Polyurethane spray nozzle for abrasive slurries

A polyurethane spray nozzle for high pressure abrasive aqueous slurries of limestone and the like. The nozzle is comprised of a hollow body of urethane having a restricted inlet and outlet with internal vanes adjacent the inlet to provide a swirling motion to the slurry. The polyurethane construction is characterized by a high degree of abrasion resistance with a slick surface to inhibit solids build up and a degree of flexibility to inhibit clogging of the vanes by solid pieces of limestone. In a modification the body may be made in a first piece while the vanes may be inserted therein in a second integral piece held together by a ring. An outwardly extending flange which may be reinforced with a metallic member is provided for connection to a pipe line source for the slurry. The flange portion connected to the pipe line source may be constructed of a softer polyurethane than the remainder of the spray nozzle to enhance the flange sealing connection.

BACKGROUND OF THE INVENTION 
In the past various types of spray nozzles have been employed for high 
pressure aqueous slurries to provide a spray for one or more purposes. 
Such a use is typified in spraying limestone slurry in a tower, stack or 
chamber where it is contacted by combustion gases from the burning of 
coal. The limestone reacts with sulfurous gases such as sulfur dioxide and 
the like to form calcium sulfate which is separated from the thus scrubbed 
gases. 
Typical of such spray nozzles is one made of stainless steel with internal 
vanes to impart a swirling motion to the high pressure slurry to enhance 
the formation of the spray through which the combustion gas or smoke from 
the burning of coal is passed. Such nozzles while initially strong and 
durable are subject over a period of time to pitting and corrosion on the 
surfaces contacted by the slurry and wear which greatly shortens their 
life. The rigidity of the vanes further causes problems in occasional 
clogging of the vanes. All of this contributes to downtime and the 
attendant expense and reduced efficiency necessitated by repairs and 
replacement. 
Ceramic spray nozzles have likewise been employed in such sustems. While 
they exhibit improved corrosion and pitting resistance they are relatively 
fragile and have lessened shock resistance and are subject to breakage. 
Due to their rigidity they further experience objectionable clogging 
tendencies to larger sizes of slurry solids. Their increased expense adds 
to problems in their advantageous employment. 
SUMMARY OF THE INVENTION 
By means of the instant invention there has been provided an improved spray 
nozzle of polyurethane which has a good serviceable period of use and has 
a high degree of abrasion and wear resistance against the slurries with 
which it is employed. The polyurethane has a slick surface which inhibits 
the build up of solids from the slurry. A slight degree of flexibility 
provides for some flexing of the vanes which reduces the tendency to clog 
from larger particles of limestone or the like employed in the slurry. 
The spray nozzle may be formed by casting or molding in one piece of 
polyurethane. The polyurethane is formed from conventional commercial 
prepolymers which are reacted with conventional curing agents to form the 
polyurethane. A hardness of about 90 duremeter reading is preferred which 
provides optimum abrasion and wear resistance coupled with a slick surface 
and slight flexing of the internal vanes to prevent clogging. 
The spray nozzle physical characteristics embody the physical features of 
proven spray nozzles utilizing a hollow body with a restricted inlet 
within which the vanes act to impart a swirling motion to the slurry and a 
restricted outlet which emits the spray to perform the exhaust gas 
scrubbing action. The strength of the polyurethane coupled with the other 
advantageous features further permits the use of flanges for connection to 
a high pressure pipe line source which is employed in the distribution 
system for the limestone slurry. 
In a modification the spray nozzle may be employed in a two piece 
construction. A bell shaped hollow body having a restricted outlet opening 
is formed as a first piece while a second piece insert incorporating the 
internal vane construction and inlet may be molded as the second piece and 
nested and sealed within the first piece to form the finished spray nozzle 
device. The flange of the insert which is connected to the pipe line may 
be formed of a somewhat softer polyurethane to improve the seal against 
the pipe line source connection. A durometer reading of about 60 for this 
softer flange portion may be desirably employed. 
A reinforcement may also be employed in the flange around flange holes to 
provide added strength. Such reinforcement may be in the form of metallic 
washers or a metallic ring provided with registering holes molded in situ 
around the flange holes. 
