Patent Application
20180291272
The present invention relates to the chemical engineering field, in particular to a system and a method for fast pyrolysis of coal.
Fast pyrolysis method is an advanced upgrading technique based on medium-temperature pyrolysis for medium-low-rank coal in powder form, and it requires a high heating rate of the material in a uniform temperature field. Viewed from the reaction mechanism, the method forces macro-molecules in low-rank coal to have bond breaking reactions rapidly, inhibits secondary pyrolysis reaction and cross-linking reaction of the pyrolysis product, and reduces fuel gas and semi-coke products in the pyrolysis process of low-rank coal. Therefore, that technique is more suitable for use in China in view of the actual situation in China, and can improve economic and social effects of low-rank coal utilization. In the prior art, a gas or solid heat carrier is utilized to meet the requirement for temperature field and heating rate. At present, fast pyrolysis reactors of low-rank coal developed in China and foreign countries mainly include fluidized bed reactors and downer reactors, etc., which employ a gas or solid heat carrier. However, since the process involves heat carrier heating and separation, temperature field control, and oil-gas purification and recovery systems, etc., the process flow is very complex. Consequently, the fast pyrolysis systems of low-rank coal available in the market have high failure rate and low heat efficiency, and can't operate in a long term. As a result, the development of this technique is limited. Therefore, the existing techniques for fast pyrolysis of coal should be further improved.
The object of the present invention is to solve one of the technical problems in relevant techniques at least to some extent. To that end, one object of the present invention is to provide a system and a method for fast pyrolysis of coal. The system can remarkably improve the yield ratio of tar, and greatly simplifies the process flow of fast pyrolysis reaction.
In an aspect of the present invention, the present invention provides a system for fast pyrolysis of coal. According to the embodiments of the present invention, the system comprises:
a fast pyrolysis reactor,
said fast pyrolysis reactor comprises:
a reactor body defining a reaction space that forms a dispersion region, a pyrolysis region, and a discharge region from top to bottom;
multilayer regenerative radiant tubes, which are distributed at an interval in the height direction of the reactor body in the pyrolysis region, and each layer of regenerative radiant tubes consists of a plurality of regenerative radiant tubes distributed at an interval in the horizontal direction;
a material distributor;
a coal inlet arranged in the dispersion region above the material distributor;
a material distribution gas inlet, which is arranged in the dispersion region and communicates with the material distributor so as to utilize a material distribution gas to blow out the coal in the material distributor into the dispersion region, so that the coal falls into the pyrolysis region uniformly;
a plurality of pyrolysis gas outlets, which are arranged in the dispersion region and/or the pyrolysis region respectively; and
a semi-coke outlet arranged in the discharge region;
the fast pyrolysis reactor is adapted to treat the coal by fast pyrolysis with the regenerative radiant tubes, so as to obtain semi-coke and pyrolysis gas;
a slag cooler connected to the semi-coke outlet and adapted to cool the semi-coke; and
a cooling device connected to the pyrolysis gas outlet and adapted to cool the pyrolysis gas, so as to obtain tar and fuel gas.
In the system for fast pyrolysis of coal in the present invention, the regenerative radiant tubes are arranged in multiple layers. Adjacent regenerative radiant tubes are spaced from each other at an interval in the horizontal direction and the vertical direction.
According to an embodiment of the present invention, multilayer regenerative radiant tubes are used to provide heat sources, so that one or more temperature fields are formed in the pyrolysis region, and the temperature in each temperature field is uniform; thus, a temperature gradient is formed in the pyrolysis region.
For example, in an embodiment of the present invention, the pyrolysis region forms a preheating section, a fast pyrolysis section, and a complete pyrolysis section from top to bottom (i.e., three temperature fields are formed).
The number of the temperature fields and the temperature gradient in the temperature fields can be set as required.
The temperature in the temperature field may be adjusted in many ways. For example, the number of regenerative radiant tubes in the horizontal direction and/or vertical direction may be adjusted; the number of layers of regenerative radiant tubes may be adjusted; the spacing between regenerative radiant tubes (in vertical direction and/or horizontal direction) may be adjusted; the temperatures of the regenerative radiant tubes may be adjusted, etc.
In an embodiment of the present invention, a fuel gas regulating valve is provided on a regenerative radiant tube to adjust the flow rate of the fuel gas charged into the regenerative radiant tubes and thereby accurately control the temperature of the regenerative radiant tubes.
A regenerative radiant tube has a burner at each end of the tube respectively. A temperature gradient is formed when the flame created by combustion of the burner at one end is jetted out, i.e., the temperature decreases gradually from the burner to the exterior. Similarly, a temperature gradient is also formed when the flame created by combustion of the burner at the other end is jetted out. When the burners at the two ends of the tube combust alternately, the two temperature gradients are overlapped with each other so as to achieve temperature complementation. As a result, the overall temperature in the entire regenerative radiant tube is uniform. For example, the temperature difference in a single regenerative radiant tube is not higher than 30° C.
The system for fast pyrolysis of coal provided in the present invention employs the regenerative radiant tube arrangement described in the present invention. Owing to inherent attributes of regenerative radiant tube (as described above, the burners at the two ends of a regenerative radiant tube can combust rapidly and alternatively and realize regenerative combustion), one or more different temperature fields are permitted in the reactor as required, to create temperature gradients and ensure uniform temperature in each temperature field.
In an embodiment of the present invention, the temperatures in the regenerative radiant tubes may be the same or different, as long as the temperature in each temperature field is uniform.
In an embodiment of the present invention, the spacing between adjacent regenerative radiant tubes may be the same or different, as long as the temperature in each temperature field is uniform. For example, the horizontal spacing and vertical spacing between the outer walls of adjacent regenerative radiant tubes may be 100-500 mm respectively and independently, such as 200-300 mm, e.g., 200 mm or 300 mm.
In an embodiment where the pyrolysis region forms a preheating section, a fast pyrolysis section and a complete pyrolysis section from top to bottom, the temperatures in the regenerative radiant tubes in the preheating section may be the same or different, preferably be the same, as long as the temperature in the preheating section is uniform.
In an embodiment where the pyrolysis region forms a preheating section, a fast pyrolysis section and a complete pyrolysis section from top to bottom, the temperatures in the regenerative radiant tubes in the fast pyrolysis section may be the same or different, preferably be the same, as long as the temperature in the fast pyrolysis section is uniform.
