Note: Descriptions are shown in the official language in which they were submitted.
:1 16~31 1
13AC1CGROUND 01~ NV13N'1':[0N
l. Field o:E_the Lnvention
'1'he present invention relates to a heating boiler for
substantially continuous controlled combustion of baled
straw.
2. Prior Art
Heating boilers oE the type taught in West German
Offenlegungsschrift 24 00 778 are refuse incinerators in
which a plug of refuse is shoved through a shaft, by means
for example of a convey-lr ~crew, into a rire box. 'L'his type
of heating boiler is unsuitable for continuous controll.ed
combustion of baled st,raw due to the different combustion
characteristics of baled straw relative to typical refuse,
and even relative to straw that has not been so compressed.
The use of a heating boiler of the type taught in ~est
German Offenlegungsschrift 2~1 00 778 for the combustion of
straw results in an uncontrolled fire within the feect channel
or a fire which either self-extingL1ishes or salolclers ancl
provides very incomplete combustion of the straw clue to the
formation of an ash crust whic}~ interferes wLth aces~ to the
straw of the necessary combustlon air.
~UMMAI~Y 01~' '1'tll3 INVEN'l'I~N
The present invention provides a heating boiler for
substantially continuous combustion of 'baled straw.
The heating boiler includes a straw feed channel communicating
with a combustion chamber having a combustion zone adjacent
:~ the rear wall of the combustion chamber, a flue gas heat
excllange chamber above the combust:ion chamber in communication
with a flue gas vent and an ash collecting pit below the
. _, ... . . . , , ., . . . . , . ...... , ~ . ,.. , .. , .... _ , . ... . . _ _ , , ___~
-- .
.
,
3 1 ~
. .
combustion challlber. ~ horlzonLal ELoor :i9 (ILsposed between
the combustion challlber an~l tllr as~l coLlecting plt, the ~loor
having a slot a~ljacerlt the rear wa:ll o~ tlle combustion
chamber Eor passage of ash from the combustion zone into the
ash collecting pit and for :intake of primary a:ir into the
combustion zone. ~ vertically rotatab].e ash stripper assembly
extends from the rear wall of the combustion chamber, ancl
serves to strip ash from the straw bale surface being combusted
in the combustion %one. 'rhe ash stripper assembly can be
rotated by means of a hollow sllaft whicll also constitutes a
secondary air intake. The boiler provides for substantially
continuous combustion o~ the baled straw in a controlled
fashiorl by restricting combustion to the area of the combustion
zone adjacent the rear wall of the combustion chamber.
In one particular aspect the present invention provides
a heating boiler for the combustion of baled straw, comprising ~i
an enclosed straw ~eed channel, provided with conveyor ,$
means, communicating with a combustion chamber llaving a
combustion zone adjacent the rear wall of the combust:Lon
chamber, a flue gas heat exchallge chclnlber above the combust:ion
challlber and in comlllurlica~ l wLtll a L~luc gns vent, all nsh
collecting pit below the combustion challlber, a horizontal
floor disposed between the combustion chamber and the ash
collecting pit and having a slot adjacent tlle rear wall of
the combustion chamber for passage of ash from the combustion
zone into the ash collecting pit and for intake of primary
air into the combustion zone, an ash stripper assembly
extending from the rear wall of the combustion chamber and
movable in a vertical plane to strip ash from the surface of
.
.
..
:l ~6g31. '~
a straw bale bein~ combusted in the combustion ~one, and at
least one secon(lary air intake in the rear wal~ of the
combustion chamber.
It has been Eound that the feeding of prinnary air by
way of ~he slot above which the combustion zone is located,
that is the zone in which the leading face of the straw bale
is combusted, together with the feeding of secondary air tn
the center of tbe combustion~zone and the concurrent stripping
of ash, by the ash stripper assembly, without disturbing the
straw being combusted per se, permits continuous uniform ,'
combustion of the leading surEace of the straw bale.
~ n important feature oE the heating boiler is the fact
that the entire floor of the combustion cllamber is not
simply designed in the form oE a grate, as is customary, but
rather is a solid floor with the slot which restricts ~he
access of primary air to substantially only the combustion ;'
zone.
