Application of quaternary ammonium salt surfactant

Abstract

The invention relates to an application of a quaternary ammonium salt surfactant, the quaternary ammonium salt surfactant is used as a coal slime dehydration conditioner and applied to coal slime dehydration, and the application specifically comprises the following steps: 1) mixing coal slime with the quaternary ammonium salt surfactant to obtain a mixture; and 2) carrying out solid-liquid separation on the mixture in the step 1) to obtain a dehydrated mud cake. Compared with the prior art, the quaternary ammonium salt surfactant is used as the coal slime dehydration conditioner for efficient coal slime dehydration, the treatment method is simple and easy to implement, a coal slime pretreatment process is not needed, and the defects that a traditional coal slime dehydration process is large in agent dosage, low in dehydration efficiency, high in energy consumption and the like can be overcome; besides, after the coal slime conditioning and dewatering process is completed, the clarity of tail water is improved, most coal slime in water exists in a floc form, tail water treatment is facilitated, the clarity of circulating water of a coal preparation plant is guaranteed, and the method has high social and environmental benefits and economic benefits and wide market application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and relates to application of a quaternary ammonium salt surfactant, in particular to application of a quaternary ammonium salt surfactant in coal slime dewatering. Background Art

[0002] my country's coal resources are large in total and rich in variety, but they are becoming increasingly depleted. Clean and efficient use of coal needs to be achieved by improving the coal washing and processing technology. Coal washing generally refers to the process of removing gangue or other impurities from coal. Coal washing is generally carried out by utilizing the different physical properties of coal and gangue, and separating coal and gangue (impurities) in media of different densities or characteristics. Coal slime dehydration is an important part of the coal washing process. Dehydrated coal slime can reduce transportation costs, increase calorific value, and reduce environmental impact.

[0003] With the improvement of coal mining mechanization, the proportion of fine coal slime in the selected raw coal continues to increase. Studies have pointed out that the content of coal slime with a particle size of less than 0.5 mm in raw coal is preliminarily estimated to be between 25% and 30%, or even higher. Due to its small particle size, large specific surface area, small particle gap, and strong capillary effect, it is difficult to remove the water in the coal slime, which affects its subsequent production and utilization. Therefore, achieving efficient dehydration of coal slime is of great significance to improving product quality, protecting the environment, resource recovery, and green and clean use of energy.

[0004] At present, the commonly used methods for dehydrating coal slime are centrifugal dehydration and filtration dehydration. Centrifugal dehydration has high power consumption and high instrument cost; filtration dehydration generally uses vacuum filtration and pressure filtration. Due to the small particle size of coal slime, higher pressure is often required to dehydrate the coal slime, which also has the problem of high energy consumption. In order to improve the efficiency of mechanical dehydration, conditioning agents are often added to the coal slime. On the basis of not changing the original dehydration equipment and process, the moisture content of the filter cake can be reduced more quickly. Currently, the commonly used conditioning agents are PAM (polyacrylamide), PAC (polyaluminum chloride) and Fe 3+ The existing conditioning agents have defects such as large dosage, corrosion to dehydration equipment, and secondary pollution to the environment, which limits the sustainable promotion and application of conditioning agent addition in the coal slime dehydration process. Therefore, under the premise of taking into account the effective conditioning of coal slime dehydration, if the mechanical dehydration efficiency can be greatly improved and the dehydration time can be reduced while adding less conditioning agent, it is of great significance to the green and clean utilization technology level of coal mine resources, and also has broad market application prospects and good social and environmental benefits. Summary of the invention

[0005] The purpose of the present invention is to provide an application of a quaternary ammonium surfactant in coal slime dewatering, wherein the quaternary ammonium surfactant is used as a coal slime dewatering conditioning agent, and the quaternary ammonium surfactant is added to the coal slime, and high-efficiency coal slime dewatering is achieved by filter pressing. While adding less conditioning agent, the mechanical dewatering efficiency is greatly improved, the dewatering time is reduced, and the defects of traditional conditioning agents such as large dosage, corrosion to dewatering equipment, and secondary pollution to the environment are solved.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The present invention provides an application of a quaternary ammonium salt surfactant, wherein the quaternary ammonium salt surfactant is used as a coal slime dehydration conditioning agent and applied to coal slime dehydration, and specifically comprises the following steps:

[0008] 1) mixing coal slime with the quaternary ammonium salt surfactant to obtain a mixture;

[0009] 2) The mixture in step 1) is subjected to solid-liquid separation to obtain a dehydrated mud cake.

