| Ammonium persulfate((NH4)2S2O8)exhibiting strong oxidizing property has been widely used in the fields of chemical engineering,electronics,petroleum and storage battery industries and so on,mainly used as the initiator agent in the organic synthesis industries,the etchant agent in printed circuits and the additive for petroleum fracturing agents and so on.At present,ammonium persulfate is produced by electrolysis in the industry.Nowadays the membrane used for the electrosynthesis of ammonium persulfate in China is mainly the ceramic membrane,but the life of the ceramic membrane is shorter with higher resistance,which results in the lower current efficiency,the higher energy consumption and the increase of production cost.The life of the ion exchange membranes is longer with lower resistance,so it has practical application value for improving current efficiency and reducing energy consumption to study the electrolytic performance of the ion exchange membranes in the electrosynthesis of ammonium persulfate.In this paper,the theoretical basis of electrosynthesis of ammonium persulfate was studied and a small-scale experimental device was built up and the numerical simulation was carried out in order to optimize the structure of the inlet pipe of the small-scale experimental electrolyzer.A self-made electrolyzer was adopted in the small-scale experiments with a sintered platinized titanium as anode,a Pb-Sb-Sn alloy as cathode and ion exchange membranes as the electrolyzer membranes.The small-scale electrolyzer used the polytetrafluoroethylene pipe as the inlet pipe and the outlet pipe with an inner diameter of 1 mm and an outer diameter of 2 mm.The simulation results showed that the flow field distribution on the electrode surface was relatively uniform with the relatively uniform current density distribution on the electrode surface,the higher current efficiency and the lower energy consumption when the inlet pipe structure was as follows:the depth of the inlet pipe was 18 mm,a small pore with a diameter of 1 mm at a distance of 12 mm from the electrolyte inlet,and another small pore with an inner diameter of 0.5 mm at the inlet.The electrolytic properties of the small-scale experimental electrolyzer of ion exchange membranes in the electrosynthesis of ammonium persulfate were inveatigated by the numerical simulation.The simulation results showed that the current efficiency of the anion exchange membrane(HDJAM membrane)reached 86.0%with its energy consumption of 1229 kW h/t under certain conditions.The effects of cell voltage,electrolyte flow rate and ammonium sulfate concentration of catholyte on current efficiency and energy consumption of the quaternary amine anion exchange membranes(HDJAM membrane and HDAMI membrane)were investigated in the small-scale experiments.The experimental results showed that the current efficiency and the energy consumption of HDJAM membrane and HDAMI membrane were 87.0%,71.5%and 1215 kW·h/t,1807 kW·h/t,respectively,under the optimal conditions.The anion exchange membrane was used as the membrane in electrosynthesis of ammonium persulfate,which proposed a new membrane electrolysis method for electrosynthesis experiments of ammonium persulfate.This was an innovation of the experimental method in the subject.The electrolytic properties of four perfluorosulfonic acid cation exchange membranes(HDGN membrane,HDJCM membrane,HDNAF membrane,and HDCMI membrane)were investigated at different cell voltage and electrolyte flow rate in the small-scale experiments.The experimental results showed that the current efficiency and the energy consumption of HDGN membrane,HDJCM membrane,HDNAF membrane and HDCMI membrane,were 91.5%,88.5%,79.4%,74.5%and 1155 kW·h/t,1195 kW·h/t,1479 kW·h/t,1734 kW·h/t,respectively,under the optimal conditions.Considering the cost of ion-exchange membranes,the requirements of the installation of the pilot electrolyzer and so on,the HDGN membrane and the HDCMI membrane selected as membranes were installed in the electrolyzer of the industrial electrosynthesis of ammonium persulfate.Through the pilot experiments,electrolytic performance of the two ion exchange membranes were investigated in the condition of industrial electrosynthesis of ammonium persulfate compared with the ceramic membrane currently used in the industry.The experimental results showed that the current efficiency and the energy consumption of HDGN membrane,HDCMI membrane and ceramic membrane under optimal conditions were 95.0%,75.0%,72.7%and 1113 kW·h/t,1723 kW·h/t,1777 kW·h/t,respectively.Therefore,HDGN membrane could effectively improve current efficiency and reduce energy consumption of the industrial electrosynthesis of ammonium persulfate.This was an innovation of the application in the subject.In order to analyze the effect of the shared catholyte on the electrolytic performance of the membrane electrolyzers in electrosythesis of ammonium persulfate,equivalent circuit models of membrane electrolyzers were established and the electrolytic performance of two electrolyzers with independent catholyte and shared catholyte was investigated by numerical simulation.The simulation results showed that the shared catholyte resulted in the bias current from the electrolyzer cathode with lower electrical resistance membrane to the electrolyzer cathode with higher electrical resistance membrane and changed the cell voltage of the two electrolyzers.Analysis of the simulation results illustrated that the bias current caused a decrease in current efficiency and an increase in energy consumption of the two electrolyzers.Using the HDGN membrane electrolyzer and the ceramic memebrane electrolyzer,experiments were carried out to investigate the electrolytic performance of the two electrolyzers with independent catholyte and shared catholyte.The experimental results showed a good agreement with those of simulation,which demonstrated the correctness of the equivalent circuit models of membrane electrolyzers with shared catholyte.This was an innovation in the theory in the subject.A new type of the industrial electrolyzer for electrosynthesis of ammonium persulfate was designed using the HDGN membrane as the electrolyzer membrane.The industrial electrolyzer was a kind of the bipolar electrolyzer.The structure innovation of the industrial electrolyzer in the field of ammonium persulfate production electrolyzers were as follows:the adoption of the ion exchange membrane as the electrolyzer membrane and the adoption of the compound plate made of the platinized titanium plate and the lead-antimony alloy plate as the bipolar plate.By numerical simulation method,the structure of the stream guidance rib plates of the electrolyzer unit was optimized and the effects of cell voltage and electrolyte flow rate on current efficiency and energy consumption were studied.The simulation results showed that the current efficiency of the electrolyzer unit reached 94.0%,and its energy consumption reduced to 1137 kW·h/t when the cell voltage was 4.5 V with the electrolyte flow rate of 2 L/min.The numerical simulation results preliminarily indicated that the new type of the industrial electrolyzer designed had good electrolytic performance of electrosynthesis of ammonium persulfate.This was an innovation in the structure design in the subject. |
