US2956680A

US2956680A - Method of and apparatus for separating ash and cleaning shot

Info

Publication number: US2956680A
Application number: US631116A
Authority: US
Inventors: Puhr-Westerheide Jurgen; Frose Wilfried
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1956-01-27
Filing date: 1956-12-28
Publication date: 1960-10-18
Anticipated expiration: 1977-10-18

Description

Oct. 18, 1960 J PUHR-WESTERHEIDE ETAL METHOD OF AND APPARATUS FOR SEPARATING ASH AND CLEANING SHOT Filed Dec. 2a, 1956 INVENTORS Jurgen -Puhr -Wesrerhe|de BY Wilfried Frose ATTORNEY Unite States Patent METHOD OF AND APPARATUS FOR SEPARATING ASH AND CLEANING SHOT Jiirgen Puhr-Westerheide, Oberhausen, Rhineland, and Wilfried Frtise, Duisburg, Germany, assignors to The Babcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Filed Dec. 28, 1956, Ser. No. 631,116

Claims priority, application Germany Jan. 27, 1956 7 Claims. (Cl. 209-151) The present invention relates to a method of and apparatus for the separation of shot and flue dust in a shot cleaning installation wherein the shot consists of steel balls or pellets of relatively high density which follow and cascade over the heating areas to be cleaned whereby the deposits and ash particles sticking to the heating areas are removed. More particularly the invention relates to the separation of the removed ash from the shot by the movement of the mass of ash and shot downwardly by gravity effects from the heating areas into a separating zone wherein the mass cascades over inclined louver blades with separating gases passing between the blades to remove the ash. The ash entrained with the gases is carried away by differential pressure actuated gas flow and the cleaned shot is discharged to a shot reservoir for subsequent use.

In the shot cleaning of heat exchange elements, such as in vapor generators, a mass of metallic shot or pellets is cascaded downwardly over the surfaces of the heat exchange elements. The contact between the coarse materials and the surfaces of theheat exchange elements dislodges dust deposits on those surfaces so that the shot and dislodged material flows downwardly in the direction of gas flow toward the outlet of the gas-pass. It is desirable to separate the coarse shot or other cleaning particles from the dislodged ash particles so that the shot may be re-cycled for subsequent cleaning use. Heretofore, the separation of the shot from the dust has been accomplished in general by either an increase in the flow velocity of the flue gases leaving the gas pass, or'by use of air streams which are projected through the'mixture of shot and ash at a sufficient velocity to entrain the finer particles for subsequent disposal. Unfortunately, operation of vapor generators or the like at reduced ratings reduces the volume of gas flow and frequently the gas velocities are inadequate for the separation of the ash particles. The use of air jets for ash separating purposes reduces the overall thermal efficiency of the unit.

According to the present invention, the shot is sep arated from the heating gases in a gas turning zone, where a major portion of the gas is passed over an additional bank of heat exchange elements. The fine particles of ash will be entrained in the heating gas, while the larger particles will be separated from the heating gases with the cleaning materials and delivered to a separating zone. Within the separating zone the gravitational movement of the solid materials is hindered or retarded while a stream of heating gas is passed at relatively high velocity through the mixture of coarse cleaning solid and ash particles to entrain the latter in the gas. After entrainment of the ash particles the gas is directed through a connecting duct to a downstream position in the spent heating gas flow path where the gas streams are recombined and discharged to the atmosphere.

The various features of novelty which characterize our invention are pointed out with particularity in .the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of the invention.

0f the drawings:

Fig. 1 is an elevation, in section, of the lower position of a vapor generator constructed and arranged in accordance with the present invention; and

Fig. 2 is an enlarged elevation, in section, showing the separating device illustrated in Fig. 1.

A vapor generator arranged for shot cleaning involves a substantially upright gas pass for the flow of heating gases downwardly over horizontally arranged heat exchange surfaces, such as the convection banks of the vapor generator. For an effective contact cleaning of the convection tube banks the shot is projected into the upper portion of the upright gas pass in a manner such as shown in U.S. Patent 2,762,610 for gravitational movement downwardly through the pass. Thus, the heating gas and the contact cleaning material-flow is concurrent.

