5 Technical Characteristics

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Alfred Mosley
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1 5 Technical Characteristics 5.1 Plant Overview The Apollo Model DMX 50 Continuous Mixing Asphalt Plant is a portable, continuous mixing type, fully automatic asphalt mixing plant with a capacity of 90 Tons per Hour. The Asphalt Mixing Plant will be supplied by an Indian based company, APOLLO, who has over 35 years in the supply of asphalt manufacturing equipment. The company has considerable years of experience in the business and has fully mastered the continuous drum mixing asphalt technology. The company is committed in providing utmost satisfaction on the quality of mix produced by its plants. The technology with design roots from Barber Greene, USA, has been found to exceed the specifications laid by International consultants and contractors all across the globe. Constant up-gradation of products offers customers the best and most appropriate design for their requirements. The APOLLO design team facilitates custom built asphalt plants to meet specific site demands and requirements. The Drum Mix (DM) series offers customers, the industries finest & proven technical solution, with international product support, latest generation process controls and automation together with total installation and site support, aimed to deliver precisely mixed quality asphalt productively and profitably. The supplier of the Asphalt plant will provide the most state of the art equipment for proceeding with the asphalt production activity. The promoter of this project has purchased a brand new Asphalt Plant with the latest environmental controls which can comply with stringent environmental law of several countries including norms and regulations prevailing in Mauritius. The supplier is constantly investing in R & D in order to improve the designs, thus conforming to the specifications of a wide range of customers and applications. Apollo will also provide commissioning services to the promoter by experienced and fully trained engineers. Furthermore, the supplier will also offer maintenance services throughout the lifecycle of the asphalt plant. 21 P a g e

2 The supplier of the equipment has been in the road construction industry for a long time. From a modest beginning in the year 1972, the group today offers almost the entire range of equipment that lends itself admirably to the bituminous road building industry. The supplier always keeps abreast of the changes and aim to maintain leadership through innovation and world class technology. Value engineering is a way of life at Apollo and no wonders why the advances in Production Engineering that is noticed in Apollo equipment can be rarely matched by competition. The full turn key asphalt mixing unit which Apollo has recommended to the promoter will ensure optimization of the activities and also contribute substantially to cost savings. Figure 5.1: Proposed Plant The Salient Features of the Asphalt Mixing Plant are as follows: Easy Operation and Less Maintenance. Designed For the International Market. Modern Drum Mix Technology. High Production Rate. Low Dust Emissions. Proper Drying and Homogeneous Mixing of Aggregate. Modular Design or Containerized Transport Proper Asphalt Coating and Saving. Easy to Operate. 22 P a g e

3 Less Fuel Consumption. Fully Automatic Computerized Control Panel Board. Accuracy in Quality Control. 23 P a g e

5.2 Asphalt Plant Components The asphalt plant will consist of the following main equipment: Cold Aggregates Bin Feeders Continuous Electronic Belt Weighting Systems Drying & Mixing Drum Burner

4 5.2 Asphalt Plant Components The asphalt plant will consist of the following main equipment: Cold Aggregates Bin Feeders Continuous Electronic Belt Weighting Systems Drying & Mixing Drum Burner Load-out Conveyor Bitumen Tanks and auxiliary Equipment Pollution Control Unit Control Cabin Cold Aggregates bin feeders Cold Feeder Conveyor Belt Adjustable Strike-off gate Figure 5.2: Bin Feeders 24 P a g e

