A low-quality coal dewatering-dry method deslagging and whole grain upgrading process and method

Abstract

The present application relates to the technical field of coal separation, and provides a low-quality coal dehydration-dry method deslagging and full-grain-level upgrading process and method.According to the water content of different grain-level coal and its interference effect on the separation effect, the upgrading process of dehydrating the fine particles under the screen first and then deslagging, and deslagging the coarse coal above the screen first and then dehydrating, can realize the full-grain-level upgrading of low-quality coal, greatly improve the calorific value and clean coal yield of low-quality coal, and reduce energy loss and production cost;and the present application has high separation precision, does not need to use water in the separation process, and will not produce coal slurry and coal slime, and the process flow is simple.The results of the examples show that the present application can effectively upgrade the high-moisture sticky low-quality coal, and the yield and calorific value of the obtained clean coal are high.

Description

Technical Field

[0001] This invention relates to the field of coal sorting technology, and in particular to a process and method for synergistic whole-size upgrading of low-quality coal by dehydration-dry deashing. Background Technology

[0002] Coal, as my country's primary energy source, occupies a crucial position in the country's energy production and consumption structure. However, with the development of the industrial economy, the consumption of high-quality coal resources is enormous, while the demand for and utilization rate of low-quality coal resources are increasing. However, low-quality coal has disadvantages such as high impurity content, high moisture content, and low calorific value, severely limiting its utilization value.

[0003] Low-quality coal is characterized by high impurity content, high moisture content, and low calorific value, necessitating deashing and dehydration for upgrading before utilization. However, low-quality coal is prone to mud formation, making wet sorting difficult, while dry sorting has strict requirements on the external moisture content of the raw coal, limiting the application of deashing technology. Furthermore, existing coal dewatering technologies suffer from high processing costs and pollutant emissions. Therefore, dewatering and deashing low-quality coal has become a key issue in its processing and utilization.

[0004] The patent with publication number CN111841872A discloses a comprehensive process for improving the quality and efficiency of low-quality coal resources. In this process, narrow-particle-size raw coal and fine-particle-size raw coal obtained from screening are separated in a shallow trough separator. The shallow trough separator is a trough-type separation device that works based on the principle of sinking and floating of materials with different specific gravities in a heavy medium suspension. Water is required during the separation process, and a large amount of coal slurry and coal mud that are difficult to handle are generated during the separation process. Furthermore, the coal will absorb water again during the separation process, which will reduce the quality of the coal.

[0005] In summary, there is an urgent need to provide a method for improving the quality of low-grade coal that is simple to operate, environmentally friendly, and can effectively improve the quality of low-grade coal. Summary of the Invention

[0006] In view of this, the present invention provides a process and method for synergistic whole-size upgrading of low-quality coal through dehydration and dry deashing. The method provided by the present invention is simple to operate, environmentally friendly, and can effectively improve the calorific value of low-quality coal and the yield of clean coal.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] A method for synergistic whole-particle-scale upgrading of low-quality coal through dehydration and dry deashing includes the following steps:

[0009] Low-quality coal is screened and graded to obtain oversize and undersize products; the external moisture content of the oversize product is <9 wt%.

[0010] The oversize material is separated using a composite dry separation method to obtain a first portion of clean coal and a first portion of gangue; when the net calorific value of the first portion of clean coal is lower than 19.01 MJ / Kg, the first portion of clean coal is dehydrated.

[0011] The undersize material is dehydrated and then subjected to ZM mineral high-efficiency separation to obtain a second portion of clean coal and a second portion of gangue.

[0012] Preferably, the total water and ash content in the low-quality coal is ≥30wt%.

[0013] Preferably, the screening and grading is a dry screening; the aperture of the grading sieve used for dry screening is 6 mm or 13 mm.

[0014] Preferably, the composite dry separation method is performed using a composite dry separator; the operating parameters of the composite dry separation method include: a vibration frequency of 42~45Hz and an air supply volume of 0.9~1.1m³. 3 / s, sorting time is 3~5min.

[0015] Preferably, the method for dewatering the first portion of clean coal is vibration mixing drying or steam thermo-pressure dewatering.

