Steam boilers

Two types of boilers for generating high pressure steam from gaseous effluents containing abrasive and corrosive solids are provided. Both types of boilers are vertical boilers of the fire-tube type with the gas flowing within the boiler tubes and with the water and steam surrounding the boiler tubes. In one type of boiler according to this invention, the solids-containing gas is downfed through the boiler tubes with the gas emerging from the tubes and impinging on a concave, conical deflector and a convex nose cone located below the deflector. The deflector and nose cone serve to disengage solids from the gas. In the other type of boiler according to the invention, the solids-containing gas first impinges on a baffle plate which serves to disengage solids from the gas. The solids flow down for removal, while the gas flows up the boiler tubes to generate steam.

BACKGROUND OF THE INVENTION 
The present invention concerns boilers for generating steam and removing 
solids from high temperature, solids-containing gaseous effluents. 
Steam is the foremost vehicle for power generation in the world. About 90% 
of the new electric capacity being installed utilizes steam. In the 
eighteenth century, a "shell" boiler, little more than a ketttle filled 
with water and heated at the bottom, was the most common source of 
industrial steam. This, in turn, was followed by early versions of the 
"fire-tube" boiler such as the Trevithick boiler. John Stevens, a lawyer 
instrumental in the passage of this nation's first patent act, patented a 
"water-tube" boiler in 1803. 
Steam was originally utilized to provide heat and power for local 
industrial use. With the advent of practical electrical power generation 
and distribution, utility companies were formed to serve both residential 
and commercial users. By 1881 the first electric generating station in the 
United States utilizing steam was operating in Philadelphia. 
Modern boilers are generally of the "water-tube" type. In this type of 
boiler, the water and steam are inside the tubes and the hot gases 
generated by the combustion of fuel such as natural gas, oil or coal, are 
in contact with the outer tube surfaces. 
A less common type of boiler is the "fire-tube" boiler. In this boiler, the 
hot gaseous products of combustion pass directly through the tubes. The 
tubes are surrounded by water contained in a vessel. "Fire-tube" boilers 
are designed for vertical, inclined or horizontal positions. The preferred 
position being horizontal. 
"Fire-tube" boilers represent only a small fraction of the steam generating 
devices presently in use. Many of the "fire-tube" boilers currently in 
service are used for heating small buildings. The demise of "fire-tube" 
boilers in larger sizes for process steam generation is a result of their 
large volume of water compared to their heating surfaces. Thus in case of 
mechanical failure due to tube burnout there can be an explosive release 
of a large quantity of steam. 
SUMMARY OF THE INVENTION 
This invention relates to vertical fire-tubes boilers for generating steam 
and removing solids from high temperature, solids-containing gas streams. 
In one type of boiler according to this invention which is referred to 
herein as the "particulate boiler", the boiler housing is a vessel for 
retaining water at a predetermined level so as to create a vapor space 
above the water level. A plurality of boiler tubes for receiving the 
gaseous effluent is disposed throughout the length of the vessel and thus 
the tubes are partially within the vapor space and partially within the 
water. Protective sleeves are disposed within the tubes with the sleeves 
extending in the tubes from the top of the tubes to no greater than the 
water level in the vessel to protect that portion of the tubes within the 
vapor space. A concave, conical deflector is located adjacent the bottom 
of the tubes and a convex nose cone, located below the deflector, both 
serve to disengage the solids from the gas and to direct the solids to a 
solids outlet positioned at the bottom of the vessel. A gas outlet is 
located adjacent the bottom of the tubes. This boiler may further contain 
a nose cone located between the deflector and the solids outlet to further 
aid the disengagement of the solids from the gas. Although the normal flow 
of gas through the boiler is downflow, the flow can be reversed such as in 
a cleaning cycle. 
Another vertical fire-tube boiler in accordance with this invention which 
is referred to herein as the "waste heat boiler", includes a vessel for 
retaining water at a predetermined level so as to create a vapor space 
above the water level. Within the vessel are a plurality of boiler tubes 
for receiving the gaseous effluent. A gas inlet is located adjacent to the 
bottom of the tubes. A baffle plate is disposed in the path of the gas 
emerging from the gas inlet to aid in the disengagement of the solids from 
the gas. A solids outlet is located at the bottom of the vessel. A gas 
outlet is located at the top of the vessel to serve as an exit for the 
gaseous effluent emerging from the tubes. The gas flow in this boiler can 
also be reversed such as in a cleaning cycle.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the drawings, wherein like numerals indicate like elements, 
there is shown in FIG. 1 a boiler system utilizing the boilers of this 
invention. Solids-containing effluent gas flowing in furnace tunnel 13 
into stack 11 of an existing facility is diverted so as to flow through 
primary duct 15. The gas is then blown downwards by induced draft and 
forced draft fans (not shown) through particulate boiler 12 into conduits 
29 and up into two waste heat boilers 14 which flank the particulate 
boiler 12. The gas from the waste heat boiler 14 is vented to the 
atmosphere by the use of induced draft fans 19 through stacks 21 having 
rain hoods 23. The boiler system is described in greater detail in my 
copending application Ser. No. 319,015, filed on even date herewith and 
entitled "Steam Boiler System". 
