| The coal dominated energy structure is hard to change in the short term.Coal can produce a lot of fine particles during the processes of mining,transportation,storage and combustion,which are considered as one of the main reasons leading to the reduction of atmospheric visibility,haze weather and various respiratory diseases.Chemical dust suppression technology is becoming an important way to inhibit the fugitive particle emission owing to its specificity and high efficiency.And the chemical agglomeration technology,as a pretreatment method to increase the size of particle in the coal-fired flue gas,can enhance the removal performance of conventional dust removal equipment for fine particles.Therefore,they have good industrial application value and prospects.To investigate the suppression performance of composite wetting suppressant,the suppression experiment of water-spraying on lignite dust was conducted via the self-design simulated experimental facility.It can be found that the total dust removal efficiency of the simulated spraying suppression system have improved from 75.11%to96.73%by adding a composite wetting dust suppressant with a composition of 0.1%T-1 and 0.9%CaCl2,and the mass concentration of fine lignite particles in the facility decreased from 83.37 to 15.15 mg/m3.The composite wetting dust suppressant was applied in a coal-fired power plant in Inner Mongolia,the results indicated that the mass concentration of lignite dust in the workshop was reduced dramatically from 747.20 to 22.00 mg/m3,and the suppression efficiency improved by about 82%over that when pure water was sprayed,furthermore,the effect of trapping particles smaller than PM10 was synergistically enhanced.Through proximate and FTIR analysis of lignite,it proved that the wetting ability of the suppressant on lignite dust was determined by the surface tension of the solution in addition to the structural chemical properties of the surfactant molecules,and the addition of surfactant not only reduced the diameter,but also increased the axial velocity of droplet.For controlling the fugitive emission of fine particles from the long-term storage and long-distance transportation,a dust suppressant was proposed by applying a blend of 0.7%water-soluble polymer?guar gum?and 0.1%nonionic surfactant?Triton X-100?.The polymer molecules could adhere the lignite fine particles together through the solid-bridge force to form a polymer protective film,and the solid-bridge force between the lignite particles and polymer molecules should be a type of chemical force based on the FT-IR analysis.Besides,GG solution showed excellent solidified and anti rain erosion properties and the optimal mass concentration was0.7%.The lignite dust suppressant showed superior dust suppression performance on lignite fine particles,and effectively reduced the fugitive emission of fine particles in windy weather.When the air flow speed was in the range of 5-15m/s,the dust suppression efficiency on lignite fine particles was above 98%.Chemical agglomeration technology was applied to reduce the fine particle concentration in coal-fired flue gas.The effect of chemical properties of chemical agglomeration solution on droplet atomization performance was investigated via the phase Doppler anemometry?PDA?system,the results indicated that the atomization performance of PAM was the worst among the four types of chemical agglomeration solution,while the emulsion polymer PAE and SBE solution could obtain a good atomization performance in a wider concentration range.The chemical agglomeration solution with higher mass concentration,resulting in the breakup of agglomerant solution into small droplets became more difficult under the same dynamic condition,and the effective Weber number of the agglomeration solution dramatically decreased with the increase of the solution viscosity,and the solution droplet size was larger than that of water during the secondary breakup process.When the mass concentration of agglomerant was increased from 0.02%to 1%and the air pressure was 0.3MPa,the D50 were increased from15.00 to 24.95?m?for PAM?and from 11.00 to 22.5?m?for SBE?,respectively.Furthermore,the influences of solution chemical properties on wetting and agglomeration performances for fly ash were both studied,the results suggested that the higher molecule weight of chemical agglomerant is,the better agglomeration performance on fly ahs particles.To explore the relationship between fine particle abatement and atomization performances of chemical agglomeration solutions,SBG and SBE with different chemical properties were selected as the chemical agglomerant to conduct the chemical agglomeration experiment via the simulated coal-fired facility.With an increase of chemical agglomerant mass concentration,the fine particle removal performances showed the different variation trends due to the solution viscosity.When the mass concentration was 0.5%,the median diameter?D50?and removal efficiency of SBG solution were 24.00?m and was 28.44%,respectively.However,for SBE,the removal efficiency on fine particles was 33.19%with a D50 of droplets was 16.92?m.The viscous force was increased with an increase of agglomerant mass concentration caused the breakup of agglomerant solution into small droplets became more difficult.The atomization performance of SBG solution was worse than that of SBE solution due to the higher viscosity for SBG solution,which was disadvantageous to the collection of droplets on fine particles.In addition,by measuring the concentration of fine particles at the outlet of ESP,the enhancement of removal performance of ESP on fly ash particles by chemical agglomeration technology was investigated.The results showed that chemical agglomeration,as a pretreatment technology for particles before the ESP,could effectively increase the particle size at the ESP inlet,resulting in the fly ash particles could more easily be charged and trapped by ESP,and then reduced the concentration of fine particles and total dust at the ESP outlet.After spraying chemical agglomeration solution into the flue gas,the SBE exhibited the best agglomeration performance.Compared with only the ESP opened,the mass and number concentration of PM10 at the ESP outlet was decreased by 38.30%and 36.60%,respectively,and the total dust concentration was reduced by 47.90%.When the non-ionic surfactant Trixton-100 was added into the chemical agglomeration solution,the agglomeration growth of fine particles in flue gas can be facilitated by enhancing the wetting effect of chemical agglomeration solution on fly ash fine particles and reducing the size range of agglomeration droplets.Compared with the sigle ESP technology,the number concentration of fine particles at the ESP outlet can be further reduced by 59%.During the chemical agglomeration process,the submicron fine particles were adhered together by a chemical force to form newly larger aggregate after spraying chemical agglomeration solution into flue gas,resulting in the promotion of fine particle abatement.In addition,when the polymer molecules and fly ash particles were adhered together,the shape and position of the characteristic peaks of C1s,O1s and Si2s were changed,which indicated that the the adhesion between fly ash and chemical agglomerant was achieved via the effect of chemical force. |
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