Determination of Steam and Makeup Water Requirements Of A Deaerator by EMEMERURAI O.

DETERMINATION OF STEAM AND MAKEUP WATER REQUIREMENTS OF

A DEAERATOR

BY

OGHENEOVO EMEMERURAI

PRODUCTION DEPARTMENT

WRPC EKPAN

CONTENT

WHAT IS DEAERATION? WHY DEAERATE BOILER FEED WATER

(BFW)? FUNCTIONS OF A DEAERATOR TYPES OF DEAERATORS REQUIREMENTS FOR GOOD DEAERATION MONITORING & CONTROL OF DEAERATION

WHAT IS DEAERATION?

This is the process of removing dissolved oxygen and other gases from the boiler feed water. It is the last treatment given to the BFW before introducing it to the boiler

The equipment in which the process is carried out is called a deaerator

Figure1 shows the WRFCCU deaerator as

a component of the condensate recovery unit

WHAT IS DEAERATION?

E-01

CR

C

DW TANK

D-02 DEAERATOR

P-01

VE

NT

LPS

LPC

P-03

P-02

E-22CRU WHB

COB

MPS

HPS

MPS

HP

C

FIGURE 1: WRFCCU DEAERATOR AND CONDENSATE RECOVERY UNIT

WHY DEAERATE BOILER FEED WATER (BFW)?

Longer equipment life Reduced pipeline replacement costs Lower overall maintenance Lower operating costs Reduced system shutdown

FUNCTIONS OF A DEAERATOR

Oxygen removal Carbon dioxide removal Encourages improved operation due to

heating of condensate It improves heat transfer Ensures energy savings It provides the NPSH for the BFW pumps Receives the BFW pump recirculation


OXYGEN REMOVAL Oxygen removal is the primary reason for

deaerating water. It is done in two stages : mechanical deaeration with steam and chemical deaeration with substances such as hydrazine, sodium sulphite, Mekor™.

Chemical deaeration is expensive and incomplete and always follow the mechanical


Dissolved oxygen is about 10 times more corrosive than carbon dioxide especially at high temperature

Chemistry of oxygen corrosion:

-Fe +2H2O=Fe(OH)2 +2H+ (1)-4Fe(OH)2+O2+H2O=4Fe(OH)3 (2)

-Fe(OH)2 is soluble while Fe(OH)3 is not

-Pitting corrosion results due to the latter and increases in the presence of carbon dioxide


CARBON DIOXIDE REMOVAL- Fe(OH)2 speed in becoming a soln depends

on the PH of the water: The lower the PH the faster it goes into soln.

- If the water contains dissolved CO2 it forms

carbonic acid:CO2+H2O=H2CO3 (3)

- The acid lowers the PH to 5.6-6.5 which favours the soln of Fe(OH)2 hence CO2

removal.


IMPROVED OPERATION DUE TO HEATING OF CONDENSATE

• The deaerator heats the BFW which reduces the chance of thermal shock in the boilers caused by the expansion and contraction of heating surfaces.

• As a rule of thumb, a 6oC rise in BFW temperature due to a boiler economizer or condensate recovery gives a 1% fuel savings


IMPROVED HEAT TRANSFER• Air is an excellent insulator and when

dissolved gases are present in condensate they reduce the rate of heat transfer

• The gases must be eliminated from the power plant cycle as soon as possible.

• This is achieved in the deaerator.


ENERGY SAVINGS• The flash steam lost by condensate to the

atmosphere can be recovered by the deaerator and saves boiler fuels

PROVISION OF BFW PUMP NPSH

The deaerator provides the net positive suction head for the BFW pumps. The NPSH can be found from

(4)fhDPPPNPSH SVSa )/144(*)(


BFW PUMP RECIRCULATION• The deaerator horizontal storage section

receives BFW pump recirculation • It also acts as a surge drum for the

condensate

TYPES OF DEAERATORS

Atomizing deaerators Tray type deaerators Film type deaerators The WRFCCU uses the tray type with the

feedwater in countercurrent flow with the steam flowing upwards.

REQUIREMENTS FOR GOOD DEAERATION

These are:• Temperature :Heating the water to saturation

removes all the dissolved gases• Turbulence: A complete mixing is required to shake

out all the dissolved gases• Thin film: A thin film must be created so that the

distance the dissolved gases must travel is reduced thereby enhancing the heating

• The more time allowed for the first three actions above the better

REQUIREMENTS FOR GOOD DEAERATION

Venting: The liberated dissolved gases must be released to atmosphere

Steady steam rate: The system must maintain constant steam pressure in the system for effective deaeration

MONITORING & CONTROL OF DEAERATION

Normally all the control and monitoring equipment for startups, normal operation and alarms for out of parameter operations are provided.

