Water Management in Process Plants David Puckett Débora Campos de Faria Miguel J. Bagajewicz.

Water Management in Process Plants

David Puckett

Débora Campos de Faria

Miguel J. Bagajewicz

Sources of Refinery Wastewater

Caustic Treating

Distillation

Amine Sweetening

Merox Sweetening

Hydrotreating

Desalting

NH3 and H2S Water Contamination

Water Contamination with Organics



Water Contamination with NH3, H2S, and Organics

Saline Water Contamination

Water Management Methods

Wastewater produced in industrial processes can be handled in three fashions.

End-of-Pipe Cleanup

Reuse

Regeneration

Regeneration Methods

API separator and activated carbon to remove organics from distillation and hydrotreating wastewater.

Reverse osmosis to removesaline contamination from desalting wastewater.

Chevron wastewater treatment to remove acid gas contamination from caustic treating, sweetening, and hydrotreating wastewater.

Wastewater Optimization

Current methods of optimizing water reuse and regeneration rely on several assumptions.

Operating and capital costs are functions solely of treated water flow rate.

Fixed process outlet concentrations.


22% of the amount of contaminant removed,89% of the FCI

51% of the amount of contaminant removed,78% of the FCI

AFCI

$458000

BFCI

$408000

CFCI

$317000


Depending on the contaminants present and the treatment processes used, the assumption that regeneration costs are dependent solely on flow rate may not be valid.

The optimum solution for a water allocation problem must take into account factors other than flow rate.

Removal of Organics

Distillation

Hydrotreating

Wastewater Contaminated with Organics

API Separator and Activated

Carbon Adsorber

Wastewater Free of Organics

API Separator

Removes multi-phase contamination through differences in specific gravity.

API Separator

Appropriate for use with any contaminant that forms a distinct phase in the process water.

Oil and Light Organics

Organic and Inorganic

Sediment

API Separator Simulation

The basis of the separation is Stokes’ Law.

For a given contaminant in water, rate of settling is determined solely by contaminant particle size.

Quality of separation can be improved through flocculation and coagulation.

9

22

fp

S

grV

Buoyant Force

Gravitational Force

Drag Force

API Separator Simulation

Process water contaminant concentration does not change quality of separation.

Percentage of contaminants removed on a volume basis determined based on a normal distribution of particle radii.

dr

dr

er

erRr

Rr

r

2

2

2

2

23

0

23

min

2

134

2

134

Quality of Separation vs. Length

Volume Percent of Contaminants Removed

0

20

40

60

80

100

0 10 20 30 40 50 60

Separator Length (m)

Vo

l %

of

Co

nta

min

ants

Separator Depth = 1 mSeparator Width = 2 mEntrance to Separator at 0.5 mProcess Water Flow Rate = 1 m3 / sContaminant SG = 0.95Mean Contaminant Diameter = 0.5 mm

Quality of separation improves with increasing length, but with diminishing returns.

Quality of Separation vs. Specific Gravity


0

20

40

60

80

100

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

Contaminant SG

Vo

l %

of

Co

nta

min

ants

Separator Depth = 1 mSeparator Width = 2 mSeparator Length = 25 mEntrance to Separator at 0.5 mProcess Water Flow Rate = 1 m3 / sMean Contaminant Diameter = 0.5 mm

Separation quality is poor for contaminants similar in density to water.

Quality of Separation vs. Particle Diameter


0

20

40

60

80

100

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Contaminant Particle Diameter (mm)

Vo

l %

of

Co

nta

min

ants

Separator Depth = 1 mSeparator Width = 2 mSeparator Length = 25 mEntrance to Separator at 0.5 mProcess Water Flow Rate = 1 m3 / sContaminant SG = 0.95

Quality of separation improves with increasing particle diameter, but with diminishing returns.

