Sulfuric acid double contact

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M O L T O X ~ CHEMICAL AIR

SEPARATION

SYSTEM

- A PROGRESS

REPORT

Donald C.

Er1ckson

Energy

Concepts

Co.

Annapo11s, Maryland

W111iam

R.

Brown

and

Br1an

R.

Dunbobb1n

A1r

Products

and

Chem1ca1s,

Inc.

Allentown, Pennsy1van1a

Robert G.

Massey

U.S. Department of

Energy

Wash1ngton,

D.C.

ABSTRACT

A

new

low energy route to tonnage

oxygen

product1on, the O L T O X ~ system, 1s now

commenc1ng

p110t plant test1ng. The process,

1ts h1story, and potent1a1 app11cat10ns will

be

descr1bed, 1n add1t1on to recent results of the

p110t

plant

test

program. Future development

needs and plans for commerc1a11zat10n w111 be

outlined.

INTRODUCTION

More than 300,000 TI of large tonnage

cryogen1c

oxygen

plant capac1ty was bu11t 1n the

1960's

and

1970's. The two-th1rds st111

operating w111 consume about $20 b11110n (1985

) of electr1cal energy 1n the next decade. The

HOLTOX

m

chem1ca1

a1r separat10n system

1s

being developed as a cryogen1c oxygen plant

replacement wh1ch w111 use energy

at

less than

one-half of th1s

rate.

A1r separation by cryogen1c d1st111at10n was

1ntroduced

90

years

ago

by

Carl

von

L1nde

of

Germany

and cont1nues to be the choice for

tonnage

oxygen

production. Current des1gns

requ1re 25

less

energy than plants

built

in the

1960's

and

1970's. The HOLTOX chemical air

separat10n system is being developed to offer a

lower

cost

oxygen

a1ternat1ve for

new oxygen

requ1rements by revolutionary rather than

evo1ut1onary development. The process requires

up to

40

less energy use than today's

commerc1al oxygen technology. This translates

into a five to th1rty percent reduct10n in

oxygen cost. This 1ncludes both cap1tal and

energy

costs.

In

1979,

Donald C.

Er1ckson of

Energy

Concepts

Company

received the first

of

several U.s.

patents for a chemical a1r separation process

for tonnage

oxygen

product10n.(1) Th1s new

method of

produc1ng

oxygen

uses a molten m1xture

* HOlTOX

1s

a trademark of

A1r

Products

and

Chemicals Inc.

of

a1ka11

n1trates

and nitr1tes to

chem1ca11y

react w1th oxygen 1n

compressed

a1r.

Heat1ng or

depressur1zation then

releases oxygen of greater

than

99.8%

pur1ty

1n

a revers1ble react10n. The

major port10n of the energy

used

to compress or

heat the a1r 1s recovered

from

the waste

nitrogen exhaust.

With support

from

the U.S. Department

of

Energy, Mr. Er1ckson proved his concept 1n a

bench-scale unit that produced 6 liters per

m1nute

of oxygen.(2)

In

1982 Air Products

and

Chem1cals, Inc., in a cost-shar1ng,

cooperative agreement w1th the U.S. Department

of Energy, undertook the cont1nu1ng development

of the process,

now known

as the MOlTOX

oxygen

system.

Dur1ng Task

1, laboratory support

stud1es provided technical 1nformat10n on molten

nitrate/n1tr1te

chem1stry

and

on the corros10n

res1stance of mater1a1s of construct10n.(3)

In January 1985, the dec1s10n was made to

proceed

w1th

Task

2, the construct10n

and

operat10n of a 0.25 ton per

day oxygen

p110t

plant. This

$6 m11110n,

four-year project

1s

enter1ng 1ts

f1na1

year w1th commencement of

p110t plant

test1ng. The

twelve

month

p110t

plant exper1menta1 plan

first calls

for 'Proof

of

Concept' operat1onal confirmation

and

then

for acquisition of engineer1ng design data for

scale-up

and

optimization for the next

development phase.

