Abstract:
A highly portable asphalt plant of substantial size and product manufacturing capacity carries the system components on the confines of two transportable vehicles. The two vehicles are arranged in a fashion whereby vehicle one is connected to vehicle two in an inline continuous fashion. Vehicle two contains an integrated inertial dust separator baghouse design and provides for the receiving of the rotary dryer drum mixer directly and without the use, of interconnecting ductwork.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority of U.S. Provisional Application Ser. No. 62/170,786, filed Jun. 4, 2015, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    This invention relates to the hot mix asphalt plant used to manufacture asphaltic mixes to pave highways. 
         [0004]    2. Description of the Related Art 
         [0005]    The components of the state of the art hot mix asphalt plant combine process methods to heat and dry aggregates, add coarse and fine aggregate dust particles and mix them with asphalt. The raw material virgin aggregates release dust particles as they are heated and dried that must be collected using mechanical separation for the coarse dust particles along with fine dust collection using fabric filters or baghouses to eliminate air borne particulate from entering the atmosphere. Asphalt plants use rotary dryers to tumble the aggregates in the presence of heat to remove the moisture and heat them to the process temperature. 
         [0006]    Drying aggregates with the rotary dryer involves a physical separation process designed for the purpose to remove the liquid phase or moisture using thermal energy. The liquid in this case is water that is liberated by the process of vaporization leaving a solid or aggregates with a trace of residual moisture. The dryer is a direct heat dryer as heat transfer for drying is accomplished by direct contact between the wet solid aggregate with hot gases from a combustion burner. This invention describes the dryer as a rotating cylindrical shell, slightly inclined to the horizontal with the heating medium flowing in a countercurrent direction to the flow of aggregates through the dryer. The dryer is equipped with flights or lifters on the interior for lifting and moving the wet aggregates through the hot gas stream as they pass through the cylinder. 
         [0007]    As the gases pass through the dryer the aggregates become hot and dry thus liberating aggregate dusts that cling to the aggregates. Some aggregates liberate dust as they are tumbled through the rotary dryer. The dryer operates under a suction pressure as the dust particles are pulled through the dryer and into the coarse particle mechanical dust separation devices and finally into the fabric filters for dust collection. Those dust particles must pass from the rotary dryer to the dust collection devices generally using ductwork or large round pipes or rectangular ducts to move the moisture, products of combustion and dust to the dust collection devices. This industrial size external ductwork usually requires the use of a large lifting crane to assemble the ductwork from the rotary dryer to the dust collection devices and filter house needed to collect the hot dry aggregate particles. Moving the asphalt plant from one location to another becomes cumbersome as lifting equipment is needed to assemble and disassemble the plant rotary dryer from the dust collection equipment. 
         [0008]    Making asphaltic mixes requires a recipe using a combination of sand and varying sizes of aggregates. Multiple bins are needed to contain the sand and aggregates. The bins are filled using construction bucket loading tractors from the site stored aggregates piles. 
         [0009]    The aggregate bins are each fitted with an underlying variable speed belt feeder that proportions the needed flow of raw material to combine the hot mix recipe. 
         [0010]    The raw aggregates are generally conveyed with a belt collection conveyor to a large vibrating screen to insure debris or oversize materials are eliminated from the flow of aggregates to insure a smooth road surface. A vibrating screen device of the size needed on the asphalt plant generally must be conveyed as a separate unit and mounted to a large wheeled trailer assembly in order for it to be conveyed for the portable plant. Bins of this size and capacity normally require a large individual wheeled trailer assembly as they are moved as a separate component of the portable asphalt plant. The movement of aggregates from the aggregate bins and oversize vibrating screen requires the use of a long portable conveyor belt assembly to move the aggregates to the rotary dryer for processing. These portable conveyors are fitted with truck axles and wheels as they are moved along with the portable asphalt plant. 
