A lignite dehydration and quality upgrading system

Abstract

The present invention relates to a lignite dehydration and upgrading system, comprising a first mixer, a dryer, a separator, a storage bin, and an induced draft fan. The first mixer is connected to a flue gas generator. The dryer is used to dry the lignite. The dryer comprises a first dryer, a connecting pipe, and a second dryer. The first inlet of the first dryer is connected to a raw coal storage bin storing the lignite, the second inlet of the first dryer is connected to the first mixer, the outlet of the first dryer is connected to the connecting pipe, and the connecting pipe is connected to the inlet of the second dryer. The inlet of the separator is connected to the outlet of the second dryer, and the first outlet of the separator is connected to the second inlet of the first mixer. The induced draft fan is provided in the pipeline between the separator and the first mixer to provide power for the lignite and flue gas to enter the dryer and separator. The present invention maintains a relatively sealed state during the lignite drying and dehydration process, while reducing the oxygen content in the flue, thereby preventing the lignite from burning or even exploding during drying, and improving safety and economic efficiency.

Description

Technical Field

[0001] The invention belongs to the field of lignite drying, and particularly relates to a lignite dehydration and quality-improving system. Background Art

[0002] With the continuous depletion of coal resources, the utilization of inferior, low-rank coal has become a research priority in the energy and chemical industries. my country's lignite reserves account for 13% of its total coal reserves, primarily concentrated in Inner Mongolia, Xinjiang, Heilongjiang, and Yunnan. These regions boast shallow, thick seams, making them easily accessible for mining and a key energy source for future development. While lignite boasts the advantages of cleanliness, low volatility, and low sulfur content, it also suffers from significant disadvantages: high moisture content, a low flash point, and significant greenhouse gas emissions. Lignite contains abundant oxygen-containing functional groups, with oxygen levels as high as 15% to 30%, resulting in high chemical reactivity and poor thermal stability. It is susceptible to weathering, disintegration, and spontaneous combustion due to oxidation. Lignite also has a well-developed microporous structure and a high total moisture content, ranging from 25% to 60%. Lignite's high moisture content and low calorific value limit its further development and utilization. Therefore, drying lignite to reduce its moisture content is crucial for its clean and efficient utilization.

[0003] At present, there are three main types of lignite evaporation drying technologies: rotary drum drying process, fluidized bed drying process, and airflow drying. Rotary drum drying is suitable for continuous drying operations of blocky, muddy and other materials. It has a simple structure and is easy to operate. However, due to the large equipment specifications and high one-time investment, it is not easy to install and disassemble, and there is a certain amount of back-mixing in the dryer. Fluidized bed drying makes the raw coal particles suspended or boiling, and heats the material through conduction and convection, and realizes the evaporation and migration of water, thereby achieving the purpose of drying. However, issues such as oxygen content, ignition, and combustion furnace structure need to be considered. The airflow drying device has a simple structure, a large processing capacity, gas-solid two-phase co-current operation, high thermal efficiency, significant particle dispersion, low material-to-gas ratio, large volume heat transfer coefficient, short material drying time, and low operating costs.

[0004] Chinese patent document CN213955834U discloses a system for upgrading lignite by thermal dehydration using flue gas circulation. This system uses high-temperature flue gas to dehydrate and dry the lignite through a drum dryer. However, the system has the following problems: the equipment is large in size, requires a large one-time investment, is difficult to install and disassemble, and is prone to moisture regeneration.

[0005] Chinese patent document CN104048479A discloses a two-stage fluidized bed lignite drying system based on waste heat recovery. This system uses high-temperature flue gas to dehydrate and dry the lignite through a drum dryer. However, the system has the following problems: the equipment is large in size, requires a large one-time investment, is difficult to install and disassemble, and is susceptible to moisture resorption. In addition, the drying system uses an internally heated fluidized bed as the main drying equipment, and uses steam to dehydrate the lignite. However, compared to the waste heat of the flue gas, steam has a relatively high quality and cannot reduce the oxygen content in the flue, which may cause combustion or even explosion during the drying and dehydration process. Summary of the Invention

[0006] The purpose of the present invention is to provide a lignite dehydration and upgrading system to solve the problems of large one-time investment, difficulty in installation and disassembly, and moisture regeneration in existing drying equipment.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A lignite dehydration and upgrading system, comprising:

