Study on Mid-temperature SCR DeNO x Catalyst under High SO 2 and
1B INTRODUCTION Chinese main energy resource is coal and fire power plant is the primary producer of NOx. With the rapid development of economy, the environmental damage caused by coal-fired becomes more serious. The multiplex acid rain is mainly caused by the emission of SO2 and NOx of coal fire power plants and cement kilns. The Emission Standard of Air Pollutants for Coal-fired Plants implemented at 1st Jan, 2004, has greatly prompted the development of DeNOx industry and the DeNOx industry is becoming a highlight of environmental protecting industry. The SCR technology (Selective Catalytic Reduction) is the most efficient method to control the emission of NOx, which has been widely used in coal-fired plants of developed countries. However, in domestic, the commercial application of DeNOx has just stepped out. The constitutes of coals in China vary drastically, and many coals contain high SO2, high CaO, high ash, and contains of arsenic changes greatly. It is greatly different from the east area coal of America.[1] So far, our country SCR DeNOx equipment have applied alien technology entirely and what’s more, We are short of the experience of pattern selection and operating of catalysts. The core technology of SCR is the systemic design to maintain uniform distribution of smoke and fly ash in reactor. It reported that (NH4)2SO4 and CaSO4 in smoke poisoned catalysts of SCR and reduced the efficiency of DeNOx. Aiming at high SO2 and high CaO ash in coals of China, this paper develops the DeNOx experiments of Mid-temperature SCR catalyst in high SO2 and high CaO condition. The research is a great help for the pattern selection of catalyst in domestic DeNOx industry of coal fired plants.
Optimizing SCR Catalyst Design and Performance for Coal-Fired Boilers
The design of an SCR system for a coal-fired application is a challenge due to particulate, catalyst poisons, and So2 in the flue gas. Our experience show that coalfired SCRs are successful when the system impact and catalyst deterioration factors are understood and specific countermeasure are implemented in system and catalyst design There are several factors that the system and catalyst must consider in order to assure success. They include: type of boiler, required performance, fuel and ash analysis, ash loading, type of SCR, inlet conditions, Catalyst deactivation mechanisms and impact on down stream equipment. This paper explains each system and catalyst deterioration factor that we have experienced. For each factor, it presents the specific countermeasure that has resulted in successful SCR systems. Also, it discusses the design of improved catalyst derived from our experience. Finally, two case studies illustrate the impact of optimized design.
Synthesis of 2,4-dideoxy-.beta.-D-erythro-hexopyranosyl nucleosides
The synthesis of 1-(2,4-dideoxy-β-D-erythro-hexopyranosyl)thymine (12) 1 was accomplished using two different synthetic routes. It was obtained starting either from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose or from tri-O-acetyl-D-glucal. The other modified nucleosides, with either a cytosine, guanine, or adenine moiety, were synthesized using the second reaction scheme. Deoxygenation reactions were accomplished with the (2,4-dichlorophenoxy)thiocarbonyl derivatives generated in situ