CN106635208B - The technique that a kind of coal preparation plant's thickener underflow directly prepares water-coal-slurry - Google Patents

Abstract

The invention discloses a process for directly preparing coal-water slurry from the underflow of a thickener in a coal preparation plant, including three steps of raw material preparation, preparation of coal-water slurry and delivery of finished products; Press filter dehydration treatment, and directly sent to the hydrocyclone group for classification, the qualified fine materials are sent to the coal slurry mixing tank, and a certain proportion of coal slurry is mixed into the coal slurry mixing tank according to the material feed amount and the quality requirements of the coal water slurry Clean coal powder and appropriate amount of dispersant and stabilizer are fully mixed and stirred to prepare a coal slurry with good fluidity and stability, which can be used for burning in nearby industrial kilns. The invention can not only reduce the pressure filter process in the flotation tailings treatment process, simplify the tailings treatment process, reduce the operating cost of the coal preparation plant, but also reduce the filter cake agglomeration in the process of preparing coal water slurry from coal slurry after pressure filtration The difficulty of dispersion caused by agglomeration reduces equipment wear and tear, thereby reducing the production cost of coal slurry.

Description

A process for directly preparing coal-water slurry from the underflow of thickener in coal preparation plant

technical field

The invention relates to a process for directly preparing coal-water slurry from the underflow of a thickener in a coal preparation plant, and belongs to the field of coal washing, processing and clean utilization.

Background technique

Coal washing is not only an effective and important method to improve coal quality, but also the most economical and effective technical approach to reduce coal pollution and improve the ecological environment. Flotation tailings (coal slime) are the main by-products of coal preparation plants. They have the characteristics of high moisture content, fine particle size, high particle content, high ash content and high viscosity, which brings a lot of inconvenience to comprehensive utilization. With the improvement of environmental protection awareness and coal quality requirements, the coal slime in coal washing plants is often unsalable. According to statistics, the current national annual discharge of coal slime exceeds 200 million tons, but because of its high moisture content, it cannot be directly used, and it will be blown up when it encounters water loss, and it is difficult to transport, resulting in most of the coal slime being piled up on the spot. . A large amount of coal slime accumulation not only wastes resources and pollutes the environment, but also seriously affects the normal production of coal washing plants. Therefore, the treatment and comprehensive utilization of coal slime need to be solved urgently.

At present, the utilization of coal slime mainly includes: coal slime combustion power generation, coal slime coal-water slurry technology, coal slime briquette technology, etc. Among them, coal slime coal-water slurry technology is widely used and has achieved good results. However, the current coal slurry technology generally adopts the process flow shown in Figure 1: the flotation tailings are first concentrated by a thickener in a coal preparation plant, and the bottom flow of the thickener is further dehydrated by a filter press to obtain a slime filter cake, and then The coal slime filter cake is used as the raw material, and the coal water slurry is prepared by steps such as slurry mixing and stirring. In this process, due to the strong cohesion between the coal slime particles, the filter cake formed by the coal slime raw material after pressure filtration is easy to form a block, so in the subsequent preparation process of coal water slurry, it is often necessary to use agitator and other equipment for strong stirring ( Sometimes it even needs crushing and grinding process) to disperse the coal slime filter cake, so as to prepare a coal-water slurry product with uniform particle size distribution, stable slurrying performance, and meeting the requirements of transportation and use.

For example, Document 1 (Experimental Research on Preparation of Coal-Water Slurry from Low Ash and High Calorific Value Coal Slurry, Clean Coal Technology, 2009, 16 (2): 45-48) needs to use crushing, rod milling and other processes to grind the coal slime; patent (application No.: 200710015400.X) the production process of the coal slime coal water slurry needs to adopt the ball mill and the powerful stirring device to grind and disperse the coal slime, so as to prepare the coal water slurry with better pulping property; and the patent (application number: 200810095266.3) to prepare coal-water slurry with raw coal slime and sodium lignin sulfonate powder, the twin-shaft kneading mud mixer is used to disperse the raw coal slime (dry powder), and then the slurry is processed twice by a strong stirring device. Distributed processing. Apparently, the preparation process of the above-mentioned coal-slurry coal-water slurry is relatively complicated, and there are many operating equipment and large investment, which greatly increases the production cost of the coal-water slurry.

