Apparatus And Process For Slag Deposit Removal

Abstract

An apparatus for removing slag from the heat absorption surface in the furnace section and convection section of a heat exchanger including at least one blast nozzle disposed proximate to the surface and having at least two outlet orifices. A first fluid, such as water, is delivered to one of the orifices, and a second fluid, such as steam, is delivered to the other orifice to create a thermal shock and mechanical force which causes the slag deposits to separate from the heat absorption surface.

Description

BACKGROUND OF THE INVENTION

This invention relates to an apparatus for removing slag deposits from a heat exchanger, and, more particularly, to an apparatus for removing slag deposits from the heat absorption surface of the furnace and convection sections of a vapor generator.

In the generation of power from fossil fuels utilizing vapor generators, there is a major problem attendant in the firing of fuels having a high alkali metal content, due to the severe slag deposits that are formed on the heat absorption surface in the furnace and convection section during the operation of the vapor generator. In the past, these deposits have been avoided primarily by restricting and blending the fuel and using additives. However, even with this restricted use of the fuel, the problem of fouling heat transfer surfaces has still persisted to a great degree, rendering it necessary to use a large number of soot blowers, which add to the cost of the vapor generator.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an apparatus for the removal of slag deposits from the heat absorption surface in the furnace and convection sections of a vapor generator which does not restrict the use of the fuel and which eliminates the use of additives, while minimizing the number of blowers required.

Toward the fulfillment of this object the present invention features the use of a blast nozzle comprising a hollow body member, at least two outlet orifices extending through a wall of said body member, first delivery means for delivering a first fluid to one of said orifices, and second delivery means for delivering a second fluid to the other of said orifices .

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description, as well as further objects, features, and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in connection with the accompanying drawings wherein:

FIG. 1 is a partial section-partial schematic view looking at the side and down on the furnace section of a vapor generator;

FIG. 2 is an enlarged sectional view taken along the line 2--2 of FIG. 1; and

FIG. 3 is a sectional view taken along the line 3--3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring specifically to FIG. 1 of the drawings, a portion of the furnace section of a vapor generator is shown schematically by the reference numeral 10. The furnace is formed by four walls, two of which are shown by the reference numerals 12 and 14, it being understood that corresponding walls opposite and parallel to the walls 12 and 14 are also provided to form an enclosed structure.

The walls 12 and 14 are of a fin-tube construction as shown schematically, and are surrounded by insulating walls 16 and 18, respectively. The inner surfaces of the walls 12 and 14 form the heat absorption surface of the furnace section 10 in a relatively heavy slag zone extending from the bottom portion of the furnace section up to the top height thereof. A plurality of rows of fin-tubes, shown in general by the reference numeral 20, form the superheater portion of the furnace section 10.

According to the present invention, each wall forming the furnace section 10, along with its corresponding insulating wall, is provided with a plurality of openings extending therethrough for accomodating a corresponding number of blast nozzles. For the purpose of example, only one hole 12a and its corresponding hole 16a, is shown extending through the fin-tube wall 12 and the insulating wall 16, it being understood that several more may be provided in this wall and the other walls for de-slagging the furnace walls, superheater walls in the furnace and other heat absorbing surfaces in the convection section.

The blast nozzle is shown by the reference numeral 22, and is adapted to be moved between a retracted position shown by the solid lines in FIG. 1, and an extended, operative position shown by the broken lines. This movement is achieved by means of a drive unit 24 which is connected to the nozzle 22 by means of a lance tube 26. The drive unit is more completely described in U.S. Pat. Application Ser. No. 759,184, filed Sept. 11, 1968 and assigned to the assignee of the present invention, it being sufficient for the purposes of the present application to note that it is adapted to move along a pair of tracks 28 to and from the retracted and extended position of the nozzle 22, and that it includes means to impart a rotational drive to the nozzle.

A control system 30 is operatively connected to the drive unit 24 in order to control the above-mentioned movements of the nozzle 22, and to distribute steam and water from sources 32 and 34, respectively, to the nozzle via the drive unit 24 and the lance tube 26. The connections between these components are shown schematically by the reference numeral 36.

The details of the nozzle 22 are shown in FIGS. 2 and 3. Specifically, the nozzle comprises a hollow body member 40 having a pair of axially spaced, radially extending orifices 42 and 44 extending therethrough for respectively distributing steam and water through the nozzle. In particular, the lance tube 26 is directly connected to the body member 40 for supplying steam from the source 32 to the orifice 42 via the control system 30 and the drive unit 24. A water tube 46 is coaxially disposed within the lance tube 26 and connects the water source 34 to the orifice 44 via the control system 30, the drive unit 24, and an elbow connection 48. A pair of nozzles 50 and 52 are associated with the orifices 42 and 44, and are adapted to receive the steam from the tube 26 and the water from the tube 46, respectively, and distribute it outwardly.

In operation, the control system 30 is programmed to periodically actuate the drive unit 24, which moves along the tracks 28 and causes the lance tube 26 and the nozzle 22 to move from their retracted position to their extended position within the furnace section 10. The nozzle 22 is continuously rotated, and distributes steam and water outwardly through the nozzles 50 and 52, respectively, against the inner surfaces of the walls 12 and 14.

It is understood that since several of these nozzles and associated structure will be associated with each wall, the control system 30 is adapted to sequentially actuate the nozzles according to a predetermined program based on the buildup of slag on the walls.

Several variations can be made to the above without departing from the scope of the present invention. For example, the type of fluids dispensed from the nozzle is not limited to steam and water, but may be in the form of other fluids, such as air or gas, etc. Also, each nozzle can be provided with more than one orifice for discharging its respective fluid. Of course, still other variations of the specific construction and arrangement of the apparatus disclosed above can be made by those skilled in the art without departing from the invention as defined in the appended claims.

Claims

What is claimed is:

1. A slag deposit removal apparatus for cleaning the heat absorption surfaces of a vapor generator, said apparatus comprising a plurality of blast nozzles, each comprising a body portion, at least two fluid discharge members extending through a wall of said body portion and perpendicular to the longitudinal axes of said body portion; at least two fluid supply means for delivering separate fluids to said discharge members, respectively; first drive means for translating said discharge members between an operative position inside said furnace and an inoperative position outside said furnace; second drive means for rotating said discharge members in their operative positions; and control means for controlling the operation of said discharge members, said fluid supply means and said first and second drive means according to a predetermined sequence so that said fluid is discharged against at least one of said surfaces in a manner to create a combined thermal shock and mechanical force against said surface to cause the separation of slag deposit therefrom.

2. The apparatus of claim 1 wherein said discharge members are in the form of nozzles.

3. The apparatus of claim 1 wherein said predetermined sequence is based on the buildup of slag on said surface.

4. The apparatus of claim 1 wherein said discharge members are axially spaced along said body member.