ISA Automation Conference Preheat APC-Rev.00

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ISA Automation Conference 2013- EMEA

(Dammam, Saudi Arabia) – December 10-12, 2013

Preheat APC Controller

Benefits Study

RAKAN M. BINTOHMAN Process Control Engineer

Saudi Aramco / Yanbu Refinery



ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

Agenda

Preheat Network Overview


Benefits



V25

Surge

Drum

V2

Flash

Drum

H1A

H1B

E11

V8V1

To Flare

Fuel Gas

Crude

LPG

LSRN

HSRN

RCO

HDO

LDO

KERO

V11

V09

V6C & D

Desalters

V6A & B

Desalters

CDU APC

Controller

04CU

Stabilizer /

SplitterController

04SP

Crude Preheat

Optimizer

04PH

CVs

Product Qualities

PA / Feed

DHT Surge Drum

Heaters COT

Balance

MVs

Total Draws

Total PA

Heaters COT

MVs

Reflux

Reboiler

Stabilizer feed

LSR to ISOM

CVs

STAB BTM PCT

SPLT OH RVP, 90%

OH Pressure

Reflux/Feed

Surge Drums



2 Identical Crude Preheat Trains (A/B)

V04- E1 Crude/ Naphtha PA

V04- E2 Crude/kerosene Draw

V04- E3 Crude/LDO Draw

V04- E4 Crude/1st LDO PA

V04- E5 Desalted crude/ 2nd LDO PA

V04- E6 Desalted crude/HDO Draw

V04- E7 Desalted crude/ Cold RCO

V04- E8 Desalted crude/ HDO PA

V04- E9 Desalted crude/ Hot RCO



DCS: Honeywell TDC 3000, APC: ProfitSuite R205.1

Controller covers the CDU Preheat Trains A and B for

series of exchangers E1…E9

Optimize (Balance) incremental heat duties between

exchangers in CDU Preheat Train A and B

Manipulating the crude flows and the hot stream flows

(PA and products draws) through the exchangers.



Exchanger Toolkits

Custom profit toolkits

Calculate heat exchanger performance parameters

Used to calculate the several of the controlled

variables in the APC controller.

The toolkits calculate the incremental duty for the cold

and hot streams for each exchanger.

The relative incremental duties for a pair of parallel

exchangers are calculated in DCS.



Exchanger Toolkits

INPUTS

Flow rate of adjusted stream m3/Hr

Inlet Temperature of Cold Stream Deg C.

Outlet Temperature of Cold Stream Deg C.

Inlet Temperature of Hot Stream Deg C.

Outlet Temperature of Hot Stream Deg C.

Heat Exchanger Area m2.

Adjusted stream average specific heat (CP) kCal/Kg.C

Adjusted stream average Specific Gravity SG.

OUTPUTS

Heat Exchanger Duty (Q) kCal/hr

Log Mean Temperature Difference (LMTD) Deg C.

Over all heat transfer coefficient (U) kCal/hr/m2/C

Incremental duty (dQ/dF) kCal/m3



No. MV Tag name Description

1 04FDC231.SP Cold Crude Delta Flow before V2

2 04FDC036.SP Hot Crude Delta Flow after V2

3 04FDC222.SP Naphtha PA Delta Flow – E1

4 04FDC184.SP LDO Draw Delta Flow – E3

5 04FDC171.SP LDO PA Delta Flow – E4

6 04FDC165.SP LDO PA Delta Flow – E5

7 04FDC146.SP HDO Draw Delta Flow – E6

8 04FDC005.SP RCO Draw Delta Flow – E7/9

9 04FDC109.SP HDO PA Delta Flow – E8



Total Pump around flow / Total Product Draw flow

Controlled by CDU APC controller (as MVs)

Individual stream in each train is cascaded to to the

stream master (Total) flow controller

FDC controllers are AM tags with no output

connection.