In an embodiment where the pyrolysis region forms a preheating section, a fast pyrolysis section and a complete pyrolysis section from top to bottom, the temperatures in the regenerative radiant tubes in the complete pyrolysis section may be the same or different, preferably be the same, as long as the temperature in the complete pyrolysis section is uniform.
Though not limited to the theory, it is believed that the coal may be subject to pyrolysis cracking locally in the pyrolysis process if the coal is not heated uniformly in the pyrolysis region and the local temperature is too high at some places in the pyrolysis region, and consequently a part of high-polymer substances that can produce tar in the pyrolysis product are directly turned into fuel gas and semi-coke; or the coal is not pyrolyzed completely in the pyrolysis process if the local temperature is too low at some places in the pyrolysis region, and consequently the volatile constituents in the coal can't be released and the tar yield ratio is decreased.
In the present invention, in a case that the regenerative radiant tubes are arranged to form one or more temperature fields, the coal falling into the temperature fields will be heated uniformly and their reaction degrees will be generally the same, because the respective temperatures in the temperature fields are generally uniform. Thus, the decrease of tar yield ratio can be avoided.
With the system for fast pyrolysis of coal provided in the present invention, the pyrolysis gas can be exported quickly after the coal is pyrolyzed. Specifically, in an embodiment of the present invention, the reactor of the system for fast pyrolysis of coal has one or more pyrolysis gas outlets on the side wall of the pyrolysis region and/or the top wall of the dispersion region. Pyrolysis gas is generated in the pyrolysis reaction process, and the pressure inside the reactor is increased. The pyrolysis gas is actuated by the increased pressure to export from the pyrolysis gas outlets quickly.
In a preferred embodiment of the present invention, a gas extraction device that communicates with the pyrolysis gas outlets is provided outside of the reactor to facilitate the quick export of the pyrolysis gas from the reactor.
The pyrolysis gas produced in the pyrolysis process is exported from a side of the reactor, the pyrolysis gas contacts with the falling material at the pyrolysis gas outlets at inner side of the reactor, so that the fine dust in the pyrolysis gas at the inner side of the reactor is carried by the material to fall under the gravity action of the material, the dust content in the exported pyrolysis gas is decreased, and thereby the dust content in the tar obtained after cooling is low.
At least 2 pyrolysis gas outlets are provided; for example, 2-100, 3-80, 5-70, 10-50, 20-40 or 30-40 pyrolysis gas outlets may be provided. More specifically, 8, 15, 22 or 28 pyrolysis gas outlets are provided. However, the present invention is not limited to that.
The pyrolysis gas exported from the pyrolysis gas outlets is cooled quickly via a cooling device; thus, the non-condensable gas is separated from tar.
The present invention employs a material distributor to uniformly distribute the coal in the pyrolysis region and thereby remarkably improve the stability of operation of the apparatus.
Fine particles of coal are dispersed and fed into the pyrolysis reactor uniformly via the material distribution system, and exchange heat in a uniform temperature field in the pyrolysis reactor. In that process, each particle of coal is heated uniformly; thus, the problem of decreased yield ratio of tar and gas incurred by uneven heating rate owing to coal agglomeration is avoided. For example, the particle size of the coal is smaller than 3 mm.
With the arrangement of the regenerative radiant tubes in the present invention, the coal can be heated up quickly in the reactor in the pyrolysis process. In addition, the pyrolysis gas produced in the process can be exported out of the reactor quickly and cooled quickly. Thus, secondary reactions that may happen in the pyrolysis process, export process, and cooling process is reduced (such reactions may cause a decreased tar yield ratio), and the tar yield ratio is significantly increased.
Besides, compared with traditional pyrolysis reaction apparatuses that use a gas heat carrier or solid heat carrier as a heat source for pyrolysis, the system for fast pyrolysis in the present invention doesn't require a preheating unit and a carrier separation unit, and thereby greatly simplifies the process flow of fast pyrolysis reaction and significantly decreases the failure rate of the apparatus.
The present invention employs a specific regenerative radiant tube arrangement to form one or more temperature fields in the reactor and ensure uniform temperature distribution in each temperature field; in addition, the temperatures in the temperature fields in the reactor are controllable. Thus, the coal can be heated up uniformly in the reactor, quick drying and more complete pyrolysis are realized, and thereby the tar yield ratio is improved, and the efficiency of fast pyrolysis of the coal is improved.
In addition, the system for fast pyrolysis of coal according to the above embodiments of the present invention may have the following additional technical features:
In some embodiments of the present invention, the system for fast pyrolysis of coal further comprises: a coal bunker adapted to store coal; a drying and upgrading tube connected to the coal bunker and the fast pyrolysis reactor respectively and adapted to dry and upgrade the coal with hot flue gas before the coal is controlled to have a fast pyrolysis reaction; and a first blower fan, which is connected to the flue gas outlet and the drying and upgrading tube respectively and adapted to supply the high-temperature flue gas as the hot flue gas to the drying and upgrading tube. Thus, the efficiency of pyrolysis of coal can be further improved.
In some embodiments of the present invention, the cooling device is a spraying tower, in which the pyrolysis gas is sprayed with a cooling liquid so as to cool the pyrolysis gas. Thus, the efficiency of separation between tar and fuel gas can be improved significantly.
In some embodiments of the present invention, the system for fast pyrolysis of coal further comprises: a tar trough connected to the spraying tower and adapted to treat the tar by settlement so as to obtain tar in an upper layer and tar in a lower layer; an oil pump connected to the tar trough and the spraying tower respectively and adapted to supply the tar in the upper layer as the cooling liquid to the spraying tower; a tar storage tank connected to the tar trough and adapted to store the tar in the lower layer; a water seal device connected to the spraying tower; a fuel gas storage tank connected to the spraying tower and adapted to store the fuel gas; a second blower fan connected to the fuel gas storage tank and the regenerative radiant tubes respectively and adapted to supply one part of the fuel gas to the regenerative radiant tube; and a third blower fan connected to the fuel gas storage tank and the material distribution gas inlet respectively and adapted to supply the other part of the fuel gas as material distribution gas to the material distribution gas inlet. Thus, cyclic utilization of the fuel is realized, and thereby the cost is reduced significantly.
