| Ethoxylation is commonly performed in industry for the production of many fine chemicals such as non-ionic surfactants and polypropylene glycols and so on in which ethylene oxide(EO) is typically ring-opening addition or polymerization reacted with active hydrogen-contained compounds(such as alcohol and amine,etc.). Ethoxylation is a special kind of chemical reaction and is highly exothermic reaction. In addition, ethylene oxide is a very reactive, flammable and explosible reactant. So the requirement of security for the plant is very high. The new technique of continuous catalytic distillation (CD) had been proposed by Liaoning oxichem co.ltd and a 2000t/a pilot-scale CD) column was built in order to develop a green energy-saving ethoxylation technique. Owing to the EO risky problem, safety analysis and assessment were essential for the new CD process. This paper is carried out to make a study on safety assessement for the synthesis of ethylene glycol monoethers (EGMME) from methanol and ethylene oxide aimming at establishing theoretical foundation for industrialization.1. The optimal operating parameters and the safety evaluation basic data of the CD cloumn were calculated and determined through simulation using ASPEN PLUS software.The effects of the key operating parameters (such as pressure, temperature, reboiler heat duty, molar feed ratio of methanol to EO, reaction zone and stripping zone height,etc.) on selectivity and yield of EGMME were investigated to obtain the optimal operating conditions of column.The optimal operation parameters were determined to be:EO feed rate 174.68 kg·h-1, methanol feed rate 127.04 kg·h-1, pressure 0.4Mpa,reaction zone temperature 377K,reboiler duty 186.6 kW.condensor duty-300.2 kW, boilup ratio 10, molar feed ratio of methanol to EO 1:1, height of reaction zone 3.8m, height of stripping section 4.2 m. Through simulation under the established operating conditions, it was showed that, a conversion of EO more than 99.99%, a conversion of methanol more than 95% and a selectivity of EGMME more than 91.6% could be achieved, which indicated the potential advantage of using CD for the production of EGMME. Additionally, the profiles for the column temperature, the liquid and vapor flow rate, the vapor and liquid composition along the column as well as the unconverted EO in CD column which was needed for safety assessment were obtained.2. The safety evaluation methods and safety. assessment for the new device (technology) were conducted owing to the EO risky problem.Firstly, based on EO hazards and impact factors, the EO systerm operational spaces were partitioned into four operation zones, the normal operation zone, the security-alerting zone, the security threatening zone, the security disaster zone. Accordingly, based on this, a reference standard of EO system was established for safety analysis and assessment.Secondly, security analysis and assessment were carried out for the new technology. The assessment results showed that the operating temperature and pressure were moderate and the heat transfer performance was well. Also there were no local high temperature and hot spot. Moreover, EO is almost completely converted, as a result, there was no accumulation in the vapor-liquid phase. So, the new process was in the normal operation zone. Afterwards, the security of the new CD process was compared with industrial ethylene oxidation decices for production of EO and ethoxylation loop reactors.The results showed that there was no oxygen, acetaldehyde and other dangerous substances in the CD system. Besides, the operating conditions of CD system were "moderate". Therefore, the risk degree of the new CD technology was far below the industrial EO production process ethoxylation loop process.3. Based on the accidental-consequence analysis, the risks of the CD column were assessed due to the dispersion of EO on condition of emergency discharge.Firstly, the discharge patterns and the dispersion models of EO vapor were identified according to the security evaluation criteria. The results showed that discharge pattern was continuous emission and dispersion model was heavy gas dispersion when the wind velocity is below 0.94 m·s-1 whereas passive dispersion. Secondly, the safety distances of EO passive dispersion behavior were predicted and calculated by means of gaussian plume model. The results showed that the maximum safety distances for flash fire or explosion and toxic effect in the unfavorable environment condition could reach 35.2 and 97.4 meter. As well, the maximum safety distances were also calculated by means of SLAB model for EO heavy gas dispersion. and the maximum safety distances of EO heavy gas dispersion were significantly larger than passive diffusion. Afterwards, safety distances for the lethality of human and for structural damage to buildings could be assessed by using the Multi-Energy Method when EO clouds exploded, the values were 69.45 m and 13.89m.The results obtained in this work will provide the basic information for the assessment of accidental-consequence safety and further for the establishment of emergency response plans of the CD column.
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