| The tannin extract desulfurization is a wet oxidation desulfurization method for removing H2S what has been developed by research institutes in Guangxi at first.It has been widely used in sour gas purification because of its good technical and economic indicators.Along with the environmental regulations strictly enforcing,research on the mechanism of desulfurization process begin to enter people's vision.But,because of the complexity of the tannin extract's components and structure,as desulfurizer,which is extractive of plant organ with high tannin content,its mechanism of desulphurization has not been clear explanation so far.Research on alkaline medium in tannic extract desulfurizing solution which has an effect on the sulfur transformation in desulfurization process reported rarely.Therefore,the studies aims at perfecting desulphurization mechanism and the basic data of the tannin extract desulfurization.In this paper,cyclic voltammetry and differential pulse voltammetry were selected to research the volt-ampere characteristics of plant tannic acid with tannic acid as reference.It has been indicated that,a high sensitive irreversible oxidation peak of them appeared at about 0.14 V and the electrode process is transfer 2 e-/H+which controlled by the diffusion in ammonium salt medium.The peak of the active material of plant tannic acid is speculated as tannic acid.The concentration,both of them,has a linear relation with the oxidation peak current,and the content of tannic acid in plant tannic acid can be roughly obtained.In the oxidation degradation process of the plant tannic acid,the oxidation peak current of differential pulse voltammetry gradually reduce along with time and the change trend is consistent with the oxidation reduction potential of the degradable material solution,so it can serve as a kind of evaluation method used to indicate the end point of tannin extract oxide preparation.Cyclic voltammetry was selected to research the reaction between tannic acid and HS-and vanadyl sulfate.What has been discovered is that,the electro-catalysis of the tannic acid to the oxidation of HS-was revealed,the apparent reaction rate constant of them is roughly 1.8×104 s-1(mol·L-1)-1,non-oxidation reduction reaction also exist as well.The complexation between tannic acid and vanadyl sulfate will hinder the peak of cyclic voltammetry of tannic acid.The study also found that hydroquinone as desulfurizer of the improved hydroquinone desulfurization has a quasi-reversible electrode process and the electro-catalysis of hydroquinone to the oxidation of HS-will happen as well as tannic acid on the same conditions.The apparent reaction rate constant of them is roughly 4.9×103 s-1(mol·L-1)-1.It will become 5.1×103 s-1(mol·L-1)-1 when it is in the improved hydroquinone desulfurization liquid environment.The tannin extract desulfurization process was studied when(NH4)2CO3-NH4HCO3 is used as alkali medium,the result indicates that when the concentration of tannic extract is 2.00 g·L-1,NaV03 is 1.00 g·L-1,the ammonium is 0.5 mol·L-1,pH value is 8.9 and temperature is 40?,optimal technological condition of 0.13 g·L-1 sulfur capacity will appear,just the sulfide transformation taken into account.The ability of removing sulfide was declined contrast with the former in either(NH4)2C03-NH4HCO3 or Na2CO3-NaHCO3 alkali medium,but the latter fell faster,in the same condition.Removing sulfide accelerates along with the concentration of ammonium increasing when the alkali liquor mixed with each other.A series of sulfide reduction peaks of the desulfurization liquid appear range between-0.85 V and-1.10 V,compared with Na2CO3-NaHCO3,the peak current of(NH4)2CO3-NH4HCO3 rise,divisive,decrease and level off faster,when the peak current leveling out the value is also higher.But the time of reduction peak reaching steady and the peak current of the latter change little,while the former increase obviously when the sulfur capacity increase. |
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