As shown in Fig. 1, the upright gas pass 10 of a vapor generator is provided with rows of heat exchange tubular elements 11 horizontally disposed beneath an upper heatv ing gas inlet 12. The gas pass 10 is provided with a lower flue gas passage 13 having an inclined bottom wall surface 14 which cooperates with an upwardly inclined wall surface 15 extending rearwardly from the rear wall 16 of the gas-pass 10 to form a hopper 19. The outermost wall 16 of the gas-pass 10 projects downwardly into the hopper and forms in part the front wall 17 of. a gas-pass 18 through which the gases are directed in moving across heat exchange elements 20. The gas pass 18 is provided with a gas outlet 21 which may be connected with an air heater (not shown) or may be passed directly to a stack for discharge of spent heating gases to the atmosphere.

The hopper 19 is provided with a'lower material outlet 22 which is connected with a separating chamber 23, hereinafter described in detail. The depending walls 16 and 17 of the gas-passes 10 and 18 defines a restricted gas passageway between the lowermost end 24 of the walls and the bottom outlet 22 from the hopperover the heat exchange surfaces 20 to the spent heating gas outlet. The velocity conditions of the heating gases passing through the hopper is such that at high ratings of the vapor generator, alarge portion of the dislodged dust will remain in entrainment in the gases and will be However, at lower operating ratings of the vapor generator, the flue gas velocity pass-- ing through the hopper 19 will be insufficient to entrain discharged from the unit.

more than the extremely fine dust particles.

Regardless of the load rating on the vapor generator the coarser particles of dust and the shot will be discharged from the hopper 19 into the separating chamber 23 of the present invention. As shown in Fig. 2, the separator is illustrated in the form of a polygon having walls made of steel which may be lined by refractory materials if necessary. The separating chamber is con nected by means of a duct 25 with the spent heating gas flow path downstream of the heat exchange elements 20. With this arrangement, the separating chamber receives gases through the opening 22 which are under a different pressure than the pressure at the discharge end of the duct 25. Thus, a flow of gases will occur from the discharge end of the flue gas pass 10 into the 3 separating chamber 23 and through the duct 25 to a position downstream of the heat exchange elements 20.

Within the separating chamber, a row of spaced louver blades 26 are pivotally supported in horizontally and vertically spaced relation with the pivotal axis 27 of the row lying in an inclined plane. Immediately above the blades 26 is positioned a deflecting plate 23 which is inclined in the opposite direction from the angle of inclination of the plane of the shelf support axes 27. Thus, the coarse and fine material discharging from the vapor generator hopper 19 into the separating chamber 23 will be deflected toward the upper end of the blades 26. The initial deflection of the coarse and fine material entering the separating chamber insures a retarding or hindering action on the mixture moving downwardly across the spaced over-lapping surfaces of the louver blades 26. In passing over the blades, the fine materials in the mixture will be drawn through the gap between the blades for discharge through the connecting duct 25' into the stream of spent heating gases leaving the unit. At the same time, the coarse particles, predominantly shot, will discharge downwardly into a hopper 30 and discharge opening 31 formed at one side of the bottom of the separating chamber 23. Thereafter, the cleaned shot may be transported to a conveying device (not shown) which re-cycles the shot to the upper end of the vapor generating unit for reuse of the material in cleaning the surfaces of the heat exchange elements 11.

In the separating chamber, the gases passing between the blades 26 entrain the finer dust particles which may be dropped out of suspension in the chamber 29 before the gases pass to the duct 25. Accordingly, the chamber 29 is provided with a bottom outlet 32 for the removal of ash and dust particles, where the ash may be continuously or periodically removed.

In operation, the shot and dust particles entering the separating chamber 23 may be at a relatively high temperature corresponding with the gas temperature in the lower part of the gas pass and the hopper 19. Ordinarily, the gas temperature will not be excessive and will not cause damage to the metallic parts of the separating chamber 23. However, if the temperatures exceed a desirable value, the overall temperature within the separating chamber may be controlled by the separate introduction of cooling air through an inlet duct 34 opening to the lower portion of the chamber 23. The introduction of cooling air is controlled by means or" a damper such as a slide valve 35. In regulating the flow velocity of the separating gases between the blades 26, a separate control damper 36 is positioned in the duct 25 such as shown in Figure 2.