For improved sealing of the polyurethane flange which because of its softer 
characteristic than steel or ceramic acts as a gasket and makes a separate 
gasket unnecessary a nested construction may be employed in the two piece 
construction. In this modification the exterior softer flange of the 
insert may be "caged" within a peripheral rim on the exterior of the 
flange of the body portion. Pressure exerted in connecting the insert 
flange against the pipe line causes its expansion and tight seal against 
the body flange and the peripheral rim to effect a water-tight seal 
against the high pressure employed in the distribution system. 
The above features are object of this invention. Further objects will 
appear in the detailed description which follows and will be further 
apparent to those skilled in the art. 
For the purpose of illustration of this invention preferred embodiments 
thereof are shown in the accompanying drawing. It is to be understood that 
the drawing is for purpose of description only and that the invention is 
not limited thereto.

DESCRIPTION OF THE INVENTION 
The spray nozzle of this invention is generally designated by the reference 
numeral 20 in FIG. 1 where it is shown utilized in a limestone slurry pipe 
line distribution system 22. The use of a plurality of pipe lines and 
spray nozzle provides a blanket of limestone slurry spray which the 
upwardly rising exhaust or smoke stack gases from the combustion contact 
to effect the scrubbing action and conversion of sulfur gases to 
precipitated calcium sulfate which is thereby separated from the exhaust 
gases. 
The spray nozzles are connected to the pipe line distribution system by 
bolts or the like fastening flanges 24 of the spray nozzles to flanges 26 
provided in the pipe line distribution system. 
The spray nozzle 20 is more particularly shown in FIG. 2. It is comprised 
of a hollow bell shaped or dome-like body 28 having a restricted inlet 30 
and a restricted outlet 32 at opposite ends of an interior mixing 
reservoir 34. A plurality of radially inwardly extending vanes or blades 
36 are positioned adjacent the inlet 30 to provide a swirling motion to 
the high pressure slurry introduced to the inlet and provide a turbulent 
mixing in the interior reservoir. The flange 24 extends radially outwardly 
from the inlet 30 and with the bolt holes 38 forms a means for a 
water-tight connection to the flanges 26 in the pipe line distribution 
system. 
The entire spray nozzle may be molded, potted or cast in an integral 
polyurethane construction by the use of conventional commercial isocyanate 
prepolymers and cured by conventional additives. The polyurethane 
composition is commercially available and, per se, forms no part of this 
invention. The polyurethane has a preferred hardness of about 90 durometer 
reading. The durometer reading is an international standard for hardness 
measurement of rubber, plastics and other non-metallic materials. This 
degree of hardness provides a high degree of abrasion and wear resistance 
and a slick surface which inhibits build up of limestone solids. A slight 
degree of flexing of the vanes is also provided to reduce any tendency of 
the internal vanes to clog. Further, the relative softer nature of the 
polyurethane flanges as contrasted with stainless steel or ceramic spray 
nozzles permit the flanges to provide a water-tight seal against steel 
flanges of the pipe line distribution system and eliminate the necessity 
of separate gaskets. 
The polyurethane is obtained conventionally using commercially available 
isocyanate prepolymers and curing with commercial additives and, per se, 
forms no part of this invention. Typical of such prepolymers is Uniroyal's 
B600 Vibrathane and the curative MOCA or 1,4 butanediol which is used to 
mold the nozzle body and vane sections to provide a durometer reading of 
about 90. Also typical of such prepolymers is Uniroyals B628 Vibrathane 
and a blend of curatives such as Andersons Curene 442 and Uniroyals polyal 
Vibracure A-931 which are employed to obtain a softer polyurethane having 
a durometer reading of about 60. These are exemplary and not limiting as 
will be well understood by those skilled in the art. 
A two piece modification of the spray nozzle is shown in FIGS. 3 through 8 
and is generally indicated by the reference numeral 40. The spray nozzle 
for greater ease in molding and fabrication is made in two piece as a body 
piece 42 and a turning vane insert 44. 
The body piece 42 has an external configuration generally similar to that 
of the spray nozzle. A restricted outlet 46 is provided at one end and 
outwardly extending flange 48 is connected at an opposite end. An inner 
frusto-conical surface 50 having a shoulder portion 52 receives the vane 
insert in nested relation as will appear. 
The vane insert 44 is molded to have a support ring base 54 from which 
radial vanes 56 extend inwardly. An outwardly extending flange 58 provided 
with bolt holes is adapted to register with the flange 48 and bolt holes 
of the body piece. The support ring 54 has an external frusto-conical 
surface 60 and shoulder 62 which interfit with the internal surface 50 and 
shoulder portion 52 of the body piece. The frusto-conical and tapered 
interfit ensure that the pressure on the insert vane exerted in use as the 
slurry passes through the spray nozzle tends to drive the body piece and 
vane insert closer together and separation is inhibited. 
