Mitsubishi Centrifugal Compressors and Steam Turbines for Mega Ethylene Plants HIROAKI OHSAKI* 1
KEI HASHIZUME* 1
EIJI HIRAISHI* 1
SUMIO NODA* 1 JYOU MASUTANI* 2
C om om p r e s s or or s f or or e t h y l en en e p l a n t s a r e t h e l e a d i n g m a c h i n e s of of t h e T u r b o m a c h i n e r y & G e n e r a l M a c h i n e r y D e p a r t - m e n t o f M i t s u b i s h i H e a v y I n d u s t r i e s , L t d . ( MH MH I ) . I n r e c en en t y e a r s , t h e s i z e of of e t h y l e n e p l a n t s h a s b e e n i n c r e a s i n g a n d , f ol o l l ow ow i n g t h i s t r e n d , t h e s i z e of of co co m p r e s s o r s a n d s t e a m t u r b i n e s h a s i n c r e a s e d p r o p or o r t i on on a l l y. y. T h i s r e p o r t i n t r o d u ce ce s s o m e e x a m p l e s o f t h e a p p l i ca ca t i on on o f h i g h l y e ff ff ic ic ie ie n t l a r g e - s i ze ze d c e n t r i f u g a l c om om p r e s s o r s a n d s t e a m t u r - b i n e s t h a t h a v e b e e n i n s t a l l e d in in e t h y l e n e p l a n t s , a n d t h e t e c h n o l og og i es e s a p p l i e d t o i n cr c r e a s e t h e e f fi f i ci ci e n c ie ie s a n d reliabilities of of these lar gege-sized sized machines. A proposal proposal is th en presen ted r egardin g a tr ain configura configura tion of very large- s i z ed ed c en en t r i f u g a l co co m p r e s s or or s a n d s t e a m t u r b i n e s .
ability of large-sized compr compr essors. Th is is followed followed by an
1 . I n t r o d u c t i on on
overview of some examp les of of co compr mpr essor an d stea m tu r-
In r ec ecent ent years, ethylene producers producers h ave been increas-
b i n e t r a i n c o n fi fi g u r a t i o n s , i n w h i c h t h e s e t e c h n o l og og i e s
i n g t h e s i z e o f t h e i r p l a n t s i n o r d e r t o r e d u c e t h e c os os t s
a r e a p p l i e d fo fo r m e g a e t h y l e n e p l a n t s , t h e m a r k e t f o r
associated assoc iated with th em. As As a result, th e size of of such plants
w h i ch ch i s e x p e ct ct e d t o e x p a n d i n t h e f u t u r e .
ha s ten ded to increase ra pidly from from one million million tons/year
2 . T r a n s i t i o n o f c om om p r e s s o r s f or or e t h y l e n e p l a n t s
c la la s s ( w h i c h h a s b e e n t h e m a x i m u m s i z e of of e t h y l e n e p l a n t s u n t i l n o w ) t o 1 .5 .5 m i l l io io n t o n s / y e a r a n d e v e n a s
F i g . 1 s h o w s t h e t r a n s i t i on on i n t h e s i z e of of e t h y l e n e
h i g h a s t w o m i ll ll i on on t o n s / ye ye a r c la la s s . W i t h t h i s i n c r e a s e
plants and the MHI compressor models that were
i n s i z e, e, t h e r e h a s b e e n a n e v e r -g -g r e a t e r d e m a n d f or or a n
adopted in th ese plants. The size of ethylene plants h as
increase in effic efficiency iency of th e compr compr essors an d stea m tu r-
been increasing in size size year by year, year, with with th e result th at
bines, tha n in th e past. In th is report, report, we intr intr oduc oducee some some
t h e c o m p r e s s or or m o d e l s u s e d i n t h e s e p l a n t s h a v e a l s o
e x a m p l e s of of t h e M H I c om om p r e s s o r s a n d s t e a m t u r b i n e s
been increasing in capacity. In addition, as can be seen
f o r e t h y l e n e p l a n t s , s h o wi w i n g M H I ' s s i g n i fi fi ca ca n t t r a c k
in F i g . 22,, t h e a m o u n t o f s t e a m s u p p l ie ie d t o t h e s t e a m
record, reco rd, while describing describing t he t ra nsition of th e size of of eth-
tu rbines increases st eadily in in low-pressu low-pressu re su pply lines, lines,
y l e n e p l a n t s . A b r i e f d e s c r i p t i on on i s a l s o g i v e n o f t h e
but ten ds to increase dram at ic ically ally in high-pressu high-pressu re sup-
technologies technolo gies adopted to increase th e effic efficiency iency and reli-
ply lines. lines. The The graph indic indicates ates t hat there is a r equirement
n o i t c u d ) o r r p a e y e / n s e l n o y t h t 3 e 0 f 1 x o ( e m u l o V
2000
1500
: Size of plant : High-pressure steam consumption : Low-pressure steam consumption
) r a e y / s 1500 n o t
Tendency towards rapid increase : Experience : Inquiry
800 600
3
0 1 1000 x ( t n a l p f 500 o e z i S 0
1000
500
0 85
90
95
00
05
400 200
92
94
96
98
00
02
04
0
) r u o h / s n o t ( n o i t p m u s n o c m a e t S
Year
Year of delivery Fig. 1 Trend in size of ethylene plants Plant size tends to increase year by year.
