Patent Publication Number: US-2023151560-A1

Title: System and method for producing asphalt using exhaust from a generator

Description:
FIELD OF THE TECHNOLOGY 
     The present technology is related to producing asphalt using exhaust from a generator. More specifically, this technology relates to producing hot mix asphalt from virgin aggregate (aggregate), liquid asphalt, additives, and up to 100% recycle material (combined as ‘asphalt materials’) using exhaust from a generator that provides electrical power for onsite use or to a power grid. 
     BACKGROUND 
     Hot mix asphalt plants according to the conventional art utilize an open flame burner to produce heat for drying aggregates. Excess heat is vented to the atmosphere. The open flame burner is typically a large fossil fuel burner attached to the end of a rotary dryer drum. The drum lifts the aggregate material and veils it across the heat stream of the burner to reduce the moisture content and raise the temperature of the aggregate material, which is necessary to produce hot mix asphalt. Exhaust leaves the dryer through a duct and is filtered to remove dust in the air stream. 
     Conventional hot mix asphalt plants suffer from poor efficiency and high emissions. There have been many efforts to fine tune hot mix asphalt plants for improvement in these areas, but none have been very successful. Aggregate must be super-heated in order to drive the moisture out of recycle which limits the amount of recycled asphalt product (RAP) and recycled asphalt shingles (RAS) that may be incorporated into the mixture. In addition, the conventional hot mix asphalt plants can only handle a narrow range of recycled content because of difficulties associated with adjusting the plant. For example, the dryer drum in a conventional hot mix asphalt plant needs to be re-flighted when substantially changing the percentage of recycled content to balance the heat of the virgin aggregate and RAP to meet the temperature target of the finished product. 
     SUMMARY 
     Accordingly, some embodiments of the present disclosure relate to a system for producing hot mix asphalt, the system including a generator having an exhaust port; a dryer drum having an inlet; a duct connecting the exhaust port to the inlet, the duct being configured to convey a first flow of hot gas from the exhaust port; an exhaust bypass vent configured to convey a second flow of hot gas diverging from the first flow of hot gas; and a valve disposed at a junction between the duct and the exhaust bypass vent, the valve being configured to adjust a flow rate of the second flow of hot gas. The dryer drum is configured to produce hot mix asphalt from asphalt materials using a third flow of hot gas diverging from the first flow of hot gas and entering the dryer drum through the inlet. 
     In some embodiments, the exhaust bypass vent is in fluid communication with atmosphere. In some embodiments, the generator is a gas turbine generator. In some embodiments, the valve is a gate valve. In some embodiments, the dryer drum is further configured to produce the hot mix asphalt by rotating the dryer drum with the asphalt materials inside the dryer drum and the third flow flowing through the dryer drum. In some embodiments, a flow rate of the first flow is equal to the flow rate of the second flow plus a flow rate of the third flow. In some embodiments, the valve is further configured to decrease the flow rate of the third flow by increasing the flow rate of the second flow. In some embodiments, the valve is further configured to increase the flow rate of the third flow by decreasing the flow rate of the second flow. 
     In some embodiments, the system further includes an air intake structure configured to convey ambient air into the generator. In some embodiments, the asphalt materials include virgin asphalt and recycled asphalt. In some embodiments, the dryer drum is tilted such that a first axial end of the dryer drum is at a lower elevation than a second axial end of the dryer drum. In some embodiments, the inlet is disposed at the first axial end. In some embodiments, the dryer drum further includes an opening at the second axial end for loading the asphalt materials into the dryer drum. In some embodiments, the dryer drum includes an exhaust structure, and an outlet at the second axial end. In some embodiments, the exhaust structure is connected to the outlet. In some embodiments, the third flow flows through the dryer drum, through the outlet, through the exhaust structure, and into a baghouse. 
     In some embodiments, the system further includes a support structure configured to support the dryer drum, and a drive system configured to axially rotate the dryer drum. In some embodiments, the generator is in electrical communication with a power grid to provide electrical energy to the power grid. In some embodiments, the generator is configured to provide electrical energy to equipment on a manufacturing site including the system. 
     Some embodiments of the present disclosure relate to a power generation apparatus including a generator having an exhaust port; a dryer drum having an inlet; a duct connecting the exhaust port to the inlet, the duct being configured to convey a first flow of hot gas from the exhaust port; an exhaust bypass vent configured to convey a second flow of hot gas diverging from the first flow of hot gas; and a valve disposed at a junction between the duct and the exhaust bypass vent, the valve being configured to adjust a flow rate of the second flow of hot gas. The dryer drum is configured to produce hot mix asphalt from asphalt materials using a third flow of hot gas diverging from the first flow of hot gas and entering the dryer drum through the inlet. The generator is configured to provide electrical energy to a power grid or equipment on a manufacturing site including the power generation apparatus. 
