Amine regenerator reboilers

For amine regenerator reboilers, at Amoco Oil we used a commercially available leak detector kit. Sulfur hexafluoride was injected into the reboiler steam and the reboiler vapor outlet was then monitored for SF. The detector is sensitive to 1 ppb (billion). The commercially available unit I m familiar with is sold under the trademark of Huortracer Analyzer. Both the analyzer and a SF dispenser are needed. 

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. 

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. 

Your regenerator reboiler duty should be controlled on the basis of pounds of steam per gallon of lean amine circulated (Ib/gas) proceed by cutting reboiler steam 0.1 Ib/gal. Note Scrubber sweet gas purity is controlled by the regenerator stripping steam rate, not by the amine circulation rate to the scrubber. 

The 4-psi increase in the reaction furnace pressure increased the acid gas pressure by an equivalent amount. This pressure rise backed up through the amine regenerator and raised the amine reboiler temperature by 6 F. Because the reboiler tube metallurgy was carbon steel, this increased temperature was of concern in regard to decreased reboiler tube life. To avoid accelerated corrosion, a corrosion inhibitor was injected into the reboiler... 

Reboiler tube failures. Enhanced corrosion rates are most evident in the regenerator reboilers. Dirty amine has caused tube failures after six months of service. 

If substantial reflux is provided, one can be sure that the amine is well stripped before it is drawn off the reboiler trapout tray. The regenerator reflux rale (Ib/hr water) should be 10%-30% of the reboiler steam rate. To double-check stripping efficiency, pull samples of lean amine and reboiler feed. Both should have the same H2S concentration. Remember, H2S must be stripped out of the regenerator trays, not in the regenerator reboiler. This is important enough to repeat Keep a decent reflux rate in the regenerator to prevent reboiler tube corrosion. 

Primary alkanolamine solutions require a relatively high heat of regeneration. Also excessive temperatures or localized overheating in reboilers cause the MEA to decompose and form corrosive compounds. An inhibitor system, such as the Amine Guard system developed by Union Carbide, is an effective method of corrosion control (52). Inhibitors permit the use of higher (25—35%) concentration MEA solutions, thus allowing lower circulation rates and subsequendy lower regeneration duty. 

In the amine stripper, the MEA solution is regenerated by stripping the solution of CO2 and H2S using hot vapors from the reboiler. The hot liquid from the stripper is cooled before returning to flie absorber by first preheating the feed stream to the still in an interchanger and then by air cooling. An accumulator in the line dampens the solution flow rate to the absorber. 

The principle of post-combustion capture is shown in Figure 11.9. The exhaust gas from the NGCC plant is sent to the C02 capture unit, which typically utilizes chemical solvents such as amines or alcohols.7"13 Chemical absorption of C02 using solvent is preferred because of the low concentration of C02 ( 5%) and low pressure in the flue gas. The solvent loaded with C02 is regenerated typically in a reboiler using low-quality steam. The C02 released from the solvent can be sent to a sequestration plant. 

Fig. 2.13. Split flow amine sulfur ronoval process, (a) Absorber, (b) regenerator (c) lean/rich solution heat exchanger (d) cooler, (e) reboiler, (f) reclaimer, (g) condenser...

Direct reheat bypass line, 127 Dirty amine cleanup, 94-95 corrosion inhibitors, 94—95 reboiler corrosion, 95 regenerator feed temperator, 95... 

When these calculations are completed, equipment sizing data can be generated from the results. For example, the regenerator diameter is determined by conventional column design correlations (see Chapter 1) based on the lean amine flowrate and the vapor flow generated by the reboiler duty. 

The plant equipment is basically simple, only an absorber (usually 20 plates), a rectifier or regenerator (also 20 plates), exchangers, a cooler for the amine solution, and a reboiler at the base of the rectifier for supplying heat to the process. Thus, this is an opportunity to introduce the details that are necessary in actual plant operations (Fig. 20-18), by showing a more complete type of flow diagram. 

The NGCC plant consists of a single train of an advanced gas turbine. Like in some lEA studies, the calculations have been based on a Siemens 94.3A (turbine inlet temperature 1300°C and pressure ratio of 15-16) with a triple pressure reheat steam cycle (106 bar/30 bar/4.5 bar) (Fig. C-14). Due to the low partial pressure in the gas turbine exhaust gas, a CO2 removal process based on chemical absorption, using a solvent such as MEA (MonoEthanol Amine), will be required. The assiuned CO2 removal efficiency is 85 percent. Regeneration of the solvent is performed by reboiling and stripping. Low-pressure steam for the regeneration is extracted from the steam cycle. 

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