WO2010054453A1 - A method and a plant for preparing hot-mix asphalt - Google Patents
A method and a plant for preparing hot-mix asphalt Download PDFInfo
- Publication number
- WO2010054453A1 WO2010054453A1 PCT/BR2009/000367 BR2009000367W WO2010054453A1 WO 2010054453 A1 WO2010054453 A1 WO 2010054453A1 BR 2009000367 W BR2009000367 W BR 2009000367W WO 2010054453 A1 WO2010054453 A1 WO 2010054453A1
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- hot
- size
- plant
- asphalt
- mix asphalt
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
- E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
- E01C19/1013—Plant characterised by the mode of operation or the construction of the mixing apparatus; Mixing apparatus
- E01C19/104—Mixing by means of movable members in a non-rotating mixing enclosure, e.g. stirrers
Definitions
- the present invention relates in general to an improvement over the prior art hot-mix asphalt plants that use a drier with a fossil fuel burner, that is, direct application of flame for heating and drying cold ingredients (gravel, sand and stone powder) in order to produce hot-mix asphalt.
- the invention further relates to an improvement over the prior art hot-mix asphalt plants that take a short time to heat, dry and mix the cold ingredients with liquid asphalt cement for producing the hot-mix asphalt.
- Hot-mix asphalt products are produced by means of two types of hot-mix asphalt plants: gravity-driven (gravimetric) plants and volumetric plants (known as drum-mixer type plants).
- the gravimetric plants are those wherein the hot-mix asphalt is produced by heating the cold ingredients with direct incidence of a flame in the heater, whereupon the said cold ingredients upon being heated are conveyed to the hot elevator and to the hot metering silos/tanks, wherein they are weighed to be subsequently conveyed to the pugmill mixer, wherein there is then added cold filler and hot asphalt, the whole mass being subjected to mixing during a period of up to forty-five seconds, at most, there being thus provided a ready batch of hot-mix asphalt.
- the volumetric type plants are those wherein the hot-mix asphalt is produced by heating the cold ingredients (gravel, powdered stone, sand) with the use of an exhaust system and a directly applied flame thereon at the drier, whereupon they are metered and weighed using a set of scales integrated with the asphalt pump, within a zone located outside of the reach of the flame in an outer sleeve next to the drier or in the pugmill, the whole mass being then mixed with asphalt for a period of up to thirty seconds, at most, with continuous output of the ready hot-mix asphalt.
- the cold ingredients gravel, powdered stone, sand
- the conventional plants use a series of equipment items that could be substituted with a sole item, to wit, a drier, exhaust fan, exhaust ducting, pugmill, pre-separator cyclone means, silo/tank for storing the hot-mix asphalt without harming the quality and the quantity of the hot-mix asphalt having been produced.
- the conventional plants produce a hot-mix asphalt product that does not withstand for a long time the heavy traffic on paved roadways and airport runways.
- the conventional plants damage the cold ingredients every time they are calibrated to produce hot-mix asphalt. Each time that a conventional plant is shut down, there will be lost the heated and dried cold ingredients that remain trapped within the silo/tank or the pugmill for hot-mix asphalt, which in addition contribute to soiling the plant.
- the conventional plants damage the cold ingredients and reverse the direction of transport of the cold feed every time they are calibrated for producing hot-mix asphalt.
- the conventional plants are forced to remove and further lose the heated and dried cold ingredients that remain trapped within the plants every time that the plants are shut down. This fact, in addition to entailing a loss of material, fills the plant with dust and dirt.
- the filler charge one of the components of the hot-mix asphalt, is not heated, but rather added while cold, at ambient temperature, together with the cold ingredients that were heated and dried in the pugmill.
- the conventional plants take only a short time for heating, drying and mixing. They do not allow sufficient time for mixing the liquid asphalt cement with the cold ingredients upon the latter being heated to allow for the provision of a hot-mix asphalt of better quality.
- Such plants involve a difficult control of dust and soot arising from the stream of hot gasses originating from the combustion in a burner, since the air purifier filter of these plants operates in dry mode, with a cyclone means, a pre-collector and extractor coils that integrate into the production process (with extremely poor physical and quantitative control) a certain amount of dust particles, also by means of a screw-type auger conveyor and a fines recovery valve.
- the cold ingredients are heated and dried in small amounts for production of the hot-mix asphalt (The plants are unable to produce, at one sole time, the entire load capacity of a dumper truck. They produce, at most, a pull- cart-sized amount (about 3 tons or 1.5 cubic meters) of hot-mix asphalt in each cycle of operation). These are small batches, and such small-sized batches are prone to entailing variance of the asphalt content, causing premature disaggregation due to lack of enough binder, or causing an undesirably smooth surface, subject to deformation, due to the presence of an excessive amount of binder.
- the conventional plants use combustion processes, with fire in the form of direct incidence of a flame of a fossil fuel burner for heating and drying the cold ingredients in order to produce the hot-mix asphalt.
- the stream of hot gasses produced by the combustion that takes place at the burner is discharged into the atmosphere at a high flow rate, in the order of 100,000 m 3 /h (one hundred thousand cubic meters per hour). They do not allow to reduce, in the process of production, the emissions of CO 2 (carbon dioxide or carbon gas) per ton of hot-mix asphalt produced.
- the hot-mix asphalt plant and method according to the present invention were designed to produce hot-mix asphalt without using exhaust means or direct flame incidence on the cold ingredients, thereby providing an improved and stronger hot-mix asphalt, intended to extend the useful life of asphalt pavements, with due regard to the extremely important requisite of protection to the environment, with lower emission of pollutants, noise and heat.
