View source for Lean/Rich Exchangers(HT-1105A/B/C)

=Introduction=
The Three parallel Lean/Rich Exchangers (HT-1105A/B/C) are plate-type heat exchangers which are normally all in service. As shown in Figure 3, rich amine passing through each exchanger absorbs heat from the hot lean amine leaving the amine regeneration operations at the amine regenerator. Via this heat transfer:
*The rich amine warms from about 160°F to 220°F.
*The lean amine cools from about 275°F to 175°F.

[[File:LRX.png|center|frame|Lean/Rich Exchanger Flows]]

The heat transfer from lean to rich Amine is important to the operation of Amine sweetening process operations because:
*Preheating the rich Amine before its regeneration contributes to the thermal efficiency of T1’s Amine process operations; preheating reduces the amount of 65# steam required during Amine regeneration by the downstream Regenerator’s Amine.
*The hot, regenerated lean Amine must be cooled to prepare for its reuse in absorbing acid gases in the A+B Amine contactors.


=Operation and Valving=

The three lean/rich amine exchangers are plate-type heat exchangers located side-by-side in the Amine Regenerator Building.

Each lean/rich exchanger consists of a series of corrugated plates separated by gaskets. A narrow passage between the plates permits liquid to flow. Referring to figure 4, inlet and outlet ports for both fluids (lean amine and rich amine) that pass through the heat exchanger are located at the corners of each plate. These ports are aligned and sealed to allow the rich and lean amine to flow countercurrent through the narrow plate passages.

<u>'''Note:'''</u> In the exchangers, contaminants in the amine can coat the plates of the exchanger with fouling deposits. This fouling:
*acts as an insulating barrier that decreases the heat transfer between lean and rich Amine. Amine temperatures that show insufficient lean Amine cooling and insufficient rich Amine preheating are indicators of fouling.
*restricts the Amine flow between the plates. Abnormally low flow through an exchanger is an indicator of fouling.

[[File:LRXFlows.png|center|frame|Lean/Rich Exchanger Plates]]


=Rich Amine Inlet/Outlet=

===Rich Amine Inlet===
Cool, rich Amine flows to each exchanger’s rich Amine inlet to be heated; the rich Amine inlet is equipped with:
*a manual inlet block valve
*A temperature Transmitter of the Rich Amine before they branch off into the exchanger inlets (TIT-1781)
*a manual low point drain valve to the Amine Drain Vessel on each exchanger
*a rich Amine Pressure relief valve set at 147 psig to relieve overpressure to piping upstream of the exchangers. (Each exchanger has its own rich Amine PRV; they are (PRV-1783, 1785,1787)
*A differential pressure transmitter ( PDIT-1790) which takes the differential across the Rich Amine Inlet and Outlet headers
*a drain connection

===Rich Amine Outlet===
Preheated, rich amine leaves each exchanger’s rich Amine outlet; the rich Amine outlet is equipped with:
*An outlet flow control valve, which functions to control the level in the Amine Flash drum (PV-1104).
*an outlet manual block valve
*local pressure and temperature indication
*a top 2” breather valve to prevent vacuum during drainage/exchanger shutdown
*a drain connection
*a temperature transmitter ( to relay the outlet temperature to Control Room DCS workstations

The preheated, rich amine outlet flows from the three lean/rich exchangers merge; this combined flow then heads to the [[Amine Regenerator(PV-1102)]].


=Lean Amine Inlet/Outlet=

===Lean Amine Inlet===
Hot, lean amine flows to each exchanger’s lean Amine inlet to be cooled; the lean Amine inlet is equipped with:
*a manual inlet block valve
*A temperature Transmitter of the Rich amine before they branch off into the exchanger inlets (TIT-1775)
*A Lean amine Pressure relief valve set at 150 psig to relieve overpressure to the amine Drain vessel. (Each exchanger has its own lean Amine PRV; they are (PRV-1784, 1786, 1788)
*a 1” drain connection
*A warm up line from the discharge of the amine booster pumps, used for startup after shutdowns

===Lean Amine Outlet===
Cool, lean amine leaves each exchanger’s lean Amine outlet; the lean Amine outlet is equipped with:
*a manual outlet block valve
*a manual low point drain valve to the Amine Drain Vessel
*a 2” drain connection
*a temperature transmitter (TIT-1775,1777,1779) to relay the outlet temperature to the Control Room DCS workstations

Downstream of the outlets, the three cool, lean amine outlet flows merge and head to the [[Amine Surge Tank(SV-1101)]] . Before arriving at the surge tank (described in [[Lean Amine Feed]]), the combined flow passes through level control valve (LV-1816), which modulates to maintain the level in the Regenerator at setpoint


=Process Controls=

The three lean/rich exchangers have no process controls of their own. Instead, the rich Amine flow and the lean Amine flow through the exchangers is affected by the liquid level control actions of upstream process vessels:
*The flow of rich Amine is affected by the actions of the Amine Flash Drum’s level control system, which controls the Level control valve located on exchanger’s outlet header as described below.
*The flow of lean Amine is affected by the actions of the level control valve for the [[Amine Regenerator(PV-1102)]].

==Rich Amine Flow Control==
Figure 3 and 5 shows the control system for maintaining the rich amine level in the Amine flash Drum at setpoint (LV-1755) downstream of the lean/rich amine exchanger outlets. The level control valve located at the Regenerators rich inlet line to ensure that the rich side of the exchangers are full at all times. This will prevent gas from flashing off in the exchanger which will reduce it heat exchange efficiency. The FNNPF’s level control strategy operates as follows:
*The flash Drums’s level controller (LV-1755). The Control Room Operator configures the level controller’s level setpoint.
*A Flow transmitter (FIT-1761) takes a flow indication of the Rich Amine Flowing through the flow control valve (FV-1761) upstream of the rich Amine inlet measures inlet flow and transmits the data to DCS. The flow controller continually compares the measured flow with the setpoint received from the level controller and modulates the flow control valve to maintain the setpoint.


=Operations Monitoring=

During monitoring rounds at the Lean/Rich Exchangers (HT-1105A/B/C), the Area Operator:
*checks the concrete pad under the exchangers to ensure the exchanger plate gaskets are not leaking Amine
*monitors the Amine temperatures to verify lean Amine cooling and rich Amine preheating
*compares the inlet and outlet pressures of the Amine flows to ensure no internal flow blockages or restrictions are present
*Verifies the exchanger’s Amine flowrate. If the flowrate are not normal , the Area Operator consults with the Control Room Operator to:
:-investigate/assess exchanger fouling and determine corrective action
:-Checks the differential across the Inlet and outlet headers
:-Checks Outlet temperatures of each outlet line on the filters


=Preheated Rich Amine Flow To Regeneration=

Downstream of each exchanger, the three rich Amine flows each pass through a manual block valve. The three flows then combine into one flow to the [[Amine Regenerator(PV-1102)]].