通风策略对污泥生物干化过程中含氮气体和甲烷排放的影响

我国污泥生物干化过程中含氮气体(NH_3、N_2O、NO)排放的数据十分缺乏,尤其是NO,因其化学性质极其活泼,在以往的研究中甚少涉及.本研究以东北某大型污泥生物干化厂的连续流强制通风槽式污泥生物干化为研究对象,通过现场试验,考察不同通风策略下干化效率以及含氮气体、温室气体的排放特征.结果表明,当污泥初始含水率约50%时,采用前期供氧为主、中期温度控制为主、后期以除湿和散热为目的的通风策略,可以明显加快污泥干化速率(试验组在第11 d时的含水率为36.6%,对照组为42%),提升干化效果(最终含水率试验组为33.6%,对照组为37.6%),减少氨气累积排放量5%(试验组氨气累积排放为208 mg·m~(-3),对照组为219.8 mg·m~(-3));同时降低温室气体累积排放当量[试验组每吨干物料的温室气体排放当量(eCO_2)为3.61 kg·t~(-1),对照组为3.73 kg·t~(-1)].但NO累积排放量试验组比对照组高出15.9%(试验组为1.9g·m~(-2),对照组为1.6 g·m~(-2)).     

Methane fluxes from artificial wetlands: A global appraisal

Methane emissions make an important contribution to the enhanced greenhouse effect, emissions from rice growing being one of its major anthropogenic sources. The estimation of global fluxes of methane from rice and from coarse fiber production depends on extrapolating observed data across countries and agroclimatic zones: the estimates are therefore imprecise. We present a revised estimate of global emissions of 96 Tg CH₄/yr, given 1991 rice areas, and 1991 production data for those tropical coarse fibers that also produce methane under anaerobic conditions. This is higher than many previous studies, which systematically underestimated the fluxes from tropical countries. As the world's population increases, the demand for rice will rise. This demand can only be satisfied through greater rice production, either by bringing new areas into rice growing or by using the present area more intensively. Strategies based on improved water management and fertilizer use will allow increased rice production and yields and reduce the methane flux per unit or rice production.     

纳米材料催化净化燃煤烟气中NOx的新技术

现有的氮氧化物治理技术，虽已取得了一些成果，但都存在一定缺点。通过综合分析催化剂在氮氧化物治理中的应用研究现状，提出以介孔沸石分子筛为载体，以纳米过渡金属Fe、纳米CaO等为助催化剂，纳米TiO2为主催化剂，进行光催化氧化反应降解燃煤烟气中氮氧化物的研究方法，并从分子反应机理上进行了分析。该技术不仅具有高效经济的工业应用前景，而且对保护大气环境具有重要意义。     

The contribution of the paper cycle to global warming

Worldwide, paper production is a major industry that contributes about 3 percent of Gross World Product. The paper cycle involves a broad range of natural resource and environmental impacts because fiber supply relies on trees, paper manufacturing requires fuel inputs, and paper waste disposal can contribute to emissions of the potent greenhouse gas (GHG), methane (CH₄). In some countries, the paper cycle may be seen as a net sink for GHG because of reliance on renewable wood by-products and the maintenance of forest plantations. On a worldwide basis, however, this study demonstrates that the paper cycle is a significant contributor to GHG emissions, adding emissions at least comparable in magnitude to that of Australia each year. The estimated global warming contribution of paper in landfills is estimated to be similar to that of paper manufacturing processes, on a heating-equivalent basis. In some temperate regions, original old-growth forests are still harvested to supply pulpwood, resulting in a significant loss of carbon (C) storage. In theory, the paper cycle holds the promise of achieving zero net emissions if pulpwood production, consumption and disposal are carefully managed. In practice, even stabilization of emissions at current levels would be challenging and entail changes comparable to a 20 percent reduction in CH₄ generation from landfilled paper, and a 2.5 percent annual increase in plantation establishment would be needed to offset the projected increase in emissions from paper manufacturing.     