         [0011]    The dust particle size separation and collection equipment needed on the portable plant is generally conveyed as a separate component with truck axles and wheels that also must be positioned on the plant site to mount the large connecting duct pieces between the rotary dryer and dust separation equipment. The large portable rotary dryers as well are conveyed as a separate component with truck axles. Ductwork connection and feed conveying plant components must be connected to the rotary dryer once it is in place at the portable plant site. 
         [0012]    Once the hot mix asphalt is produced it must be conveyed away from the rotary dryer, stored and weighed and then transferred to a dump truck to be carried to the road paving site. Each of these devices must be made portable and carried along with the other plant components as a separate piece of equipment with truck axles as trailer assemblies. 
         [0013]    Each time a portable hot mix asphalt plant is moved, each site must be graded, leveled and compacted to insure the proper soil surface conditions exist to allow the equipment to be assembled and parked for alignment and safety. As described, the portable hot mix asphalt plant can easily contain ten individual plant components. Transporting and preparing the site represents time taken away from actual plant production; the cost to prepare the site, grading for each piece of equipment and the cost of additional site preparation materials such as soil and aggregates to prepare and level the site. 
       SUMMARY 
       [0014]    As can be derived from the aforementioned description of a typical portable hot mix plant, there is a significant advantage for a highly portable plant that can be manufactured with fewer major components and can be erected and operational faster than a typical plant. Such a plant would be designed so as to not require lifting cranes to erect the plant; require fewer transport truck loads; have a smaller geographical footprint; and can be quickly erected and assembled thus saving time, energy and financial burden. 
         [0015]    In one aspect, a highly portable asphalt plant of substantial size and product manufacturing capacity carries the system components on the confines of two transportable vehicles. The two vehicles are arranged in a fashion whereby vehicle one is connected to vehicle two in an inline continuous fashion. Vehicle two contains an integrated inertial dust separator baghouse design and provides for the receiving of the rotary dryer drum mixer directly and without the use, of interconnecting ductwork. 
         [0016]    In another aspect, a transportable hot mix asphalt plant apparatus includes a first vehicle having an aggregate collector conveyor, at least one aggregate storage bin disposed above the aggregate collector conveyor, at least one aggregate storage bin equipped with a variable speed aggregate feeder belt discharging onto a vibrating screen, the aggregate collector conveyor having a collector belt weigh scale disposed at an output end, the output end discharging onto an aggregate collector belt extension, and a second vehicle having a counter-flow aggregate rotary dryer and mixer, the counterflow aggregate rotary dryer and mixer receiving aggregate from a discharge end of the aggregate collector belt extension, a hot mix asphalt elevating drag slat conveyor to convey asphalt mix to a storage hopper, a self-erecting frame for the hot mix asphalt elevating drag slat conveyor, and a support stand for the storage hopper. 
         [0017]    In another aspect, a transportable hot mix asphalt plant carries a plurality of major components on a first and a second vehicles for transport within guide lines of typical road transportation limits. 
         [0018]    In another aspect, a transportable hot mix asphalt plant apparatus assembles a first and a second vehicles at a job site without a need of inter-connecting ductwork between a rotary dryer and a dust collection device. 
         [0019]    In another aspect, a transportable hot mix asphalt plant apparatus erects an apparatus in a field without a need of auxiliary lifting devices or lifting cranes. 
         [0020]    In another aspect, a transportable hot mix asphalt plant apparatus connects a rotary dryer to an inlet of a primary collector, and connects a primary collector directly to a filter baghouse without inter-connecting ductwork. 
         [0021]    In another aspect, a transportable hot mix asphalt plant allows dust laden exhaust gases from a rotary dryer to be directed to an inlet of a primary collector without inter-connecting ductwork. 
         [0022]    In another aspect, a transportable hot mix asphalt plant apparatus includes a floating seal assembly located on a rotary dryer for direct connection to a primary collection box on a baghouse without external inter-connecting ductwork. 
         [0023]    In another aspect, a transportable hot mix asphalt plant apparatus includes a small dynamic in-motion scalping screen disposed on a at least one aggregate storage bin. 