Quality of Separation vs. Wastewater Velocity


0

20

40

60

80

100

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Wastewater Velocity (m/s)

Vo

l %

of

Co

nta

min

an

ts

Separator Depth = 1 mSeparator Width = 2 mSeparator Length = 25 mEntrance to Separator at 0.5 mContaminant SG = 0.95Mean Contaminant Diameter = 0.5mm

Quality of separation improves with decreasing velocity. A velocity of zero would give perfect separation.

Quality of Separation vs. Settling Distance


0

20

40

60

80

100

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Height of Separator Entrance (m)

Vo

l %

of

Co

nta

min

ants

Separator Depth = 1 mSeparator Width = 2 mSeparator Length = 25 mContaminant SG = 0.95Process Water Flow Rate = 1 m3 / s

Quality of separation improves with decreasing settling distance. Separators that handle oil will have entrance as close to water surface as possible.

Equipment Cost vs. Flow rate

Equipment Cost for API 40 Oil Removal

$2,000.00

$4,000.00

$6,000.00

$8,000.00

$10,000.00

$12,000.00

$14,000.00

0 0.2 0.4 0.6 0.8 1

Flow Rate (m3 / s)

Eq

uip

men

t C

ost

($ a

t M

&S

In

dex o

f 1000)

75% Drop in Concentration





99.5% Drop in Concentration

Separator Depth = 1 mSeparator Width = 2 mMean Particle Diameter = 1 mmProcess Water Flow Rate = 0.5 m3 / s

Equipment cost is sensitive to both flow rate and separation quality.

Operating Cost vs. Flow rate

Operating Cost for API 40 Oil Removal

$0.00

$20,000.00

$40,000.00

$60,000.00

$80,000.00

$100,000.00

$120,000.00

0 0.2 0.4 0.6 0.8 1

Flow Rate (m3 / s)

Op

era

tin

g C

ost

($ /

yr)

Separator Depth = 1 mSeparator Width = 2 mMean Particle Diameter = 1 mmProcess Water Flow Rate = 0.5 m3 / s

Operating cost is sensitive only to flow rate.

API Separator Performance

With a normal distribution of particle diameters, quality of separation can be solved analytically.

A bit impractical to implement.

API Separator Performance

Varying h

Varying L

Varying SG

Varying DpVarying F/A

The approximation is quite close for all variables. The worst fit is for changes in settling height.

API Separator Equipment Cost

Equipment cost is dependent on flow rate, quality of separation, specific gravity of contaminant, contaminant particle size, settling distance, and the price of steel.

Varying F and %QS

Varying ΔSG, Dp, h

API Separator Operating Cost

Operating cost is dependent solely on flow rate.

Activated Carbon

Removes soluble contaminants through adsorption onto the activated carbon surface.

Activated Carbon

Appropriate for use with liquid or gaseous contaminants that are water soluble or form emulsions.

Dissolved Organics

Insoluble Organics of < 150 micronsDroplet Size

Dissolved Gases

Activated Carbon Simulation

Separation will follow the Langmuir isotherm.

For the Langmuir isotherm, the rate of adsorption, assuming negligible pore holdup and spherical adsorbate particles, is as follows.

CKCKNNII

IIISI 1

rr

rrdCdNt

CDC I

I

IPP

PIPI

2

2

Activated Carbon Simulation

For a fixed bed adsorber,

process water should reach

equilibrium with activated

carbon prior to end of bed.

A constant length of bed

is required for adsorption.

Water Treatment Rate vs. Adsorbant Surface Area

Activated Carbon Adsorption

05

101520

2530

3540

200 700 1200 1700 2200

Adsorbant Surfac e Area (m2 / kg)

Max

Wat

er T

reat

ed (

m3

/ h

r)

Contaminant Diffusivity = 5 * 10 ^ -11 m2 / sLangmuir Coefficient = 0.06 m3 / kgSaturation Adsorption = 0.4 kg / kg adsorbantInlet Contaminant Concentration = 0.25 kg / m3

Greater adsorbant surface area results in faster adsorption and a faster rate of treatment.

