Panel Discussion

A stack design procedure is developed which accounts for the effect of plume interception by downwind buildings, and which provides information on effluent concentrations in a form useful to planning authorities. The information presented in this paper is directed to engineers carrying out stack designs for locations where downwind buildings are of comparable height to the stack. A wind tunnel investigation using tracer gas techniques indicates that, for a plume at building height, downwash on the upwind face of a building causes the high concentrations observed near the roof to be transported to ground level. The effect of a plume on elevated points is determined by the concept of the minimum descent height of the maximum allowable ambient concentration isopleth. This minimum descent height, computed using Gaussian plume dispersion theory, defines a building height below which pollutant concentrations will always lie within safe limits. A case study is presented for the use of the design procedure for a small thermal power plant in an urban area.     

Energy and Efficiency Characteristics of the Ejector Venturi Scrubber

The scrubbing and pumping actions in the Ejector Venturi Scrubber are two separate phenomenon occurring simultaneously. Each phenomenon requires energy and has efficiency of operation and collection efficiency. These energy and efficiency relationships are discussed and illustrated in form of numerous graphs. The scrubbing energy requirements and how they vary with particle sizes down to one micron are also discussed and presented in form of numerous graphs.     

Das International Panel on Chemical Pollution (IPCP)

Ohne Zusammenfassung     

A Federal Tax on Energy

Abstract

In this investigation, the collection efficiency of particulate emission control devices (PECDs), particulate matter (PM) emissions, and PM size distribution were determined experimentally at the inlet and outlet of PECDs at five coal-fired power plants. Different boilers, coals, and PECDs are used in these power plants. Measurement in situ was performed by an electrical low-pressure impactor with a sampling system, which consisted of an isokinetic sampler probe, precut cyclone, and two-stage dilution system with a sample line to the instruments. The size distribution was measured over a range from 0.03 to 10 µm. Before and after all of the PECDs, the particle number size distributions display a bimodal distribution. The PM_2.5 fraction emitted to atmosphere includes a significant amount of the mass from the coarse particle mode. The controlled and uncontrolled emission factors of total PM, inhalable PM (PM₁₀), and fine PM P(M_2.5) were obtained. Electrostatic precipitator (ESP) and baghouse total collection efficiencies are 96.38–99.89% and 99.94%, respectively. The minimum collection efficiency of the ESP and the baghouse both appear in the particle size range of 0.1–1 µm. In this size range, ESP and baghouse collection efficiencies are 85.79–98.6% and 99.54%. Real-time measurement shows that the mass and number concentration of PM₁₀ will be greatly affected by the operating conditions of the PECDs. The number of emitted particles increases with increasing boiler load level because of higher combustion temperature. During test run periods, the data reproducibility is satisfactory.     

Renewable Energy

The Energy Committee of the Royal Swedish Academy of Sciences has in a series of projects gathered information and knowledge on renewable energy from various sources, both within and outside the academic world. In this article, we synthesize and summarize some of the main points on renewable energy from the various Energy Committee projects and the Committee’s Energy 2050 symposium, regarding energy from water and wind, bioenergy, and solar energy. We further summarize the Energy Committee’s scenario estimates of future renewable energy contributions to the global energy system, and other presentations given at the Energy 2050 symposium. In general, international coordination and investment in energy research and development is crucial to enable future reliance on renewable energy sources with minimal fossil fuel use.     

Nuclear Energy

Nuclear energy can play a role in carbon free production of electrical energy, thus making it interesting for tomorrow’s energy mix. However, several issues have to be addressed. In fission technology, the design of so-called fourth generation reactors show great promise, in particular in addressing materials efficiency and safety issues. If successfully developed, such reactors may have an important and sustainable part in future energy production. Working fusion reactors may be even more materials efficient and environmental friendly, but also need more development and research. The roadmap for development of fourth generation fission and fusion reactors, therefore, asks for attention and research in these fields must be strengthened.     