On the other hand, according to the fluidity and stability requirements of coal-water slurry, the concentration of coal-water slurry is generally about 65%, and the coal slime after pressure filtration generally has a water content of about 20-30%, which can be directly used as water The flow of coal slurry is difficult, and it is very easy to block the transportation pipeline. Therefore, it is necessary to add a large amount of water and a small amount (about 1%) of dispersant and stabilizer (as shown in Figure 1) in the later preparation process of coal slurry to form a slurry. Coal water slurry with uniform slurry, good fluidity and stability. In the process of flotation tailings coal treatment, the bottom flow of the thickener goes through the filter press operation just to remove most of the water in the coal slime. Therefore, if the bottom flow of the thickener is directly used to prepare the coal slurry, it can not only reduce the flotation The filter press process in the tailings treatment process simplifies the tailings treatment process, reduces production costs, and can reduce the difficulty of dispersion caused by the agglomeration of filter cakes in the process of preparing coal-water slurry from coal slurry after pressure filtration, reducing stirring (even crushing, grinding) equipment wear, thereby simplifying the preparation process of coal slurry.

In addition, in order to facilitate the rapid settlement of flotation tailings, coal preparation plants often add a certain amount of flocculant to the thickener to speed up the sedimentation of coal slime to improve the concentration efficiency, and remove it together with water in the subsequent filter press dehydration process , but this part of the agent has a good promoting effect on improving the stability of the coal-water slurry during the preparation of the coal-water slurry. Therefore, if the underflow of the thickener is used to prepare the coal-water slurry, the flocculant added in the process of thickening and settling of the coal slime can be effectively used to improve the stability of the coal-water slurry product, thereby reducing the production cost.

Contents of the invention

The purpose of the present invention is aimed at the existing coal slime coal-water slurry production process in which the coal slime is firstly dewatered by press filtration, and then added a large amount of water to disperse in the subsequent pulping process, the process is complex, the energy consumption is high and the coal slime after press filtration The filter cake is easy to agglomerate into blocks, which makes it difficult to disperse, and the flocculant in the thickener is not fully utilized. A process is proposed in which the underflow of the thickener in the coal preparation plant is directly used to prepare coal-water slurry without being dewatered by pressure filtration. In the present invention, after the flotation tailings are concentrated by the concentrator, the underflow of the concentrator is directly sent to the hydrocyclone for grading treatment without undergoing pressure filtration and dehydration treatment, and the qualified fine materials are sent to the coal slurry mixing tank and dispersant, Stabilizer and fine coal powder (if necessary, sulfur fixing agent can also be added) are mixed uniformly to prepare coal water slurry, which is used for combustion in nearby industrial kilns, and coarse materials are finely ground by wet ball mills and then enter the hydraulic classification system again. The invention can not only simplify the treatment process of flotation tailings in existing coal preparation plants, reduce the production cost of coal slurry, but also effectively solve the problems of land occupation and environmental pollution caused by coal slime stacking in coal preparation plants ; Ultimately realize the high value-added utilization of coal slime and increase the economic benefits of the enterprise.

The purpose of the present invention can be achieved through the following technical measures.

The process for directly preparing coal-water slurry from the underflow of a thickener in a coal preparation plant provided by the present invention mainly includes three steps of raw material preparation, coal-water slurry modulation and finished product delivery. The specific steps are as follows:

a. Raw material preparation: After the flotation tailings are concentrated by the thickener, the overflow enters the circulating water system of the coal preparation plant for recycling, and the underflow is directly sent to the hydrocyclone group through the slurry pump I for efficient classification; after classification After treatment, the qualified material with a particle size of less than 75 μm enters the coal slurry mixing tank directly from the overflow port, while the coarse material with a particle size greater than 75 μm is sent to the wet ball mill through the underflow sand discharge port of the hydrocyclone group for fine grinding; the finely ground material The slurry is returned to the hydrocyclone group through the slurry pump II and mixed with the raw materials delivered by the slurry pump I for re-classification, so that the materials entering the coal slurry mixing tank can meet the particle size requirements of the coal water slurry, which is conducive to improving the subsequent water quality. The stability of the finished coal slurry ensures that the material entering the coal slurry mixing tank meets the particle size requirements of the coal-water slurry, effectively avoiding the phenomenon of "running coarse".