5 This unit will consist of four bin feeders having a total storage capacity 50 tons with individual Feeder weighing arrangement comprising of Load cells under each bin. Complete unit with individual AC variable frequency invertors based variable speed drives, programmable bin vibrator on aggregate bin, Gathering conveyor & Slingers conveyor. Aggregate flow indicators are mounted on each bin to indicate the on/off flow of the aggregates from each bin. The bins shall be fabricated from special Structural steel, with a thickness of 5/6mm and supplied with wear strips. They are supplied with zero maintenance and with direct shaft mounted helical high efficiency gear boxes. The unit shall be supplied complete with safety mesh and protection. The feeders are fully computerised controlled and gradation can be changed on the go. The unit shall also be supplied with calibrated gate openings for very precise controls of the cold mix gradation. The hoppers have been properly designed with slopes, allowing a constant discharge without bridge forming. The first bin meant for the small size aggregate or dust is fitted with vibratory motor to ensure the free flow. Each hopper is equipped with an adjustable opening door that determines the discharge quantity for the materials capacity in outlet, as a function of specific weight of materials Continuous Electronic Belt Weighting System A continuous electronic belt weighing system with load cell is mounted on the gathering conveyor for weighing the aggregates flow in tons per hour. The belt weighing system is further synchronised by the computer to ensure precise metering of bitumen and filler. A conveyor below the cold feed bins transfers the aggregate to the dryer where the aggregate is dried and heated. Because drum plants produce mix continuously, a weigh scale is used to weigh the aggregate before it enters the dryer so the amount of asphalt binder can be accurately added Drying and Mixing Drums The Dryer unit is long rotating cylindrical drum. It is mounted on sturdy and robust steel structure. The whole structure has adjustable height legs to give proper degree to the unit for accurate results. Both the Drying and the Mixing drum are made up of Stainless Steel. The Drying unit with cradle type low maintenance and low noise chain drum drive, automatic 25 P a g e

lubrication system, trunnion rings and wheels, thrust wheels etc. The burner is a fully automatic burner unit and suitable for Diesel oil. Figure 5.3: Dryer & Mixing Drum 5.2.

Burners are fitted with remote control system to detect flame failure and have Electric spark ignition system.

6 lubrication system, trunnion rings and wheels, thrust wheels etc. The burner is a fully automatic burner unit and suitable for Diesel oil. Figure 5.3: Dryer & Mixing Drum Burner Thermo - drum Burner is the heart of the entire system and hence its efficiency, ease of serviceability etc. are most important factors. Burners are fitted with remote control system to detect flame failure and have Electric spark ignition system. The temperature is controlled through thermostatic control device to be at bitumen in desired temperature range. Aggregates are dried and heated in a dryer drum as they are tumbled through a hot air stream. The hot air is created by a burner and is pulled through the drum by a fan. The direction of air flow relative to the direction of aggregate flow as described by the two types of dryers: Parallel-Flow and Counter- Flow. Figure 5.4: Burner 26 P a g e

7 Salient Features of dryer burner: Two stage High & low Capacity to reduce the moisture up to 0.5% and achieve 180 Deg Celsius for aggregate. Able to use HFO/ diesel as fuel. Nozzle cleaning is possible during running conditions. Remote controlled & fully automatic operation Load Out Conveyor Anti-segregation gob hopper complete with high temperature conveyor for discharge of mix to waiting dumpers / trucks. The Hopper consists of a hydraulic cylinder and hinged doors for opening and closing of the hopper. A hydraulic power pack is supplied for operating the hopper, complete with hosepipe connections mounted separately. The gob hopper shall have a minimum 1000 Kg surge capacity. A material scrapper is supplied at the end of the discharge conveyor for scrapping the material from the belt in to the hopper. Mixed hot material taken out from mixer drum is carried by inclined hot conveyor belt & discharged into the Tipper/Truck through automatic Hydraulic surge storage hopper. The urge storage hopper of approximately 350 to 1000 kg is provided at the discharge end of the conveyor. The surge storage hopper is hydraulically actuated, for opening and closing hopper door and scrapper plate to scrape out the mixed material sticking to the conveyor Bitumen Tanks and Auxiliary Equipment Fully insulated cylindrical bitumen tanks, 2 x 30 Tons storage capacity complete with hot oil heating system and asphalt piping system complete with foldable screw type legs. Other auxiliary equipment consists of mineral filler of circular type. A thermal heater will also be installed. A sludge pond is constructed in order to ensure the settling of solids before the water is recycled. 27 P a g e