In some embodiments of the present invention, each layer of regenerative radiant tubes consists of a plurality of regenerative radiant tubes that are parallel to each other and evenly distributed, and each regenerative radiant tube is parallel to each regenerative radiant tube in adjacent upper and lower layers of regenerative radiant tubes and is staggered from each regenerative radiant tube in adjacent upper and lower layers of regenerative radiant tubes in the height direction of the reactor body. Thus, the material can be fed into the reactor uniformly and retained for the same time in the reactor, and thereby the efficiency of fast pyrolysis of the coal can be further improved.
In some embodiments of the present invention, the reactor body is in 2-20 m height, the regenerative radiant tubes are in 100-500 mm diameter, and the horizontal spacing and vertical spacing between the outer walls of adjacent regenerative radiant tubes are 100-500 mm respectively and independently. Thus, the material can be retained for 2-30 s to meet the requirement of fast pyrolysis of the coal for retention time.
In some embodiments of the present invention, the regenerative radiant tubes are regenerative fuel gas radiant tubes; namely, the heat generated from combustion of a fuel gas is supplied through the radiant tube bodies by heat radiation.
In some embodiments of the present invention, a fuel gas regulating valve is provided on the regenerative radiant tubes, and a multilayer regenerative radiant tubes are used to provide a heat source required for the pyrolysis process; thus, the flow rate of the fuel gas charged into the regenerative radiant tubes can be adjusted, and thereby the temperature in the pyrolysis process can be controlled accurately.
In some embodiments of the present invention, the multilayer regenerative radiant tubes may be 6-30 layers. The inventor has found that such an arrangement is helpful for creating a uniform temperature field in the pyrolysis region and thereby remarkably improves the efficiency of fast pyrolysis of coal; thus, the yield ratio of tar can be improved.
In some embodiments of the present invention, the temperature difference in a single regenerative radiant tube is not greater than 30° C., the pyrolysis region forms a preheating section, a fast pyrolysis section and a complete pyrolysis section from top to bottom, the temperature in the regenerative radiant tubes in the preheating section is 550-900° C., the temperature in the regenerative radiant tubes in the fast pyrolysis section is 500-800° C., and the temperature in the regenerative radiant tubes in the complete pyrolysis section is 500-800° C. Thus, the temperature in each region of the reactor is uniform, and the temperatures in the regions of the reactor can be adjusted, so as to dry and completely pyrolyze the coal rapidly, and thereby the efficiency of fast pyrolysis of the coal can be further improved.
In another aspect of the present invention, the present invention provides a method for fast pyrolysis of coal with the system for fast pyrolysis of coal described above. According to the embodiments of the present invention, the method comprises:
supplying a material distribution gas via the material distribution gas inlet to the material distributor, supplying coal via the coal inlet to the reaction space, supplying a combustible gas and air into the regenerative radiant tubes, so that the combustible gas is combusted in the regenerative radiant tubes and generate heat to carry out fast pyrolysis of the coal, so as to obtain pyrolysis gas and semi-coke;
supplying the semi-coke via the semi-coke outlet to the slag cooler, so as to cool the semi-coke; and
cooling the pyrolysis gas discharged via the pyrolysis gas outlets in a cooling device, so as to obtain tar and fuel gas.
Thus, the method for fast pyrolysis of coal according to the embodiments of the present invention employs a multilayer regenerative radiant tubes to provide heat sources for the pyrolysis process, the temperature in the pyrolysis process can be controlled accurately by adjusting the flow rate of the fuel gas charged into the regenerative radiant tubes, and the uniformity of temperature field is ensured by quick changeover and regenerative combustion at the two ends of the regenerative radiant tubes; thus, the efficiency of fast pyrolysis of the coal can be significantly improved and thereby the tar yield ratio can be improved. Besides, compared with traditional pyrolysis reaction apparatuses that use a gas heat carrier or solid heat carrier as a heat source for pyrolysis, the method for fast pyrolysis of coal according to the present invention doesn't require a preheating unit and a carrier separation unit, and thereby greatly simplifies the process flow of fast pyrolysis reaction and significantly decreases the failure rate of the apparatus and lower the dust content in the obtained tar. In addition, the apparatus in the present invention employs a material distributor to uniformly distribute the coal in the pyrolysis region and prevent abrasion of the radiant tubes resulted from the coal, and thereby the operating stability of the apparatus is significantly improved.
In addition, the method for fast pyrolysis of coal according to the above embodiments of the present invention may have the following additional technical features:
In some embodiments of the present invention, the temperature difference in a single regenerative radiant tube is not greater than 30° C., the pyrolysis region forms a preheating section, a fast pyrolysis section and a complete pyrolysis section from top to bottom, the temperature in the regenerative radiant tubes in the preheating section is 550-900° C., the temperature in the regenerative radiant tubes in the fast pyrolysis section is 500-800° C., and the temperature in the regenerative radiant tubes in the complete pyrolysis section is 500-800° C. Thus, the temperature in each region of the reactor is uniform, and the temperatures in the regions of the reactor can be adjusted, so as to dry and completely pyrolyze the coal rapidly, and thereby the efficiency of fast pyrolysis of the coal can be further improved.
In some embodiments of the present invention, the method for fast pyrolysis of coal further comprises: drying and upgrading the coal with a hot flue gas in the drying and upgrading tube before the coal is supplied to the reaction space; and supplying the high-temperature flue gas produced in the regenerative radiant tubes to the drying and upgrading tube by means of the first blower fan. Thus, the moisture content in the powder coal loaded into the reactor can be decreased, and the powder coal is preheated, to improve the heating rate of the powder coal after the powder coal is loaded into the reactor and thereby further improve the efficiency of fast pyrolysis of the coal.
In some embodiments of the present invention, the cooling device is a spraying tower.
In some embodiments of the present invention, in the spraying tower, the pyrolysis gas is sprayed with a cooling liquid so as to cool the pyrolysis gas. Thus, the pyrolysis gas can be sprayed and captured rapidly and intensively, and thereby the efficiency of separation between fuel gas and tar can be improved significantly.
In some embodiments of the present invention, the method for fast pyrolysis of coal further comprises: storing the fuel gas in the fuel gas storage tank; supplying one part of the fuel gas as fuel to the regenerative radiant tubes by means of the second blower fan; and supplying the other part of the fuel gas as material distribution gas to the material distribution gas inlet by means of the third blower fan. Thus, cyclic utilization of the fuel is realized, and thereby the cost is reduced significantly.