b. Coal water slurry preparation: In the coal slurry mixing tank, according to the feed amount of qualified materials in step a per unit time and the quality requirements of coal water slurry, use the automatic dosing device to add 0.6~1.0% of the total amount of coal water slurry Dispersant and stabilizer agents, and mixed into clean coal powder, wherein, the ratio X of clean coal powder is calculated according to the formula: X=(M ₁ C ₁ -M ₂ C ₂ )/M ₁ , where M ₁ is The total amount of coal-water slurry products, C ₁ is the concentration requirement of coal-water slurry products, M ₂ is the feed amount of qualified materials, and C ₂ is the solid concentration of qualified materials; The mixing amount can effectively adjust the concentration of coal-water slurry and the calorific value of the final coal-water slurry product; when the above-mentioned materials and additives are mixed evenly, the slurry is sent to the slurry storage tank with a mechanical stirring device through the slurry pump III spare.

c. Finished product delivery: use the high-speed shear pump to transport the finished coal-water slurry in the slurry tank to the industrial kiln for efficient combustion. The high-speed shear emulsification of the shear pump can further improve the uniformity and stability of the coal-water slurry , so as to facilitate the subsequent transportation and combustion.

The concentration of solid particles in the underflow described in step a of the present invention is 40 to 60%; the dispersant described in step b is a polycarboxylate composite dispersant, and the stabilizer is a polyacrylamide stabilizer; the dispersant and stabilizer The mass ratio is 1~4:1.

Compared with the existing coal slime coal water slurry production process, the beneficial effects of the present invention are as follows:

(1) The underflow of the thickener is directly used to prepare coal water slurry without filter press dehydration treatment, which can not only eliminate the agglomeration and agglomeration of coal slime caused by filter press, but also reduce the energy consumption and equipment in the subsequent preparation process of coal slurry coal water slurry (such as mixer or crushing and grinding machinery) wear; and it can simplify the treatment process of flotation tailings, greatly reducing the operating cost of the coal preparation plant.

(2) Make full use of the flotation agent contained in the underflow of the thickener and the flocculant added during the tailing coal concentration process, and properly adjust the dispersion and stability of the coal-water slurry to produce a coal-water slurry with good slurryability. Greatly reduce the dosage of CWS additives, effectively reduce the production cost of CWS.

(3) According to the user's requirements for calorific value and pollutant discharge, the combustion calorific value and pollutants of the coal-water slurry product can be properly regulated by adjusting the amount of fine coal powder and sulfur-fixing agent mixed in the process of coal-water slurry preparation The emission concentration, the whole production process has strong adaptability, and the quality control of coal water slurry products is simple, which can meet the needs of different users.

Description of drawings

Fig. 1 is the prior art coal slime coal-water slurry preparation process.

Fig. 2 is a process flow diagram of the present invention.

Serial numbers in the drawings: 1. Concentrator, 2. Slurry pump I, 3. Hydrocyclone group, 4. Wet ball mill, 5. Slurry pump II, 6. Coal slurry mixing tank, 7. Clean coal powder bin , 8, electronic belt scale, 9, automatic dosing device, 10, slurry pump Ⅲ, 11, storage tank, 12, high-speed shear pump, 13, industrial furnace.

detailed description

The present invention will be described in further detail below in conjunction with embodiment (Fig. 2):

Example 1

Taking the thickener underflow of a certain coal preparation plant of Shenhua Group as an example to further describe the present invention:

The flotation tailings of a coal preparation plant of Shenhua Group belong to low-ash slime, with an ash content of about 30% and a calorific value of 13.5MJ/kg. After the flotation tailings of the coal preparation plant are concentrated by the concentrator 1, the overflow is returned to the circulating water system of the coal preparation plant for use. 82% of the amount) is directly sent to the hydrocyclone group 3 through the slurry pump I2 for high-efficiency classification. After grading treatment, the qualified materials with a particle size of less than 75 μm in the hydrocyclone group 3 (accounting for about 82% of the total solids, assuming that the underflow of the concentrator is completely classified) enter the coal slurry mixing tank 6 directly from the overflow port, while the particle size is greater than The 75μm coarse material (accounting for about 18% of the total solids) is sent to the wet ball mill 4 through the underflow sand outlet of the hydrocyclone group 3 for fine grinding. The finely ground slurry is returned to the hydrocyclone group 3 through the slurry pump II5 and mixed with the raw materials delivered by the slurry pump I2 for further classification.

