澳洲大学石油工程讲座17-3950-gas sweetening.ppt

GAS SWEETENING Fundamentals Purity requirements demand that H2S and CO2 concentrations be within contract specs. Hydrogen sulfide (H2S) is very toxic. Inhaled gas can cause headaches, even death. Combustion products are sulfur dioxide or trioxide, both make extremely corrosive acid with water. Colorless with a foul odor, heavier than air. Soluble to a degree and valuable as sulfur dioxide to sulfuric acid plants and for the production of elemental sulfur. Carbon dioxide (CO2) has a similar acid character to H2S, but is not toxic and has no odor. Removal is desirable to increase heating value and decrease corrosion (with water). However, removal may be undesirable as it causes gas volume to shrink and less gas is sold. Processes Sulfinol Uses less circulation rate and lower temperatures, thus less degradation. Reduced foaming tendencies and good mercaptan removal. Less steam heat load. Capital cost is more for throughput volume. Loading or circulation rate specifications of 6 scf acid gas/gallon solvent. Processes DGA 80% cost of amine Plant identical to Amine and Sulfinol Higher acid gas loading The Amine Process Liquid moves countercurrent to sour gas, and is either Monoethanolamine (MEA), Diethanolamine (DEA), or Triethanolamine (TEA). Equipment includes a contactor, filter, regenerator, heat exchangers, and a pump Process principles H2S and CO2 react with a weak base to give a water soluble acidic salt. The reaction is reversible with heat. Acid gases are absorbed from 80-120°F and desorbed from 240-300°F, and both are influenced by acid gas partial pressure. Properties of Amine MEA is a stronger base with a lower molecular weight which allows use of a smaller pump, less heat, etc. Molecular weight comparison of MEA:DEA:TEA as 1.00:1.72:2.44. MEA has a lower boiling point (distillation). However, MEA losses are greater as the vapor pressure is higher. Properties of Amine Contactor usually has 16 to 20 trays Sour gas flows upward (80-100?) through the amine-wa