Pilot plant/full scale EP system design and performance on a BOF application

An ESP pilot plant study was done on emissions from a BOF process which is cyclic with very high and low gas volumes, temperature and grain loadings. Data collected were EP performance vs. gas velocity, and collection area. Also measured was particle size distribution, dust resi opacity at the EP outlet. From this data, a full size EP system was designed and installed. Recent performance tests indicate the data agrees well with the initial pilot plant study. Emissions have been reduced from 11 grs/scf (27.1 g/m³) to less than 0.033 grs/scf (81 mg/m³) and opacity to 20% or less.     

Electrostatic enhancement of moving-bed granular filtration

The electrostatic granular filter developed by Combustion Power Company combines a moving-bed filter with an electrostatic grid for high-efficiency collection of particulate. The coulomb charge occurring naturally on particulate from combustion or other processes in which tribocharging occurs is sufficient such that imposition of an electric field substantially enhances mechanical collection in the packed filter. A mathematical model is presented which accounts for the major parameters affecting electrostatic performance. Experimental data developed in an industrial unit retrofitted with electrostatic equipment and a pilot-scale filter demonstrates dramatic improvement in opacity and outlet loading; the industrial unit achieved 99% collection efficiency with less that 4 Iwd (1kPa) pressure drop. Data from the pilot-scale filter has shown that collection of micron-size particulate is especially enhanced with the electric field and has confirmed the 99% overall collection capability demonstrated in the industrial unit. The design of a 420,000 acfm (1200 m³/min) system being installed at Weyerhaeuser Company's Longview, Washington plant is also discussed.     

Evaluation of the Ceilcote ionizing wet scrubber

The Ceilcote ionizing wet scrubber installed on a refractory brick kiln was evaluated with tests involving particulate mass emission, particle size distribution, and opacity. The overall efficiency was 93% with an average outlet opacity of 8% on a 1.68 m (5.5 ft) path length. The average particle cut diameter of the scrubber is 0.5 microns with a theoretical power input of 67 W/am³ (2.5 hp/1000 acfm). The theoretical power requirement for the ionizing wet scrubber was 41 W/am³ (1.54 hp/1000 acfm). A cooling tower supplying chilled water to the prescrubber required an additional 26 W/am² (0.96 hp/1000 acfm) for a total system input of 67 W/am³ (2.5 hp/1000 acfm). It is recommended that the scrubber be considered where practical for the removal of fine particulate matter.     

Demonstration of a high field electrostatically enhanced venturi scrubber on a magnesium furnace fume emission

A 566 m³/m (20,000 acfm) permanent installation demonstration system, consisting of the Air Pollution Systems' High Intensity Ionizer and a variable throat venturi scrubber (called the Scrub-E) has been installed on a magnesium recovery furnace. The furnace produces submicron fume particles of MgO, MgCl₂, and ZrCl₄. The system is designed to demonstrate the effectiveness of the High Intensity Ionizer versus high venturi pressure drop on the furnace emissions. The High Intensity Ionizer array operates stably at field strengths of 10–15 kV/cm and at velocities in excess of 18 m/sec (60 fps) while maintaining high charging efficiencies. The report covers the system design, technology, applications, and project developments. An Environmental Protection Agency proposed charged droplet Scrub-E is also discussed covering the design, technology, and proposed demonstration program.     

High velocity fabric filtration for control of coal-fired boilers

As a follow-up to a pilot study, a full scale investigation of applying high velocity fabric filtration to coal-fired boiler fly ash control was conducted. Two filter systems were separately applied to two 60,000 lb/h coal-fired boilers. Performance evaluations conducted over the course of a year included total mass removal efficiency and fractional efficiencies. One filtration system employed Teflon felt as the filter media while the second system employed Gore-Tex, a Polytetrofluorethylene (PTFE) laminate on PTFE woven backing. During the course of the year, a limited number of glass felt and woven glass bags were introduced into the house containing Gore-Tex. As a separate option, the second system was outfitted entirely with woven glass bags. Preliminary results indicate acceptable performance at air-to-cloth ratio of 6 to 1. Future plans call for utilizing one of the baghouse systems for SO₂ removal.     