The louver blades 26 of the separating chamber 23 are pivotably supported so that upon need all of the solid materials entering the separating chamber 23 may be diverted toward the ash removal outlet 32 of the chamber 29. Such an occasion might arise by the accumulation of large lumps of ash which may cascade into the ash separation chamber 23 with or without the shot used for cleaning purposes. Under such circumstances, it will be desirable to close the shot outlet 31 so that none of the materials within the ash separating chamberwill be conducted to the shot transportation system. This can be accomplished by a flap valve 37 which is indicated in Figure 2. As shown, the valve is mounted on theaxis of the lowermost louver blade so as to be adjustable in closing relationship to the shot outlet 31, when the blades are tipped toward the chamber 29 and during normal operations, the valve will be positioned, as shown, for a free discharge of shot to the outlet 31.

It will be noted that the flow of flue gases through the ash separating chamber 23 is accomplished by means of differential pressures within the gas flow path of the heating gases. Thus, the duct 25 from the ash separating chamber 23 terminates at a position downstream from the heat exchange elements 20 so that the differential pressure drop across such heat exchange elements is equal to the differential pressure drop through the ash separating chamber 23 and the connecting duct 25 when suflicient volume of gases flow through duct 25. In this connection, it will also be understood that the heat exchange surfaces interposed in the flue gas flow passageway may take the form of economizer elements, or may be in the form of an air heater of the rotating or stationary type. in any event, the terminal point of the connecting duct 25 is located so as to effect a fluid gas flow through the ash separating chamber 23 and the connecting duct 25 as such flow is caused by differential pressure conditions.

Advantageously, the use of heating gases for dust removal as hereinbefore described contributes to the overall heat etliciency of the unit and in turn eflfectively utilizes existing facilities without the addition of external fans or the like.

While in accordance with the provisions of the statutes we have illustrated and described herein the best form and mode of operation of the invention now known to us, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of our invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. Apparatus for separating cleaning pellets from ash containing products of combustion comprising walls defining a casing of polygonal vertical cross-section having an upwardly facing inlet opening for the gravitational receipt of pellets and ash to be separated and separating gases and having spaced outlets in the lower portion thereof for the discharge of separated pellets and ash, an inclined row of spaced louver blades extending upwardly from a position between said spaced outlets to an upper position between said inlet opening and one of said outlets, each of said blades being pivoted about an axis, the lowermost blade having a plate attached thereto operable to close one of said outlets, and a conduit opening to said casing beneath said row of louver blades and connected with a zone having a lower static pressure than that within said casing whereby a flow of gas may be induced through the gap between said spaced louver blades to separate ash from said pellets.

2. Apparatus for separating cleaning pellets from ash containing products of combustion comprising walls defining a casing of polygonal vertical cross-section having an upwardly facing inlet opening for the gravitational receipt of pellets and ash to be separated and separating gases and having spaced outlets in the lower portion thereof for the discharge of separated pellets and ash, an inclined row of spaced louver blades extending upwardly from a position between said spaced outlets to an upper position between said inlet opening and one of said outlets, each of said blades being pivoted about an axis, the lowermost blade having a plate attached thereto operable to close one of said outlets, an inclined impact plate positioned adjacent said inlet opening in vertical overlapping relationship to the lower portion of said louver blades to direct the gravitational flow of pellets and ash to said louvers, and a conduit opening to said casing beneath said row of louver blades and connected with a zone having a lower static pressure than that within said casing whereby a flow of gas may be induced through the gap between said spaced louver blades to separate ash from said pellets.

