A two-stage optimal design procedure is suggested for alkane pyrolysis processes and is applied to propane pyrolysis. The first stage considers only hydrocarbon decomposition, the primary reaction in the process. A mathematical model consisting of an overall stoichiometric, an empirical rate, and a heat-balance and hydrodynamic equation is constructed. This model is analyzed for a varied tube diameter and a fixed propane conversion to optimize the design parameters of the propane pyrolysis reactor. At the second stage, the main reaction is considered together with secondary and tertiary reactions and a complete model taking into account recycling of the unreacted raw material is constructed. The optimum inlet temperature and recycle ratio are determined as a function of the total feed rate. An economic optimality criterion is suggested, and final process optimization is carried out.
Резюме. Приводятся материалы по накоплению тяжелых металлов, ароматических углеводородов в тканях и органах гидробионтов на участке «Центрально-Каспийский», которые указывают на целесообразность расширения исследований, позволяющих оценить влияние загрязнения водной среды и кормовых гидробионтов на организм рыб.Abstract. Aim. Incorporation rate of heavy metals in fish is an important informative integrant index that allows estimating the impact of water pollution and fodder hydrobiont contamination on fish organisms. Unlike other contaminating anthropogenic factors of the Caspian Sea, metals are always present in the sea interacting with fish organisms many thousands times as the result of biological and chemical circuit.Methods. We analysed the grade of concentration of heavy metals in tissues and organs of hydrobionts under the program "the Central Caspian District of the Caspian Sea marine environment". The procedure for determining metals consisted in determination of concentration of heavy metals in accordance with the methodology recommendations of atomic absorption analysis of Dagestan 52.24.28-86, with the help of atomic absorption spectrophotometer Hitachi 180-50.Results. The results after analysis of concentration of heavy metals in the tissues and organs of fish caught in the Central Caspian Sea marine environment are compared with the average annual estimation. The results obtained on the analysis of concentration of hydrocarbons in hydrobionts selected in the Central Caspian District of the Caspian Sea marine environment are within the long-term annual average data that are typical of the Northern and Middle Caspian Sea.Main conclusions. The results obtained help to form scientific foundation of ecological regulation that takes into account some ecosystems' anthropogenic stability. Concentration of pollutants (heavy metals and hydrocarbons) in hydrobiont tissues characterizes the ecological situation on the whole of the Caspian Sea due to hydrobionts' large-scale migrations. The analysis of the dynamics of the pollutant concentration in tissues reflects the situation created in the drilling areas; it will help forecast and avert the negative impact of hydrocarbon production on the Caspian Sea ecosystem Ключевые слова: Каспийское море, гидробионты, тяжелые металлы, ароматические углеводороды, загрязняющие факторы.Оценить реальный уровень загрязнения водных масс и влияние кормового бентоса на организм рыб можно с помощью анализа степени накопления тяжелых металлов в рыбе. В свою очередь уровень тяжелых металлов является главным обобщающим показателем состояния водного мира. Основными компонентами загрязнения среднекаспийских вод являются тяжелые и переходные металлы.Изменение концентрации определенных видов водных животных возникает на фоне изменения количества загрязняющих элементов в среде, которые зачастую играют существенную роль в жизни водных организмов. Тяжелые и переходные металлы отличаются от других факторов загрязнения каспийских вод тем, что они практически всегда обнаруживаются в водах Кас...
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