- the method according to the present invention does not use direct flame for heating and drying the cold ingredients, thereby allowing the soot (the powder generated by the heating of the cold ingredients) to avoid being subjected to dynamic separation from the cold ingredients while the same are being heated, such that the particles larger than 2.00 mm, micro-particles larger than 0.75 mm and smaller than 2.00 mm and very small fractions of the soot of sizes smaller than 0.75 mm, remain incorporated to the production of hot-mix asphalt, since the force of gravity is acting on these particles, without interference from the mechanical action of forced exhaust (the soot is not sucked into an exhaust system), and furthermore, such that the variable velocity of the axles be adequate for performance of the various functions, to wit: in the range of 3.3 rpm for drying; in the range of 6.6 rpm for mixing; in the range of 9.9 rpm for discharging, allowing a longer time span for heating, drying and mixing the cold ingredients with asphalt, providing enhanced action on the hot-mix asphalt until the same is rendered fully uniform
- the hot-mix asphalt plant that constitutes the object of the present invention allows the petroleum refining plants to increase their sales of asphalts and emulsions, since the various economic, environmental and other characteristics thereof will certainly render feasible a number of roadway- projects presently awaiting proper budget allowances to become a reality; the production of hot-mix asphalt plants that do not use direct flame on the cold ingredients, will allow a greater flexibility and strength by means of the mixture of cold ingredients that cannot withstand the application of direct flame thereto (for example, discarded and ground tires for increasing the friction conditions of the asphalt paving); allows the concessionary companies that manage the roadways the benefits of lesser cost and better quality, without variations of the asphalt in the hot-mix asphalt product and with enhanced flexibility and better resistance to wear, by lengthening the intervals between maintenance actions performed in connection therewith, entailing a positive trend towards a reduction of the number of complaints relative to work performed on the asphalt-paved roadways .
- the hot-mix asphalt plant that constitutes the object of the present invention allows the production of hot-mix asphalt products with mineral grain sizes passing through the square mesh screens of 3" x 3" (7.62 cm x 7.62 cm) for replacement of broken slabs of plain concrete or armored concrete in the system of runways and taxiing and parking aprons in airports, and in roadways in sections located on the slopes of mountains.
- the hot-mix asphalt plant that constitutes the object of the present invention is useful for companies that make repairs in flexible hot-mix asphalt paved surfaces, such as public service concessionary companies that operate potable water, sewage, gas, electric power, landline telephone systems, etc.
- the present invention teaches a method for the preparation of hot-mix asphalt, aimed at producing better and stronger hot-mix asphalt products, characterized by using a hot-mix asphalt plant without exhaust means or direct flame incidence on the cold ingredients, allowing a longer time for heating, drying and mixing the filler charge and the cold ingredients, upon the latter being heated, with the asphalt, wherein the cold ingredients are fed through a feeding inlet, with the ingredients being gradually mixed in the hot- mix asphalt plant, using a drier and mixer assembly, provided parallel to the horizontal, using removable rotary axles provided with vanes and a speed variation means for each function of drying, mixing and discharging, operating at a temperature of 150 deg. C to 160 deg. C, there being thereafter added the asphalt at a temperature of 160 deg.
- the invention also teaches a plant for the production of hot-mix asphalt, intended to produce better and stronger hot-mix asphalt products, such plant having: an inlet through which are added the sorted, metered and weighed cold ingredients, ready for the production process; and a discharge outlet through which the hot-mix asphalt is withdrawn, upon the same being fully uniform and ready, characterized by being provided, in the interior thereof, with a circular drier and mixer assembly provided parallel to the horizontal, such circular drier and mixer assembly being provided with removable rotary axles and a speed variation means, and with vanes for mixing the heated and dried cold ingredients and the filler charge with the liquid asphalt cement; and provided, at the underside and lateral sides thereof, externally to the parallel circular heater and mixer assembly, with heating devices to provide a heat exchange that initially takes place by conduction, followed by irradiation and convection for full heat transfer as required for the production of the hot-mix asphalt.
- the heating devices are selected from among electrical resistors, gas-fueled heaters, or any other thermal energy source, provided that such thermal source does not use any exhaust means.
- the same is equipped with a purifier filter coupled to the drier and mixer assembly.
- the method and the plant according to the invention produce hot- mix asphalt products with size #2 and/or size #3 stone in the particle size of the cold ingredients.
- size #2 stone means a particle with a size able to pass through the square passages of a square mesh screen having a size or diameter of up to 38.10 mm (1.5”) and that is retained and will not pass through the square passages of a mesh screen having a size or diameter of 19.10 mm (3/4")
- size #3 stone means a particle with a size able to pass through the square passages of a square mesh screen having a size or diameter of up to 76.20 mm (3") and that is retained and will not pass through the square passages of a mesh screen having a size or diameter of 38,10 mm (1.5").
- Such method and plant according to the invention further allow the mixing of the filler charge together with the cold ingredients to be heated and dried in order to produce hot-mix asphalt.
- the plant according to the present invention does not use direct flame on the cold ingredients; the plant according to the present invention is equipped with a speed variation means, while such means is not found in any other asphalt plant, intended to control and provide a correct speed for each function in the process; in the plant according to the present invention there is no mechanical exhaust, as opposed to the exhaust of up to 100,000 m 3 /h of the plants known to date; the plant according to the present invention does not have a flame with up to six meters of length in the burner; the plant according to the present invention does neither perform heating nor drying at temperatures of 850 deg.
