FI80783B - Method of removing coatings from tubes in a boiler - Google Patents

Description

80783 ^ Method for removing cladding from boiler lines Sätt att avlägsna beläggningar pa rör i en panna 5

The present invention relates to a method for removing coatings from interconnected lines of substantially parallel lines in a boiler, such as steam and water lines in a soda boiler superheater, convection section or preheater used for pulp production. a sootblower equipped with a nozzle tube which is placed longitudinally in the boiler and which is moved back and forth along a row of conductors and which has two oppositely arranged nozzles for blowing a cleaning agent, such as steam or air, with the nozzle tube in circulation.

When making paper pulp using the so-called. the sulphate process is boiled in chopped pulp in the alkaline yellow liquor. By means of this cooking, cellulose is separated from the wood and lignin and other substances are removed. In order for the process to be economically viable, the chemicals used in the yellow liquor (sodium hydroxide and sulphide) must be recovered so that they can be reused in the process. Thus, after cooking, the cooking liquor is recovered and burned after evaporation in a high-pressure steam boiler, such as said soda compartment boiler. The evaporated lye is injected into the boiler, whereby the substances separated from the wood during cooking are burned. The steam generated by this operation is used in the manufacturing process. The inorganic constituents in the liquor accumulate as a molten mass in the bottom of the soda-boiler-30 boiler, which is fed sodium sulphate (hence the name sulphate process) to replace the inorganic chemicals burned during the process and used to make new yellow liquor for the process.

35 The soda compartment boiler includes a superheater, a convection section and a preheater, each of which has a number of coils containing steam or water. The pipe coils form parallel rows of vertical ducts, 2 80783 1 with the ducts in each row arranged at mutual intervals, forming transverse flue gas passages between the rows. During the use of the soda compartment boiler, the hot flue gases pass through the different pipe coils in the boiler, whereby the flue 5 carried by the flue gases accumulates as cover layers in the pipe coils. These overlays impede the operation of the boiler, on the one hand, by preventing heat transfer from hot flue gases to steam or water in the coils, and on the other hand by reducing the size of the flue gas passages between the ducts and, in the worst case, completely blocking them.

10 In order to eliminate these disadvantages, it is therefore desirable to remove these coating layers. In the cleaning of the tube coils of a soda compartment boiler, the so-called sootblowers, each of which includes a nozzle tube with two opposite nozzles at its front end.

In the known cleaning method, a plurality of sootblower nozzle tubes are placed longitudinally in a boiler between rows of conductors and rotated back and forth along these rows mainly in a straight-up direction against the lines, whereby high-pressure steam or air is continuously blown out of the nozzles. This method often achieves only a very inefficient cleaning of the tube coils, and the cleaning often takes a lot of time with each cleaning due to the fact that the nozzle tubes have to be moved back and forth several times between the lines to remove the coating layers sufficiently. Using this method, the tube coils are subjected to rotational movements, whereby they are exposed to such high stresses that they often break. This causes costly downtime.

It is therefore a particular object of the present invention to provide a method for efficiently cleaning tubular coils in a soda compartment boiler without subjecting the tubular coils to rotational movements which result in their rupture.

It is a more general object of the present invention to provide a method for removing coatings from conduits in a more common type of boiler.

Il 3 80783 1 These objects are achieved in a manner as described according to the present invention, characterized in that the reciprocating and rotational movement of the nozzle tube is equated so that both nozzles of equivalent diameter are substantially parallel to the lines 5 whenever they pass through a line during reciprocating movement of the nozzle tube. .

Due to this nozzle tube movement arrangement, no steam or air jets are applied to the lines from the nozzles when the rotational positions of the nozzle tube are such that the nozzles are perpendicular to the lines, i.e. the force of the jets is at its maximum. In this way, the risk of the cables circulating and thus also breaking the cables is reduced. The movement arrangement of the nozzle tube also enhances the cleaning due to the fact that the nozzles in said rotating positions of the nozzle tube are directed to the spaces between the lines, thus achieving the maximum cleaning force to remove clogging cover layers from these spaces which form flue gas passages.

The reciprocating movement of the nozzle tube is mainly performed step by step py-20 by adjusting it to positions in which the nozzles are in the middle of the space between each adjacent line in the row. In this case, it may be advisable to rotate the nozzle tube from its base during said stops in a stepped reciprocating position, the nozzle tube being held in a rotational position during each movement such that the nozzles are oriented substantially parallel to the lines. The cleaning agent is mainly blown only during said stops in a step-and-step reciprocating device.

In the preferred procedure, a nozzle tube with nozzles of the same diameter but axially displaced is used, the axial distance between the nozzles being preferably slightly larger than the diameter of the wires.

The invention will now be described in more detail below with reference to the accompanying drawings.

a 80783 1 Fig. 1 schematically shows a horizontal nozzle tube in connection with the cleaning of a vertical row of conduits placed in a boiler, used to maintain transverse flue gas passages between the conduits.

Fig. 2 schematically shows the horizontal nozzle pipe according to Fig. 1 in connection with the cleaning of vertical lines arranged in two parallel rows in a boiler, when used to maintain flue gas passages extending transversely to the conductor lines between the lines.

