Low-Temperature Denitrification Performance of Cu2O/Activated Carbon Catalysts for Selective Catalytic Reduction of NOx by CO

To improve the denitrification performance of carbon-based materials for sintering flue gas,we prepared a composite catalyst comprising coconut shell activated carbon(AC)modified by thermal oxidation air.The microstructure,the specific surface area,the pore volume,the crystal structure,and functional groups presented in the prepared Cu2O/AC catalysts were thoroughly characterized.By using scanning electron microscopy(SEM),nitrogen adsorption/desorption isotherms,Fourier-transform infrared(FTIR)spectroscopy and X-ray diffractometry(XRD),the effects of Cu2O loading and calcination temperature on Cu2O/AC catalysts were investigated at low temperature(150℃).The research shows that Cu on the Cu2O/AC catalyst is in the form of Cu2O with good crystalline performance and is spherical and uniformly dispersed on the AC surface.The loading of Cu2O increases the active sites and the specific surface area of the reaction gas contact,which is conducive to the rapid progress of the carbon monoxide selective catalytic reduction(CO-SCR)reaction.When the loading of Cu2O was 8%and the calcination temperature was 500℃,the removal rate of NOx facilitated by the Cu2O/AC catalyst reached 97.9%.These findings provide a theoretical basis for understanding the denitrification of sintering flue gas.

Waste Activated Sludge Alkaline Fermentation Liquid as Carbon Source for Biological Nutrients Removal in Anaerobic Followed by Alternating Aerobic-Anoxic Sequencing Batch Reactors

Activated sludge process has been widely used to remove phosphorus and nitrogen from wastewater. However,the nitrogen and phosphorus removal is sometimes unsatisfactory due to the low influent COD.Another problem with the activated sludge process is that large amount of waste activated sludge is produced,which needs further treatment.In this study,the waste activated sludge alkaline fermentation liquid was used as the main carbon source for phosphorus and nitrogen removal under anaerobic followed by alternating aerobic-anoxic conditions,and the results were compared with those using acetic acid as the carbon source.The use of alkaline fermentation liquid not only affected the transformations of phosphorus,nitrogen,intracellular polyhydroxyalkanoates and glycogen, but also led to higher removal efficiencies for phosphorus and nitrogen compared with acetic acid.It was observed that ammonium was completely removed with either alkaline fermentation liquid or acetic acid as the carbon source. However,the former resulted in higher removal efficiencies for phosphorus(95%)and nitrogen(82%),while the latter showed lower ones(87%and 74%,respectively).The presence of a large amount of propionic acid in the alkaline fermentation liquid was one possible reason for its higher phosphorus removal efficiency.Exogenous instead of endogenous denitrification was the main pathway for nitrogen removal with the alkaline fermentation liquid as the carbon source,which was responsible for its higher nitrogen removal efficiency.It seems that the alkaline fermentation liquid can replace acetic acid as the carbon source for phosphorus and nitrogen removal in anaerobic fol- lowed by alternating aerobic-anoxic sequencing batch reactor.

Effect of activation agents on the surface chemical properties and desulphurization performance of activated carbon

Flue gas pollution is a serious environmental problem that needs to be solved for the sustainable development of China.The surface chemical properties of carbon have great influence on its desulphurization performance.A series of activated carbons (ACs) were prepared using HNO3,H2O2,NH3·H2O and steam as activation agents with the aim to introduce functional groups to carbon surface in the ACs preparation process.The ACs were physically and chemically characterized by iodine and SO2 adsorption,ultimate analysis,Boehm titration,and temperature-programmed reduction (TPR).Results showed that the iodine number and desulphurization capacity of NH3·H2O activated carbon (AC-NH3) increase with both activation time,and its desulphurization capacity also increases with the concentration of activation agent.However,HNO3 activated carbon (AC-HNO3) and H2O2 activated carbon (AC-H2O2) exhibit more complex behavior.Only their iodine numbers increase monotonously with activation time.Compared with steam activated AC (AC-H2O),the nitrogen content increases 0.232% in AC-NH3 and 0.077% in AC-HNO3.The amount of total basic site on AC-HNO3 is 0.19 mmol·g-1 higher than that on AC-H2O.H2O2 activation introduces an additional 0.08 mmol·g-1 carboxyl groups to AC surface than that introduced by steam activation.The desulphurization capacity of ACs in simulate flue gas desulphurization decreases as follows: AC-NH3 】 AC-HNO3 】 AC-H2O2 】 AC-H2O.This sequence is in accord with the SO2 catalytic oxidation/oxidation ratio in the absence of oxygen and the oxidation property reflected by TPR.In the presence of oxygen,all adsorbed SO2 on ACs can be oxidized into SO3.The desulphurization capacity increases differently according to the activation agents;the desulphurization capacity of AC-NH3 and AC-HNO3 improves by 4.8 times,yet AC-H2O increases only by 2.62 as compared with the desulphurization of corresponding ACs in absence of oxygen.