     Some embodiments of the present disclosure relate to a method of producing hot mix asphalt and providing electrical energy, the method including providing a generator having an exhaust port; providing a dryer drum having an inlet; providing an exhaust bypass vent; connecting the exhaust port to the inlet using a duct; installing a valve at a junction between the duct and the exhaust bypass vent; running the generator to produce hot gas such that a first flow of the hot gas flows through the duct, the first flow of the hot gas diverging into a second flow of the hot gas and a third flow of the hot gas, the second flow of the hot gas flowing through the exhaust bypass vent, and the third flow of the hot gas flowing through the inlet and into the dryer drum; controlling a flow rate of the third flow of the hot gas by controlling the valve to control a flow rate of the second flow of the hot gas; producing hot mix asphalt from asphalt materials in the dryer drum using the third flow of the hot gas; and providing, to a power grid or to equipment on a manufacturing site having the generator, electrical energy generated by the running of the generator. 
     In some embodiments, the hot gas is exhaust gas produced by the running of the generator. In some embodiments, the producing of the hot mix asphalt and the providing of the electrical energy to the power grid occur simultaneously. 
     Additional details and feature of embodiments of the technology will now be described in connection with the following drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings show embodiments of the disclosed subject matter for the purpose of illustrating the invention. However, it should be understood that the present application is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein: 
         FIG.  1 A  is a schematic representation of a system for producing hot mix asphalt according to some embodiments of the present disclosure. 
         FIG.  1 B  is a schematic representation of a system for producing hot mix asphalt according to some embodiments of the present disclosure. 
         FIG.  2    is a schematic representation of a dryer drum of a system for producing hot mix asphalt according to some embodiments of the present disclosure. 
         FIG.  3    is a temperature graph superimposed on a schematic representation of a dryer drum of a system for producing hot mix asphalt according to some embodiments of the present disclosure. 
         FIG.  4    is a chart of a method for producing hot mix asphalt according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Some embodiments of the present disclosure are directed to a system for producing hot mix asphalt from asphalt materials using exhaust from a generator. As used herein, “hot mix asphalt” refers to a composition of minerals such as stone, sand, gravel, and/or recycled products bound together by a product of crude oil and processed with heat. As used herein, “asphalt materials” refers to aggregate asphalt product (including stone, sand, gravel, additives, and/or recycled products. As used herein, unless context indicates otherwise, “flow rate” refers to mass flow rate. As used herein, “hot gas” refers to any gas hotter than ambient temperature, although in most examples in the present disclosure, the hot gas is at least several hundred degrees Fahrenheit or more. 
     Referring to  FIGS.  1 A- 1 B , the system  100  includes a generator  102  (e.g., a gas turbine generator) having an exhaust port (not shown). In some embodiments, an air intake structure  104  conveys ambient air  1000  into the generator  102 . In some embodiments, inside the generator  102 , petroleum fuel  2000  is mixed with the ambient air  1000  and combusted to turn mechanical components in order to generate electrical energy  3000 . In a preferred embodiment, the petroleum fuel  2000  is natural gas. In some embodiments, the generator  102  is in electrical communication with a power grid (not shown) and provides the electrical energy  3000  to the power grid. In some embodiments, the generator  102  is configured to provide electrical energy  3000  to equipment on a manufacturing site including the power generation apparatus. In some embodiments, the electrical energy  3000  generated by the generator  102  is utilized for a process other than producing asphalt. The generator  102  also produces hot gas  4000  (i.e., exhaust) from burning the mixture of petroleum fuel  2000  and ambient air  1000 . Unlike the asphalt plants according to the conventional art, in a preferred embodiment, the system  100  does not include a direct fire burner. 
     The system  100  further includes duct  106 , valves  108  and  109 , an exhaust bypass vent  110 , and a dryer drum  112  having an inlet (not shown). The duct  106  connects the exhaust port of the generator  102  to the inlet of the dryer drum  112 . In some embodiments, the exhaust bypass vent  110  is in fluid communication with the atmosphere. The valve  108  is disposed where the duct  106  meets the exhaust bypass vent  110  (i.e., at a junction between the duct  106  and the exhaust bypass vent  110 ). In some embodiments, the valve  108  is a gate valve. In some embodiments, the valve  109  is disposed where the duct  106  meets the dryer drum  112  (i.e., at a junction between the duct  106  and the dryer drum  112 ). In other embodiments, the valve  109  is disposed along the duct  106 . In some embodiments, the valve  109  is a gate valve. 
