Title of Invention	A METHOD OF CLEANING SURFACES OF FURNACES IN OPERATION
Abstract	The present invention relates to a method of cleaning surfaces (2) of furnaces (I) in operation, in particular the flue gas side of metal heat-exchange surfaces in industrial furnaces, and also in industrial boilers, comprising the steps of: generating a jet of gas that is directed towards the surfaces to be cleaned; integrating particles (6) in the solid state. in the jet of gas and projecting the particles at a speed such that the particles disintegrate on coming into contact with said surfaces for cleaning; and moving the jet of gas and particles along the surfaces to be cleaned; said method being characterized in that the particles used have a formulation that is constituted by a majority of carbamide. 0"

Title of Invention

A METHOD OF CLEANING SURFACES OF FURNACES IN OPERATION

Abstract

The present invention relates to a method of cleaning surfaces (2) of furnaces (I) in operation, in particular the flue gas side of metal heat-exchange surfaces in industrial furnaces, and also in industrial boilers, comprising the steps of: generating a jet of gas that is directed towards the surfaces to be cleaned; integrating particles (6) in the solid state. in the jet of gas and projecting the particles at a speed such that the particles disintegrate on coming into contact with said surfaces for cleaning; and moving the jet of gas and particles along the surfaces to be cleaned; said method being characterized in that the particles used have a formulation that is constituted by a majority of carbamide. 0"

