wool and cladding is done with SS / GI / Aluminium sheet”.
The burner will be capable of heating the aggregate to a temperature not less than 160 Degree Centigrade without any un- burnt fuel or carbon residue on the aggregate and reducing the moisture contents to 0.5% by weight. The drive to the dryer drum and burner pump and blower will be interlocked, so that the burner can be lit only when dryer drum is rotating. The dryer and mixing drum will have a sweep discharge chute for giving an even and positive discharge from the side of the mixer. The dryer discharge chute will be so designed that it will discharge the material directly on the load out conveyor.
The bitumen pumping system will include a skid mounted positive displacement bitumen jacketed pump with a variable speed A.C. Motor drive. Depending on the grade of Bitumen it will be heated to between 140°C-170°C before being mixed with aggregate and applied. Due to asphalts viscous nature, a typical bitumen pump specification will be cast iron gear pumps which are running slowly to minimize wear with hardened teeth.
A loadout conveyor in an asphalt drum mix plant carries hot mix material from the Thermogram to a truck or tipper. The loadout conveyor is an inclined belt that is heat resistant. It is fitted with hydraulically operated hopper is provided at the discharge end of the dryer drum which feeds the hot mix material into tippers.
Mineral filler system will be provided to add the mineral filler from a hopper. A 1.5 / 2 Ton capacity hopper will be fabricated of steel plates with loading doors. A pneumatic dust and filler conveying system will include a rotary valve with AC motor, adapter chute and with fines piping back to drum mixer and blower skid with compressor electric motor.
A bitumen tank stores and heats bitumen for mixing with hot aggregates in the drum mixer. Bitumen tank of 15 to 40 MT capacity will be provided based on capacity of Asphalt plant or as per client’s requirements. Tanks are thermally insulated on all sides and covered by SS/GI/ Aluminium sheet. The bitumen tank is equipped with a burner system to keep the bitumen in a liquid state. When the control panel signals, the bitumen tank releases bitumen into the drum unit via a bitumen pump. The flow of bitumen is controlled by a variable speed drive motor. The burner that comes with the tank is single phase burner and strong to give fast heat to the tank. Temperature gauge and asphalt level indicator is mounted on the tank. A hot oil circulating system for the bitumen will be provided off adequate capacity to provide for proper and continuous circulation between storage tanks, and mixer during the entire operating period. All the bitumen pipelines to and from the bitumen tanks, bitumen transfer and fittings will be hot oil jacketed and properly insulated to prevent loss of heat and clogging. The chimney shall be fitted at the outlet of the fire tube of bitumen tank and a lid to prevent the ingress of rain water.
The entire functioning of the plant will be fully automated with provision for manual operation. A fully automated centralized control panel with off/on push buttons, indication lights/gauges will be provided inside a cabin to switch on and off any drive motor of the plant independently and with interlocking relays. The metal constructed cabin will be weatherproof and dust resistant with automatically closing doors and one-piece window. Glass panels will be provided on all sides of the cabin for all-round vision. The cabin will have fully prewired internal lighting and will be equipped with an air conditioner. Wooden planks will be laid on the floor and suitable rubber matting will be provided for protection against electric shock.
All exposed parts of the plant shall be cleaned, treated and painted with suitable anti-corrosion protective paint conforming to relevant Indian Standards (or equivalent). Electrical equipment, power units and parts subjected to high temperatures shall be painted with special paint suitable for this purpose. Colours of the approved colour code shall be used to distinguish the units and pipelines of the plant. Electrical connections including terminal and circuit connections, components and circuit elements shall be suitably treated to prevent the growth of fungi.
A sturdy toolbox with lock and key containing the necessary tools and accessories for normal maintenance adjustment and lubrication of the plant and list of tools and items required and instructions shall be provided. Provisions shall be made for properly affixing the toolbox on the machine. If the bidders have recommended some special tools, only the details thereof shall be filled in the schedule of tools.
A venturi type-high efficiency wet dust collector shall be provided. The wet dust collector shall be designed to achieve the most efficient control for air pollution caused by emissions from the exhaust chimney. An exhaust fan of adequate capacity shall be provided to ensure effective air flow through the dryer and dust collection system. The wet collector shall operate on the principle of wetting the dust particles entering the exhaust gases and trapping them in water droplets, which are discharged from the system as water sludge. The dusty exhaust gas shall be drawn from the drum mixer into the venturi by the exhaust fan. At the venturi throat, the exhaust gas shall pass through a water spray introduced by a number of nozzles. The dust particles in the exhaust stream shall be “encircled” by the water and wetted. Extreme turbulence in the venturi shall promote very intimate contact of the water and dust particles to ensure thorough mixing. As the exhaust gas enters the separator, the dust-laden water shall be removed by centrifugal action and skimmer blades. The dust-laden water shall be drained from the separator into a settling pond. The large spray nozzle will provide clog free operation and ensure minimum water requirement for Venturi type collectors. The wide opening nozzle will allow easy recirculation of dirty water without long clarification periods. The deflector in the nozzle will direct the water stream into a full cone spray pattern for maximum wetting of dust particles. The high pressure in the air stream will ensure more efficient operation of the Venturi type collectors with less maintenance. The air stream will accelerate to more than twice its rate of motion when forced through the Venturi and this rapid acceleration will create extreme turbulence in the air stream causing highly effective mixing and wetting action between the dust particles and the spray water. The adjustable Venturi throat will allow “fine turning” to achieve optimum cleaning efficiency for the plant operating conditions. A. As shown in our drawing, a sludge pond setup has been provided, divided into three sections by weirs. The sludge from the separator enters section A where most of the sludge settles out before flowing into section B. By the time the water enters section C the water becomes clear enough for re-circulation. Wire fencing has been provided around the pond as a safety requirement as the water temperature during operation is at 80 deg. cl. The water requirement will be about 1000 lit. and about 10 lpm of water is formed.
Technical Specifications |
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|---|---|
| Model | Capacity |
| LDMX – 30 | 25 TO 30 TPH |
| LDMX – 45 | 30 TO 45 TPH |
| LDMX – 60 | 45 TO 60 TPH |
| LDMX – 90 | 60 TO 90 TPH |
| LDMX – 120 | 90 TO 120 TPH |
| LDMX – 150 | 120 TO 150 TPH |
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