Major Plant Components Research Articles

Dynamic Optimization of Startup and Load-Increasing Processes in Power Plants—Part I: Method

The fast startup and load-increasing process of power plants is a complex task involving several restrictions that have to be fulfilled simultaneously. An important restriction is the maximum allowed thermal stress of the steam generator pipes and the steam turbines caused by temperature gradients. In this paper the startup process is treated as a dynamic optimization problem. Any appropriate objective function can be used in this optimization problem. Examples include the minimization of fuel consumption or the minimization of the time required to reach the desired load. The maximum allowable temperature and pressure gradients in major plant components appear as additional constraints. In this paper a general method for solving these problems is presented: The dynamic process model, consisting of first-order ordinary differential equations (ODEs) and algebraic equations, is discretized over the time horizon using well established methods for the solution of ODEs. Thus, the continuous dynamic optimization problem is transformed into a large-scale non-linear parameter optimization problem with up to 20,000 optimization parameters and constraints. Such parameter optimization problems can be solved with appropriate sequential quadratic programming (SQP) methods that have become available lately. An application of this method is presented in the second part of this study by optimizing the process of rapid load increase in a single-pressure combined-cycle power plant on the basis of a simplified model.

The essential oil of cultivatedArtemisia afra (Jacq.) from Zimbabwe

The steam-distilled essential oils from plants of Artemisia afra (Jacq.) (Compositae) from the wild and organically cultivated at two pilot sites in Zimbabwe were analysed by GC–MS. The major components of plants in the wild were artemisia ketone (6.3–41.9%), 1,8-cineole (0.1–27.9%), α-copaene/camphor (8.5–27.1%) and santolina alcohol (3.1–10.1%). Two chemotypes were identified from the cultivated plants. The major components of oil for fresh and semi-dried herb from the cultivated plants from one site were artemisia ketone (32.1–34.8%), α-copaene/camphor (21.8–24.4%), 1,8-cineole (10.9–15.7%) and santolina alcohol (2.7–8.0%). The major components of oil from the other site from fresh and semi-dried herb of cultivated plants were 1,8-cineole (22.5–29.3%), α-copaene/camphor (6.2–21.3%), borneol (14.2–19.1%), and camphene (3.0–5.6%). Bornyl acetate (1.6–4.2%), β-caryophyllene (2.0–5.0%), sabinene (0.6–7.9%), γ-terpinene (0.2–2.6%) and p-cymene (1.3–2.7%) were notable minor constituents. Copyright © 1999 John Wiley & Sons, Ltd.

The essential oil of cultivated Artemisia afra (Jacq.) from Zimbabwe

The steam-distilled essential oils from plants of Artemisia afra (Jacq.) (Compositae) from the wild and organically cultivated at two pilot sites in Zimbabwe were analysed by GC–MS. The major components of plants in the wild were artemisia ketone (6.3–41.9%), 1,8-cineole (0.1–27.9%), α-copaene/camphor (8.5–27.1%) and santolina alcohol (3.1–10.1%). Two chemotypes were identified from the cultivated plants. The major components of oil for fresh and semi-dried herb from the cultivated plants from one site were artemisia ketone (32.1–34.8%), α-copaene/camphor (21.8–24.4%), 1,8-cineole (10.9–15.7%) and santolina alcohol (2.7–8.0%). The major components of oil from the other site from fresh and semi-dried herb of cultivated plants were 1,8-cineole (22.5–29.3%), α-copaene/camphor (6.2–21.3%), borneol (14.2–19.1%), and camphene (3.0–5.6%). Bornyl acetate (1.6–4.2%), β-caryophyllene (2.0–5.0%), sabinene (0.6–7.9%), γ-terpinene (0.2–2.6%) and p-cymene (1.3–2.7%) were notable minor constituents. Copyright © 1999 John Wiley & Sons, Ltd.

The polyphenolic content of fruit and vegetables and their antioxidant activities. What does a serving constitute?