8 5.2.7 Pollution Control Unit Wet dust type extreme turbulence venturi dust collector complete with pumping unit, stainless steel nozzles and control device. The unit shall be supplied with a venturi controller to throttle the air flow rate. The wet dust collector will enhance the particulate matter removal in addition to the presence of a dry particulate matter collector. As hot air passes through the aggregate it picks up some fine sand and dust particles. These particles are removed by the emissions control system before the air goes into the atmosphere. The plant will have primary and secondary collectors to remove these particles. The fine sand and some dust is collected in the primary collector and returned to the mix. The secondary collector removes the remaining fine dust. In most cases this dust will also be returned to the mix. The Zero Maintenance Bag House Filter will comprise of the following features: 1. Dual stage pollution control system 2. Based on Free Air flow system 3. Meets international emission standards 4. Lowest Maintenance & Operating costs 5. Lowest power consumption 6. Guaranteed Longer Filter element life 28 P a g e

9 5.2.8 Control Cabinet The Hot Mix Asphalt (HMA) plant will control the asphalt production using computers and automation. Fully automatic with manual overdrive controls, Computerised ultra modern power controls, Sequence controls, Distribution power controls, Automatic Burner controls, Temperature indications, Printer, Totally prewired and & Air conditioned. In particular cases where it is necessary, the plant may still be operated manually. Insulated control cabin will be fitted with air conditioner. Figure 5.5: Control Cabinet Controls o Latest State-of-the-art technology o Built on proven technology from U.S based companies o Fully automatic plant controls and automation o Fail proof power interlock and online fault detection and solution o Energy saving components Salient Features of control panel: The plant is supplied with centralized Control Panel. All controls, including the motor control centre circuit breakers, are provided in the control panel. The control Panel comprises of the Automatic Burner Controls, Aggregate and Asphalt Blending Controls, Motor Controls, Feeder Bin Controls and Electric Switchgear. All the parameters like, temperature of bitumen-hot mix material-exhaust gases and aggregate weight, asphalt percentage, hot mix material weight etc. are displayed on the control panel. It is equipped with protections like Single Phasing, Overload, fuses, Sequence Interlock etc. 29 P a g e

10 5.3 Process Description Asphaltic concrete also known as Hot Mix Asphalt (HMA) is made from crushed rock and bitumen, which is a mixture of petroleum compound produced by the fractional distillation of crude oil. Dry aggregates of different sizes are sent to the cold aggregate bin feeders. By means of the continuous electronic belt weighing system, the aggregates are fed into the drying and mixing drum. The raw materials used for the production of the pre-mixed asphaltic concrete products, are dried and mixed in the drum having a capacity of 90T/Hr. The burner which is located at the discharging end of the drum has a long flame tube which passes horizontally through the rotary mixer. The flame then passes through the combustion zone of the dryer. The aggregates are dried, heated and then mixed and coated with bitumen in the drum. A spraying system is used through the chimney to prevent dust from escaping into air. Water is spread by means of spraying nozzles all along the chimney and then sent to the primary and secondary collectors by gravity along PVC Heavy duty pipes. The dust collectors are divided into three compartments to allow settling of dust from the water. Once freed from dust, the clear water is pumped back to the chimney from the other end of the and the cycle goes on. The mixing is carried out in a rotary mixer inside a zone which is completely isolated from the flame of the burner. Thus, the asphaltic concrete is protected from the flame preventing the production of blue smoke and toxic gases. 30 P a g e

5.4 Raw Materials Constituents 5.4.1 Aggregates Aggregates (or mineral aggregates) are hard, inert materials such as sand, gravel, crushed stone, slag, or rock dust.