It is also advantageous to construct the as'h stripper
assembly in such a manner as to additionally constitLIte a
secondary air intake. This can be accompl-Lshed 'by employillg
an ash stripper assembly having one or more arms bea-ring ash
stripper e'Lements mountecl upon a hollow shaft, of suitable
proportions, which extends through the rear wall of the
combustion chaolber and through which secondary air can be
drawn or, if necessary, injected by means Eor example of a
blower fan. Tlle use of the hollow shaft as the secondary air
intake provides E~r cooling of the ash stripper assembly and
concurrent preheating of the secondary air. The hollow
shaft can be rotated, in alternate directions and at preset
--3--
;~693~1
intervals if desire(l, by sultabLe ~Irive means remote froln
the combustion challlber.
The ash stripper assembly can also be constructed so
that the hollow shaft is axially movable against the pressure
of spring means remote Erom the combustion chamber and can
be associated with a regulating element, which senses or is
indicative of the shaft position, and which in turn is
associated with means, such as an impulse tralsmittor,
connected to the drive means for either or both the ash
stripper assembly and the conveyor means.
It has also been found that the eEficiency of the combustion
zone is enhanced by providillg wedge-like elements in the
corners of the combustion chamber which further compress the
baled straw entering the ~ombustion zone. 'l'he wedge-li~e
elements, which can if desired be readily formed integrally
as a part of the masonry lining, are particularly useful
when horizontally fed round straw bales are used as fuel
since thP leading edge being fed to the combustion zone is
compressed to a generally circular shape substanti~Lly of
the size and shape oE the area acted upon by the ash strLpper
elements of the ash stripper assembly. ~)therwise, corner
areas of the leading face of a bale would be comhusted at a
substantially slower rate than that portion of the leading
face from which ash is stripped by the ash stripper assembly.
It is of course possible, dependent upon the cross-
sectional size of the overall combustion chamber and the
cross-secLional siæe oE the combustion zone, considerations
affected by the straw bale size or the number of s~raw bales
intended to be fed concurrently, to provide a plurality of
.... ....... . .. .. _ _
3 ~ ~.
asll stripper asselllblies distributecl sy~net-rlca:l:Ly about ttle
central point of the combustion ~one.
B~ F DFSCRLPr-lON OF_rllE DR~WLNGS
Fig. 1 is a schematic longitudinal sectlon of a heating
boiler according to the present invention;
Fig. 2 is a front elevation of one embodiment of an ash
stripper assembly;
Fig. 3 is a schematic cross-section of an ash stripper
assembly similar to ~hat of l~i~. 2 mountecl in association
Wittl the rear wclll oE a comb-lstion chamber;
Fig. 4 is a schematic top plan of an emhocliment of a
combustion chamber according to the present invention;
1'`~ g. 5 i9 a scllematic Eront elevation of a combustion
chamber as viewed from the straw feed channel;
Fig. 6 is a top plan of a portion oE a particularly
preferred embodiment of an ash stripner assembly;
Fig. 7 is a front elevation of the ash stripper assembly
of Fig. 6;
Fig. ~ is a side elevation. part:ly in sectioll, oE a
preferre~ embocliment of a combusl:ion cllalTIber -rear wall door
and associated asll stripper a~elllbly mountillg an~l drLve
means;
Fig. 9 is a schematic top plan of an alternate embodiment
of a combustion chamber Eloor;
I~ig. 10 is a schematic front elevation, partly in
section, of the combustion chamber oÇ Fig. 9;
Fig. 11 is a schema~ic longitudinal section of an
embodiment particularly aclapted for combustion of round
; straw bales;
:~0
--5--
. . , . _, . . .
693~1
Fi~. 12 is ~ Ycllematic hor,izontal cross-section of an
embodiment particularly adcll~te~l ror coml~ustlon of rourld
straw bales;
Fig. 13 is a long'itudinal section of a preferred
embodiment of a flue gas heat exchange chamber;
Fig. 14 is a cross-section of the upper portion of the
flue gas heat exchange chamber of ~ig. 13; and
Fig. 15 is a side elevation of a slide plate of a
cleaning element for cleaning a passage of the flue gas heat
exchange chamber.
