Search

With the increasingly serious impacts of NOx on environment, measures of controlling NOx are extremely necessary. Reburning technology has become a proven and effective method to control the emissions of NOx. In this paper, CFD software has been used to simulate the reburning process of South American coal (SAm) so as to study the effect of the reburning on the combustion in the furnace and NOx reduction. The result shows that, SAm reburning can reduce NOx emissions effectively, and removal rate of NOx reaches 50.63% with respect to the conventional combustion.

Flue gas of boiler is a kind of great potential waste heat resource. Relatively high temperature of exhaust has caused a vast waste of energy and serious environmental thermal pollutions. To make a full and reasonable use of the heat resource, a simplified single-tube heat exchanger is introduced in this paper. Dry air and wet air with different temperatures transfer heat with flue gas in the same model. And the results show that heat near the inner wall exchanges more violently than any other space in the heater. For dry air, the higher temperature of the air enters into the heater, the lower heat transfer effect of the heater. Heat exchange effect of the wet air with 0.03 mole fraction of water is more higher than that of dry air in this model.

In low-temperature SCR, corn straws pyrolysis carbon (CS) was prepared as a catalyst support and activated carbon (AC) was a comparison. Manganese (7 wt.%) was loaded respectively on this two supports (Mn/AC and Mn/CS). In 50°C~300°C SCR experiment, the highest NO conversion by using CS is 36.6 Vol.% at 300°C, while AC 37.9 Vol.% at 200°C. After loaded the manganese element, NO conversion increases with the temperature. At 300°C, Mn/AC has the highest NO conversion (81.9 Vol.%), while Mn/AC is 65.3 Vol.%. The sulfur resistance performance test shows that NO conversion decreases with the increasing of SO2 concentration. In the 400ppm SO2 fuel gas at 300°C, using Mn/CS, NO conversion reduces 16.7 Vol.%, however, using Mn/AC, it reduces 22.6 Vol.%. It is promising to apply biomass pyrolysis carbon modified catalyst.

Spiral tube exchanger is one of the most important heat transfer devices among the electric water boilers. In this paper, CFD software is introduced to simulate the process of the flow of the spiral tube exchanger. Cases with different inlet velocities of the cold water have been conducted and results show that, temperature increment of the cold water reaches 38.87 K, 20.21 K and 12.12 K with the inlet velocity of the cold water set as 0.05 m/s, 0.09 m/s and 0.13 m/s respectively.

In this paper, a tube electric furnace is used to process the co-combustion of biomass and crude oil in air atmosphere, the influence of the biomass mass fraction and the temperature on NO and SO2 emissions are analysed. Research shows that with the increasing addition ratio of biomass to crude oil, the amount of NO in per unit heat reduces. This tendency is more apparent at high temperatures. Compared with crude oil, the NO emission of 20% biomass mass fraction at 1100°C is reduced by 25.8% while 19.02% at 700°C. SO2 emission in per unit heat decreases with the increasing biomass mass fraction. This tendency is more apparent at low temperatures. Compared with crude oil The generation of SO2 of 20% biomass mass fraction can reduce 91.5% at 700°C while 36.7% at 1100°C.

The revamping project of turning coal-burning boiler into gas-fired boiler for urban heat supply in Tianjin causes high vapor content in flue gas, which has great influences on the day lighting of surrounding buildings. In this paper, CFD software is introduced to simulate the distributions of NOx, SO2 and vapor in space after leaving the chimney and their impacts on surrounding buildings with the effect of the atmosphere. Result shows that flue gas discharged from the chimney with the height of 30 m has significant impacts on the surrounding buildings.

Experiments of biomass char combustion in 10%O2/90%CO2, 21%O2/79%CO2, 10%O2/90%N2 and 21%O2/79%N2 atmospheres were performed in the fixed-bed reactor system at the temperature of 800°C-1200°C. The results show that at the same temperature, NO emission is higher in O2/N2 atmosphere than that in O2/CO2 atmosphere. The higher the O2 concentration is, the higher the NO yield is. As the temperature rises, the NO yield rises at first and then decreases at the same O2 concentration and atmosphere.

The method of selective catalytic reduction (SCR) to removal NOx is very mature. However, its initial investment and operation cost are still high, which limits the development of SCR technology. Low temperature SCR catalysts can significantly reduce the cost. Catalyst active component and its carrier is the key to the efficiency of denitration. This paper summarizes the research progress of noble metal catalyst of low temperature SCR.

Low temperature SCR method has caused concern for the scholars in recent years. This SCR unit can be installed downstream of the desulfurization and particulate control devices, which is conducive to match the existing boiler system. It can relief the poisoning and blocking of SO2 and dust, so as to extend the life of catalyst. This paper summarizes the research progress of molecular sieve catalyst of low temperature SCR.

The method of selective catalytic reduction (SCR) is now one of the mature applications of NOx removal technology, which has the higher denitration rate, less secondary pollution and lower cost. However, the active temperature of traditional SCR catalyst is usually in the temperature range of 300-400°C. This kind of installation leads to the reduction of catalyst activity, and the shortage of working life. The development of efficient and stable performance of catalyst at low temperature has become a key point in the research of SCR.This paper reviews the research progress of carbon catalyst of low temperature SCR. In addition, the future research work is discussed.

Precise control of the inclination and azimuth is of great significance for the efficient drilling of dynamic point-the-bit rotary steerable drilling tool. The design details of offsetting steerable mechanism for rotary steerable drilling tool based on inner and outer double eccentric rings are demonstrated in the paper. While drilling, the tool collar rotates and passes the torque and drilling pressure to the drill bit efficiently, and the stable platform mounted inside the collar is maintained geostationary by rotating it counter to collar rotation at the same frequency. And an offsetting steerable mechanism in the stable platform provides selectively and axially inclination to the collar by adjusting the relative position of the inner to the outer double eccentric rings. It is shown that the maximum oriented inclination can be reached as 1.0 degree flexibly for the presented structure.