Conversion of Concentrated Solar Thermal Energy into Chemical Energy

When a concentrated solar beam is irradiated to the ceramics such as Ni-ferrite, the high-energy flux in the range of 1500–2500 kW/m² is absorbed by an excess Frenkel defect formation. This non-equilibrium state defect is generated not by heating at a low heating-rate (30 K/min), but by irradiating high flux energy of concentrated solar beam rapidly at a high heating rate (200 K/min). The defect can be spontaneously converted to chemical energy of a cation-excess spinel structure (reduced-oxide form) at the temperature around 1773 K. Thus, the O₂ releasing reaction (α-O₂ releasing reaction) proceeds in two-steps; (1) high flux energy of concentrated solar beam absorption by formation of the non-equilibrium Frenkel defect and (2) the O₂ gas formation from the O^2? in the Frenkel defect even in air atmosphere. The 2nd step proceeds without the solar radiation. We may say that the 1st step is light reaction, and 2nd step, dark reaction, just like in photosynthesis process.     

Energy return on investment: toward a consistent framework

Numerous technologies have been proposed as partial solutions to our declining fossil energy stocks. There is a significant need for consistent metrics to compare the desirability of different technologies. The ratio of energy produced to energy consumed by an energy production technology-known as the energy return on investment (EROI)-is an important first indicator of the potential benefits to society. However, EROI analysis lacks a consistent framework and has therefore yielded apparently conflicting results. In this article, we establish a theoretical framework for EROI analysis that encompasses the various methodologies extant in the literature. We establish variations of EROI analysis in two different dimensions based on the costs they include and their handling of nonenergy resources. We close by showing the implications of the different measures of EROI upon estimating the desirability of a technology as well as for estimating its ultimate net energy capacity.     

Correlation of Dust Scrubber Efficiency

The grid-type electrostatic precipitator¹ evolved from some basic research into the collection of airborne charged dust particles in the wake of a flat, metallic, perforated plate under the action of an externally applied electric field. In the earliest experiments in the laboratory² a flat grounded perforated plate (or grid) was placed at right angles to an air stream moving at 6 ft/sec and an electric field was created on its downstream side by the placement of a second grid, bearing high negative potential, just downstream of the first. Negatively charged dust particles, carried along by the air stream through the openings in the first of the two grids, collected on the downstream face of the upstream grid as a result of the electric force acting on them in the direction opposing the air flow. Measured values of dust collection efficiency could not be accounted for simply by resolving the directly opposing mainstream air flow and electrostatic forces. The concept of vortex-enhanced precipitation was therefore proposed in order to explain the experimental results.     

Estimating Overall Sample Train Efficiency

A common part of many gas analyses using bubblers is to combine the contents of the first n-1 impingers and analyze them separate from the nth. The nth impinger, yielding as it should a nil result, confirms that all of the sample entering the train was caught and that the concentration calculated therefrom represents the “true” value.

Many a hapless analyst has found himself stuck with nonzero nth impingers on occasion. Bemgloath tb reject the whole test, the analyst will often report the concentration based on the total catch (with appropriate qualifiers, of course). Another common practice is to calculate the percentage of the total catch in the first n-1 impingers. Sometimes this is reported, erroneously, as the sampler efficiency. The true sampler efficiency cannot be known (if it is less than 100%) because the presence of sample in the last impinger indicates that some unknown amount has passed through the train entirely.     

Efficiency of deposition of pesticide droplets on flat cards and spheres

Abstract

The mass flux of a cloud of droplets heading towards a collector can be decomposed into its horizontal and vertical components. While only the vertical mass flux contributes to droplet deposition on a flat card by the mechanism of sedimentation, both flux components contribute to deposition on a sphere by both mechanisms of inertial impaction and sedimentation. Calculated collection efficiencies decrease as wind speed increases for cards but as wind speed increases for spheres, a minimum collection efficiency is reached at a certain wind speed. The average collection efficiencies, as measured in the field trial portion of this study, are highly linearly correlated with wind speed for cards. For spheres, however, no correlation was found between the average collection efficiency and wind speed.     

规划环境影响评价初探

通过规划环评与项目环评的比较研究，从评价对象、范围、评价指标等方面，提出目前在科学发展观指导下的我国规划环评应实施的战略对策。     

浅谈视觉影响评价

分别概述了视觉影响评价的产生背景及其发展概况，视觉影响评价的概念和作用，评价程序和基本技术以及在我国的实施及发展前景。