Fig. 2 Trend in steam conditions in ethylene plants The amount of steam in low-pressu low-pressure re supply lines increases smoothly, whereas pressure in high-pressure supply lines tends to increase dramatically.
Mitsubishi Heavy Industries, Ltd. Technical Review Vol. Vol. 41 No. 3 (Ju n. 2004)
*1 Hiroshima Machinery Works *2 Takasago Research & Development Center, Technical Technical Headquarters
1
to develop a lar ge steam inta ke. As shown in F ig . 3 , t h e
(1) Reduction in constr uction costs by saving spa ce
efficiency of th e compr essors h as a lso been increa sing in
(2 ) Re d u c t i on i n t h e n u m b e r o f s p a r e p a r t s r e q u i r e d
k e e p i n g w it h t h e i n cr e a s e i n t h e s i ze o f t h e p l a n t s . I n
(3) Impr ovemen t of ma inta inability
1986, MHI im pr oved compr essor efficiency by 5% by ap-
An o t h e r a d v a n t a g e is t h a t M H I c a n s u p p l y b ot h t h e
plying a highly efficient three-dimensional impeller in
c om p r e s s o r s a n d s t e a m t u r b i n e s o f t h e s a m e c l a s s w i t h -
th e compressors. To improve efficiency even fur th er, MHI
o u t t h e s u p p o r t o f o t h e r c om p a n i e s . In g e n e r a l , t h e
actively continues to engage in research and develop-
centr ifuga l compressor is sa id to be limited to ethylen e
ment.
plant s of th e 1.4 million t ons/year class. In order to sup-
F i g . 4 s h o w s a s c h e m a t i c of M H I ' s l a r g e s t c l a s s o f
p l y h i g h l y e ff ic ie n t a n d h i g h l y r e l i a b l e ce n t r i f u g a l
c h a r g e g a s c e n t r i fu g a l c om p r e s s o r s a n d s t e a m t u r b i n e s
compr essors t o lar ger plan ts, however, MHI is develop-
fo r e t h y l e n e p l a n t s . T h e t r a i n c on f ig u r a t i on fo r t h e s e
ing and verifying various technologies that ar e required
m a c h i n e s c on s i s t s o f a s t e a m t u r b i n e + a n i n t e r m e d i a t e -
for very lar ge-sized compr essors.
