Answers to questions on the theoretical air supply volume
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Acidic gas enters the sulfur production furnace, where the air supply is adjusted so that approximately 65% of the H2S in the acidic gas is converted into elemental sulfur. One-third of the remaining H2S is converted into SO2. The hydrocarbons present in the acidic gas are completely burned to produce CO2 as part of the air supply. Let the flow rate of the acidic gas be V, its concentration be a%, and the hydrocarbon content be b%. According to the reactions: H2S + 1/2 O2 → S + H2O, and H2S + 3/2 O2 → SO2 + H2O, it can be seen that 1 mol of H2S requires 1/2 mol of O2 to be completely converted into elemental S, while 1 mol of H2S requires 3/2 mol of O2 to be completely converted into SO2. Therefore, approximately 65% of the H2S is converted into elemental S, and one-third of the remaining (1–65%) H2S is converted into SO2. The amount of O2 required for this is: V × a% × 65% × 1/2 + V × (1–65%) × 1/3 × a% × 3/2 = 0.5 × V × a%. According to the reaction CnH2n+2 + (3n+1)/2 O2 → n CO2 + (n+1) H2O, 1 mol of hydrocarbons requires (3n+1)/2 mol of O2 to be completely burned to produce SO2. The amount of O2 required for complete combustion of hydrocarbons to produce CO2 is: V × b% × (3n+1)/2. Thus, the total amount of O2 required is the sum of the O2 needed to convert approximately 65% of the H2S into elemental S and the O2 needed to convert the remaining H2S into SO2, plus the O2 needed to burn the hydrocarbons completely to produce CO2: 0.5 × V × a% + V × b% × (3n+1)/2. Assuming that the oxygen content in air is 21%, the amount of air required is: V% / 2 × 100 / 21 = V/42. I have a question for everyone: when calculating the oxygen demand of hydrocarbons, what is n in the expression Vxb%x(3n+1)/2 – is it a unit or a number? The oxygen demand of hydrocarbons will not be calculated; please explain this to me, experts. Thank you! ! ! ! ! ! ! ! ! ! ! :handshake Last edited by Ma Hai on 2009-4-3 19:14 ]
n is the carbon atom content of the hydrocarbon.
n is indeed the number of carbon atoms in the hydrocarbons. In acid gas, methane is usually the predominant hydrocarbon; if there is only methane, then n=1. If other hydrocarbons are present, then b% should be distributed among those respective hydrocarbons, with calculations performed for each one separately.
On this issue, the original poster must first understand the specific meaning of CnH2n+2; the value of n must be a natural number greater than zero, such as 1, 2, 3, 4, …. This is what leads to the different components of the fuel, such as methane, ethane, and so on. Then, the oxygen requirement for the combustion of hydrogen sulfide is calculated separately (in two parts: one part resulting in sulfur and the other part resulting in sulfur dioxide), as well as the oxygen requirement for the combustion of the remaining hydrocarbon components; by adding these values together, the total oxygen requirement is obtained.
n is the number of carbon atoms in the molecular formula of a hydrocarbon; for example, if the hydrocarbon is propane, then n=3, which corresponds to C3H6. As for the main components of hydrocarbons in acidic gas, it depends on the feedstock used in the upstream desulfurization unit that generates the acidic gas. If the acidic gas comes from a liquefied gas desulfurization unit, then the hydrocarbons are likely to be C3 and C4 compounds; whereas if it comes from a dry gas desulfurization unit, the hydrocarbons are mainly C1 and C2 compounds ； In fact, the acidic gas processed by the sulfur recovery unit should include these two components; the volume of acidic gas coming from the liquefied gas desulfurization unit constitutes the main part. In theoretical calculations, the value of n can be taken as an intermediate value for estimation, with n=3 generally being used, corresponding to propylene or propane. This post was last edited by zxh6267 on 2009-4-4 15:05.]