In order to solve the problems of uneven flow field distribution in the inlet flue of SCR reactor in the form of upper inlet and lower outlet, abrasion in the center area of catalyst layer and ash deposition near the flue wall, etc. In this study, the flow field simulation and flow field optimization were conducted for a medium temperature medium dust SCR denitration device with a design capacity of 2 000 t/d for a second line cement kiln in Tianjin Zhenxing cement company. The flow field distribution characteristics in the flue of a fullsize SCR reactor were simulated by the Ansys fluent software. A flow field optimization scheme was proposed to set a group of guide grids at the inlet of the flue in the expansion section of the reactor,a layer of uniform distribution plate and a second group of guide grids at the middle of the flue in the expansion section. In the optimization scheme, the guide grid plays an auxiliary role in guiding the diffusion and flow of flue gas, and the uniform distribution plate plays a major role in current sharing. In this study, 50% opening rate, 60° staggered round holes and 60 mm hole aperture were selected as the optimal parameters of the uniform distribution plate through simulation test. The feasibility of the optimization scheme was verified through engineering cases. The calculation results show that the optimized scheme has less burden on the system pressure loss, can effectively improve the uniformity of flue gas distribution, and achieve the technical requirements of catalyst inlet velocity distribution Cv＜15%. The field measurement results after optimization and reconstruction show that the uniformity of catalyst inlet velocity distribution is optimized from Cv=48.5% to Cv=14.5%, the system resistance is increased by 91.5 Pa, and the denitrification efficiency is improved by 11.2% to 86.4%.

The uniform flow field in denitrification reactor is rather important for the denitrification system,while the performance of baffle plate above the bed layer of catalyst is the key regarding uniformity of the flow field.By using fluid mechanics calculating software CFD and changing the structure parameters,such as interval between baffle plates,the length of baffle plate,the included angle with the Z axis,as well as the distance between first baffle plate and side-wall of the reactor etc.,the gas straightening grattings(GSG) have been simulated,thereby,the influence of GSG structure parameters upon the flow field distribution in the reactor being analysed.Results show that the variation of distance between first baffle plate and side-wall of the reactor has very little influence upon the flow field performance,and thus can be ignored.The value of structure parameters has a range which makes flow field in the reactor to be the best.The original scheme is optimal in aspects of uniformity,vector index of the gas flow velocity,and the pressure drop etc.,can be used as the basis of design.

Several kinds of commercial carbon black(CB) were tested as catalysts of methane decomposition reaction in this study.The catalytic activity was analyzed with a thermo-gravimetric analyzer(TGA).Pore structure,crystal structure and microscopic feature of CB samples at different reaction stages were also analyzed by N2 adsorption-desorption method,scan electron microscope(SEM) and X-ray diffractometer(XRD),respectively.The tested samples showed high initial reaction rate at 1 073—1 173 K,but they deactivated by 30%—40% after a period of reaction.The reaction order was 0.5 and the activation energy was about 213—222 kJ/mol.The deposited carbon enlarged the particles and decreased the specific surface area and the total surface area.There were two stages in methane decomposition which have different kinds of active sites.

Compared with traditional layout scheme of the absorption tower with single inlet,the flue duct layout scheme of absorption tower with double inlets for wet flue gas desulphurization(WFGD)boasts the aduantages of low energy consumption and small area of occupation.Taking 660 MW coal-fired unit as example,the numerical simulation of flue gas flow field in the absorption tower with double inlets and single inlet has been carried out respectively.Results show that the flue duct layout scheme of absorption tower with double inlets isn't easy to make fouling in the entrance,and the uniformity of flow field is also good,being a more advantageous design scheme for WFGD

The development in the research of natural gas decomposition into hydrogen,including characteristics and status in the research of catalytic decomposition,plasma reforming,plasma catalytic reforming as well as solar-thermal dissociation of natural gas were reviewed and analyzed in this paper.The emphases for study of natural gas decomposition into hydrogen were put forward based on the reviews and analyses.

Several kinds of commercial activated carbon (AC) were tested as catalyst of methane decomposition reaction in this study.The catalytic activity was analyzed with thermo-gravimetric analyzer (TGA).Pore structure、crystal structure and microscopic feature of AC samples at different reaction stages were also analyzed by N_2 adsorption-desorption method,scan electron microscope (SEM) and X-ray diffractometer (XRD),respectively.The tested samples showed high initial reaction rate at 1073—1173 K,but deactivated rapidly after a period of reaction with a drop of surface area because carbon deposit made pore block.The final increasing weight of the AC samples was in direct radio of the surface area of the original sam- ples.