Fig. 3 schematically shows a modified horizontal nozzle tube in connection with the cleaning of vertical lines arranged in two parallel rows in a boiler, used to maintain flue gas passages extending transversely of the lines between the lines.

Fig. 4 schematically shows the position of the nozzles of the nozzle tubes shown in Figs. 2 and 3 with them in the middle of the wires in both rows.

The drawings show a nozzle tube 1 of a sootblower, which can be placed longitudinally horizontally in a boiler 2, such as a soda compartment boiler used in the production of pulp, to remove the coating of the vertical lines 3 in the boiler 2. In the example according to Fig. 1, the nozzle line 1 is shown placed along the lead row 3, and in the example according to Figs. 2 and 3, between the two lead rows 3.

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When the boiler 2 is a soda compartment boiler, the wires form parts of the tube coils in the boiler superheater, convector part or preheater. Lines 3 contain steam or water heated by hot flue gases in a soda compartment boiler, these gases passing through lines 30 3 transversely to the line or lines of line. Transverse flue gas passages are thus formed between the lines 3. During the operation of the boiler, the flue brought by the flue gases accumulates in the lines 3, whereby the flue gas passages become narrower and can even become completely blocked. As mentioned above, the deposits 35 in the lines 3 caused by this accumulation prevent the heat transfer from the hot flue gases to the steam or water in the lines 3.

li 5 80783 1 At the front end of the nozzle tube 1 there are two oppositely arranged nozzles 4 for blowing a cleaning agent such as steam or air. In the embodiment shown in Figures 1 and 2, the nozzles 4 of the nozzle tube 1 are located opposite each other, while in the embodiment 5 shown in Figure 3 they are slightly displaced axially with respect to each other. The axial distance between the nozzle 4 of the nozzle tube 1 according to Fig. 3 is slightly larger than the diameter of the lines 3. In this case, it must be taken into account that this axial distance must be limited due to the fact that the cleaning agent is blown under very high pressure, so that the resulting deflection of the nozzle tube 1 does not become too great.

The nozzle tube 1 can be pulled out from inside the boiler 2 and placed in the boiler only when the cover layers have to be removed from the lines 3. During this cleaning, the nozzle tube 15 is moved back and forth along lines or lines of lines 3, whereby the cleaning agent is blown out.

According to the present invention, even the back and rotation of the nozzle tube 1 is thus equated so that the two oppositely arranged nozzles are directed upwards and downwards, i.e. parallel to the lines 3 (see Fig. 4), whenever they pass the line 3 in the row or rows in connection with the reciprocating movement of the nozzle tube 1. The movement arrangement of this nozzle tube 1 achieves the above-mentioned advantages so as to reduce the risk of tube damage and efficient cleaning.

The nozzle tube can advantageously be moved back and forth in stages by making a stop at the points where the nozzles 4 are located in the middle of the space 30 between the two adjacent lines in the row or rows. In this case, it may be advisable to rotate the nozzle tube 1 only during these stops, keeping it in connection with each reciprocating transfer stage in such a rotational position that the nozzles 4 are oriented as shown in Fig. 4, i. parallel to wires 3.

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The blowing of the cleaning agent can be controlled so that the blowing only takes place during said stops in a step-and-turn motion.

6 80783 1 The nozzle tube 1 is moved back and forth and rotated by two separate motor units of known type (not shown in the figure). These motor units are controlled to produce parallel movements as described in the known programmable regulation and control equipment. However, these devices do not form any part of the present invention and will therefore not be described in more detail in this context. The blowing of the cleaning agent is controlled in the same way by means of known equipment.

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II

Claims (6)

1 Patent claim 1. A method of removing coatings pi in a series of mutually arranged substantially parallel rows (3) in a boiler (2), such as and containing water containing 1 rd, in the manufacture of pulp using soda boiler superheater, convection section or economizer , world is utilized a so-called soot blower, comprising a nozzle tube (1) which is inserted longitudinally into the boiler and is passed back and forth along the row of tubes and which at the front end has two diametrically opposed nozzles (A) for blowing out the soothing medium, such as air or air, during rotation of the nozzle tube, characterized in that the forward and reverse movement and rotation movement of the nozzle bar (1) are coordinated so that they bite diametrically opposed nozzles (A) are aligned substantially parallel to the tubes (3) each of the nozzles (3). 1) forward and reverse passes an rBr (3) in the row. 2. A method according to claim 1, characterized in that the forward and reverse nozzle (1) of the nozzle bar (1) is carried out incrementally with stop 1 such positions in which the nozzles (A) are located opposite a gap between adjacent tubes (3) in the row. . 3. A method according to claim 2, characterized in that the nozzle tube (1) is rotated only during said stop in the stepwise forward and backward movement, each nozzle tube (1) during each forward and reverse step is held in such a rotational position (A nozzle). ) are aligned substantially parallel to the tubes. A. A method according to claim 2 or 3, characterized in that the soot medium is blown out only during said stop 1 the stepwise forward and reverse return movement. 5. A method as claimed in claim 1, characterized in that a nozzle bar (1) with diametrically opposed but axially displaced nozzles (A) is used. 35 6. A method according to claim 5, characterized in that a nozzle bar (1), in which the axial spacing between the nozzles (4) is slightly larger than the diameter of the rudder (3), is used. 5 10 15 20 25 30 35 li