[0016] Preferably, the operating parameters of the vibratory mixed-flow dryer include: a feed rate of 80~100 t / h and a hot air volume of 160,000~200,000 m³ / h. 3 / h, the dryer inlet temperature is 230~250℃;

[0017] The operating parameters for steam temperature and pressure dehydration include: pressure of 2~4MPa and pressure holding time ≤10min.

[0018] Preferably, the method for dehydrating the undersize material is steam thermo-pressure dehydration or drum drying.

[0019] Preferably, the operating parameters of the drum dryer include: hot flue gas temperature of 420~450℃ and inclination of 3%~5%.

[0020] Preferably, the undersize material is dehydrated to an external moisture content of ≤10wt%.

[0021] Preferably, the high-efficiency separation of ZM minerals is carried out in a high-efficiency ZM mineral separator; the operating parameters of the high-efficiency separation of ZM minerals include: feed rate of 100~120t / h and feed particle size of -13mm.

[0022] This invention provides a method for the synergistic upgrading of low-quality coal through dehydration and dry deashing across the entire particle size distribution, comprising the following steps: screening and classifying the low-quality coal to obtain oversize and undersize; the external moisture content of the oversize is <9wt%; using a composite dry separation method to separate the oversize to obtain a first portion of clean coal and a first portion of gangue; when the net calorific value of the first portion of clean coal is lower than 19.01 MJ / Kg, the first portion of clean coal is dehydrated; after dehydration, the undersize is subjected to ZM mineral high-efficiency separation to obtain a second portion of clean coal and a second portion of gangue. This invention, based on the moisture content of different coal particle sizes and its interference with the separation effect, employs an upgrading process that first dehydrates and then deashes the fine particles under the screen, and first deashes and then dehydrates the coarse particles over the screen. This process can achieve full-size upgrading of low-quality coal, significantly increasing the calorific value and clean coal yield, while reducing energy loss and production costs. Furthermore, this invention uses a composite dry separation method to separate the coarse particles over the screen and a ZM mineral high-efficiency separation method to separate the fine particles under the screen. This results in high separation accuracy, eliminates the need for water during the separation process, and avoids the generation of coal slurry and mud, thus eliminating the need for a coal slurry treatment system. The process is simple, low-cost, and does not cause the coal to absorb water during separation, further ensuring the quality of the clean coal. Example results show that the method of this invention can effectively upgrade high-moisture, sticky, low-quality coal, resulting in high clean coal yield, high calorific value, and high separation accuracy (E value: 0.15~0.18 g / cm³). 3 . Attached Figure Description

[0023] Figure 1 A process flow diagram for a method of synergistic whole-size upgrading of low-quality coal through dehydration, dry deashing, and processing. Detailed Implementation

[0024] This invention provides a method for synergistic whole-size upgrading of low-quality coal through dehydration and dry deashing, comprising the following steps:

[0025] Low-quality coal is screened and graded to obtain oversize and undersize products; the external moisture content of the oversize product is <9 wt%.

[0026] The oversize material is separated by a composite dry separation method to obtain a first portion of clean coal and a first portion of gangue. When the net calorific value of the first portion of clean coal is lower than 19.01 MJ / Kg, the first portion of clean coal is dehydrated.

[0027] The undersize material is dehydrated and then subjected to ZM mineral high-efficiency separation to obtain a second portion of clean coal and a second portion of gangue.

[0028] In this invention, the low-quality coal specifically refers to high-moisture, viscous, low-quality coal.

[0029] The total water and ash content in low-quality coal is preferably ≥30wt% (water is calculated as total moisture content), more preferably 30~65%; specifically, the water content of the low-quality coal is preferably 20~35wt%, and the ash content is preferably 10~30wt%; unless otherwise specified, the "water content" in this invention refers to the total moisture content, and will not be elaborated further.

[0030] This invention classifies low-quality coal (hereinafter referred to as raw coal) by screening to obtain oversize and undersize materials. In this invention, the screening and grading are preferably performed using dry screening; the aperture of the grading screen used for dry screening is preferably 6mm or 13mm; and the external moisture content of the oversize material is preferably <9wt%. In a specific embodiment of this invention, the particle size for screening is preferably determined based on the external moisture content of different particle sizes of raw coal. Specifically, the external moisture content of raw coal with a particle size of +6mm and +13mm is first tested. If the external moisture content of +6mm raw coal is <9wt%, a 6mm screen is used for screening; if the external moisture content of +13mm raw coal is <9wt%, a 13mm screen is used for screening. This invention controls the external moisture content of the oversize material to <9wt%, ensuring the separation effect of the oversize material entering the composite dry separator.