DETAII.ED DESCRIP'rION OF THE 'LNVENTION
Referring now to Fig. 1, straw bales are fed continuously
from a straw feed channel 14 through a feed opening 1 into
a combustion rear wall,~ The straw feed channeL 14 can be
provided, if des:ired, with a double-cased wall 13 in the zone
adjacent the combustion chamber 4 to permit cooling of that
zone of the straw feed channel 14. The so:Lid, horizontal
floor 3 of the combustion~chamber 4 is provided with a slot
7 which extends across the width of the combustion chamber
4 adjacent the rear wall 5 to permit flow of primary air from
an ash collecting plt 6 to the combustion zone 8. ~ flue gas
heat exchange chamber 16 is disposed above the combustion
chamber 4 and is provided with a flue gas vent 17~ An ash
stripper assembly is mounted for rotation in a journal aperature
2 provided in a combustion chamber door 5' in the combustion
chamber rear wall 5.
The ash stripper assembly, better seen in Figs. 2 and
3, includes a hollow shaft 11 having a c'ross arm member 9
--6--
'3 3 ~ 1
provided with stripper element~s 10 which can be in ~he orm
of vanes or fingers. rl'he asll stripper assembly, as seen
particularly in Fig. 3, is mounted ln the llquid-iacketed
combustion chamber door 5' which is approximately of the
dimensions of the feed opening 1 of the combustion chamber
4. The hollow shaft ll, which constitntes a secondary air
intake, is axially movable against the pressure of spring
means 12, and can be rotated by drive means 18.
In operation of the heating boiler, combllstion of the
baled straw is restricted substantially to the area of the
combustion æone 8 ~bove the primary air intake slot 7. The
rotating ash stripper assembly gently brushes oEf the ash
forming on the leading surface of the straw bale being
combusted without disturbing the combustion process per se,
while concurrently feeding secondary air to the combustion
zone to enhance combustion rate and uniformity.
Combustion uniformity over the straw bale leading
surface is also enhanced by providing wedge-].ike members 15,
as illustrated in Figs. 4 and 5, in the combustion chamber 4
to further compress the baled straw entering the combustion
zone into a generslly circuLar shape substantially of the
size and shape of the area acted upon by the ash stripper
elements of the ash stripper assembly.
The intake of secondary air by means of the hollow
shaft ll generally render.s unnecessary the provision of
further secondary air intake openings~ althou~h further
secondary intake openings 2' can be provided, as can be seen
for example in Fig. 4, in the flanking walls 4" of the
combustion chamber 4 if required.
--7--
.. . . .. . ..
1~6~3 1 1
A particuL~r,Ly preLerresl embodilll(ent nl' an ash ulripl)er
assembly is il:Lustra~ed in l~ s. 6 and 7. 'I'o the l~o:L:L~w
shaft 11 are atLaclle{l, by nlenn~ of tr:lan~,ular support pl,ates
25, complementary arms 19', which together form the bar 19,
bearing the trianglllar ash stripper elements 27 on the leading '~
face 26.
'rhrough an opening 23 between the ends 22 oE arms 19'
extends a central stripper 21" mounted in the shaft 11 so
that the end 24 of the stripper 21" projects somewhat in
advance of the arms 19'.
Flanking strippers 21 are rotatably mounted for movement
alon~ the arms 19' between th~ hollow shaft 11 and stops 20
so that during rotation oE the ash stripper assembly tlle
flanking strippers 21 prevent the build-up of ash, -residue
or ^rust on arms 19'.
On the same axis as that of the central stripper 21",
which moves back and forth during rotation of the hollow `~
shaft 11, are attached strippers 21''' which also move back '~
and forth to prevent material build-up in the area of the
end portinns 22 of the arms 19'.
l~urther stripperY 21.' call a:Lso be mounted e~terlla'l:ly on
~he hollow sha[t 11 lor nl~velllellt betweerl l~..lLe-sllclped StOpS
20'.
During rotation of the ash stripper assembly, all of
the strippers move back and forth between their stops while
concurrently the arms 19' bearing the ash stripper elements
27 act as ash dislodging beaters.
'l`he arms 19' can be designed as narrow rectangular
tubes, and can be in f'luid communication with the 1nLerior
'' , ~ ' '. ~'' .
1 ~6'~3 ~ 1
of the hollow shaft 'I..L~ .iE de~ired, t~ take aclvantagl of the
cooling ef~ect im~?arteci by tl-e intake of secondary air
through the hollow shaft 11.
lt is also contemplated, dependent upon the particular
conl:igurat1On Or the asi~ stripper assembly, that the build-
up of ash, residue nr crust could be prevented by provision
solelv of suitably dimensionecl flanking strippers 21.