Time in Service vs. Adsorber Diameter


0200

400600800

10001200

14001600

0 0.5 1 1.5 2

Adsorber Diameter (m)

Tim

e B

etw

een

R

egen

erati

on

s (h

rs) Contaminant Diffusivity = 5 * 10 ^ -11 m2 / s

Langmuir Coefficient = 0.06 m3 / kgSaturation Adsorption = 0.4 kg / kg adsorbantInlet Contaminant Concentration = 0.25 kg / m3

A greater diameter has more adsorbant per unit length and thus will take longer to saturate.

Time in Service vs. Adsorber Height


0

50

100

150

200

250

300

0 5 10 15 20 25

Adsorber Height (m)

Tim

e B

etw

ee

n

Re

ge

ne

rati

on

s (h

rs)


The saturation wave travels through the adsorber at a constant speed.

Outlet Concentration vs. Inlet Concentration


0

0.01

0.02

0.03

0.04

0.05

0.06

0 0.2 0.4 0.6 0.8 1

Inlet Conc entration (kg / m3)

Ou

tlet

Co

nce

ntr

atio

n (

kg

/ m

3)

Contaminant Diffusivity = 5 * 10 ^ -11 m2 / sLangmuir Coefficient = 0.06 m3 / kgSaturation Adsorption = 0.4 kg / kg adsorbant

Outlet concentration from adsorber is dictated by adsorption thermodynamics.

Equipment Cost vs. Flow Rate


$0.00

$2,000.00

$4,000.00

$6,000.00

$8,000.00

$10,000.00

$12,000.00

0 5 10 15 20 25

Flow Rate (m3 / hr)

Equ

ipm

ent

Co

sts

($)


Wastewater pump and column diameter must scale for flowrate.

Operating Costs vs. Flowrate


$0.00

$50,000.00

$100,000.00

$150,000.00

$200,000.00

$250,000.00

0 5 10 15 20 25

Flow Rate (m3 / hr)

Op

erati

ng

Co

sts

($ /

yr) Contaminant Diffusivity = 5 * 10 ^ -11 m2 / s

Langmuir Coefficient = 0.06 m3 / kgSaturation Adsorption = 0.4 kg / kg adsorbantInlet Contaminant Concentration = 0.25 kg / m3

A greater flow rate means more regenerations per year in addition to increased pumping work.

Equipment Cost vs. Inlet Concentration


$0.00

$2,000.00

$4,000.00

$6,000.00

$8,000.00

$10,000.00

0 0.2 0.4 0.6 0.8 1


Equ

ipm

ent

Co

sts

($)

Contaminant Diffusivity = 5 * 10 ^ -11 m2 / sLangmuir Coefficient = 0.06 m3 / kgSaturation Adsorption = 0.4 kg / kg adsorbantInlet Contaminant Flow Rate = 7.035 m3 / hr

No changes in the adsorber need to be made to accommodate a greater inlet concentration.

Activated Carbon Aerogel


$0.00

$50,000.00

$100,000.00

$150,000.00

$200,000.00

$250,000.00

0 0.2 0.4 0.6 0.8 1


Op

erati

ng

Co

sts

($ /

yr) Contaminant Diffusivity = 5 * 10 ^ -11 m2 / s

Langmuir Coefficient = 0.06 m3 / kgSaturation Adsorption = 0.4 kg / kg adsorbantInlet Contaminant Flow Rate = 7.035 m3 / hr

A greater inlet concentration has the same effect as a greater flow rate. More contaminant must be adsorbed necessitating more regenerations.

Activated Carbon Performance

Outlet concentration can be calculated analytically.

Activated Carbon Equipment Cost

Equipment cost is dependent on flow rate, inlet concentration, column measurements, and the prices of steel and activated carbon.

Varying F and CIN

Varying DVarying H

Activated Carbon Operating Cost

Operating cost is dependent only on flow rate and concentration.