3. In the cleaning of heat exchange elements contacted with ash-bearing heating gases by cascading shot over the elements, the method of separating the ash dislodged from said elements from said shot which comprises the steps of passing a major portion of the heating gases through a path of changing direction to deentrain and thereby separate the shot and the larger particles of removed ash from said heating gases, gravitationally passing said shot and larger ash particles through a separating zone, passing a controlled minor portion of said heating gases into said separating zone with said shot and ash particles, passing said heating gas at an entraining velocity through said shot and said ash particles within said separating zone to separate the latter from the former, discharging said controlled minor portion of said heating gas from said separating zone with entrained fine particles of ash to recombine with the remaining heating gas downstream of said path of changing direction, and gravitationally discharging said larger ash particles and said shot separately from said separating zone.

4. In the cleaning of heat exchange elements contacted with ash-bearing heating gases by cascading shot over the elements, the method of separating the ash dislodged from said elements from said shot which comprises the steps of passing a major portion of the heating gases through a path of changing direction to separate said shot and the larger particles of removed ash from said heating gases, gravitationally passing said shot and ash particles through a separating zone, passing a controlled minor portion of said heating gases into said separating zone With said shot and ash particles, passing said heating gas at an entraining velocity through said shot and said ash particles within said separating zone to separate the latter from the former, selectively passing a cooling gaseous fluid through said separating zone to cool said minor portion of said heating gases, discharging said controlled minor portion of said heating gas from said separating zone with entrained fine particles of ash to recombine with the remaining heating gas downstream of said path of changing direction, and discharging said ash particles and said shot separately from said separating zone.

5. In the cleaning of heat exchange elements contacted with ash-bearing heating gases by cascading shot over the elements, the method of separating the ash dislodged from said elements which comprises the steps of passing a major portion of the heating gases through a path of changing direction to separate said shot and the larger particles of removed ash from said heating gases, gravitationally passing said shot and ash particles through a separating zone, passing a controlled minor portion of said heating gases into said separating zone with said shot and ash particles, passing said heating gas at an entraining velocity through said shot and said ash particles within said separating zone to separate the latter from the former, discharging said shot separately from said separating zone, separating some of the ash from the entraining gas within said separating zone, separately discharging said separated ash from said separating zone, and discharging said gas and entrained ash particles from said separating zone to recombine with the major portion of said heating gases downstream of said path of changing direction.

6. Apparatus for separating cleaning pellets from ashcontaining products of combustion comprising means forming a furnace with a gas flow zone, walls defining a casing of polygonal vertical cross-section having an upwardly facing inlet opening to said gas flow zone for the gravitational receipt of pellets and ash to be separated and separating gases and having spaced outlets in the lower portion thereof for the separate discharge of separated pellets and ash, an inclined row of spaced louver blades extending upwardly in overlapping relationship from a position between said spaced outlets to an upper position between said inlet opening and one of said outlets, and a conduit opening to said casing beneath said row of louver blades and connected to said gas flow zone for gas discharge to said zone at a location having a lower static pressure than that within said casing whereby a flow of said gas may be induced through the gap between said spaced louver blades to separate ash from said pellets.

7. Apparatus for separating cleaning shot from ashcontaining products of combustion comprising means forming a furnace with a gas flow zone walls defining a casing of polygonal vertical cross-section having an upwardly facing inlet opening for the gravitational receipt of shot and ash to be separated and the inflow of gases from said gas flow zone and having spaced outlets in the lower portion thereof for the separate discharge of separated shot and ash, an inclined louver blade extending upwardly from a horizontally disposed pivot axis positioned below said inlet opening and extending substantially across said inlet opening, an inclined plate secured adjacent said inlet open-ing in opposite inclination to said louver blade to deflect said downwardly moving mass of shot and ash against the surface of said louver blade, and a conduit opening to said casing beneath said louver blade and connected to said gas flow zone for gas discharge to said zone at a location having a lower static pressure than that within said casing whereby a flow of gas may be induced through said upwardly facing opening and a gap above and below said louver blade to separate ash from said shot.

References Cited in the file of this patent UNITED STATES PATENTS 844,620 Saunders Feb. 19, 1907 1,506,494 Lindsay Aug. 26, 1924 1,846,210 Kramer Feb. 23, 1932 2,762,610 Puhr-Westerheide Sept. 11, 1956 2,792,316 Broman May 14, 1957 FOREIGN PATENTS 284,790 Switzerland Dec. 1, 1952 471,273 Canada Feb. 6, 1951