- the plant according to the present invention stores within itself the hot-mix asphalt having been produced, using dynamic thermal heating, instead of a static thermal silo/tank; with the plant according to the present invention all the soot is retained in the hot-mix asphalt; with the plant according to the present invention there is no mechanical return of the soot; with the plant according to the present invention there is no segregation of the hot-mix asphalt, due to an enhanced mechanical action on the hot-mix asphalt, whereby is generated a hot-mix asphalt of superior quality with the added benefit of using a lesser amount of asphalt.
- the plant according to the present invention is easier to transport with diameters of up to four meters, the plant has its own chassis with wheels, and larger plants can be easily assembled on-site.
- the plant according to the present invention has a purifier filter coupled to the plant's drier and mixer assembly, allowing ample control of environmental pollution.
- the plant according to the present invention provides an enhanced mechanical action on the hot-mix asphalt, during the process of production thereof, which is fundamental in terms of quality and uniformity of the hot-mix asphalt, and further allows the production of hot-mix asphalt products using ingredients that have been subjected to exposure to the weather, having thereby become wet, without hindering the asphalt recapping operations and the control of temperature.
- the plant according to the present invention is much more economical than the prior art plants, since it does not require a vertical cyclone device, a horizontal cyclone device, a bucket elevator for heated cold ingredients and air intake blowers. Moreover, it is much easier to operate due to the fact that since there is no direct flame applied to the cold ingredients, there is no mechanical exhaust of up to 100,000 m 3 /h as occurs with the prior art plants, whereby the environmental control is substantially simplified, as the soot is not sucked in, and simply stays in the hot-mix asphalt plant due to the action of gravity, there occurring but a minimal natural exhaust of hot gasses, such exhaust being spaced along the time of production of the hot- mix asphalt.
- Figure 1 represents a vertical cross-sectional view diametrally in the form of a ground plan of the hot-mix asphalt plant according to the present invention
- Figure 2 is a horizontal cross sectional view of the hot-mix asphalt plant depicted in Figure 1,
- Figure 3 is a vertical cross-sectional view in the form of a ground plan of the hot-mix asphalt plant that constitutes the object of the present invention, together with the cold storage silos/tanks for the ingredients as well as the drag elevator for conveying the hot-mix asphalt upon the same being ready, and
- Figure 4 is a top view of the hot-mix asphalt plant that constitutes the object of the present invention together with the cold storage silos/tanks for the ingredients, as well as the drag elevator for conveying the hot-mix asphalt upon the same being ready, as shown in Figure 3.
- the hot-mix asphalt plant 1 that constitutes the object of the present invention is provided with a circular drier and mixer assembly provided parallel to the horizontal direction, allowing the production of up to five hundred tons of hot-mix asphalt products per batch with a time of production of twenty-five to thirty minutes per batch, the plant being equipped with a purifier filter coupled to the drier and mixer assembly.
- the plant has an inlet 2 through which are added the sorted, metered and weighed cold ingredients, ready for the process of production of hot-mix asphalt.
- removable rotary axles 3 with a speed variation means and equipped with vanes for mixing the heated and dried cold ingredients with the hot asphalt which acts as a binder for the heated cold ingredients in the process of production of hot-mix asphalt.
- the plant 1 is further provided with an outlet 4 through which is withdrawn the hot-mix asphalt upon the same being fully uniform and ready.
- the plant 1 is further preferably provided, at its underside and lateral parts, externally to the parallel circular heater and mixer assembly, with heating means 5 for providing a heat transfer by conduction, followed by irradiation and convection, thereby avoiding the incidence of any direct flame on the cold ingredients.
- heating means 5 may be positioned at other appropriate locations in the plant 1, in order to provide heating and drying without any direct flame incidence on the cold ingredients intended to be heated.
- the said heating means 5 may be located immediately below the parallel circular drier and mixer assembly.
- Such heating means 5 may be selected from among electrical resistors, gas-fueled heaters, or any other source of thermal energy.
- the geometric shape of the hot-mix asphalt plant that constitutes the object of the present invention is different from that of any hot-mix asphalt plant known in the prior art, providing at least five times less environmental impact (i.e., in terms of tons of CO 2 emissions) and thermal heating, for a cost of manufactured ton of product that is 30% lower than the present average cost to be met.
- the removable rotary axles 3 with speed variation means and with vanes for mixing the heated and dried cold ingredients with the asphalt may be used at various speeds of operation, preferably at speeds of 3.3 rpm for drying; of 6.6 rpm for mixing; and of 9.9 rpm for discharging the product, allowing more time for heating, drying and mixing the heated cold ingredients with pure asphalt or asphalt enriched with polymers, until there is achieved full uniformity, thereby providing an enhanced mechanical action on the hot-mix asphalt, improving the quality of the latter and providing a greater strength thereof.
- the hot-mix asphalt plant 1 that constitutes the object of the present invention is the only plant known from this time onwards that keeps on mixing the contents thereof while simultaneously providing the storage therein of the hot-mix asphalt produced with dynamic thermal heating, instead of using a static thermal silo/tank.
- the hot-mix asphalt plant 1 that constitutes the object of the present invention produces hot-mix asphalt products with mineral material grain size of up to 75 mm, for replacement of slabs of plain concrete or armored concrete in airports and roadways.
