Dehydration process selection for removing water form natural gas
Process Introduction
The presence of water in natural gas often leads to serious consequences: water and natural gas form hydrates under certain conditions, which block pipelines; in addition, in order to meet the quality indicators of water content (or dew point) of natural gas products, dehydration is necessary.
The natural gas dehydration process generally includes:
- Low temperature freeze dehydration
- Solid desiccant adsorption
- Solvent absorption
- Membrane separation
Low-temperature freezing dehydration is generally combined with light hydrocarbon recovery projects. When natural gas is dehydrated by freezing separation, the natural gas needs to have a higher pressure or an external cold source. Since it needs to be pressurized or an external cold source is provided, it is not economical for this device .
The common solid desiccant adsorption dehydration methods are silica gel method, molecular sieve method or a combination of these two methods . The investment and operating costs of the adsorption method device are higher than those of the glycol dehydration device.
Solvent absorption is the most commonly used method. Although there are many solvents to choose from, most devices use glycol solvents. The comparison of different dehydration solvents is shown in table comparison of dehydration solvents.
Comparison of dehydration solvents
|
Dehydration solvent |
advantage |
shortcoming |
Remark |
|
Calcium chloride aqueous solution |
Low operating cost and simple equipment |
The equipment is severely corroded, the dew point drop is small (about 11°C), and the H2S in the natural gas will form precipitation |
It is rarely used now, mainly used in remote gas wells and extremely cold areas. |
|
Lithium chloride aqueous solution |
The dew point can drop to 22~36℃, which is less corrosive to equipment than calcium chloride aqueous solution. |
Expensive |
Mainly used for air dehydration |
|
Diethylene glycol solution |
Concentrated solution will not solidify, solvent is stable at operating temperature, high hygroscopicity |
The dew point is reduced by 28℃, which is lower than that of triethylene glycol solution. The carryover loss is larger than that of triethylene glycol, and the device investment is high. |
Not widely used in the natural gas industry |
|
Triethylene glycol solution |
The concentrated solution will not solidify, the solvent is stable at the operating temperature, and the hygroscopicity is very high. The vapor pressure is low, the carryover loss is small, and the dew point can drop to 40℃ |
The device investment is high, and the solution has a certain tendency to foam |
It is the most widely used dehydration method in the natural gas industry |
Since triethylene glycol has a large dew point drop, low cost and reliable operation, it is the most economical among glycol compounds. Therefore, this device uses triethylene glycol for dehydration.
Process equipment composition
1) Triethylene glycol dehydration unit:
(1) Absorption tower (including filler)
(2) Gas-lean TEG heat exchanger
2) Triethylene glycol regeneration unit:
(1) Glycol rich liquid mechanical filter
(2) Glycol rich liquid activated carbon filter
(3) Fuel gas buffer tank
(4) Triethylene glycol lean-rich liquid heat exchanger
(5) Triethylene glycol circulation pump
(6) The triethylene glycol regeneration combined device includes:
(a) Triethylene glycol regeneration tower
(b) TEG reboiler
(c) Triethylene glycol tank
(d) Burner
Contact:
Sichuan Rongteng Automation Equipment Co., Ltd.
Phone/WhatsApp/Wechat : +86 177 8117 4421
Website: www.rtgastreat.com Email: info@rtgastreat.com
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