The ash stripper assembly ~s preferably mounted as '.
illustrated in F-ig. 8, in such a manner as to provide means u
.L0 for regulatillg Lhe sl)eed Or tl~e conveyor means by wh.ich the
haled straw is fed to the combustion chamber. In the embodiment :.
illustrated the hollow shaft l.l> upon which is mounted the
stripper arms/stripper elements which are simp'ly iclentified
in stippled lines as component 9 is mounted in the combustion
chamber door ~' by means of a bracket 29 from the upper end
29' of which is pivotally suspended a bearing mounting
assembly 30 which includes a housing 33 ~or the ho11Ow shaft
11. Shaft bearings (not shown) are seatecl in the housing
: 33, as is a pinlon ~ear 34 which enc:irclf~s llollow sha~t 11
and meshes with a clriving pi~lion gear 35 powerecl by a motor
36 atta(llecl to Lhe e~teriol- Or the housing 33. 'I'he bottom
31 of the housing 33 is provicled with a downwardly extending
plate 39 through which projects a rnd 37 attached to the
comb-lstion chamber door 5'. Springs 38 are maintained on
- the rod 37 on either side of the plate 39 by means of adjusting
nuts 40. Ln adcliti.on the bottom 31 of the housing 33
includes a control extension member 32, opposite from which
is suitahly mounted an impulse transmittor 41 connected to
the drive Eor the conveyor means by whi-h the baled straw
_9_
.
.
9 3 ~ ~
is Eed to tlle combustion cllalllber.
lllus, activation of the :iml)ul~e transm:ittor ~:l due to
contact by the control extens:Lon member 32, clue in turn to
axial movement of the hollow shaf t 11 because of pressure
imparted to the ash stripper assembly by the face of a straw
bale, can result in slow:ing and/or temporary stoppage of
drive for the conv~yor. means while combustion proceeds to a
degree snfficient to per~lit return of the hollow shalt 11 to
a normal operation position.
lo Ille lellgtlls Or the bracket 29 and tlle bearing mounting
assembly 30 can be selected so that axiaL movement of the
hollow shaft 11 tran~lates as a relative radial movement
sufficiently small as to permit retention of an effective
seal between the journal opening 2 and the hollow shaft 11.
rhe weight of all oE the component parts 9, 11, 3U, 31,
32, 33, 34, 35, 36 and 39 is carried by the bracket 29, the
result of which is an extreme:Ly sensit:ive pendulum action,
controllable by means o.F the adjusting nuts 40.
In the embodiment illustrated :in Figs. 9 to :i2, an
2~ alternate form of floor 3 ls employecl in the conlbustion
chamber 4. ~pecl~ica:Lly, a section of tll~ E.loor acl)acent
the primary air ~.Lnt 7 is prov:ided wltll a central:ly clisposed
longitu~linal slot 7' intermediate complementary downwardly
curved portions 19". As in the case of Fig. 8, in each of
Figs. 9, 11 and 12 the ash stripper arms/str:ipper elements
are simply identiEied in stippled lines as component 9,
having previously be~n described in detai:L. In the case of
Fig. 10, the ~ircle 9 appearing in stippled lines simply
identifies the working area of the ash stripper asselTIbly.
:~
-10-
',
.
16~31~
Llle l-sllapecl slot lormecl by slots 7 sallcl 7', when viewecl
in top plan, to~ether with the sloping of curved portlons 19"
results in the leading surface oE the straw bale being
disposecl clear of the floor ab~ve the slot 7'. Thus, the
primary air can make particularly good contact with the
bottom of tlle bale which thereby combusts, w-ith reEerence to
Fig. 11, in the area 43 at the face of the bale. rhi~
particular form of floor structure is particularly efficient,
in conjunction with the action of the ash stripper assembly,
in achievlng con~inuous, relatively uniEorm combustion.
Large round baLes of straw (e.g. 1.5 1n long and 0.8 m
thick/300,000 k cal/h) can be combusted most advantageously
by feedin~ such bales in lying on their sides. ~or this
reason, the straw feed channel 14 can be designed in a
hori,ontally rectangular shape with a ~ross-section matched
to accept round bales 44 lying on their sides as shown in
Fig. 12. Becau~se of compacting occuring in the straw feed
chanLIel 14 as a result Or tl~e conveying means the rour~d
bales are pressed into a generally rectangular shape (as
shown in outline only) for whicl~ reason a unitary or sectional
shaper means 45 can be provided to reshape the strslw bsl:Le
into approximately the si,e alld sllape ~r ~11(-~ ares~ slcte~l upon
by the ash stripper elements oE the ash stripper assembly.