[0009] A first mixer has a first inlet and a second inlet, wherein the first inlet of the first mixer is connected to the flue gas generator;

[0010] A dryer for drying lignite, the dryer comprising a first dryer, a connecting pipe, and a second dryer, the first dryer having a first inlet and a second inlet, the first inlet of the first dryer being connected to a raw coal storage bin storing lignite, the second inlet of the first dryer being connected to an outlet of the first mixer, the outlet of the first dryer being connected to the inlet of the connecting pipe, and the outlet of the connecting pipe being connected to the inlet of the second dryer;

[0011] a separator for separating pulverized coal from flue gas, the separator having a first outlet and a second outlet, the inlet of the separator being connected to the outlet of the second dryer, and the first outlet of the separator being connected to the second inlet of the first mixer;

[0012] A storage bin for storing the dried lignite, the storage bin being in communication with the second outlet of the separator;

[0013] The induced draft fan is arranged on the pipeline between the first outlet of the separator and the second inlet of the first mixer and is used to provide power for the lignite and smoke to enter the dryer and the separator.

[0014] Preferably, the first dryer is connected to the flue gas generator via a pipeline, and a flow meter is provided on the pipeline, and the flow meter is used to adjust the flow of flue gas entering the dryer.

[0015] Preferably, a flow meter is provided on the pipeline connecting the first inlet of the first mixer and the flue gas generator, and the flow meter is used to adjust the flow of flue gas entering the first mixer.

[0016] Preferably, the system further comprises a second mixer, and the second mixer is arranged between the first dryer and the connecting pipe, or between the connecting pipe and the second dryer.

[0017] Preferably, the connecting pipe is arc-shaped, and the arc-shaped connecting pipe bends in a direction away from the first dryer and the second dryer.

[0018] Preferably, the first dryer and the second dryer are both columnar, and the diameter of the second dryer is larger than that of the first dryer.

[0019] Preferably, the first mixer, the dryer, and the separator are detachably connected.

[0020] Preferably, the diameter of the second inlet of the first dryer gradually increases; and the diameter of the outlet of the first dryer gradually narrows.

[0021] Preferably, the diameter of the inlet of the second dryer gradually increases, and the diameter of the outlet of the second dryer gradually narrows.

[0022] Preferably, the system also includes a dust collector, the separator has a first outlet and a second outlet, the inlet of the separator is connected to the outlet of the second dryer, the first outlet of the separator is connected to the storage bin, and the second outlet of the separator is connected to the inlet of the dust collector; the dust collector has a first outlet and a second outlet, the first outlet of the dust collector is connected to the storage bin, and the second outlet of the dust collector is connected to the first mixer.

[0023] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: the present invention provides a first mixer, a dryer, a separator, and an induced draft fan, so that the lignite drying and dehydration process is in a relatively sealed state, while reducing the oxygen content in the flue, avoiding the occurrence of lignite combustion or even explosion during the drying and dehydration process, thereby improving system safety and lignite quality; the flue gas recycling utilizes the waste heat of the power plant boiler flue gas, reduces flue gas emissions, and improves operating economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Attachment Figure 1 This is a schematic structural diagram of the lignite dehydration and upgrading system of the present invention;

[0025] Attachment Figure 2It is a structural schematic diagram of the dryer of the present invention.

[0026] In the above drawings: 1-raw coal storage bin, 2-screw feeder, 3-dryer, 31-first dryer, 32-connecting pipe, 33-second dryer, 4-second mixer, 5-separator, 7-induced draft fan, 8-storage bin, 9-first mixer, 10-flow meter on the pipeline connecting the first mixer and the flue gas generator; 11-flue gas generator; 12-flow meter on the pipeline between the first dryer and the flue gas generator. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings.

[0028] like Figure 1 、 Figure 2 The lignite dehydration and upgrading system shown includes a first mixer 9, a dryer 3, a separator 5, a storage bin 8, and an induced draft fan 7.

[0029] The lignite to be processed is stored in the raw coal storage bin 1. The lignite in the raw coal storage bin 1 is fed into the dryer 3 through a screw feeder 2. The speed of the screw feed motor can be adjusted according to the moisture content of the lignite to control the flow of the lignite entering the dryer 3.