FIG. 2 depicts the particulate boiler 12 in detail. Gaseous 
solids-containing effluent flows horizontally into the particulate boiler 
12 through the particulate boiler gas-solids inlet 16 into header 17 and 
then downward. The header 17 can be fabricated from any suitable material 
such as, for example, stainless steel. The gaseous solids-containing 
effluent then passes through numerous boiler tubes 18 supported by a top 
tube sheet 20. The boiler tubes 18 are constructed from a material that 
provides suitable heat transfer such as carbon steel. The boiler tubes 18 
can be any convenient size. The size of the tubes would depend on the 
flowrate of gas and solids and the temperature and pressure of the 
effluent. The number of boiler tubes 18 would depend on heat transfer. The 
boiler tubes 18 are supported at the bottom thereof by a bottom tube sheet 
22 and the top thereof by top tube sheet 20. Both the top tube sheet 20 
and the bottom tube sheet 22 are constructed from suitable material such 
as carbon steel. 
The gaseous effluent containing solids exits the boiler tubes 18 and flow 
through a concave, conical deflector 24 which serves to partially 
disengage the solids from the gas and to direct the solids to a convex 
nose cone 28. The gas flows around the deflector 24 and exits the 
particulate boiler 12 through two horizontally disposed gas outlets 26. 
The gas outlets 26 are connected to conduits 29 (see FIG. 1) which are 
respectively linked to the two waste heat boilers 14 that flank the 
particulate boiler 12. 
The side walls of the deflector 24 are disposed at any suitable angle from 
the horizontal such as between about 15.degree. and about 75.degree., and 
more particularly between about 25.degree. and about 50.degree.. This 
angle, the opening of the deflector, the distance between the deflector 
and the nose cone and the included angle of the nose cone are of such 
dimensions so as to maximize disengagement of solids. Both the deflector 
24 and nose cone 28 may be constructed from any suitable material such as 
carbon steel. The deflector 24 may be perforated for further disengagement 
of solids. The deflector 24 may be constructed from any suitable material 
such as, for example, carbon steel or stainless steel. 
The solids pass around the nose cone 28 and exit the particulate boiler 12 
via solids outlet 30. The nose cone 28 serves to break-up large 
particulates. The nose cone 28 can be fabricated from any suitable 
material such as, for example, stainless steel. The included angle of the 
apex of the nose cone can be any suitable angle, for example, between 
about 20.degree. and about 60.degree.. The bottom portion of the 
particulate boiler 12 has a solids disengagement section 31. The solids 
disengagement section 31 (collector hopper) is in the shape of an 
inverted, truncated cone and functions as a hopper to remove solids. The 
side walls of the solids disengagement section 31 are disposed from the 
horizontal at a suitable angle such as between about 45.degree. and 
20.degree.. A rotary feeder (not shown) located at solids outlet 30 
facilitates the exit of solids from the particulate boiler 12. 
A predetermined water level is maintained in the particulate boiler 12 by 
level control 32. The space above the water level is a vapor space 33 
which is occupied by the steam generated in the boiler. The level of water 
maintained in the particulate boiler 12 and the volume of vapor space 33 
depends on the amount of steam produced and the steam conditions (pressure 
and temperature). The particulate boiler 12 can operate as a boiler 
feedwater preheater (economizer-heat exchanger), rather than a steam 
generator. In such case, the vapor space 33 is nil and water completely 
surrounds the full length of the boiler tubes 18. 
Boiler feedwater enters the particulate boiler 12 via the boiler feedwater 
makeup inlet 34. Steam exits the particulate boiler 12 through steam 
outlet 36. Blowdown from the particulate boiler 12 leaves the vessel 
through blowdown outlet 38. The water and steam in the particulate boiler 
12 are segregated from the gaseous-solids effluent at the top of the 
vessel by top tube sheet 20 and at the bottom of the vessel by bottom tube 
sheet 22. 
FIG. 3 shows a top view depicting the layout of the tubes in the 
particulate boiler 12. The boiler tubes 18 are layed out on a square pitch 
to facilitate water side cleaning of the boiler. 
A top view of the deflector 24 is shown in FIG. 4. The deflector 24 is 
supported in the particulate boiler 12 by means of four to eight rods 40. 