PROCESS

DESCRIPTION

The MOLTOX system is based on the reversible

react10n of

oxygen

with

sod1um

and

potassium

nitrite

to

form nitrate.

This reaction

can

be

used

in

one

or both of

two HOLTOX

system

salt

loop types, Pressure Swing Absorption (PSA)

and

Thermal Swing

Absorpt1on (TSA). The basic

operating modes

are:

ESL-IE-86-06-78

Proceedings from the Eighth Annual Industrial Energy Technology Conference, Houston, TX, June 17-19, 1986


2/6

1. PSA - (PRESSURE SWING ABSORPTION)

1.

Pure

Pressure

Swing

- For 1ntegrat10n w1th

the pressur1zed gases

of gas turb1ne power

plants.

2.

Pure Thermal Swing - For 1ntegrat10n with

the heat recovery and

steam generation

section of

industrial

and utility

steam

boilers.

2.

TSA -

(TEMPERATURE SWING

ABSORPTI0r-N,"-)--+-_"",

3. Combined Pressure

For any application

and Thermal Swing

in wh1ch heat

and

pressure energy are

avallable.

Simplified process diagrams of the two salt

loop types are shown 1n F1gure 1. These

d1agrams show the absorber and desorber salt

flows, the gaseous a1r

and

product flows,

and

the integrat10n of the salt loop w1th external

processes. For e1ther type of MOlTOX system

I

salt

loop, dry,

C02

free a1r enters the

I

absorber

at

a temperature of

783

to

922K

(950 to

I

(950F)

1200F)

and

a pressure of 0.41 to 1.2

MPa

(60 to

I

186

ps1a)

and 1s

contacted with the molten

=

INTEGRATION

I

O

MEANS WITH

-c;;z-joABSORBER

salt.

The oxygen

reacts chem1cally w1th the

EXTERNAL

salt (N02

+

1/202

N03)

and

1s removed w1th

PROCESS

the salt from the bottom of the absorber. The

Figure 1

n1trogen

and

1nert gases, along with some

Integrated

l T X ~ System

Salt

loop

un

reacted oxygen, are

removed

from the top of

the absorber

at

essentially the same pressure

EXISTING

and

temperature as they entered. The molten

500

CRYOGENIC

salt

from

the absorber flows to the desorber

0,

PLANT(S)

where the chem1cal reaction 1s reversed

(N03

N02

+ 1/202),

and

gaseous oxygen

is

released from the salt

and

removed

as

product.

400

The reversal of the chemical reaction in the

The

salt 1s

c1rculated around th1s

TSA

loop by a

Cl

100

a:

pump

operat1ng

at

the

783K

(950F) salt

LU

temperature.

z

LU

For

the PSA salt loop, the pressure of the

o

L ~ 2 4 L . . . . . L 6 . . . J 8 1

molten salt from the absorber is reduced across

the pressure letdown valve before the salt

HEAT EXPORT (MM BTU/TN 0,

enters the desorber.

The

pressure of the

desorber is controlled by the gaseous oxygen

' - - -MOLTOX

PROCESS TYPE--

pressure through a vacuum oxygen compressor.

PRESSURE

THERM L

The salt 1s removed from the desorber by a salt.

SWING

SWING

pump and

rec1rculated

back

to the absorber

at

F1gure 2 -

Energy

Advantage for Integ ated

the necessary pressure for recontact with M O L T O X ~ Cases vs.

Cryogen1c

Plants

compressed a1r.

497

ESL-IE-86-06-78



3/6

l1mlted heat aval1abl11ty for certaln TSA

HOlTOX process app11catlons led to the

deve10pmentof p ~ o s s des1gns for

ccimblned

PSA/TSA and. TSA/PSA HOlTOX

systems/:F1gure 2

graphIcally summar1

zes

the

des19n flex1bll l tyof

these

HOllOX

systems

by

show1ng

the

total

energy

requIred per ton.of

oxygen

versus the heat

1nput/output for the var10u( desIgns. The

thermal

slo/1ng

HOllOX system ut1l1zes the

least

net energy and cogenerates steam. Th1s f1gure

also

shows that

the net energy requ1red for

HOlTOX

system

oxygen

production

1s

substant1a11y

below that for the cryogen1c process. Exlst1ng

plants

were

largely bul1t 1n the

1960

to

1973

perlod

and

requlre ln excess of

450 KW

per ton

of oxygen,

whl1e new oxygen

cryogen1c plants

can

be

deslgned for about

350 KW

per ton of

oxygen.