Analysis of the major flavone, flavonol, anthocyanidin and hydroxycinnamic acid constituents (and their glycosides) of onion, tomato, egg plant and apple has been undertaken and the antioxidant activities of the phenolic extracts determined. The major phenolic antioxidant components of egg plant are chlorogenic acid in the flesh and a delphinidin conjugate in the skin. In the case of apple, the major phenolic antioxidants detected are chlorogenic acid, procyanidins/catechin compounds, rutin and phloridzin. Quercetin glycosides are well-known to be the major phenolic components of onion. Assessment of the antioxidant activities of a serving of 100 g fresh weight fruit, vegetable and comparison with previously reported findings for 150 ml beverage (500 ml portion in the case of beer), expressed in μmol Trolox equivalents show that the antioxidant activities of 1 glass (150 ml) red wine ≡ 12 glasses white wine ≡ 2 cups of tea ≡ 4 apples ≡ 5 portions of onion ≡ 5.5 portions egg plant ≡ 3.5 glasses of blackcurrant juice ≡ 3.5 (500 ml) glasses of beer ≡ 7 glasses of orange juice ≡ 20 glasses of apple juice (long life).

Determination of the Fatty Acid Content of Pumpkin Seed, Pygeum, and Saw Palmetto

Fatty acids are major components of many plants, foods and medicines, including pumpkin seeds (Cucubita pepo), pygeum bark (Prunus africana) and saw palmetto (Serenoa repens). With the gas chromatography methods reported here, free fatty acids of these species can be quantified as their trimethylsilyl derivatives. Because of their different fatty acid contents and composition, the gas chromatography method can distinguish which of three plant species was extracted, and, in the case of S. repens, the method of extraction. Although phytosterols can be separated by this method, their content is too low to be assigned directly. The total fatty acid content can be determined through formation of the methyl esters. This is helpful for estimation of the kind and percentage of fatty acids that are present as triglyceride esters in the plant material and for standardization of the products.

Tracing the Origin and Fate of Lipids in Soils from the Rothamsted Classical Experiment

Soil lipids originate from both plants and animals as products of deposition, exudation, and decomposition as well as various other sources, such as fungi, bacteria and mesofauna. The composition, concentration and diagenetic fate of soil lipids varies between environments due to differences in sources of organic matter and changes in inorganic mineral components (Miller and Donahue, 1995). For example, it has been shown that a relatively greater lipid content is found in soils with a low microbiological activity, whilst soil pH also affects lipids with strongly acidic environments exhibiting higher lipid contents (Fridland, 1976). Lipids can exist in a number of microenvironments within the soil being either free entities in the soil matrix, chemically bound components of humic material or physically adsorbed to clay particles (Jambu et al., 1978). In this paper we will consider the lipid compositions of soils sampled from the Rothamsted Classical Experiment. The research employed a combination of analytical techniques to investigate both free, solvent extractable components, and those associated with insoluble residues of the vegetation and soils in order to assess the fate of the various lipid classes present in the original biological inputs. The Rothamsted Classical Experiment. This site is the oldest and best-documented agricultural site in the world. Long-term experiments have been in progress for more than 150-years and records detailing histories of use are available. It consists of plots which have supported continuous growth of arable crops such as barley (Hoosfield Spring Barley) and wheat (Broadbalk), as well as continuous grass land (Park Grass Experiment) and other areas which have been allowed to revert back to natural woodland following cultivation (Broadbalk Wilderness and Geescroft Wilderness). Thus, this site provides a unique opportunity to study the effects of changing vegetation and agricultural practices on solvent soluble organic matter and thereby improve our understanding of the fate of soil lipids. The work focused on: (i) characterising the lipid composition of soils with well-defined biological inputs, (ii) assessing the fate of specific lipid classes in a soil profile relative to biomacromolecules, and (iii) determining the factors which control the preservation of soil organic matter. Lipid composition of soils with known recent histories of use. Broadbalk Wilderness is composed of three distinct sub-plots each of which exhibits a different type of overlying vegetation (i.e. woodland, grassland and mixed herband grassland). Analyses were made on total lipid extracts using high temperature gas chromatography (HT-GC) and HTGC mass spectrometry (HT-GC/MS). Samples of vegetation were examined in parallel with underlying soils in an effort to follow the fate of major plant components. A number of different compound classes were identified including, n-alkanes, nalkanols, (hydroxy-) n-alkanoic acids, steroids, triterpenoids, wax esters, mono-, diand triacylglycerols. Lipids from the woodland are dominated by inputs from leaf-derived components. In contrast, the lipid extracts of soils from the grassland and mixed vegetation area are markedly different reflecting the mixed vegetation cover dominated by grass species. Particularly important classes of compounds are the n-alkanols and wax esters, i.e. a very strong predominance exists of the Cz6 alkanol (and wax esters based on this alkanol) in the soils with grass input whereas the alkanols and wax esters of the woodland are dominated by the C24 homologue. These data quite clearly indicate that molecular signals derived from the standing vegetation are reflected in the soils. Fate of specific lipids in a soil prof i le.The main soil horizons from another reverted woodland (Geescroft Wilderness) were studied to determine the fate of