Carbon storage potential in natural fiber composites

The environmental performance of hemp based natural fiber mat thermoplastic (NMT) has been evaluated in this study by quantifying carbon storage potential and CO₂ emissions and comparing the results with commercially available glass fiber composites. Non-woven mats of hemp fiber and polypropylene matrix were used to make NMT samples by film-stacking method without using any binder aid. The results showed that hemp based NMT have compatible or even better strength properties as compared to conventional flax based thermoplastics. A value of 63 MPa for flexural strength is achieved at 64% fiber content by weight. Similarly, impact energy values (84–154 J/m) are also promising. The carbon sequestration and storage by hemp crop through photosynthesis is estimated by quantifying dry biomass of fibers based on one metric ton of NMT. A value of 325 kg carbon per metric ton of hemp based composite is estimated which can be stored by the product during its useful life. An extra 22% carbon storage can be achieved by increasing the compression ratio by 13% while maintaining same flexural strength. Further, net carbon sequestration by industrial hemp crop is estimated as 0.67 ton/h/year, which is compatible to all USA urban trees and very close to naturally, regenerated forests. A comparative life cycle analysis focused on non-renewable energy consumption of natural and glass fiber composites shows that a net saving of 50 000 MJ (3 ton CO₂ emissions) per ton of thermoplastic can be achieved by replacing 30% glass fiber reinforcement with 65% hemp fiber. It is further estimated that 3.07 million ton CO₂ emissions (4.3% of total USA industrial emissions) and 1.19 million m³ crude oil (1.0% of total Canadian oil consumption) can be saved by substituting 50% fiber glass plastics with natural fiber composites in North American auto applications. However, to compete with glass fiber effectively, further research is needed to improve natural fiber processing, interfacial bonding and control moisture sensitivity in longer run.     

Evaluation of energy savings by using high efficiency motors in a thermal power station

This paper presents potential energy savings by installing high-efficiency motors instead of existing ones and their impact on greenhouse gases emissions reductions. This research study of the energy efficiency of electric motors has been performed in a typical thermal power plant. In the literature, the focus has been mainly on separate and away electric motors from operating facilities. The important advantage of this paper over other studies is that it uses the actual motors’ efficiency in the evaluation. The gains both in terms of electrical energy savings and in terms of financial economy by using high-efficiency motors have been discussed. As a result, the energy saving can be expected as 12.6% at the operating rate. This excellent result also reduces greenhouse gas emission by 1,423 tons every year. The analysis of the data provided an overview on energy losses often generated by the degradation and rewinding of electrical motors. This study represents very encouraging results that will help energy managers of industrial plants to become more involved in energy efficiency strategies.     

Pyrolysis of commingled waste textile fibers in a batch reactor: Analysis of the pyrolysis gases and solid product

The main object of this study was the investigation of the thermal recycling of commingled waste textile fibers, with the aim of the production of useful end products. Differential scanning calorimetry/Thermo gravimetric analysis (DSC/TGA) was applied to determine the thermal degradation characteristics of the commingled waste textile fibers and there are two peaks located at the temperature ranges of 299–360°C and 399–500°C. Commingled waste fiber was pyrolyzed in a nitrogen atmosphere in relation to three different temperatures (500, 600, and 700°C), heating rates (25 and 50°C min^?1), and retention times (15 and 30 min). The effect of the experimental conditions such as pyrolysis temperature, heating rates, and retention time on the formation of char and gas--liquid products was investigated and the product yields were determined from the rate of the weight loss. The highest conversion rate 82.9 wt.% liquid--gas product and 17.1 wt.% char product was achieved at 700°C. Pyrolysis gases were taken for every 7, 15, and 25 min and were analyzed for major components such as CO, CO₂, CH₄, and H₂ by gas chromatography. The pyrolysis char called as carbon black derived from the pyrolysis of commingled waste textile fibers was analyzed for a range of properties, including the elemental analysis, moisture content, ash content, calorific value, and trace metal analysis.     

粉煤灰净化低浓度SO2烟气试验研究

中国是一个以煤为主要燃料的国家,粉煤灰的综合利用问题早已受到人们的关注。褐煤粉煤灰中含有较多的碱性物质,它是一种优良且价廉的低浓度二氧化硫烟气脱硫吸收剂。试验研究结果表明,采用粉煤炭吸收液碱法脱硫在技术上是可行的,控制吸收液pH值大于6即可获得良好的脱硫效果。试验中考察了固液比、pH、温度、SO₂浓度和气体流墓等因素对粉煤灰吸收液净化效率的影响情况。粉煤灰碱法脱硫在经济性方面优于石灰/石灰石法。      

RS-1型含硫有机废气燃烧催化剂

考察了RS-1型催化剂对乙硫醇、丁硫醇、二硫化碳、硫酸二甲酯、乙醇、二甲苯等有机物的氧化活动性。实验结果表明,这种催化剂对乙硫醇等含硫有机物均有较高的氧化活性,且有机硫的氧化产物SO_x不与催化剂发生化学反应。经分析检测,氧化产物SO_x放出率接近100％。在反应温度380℃,空速10000h~(-1),乙硫醇和丁硫醇浓度分别为4000—8000mg/m~3、6000—8000mg/m~3时,净化率≥99％。该催化剂适用于净化制药厂、农药厂等生产排放的含硫废气。     

垃圾堆放场释气源强确定与评价及其污染控制

对北京北神树垃圾堆放场释气采样并定性定量分析,用上、下风测试和现场测试记录２种方法监测污染气体浓度,用改型扩散算出释气源强;通过室内模拟试验,找出产气量规律,产气成分所占比例,得出单位重量垃圾的产气量,进而推算出源强;评价垃圾释气对环境的影响并提出可行的控制污染对策。