Deaerator level and pressure must be controlled by adjusting control valves.

The level is regulated by condensate flow, pressure by steam flow.

The WRFCCU deaerator has level control in place but no steam flow regulation.


Thus the objective of this paper is to determine the steam and makeup water requirement of the deaerator.

The deaerator material and energy balance equations are presented as follows :

MS+ ∑MC +MM=MF (5)

MShS+ ∑MChC +MMhM=MFhF (6)


The solution of equations 5 and 6 requires knowledge of the flow rates as well as reference to steam tables.

The design data of the deaerator are given in Table 1 for two cases


PARAMETER VALUE

CASE I CASE II

No of condensate Returns 2 Nil

LP condensate Flow,Ib/hr 80437.03560 Nil

LP condensate Temperature,oF 212 Nil

Clean condensate flow, Ib/hr 128175.4440 Nil

Clean condensate temperature,oF 165.2 Nil

Steam pressure psia 78.35 78.25

Deaerator temperature,oF 311 311

Makeup H2O Temperature,oF Nil 80.6

Makeup H20 flow Ib/hr Nil 291227.66


It takes time when steam tables are used to solve equations 5 and 6. Three Matlab programmes were therefore written to solve them with the aid of correlations in literature. The programmes are given in Appendices 1 , 2 and 3:

APPENDIX 1:MATLAB PROGRAMME TO DETERMINE DEAERATOR STEAM AND MAKE-UP WATER REQUIREMENT

%APPENDIX 1:MATLAB PROGRAMME TO DETERMINE STEAM AND MAKE-UP WATER REQUIREMENT

% Deaerator2.m % % Title: Deaerator2.m % Created: Thursday, February 26, 2009 % Submitted by:Ememerurai,O.J Production Dept.WRPC, Ekpan %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% %DEFINITION OF VARIABLES AND CONSTANTS %WCR-Mass flow rate of condensate return stream,Ib/hr %HR-Enthalpy of condensate return stream,Btu/Ib %WS-Steam mass flow rate or steam required,Ib/hr %FWF-feed water flow rate,Ib/hr %HFW-Enthalpy of feed water,Btu/Ib %WM-Make-up water flow rate,Ib/hr %HM-Enthalpy of Make-up water,Btu/Ib %HSS-Enthalpy of steam,Btu/Ib %TM- Temperature of make-up water,oF %TSAT-Temperature of saturated steam,oF %NCR-Number of condesate return streams- %DP-Deaerator pressure,psia %PS-Steam pressure,psia %TS-Steam temperature,oF


%PROGRAM INPUT disp('Deaerator Steam and Make-up water requirement by O.J Ememerurai') DP=input('Deaerator pressure(psia)='); FWF=input('Feed water flow rate(Ib/hr)='); TM=input('Make-up water temperature(oF)='); PS=input('Steam pressure(psia)='); %Delete lines 29 to 36 for maximum make-up water(Zero condensate return) NCR=input('Number of condensate returns='); K=NCR; for I=1:K WCR(I)=input('Condensate return flow rate(Ib/hr)='); TCR(I)=input('Temperature of condensate return(oF)='); HR(I)=TCR(I)-32; end PA=DP; HM=TM-32; TSAT=-.17724*PA+(3.83986/PA)+11.48345*sqrt(PA)+31.1311*log(PA)+8.762969e-5*(PA)^2-

2.78794e-8*(PA)^3+86.594; HF=-.15115567*PA+(3.671404/PA)+11.622558*sqrt(PA)+30.832667*log(PA)+8.74117e-5*(PA)^2+(-

1.569916e-8*(PA)^3)+54.55; HS=-.14128*PA+(2.258225/PA)+3.40148*sqrt(PA)+14.438078*log(PA)+4.22624e-05*(PA)^2+(-

1.569916e-8*(PA)^3)+1100.5;


TFW=TSAT; HFW=HF; TS=1.8*exp(4.61+0.250336*(log(PS)-2.686))+32; T=TS; P=PS; T=273.15+(T-32)/1.8;P=P/14.696; c1=80870/(T^2);c2=10^c1*(-2641.62/T);c3=1.89+c2;c4=c3*(P^2/T^2);c5=2+372420/