     In some embodiments, the hot gas  4000  flows out of the gas turbine generator  102  through the outlet and flows inside the duct  106  (i.e., the duct  106  conveys a first flow Q 1  of hot gas  4000  from the exhaust port). In some embodiments, when the valve  108  is at least partially open, at least some of the hot gas  4000  flows through the valve  108  and through the exhaust bypass vent  110  to atmosphere (i.e., the exhaust bypass vent  110  conveys a second flow Q 2  of hot gas  4000  diverging from the first flow Q 1  of hot gas  4000 ). In some embodiments, the valve  108  controls the flow of hot gas  4000  from the generator  102  to the atmosphere (i.e., the valve  108  is configured to adjust a flow rate of the second flow Q 2  of hot gas  4000 ). In some embodiments, at least some of the hot gas  4000  from the generator  102  flows through the inlet of the dryer drum  112  (i.e., a third flow Q 3  of hot gas  4000  diverges from the first flow Q 1  of hot gas  4000  and enters the dryer drum  112  through the inlet). In some embodiments, after the second flow Q 2  of hot gas  4000  passes through the exhaust bypass vent  110 , the second flow of Q 2  of hot gas  4000  further passes through an emissions control system before being vented to the atmosphere. The valve  109  also controls how much hot gas  4000  flows from the generator  102  through the inlet of the dryer drum  112  (i.e., the valve  109  is configured to adjust a flow rate of the third flow Q 3  of hot gas  4000 ). 
     Aggregate asphalt material  5000  inside the dryer drum  112  is heated by the hot gas  4000  to produce the hot mix asphalt  6000 . If the temperature is too low, the aggregate asphalt material  5000  inside the dryer drum  112  does not dry fast enough to produce hot mix asphalt  6000 . At a nominal temperature, the aggregate asphalt material  5000  inside the dryer drum  112  dries sufficiently quickly and attains a sufficient temperature (e.g., 280° F. to 330° F.) to produce hot mix asphalt  6000 . However, if the temperature is too high, the aggregate asphalt material  5000  inside the dryer drum breaks down, produces hydrocarbon fumes, and/or smokes. For successful production of hot mix asphalt  6000  from the aggregate asphalt material  5000 , regulation of the temperature inside the dryer drum  112  is important. The temperature inside the dryer drum  112  is regulated at least in part by the valve  108 . Control of the position of valve  108  is important for successfully processing the aggregate asphalt material  5000  into hot mix asphalt  6000 . In some embodiments, the temperature inside the dryer drum  112  is also regulated at least in part by the valve  109 . 
     In some embodiments, when the valve  108  is completely open, the flow of hot gas  4000  from the generator  102  to the atmosphere is maximized (i.e., the flow rate of the second flow Q 2  of hot gas  4000  is maximized) and the flow of hot gas  4000  from the generator  102  to the dryer drum  112  is minimized (i.e., the flow rate of the third flow Q 3  of hot gas  4000  is minimized). Thus, the interior of the dryer drum  112  tends to attain a relatively low temperature. In some embodiments, when the valve  108  is completely closed, there is no flow of hot gas  4000  from the generator  102  to the atmosphere (i.e., the flow rate of the second flow Q 2  of hot gas  4000  is zero) and the flow of the hot gas  4000  from the generator  102  to the dryer drum  112  is maximized (i.e., the flow rate of the third flow Q 3  of hot gas  4000  is maximized). Thus, the interior of the dryer drum  112  tends to attain a relatively high temperature, which is moderated by evaporating moisture from the aggregate, RAP, and RAS. In some embodiments, when the valve  108  is partially closed, the flow of hot gas  4000  to the generator  102  is moderate (i.e., the flow of the second flow Q 2  of hot gas  4000  is moderate) and the flow of hot gas  4000  from the generator  102  to the dryer drum  112  is moderate (i.e., the flow rate of the third flow Q 3  of the hot gas  4000  is moderate). Thus, the interior of the dryer drum  112  tends to attain a moderate temperature. In some embodiments, a flow rate of the first flow Q 1  of hot gas  4000  is equal to the flow rate of the second flow Q 2  of hot gas  4000  plus the flow rate of the third flow Q 3  of hot gas  4000 . In some embodiments, the valve  108  decreases a flow rate of the third flow Q 3  of hot gas  4000  by increasing the flow rate of the second flow Q 2  of hot gas  4000 . In some embodiments, valve  108  is increases a flow rate of the third flow Q 3  of hot gas  4000  by decreasing the flow rate of the second flow Q 2  of hot gas  4000 . 