- the hot-mix asphalt plant 1 that constitutes the object of the present invention is fully computerized, is capable of producing up to five hundred tons of hot-mix asphalt per batch for a batch production time of twenty-five minutes for dry ingredients and thirty minutes using wet ingredients, eliminating any type of contact of the heated cold ingredients with the environment, having sensors installed in each of its components for detecting possible problems and thereby immediately interrupting the production process.
Abstract
The invention refers to a method and plant (1) to produce hot-mix asphalt products with enhanced quality and strength, without using direct flame incidence an the cold ingredients, allowing a longer time for drying, heating and mixing the heated cold ingredients with the asphalt, the cold ingredients and the filter being gradually mixed in the plant, With a drier and mixer assembly, provided parallel to the horizontal direction, by rotary axles (3) equipped with vanes and a speed variation means for each function. The cold ingredients being mixed in each batch for at least twenty-five minutes (when dry) and at most thirty minutes (when moist or wet), with all the heat used for heating being provided by thermal conduction followed by irradiation and convection at the underside and lateral portions of the plant, without using forced mechanical return of the dust particles by means of an endless auger SCREW.
Description
A METHOD AND A PLANT FOR PREPARING HOT-MIX ASPHALT
Field of the Invention
The present invention relates in general to an improvement over the prior art hot-mix asphalt plants that use a drier with a fossil fuel burner, that is, direct application of flame for heating and drying cold ingredients (gravel, sand and stone powder) in order to produce hot-mix asphalt. The invention further relates to an improvement over the prior art hot-mix asphalt plants that take a short time to heat, dry and mix the cold ingredients with liquid asphalt cement for producing the hot-mix asphalt.
Prior Art Hot-mix asphalt products are produced by means of two types of hot-mix asphalt plants: gravity-driven (gravimetric) plants and volumetric plants (known as drum-mixer type plants). The gravimetric plants are those wherein the hot-mix asphalt is produced by heating the cold ingredients with direct incidence of a flame in the heater, whereupon the said cold ingredients upon being heated are conveyed to the hot elevator and to the hot metering silos/tanks, wherein they are weighed to be subsequently conveyed to the pugmill mixer, wherein there is then added cold filler and hot asphalt, the whole mass being subjected to mixing during a period of up to forty-five seconds, at most, there being thus provided a ready batch of hot-mix asphalt. The volumetric type plants (known as drum-mixer type plants) are those wherein the hot-mix asphalt is produced by heating the cold ingredients (gravel, powdered stone, sand) with the
use of an exhaust system and a directly applied flame thereon at the drier, whereupon they are metered and weighed using a set of scales integrated with the asphalt pump, within a zone located outside of the reach of the flame in an outer sleeve next to the drier or in the pugmill, the whole mass being then mixed with asphalt for a period of up to thirty seconds, at most, with continuous output of the ready hot-mix asphalt.
Such prior art hot-mix asphalt plants presently entail serious problems in economic terms, in terms of quality and from the environmental perspective.
Economic Disadvantages of the Conventional Plants
The conventional plants use a series of equipment items that could be substituted with a sole item, to wit, a drier, exhaust fan, exhaust ducting, pugmill, pre-separator cyclone means, silo/tank for storing the hot-mix asphalt without harming the quality and the quantity of the hot-mix asphalt having been produced.
The conventional plants produce a hot-mix asphalt product that does not withstand for a long time the heavy traffic on paved roadways and airport runways.
The conventional plants damage the cold ingredients every time they are calibrated to produce hot-mix asphalt. Each time that a conventional plant is shut down, there will be lost the heated and dried cold ingredients that remain trapped within the silo/tank or the pugmill for hot-mix asphalt, which in
addition contribute to soiling the plant.
The conventional plants damage the cold ingredients and reverse the direction of transport of the cold feed every time they are calibrated for producing hot-mix asphalt.
The conventional plants are forced to remove and further lose the heated and dried cold ingredients that remain trapped within the plants every time that the plants are shut down. This fact, in addition to entailing a loss of material, fills the plant with dust and dirt.
Quality Disadvantages of the Conventional Plants
The filler charge, one of the components of the hot-mix asphalt, is not heated, but rather added while cold, at ambient temperature, together with the cold ingredients that were heated and dried in the pugmill.
The conventional plants take only a short time for heating, drying and mixing. They do not allow sufficient time for mixing the liquid asphalt cement with the cold ingredients upon the latter being heated to allow for the provision of a hot-mix asphalt of better quality.
Such plants involve a difficult control of dust and soot arising from the stream of hot gasses originating from the combustion in a burner, since the air purifier filter of these plants operates in dry mode, with a cyclone means, a pre-collector and extractor coils that integrate into the production process (with extremely poor physical and quantitative control) a certain amount of dust
particles, also by means of a screw-type auger conveyor and a fines recovery valve.
The cold ingredients are heated and dried in small amounts for production of the hot-mix asphalt (The plants are unable to produce, at one sole time, the entire load capacity of a dumper truck. They produce, at most, a pull- cart-sized amount (about 3 tons or 1.5 cubic meters) of hot-mix asphalt in each cycle of operation). These are small batches, and such small-sized batches are prone to entailing variance of the asphalt content, causing premature disaggregation due to lack of enough binder, or causing an undesirably smooth surface, subject to deformation, due to the presence of an excessive amount of binder.
Environmental Disadvantages of the Conventional Plants The conventional plants use combustion processes, with fire in the form of direct incidence of a flame of a fossil fuel burner for heating and drying the cold ingredients in order to produce the hot-mix asphalt.