In some embodiments of the present invention, the fast pyrolysis time is 2-30 s, and the particle size of the coal is smaller than 3 mm. Thus, the heating rate of the coal in the reactor is high, the coal retention time is short, tar and gas can be extracted from the coal rapidly, production of semi-coke from the volatile constituents in the coal in the pyrolysis process can be inhibited, and the yield ratio of tar can be improved significantly.
Additional aspects and advantages of the present invention will be shown and become apparent in the following description partially, or can be understood in the practice of the present invention.
The above-mentioned and/or additional aspects and advantages of the present invention will become more apparent and more easily to understand in the description of embodiments with reference to the accompanying drawings. Among the drawings:
Hereunder some embodiments of the present invention will be detailed. The embodiments are illustrated in the accompanying drawings, wherein, identical or similar marks indicate identical or similar elements or elements with identical or similar functions. It should be noted that the embodiments described with reference to the accompanying drawings are only exemplary and are provided only to explain the present invention rather than constitute any limitation to the present invention.
In the description of the present invention, it should be understood that the orientation or position relations indicated by terms “center”, “longitudinal”, “transverse”, “length”, “width”, “thickness”, “above”, “below”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counter-clockwise”, “axial”, “radial”, or “circumferential”, etc., are based on the orientation or position relations indicated in the accompanying drawings. They are used only to ease and simplify the description of the present invention, rather than indicate or imply that the involved device or component must have a specific orientation or must be constructed and operated in a specific orientation. Therefore, the use of these terms shall not be deemed as constituting any limitation to the present invention.
In addition, the terms “first” and “second” are used only for description purpose, and shall not be interpreted as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical feature. Hence, a feature confined by “first” or “second” may explicitly or implicitly comprises at least one such feature. In the description of the present invention, “a plurality of” or “multiple” means at least two, such as two or more, etc., unless otherwise specified explicitly.
In the present invention, unless otherwise specified and defined explicitly, the terms “install”, “connect”, “fix”, etc. shall be interpreted in their general meaning. For example, the connection can be fixed connection, detachable connection, or integral connection; can be mechanical connection or electrical connection; can be direct connection or indirect connection via an intermediate medium, or internal communication or interactive relation between two elements. Those having ordinary skills in the prior art may interpret the specific meanings of the terms in the present invention in their context.
In the present invention, unless otherwise specified and defined explicitly, a first feature “above” or “below” a second feature may represent that the first feature and the second feature directly contact with each other or the first feature and the second feature contact with each other indirectly via an intermediate medium. In addition, a first feature “above” or “over” a second feature may represent that the first feature is right above or diagonally above the second feature, or may only represent that the elevation of the first feature is higher than that of the second feature. A first feature being “below” or “under” a second feature may represent that the first feature is right below or diagonally below the second feature, or may only represent that the elevation of the first feature is lower than that of the second feature.
In an aspect of the present invention, the present invention provides a system for fast pyrolysis of coal. Hereunder the system for fast pyrolysis of coal in embodiments of the present invention will be detailed with reference to
a fast pyrolysis reactor 100: according to the embodiments of the present invention, as shown in
According to the embodiments of the present invention, multilayer regenerative radiant tubes 15 and a material distributor 16 are arranged in the reaction space 11.
According to the embodiments of the present invention, the reactor body 10 is arranged with a coal inlet 101, a material distribution gas inlet 102, a plurality of pyrolysis gas outlets 103, and a semi-coke outlet 104.
According to the embodiments of the present invention, the coal inlet 101 is arranged in the dispersion region 12 above the material distributor 16, and is adapted to supply coal to the reaction space 11, so that the coal is uniformly distributed via the material distributor in the pyrolysis region. Specifically, the coal inlet 101 may be arranged on a side wall of the dispersion region 12.
According to the embodiments of the present invention, the material distribution gas inlet 102 is arranged in the dispersion region 12 and communicates with the material distributor 16, and is adapted to supply a material distribution gas (nitrogen, etc.) into the material distributor 16, so that the coal in the material distributor 16 is blown out into the dispersion region 12 and thereby is uniformly distributed in the pyrolysis region; thus the efficiency of fast pyrolysis of the coal is further improved. Specifically, the material distribution gas inlet 101 may be arranged on a side wall of the dispersion region 12.
According to the embodiments of the present invention, the multilayer regenerative radiant tubes 15 are distributed at an interval in the height direction of the reactor body 10 in the pyrolysis region 13, and each layer of regenerative radiant tubes consists of a plurality of regenerative radiant tubes distributed at an interval in the horizontal direction. According to a specific embodiment of the present invention, each layer of regenerative radiant tubes consists of regenerative radiant tubes that are parallel to each other and evenly distributed, and each regenerative radiant tube is parallel to each of the regenerative radiant tubes in adjacent upper and lower layers of regenerative radiant tubes and is stagger from each regenerative radiant tube in adjacent upper and lower layers of regenerative radiant tubes in the height direction of the reactor body. According to a specific example of the present invention, the regenerative radiant tubes may be in diameter of 100-500 mm. Thus, the efficiency of fast pyrolysis of coal can be improved remarkably, and thereby the yield ratio of tar can be improved.
According to a specific embodiment of the present invention, the horizontal spacing and vertical spacing between the outer walls of adjacent regenerative radiant tubes are 100-500 mm respectively and independently. Thus, the yield ratio of tar can be further improved. It should be noted that the horizontal spacing between the outer walls of adjacent regenerative radiant tubes may be comprehended as the spacing between the outer walls of regenerative radiant tubes in the same layer, and the vertical spacing between adjacent regenerative radiant tubes may be comprehended as the spacing between the outer walls of adjacent regenerative radiant tubes in adjacent upper and lower layers.
According to a specific embodiment of the present invention, multilayer regenerative radiant tubes may be 6-30 layers. The inventor has found that such an arrangement is helpful for creating a uniform temperature field in the pyrolysis region and thereby remarkably improves the efficiency of fast pyrolysis of coal; thus, the yield ratio of tar can be improved.
