A process and method for synergistically dehydrating and improving the quality of coal slime materials

Abstract

The present invention relates to the technical field of coal slime dehydration, and provides a process and method for the coordinated dehydration and quality improvement of coal slime materials. The present invention first performs filter pressing dehydration on the coal slime water to be treated, crushes the obtained filter cake and then performs screening and grading, and performs steam transient dehydration on the obtained screen material to obtain dehydrated coal slime. The present invention combines filter pressing dehydration with steam transient dehydration, which can break through the lower limit of dehydration and is beneficial to improving the drying efficiency of steam transient dehydration. The method provided by the present invention has a high dehydration rate, can effectively reduce the moisture content of coal slime, and increase the calorific value, thereby improving the utilization value of coal slime products and overcoming the difficulties encountered in the storage, transportation and sales of coal slime.

Description

Technical Field

[0001] The present invention relates to the technical field of coal slime dehydration, and in particular to a process and method for synergistically dehydrating and improving the quality of coal slime materials. Background Art

[0002] Coal is the main energy source in my country. During the coal processing, it needs to be sorted to reduce the content of minerals and harmful impurities as much as possible. The main coal preparation method currently used in my country is heavy medium wet coal preparation, that is, water or a mixture of water is used as the sorting medium. The sorting process produces a large amount of coal slime water. Coal slime water is a suspension containing a large number of fine coal powder particles and other impurities. If it is directly discharged, it will cause great harm to the water area.

[0003] At present, the coal slime water is usually concentrated and then dehydrated using mechanical dehydration equipment such as quick-opening filter presses and plate-and-frame filter presses, and then the dehydrated coal slime is recycled. However, the water content of the coal slime treated by this method is still high and the calorific value is low, which has an adverse effect on the storage, transportation and sales of the coal slime. Summary of the invention

[0004] In view of this, the present invention provides a process and method for synergistic dehydration and quality improvement of coal slime materials. The method provided by the present invention has a high dehydration rate, can effectively increase the calorific value of coal slime products, thereby improving the utilization value of coal slime products and overcoming the difficulties encountered in the storage, transportation and sales of coal slime.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A method for collaborative dehydration and quality improvement of coal slime materials, comprising the following steps:

[0007] The coal sludge water to be treated is subjected to filter pressing and dehydration to obtain a filter cake;

[0008] The filter cake is crushed and then screened and classified, and the obtained oversize material is transiently dehydrated by steam to obtain dehydrated coal slime.

[0009] Preferably, the concentration of the coal slime in the coal slime water to be treated is 300-500 g / L.

[0010] Preferably, the pressure of the filter pressing dehydration is 0.5-10 MPa; the water content of the filter cake is less than 25 wt%.

[0011] Preferably, the particle size of the crushed product is ≤50 mm.

[0012] Preferably, the screening and grading is dry screening; the screening particle size of the screening and grading is 1 to 6 mm.

[0013] Preferably, the operating conditions of the steam transient dehydration include: a steam pressure of 5 to 8 MPa, a pressure holding time of less than 5 minutes, and a saturated steam temperature of 264 to 295°C.

[0014] Preferably, the water content of the dehydrated coal slime is ≤15wt%.

[0015] Preferably, the filtration is performed by a filter press; the coal sludge water to be treated is fed into the filter press by a feed pump; the crushing is performed by a crusher, and the filter cake obtained by filtration is fed to the crusher by a belt conveyor; the screening and grading is performed by a grading screen, and the screened material obtained by screening and grading is transported to a coal sludge bin by a belt conveyor for recovery.

[0016] Preferably, the steam transient dehydration system includes a steam dehydration system, a steam generating system and a steam recovery system; the screened material is transported to the dehydration chamber of the steam dehydration system by a belt conveyor and the dehydration chamber is sealed, the saturated steam generated by the steam generating system is introduced into the dehydration chamber of the steam dehydration system, and the pressure is maintained after reaching the pressure. After the pressure maintenance ends, the steam is released, and the released steam enters the steam recovery system for recycling; the dehydrated coal slime is transported to the product bin by the belt conveyor.

[0017] Preferably, the coal slime water to be treated is obtained by the following method: wet sorting high-water-content raw coal to obtain primary coal slime water, and concentrating the primary coal slime water to obtain coal slime water to be treated; the water content of the high-water-content raw coal is ≥30wt%.

