The definition and interpretation of process technique and the role of process engineering in Clean energy technologies field. Basic concepts and definitions in Process engineering. Fundamentals of dimensional analysis. The concept of mixture, types of mixtures. Possibilities of definition and concentrations' expression. Balance equations (conservation principles). Examples of governing equations. Transfer equations. Review and description of unit operations which are of interest in Clean Energy Technologies. Classifications of Unit Operations. Mechanical unit operations. Thermo diffusive unit operations. Models for expression of interphase exchange on the contact elements. Model of ideal (equivalent) stage. Diffusive unit operations. The concept of equilibrium and transport phenomena in multicomponent systems. Process plants.