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EN
The intermittent flow (slug and plug type) of liquid–gas mixtures in a horizontal pipeline measured by the specific radiometric apparatus is presented. The measurement system consists of two sources of Am-241 gamma radiation and two scintillation probes. An analysis of the signals measured by the radiometric equipment is performed in the domain of time and of frequency. Recognised signal parameters are directly referred to physical quantities associated with a liquid–gas flow. The employed methodology enables determination of gas-phase flow velocity and estimation of the average depth and length of bubble gas structures. In the paper, the processing and interpretation results of the selected experiment are presented to show the in-depth description of gas structures and the type of flows recognition.
EN
Gamma scanning and radiotracer applications are very effective and inexpensive tools to understand and optimize the process as well as troubleshoot the various types of problems in many chemical, petrochemical industries and refineries. These techniques are non-invasive; hence, the problems can be pinpointed online, which leads to reduce the downtime, schedule the shutdown and maintenance of the plant equipment, rendering huge economic benefits. In a leading refinery of India, the catalytic cracking unit (CCU) was malfunctioning. It was suspected by the refinery engineers that the catalyst powder was being carried over to the fractionator, which could have led to erosion of the fractionator column internals resulting in their rupture, and consequentially, to the fire hazard. To understand the flow behaviour of the catalyst powder and to ensure the mechanical integrity, catalyst accumulation and choking, both radiotracer study and gamma scanning of the CCU reactor was carried out. The reactor consists of a riser, three primary cyclones and three secondary cyclones. Gamma scanning of the reactor was carried out with the help of an automatic gamma scanner using 1.8 GBq of Co-60 sealed source. Results showed that the catalyst powder was accumulated in one of the secondary cyclones and uneven density distribution was observed in another secondary cyclone. The radiotracer study was carried out using the irradiated catalyst powder as a radiotracer, which contains 0.9 GBq of Na-24. The radiotracer was injected in the reactor through the specially fabricated injection system. Radiation measurement was done using the thermally insulated and collimated NaI(Tl) scintillation detectors located at various strategic locations coupled to a multi-detector data acquisition system. The data were mathematically analysed. It was confirmed that the catalyst powder was accumulated in one of the secondary cyclones with no flow downwards. This resulted in excess powder available to travel along with hydrocarbon towards fractionator. Since the quantity of powder released through the hydrocarbon outlet of CCU was higher than the designed value, the catalyst powder was observed in various zones of the fractionator. Mathematical modelling of the radiotracer data obtained at various locations corroborated the scanning results; also, the flow pattern was obtained. Partially blocked secondary cyclone showed plug flow with recirculation; normal working cyclone had plug flow behaviour and the vortex breaker showed parallel flow.
3
Content available remote Assessing continuous casting tundish operation with a new-generation impact pad
EN
The continuous casting tundish is an important metallurgical reactor whose operation influences essentially the manufacturing costs. It is therefore important that all activity aiming at the reduction of costs shall be assessed not only with regard to the efficiency achieved but also to the changes in tundish operation as a metallurgical reactor. An experimental assessment of a new design of internal tundish construction was investigated. Employing strictly defined criteria, an assessment was made of using a central impact pad as the device to prevent the occurrence of a large single-lump skull after casting is finished.
PL
Kadź pośrednia urządzenia do ciągłego odlewania stali jest ważnym reaktorem pod względem metalurgicznym. Jej praca ma również istotny wpływ na koszty produkcji. Dlatego wszelkie działania mające na celu obniżenie kosztów powinny być oceniane nie tylko ze względu na osiągniętą efektywność, ale również pod kątem zmian w pracy kadzi jako reaktora metalurgicznego. W badaniach dokonano eksperymentalnej oceny nowego rozwiązania konstrukcji wewnętrznej kadzi. Stosując ściśle zdefiniowane kryteria, poddano ocenie możliwość zastosowania nowej wkładki centralnej, której głównym celem jest zapobieganie powstawania dużego jednokawałkowego skrzepu po zakończeniu odlewania.
4
Content available remote O dwóch zagadnieniach optymalizacyjnych w projektowaniu reaktorów rurowych
PL
Analizowano dwa popularne modele nieizotermicznych reaktorów rurowych, a mianowicie model z dyspersją wzdłużną i model przepływu tłokowego. Wykazano istnienie optymalnej wartości liczby Pecleta w politropowym reaktorze rurowym z dyspersją wzdłużną. Podjęcie analizy ekonomicznej prowadzi również do zagadnienia optymalnej temperatury surowca w reaktorze adiabatycznym o przepływie tłokowym nawet dla reakcji nieodwracalnych.
EN
Two common models of nonisothermal tubular reactors were analysed, i.e. the model with axial dispersion and the plug flow model. The existence of optimal values of the Peclet number in a polytropic tubular reactor with axial mixing was shown. Undertaking of the economic analysis leads also to the problem of optimal feed temperature in a plug flow reactor even for irreversible chemical reactions.
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