Full Text	A METHOD OF CLEANING HEAT EXCHANGE SURFACES OF FURNACES IN OPERATION The invention relates to a method of cleaning surfaces of furnaces in operation, in particular metal heat-exchange surfaces on the flue-gas side of industrial furnaces, such as petrochemical and oil refinery stills, and industrial boilers. Such furnaces often burn heavy fuel oil for economic reasons. However, since the combustion of heavy fuel oil is incomplete, deposits form on the heat-exchange surfaces. These deposits are constituted in particular by heavy fractions of hydrocarbons, silica, heavy metals, and stable components that retain a solid state inside the furnace, even at high temperature. Similar problems can also be observed with other liquid or gaseous fuels. These deposits reduce heat exchange between the combustion gas and the fluid to be heated to a considerable extent, thereby leading to a loss of furnace efficiency. Various techniques are already known that enable the heat-exchange surfaces of a furnace to be cleaned, while keeping the furnace in operation. In particular, EP-A-0 410 867 discloses performing the following steps: • generating a jet of gas that is directed towards the surfaces for cleaning; • integrating solid-state particles in the fluid jet, and projecting the particles at a speed such that the particles disintegrate on coming into contact with said surfaces to be cleaned; and • moving the jet of fluid and particles along the surfaces to be cleaned. The particles eliminate the deposit by an oxidizing chemical effect and by a mechanical effect due to the speed of the particles which sublime only after coming into contact with the surfaces to be cleaned. However, that method raises severe safety problems in supplying the oxidizing agent insofar as the most satisfactory agent is constituted by ammonium nitrate, which in association with other substances can constitute a powerful explosive. Consequently, the invention seeks to propose a solution that solves those problems while being inexpensive and while retaining good effectiveness in eliminating the deposit. To do this, in accordance with the invention, particles are used having a formulation that is constituted for the most part (more than 50% by weight) by carbamide. Carbamide (urea) is inexpensive and is obtained without major difficulty in the form of solid beads. In addition, although carbamide is not an oxidizer, it has been found to be more effective in eliminating deposits than the substances used in the past, and to be less polluting overall. Finally, the presence of carbamide as the major ingredient of the formulation makes it possible to obtain a melting temperature for the formulation that is high enough to ensure that the particles do not sublime before coming into contact with the surfaces for cleaning, while also being low enough to neutralize the acidic components of the deposit, to weaken the physical structure of the deposit by chemical action, and then to sublime or vaporize completely under the heat of the combustion gas. Given the advantages obtained by using carbamide in accordance with the invention, at least 95% (by weight) of carbamide is introduced in the formulation of the particles. Only a few additives are added in small quantities for targeted actions. In particular, in accordance with the invention, a magnesium salt is added to the formulation of the particles, advantageously magnesium carbonate or magnesium silicate. Since carbamide is hygroscopic, the magnesium salt makes it possible to sequester moisture and avoid particles agglomerating and clogging the device that generates the gas jet. In addition, the magnesium captures vanadium that is often present in the deposit and that leads to heat-exchange surfaces corroding. In addition, it makes it possible to raise the melting temperature of the particles a little, thus further improving the effectiveness of the cleaning. Advantageously, 0.5% to 5% of magnesium salt is added to the weight of the particle formulation. This quantity makes it possible to obtain satisfactory effectiveness while generating only a minimum amount of solid residues. A portion of the magnesium salt is not vaporized and it drops onto the hearth of the furnace together with a portion of the deposit detached from the cleaned surfaces. According to another advantageous characteristic of the invention, in order to obtain good effectiveness for the formulation, the furnace is adjusted so that the temperature of said surfaces for cleaning is higher than 250°C. Thus, the formulation, and in particular the carbamide, changes state on coming into contact with the surfaces to be cleaned, thus obtaining much higher performance in terms of reacting with the components of the deposit. In addition, the particles are advantageously projected into contact with the surfaces for cleaning at a speed of at least 50 meters per second (m.s-1) . This achieves satisfactory disintegration of the solid particles of the formulation, thereby further improving its effectiveness and ensuring even better chemical and mechanical effect cleaning of said surfaces. The accompanying figure is a diagram showing a method of cleaning tubes 2 of a cylinder furnace 1 of an oil refinery unit. The furnace 1 is kept in operation, being heated by a burner (not shown). The tubes 2 extend inside the furnace between a first end 2a and a second end 2b. Hydrocarbons flowing in said tubes 2 are heated between said two ends by exchanging heat with the combustion gas. The presence of a deposit on the outsides of the tubes 2 thermally isolates the fluid for heating (in this case the hydrocarbons) from the combustion gas, thus requiring an increase in the power delivered by the burner in order to maintain the same level of heat exchange. In order to detach the deposit, an injector nozzle 4 is passed through an opening 8 formed in the wall 10 of the furnace. This nozzle projects solid particles 6 against one of the tubes. The nozzle 4 is fed with compressed air at a pressure of about 5 bars to 10 bars and with solid particles 6 by a device provided for this purpose. The particles 6 are substantially spherical and of size lying in the range 1 millimeter (mm) to 5 mm, and advantageously in the range 2 mm to 4 mm. They reach the tube 2 at a speed of at least 50 m.s1, and advantageously lying in the range 100 m.s*1 to 200 m.s-1. The formulation of the particles preferably contains about 98% carbamide - (NH2)2CO - and about 2% magnesium carbonate, by weight. On coming into contact with the tube 2, which is at a temperature of at least 250°C, the particles 6 detach a fraction of the deposit, all of the carbamide contained in the particles vaporizes, and only a very small quantity of solid residues drops onto the hearth of the furnace. Acidic derivatives of the deposit are neutralized by the gas obtained by the formulation decomposing, which advantageously gives off sulfur oxide, nitrogen, and water vapor. The user then moves the injection nozzle, as represented by arrow 12, between the first and second ends 2a and 2b of the tube 2 in order to remove the deposit over the entire tube. As necessary, the user passes the nozzle through other existing openings or through openings made specially through the walls of the furnace and proceeds in analogous manner with the other tubes 2. CLAIMS 1. A method of cleaning surfaces (2) of furnaces (1) in operation, in particular the flue gas side of metal heat- exchange surfaces in industrial furnaces, and also in industrial boilers, which method comprises the following steps: • generating a jet of gas that is directed towards the surfaces to be cleaned; • integrating particles (6) in the solid state in the jet of gas and projecting the particles at a speed such that the particles disintegrate on coming into contact with said surfaces for cleaning; and ■ moving the jet of gas and particles along the surfaces to be cleaned; said method being characterized in that the particles used have a formulation that is constituted by a majority of carbamide. 2. A method according to claim 1, characterized in that at least 95% of carbamide is introduced into the formulation of the particles. 3. A method according to claim 1 or claim 2, characterized in that a magnesium salt is added to the formulation of the particles. 4. A method according to claim 3, characterized in that 0.5% to 5% of magnesium salt is added to the formulation of the particles. 5. A method according to claim 3 or claim 4, characterized in that magnesium carbonate is added to the formulation of the particles. 6. A method according to claim 3 or claim 4, characterized in that magnesium silicate is added to the formulation of the particles. 7. A method according to any preceding claim, characterized in that the furnace is adjusted so that the temperature of the surfaces for cleaning is higher than 250°C. 8. A method according to any preceding claim, characterized in that the particles are projected into contact with the surfaces for cleaning at a speed of at least 50 m.s-1. 9. A method according to any preceding claim, characterized in that for a duct containing a fluid to be heated and extending inside the furnace between a first end (2a) and a second end (2b), the fluid jet is moved from the first end to the second end.

