Gongcheng Kexue Yu Jishu/Advanced Engineering Science

The secondary fly ash problem in the application process of fly ash of municipal solid waste incineration (shorter form, fly ash) melting treatment technology has become a constraint. It is beneficial to the development of harmless and resource utilization technology of secondary fly ash by mastering the distribution law of salt in the gas phase product of fly ash melting, and it can be used as a reference for the design of tail gas purification equipment and operation. The fly ash released from one municipal solid wastes incineration plant in Jiangsu Province was adopted. The fly ash melting experiments were performed in a self-designed high-temperature pilot-scale plasma arc furnace system. The weight subtraction method, X–ray fluorescence spectroscopy, atomic absorption spectrometry and electrochemical process were used to analyze melting fly ash and slag during melting and to abtain gaseous phase migration rate of Na, K, Ca, Mg and Fe. The thermodynamic model was used to simulate the distribution rules of gaseous phase salts at 1000～1600 ℃, with 0～50% auxiliary material, at different atmosphere (without gas, nitrogen or air) and 0～12% water content of fly ash. The simulation results showed that NaCl, (NaCl)2, KCl, (KCl)2, CaCl2, KCaCl3, KMgCl3, FeCl2 etc. were main compositions of gaseous phase salts during fly ash melting. These compositions distribution was greatly effected by melting temperature and was little effected by melting atmosphere, auxiliary material amount and water content of fly ash. At atmosphere, there were new product Na2SO4 in gaseous phase salts. The simulation values and the experimental values of gaseous phase migration ratio of Na and K fitted well, and the simulation values were largely smaller than the experimental ones of Ca, Mg and Fe. It is suggested that the distribution law of gaseous product salt should be used to develop the technology of salt separation or chloride salt utilization, so as to realize the comprehensive utilization of secondary fly ash, change the current situation that the secondary fly ash is mainly landfill, and thoroughly realize the harmless and resource utilization of fly ash.

High entropy alloys break through the traditional alloy design concept with one or two elements as basic elements, and have a simple phase structure and excellent comprehensive performance prepared by equimolar ratio or near equimolar ratio, which is expected to further expand the performance limit and application of metal materials. In order to study the effect of element doping on phase structure, microstructure and wear resistance, CoCrCuFeMn and CoCrCuFeMnZr high entropy alloys with equal molar ratio were prepared by vacuum melting method. The phase structure, microstructure, hardness and wear resistance of CoCrCuFeMn alloy before and after Zr addition were investigated by XRD, OM, SEM, EDS, microhardness tester and friction-wear tester. It was found that after Zr addition, the phase structure of CoCrCuFeMnZr alloy was changed from the original two FCC phases to two HCP phases, and the microstructure was obviously refined. The two alloys were typical dendrite structure. The friction curves of the two alloys showed a trend of first increasing, then decreasing, and then stabilizing. After Zr addition, the friction coefficient and mass loss rate decreased from 0.57 and 4.14% to 0.47 and 0.49% respectively, and the microhardness increased from 219.6 HV to 983.5 HV. The results showed that the HCP transformation of alloy phase structure was mainly related to the formation of a rough solid-liquid interface rich in Zr with large atomic radius and Z-shaped HCP orientation. The reason why Cu is enriched in the interdendrite region is that its melting point is the lowest, its electronegativity is the largest, its atomic radius is second only to Zr, and it has the corresponding largest positive mixing enthalpy with all alloy elements except Zr, so it is enriched in the interdendrite region with the latest solidification. Due to the fact that the melting point of Mn is only higher than that of Cu, Mn has the largest electronegativity difference except Zr, and there is a negative mixing enthalpy between Mn and Co or Zr and the largest positive mixing enthalpy between Mn and Cu, which is not conducive to its long-range diffusion and entering into the lattice site of the leading phase, the segregation coefficient of Mn is the smallest. The increase of hardness and wear resistance of the alloy with Zr element is due to fine grain strengthening, solid solution strengthening and phase structure transformation.