Effect of mixing chamber venturi,injection timing,compression ratio and EGR on the performance of dual-fuel engine operated with HOME and CNG

Stringent environmental policies and the ever increasing demand for energy have triggered interest in novel combustion technologies that use alternative fuels as energy sources. Of these, pilot-ignited compressed natural gas (CNG) engines that employ small biodiesel pilot to ignite a premixed natural gas–air mixture have received considerable attention. This paper discusses the effect of mixing chamber venturi, injection timing, compression ratio and exhaust gas recirculation (EGR) on the performance of dual-fuel engine operated on biodiesel derived from honge oil and is called honge oil methyl ester (HOME) and CNG. The proposed study mainly focuses on the manifold induction of CNG along with HOME injection. However, CNG can also be injected using port or direct gas injector (Lakshmanan and Nagarajan 2010, Energy 35, pp. 3172–3178). The future study will involve these methods of CNG injection. From this study, it is concluded that an advanced injection timing and an increased compression ratio resulted in increased brake thermal efficiency and reduced smoke, hydrocarbons and carbon monoxide emissions. However, nitrogen oxides (NO _x ) emission increased significantly. The increased NO _x emission was effectively reduced with EGR method. A mixing chamber venturi of 3 mm size, injection timing of 27° before top dead centre (BTDC), compression ratio of 17.5 and 10% EGR were found to be optimum for the modified compression ignition engine that was operated on CNG–HOME dual-fuel mode.     

Effect of hydrogen addition to CNG in a biodiesel-operated dual-fuel engine

Alternative fuels for diesel engine applications are gaining more prominence as they have numerous advantages compared to fossil fuels. They are renewable, biodegradable; provide food and energy security and foreign exchange savings. They address environmental concerns and socio-economic issues as well. Gaseous fuels such as compressed natural gas and hydrogenated compressed natural gas (HCNG) appear more attractive fuels for diesel engine applications operated in dual-fuel mode. Such dual fuel engines can replace considerable amount of liquid-injected pilot fuels by gaseous fuels besides being friendly to the environment. A small quantity of liquid fuel injected towards the end of the compression stroke initiates combustion of the inducted gas in the dual-fuel engines. The main advantage of dual-fuel engines is their lower nitrogen oxides (NO_x) and particulate emissions. Hence renewable fuels such as biodiesels and gaseous fuels can be used predominantly for transportation and power generation applications. Gaseous fuels are clean burning and are more economical as well. A suitable carburettor was designed to supply a stoichiometric mixture of air and HCNG to the modified diesel engine operated in dual-fuel mode. The biodiesel used in this study is derived from Honge oil called the Honge oil methyl ester (HOME). This paper presents the performance, combustion and exhaust emission characteristics of a single cylinder, four stroke, direct injection, stationary diesel engine operated on HOME and HCNG in dual-fuel mode. From the results it is observed that HOME–HCNG combination gave lower brake thermal efficiency (BTE) and improved emission levels when compared with diesel/HOME in single fuel operation. Lower smoke and particulate matter were obtained with dual-fuel operation. Comparative measures of BTE, peak pressure, pressure–crank angle variation, smoke opacity, hydrocarbon, carbon monoxide and NO_x emissions have been made and analysed.     

Electrostatic precipitator emission and opacity performance control through rapper strategy

The opacity and emission performance of two “identical” cold-side precipitators at a power plant utilizing a Western coal source was investigated through an extensive test program. The test program included establishment of outlet emission versus opacity correlations for the two “identical” units, correlation of rapper strategy (frequency and amplitude) with opacity, and correlation of power-off rapping strategy with opacity. Analysis of the test program data demonstrates that the opacity-emission correlations from the two “identical” units can be significantly different. The potential reasons for the differences between the two units are identified and examined in light of the test program data. Strong correlation of opacity with rapping strategy was developed from the test program. Results demonstrate that an automatic power-off rapping technique can significantly enhance precipitator performance on ash from Western coal.     

