Experimental Study On CO₂ Sorption Performance Of Steel Slag Derivatives And Its Enhancement On Hydrogen Production From Typical Organic Solid Waste Via On-line Pyrolysis-reforming

A large amount of solid waste is generated in the production and life of the human species,among which organic solid waste has the triple characteristics of waste,resource and energy.Pyrolysis/gasification can efficiently transform organic solid waste into hydrogen or hydrogen-rich gas,which has a broad application prospect.However,hydrogen production by pyrolysis/gasification of organic solid waste（OSW）is faced with problems such as tar condensation and catalyst deactivation.Steel slag is a solid waste produced in the steelmaking process,rich in Ca,Fe,Mg and other elements.To efficiently improve the quality of hydrogen produced from pyrolysis/gasification of OSW,a series of highly active and stable Ca O-based carbon acceptor and steel slag-based tar removal catalysts were prepared from steel slag,and a new method on hydrogen production with CO₂ capture via on-line pyrolysis-reforming of organic solid waste（OSW）enhanced by steel slag was developed.Resultantly,synergistically resource utilization of steel slag and OSW was realized.The main research contents and results of this thesis are discussed below:Firstly,a cascade utilization method of steel slag based on NH₄Cl solution and acetic acid solution extraction was experimentally developed.Steel slag Ca O-based CO₂ adsorbent and tar removal catalyst were prepared by extracting steel slag with NH₄Cl solution and acetic acid solution.The CO₂ sorption stability of steel slag Ca O was tested by cyclic carbonation-calcination experiments.With the increase of NH₄Cl solution concentration,Ca O content in steel slag Ca O increased first and then decreased.The best CO₂ sorption performance was observed in Ca O（SS）-0.5,with initial and final sorption capacities of 0.559 and 0.172 g _CO2/g_sorbent,respectively.Ca O（SS）-0.5 and Ca O（SS）-AA had similar cyclic stability between cycles 5-15.Mg O,Al₂O₃ and Si O₂could act as stable skeleton against sintering,improving the pore structure of the adsorbent,and facilitating the adsorption and desorption of CO₂.Second,high temperature rapid pyrolysis experiments were used to examine the pyrolysis properties of various OSW.The pyrolysis rate,product distribution,and tar yield of Chinese Medical Residue（CMR）,Waste Plastic（WP）,and Waste Rubber（WR）were explored by varying the pyrolysis temperature and carrier gas flow rate,which lay the groundwork for hydrogen generation by pyrolysis-reforming.,which laid the foundations for hydrogen production by pyrolysis-reforming.An increase temperature could encourage the secondary cracking reaction of volatiles to convert them into light small molecule gases.When the pyrolysis temperature was increased,the light small molecule gases was volatilized from OSW faster and the moment corresponding to the release peak was advanced,which ultimately lead to a decrease in liquid product yield and an increase in pyrolysis gas yield.Drop pyrolysis gas quality will be the outcome of a greater pyrolysis temperature,which will considerably drop the hydrogen concentration in pyrolysis gas.A higher carrier gas flow rate decreased the residence time of primary pyrolysis production,inhibiting the secondary cracking reaction of volatile substances,and also led to an increase in tar yield and a decrease in gaseous yield.As a result,an increase in carrier gas flow rate typically first increased and then decreased the yield of pyrolysis gas.Among the three typical OSW,CMR had the greatest potential for hydrogen production,and a gas yield more than 46 wt.%could be aheived at T_pyrolysis>800 ^oC,F_N2<250 ml _STP/min,which was significantly higher than that of WP and WR samples.The viability and procedure of on-line pyrolysis-reforming of CMR for hydrogen production with enhancement of steel slag Ca O and catalyst for steel slag tar removal were then explored.Experimental research was done on how the mode of reforming,the components of the accessory ingredient,and the reforming temperature affected hydrogen production.Hydrogen content increased from 43.10 vol.%to 61.87 vol.%,H₂yield increased from 7.57 mmol/g _CMR to 11.45 mmol/g _CMR under the assistance of Ca O（SS）-10 wt.%LR.Because the coupling of steel slag Ca O promoted the water gas shift,methane reforming reaction and tar cracking and reforming.Doping with LR can significantly enhance syngas quality,and a compound containing 20%wt.%LR+80%wt.%Ca O（SS）even had the potential to attain reforming performance on par with NCA catalyst.After doping 10 wt.%LR in Ca O（SS）-NCA,hydrogen concentration was further increased from～60 vol.%to 66.33 vol.%,because LR could effectively enhance carbon-removal on the catalyst surface and prevent the catalyst from sintering at high temperature.A maximum hydrogen yield has been obtained by Ca O（SS）-20 wt.%LR at700 ^oC,along with hydrogen content of 67.50 vol.%in product gas.