Views: 1 Author: Site Editor Publish Time: 2023-04-02 Origin: Site
Abstract: Using hydroxypropyl methylcellulose, acrylic acid, acrylamide, etc. as raw materials, ammonium persulfate as an initiator, and dimethyl diallyl ammonium chloride as a crosslinking agent, under the action of ultrasound, the aqueous solution polymerization method A hydroxypropyl methylcellulose dust suppressant was synthesized, and its structure was characterized by FT-IR, TGA, DSC, SEM and its dust suppression performance was tested. The results show that the synthesized dust suppressant solution is stable, the film is soft and has high tensile strength. The water retention rate of the coal sample sprayed with dust suppressant can still reach 74.52% after being placed at room temperature for 40 hours, and the coal dust loss rate is only 1.26% after continuous blowing with 14-15 m/s wind for 3 hours. The pulverized coal loss rate is only 5.06% after shaking for 40 h under the condition of min.
Key words:hydroxypropyl methylcellulose; dust suppressant; ultrasonic; aqueous solution polymerization
Coal has always occupied a major position (60% to 70%) in my country's energy production and consumption structure. It will generate a lot of dust in the process of mining, transportation and storage, which not only causes a serious waste of coal resources, but also pollutes the surrounding environment. Excessive coal dust can also cause dust explosions, posing a threat to people's lives. With the continuous development of dust suppression technology, chemical dust suppressants are more and more popular because of their excellent dust suppression performance. The knot layer is hard and brittle, and it is easily broken by the shock and wind during transportation, thus losing the dust suppression effect.
In view of this problem, this paper uses hydroxypropyl methylcellulose (HPMC), acrylic acid (AA), acrylamide (AM) as raw materials, ammonium persulfate (APS) as the initiator, and dimethyl diene Propyl ammonium chloride (DMDAAC) is used as a cross-linking agent to prepare a soft film-type environmental dust suppressant with soft film formation, high tensile strength and thermal stability, and good application performance. It can effectively inhibit coal dust pollution, It has a good application prospect.
2. Experimental part
2.1 Experimental reagents and instruments
HPMC: Industrial grade, KIMA CHEMICAL CO., LTD; AA, AM, APS, sodium bicarbonate, analytically pure, Tianjin Damao Chemical Reagent Factory; DMDAAC, sodium dodecylbenzenesulfonate (SDBS), glycerol, Analytical grade, Tianjin Tianli Chemical Reagent Co., Ltd.
MS-600N Ultrasonic Processor, Shanghai Shengji Ultrasonic Chemical Instrument Co., Ltd.; VECTOR-22 Fourier Transform Infrared Spectrometer (FT-IR), Germany Bruker; S4800 Scanning Electron Microscope (SEM), Japan Rigaku Co., Ltd. ; Q500 Thermogravimetric Analyzer (TGA), American TA Company; Q2000 Differential Scanning Calorimeter (DSC), American TA Company; XWW-20B Universal Testing Machine, Chengde Jinjian Testing Instrument Co., Ltd.; HY-4 Adjustable speed multi-purpose oscillator, Guohua Electric Co., Ltd.
2.2 Preparation of HPMC dust suppressant
Weigh 2 g of HPMC into a beaker, add 80 g of deionized water, ultrasonically dissolve for 5 min, and keep it for later use. Weigh 6 g of AA, neutralize it to 80% with sodium bicarbonate solution under an ice-water bath, then add 2 g of AM, and stir rapidly until it is completely dissolved. Add the prepared monomer solution, 0.08 g initiator APS and 0.04 g cross-linking agent DMDAAC into the beaker containing HPMC solution, then add 0.1 g SDBS and 0.5 g plasticizer glycerol, under 200 W ultrasonic power After reacting for 70 min, cool to room temperature to obtain dust suppressant solution. Then wash with absolute ethanol and dry at 0.7 MPa, 70 °C for 12 h under vacuum conditions, then grind and pass through a 100-mesh sieve to obtain a powdery dust suppressant.
2.3 Structural characterization and performance testing
2.3.1 Infrared spectrum characterization (FT-IR)
Prepare the sample by KBr tableting method, grind the prepared dry dust suppressant powder again, and then fully mix it with KBr, and prepare it according to the ratio of 1:100, then pour the prepared sample and KBr powder into the tablet machine Thin slices are made, placed in the sample compartment, and infrared spectra are measured.
2.3.2 Thermogravimetric Analysis (TGA)
Weigh 10 mg of the dried and purified product, put it into a crucible, and test it in a nitrogen atmosphere of 20 mL/min to obtain a thermogravimetric curve. The test conditions are: heating rate 20 ℃/min, temperature range 20-600 ℃.
2.3.3 Differential Scanning Calorimetry (DSC)
The glass transition temperature Tg and melting temperature Tm of the dust suppressant can be measured with a differential scanning calorimeter, and the test parameters are set as: heating rate 20 ℃/min, temperature range 20-280 ℃; the test obtains the DSC curve.
2.3.4 Scanning Electron Microscope (SEM)
SEM was used to observe the dry coal powder surface layer (gold spray) after spraying dust suppressant solution (or water).
2.3.5 Film tensile test
Take an appropriate amount of dust suppressant prepared under different monomer ratios, prepare 5% dust suppressant solution respectively, pour it into a polytetrafluoroethylene plate, and cast it into a film. Cut the dust suppressant film into a 10mm×50mm sample strip, and then measure its elongation at break when stretched on a universal testing machine.