The stream of hot gasses produced by the combustion that takes place at the burner is discharged into the atmosphere at a high flow rate, in the order of 100,000 m3/h (one hundred thousand cubic meters per hour). They do not allow to reduce, in the process of production, the emissions of CO2 (carbon dioxide or carbon gas) per ton of hot-mix asphalt produced.
Therefore, it is an object of the present invention to provide a method and a plant for producing hot-mix asphalt, without being burdened with
the disadvantages evidenced by the prior art plants.
The hot-mix asphalt plant and method according to the present invention were designed to produce hot-mix asphalt without using exhaust means or direct flame incidence on the cold ingredients, thereby providing an improved and stronger hot-mix asphalt, intended to extend the useful life of asphalt pavements, with due regard to the extremely important requisite of protection to the environment, with lower emission of pollutants, noise and heat.
The method according to the present invention does not use direct flame for heating and drying the cold ingredients, thereby allowing the soot (the powder generated by the heating of the cold ingredients) to avoid being subjected to dynamic separation from the cold ingredients while the same are being heated, such that the particles larger than 2.00 mm, micro-particles larger than 0.75 mm and smaller than 2.00 mm and very small fractions of the soot of sizes smaller than 0.75 mm, remain incorporated to the production of hot-mix asphalt, since the force of gravity is acting on these particles, without interference from the mechanical action of forced exhaust (the soot is not sucked into an exhaust system), and furthermore, such that the variable velocity of the axles be adequate for performance of the various functions, to wit: in the range of 3.3 rpm for drying; in the range of 6.6 rpm for mixing; in the range of 9.9 rpm for discharging, allowing a longer time span for heating, drying and mixing the cold ingredients with asphalt, providing enhanced action on the hot-mix asphalt until the same is rendered fully uniform.
The hot-mix asphalt plant that constitutes the object of the present
invention allows the petroleum refining plants to increase their sales of asphalts and emulsions, since the various economic, environmental and other characteristics thereof will certainly render feasible a number of roadway- projects presently awaiting proper budget allowances to become a reality; the production of hot-mix asphalt plants that do not use direct flame on the cold ingredients, will allow a greater flexibility and strength by means of the mixture of cold ingredients that cannot withstand the application of direct flame thereto (for example, discarded and ground tires for increasing the friction conditions of the asphalt paving); allows the concessionary companies that manage the roadways the benefits of lesser cost and better quality, without variations of the asphalt in the hot-mix asphalt product and with enhanced flexibility and better resistance to wear, by lengthening the intervals between maintenance actions performed in connection therewith, entailing a positive trend towards a reduction of the number of complaints relative to work performed on the asphalt-paved roadways .
The hot-mix asphalt plant that constitutes the object of the present invention allows the production of hot-mix asphalt products with mineral grain sizes passing through the square mesh screens of 3" x 3" (7.62 cm x 7.62 cm) for replacement of broken slabs of plain concrete or armored concrete in the system of runways and taxiing and parking aprons in airports, and in roadways in sections located on the slopes of mountains.
The hot-mix asphalt plant that constitutes the object of the present invention is useful for companies that make repairs in flexible hot-mix asphalt paved surfaces, such as public service concessionary companies that operate
potable water, sewage, gas, electric power, landline telephone systems, etc.
The Solution Proposed by the Invention
Thus, the present invention teaches a method for the preparation of hot-mix asphalt, aimed at producing better and stronger hot-mix asphalt products, characterized by using a hot-mix asphalt plant without exhaust means or direct flame incidence on the cold ingredients, allowing a longer time for heating, drying and mixing the filler charge and the cold ingredients, upon the latter being heated, with the asphalt, wherein the cold ingredients are fed through a feeding inlet, with the ingredients being gradually mixed in the hot- mix asphalt plant, using a drier and mixer assembly, provided parallel to the horizontal, using removable rotary axles provided with vanes and a speed variation means for each function of drying, mixing and discharging, operating at a temperature of 150 deg. C to 160 deg. C, there being thereafter added the asphalt at a temperature of 160 deg. C to 170 deg. C, in batches of up to 500 tons per single batch, with the ingredients being mixed in each batch for at least twenty-five minutes (dry) and at most thirty minutes (wet), irrespective of the amount intended to be produced, where the stored ingredients may remain exposed to the weather without entailing thereby a change of quality of the hot- mix asphalt, where all the heat used for heating is provided by means of electrical resistors adapted at the lower part and the sides of the plant by thermal conduction over the outer part of the bottom and side plates, such heat being removed through the surface by means of a combination of radiation and convection, transferring heat for heating and drying the cold ingredients for production of the hot-mix asphalt for any period of time that may be necessary.
In a preferred embodiment, the heating of the hot-mix asphalt plant is realized in the lower part and sides by means of thermal sources, with a discharge outlet at the underside of the plant, such that the hot-mix asphalt may be allowed to discharge therefrom upon having become uniform.
The invention also teaches a plant for the production of hot-mix asphalt, intended to produce better and stronger hot-mix asphalt products, such plant having: an inlet through which are added the sorted, metered and weighed cold ingredients, ready for the production process; and a discharge outlet through which the hot-mix asphalt is withdrawn, upon the same being fully uniform and ready, characterized by being provided, in the interior thereof, with a circular drier and mixer assembly provided parallel to the horizontal, such circular drier and mixer assembly being provided with removable rotary axles and a speed variation means, and with vanes for mixing the heated and dried cold ingredients and the filler charge with the liquid asphalt cement; and provided, at the underside and lateral sides thereof, externally to the parallel circular heater and mixer assembly, with heating devices to provide a heat exchange that initially takes place by conduction, followed by irradiation and convection for full heat transfer as required for the production of the hot-mix asphalt.
