Patent Application
20160068771
A gasification system is designed to heat biomass feedstock (e.g., straw) to extremely high temperatures in order to break apart the molecular bonds. During this process, the resultant syngas and byproducts are super-heated as they exit the gasifier. Thus, the syngas and other byproducts need to be cooled before collection and storage. Conventional gasifier systems do not provide a mechanism for cooling these materials.
An example system is disclosed herein. The example system may include a char cooling auger coupled to a gasifier. The char cooling auger may include a receiving hopper and a screw conveyor that is housed within an outer tube. The receiving hopper is configured to receive and hold biochar from the gasifier and is further configured to feed the biochar to flighting on the screw conveyor. As the screw conveyor rotates, the biochar is moved within and along the outer tube as it is transported from a first end of the auger to an outlet port near a second end of the auger. Because the temperature of the outer tube is less than a temperature of the biochar, the biochar is cooled as transported through the outer tube. The temperature of the outer tube may be maintained via a fan (i.e., via forced convection), or simply through natural convection.
Another example system may include a gasifier configured to gasify biomass to provide syngas and biochar, and a hopper configured to collect and store the biochar. The example system may further include a char cooling auger configured to cool the biochar received from the gasifier prior to providing the biochar to the hopper.
Example methods are disclosed herein. An example method may include receiving biochar from a gasifier. The biochar may be generated by gasifying organic feedstock. The example method may further include transporting the biochar through a char cooling auger. The biochar may be cooled as it is transported through the char cooling auger. The example method may further include collecting and storing the biochar in a hopper after transporting the biochar through the char cooling auger.
There has thus been outlined, rather broadly, some of the features and embodiments of the invention in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features and embodiments of the invention that will be described hereinafter and that will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction or to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.
Various other examples, features, and attendant advantages of examples described herein will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, wherein:
The present invention is generally directed to a cooling auger used in a mobile gasification system that may be configured to cool biochar or another byproduct (hereinafter referred to a biochar) generated during gasification of an organic feedstock. The cooling auger may transfer or conduct heat away from the biochar as it is propagated through the char cooling auger. Many of the specific details of certain embodiments of the invention are presented in the following description and in
A second end of outer tube 130 may be attached to an outlet port 180. Outlet port 180 may provide cooled biochar to a hopper (not shown) for collection. Char cooling auger 104 may include rotation mechanism 160 that includes a motor 162 to rotate a screw conveyor 165 within outer tube 130 to transfer biochar from receiving hopper 120 to outlet port 180. Rotation mechanism 160 may include a center rod 164 that is splined at the top to connect to motor 162. Motor 162 may be connected directly to center rod 164 or may be connected indirectly via a drive chain or belt 163 and a drive wheel/gear 161. The flighting of screw conveyor 165 may be affixed (e.g., welded) to center rod 164. Center rod 164 may include an attachment means at each end to hold center rod 164 in place within outer tube 130 (e.g., a lock collar). The speed of the rotation of center rod 164 may be controlled by the rotational speed of motor 162.
Char cooling auger 104 may further include one or more thermocouples 172 that measure a temperature of the biochar leaving receiving hopper 120 via outer tube 130 near the first end. Char cooling auger 104 may further include one or more thermocouples 170 that measure a temperature of the biochar near the second end. The temperature information received via thermocouples 172 and thermocouples 170 may be used to control residence time of the biochar within outer tube 130 by controlling the rotation speed of center rod 164.
In operation, receiving hopper 120 may receive heated biochar via inlet port 112. The heated biochar may be received from a cyclone that separates the biochar from a syngas stream provided from a gasifier. Receiving hopper 120 may feed (e.g., via gravity or some other feed mechanism) the heated biochar to screw conveyor 165 for transport up outer tube 130. Char cooling auger 104 may cool the biochar by conducting heat away from the biochar via outer tube 130 as it is transported from receiving hopper 120 to outlet port 180. The cooled biochar may exit char cooling auger 104 via outlet port 180 at the top of outer tube 130. In some examples, outer tube 130 may be exposed to ambient air temperatures, which are significantly lower than the temperatures of the superheated biochar received in receiving hopper 120 via inlet port 112. Center rod 164 of char cooling auger 104 may rotate screw conveyor 165 at a relatively slow rate to ensure significant residence time (e.g., 10 minutes or more) of the biochar within outer tube 130. The longer the biochar is resident in outer tube 130, the greater the amount of heat transferred from the biochar. Two factors may control residence time within outer tube 130: 1) length of outer tube 130, (and ultimately auger 104), and 2) rotation speed of center rod 164. The rotation speed of center rod 164 may be based on the dimensions (e.g., circumference and length) of outer tube 130, as well as the temperature of the biochar received at receiving hopper 120. In some examples, center rod 164 may rotate at less than five rotations-per-minute (RPMs). In some examples, the residence time may be set such that the temperature of the biochar may be less than 160 degrees Celsius at outlet port 180.
