Amine units, design

Figure 10.5 Design of the amine units using the Elf Activated MDEA process.

The possibility of sulfur dioxide contamination of the DIPA has been considered so remote and the rate of DIPA degradation is so low that none of the plants now being designed and constructed have DIPA reclaiming facilities, as is common practice in MEA and DEA amine units. Since November 1973, none of the startup problems have recurred in the Champlin Unit, and the plant has operated well below the sulfur emission levels guaranteed by Shell and required by APCD regulations. 

Drop size decrease] feed distributor plugged/feed velocity > expected/feed flows puncture interface/local turbulence/distributor orifice velocity > design for amine units for amine > 0.8 m/s for hydrocarbon > 0.4 m/s/[Marangoni effects] /upstream pump generates small drops/[secondary haze forms] /poor design of feed distributor. 

The bis(2-picolyl)amine (Dpa) unit designed for zinc complexation has also been incorporated into various receptors for pyrophosphate sensing and detection. Smith and coworkers studied a series of dinuclear zinc receptors (34, 35, and 36) and found that receptor 35 shows high selectivity and affinity for pyrophosphate under physiological conditions. " Other receptors with only one appended Dpa arm (34) or jiara-substituted Dpa arms (36) show no binding toward pyrophosphate. The binding constant for this receptor with pyrophosphate and phosphate was determined to be 1.52 X 10 and 7.3 x 10 M , respectively. A fluorescent IDA was developed for pyrophosphate using a coumarin-derived indicator 37. A more recent study... 

A number of hnker units designed specifically for immobihzation of amines have also been developed. One noticeable example exploits the versatility of the 9-phenylfluorenyl-9-yl group (PHFI). The PHEI group has previously been used as a protecting group for amines and was adapted into a hnker unit by Bleicher (Table 1.1, Entry 12). Cleavage from this... 

Fluorescent chemosensor 25 [53] (Fig. 28.6) with calix[4]arene in the 1,3-altemate conformation, a conjugated crown ether unit, and an anthracenyl amine showed strong fluorescence under acidic conditions but very weak emission in neutral and basic media. The strong fluorescence is due to the inhibition of PET to the anthracene moiety from the amine units. The addition of K ions leads to the formation of complexes with the crown ether moiety, which induce deprotonation of ammonium ion, causing resumption of the PET process. This metal ion-induced deprotonation is interesting for the design of improved receptors for specific cations. 

For reactions with dissimilar reacting groups such as ampiciUin, where the connective groups are an amine and an oxygen, there are three possible repeat units designated as 5-7. ... 

Anune units must be designed to overcome these special problems. This chapter reviews both the causes of corrosion problems and possible solutions. It describes the locations within amine units where the various agents cause corrosion, discusses the corrosion mechanisms in these places, and reviews the design practices and preventive measures required to mitigate corrosion. These measures include control of velocities and inqiingement, process con-... 

In work sponsored by the U.S. Department of Energy (1989). the cost was developed for a membrane unit installed upstream of an amine unit. The membrane unit was designed to process 170 MMsefd of feed gas containing 17% H2S and 45% CO2. It was estimated that 280,000 ft of membrane would be required to remove 70% of the acid gas. At an installed first cost of 20 per ft of membrane, the cost of the unit would be 5.6 million. The estimated annual steam savings in the amine plant were 5 million to 10 million based on 0.8 to 1.6 pounds of steam per pound of acid gas removed and a cost of 2.28 per 1,000 pounds of steam. The net annual savings, including membrane replacement, were 4.4 million to 9.4 million. 

The amine unit is based on a 30% DEA solution. The feed gas is compressed to 285 psia and pretreated to remove heavy hydrocarbons. After passing through the DEA absorber, the sweet offgas is compressed to 650 psia and sent to the existing gas plant. The sour CO2 stream from the DEA stripper, at 20 psig, is compressed to 450 psia and sent to a Selexol sweetening process designed to reduce the H2S content of the CO2 product gas to less than 100 ppm. 

For most field gas units it is not necessary to specify a stripper size. Vendors have standard design amine circulation packages for a given amine circulation rate, acid-gas loading, and reboiler. These concepts can be used in a preliminary check of the vendor s design. However, lor detailed design and specification of large units, a process simulation computer model should be used. 

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