Study On The Intensification Of The Gas-Liquid Reaction Process In The Production Of Ammonium Alkali From Waste Sodium Chloride Salt

During the production of fine chemical products such as hydrazine hydrate,furan phenol,glyphosate,and polyphenylene sulfide in China,a large amount of by-product sodium chloride salt residues are produced every year.These by-product sodium chloride slag will not only cause serious pollution to the environment,but also become an obstacle to the development of enterprises.At present,the treatment methods of sodium chloride waste salt include incineration method,landfill method,salt washing method,high temperature treatment method and alkali-making method.Among them,the alkali-making method meets the needs of the green development of the enterprise,makes rational use of sodium chloride waste salt,and realizes circular economy.In order to realize the purpose of recycling sodium chloride salt residue,it is necessary to study the gas-liquid process enhancement in the system.The key to the enhancement of the gas-liquid reaction process is that the gas-liquid two phases can be continuously and efficiently mixed and reacted.This paper combines numerical simulation with experiment,takes the airlift loop reactor as the research object,optimizes and screens the structure of the airlift loop reactor by using FLUENT software,obtains the best structural parameters and operating parameters,realizes the process enhancement between gas and liquid,and studies the mass transfer coefficient and bubble particle size change of the reactor in the amplification process.Then,the airlift loop reactor was employed to the process of recycling sodium chloride type waste salt to obtain the best time for ammonium,carbonation and secondary ammonium,and finally a new process for producing ammonium alkali from sodium chloride waste salt was obtained.The above study had yielded the following conclusions:（1）The optimal height-diameter ratio of the airlift loop reactor for the gas-liquid two-phase reaction was 7,the inner and outer diameter ratio was 0.6,the height of the guide tube is 800 mm,the opening of the aerator was 3 mm,and the opening of bell mouth in expanded section was 30°.（2）Considering the practical application of the airlift loop reactor,the changes of fluid in the flow field during the amplification process of airlift loop reactor and the influence of the amplification process on bubble particle size distribution and mass transfer effect were explored.The gas holdup and circulating liquid velocity both increased with the amplification of the reactor;for the particle size distribution of bubbles,the ratio of the large bubbles also increased with the amplification of the reactor;when the apparent gas velocity was controlled,the volume mass transfer coefficient decreased with the amplification of the reactor.（3）A pilot scale airlift loop reactor was designed,and the hydrodynamic properties of the loop reactor were measured experimentally.It was obtained that with the increase of apparent gas velocity,the total gas holdup in the loop reactor and the gas holdup in the outer loop,circulating liquid velocity and mass transfer coefficient increased,and compared with the simulation results,the change trend was basically consistent,that is,the simulation results of the loop reactor were reliable;the mixing time of the loop reactor was also measured,and the mixing time of the loop reactor was obtained.The time was 15 s,indicating that the mixing effect of the reaction equipment was better.（4）According to the airlift loop reactor designed in this paper,the ammonium process,carbonization process and post-treatment process in waste salt treatment were experimentally studied.Under the condition of an apparent gas velocity of 0.0444 m/s,the results showed that the time of passing NH₃ in the ammoniumization process was 70 min,the time for passing CO₂ in the carbonization process was 105 min,the time for passing NH₃ through the second ammonium process was 40 min,the purity of Na HCO₃ product was89.68%and the purity of NH₄Cl product was 99.9%purity by chemical sublimation.The purity of Na HCO₃ and NH₄Cl products meets the market demand.