Applied Mechanics and Materials Vol. 768

Abstract: In order to determine the optimum air injection craftwork for the aerobic-anaerobic landfill method, three pilot-scale lysimeters were constructed. Through experiment in the lysimeters, it was concluded that air injection at bottom layer (in this research it’s 2.5 m) is the optimum position in terms of improving on the solid organic matters stabilization, amelioration on leachate quality, the restraint of GHE (Green House Effect) by CH₄. For instance, air injected at bottom layer may get more TOC minimization in leachate under lower temperature (-4-10°C) and high temperature (20-35°C) compared with other conditions. NH₄⁺-N content expressed similar advantages with air injected at bottom layer case. Meanwhile, accompanied with the high dissolved oxygen (DO) and higher TOC consumption in leachate, aerobic fermentation was activated in this case, and most organic carbon was transformed in term of CO₂, in which the goal of restraint on GHE was realized. On basis of mechanism assumption, mathematical model was developed and according to the simulated results for 5 years, air injected at 2.5 m achieved improvements on stabilization of solid phase organic carbon and nitrogen for 34 % and 13 %, amelioration on leachate quality for 35 % and 62 % of TOC and T-N, and the restraint of GHE for 14 times compared with no air injection case.

Abstract: Distribution of hazardous substances and their release potential were investigated in industrial construction and demolition waste (ICDW) of several chemical and metallurgical factories. Results showed that inorganic matters like heavy metals, organic matters like pyrethroids exist as a result of industrial pollution, which might pose a potentially serious threat to the nearby surroundings while abandoned. In this study, wash-off coupled with ultrasonic process, immobilization and natural degradation experiments were performed on the simulated ICDW on basis of different pollutants. Up to 65% of Cl was reduced through ultrasonic wave pretreatment. Addition of CaO and construction & demolition waste(C&D) powder inhibited the mobilization of heavy metals with rainfall tremendously, among which Cr and Cu, in particular, was cut by 80-100% in aqueous. Compared with being stacked and abandoned inside the workshop, heat and direct sunlight largely accelerated the degradation of pyrethroids. This study provides a new insight into strategies to the ICDW management, and the achievement of source pollution control as well.

Abstract: Based on characteristics of stainless steel cold-rolled products pickling wastewater, a new process route with advantages of sludge originally reduction, wastewater two-stage treatment, Heavy metal-contained sludge and calcium-salt sludge separately recovery is developed. As 2 waste-water treatment stations operation results have shown, during the passed 6 years, annual sludge reduction ratios (per tons product) reach 43.64% and 50.29% respectively, realizing 105.6 thousands tons of sludge reduction effect and 68.04 millions CNY economic benefits. After two-stage process treatment, effluent water can reach emission standards steadily, Fe,Cr and Ni total contents in the front-part heavy-metal sludge increase from 10% to 30~40% compared with that of one-stage wastewater traditional treatment process, with dramatically decrease of F and S impurities content, therefore it can be used as ferric-contained sludge; while among the post-part calcium-salt sludge, F and S recovery ratios reach 20~40%, with Fe,Cr and Ni total content falls below 3%, therefore it can be used as fluorgypsum or fluorite. Since this technology fit the trend of hazardous waste original reduction and resource categorized recycle, it has a broad application prospect in stainless steel enterprise.

Abstract: Several physical and chemical detection methods were used to study the basic properties of sintering dust collected from Baogang Steel Corporation. The result shows that the major constituents of the electrostatic precipitator dust (ESP dust) were KCl, NaCl, Fe₂O₃ and Fe₃O₄. Water leaching experiment on the sintering dust had shown that the KCl in the ESP dust could be separated and recovered by water leaching and fractional crystallization. Component analysis of leaching solution showed that the massive calcium sulfate in the leaching solution should be removed first in order to obtain the pure potassium salt. In order to provide theoretical guidance to inhibit the dissolution of calcium ions from the sintering dust, the water leaching experiment of ESP dust and the dissolution behavior of CaSO₄ in the potassium chloride, sodium chloride, potassium sulfate and their mixed salt solution were studied. Result showed that, a lower liquid-solid ratio should be chosen in the leaching process to inhibit the dissolution of calcium sulfate dehydrate. Using sodium carbonate solution as a precipitating agent, the influences of the concentration of sodium carbonate solution, reaction temperature, stirring speed on the preparation of the spherical calcium carbonate were studied. Spherical calcium carbonate with good dispersing performance and grain size distribution in nanometer range of less than 10μm was obtained. The production technology of potassium sulfate by double decomposition was sutdied, the results showed that over 80% and 12.76% of the recovery rate of potassium sulfate and potassium chloride ammonium compound fertilizer could be obtained. Furthermore, a potassium recovery process with joint production of spherical calcium carbonate and potassium sulfate was designed. This process is technically viable and considerable in economic benefit.