Nitrification and denitrification in biological activated carbon filter for treating high ammonia source water

Since the ammonia in the effluent of the tradi-tional water purification process could not meet the supply demand,the advanced treatment of a high concentration of NH4+-N micro-polluted source water by biological activated carbon filter(BACF)was tested.The filter was operated in the downflow manner and the results showed that the remov-ing rate of NH_(4)^(+)-N was related to the influent concentration of NH_(4)^(+)-N.Its removing rate could be higher than 95%when influent concentration was under 1.0 mg/L.It could also decrease with the increasing influent concentration when the NH_(4)^(+)-N concentration was in the range from 1.5 to 4.9 mg/L and the dissolved oxygen(DO)in the influent was under 10 mg/L,and the minimum removing rate could be 30%.The key factor of restricting nitrification in BACF was the influent DO.When the influent NH_(4)^(+)-N concentration was high,the DO in water was almost depleted entirely by the nitrifying and hetetrophic bacteria in the depth of 0.4 m filter and the filter layer was divided into aerobic and anoxic zones.The nitrification and degradation of organic matters existed in the aerobic zone,while the denitrification occurred in the anoxic zone.Due to the limited carbon source,the denitrifica-tion could not be carried out properly,which led to the accu-mulation of the denitrification intermediates such as NO_(2)^(−).In addition to the denitrification bacteria,the nitrification and the heterotrophic bacteria existed in the anoxic zone.

低热-NaOH联合处理破解浓缩活性污泥释放碳源的试验研究

以低热-NaOH联合处理破解剩余活性污泥,考察NaOH投加量、加热温度、反应时间对污泥破解释放碳源的影响,通过总氮去除率分析污泥破解液代替生物脱氮外加碳源的效率,并研究该方法对污泥减量化的效果。结果表明:SCOD溶出率随NaOH投加量、加热温度和反应时间的增加而增大;当NaOH投加量为3.0g/L、加热温度为70℃、反应时间为24h时剩余活性污泥的破解效果最佳,污泥上清液中SCOD浓度可达1.829×10^(4)mg/L,总氮、氨氮、硝酸盐氮和总磷浓度分别达到943、419、487、204mg/L;污泥破解前后固体残渣中TSS含量由61.70 g/L下降至29.25g/L,VSS含量由31.95g/L下降至6.95g/L,生物减量化效果非常显著;污泥破解前后中值粒度D50分别为30.2、8.7μm,污泥破解过程中产生了大量的粒径为0.15μm左右的超细颗粒;扫描电镜结果显示污泥絮体和微生物细胞被破坏;在反硝化试验中,以最佳破解条件下释放的污泥破解液作为反硝化试验的补充碳源,结果显示COD利用率为83.4%,总氮的去除率为60.1%,脱氮的效果显著。低热-NaOH联合处理可在较低能耗下实现剩余活性污泥的碳源充分释放,且污泥减量化和资源化的效果优异,可为优化热碱法预处理剩余活性污泥提供依据。