[0030] The first mixer 9 is structured as follows: it has an inlet, a first inlet, and a second inlet. The first inlet of the first mixer 9 is connected to the flue gas generator 11. High-temperature hot air is used as the dryer's heat source. The flue gas waste heat generated by the high-temperature flue gas generator 11 enters the dryer 3. The waste heat passes through the first mixer 9 before entering the dryer 3. The first mixer 9 allows the new high-temperature flue gas to be fully mixed with the old flue gas, regulating the flue gas temperature and preventing excessive temperatures from causing combustion or even explosion during the lignite drying and dehydration process.

[0031] The structure of the dryer 3 is as follows: Figure 2 The dryer 3 is used to dry lignite. The dryer 3 includes a first dryer 31, a connecting pipe 32 and a second dryer 33. The first dryer 31 has a first inlet, a second inlet and an outlet. The first inlet of the first dryer 31 is connected to the raw coal storage bin 1 for storing lignite, the second inlet of the first dryer 31 is connected to the outlet of the first mixer 9, and the outlet of the first dryer 31 is connected to the inlet of the connecting pipe 32.

[0032] The connecting pipe 32 and the second dryer 33 both have an inlet and an outlet. The inlet of the connecting pipe 32 is communicated with the outlet of the first dryer 31 , and the outlet of the connecting pipe 32 is communicated with the inlet of the second dryer 33 .

[0033] Both the first dryer 31 and the second dryer 33 are graded pulse dryers. After the lignite enters the first dryer 31 and undergoes thermal dehydration and drying, the flue gas and lignite then enter the connecting pipe 32 and the second dryer 33, where thermal dehydration and drying continue, improving the quality of the lignite. Pulse dryers are large-scale drying equipment that utilizes the principle of instantaneous drying. They utilize the rapid movement of heated air to propel the wet material, suspending it in the hot air. This intensifies the drying process and increases the rates of heat and mass transfer. Airflow drying virtually eliminates all unbound moisture from the material, preventing deterioration. This significantly increases yield compared to conventional dryers.

[0034] The connecting pipe 32 is arc-shaped and bends in a direction away from the first dryer 31 and the second dryer 33. If the connecting pipe 32 is semicircular, the connecting pipe 32 serves to slow down the flow rate of the flue gas and lignite to increase the residence time of the two, increase the contact time between the two, and further dry the lignite.

[0035] The second dryer 33 further dries the lignite and removes moisture from the lignite to improve the quality of the lignite.

[0036] The first dryer 31 and the second dryer 33 are both columnar. The diameter of the second dryer 33 is larger than that of the first dryer 31 to increase the residence time of the flue gas and the lignite in the second dryer 33, thereby increasing the drying time and further drying the lignite.

[0037] After thermal dehydration and drying in the dryer, the lignite passes through separator 5, which is used to separate the pulverized coal from the flue gas. Separator 5 has a first outlet and a second outlet. The inlet of separator 5 is connected to the outlet of second dryer 33. The first outlet of separator 5 is connected to the second inlet of first mixer 9, and the second outlet of separator 5 is connected to storage bin 8. The separated pulverized coal enters storage bin 8 for storing the dried lignite. The separated flue gas enters first mixer 9 through induced draft fan 7.

[0038] The diameter of the second inlet of the first dryer 31 gradually increases, that is, the diameter of the second inlet of the first dryer 31 gradually increases from close to the first mixer 9 to away from the first mixer 9, and the flue gas and lignite gradually enter; the diameter of the outlet of the first dryer 31 gradually narrows, that is, the diameter of the outlet of the first dryer 31 gradually narrows from close to the connecting pipe 32 to away from the connecting pipe 32, slowing down the flow rate and increasing the residence time of the flue gas and coal powder.

[0039] The diameter of the inlet of the second dryer 33 gradually increases, that is, the diameter of the second inlet of the second dryer 33 gradually increases from close to the connecting pipe 32 to away from the connecting pipe 32, and the flue gas and lignite gradually enter; the diameter of the outlet of the second dryer 33 gradually narrows, that is, the diameter of the outlet of the second dryer 33 gradually narrows from close to the separator 5 to away from the separator 5, slowing down the flow rate and increasing the residence time of the flue gas and coal powder.