The organic geochemistry of coal: from plant materials to coal

Coalification is a process that transforms plant remains under the influence of time, temperature, and possibly pressure to a black, generally lustrous solid organic fossil fuel having a very complex chemistry. Although much has been learned in the past two centuries on coal chemistry, we still have little knowledge of the way plant materials undergo these transformations. The problem has been the existence of adequate characterization tools. The advent of some new tools for structural elucidation of macromolecules has led to some revised thinking on coalification. Originally thought to be a process involving the full degradation of plant remains and subsequent reconstitution of these remains, the general consensus today is that the process involves a selective preservation of certain resistant plant components followed by some minor reorganization of the biopolymers that survive. The major components of plants do degrade, and the resistant ones often constitute only a small fraction of the original mass of the plant materials. This paper examines the most recent literature concerning coalification and focuses on the chemistry associated with coalification of certain recognizable plant remains that have been at the center of research activity for the past two decades. Thus, we examine the recent knowledge of the chemistry of resistant biopolymers in extant and fossil wood, cuticles, resins, spores, and algae, knowledge that has been assembled to establish the reaction pathways towards coal macromolecules.

Organic geochemical studies of soils from the Rothamsted Classical Experiments—I. Total lipid extracts, solvent insoluble residues and humic acids from Broadbalk Wilderness

Total lipid extracts and insoluble organic matter, i.e. solvent insoluble matter and humic acids, were studied from soil samples taken from the three adjacent plots comprising the Broadbalk Wilderness at Rothamsted Experimental Station, Harpenden, Hertfordshire, U.K. Analyses involved high-temperature gas chromatography (HT-GC) and HT-GC-mass spectrometry (HT-GC-MS) to investigate trimethylsilylated total lipid extracts and Curie-point pyrolysis-GC (Py-GC) and Py-GC-MS to investigate solvent insoluble fractions. The plots were chosen specifically for their different types of vegetation cover. Samples of the vegetation were examined in parallel with the underlying soils in an effort to follow the fate of the major plant components in soil. The application of HT-GC and HT-GC-MS allowed changes in high molecular weight lipids, particularly intact acyl lipids, such as triacylglycerols, wax esters, steryl and triterpenyl esters, to be studied in leaf and soil extracts. The total lipid extracts of the soil samples from the wooded area were dominated by the input from leaf-derived lipids. The lipid extracts of soils from the grazed and stubbed areas were markedly different from those from the wooded area, and reflected the mixed vegetation cover dominated by grass species. In marked contrast, the pyrolysis data from the insoluble organic matter and humic fractions of the soils did not reflect the composition of the lignin comprising the overlying vegetation, but rather showed evidence of amino acid moieties probably present as polypeptides. The absence of the lignin signal is possibly due to rapid diagenetic changes presumed to be influenced by the slightly alkaline pH of the soil. The ability to recover recognizable chemical signals from soil lipids has important implications for archaeological investigations aimed at revealing temporal changes in vegetation cover and/or differences in land use at specific site locations.