Preferably, the heating devices are selected from among electrical resistors, gas-fueled heaters, or any other thermal energy source, provided that such thermal source does not use any exhaust means.
In a preferred embodiment of the plant, the same is equipped with a
purifier filter coupled to the drier and mixer assembly.
Therefore, with the method and the plant that constitute the objects of the present invention, it is possible to substantially mitigate the problems of environmental pollution, of global heating and excessive noise, and it is possible to improve the quality of the hot-mix asphalt products used in hot-mix asphalt paved surfaces, prolonging the useful life thereof with the consequent enhancement of safety entailed thereby.
The method and the plant according to the invention produce hot- mix asphalt products with size #2 and/or size #3 stone in the particle size of the cold ingredients. For the purposes of the present invention, the expression "size #2 stone" means a particle with a size able to pass through the square passages of a square mesh screen having a size or diameter of up to 38.10 mm (1.5") and that is retained and will not pass through the square passages of a mesh screen having a size or diameter of 19.10 mm (3/4"), and the expression "size #3 stone" means a particle with a size able to pass through the square passages of a square mesh screen having a size or diameter of up to 76.20 mm (3") and that is retained and will not pass through the square passages of a mesh screen having a size or diameter of 38,10 mm (1.5"). Such method and plant according to the invention further allow the mixing of the filler charge together with the cold ingredients to be heated and dried in order to produce hot-mix asphalt.
Among the advantages afforded by the method and the plant of the present invention, compared with the prior art plants, one may cite the following: the plant according to the present invention does not use direct flame
on the cold ingredients; the plant according to the present invention is equipped with a speed variation means, while such means is not found in any other asphalt plant, intended to control and provide a correct speed for each function in the process; in the plant according to the present invention there is no mechanical exhaust, as opposed to the exhaust of up to 100,000 m3/h of the plants known to date; the plant according to the present invention does not have a flame with up to six meters of length in the burner; the plant according to the present invention does neither perform heating nor drying at temperatures of 850 deg. C at the beginning of the flame as occurs with the prior art plants, which contributes to the harmful effects of global warming, compromises the physical qualities of the ingredients, and increases the emission of CO2; the plant according to the present invention stores within itself the hot-mix asphalt having been produced, using dynamic thermal heating, instead of a static thermal silo/tank; with the plant according to the present invention all the soot is retained in the hot-mix asphalt; with the plant according to the present invention there is no mechanical return of the soot; with the plant according to the present invention there is no segregation of the hot-mix asphalt, due to an enhanced mechanical action on the hot-mix asphalt, whereby is generated a hot-mix asphalt of superior quality with the added benefit of using a lesser amount of asphalt.
In addition to the advantages mentioned above, the plant according to the present invention is easier to transport with diameters of up to four meters, the plant has its own chassis with wheels, and larger plants can be easily assembled on-site.
Additionally, the plant according to the present invention has a
purifier filter coupled to the plant's drier and mixer assembly, allowing ample control of environmental pollution.
The plant according to the present invention provides an enhanced mechanical action on the hot-mix asphalt, during the process of production thereof, which is fundamental in terms of quality and uniformity of the hot-mix asphalt, and further allows the production of hot-mix asphalt products using ingredients that have been subjected to exposure to the weather, having thereby become wet, without hindering the asphalt recapping operations and the control of temperature.
Additionally, it should be noted that the plant according to the present invention is much more economical than the prior art plants, since it does not require a vertical cyclone device, a horizontal cyclone device, a bucket elevator for heated cold ingredients and air intake blowers. Moreover, it is much easier to operate due to the fact that since there is no direct flame applied to the cold ingredients, there is no mechanical exhaust of up to 100,000 m3/h as occurs with the prior art plants, whereby the environmental control is substantially simplified, as the soot is not sucked in, and simply stays in the hot-mix asphalt plant due to the action of gravity, there occurring but a minimal natural exhaust of hot gasses, such exhaust being spaced along the time of production of the hot- mix asphalt.
Brief Description of the Drawings In order to better illustrate the present invention, there will now be provided a description thereof with reference to the attached drawings, wherein:
Figure 1 represents a vertical cross-sectional view diametrally in the form of a ground plan of the hot-mix asphalt plant according to the present invention,
Figure 2 is a horizontal cross sectional view of the hot-mix asphalt plant depicted in Figure 1,
Figure 3 is a vertical cross-sectional view in the form of a ground plan of the hot-mix asphalt plant that constitutes the object of the present invention, together with the cold storage silos/tanks for the ingredients as well as the drag elevator for conveying the hot-mix asphalt upon the same being ready, and
Figure 4 is a top view of the hot-mix asphalt plant that constitutes the object of the present invention together with the cold storage silos/tanks for the ingredients, as well as the drag elevator for conveying the hot-mix asphalt upon the same being ready, as shown in Figure 3.
Description of the Invention Illustrated in the Drawings As shown in the drawing figures, the hot-mix asphalt plant 1 that constitutes the object of the present invention is provided with a circular drier and mixer assembly provided parallel to the horizontal direction, allowing the production of up to five hundred tons of hot-mix asphalt products per batch with a time of production of twenty-five to thirty minutes per batch, the plant being equipped with a purifier filter coupled to the drier and mixer assembly.
The plant has an inlet 2 through which are added the sorted, metered and weighed cold ingredients, ready for the process of production of hot-mix asphalt.