污水生化处理工艺发展阶段化技术特征及未来趋势

百余年来,伴随人类社会和科技日新月异,污水生化处理技术也在实现快速发展与不断迭代,新工艺与新反应器、新功能微生物与新生化代谢途径不断被提出、发现和解析,并进一步推动了污水处理技术的进步与升级。回顾了过去百余年污水生化处理技术发展历程,就典型污水生化工艺,结合技术研发进展、技术成熟度及案例应用情况,给出了不同生化处理工艺代际划分与技术发展期“S曲线”,分析了近些年来新涌现出的一些革新性污水生化处理工艺的技术原理、技术特征,结合实际案例分析了工艺技术特征、技术优势与总体效能,从工艺强化、绿色低碳与集约高效等方面总结了未来污水处理发展的技术趋势,以期为“双碳背景”下排水系统提质增效工作、未来国内前瞻性污水厂工艺设计与运行提供参考和借鉴。

Denitrification Rate and Controlling Factors for Accumulated Nitrate in the Deep Subsoil of Intensive Farmlands: A Case Study in the North China Plain

Denitrification in subsoil(to a depth of 12 m) is an important mechanism to reduce nitrate(NO3^-) leaching into groundwater.However, regulating mechanisms of subsoil denitrification, especially those in the deep subsoil beneath the crop root zone, have not been well documented. In this study, soil columns of 0–12 m depth were collected from intensively farmed fields in the North China Plain. The fields had received long-term nitrogen(N) fertilizer inputs at 0(N0), 200(N200) and 600(N600) kg N ha^-1 year^-1. Main soil properties related to denitrification, i.e., soil water content, NO3^-, dissolved organic carbon(DOC), soil organic carbon(SOC),pH, denitrifying enzyme activity(DEA), and anaerobic denitrification rate(ADR), were determined. Statistical comparisons among the treatments were performed. The results showed that NO3^- was more heavily accumulated in the entire soil profile of the N600 treatment, compared to the N0 and N200 treatments. The SOC, DOC, and ADR decreased with increasing soil depth in all treatments,whereas considerable DEA was observed throughout the subsoil. The long-term fertilizer rates affected ADR only in the upper 4 m soil layers. The ADRs in the N200 and N600 treatments were significantly correlated with DOC. Multiple regression analysis indicated that DOC rather than DEA was the key factor regulating denitrification beneath the root zone. Additional research is required to determine if carbon addition into subsoil can be a promising approach to enhance NO3^- denitrification in the subsoil and consequently to mitigate groundwater NO3^- contamination in the intensive farmlands.

安钢永通公司烧结烟气脱硫脱硝工艺优化实践

烧结烟气在基准φ(O_(2))为16%的条件下,颗粒物、二氧化硫、氮氧化物排放质量浓度需分别不高于10 mg/m^(3)、35 mg/m^(3)、50 mg/m^(3)。安钢集团永通球墨铸铁管有限责任公司为响应新要求,对其105 m^(2)烧结机进行了技术升级,淘汰原有湿法脱硫工艺,新建一套活性炭烟气脱硫脱硝净化装置。活性炭脱硫脱硝净化装置投用前期运行良好,但随着运行时间的增长,逐渐出现净化塔温度超温、净化塔床层阻力过高、制酸效率低等问题,制约烧结生产。后通过工艺升级和设备优化改造,实现了活性炭脱硫脱硝装置的稳定运行,并显著提高了脱硫脱硝效率,降低了烧结烟气中的污染物排放,为类似企业的烟气治理提供了参考和借鉴。

低温下改性活性炭对铅锌冶炼烟气中氮氧化物的吸附性能研究

针对传统技术在低温条件下烟气脱硝率低、活性炭吸附速率小等问题,结合温度条件改进研究了一种适用于低温条件的改性活性炭。分析铅锌冶炼排放烟气中的氮氧化物性质,利用氨气催化分离烟气中的NOx,通过扩孔和活化剂进行结构表征改性,增加活性炭比表面积,刺激活性炭吸附能力,以适应低温条件环境。利用Langmuir模型与Freundilch理论,计算活性炭吸附容量与温度、自由度的平衡关系,提高NO_x吸附数据监测与计算的精准度。实验结果表明,加入碳酸钾与羟基铁改进后的活性炭对NOx的脱硝率达到70%~100%,吸附速率最快可达0.7 mg/min。

