Development Of The Production Process Of Hydrazine Hydrate And Its Energy-Saving Research

Because of its strong reducing property,hydrazine hydrate is widely used in organic synthesis and is an important fine chemical intermediate and raw material.At present,four processes,namely,lassie method,urea method,ketone linked nitrogen method and hydrogen peroxide method,have realized industrial production,among which urea method and ketone linked nitrogen method are the most applied processes by hydrazine hydrate manufacturers in China.Due to the technology blockade of hydrogen peroxide method in foreign countries,the ketone linked nitrogen method will develop rapidly in China in the next few years.This paper takes the basic process of ketone linked nitrogen method as the starting point,and optimizes the basic process around energy saving and consumption reduction,so as to provide some theoretical reference for the actual production of hydrazine hydrate and energy saving technology transformation.Since the physical property data of acetone-linked nitrogen is missing from the database that comes with Aspen Plus,it is necessary to estimate the relevant physical property data of this substance using Property Estimation based on the group contribution method.Also,to ensure the reliability of the simulation results,the binary gas-liquid phase equilibrium data between the key components were corrected according to the gas-liquid phase equilibrium data of the key components in the literature.For the reaction process in the process,a suitable kinetic equation was selected to describe the reaction process.Based on the characteristics of the material systems involved in the process,the NRTL equation was selected as the thermodynamic model for the process simulation calculations.The basic production process of ketone with nitrogen method was simulated by Aspen Plus,and then the parameters of each tower were optimized by sensitivity analysis.Finally,a solution of hydrazine hydrate with 80%mass fraction was obtained,and the conversion of acetone with nitrogen reached 99.47%and the yield reached99.45%（in terms of nitrogen）.The process operating parameters were optimized based on the sequential iterative method with the minimum total annual cost（TAC）as the optimization objective while ensuring the product index and yield remained unchanged,and the optimized process corresponded to a 14.03%reduction in TAC compared with that before optimization.In order to solve the problem of excessive energy consumption in the production process,an attempt was made to use the latent heat of vaporization at the top of the tower in the process twice and to thermally integrate the logistics that can be heat exchanged in the process.Through the analysis,it was found that there is no direct heat exchange flow between the hot and cold logistics,but it was found that there is only a temperature difference of 7.8°C between the top of the concentrator tower and the kettle of the acetone tower,so the variable pressure heat integration process was proposed.In other words,by increasing the operating pressure of the concentrator tower,the top heat flow unit of the concentrator tower can satisfy the condition of heating the acetone tower kettle.On the basis of satisfying the heat exchange,the effect of different operating pressures of the concentrator on the TAC was analyzed,and it was found that when the operating pressure of the concentrator was 130 k Pa,the equipment cost after heat integration increased by 8.3%and the operating cost decreased by 16.1%,and the corresponding TAC after heat integration was at least 4.907×10~6$/y,which decreased by 14.84%compared with the optimized TAC of the basic process.14.84%relative to the optimized base process TAC.In order to further reduce the energy consumption of the process,the modules were analyzed and the energy consumption of the acetone with nitrogen column was found to be too high,so the acetone with nitrogen distillation column was improved using the down-flow double-effect distillation energy-saving technology.Through the double tower with different operating pressures,the secondary utilization of latent heat of vaporization at the top of the tower is realized to achieve energy saving.By analyzing the economics of the simulated optimized double-effect distillation,it was found that the operating cost was reduced by 12.7%relative to the variable pressure heat integration process,and the total TAC was reduced by The total TAC was reduced by 11.77%,and the TAC was reduced by 24.86%compared to the basic process.In order to ensure the stable operation of the hydrolysis distillation column,the dynamic control of the hydrolysis column was studied,and the corresponding sensitivity of the temperature and temperature-component tandem control structure was evaluated,and it was found that the temperature-component tandem control structure could not only make quick response but also ensure the purity of the components.The problem of high-salt wastewater generated in the process of producing hydrazine hydrate by ketone linked nitrogen process was studied,and the aerodynamic energy low temperature evaporation process was applied to treat the wastewater and the process was improved and optimized.The results showed that the water recovery rate was about 65.5%and the COD was reduced by 95.3%compared with the raw water,which could be degraded to the discharge standard by the subsequent biochemical treatment unit.Finally,the process was simulated by Aspen Plus,and it was found that the temperature at the top of the scrubber tower had a greater impact on the cost of the process,and four of the modification processes were proposed,and the theoretical treatment cost of the optimal process was only 33.5￥/t（the operating cost of the existing process is about 200￥/t）,which had greater economy.