POTENTIAL HARKETS

Electrlc

power

ls forecast to cost 7.5t/kwh

(1985 $)

ln the U.S. ln the mld-1990 s, when the

MOLT

OX system will

be

commercialized. The

MOlTOX oxygen system ls projected to

be most

competitive

wheresignlficant

process heat

lntegration

can be

achleved. for

most

app11cations, a 30 to

40%

reduction ln

total

energy 1s anticlpated,

compared

to new

e1ectrlc

drlve cryogenlc plants. Slnce

65%

of the cost

of oxygen from cryogenic plants 1s energy

related, use of the

HOlTOX

system results 1n a

projected

12

to 23% improvement over new

cryogenIc plants. This

HOlTOX

system

oxygen

cost improvement ls shown graphically in

Figure 3.

70

60

i=

SO

0

C l

U

Z

UJ

Cl

40

x

0

30

20

2

4 6 B 10 12

ELECTRIC ENERGY COST /kwh)

Flgure 3 -

Oxygen

Cost

Comparison

$600

psia,

9 9 5 ~

Purity

(l)New

1000

T/o Plant;

. .

15 Year,

100%

Capacity,

340 o/Yr

98

Figure 3 also

shows oxygen

~ o s t s from

ex1st1ng (circa 1960/73) fUlly depreclated

cryogenlc

oxygen

plants. Replacement of

exlsting cryogenlc o x ~ g e n p1antsservlng the

steel and

chem.iea

1 1ndustries represents

one

1mportant market opportunity

..

A

good example

ls

lntegrat10n with-blast furnace off-gas boilers

at

integrated steel mi11s.(4)

Twenty

percent

of the offgas to the existlng bol1ers ls

dlverted to a

new

steam/salt

heater bol1er

at

the

HOlTOX oxygen

plant.

The

remaining 80% is

burned in the existing bol1ers, whlch

results

ln

lower stack temperature and

more

steam

generation. Thls HOlTOX plant could supply

approximately half of

an

lntegrated steel ml11 s

oxygen

requirements, whl1e reduclng the ml11 s

electrical energy consumptlon.

Emerging

new

oxygen

markets also are

candidates for

MOLTOX

process

lntegratlon.

Several applications (oxygen enrichment of coal

for furnaces and bol1ers, refinery fluidized

cat-cracker

catalyst

regenerators, sulfur

recovery plants,

and oxygen

secondary reforming)

have

sufficient

heat available to provide the

entire

energy requirements for a

HOlTOX

TSA

plant.

New

applications with very large oxygen

requirements (coal gaslficatlon for synfuels

and/or combined cycle power generation; and

coal-based direct smelting of iron) have enough

available heat to provide for a combination

HOlTOX TSA/PSA plant.

PILOT PLANT

In

January

1985

the declsion was

made

to

proceed with

Task

2, for the construction

and

operation of the

pilot

plant. The areas of

technical uncertalnty to

be

addressed

by

pl10t

plant operation include:

TSA/PSA and TSA modes of operatlon

Salt

losses (vapor, corrosion,

salt

stabllay)

Absorption/desorption kinetics

Salt

loop equipment designs

Adequacy of materials of construction

Long-term operability,

and

Gas purity, impurities,

and

by-products.

Consideration of the above objectives led to

the p110t plant depleted in the slmp11fled

process flow diagram

shown

in Flgure 4. Thls

flowsheet includes a slngle absorber, a slng1e

desorber, a

salt pump,

a

salt

cooler,

and

a

salt/salt heat exchanger. Thls equtpment ls

sufflcient

to

test

all

key

parts of the thermal

swing

HOLTOX

process.

