Sorption of Carbon Dioxide from Oxy-fuel Combustion by Basic Oxygen Furnaces Slag in a Fluidized Bed Reactor

  • 沈 甯堯

Student thesis: Master's Thesis

Abstract

In recent years the increasing concentration of CO2 in the atmosphere is resulted from the use of huge amounts of fossil fuels with the progress of the growth of economy and technology That has also exacerbated the greenhouse effect and global climate change Carbon capture and sequestration technologies are therefore under developed to effectively solve these issues The oxy-fuel combustion is considered as a sustainable and potential system which can concentrate CO2 increase the capture efficiency reduce the processing cost and easy alterations This study used the Basic Oxygen Furnaces (BOF) slag to be the sorbent to remove CO2 with a laboratory fluidized bed reactor Utilizing BOF slag as sorbent not only reduces the cost of the traditional sorbent but also increases the recyclability of the waste Therefore this study simulated the condition of the oxy-fuel combustion to removal CO2 with BOF slag in a fluidized bed reactor at high temperature Results of this study are described as follows: 1 The minimum fluidized velocity at various temperatures have the same trend for empirical model prediction and experimental results The minimum fluidized velocity values calculated from the empirical equations are slightly different from the values determined in this study due to the different basic temperature 2 According to the results by using ICP and XRD analysis the calcium hydroxide contents of the BOF slags of 150-300 μm and 75-106 μm are 34 5% and 36% respectively; the calcium oxide contents of the slags are 10 6% and 2% respectively; the calcium carbonate contents are 6 5% and 7 3% respectively 3 From TGA analysis the utilizations of the BOF slags of 150-300 μm and 75-106 μm are 17 6% and 9 5% respectively The utilizations of the calcined BOF slags of 150-300 μm and 75-106 μm are 24 8% and 24 5% respectively 4 After the experiment of BOF slag utilization for CO2 capture in a fluidized bed reactor at various operating conditions it can be found that the concentration of CO2 has significant impact for the sorbent utilization due to the diffusion capacity The water vapor may activate CaO to become Ca(OH)2 for the better utilization by the larger calcined BOF slag However 10% water vapor may cause an increasing cohesion between particles to form a laminar flow for the smaller calcined BOF slag Therefore its sorbent utilization declines Besides the larger size of BOF slags the higher of the utilization 5 The impact of sulfur-containing flue gas shows that the overall utilization of BOF slag decreases from 71 6% to 20 5% The results are speculated that SO2 will poison the BOF slag and occupy active sites 6 The results of XRD SEM EDS Mapping and FTIR analyses present the element composition structure change and bonding for BOF slags before and after carbonation It confirms that the final carbonated product is calcium carbonate 7 The type I deactivation model is in good agreement with the experimental data of carbonation of BOF slag at various operating conditions
Date of Award2016 Aug 15
Original languageEnglish
SupervisorHsin Chu (Supervisor)

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