Inside the heater and drier assembly there are provided removable rotary axles 3 with a speed variation means and equipped with vanes for mixing the heated and dried cold ingredients with the hot asphalt which acts as a binder for the heated cold ingredients in the process of production of hot-mix asphalt.
The plant 1 is further provided with an outlet 4 through which is withdrawn the hot-mix asphalt upon the same being fully uniform and ready.
The plant 1 is further preferably provided, at its underside and lateral parts, externally to the parallel circular heater and mixer assembly, with heating means 5 for providing a heat transfer by conduction, followed by irradiation and convection, thereby avoiding the incidence of any direct flame on the cold ingredients. Such heating means 5 may be positioned at other appropriate locations in the plant 1, in order to provide heating and drying without any direct flame incidence on the cold ingredients intended to be heated. For example, the said heating means 5 may be located immediately below the parallel circular drier and mixer assembly. Such heating means 5 may be selected from among electrical resistors, gas-fueled heaters, or any other source of thermal energy.
The geometric shape of the hot-mix asphalt plant that constitutes the object of the present invention is different from that of any hot-mix asphalt
plant known in the prior art, providing at least five times less environmental impact (i.e., in terms of tons of CO2 emissions) and thermal heating, for a cost of manufactured ton of product that is 30% lower than the present average cost to be met.
The removable rotary axles 3 with speed variation means and with vanes for mixing the heated and dried cold ingredients with the asphalt, may be used at various speeds of operation, preferably at speeds of 3.3 rpm for drying; of 6.6 rpm for mixing; and of 9.9 rpm for discharging the product, allowing more time for heating, drying and mixing the heated cold ingredients with pure asphalt or asphalt enriched with polymers, until there is achieved full uniformity, thereby providing an enhanced mechanical action on the hot-mix asphalt, improving the quality of the latter and providing a greater strength thereof.
The hot-mix asphalt plant 1 that constitutes the object of the present invention is the only plant known from this time onwards that keeps on mixing the contents thereof while simultaneously providing the storage therein of the hot-mix asphalt produced with dynamic thermal heating, instead of using a static thermal silo/tank. The hot-mix asphalt plant 1 that constitutes the object of the present invention produces hot-mix asphalt products with mineral material grain size of up to 75 mm, for replacement of slabs of plain concrete or armored concrete in airports and roadways. The hot-mix asphalt plant 1 that constitutes the object of the present invention is fully computerized, is capable of producing up to five hundred tons of hot-mix asphalt per batch for a batch production time of twenty-five minutes for dry ingredients and thirty minutes using wet
ingredients, eliminating any type of contact of the heated cold ingredients with the environment, having sensors installed in each of its components for detecting possible problems and thereby immediately interrupting the production process.
Claims
1. A method for producing hot-mix asphalt, intended to produce better and stronger hot-mix asphalt products, characterized by using an asphalt production plant (1) which does not use direct flame on the cold ingredients, allowing a longer time for drying, heating and mixing the heated cold ingredients with the asphalt, the ingredients being fed into the process through a feed inlet (2), whereby the materials and the filler charge are gradually mixed in the asphalt plant, with a drier and mixer assembly provided parallel to the horizontal direction, by means of removable rotary axles (3) equipped with vanes and a speed variation means, for each function of drying, mixing, and discharging the product, at a temperature up to a range of 150 deg. C to 160 deg. C, whereupon the asphalt is introduced into the process at a temperature of 160 deg. C to 170 deg. C, in batches (lots) of up to 500 tons per single batch, the cold ingredients intended to be heated being mixed in each batch for at least twenty-five minutes (when dry) and at most for thirty minutes (when moist or wet), irrespective of the amount produced, where the ingredients may be stored and exposed to the weather without thereby altering the quality of the mixture, where the whole heat used for heating is provided by means of heat transfer, by conduction followed by irradiation and convection to heat the cold ingredient in order to produce the hot-mix asphalt.
2. A method, as claimed in claim 1, characterized in that the heating of the asphalt plant (1) is provided at the underside and the sides thereof by means of thermal sources (5) and in the discharge hopper (4), on the underside of the plant, such that the hot-mix asphalt is discharged upon being ready and uniform.
3. A method, as claimed in claim 2, characterized in that the thermal sources are electrical.
4. A method, as claimed in any one of claims 1 to 3, characterized in that the cold ingredients are fed through the feed inlet (2) by means of conveyor belts or by gravity.
5. A method, as claimed in any one of claims 1 to 4, characterized in that the functions of drying, mixing and discharging, at the step of gradual mixing of the cold ingredients in the asphalt plant (1), with a drier and mixer assembly provided parallel to the horizontal direction, by means of removable rotary axles (3) provided with vanes and a speed variation means, are performed respectively at the speeds of 3.3 rpm (drying); 6.6 rpm (mixing); and 9.9 rpm (discharging).
6. A method, as claimed in any one of claims 1 to 5, characterized by being the only known process that produces hot-mix asphalt with size #2 stone or size #3 stone in the particle size of the cold ingredients, wherein the expression "size #2 stone" means a particle with a size able to pass through the square passages of a square mesh screen having a size or diameter of up to 38.10 mm (1.5") and that is retained and will not pass through the square passages of a mesh screen having a size or diameter of 19.10 mm (3/4"), and the expression "size #3 stone" means a particle with a size able to pass through the square passages of a square mesh screen having a size or diameter of up to 76.20 mm (3") and that is retained and will not pass through the square passages of a mesh screen having a size or diameter of 38,10 mm (1.5").
