Improving emulsifying performance of bio-oil/diesel by emulsion and co-emulsifier

Abstract: Bio-oil is easy to extract，transport and storage. It is a kind of potential clean and renewable energy and can be used as fuel in oil burning boiler and turbine engine directly. Furthermore, Bio-oil can be blended with gasoline, diesel in certain percentage through using advanced emulsion process to produce clean, environment-friendly bio-oil/disel mixed emulsification fuel. It not only improves the calorific value of fuel and the combustion performance, the emulsified oil also can be directly applied to ordinary diesel engine with or without modification. Bio-oil is a mixture with high percentage of water and acid, the stability of the emulsion products is an important factor for its large-scale application. Meanwhile, the choice of emulsifier and auxiliary emulsifier is important for the stability of bio-oil. In this paper, the impact of emulsifier types, HLB value, dosage of emulsifier, types of auxiliary emulsifier and dosage of auxiliary emulsifier on the stability of the emulsified bio-oil/diesel oil were studied using non-ionic compound surfactants. The stability of the emulsified oil and absorbance ratio K was used as observation object at the macroscopic level. the average particle size of emulsified oil and the distribution of emulsified oil droplets were used as observation objects at the micro level. The experimental results showed that the stabilization time of the emulsified oil reached up to 17 days using Tween80 and Span80 as mixed emulsifier when B-oil content was blended with 5%, 90% of diesel fuel, and 5% of emulsifier. The absorbance ratio K was 1.11, which means the stability is best with the particle size of 1.56 um in the microscopic observation. The best HLB value range was 5.0-5.8, the peak curve is higher on the particle size distribution, and there was more number of small oil droplets. The highest peak and the most number of droplets were reached when the HLB value was set as 5.4. As the HLB value increase, the oil droplets number was reduced and the particle size become bigger. Within a certain range, the stability time is proportional to the content of emulsifier. Since the price of emulsifier is higher than Bio-oil, we recommend that the suitable amount of emulsifier is 5% during the emulsified oil production. The stability time of the emulsified oil increased 7 or 8 days using n-octanol and methanol as co-emulsifier. The stability time of emulsified oil can be increased using co-emulsifier. Adding methanol as auxiliary emulsifier is more economically effective. The best emulsified oil stability was reached when the methanol content was set as 20%. The stability of the emulsified oil was decreased with increased Bio-oil content. The emulsified oil is experienced with stratification, flocculation, coalescence and demulsification process. It is our expectation that this study will assist in support of industrial development and application of the bio-oil.