(T^2);c6=c5*c2;c7=1.89+c6; c8=0.21878*T-(126970/T);c9=2*c8*c7-(c3/T)*126970;c10=82.546-(162460/T);c11=2*c10*c7-(c3/

T)*126460; HSS=775.596+0.000162467*T^2+20.5697*log(T)+.043557*(c7*P+0.5*c4*(c11+c3*(c10+c9*c4)))

+0.63296*T; P=14.696*P;T=(T-273.15)*1.8+32; %Delete lines 53-57 and FLO in line 58 & 59 for zero condensate return and for % zero make-up water delete HM from line 59 and line 60 SIGMA=0; FLO=0; for I=1:NCR SIGMA=SIGMA+sum(WCR(I)*HR(I)); FLO=FLO+sum(WCR(I)); WS=(FWF*(HFW-HM)-SIGMA+FLO*HM)/(HSS-HM); WM=FWF-WS-FLO; end


%The results are printed in English units fprintf('Feed water flow(Ib/hr)=%1.4e\n',FWF); fprintf('Feed water temperature(oF)=%1.4e\n',TFW); fprintf('Feed water enthalpy(Btu/Ib)=%1.4e\n',HF); fprintf('Steam pressure(psia)=%1.4e\n',PS); fprintf('Steam temperature(oF)=%1.4e\n',TS); fprintf('Steam flow(Ib/hr)=%1.4e\n',WS); fprintf('Steam enthalpy(Btu/Ib)=%1.4e\n',HSS); %Delete lines 70 to 72 for zero make-up water fprintf('Make-up water temperature(oF)=%1.4e\n',TM); fprintf('Make-up water enthalpy(Btu/Ib)=%1.4e\n',HM); fprintf('Make-up water flow(Ib/hr)=%1.4e\n',WM); %Delete lines 72 to 76 for zero condensate return for I=1:NCR fprintf('Condensate return flow(Ib/hr)=%1.4e\n',WCR(I)); fprintf('Condensate return temperature(oF)=%1.4e\n',TCR(I)); fprintf('Condensate return enthalpy(Ib/hr)=%1.4e\n',HR(I));


end %The results are printed in S.I units fprintf('Feed water flow(Kg/s)=%1.4e\n',FWF/7936.56); fprintf('Feed water temperature(oK)=%1.4e\n',((TFW-32)/1.8)+273); fprintf('Feed water enthalpy(KJ/Kg)=%1.4e\n',HF*2.326); fprintf('Steam pressure(Kpa)=%1.4e\n',PS*6.8929); fprintf('Steam temperature(oK)=%1.4e\n',((TS-32)/1.8)+273); fprintf('Steam flow(Kg/s)=%1.4e\n',WS/7936.56); fprintf('Steam enthalpy(KJ/Kg)=%1.4e\n',HSS*2.326); %Delete lines 70 to 72 for zero make-up water fprintf('Make-up water temperature(oK)=%1.4e\n',((TM-32)/1.8)+273); fprintf('Make-up water enthalpy(KJ/Kg)=%1.4e\n',HM*2.326); fprintf('Make-up water flow(Kg/s)=%1.4e\n',WM/7936.56); %Delete lines 72 to 76 for zero condensate return for I=1:NCR fprintf('Condensate return flow(Kg/s)=%1.4e\n',WCR(I)/7936.56); fprintf('Condensate return temperature(oK)=%1.4e\n',((TCR(I)-32)/1.8)+273); fprintf('Condensate return enthalpy(Kg/s)=%1.4e\n',HR(I)*2.326); end

APPENDIX 2:MATLAB PROGRAMME TO DETERMINE DEAERATOR STEAM REQUIREMENT FOR ZERO MAKEUP WATER (CASE I)

% DeaeratorZMW.m % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%% % Title: DeaeratorZMW.m % Created: Thursday, February 26, 2009 % By:Ememerurai,O.J Production Dept.,WRPC,Ekpan %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%% %THIS PROGRAM IS FOR ZERO MAKE-UP WATER FLOW (MAXIMUM CONDENSATE RETURN) %DEFINITION OF VARIABLES AND CONSTANTS %WCR-Mass flow rate of condensate return stream,Ib/hr %HR-Enthalpy of condensate return stream,Btu/Ib %WS-Steam mass flow rate or steam required,Ib/hr %FWF-feed water flow rate,Ib/hr %HFW-Enthalpy of feed water,Btu/Ib %HSS-Enthalpy of steam,Btu/Ib %TSAT-Temperature of saturated steam,oF %NCR-Number of condesate return streams- %DP-Deaerator pressure,psia %PS-Steam pressure,psia %Ts-Steam Temperature,oF