Varying F

Varying CIN

Removal of Salts

DesaltingWastewater

Contaminated with Salts

Reverse Osmosis

Separation

Wastewater Free of Salts

Reverse Osmosis

Removes salts from process water by forcing water against the salt concentration gradient.

Reverse Osmosis

Suitable for the removal of any soluble contamination.

Soluble Salts

Soluble Organics

Microorganisms

Reverse Osmosis Simulation

Separation proceeds based on Fick’s First Law.

For reasonably dilute solutions, the van’t Hoff approximation of osmotic pressure can be used.

Quality of separation is fixed by type of membrane used.

Pz

N PWI

iMRT

Flow Rate vs. Membrane Area

Purified Water Flow Rate

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0 50 100 150 200 250 300 350 400 450 500

Membrane Area (m2)

Wat

er F

low

Rat

e (m

3/s)

Membrane Thickness = 0.002 mMembrane Permeability = 1.92 * 10-9 ((m3 m) / (m2 sec atm))Brine Pressure = 10 atmBrine Ion Concentration = 100 mol / m3

Ion Rejection Percentage = 0.99

Flow rate and membrane area are linearly related, as would be expected from Fick’s Law.

Flow Rate vs. Membrane Thickness


0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0 0.0005 0.001 0.0015 0.002

Membrane Thickness (m)

Wat

er F

low

Rat

e (m

3/s)

Membrane Area = 100 m2

Membrane Permeability = 1.92 * 10-9 ((m3 m) / (m2 sec atm))Brine Pressure = 10 atmBrine Ion Concentration = 100 mol / m3


Flow rate and membrane thickness are inversely related, as would be expected from Fick’s Law.

Flow Rate vs. Brine Pressure


-0.0004

-0.0002

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

1 3 5 7 9 11 13 15

Brine Pressure (atm)

Wat

er F

low

Rat

e (m

3/s)


Membrane Thickness = 0.002 mMembrane Permeability = 1.92 * 10-9 ((m3 m) / (m2 sec atm))Brine Ion Concentration = 100 mol / m3


Flow rate is zero when the pressure gradient is equal and opposite to the osmotic pressure gradient.

Flow Rate vs. Rejection Percentage


00.00010.00020.00030.00040.00050.00060.00070.00080.0009

0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95

Rejection Percentage

Wat

er F

low

Rat

e (m

3/s)


Membrane Thickness = 0.002 mMembrane Permeability = 1.92 * 10-9 ((m3 m) / (m2 sec atm))Brine Pressure = 10 atmBrine Ion Concentration = 100 mol / m3

A higher rejection percentage results in a larger osmotic pressure gradient.

Flow Rate vs. Brine Concentration


-0.0004

-0.0002

0

0.0002

0.0004

0.0006

0.0008

0.001

0 50 100 150 200 250 300 350 400 450 500

Brine Concentration (mol/m3)

Wat

er F

low

Rat

e (m

3/s)


Membrane Thickness = 0.002 mMembrane Permeability = 1.92 * 10-9 ((m3 m) / (m2 sec atm))Brine Pressure = 10 atmIon Rejection Percentage = 0.99

Again, flow rate is zero when the pressure gradient is equal and opposite to the osmotic pressure gradient.

Flow Rate vs. Temperature


0.000610.0006150.00062

0.0006250.00063

0.0006350.00064

0.0006450.00065

0.000655

273 278 283 288 293 298 303 308 313 318 323

Temperature (K)

Wat

er F

low

Rat

e (m

3/s)


Membrane Thickness = 0.002 mMembrane Permeability = 1.92 * 10-9 ((m3 m) / (m2 sec atm))Brine Pressure = 10 atmBrine Concentration = 100 mol/m3


The van’t Hoff approximation introduces a dependence of osmotic pressure on temperature.