2.3.6 Application Performance Test
The water retention, wind erosion resistance, and shock resistance performance tests of the prepared dust suppressant solution were tested according to the methods in the references.
3. Results and Discussion
3.1 Infrared spectral analysis
3 474 cm-1 is the -OH stretching vibration absorption peak on the hydroxypropyl methylcellulose sugar ring, and 2 931 cm-1 is the CH-H stretching vibration absorption peak on the -CH3. The absorption peak intensity of -OH in HPMC is obviously stronger than that in the HPMC-AA-AM curve. According to this result, it can be judged that the active hydroxyl group in HPMC participates in the reaction extensively. 1 724 cm-1 is the stretching vibration absorption peak of C=O on the amide bond, and 1 594 cm-1 is the stretching vibration absorption peak of C-N bond. The results showed that the chains of HPMC contained AM and AA segments, which proved that graft polymerization had occurred.
3.2 Thermogravimetric analysis
It can be seen from the thermogravimetric analysis curve that at the beginning, due to the thermal decomposition of -OH, the mass loss is relatively fast. The graft copolymer begins to decompose at 309.41 ℃, and then as the temperature continues to increase, the corresponding decomposition is faster, and after 534.64 ℃ It is basically finished and shows good thermal stability, so the temperature will not affect the application of the dust suppressant.
3.3 Differential scanning calorimetry analysis
From the differential scanning calorimetry analysis of HPMC and HPMC-AA-AM, it can be seen that the glass transition temperature Tg is 12.56 ℃, so it can be explained that the film is soft at room temperature; Tm is 146.05 ℃, so it can explain the melting of the film. The temperature is higher, and the heat resistance of the film is good.
3.4 SEM analysis
It can be seen from the surface morphology of coal powder after water spraying that the particle arrangement of coal powder shows loose characteristics after water evaporation, so the dust suppression effect of water spraying is limited, and dust can only be suppressed by wetting and coagulation in a short time. It can be seen from the surface morphology of the coal powder after spraying the dust suppressant that after spraying the dust suppressant, the surface particles of the coal powder are tightly bonded together, forming a solidified layer with a certain thickness, which can effectively prevent the coal dust from flying, Play a better role in dust suppression.
3.5 Analysis of performance test results
3.5.1 Film tensile properties test results
The greater the tensile strength of the dust suppressant after film formation, the better the toughness, and it will not be easily damaged after film formation, and can have a better dust suppression effect. The tensile elongation at break test was carried out on the prepared samples.
It can be seen from the stretching results of the film that the dust suppressant has a high tensile strength after film formation, which can ensure that it will not be easily damaged during use.
3.5.2 Water retention test results
From the relationship between the water retention rate of pulverized coal and the storage time, it can be known that the pulverized coal loses a high proportion of water in the first 16 hours, and the drop rate of the curve of spraying water in this interval is obviously higher than that of spraying dust suppressant. In addition, it can also be seen that the water retention rate after spraying dust suppressant for 40 hours is as high as 74.52%, while the water retention rate after spraying water is only 15.69%.
3.5.3 Wind erosion resistance test results
According to the test results of wind erosion resistance performance, the coal dust loss rate of the coal sample sprayed with dust suppressant is only 1.26% after continuous blowing with 14-15 m/s wind for 3 hours, and the coal dust surface is relatively flat, while sprayed with water After the coal sample was blown by the wind for 3 hours, the pulverized coal surface was uneven, resulting in a large amount of pulverized coal loss, with a loss rate of 7.91%. According to this result, it can be judged that the wind erosion resistance of this dust suppressant has also reached a relatively high level.
3.5.4 Anti-shock test results
It can be seen from the results obtained within 40 hours of low-speed vibration treatment of pulverized coal that after a period of shaking, the loss rate of pulverized coal sprayed with dust suppressant solution on the surface is much lower than that of pulverized coal sprayed with water on the surface. During the 40 h shaking experiment under the condition of 150 r/min, the final pulverized coal loss rate of the coal sample sprayed with water on the pulverized coal surface layer reached 69.14%, while the pulverized coal loss rate of the surface sprayed with dust suppressant solution was only 5.06%. Therefore, the anti-shock performance of the dust suppressant for pulverized coal has been significantly improved.
(1) A soft film coal dust suppressant was prepared under the action of ultrasound. The infrared analysis of the obtained product shows that under the action of ultrasound, HPMC, AA, AM can undergo graft copolymerization reaction, and the dust suppressant obtained has good thermal stability. They can be closely bonded to each other to form a solidified layer with a certain thickness, which has a good dust suppression effect.
(2) The water retention rate of the dust-suppressant-sprayed pulverized coal can still reach 74.52% after 40 hours at room temperature, and the loss rate of the pulverized coal is only 1.26% after continuous blowing with 14-15 m/s wind for 3 hours. The pulverized coal loss rate is only 5.06% after shaking for 40 h under the condition of r/min, which shows that the dust suppressant has good water retention, wind erosion resistance and shock resistance.
(3) The dust suppressant can not only effectively solve the problem of coal dust pollution in coal storage and transportation, but also can be used in places with a lot of dust such as buildings, mining areas, roads, etc., and has broad application prospects.