         [0024]    In another aspect, a transportable hot mix asphalt plant apparatus includes a plurality of aggregate storage bins, each of the plurality of aggregate storage bins having a small dynamic in-motion scalping screen in place of one large dynamic scalping screen for a plurality of aggregate storage bins. 
         [0025]    In another aspect, a transportable hot mix asphalt plant apparatus includes a unique counter-flow baghouse design that does not require a use of an air compressor to pulse clean dust filter bags. 
         [0026]    In another aspect, a transportable hot mix asphalt plant apparatus includes a unique portable counter-flow baghouse that incorporates an integral coarse dust inertial separator—primary dust collector. 
         [0027]    In another aspect, a transportable hot mix asphalt plant apparatus includes a combination portable counter-flow baghouse—inertial dust collector that includes screw augers to remove dust from a baghouse and a cross auger assembly to collect a dust from an inertial dust collector. 
         [0028]    In another aspect, a transportable hot mix asphalt plant apparatus includes a unique portable baghouse and inertial dust collector assembly that incorporates a collecting dust system of screw augers for fine and coarse dust collection in one assembly. 
         [0029]    In another aspect, a transportable hot mix asphalt plant apparatus includes a unique portable baghouse dust collector design assembly that provides for acceptance of a rotary dryer directly to an inertial dust collector assembly. 
         [0030]    In another aspect, a transportable hot mix asphalt plant apparatus includes a unique portable baghouse and inertial dust collector assembly that includes a complete dust removal system to collect both fine and coarse dust particles. 
         [0031]    In another aspect, a transportable hot mix asphalt plant apparatus includes a combination portable counter-flow baghouse—inertial dust collector assembly that includes a pneumatic dust transport system from a baghouse to a mixing zone of a counter-flow aggregate rotary dryer and mixer in which hot liquid asphalt is combined with aggregates. 
         [0032]    In another aspect, a transportable hot mix asphalt plant apparatus includes a portable counter-flow baghouse with a multiple pocket, elliptical design filter for increased filter media surface area in a smaller geographical footprint. 
         [0033]    In another aspect, a transportable hot mix asphalt plant apparatus includes a unitized transportable vehicle assembly that contains at least one aggregate storage bin, conveyor belt feeders, scalping screen for each feeder, aggregate collector conveyor, collector belt weigh scale, aggregate collector belt extension to move aggregates to a rotary dryer, coarse dust primary collector, fine dust baghouse filter, baghouse exhauster fan, exhauster fan damper, system exhaust stack, baghouse dust hopper screw augers, dust collection cross auger, wheeled truck axles for portability, and trailer connection pin to connect transport truck tractor with unitary frame design for transport. 
         [0034]    In another aspect, a unitized transportable vehicle assembly contains a counter-flow aggregate rotary dryer and mixer, a hot mix asphalt elevating drag slat conveyor, a self-erecting frame, a support stand for a storage hopper, an asphalt injection system, a combustion burner, rotary dryer drive components, wheeled truck axles for portability, and a trailer connection pin to connect transport truck tractor with a unitary frame design for transport. 
         [0035]    The above and other features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments of the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. In the drawings, like reference numbers indicate identical or functionally similar elements. A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
           [0037]      FIG. 1  shows a first vehicle in transport mode according to an embodiment; 
           [0038]      FIG. 2  shows a second vehicle in transport mode according to the embodiment; 
           [0039]      FIG. 3  shows a silo of the second vehicle being erected; 
           [0040]      FIG. 4  shows the silo of the second vehicle being erected; 
           [0041]      FIG. 5  shows a baghouse for the second vehicle; 
           [0042]      FIG. 6  shows the first and the second vehicles in an installed condition; 
           [0043]      FIG. 7  shows the collector belt weigh scale device; 
           [0044]      FIG. 8  shows the first vehicle mated to the second vehicle; and 
           [0045]      FIG. 9  shows the first vehicle and the second vehicle in operation. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0046]    In  FIG. 1  is shown a first vehicle  100  in transport mode according to an embodiment. The first vehicle  100  includes up to four virgin aggregate feed bins  102  of substantial size that can be charged with virgin aggregates using large wheeled loader tractors. Each of the aggregate feed bins  102  is equipped with a variable speed aggregate feeder belt  104  used to accurately control the flow of varying sizes of aggregates and sand to manufacture hot mix asphalt of any specification. 