%PROGRAM INPUT disp('Deaerator Steam requirement for zero make-up water by O.J

Ememerurai') DP=input('Deaerator pressure(psia)='); FWF=input('Feed water flow rate(Ib/hr)='); TM=input('Make-up water temperature(oF)='); PS=input('Steam pressure(psia)='); NCR=input('Number of condensate returns='); K=NCR; for I=1:K WCR(I)=input('Condensate return flow rate(Ib/hr)='); TCR(I)=input('Temperature of condensate return(oF)='); HR(I)=TCR(I)-32; end


PA=DP; TSAT=-.17724*PA+(3.83986/PA)+11.48345*sqrt(PA)+31.1311*log(PA)+8.762969e-5*(PA)^2-



1.569916e-8*(PA)^3)+1100.5; TFW=TSAT; HFW=HF; TS=1.8*exp(4.61+0.250336*(log(PS)-2.686))+32; T=TS; P=PS; T=273.15+(T-32)/1.8;P=P/14.696; c1=80870/(T^2);c2=10^c1*(-2641.62/T);c3=1.89+c2;c4=c3*(P^2/T^2);c5=2+372420/


T)*126460; HSS=775.596+0.000162467*T^2+20.5697*log(T)+.043557*(c7*P+0.5*c4*(c11+c3*(c10+c9*c4)))

+0.63296*T; P=14.696*P;T=(T-273.15)*1.8+32;


SIGMA=0; FLO=0; for I=1:NCR SIGMA=SIGMA+sum(WCR(I)*HR(I)); FLO=FLO+sum(WCR(I)); WS=(FWF*HFW-SIGMA)/HSS; end %These results are printed in English Units disp('%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%'); disp('RESULTS IN ENGLISH UNITS'); fprintf('Feed water flow(Ib/hr)=%1.4e\n',FWF); fprintf('Feed water temperature(oF)=%1.4e\n',TFW); fprintf('Feed water enthalpy(Btu/Ib)=%1.4e\n',HF); fprintf('Steam pressure(psia)=%1.4e\n',PS); fprintf('Steam temperature(oF)=%1.4e\n',TS); fprintf('Steam flow(Ib/hr)=%1.4e\n',WS); fprintf('Steam enthalpy(Btu/Ib)=%1.4e\n',HSS);


for I=1:NCR fprintf('Condensate return flow(Ib/hr)=%1.4e\n',WCR(I)); fprintf('Condensate return temperature(oF)=%1.4e\n',TCR(I)); fprintf('Condensate return enthalpy(Ib/hr)=%1.4e\n',HR(I)); end % %The results are printed in S.I Units here disp('%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%'); disp('RESULTS IN S.I UNITS'); fprintf('Feed water flow(Kg/s)=%1.4e\n',FWF/7936.56); fprintf('Feed water temperature(oK)=%1.4e\n',((TFW-32)/1.8)+273); fprintf('Feed water enthalpy(KJ/Kg)=%1.4e\n',HF*2.326); fprintf('Steam pressure(Kpa)=%1.4e\n',PS*6.8929); fprintf('Steam temperature(oK)=%1.4e\n',((TS-32)/1.8)+273); fprintf('Steam flow(Kg/s)=%1.4e\n',WS/7936.56); fprintf('Steam enthalpy(KJ/Kg)=%1.4e\n',HSS*2.326); for I=1:NCR fprintf('Condensate return flow(Kg/s)=%1.4e\n',WCR(I)/7936.56); fprintf('Condensate return temperature(oK)=%1.4e\n',((TCR(I)-32)/1.8)+273); fprintf('Condensate return enthalpy(Kg/s)=%1.4e\n',HR(I)*2.326); end

APPENDIX 3:MATLAB PROGRAMME TO DETERMINE DEAERATOR STEAM REQUIREMENT FOR ZERO CONDENSATE RETURN (CASE II)

% DeaeratorZCR.m % Title: DeaeratorZCR.m % Created: Thursday, February 26, 2009 % By:Ememerurai,O.J Production Dept. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % THIS PROGRAM IS FOR ZERO CONDENSATE RETURN OR MAXIMUM MAKE-UP WATER

