Export Gases and their Utilization Potential Technical and Economical Evaluation of selected Processes for Chemical Syngas Generation

Doris Wall

Research output: ThesisDoctoral Thesis

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Abstract

Over the last four decades alternative smelting reduction processes for iron making have been introduced to economically compete with the classical blast furnace route. Besides process optimization to lower material and energy consumption and to cause less environmental impact, a focus has been set on an economic and environmental friendly utilization of by-products. The excess gases are typically used as fuel for heat and power plants within the iron and steel work. But due to their comparatively low calorific value, the material recycling becomes a matter of interest. For example the export gas from the alternative smelting reduction process COREX® has been recycled as reducing gas for direct reduction of iron ores and as feedstock for microbiological ethanol production at pilot scale. Due to the high share of CO and H2 and the low content of N2, as a result of the gasification of coal with oxygen, COREX® and FINEX® export gases are presumed to be a valuable feedstock for the synthesis of basic chemicals, but technical feasibility has not been proven yet. This thesis will provide thermo-chemical process designs for export gas utilization into specific syngases for the production of main intermediate chemicals (CO, oxo chemicals, acetic acid, methanol, Fischer-Tropsch liquids, ammonia and H2) including CO2 balance and production cost estimate for environmental and economic evaluations of the process technologies. The literature review provides an overview of conventional synthesis and syngas production technologies for the synthesis of the main intermediate chemicals, including the market potential and the production cost estimates for the standard feedstock natural gas. Based on common gas process technologies, thermo-chemical process designs (CHEMCAD) have been set up for the conversion of COREX® and FINEX® export gases into the specific syngases. For the calculations of the production costs, a model has been developed related to the cost calculation scheme for natural gas based syngas production. The CO2 balance – as a factor for environmental impact – includes process related CO2 emissions as well as CO2 emissions related to the import of electric energy, steam and heat. Economic analyses showed that export gas treatment is a feasible option to produce CO product and oxogas (H2:CO-ratio ≤1) including the downstream synthesis of acetic acid and oxo-chemicals respectively. The economic advantage is related to the high content of CO in the export gases even considering compression and export gas treatment costs. H2-rich syngas production (H2:CO-ratio ≥2) from export gas is less economic compared to syngas generated by steam reforming of natural gas. The CO2 balance showed high process related emissions for carbon monoxide shift, resulting in higher overall CO2 emissions for export gas based oxo- and syngas production ( H2:CO-ratio ≥1) compared to the feedstock natural gas. As no shift reaction is required for CO production, the bulk of CO2 emissions result from the import of electric energy for gas compression and cryogenic separation of N2 and CO, leading to net CO2 emission savings for export gas utilization compared to natural gas based syngas production. With the substitution of the smelting reduction carrier gas N2 by recycling of CO2 from the Rectisol absorber or with polygeneration concepts combining two or more chemical syngas production processes, a reduction of the utility demand and the capital expenditures can be expected, reducing overall production costs for export gas based syngas production.
Translated title of the contributionExportgase und deren Verwertungspotential Technische und ökonomische Evaluierung von ausgewählten Verfahren zur Synthesegaserzeugung
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Kepplinger, Werner Leopold, Assessor A (internal)
  • Schenk, Johannes, Assessor B (internal)
Publication statusPublished - 2012

Bibliographical note

embargoed until 12-09-2022

Keywords

  • smelting reduction
  • alternative
  • COREX
  • FINEX
  • export gas
  • chemical
  • utilization
  • synthesis
  • acetic acid
  • methanol
  • ammonia
  • hydrogen
  • Fischer-Tropsch
  • syngas
  • treatment
  • shift
  • water gas shift
  • cryogenic separation
  • Rectisol
  • pyhsical absorption
  • gas purification

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