Due to the weak integrity of the damaged masonry pagodas, it is easily to be destroyed heavily for the pagodas affected by earthquake again, even are collapsed. Using rigid hoops to restrain and strengthen the masonry can improve the mechanical properties of ancient masonry pagodas. To study the seismic performance of damaged masonry pagoda reinforced with rigid hoop, three sub-structure models of the masonry pagoda were designed and constructed, and the pseudo-static tests were carried out. The failure phenomena of seismic damaged specimens and the specimens restrained by angle steel hoops were observed, and the load-displacement curves of the restrained specimens were obtained. The numerical models were established to calculate the stress, strain and deformation of the ancient pagoda substructure, and the seismic performance indexes of the reinforced ancient pagoda substructure were obtained through comparative analysis with the test results. As results, the hoop device can effectively confine the horizontal deformation and the expansion of diagonal cracks, improve the ability of the ancient pagoda substructure to resist horizontal deformation, and delay the degradation of structural rigidity. The numerical model can reflect well to the damage of the structure and reinforcement device the characteristics of collaborative work with the structure of the pagoda, and the research results can provide references for the seismic reinforcement of ancient masonry pagoda.

As the controlling reservoir that possesses a large storage capacity in Yellow River, the operation of Xiaolangdi Reservoir (XLD) is of great importance to the reservoir maintenance and the downstream channel shaping. Considering the integrated economical profit of power generation and sediment discharge, an operation model of XLD was established by coupling the calculations of water-sediment balances with the calculation of power generation. There were two types of optimization objectives: the maximum of power generation and the maximum of integrated profits. The hydrographs of water level, discharge and turbine output were constrained according to the regulation rules during the late sediment-retaining period of the XLD Reservoir. The model was solved by the dynamic programming,and was adopted to obtain different operation schemes under different optimization objectives in a typical dry year of 2015 and a typical high flood year of 2012. The results showed that: 1) with the power generation as the optimization objective, the operation scheme could to energy outputs of 7.130×109 kW·h in 2015 and 10.215×109 kW·h in 2012, 2) with the integrated profits as the optimization objective, an annual power outputs of 7.017×10 9 kW·h and 9.524×10 9 kW·h could be achieved in 2015 and 2012 respectively, along with sediment discharges of 31×10 6 t and 166×10 6 t; 3) when comparing these two schemes with different optimization objectives, it could be found that both schemes would finally achieve an increase in the integrated profits, whereas the latter would result in a larger increase by sacrificing part of the power generation in exchange for profits a silting reduction in the reservoir; 4) optimization schemes in both typical years would produce an increase in power generation and integrated profits, with a larger increase being obtained for the typical high flow year. Furthermore, some suggestions were also proposed for improving the current operation schemes in some typical years.

A deep understanding of the loading and unloading rate effect of rock mass mechanical response under mining stress path is an important basis for defining the optimal advancing rate of actual working face. Based on the initial crustal stress environment of Pingdingshan mining area, the evolution law of stress under the condition of protective layer mining with the depth of kilometer was analyzed quantitatively. The research on the mechanical behavior of coal and rock mass under different unloading rates was carried out, which was more in line with the real stress state. At the same time, the comparative analysis with the results of tests without considering the mining was carried out. The results showed that 1) In the conventional triaxial compression test, the strength of the sample was less affected by the unloading rate, and there was no obvious change at 1～4 MPa/min, and only when it reached 5 MPa/min, the strength increased significantly to about 115 MPa. 2) With the increase of unloading rate, the strength of coal and rock mass showed a trend of decreasing, rising and falling again. The strength of coal and rock mass reached the maximum under the unloading rate of 1 MPa/min and 4 MPa/min, and its peak stress was about 64 MPa, which was 12% higher than that of 3 MPa/min sample. 3) The micro cracks could be fully developed and expanded under low unloading rate, and the fracture density of the specimen decreased with the increase of unloading rate, and it was 1.61 times for 1 MPa/min and 5 MPa/min, respectively, and thus the gas drainage efficiency could be improved by properly reducing the mining speed. 4) The volume strain of coal and rock in the whole mining process at different mining speeds not only had the volume compression in the relative initial state, but also had the volume expansion in the failure stage, which could be regarded as the mining characteristics. This was obviously different from that in the relative initial state without considering the mining test, which was always volume compression under mining. The strength of coal and rock was obviously smaller, and the damage degree was greater. The research results can lay a theoretical foundation for similar geological conditions to carry out protective layer mining design.