Experimental And Mechanism Study On Silicate Carbonation For CO₂ Sequestration

Carbon dioxide from coal combustion mainly is a serious pollutant considered after SO₂, NO_x, particulate matters and poisonous trace elements, it makes a great contribution to"Greenhouse effect"what exacerbates human's living environment, and"the global warming"has attracted more and more attention. CO₂ separation and sequestration have been an emerging and frontier area in the research fields of pollutants emission from coal combustion. At present, the researches on CO₂ separation are mainly focused on membrane separation, solvents adsorb and new methods of utilizing fossil fuel. While the researches on CO₂ storage are mainly focused on storaging CO₂ in the ocean, adsorbing CO₂ by tree planting and geological sequestration. The new ways of fossil fuel utilization are oxy-fuel combustion (O₂/CO₂ combustion), Chemical-Looping Combustion (CLC), zero emission coal-based power generation and so on. The methods of CO₂ geological sequestration are injected CO₂ into uneconomic coal seams,oil reservoirs or saline aquifers under the earth, and fixation of CO₂ by mineral carbonating.This paper studied the theoretic calculation of producing hydrogen by coal-steam gasification and absorbing CO₂ by CaO, and sequestrating CO₂ by reaction with wollastonite at high press and high temperature. The main contents are as follows:Calculation models of chemical thermal dynamical equilibrium are used to predict gas component produced by coal gasification with or without calcium oxide at different pressure (1.0--50.0atm) and different temperature (700--1000K ), to work out the optimal pressure and temperature for coal-steam gasification with calcium oxide.According to prevenient researcher's results, we studied the processes of wollastonite reacted with carbon dioxide in both direct carbonation and indirect carbonation. There was no calcium carbonate formed finally in our indirect carbonation, in which calcium ions was extracted by acetic acid from wollastonite. But there was calcium carbonate crystal in the products from direct carbonation. After the products heat treatment under 900℃, worked out the conversion of calcium silicate to calcium carbonate according to the weight loss during heat treatment. Displayed the effect of the individual process variables on the conversion. Then compared with the experimental results of serpentine, wollastonite is more suitable for CO₂ mineral sequestration.In order to reduce the cost of carbon sequestration, produce less wastes, utilize resource more reasonable, we try to find the way how to use the production from the direct carbonate process, and give some advices to improve the process.