Individual burner air/fuel ratio control optical adaptive feedback control system

On cover : Combustion Research Facility.Conventional combustion control systems for multiburner installations which rely on monitoring the average C02 and/or 02 content of the gases have a number of inherent limitations on their ability to maintain efficient plant operation. Air infiltration'into the flue or sampling lines has the same effect as an instrumental error in causing the control system to adjust the stoichiometry to an incorrect level. Even' when the overall stoichiometry of the furnace is correctly and accurately controlled it is still extremely difficult to ensure that no individual burners are operating inefficiently due to local maldistributions of air or fuel, or to poor nozzle spray characteristics. The potential for fuel savings and for'improved limitation of pollutant emissions has provided strong incentive for the development of individual burner fuel/air ratio control systems which would eliminate the shortcomings associated with the global control method. The present report first reviews past attempts to identify some unique property of an individual flame which can be reliably interpreted as an indicator of the flame behavior over a wide range of operating conditions.. Information potentially usable in this manner could be contained in the acoustic characteristics of the flame, in the local distribution of key chemical species, or in the electromagnetic radiation or absorption behavior of regions of the flame. For many reasons the previous studies have tended to concentrate on the optical portion of the electromagnetic spectrum, with particular emphasis on emission from flames over much of the ultraviolet (u.v.), visible and infrared (i.r.) wavelength regions. A brief review is given of the pioneering work of Penzias and his associates, and of the later work carried out at Sheffield University by Smith which led to the development of the LandTM control system. All of these studies dealt with the infrared emission from flames, wilth particular emphasis on the CO2 barnd at 4.3 pm, and on the H0/CO2 binds near 2.8 m. The report then addresses the experimental work carried out at M.I.T under the sponsorship of five utility companies supporting the M.I.T. Energy Laboratory Electric Power Program. This focused initially on attempts to use a Land control system in the Combustion Research Facility (CRF), with limited success in terms of achieving stability and adequacy of control when operating conditions were varied over a moderate range. The experiments in the CRF also yielded very useful data on the intensities and sources of u.v. emission from No. 6 fuel oil flames over a wide range of fuel equivalence ratio. One other set of experiments carried out in the CRF made use of equipment and personnel supplied by the Foxboro Company, and results of this work are discussed. Also included in the report is a summary of measurements carried out on a small methane-fueled burner which add appreciably to the available information on the dependence of the infrared emission on viewing location relative to the flame front and on fuel equivalence ratio. The overall results obtained under this program do not leave the prospect of individual fuel/air ratio controllers within immediate grasp, but they substantially advance the state of knowledge required for attainment of such control. They give a strong indication that satisfactory control could be obtained over a wide range of furnace operating conditions if both i.r. and u.v. signals were monitored and used in the control system

Chemical Profiles of Essential Oils and Non-Polar Extractables from Sumac (Rhus spp.)

Sumac is the common name for a genus (Rhus) with >250 individual species of flowering plants in the family Anacardiaceae. These plants are globally distributed in temperate and tropical regions and can grow on marginal lands, making them strong candidates for renewable bioproduct sources. Despite the extensive historical use of some members of Rhus spp. for tannins and other commercial phenolics, little is known about the non-phenolic components of extracts and essentials oils. The current review highlights opportunities available to extend these limited prior studies to other sumac species, and for obtaining value-added compounds to complement already established phenolic extractions in these commercial plant species. To date, a number of individual aldehydes, fatty acids, long chain alcohols, terpenes and terpenoids, and waxes of commercial or bioactive potential in essential oils and non-polar extractables from selected members of the Rhus genera have been identified. Additional studies are needed to broaden the phytochemical database from other sumac species, and to better quantify the potential yields of these valuable compounds from the plants under natural and agriculturally managed conditions

Experimental investigation of premixed ammonia combustion at high Karlovitz number conditions

This thesis aims to acquire deep knowledge on turbulent premixed combustion at high Karlovitz (Ka) number conditions with the help of laser-based diagnostic measurements.Considering that ammonia (NH3), as a carbon-free energy carrier, is a promising candidate for replacing conventional fossil fuels in the future, all the investigations in this work were carried out on ammonia/air premixed flames. Different optical diagnostic techniques, including planar laser-induced fluorescence (PLIF), laser Doppler anemometry (LDA) and Rayleigh scattering thermometry, have been employed for the measurement of key species, flow velocity and temperature, respectively.Firstly, experimental research on ammonia/air premixed flames was conducted on the Lund University Pilot Jet burner (LUPJ). The flame structure was visualised through the simultaneous measurement of the temperature field together with NH radical distribution or with NO distribution. Five stoichiometric flames withKarlovitz (Ka) numbers ranging from 274 to 4720 were studied. The NH layer, used as a marker of fuel consumption layer, remains thin at the burner exit, but becomes progressively thickened along the flame height with increasing turbulent intensity (u'/SL) when the Ka is higher than 1900. This thickness increase is attributed to the penetration of the small eddies and the merging of flame branches. The NO pollutant, mainly generated in the reaction zone, was observed to exist in a wide region, across the whole flame, because of the turbulent diffusivity and the flow convection.Limited by the geometric scale, the turbulent Reynolds number (Ret) in the LUPJ flame is much smaller than the operational ranges in industrial applications. For a better understanding of highly turbulent premixed combustion, a DRZ (distributed reaction zone) burner was introduced. This burner has integral scales (l0) between 30 – 40 mm and wider working conditions with a maximum turbulent intensity (u'/SL) and Karlovitz (Ka) number up to 240 and 1008. OH-/NH-PLIF and LDA measurements have been carried out to expand fundamental understanding. The results show that NH layer thickness remains almost constant and independent of turbulent intensity (u'/SL), although all the cases are located in the distributed reaction zone regime (Ka > 100). The turbulent eddies can only wrinkle the flame surface instead of penetrating into the inner structures. The ratio of turbulent to laminar burning velocity (ST/SL) increases monotonously with the Karlovitz (Ka) number. All the signs indicate that the flamelet theory is still applicable for ammonia premixed combustion at high Karlovitz (Ka) number conditions, which is inconsistent with Peters’ assumption in the Borghi-Peters diagram

