This master’s thesis deals with the issue of design heat recovery steam generator. In the first part is realized calculation of stoichiometry and further the thermal balance of the boiler. The boiler was divided on the basis of thermal analysis in two heating surfaces that have been designed separately. The thesis also includes structural design and drawings of evaporator, economizer and their compilation.

>Magister Scientiae - MSc / Over the past 5 years, South Africa has been experiencing a severe drought. This has caused industrial and agricultural processes, to compete for a limited supply of water. Since the economy relies mostly on agricultural activities, water consumption by industrial processes is taking its toll. One of these processes is the introduction of wet flue gas desulphurization (FGD) treatment at Eskom coal fired power stations. This dissertation explores the possibility of using membrane technology as a means of water recovery after the coal combustion flue gas has been treated with wet FGD. A lab-scale permeance testing system was specially built and modified to have complete thermal control of the environment inside the system. The permeance testing system produced a gas, similar to that of a wet FGD treated flue gas, which was then tested. A tubular lab-scale membrane module was designed and produced for the permeance testing system. The permeance figures of both Nitrogen gas and water vapour were determined for the membrane used in module production. These figures coincided with figures provided by the supplier, which warranted successful permeance testing. After success of the lab-scale testing, the data was used to design and develop a pilot-scale membrane module. This module was designed to meet pre-determined requirements as set forth by the project team. Producing lab-scale membrane modules helped identify and address possible problems in pilot-scale module design. This lead to the successful design and construction of a pilot-scale membrane module that could be used to recover the water that is needed to run the wet FGD process.

Metallurgical activities are one of the important sources of environmental pollution, especially due to inappropriate treatment of waste materials containing potentially harmful elements. Soils in the vicinity of smelting operations are the main target reservoirs for these emitted contaminants. The aim of this study was to depict reactivity of copper smelter flue dusts and slags in aqueous and soil environments using laboratory and field experiments. Slags exhibited high concentrations of As (up to 0.95 wt.%), Cu (up to 2.4 wt.%), Pb (up to 1.02 wt.%), Sb (up to 0.37 wt.%), and Zn (up to 2.45 wt.%). Copper and other metal(loid)s were predominantly bound in sulphides, especially bornite, digenite, chalcocite, and galena. Flue dusts were mainly composed of As2O3 phase (arsenolite and claudetite), with minor amounts of gypsum, galena, quartz and covellite. The main contaminants in the dust were As (53.3 wt.%), Pb (3.41 wt.%), Sb (1.26 wt.%), Zn (1.41 wt.%), Cu (1.07 wt.%) and Bi (0.80 hm.%). The leaching tests performed in the pH range of 3-12 indicated that the release of metal(loid)s from both types of metallurgical wastes was highly pH-dependent. During the leaching in deionised water, up to 42 mg/kg As was released from slags and up to 52.6 g/kg was leached from the flue dust; the latter highly...

Seawater flue gas desulphurization (SWFGD) is a reliable and efficient process to re-move sulfur dioxide in flue gases in power plants and industries. The characteristics and applications of seawater treatment plant of three SWFGD process are described firstly. A literatual survey looking at different air injection techniques in shallow water basin applications are investigated, also including best practice from similar applications in other types of industries. A number of promising alternatives is then selected and compared with today’s system. The relevant experimental data of these systems are collected. A rate-based model is developed to simulate and optimize the aeration process in seawater treatment plant after its reliability is verified by the experimental data.

Seawater flue gas desulphurization (SWFGD) is a reliable and efficient process to re-move sulfur dioxide in flue gases in power plants and industries. The characteristics and applications of seawater treatment plant of three SWFGD process are described firstly. A literatual survey looking at different air injection techniques in shallow water basin applications are investigated, also including best practice from similar applica-tions in other types of industries. A number of promising alternatives is then selected and compared with today’s system. The relevant experimental data of these systems are collected. A rate-based model is developed to simulate and optimize the aeration process in seawater treatment plant after its reliability is verified by the experimental data.

This study evaluated the effect of several heavy metals that are present in flue gases on the algae, focusing on the growth and accumulation of lipids in the algae that can be converted to biodiesel. Concentrations for the heavy metals were calculated based on literature and assumptions. Metals were tested individually first at the highest concentrations that might be present (reference concentrations). The metals and their reference concentrations were: arsenic at 1.56 mg/L, cadmium at 0.3 mg/L, chromium at 2.6 mg/L, cobalt at 0.32 mg/L, copper at 2.62 mg/L, lead at 1.09 mg/L, nickel at 5.08 mg/L, mercury at 0.2 mg/L, selenium at 0.2 mg/L, and zinc at 8.8 mg/L. At these concentrations, most of the metals had a negative effect on the growth and lipid content of the algae. All of the metals were then tested at lower concentrations. At 1/20 the reference concentrations, the metals enhanced growth as well as lipid accumulation in the algae. At higher concentrations there was a negative effect.