The materials of constructlon for the pilot

plant were selected based on corroslon test

results from Task 1.(3,5) Our

estlmate of the

maximum

use temperature for

common

engineering

alloys is given below.

ESL-IE-86-06-78



4/6

Alloy

Maximum Use

Temperature

Carbon

Steel

840F

316 SS

1150F

Incoloy 800

1250F

Inconel 600

1300F

The p110t plant s1mp11f1ed flow d1agram

shows

expected operat1ng temperatures along

w1th

the recommended mater1als.

The

p110t plant w111 allow further study of

the corros1veness of the

salt. The

corros10n

w111

be mon1tored

w1th

v1sual and ultrason1c

thickness measurements of vessels and p1p1ng;

1nstallat10n of corros10n

coupon

racks and

corros10n probes; and

1nstallat10n

of

p1pe

spools of test mater1als. The mater1als

be1ng

tested are those that can w1thstand hot,

oxid1zing cond1tions

and

1nclude sta1nless

steels

and h1gh nickel alloys wh1ch have shown

good performance in ear11er bench

scale

corros10n

tests. Bulk

n1ckel alum1n1de

alloy,

developed by Oak R1dge Nat10nal Laboratory,

and

FECRALLOY steels, developed by Harwell 1n the

U.K., are both cons1dered strong cand1dates for

serv1ce

1n

the h1gher corros10n areas of the

un1t. Ceramics, such

as h1gh

dens1ty fused

alum1na and z1rcon1a,

are also

under study, as

are var10us coat1ng techn1ques. Of part1cular

interest

are alum1niz1ng, MCrA Y and N1-Al

coatings.

The p110t

plant w11l

allow

tests

under salt flow cond1t10ns that resemble

commerc1al operations. Salt

samples w111 be

taken per10d1cally to mon1tor salt chem1stry and

corrosion product accumulat10n.

The

proposed t1metable for the f1rst twelve

months

of p110t plant operat10n 1s shown

on

the

Exper1mental Plan (F1gure 5 .

Th1s

t1metable 1s

broken into three phases. Phase

A,

Proof of

Concept,

w111

demonstrate steady-state operat10n

of the absorber/desorber comb1nat10n

at

a s1ngle

cond1tion for a long per10d of

t1me

(durab111ty

run). This w11l also ver1fy the des1gn 02

production rates, product pur1t1es,

and

energy

consumpt10n; and w111 determ1ne the

rate

of

corros10n

1n

various

parts

of the

absorber/desorber system. Phase

B,

Opt1m1zat10n, w111 probe the poss1b111ty of

1mproved process economlcs at more severe

operat1ng cond1t10ns. Phase

C,

Parametr1c

Stud1es, w111 def1ne the

effects

of the major

process var1ables, 1nclud1ng absorber pressure,

desorber pressure, absorber 1nlet temperature,

and

molten salt circulat10n rate/a1r feed

rate;

and prov1de the eng1neer1ng data needed for

scaleup and des1gn of the sem1works plant.

PILOT

PLANT

RESULTS

The p110t

plant started up 1n

March 1986.

The 1nstrumentat10n and mechanical operat10n

were

checked and the Run I absorber column

hydrau11c tests

showed

that the column could

operate

successfully

at des1gn cond1t10ns

w1thout flooding the column.

Sod1um perox1de catalyst was added to t e

salt

and

the low temperature oxygen generat on

tr1als

of Run II began.

The

plant ach1eved 0.12

T/D of oxygen product10n with 99.9 02

purity. Th1s

Is

92

of the theoret1cal

(equ111brum) 02 recovery for the 1130F

desorber and 930F absorber operat1ng

temperatures.

The un1t performed well for 4 days, at ~ h c h

t1me

the

316

sta1nless

steel

centr1fugal

fa11ed due to corrosion, cav1tation or a i

comb1nat10n of these processes . A redes1gned

pump

with a

low

cavitat10n potent1al impellrr

and Inconel 600 mater1als of construct10n

WpS

ordered, and

an

exper1mental program was

developed to separate the

effects

of c a v t a ~ n

and

corros10n 1n the

pump.