In the coal slurry mixing tank 6 with a high-speed rotating impeller, according to the feed rate of 24.6m ³ /h of qualified materials (assuming that the rated capacity of the hydrocyclone group is 30m ³ /h, 82% of the qualified materials are all from overflow The orifice enters the coal slurry mixing tank 6, and its concentration is the same as that of the feed material) and the quality requirements of the coal water slurry (the solid concentration of the coal water slurry is required to be 66%). The amount of clean coal powder added per unit time M can be determined by Formula: (M+24.6m ³ /h×1500kg/m ³ )×66%-(24.6m ³ /h×1500kg/m ³ )×50%=M calculation.

In the formula, 24.6m ³ /h is the feed volume per unit time in the coal slurry mixing tank 6, 1500kg/m ³ is assumed to be the density of the feed in the coal slurry mixing tank 6, and the feed volume M ₂ of qualified materials is 24.6m ³ /h×1500kg/m ³ ; 66% is the solid concentration C ₁ required by the coal-water slurry product, and 50% is the solid concentration C ₂ of the qualified material in the coal slurry mixing tank 6 .

Through calculation, the amount M of clean coal powder added per unit time is about 17364.7kg/h, and according to the calculation formula X=(M ₁ C ₁ -M ₂ C ₂ )/M ₁ , the proportion X of clean coal powder is calculated to be about 32% (the total amount of coal water slurry M ₁ =M+M ₂ =17364.7kg/h +24.6m ³ /h×1500kg/m ³ =54264.7kg/ h, calculated in unit time, and the mass of dispersant and stabilizer is ignored).

Evenly add a certain amount of clean coal powder (the amount of clean coal powder added per unit time calculated by calculation) to the coal slurry mixing tank 6 through the clean coal powder bin 7 via the electronic belt scale 8 (the clean coal powder feeding speed control 17364.7kg/h), and use the automatic dosing device 9 to add about 0.8% of the total amount of coal-water slurry polycarboxylate composite dispersant and polyacrylamide stabilizer (the ratio of dispersant to stabilizer is 1.5:1 ). After the above-mentioned materials and additives are mixed evenly, the slurry is sent to the slurry storage tank 11 with a mechanical stirring device through the slurry pump III10 for standby. Finally, use the high-speed shear pump 12 to transport the finished coal-water slurry in the slurry tank 11 to the industrial kiln 13 about 5km away for combustion. After testing, the calorific value can reach 11.12MJ/kg, and the coal-water slurry flows Good stability (viscosity of 948mPa·s at a shear rate of 100s ^-1 ) and good stability, it fully complies with the national coal water slurry technical standard (GB/T18855-2008), and can meet the combustion requirements of general industrial kilns.

Example 2

Taking the thickener underflow of a coal preparation plant of Henan Energy and Chemical Industry Group as an example, the present invention is further described:

The flotation tailings of a coal preparation plant of Henan Energy and Chemical Industry Group belong to medium ash slime, with an ash content of about 40% and a calorific value of 12.1MJ/kg. After the flotation tailings of the coal preparation plant are concentrated by the thickener 1, the overflow is returned to the circulating water system of the coal preparation plant for use. 78% of the amount) is directly sent to the hydrocyclone group 3 through the slurry pump I2 for high-efficiency classification. After grading treatment, the qualified materials with a particle size of less than 75 μm in the hydrocyclone group 3 (accounting for about 78% of the total solids, assuming that the underflow of the concentrator is completely classified) enter the coal slurry mixing tank 6 directly from the overflow port, while the particle size is greater than The 75μm coarse material (accounting for about 22% of the total solids) is sent to the wet ball mill 4 through the underflow sand outlet of the hydrocyclone group 3 for fine grinding. The finely ground slurry is returned to the hydrocyclone group 3 through the slurry pump II5 and mixed with the raw materials delivered by the slurry pump I2 for further classification.

In the coal slurry mixing tank 6 with a high-speed rotating impeller, according to the feed rate of 23.4m ³ /h of qualified materials (assuming that the rated processing capacity of the hydrocyclone group is 30m ³ /h, 78% of qualified materials are all from overflow The orifice enters the coal slurry mixing tank 6, and its concentration is the same as that of the feed material) and the quality requirements of the coal water slurry (the solid concentration of the coal water slurry is required to be 65%). The amount of clean coal powder added per unit time M can be determined by Formula: (M+23.4m ³ /h×1500kg/m ³ )×65%-(23.4m ³ /h×1500kg/m ³ )×53%=M calculation.