11 5.4 Raw Materials Constituents Aggregates Aggregates (or mineral aggregates) are hard, inert materials such as sand, gravel, crushed stone, slag, or rock dust. Properly selected and graded aggregates are mixed with the cementing medium asphalt to form pavements. Aggregates are the principal load-supporting components of an Asphalt Concrete pavement. They total 90 to 95 percent of the mixture by weight and 75 to 85 percent by volume The Paving Bitumen The selection of a particular bituminous material depends on the type of pavement, the range of temperatures, the amount of rainfall, the type and volume of traffic, and the type and availability of equipment. In general, hard-penetration grades of bitumen are used in warm climates and soft-penetration grades are used in cold climates. Heavy grades of asphalt cutback and tar are normally used in warm regions, and light grades are used in cool regions. The paving bitumen is usually used in hot-mix pavements and is solid at 25 C. To make it fluid enough for mixing with aggregate or for spraying, it is heated to a temperature of 121 C to 177 C. The various penetration grades of paving bitumen are suitable for plant mixes, penetration aggregates, and surface treatments. The most common types of paving bitumen used in Mauritius are penetration grades 40/50 and 60/70. This is the only raw material which will be imported for the production of premixed asphaltic concrete. According to the Safety Data Sheet enclosed Annex 6, raw bitumen is not classified as a hazardous material. However, precautionary, measures should be taken when manipulating bitumen to avoid health and environmental hazard. 31 P a g e

12 5.5 Storage of Materials Storage of Bitumen Bitumen is shipped in containers of a capacity of 20 tonnes. The latter will be stored within the Freeport area and transported to the plant site at a rate of 1-2 containers per week. The bitumen containers will be placed on concrete base surrounded by wall within the yard of the asphalt plant so as prevent soil or water pollution in case of accidental spill Storage of Aggregates The aggregates will be stocked in designated bins and covered, thus minimising dust emissions. Moreover, the aggregates will be dry and reduce the fuel requirements for the burner Diesel Diesel will be stored in a designated tank of a maximum retention capacity of about 25,000 litres. The tank will be placed on a concrete base surrounded by a bundwall to prevent pollution in case of spillage. 5.6 Transportation Raw materials need to be transported to the St. Julien for the production of asphaltic concrete while the latter will be transported to the different construction sites around the island. The predominant mode of transport used is road via use of heavy good vehicles including trucks Bulk Bitumen Bitumen will be imported and stored within the port area, from which it will be delivered to the asphalt plant site. It is estimated that 200 tonnes of bitumen will be imported each month. About 10 lorry trips per month will be required to transport the monthly imported bitumen to the site. 32 P a g e

13 Bitumen will be transported on site depending upon the demand and the rate of production. It is estimated that a maximum of 2 lorries load will be required each day for the production of asphaltic concrete. The environmental impact of this level of additional traffic from Port-Louis to the site on the existing road network and traffic pattern is practically negligible Aggregates The aggregates will be supplied by United Basalt Products (UBP) which is situated within 50 to 100 metres of the proposed site. This will considerably reduce the transportation cost for conveying of raw materials. Covered lorries will be used for that purpose so as to avoid dispersal of dust into the surroundings Diesel The refuelling of the diesel tank will be done through the supplier s lorries, once a week Asphaltic Concrete Asphaltic concrete will be distributed to the promoter s sites through the Company s lorries or if need be will hire at peak times. The capacity of the lorries will be 15 to 30 tons depending on the amount needed on site. All the lorries will be ensured that it is well covered before leaving the plant. The peak production for the plant will be around 500 tons per day, required around 17 lorries. At normal time the plant will produce around 300 tons per day, however the plant will not be put into operation if the quantity is less than 200 tons per day. 33 P a g e

DM 45 (40-60 TPH) ASPHALT DRUM MIX PLANT - DM 50 (60-90 TPH) I TECHNICAL SPECIFICATIONS DM 60 ( TPH) COLD AGGREGATE FEEDER.

DM 45 (40-60 TPH) ASPHALT DRUM MIX PLANT - DM 50 (60-90 TPH) I TECHNICAL SPECIFICATIONS DM 60 (90-120 TPH) ROAD BUILDING COLD AGGREGATE FEEDER Stationary four bin cold aggregate feeder unit is with each