This program

was

undertaken and completed 1n May 1986.

As of May 28 1986, the p110t plant

1s

undergoing a planned two week turnaround.

old salt charge

1s

being replaced

and d d t ~ o n l

corros10n spool p1eces are be1ng

1nstalled Wor

test1ng

at

actual salt flow cond1t10ns.

base case des1gn and durab11ity run will i

commence

1n

early

June.

i

DEVELOPMENT PLAN I

In

parallel

with pilot plant operation,

separate laboratory and bench-scale f

exper1mentation

will

address salt losses,

k1net1cs, a1r pur1f1cat10n, alternative salts,

and better mater1als of construction.

Pro

ess

heat

1ntegration

and optimization

will

be

addressed by further engineer1ng stud1es a ter

the Proof of Concept p110t plant operat1jn.

Results from these laboratory and eng1neer ng

studies

will

be

1ncorporated into future p ot

plant

operation plans.

The

p110t plant ha been

designed for easy modif1cat10n, so that th se

future process improvements can

be

tested

nd

confirmed.

Support

by

the

DOE

for the MOLTOX proc ss

development w111 end

after

complet10n

of the

1n1tial

twelve month p110t

plant

operation.

The next phase of development

111

requ1re construct10n

and

operat10n of a no 1nal

50 ton per

day

semi-works plant, as well a

continued p110t plant and laboratory work. Air

Products

will

seek development support fro

partners who are e1ther oxygen users or

suppliers

of oxygen us1ng technology and w 0

can

also prov1de high temperature metallurg1ca

expert1se. The areas of technical uncerta nty

to be addressed by the semi-works plant ar

plant scaleup and process heat 1ntegrat10n at

an

oxygen

us1ng host

site.

ACKNOWLEDGMENTS

The authors

would 11ke

to thank Air Pr ducts

and Chem1cals, Inc. and the U.S. Departmen of

Energy for perm1ss10n to pub11sh th1s pape

ESL-IE-86-06-78



5/6

0783

SALT

__ SEPARATOR

('200'

20

PSIAI

I I I

07 02 I

DESQRBER

T

07 80 I

r - ...L -

FLUIDIZED

SALT

1215F

SAND

HEATER

I

EPARATOR

i

I

11111111

I

11111111

11111111

I

I

I

I

t

I

tTl

i

0540

SALT SALT

EXCHANGER

10.30

05 41

SALT PUMP

SALT

COOLER

05.09

AlA 0

1

EXCHANGER

AlA

05 10

AIRIN

EXCHANGER

FIGURE 4

MOL TOX M PILOT PLANT FLOW DIAGRAM

c.w

LEGEND

CARBON STEEL

316SS

OR

304SS

INCOLOY 800H

INCONEL 600

to O

~ ~

?

....

ESL-IE-86-06-78



6/6

EXPERIMENTAL

PLAN

REFERENCES

M O L T O X ~ PILOT PLANT

1. Er1ckson. D. C.

S e p a r a ~ l g Q

of

Oxygen

rom

OVERALL

Gaseous H1xtures W1th

Mo,t@n Alka11

Met

1

SCHEDULE

OBJECTIVES

S,alj:,s" U.S. Patent 4.132.766; 2 Janu

ry

12 STEPS TO SUCCESSFUL ENERGY PROJECT K A N A G E H E N t 9 7 , ~ l t f ~ l f 6

4.2B7.170;

~ g 6 0 . 5 7 8 )

A.

~ ~ ~ r a t i o n

Anderlon. SC

.. ..

2 h . ~ r t ~ ~ n . , D . . .

'Oxygen Product1on by

he

A C O U R A 1 J h ~ r f . ~ ~ ~ A R

RESPONSE R ~ f ' t l t t - ' p r 8 e J ~ ~ . F1nal 6 ~ l t o r t

H.

~ d ~ g e

Grant

Company,

Bixlon,

T N ' O O ~ / C S / 4 0 2 8 7 ~ T 2 ' ( O t 8 j 0 1 2 8 4 7 ) ;

February

1983.