Current status of materials selection for MSF distillation plants

The trends in the choice of materials for the major components of MSF and other distillation plant are described. The historical experiences which have driven the move towards the increasing application of higher-grade materials such as stainless steels, copper-nickel alloys and titanium, are alluded to. These developments have been crucial in contributing to improved performance of plant, but it is argued that there are some circumstances in which a lower cost strategy, using lower grade materials, may be acceptable.

The Effect of the Fuel-Cell Unit Size on the Efficiency of a Fuel- Cell-Topped Rankine Power Cycle

Dunbar, Lior and Gaggioli (1991) proposed a configuration of a fuel-cell-topped electrical Rankine power generating station and analyzed its performance. That study revealed that the fuel-cell topping improved plant efficiency to values up to 62 percent, versus the conventional plant efficiency of 41.5 percent. This work lays the foundation for a thermoeconomic analysis of such systems by relating exergy consumption to fuel-cell unit size, as follows: 1) the relationship between system efficiency (and hence fuel consumption) and fuel-cell unit size is presented for a number of fuel-cell operating conditions; 2) the relationship between fuel flow rate and fuel-cell unit size is shown; and 3) the exergetic effects of the major plant components are discussed as a function of fuel-cell unit size. The results reveal that specific fuel consumption may be reduced by as much as 32 percent when incorporating fuel-cell units into electrical power plants.

The petroleum geochemistry of Canadian Beaufort Tertiary “non-marine” oils

Molecular, isotopic and elemental data for a set of 28 Paleogene and 3 Cretaceous oils from the Mackenzie Delta and offshore Canadian Beaufort Sea have been evaluated. The depositional environment and organic matter characteristics of the source units for these oils have been predicted. The Paleogene oils of the Canadian Beaufort are molecularly distinctive, and clearly contain a major land plant component. Oleanane and the 17α(H)- and 17β(H)-24,28-bisnorlupanes are present, as well as the following compound types: 24-norlupanes (and possibly higher homologues); de-A-lupane; noroleanenes; norursene; dehydroabietane; 28,30-bisnorhopanes. Several molecular and isotopic characteristics are useful in assessing and ordering the extent of biodegradation and thermal maturation of these oils. The Cretaceous oils are separately sourced from the Paleogene oils. The latter oils comprise two distinct land plant-derived genetic families, distinguished by the presence/absence of 24,28-bisnorlupanes, 24-norursene, 24-norlupane and 24-noroleanenes. The Kugmallit/Richards family contains each of these compound types, and is considered to originate from the Eocene Richards Formation. In contrast, lupanoids and noroleanenes are absent in oils of the Reindeer/Moose Channel family; the occurrence of 28,30-bisnorhopane and/or oleanane in these oils suggests a Paleocene origin. Although these source rock predictions are supported by the available data, they must be considered speculative until detailed molecular, isotopic and elemental compositional data are available regionally for potential source rocks of the Eocene and Paleocene source units in the Canadian Beaufort.

A Comparison of Hybrid Heating Systems and New Generation Facilities for Peak Electricity Load Management

This paper presents a preliminary evaluation of hybrid heating systems as an electric load-management tool for Canadian utilities, based on an analysis of data for the Province of New Brunswick. In comparison to all-electric systems, the study indicates that hybrid heating systems offer many advantages: they are less costly when peak electricity generation is provided by combustion turbines; they can eliminate the need for new peak generating capacity within the 15 year planning horizon of the utility; the higher energy conversion efficiency of hybrid systems reduces oil consumption, and C02 and SOx emissions; and they can be produced, installed and maintained locally, unlike the major components of power plants and many of their installation and maintenance services, which are imported. The constraints upon implementation of the technology are also discussed. A demand management leasing scheme, in which the utility leases the hybrid heating technology from the customer, is described. It offers political and public relations advantages over more traditional cost allocation schemes and ensures the long-term availability of the technology.

