250000 T/a C3-C4 Paraffin's Dehydrogenation Device Simulation And HEN Optimization

The light olefins such as propylene and butylene are widely used in the petrochemical field.Propylene as an important intermediate can be used in the production of polypropylene,acrylonitrile,propylene oxide and other chemical products.As low pollution and high octane number gasoline oxygenate,MTBE can be generated by isobutylene through etherification reaction.At present,propylene and isobutylene are mainly from the byproducts of catalytic cracking and petroleum cracking to ethylene,what's more,whose output is unable to keep up with growing needs of market.Alkane dehydrogenation technology chose light olefins as the main product possess the advantages of high yield and high selectivity can fill the market gap in some content.Pinch technology combined the thermodynamic principle to integration process and the heat exchange network design.Conduct pinch analysis to the object of study can predict the energy conserving potential and finds out the unreasonable problems.The purpose of energy-saving and increasing economic efficiency can be achieved by propose energy saving scheme on the basis of pinch analysis.The 250 k t/a C3-C4 paraffin's dehydrogenation device was modeled with the Aspen plus software,on that basis,pinch analysis was applied to the existing heat exchanger network(HEN)and a practical HEN scheme was proposed.The main work of this paper as follows:(1)The processes of reaction,cooling box,product separation MTBE and isomerization unit were simulated by Aspen plus software.All the simulation results showed good coincidence with the site data so that the models can be used for subsequent process of optimization.(2)Optimized the operating parameter on the base of Aspen plus models,the influence of methanol isobutylene ratio and reflux ratio of C801 on energy consumption and product purity of MTBE unit was studied,what's more the optimal value interval was given.(3)Chose product separation unit,MTBE unit,isomerization unit as the system to optimize.Conducts statistics of the system on the base of current condition,the results showed that the amounts of cold and hot utilities are 34.3MW and 45.3MW pesectively.The system was analyzed by pinch technology,followigly,the pinch was point out and the energy saving potential was calculated.Results showed that compared to the isomerization unit the unit of product seperation and MTBE have larger energy saving consumption.(4)Several practical HEN schemes were proposed by use of pinch analysis,the scheme of product separation unit and scheme 1 of MTBE unit were chosed finally through comprehensive trade-off between energy saving efficiency and capital costs.The final scheme which might save the consumption of cold and hot utilities up to 8.04% and 12.32%,save the low pressure steam(0.35mpag)10.05t/h.At present C3-C4 paraffin's dehydrogenation device is rare,the work of this paper is helpful for understand the process and mechanism in deep.The energy saving scheme which proposed by this paper not only can provide a reference for enterprise but also can achieve the goal of energy saving and improve economic benefit.