[0031] After obtaining the oversize material, this invention employs a composite dry separation method to separate the oversize material, obtaining a first portion of clean coal and a first portion of gangue. When the net calorific value of the first portion of clean coal is lower than 19.01 MJ / Kg, the first portion of clean coal is dewatered. In this invention, the composite dry separation method preferably uses a composite dry separator; the preferred operating parameters of the composite dry separation method include: a vibration frequency of 42~45Hz, preferably 43~44Hz, and an air supply of 0.9~1.1 m³ / kg. 3 / s, preferably 1.0m 3 / s, sorting time is 3~5min.

[0032] In this invention, after sorting, the calorific value of the first portion of clean coal is preferably tested. If the received lower heating value is greater than or equal to 19.01 MJ / Kg, dehydration is not required, and it is directly collected as a product. If the received lower heating value is less than 19.01 MJ / Kg, the first portion of clean coal is dehydrated. Unless otherwise specified, the calorific value mentioned in this invention is based on the received lower heating value. In this invention, the method for dehydrating the first portion of clean coal is preferably vibratory mixed-flow drying or steam thermo-pressure dehydration. This invention does not have special requirements for the equipment used in the vibratory mixed-flow drying or steam thermo-pressure dehydration; any equipment well known to those skilled in the art can be used. The vibratory mixed-flow drying system preferably includes a hot blast stove, a settling chamber, a hot blast fan, a dryer, a coal feeder, a coal discharger, a bag filter, a discharger, and an exhaust fan. The equipment used in the steam thermo-pressure dehydration preferably consists of a steam generator, a steam dehydration device, a steam recovery device, and a feeding system.

[0033] In this invention, the preferred operating parameters for the vibratory mixed-flow drying include: a feed rate of 80-100 t / h, preferably 90-100 t / h, and a hot air volume of 160,000-200,000 m³ / h. 3 / h, preferably 180,000~200,000m 3 The dryer inlet temperature is 230~250℃ / h; the preferred operating parameters for the steam temperature and pressure dehydration include: pressure of 2~4MPa and holding time ≤10min. Through the vibration mixed-flow drying or steam temperature and pressure dehydration, the moisture content (total moisture) of the clean coal can be reduced to approximately 10wt%. In a specific embodiment of the invention, the dehydration rate of the clean coal is preferably calculated based on an increase in calorific value of 0.251MJ / Kg for every 1wt% decrease in moisture content. In other specific embodiments of the invention, even after dehydration to a very low moisture content, the calorific value of some coals remains below 19.01MJ / Kg, or calculations show that the maximum dehydration rate of the drying equipment cannot reach the calculated dehydration rate. In such cases, the target product moisture content is determined by the maximum moisture removal rate of the dehydration equipment.

[0034] After obtaining the undersize, the present invention dehydrates the undersize and then performs ZM mineral high-efficiency separation to obtain a second portion of clean coal and a second portion of gangue. In this invention, the dehydration method for the undersize is steam thermo-pressure dehydration or drum drying; the operating parameters for drum drying include: hot flue gas temperature of 420~450℃, preferably 420~430℃, and inclination of 3%~5%, preferably 3%~4%; drum drying can reduce the moisture content of the clean coal to approximately 10wt%. In this invention, the steam thermo-pressure dehydration method is preferably the same as the above-described scheme, and will not be repeated here. This invention weakens the liquid bridge adhesion and agglomeration of fine particles through dehydration, thereby enhancing the separation effect of coal and gangue in the ZM mineral high-efficiency separator.

[0035] In this invention, the undersize material is preferably dehydrated to an external moisture content of ≤10wt%; the received low-base calorific value of the second portion of clean coal is preferably ≥19.01MJ / kg; in a specific embodiment of this invention, if some coal still has a calorific value of less than 19.01MJ / kg even after dehydration to a very low moisture content, then the moisture content of the target product is determined by the maximum moisture removal rate of the dehydration equipment.