Equipment Cost vs. Flow Rate at 1463 ppm Inlet

TDS = 50 mol / m3 Equipment Cost

$0.00

$500,000.00

$1,000,000.00

$1,500,000.00

$2,000,000.00

$2,500,000.00

$3,000,000.00

$3,500,000.00

$4,000,000.00

0 5 10 15 20 25 30 35

Flow Rate (m3 / hr)

Eq

uip

men

t C

ost

($ a

t M

&S

In

dex o

f 1000)

80% Rejection

96% Rejection

99.2% Rejection

99.84% Rejection

Inlet = 1463 ppm80% = 293 ppm96% = 59 ppm99.2% = 12 ppm99.84% = 2 ppm

Membrane Thickness = 0.0001 mMembrane Permeability = 9.17 * 10-10 ((m3 m) / (m2 sec atm))Brine Pressure = 10 atmBase Ion Rejection Percentage = 0.8

Equipment cost increases exponentially with process water purity as membrane rejection is fixed so membranes must be worked in series to achieve higher purity.

Equipment Cost vs. Flow Rate at 59 ppm Inlet

TDS = 2 mol / m3 Equipment Cost

$0.00

$500,000.00

$1,000,000.00

$1,500,000.00

$2,000,000.00

$2,500,000.00

$3,000,000.00

$3,500,000.00

$4,000,000.00

0 5 10 15 20 25 30 35

Flow Rate (m3 / hr)

Eq

uip

men

t C

ost

($ a

t M

&S

In

dex o

f 1000)

80% Rejection

96% Rejection

99.2% Rejection

99.84% Rejection

Inlet = 59 ppm80% = 12 ppm96% = 2 ppm99.2% = 0.5 ppm99.84% = 0.09 ppm


Equipment costs are dependent on the relative inlet/outlet concentrations, not the absolute concentrations.

Operating Cost vs. Flow Rate at 1463 ppm Inlet

TDS = 50 mol / m3 Operating Cost

$0.00

$200,000.00

$400,000.00

$600,000.00

$800,000.00

$1,000,000.00

$1,200,000.00

$1,400,000.00

$1,600,000.00

0 5 10 15 20 25 30 35

Flow Rate (m3 / hr)

Op

erati

ng

Co

st

($ a

t M

&S

In

dex o

f 1000)

80% Rejection

96% Rejection

99.2% Rejection

99.84% Rejection

Inlet = 1463 ppm80% = 293 ppm96% = 59 ppm99.2% = 12 ppm99.84% = 2 ppm


The same trends as observed in equipment costs are observed in operating costs.

Operating Cost vs. Flow Rate at 59 ppm Inlet

TDS = 2 mol / m3 Operating Cost

$0.00

$200,000.00

$400,000.00

$600,000.00

$800,000.00

$1,000,000.00

$1,200,000.00

$1,400,000.00

$1,600,000.00

0 5 10 15 20 25 30 35

Flow Rate (m3 / hr)

Op

erati

ng

Co

st

($ a

t M

&S

In

dex o

f 1000)

80% Rejection

96% Rejection

99.2% Rejection

99.84% Rejection

Inlet = 59 ppm80% = 12 ppm96% = 2 ppm99.2% = 0.5 ppm99.84% = 0.09 ppm


The same trends as observed in equipment costs are observed in operating costs.

Reverse Osmosis Performance

Outlet concentration defined by membrane properties.

Reverse Osmosis Flow Rate

Reverse Osmosis Equipment Cost

Varying F and CIN

Equipment costs are dependent on flow rate, brine concentration, and membrane cost for single membrane. Cost scales based on bypass ratio and number of membranes in series for a series of membranes.

Reverse Osmosis Operating Cost

Varying F

Operating costs are dependent solely on flow rate. Cost scales based on bypass ratio and number of membranes in series for a series of membranes.