According to the embodiments of the present invention, the regenerative radiant tubes may be regenerative fuel gas radiant tubes; namely, the heat generated from combustion of a fuel gas is supplied through the radiant tube bodies by heat radiation. According to a specific embodiment of the present invention, a fuel gas regulating valve (not shown) may be provided on the regenerative radiant tubes. Thus, the temperature in the pyrolysis process can be controlled accurately by adjusting the fuel gas regulating valve to adjust the flow rate of the fuel gas charged into the regenerative radiant tubes, and thereby the efficiency of fast pyrolysis of the coal can be improved significantly, and the tar yield ratio can be improved.
Specifically, the temperature in the pyrolysis process can be controlled accurately by adjusting the flow rate of the fuel gas charged into the regenerative radiant tubes, and a quick changeover value is utilized to control the temperature difference in the temperature field of a single radiant tube to be no more than 30° C. and thereby ensure temperature uniformity in the temperature field in the reaction space.
According to the embodiments of the present invention, the pyrolysis region forms a preheating section, a fast pyrolysis section and a complete pyrolysis section from top to bottom, the temperature in the regenerative radiant tubes in the preheating section is 550-900° C., the temperature in the regenerative radiant tubes in the fast pyrolysis section is 500-800° C., and the temperature in the regenerative radiant tubes in the complete pyrolysis section is 500-800° C. Thus, the efficiency of pyrolysis of coal can be further improved.
According to the embodiments of the present invention, the material distributor 16 may be arranged inside the dispersion region 12 and is adapted to blow the coal in the material distributor 16 into the dispersion region with an inert gas (e.g., nitrogen), so that the coal falls into the pyrolysis region uniformly and thereby is dispersed uniformly in the pyrolysis region. Thus, compared with the traditional fast pyrolysis process, by utilizing the material distributor, the present invention omits a rotating (stirring) unit, and thereby significantly decreases the failure rate of the apparatus. It should be noted that the “material distributor” described here may be any device that blow out the coal with a gas in the prior art. Specifically, the material distributor 16 may be arranged on the side wall of the dispersion region 12.
According to the embodiments of the present invention, a plurality of pyrolysis gas outlets 103 may be arranged in the dispersion region 12 and/or pyrolysis region 13. According to a specific embodiment of the present invention, a plurality of pyrolysis gas outlets 103 may be arranged on the top end of the dispersion region 12 and/or on the side wall of the pyrolysis region 13 respectively. The inventor has found: by using top-end export of gas and/or side-wall export of gas in combination, the semi-coke in the pyrolysis gas can settle down and be separated, and thereby the dust content in the pyrolysis gas can be decreased significantly. Viewed from the aspect of process design, gas export via the side wall of the pyrolysis region is preferred.
According to the embodiments of the present invention, the semi-coke outlet 104 may be arranged in the discharge region 14 and is adapted to discharge the semi-coke produced through pyrolysis out of the discharge region. Specifically, the semi-coke outlet 104 may be arranged on the bottom end of the discharge region 14.
According to the embodiments of the present invention, the inner wall surface of the dispersion region 12 may be in a spherical or conical shape. Thus, the material scattered by the material distributor can be dispersed into the pyrolysis region uniformly via the dispersion region, and thereby the efficiency of pyrolysis of the coal can be further improved.
According to the embodiments of the present invention, the discharge region 14 may be in an inverted cone shape. Thus, the semi-coke produced through pyrolysis can be discharged successfully out of the discharge region.
According to the embodiments of the present invention, the height of the reactor body 10 may be 2-20 m. Thus, the coal can be completely pyrolyzed.
According to the embodiments of the present invention, the fast pyrolysis reactor is adapted to treat the coal by fast pyrolysis with the regenerative radiant tubes, so as to obtain semi-coke and pyrolysis gas. According to an embodiment of the present invention, there is no restriction on the particle size of the coal. Those skilled in the art can select the particle size according to the actual requirement. According to a specific embodiment of the present invention, the particle size of the coal is smaller than 3 mm. Thus, a challenge that powder coal can't be utilized in the prior art is overcome. According to another embodiment of the present invention, the fast pyrolysis time of the coal is 2-30 s. Thus, the degree of secondary pyrolysis reaction and cross-linking reaction of the pyrolysis product can be decreased effectively, the yield of fuel gas and semi-coke in the pyrolysis process can be reduced, and thereby the yield ratio of tar can be improved remarkably.
Slag cooler 200: According to the embodiments of the present invention, the slag cooler 200 is connected to the semi-coke outlet 104 and adapted to cool the semi-coke so as to obtain cooled semi-coke. Specifically, the temperature of the semi-coke obtained from the semi-coke outlet is 500-600° C., and the temperature of the cooled semi-coke obtained from the slag cooler is lower than 50° C.
Cooling device 300: According to the embodiments of the present invention, the cooling device 300 is connected to the pyrolysis gas outlet 103 and adapted to cool the pyrolysis gas so as to obtain tar and fuel gas. According to a specific embodiment of the present invention, as shown in
The system for fast pyrolysis of coal according to the embodiments of the present invention employs multilayer regenerative radiant tubes to provide heat sources for the pyrolysis process, the temperature in the pyrolysis process can be controlled accurately by adjusting the flow rate of the fuel gas charged into the regenerative radiant tubes, and the uniformity of temperature field is ensured by quick changeover and regenerative combustion at the two ends of the regenerative radiant tubes; thus, the efficiency of fast pyrolysis of the coal can be significantly improved and thereby the tar yield ratio can be improved. Besides, compared with traditional pyrolysis reaction apparatuses that use a gas heat carrier or solid heat carrier as a heat source for pyrolysis, the system for fast pyrolysis of coal according to the present invention doesn't require a preheating unit and a carrier separation unit, and thereby greatly simplifies the process flow of fast pyrolysis reaction and significantly decreases the failure rate of the apparatus and lower the dust content in the obtained tar. In addition, the apparatus in the present invention employs a material distributor to uniformly distribute the coal in the pyrolysis region and prevent abrasion of the radiant tubes resulted from the coal, and thereby the operating stability of the apparatus is significantly improved.
As shown in
A coal bunker 400: according to the embodiments of the present invention, the coal bunker 400 is adapted to store coal. It should be noted that the “coal bunker” described here may be any device that can be used to store coal in the prior art.