In the formula, 23.4m ³ /h is the feed volume per unit time in the coal slurry mixing tank 6, 1500kg/m ³ is assumed to be the density of the feed in the coal slurry mixing tank 6, and the feed volume M ₂ of qualified materials is 23.4m ³ /h×1500kg/m ³ ; 65% is the solid concentration C ₁ required by the coal-water slurry product, and 53% is the solid concentration C ₂ of the qualified material in the coal slurry mixing tank 6 .

Through calculation, the addition amount M of clean coal powder per unit time is about: 12034.3kg/h, and according to the calculation formula X=(M ₁ C ₁ -M ₂ C ₂ )/M ₁ , the proportion X of clean coal powder is calculated to be about 25.5% (the total amount of coal-water slurry M ₁ =M+M ₂ =12034.3kg/h +23.4m ³ /h×1500kg/m ³ =47134.3kg/ h, calculated in unit time, and the mass of dispersant and stabilizer is ignored).

Evenly add a certain amount of clean coal powder (the amount of clean coal powder added per unit time calculated by calculation) into the coal slurry mixing tank 6 through the clean coal powder bin 7 via the electronic belt scale 8 (the clean coal powder feeding speed control 12034.3kg/h) and sulfur-fixing agent (about 0.2% of the total amount of coal-water slurry), and use the automatic dosing device 9 to add about 0.9% of the total amount of coal-water slurry polycarboxylate composite dispersant and polypropylene Amide stabilizer (the ratio of dispersant to stabilizer is 1:1). After the above-mentioned materials and additives are mixed evenly, the slurry is sent to the slurry storage tank 11 with a mechanical stirring device through the slurry pump III10 for standby. Finally, the high-speed shear pump 12 is used to transport the finished coal-water slurry in the slurry tank 11 to the industrial kiln 13 for combustion. After testing, the calorific value can reach 10.65MJ/kg, and the fluidity of the coal-water slurry (shear When the speed is 100s ^-1 , the viscosity is 748mPa·s) and the stability is good, which fully complies with the national coal water slurry technical standard (GB/T18855-2008), and can meet the combustion requirements of general industrial kilns.

Claims (1)

1. a kind of technology that coal-washing plant thickener underflow directly prepares coal-water slurry, it is characterized in that: described technology realizes by following steps: a. Raw material preparation: After the flotation tailings are concentrated by the thickener, the overflow enters the circulating water system of the coal preparation plant for recycling, and the underflow is directly sent to the hydrocyclone group through the slurry pump I for efficient classification; after classification After treatment, the qualified material with a particle size of less than 75 μm enters the coal slurry mixing tank directly from the overflow port, while the coarse material with a particle size greater than 75 μm is sent to the wet ball mill through the underflow sand discharge port of the hydrocyclone group for fine grinding; the finely ground material The slurry returns to the hydrocyclone group through the slurry pump II and mixes with the raw materials delivered by the slurry pump I for further classification; the solid particle concentration in the underflow is 40-60%; b. Coal water slurry preparation: In the coal slurry mixing tank, according to the feed amount of qualified materials in step a per unit time and the quality requirements of coal water slurry, use the automatic dosing device to add 0.6~1.0% of the total amount of coal water slurry Dispersant and stabilizer agents, and mixed into clean coal powder, wherein, the ratio X of clean coal powder is calculated according to the formula: X=(M ₁ C ₁ -M ₂ C ₂ )/M ₁ , where M ₁ is The total amount of coal water slurry products, _C1 is the concentration requirement of coal water slurry products, _M2 is the feed amount of qualified materials, and _C2 is the solid concentration of qualified materials; when the above materials and additives are mixed evenly, pass through the slurry Pump III sends the slurry into a slurry storage tank with a mechanical stirring device for standby; the dispersant is a polycarboxylic acid-based composite dispersant, and the stabilizer is a polyacrylamide-based stabilizer. The dispersant and stabilizer The mass ratio is 1~4:1; c. Finished product transportation: use high-speed shear pump to transport the finished coal-water slurry in the slurry storage tank to the industrial kiln for efficient combustion.