         [0047]    Each of the aggregate feeder belts  104  discharges onto a vibrating screen  106  used to screen out any over size aggregates, rocks or debris. The debris is directed over the side of the feed assembly away from the equipment. The vibrating screens  106  are sized to accommodate the flow of aggregates from only one feed bin feeder allowing the use of a smaller size screening unit. 
         [0048]    The screened aggregates are then directed onto a collection conveyor belt  108 . The collection conveyor belt  108  moves under each of the aggregate feed bins  102  collecting the portions of aggregate from each feeder. As the collection conveyor belt  108  progresses forward, it passes over a collector belt weigh scale device  110  that develops an electrical output signal used by the control system to measure the total flow of aggregates across the collector belt weigh scale device  110  to accurately weigh the plurality of aggregates as they progress toward the rotary dryer  202  (shown in  FIG. 2 ). To save space the collection conveyor belt  108  progresses under the primary and secondary dust collection devices or baghouse. 
         [0049]    In  FIG. 5  is shown a baghouse  500  according to an embodiment of the invention. The collection conveyor belt  108  is enclosed into a rectangular housing as it is elevated in height and passes up and through the baghouse  500  and primary collector. Aggregates carried on the belt are deposited into the rotary dryer  202  located on the second vehicle  200 , which is shown in  FIG. 2 . The dust laden gases exiting the rotary dryer  202  on the second vehicle  200  enter the primary collector where the heavier dust particles are separated as the gases continue and move into the baghouse where the finest of aggregate particulate are collected. 
         [0050]    The floor of the baghouse  500  is separated into two dust collection, v-shaped hoppers  502  on the left and right side. Each of the hopper sections  502  encloses a screw auger conveyor  504  to move the dust from one end of the baghouse  500  forward and into a cross auger assembly  506  perpendicular to the baghouse hopper augers  504 . The cross auger assembly  506  then carries all of the coarse and fine dust particles to one side of the baghouse  500  and discharges the dust to a rotary airlock feeder  508 . The rotary air lock feeder  508  stops air and dust back flow from re-entering the baghouse dust augers, and allows the dust to be blown to the end of the rotary dryer  202  on the second vehicle  200  into the mixing zone of the drum mixer dryer. This rotary airlock feeder  508  transfers the dust to an air eductor device on the dust line that is under positive air pressure from a motor driven dust blower. 
         [0051]    In  FIG. 8  is shown a floating seal assembly  802  located on the rotary dryer for direct connection to a primary collection box on a baghouse without interconnecting ductwork. This floating seal assembly  802  allows the dust laden exhaust gases from the rotary dryer to be directed to the air Inlet of the primary collector. The floating seal assembly  802  prevents dust laden gases from escaping to the atmosphere. 
         [0052]    The counter-flow dust collection baghouse  500  operates at low differential air pressure across the body of the baghouse  500 . Lower differential air pressure requires less fan horsepower which is the advantage to this operational design. The counter-flow self-cleaning baghouse  500  does not use compressed air to pulse clean the bag filter elements. Therefore, an air compressor is not required to supply the motive force to clean the filter bags which is an additional advantage in using the counter flow baghouse design. In addition, an air compressor is not required for the plant components nor is electrical power or air piping. This is an additional advantage to the counter-flow baghouse. 