These rods 40 can be fabricated from metal, such as stainless steel. 
In FIG. 5, a top view is shown for the nose cone 28. The nose cone 28 is 
held in place by means of two to four spiders 42. The spiders can be 
one-half inch diameter stainless steel rods. 
In FIGS. 6 through 8, protective sleeves 44 for the particulate boiler 12 
are depicted. The protective sleeves 44 extend within the boiler tubes 18 
from the top of the boiler tubes 18 to the water level in the particulate 
boiler 12 so as to protect that portion of the boiler tubes 18 in the 
vapor space 33. The protective sleeves 44 are fabricated from a material 
such as stainless steel to withstand the corrosion, erosion and 
abrasiveness of the hot, solids containing gaseous effluent. The diameter 
of the protective sleeves 44 will be dictated by the diameter of the 
boiler tubes 18. Thus, for example, sleeves 44 fabricated from 3" Schedule 
pipes would be utilized for four inch outside diameter boiler tubes. Those 
sections of the boiler tubes 18 which are not shielded by protective 
sleeves 44 derive their protection from the cooling effect of the water in 
the particulate boiler 12. The purpose of the protective sleeves 44 is to 
shield the boiler tubes 18 from the high temperature, corrosive effluent 
for only part of the boiler tube length. If the protective sleeves 44 were 
to cover the entire inner surface of the boiler tubes 18, the heat 
transfer rate of the boiler tubes 18 would be severely reduced. 
The protective sleeves 44 are held in place on the top tube sheet 20 of the 
particulate boiler 12 by means of sleeve retainer boxes 46. The retainer 
boxes are generally square and are constructed from stainless steel. The 
retainer boxes 44 are filled with castable refractory 47 (see FIG. 7) to 
withstand the high temperatures of the gaseous effluent. A typical sleeve 
box 44 would be an eight inch square having a four inch depth. Locking 
clips 48 serve to connect the sleeve retainer boxes 46 to each other. 
FIGS. 9 and 8 show the waste heat boiler 14 of the present invention. 
Effluent solids-containing gas from the particulate boiler 12 enters the 
waste heat boiler 14 via gas inlet 50. The incoming gas directly impinges 
on baffle plate 52, which is positioned adjacent to gas inlet 50. The 
baffle plate 52 serves to knock-out solids from the gas. The baffle plate 
52, constructed from any suitable material such as carbon steel, is 
disposed at any suitable angle from the horizontal such as between about 
15.degree. and about 75.degree., more particularly between about 
25.degree. and about 50.degree.. The baffle plate 52 can be a flat plate 
or curved so as to extend from 5.degree. to 360.degree. adjacent the 
circumference of the waste heat boiler 14. The size of baffle plate 52 is 
dependent on the diameter of the gas inlet 50 and the desired degree of 
solids knock-out. Generally, the larger the diameter of the gas inlet, the 
longer the length of baffle plate 52. The baffle plate 52 directs the exit 
of solid particles through solids outlet 54. The bottom portion of the 
waste heat boiler 14 is the solids disengagement section 56. The solids 
disengagement section 56 is in the shape of an inverted, truncated cone 
and functions as a hopper to remove solids. The solids disengagement 
section 56 is disposed from the horizontal at a suitable angle such as 
between about 45.degree. and about 20.degree.. A rotary feeder (not shown) 
located at solids outlet 54 aids in the withdrawal of solids from the 
waste heat boiler 14. 
After solids disengagement, the gas flows upwards through boiler tubes 58. 
The waste heat boiler tubes 58 are typically carbon steel tubes. The 
boiler tubes 58 can be of any suitable diameter such as 2" o.d. The boiler 
tubes 58 are supported at the bottom by lower tube sheet 60 and at the top 
by upper tube sheet 62. 
Water is maintained at a predetermined level in the waste heat boiler 14 by 
level control 64. The space above the water level is a vapor space 66 
which is occupied by the steam generated in the waste heat boiler 14. The 
level of water maintained in the waste heat boiler 14 and the volume of 
the vapor space 66 depend on the amount of steam produced and the steam 
conditions (pressure and temperature). 
Boiler feedwater enters the waste heat boiler 14 via boiler feedwater 
makeup inlet 68. Steam exits the waste heat boiler 14 through steam outlet 
70. Blowdown from the waste heat boiler 14 leaves through blowdown outlet 
72. The effluent gas from the waste heat boiler tubes 58 exits the waste 
heat boiler 14 through the gas outlet 74. The gas from the waste heat 
boiler 14 can be vented to the atmosphere as shown in FIG. 1, or can be 
directed to an air pollution control device (not shown), such as an 
electrostatic precipitator, cyclone, scrubbing unit or a combination of 
such devices. The waste heat boiler 14 can have a post burner 76 
downstream of stack 21 to maintain a certain temperature, such as 
450.degree. F. The post burner 76 allows for sufficient heating of the 
exit gas to avoid condensing water in the gas which can form corrosive 
solutions with the solids. 