[0018] The present invention provides a method for synergistically dehydrating and improving the quality of coal slime materials, comprising the following steps: dehydrating the coal slime water to be treated by filter pressing (primary dehydration) to obtain a filter cake; crushing the filter cake and then sieving and grading it, and transiently dehydrating the obtained oversize material by steam (secondary deep dehydration) to obtain dehydrated coal slime. When mechanical dehydration is used alone, the moisture content of the dehydrated coal slime can be reduced to about 20% at the lowest, which cannot meet the moisture content requirements of specific products; when steam transient dehydration is used alone, the dehydration rate is about 50%, which also cannot meet the moisture content requirements of the product; the present invention combines filter press dehydration and steam transient dehydration to break through the lower limit of dehydration, and at the same time, filter press dehydration is performed first and then steam transient dehydration is performed, which is beneficial to improve the drying efficiency of steam transient dehydration; and, the steam transient dehydration has too low a moisture removal rate for coal slime particles with small particle sizes. The present invention first performs filter press dehydration, forms filter cakes with small particles of coal slime, and then crushes and screens them, and performs steam transient dehydration on the sieve with larger particles, which helps to improve the dehydration effect of steam transient dehydration, and mechanical filter press dehydration can preliminarily remove interstitial water of coal slime particles, which is beneficial to shorten the pressure holding time of the subsequent steam transient dehydration stage, and improve the treatment capacity of coal slime water and the continuity of the treatment process. In summary, the method provided by the present invention has a high dehydration rate, can effectively increase the calorific value of coal slime products, thereby improving the utilization value of coal slime products, and overcoming the difficulties encountered in the storage, transportation and sales of coal slime.

[0019] Furthermore, the present invention can recycle the waste heat of steam after drying, which is green and environmentally friendly, and has strong safety, large processing capacity and high degree of automation.

[0020] The results of the embodiment show that after the initial filter press dehydration and the secondary deep dehydration, the moisture content of the dehydrated coal slime is about 10% lower than that of the product obtained by single mechanical dehydration, and the calorific value of the coal slime product is about 2.5MJ / Kg higher than that of single mechanical dehydration. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the system used in the method for collaborative dehydration and quality improvement of coal slime materials in an embodiment of the present invention, wherein: 1-feeding pump; 2-filter press; 3-first belt conveyor; 4-crusher; 5-grading screen; 6-second belt conveyor; 7-coal slime bin; 8-third belt conveyor; 9-steam dehydration system; 10-steam generation system; 11-steam recovery system; 12-fourth belt conveyor; 13-product bin. DETAILED DESCRIPTION

[0022] The present invention provides a method for collaborative dehydration and quality improvement of coal slime materials, comprising the following steps:

[0023] The coal sludge water to be treated is subjected to filter pressing and dehydration to obtain a filter cake;

[0024] The filter cake is crushed and then screened and classified, and the obtained oversize material is subjected to steam transient dehydration to obtain dehydrated coal slime.

[0025] The present invention performs filter pressing and dehydration on the coal slurry water to be treated to obtain a filter cake. In the present invention, the coal slurry water to be treated is obtained by the following method: wet sorting high-water raw coal to obtain primary coal slurry water, and concentrating the primary coal slurry water to obtain the coal slurry water to be treated; the water content of the high-water raw coal is ≥30wt%, preferably 30-50wt%; the concentration of coal slurry in the coal slurry water to be treated is preferably 300-500g / L, more preferably 350-450g / L.

[0026] In the present invention, the water content of the filter cake is preferably below 25wt%, preferably 20-24%; the pressure of the filter pressing dehydration is preferably 0.5-10MPa; the filter pressing is preferably carried out by a filter press, and the filter press is preferably an ultra-high pressure filter press or a fast-opening diaphragm filter press; the cycle time of the ultra-high pressure filter press is preferably 45min, and the cycle time of the fast-opening diaphragm filter press is preferably 20min. In a specific embodiment of the present invention, the type of filter press is preferably selected according to the moisture content of the coal slurry water; the coal slurry water to be treated is preferably fed into the filter press by a feed pump, specifically, the coal slurry water to be treated is injected into the closed filter chamber of the filter press, and then the coal slurry is forced to form a filter cake with a certain mechanical strength under the pressure of the filter press.

[0027] In a specific embodiment of the present invention, the filter press dehydration preferably includes low-pressure dehydration and high-pressure dehydration performed in sequence; first, the coal slime is forced to form a filter cake under low pressure, and then high-pressure pressing is performed to improve the dehydration efficiency; when the ultra-high pressure filter press is used for filter press dehydration, the pressure of the low-pressure dehydration is preferably 1.7-1.9MPa, more preferably 1.8MPa, and the pressure of the high-pressure dehydration is preferably 8-10MPa, more preferably 8.5MPa; when the quick-opening diaphragm filter press is used for filter press dehydration, the pressure of the low-pressure dehydration is preferably 0.5-0.6MPa, more preferably 0.5MPa, and the pressure of the high-pressure dehydration is preferably 0.8-1.0MPa, more preferably 0.8MPa.