基于逆流活性炭工艺的钢铁烧结废气模块化脱硫脱硝技术研究

随着人们对环保意识的提高,消费者对环保产品的需求也越来越强烈。然而传统的脱硫脱硝技术需要消耗大量的能源和化学药剂,易产生二次污染。基于活性炭脱硫脱硝技术,采用逆流式活性炭工艺对钢铁烧结废气进行脱硫脱硝处理。应用结果表明,通过该研究技术使脱硫率达到极大值,为92.3%,其平均脱硫率最高为85.5%。相比于其他常用脱硫技术,逆流式活性炭技术可更有效脱硫,并可有效减少钢铁烧结废气中的污染物排放。

陕钢集团汉钢公司活性炭一体化脱硫脱硝系统运行实践

汉钢公司引进应用了国际先进的烧结烟气活性炭脱硫脱硝技术,该工艺活性炭体量大,存在调整滞后,安全风险大。烧结厂结合原料混匀矿配比,采取厚料层烧结,不断探索运行管控,降低生产成本,确保系统稳定顺行。

活性砂反硝化系统调试技术研究

文章详细介绍了广东省某污水厂提标改造三期工程中活性砂反硝化系统的调试技术。研究目的是提高污水处理效率,特别是在脱氮除磷方面,采用了碳源投加、混凝加药及反硝化型连续流砂过滤器工艺,确保出水水质满足要求。文章不仅讨论了系统的装配和运行调试,还强调了运行过程中的关键步骤,如滤砂沉降速度监测和清洗水流速调试。研究表明,合理的调试和操作可以有效提升系统的处理能力,确保污水处理高效与稳定。

活性焦烟气脱硫脱硝的静态实验和工艺参数选择

在自制活性焦烟气脱硫脱硝静态实验系统上,考察了温度、空速、二氧化硫浓度、氧气浓度、水蒸气浓度、NO浓度、氨氮体积比等工艺参数对活性焦脱硫脱硝性能的影响,探索了使活性焦脱硫脱硝效率达到较优的工艺参数.结果表明:温度在120～180℃范围内时,温度越低越有利于活性焦的脱硫性能,而温度为130℃时,脱硝效果较好;空速在小于1 000/h时,随着空速的增大,活性焦的吸附性能显著增加,继续增大空速,活性焦相对质量的增加明显降低;烟气中SO2浓度小于2L/m3时,活性焦对SO2的吸附量有明显增大的趋势,但SO2浓度继续增大时,超过了活性焦的饱和吸附量,吸附性能下降;氧气、水蒸气体积分数含量均为6%时,大大促进了活性焦对SO2的吸附性能,含量过高或过低都不能达到最佳效果,而氧气浓度、NO浓度对脱硝性能影响不大.通过实验得到的较优脱硫工艺参数值为反应温度120℃、空速1 000/h、SO2体积比2L/m3、O2体积分数6%、H2O体积分数6%时,脱硫效率高达98%;脱硝工艺参数值为温度130℃、空速1 000/h、O2体积分数6%、NO体积分数500mL/m3、φNH3/φNO=1时,脱硝效率为70%.

消除及回收烟气中SO_2的糠醛渣活性炭研究

利用糠醛渣废料研制成一种新型改质炭(简称渣炭),采用温度程序脱附(TPD),色谱质谱连用(GC-MS),比表面测定(BET),静态与动态吸附以及二氧化硫氧化反应等方法,对渣炭的物化性质进行表征,并与几种商品炭进行比较;考察其反应条件,表明该渣炭无需添加任何活性组分便具有良好的脱硫性能,适用于烟气脱硫制酸过程。认为渣炭上某些羟基及羰基表面基团是脱硫活性中心,丰富的中孔有利于反应扩散。在烟气量5000Nm^3/h的中试装置上,于空速500h^(-1)。入口烟温70℃以及二氧化硫浓度1500—2500ppm的条件下,对工业放大渣炭进行验证,连续累计操作6000多小时,二氧化硫消除率约70％及副产硫酸的浓度约30％,并且,该渣炭的成本可以比碘炭降低40％左右。