Removal of H2S and NH3

Wastewater Contaminated with H2S and

NH3

Chevron Wastewater Treatment

Wastewater Free of H2S and NH3

Caustic Treating

Amine Sweetening

Merox Sweetening

Hydrotreating


Removes dissolved gases from wastewater through stripping and absorption.

Chevron Waste Water Treatment PFD

Ammonia Stripper

Partial Condenser

Ammonia Stream

Water feed

Hydrogen Sulfide Stripper

Hydrogen Sulfide Stream

Partial Reboiler Partial Reboiler

Stripped water


Suitable for the removal of any suitably volatile contaminant.

Hydrogen Sulfide

Ammonia

Chevron Wastewater Treatment Simulation

Hydrogen Sulfide - Water Stripping

0

0.2

0.4

0.6

0.8

1

0 0.01 0.02 0.03 0.04 0.05 0.06

Liquid Mole Fraction Hydrogen Sulfide

Vap

or

Mo

le F

ract

ion

H

ydro

gen

Su

lfid

e

m=L/Gb=Yo-XI(L/G)

Equilibrium Line

McCabe-Thiele Method can be used.

Quality of Stripping vs. Reboil Ratio

H2S Stripping

0.0070.00720.00740.00760.0078

0.0080.00820.00840.00860.0088

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Reboil Ratio

Proc

esse

d W

ater

H2S

%

Inlet H2S Concentration = 1000 mol/m3Tray # = 6Outlet Gas = 50% H2S

Superior quality of separation achieved with less of the wastewater boiled.

Quality of Stripping vs. Number of Trays

H2S Stripping

0

0.005

0.01

0.015

0.02

1 3 5 7 9 11

Tray Number

Pro

cess

ed W

ater

H2S

%

Inlet H2S Concentration = 1000 mol/m3Outlet Gas = 50% H2SReboil Ratio = 0.6

Superior separation achieved at greater number of trays, though diminishing returns are noted.

Quality of Stripping vs. Inlet Concentration

H2S Stripping

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.01 0.02 0.03 0.04 0.05 0.06 0.07

Inlet Water H2S %

Pro

cess

ed W

ater

H2S

%

Inlet H2S Concentration = 1000 mol/m3Outlet Gas = 50% H2SReboil Ratio = 0.6Tray # = 6

An increase in inlet concentration will always increase the outlet concentration if all other factors remain constant.


H2S Stripping

$0.00

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

0 10 20 30 40

Flow Rate (m3 / hr)

Equi

pmen

t Cos

t ($)

Inlet Concentration = 0.0146





Outlet Gas = 50% H2SReboil Ratio = 0.6Tray # = 6

Equipment costs increase in stepped fashion based on need for additional tray to maintain specified outlet concentrations.

Operating Cost vs. Flow Rate

H2S Stripping

$0.00$1,000,000.00$2,000,000.00$3,000,000.00$4,000,000.00$5,000,000.00$6,000,000.00$7,000,000.00$8,000,000.00$9,000,000.00

0 10 20 30 40

Flow Rate (m3 / hr )

Ope

ratin

g Co

st ($

)






Outlet Gas = 50% H2SReboil Ratio = 0.6Tray # = 6

Operating costs insensitive to inlet concentration as primary operating costs is heating of large amounts of water.


H2S Stripping

$0.00

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

$35,000.00

0 10 20 30 40


Equi

pmen

t Cos

t ($)

Outlet Concentration = 0.012






Same trends as observed with varied inlet concentrations.


H2S Stripping

$0.00$1,000,000.00$2,000,000.00$3,000,000.00$4,000,000.00$5,000,000.00$6,000,000.00$7,000,000.00$8,000,000.00$9,000,000.00

0 10 20 30 40


Ope

ratin

g Co

st ($

/ y

r)







Same trends as observed with varied inlet concentrations.

Chevron Wastewater Treatment Simulation

Ammonia - Water Distillation

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

Liquid Mole Fraction Ammonia

Vap

or

Mo

le F

ract

ion

A

mm

on

ia

m=Reflux Ratio

(YI,YI)

McCabe-Thiele Method can be used.

