Systematic Approach to Design Tailor Made Fuel Blends That Meets ASTM Standards

Blending of chemicals to design a tailor-made product for desired characteristics is a common practice in industry. Similarly, blending of liquid fuel is done to formulate a chemical mixture in liquid state that is stable in ambient conditions and has desired target fuel properties. Designing such tailor-made fuel is a challenging task which includes finding suitable chemicals and their compositions within the blend that meets the desired target fuel properties. In this study a computer aided model based technique “Mixed Integer Non-Linear Programming” (MINLP) was used to design the tailor made blends [1]. The main architecture in MINLP has four structures viz., (i) problem definition (ii) property model identification (iii) mixture blend design and (iv) model-based verification. These structures are further subdivided in to sub-problems and a decomposition based solution approach was adopted to solve them [2]. Two tailor-made liquid fuels viz., model gasoline and model diesel were formulated by our collaborator at the Technical University of Denmark conducting the MINLP program [3]. Different set of target properties were calculated for each type of fuel in order to design a set of suitable blend. The target properties calculated for tailor-made gasoline were flash point (Tf), Reid vapor pressure (RVP) and kinematic viscosity (n). Target properties calculated for tailor-made diesel were high heating value (HHV), dynamic viscosity ( h), lethal concentration ( -logLC50), weight percent of oxygen (WtO2), density (r) and Reid vapor pressure (RVP). Model gasoline blend (main ingredient) designed using MINLP, comprised of six different chemicals viz. n-pentane, n-heptane, iso-octane, 1-pentene, methyl cyclopentane and toluene in different volumetric ratios. Similarly, model diesel blend (main ingredient) designed using MINLP, comprised of seven n-paraffinic compounds viz., n-decane, n-undecane, n-dodecane, n-tetradecane, n-hexadecane, n-octadecane and n-eicosanein different volumetric ratios.

The paper is focused on the experimental verification of the properties of diesel and gasoline models (main ingredients), according to composition of computational model identified by our collaborator at DTU. The composition of blends was verified using Gas Chromatograph (GC) analysis and through a comparison of measured and theoretical densities. Following that, different fuel properties such as flash point, vapor pressure, and heat content were determined using analytical instruments according to their respective American Society for Testing and Materials (ASTM) standards. Most of the properties complied well with the industry standards. However, model gasoline had a comparatively low RVP. On the other hand, model diesel had a significantly higher cloud point and pour point than what is recommended. This deviation will have an impact on the cold flow properties of the fuels. For both fuels, different additives along with their composition have also been determined using the same computational model. These additives will be added to the main ingredient and the complete experimental analysis will be carried out. The work will be further continued to study the engine performance and emission characteristic of both types of fuel blends along with their additives. This would provide a more realistic approach to design tailor made fuels. Result of this study would provide a scientific approach for formulation of blended fuels and could be used as basis for tailor made blends.