In other words, the function oE the unitary or sectional
shaper means 45 is s;milar to that o- the wedge-like members
15 -illustrated in Figs. 4 and 5. A deElector plate 4O,
shown in Fig. 11, can be positionecl intermediate the straw
Eeed chanllel 14 and the shaper means 45 ~o provide a smoothly
sloning connection. rhe wal]s 4" and roof 21 of the com~ustion
--11.--
. _ .
3 1 1
chamber 4 are tyrically :Linecl Wittl a f:Lre-l7-roor IDatL!ri~
and the unitary or sec~.ional sllaper means ~5 and any deElector
plate 46 can be formed of similar fire-proof material or
even formed integrally during installation.
Control of tlle bale conveyor speed to substantially
match the progress of combustion need not necessari.ly be
done by means of the ash stripper assembly. It is also
entirely possible to provide means associated with the
conveyor means to retard the rate of and/or shut off the
drive when the sensed resistance to forward movement of the
baled straw in the straw feed channel 1~ becomes too great.
ln such a case, the hollow shaEt 11 of the ash stripper
assembly need not be axially movable, and any associated
sensing and trflnsmitting means could be dispensed with.
While the heating boiler has been discussed primarily
with reference to the use of round straw bales as the feed
materi~l form, the inventive concept is equally appLicahle
to the feed straw mater:ia.L being in the form of cubes o-r
rectanL~ular prisms.
Figs. 13 to 15 re:Late to cl Foral oE Elue gas heat exchange .:
chamber 16 parL:icu:l.ar:Ly cles:iglled for o!)t:iala:l. ut:il:izat:lon oE
the heat of combustion of the straw.
l`he flue gas heat excllange chamber 16 comprises a
l.iquid-jacketed housinP ~8 within whicll are liquid-conducting
partitions 5() defining sel-arate horizontal passages 49 which
collectively form a maze-like draft channel Sl between the
f lue ~as intake passages 63 and the discharge pa.~sage 56
through which the flue gas enters chamber 62. The underside
of each of the partitions ~0, as well as the underside of
: 3
-12-
the ceiling above the upper pa~sage 49, :is provlded w:ith a
series oF ribs extending longitudinally in tlle direction of
flue gas flow through each passage 49. Access to ~he interior
of the housing 48 is afforded by a means of a closure plate
61 whi(h encloses and encompasses all of the separate
passages 49.
lo ensure goocl liquid circulation, the liquid-conducting
partitions 50, as can be seen from Fig. 14, are disposed at a
slight slant from sidewal.l to sidewall.
ln tlle embodilllellt illustrated, the continously rising
flue gas reverses direction twice during flow through the
passages 49, a process which naturally involves ash.prec:ipitation,
particularly where changes in direction take place. There
is accordingly provided, beneath the turning zone 55, an ash
pit chamber 5~' equipped with a removable ash collecting box
57'. ~ functionally equivalent, removable ash collecting
box ~7 is provided in ash pit chamber 5~ beneath the flue
gas venL 52 in chamber 62. rhe flue gas vent 52 preferably
extends downwardly in sul-stantially the manner illustrated
0 in Fig. 13 so as to enhance preclpitatLon eEflclency.
lhe separate pa~ages ~i9 can be cleaned by means of
associated cleanin~ elements 58 which extencl through the
closure plate 61. Each cleaning element 58 consists of a
rod 59 and slide plate 60. A tvpical slide plate 60, as
illustrated in Fig. 15, is complementary in profile to the
longitudinal ribs 54 and so dimensioned that when the cleaning
element 58 is shov~d through the passage 49. either automatically
or by hand, it not only meshes with ~he longitudinal ribs 54
but also sweep~ the floor of the passage 49.
0
-13~
lt has been Eound tl~at the rellloval. of asll is so thornugl
that a heating boiler equ:ipped with a flue gas heat exchange
chaMber 1~. as described above, can be readily vented through
a norDia' chimney without the intermediary addition of any
special asll extractor which would :increase venting re.slstance.
The heating boiler can suitably be provided with any
required, or desired, masonry linings and/or insulation, a
matter well within the purview of a person skilled in the
art. Additionally, various modifications within the true
broad spirit ancl s~ope Or tl~e .invention will also be obvious
to a person skl:lled in the art.
.
; -