Distillation Quality vs. Number of Trays

NH3 Distillation

0

0.005

0.01

0.015

0.02

1 3 5 7 9 11

Tray Number

Pro

cess

ed W

ater

NH

3 % Inlet NH3 Concentration = 1000 mol/m3

Outlet Gas = 98% NH3Reboil Ratio = 0.6Reflux Ratio = 0.6

Same trends as observed with stripping column.

Distillation Quality vs. Reboil Ratio

NH3 Distillation

0

0.001

0.002

0.003

0.004

0.005

0.006

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Reboil Ratio

Pro

cess

ed W

ater

NH

3 %

Inlet NH3 Concentration = 1000 mol/m3Outlet Gas = 98% NH3Reflux Ratio = 0.6Stripping Tray # = 6


Distillation Quality vs. Reflux Ratio

NH3 Distillation

0

0.005

0.01

0.015

0.02

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Refl ux Ratio

Pro

cess

ed W

ater

NH

3 %

Inlet NH3 Concentration = 1000 mol/m3Outlet Gas = 98% NH3Reboil Ratio = 0.6Stripping Tray # = 6

Increasing reflux ratio will improve the quality of the separation. Note the break in the graph at the minimum reflux ratio.


NH3 Distillation

$0.00

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

0 10 20 30 40


Equi

pmen

t Cos

t ($)






Outlet Gas = 98% NH3Reboil Ratio = 0.6Reflux Ratio = 0.6Stripping Tray # = 6



NH3 Distillation

$0.00$1,000,000.00$2,000,000.00$3,000,000.00$4,000,000.00$5,000,000.00$6,000,000.00$7,000,000.00$8,000,000.00$9,000,000.00

0 10 20 30 40

Flow Rate (m3 / hr)

Ope

ratin

g Co

st ($

)






Outlet Gas = 98% NH3Reboil Ratio = 0.6Reflux Ratio = 0.6Stripping Tray # = 6



NH3 Distillation

$0.00$5,000.00

$10,000.00$15,000.00$20,000.00

$25,000.00$30,000.00

$35,000.00$40,000.00

0 10 20 30 40

Flow Rate (m3 / hr)

Equi

pmen

t Cos

t ($)

Outlet Concentration =0.00982





Inlet NH3 Concentration = 1000 mol / m3Outlet Gas = 98% NH3Reboil Ratio = 0.6Reflux Ratio = 0.6



NH3 Distillation

$0.00

$2,000,000.00

$4,000,000.00

$6,000,000.00

$8,000,000.00

$10,000,000.00

0 10 20 30 40


Oper

ating

Cos

t ($

/ yr)






Inlet NH3 Concentration = 1000 mol / m3Outlet Gas = 98% NH3Reboil Ratio = 0.6Reflux Ratio = 0.6


Performance of Chevron Wastewater Treatment

H2S Removal

NH3 Removal

Chevron Wastewater Treatment Equipment Costs

Varying F

Varying Tray Number

Varying D

Equipment costs strongly dependent on number of trays, column diameter, and the price of stainless steel.

Chevron Wastewater Treatment Operating Costs

For both the stripping and the distillation columns, operating costs follow the below relation.

Conclusions

Capital costs for API separators are heavily dependent on inlet/outlet concentration ratio. Operating costs for API separators are independent of concentration.

Capital costs for activated carbon adsorption are independent of concentration. Operating costs for activated carbon adsorption are heavily dependent on concentration.

Conclusions

Both capital costs and operating costs for reverse osmosis are heavily dependent on inlet/outlet concentration ratio.

Capital costs for Chevron Wastewater Treatment are dependent on concentration. Operating costs for Chevron Wastewater Treatment are nearly independent of concentration.

Water Management

Questions?

Water Management in Process Plants David Puckett Débora Campos de Faria Miguel J. Bagajewicz.

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