In a preferred embodiment, outer tube 130 may be between 90 and 110 inches in length with a diameter of between 5 and 7 inches, although other dimensions are within the scope of the invention. In a specific example, the flighting of screw conveyor 165 may be between four and 6.5 inches in diameter with a half pitch, although other dimensions are within the scope of the invention as well. The tight clearance between screw conveyor 165 and outer tube 130 may prevent large amounts of the biochar from sliding back down outer tube 130 into receiving hopper 120. Further, the half pitch may allow char-cooling auger 104 to transfer the biochar when installed at a steep angle. At 2.5 inch pitch (e.g., half-pitch of a 5 inch diameter of the flighting of screw conveyor 165) and a 100 inch length of outer tube 130, it would take 40 revolutions to traverse the entire length of outer tube 130. A char cooling auger with these dimensions and a rotation speed of 4 RPMs may result in a bio char residence/cooling time of at least 10 minutes. In this example, char cooling auger 104 may be able to drop the temperature of the biochar from 800 degrees Celsius to under 150 degrees Celsius. In some examples, char cooling auger 104 may be part of a continuously pressurized system that allows collection of the syngas produced during the gasification process (e.g., by preventing the syngas from escaping into the atmosphere). By dropping the temperature to under 150 degrees Celsius, damage to the airlock components that are used to pressurize the system may be prevented. Thus, by cooling the biochar before passage outside of the pressurized system and collection, less expensive, low-temp airlock components may be used.
The dimensions of char cooling auger 104 discussed with reference to
The
In some embodiments, gasification system 400 may include a fan 427 configured to blow air across char cooling auger 428 to enhance heat transfer from the biochar. In some embodiments, char cooling auger 428 may include fins that are affixed to the outside of the outer tube to enhance heat transfer away from char cooling auger 428. The fins may improve heat transfer of the biochar as it traverses char cooling auger 428. Fins 736(0-7) may be extruded fin stock, folded fin stock, lanced and offset fins, or other common fins that are welded, brazed, or otherwise permanently affixed to the char cooling auger.
Heat exchanger 429 may extract heat from the syngas provided to it by cyclone 426. Heat exchanger 429 may provide the cooled syngas to an engine 442. Engine 442 may use the syngas as fuel to operate. Engine 442 may be coupled to a generator 440, and may drive generator 440 to provide electrical power.
In operation, gasification system 400 may gasify feedstock generated from residual biomass. The feedstock may be provided from hopper 422 to gasifier 460 via staging hopper 462. Gasification system 400 may be a continuous flow system such that the feedstock is delivered from hopper 422 to gasifier 460 via staging hopper 462 in a continuous fashion to enable an uninterrupted flow of feedstock within the combustion chamber of gasifier 460 for continual operation thereof Gasifier 460 may gasify the feedstock by reacting it with heat and combustion air. The combustion air may be introduced to gasifier 460 via blower 480. Blower 480 may be coupled to gasifier 460 such that airflow through gasifier 460 may be controlled in two different ways. That is, blower 480 may be connected to gasifier 460 to push combustion air into gasifier 460, or to pull resultant gasses from gasifier 460. In other words, gasifier 460 may operate under vacuum (e.g., with blower 480 coupled between the output of gasifier 460 and the input of cyclone 426) or under pressure (e.g., with blower 480 coupled to an input of gasifier 460). Each method has its advantages. The use of a vacuum system removing the syngas from gasifier 460 may eliminate a potential for leakage of flammable gas to the atmosphere, as the entire system is at a negative pressure relative to the atmosphere. If a leak did develop, ambient air would be forced into gasifier 460, rather than flammable syngas leaking out.
The use of a pressure system to inject the combustion air into gasifier 460 may reduce a likelihood of fouling of blower 480, because the combustion air is relatively clean as compared to the syngas stream, which may include tars and other entrained particulates that can foul blower 460 and degrade its operation or cause it to malfunction. In some examples, the gasification system 400 may be configurable to switch between pressure and vacuum operation based on desired operating conditions.