Full Text

A METHOD OF CLEANING HEAT EXCHANGE SURFACES OF FURNACES IN OPERATION
The invention relates to a method of cleaning surfaces of furnaces in operation, in particular metal heat-exchange surfaces on the flue-gas side of industrial furnaces, such as petrochemical and oil refinery stills, and industrial boilers.
Such furnaces often burn heavy fuel oil for economic reasons. However, since the combustion of heavy fuel oil is incomplete, deposits form on the heat-exchange surfaces. These deposits are constituted in particular by heavy fractions of hydrocarbons, silica, heavy metals, and stable components that retain a solid state inside the furnace, even at high temperature. Similar problems can also be observed with other liquid or gaseous fuels.
These deposits reduce heat exchange between the combustion gas and the fluid to be heated to a considerable extent, thereby leading to a loss of furnace efficiency.
Various techniques are already known that enable the heat-exchange surfaces of a furnace to be cleaned, while keeping the furnace in operation. In particular, EP-A-0 410 867 discloses performing the following steps:
• generating a jet of gas that is directed towards the surfaces for cleaning;
• integrating solid-state particles in the fluid jet, and projecting the particles at a speed such that the particles disintegrate on coming into contact with said surfaces to be cleaned; and
• moving the jet of fluid and particles along the surfaces to be cleaned.
The particles eliminate the deposit by an oxidizing chemical effect and by a mechanical effect due to the speed of the particles which sublime only after coming into contact with the surfaces to be cleaned.
However, that method raises severe safety problems in supplying the oxidizing agent insofar as the most

satisfactory agent is constituted by ammonium nitrate, which in association with other substances can constitute a powerful explosive.
Consequently, the invention seeks to propose a solution that solves those problems while being inexpensive and while retaining good effectiveness in eliminating the deposit.
To do this, in accordance with the invention, particles are used having a formulation that is constituted for the most part (more than 50% by weight) by carbamide.
Carbamide (urea) is inexpensive and is obtained without major difficulty in the form of solid beads. In addition, although carbamide is not an oxidizer, it has been found to be more effective in eliminating deposits than the substances used in the past, and to be less polluting overall. Finally, the presence of carbamide as the major ingredient of the formulation makes it possible to obtain a melting temperature for the formulation that is high enough to ensure that the particles do not sublime before coming into contact with the surfaces for cleaning, while also being low enough to neutralize the acidic components of the deposit, to weaken the physical structure of the deposit by chemical action, and then to sublime or vaporize completely under the heat of the combustion gas.
Given the advantages obtained by using carbamide in accordance with the invention, at least 95% (by weight) of carbamide is introduced in the formulation of the particles.
Only a few additives are added in small quantities for targeted actions.
In particular, in accordance with the invention, a magnesium salt is added to the formulation of the particles, advantageously magnesium carbonate or magnesium silicate.

Since carbamide is hygroscopic, the magnesium salt makes it possible to sequester moisture and avoid particles agglomerating and clogging the device that generates the gas jet. In addition, the magnesium captures vanadium that is often present in the deposit and that leads to heat-exchange surfaces corroding. In addition, it makes it possible to raise the melting temperature of the particles a little, thus further improving the effectiveness of the cleaning.
Advantageously, 0.5% to 5% of magnesium salt is added to the weight of the particle formulation.
This quantity makes it possible to obtain satisfactory effectiveness while generating only a minimum amount of solid residues. A portion of the magnesium salt is not vaporized and it drops onto the hearth of the furnace together with a portion of the deposit detached from the cleaned surfaces.
According to another advantageous characteristic of the invention, in order to obtain good effectiveness for the formulation, the furnace is adjusted so that the temperature of said surfaces for cleaning is higher than 250°C.
Thus, the formulation, and in particular the carbamide, changes state on coming into contact with the surfaces to be cleaned, thus obtaining much higher performance in terms of reacting with the components of the deposit.
In addition, the particles are advantageously projected into contact with the surfaces for cleaning at a speed of at least 50 meters per second (m.s-1) .
This achieves satisfactory disintegration of the solid particles of the formulation, thereby further improving its effectiveness and ensuring even better chemical and mechanical effect cleaning of said surfaces.
The accompanying figure is a diagram showing a method of cleaning tubes 2 of a cylinder furnace 1 of an oil refinery unit.