7. A method, as claimed in any one of claims 1 to 6, characterized in that the filler charge is mixed together with the cold ingredients materials intended to be heated and dried for the production of hot-mix asphalt.
8. A plant for producing hot-mix asphalt, intended to produce better and stronger hot-mix asphalt products, characterized in that the said plant (1) comprises: an inlet (2) through which are added the sorted, metered and weighed cold ingredients, ready for the production process; and an outlet (4) through which there is withdrawn the hot-mix asphalt upon the same being fully uniform and ready, characterized by being provided, inside the same, with a circular drier and mixer assembly provided parallel to the horizontal direction, such circular drier and mixer assembly being provided with removable rotary axles (3) with a speed variation means and with vanes for mixing the dried and heated cold ingredients with the asphalt, and provided, on the underside and lateral regions thereof, externally to the parallel drier and mixer assembly, with heating devices (5) intended to provide a heat transfer by thermal conduction followed by irradiation and convection.
9. A plant, as claimed in claim 8, characterized in that the heating devices (5) are selected from among electrical resistors, gas-fueled heaters, or any other source of thermal energy without any combustion involving the cold ingredients that make up the hot-mix asphalt.
10. A plant, as claimed in any one of claims 8 or 9, characterized in that it is provided with a purifier filter coupled to the drier and mixer assembly.
11. A plant, as claimed in any one of claims 8 to 10, characterized by being the only known plant that produces hot-mix asphalt with size #2 stone or size #3 stone in the particle size of the untreated materials, wherein the expression "size #2 stone" means a particle with a size able to pass through the square passages of a square mesh screen having a size or diameter of up to 38.10 mm (1.5") and that is retained and will not pass through the square passages of a mesh screen having a size or diameter of 19.10 mm (3/4"), and the expression "size #3 stone" means a particle with a size able to pass through the square passages of a square mesh screen having a size or diameter of up to 76.20 mm (3") and that is retained and will not pass through the square passages of a mesh screen having a size or diameter of 38,10 mm (1.5").
12. A plant, as claimed in any one of claims 8 to 11, characterized in that it allows the mixing of the filler charge together with the cold ingredients, without requiring forced mechanical return of the soot particles to be heated and dried in order to produce hot-mix asphalt.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| BRPI0805002 BRPI0805002A2 (en) | 2008-11-13 | 2008-11-13 | hot asphalt process and power plant to produce better and more resistant hot asphalt mixtures |
| BRPI0805002-3 | 2008-11-13 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| WO2010054453A1 true WO2010054453A1 (en) | 2010-05-20 |
| WO2010054453A8 WO2010054453A8 (en) | 2010-07-15 |
Family
ID=41077902
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/BR2009/000367 WO2010054453A1 (en) | 2008-11-13 | 2009-11-06 | A method and a plant for preparing hot-mix asphalt |
Country Status (2)
| Country | Link |
|---|---|
| BR (1) | BRPI0805002A2 (en) |
| WO (1) | WO2010054453A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112341046A (en) * | 2020-10-29 | 2021-02-09 | 四川中广建材有限公司 | Novel asphalt cold-patch material and preparation method thereof |
| CN114367232A (en) * | 2021-12-13 | 2022-04-19 | 陕西交通职业技术学院 | Composite modified asphalt mixing device based on combination of dry method and wet method |
| CN114920498A (en) * | 2022-06-28 | 2022-08-19 | 重庆诚邦路面材料有限公司 | Bio-based normal-temperature asphalt mixture and preparation method thereof |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BR202015013385Y1 (en) * | 2015-06-09 | 2020-06-16 | Ciber Equipamentos Rodoviários Ltda | IMPROVEMENT APPLIED IN MOBILE ASPHALT PLANTS WITH SIDE PROTECTIONS |
| CN106868985A (en) * | 2017-02-27 | 2017-06-20 | 成都佰思汇信科技有限责任公司 | A kind of continous way hot-mix asphalt mixture mixing plant |
| CN115160807B (en) * | 2022-07-26 | 2023-03-21 | 长沙理工大学 | Biological modified asphalt and preparation method thereof |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3394094A (en) * | 1964-04-20 | 1968-07-23 | Ind Asphalt Of California Inc | Process of preparing a paving composition |
-
2008
- 2008-11-13 BR BRPI0805002 patent/BRPI0805002A2/en not_active Application Discontinuation
-
2009
- 2009-11-06 WO PCT/BR2009/000367 patent/WO2010054453A1/en active Application Filing
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3394094A (en) * | 1964-04-20 | 1968-07-23 | Ind Asphalt Of California Inc | Process of preparing a paving composition |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112341046A (en) * | 2020-10-29 | 2021-02-09 | 四川中广建材有限公司 | Novel asphalt cold-patch material and preparation method thereof |
| CN114367232A (en) * | 2021-12-13 | 2022-04-19 | 陕西交通职业技术学院 | Composite modified asphalt mixing device based on combination of dry method and wet method |
| CN114367232B (en) * | 2021-12-13 | 2022-09-06 | 陕西交通职业技术学院 | Composite modified asphalt mixing device based on combination of dry method and wet method |
| CN114920498A (en) * | 2022-06-28 | 2022-08-19 | 重庆诚邦路面材料有限公司 | Bio-based normal-temperature asphalt mixture and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| BRPI0805002A2 (en) | 2009-09-22 |
| WO2010054453A8 (en) | 2010-07-15 |
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