[0028] After obtaining the filter cake, the present invention crushes the filter cake and then screens and grades it, and steam transiently dehydrates the obtained screen material to obtain dehydrated coal slime. In the present invention, the particle size of the crushed material obtained by the crushing is preferably ≤50mm, more preferably 6-50mm; the crushing is preferably performed by a crusher, and the filter cake obtained by filter pressing is sent to the crusher by a belt conveyor (referred to as the first belt conveyor).

[0029] In the present invention, the screening and grading is preferably dry screening; the screening particle size of the screening and grading is preferably 1 to 6 mm, more preferably 1 mm or 3 mm; the screening and grading is preferably carried out using a grading screen, and the screened material obtained by the screening and grading is preferably transported to the coal slime bin by a belt conveyor (recorded as the second belt conveyor) for recovery. After the filter cake is screened and graded, the screened material is subjected to steam transient dehydration. The particle size of the screened material is relatively large, and it has a certain porosity after being accumulated in the dehydration chamber of the steam dehydration system. The fluid convection heat exchange effect between the particle gaps is strong, which increases the drying efficiency, and the large porosity of the material can reduce the water holding capacity of the material after drying.

[0030] In the present invention, the operating conditions of the steam transient dehydration preferably include: a steam pressure of 5 to 8 MPa, preferably 5.5 to 7.5 MPa, a pressure holding time of less than 5 minutes, preferably 1 to 3 minutes, and a saturated steam temperature of 264 to 295°C, preferably 270 to 290°C; the system for steam transient dehydration preferably includes a steam dehydration system, a steam generation system and a steam recovery system; the screened material is preferably transported to the dehydration chamber of the steam dehydration system by a belt conveyor (referred to as the third belt conveyor), and then the dehydration chamber is sealed, and the saturated steam generated by the steam generation system is passed into the dehydration chamber, and the pressure is maintained after reaching the pressure, and the steam is released after the pressure holding ends, and the released steam preferably enters the steam recovery system for recycling; in the present invention, the system for steam transient dehydration can control the amount of steam passed into the dehydration chamber, and can monitor the pressure changes inside the dehydration chamber in real time to achieve automatic control of the system.

[0031] In the present invention, the dehydrated coal slime is preferably delivered to the product bin by a belt conveyor (referred to as the fourth belt conveyor).

[0032] In the present invention, the water content of the dehydrated coal slime is preferably ≤15wt%, more preferably ≤13wt%, and further preferably 9-13wt%.

[0033] Figure 1 It is a structural schematic diagram of the system used in the method for collaborative dehydration and quality improvement of coal slime materials in an embodiment of the present invention, wherein: 1-feeding pump; 2-filter press; 3-first belt conveyor; 4-crusher; 5-grading screen; 6-second belt conveyor; 7-coal slime bin; 8-third belt conveyor; 9-steam dehydration system; 10-steam generation system; 11-steam recovery system; 12-fourth belt conveyor; 13-product bin.

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] The filter press used in this embodiment is an ultra-high pressure filter press.

[0037] The moisture content of raw coal is 40wt%. After wet sorting, the raw coal produces primary coal slime water. The primary coal slime water is concentrated in the concentration tank to a concentration of 400g / L. The concentrated coal slime water is treated as follows. The target moisture content of the dehydrated coal slime product is 13wt%:

[0038] The concentrated coal slurry water is fed into the ultra-high pressure filter press 2 by the feed pump 1. After the coal slurry water is injected into the closed filter chamber, the coal slurry is forced to form a filter cake under a pressure of 1.8MPa. The filter cake is subjected to secondary squeezing and dehydration under a high pressure of 8.5MPa. At this time, the water content of the filter cake obtained after dehydration is 23wt%. The filter cake is unloaded and fed into the 50mm crusher 4 by the first belt conveyor 3. The crushed material enters the 3mm grading screen 5. The undersize material is transported to the coal slurry bin 7 by the second belt conveyor 6. The oversize material is fed into the dehydration chamber of the steam dehydration system 9 by the third belt conveyor 8. The steam generation system 10 generates saturated steam and passes it into the dehydration chamber. When materials larger than 3mm are piled up in the dehydration chamber, the void ratio is about 50%. The fluid convection heat transfer effect between the particle gaps is strong, which increases the drying efficiency. In addition, the larger void ratio of the material can reduce the water holding capacity of the material after drying. Under the operating conditions of 7.5MPa and 290℃, the pressure is maintained for 5min, and then the steam is quickly released to complete the secondary deep dehydration. At this time, the moisture content of the dehydrated coal slime product is 12wt%), and the calorific value is 2.76KJ / Kg higher than that of the filter press coal slime. The coal slime product is unloaded and transported to the product bin 13 by the fourth belt conveyor 12, and the released steam enters the steam recovery system 11 for recycling.

