An Efficient Method for Extraction and Enrichment of γ-Linolenic Acid (GLA) from Spirulina

γ-linolenic acid (GLA) is useful for improving and treating various diseases, including immune system-related diseases. In the world of commerce, GLA production has problems that compel scientists to search for a simpler, safer, and less costly way. Some microalgae have been introduced as a rich source of fatty acids; Spirulina platensis has attracted scientists due to the presence of 31% GLA in its fatty acid profile. In the present study, the Iranian strain of spirulina was investigated. Cell culture was performed under optimized conditions and after dry biomass production; the powder was used to continue the study. Finally, the extraction and enrichment steps were performed, and the IR spectra and gas chromatography methods were used for identification and final measurements, respectively. After enrichment by one-step urea crystallization, the percentage of GLA enriched in the total lipid was increased to 61.17%. These results suggest that employing simple, relatively inexpensive, and modified methods for the GLA isolation from the Iranian strain of spirulina may have a potential for industrialization.

Urea Injection and Uniformity of Ammonia Distribution in SCR System of Diesel Engine

The kinetic mechanism of chemical reaction was used to calculate the coupling of the fluid kinetics with the urea decomposition reaction and the SCR reaction kinetics. Combined with the engine test and simulation, the distribution uniformity of the urea injection and ammonia gas was studied. Through numerical simulation on urea spray and exhaust flow in Urea-SCR system, the flow field characteristics in whole after-treatment system are gotten. By using numerical calculation in different urea injection angle and orifice sizes, the urea-crystallization and ammonia distribution have been studied and the optimal urea spray angle and nozzle size are given.

Experimental Study of Urea Depositions in Urea-SCR System

Avoiding the urea deposition in the exhaust stream is one of the basic requirements for SCR system normal application. Unreasonable structure design, machining and installation position all could lead to urea crystallization on the wall of exhaust pipe and the front end surface of the catalyst, in addition, unreasonable control strategy also could deteriorate this phenomenon. The components of the urea depositions are the urea and cyanuric acid analyzed by thermogravimetry - FTIR technology. The integrated injector mounting is designed to alleviate the urea crystallization based on analysis results. The engine test and the vehicle road test are all shown that the optimal structural design and calibration strategies could avoid crystallization and sedimentation effectively in the exhaust system.