         [0053]    In total, the first vehicle  100  contains the aggregate storage bins  102 , conveyor belt feeders, scalping screen for each feeder, aggregate collector conveyor  108 , collector belt weigh scale device  110 , aggregate collector belt extension to move the aggregates to the rotary dryer  202 , coarse dust primary collector, fine dust baghouse filter collector, baghouse exhauster fan, automatic exhauster fan damper, system exhaust stack, (2) baghouse dust hopper screw augers, dust collection cross auger, wheeled truck axles for portability, and trailer connection pin to connect transport truck tractor with unitary frame design. 
         [0054]    In  FIG. 2  is shown a second vehicle  200  in transport mode according to an embodiment. The rotary dryer  202  is located on the second vehicle  200 . Aggregates from the first vehicle  100  are fed into the feed end of the rotary dryer  202  from the collection conveyor belt  108  elevating extension  112  (shown in  FIG. 1 ). The aggregates start at the dryer exhaust gas end of the rotary dryer  202  and slowly move forward into the counter-flow dryer drum  204 . The counter-flow dryer drum  204  is positioned at a downward angle to allow the cascading aggregates inside the rotary dryer  202  to advance toward the discharge end of the rotary dryer  202  as it rotates. Once the aggregates are hot and dry they advance into the mixing portion of the drum mixer  206  where dust, additives and liquid hot asphalt are injected to formulate the hot mix asphalt. 
         [0055]    The rotary dryer  202  is heated using a combustion burner that mounts inside the support structure in the mixing portion of the counter-flow dryer drum  204 . The combustion burner supplies the heat necessary to the aggregates in the rotary dryer  202 . The firing end of the burner extends into the discharge end of the rotary dryer  202  beyond the mix section so as not to overheat the aggregates and liquid asphalt as they are mixed together in the mixing zone of the dryer prior to being discharged as final product. 
         [0056]    The final hot mix asphalt flows from the discharge of the rotary dryer  202  into a drag slat elevating conveyor  208 . The final hot mix asphalt moves to an elevation to allow it to flow into a storage hopper  210 . A dump truck is positioned under the storage hopper  210  and the final hot mix asphalt is dispensed into the dump truck. The truck moves away and the process continues as another truck moves into position to receive hot mix asphalt from the hopper above. 
         [0057]    The trailer  212  under the rotary dryer  202  is equipped with truck axles  214  for transport by a tractor trailer. The drag slat elevating conveyor  208  is mounted on a pivot pin connection that allows the unit to be elevated when the plant is set for operation. As the plant is prepared for moving, the drag slat elevating conveyor  208  is lowered. In the transport position, the drag slat elevating conveyor  208  is reduced in height to meet typical road transport height requirements. The drag slat elevating conveyor  208  lowers on its pivot connection to travel with the second vehicle  200  fully assembled and is not removed for transport. The storage hopper  210  is part of the drag slat elevating conveyor  208  assembly which folds over to allow transport on the same vehicle assembly. 
         [0058]    In total, the second vehicle  200  contains the counter-flow aggregate rotary dryer  202  and mixer combination, asphalt injection system, combustion burner, rotary dryer  202  drive components, wheeled truck axles  214  for portability, trailer connection pin  218  to connect the transport truck tractor  220  with unitary frame, self-erecting trailer frame  216  to be used in the transport position, hot mix asphalt drag slat elevating conveyor  208  to convey asphalt mix to the storage hopper for delivery into trucks and the support stand for the storage hopper. All of these devices are stored on the trailer assembly in the transport position and are transported as a single unit. 
         [0059]    In  FIG. 3  is shown the silo of the second vehicle  200  being erected. The trailer support legs  302  are down, while the cylinders  304  that will raise the drag slat elevating conveyor  208 , the storage hopper  210 , and the vertical self-erecting legs  216  are shown being extended in  FIG. 3 . The support legs  306  are still stowed. 
         [0060]    In  FIG. 4  is shown the silo of the second vehicle  200  being erected. The cylinders  304  that will raise the drag slat elevating conveyor  208 , the storage hopper  210 , and the vertical self-erecting legs  216  are shown being extended in  FIG. 4 . The support legs  306  are swinging into position. 