A drying and upgrading tube 500: according to the embodiments of the present invention, the drying and upgrading tube 500 are connected to the fast pyrolysis reactor 100 and the coal bunker 400 respectively, and are adapted to dry and upgrade the coal with hot flue gas before the coal is controlled to have a fast pyrolysis reaction, so as to obtain a mixture that contains cooled flue gas and dry coal. According to an embodiment of the present invention, there is no particular restriction on the temperature of the hot flue gas. Those skilled in the art can select the temperature according to the actual requirement. According to a specific embodiment of the present invention, the temperature of the hot flue gas may be 200-250° C. Thus, the residual heat of the flue gas can be fully utilized to reduce the energy consumption of the system significantly, and any fire hazard incurred by extremely high temperature of the coal can be avoided effectively. Specifically, those skilled in the art may use a cyclone separator to treat the mixture that contains cooled flue gas and dry coal for gas-solid separation, and store the obtained dry coal in the dry coal bunker and then supply the dry coal from the dry coal bunker to the fast pyrolysis reactor for fast pyrolysis reaction; at the same time, the obtained cooled flue gas may be purified and then discharged.
A first blower fan 600: according to the embodiments of the present invention, the first blower fan 600 is connected to the regenerative radiant tubes 15 and the drying and upgrading tube 500 respectively and adapted to supply the high-temperature flue gas produced in the regenerative radiant tubes as hot flue gas to the drying and upgrading tube. Thus, the residual heat of the flue gas can be fully utilized to further reduce the production cost.
As shown in
A tar trough 700: according to the embodiments of the present invention, the tar trough 700 is connected to the spraying tower 300 and adapted to treat the tar by settlement, so as to obtain tar in an upper layer and tar in a lower layer. Specifically, a stratification plate is provided in the tar trough, and the tar in the upper layer and the tar in the lower layer are separated from each other owing to difference in density.
An oil pump 800: according to the embodiments of the present invention, the oil pump 800 is connected to the tar trough 700 and the spraying tower 300 respectively and adapted to supply the tar in the upper layer as a cooling liquid to the spraying tower. Thus, by using the tar separated from the system as a cooling liquid, an additional cooling liquid replenishment system can be omitted, and thereby the capital cost of equipment can be reduced.
A tar storage tank 900: according to the embodiments of the present invention, the tar storage tank 900 is connected to the tar trough 700 and adapted to store the tar in the lower layer. Specifically, the tar in the lower layer can be pumped from the tar trough to the tar storage tank by the oil pump.
A water seal device 1000: according to the embodiments of the present invention, the water seal device 1000 is connected to the spraying tower 300 and adapted to relieve the pressure timely according to the internal pressure in the spraying tower and thereby prevent the occurrence of any safety accident.
As shown in
A fuel gas storage tank 1100: according to the embodiments of the present invention, the fuel gas storage tank 1100 is connected to the spraying tower 300 and adapted to store fuel gas.
A second blower fan 1200: according to the embodiments of the present invention, the second blower fan 1200 is connected to the fuel gas storage tank 1100 and the regenerative radiant tubes 15 respectively and adapted to supply one part of the fuel gas to the regenerative radiant tubes 15. Thus, cyclic utilization of the energy in the system is realized, and thereby the treatment cost is reduced significantly.
A third blower fan 1300: according to the embodiments of the present invention, the third blower fan 1300 is connected to the fuel gas storage tank 1000 and the material distribution gas inlet 102 respectively and adapted to supply the other part of the fuel gas as material distribution gas to the material distribution gas inlet 102. Thus, the coal fed via the coal inlet 101 can be scattered with the fuel gas and thereby uniformly falls into the pyrolysis region.
To facilitate understanding the present invention, hereunder the process in which the system for fast pyrolysis of coal in the embodiments of the present invention is utilized will be detailed.
Specifically, coal (in particle size smaller than 3 mm) is fed via a discharge port on the bottom of the coal bunker into the drying and upgrading tube, the coal in the drying and upgrading tube is dried and upgraded under the action of a hot flue gas (at 200-250° C.) to obtain a mixture that contains cooled flue gas and dry coal (at 80-100° C.); then, the obtained mixture that contains cooled flue gas and dry coal is supplied to the first cyclone separator for gas-solid separation to obtain dry coal and cooled flue gas, the obtained dry coal is stored in the dry coal bunker, and then the dry coal stored in the dry coal bunker is supplied via the first screw conveyer into the reaction space in the fast pyrolysis reactor; the temperature in the pyrolysis process is controlled accurately by adjusting the flow rate of fuel gas and air charged into the regenerative radiant tubes, so that the temperature in the regenerative radiant tubes in the preheating section is controlled within a range of 550-900° C., the temperature in the regenerative radiant tubes in the fast pyrolysis section is controlled within a range of 400-800° C., and the temperature in the regenerative radiant tubes in the complete pyrolysis section is controlled within a range of 500-800° C.; the coal is scattered by the material distributor disposed below the coal inlet and falls down into the dispersion region, so that the coal is uniformly dispersed in the pyrolysis region; the produced pyrolysis gas is discharged via the pyrolysis gas outlets on the side wall and/or the top end of the reactor body, while the semi-coke produced in the pyrolysis process is discharged via the semi-coke outlet to the discharge region, and the high-temperature flue gas produced in the regenerative radiant tubes is supplied by the first blower fan as hot flue gas to the drying and upgrading tubes for drying and upgrading the coal; the pyrolysis gas discharged via the pyrolysis gas outlets is supplied to the second cyclone separator for gas-solid separation to obtain semi-coke particles and pure pyrolysis gas; the obtained semi-coke particles are stored in the semi-coke bunker, and then the semi-coke obtained from the semi-coke outlet and the semi-coke particles stored in the semi-coke bunker are supplied via the second screw conveyer to the slag cooler for cooling, the obtained semi-coke is stockpiled, and the obtained pure pyrolysis gas is supplied to the spraying tower for cooling by spraying; the pyrolysis gas is cooled from 450-500° C. to a temperature lower than 60° C. within 1-2 s, wherein, the oil vapor is captured to form tar and thereby is separated from the fuel gas, and the obtained tar is supplied to the tar trough for settlement treatment; a stratification plate is provided in the tar trough, and the tar is separated into tar in an upper layer and tar in a lower layer owing to the difference in density; the obtained tar in the upper layer is supplied by an oil pump to the spraying tower for spraying the pyrolysis gas, and the obtained tar in the lower layer is pumped by an oil pump into the tar storage tank; at the same time, the fuel gas obtained through separation is stored in the fuel gas storage tank, and then one part of the fuel gas stored in the fuel gas storage tank is supplied by the second blower fan into the regenerative radiant tubes, and the other part of the fuel gas stored in the fuel gas storage tank is supplied by the third blower fan as material distribution gas to the material distribution gas inlet for scattering the coal fed into the coal inlet, so that the coal is dispersed uniformly in the pyrolysis region; the cooled flue gas obtained in the first cyclone separator is supplied to the gas purification unit for purification to obtain purified flue gas, and then the purified flue gas is emitted through a chimney to the air.
