Kinetics characteristics of coal low-temperature oxidation in oxygen-depleted air

The longwall gob (mined-out) area is one of the main places that are prone to coal spontaneous combustion and most of the residual coal in it is in oxygen-depleted air as it is a semi-enclosed space. A DSC (Differential scanning calorimetry) test system was designed to accurately test the heat generation of coal oxidation in different oxygen concentration atmosphere, based on which the kinetics parameters (activation energy and pre-exponential factor) of coal low-temperature oxidation in oxygen-depleted air were solved out. The results show that the kinetics parameters present obvious stage features and the lower the oxygen concentration is, the smaller is the difference of the kinetics parameters that in different oxidation stages. When the oxygen concentration is lower than 5% and 3% for jet coal and meagre coal respectively, the kinetics parameters of slow oxidation start to be greater than that of rapid oxidation. Both in the slow oxidation and rapid oxidation stage, with the decrease of oxygen concentration, kinetics parameters present significant decline on the whole while in different oxygen concentration range, the decline rate is different. It's concluded that when assessing the residual coal's self-heating risk, we need to use the corresponding kinetics parameters of coal oxidation in the oxygen concentration of the location where the residual coal is and the safety factor will be greater to only use the kinetics parameters of coal oxidation in slow oxidation stage. This study is of great significance for the assessment and control of the self-heating risk of coal that in different oxygen concentration atmospheres of the longwall gob areas.     

低温等离子体技术改善生物膜反应器载体表面性能的研究

通常，微生物及广为应用的多聚体型生物载体表面均带有有负电荷。两者间产生的静电斥力严重阻碍了载体表面生物膜的形成。为强化微生物的载体上附着，提出了载体表面电荷改性新技术；低温等离子体氧化－Ｆｅ离子沉积技术。研究了４种等离子体对４种聚合载体（ＰＥ、ＰＰ、ＰＳ和ＰＶＣ）的氧化强度及Ｆｅ＾３＋在处理后载体上的沉积。实验表明，处理后的载体表面生物膜形成速度加快，生物量显著增加，这项新技术为开发生物膜反应器新     

Promotional effect of ion-exchanged K on the low-temperature hydrothermal stability of Cu/SAPO-34 and its synergic application with Fe/Beta catalysts

• K⁺ hinder the structural degradation of Cu/SAPO-34 under humid condition<100°C. • K⁺ on Cu/SAPO-34 brings lower acidity and inferior SCR activity at high temperature. • Fe/Beta was used to compensate the low activity of Cu/SAPO-34 at high temperature. • The hybrid catalysts with KCu/SAPO-34 and Fe/Beta show a great potential for using. K ions were introduced onto Cu/SAPO-34 catalysts via the ion-exchange process in order to improve their stability under low-temperature hydrothermal aging. The changes in structure and copper-species contents of these catalysts upon hydrothermal aging were probed in order to investigate their effects on selective catalytic reduction (SCR) activity. For the fresh Cu/SAPO-34 catalysts, K ions had little influence on the chabazite framework but effected their acidities by exchanging with acid sites. After hydrothermal aging, the structural integrity and amount of active sites decreased on pure Cu/SAPO-34. While the K-loaded catalysts showed improved chabazite structure, acidity, and active site conservation with increasing K loading. However, although the 0.7 wt% K catalyst maintained the same crystallinity, active site abundance, and low-temperature SCR activity as the fresh catalyst upon aging, an apparent decrease in SCR activity at high temperature was observed because of the inevitable decrease in the number of Brönsted acid sites. To compensate for the activity disadvantage of K-loaded Cu/SAPO-34 at high temperature, Fe/Beta catalysts were co-employed with K-loaded Cu/SAPO-34, and a wide active temperature window of SCR activity was obtained. Thus, our study reveals that a combined system comprising Fe/Beta and K-loaded Cu/SAPO-34 catalysts shows promise for the elimination of NO_x in real-world applications.     

生化法处理生活污水中的耐冷菌特性研究

当水温低于10℃时，常规生化法中的微生物活性迅速下降，水处理效果急剧下降。研究分离出冷适应微生物用于低温生活污水的处理。实验证明北方地区市政下水道里的沉淀物中存在着耐冷细菌，它们均能在10℃以下生长、繁殖。     

Low-temperature plasma induced phosphate groups onto coffee residue-derived porous carbon for efficient U(VI) extraction

For the continuous utilization of nuclear energy and efficient control of radioactive pollution, low-cost materials with high efficient U(VI) removal are of great importance. In this study, low temperature plasma method was applied for the successful modification of O-phosphorylethanolamine (O-PEA) on the porous carbon materials. The produced materials (Cafe/O-PEA) could adsorb U(VI) efficiently with the maximum sorption capacity of 648.54 mg/g at 1 hr, T=298 K, and pH=6.0, much higher than those of most carbon-based composites. U(VI) sorption was mainly controlled by strong surface complexation. From FTIR, SEM-EDS and XPS analyses, the sorption of U(VI) was related to the complexation with -NH₂, phosphate and -OH groups on Cafe/O-PEA. The low temperature plasma method was an efficient, environmentally friendly and low-cost method for surface modification of materials for the effective enrichment of U(VI) from aqueous solutions.     

