Study On Economical And Efficient Foaming Agent For Mine Dust Suppression Based On Synergistic Effect Of Surfactant And Macromolecule Stabilizer

As one of the five major hazards in coal mine,dust will be produced in a large number of production operations,leading to pneumoconiosis and coal dust explosion and seriously threatening the occupational health of miners and the safety of coal mine production.The foam dust suppression technology has the advantages of low water consumption and high dust suppression efficiency,which provides a solution for the effective control of mine dust.However,in the current foam dust suppression technology,the adding proportion and total consumption of foaming agent are very high.Economic cost seriously restricts the wide application of foam dust suppression technology.As the key material in foam dust suppression technology,foaming agent is the critical factor to determine the cost and performance of foam.In order to reduce the economic cost and promote the application of foam dust suppression technology,the study of new and efficient foaming agents has become an inevitable choice.Based on the basic theory of surface physical chemistry and the combination of experimental research and molecular dynamics simulation,in this dissertation,the foaming agent composed of surfactant and macromolecule stabilizer has been studied from the following aspects:the ability of surfactants to resist hard water,the synergistic effect of surfactant and macromolecule stabilizer and the wetting mechanism of coal dust by surfactants.Industrial experiments and field applications of a new foaming agent were carried out in order to reduce the adding ratio of foaming agent and to improve the suppression efficiency of mine dust.The main results and conclusions are as follows:The idea of introducing non-ionic oxygen-containing hydrophilic groups into the molecular structure of anionic surfactants to improve their resistance to hard water was adopted.The foaming ability and the adsorption behavior at the air/water interface of anionic-nonionic surfactant?SDES with EO groups?and sodium dodecyl sulfate?SDS without EO groups?in hard water were compared.The experimental results show that SDES has better foaming ability than SDS under high water hardness.The simulation results show that with increasing the number of EO groups,the total number of hydrogen bonds between surfactants and water molecules and the thickness of interfacial layer increases,the total number of calcium ions in the interface layer reduces,the distribution intensity of Ca²⁺around the SO₄^-decreases,and the distribution intensity of Ca²⁺around the EO groups increases.This indicates that the introduction of EO group can increase the hydration strength and reduce the probability of complexation between Ca²⁺and SO₄^-,which is helpful to improve the surface activity and foaming ability of surfactants in hard water.The synergistic effect of surfactant and macromolecule stabilizer was used to strengthen the bubble film and to improve the foam performance.The influence of macromolecule stabilizer?WP?on the solution and foam properties of SDES was studied.When SDES concentration is low,the addition of WP can reduce the surface tension.While at high SDES concentrations,WP does not affect the surface tension.The higher the concentration of WP,the larger the bulk viscosity of the mixed solution.At low SDES concentrations,adding WP can enhance the strength of bubble films,reduce the breakup of bubbles,shorten the foaming time of the solution,increase the foaming ability and liquid carrying capacity of foam,and reduce the average radius of the bubbles.However,at high SDES concentrations,the effect of WP on the above foam properties was not significant.With the increase of SDES concentration,the average radius of bubbles first decreases rapidly,then slowly declines and gradually reaches a stable value.Increasing the concentration of SDES and WP can slow down the drainage rate of foam and help to maintain the liquid film thickness for a longer time.In order to reveal the synergistic effect of surfactant and macromolecule stabilizer and the mechanism of WP improving the foam performance at low SDES concentrations from the microscopic level,the interaction and adsorption structure of SDE₃S and WP at the air/water interface were studied by molecular dynamics simulation.As the adsorption density of SDE₃S increases,the interfacial layer thickness increases gradually,and the layer thickness of SDE₃S/WP systems is always larger than that of pure SDE₃S systems.After the addition of WP,the tail chain of SDE₃S is more perpendicular to the air/water interface,and the hydrophilic group is more parallel to the air/water interface,which improves the coverage area and hydration of the surfactant hydrophilic group at the air/water interface.WP is distributed in the hydration layers of oxygen atoms in SDE₃S head group,which contains a large numbers of hydroxyl groups to enhance the hydration of surfactants.A three-dimensional hydrogen bon network can be formed between SDE₃S,WP and water molecules,thereby increasing the strength of bubble films and improving the anti-strike performance of bubble films.The increase in the surfactant adsorption density gradually reduces the number of hydrogen bonds between WP and water molecules.When the surfactant adsorption density is lower,WP forms more hydrogen bonds with water molecules,and the strength of bubble films is enhanced more greatly.Therefore,at low SDES concentrations,the addition of WP can significantly improve the foam performance.In order to reveal the wetting mechanism of coal dust by surfactants and to explore the deep reasons of different wetting effects caused by the differences of surfactant molecular structure,the adsorption and wetting characteristics of three similar anionic surfactants were studied.The lower the surface tension of the solution,the smaller the energy barrier of coal dust entering the solution,leading to better wetting effects.When the surface tension reaches a stable value,the wetting effect is determined by the adsorption density of surfactant on coal dust surface and its hydrophilic-lipophilic balance?HLB?value.The weaker the electrostatic repulsion between the anionic surfactant head group and coal dust,and the stronger the hydrophobic interaction between the surfactant tail chain and coal dust,the larger the adsorption density of anionic surfactant on the coal dust surface.The surfactant adsorption density determines the number of hydrophilic sites on the surface of coal dust,and the HLB value determines the dynamic immersion rate of coal dust.The higher the adsorption density and HLB value,the better the wetting effect of surfactant.Among the three surfactants selected,sodium dodecyl sulfonate has the best wetting performance.A kind of foaming agent with excellent environmental protection performance was developed.Industrial experiments and field applications of the new foaming agent and conventional foaming agent without macromolecule stabilizer?i.e.ordinary foaming agent?were carried out.Under the conditions of low adding ratio?0.1%-0.3%?and high air pressure?0.3-0.6Mpa?,the foaming performance of the new foaming agent is significantly better than that the ordinary foaming agent.The application results show that when the foaming agent is added at 0.1%,the suppression efficiency of total dust and respirable dust reaches 90.3%and89.9%,respectively,which is almost the same with the dust suppression efficiency when the ordinary foaming agent is added at the concentration of 0.3%.This indicates that when using the new foaming agent in dust suppression technology,the adding proportion can be reduced to 1/3 of the ordinary foaming agent,and at the same time,ensures the good dust suppression effect,achieving the goal of reducing the economic cost and improving the dust suppression efficiency in foam dust suppression technology.This dissertation contains 82 figures,25 tables and 147 references.