Sr. Business Development Manager
Sr. Chemical Engineering Manager
09:45 - 10:15
Thursday, 19 September 2019
T3.7 Membrane-Amine Hybrids for CO2 Removal-Technology Discussion and Case Studies
A variety of technology options can be used for CO2 removal or pretreatment of cryogenic plants. Amine absorption processes have traditionally been used for treatment of feed gas for onshore plants. Since the early 1990s membrane process have become an increasingly attractive alternative and are the technology of choice for offshore bulk CO2 removal units. Large membrane units processing many 100 MMSCFD up to 1,000 MMSCFD with CO2 as high as 50% have been operating successfully for many years. Both membranes and amines have their advantages and disadvantages, for example, amines are best suited to meeting ppm level CO2 products but are not optimal for treating high CO2 feeds, whereas membranes are excellent for bulk CO2 removal and typically can’t achieve very low CO2 product specifications. Hybrid units with membranes providing bulk CO2 removal followed by amines for meeting low CO2 product targets are often an attractive combination.
PTT's GSP-6 plant will be presented as one of the case studies. PTT is the largest gas separation operator in Thailand and runs six gas separation plants (GSP) approaching a total processing capacity of 3,000 MMSCFD. The GSP units treat gas from the Gulf of Thailand and separate it into methane, ethane, propane, liquefied petroleum gas (LPG) and natural gasoline (C5+) fractions. The products from the plants feed Thailand's power, fuel, fertilizer and petrochemical industries and are also exported regionally. The GSP-6 plant located in Rayong province processes 800 MMSCFD and started up in early 2011. It is the largest gas separation plant in the world in terms of number of production-through-fractionation units. The feed to the GSP plants contains between 19 and 23 mol% CO2, which needs to be removed to less than 900 ppm to ensure efficient operation of the cryogenic fractionation units (CO2 freeze avoidance.)
The GSP-6 plant was originally installed with amine technology for CO2 removal to meet the <900 ppm CO2 product. However as production from the plant increased, PTT needed to investigate ways to increase the CO2 removal capacity of the amine unit. The most efficient debottlenecking solution turned out to be installation of a membrane unit for bulk CO2 removal on a portion of the feed gas, upstream of the amine unit. The modular nature of membrane systems, where multiple duplicate skids are used to meet the total processing capacity, made the 120 km move and re-installation much simpler. The relocated membrane unit started operation in early 2015 and has been in stable operation since.
This presentation will cover the basic operation and advantages/disadvantages of amines and membrane systems and why hybrid membrane-amine units can provide a better solution than either technology alone. It will also describe specific projects, including the GSP-6 amine debottlenecking project.