[0036] In this invention, the high-efficiency separation of ZM minerals is carried out in a high-efficiency ZM mineral separator. The operating parameters of the high-efficiency ZM mineral separator include: a feed rate of 100~120 t / h, preferably 105~115 t / h, and a feed particle size of -13 mm. In this invention, the high-efficiency ZM mineral separator operates in a fully enclosed state, and the equipment uses a bag filter for dust removal, resulting in no dust emissions and making it environmentally friendly.

[0037] In this invention, the two products, clean coal and gangue, are preferably transported to the clean coal silo and gangue silo respectively by belt conveyors.

[0038] Figure 1 This invention presents a process flow diagram for a method of synergistic whole-size upgrading of low-quality coal through dehydration and dry deashing. Based on the moisture content of different coal particle sizes and its interference with the sorting effect, this invention employs a method of grading – dehydration followed by deashing of undersize fine particles – deashing followed by dehydration of oversize coarse particles for whole-size upgrading of low-quality coal. Specifically, the grading process uses 13mm or 6mm grading screens. Oversize lump coal undergoes composite force field separation (i.e., composite dry separation). Dehydration is assessed based on the calorific value of the product. Undersize fine coal is first dried and dehydrated, and then subjected to composite force field separation (i.e., ZM mineral high-efficiency separation). The method provided by this invention is suitable for upgrading low-quality coal with high water and ash content. It has the advantages of simple process, high sorting accuracy, high calorific value of the obtained clean coal, high clean coal yield, and low energy loss and production cost.

[0039] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] Example 1

[0041] The raw coal has a moisture content of 27% (total moisture) and a total water and ash content of 43%. Its net calorific value (LCV) is 13.2 MJ / kg. The external moisture content of the +13mm raw coal is less than 9%. The raw coal enters a 13mm grading screen and is classified using a dry screening method. The oversize material after grading enters a compound dry separator to obtain two products: clean coal and gangue. The LCV of the clean coal after separation is 14.9 MJ / kg, lower than 19.01 MJ / kg. The gangue product is transported to the gangue silo by a belt conveyor. The clean coal undergoes vibratory mixed-flow drying (dryer inlet temperature 230℃, hot air volume 170,000 m³ / h). 3 The difference between the received lower heating value of the first part of the clean coal and the heating value of the target product is 4.1 MJ / Kg. Based on the calculation that a 1 wt% decrease in moisture content increases the heating value by 0.251 MJ / Kg, the moisture content of the target product needs to be lower than 10.7 wt%. After dehydration, the moisture content of the clean coal product is 10%, and the received lower heating value is 19.2 MJ / Kg. The dehydrated clean coal is transported to the clean coal silo by a belt conveyor. After the raw coal is graded, the undersize material is first dried by drum drying (hot flue gas temperature is 420℃, inclination is 3%) to dehydrate to an external moisture content of less than 10%. The dehydrated product enters the ZM mineral high-efficiency separator for separation to obtain two products: clean coal (external moisture content is 4%, received lower heating value is 19.3 MJ / Kg) and gangue, which are transported to the clean coal silo and gangue silo by belt conveyors, respectively. Calculations show that the total clean coal yield in this embodiment is 98.5%, and the separation accuracy E value is 0.17 g / cm³. 3 .

[0042] Example 2

[0043] The raw coal has a moisture content of 35% (total moisture), a total water and ash content of 55%, and a net calorific value of 8.2 MJ / Kg on an as-received basis. The external moisture content of the +6mm raw coal is less than 9%. The raw coal enters a 6mm grading screen and is graded by dry screening. After the raw coal is graded, the oversize material enters a compound dry separator to separate into two products: clean coal and gangue. The net calorific value of the clean coal after separation is 10.6 MJ / kg, which is lower than 19.01 MJ / kg. The gangue product is transported to the gangue silo by a belt conveyor. The clean coal undergoes steam thermo-pressure dehydration (pressure 3MPa, holding time 6min). The difference between the net calorific value of the first part of the clean coal and the calorific value of the target product is 8.41 MJ / kg. According to the principle that a 1wt% decrease in moisture content increases the calorific value by 0.251 MJ / kg, the moisture content of the target product must be lower than 1.5wt%. At this point, the moisture content of the target product can be determined based on the maximum moisture removal rate of the dehydration equipment. After dehydration, the moisture content of the clean coal product is 11wt%, and the net calorific value is 16.6 MJ / kg. It is then transported to the clean coal silo by a belt conveyor. After raw coal grading, the undersize material is first subjected to steam thermo-pressure dehydration (pressure 4 MPa, holding time 6 min). The moisture content of the target product is determined based on the maximum moisture removal rate of the dehydration equipment. The dehydrated product then enters a ZM high-efficiency mineral separator for further separation, yielding two products: clean coal (external moisture content 5%, net calorific value 16.8 MJ / kg) and gangue. These products are then transported to the clean coal silo and gangue silo respectively by conveyor belts. Calculations show that the total clean coal yield in this embodiment is 98.2%, and the separation accuracy E value is 0.18 g / cm³. 3 .