Both the body piece and vane insert are molded from isocyanate prepolymers 
as aforedescribed for the spray nozzle 20 and have a preferred durometer 
reading of about 90. The two pieces are cemented together by conventional 
cements which may be for example, a polyurethane. 
A further two piece modification is shown in FIG. 9 and is generally 
designated by the reference numeral 70. The spray nozzle is generally 
similar to the two piece spray nozzle 40 described in FIGS. 3 through 8 
but features a softer polyurethane portion of the vane insert and improved 
sealing and reinforcing functions for the flange as will appear 
hereinbelow. 
The two piece spray nozzle 70 is comprised of a body 72 and a vane insert 
piece 73. The body piece is provided with a restricted outlet opening 74 
at one end and outwardly extending flange 76 at an opposite end. The 
flange has a vertical rim-like border 78 which closely receives a mating 
flange of the vane insert. Metallic washer-like reinforcing members 80 are 
molded in situ to provide additional strength to the flange when bolted to 
connecting flanges of the pipe line slurry distribution system. An inner 
frusto-conical surface 82 having a shoulder portion 84 receives the vane 
insert in snug relation as in the two piece spray nozzle 40 as 
aforementioned. 
The vane insert 73 is molded similarly to the vane insert 44 and has a 
support ring 86 from which radial vanes 88 extend inwardly. An outwardly 
extending flange 90 having bolt holes is adapted to register the flange 76 
and bolt holes of the body piece. The flange 90 is of a lesser diameter 
than the flange 76 and is dimensioned to fit snugly inside the border rim 
78 so as to be caged therein. 
As in the two piece spray nozzle the vane insert is provided with an 
exterior frusto-conical surface 92 on the support ring and a shoulder 94 
which interfit snugly with the internal surface 82 and shoulder portion 84 
of the body piece. 
In order to provide an increased flange sealing function the flange 90 has 
an outer portion 96 which is softer. The pressure exerted in connecting 
the spray nozzle to the connecting flange of the pipe line distribution 
system when connecting bolts or the like tighten the respective flanges 
together cause the external flange portion 96 to expand against the rim 78 
of the body flange and improve the flange seal. 
The flange portion 96 is desirably of a durometer reading of about 60. The 
remaining portion of the vane insert 73 including the flange 90 and the 
body piece are molded to provide a polyurethane having a hardness of a 
durometer reading of about 90. 
While the insert vane has been described above as having a durometer 
reading of about 90 except for the softer flange portion, the entire 
insert vane may be of a lower durometer reading to provide increased 
flexibility to the vanes to inhibit cloggin by solids or only the vanes. 
Thus, the polyurethane construction may be varied as desired. 
USE 
The polyurethane spray nozzle of this invention is employed in a like 
manner to the stainless steel and ceramic spray nozzle of conventional 
construction. The spray nozzle whether it be the one piece nozzle 20, or 
the two piece embodiments 40 or 70 is simply employed by connecting the 
flanges to flanges of the pipe line distribution system. Due to the 
polyurethane relative softness as compared to steel or ceramic the 
connection may be made without the required use of a separate gasket. 
Where an especially tight seal is required for some extremely high 
pressure slurry systems the spray nozzle 70 may be employed with the 
softer polyurethane flange. 
The spray nozzle when connected to the pipe line distribution system for a 
slurry such as limestone conventionally employing, as an example 12% 
limestone, may be used to provide a blanket of spray for sulfur containing 
coal combustion gases in a scrubbing system. In such systems it has been 
found that the life of the spray nozzle may be substantially extended over 
that of stainless steel nozzles. The wear and abrasion resistance of the 
polyurethane construction coupled with the slick surface provided by the 
polyurethane resist the build up of solids and inhibit corrosion and 
pitting. The slight flexibility of the vanes further increases efficiency 
by lessening the tendency to clog. These advantages along with 
substantially less cost than stainless steel or ceramic provide for 
significant efficiencies in use. 
Various changes and modifications may be made within this invention as will 
be apparent to those skilled in the art. Such changes and modifications 
are within the scope and teaching of this invention as defined in the 
claims appended hereto.