04FLWBAL, Flow Balance Controller

AM CL program

Reads an operator-entered flow split %

Calculates & Writes bias values for 2 flow controllers

(04FLWBAL) adjusts the PID controller bias parameters

in DCS for parallel flow streams



04FLWBAL, 04PH Controller

AM CL Program 04PRHTDF

Transfers the output signal of the MV (FDC) to the

appropriate flow split percentage

Target parameter of the existing custom flow balance

controller, 04FLWBAL



No. CV Tag name Description

1 04QD001C.PV Delta dQ/dF Crude before V2

2 04QDE1H.PV Delta dQ/dF E1 - Naphtha

3 04QDE3H.PV Delta dQ/dF E3 - LDO

4 04QDE4H.PV Delta dQ/dF E4 – LDO PA

5 04TI173.PV Crude to Desalter Temperature – Train A

6 04TI168.PV Crude to Desalter Temperature – Train B

7 04QDE5H.PV Delta dQ/dF E5 – LDO PA

8 04QDE6H.PV Delta dQ/dF E6 – HDO Draw

9 04QDE79H.PV Delta dQ/dF E7/9 – RCO Draw

10 04QD002C.PV Delta dQ/dF Crude after V2

11 04QDE8H.PV Delta dQ/dF E8 – HDO PA

12 04TI008.PV Crude Heater A Inlet Temperature

13 04TX004.PV Crude Heater B Inlet Temperature



No. CV Tag name Description

14 04FC222.OP Naphtha Circulation to E1 - A/B OP

15 04FC223.OP Naphtha Circulation to E1 - C/D OP

16 04FC163.OP LDO #2 Circulation to E5 - B OP

17 04FC165.OP LDO #2 Circulation to E5 - A OP

18 04FC169.OP LDO #1 Circulation to E4 - B OP

19 04FC171.OP LDO #1 Circulation to E4 - A OP

20 04FC109.OP HDO Circulation to E8 - A OP

21 04FC111.OP HDO Circulation to E8 - B OP

22 04TXH1OP.OP Sum of 04TC044G.OP and 04TC048G.OP

23 04TXH2OP.OP Sum of 04TC078G.OP and 04TC082G.OP


Benefits Study

Preheat Controller was down for long time due to flow

& temperature measurements issues.

Preheat Controller was successfully re-commissioned

Prior commissioning, complete checks of

instrumentation, toolkits & interface points.

Conservative tuning of ramp rates & maximum

moves to avoid high fluctuations in heat exchangers

operations.


Benefits Study

670

680

690

700

710

720

730

271

272

273

274

275

276

277

278

279

280

E9A5_OUT Deg C

E9B5_OUT Deg C

H1A TOTL M3/Hr

H1B TOTL M3/Hr

Preheat APC

OFF

Preheat APC

ON

Operations reduced

crude feed due to high

ambient temperature

and crude column

pressure


Benefits Study

There are 2 elements of calculations to determine the

true value of APC optimizer:

1- Pre-heat energy recovery loss/gain

2- Overall fuel gas consumption

Following basis are used in estimating the benefit:

Fuel Gas Heating Value = 26,000 Btu/M3

Crude Heater Efficiency = 77% (based on actual

operation)


Benefits Study

Table 1: Crude Preheat Recovery

Controller Status OFF ON

Train A Train B Train A Train B

Crude Feed, m3/hr 709 709 699 719

Temperature, oC 272.9 276.6 274.3 275.7

Heat MMBtu/Hr 428 434 425 438

Net Gain, MMBtu/Hr 1.0


Benefits Study

670

675

680

685

690

695

700

705

710

715

1

1.2

1.4

1.6

1.8

2

2.2

04PI513

04PT001

H1A M3/HrPreheat APC

OFF

Preheat APC

ON

Operations

reduced crude

feed due to high

ambient

temperature

and crude

column

pressure


Benefits Study

670

680

690

700

710

720

730

15000

16000

17000

18000

19000

20000

21000

TOT_FG

04HC036

04HC070

Preheat APC

OFF Preheat APC

ON

Operations reduced crude

feed due to high ambient

temperature and crude

column pressure


Benefits Study

Collected data showed insignificant changes in fuel gas

composition and heaters flue gas oxygen contents

441 NM3/Hr = 11.5 MMBtu/hr = 581,773 U.S.$/Year.


Conclusion

Preheat APC controller benefits can be described as

follow:

Operational benefits of reducing Heater A fuel gas

pressure.

Preheat recovery gain of 1MMBtu/Hr.

Overall Fuel gas consumption reduced by 441

NM3/Hr which is equivalent to savings of 11.5

MMBtu/Hr or > 0.5 MM $ / year

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ISA Automation Conference Preheat APC-Rev.00

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