[0010] Further, in step 1), the quaternary ammonium surfactant is selected from any one of octadecyl trimethyl ammonium bromide, dioctadecyl dimethyl ammonium chloride or behenyl dimethyl benzyl ammonium chloride. The quaternary ammonium surfactant can effectively reduce the solid-liquid interface affinity of the coal slime. In the compression filtration stage, the quaternary ammonium surfactant can form a skeleton structure to improve the pore connectivity in the filter cake, thereby improving the water permeability and drainage performance, and improving the solid-liquid separation performance of the coal slime.

[0011] Furthermore, in step 1), the quaternary ammonium salt surfactant is a stock solution of a viscous quaternary ammonium salt surfactant, the concentration of the stock solution is 0.05 g / mL, and the solvent of the quaternary ammonium salt surfactant is water.

[0012] Furthermore, the mass ratio of the quaternary ammonium salt surfactant to the dry basis of coal slime is (0.015-0.1):1.

[0013] Furthermore, in step 1), the mixing is performed by stirring at a speed of 200 to 600 rpm.

[0014] Furthermore, the stirring time is 2 to 15 minutes. Preferably, the stirring time is 5 to 10 minutes.

[0015] Furthermore, in step 2), the solid-liquid separation is carried out by filter press.

[0016] Furthermore, in the filter pressing, the filter pressing pressure is 0.1 to 0.6 MPa.

[0017] Furthermore, the filtration time is 10 to 40 minutes. Preferably, the filtration time is 15 to 30 minutes.

[0018] Furthermore, the coal slime dehydration process is carried out at room temperature.

[0019] The present invention improves the overall hydrophobicity of the coal slime by contacting the hydrophilic end of the quaternary ammonium salt surfactant agent with the surface of the coal slime, and at the same time further improves the solid-liquid separation performance of the coal slime by constructing a skeleton structure and building a water molecule channel, and realizes the final solid-liquid separation by filter pressing.

[0020] Compared with the prior art, the present invention has the following characteristics:

[0021] 1) The present invention uses a quaternary ammonium salt surfactant as a coal slime dehydration conditioning agent and is applied to coal slime dehydration. The treatment method is simple and easy, and no coal slime pretreatment process is required. The shortcomings of the traditional coal slime dehydration process, such as large dosage of reagents, low dehydration efficiency, and high energy consumption, can be overcome, and the advantages of low dosage and mild reaction conditions are achieved;

[0022] 2) The present invention reduces the consumption of dehydration conditioning agents in the coal slime dehydration process, and can significantly improve the mechanical dehydration efficiency and reduce the dehydration time while adding less conditioning agents (<0.5wt.% of the dry basis mass of the coal slime);

[0023] 3) The coal slime dehydration efficiency of the present invention is high, and the consumption of dehydration conditioning agents in the coal slime dehydration process is reduced. After the coal slime conditioning and dehydration process is completed, the clarity of its tail water is improved, and the residual coal slime in the process tail water is greatly reduced, which effectively improves the tail water treatment efficiency and helps the recycling of tail water in the coal preparation plant. Most of the coal slime in the water exists in the form of flocs, which is convenient for its tail water treatment and ensures the clarity of the circulating water of the coal preparation plant. Therefore, the treatment method of the present invention has high social and environmental benefits, economic benefits and broad market application prospects;

[0024] 3) The present invention significantly reduces the energy consumption of the coal slime dehydration process, provides a new technical approach for environmentally friendly coal slime dehydration conditioning, and has important social and environmental benefits and broad market application prospects. DETAILED DESCRIPTION

[0025] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0026] The following are more detailed implementation cases, which further illustrate the technical solutions of the present invention and the technical effects that can be obtained.

[0027] In the following examples, unless otherwise specified, raw materials, reagents or processing techniques are all conventional commercial products or conventional processing techniques in the art.