     In some embodiments, the position of the valve  108  is controlled manually (e.g., by human input into a control panel managing a mechanical actuator or by a technician turning the valve  108  with a wrench) or automatically (e.g., by computer control). In some embodiments, a sensor (not shown) monitors temperature at the discharge of the dryer drum. In some embodiments, a processor (not shown) adjusts the position of the valve  108  by sending an electronic signal to the valve  108  based on the temperature detected by the discharge temperature sensor. In some embodiments, in response to detecting that the temperature is greater than a threshold, the processor opens the valve  108  by an amount. In some embodiments, the amount that the valve  108  is opened corresponds to an amount that the processor predicts will return the temperature to nominal. In some embodiments, in response to detecting that the temperature is less than a threshold, the processor closes the valve  108  by an amount. In some embodiments, the amount that the valve  108  is closed corresponds to an amount that the processor predicts will return the temperature to nominal. 
     Although in the embodiments described herein the exhaust (i.e., hot gas  4000 ) from the generator  102  is used to heat the asphalt material  5000  in the interior of the dryer drum  112 , it is contemplated that in some embodiments, one or more other means of heating the aggregate asphalt material  5000  in the interior of the dryer drum  112  are additionally used. It is further contemplated that in some embodiments, the exhaust (i.e., hot gas  4000 ) is used for other purposes in addition to heating the aggregate asphalt material  5000  in the interior of the dryer drum  112 . 
     Referring to  FIGS.  1 A,  1 B, and  2   , in some embodiments, the dryer drum  112  is configured to produce hot mix asphalt  6000  from the aggregate asphalt material  5000  using the hot gas  4000  from the generator  102 , which exits the generator  102  through the outlet, travels through the duct  106 , and enters the dryer drum  112  through the inlet. That is, the dryer drum  112  is configured to produce hot mix asphalt  6000  from asphalt materials  5000  using the third flow Q 3  of hot gas  4000 , which diverges from the first flow Q 1  of hot gas  4000 . In some embodiments, the aggregate asphalt material  5000  includes recycled asphalt material and virgin asphalt material. In other embodiments, the asphalt material  5000  includes only recycled asphalt material. In still other embodiments, the asphalt material  5000  includes only virgin asphalt material. In some embodiments, the aggregate asphalt material  5000  is loaded into the dryer drum  112  by conveyer or by any other means known to those skilled in the art. In a preferred embodiment, a product of crude oil (e.g., a binder) is added to the dryer drum  112  along with the aggregate asphalt material  5000 . In some embodiments, after the hot mix asphalt  6000  is produced from the asphalt material  5000 , the hot mix asphalt  6000  exits the dryer drum  112  and is carried away by conveyer or by any other means known to those skilled in the art. 
     Referring to  FIGS.  1 B- 2   , in some embodiments, the dryer drum  112  is supported by a support structure  114 . In some embodiments, the support structure  114  supports the dryer drum  112  such that the dryer drum  112  is tilted. That is, in some embodiments, a first axial end  1122  of the dryer drum  112  is at a lower elevation than a second axial end  1124  of the dryer drum  112 . 
     In some embodiments, the inlet (not shown) is disposed at the first axial end  1122 . In some embodiments the dryer drum  112  further comprises an opening (not shown) at the second axial end  1124  for loading the asphalt material  5000  and recycled materials into the dryer drum. 
     In some embodiments, a drive system (not shown) is configured to axially rotate the dryer drum. In some embodiments, the generator  102  supplies electrical energy to the drive system (i.e., the drive system is powered by the generator  102 ). In some embodiments, the dryer drum  112  produces the hot mix asphalt  6000  through the rotation of dryer drum  112  with the aggregate asphalt material  5000  inside the dryer drum  112  and the third flow Q 3  flowing through the dryer drum  112 . The rotation of the dryer drum mixes the aggregate asphalt material  5000  so that the aggregate asphalt material  5000  is more uniformly exposed to the flow of hot gas  4000  inside the dryer drum  112  and therefore is heated and dried more uniformly. The tilt of the dryer drum  112  helps draw aggregate asphalt material  5000  closer to the first axial end  1122 , where the temperature is the greatest. 
