Study On Technology And Engineering Of Combined Treatment On Waste Catalyst And Wastewater Of Composite Ionic Liquid Alkylation(CILA) Process

Composite Ionic Liquid Alkylation(CILA)process is a new petrochemical process for producing high octane number gasoline in refineries.Meanwhile,CILA process also produces various hazardous wastes.The absence of treatment technology for wastes restricts the engineering popularization of CILA process.This paper focuses on studying the by-product wastes,and aims for developing a treatment process and its' engineering application.Waste ionic liquid and alkali washing wastewater are the two main wastes of CILA process.The waste ionic liquid shows strong reactivity,acidity and contains acid-soluble oil and metal resources.The alkali washing wastewater leads to high pollution load and is of strong alkalinity.Based on analysis of the comprehensive characteristics,this paper puts forward an idea of ‘treating wastes with wastes' which combines the treatment on both waste ionic liquid and alkali washing wastewater.A ‘two steps' process of hydrolysis followed by neutralization is explored which is able to mildly eliminate the reactivity and acidity.In the process,the metal resources are transformed into sediment,and acid-soluble oil is separated and then recycled.A 0.14 kg/L small-scale plant is desigined to test the technological assumption of ‘mild-hydrolysis,rapid neutralization,flocculation sedimentation'.It is the mildest hydrolysis reaction of brine and waste ionic liquid at the volume ratio of 50:1 that performs the lowest exothermic and best quality of acid-soluble oil.Maximum value of metal sediment appears at the neutralizing range of p H value between 8.0 and 8.5.The hydrolyzed polyacrylamide can significantly accelerate the flocculation of sediment.A 100kg/d pilot-scale experiment is desigined to verify the feasibility.Considering the reduction of metal sediment,the dehydration and drying unit is added in the process.The long-term operation shows that when the hydraulic retention time(HRT)of the hydrolysis reactor is set at 6h,the recovery percent of acid-soluble oil is more than 95%,and the oil content in hydrolysate is less than 150mg/L.When the HRT of neutralizer and flocculation are set as 1.5h and 6h respectively,the water content of residue can be reduced to less than 70% by adding 25mg/L hydrolyzed polyacrylamide.The water content of residue can be reduced less than 15% after drying.The acid-soluble oil is mainly olefins with water content less than 1%,which can be used as refining material.The oil content of residue is less than 0.5%,and it is not flammable,corrosive,reactive and leaching toxicity,which is not hazardous waste.The content of copper and aluminum in residue is more than 5% and 10% respectively,which can be used as metallurgical materials.On the basis of pilot-scale experiment,a 2000 t/a waste ionic liquid and alkali washing wastewater combined treatment device is designed to provide a complete set for a 300000 t/a CILA plant.The main process route is ‘hydrolysis reactor,neutralizer,flocculation settling tank,plate-frame filter,low temperature drying device'.It has been constructed in many petrochemical enterprises and is expected to contribute substantially to the green upgrading of CILA process.