| The problem of dust pollution widely occurs in the industrial production process such as mining and construction industry,which is increasingly harmful to employees and the environment.Therefore,efficient dust prevention and control technologies are urgently needed.Foam dust suppression technology has become one of the important means of dust removal because of its low water consumption and high dust suppression efficiency,especially for respiratory dust.As an important material in foam dust suppressant technology,the main chemical surfactant is commonly used at present,which has the defects of insufficient performance,large dosage,high cost and not in line with green environmental protection.In addition,the synthesis process of the material is generally a chemical process,which has the threat of secondary pollution.Therefore,this thesis proposes to synthesize and produce biological dust-inhibiting foaming agent by microbial fermentation synthesis,and explore its interface performance,foaming performance,biodegradability,non-toxic and innocuity and performance improvement,and carry out foam dust suppression experiments to study the dust-reducing performance of biological dust-inhibiting foaming agent.The main work achievements are as follows:The optimization of culture conditions and the amplification of synthesis efficiency of biological dust inhibiting and foaming agent(BDF)were studied.The operating conditions of the expanded culture stage and the fermentation synthesis stage in the synthesis process were studied by the self-developed biological dust suppression test system.Compared with the water bath shaker fermentation culture,the efficiency of BDF synthesis using the biological dust suppression test system was significantly improved.In the expanded culture stage,under the conditions of different dissolved oxygen values,the growth rate of the bacteria increased with the increase of dissolved oxygen value,but when the dissolved oxygen value was too high,the loss of activity of the bacteria was also accelerated.According to the influence trend of the stirring speed and ventilation rate in the tank on the growth and reproduction of the bacteria,when the stirring speed was 300r/min,the ventilation rate was 4L/min,the growth rate of the strain was the fastest,and it entered the mass death stage later.It could maintain a high activity for a long time,and it was most suitable as a pure-species inoculation strain.According to the sampling results of fermentation liquid under different dissolved oxygen values in the fermentation and synthesis stage,the fermentation time of the strain should not be too long,and 30-36 h is the best.Through the response surface analysis of three factors and three levels of stirring speed,ventilation volume and liquid volume,the best operating condition is when the stirring speed is 333r/min,ventilation volume is 4L/min,and liquid volume is 2.9L.A homogeneous fermentation environment was formed,which was most suitable for the growth,reproduction and metabolic activities of the strain.Under this condition,the effect of inoculum size on BDF synthesis yield was studied,and the inoculum size was 3.5% when the maximum BDF yield was obtained.The performance of BDF is explored and its performance is characterized systematically.The characterization results showed that BDF could reduce the surface tension of pure water to 25 m N/m at a lower concentration,and the critical micelle concentration(CMC)was about 34mg/L.The viscoelastic modulus of BDF solution decreased with the increase of the concentration,and reached the lowest at the concentration of 60mg/L.After that,the viscoelastic modulus tended to be stable with the increase of the concentration of foaming agent.The foaming ability and foam stability of BDF increased with the increase of solution concentration.When the concentration of BDF was greater than 150mg/L,the foaming ability was basically unchanged.The foam size decreased significantly with the increase of foaming solution concentration,and the increasing rate of bubble size with time slowed down.The distribution of bubbles was mainly small bubbles,followed by large bubbles.With the decay of bubbles,the distribution range of the three kinds of bubbles was gradually averaged.The biodegradability and non-toxic performance tests showed that BDF had excellent biodegradability compared with common surfactants,and its toxicity grade was practically non-toxic.The synergistic effect of BDF and polymer on foaming performance and the dust suppression performance of BDF-polymer under different working conditions were studied,and the dust suppression effect was compared with that of ordinary foaming agent.The results showed that the foamability FC of BDF was relatively little affected by the addition of xanthan gum,while the surface tension showed a gradual decreasing trend,and the decreasing rate gradually slowed down.Considering the stability and economic factors of foam,when the concentration of BDF is 0.15 ‰ and the concentration of xanthan gum is 0.1%,the half-life of foam is longer,the liquid carrying capacity of bubbles is larger and the drainage speed is small.In addition,the viscoelastic modulus of foam is lower,the surface tension repair ability is the strongest,the bubble size is relatively small,the foam uniformity is higher,and the use of raw materials is less.More economical and efficient.Compared with ordinary foaming agent,the foaming multiple of BDF is much higher than that of ordinary foaming agent.The foaming multiple increases first and then decreases with the increase of liquid suction flow,and its turning point is about 5L/h,which has the maximum foaming performance under this working condition.The dust removal efficiency of BDFxanthan gum foam on respirable dust and total dust was always higher than that of ordinary foaming agent,indicating that BDF-xanthan gum has a good dust removal effect on dust particles of different particle sizes.When the suction flow rate is 4L/h-5L/h,the dust removal effect of BDF-xanthan gum foam is the best,and the additive xanthan gum is easy to degrade and non-toxic and harmless raw material.Its addition will not destroy the green safety characteristics of BDF. |
PDF Full Text Request