As described above, the system for fast pyrolysis of coal according to the embodiments of the present invention may have at least one of the following advantages:
The system for fast pyrolysis of coal according to the embodiments of the present invention can treat medium-rank or low-rank coal in powder form, and can achieve a tar yield ratio higher than the tar yield ratio achieved in Gray-king experiments by 50%. Since tar is a high-value product, the process attains high economic efficiency and benefits, and will be favored widely in the market.
The system for fast pyrolysis of coal according to the embodiments of the present invention employs a regenerative radiant tube technique, can accomplish pyrolysis completely isolated from air in a pyrolysis oven, and utilizes 200° C. hot flue gas to dry the coal, and thereby avoids any fire hazard in the coal drying operation and ensures safety of system operation.
The system for fast pyrolysis of coal according to the embodiments of the present invention utilizes regenerative radiant tubes to provide heat and use heat convection and heat conduction in combination. Thus, the system can provide required temperature field condition and eliminates any heat carrier in the entire process. As a result, the process flow is simplified greatly, the floor space and manufacturing cost of equipment are reduced by a half approximately when compared with similar equipment having the same processing capacity, and the failure-free operation time of the system is increased.
In another aspect of the present invention, the present invention provides a method for fast pyrolysis of coal. According to the embodiments of the present invention, the method utilizes the system for fast pyrolysis of coal described above. Hereunder the method for fast pyrolysis of coal in embodiments of the present invention will be detailed with reference to
S100: treating coal by fast pyrolysis in the fast pyrolysis reactor.
According to the embodiments of the present invention, a material distribution gas is supplied via the material distribution gas inlet to the material distributor, coal is supplied via the coal inlet into the reaction space, a combustible gas and air are supplied into the regenerative radiant tubes respectively, so that the combustible gas is combusted in the regenerative radiant tubes to generate heat to treat the coal by fast pyrolysis and thereby obtain pyrolysis gas and semi-coke.
According to an embodiment of the present invention, there is no restriction on the particle size of the coal. Those skilled in the art can select the particle size according to the actual requirement. According to a specific embodiment of the present invention, the particle size of the coal may be smaller than 3 mm. Thus, a challenge that powder coal can't be utilized in the prior art is overcome. According to another embodiment of the present invention, the fast pyrolysis time of the coal is 2-30 s. Thus, the degree of secondary pyrolysis reaction and cross-linking reaction of the pyrolysis product can be decreased effectively, the yield of fuel gas and semi-coke in the pyrolysis process can be reduced, and thereby the yield ratio of tar can be improved remarkably.
Specifically, the temperature in the pyrolysis process can be controlled accurately by adjusting the flow rate of the fuel gas charged into the regenerative radiant tubes, and a quick changeover value is utilized to control the temperature difference in the temperature field of a single radiant tube to be not higher than 30° C. and thereby ensure temperature uniformity in the temperature field in the reaction space; in addition, through adjustment, the temperature in the regenerative radiant tubes in the preheating section is controlled with a range of 550-900° C., the temperature in the regenerative radiant tubes in the fast pyrolysis section is controlled within a range of 500-800° C., and the temperature in the regenerative radiant tubes in the complete pyrolysis is controlled within a range of 500-800° C.
S200: cooling the semi-coke in the slag cooler
According to the embodiments of the present invention, the semi-coke is supplied via the semi-coke outlet to the slag cooler so as to cool the semi-coke. Specifically, the temperature of the semi-coke obtained from the semi-coke outlet is 500-600° C., and the temperature of the cooled semi-coke obtained from the slag cooler is lower than 50° C.
S300: cooling the pyrolysis gas in the cooling device
According to the embodiments of the present invention, in the cooling device, the pyrolysis gas discharged via the pyrolysis gas outlets is cooled so as to obtain tar and fuel gas. According to a specific embodiment of the present invention, the cooling device may be a spraying tower, in which the pyrolysis gas is sprayed with a cooling liquid to cool the pyrolysis gas. Specifically, there is no particular restriction on the type of the cooling liquid. Those skilled in the art can select the type of the cooling liquid according to the actual requirement. According to a specific embodiment of the present invention, the cooling liquid may be tar. According to another embodiment of the present invention, the pyrolysis gas is cooled from 450-500° C. to a temperature lower than 60° C. within 1-2 s in the spraying tower. Thus, the efficiency of separation between fuel gas and tar can be further improved. Specifically, the pyrolysis gas may be treated with a cyclone separator for gas-solid separation before the pyrolysis gas is supplied to the spraying tower for cooling by spraying, so as to effectively remove semi-coke particles carried in the pyrolysis gas and thereby significantly decrease the dust content in the tar.
The method for fast pyrolysis of coal according to the embodiments of the present invention employs a multilayer regenerative radiant tubes to provide heat sources for the pyrolysis process, the temperature in the pyrolysis process can be controlled accurately by adjusting the flow rate of the fuel gas charged into the regenerative radiant tubes, and the uniformity of temperature field is ensured by quick changeover and regenerative combustion at the two ends of the regenerative radiant tubes; thus, the efficiency of fast pyrolysis of the coal can be significantly improved and thereby the tar yield ratio can be improved. Besides, compared with traditional pyrolysis reaction apparatuses that use a gas heat carrier or solid heat carrier as a heat source for pyrolysis, the method for fast pyrolysis of coal according to the present invention doesn't require a preheating unit and a carrier separation unit, and thereby greatly simplifies the process flow of fast pyrolysis reaction and significantly decreases the failure rate of the apparatus and lowers the dust content in the obtained tar. In addition, the apparatus in the present invention employs a material distributor to uniformly distribute the coal in the pyrolysis region and prevent abrasion of the radiant tubes resulted from the coal, and thereby the operating stability of the apparatus is significantly improved.