FLOW %DEFINITION OF VARIABLES AND CONSTANTS %WS-Steam mass flow rate or steam required,Ib/hr %FWF-feed water flow rate,Ib/hr %HFW-Enthalpy of feed water,Btu/Ib %WM-Make-up water flow rate,Ib/hr %HM-Enthalpy of Make-up water,Btu/Ib %HSS-Enthalpy of steam,Btu/Ib %TM- Temperature of make-up water,oF %TSAT-Temperature of saturated steam,oF %DP-Deaerator pressure,psia %PS-Steam pressure,psia %TS-Steam temperature,oF


%PROGRAM INPUT disp('Deaerator Steam and Make-up water requirement for zero condensate return by O.J Ememerurai') DP=input('Deaerator pressure(psia)='); FWF=input('Feed water flow rate(Ib/hr)='); TM=input('Make-up water temperature(oF)='); PS=input('Steam pressure(psia)='); PA=DP; HM=TM-32; TSAT=-.17724*PA+(3.83986/PA)+11.48345*sqrt(PA)+31.1311*log(PA)+8.762969e-5*(PA)^2-



1.569916e-8*(PA)^3)+1100.5; TFW=TSAT; HFW=HF; TS=1.8*exp(4.61+0.250336*(log(PS)-2.686))+32; T=TS; P=PS; T=273.15+(T-32)/1.8;P=P/14.696; c1=80870/(T^2);c2=10^c1*(-2641.62/T);c3=1.89+c2;c4=c3*(P^2/T^2);c5=2+372420/


T)*126460;


HSS=775.596+0.000162467*T^2+20.5697*log(T)+.043557*(c7*P+0.5*c4*(c11+c3*(c10+c9*c4)))+0.63296*T;

P=14.696*P;T=(T-273.15)*1.8+32; WS=(FWF*(HFW-HM))/(HSS-HM); WM=FWF-WS;

%These results are printed in English Units disp('%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%'); disp('RESULTS IN ENGLISH UNITS'); fprintf('Feed water flow(Ib/hr)=%1.4e\n',FWF); fprintf('Feed water temperature(oF)=%1.4e\n',TFW); fprintf('Feed water enthalpy(Btu/Ib)=%1.4e\n',HF); fprintf('Steam pressure(psia)=%1.4e\n',PS); fprintf('Steam temperature(oF)=%1.4e\n',TS); fprintf('Steam flow(Ib/hr)=%1.4e\n',WS); fprintf('Steam enthalpy(Btu/Ib)=%1.4e\n',HSS); fprintf('Make-up water temperature(oF)=%1.4e\n',TM); fprintf('Make-up water enthalpy(Btu/Ib)=%1.4e\n',HM); fprintf('Make-up water flow(Ib/hr)=%1.4e\n',WM);


%The results are printed in S.I Units here disp('%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%'); disp('RESULTS IN S.I UNITS'); fprintf('Feed water flow(Kg/s)=%1.4e\n',FWF/7936.56); fprintf('Feed water temperature(oK)=%1.4e\n',((TFW-32)/1.8)+273); fprintf('Feed water enthalpy(KJ/Kg)=%1.4e\n',HF*2.326); fprintf('Steam pressure(Kpa)=%1.4e\n',PS*6.8929); fprintf('Steam temperature(oK)=%1.4e\n',((TS-32)/1.8)+273); fprintf('Steam flow(Kg/s)=%1.4e\n',WS/7936.56); fprintf('Steam enthalpy(KJ/Kg)=%1.4e\n',HSS*2.326); fprintf('Make-up water temperature(oK)=%1.4e\n',((TM-32)/1.8)+273); fprintf('Make-up water enthalpy(KJ/Kg)=%1.4e\n',HM*2.326); fprintf('Make-up water flow(Kg/s)=%1.4e\n',WM/7936.56);

APPENDIX 4: OUTPUT OF COMPUTER PROGRAMME FOR CASE I

>> Deaerator Steam requirement for zero make-up water by O.J Ememerurai Deaerator pressure(psia)=78.25 Feed water flow rate(Ib/hr)=237644.8570 Make-up water temperature(oF)=80.6 Steam pressure(psia)=78.25 Number of condensate returns=2 Condensate return flow rate(Ib/hr)=80437.03560 Temperature of condensate return(oF)=212 Condensate return flow rate(Ib/hr)=128175.4440 Temperature of condensate return(oF)=165.2 RESULTS IN ENGLISH UNITS Feed water flow(Ib/hr)=2.3764e+005 Feed water temperature(oF)=3.1061e+002 Feed water enthalpy(Btu/Ib)=2.8054e+002 Steam pressure(psia)=7.8250e+001 Steam temperature(oF)=3.0702e+002 Steam flow(Ib/hr)=2.9742e+004