糠醛渣活性炭的制备和性能研究

以糠醛渣为原料，成功地制备出脱硫活性炭，并详细考察了制备过程中影响炭性能的诸因素。该炭表面基团丰富，中孔发达；特别是经ＣＯ＿２改质后，脱硫性能显著提高。

微波改性活性炭用于烟气脱硫脱硝的实验研究

在用浓硝酸、氢氧化钾化学改性活性炭的基础上,使用专门设计的微波发生器对活性炭进行热处理,制备了一种高效的活性炭吸附剂用于烟气脱硫脱硝。改性活性炭对模拟烟气的吸附实验表明,活性炭经微波改性后的脱硫吸附量明显提高,氢氧化钾浸泡加微波改性的脱硫效果最好,浓硝酸浸泡加微波改性的活性炭对氮氧化物也有比较好的吸附效果,NO的吸附容量可达到36.8×10-3。扫描电镜(SEM)显示,微波改性后的活性炭微孔充分,有利于污染物的脱除。此外,还对各种改性方法提高活性炭脱硫脱硝性能的机理进行了分析。

胺化竹木/褐煤活性炭的表面特性及其脱除SO_2性能

以竹炭与褐煤混合料压块制备出柱状母料，500℃炭化30min后，经0-21．91％氨水气化，850℃活化2h，获得胺化竹村褐煤活性炭。采用BET和XPS研究竹木／褐煤活性炭的孔结构和表面化学，在100℃下考察活性炭对模拟烟气（0．1439％SO2、8．02％O2和10．11％水蒸气）中SO2的脱除性能。结果表明，氨水活化与水蒸气活化形成的竹木／褐煤活性炭孔径分布类似，主要分布于1～2．5nm，2．42％氨水活化制备的活性炭硫容是水蒸气活化的1．52倍；两种活性炭表面有相同种类的含碳基团，氨水活化后活性炭表面出现了类吡啶或类腈基团和胺、酰胺、酰亚胺及类吡咯基团；竹木／褐煤活性炭的脱硫性能主要与类吡啶基团有关。

微波诱导催化还原脱硫脱硝实验研究

针对我国电厂烟气治理的现状,进行了微波诱导催化还原脱硫、脱硝实验研究。该方法具有同时脱除烟气中污染物二氧化硫、氮氧化物的能力。利用微波装置和活性炭研究了模拟烟气同时脱硫脱硝,利用此技术可以将96%的一氧化氮和二氧化硫一步分解为环境友好的氮气和可以回收的有价值的单质硫。利用正交实验设计,对一些主要反应参数对脱硫脱硝的影响进行了分析。

粉状活性炭流化床吸附SO_2的实验研究及吸附动力学分析

对粉状活性炭在循环流化床内的脱硫特性进行了实验研究,结果表明:活性炭表面化学特性对脱硫性能具有重要影响;C/S摩尔比是影响脱硫率的重要参数,随着C/S摩尔比的增加,脱硫率迅速增加,但其吸附速率迅速下降;粉状活性炭具有较高的吸附速率,但随着吸附时间的延长,活性炭的吸附容量和吸附速率迅速衰减,12 s后基本不再具备吸附能力;采用Bangham模型进行拟合,得到的模拟值和实验值吻合良好。

微波辐照活性炭脱硫脱硝过程中炭损失研究

微波辐照结合活性炭的吸附和还原性能可以获得较高的脱硫脱硝效率,但该过程中活性炭会产生一定的质量损失。通过实验研究微波功率、氧含量、活性炭质量、辐照时间等因素对活性炭质量损失的影响。结果表明:微波功率升高,活性炭损耗率增加;辐照时间延长,活性炭质量损耗率增大,150 s内活性炭损耗严重;氧含量升高,活性炭损耗率升高,氧含量在2%～4%浓度范围内活性炭损失明显;活性炭质量增加,其损耗率下降,且呈线性关系。BET结果表明,微波辐照条件下活性炭比表面积略有减小,平均孔径增大。