Control of salt laden particulate emissions from hogged fuel boilers

This paper presents the results of an evaluation of excessive salt emissions from 16 hogged fuel boilers in Washington, Oregon, and Alaska. Logs transported or stored in sea water, absorb substantial amounts of salt which is noncombustible, and is emitted as a fine particulate when the hogged fuel is burned, contributing to opacity and particulate emissions. Control measures considered are fuel pretreatment, combustion modification, use of conventional particulate control devices (electrostatic precipitators, fabric filters, and wet scrubbers), and several novel particulate control devices.The best available control technology appears to be a mechanical collector-fabric filter combination; some electrostatic scrubber type devices have also shown excellent capability.     

A CO2-controlled ventilation system

For buildings in which the emissions from people is the main source of pollution, the number of people is the limiting factor for air ventilation. When such buildings are not used at full capacity, the ventilation, and consequently the energy consumption, is unnecessarily high. A great deal of the energy could be saved if the ventilation system could be developed to adjust the air flow to the actual requirements. One possible system would allow the amount of CO₂ in the exhaust air to control the ventilation rate. To study if this principle is practicable and economic, a CO₂ indicator has been installed in an office building in Helsinki. The mixture of exterior air and recirculated air is adjusted so that the amount of CO₂ during working hours is kept on ca 700 ppm (μL/L). The equipment was used during winter 1981-82, and the variation of CO₂ and the exterior air flow has been registered. The proportion of CO₂ has also been measured locally in order to study occasional variations that may occur. The proportion of other pollutants in the room air has been studied simultaneously with a gas chromatograph. Different types of CO₂ indicators were used to study the efficiency of the control system. The successful results indicate that the system can be used in new constructions, as well as in existing buildings.     

Start-up and initial operational experience on Colorado Springs' Martin Drake unit no. 6 baghouse

A fabric filter baghouse was installed on an 85 MW unit at the City of Colorado Springs' Martin Drake Power Plant. This baghouse retrofit was placed on line in September 1978. During the initial operation, some minor design and operational problems arose. Minor modifications were made to the baghouse system which eliminated these problems. The baghouse is experiencing a relatively low operating pressure drop and continues to maintain zero visible emissions.     

Tidal variations in dissolved and particulate phase radionuclide activities in the Esk estuary,England, and their distribution coefficients and particulate activity fractions

Measurements have been made of the radionuclide activities, particularly for plutonium isotopes, of the particulate and dissolved fractions of the tidal waters of the Esk Estuary. A wide range of K_d values indicates the lack of equilibrium conditions in this dynamically changing environment. The particulate activity contributes a major part of the activity of the suspension, with reworked estuarine sediment providing an important component of this. The estuarine circulation system results in the dispersion of particulate radionuclides into the low salinity upper reaches of the estuary, where plutonium isotopes are apparently mobilised, enriching the dissolved fraction activity.     

Accuracy and reliability of Chile's National Air Quality Information System for measuring particulate matter: Beta attenuation monitoring issue

A critical analysis of Chile's National Air Quality Information System (NAQIS) is presented, focusing on particulate matter (PM) measurement. This paper examines the complexity, availability and reliability of monitoring station information, the implementation of control systems, the quality assurance protocols of the monitoring station data and the reliability of the measurement systems in areas highly polluted by particulate matter. From information available on the NAQIS website, it is possible to confirm that the PM_2.5 (PM₁₀) data available on the site correspond to 30.8% (69.2%) of the total information available from the monitoring stations. There is a lack of information regarding the measurement systems used to quantify air pollutants, most of the available data registers contain gaps, almost all of the information is categorized as “preliminary information” and neither standard operating procedures (operational and validation) nor assurance audits or quality control of the measurements are reported. In contrast, events that cause saturation of the monitoring detectors located in northern and southern Chile have been observed using beta attenuation monitoring. In these cases, it can only be concluded that the PM content is equal to or greater than the saturation concentration registered by the monitors and that the air quality indexes obtained from these measurements are underestimated. This occurrence has been observed in 12 (20) public and private stations where PM_2.5 (PM₁₀) is measured. The shortcomings of the NAQIS data have important repercussions for the conclusions obtained from the data and for how the data are used. However, these issues represent opportunities for improving the system to widen its use, incorporate comparison protocols between equipment, install new stations and standardize the control system and quality assurance.     