[0040] The system also includes a dust collector, the separator 5 has a first outlet and a second outlet, the inlet of the separator 5 is connected to the outlet of the second dryer 33, the first outlet of the separator 5 is connected to the storage bin 8, and the second outlet of the separator 5 is connected to the inlet of the dust collector; the dust collector has a first outlet and a second outlet, the first outlet of the dust collector is connected to the storage bin 8, and the second outlet of the dust collector is connected to the first mixer 9.

[0041] The separator 5 separates the large particles of lignite and retains them in the separator 5 under the action of its own gravity. The large particles of lignite then directly enter the storage bin 8. The coarse-fine separator 5 is the best separator 5; the small particles of coal powder enter the dust collector, and after being captured by the dust collector, they also enter the storage bin 8. The dust collector is the best dust collector. The dust is collected in the bag of the bag dust collector, further improving the quality of the lignite. The coarse-fine separator 5 relies on its own gravity to collect large particles of lignite and does not require electricity consumption. The bag dust collector collects dust from the flue gas and lignite when it is powered on, which consumes a lot of energy. The large particles of lignite are first separated by the separator 5, and then the dust is collected by the bag dust collector, which greatly reduces energy consumption. The coarse-fine separator 5 and the bag dust collector are both conventional equipment in this technical field, and their structures are not described in detail.

[0042] The induced draft fan 7 is arranged on the pipeline between the first outlet of the separator 5 and the second inlet of the first mixer 9 to provide power for the lignite and flue gas to enter the dryer and separator 5. The lignite is relatively light in weight, and the negative pressure at the induced draft fan 7 is large. The lignite and flue gas enter the dryer and separator 5 in sequence. In the process of mixing the lignite and the flue gas, the high temperature of the flue gas is used to dry the lignite; the flue gas separated by the separator 5 is recycled into the first mixer 9 through the induced draft fan 7.

[0043] Flue gas is circulated between the first mixer 9, dryer, separator 5, and induced draft fan 7, fully utilizing the flue gas and saving energy. Furthermore, as the flue gas temperature decreases during circulation, new high-temperature flue gas can be introduced into the first mixer 9 (the new high-temperature flue gas is relatively high in temperature and could cause the lignite to burn if introduced directly into the dryer). Once the new high-temperature flue gas is evenly mixed with the old relatively low-temperature flue gas in the first mixer 9, the temperature is adjusted to a moderate level. The mixed flue gas then enters the dryer, effectively drying the lignite. Furthermore, due to the flue gas circulation, moisture reversal is prevented.

[0044] In order to better improve the drying effect, the system also includes a second mixer 4, which is arranged between the first dryer 31 and the connecting pipe 32, or between the connecting pipe 32 and the second dryer 33. When the water content of the lignite is large, the second mixer 4 is added, and the new high-temperature flue gas and the old high-temperature flue gas are further mixed in the second mixer 4, and an additional flue gas conveying channel is provided, so that the lignite and flue gas can be fully and evenly mixed in the second dryer 33, thereby increasing the contact time between the flue gas and the lignite, increasing the drying time, and further drying the lignite.

[0045] The first mixer 9 and the second mixer 4 can both be shells with accommodating space, and guide plates are provided in the shells to increase the time that the flue gas and lignite stay in the shells, so that the surface of the lignite is fully in contact with the hot mixed airflow, achieving a good drying effect.

[0046] The first dryer 31 is connected to the flue gas generator 11 through a pipeline, and a flow meter 12 is provided on the pipeline. The flow meter 12 is used to adjust the flue gas flow entering the dryer. One end of the pipeline is connected to the flue gas generator 11, and the other end is connected to the first dryer 31. It is optimal when the other end is connected to the outlet of the first dryer 31; a flow meter 10 is provided on the pipeline connecting the first inlet of the first mixer 9 and the flue gas generator 11. The flow meter 10 is used to adjust the flue gas flow entering the first mixer 9.

