Rich amine

The rich amine loaded with H2S is regenerated and recycled to the contacting column. 

The acid gases in the rich amine are extremely corrosive. The cono sion commonly shows up on areas of carbon steel that have been... 

The rich amine solution from the absorber is flashed to a separator to remove any hydrocarbons. A small percentage of acid gases will also flash when the pressure is reduced. The dissolved hydrocarbons should flash to the vapor phase and be removed. Flowever, a small amount of hydrocarbon liquid may begin to collect in this separator. Therefore, a provision should be made to remove these liquid hydrocarbons. 

The typical stripper consists of a tower operating at 10-20 psig w ith 211 trays, a reboiler, and an overhead condenser. The rich amine feed is introduced on the third or fourth tray from the top. The lean amine i.s removed at the bottom of the stripper and acid gases are removed from the top. 

Rich/lean amine exchangers are usually shell-and-tube exchangers with the corrosive rich amine flowing through the tubes. The purpose of these exchangers is to reduce the reboiler duty by recovering some of the sensible heat from the lean amine. 

Rich amine from the bottom of the HjS contactor goes to a flash separator to remove dissolved hydrocarbons from the amine solution. The rich amine is pumped from the separator to the amine regenerator,... 

In the amine regenerator, the rich amine solution is heated to reverse the acid-base reaction that takes place in the contactor. The heat is supplied by a steam reboiler. The hot, lean amine is pumped from the bottom of the regenerator and exchanges heat with the rich amine in the lean-rich exchanger and a cooler before returning to the contactor. 

A portion of the rich amine flows through a particle filter and a carbon bed filter. The particle filters remove dirt, rust, and iron sulfide The carbon filter, located downstream of the particle filters, remo cs residual hydrocarbons from the amine solution. 

We would rather leave the OMe group alone (guideline 6), the amino group will be added via nitration and reduction which gives us some flexibility of orientation (guideline 3), and the chlorine can be added by direct chlorination or by diazoniura displacement. The most obvious disconnection is to remove the chlorine. Unfortunately chlorination of the very electron-rich amine (16) oxidises it to black tars it would in any case give a mixture of isomers as all positions in the ring in (16) are activated. 

As C02 is absorbed, rich amine from the absorber bottom is fed into a cross-exchanger with lean amine before it is introduced into the stripper. The stripping temperature varies between 120 and 150°C, and the operating pressure reaches up to 5 bar. A water saturated C02 stream is released from the top and is subsequently ready for transport and storage, while lean amine leaving the stripper is pumped back into the absorber. 

In another route, PCI3 is first reacted with the secondary amine, and the product treated with the binaphthol or biphenol to give the phosphoramidite [35]. This procedure can also be carried out with the hydrochloride of the amine, which is convenient for storage [25]. Methylene chloride or THF are usually applied as solvents. According to the author s experience, this route is well suited in conjunction with electron-rich amines. 

The gas mixture from the converter is cooled and passed to a hydrogen purifying system where carbon dioxide is absorbed into amine solutions and later driven off to the atmosphere by heating the rich amine solution in the reactivator. 

The electron rich amine function is a good acceptor for hydrogen bonds. On the other hand, the basic character of the amine causes proton transfer from acidic groups. Both types of interaction occur on the silica surface. Together with the siloxane bond formation, three types of hydroxyl-specific interaction of the aminosilane molecule with the silica surface may be described, for the modification in organic solvent. These are displayed in figure 9.23. 

Triphosgene, CH2CI2, 0°C, 77% yield. This method is quite general and in competition experiments the most electron rich amine is converted to the carbamoyl chloride. These can be hydrolyzed to the amine or converted to various carbamates if desired. 

Feed, 2. Hydrogen, 3. Wash water, 4. Sour water, 5. Amine solution, 6. Hydrogen sulfide rich amine solution, 7. Gases 8. Hydrogenated product... 

The sweetened gas goes overhead and is sent to the fuel gas system. The rich amine exits the bottom of the scrubber and is heated in the lean—rich exchanger. It then enters the amine regenerator, where a steam reboiler is used to heat the amine to 225—250 °F. At these temperatures, the salts are thermally dissodated to regenerate the amine. The add gas, composed primarily of H2S, is sent to a sulfur recovery unit that generates elemental sulfur. 

The large stripping heat supplied was insufScient to adequately strip H2S fiom a rich amine solution due to excessive amine circulation rate. An eightfold cut in circulation permitted an eightfold cut in stripping heat si-miiltaneaus wiHi a m or improvement... 

By analogy with the rhodium carbene intermediate proposed in the C H insertion reaction with diazo compounds, C— H amination is believed to proceed via a rhodium nitrene species, although such an intermediate has never been characterized. However, as chiral dimeric rhodium complexes lead to the formation of enantioen-riched amination products, it suggests that the metal center is closely associated with the reactive nitrogen during the C—H insertion step. Both a rhodium nitrene or rhodium phenyliminoiodinane species may be involved (Figure 5.2). 

Figure 4-1 is a process flowsheet showing how amine solution is circulated to various refinery scrubbers to absorb H2S. The lean amine chemically combines with H2S (and unavoidably some CO2) in the scrubbers. The resulting rich amine is stripped in the regenerator. Released acid gases (H2S and CO2) are charged to the sulfur recovery plant. 

Rich amine leaking into lean amine in the cross exchanger. 

Rich amine flow control. Locate the regenerator feed control valve downstream of the cross exchanger. This will minimize va X)rizalion of corrosive gases in this exchanger. The control valve internals and piping downstream of the control valve should lx 300-series stainless steel. 

Regenerator internals. Replace all carbon steel trays and tray parts with 304 stainless steel. Use Teflon gaskets. Remove all copper and copper alloy equipment from rich amine service. 

Amine dehydration. A steam or water leak into the system will dilute the amine. Weak, rich amine becomes acidic and corrosive. To increase amine concentration, reflux water can be diverted to a closed drain. This will require piping the reflux water to a place where H2S can be safely flashed off. Do not drain this water to an open sewer it is supersaturated with deadly HjS. This is one mistake nobody makes more than once. 

In the real world, there is only one reliable way to prevent such situations. Liquid hydrocarbons must be separated from the rich amine upstream of the amine regenerator (see Chapter 4). 

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