[0044] Example 3

[0045] The raw coal has a moisture content of 22% (total moisture) and a total water and ash content of 34%. Its net calorific value (calorific value) on an as-received basis is 18.8 MJ / kg. The external moisture content of the +6mm raw coal is less than 9%. The raw coal enters a 6mm grading screen and is classified using a dry screening method. After grading, the oversize material enters a compound dry separator to obtain two products: clean coal and gangue. The calorific value of the clean coal after separation is 19.1 MJ / kg, higher than 19.01 MJ / kg. The clean coal and gangue products are transported to the clean coal silo and gangue silo respectively by belt conveyors. After the raw coal is graded, the undersize material is first dried in a drum dryer (hot flue gas temperature 430℃, inclination 4%) to remove moisture to below 10%. The dehydrated product then enters a ZM high-efficiency mineral separator for further separation, yielding two products: clean coal (external moisture 8%, net calorific value 21.1 MJ / Kg) and gangue. These are then transported to the clean coal and gangue silos by conveyor belts, respectively. Calculations show that the total clean coal yield in this embodiment is 99.7%, and the separation accuracy E value is 0.15 g / cm³. 3 .

[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synergistic whole-scale upgrading of low-quality coal through dehydration-dry deashing, characterized in that, The steps are as follows: Low-quality coal is screened and graded to obtain oversize and undersize materials; the external moisture content of the oversize material is <9 wt%; the screening and grading is a dry screening method; the aperture of the grading sieve used for dry screening is 6 mm or 13 mm; the particle size for screening is determined according to the external moisture content of different particle sizes of raw coal. If the external moisture content of +6 mm raw coal is <9 wt%, a 6 mm sieve is used for screening; if the external moisture content of +13 mm raw coal is <9 wt%, a 13 mm sieve is used for screening; the moisture content of the low-quality coal is 20-35 wt%, and the ash content is 10-30 wt%. The oversize material is separated using a composite dry separation method to obtain a first portion of clean coal and a first portion of gangue; when the net calorific value of the first portion of clean coal is lower than 19.01 MJ / Kg, the first portion of clean coal is dehydrated. The undersize material is dewatered and then subjected to ZM mineral high-efficiency separation to obtain a second portion of clean coal and a second portion of gangue; the undersize material is dewatered to an external moisture content of ≤10wt%; The method for dewatering the first portion of clean coal is vibration mixed-flow drying or steam thermo-pressure dewatering; the operating parameters for vibration mixed-flow drying include: feed rate of 80-100 t / h, hot air volume of 160,000-200,000 m³ / h. 3 / h, the dryer inlet temperature is 230~250℃; the operating parameters of the steam temperature and pressure dehydration include: pressure 2~4MPa, pressure holding time ≤10min; The method for dehydrating the undersize material is steam temperature and pressure dehydration or drum drying; the operating parameters for drum drying include: hot flue gas temperature of 420-450℃ and inclination of 3%-5%.

2. The method according to claim 1, characterized in that, The composite dry separation method is performed using a composite dry separator; the operating parameters of the composite dry separation method include: a vibration frequency of 42–45 Hz and an air supply volume of 0.9–1.1 m³ / s. 3 / s, sorting time is 3-5 minutes.

3. The method according to claim 1, characterized in that, The ZM mineral high-efficiency separation is carried out in a ZM mineral high-efficiency separator; the operating parameters of the ZM mineral high-efficiency separation include: feed rate of 100-120 t / h and feed particle size of -13 mm.

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