[0047] According to the moisture content of the lignite (approximately 25% to 60%), the flue gas volume is distributed by adjusting either or both of the two flow meters: when the moisture content of the lignite is high (the moisture content of the lignite is 45%-60%), the flow meter on the pipeline between the first dryer 31 and the flue gas generator 11 can be adjusted to increase the flow of high-temperature flue gas. The flue gas is decelerated after passing through the connecting pipe 32 and enters the second mixer 4 or the second dryer 33 for uniform mixing. When the moisture content of the lignite is low (the moisture content of the lignite is 25%-45%), the flow meter on the pipeline between the first dryer 31 and the flue gas generator 11 does not need to be adjusted. Only the flow meter on the pipeline connecting the first inlet of the first mixer 9 and the flue gas generator 11 needs to be adjusted to adjust the flue gas flow.

[0048] The first mixer 9, the dryer, and the separator 5 are detachably connected. When in use, the first mixer 9 is connected to the dryer, and the dryer is connected to the separator 5, so that the lignite drying and dehydration process is in a relatively sealed state. When not in use, the first mixer 9 is separated from the dryer, and the dryer is separated from the separator 5. The first mixer 9, the dryer, and the separator 5 can be stored separately. The overall system is easy to install and disassemble, the overall system specifications are not large, and the one-time investment is not much.

[0049] During the lignite drying and dehydration process, this system is in a relatively sealed state after the first mixer, dryer, separator, storage bin, and induced draft fan are connected. Combined with the use of waste heat from the flue gas of the power plant boiler through flue gas recycling, compared with drying the lignite by air heating, it can reduce the oxygen content in the lignite circulation channel (the oxygen content in hot flue gas is low), avoid the occurrence of lignite combustion or even explosion during the drying and dehydration process, and improve system safety; by fully utilizing the flue gas, flue gas emissions are reduced and operating economy is improved.

[0050] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A lignite dehydration and upgrading system, characterized by: The system comprises: A first mixer has a first inlet and a second inlet, wherein the first inlet of the first mixer is connected to the flue gas generator; A dryer for drying lignite, the dryer comprising a first dryer, a connecting pipe, and a second dryer, the first dryer having a first inlet and a second inlet, the first inlet of the first dryer being connected to a raw coal storage bin storing lignite, the second inlet of the first dryer being connected to an outlet of the first mixer, the outlet of the first dryer being connected to the inlet of the connecting pipe, and the outlet of the connecting pipe being connected to the inlet of the second dryer; a separator for separating pulverized coal from flue gas, the separator having a first outlet and a second outlet, the inlet of the separator being connected to the outlet of the second dryer, and the first outlet of the separator being connected to the second inlet of the first mixer; A storage bin for storing dried lignite, the storage bin being connected to the second outlet of the separator; an induced draft fan disposed on a pipeline between the first outlet of the separator and the second inlet of the first mixer for providing power for the lignite and flue gas to enter the dryer and the separator; The first dryer is connected to the flue gas generator via a pipeline, and a flow meter is provided on the pipeline to adjust the flow of flue gas entering the dryer; A flow meter is provided on the pipeline connecting the first inlet of the first mixer and the flue gas generator, and the flow meter is used to adjust the flow of flue gas entering the first mixer; The system further includes a second mixer, which is disposed between the first dryer and the connecting pipe, or between the connecting pipe and the second dryer; the connecting pipe is arc-shaped, and the arc-shaped connecting pipe is bent in a direction away from the first dryer and the second dryer; The first dryer and the second dryer are both columnar, and the diameter of the second dryer is larger than that of the first dryer; The first mixer and the second mixer are both provided with guide plates; The diameter of the second inlet of the first dryer gradually increases; the diameter of the outlet of the first dryer gradually narrows; The diameter of the inlet of the second dryer gradually increases, and the diameter of the outlet of the second dryer gradually narrows; The system also includes a dust collector, the separator has a first outlet and a second outlet, the inlet of the separator is connected to the outlet of the second dryer, the first outlet of the separator is connected to the storage bin, and the second outlet of the separator is connected to the inlet of the dust collector; the dust collector has a first outlet and a second outlet, the first outlet of the dust collector is connected to the storage bin, and the second outlet of the dust collector is connected to the first mixer.

2. The lignite dehydration and upgrading system according to claim 1, characterized in that: The first mixer, the dryer and the separator are detachably connected.

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