[0039] Example 2

[0040] The filter press used in this embodiment is a quick-opening diaphragm filter press.

[0041] The moisture content of raw coal is 30wt%. After wet sorting, the raw coal produces primary coal slime water. The primary coal slime water is concentrated in the concentration tank to a concentration of 420g / L. The concentrated coal slime water is treated as follows. The target moisture content of the dehydrated coal slime product is 15wt%:

[0042] The concentrated coal slurry water is fed into the quick-opening diaphragm filter press 2 by the feed pump 1. After the feed pump injects the coal slurry water into the closed filter chamber of the quick-opening diaphragm filter press, the slurry is sprayed under a pressure of 0.5MPa to lose pressure, causing the coal slurry to form a filter cake. Subsequently, the filter cake is squeezed and dehydrated for the second time under the action of 0.8MPa high-pressure wind. After the dehydration is completed, the moisture content of the obtained filter cake is 24wt%. The filter cake is unloaded and fed into the filter cake crusher 4 by the first belt conveyor 3. The crushed material enters the 1mm grading screen 5. The undersize material is transported to the coal slime bin 7 by the second belt conveyor 6. The oversize material is fed into the dehydration chamber of the steam dehydration system 9 by the third belt conveyor 8. The steam generating system 10 generates saturated steam which is passed into the dehydration chamber. The pressure is maintained for 3 minutes under the operating conditions of 5.5MPa and 270℃, and then the steam is quickly released to complete the secondary deep dehydration. At this time, the moisture content of the dehydrated coal slime product is 13wt%, and the calorific value is 2.76KJ / Kg higher than that of the filter press coal slime. The coal slime product is unloaded and transported to the product bin 13 by the fourth belt conveyor 12. The released steam enters the steam recovery system 11 for recycling.

[0043] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for synergistic dehydration and quality improvement of coal slime materials, characterized in that: The following steps are involved: The coal sludge water to be treated is subjected to filter pressing and dehydration to obtain a filter cake; The filter cake is crushed and then sieved and graded, and the obtained oversize material is transiently dehydrated by steam to obtain dehydrated coal slime; The concentration of the coal slime in the coal slime water to be treated is 300-500 g / L; The pressure of the filter press dehydration is 0.5-10 MPa; the water content of the filter cake is less than 25wt%; The screening particle size of the screening and grading is 1 to 6 mm; The operating conditions of the steam transient dehydration include: a steam pressure of 5.5-8 MPa, a pressure holding time of less than 5 minutes, and a saturated steam temperature of 264-295°C.

2. The method according to claim 1, characterized in that The particle size of the crushed product obtained by the crushing is ≤50mm.

3. The method according to claim 1, characterized in that The screening and classification is dry screening.

4. The method according to claim 1, characterized in that: The water content of the dehydrated coal slime is ≤15wt%.

5. The method according to claim 1, characterized in that The filtration is carried out by a filter press; the coal sludge water to be treated is fed into the filter press by a feed pump; the crushing is carried out by a crusher, and the filter cake obtained by filtration is fed to the crusher by a belt conveyor; the screening and grading is carried out by a grading screen, and the screened material obtained by screening and grading is transported to the coal sludge bin by a belt conveyor for recovery.

6. The method according to claim 1, characterized in that The steam transient dehydration system includes a steam dehydration system, a steam generation system and a steam recovery system; the screened material is transported to the dehydration chamber of the steam dehydration system by a belt conveyor and the dehydration chamber is sealed, the saturated steam generated by the steam generation system is introduced into the dehydration chamber of the steam dehydration system, and the pressure is maintained after reaching the pressure. After the pressure maintenance is completed, the steam is released, and the released steam enters the steam recovery system for recycling; the dehydrated coal slime is transported to the product bin by the belt conveyor.

7. The method according to claim 1, characterized in that The untreated coal slime water is obtained by the following method: wet sorting high-water-content raw coal to obtain primary coal slime water, and concentrating the primary coal slime water to obtain the untreated coal slime water; the water content of the high-water-content raw coal is ≥30wt%.

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