Objectives and status of fabric filter performance study

In October 1977, Southwestern Public Service Company executed a contract with the U.S. Environmental Protection Agency that called for a study to assess the performance of a fabric filter system installed on a large utility boiler that utilizes low sulfur Western coal. The project is now into its second year and the objectives of this paper are to describe the scope and intent of the study, as well as to report progress to date. In addition, some of the difficulties that we have encountered are discussed. Although some of these problems have resulted in procedural changes, the intent of the study has not been altered. This paper describes work being done in specific areas with which both the EPA and Southwestern are connected. These include fabric assessment, data collection, selection and installation of instrumentation, and overall fabric filter system performance. Results of the first performance test are also reviewed and the installation of a pilot baghouse is discussed.     

Sidestream tobacco smoke constituents in indoor air modelled in an experimental chamber— Polycyclic aromatic hydrocarbons

Exposure to sidestream tobacco smoke is concerned with constituents in suspension in the indoor atmosphere. The natural dissipation of sidestream tobacco smoke has been investigated in a static atmosphere in a 10 m³ experimental chamber, and the rate of dissipation is expressed as T_0.5, the half-life of residence in the air. Respective T_0.5 of smoke components are calculated from the various sample data points, assuming a kinetic equation of the first-order process. Sidestream smoke has been generated by a smoking machine according to the Coresta standard protocol and then left to age over an 8-hour period, with subsequent sampling at defined time intervals. The experiments have been repeated over five days, and eight data point samples are obtained for each experiment. Besides nicotine, CO, and smoke particulate matter, interest has been focused on polycyclic aromatic hydrocarbons (PAH). The initial concentrations, C₀ for smoke particulate matter and nicotine (gas and particulate phases) are found to be 13.8 mg and 92 μg per cigarette per cubic meter, with T_0.5 being 2.6 and 2.1 hours, respectively. Low molecular-weight PAH have T_0.5 up to 20 hours, explainable only by their high concentrations in the gas phase, while the 3- to 7-ring PAH have T_0.5 of about 2 hours. The contribution of CO to ambient concentration is 91 mg per cigarette per cubic meter. The data can be useful in mathematical modellization studies regarding ventilation or exposure to sidestream smoke.     

Simulation and analysis of a combined cycle heat and power plant process

The regulations of process efficiency and stricter environmental policies require analysis of large-scale thermal energy systems to produce highly efficient, cost effective and low environmental impact energy. For analysis, it is beneficial to simulate an energy system. In this paper, simulation models are developed for the analysis of a combined cycle heat and power plant located in Göteborg, Sweden. With the help of simulation models, characteristics between district heating (DH) water temperature and key parameters such as overall district heat duty, electrical power and electrical efficiency has been developed. The characteristics are useful to estimate and maximize the key parameters during varying DH water temperature. According to a comparison between the full-load simulation models of 2006 and 2013 for the selected power plant, a loss of 2 MW is noticed for gas turbine and a loss of 2.18 MW of heat flow occurs for heat recovery steam generator in the year 2013. The feasibility analysis of modifying the connection between DH economizer and main DH line provides good performance indicators in a winter scenario. The conclusions in this paper are good references to plan and improve the performance of existing large-scale thermal power plants.     

mSpray: A mobile phone technology to improve malaria control efforts and monitor human exposure to malaria control pesticides in Limpopo,South Africa

