tailieunhanh - ARNOLD, K. (1999). Design of Gas-Handling Systems and Facilities (2nd ed.) Episode 1 Part 10

Tham khảo tài liệu 'arnold, k. (1999). design of gas-handling systems and facilities (2nd ed.) episode 1 part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Gas Dehydration 21 1 well as using stripping gas. Sometimes the addition of a vacuum will help extend the range of an existing glycol system. Figure 8-11 can be used to estimate the effect of vacuum on lean glycol concentration. s trippi ng Ga s The lean glycol concentration leaving the reboiler can be lowered by contacting the glycol with stripping gas. Often wet gas that is saturated with water vapor at ambient temperature and 25 to 100 psig is used. At 25 psig and 100 F this gas is saturated with 1 500 Ib MMscf of water vapor. At atmospheric pressure and the temperatures in the reboiler the gas can absorb over 100 000 Ib MMscf. In most situations the additional fuel gas required to heat the reboiler to increase lean glycol concentration is less than the stripping gas required for the same effect. Thus it is normally desirable to use stripping gas only to increase lean glycol concentration above to which can be reached with normal reboiler temperatures and normal back pressure on the still column. If the glycol circulation rate must be increased above design on an existing unit and the reboiler cannot reach desired temperature it is often possible to use stripping gas to achieve the desired lean glycol concentration. Figure 8-12 shows the effects on the glycol purity of stripping gas flow rate for various reboiler temperatures assuming the gas is injected directly into the reboiler. Greater purities are possible if stripping gas contacts the lean glycol in a column containing one or more stages of packing before entering the reboiler. Glycol Circulation Rate When the number of absorber trays and lean glycol concentration are fixed the dew-point depression of a saturated gas is a function of the glycol circulation rate. The more glycol that comes in contact with the gas the more water vapor is stripped out of the gas. Whereas the glycol concentration mainly affects the dew point of the dry gas the glycol rate controls the total amount of water that can .