[0028] The following examples and comparative examples were all carried out at room temperature. The coal sludge used was taken from a coal preparation plant in Ordos City, Inner Mongolia. The added quaternary ammonium surfactant was first dissolved in water to form a viscous quaternary ammonium surfactant stock solution with a concentration of 0.05 g / mL.

[0029] Embodiment 1:

[0030] In this embodiment, a quaternary ammonium surfactant (octadecyl trimethyl ammonium bromide) is used as a dehydration conditioning agent. Octadecyl trimethyl ammonium bromide is added to the coal slime, mixed and stirred for reaction, and then the coal slime is subjected to solid-liquid separation by filter pressing to achieve the purpose of deep dehydration of the coal slime. The specific conditions and steps are as follows:

[0031] (1) The initial moisture content of the coal sludge was 90%, and the amount of octadecyltrimethylammonium bromide added was 0.1 g / g dry weight of the coal sludge, and the mixture was mixed and stirred with the coal sludge at a speed of 200 rpm for 5 min;

[0032] (2) The solid-liquid separation was carried out by filtration pressing, the filtration pressure was 0.6 MPa, and the filtration time was 15 min.

[0033] After conditioning with octadecyltrimethylammonium bromide, the capillary water absorption time of the sludge decreased from 33.0s to 22.9s, and the final moisture content of the mud cake obtained by filtration was 32.1%.

[0034] Embodiment 2:

[0035] In this embodiment, a quaternary ammonium surfactant (dioctadecyl dimethyl ammonium chloride) is used as a dehydration conditioning agent. Dioctadecyl dimethyl ammonium chloride is used for coal slime dehydration, and the specific conditions and steps are as follows:

[0036] (1) The initial moisture content of the coal sludge was 95%, and the dosage of dioctadecyl dimethyl ammonium chloride was 0.05 g / g dry weight of the coal sludge, and the mixture was mixed and stirred with the coal sludge at a speed of 400 rpm for 10 min;

[0037] (2) The solid-liquid separation was carried out by filtration pressing, the filtration pressure was 0.6 MPa, and the filtration time was 30 min.

[0038] After conditioning with dioctadecyl dimethyl ammonium chloride, the final moisture content of the mud cake obtained by filter pressing was 32.9%.

[0039] Embodiment 3:

[0040] In this embodiment, a quaternary ammonium surfactant (behenyl dimethyl benzyl ammonium chloride) is used as a dehydration conditioning agent. Behenyl dimethyl benzyl ammonium chloride is used for coal slime dehydration, and the specific conditions and steps are as follows:

[0041] (1) The initial moisture content of the coal sludge is 90%, and the amount of docosyl dimethyl benzyl ammonium chloride added is 0.025 g / g dry weight of the coal sludge, and the mixture is mixed and stirred with the coal sludge at a speed of 600 rpm for 8 minutes;

[0042] (2) The solid-liquid separation was carried out by filtration pressing, the filtration pressure was 0.2 MPa, and the filtration time was 30 min.

[0043] After conditioning with behenyl dimethyl benzyl ammonium chloride, the final moisture content of the mud cake obtained by filter pressing was 34.0%.

[0044] Embodiment 4:

[0045] In this embodiment, a quaternary ammonium surfactant (octadecyl trimethyl ammonium bromide) is used as a dehydration conditioning agent. Octadecyl trimethyl ammonium bromide is used for coal slime dehydration, and the specific conditions and steps are as follows:

[0046] (1) The initial moisture content of the coal sludge was 90%, and the amount of octadecyltrimethylammonium bromide added was 0.1 g / g dry weight of the coal sludge, and the mixture was mixed and stirred with the coal sludge at a speed of 600 rpm for 10 min;

[0047] (2) The solid-liquid separation was carried out by filtration pressing, the filtration pressure was 0.4 MPa, and the filtration time was 30 min.

[0048] After conditioning with octadecyltrimethylammonium bromide, the capillary water absorption time of the sludge decreased from 33.0s to 25.9s, and the final moisture content of the mud cake obtained by filter pressing was 33.0%.