Steady state of operat1on

FUEL C L L ~ 1 t h

1100F

desorber.

Close

3. Archer.

R.

A.

and Dunbobb1n. B. R "Pllot

--mater1aland

energy balance

Plant Development of A

Chem1cal

A1r

Seuion

cwtftaat'gefl.

I i t ~ ..

Konlanto

C O l I p a n Y 6 ~ c Y

Process." F1nal Task I DOE

Report

DE-AC07-82CE40544; May

1985.

4

Months

FUEl. c ~ b S e N 8

A t S l _ ~ m C H N O L O G Y , Douglas M. Jewel,

M o r g H w k l i i t l l l M l r o ~ c J R c 1 ;

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M o r g ~ t e r J t R J t l < J 6 f ) h l ,

'8'.' 'R' 'B"r"o\on, ~ ? 7 R .

pur1tles.

and

energy Cassano.

A.

A

.

and

Massey.

R.

G

.

THE O N g ~ ' I U ' t I l . o o E f D r c e u R l a n O SYSTEM, Root

_ _

< t m n J J S ~ t e m Integrat10n for The i

John(,nOeMtlluo.iI.rtaren A.

Trimble,

Gas R e ~ r f l l t 8 l ~ t ' f l ' f e O x y g e n aniHeam." AICh

Chicago,

IL

. . . . . . . . . . o y I l 1 P 0 5 . , u 5 e f . , ~ lIugust 1985.

5 ~ 8 t t l e ,

Durab1l1ty run. Long term

P O T E N ~ A t s r t o i

,oiLeOltU. IN. REFINERIES A N D 5 C H 5 Q i ~ ~ L ~ . W

T1tcomb. J. B

.

PLANt8}acrili;Allllt".naddtlred

Roach,

Los A ~ ' f l f 1 n g e r .

H.

T

. and D ~ n P o b b 1 n .

B

,

National Laboratory, LOl Alamos,

NK

~ r r e s 4 e f t 4 f t H o ~ t e n N 1 t r a 1 ~ ~ N 1 t r 1 t eSalts"

B

Opt1m1zat1on _ Journal of Metals - July 1985.

r

PLANNING ACOMMERCIAL FUEL CELL

INSTALLATION, Ji

ie R.

J l o w ~ M . ~ c Q e f l 1 g ' 9 4 Y I i 8 h t e l N a t 1 o n ~ 1 Inc.,

San

F r a ~ ' l w ~ t t : w l . r . i 1 t ~ .

glJt1

ty

.aod..

633

energy use for

Base Case B

E N C O U w . b i R ; I i ~ t . L ) DEMONSTRATIONS

OF

FUEL CELL

APPLICATIONS,

JOleph

M.

Anderlon,

I n d u ~ t r i a l

Fuel Cell Association,

Lake

2

Months

643

1

t h a i l ~ 1 , e ' t f A , 1 . R J R r , q V . ~ < t . Q R ~ r . < i t t n

at more severe operat1ng

cond1t1ons (1250F

C O M B U S T l o W ~ C Y HEAT

RECOVERY

ho. .

&.raRleJ:f,w.l

Sess\on

~ l ~ r ~ ~ o s l ~ ~ n

A. Mozzo, Jr . Aaerican ~ t a n d a r d ,

Inc.,

pallcU'Tar * e ~ \ i h

NY

concentrat1on '

COGENERATION

AT IOWA METHODIST MEDICAL

CENTER.

Cabot

Thunem,

and Steve

Schebler,

Stanley ConsultanU, Inc., Muscatine,

IA

and Glenn Love,

Iowa

Methodist Medical Center,

Des

Moinel, IA

677

I N D U s t i p ~ e c O b E N E R A T I O N

APPLICATION, Martin

A. Mozzo, Jr .

American Standard.

Inc.,

New York.

NY .. . . . . . . . . . . . . . . . . . . . .. . . . . . . 684

x v ~ P l

ESL-IE-86-06-78


Documents

Sulfuric acid double contact