Gasifier 460 may include a preheater that preheats the combustion air and feedstock using hot syngas output from the preheater prior to cyclone 426. Heating the combustion air and/or the feedstock improves gasification efficiency. For example, heating the feedstock may reduce its moisture content prior to entering gasifier 460. Additionally, preheating the combustion air using the generated syngas drives up system efficiency by reducing the time required for gasification temperatures within gasifier 460 to be reached.
Cyclone 426 may be used for separating biochar that has become entrained in the syngas flow and for providing cleaned syngas to the heat exchanger 429. Char cooling auger 428 may collect the biochar separated from the syngas by cyclone 426 and provide the collected biochar to hopper 484 via airlocks 482. Airlocks 482 may meter an amount of syngas that escapes during the transfer of the biochar to hopper 484 and when biochar is offloaded from hopper 484, and char cooling auger 428 may cool the biochar to be within operational limits of airlocks 482. In some embodiments, fan 427 may blow air across char cooling auger 428 to enhance cooling of the biochar. Upon receiving cleaned syngas from cyclone 426, heat exchanger 429 may provide cooled syngas to engine 442. Engine 442 may use the provided syngas as fuel to operate. Engine 442 may be coupled to generator 440, and may drive generator 440 to provide electrical power. In some examples, engine 442 and/or generator 440 may be replaced with any combination of a storage tank, a furnace, a pump, or other device which may use or be driven by the syngas produced by gasifier 460 or through which stored syngas energy or syngas can be output (turbine, blower, etc.). Control system 470 may be used to control various components of gasification system 400 based on data collected from its components. In some embodiments, control system 470 may measure a power output of generator 440 to determine whether too little or too much syngas is being produced, for example, to operate engine 442.
In some embodiments, control system 470 may control char cooling auger 428. For example, control system 470 may receive temperature data from thermocouples attached to char cooling auger 428 (e.g., thermocouples 172 and the thermocouples 170 of
Char cooling auger 704 may include an outer tube 730 that extends from a bottom plate 132 to a top plate 138. Outer tube 730 may include a first attachment band 734 and a second attachment band 736 configured to attach or support the weight of the installed char cooling auger 704, or to attach a fan or other mechanism to char cooling auger 704. A first end of outer tube 730 may be attached to a receiving hopper 120. A second end of outer tube 730 may be attached to an outlet port 180. Outlet port 180 may provide cooled biochar to a hopper (not shown) for collection.
Char cooling auger 704 may include fins 736(0-7) that are affixed (e.g., welded or secured via another attachment means) to the outside of outer tube 730. Fins 736(0-7) may enhance heat transfer away from outer tube 730, which may improve heat transfer of the biochar as it traverses outer tube 730. The fins 736(0-7) may be extruded fin stock, folded fin stock, lanced and offset fins, or other common fins that are welded, brazed, bolted, riveted or otherwise permanently or removably affixed to outer tube 730 so as to conduct heat. Fins 736(0-7) may be any shape and/or type as are commonly used to increase surface area. Outer tube 736(0-7) may simply have a rough surface, such as a hammered, beaded, or blasted surface to enhance heat transfer.
In operation, receiving hopper 120 may receive heated biochar via inlet port 112. Receiving hopper 120 may feed (e.g., via gravity or some other feed mechanism) the heated biochar to screw conveyor 165 for transport up outer tube 130. Char cooling auger 704 may cool the biochar by conducting heat away from the biochar via outer tube 730 as it is transported from receiving hopper 120 to outlet port 180. Fins 736(0-7) may enhance the heat transfer properties of outer shell 730. Fins 736(0-7) may be exposed to ambient air or may be exposed to a fan or blower that blows ambient air across fins 736(0-7). The cooled biochar may exit char cooling auger 704 at outlet port 180.
The number, position, orientation, and shape of fins 736(0-7) shown in
The above description of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed. While specific embodiments of, and examples of, the invention are described in the foregoing for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will realize. Moreover, the various embodiments described above can be combined to provide further embodiments. Accordingly, the scope of the invention is to be determined entirely by the following claims.
We hereby claim benefit under Title 35, United States Code, Section 119(e) of U.S. provisional patent application Ser. No. 62/046,080, filed Sep. 4, 2014. The 62/046,080 application is hereby incorporated by reference into this application.
| Number | Date | Country | |
|---|---|---|---|
| 62046080 | Sep 2014 | US |