pressure compressor + a low-pressure compressor + a
3. Technologies for increa sing th e capa city, efficiency, an d reliability of lar ge-sized cent rifugal compr essors
high-pressur e compressor. The low-pressu re compr essor is a double flow type, while the int ermed iate- and highp r e s s u r e c om p r e s s o r s a r e a b a c k t o b a c k t y p e . I n o r d e r
3.1 Developmen t of highly efficient im pellers
to reduce the weight, the low-pressure and intermedi-
As plant s ha ve increas ed in size, th e efficiency of cen-
(1)
at e-pressur e compressors use a fabricated casing , a n d
t r i f u g a l c om p r e s s o r s h a s c om e t o h a v e a n e v e r -g r e a t e r
t h e h i gh - p r e s s u r e c om p r e s s o r u s e s a c a s t s t e e l c a s i n g
a f fe c t o n t h e r u n n i n g c o s t s o f a p l a n t . T h e m o s t i m p o r -
w i t h a h i g h d e s i g n p r e s s u r e . I n g e n e r a l , a o n e m i l li on
t a n t f a ct o r i n i n c r e a s i n g t h e e ff ic ie n c y of a c e n t r i fu g a l
tons/year class char ge gas tra in is formed us ing four com-
compr essor is th e impe ller. To achieve h igh efficiency,
p r e s s or s . M H I c a n c on f ig u r e t h e c h a r g e g a s t r a i n s u p t o
M H I ' s c om p r e s s o r a d o p t s a t h r e e -d i m e n s i on a l i m p e l le r
a 1.5 million tons/year class with th ree compr essor cas-
a t a l l s t a g e s . F u r t h e r , i n or d e r t o ob t a i n t h e m a x i m u m
ings. The following advantages can be obtained by
l e v e l of p e r f or m a n c e u n d e r a w i d e r a n g e o f g a s c o n d i -
reducing the number of compressors.
t i on s a n d o p e r a t i n g c on d i t i on s , M H I h a s d e s i g n e d a s e t of high efficiency imp ellers (2 ). To a c co m m o d a t e t h e r e c en t t r e n d t o wa r d s l a r g e r s i z ed e t h y l e n e p l a n t s , M H I
Efficiency of high-efficiency centrifugal compressor (2nd generation)
) 90 % ( y c n e i c i f f e c i p o r 80 t y l o P
h a s a l r e a d y c o m p l e t e d d e v e l o p m e n t o f n e w l a r g e f lo w, h i g h e f fi ci e n c y im p e l l e r s t h a t c a n b e a p p l i e d t o l a r g e s i z e d c om p r e s s o r s . F i g . 5 s h o ws o n e e x a m p l e o f a n
Improvement of 2%
impeller th at is capable of coping with large flows. This new impeller ha s th e following cha ra cteristics.
Efficiency of conventional machine
Improvement of 5%
(1) High efficiency The h igh efficiency impeller h as been developed u sing CFD (Fig. 6), an d polytr opic efficiency is incre as ed Fig. 6 by 2%. Fig. F i g . 7 s h o w s t h e r e s u l t s o f p er f or m a n c e t e s t s
Second oil shock 70
80
90
on t h e s y s t e m .
00
Year Fig. 3 Trend in efficiencies of compressors in ethylene plants As ethylene plants grow in size, the efficiency of the compressor used in such plants has also been on the rise. This indicates that further improvement in efficiency is necessary.
Steam turbine
Intermediate-pressure compressor
Low-pressure compressor
High-pressure compressor
Fig. 4 Configuration of compressor and steam turbine for mega ethylene plants MHI's maximum class centrifugal compressor and steam turbine for ethylene plants are introduced.
Fig. 5 Large flow impeller This photo of an impeller capable of coping with large flow rates shows that the impeller has a wide suction flow passage and a shape that is nearly cylindrical in form.
Mitsubishi Heavy Industries, Ltd. Technical Review Vol. 41 No. 3 (Ju n. 2004)
2
X Z
: Newly developed impeller : Conventional impeller
Y
y c n e i c i f f e c i p o r t y l o P
Diffuser Diffuser
Increased by 2%
Y
Flow coefficient
ZX Impeller
Fig. 7 Comparison of impeller efficiency The efficiency of impellers has increased by 2% compared with that of conventional systems.
Impeller
Fig. 6 Analysis of impeller CFD A highly efficient impeller has been developed using CFD in order to realize a high performance impeller.
Control valve
Extraction steam control valve
Compressor casing
Casing
Steam inlet
Fig. 8 Design of casing using FEM In order to cope effectively with the increase in size, highly reliable design is carried out using FEM analysis.
Extraction mouth Fig. 9 Steady temperature distribution of high-pressure casing
(2) High pressure coefficient To co p e w it h a n i n c r e a s e i n l a r g e f l ow d u e t o t h e
t u r e , wh e n d e s i g n i n g t h e t u r b i n e s u s e d fo r m e g a e t h y l -
i n c r e a s e d s i z e of p la n t s , M H I h a s d e v e l o p e d h i g h l y
e n e p l a n t s , e f fe c t i ve s o l u t i o n s n e e d t o b e f ou n d f or t h e
efficient impellers with a high pressure ratio.
following techn ical a rea s:
(3) High boss rat io
( 1) l a r g e c a p a c i t y a n d h i g h - p r e s s u r e / h i g h - t e m p e r a t u r e
I n o r d e r t o r e d u c e s h a f t v i b r a t i on , w h i c h c a u s e s
casings;
problems with large rotat ing bodies, the impeller shaft
( 2 ) l a r g e c a p a c it y a n d h i g h - lo a d s p e e d c o n t r o l s t a g e
d i a m e t e r i s i n c r e a s e d b y 5 t o 1 0 % ( h i gh b o s s r a t i o) .
blades; and
This resu lts in th e realization of a h ighly rigid rotor.
( 3 ) h i g h l o a d a n d h i g h c e n t r i fu g a l fo r c e , l ow p r e s s u r e
(4) Improvement of manufacturing method
stage blades.
To achieve predicted per form an ce by prevent ing de-
M H I h a s s o lv e d t h e s e p r o b le m s a s s u m m a r i z e d
form at ion du e to welding, the n um ber of weld points
below. 4.1 Developmen t of large capacity an d high-pressu re/
f or t h e i m p e l le r i s r e d u c e d , a n d t h e m a n u f a ct u r i n g
high-temperature casings
accuracy is increased. Development of this impeller m a k e s i t p o s s ib l e t o p r o v id e c om p r e s s o r s w i t h s u p e -
I n o r d e r t o p r e v en t a b n o r m a l s t r a i n a n d d e fo r m a -
rior performa nce an d high reliability.
t i on c a u s e d b y t r a n s i e n t t e m p e r a t u r e d i s t r i b u t i on s
3.2 Design of lar lar ge-sized compr compress essor or casin casings gs large-sized
w h e n t h e t u r b i n e i s s t a r t e d a n d s t op p e d or t h e l o a d
The increa se in size of compr essors a lso resu lts in a
v a r i es d u e t o h i g h p r e s s u r e a n d h i gh t e m p e r a t u r e
d e m a n d f or m o r e a d v a n c e d t e c h n o l og i e s fo r t h e d e s i g n
s t e a m , a n o zz l e b ox s t r u c t u r e i s a d o p t e d . I n a d d i t i o n , a
of compr essor casin gs. In order t o impr ove th e reliabil-
stress deformation analysis was performed using a
ity of th e compr essor casing, MHI ha s carefully exam ined
three-dimensional solid model for verification in order
increases in weight , the effects of th erm al expan sion, an d
t o e va l u a t e t h e s t r u ct u r e a f t e r p l a n n i n g a n d d e s i g n , a s
deformations due to inter na l pressure using FE M analy-
s h o w n i n F ig . 9 .
s i s t e ch n i q u e s a t t h e d e s i gn s t a g e , a s s h o w n i n Fig. 8 8.
In evalua ting th e leakage of stea m from th e horizontal joint surface which may occur under conditions of
4 . H i g h e f fi ci e n c y s t e a m t u r b i n e s f o r m e g a e t h y l e n e plants
high-pressur e/high-tempera tu re an d large capacity, bolt m a t e r i a l s w it h s m a l l r e l a x a t i on a g a i n s t b o lt t i g h t e n i n g
In order t o ta ckle th e problem of scaling up th e present
f or c e a r e u s e d , a n d a t h e r m a l s h i e l d is a l s o a d o p t e d i n
d e s i gn c o n ce p t a n d e x p a n d i n g t h e p r e s e n t d e s i g n s t r u c -
or d e r t o e a s e t h e a b r u p t t e m p e r a t u r e g r a d i en t . Mitsubishi Heavy Industries, Ltd. Technical Review Vol. 41 No. 3 (J un . 2004)
3
High-pressure compressor
Speed control stage blade
Low-pressure stage blade
Low-pressure compressor Intermediate-pressure compressor
Steam turbine Z Y X Fig. 10 Three-dimensional solid model of speed control stage blade
Fig. 11 Three-dimensional solid model of lowpressure stage blade
Fig. 12 View of large compressor and steam turbine under string test
4.2 Developmen t of large capa city and h igh load sp eed c on t r o l s t a g e b l a d e s
cascade using a th ree-dimensional solid m odel, as sh own
To m e e t t h e r e q u i r e m e n t s o f l a r g e c a p a c it y a n d h i g h
An a n a l y s i s of s t a t i c s t r e s s w a s p e r f or m e d u n d e r
load, Integral Shrouded Blade (ISB) type speed control
mu ltipoint bounda ry condit ions for each blad e. An ana ly-
sta ge blades are a dopted to increase reliability. In order
sis of vibration characteristics and stress was also
to design t hese blades in det ail, as shown in F ig . 10 10, vari-
c on d u c t e d u s i n g t h e C y cl i c s y m m e t r y m e t h o d . I t w a s
ous effects and design factors were verified using FEM
confirmed t ha t st resses at all sections sa tisfy the r equire-
a n a l y s i s , a n d r o t or s t a b i li t y t e s t s , ca s c a d e t e s t s , a n d
ments specified in the design criteria.
1. in Fig. 1 11
r u n n i n g t e s t s w i t h a i r w e r e a l s o co n d u c t e d .
By trial-ma nu factur e of actua l blades an d a rotor sta-
Adoption of the ISB blades confirmed that the fre-
bility test, it was also verified that the trial-
q u e n c y of t h e m i n i m u m m o d e w a s e l im i n a t e d , a n d t h e
m a n u f a ct u r e d b la d e g r ou p h a d t h e s t a t i c a n d v i b r a t i n g
reliability of th e speed cont rol stage blades wa s increased
c h a r a c t e r i s t i cs o b t a i n e d i n t h e a b o ve a n a l y s e s .
t o a l e v e l g r e a t e r t h a n t h a t o f c on v e n t i o n a l s h r o u d e d
5 . Te s t e q u i p m e n t
blades. 4.3 Development of high load and high centrifugal
As can be seen in Fig. 12 12, MHI already has test equip-
force low press ur e blocks
m e n t c a p a b l e o f p e r f or m i n g s t r i n g t e s t s f o r v a r i o u s
It wa s essen tial to develop a variable speed, low-pres-
combinat ions of compressors an d stea m t urbines for eth -
sure block capable of withstanding high loads and high
ylene plan ts of th e 1.5 million tons/year clas s. To su pply
c en t r i fu g a l f or c e s t h a t w e r e n o t s e e n i n t h e p a s t .
highly reliable products, performance can be verified
Firs t, the specifications of th e blades were deter mined
before delivery by carrying out a str ing test a nd per for-
u s i n g o n e - d im e n s i o n a l r o w - b y- r ow c a l cu l a t i o n a n d
mance test.
axisymmetrical flow pattern analysis, while the basic
For eth ylene pla nts of the two million tons/year class,
b l a d e s h a p e w a s d e t e r m i n e d b y e xa m i n i n g t h e s t r e n g t h
d e m a n d f or w h i c h i s e x p e ct e d t o i n cr e a s e i n t h e f u t u r e ,
o f t h e r e s u l t i n g s y s t e m u s i n g s h e l l m o d el s . T h e n , a d e -
MHI is planning to const ruct new t est equipment , lar ger
t a i l e d e v a l u a t i on o f s t r e n g t h w a s p e r fo r m e d f or t h e
t h a n a n y e x is t i n g t e s t s t a n d . On c e t h i s n e w t e s t s t a n d i s
Low-pressure compressor
Intermediate-pressure compressor
Steam turbine
High pressure compressor No. 1 High pressure compressor No. 2
Fig. 13 Train configuration of very large-sized charge gas centrifugal compressor and steam turbine This figure shows an example of a very large train in the future. MHI has been examining such systems in great detail and has been preparing basic plans for these systems.