The waste heat boilers 14 may in some instances also be equipped with 
protective sleeves such as those described herein for the particulate 
boiler. In normal use, however, it is anticipated that the protective 
sleeves will not be required for the boiler tubes since the gas 
temperature has already been lowered and particulate loading has been 
reduced before the gas reaches the upper section of the boiler tubes 58. 
The boilers of this invention can be utilized in many existing facilities 
such as coal gasification plants, acid plants and glass making plants. 
The boilers of the present invention have a primary purpose of recovering 
waste heat and converting same to steam. As a secondary purpose, the 
boilers of this invention serve to reduce particulate matter from 
solids-containing effluent gases such as to act as an air pollution 
control unit or as an adjunct to an air pollution control system, such as 
an electrostatic precipitator. 
By way of example, the following is offered as a typical gas analysis such 
as that from an effluent of a glass manufacturing facility that can be 
utilized in the boilers of the present invention: 
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Flue Gas Temperature 
1200.degree. F. to 2000.degree. F. 
Flue Gas Flow 3,025,000 Standard 
Flue Gas Analysis dry CFH 
% O.sub.2 7.6 
% CO.sub.2 8.4 
% H.sub.2 O 13.2 
NO.sub.x (nitrous oxides) 
1296 ppm 
Concentration 
NO.sub.x (nitrous oxides) 
555.5 lb/hr. 
Emission 
SO.sub.2 Concentration 
31.4 ppm 
SO.sub.2 Emission 18.6 lb/hr. 
SO.sub.3 Concentration 
.7 ppm 
SO.sub.3 Emission 0.6 lb/hr. 
Particulate (90% Na.sub.2 SO.sub.4) 
Concentration .076 gr/scfd 
Emission 32.4 lb/hr. 
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Based on the above example, the particulate boiler 12 would have the 
following dimensions: 
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Inside Diameter 10 feet 
Total Length Approximately 29 feet 
Total Length of Boiler 
15 feet 
Section 
Steaming Water Level 
11 feet 
Length of Header 4 feet 
Boiler Tubes and Sleeves 
Approximately 4" o.d. 
tubes; 12 feet long; 
sleeves extending 3 
feet within tubes; 
3" Schedule Pipes as 
sleeves 
Length of Deflector 3 feet 
Diameter of Nose Cone 
Approximately 3 feet 
Length of Solids 7 feet 
Disengagement Section 
______________________________________ 
Each of two waste heat boilers 14 would have the following dimensions based 
on the above example: 
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Total length Approximately 28 feet 
Total Length of Boiler 
9 feet 
Section 
Length of Solids Approximately 71/2 
Disengagement Section 
feet 
Diameter of Boiler Tubes 
2 inches 
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The boilers of the present invention provide the following advantages: 
(1) the use of sleeves fabricated from a material which can withstand 
corrosion, erosion and high temperatures serves to protect tubes 
fabricated from less expensive material, such as carbon steel and thus 
reduce the cost of the boilers; 
(2) the particulate boiler of this invention has the ability to serve 
either as an economizer (water preheater) to each of the waste heat 
boilers or as a separate fired steam boiler unto itself without the need 
for a steam drum; 
(3) the particulate boiler which is downfed can be used to preheat water, 
generate steam, or do both simultaneously; 
(4) the gas flow through the boilers of this invention can be reversed to 
aid in cleaning of the boiler tubes; 
(5) a straight single pass drop through the tubes is provided; 
(6) the sleeves are interlocking which provides a total protective field 
for the boiler tube sheet and boiler tubes; 
(7) the sleeves are removable, cleanable, reusable and replaceable; and 
(8) solid particles down to about 325 mesh can be removed. 
The boilers of the present invention can produce 185 psi (approximately 
400.degree. F.) steam for direct plant usage. This steam could also be 
superheated and utilized in a compatible turbo electric generator for 
direct electrical generation with an 18 psi steam exhaust. The 18 psi 
exhaust system can be used in winter for plant heating and in the summer 
for recuperative air conditioning systems. The 185 psi steam can also be 
used throughout plants for direct drive of air compressors, turbine driven 
fans and in all instances where large electrical driven motors are 
presently in use. 
The present invention may be embodied in other specific forms without 
departing from the spirit or essential attributes thereof and, 
accordingly, reference should be made to the appended claims, rather than 
to the foregoing specification, as indicating the scope of the invention.