Improvement of the activity and SO2 tolerance of Sb-modified Mn/PG catalysts for NH3-SCR at a low temperature

A series of MnM/palygorskite (PG) (M = La, W, Mo, Sb, Mg) catalysts was prepared by the wetness co-impregnation method for low-temperature selective catalytic reduction (SCR) of NO with NH₃. Conversion efficiency followed the order Sb > Mo > La > W > Mg. A combination of various physico-chemical techniques was used to investigate the influence of Sb-modified Mn/PG catalysts. MnSb_0.156/PG catalyst showed highest NO conversion at low temperatures in the presence of SO₂ which reveals that addition of Sb oxides effectively enhances the SCR activity of catalysts. A SO₂ step-wise study showed that MnSb_0.156/PG catalyst displays higher durable resistance to SO₂ than Mn/PG catalyst, where the sulfating of active phase is greatly inhibited after Sb doping. Scanning electron microscopy and X-ray diffraction results showed that Sb loading enhances the dispersion of Mn oxides on the carrier surface. According to the results of characterization analyses, it is suggested that the main reason for the deactivation of Mn/PG is the formation of manganese sulfates which cause the permanent deactivation of Mn-based catalysts. For Sb-doped Mn/PG catalyst, SO_x ad-species formed were mainly combined with SbO_x rather than MnO_x. This preferential interaction between SbO_x and SO₂ effectively shields the MnO_x as active species from being sulfated by SO₂ resulting in the improvement of SO₂ tolerance on Sb-added catalyst. Multiple information support that, owing to the addition of Sb, original formed MnO_x crystallite has been completely transformed into highly dispersed amorphous phase accounting for higher SCR activity.     

Structures and catalytic performances of Me/SAPO-34 (Me = Mn, Ni, Co) catalysts for low-tem perature SCR of NOx by ammonia

Me/SAPO-34 (Me = Mn, Ni, Co) series of catalysts were prepared by a wetness impregnation method and investigated for the selective catalytic reduction of nitrogen oxides with ammonia (NH₃-SCR). Among them, Mn/SAPO-34 catalyst was found as the most promising candidate based on its superior low-temperature activity. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy images (TEM), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction and desorption (TPR and TPD), and diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) of NH₃/NO_x adsorption. Mn/SAPO-34 is obviously different from Ni/SAPO-34 and Co/SAPO-34 in the active species state and distribution. Surface MnO_x species which play an essential role in NO oxidation and NO₂ adsorption, act as better active sites than nickel and cobalt mostly in the form of the aluminates and silicates.     

Pulsed corona discharge for improving treatability of coking wastewater

Coking wastewater(CW) contains toxic and macromolecular substances that inhibit biological treatment. The refractory compounds remaining in biologically treated coking wastewater(BTCW) provide chemical oxygen demand(COD) and color levels that make it unacceptable for reuse or disposal. Gas-phase pulsed corona discharge(PCD) utilizing mostly hydroxyl radicals and ozone as oxidants was applied to both raw coking wastewater(RCW) and BTCW wastewater as a supplemental treatment. The energy efficiency of COD,phenol, thiocyanate and cyanide degradation by PCD was the subject of the research. The cost-effective removal of intermediate oxidation products with addition of lime was also studied. The energy efficiency of oxidation was inversely proportional to the pulse repetition frequency: lower frequency allows more effective utilization of ozone at longer treatment times. Oxidative treatment of RCW showed the removal of phenol and thiocyanate at 800 pulses per second from 611 to 227 mg/L and from 348 to 86 mg/L, respectively, at 42 k Wh/m~3 delivered energy, with substantial improvement in the BOD5/COD ratio(from 0.14 to 0.43).The COD and color of BTCW were removed by 30% and 93%, respectively, at 20 k Wh/m~3,showing energy efficiency for the PCD treatment exceeding that of conventional ozonation by a factor of 3–4. Application of lime appeared to be an effective supplement to the PCD treatment of RCW, degrading COD by about 28% at an energy input of 28 k Wh/m3 and the lime dose of 3.0 kg/m~3. The improvement of RCW treatability is attributed to the degradation of toxic substances and fragmentation of macromolecular compounds.     

Superior activity of iron–manganese supported on kaolin for NO abatement at low temperature

A series of Fe–Mn catalysts was prepared using different supports(kaolin, diatomite, and alumina) and used for NO abatement via low-temperature NH_3-selective catalytic reduction(SCR).The results showed that 12 Fe–10 Mn/Kaolin(with the concentration of Fe and Mn 12 and 10 wt.%, respectively) exhibited the highest activity, and more than 95.8% NO conversion could be obtained within the wide temperature range of 120–300℃.The properties of the catalysts were characterized by inductively coupled plasma-atomic emission spectrometry(ICP-AES), thermogravimetry(TG), Brunner–Emmet–Teller(BET)measurements, X-ray diffraction(XRD), H_2-temperature programmed reduction(H_2-TPR),NH_3-temperature programmed desorption(NH_3-TPD), X-ray photoelectron spectroscopy(XPS), scanning electron microprobe(SEM) and energy dispersive spectroscopy(EDS)techniques.The support effects resulted in significant differences in the components and structures of catalysts.The 12 Fe–10 Mn/Kaolin catalyst exhibited better dispersion of active species, optimum low-temperature reduction behavior, the largest amount of normalized Br?nsted acid sites, and the highest Mn~(4+)/Mn and Fe~(3+)/(Fe~(3+)+ Fe~(2+)), all of which may be major reasons for its superior catalytic activity.     

CASS工艺在处理低温生活污水中的应用研究

本文以CASS工艺为研究对象,重点探讨CASS工艺处理低温生活污水的可行性,为CASS工艺在我国寒冷地区的推广应用奠定基础,同时也为低温条件下污水处理厂的运行管理提供帮助。