Biological Treatment of Hazardous Waste Sludges in Suspended Growth Systems for Removal of Benzo(a)pyrene and Other Polynuclear Aromatics.

The scope of this research project was to develop a bioremediation process for accelerated oxidation of bioresistant hazardous waste sludges in continuous flow sludge reactors. Benzo(a)pyrene (BaP) was selected as the target compound due its strong bioresistance, highly carcinogenic nature, extremely low aqueous solubility, and extremely low allowable release limits for land disposal. BaP is often a major hazardous organic component in many hazardous waste impoundments when source wastes have originated from either petroleum refining or associated petrochemical facilities. There is evidence that the biodegradation rate of high molecular weight polynuclear aromatic hydrocarbons (PNA\u27s) is the rate limiting step in liquid-solids contact systems in spite of the low solubilities of these compounds (Sherman et al., 1989). The biological half-lives reported in the technical journals for low concentrations of high molecular weight PNA\u27s typically varies from 1-3 years for land disposal, 1-3 days in static batch reactors, and 2-3 days in mixed batch reactors. There is virtually no published data for successful treatment of high concentrations of PNA\u27s in high-solids suspended growth reactors. The recalcitrance of the PNA\u27s is believed due to the lack of suitable co-substrates containing primary source carbon which would permit rapid acceleration of the biodegradation process and foster fortuitous transformation of BaP and other PNA\u27s. Bench-scale pulsed-flow continuous sludge reactors feeding petrochemical sludge containing 8,700-35,000 mg BaP/kg of dry feed solids averaged 90% w/w destruction at equilibrium conditions. The biological half-life of BaP varied from 0.8-1.4 days and demonstrated that an enhanced environment increased the destruction of BaP at rates up to 2.5 times faster than mixed batch reactors, and 300-1000 times faster than land treatment. Steady state models were developed which predicted total suspended solids, BaP substrate, and oil co-substrate concentrations. The rapid contact bioremediation process (RCBP) developed in this dissertation research, has demonstrated that destruction of the anthropogenic-source annual production and existing accumulations of bioresistant toxic hydrocarbons is a practical goal. This research describes how indigenous microbial consortia can adapt to new strategies for destruction of bioresistant compounds if the microbial environment is appropriately enhanced

Dynamics of Cellular Flame Propagation for Hydrogen, Methane, and Propane

Since the outbreak of the economic crisis in 2009 and the explosion of the nuclear power plant in Japan in 2011, the price and needs of fossil fuel have gradually decreased, and environmental problems, e.g. greenhouse gas, have directed the world’s attention to other energy resources, so-called green energy. However, not only are oil reserves many in the world, but also a boom of shale gas, which the US has triggered, plays an important role in developing relevant technologies and has the possibility of making tectonic shifts in energy initiative. Moreover, although many kinds of electric cars have been released by major companies, a massive number of vehicles are still equipped with internal combustion engines, and power plants involving the combustion of fossil fuels are also used to produce electricity. It is certain that the technologies relevant to the combustion of fossil fuels are still essential and should exist for a fairly long time. The ultimate goal of combustion research is enhancing the understanding of the mechanism of combustion, fuel efficiency, and so forth, of which practical results end up helping us control combustion process safely and efficiently. Among such research subjects, the measurement of burning velocities about laminar and turbulent flames have been studied and discussed in the last decades. Regrettably, there is still doubt on how a variety of factors affect the burning rate. Especially, cellular flame structures that appear in a certain condition require more considerable observation and research to investigate their characteristics. The aim of this research is to examine the characteristics of cellular flame. In order to observe the flame, LUPOE-2D, Leeds University Ported Optical Engine version 2 with Disc-head, was used and an optical-accessible engine. In order to measure flame propagation speed, unburned gas velocity, burning velocity, and others, the research engine was modified, and the appropriate diagnostic system was installed. Hydrogen, methane, and propane were employed as fuels in this research. In the case of hydrogen, many researchers and major companies have paid much attention to it as a clean energy source to alleviate the global warming. And methane and propane have been widely used in the industrial fields. Using these three fuels, the experiment was carried out, and it was investigated how their cellular flames were locally changed