Abstract: Mechanochemical destruction (MCD), a novel non-combustion technology based on the high energy ball milling, has proven to be promising in the destruction of these chemicals in various wastes, and cannot product secondary pollution such as dioxin. So far, the areas that MCD research carried on can be categorized in metal oxide/hydroxide and salt, and elemental metals and hydrogen donor. This paper reviews the effects of the reaction conditions on the destruction efficiency of MCD, such as dehalogenation, milling time, rotation speed, and charge ratio. Based on the requirements of industrial application for Halogenated Organic Wastes removal, the research trends of MCD for the future are brought up in order to further improve destruction efficiency and cost saving.

Abstract: In this paper, ecotype cementing materials (with steel slag, mineral slag etc. as the main raw materials), waste aerated concrete, regeneration light sand and etc. were used as the main materials to prepare thermal insulation masonry mortar. Then the impacts of materials on the mortar’s performances such as strength, density and thermal conductivity were analyzed. At last, it obtained the optimal mixture ratio to prepare thermal insulation masonry mortar with a strength degree of M5. This kind of mortar used a lot of solid wastes as raw materials but with many advantages such as light weight, low thermal conductivity and low cost, all of this made it became a new environmental friendly thermal insulation masonry mortar.

Abstract: Cement-based solidification/stabilization (S/S) has been considered as an effective method to deal with hazardous wastes such as textile dyeing sludge. In this study, sludge from textile wastewater treatment plant was solidified by Portland cement and attapulgite at different mass ratios (sludge 0.1~0.8, cement 0.1~0.8, attapulgite 0.1~0.8), and the characteristics of the solidified blocks were evaluated. The maximum unconfined compressive strength (UCS) of 15.8 MPa was obtained at 28 d when the mass ratio of attapulgite, sludge and cement was 0.1:0.1:0.8, while in toxicity characteristic leaching procedure (TCLP) test, relatively low concentrations of COD (100~150mg/L) in the leachate were found when the mass ratio was set to 0.3:0.1:0.6. Results of XRD and SEM/EDS indicated the existence of calcium silicate hydrate (CSH) in the solidified blocks. ANOVA results proved that the quadratic model could be utilized to characterize the relationship between COD of the leachate and the components in the mixture.

Abstract: Anosovite (Mg_0.3Ti_2.7O₅) phase was successfully separated from synthesized titanium bearing blast furnace slag by super gravity. Supposing that the titanium exists in the slag in terms of TiO₂, the mass fraction of TiO₂ is 23.49% in the parallel sample without centrifugal separation. With the parameter of t=5min, T=1553K and the gravity coefficient ranged from 600 to 1000, the mass fraction of TiO₂ in the concentrate increase from 40.17% to 58.35%, while the recovery ratio of Ti in the concentrate slightly decrease from 83.49% to 81.81%.

Abstract: This study investigated catalytic fast pyrolysis (CFP) of beech wood, low-density polyethylene (LDPE), and their mixture (mass ratio of 1) with a conventional microporous ZSM-5 and mesoporous bifunctional Zn/ZSM-5_meso zeolite prepared by desilication of the conventional ZSM-5 with NaOH solution and then impregnation with Zn.The generation of mesopores by desilication improved the diffusion property of the zeolite, which decreased the formation of undesired polyaromatic hydrocarbons from secondary polymerization reactions of monoaromatics in CFP. In addition, the impregnation of Zn increased the dehydrogenation activity of the zeolites, and thus enhanced the conversion of low-value alkanes to valuable olefins. As a result, Zn/ZSM-5_meso produced higher yields (56.0 C%) of valuable petrochemicals (monoaromatic hydrocarbons and olefins) and lower yields of undesired polyaromatics (1.70 C%) and alkanes (10.2 C%) in co-feed CFP of the beech wood and LDPE mixture than ZSM-5 (48.2 C%, 4.18 C%, and 18.7 C% for petrochemicals, polyaromatics, and alkanes, respectively).ZSM-5 desilication and impregnation with Zn thus have a beneficial effect on improve the product distribution in CFP of biomass and plastic mixtures. In addition, the results suggest that CFP may provide a promising technology for producing renewable petrochemicals from municipal and agricultural solid wastes, which usually contain high contents of biomass and waste plastics.

Abstract: A new method to make SMA is developed by using SBS modified asphalt when the coarse aggregate steel slag and the fine basalt aggregate are selected respectively. The Mix Proportion is 1#(16-9.5mm, steel slag):2#(9.5-4.75mm, steel slag):3#(3-4.75mm, basalt):4#(3-0mm, basalt):5# (mineral powder)=38%:36%:8%:8%:10%.The optimal asphalt content (OAC) is 6.4%. The mass percentage of steel slag is reached 74%. The costs of this kind of high quality road material can be saved because the amount of asphalt is not increased. Based on Marshall Stability and Splitting Strength test, it is shown that the Marshall stability of SMA is 10.6 kN, dynamic stability is 7800, and tensile strength ratio is 89.2%. All above test values are superior to the standards in China's traffic regulations. The water permeability coefficient of SMA is 65, which means that SMA has an excellence Wear-Resistant performance. Therefore, SMA can increase the road useful life and reduce the road maintenance costs.