Recent estimates indicate that malaria has led to over half a million deaths worldwide, mostly to African children. Indoor residual spraying (IRS) of insecticides is one of the primary vector control interventions. However, current reporting systems do not obtain precise location of IRS events in relation to malaria cases, which poses challenges for effective and efficient malaria control. This information is also critical to avoid unnecessary human exposure to IRS insecticides. We developed and piloted a mobile-based application (mSpray) to collect comprehensive information on IRS spray events. We assessed the utility, acceptability and feasibility of using mSpray to gather improved homestead- and chemical-level IRS coverage data. We installed mSpray on 10 cell phones with data bundles, and pilot tested it with 13 users in Limpopo, South Africa. Users completed basic information (number of rooms/shelters sprayed; chemical used, etc.) on spray events. Upon submission, this information as well as geographic positioning system coordinates and time/date stamp were uploaded to a Google Drive Spreadsheet to be viewed in real time. We administered questionnaires, conducted focus groups, and interviewed key informants to evaluate the utility of the app. The low-cost, cell phone-based “mSpray” app was learned quickly by users, well accepted and preferred to the current paper-based method. We recorded 2865 entries (99.1% had a GPS accuracy of 20 m or less) and identified areas of improvement including increased battery life. We also identified a number of logistic and user problems (e.g., cost of cell phones and cellular bundles, battery life, obtaining accurate GPS measures, user errors, etc.) that would need to be overcome before full deployment. Use of cell phone technology could increase the efficiency of IRS malaria control efforts by mapping spray events in relation to malaria cases, resulting in more judicious use of chemicals that are potentially harmful to humans and the environment.     

A new approach to spatial source apportionment of haze pollution in large scale and its application in China

Long-lasting expansion of haze pollution in China has already presented a stern challenge to regional joint prevention and control. There is an urgent need to enlarge and reconstruct the coverage of joint prevention and control of air pollution in key area. Air quality models can identify and quantify the regional contribution of haze pollution and its key components with the help of numerical simulation, but it is difficult to be applied to larger spatial scale due to the complexity of model parameters. The time series analysis can recognize the existence of spatial interaction of haze pollution between cities, but it has not yet been used to further identify the spatial sources of haze pollution in large scale. Using econometric framework of time series analysis, this paper developed a new approach to perform spatial source apportionment. We applied this approach to calculate the contribution from spatial sources of haze pollution in China, using the monitoring data of particulate matter (PM_2.5) across 161 Chinese cities. This approach overcame the limitation of numerical simulation that the model complexity increases at excess with the expansion of sample range, and could effectively deal with severe large-scale haze episodes.     

Smoke-haze pollution: a review of the 1997 episode in Southeast Asia

In the second half of 1997, large areas in Southeast Asia were severely affected by a smoke-haze pollution episode caused by the emissions of an estimated 45,600 km² of vegetation that burnt on the Indonesian islands Kalimantan and Sumatra. To document the impacts of these fires on air quality, data for total suspended particulate matter (TSP) and for particulate matter below or equal to 10 microns in diameter (PM₁₀) from selected sites in Indonesia, Malaysia and Singapore are analysed in this paper. These data are supplemented by meteorological data, satellite images and a summary of related research. TSP was above 2,000 μg m^–3 for several days in Indonesian locations close to the most extensive fire activity. In Malaysia and Singapore, ambient particle concentrations increased to several times their average September levels. Characteristically for emissions from vegetation burning, the additional atmospheric particle loading during the smoke-haze episode was predominantly due to an increase of the fraction below or equal to 2.5 microns in diameter (PM_2.5). Due to the dominance of respirable particles (PM_2.5) in the smoke-haze, air quality reporting based on TSP or PM₁₀ may be inadequate to assess the health risk. Upgrading of PM_2.5 monitoring facilities is therefore needed. Reducing the probability of similar smoke-haze events in future would require appropriate fire use and smoke management strategies. Electronic Publication     

Design guidelines for an optimum scrubber system

The revised New Source Performance Standards (NSPS) for the utility industry mandates reduced particulate matter and sulfur dioxide emissions from new utility boilers. A wet scrubber system can be an advantage in controlling both of these emissions. Existing wet scrubber systems may meet the new standards with significant increase in power consumption. A careful design of the entire scrubber system, based on the experience gained at the existing installations, is necessary to ensure cost effectiveness. The experience with existing wet scrubber systems used on coal-fired utility boilers is reviewed and their performance is correlated with power consumptions. Based on a correlation of scrubber pressure drop against outlet concentration, conventional scrubber systems would be able to meet the revised NSPS for particulate matter with a theoretical scrubber pressure drop of 43±5 cm H₂O. Overall system pressure drop, however, could easily run as high as 76 cm H₂O. Novel scrubber systems such as the electrostatically augmented scrubber may provide the necessary collection performance at lower pressure drops. The performance of the various scrubber components such as mist eliminators and reheaters is reviewed. Operating problems are also discussed.