Steam enthalpy(Btu/Ib)=1.1807e+003 Condensate return flow(Ib/hr)=8.0437e+004 Condensate return temperature(oF)=2.1200e+002 Condensate return enthalpy(Ib/hr)=1.8000e+002 Condensate return flow(Ib/hr)=1.2818e+005 Condensate return temperature(oF)=1.6520e+002 Condensate return enthalpy(Ib/hr)=1.3320e+002 RESULTS IN S.I UNITS Feed water flow(Kg/s)=2.9943e+001 Feed water temperature(oK)=4.2778e+002 Feed water enthalpy(KJ/Kg)=6.5253e+002 Steam pressure(Kpa)=5.3937e+002 Steam temperature(oK)=4.2579e+002 Steam flow(Kg/s)=3.7475e+000 Steam enthalpy(KJ/Kg)=2.7463e+003


Condensate return flow(Kg/s)=1.0135e+001 Condensate return temperature(oK)=3.7300e+002 Condensate return enthalpy(Kg/s)=4.1868e+002 Condensate return flow(Kg/s)=1.6150e+001 Condensate return temperature(oK)=3.4700e+002 Condensate return enthalpy(Kg/s)=3.0982e+002 >>

APPENDIX 5: OUTPUT OF COMPUTER PROGRAMME FOR CASE II

>> Deaerator Steam and Make-up water requirement for zero condensate return by O.J Ememerurai

Deaerator pressure(psia)=78.25 Feed water flow rate(Ib/hr)=363759 Make-up water temperature(oF)=80.6 Steam pressure(psia)=78.25 RESULTS IN ENGLISH UNITS Feed water flow(Ib/hr)=3.6376e+005 Feed water temperature(oF)=3.1061e+002 Feed water enthalpy(Btu/Ib)=2.8054e+002 Steam pressure(psia)=7.8250e+001 Steam temperature(oF)=3.0702e+002 Steam flow(Ib/hr)=7.4525e+004 Steam enthalpy(Btu/Ib)=1.1807e+003 Make-up water temperature(oF)=8.0600e+001 Make-up water enthalpy(Btu/Ib)=4.8600e+001 Make-up water flow(Ib/hr)=2.8923e+005

APPENDIX 5: OUTPUT OF COMPUTER PROGRAMME FOR CASE II

RESULTS IN S.I UNITS Feed water flow(Kg/s)=4.5833e+001 Feed water temperature(oK)=4.2778e+002 Feed water enthalpy(KJ/Kg)=6.5253e+002 Steam pressure(Kpa)=5.3937e+002 Steam temperature(oK)=4.2579e+002 Steam flow(Kg/s)=9.3901e+000 Steam enthalpy(KJ/Kg)=2.7463e+003 Make-up water temperature(oK)=3.0000e+002 Make-up water enthalpy(KJ/Kg)=1.1304e+002 Make-up water flow(Kg/s)=3.6443e+001 >>

TABLE 2:COMPARISON OF CALCULATED DATA WITH DESIGN VALUES

PARAMETER Case I Design Case II Design

Steam flow,kg/s 3.75 3.66 9.39 9.14

BFW flow kg/s 45.83 29.94

DISCUSSION OF RESULTS

• From the results in Table 2 we can calculatethe relative error for the two cases.• For case I the absolute relative error in steam flow is:

((3.66-3.75)/3.66)*100=2.5%• For case II, the absolute relative error in steamflow is (( 9.14-9.39)/9.14)*100=2.74%• The absolute relative error is low for both cases and thus the main programme can be used for off-design analysis since the make-up water in an off-design situation must vary between zero and maximum.

DISCUSSION OF RESULTS

In other words, since the condensate recovery unit recovers condensate from the entire refinery complex, the make-up water requirement will depend on the efficiency of the return of condensate and will therefore vary.

CONCLUSION

The main programme can be used to calculate the amount of steam required in an off-design situation.

A low pressure drop steam control valve needs to be installed with appropriate instrumentation to measure the exact amount of steam required in the deaerator.

This will reduce the excess steam that vents to the atmosphere, thereby reducing operating costs.

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Determination of Steam and Makeup Water Requirements Of A Deaerator by EMEMERURAI O.

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Transcript of Determination of Steam and Makeup Water Requirements Of A Deaerator by EMEMERURAI O.