         [0061]    The major plant components are contained within two main trailer vehicles, as shown in  FIG. 9 . Both vehicles  100  and  200  are backed into each other using a transport truck tractor, as shown in  FIG. 6 . The plant operates as follows: 
         [0062]    Each of the aggregate storage bins  102  are charged or filled with aggregate needed to meet the needs of the hot mix asphalt design. 
         [0063]    The conveyor belt feeders under each of the bins  102  is electrically turned on. The speed of the feeder belts  104  are varied so as to control the needed percentage of each raw material component required for the hot mix asphalt design. 
         [0064]    Each of the conveyor belt feeders discharges the aggregates over each of the small, electrically operated vibrating scalping screens  106  located at the end of the feeder belts  104 . Any oversize aggregates or debris is discarded off to the side to insure the integrity of the raw material mix design. 
         [0065]    The select aggregates discharge onto a centrally located belt conveyor or collection conveyor belt  108  that is in motion under the aggregate bins  102  and feeders. The collection conveyor belt  108  travels under the aggregate bins  102  and longitudinally conveys the aggregates under and through the baghouse and up and into the rotary dryer  202 . 
         [0066]    A conveyor belt weigh scale device  110  is mounted on the collection conveyor belt  108  downstream of the aggregate bins  102  to electrically measure the flow of aggregates on the collection conveyor belt  108 , as shown in  FIG. 7 . 
         [0067]    The flow of exhaust gases from the rotary dryer  202  pass through the primary coarse dust collector prior to flowing into the fine particle baghouse filter collection assembly. Those coarse dust particles fall into a hopper and are directed to the baghouse dust collection auger. 
         [0068]    The fine particle collection baghouse collects and disperses internally the dust into two hopper mounted dust screw auger assemblies driven by electric motors. The screw augers convey the dust from the baghouse to the dust cross auger assembly mounted perpendicular to the back side of the baghouse. 
         [0069]    Coarse dust from the primary collector and fine dust from the baghouse is collected onto the baghouse cross auger. Dust is then delivered to a rotary valve feeder and airlock to convey the dust under negative suction pressure from the baghouse. The rotary valve directs the dust to an eductor assembly attached to a pressure blower. The pressure pneumatically forces the dust through a dust pipe and directs the dust into the mixing section of the rotary dryer  202 . The dust is combined with liquid asphalt and aggregates to produce the end product hot mix asphalt design. 
         [0070]    The rotary dryer  202  located on the second vehicle  200  receives the raw aggregates from the aggregate collection conveyor on the first vehicle  100 . Aggregates pass from the feed end of the dryer and are heated and dried to remove internal moisture. Next, the aggregates are mixed with liquid asphalt and dust conveyed from the baghouse to produce the final hot mix asphalt design. 
         [0071]    The hot mix asphalt is directed from the discharge end of the rotary drum mixer into a drag slat elevating conveyor  208 . The hot mix asphalt is conveyed to an elevation above the hot storage hopper  210 . The drag slat elevating conveyor  208  is driven by an electric motor continually moving hot mix asphalt in incremental amounts between the slats of the conveyor chain. The asphalt falls off the discharge end of the conveyor into the storage hopper  210 . 
         [0072]    The interim storage hopper  210  is held in place by the drag slat elevating conveyor  208  of one side and vertical self-erecting legs  216  on the opposite side of the assembly to support the weight of the hopper  210  and hot mix asphalt delivered into the hopper  210 . 
         [0073]    The foregoing has described the principles, embodiments, and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments described above, as they should be regarded as being illustrative and not restrictive. It should be appreciated that variations may be made in those embodiments by those skilled in the art without departing from the scope of the present invention. 
         [0074]    While a preferred embodiment of the present invention has been described above, it should be understood that it has been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by the above described exemplary embodiment. 
         [0075]    Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described herein.