       FIG.  3    is a graphical representation of temperatures in the dryer drum  112  according to an embodiment. The temperature is generally highest proximate the first axial end  1122 , and the temperature is generally lowest proximate the second axial end  1124 . In a preferred embodiment, the hot gas  4000  emitted from the generator  102  is sufficiently hot such that the hottest point of the hot gas  4000  inside the dryer drum  112  is about 925° F. after the system  100  has reached steady state. In a preferred embodiment, the coolest point of the hot gas  4000  inside the dryer drum  112  is managed to maintain less than 85% humidity after the system  100  has reached steady state. In a preferred embodiment, the hottest point in the aggregate asphalt material  5000  inside the dryer drum  112  is about 300-330° F. after the system  100  has reached steady state. In a preferred embodiment, the coolest point in the aggregate asphalt material  5000  inside the dryer drum  112  is about 50° F. after the system  100  has reached steady state. 
     Referring to  FIG.  1 B , in some embodiments, the dryer drum  112  includes an exhaust structure  1126 , which is connected to the outlet (not shown). In some embodiments, the third flow Q 3  flows through the dryer drum  112 , through the outlet, through the exhaust structure  1126 , and into a baghouse  116 . The baghouse  116  filters the hot gas  4000  in the third flow Q 3  to remove dust particulates. In some embodiments, clean air  7000  (i.e., air having at least some dust particulates removed) is then vented to the atmosphere. 
     Referring now to  FIG.  4   , some aspects of the present disclosure are directed to a method  400  for producing hot asphalt mix and providing electrical energy to a power grid. In an embodiment, at  402 , a generator having an exhaust port is provided. At  404 , a dryer drum having an inlet is provided. At  406 , an exhaust bypass vent is provided. At  408 , the exhaust port is connected to the inlet using a duct. At  410 , a valve is installed at a junction between the duct and the exhaust bypass vent. At  412 , a generator is run to produce hot gas. In some embodiments, while the generator is running and producing the hot gas, a first flow of the hot gas flows through the duct. The first flow of the hot gas diverges into a second flow of the hot gas and a third flow of the hot gas. The second flow of the hot gas flows through the exhaust bypass vent, and the third flow of the hot gas flows through the inlet and into the dryer drum. At  414 , the flow rate of the hot gas from the generator to the dryer drum is controlled. In some embodiments, a flow rate of the third flow of the hot gas is controlled by controlling the valve, which controls a flow rate of the second flow of the hot gas. At  416 , hot mix asphalt is produced from asphalt material in the dryer drum using the hot gas. Specifically, in some embodiments, the hot mix asphalt is produced from the asphalt material in the dryer drum using the third flow of the hot gas. At  418 , electrical energy generated by the running of the generator is provided to a power grid or used onsite (i.e., electrical energy generated by the running of the generator is provided to a power grid or equipment on a manufacturing site having the generator). 
     In some embodiments of the method  400 , the hot gas is exhaust gas produced by the running of the generator. In some embodiments of the method, the producing of the hot mix asphalt and the providing of the electrical energy to the power grid occur simultaneously. 
     The method and system of the present disclosure provide electrical energy  3000  and hot mix asphalt  6000 . Instead of producing asphalt using a burner as in the related art, the method and system according to the present disclosure offer the advantage of producing substantial amounts of electricity in conjunction with asphalt production. The electricity produced by the system  100  can be sold to utility companies. 
     By drying the asphalt material  5000  with exhaust heat from the generator  102 , the system  100  has the advantage of being capable of adjusting recycled content percentage of the aggregate asphalt material  5000  from 0-100% without limitation. The system  100  of the present disclosure also has the capacity to handle higher levels of recycled contents in the aggregate asphalt material  5000  as compared to the related art. For example, the system  100  of the present disclosure can use recycled asphalt products and recycled shingles at amounts of up to 100% of the aggregate asphalt material  5000  without the risk of fires and product damage caused by the direct flame burners of the conventional art. 
     The method and system according to the present disclosure also have the advantage of reduced emissions as compared to the conventional art. The method of producing the hot mix asphalt according to the present disclosure is more efficient than the conventional art because providing the heat for drying the aggregate asphalt material  5000  does not cause any emissions beyond those required for the generator  102  to generate useful electricity. The heat from running generator  102  (which would otherwise be wasted) is used to heat the aggregate asphalt material  5000  to produce the hot mix asphalt  6000 . 
     Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention.