This feeder concept uniquely combines the functions of solids feeding, metering, and pressurization into one compact system. Success with the rotary-piston concept would provide a lower-cost alternative to lock-hopper systems. The design of the feeder is presented, with special emphasis on the difficult problem of seal design. Initial tests will be to check seal performance. Subsequent tests will evaluate solids-feeding ability

Gardner, J. F.

Gencsoy, H. T.

Strimbeck, D. C.

English

NASA Technical Reports Server

HIGH PRESSURE ROTARY PISTON COAL FEEDER 
J. F. Cardner 
U. S. Energy Research and Levelopment 
Administration, Morgantown Energy Research 
Center 
Morgantown, West Virginia 
H. T .  Gencsoy 
West \:ii yinia Uzivers i ty  
Morgantown, West Virginia 
D. C. Strimbeck 
U. S. Energy and Research and Development 
Administration, Morgantown Energy Research 
Center 
Morgantown, West Virginia 
https://ntrs.nasa.gov/search.jsp?R=19780005318 2020-03-22T05:39:30+00:00Z
ABSTRACT 
This  feeder  concept uniquely combines the functions of sol ids feeding, 
m e t e  r ing,  and p ressur i za t ion  into one compact  sys tem.  Success  with the 
rotary-piston concept would provide a lower-cos t  a l te rnat ive  to lock- 
hopper s y s t e m s .  
The rotary-piston coal  feeder  was conceived a t  MERC. Initial design 
of the feeder  was  accomplished by W V U  personnel  under cont rac t  to  ERDA. 
The design of the feeder  i s  presented ,  with special  emphasis  on the diffi- 
cult  problem of s e a l  design. Initial t e s t s  will be to check s e a l  performance.  
Subsequent t e s t s  will evaluate solids-feeding ability. 
HIGH PRESSURE ROTARY P:: TON COAL FEEDER 
INTRODUCTION 
An important step i n  a l l  gasi f icat ion processes i s  the feeding o f  
coal from atmospheric pressure i n t o  gasi f iers operating a t  pressures up 
t o  1500 psip. The ult imate objective o f  t h i s  work i s  a coal feeder wi th 
discharge capabi l i t ies o f  1500 psig and 350°F. The c r i t i c a l  design 
problems are the rotary-pi ston mechanism, and 1 ubrication, wear and seal - 
ing o f  feeder components. A two-step design procedure thus was followed. 
The basic mechanisms o f  a rotary feeder were f i r s t  developed. Con- 
sideration then was given t o  sealing, wear, and lubr icat ion.  The i n i t i a l  
design i s  f o r  100 psig discharge pressure a t  300°F, w i th  a feed capacity 
o f  200 t o  1000 pounds per hour. Design problems associated wi th the 
rotary feeder must be solved a t  these modest conditions before higher 
pressures and f 1 ows can be achieved . 
This design work was done i n  Phase I, the f i r s t  year o f  a three-year 
esearch program supported by ERDA a t  West Virg in ia University. The 
design work i s  covered i n  t h i s  paper. Phase I 1  consists o f  fabr icat ion 
and test ing of the prototype pump. Phase I11 w i l l  extend the design t o  
1500 psig wi th feed rates o f  several tons o f  coal per hour. 
9 Mechanical Engineer, U.S. ERDA -- Morgantarn Energy Research Center, 
Morgan town, WV. 
i?/ Professor, Mechanical Engineering L kchan i  cs , West V i  rg ln ia  University , 
Morgantm, W 
d Chemical Engineer, U.S. ERDA -- Morgantm Energy Research Center, 
Morgantm, WV. 
ROTARY PISTON COAL FEEDER 
Feeder Operat ion  
Assembly drawings o f  the ro ta ry  p is ton  coal feeder are shown i n  
Figures 1 & 2. The main parts are an outer casing w i th  an i n l e t  hopper 
and a discharge opening, a ro ta t i ng  (hollow) d isk assembly w i th  a t h i n  
r i m  containirlg the i n j e c t i o n  chamber, p is ton  and rod, and a d r i v e  shaf t  
assembly. The rec iprocat ing act ion o f  the p is ton i s  provided by two 
f i xed conjugate cams secured t o  the outer casing and two r o l l e r  fo l low- 
ers attached t o  the piston. 
The feeder operates as follows. Coal f i l l s  the open p is ton cy l inder  
a t  top dead center (0"). The p is ton pos i t ion  then remains constant as 
the p is ton and i t s  ro ta t i ng  housing moves clockwise through an angle o f  
135". During the next 75" o f  rotat ion,  the p is ton i s  dr iven r a d i a l l y  
outward by the contact between the cams and f o l  lowers. The coal empties 
by g rav i t y  through '' discharge. During the next 60° o f  ro ta t ion ,  the 
p is ton dwells a t  the maximum outward posi t ion.  The p is ton then returns 
t o  the loading pos i t ion  durinq the next 70" of rotat ion.  The p is ton  
then dwells i n  t h i s  r e t r a c t e -  pos i t ion  for  the f i na l  15' o f  r o t a t i o n  
p r i o r  t o  charging w i th  coa; 
The ro ta t i ng  d isk i s  dr iven by an e l e c t r i c  motor through a speed 
reducer a t  rates up t o  30 rpm. This w i l l  provide a feed r a t e  o f  approx- 
imately 1200 lb /h r  (p = 30 1b/ f t3)  f o r  f i n e l y  crushed coal. 
Basic Feeder Components 
The d is t inguishing feature o f  t h i s  feeder i s  a ro ta t i ng  d i sk  con- 
ta in ing  the i n jec t i on  chamber, and a cam-activated rec iprocat ing p is ton  
which provides the pumping act ion f o r  feeding the coal p a r t i c l e s  i n t o  
a chute against the discharge pressure. The fol lowing are br ie f  
descriptions o f  some o f  the main feeder components. 
The Rotating Disk and Piston Assembl~ 
The heart o f  the rotary-piston coal feeder i s  the internal  ro ta t ing 
disk t o  which many o f  the internal  parts are supported or  connected. 
The input rotat ional  energy i s  d i r ec t l y  transferred t o  the disk through 
the drive shaft, causing the disk t o  rotate inside the outer casing on 
two 27-inch outside-diameter b a l l  bearings. With the disk rotat ing,  
the cam followers, which are attachcd t o  the piston rod, r o l l  along the 
f ixed cam prof i les,  imparting a reciprocating m o t i ~ n  t o  the piston. 
This act ion causes the coal t o  discharge, and then allows the piston t o  
re t rac t  f o r  r e f i l l i n g .  
Design o f  the ro ta t ing disk provides suf f ic ient  r i g i d i t y  f o r  proper 
ins ta l  l a t i on  o f  the large df ameter b a l l  bearings, input dr ive shaft, 
and other internal  parts. The ro ta t ing disk i s  a t h i n  cy l ind r i ca l  she l l  
which i s  closed a t  one end. The disk i s  one piece cast steel construction 
wi th a1 1 support areas cast in tegra l l y  wi th the disk. The i n t e r i o r  o f  
the disk i s  sealed from the high pressure gases a t  the discharge area. 
The ro ta t ing disk supports the piston rod a t  two locations wi th  
1 inear ba l l  bearings. This arrangement reduces f r i c t i o n  losses and 
assures perfect alignment o f  the piston i n  the cyl inder during operation. 
A r o l l i n g  diaphragm a t  the piston head prevents coal par t ic les  from 
entering the i n te r i o r  of the ro ta t ing disk. The diaphragm also seals 
against high pressure gases when the piston cyl inder i s  discharging 
coal. For added sealing protection, rod seals and wiper r ings are 
' f i t t e d  i n t o  machined grooves i n  the area d i r ec t l y  below the cyl inder 
bore o f  the ro ta t ing disk. 
The Outer Casing 
The outer casing consists o f  two semi - c i  rc!, l a r  c y l i n d r i c a l  she1 1s 
jo ined a t  the center w i t h  casing bo l ts ,  and two c i r c u l a r  end plates. 
The outer casing contains the i n l e t  a t  the top, and the discharge i s  
attached a t  the bottom. Wear compensating seals are located around 
these openings on the outer casing t o  keep high pressure gas and real 
pa r t i c l es  from penetrat ing t o  the ins ide  o f  the feeder and contaminating 
the ro ta t i ng  d isk and i t s  feeding mechanism. 
Cams and Cam Followers 
The rec iprocat ing ac t ion  o f  the p is ton  i s  caused by two f i xed  
conjugate cams attached t o  the cam side end-plate. Two cam fo l lowers 
secured t o  the p is ton  rod r i d e  on the cam p r o f i l e  o f  the r o t a t i n g  disk, 
prov id ing the forward and backward strokes o f  the p is ton  i n  the cy l inder .  
The cam p ro f i l es  are spec ia l l y  designed t o  impart a simple harmonic 
motion t o  the piston, w i th  a 2-inch stroke and a maximum pressure angle 
o f  30". 
The cam fol lowers are mounted eccent r ica l l y  on the si:uds. This 
provides a preload between the fol lowers and cam surface t o  ensure con- 
s tant  contact. 
Large Diameter Ba l l  Bearings 
Two 27-inch O.D. Ba l l  bearings support the r o t a t i n g  d i sk  a t  both 
ends i n  the outer casing. This assures low f r i c t i o n  loss, and minimizes 
de f lec t ion  and bearing problems associated w i t h  the d r i v e  shaft .  This 
ar5rangemnt also a l igns the r o t a t i n g  d isk i n  the outer casing, and thus 
maintains seal dimensions around the i n l e t  and discharge openings. 
Coal Feeder Seals 
Sealing problems associated w i t h  t h i s  feeder design a re  unusual and 
challenging, Effect ive sea l ing  o f  the p i s t o n  and rod  when fac ing  the 
h igh pressure discharge i s  achieved by the r o l l i n g  diaphragm i n  the 
p i s ton  head, and the combination o f  the seal and wiper r i n g s  i n  the rod, 
as discussed prev ious ly .  
Seals between the outer  casing and the r o t a t i n g  d i sk  a t  the i n l e t  
and discharge openings had t o  be spec ia l  l y  designed. Commercial ly 
ava i lab le  products could n o t  be used. Three types o f  wear compensating 
seals were designed f o r  the i n l e t  and discharge openings. The bas ic  
ideas behind these designs can be seen i n  Fisures 3 and 4. The p r i n -  
c i p a l  pa r t s  i n  the wear compensating seals cons is t  o f  a pr imary seal 
nose contact ing the r o t a t i n g  d isk  along the per iphery o f  the discharge 
opeoing, and a secondary seal support ing the pr imary seal w i t h  ad justab le  
pre-load elements. A p r ~ s s u r e  gap i s  incorporated i n  a l l  these seals 
between the  seal y, .-d and seal ncse back surface. The pressure o f  
surrounding gases thus helps t o  fo rce  the seal against  the r o t a t i n g  
d isk  and make the contact area leak-proof. Wear i s  a l so  au tomat ica l l y  
compensated by the de f lec t ion  o f  the  seal l i p  t o  prov ide long l i f e  f o r  
the seal. The seals are a lso  designed f o r  easy a c c e s s i b i l i t y  and main- 
tenance. 
The three seal assemblies are being bu i  1 t. The th ree  assemblies 
p r i n c i p a l l y  cons is t  o f  a pr imary seal nose and a secondary seal. Three 
d i f f e r e n t  seal mater ia ls ,  i .e. EPDM rubber, poly imide carbon composite 
and Teflon, bonded onto an epoxy glass fabr i c  laminate, w i  11 be used 
f o r  the pr imary seals. A l l  three secondary seals w i l l  be made fmtn 
EPDM rubber. The mater ia ls  selected f o r  the t e s t  seals a re  thought t o  
be the most compatible w i t h  the chemical, thermal and wear requirements 
f o r  the coal pump. These seals w i l l  be tes ted  on a feeder prototype 
being b u i l t  a t  the ERDA, Morgantown Energy Research Center, Morgantown, 
West V i rg in ia .  
A Tef lon f i b e r  gasket tape i s  used as a gasket between the ou te r  
casing she l l  and end p la tes.  The tape has exce l len t  d u r a b i l i t y  and 
seal i n g  cha rac te r i s t i c s  and i s  easi  l y  i n s t a l  led.  The l a rge  end bearings 
are a lso  protezted from contaminatfon by a bear ing seal s t r i p  snap f it- 
ted  i n t o  a groove machined i n  the  ou te r  casing. 
SUMMARY 
-- 
The feeder design cons is ts  o f  a r o t a t i n g  d i sk  i n  a c y l i n d r i c a l  
feed chamber conta in ing a r e c i p r o c a t i l ~ q  p is ton.  The p i s t o n  seals the  
feed chamber a f t e r  the coal i s  dumped i n t o  a reac to r  vessel so t h a t  
there i s  no loss  o f  gas from the reactor .  These are the o ~ l y  moving 
par ts  i n  the feeder, a ~ d  t h e i r  rugged cons t ruc t ion  should present m in i  - 
mum wear problems. 
This feeder i s  designed f o r  1200 pounds per  hour, operat ing a t  30 
rpm. The body o f  the  feeder i s  27 i ~ c h e s  i n  diameter and 12 inches 
wide. The compact design makes i t  poss ib le  t o  use more than one feeder 
i n  p a r a l l e l  t o  get h ighcr  coal feed rates.  Higher values o f  r o t a t i o n a l  
speed could a l so  increase the feed capaci ty.  The d r i v e  requirement o f  
a s i ng le  u n i t  a t  30 rpm i s  5.3 horsepower. 
The coal  pump i s  a 11-steel cons t ruc t ion  us ing c m r c i a l l y - a v a i l -  
able standard oar ts  wherever possible.  The design c o n s i i t s  o f  a minimum 
number of par ts  t h a t  can be e a s i l y  mar~ufactured and assembled t o  prov ide 
a r e l i a b l e  u n i t .  
A diaphram seal i n  the p is ton  head, and a combination o f  seal and 
wiper r ings i n  the rod, provide e f fec t i ve  seal ing o f  the coal discharge. 
Seals between the outer casing and the r o t a t i n g  d isk a t  the i n l e t  and 
discharge openings, however, present chal lenging design s i tua t ions  
requi r ing special solut ions. Three types of wear-compensating seals o f  
various conf igurat ions thus were conceived. These seals are being fab- 
r i ca te r .  They w i  11 be tcsted on a prototype feeder which i s  current ly  
being made a t  ERDA f a c i l i t i e s  i n  Morgantown, West V i rg in ia .  
Success w i th  t h i s  coal feed concept w i l l  lower the cost and d i f f i -  
c u l t y  of pressurizin&, metering, and i n j e c t i n g  coal i n t o  a reactor  
vessel. The feeder thus could replace lock-hopper feed systems now i n  
geoeral use, inc luding the valves i n  s ~ c h  systems tha t  are a source o f  
many problems. 
If the Phase I 1  tes ts  of the seals succeeds, t h i s  work w i l l  be ex- 
tended i n t o  Phase 111. This phase would be t o  design a coal feeder fov 
the 1,530 ps ig  pressure required f o r  commercial coal conversicit p iants. 
ORIGINAL PAGE IS 
OF POOR QUALFTY 
UPPER CASING 
DIAPHRAM COVER 
CAM FOLLOWER 
BALL BEARINGS 
DRIVE SHAFT SlGE END PLATE 
CAM SIDE 
DISCHARGE SUPPORT BLOCK 
F IGURE 2. - EXPLODED ASSEMBLY OF H I G H  PRESSURE ROTARY P I S T O N  COAL FEEDER 
FIGURE 3-SEAL ASSEMBLY FOR HIGH PRESSURE 
ROTARY PISTON COAL FEEDER 
PRIMARY SEAL NOSE 
SECONDARY SEAL 
NO. 4 HEX NUT SEAL GUARD 
NO. 4 HEX SOC BUTTON HD 
CAP SCREW 
BACK-UP SPRlNG 
BOLT PLACED BETWEEN SPRINGS 
AT INTERVALS 
I?yu \ \  SUPPORT PLATE 
\ BOLT TO FLANGE 
FIGURE 4 - SEAL ASSEMBLY 


High pressure rotary piston coal feeder

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server