Host resistance has become a cornerstone of sustainable production of flue-cured tobacco in regions where root-knot nematodes present a threat to growers. Resistance to races 1 and 3 of M. incognita, historically the most significant root-knot nematode threat to tobacco production, is now widely available in commercially available flue-cured tobacco varieties, and is imparted by the gene Rk1. The same gene also provides resistance to race 1 of M. arenaria. The widespread deployment of this resistance has fostered a shift in root-knot nematode population dynamics, as a result of which M. arenaria race 2 has become the predominant root-knot nematode threat in Virginia. A second resistance gene known to impart resistance to M. javanica, Rk2, has also been incorporated into numerous released cultivars in combination with Rk1. This combination has been demonstrated to impart increased resistance to M. incognita and M. javanica relative to either gene alone. In the present work, eleven greenhouse trials conducted from 2017-2019, as well as two trials conducted in 2018 and 2019 on a cooperating farm, investigated the efficacy of this stacked resistance against M. arenaria race 2 and compared the effect of stacking both resistance genes to the effect of either gene alone relative to a susceptible cultivar. We also evaluated how these forms of resistance compare with resistance possessed by a breeding line with resistance reportedly derived from N. repanda to determine if additional, novel sources of resistance to root-knot nematodes previously identified from other species in the genus Nicotiana could play a role in expanding the genetic diversity of germplasm available for the refinement of host resistance in flue-cured tobacco. Additionally, in light of potential new rule making from the FDA mandating reduced nicotine content of cured tobacco leaf, we investigated the relationship between alkaloid (nicotine) content of flue-cured tobacco and root-knot nematode parasitism, while also evaluating nematode parasitism effects on carbohydrate content. Despite considerable variability in our results, particularly under field conditions, our results demonstrate that stacking Rk1 and Rk2 imparts greater resistance to M. arenaria race 2 than either gene alone, but that an entry possessing resistance reportedly derived from N. repanda exhibited significantly greater resistance to root-knot nematodes than the combination of Rk1 and Rk2 based on root galling, and egg mass and egg production. The alkaloid content of flue-cured tobacco did not appear to have an effect on root-knot nematode parasitism under greenhouse or field conditions, but the presence of the nematode did lead to increased accumulation of nicotine in the roots of plants, while translocation of nicotine to leaves was reduced. Conversely, root-knot nematode parasitism was reduced accumulation of carbohydrates in roots, while having no significant effects on leaf carbohydrate content. / Ph.D. / Root-knot nematodes (Meloidogyne spp.) are microscopic round worms that can cause considerable damage to flue-cured tobacco (Nicotiana tabacum L.), and while not typically responsible for killing plants outright, can reduce the quality of cured tobacco leaf and may predispose plants to a host of other issues, resulting in challenges and economic burdens on growers. Chemicals that effectively control nematodes, which are animals, pose inherent threats to human applicators and may harm the environment in a number of ways, so the use of tobacco varieties that are resistant to root-knot nematodes is increasingly common and essential to sustainable tobacco production. One form of root-knot nematode resistance, called Rk1, has become common and is found in all commercially grown flue-cured tobacco. This form of resistance is effective against 2 ‘races’ of the root-knot nematode M. incognita, which has historically caused tobacco growers the most issues. However, because this resistance is so widely employed, growers have controlled these nematodes, while another species, M. arenaria, has become more prevalent, particularly ‘race’ 2, which is not controlled by Rk1. We know from previous research that another gene, Rk2, provides resistance to some root-knot nematode that Rk1 does not effect, and that combining both genes seems to provide even greater root-knot nematode control than either gene alone. We investigated whether Rk2 is effective at controlling M. arenaria race 2 when it is combined with Rk1 in greenhouse and field experiments. We also investigated how a different, novel type of resistance, which comes from a species of tobacco related to cultivated tobacco, compares with the Rk1/Rk2 resistance in greenhouse trials. Additionally, the FDA has recently suggested that nicotine levels in tobacco leaf should be dramatically reduced to help mitigate adverse human health consequences associated with tobacco consumption. Nicotine may play some role in resistance to root-knot nematode in tobacco, and conversely, root-knot nematodes may impact levels of nicotine, as well as other important chemical constituents of tobacco. We also investigated these questions in greenhouse and field experiments. Our results ultimately demonstrate that combining both Rk1 and Rk2 gives flue-cured tobacco a higher level of resistance to root-knot nematodes than either gene alone, but also suggests that the form of resistance we evaluated from a related Nicotiana species could be even more effective in controlling these nematodes. We observed that the amount of nicotine present in tobacco did not impact nematode parasitism, but that nematode parasitism could lead to lower levels of nicotine in the leaves of plants because the nematodes, which feed on plants roots, cause damage to the plant that interferes in the movement of nicotine from roots to leaves.

Utilizing resistant cultivars is a main control strategy for root-knot nematodes in flue-cured tobacco (Nicotiana tabacum L.). Most commercial cultivars possess the Rk1 gene, providing resistance to races 1 and 3 of Meloidogyne incognita and race 1 of M. arenaria. This initiated a shift in root-knot populations to other species and races, creating a need for resistance to those populations. Numerous cultivars possess a second resistance gene, Rk2. Greenhouse experiments investigated whether possessing both Rk1 and Rk2 increases resistance to a variant of M. incognita race 3 compared to either gene alone, and if high soil temperatures impact their efficacy. Root galling, numbers of egg masses and eggs, and the reproductive index were compared from roots of Coker 371-Gold (susceptible), NC 95 and SC 72 (Rk1Rk1), T-15-1-1 (Rk2Rk2), and STNCB-2-28 and NOD 8 (Rk1Rk1 and Rk2Rk2). The same data were analyzed from plants in open-top root zone cabinet growth chambers set to 25ºC, 30ºC, and 35ºC to examine if resistance is temperature sensitive. Despite variability, Rk1Rk2 entries conferred greater resistance than entries with Rk1 or Rk2 alone. Entries with Rk1 alone reduced galling and reproduction compared to the susceptible control, whereas T-15-1-1 (Rk2) did not, but often suppressed reproduction. An apparent reduction in nematode reproduction was observed at 25ºC and 30ºC on entries possessing Rk1 and Rk1Rk2 compared to the control and Rk2. However, no apparent differences in reproduction occurred on Rk1 and/or Rk2 entries at 35ºC compared to the control, indicating parasitism increased on resistant entries at higher temperatures. / Master of Science in Life Sciences

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