As shown in
S400: drying and upgrading the coal with a hot flue gas in a drying and upgrading tube in advance
According to the embodiments of the present invention, before the coal is supplied into the reaction space, it is dried and upgraded with a hot flue gas in the drying and upgrading tube to obtain a mixture that contains cooled flue gas and dry coal. According to an embodiment of the present invention, there is no particular restriction on the temperature of the hot flue gas. Those skilled in the art can select the temperature according to the actual requirement. According to a specific embodiment of the present invention, the temperature of the hot flue gas may be 200-250° C. Thus, the residual heat of the flue gas can be fully utilized to reduce the energy consumption of the system significantly, and any fire hazard incurred by extremely high temperature of the coal can be avoided effectively. Specifically, those skilled in the art may use a cyclone separator to treat the mixture that contains cooled flue gas and dry coal for gas-solid separation, and store the obtained dry coal in the dry coal bunker and then supply the dry coal from the dry coal bunker to the fast pyrolysis reactor for fast pyrolysis reaction; at the same time, the obtained cooled flue gas may be purified and then discharged.
S500: supplying the high-temperature flue gas into the drying and upgrading tubes by means of the first blower fan
According to the embodiments of the present invention, the high-temperature flue gas produced in the regenerative radiant tubes is supplied as hot flue gas by the first blower fan into the drying and upgrading tube. Thus, the residual heat of the flue gas can be fully utilized to further reduce the production cost.
As shown in
S600: supplying the tar to the tar trough for settlement treatment
According to the embodiments of the present invention, the tar is supplied to the tar trough for settlement treatment, so as to obtain tar in an upper layer and tar in a lower layer. Specifically, a stratification plate is provided in the tar trough, and the tar in the upper layer and the tar in the lower layer are separated from each other owing to difference in density.
S700: supplying the tar in the upper layer in the tar trough to the spraying tower with the oil pump
According to the embodiments of the present invention, the tar in the upper layer in the tar trough is supplied as a cooling liquid to the spraying tower with the oil pump. Thus, by using the tar separated from the system as a cooling liquid, an additional cooling liquid replenishment system can be omitted, and thereby the capital cost of equipment can be reduced.
S800: storing the tar in the lower layer in the tar trough into the tar storage tank
According to the embodiments of the present invention, the tar in the lower layer in the tar trough is stored in the tar storage tank. Specifically, the tar in the lower layer can be pumped from the tar trough to the tar storage tank by the oil pump.
As shown in
S900: storing the fuel gas in the fuel gas storage tank
According to the embodiments of the present invention, the fuel gas obtained through separation in the spraying tower is stored in the fuel gas storage tank.
S1000: supplying one part of the fuel gas as fuel to the regenerative radiant tubes by means of the second blower fan
According to the embodiments of the present invention, one part of the fuel gas is supplied as fuel to the regenerative radiant tubes by the second blower fan. Thus, cyclic utilization of the energy in the system is realized, and thereby the treatment cost is reduced significantly.
S1100: supplying the other part of the fuel gas to the material distribution gas inlet by means of the third blower fan
According to the embodiments of the present invention, the other part of the fuel gas is supplied as material distribution gas to the material distribution gas inlet by the third blower fan. Thus, the coal fed via the coal inlet can be scattered with the fuel gas and thereby uniformly falls into the pyrolysis region.
It should be noted that the features and advantages described above in relation with the system for fast pyrolysis of coal also apply to the method for fast pyrolysis of coal and will not be further detailed here.
Hereunder the present invention will be described with reference to specific embodiments. However, it should be noted that those embodiments are only provided to describe the present invention rather than constitute any limitation to the present invention in any way.
This example employs the system for fast pyrolysis of coal shown in
Lignite in particle size smaller than or equal to 1 mm is treated with the system for fast pyrolysis provided in the present invention. The analytical data of the lignite, technological operation parameters, and material balance are shown in Tables 1-3, and the fast pyrolysis time is 30 s. It is seen from Table 3: the tar yield ratio is as high as 12.3 wt %, which is 150% of the tar yield ratio achieved with a Gray-king method; in addition, the dust content in the tar is 2.4 wt %, and the tar can be used directly for coal tar hydrogenation after it is filtered.
55%
This example employs the system for fast pyrolysis of coal shown in
Lignite in particle size with a range of 1-3 mm is treated with the system pair for fast pyrolysis provided in the present invention. The analytical data of the lignite, technological operation parameters, and material balance are shown in Tables 4-6, and the fast pyrolysis time is 2 s. It is seen from Table 6: the tar yield ratio is 9.6 wt %, which is 163% of the tar yield ratio achieved with a Gray-king method; in addition, the dust content in the tar is 2.3 wt %, and the tar can also be used directly for coal tar hydrogenation after it is filtered.
This example employs the system for fast pyrolysis of coal shown in
Lignite in particle size with a range of 1-3 mm is treated with the system pair for fast pyrolysis provided in the present invention. The analytical data of the lignite is the same as that in the example 2, the technological operation parameters and material balance are shown in Tables 7-8, and the fast pyrolysis time is 2.9 s. It is seen from Table 8: the tar yield ratio is 9.9 wt %, which is 168% of the tar yield ratio achieved with a Gray-king method; in addition, the dust content in the tar is 1.5 wt %, and the tar can also be used directly for coal tar hydrogenation after it is filtered.
In the description of the present invention, the expressions of reference terms “an embodiment”, “some embodiments”, “an example”, “specific example”, or “some examples” mean that the specific aspects, structures, materials or features described in those embodiments or examples are included in at least one embodiment or example of the present invention. In this document, the exemplary expression of the above terms may not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined appropriately in any one or more embodiments or examples. Furthermore, those skilled in the art may combine or assemble different embodiments or examples and features in different embodiments or examples described herein, provided that there is no contradiction between them.
While the present invention is illustrated and described above in examples, it should be understood that the examples are exemplary only and shall not be deemed as constituting any limitation to the present invention. Those skilled in the art can made variations, modifications, and replacements to the examples within the scope of the present invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2015/090833 | 9/25/2015 | WO | 00 |
