Refines Efficiency Improvement

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Refinery processes that convert heavy oils to lighter distillate fuels require heating for distillation, hydrogen addition or carbon rejection (coking). Efficiency is limited by the formation of insoluble carbon-rich coke deposits. Heat exchangers and other refinery units must be shut down for mechanical coke removal, resulting in a significant loss of output and revenue. When a residuum is heated above the temperature at which pyrolysis occurs (340 C, 650 F), there is typically an induction period before coke formation begins (Magaril and Aksenova 1968, Wiehe 1993). To avoid fouling, refiners often stop heating a residuum before coke formation begins, using ... continued below

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23 pages

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WRI May 15, 2002.

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Description

Refinery processes that convert heavy oils to lighter distillate fuels require heating for distillation, hydrogen addition or carbon rejection (coking). Efficiency is limited by the formation of insoluble carbon-rich coke deposits. Heat exchangers and other refinery units must be shut down for mechanical coke removal, resulting in a significant loss of output and revenue. When a residuum is heated above the temperature at which pyrolysis occurs (340 C, 650 F), there is typically an induction period before coke formation begins (Magaril and Aksenova 1968, Wiehe 1993). To avoid fouling, refiners often stop heating a residuum before coke formation begins, using arbitrary criteria. In many cases, this heating is stopped sooner than need be, resulting in less than maximum product yield. Western Research Institute (WRI) has developed innovative Coking Index concepts (patent pending) which can be used for process control by refiners to heat residua to the threshold, but not beyond the point at which coke formation begins when petroleum residua materials are heated at pyrolysis temperatures (Schabron et al. 2001). The development of this universal predictor solves a long standing problem in petroleum refining. These Coking Indexes have great potential value in improving the efficiency of distillation processes. The Coking Indexes were found to apply to residua in a universal manner, and the theoretical basis for the indexes has been established (Schabron et al. 2001a, 2001b, 2001c). For the first time, a few simple measurements indicates how close undesired coke formation is on the coke formation induction time line. The Coking Indexes can lead to new process controls that can improve refinery distillation efficiency by several percentage points. Petroleum residua consist of an ordered continuum of solvated polar materials usually referred to as asphaltenes dispersed in a lower polarity solvent phase held together by intermediate polarity materials usually referred to as resins. The Coking Indexes focus on the amount of these intermediate polarity species since coke formation begins when these are depleted. Currently the Coking Indexes are determined by either titration or solubility measurements which must be performed in a laboratory. In the current work, various spectral, microscopic, and thermal techniques possibly leading to on-line analysis were explored for measuring the Coking Indexes.

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23 pages

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OSTI as DE00816031

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  • Other Information: PBD: 15 May 2002

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  • Report No.: FG36-01GO11018
  • Grant Number: /GO/11018
  • DOI: 10.2172/816031 | External Link
  • Office of Scientific & Technical Information Report Number: 816031
  • Archival Resource Key: ark:/67531/metadc739020

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  • May 15, 2002

Added to The UNT Digital Library

  • Oct. 18, 2015, 6:40 p.m.

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  • Aug. 9, 2016, 8:21 p.m.

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WRI. Refines Efficiency Improvement, report, May 15, 2002; Golden, Colorado. (digital.library.unt.edu/ark:/67531/metadc739020/: accessed September 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.