Review of engineering design considerations for battery energy management systems

A review of existing literature, demonstration project experience, and current engineering understanding related to battery energy storage plant design issues is given. The focus is on how plant design is related to the application requirements and the unique characteristics of available equipment. A description of the major components of a battery energy storage plant is given. The utility applications for battery storage currently of interest are surveyed. Some of the many design issues are discussed, and some examples of potential design/cost tradeoffs are presented. >

THE YAMMADERRY AND COWLE SMALL OFFSHORE FIELD DEVELOPMENTS

The Yammaderry and Cowle oilfields are located 22 km north-west of Onslow, Western Australia and are two and five km respectively from the Saladin oilfield. With estimated crude oil reserves of 1.6 and 2.3 MMBBLS respectively these developments are considered small.A development strategy was formulated to provide minimum facility structures and to take maximum advantage of the very competitive design and construction capabilities being offered locally. Development costs were minimised by using the existing Saladin processing facilities on nearby Thevenard Island and by sharing mobilisation costs of major construction and development plant items.The offshore monopod structures were designed to withstand cyclonic wind and wave conditions while supporting minimal production equipment and acceptable access structures.The main advantages of these structures are that they can be fabricated in any competent heavy fabrication shop, well removed from the site, and can be transported easily by road and rig tender vessel to the installation site. Installation is generally carried out by the jack-up drilling vessel mobilised to drill the production wells.The offshore pipelines were designed as paired bundles to accommodate multiphase product flow and gaslift supply and to provide greater confidence in achieving on-bottom stability.Since the development strategy embraced two independent paths, these being structure/well development and offshore pipelay, the risk of claims due to late delivery of either structures or line pipe was removed. The success of the project was kept independent of any one major component of plant and throughout all phases of the project, realistic contingency plans and procedures were available.

Exergy and cost accounting of the UANE cogeneration plant

In this paper, the concept of exergy is utilized for exergy and economic analysis of a cogeneration plant producing electric power and desalinated water. The objective is to obtain an idea about the exergy dissipation in each major plant component and to use the exergy-accounting method to obtain a fair and equitable cost allocation between electricity and water. Exergy and cost balance equations are written for each major plant component in terms of known and unknown unit exergy costs for the different streams. The resulting set of simultaneous equations is solved in association with a set of auxiliary equations. The exergy-balance equations revealed the amount of exergy dissipation for each component, and showed that the boilers and the distillers are the main offenders. The costs of electricity and water obtained using the exergy-accounting method are compared with a cost-allocation methodology that is currently used by some cogeneration utilities.

Humic Substances Formed during the Composting of Organic Matter

AbstractHumic substances (HS) were extracted from separated cattle‐manure compost (CSM) at various stages of decomposition. Carbon‐13 nuclear magnetic resonance (13C‐NMR) and Fourier‐transform infrared (FTIR) spectroscopy measurements were performed on the purified humic acids (HA) as well as crude fiber and chemical analyses. Levels of HS extracted from the CSM samples doubled during the composting (from 377 to 710 g kg−1 organic matter [OM]). The HS were divided into: (i) HA, which increased from 184 to 457 g kg−1 OM; and (ii) a fulvic fraction (FF). The FF was separated on XAD‐8 resin to: (i) fulvic acid (FA), which maintained an unchanged level during composting (80–100 g kg−1); and (ii) a nonhumic fraction (NHF), which increased from 107 to 170 g kg−1 OM during the process. The ratios between the concentrations of these fractions were tested as humification indexes. These indexes changed significantly during the process and were found to correlate exponentially with the composting time, C/N ratio, or both. Quantities of low‐molecular‐weight components (FF and NHF) rapidly increased during the first 40 d of composting and were nearly constant thereafter. The HA and HS contents reached nearly constant values after ∼90 d. Only slight compositional and structural changes in CSM HA were detected with cross‐polarization magic‐angle spinning (CPMAS) 13C‐NMR, FTIR spectra, and chemical analyses. The elemental composition and functional groups of CSM HA resembled those reported for HA of plant residues, peats, and incompletely humified materials. The CPMAS 13C‐NMR spectra of the CSM HA resembled that of lignin. The aromaticity of the HA was about 40% and the lignin content was approximately 60%. The NMR data correlated well with results obtained by FTIR spectroscopy, both indicating that the CSM HA are composed of partially degraded constituents of plant tissue, which still retain to some extent their chemical structures. The major plant components identified in the HA were lignin, carbohydrates, and long‐chain aliphatic structural groups.