The furnace 1 is kept in operation, being heated by a burner (not shown). The tubes 2 extend inside the furnace between a first end 2a and a second end 2b. Hydrocarbons flowing in said tubes 2 are heated between said two ends by exchanging heat with the combustion gas.
The presence of a deposit on the outsides of the tubes 2 thermally isolates the fluid for heating (in this case the hydrocarbons) from the combustion gas, thus requiring an increase in the power delivered by the burner in order to maintain the same level of heat exchange.
In order to detach the deposit, an injector nozzle 4 is passed through an opening 8 formed in the wall 10 of the furnace. This nozzle projects solid particles 6 against one of the tubes. The nozzle 4 is fed with compressed air at a pressure of about 5 bars to 10 bars and with solid particles 6 by a device provided for this purpose.
The particles 6 are substantially spherical and of size lying in the range 1 millimeter (mm) to 5 mm, and advantageously in the range 2 mm to 4 mm. They reach the tube 2 at a speed of at least 50 m.s*1, and advantageously lying in the range 100 m.s**1 to 200 m.s-1. The formulation of the particles preferably contains about 98% carbamide - (NH2)2CO - and about 2% magnesium carbonate, by weight. On coming into contact with the tube 2, which is at a temperature of at least 250°C, the particles 6 detach a fraction of the deposit, all of the carbamide contained in the particles vaporizes, and only a very small quantity of solid residues drops onto the hearth of the furnace.
Acidic derivatives of the deposit are neutralized by the gas obtained by the formulation decomposing, which advantageously gives off sulfur oxide, nitrogen, and water vapor. The user then moves the injection nozzle, as represented by arrow 12, between the first and second ends 2a and 2b of the tube 2 in order to remove the

deposit over the entire tube. As necessary, the user passes the nozzle through other existing openings or through openings made specially through the walls of the furnace and proceeds in analogous manner with the other tubes 2.

CLAIMS
1. A method of cleaning surfaces (2) of furnaces (1) in
operation, in particular the flue gas side of metal heat-
exchange surfaces in industrial furnaces, and also in
industrial boilers, which method comprises the following
steps:
• generating a jet of gas that is directed towards the surfaces to be cleaned;
• integrating particles (6) in the solid state in the jet of gas and projecting the particles at a speed such that the particles disintegrate on coming into contact with said surfaces for cleaning; and
■ moving the jet of gas and particles along the surfaces to be cleaned;
said method being characterized in that the particles used have a formulation that is constituted by a majority of carbamide.
2. A method according to claim 1, characterized in that at least 95% of carbamide is introduced into the formulation of the particles.
3. A method according to claim 1 or claim 2, characterized in that a magnesium salt is added to the formulation of the particles.
4. A method according to claim 3, characterized in that 0.5% to 5% of magnesium salt is added to the formulation of the particles.
5. A method according to claim 3 or claim 4, characterized in that magnesium carbonate is added to the formulation of the particles.
6. A method according to claim 3 or claim 4, characterized in that magnesium silicate is added to the formulation of the particles.

7. A method according to any preceding claim,
characterized in that the furnace is adjusted so that the
temperature of the surfaces for cleaning is higher than
250°C.
8. A method according to any preceding claim, characterized in that the particles are projected into contact with the surfaces for cleaning at a speed of at least 50 m.s-1.
9. A method according to any preceding claim, characterized in that for a duct containing a fluid to be heated and extending inside the furnace between a first end (2a) and a second end (2b), the fluid jet is moved from the first end to the second end.

Documents:

1454-chenp-2006 complete specification as granted.pdf

1454-chenp-2006 drawings.pdf

1454-chenp-2006-abstract.pdf

1454-chenp-2006-claims.pdf

1454-chenp-2006-correspondence others.pdf

1454-chenp-2006-description(complete).pdf

1454-chenp-2006-drawings.pdf

1454-chenp-2006-form 1.pdf

1454-chenp-2006-form 3.pdf

1454-chenp-2006-form 5.pdf

1454-chenp-2006-pct.pdf

abs 1454-chenp-2006 abstract.jpg

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Patent Number

234532

Indian Patent Application Number

1454/CHENP/2006

PG Journal Number

29/2009

Publication Date

17-Jul-2009

Grant Date

05-Jun-2009

Date of Filing

28-Apr-2006

Name of Patentee

CTP ENVIRONNEMENT

Applicant Address

102 rue des Poissonniers, F-75018 Paris,

Inventors:

#	Inventor's Name	Inventor's Address
1	BALLEREAU, Henri	9 Allee du Tapis Vert, F-78230 Le Pecq,
2	BARRE, Philippe	5 Chemin des Pinces Vins, F-92500 Rueil-Malmaison,

PCT International Classification Number

F23J3/00 ,C10L10/26

PCT International Application Number

PCT/FR2004/002747

PCT International Filing date

2004-10-26

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	03292721.2	2003-10-30	EUROPEAN UNION