Mitsubishi Heavy Industries, Ltd. Technical Review Vol. 41 No. 3 (Ju n. 2004)
4
completed, it will become possible to carry out str ing test s
7. Conclusion
of very large-sized compressors and turbines, and the r e l i a b i l it y of t h e co m p r e s s o r s a n d s t e a m t u r b i n e s a s a
M H I h a s s u p p l i e d m a n y h i g h e f fi ci e n c y la r g e -s i z e d
train can be assured.
c om p r e s s o r s a n d s t e a m t u r b i n e s t h a t a r e h i g h l y s u i t e d fo r e t h y l e n e p l a n t s . As p l a n t s h a v e i n c r e a s e d i n s i z e ,
6 . T r a i n ccoonnffii g u r a t i o n of c om p r e s s o r s a n d s t e a m t u r bines for t wo million t ons/year class eth ylene plant s
t h e s e m a c h i n e s h a v e a l s o be com e l a r g e r y e a r b y y ea r t o accommodate th e dema nds of the larger plant s. Already,
An example of a very lar ge-sized charge gas centrifu-
t h e s e l a r g e - s iz e d com p r e s s o r s a n d s t e a m t u r b i n e s h a v e
13 g a l co m p r e s s o r a n d s t e a m t u r b i n e i s s h ow n i n Fig. Fig. 1 3.
built a n impr essive tra ck record for high efficiency and
The t ra in configura tion consist s of a low-press ur e com-
quality. MHI h as completed t he d evelopment of th e com-
pressor + an interm ediate-pressur e compressor + a st eam
ponent techn ologies for et hylene pla nt s of th e two million
turbine + a No. 1 high-pressure compressor + a No. 2
tons/year class. The deman d for su ch plant s is expected
high-pressur e compres sor. The low-pressu re, inter medi-
t o i n c r e a s e i n t h e f u t u r e . As a r e s u l t , v e r y l a r g e - s i z e d
a t e -p r e s s u r e , a n d N o . 1 h i g h - p r e s s u r e co m p r e s s o r s u s e
compressors an d steam tur bines can be applied to a grow-
welded steel plate casings, while a cast st eel casing h av-
ing num ber of ethylene plants.
i n g a h i gh d e s i gn p r e s s u r e , i s a d op t e d f or t h e N o . 2
A n ot a b l e a d v a n t a g e o f M H I i s t h a t b ot h c en t r i fu g a l
high-pressur e compressor. The stea m t urbine is inst alled
c om p r e s s o r s a n d s t e a m t u r b i n e s ca n b e m a n u f a c t u r e d
between th e compress ors in the t ra in. With t his configu-
with MHI proprietary technologies in the same manu-
rat ion, th e output power is distributed evenly, the outpu t
factur ing plant . It is our h ope that these highly efficient,
a p p l i e d t o ea c h s h a ft i s l o we r e d , a n d t h e t r a i n s t a b i l it y
l a r g e - s i ze d c om p r e s s o r s a n d s t e a m t u r b i n e s w i l l co m e
is increased.
to ass ist in increasing t he efficiency and reliability of an
For th e tra in shown in Fig. 13, th e installat ion height
e v e r -g r e a t e r n u m b e r o f p la n t s .
(on t he 2n d floor) is increased t o as high a s 15 m, since t h e s i z e of t h e m a i n c on d e n s e r p o s i t i o n e d j u s t b e l o w
References ( 1 ) N o j im a e t a l . , D e ve l o p m e n t o f H i g h - P e r f o r m a n c e , H i g h - C a p a c i t y C e n t r i fu g a l C o m p r e s s or s , T u r b o M a c h i n e r y V ol . 1 7 No.2 (1988) p. 21 ( 2 ) F u j i m u r a e t a l . , M i t s u b i s h i C e n t r i fu g a l C o m p r e s s o r s i n R e cent Petr ochemical Plan ts, Mitsubishi J uko Giho Vol. 33 No.5 (1966)
t h e s t e a m t u r b i n e i s i n c r e a s e d , t h e r e b y a f fe ct i n g c on struction costs. However, by adopting an axial flow exhau st type stea m tu rbine, which is a MHI own special d e s i gn , t h e i n s t a l la t i o n h e i gh t c a n b e s e t a t t h e s a m e level as before.
Hiroaki Ohsaki
Kei Hashizume
Eiji Hiraishi
Sumio Noda
Jyou Masutani
Mitsubishi Heavy Industries, Ltd. Technical Review Vol. 41 No. 3 (Ju n. 2004)
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