[0049] Comparative Example 1;

[0050] In this comparative example, the coal slime was directly dehydrated by filter pressing, and the specific conditions and steps were as follows: the initial water content of the coal slime was 90%, and the solid-liquid separation was directly performed by filter pressing, the filter pressing pressure was 0.6 MPa, and the filter pressing time was 30 min. At this time, the filter pressing could not obtain a non-fluid formed mud cake, and the final water content of the dehydrated coal slime was 86.7%, which was much higher than the coal slime treated with the quaternary ammonium salt surfactant and the same filter pressing dehydration method in Examples 1-4.

[0051] Comparative Example 2;

[0052] In this comparative example, polyacrylamide + polyaluminium chloride is used as a dehydration conditioning agent. The polyacrylamide + polyaluminium chloride is used for coal slime dehydration, and the specific conditions and steps are as follows:

[0053] (1) The initial moisture content of the coal slime is 90%. Polyacrylamide at a concentration of 0.3 wt.% on a dry basis of the coal slime and polyaluminium chloride at a concentration of 10 wt.% on a dry basis of the coal slime are added in sequence as dehydration conditioning agents, and the mixture is mixed and stirred with the coal slime at a speed of 200 rpm for 5 min.

[0054] (2) The solid-liquid separation was carried out by filtration pressing, the filtration pressure was 0.6 MPa, and the filtration time was 15 min.

[0055] After conditioning with polyacrylamide + polyaluminium chloride agents, the final moisture content of the mud cake obtained by filter pressing is 62.8%, which is much higher than the moisture content of the coal slime conditioned with quaternary ammonium salt surfactant and treated by the same filter pressing dehydration method in Examples 1-4. At this time, the amount of agent added is as high as more than 10wt% of the dry basis of the coal slime, and the consumption of conditioning agents is large.

[0056] The above embodiment uses a quaternary ammonium surfactant as a coal slime dehydration conditioning agent and is applied to coal slime dehydration, and combines it with a filter press to achieve coal slime dehydration. The treatment method is simple and easy, and does not require a coal slime pretreatment process. It can overcome the shortcomings of the traditional coal slime dehydration process, such as large dosage of reagents, low dehydration efficiency, and high energy consumption, and has the advantages of low dosage and mild reaction conditions.

[0057] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. An application of a quaternary ammonium salt surfactant, characterized in that: The quaternary ammonium surfactant is used as a coal slime dehydration conditioning agent and applied to coal slime dehydration, which specifically includes the following steps: 1) mixing coal slime with the quaternary ammonium salt surfactant to obtain a mixture; 2) The mixture in step 1) is subjected to solid-liquid separation to obtain a dehydrated mud cake.

2. The use of a quaternary ammonium salt surfactant according to claim 1, characterized in that: In step 1), the quaternary ammonium salt surfactant is selected from any one of octadecyltrimethylammonium bromide, dioctadecyldimethylammonium chloride or behenyldimethylbenzylammonium chloride.

3. The use of a quaternary ammonium salt surfactant according to claim 2, characterized in that: In step 1), the quaternary ammonium salt surfactant is a stock solution of a quaternary ammonium salt surfactant, and the concentration of the stock solution is 0.05 g / mL.

4. The use of a quaternary ammonium salt surfactant according to claim 3, characterized in that: The mass ratio of the quaternary ammonium salt surfactant to the dry basis of coal slime is (0.015-0.1):

1.

5. The use of a quaternary ammonium salt surfactant according to claim 1, characterized in that: In step 1), the mixing is performed by stirring at a speed of 200 to 600 rpm.

6. The use of a quaternary ammonium salt surfactant according to claim 5, characterized in that: The stirring time is 2 to 15 minutes.

7. The use of a quaternary ammonium salt surfactant according to claim 1, characterized in that: In step 2), the solid-liquid separation is carried out by filter pressing.

8. The use of a quaternary ammonium salt surfactant according to claim 7, characterized in that: In the filter pressing, the filter pressing pressure is 0.1-0.6 MPa.

9. The use of a quaternary ammonium salt surfactant according to claim 8, characterized in that: The filtration time is 10 to 40 minutes.

10. The use of a quaternary ammonium salt surfactant according to claim 1, characterized in that: The dehydration process of the coal slime is all carried out at room temperature.