An evaluation of the male reproductive toxicity of cathinone

(−)-Cathinone is the major psychoactive component of khat plant ( Catha edulis Forssk.). Khat has been shown to produce reproductive toxicity in human beings and experimental animals. However, the chemical constituents of khat leaves responsible for sexual dysfunction are not known. In the present study cathinone enantiomers have been investigated for their reproductive toxicity in rats. Cathinone produced a dose-dependent decrease in food consumption and suppressed the gain in body weight. There was a significant decrease in sperm count and motility and increase in the number of abnormal sperms in cathinone treated animals. Histopathological examination of testes revealed degeneration of interstitial tissue, cellular infiltration and atrophy of Sertoli and Leydig's cells in cathinone treated animals. Cathinone also produced a significant decrease in plasma testosterone levels of the rats. Although both enantiomers of cathinone produced deleterious effects on male reproductive system, (−)-cathinone was found to be more toxic. From this study it may be concluded that the cathinone content in khat may be partially or totally responsible for the reproductive toxicity in khat chewers.

Cost allocation for electricity and water for the umm al nar west cogeneration plant using the exergy accounting method

In this paper, the concept of exergy has been utilized in a cost accounting and economic analysis of a cogeneration plant producing electric power and desalinated water. To obtain an equitable cost allocation between electricity and water, cost balance equations have been written for each major plant component in terms of the known and unknown exergy costs of the different streams. The resulting set of linear simultaneous equations has been solved in association with two sets of auxiliary equations. Each set of auxiliary equations represents specific assumptions related to the exergy costs of the different streams. The results are presented as the cost of electricity and water versus the full cost for each set of auxiliary equations used. It was concluded that the use of exergy cost accounting is a convenient method for estimating the unit costs of electricity and water from cogenerating plants.

The use of lipids as facies indicators

Summary An approach to palaeoenvironmental interpretation of sediments using lipid data, is developed. This approach initially attempts to summarize the major lipid components of plants, bacteria and invertebrate animals and to relate these data to sedimentary lipid distributions. Most of the major lipid groups found in sediments are used in this study. The very large amount of lipid data generated, necessitated the development of a simple system for data processing. The method of data analysis used involved the construction of a simple taxonomic hierarchy based on ‘Ruzicka’s Rules’ i.e. the biosynthetic origins of the major lipid types. By bringing in the concept of taxonomic hierarchy based on the biosynthetic pathways, a palaeontological approach towards lipid geochemistry is being evolved. Secondly, DSDP lipid data (derived from the O.G.U., Bristol University) are collated and grouped using matrices of lipid data and histograms of the lipid groups, i.e. all compounds of a common structure are ‘summed’. These data are compared with the geological data and the results briefly discussed for each sediment. In conclusion, the diagenetically stable lipid patterns of three representative environments, i.e. marine planktonic, bacterially-dominated marine, and a lacustrine facies, are presented and discussed. From these data the rules by which environments are described are extended; the parameters so derived have good potential for source correlation.

Distribution of dry matter during the growth ofSolanum laciniatum

Abstract The dry weights of root,stem, and leaves of Solanum laciniatum plants were measured for four seasons from 1974 to 1978. In 1974–75 and 1976–77 the increase in leaf dry weight was linear.In 1975–76 and 1977–78, however,there was an initial lag period followed by a linear increase in leaf dry weight.Stem and root dry weights for each season showed a lag period before a linear increase in dry weight.The proportion of dry weight in leaves was greatest in young plants and decreased as the plants matured.Stems were a minor component in young plants but increased to make up the major component of mature plants (>50%).The root component was greatest in very young plants (about 25%),then decreased,and thereafter remained at a low level (about 20%).