IE20080483U1 - Removal of combustion deposits - Google Patents

Abstract

ABSTRACT Sulphide combustion deposits are removed from at least one heated metal surface in the interior of a boiler exposed to combustion gases, by opening a port in the boiler to permit access to the heated metal surface, directing a spray of non-acidic cleaning agent to the heated metal surface via the access port, and permitting the loosened combustion deposit to exaust from the boiler via an exaust flute. The cleaning agent comprises an ainmonium-free non-effervescent solution of sodium bicarbonate, and a wetting agent for the solution, which is preferably made up immediately before use.

Description

Sulphide deposits formed by combustion of oil in domestic oil-fired pressure jet boilers tend to build up on various metal surfaces within the boiler. The actual location of deposit build-up depends upon the boiler design: the amount and nature of the deposits depend on the nature of the fuel and fuel consumption. The deposits (depending on the type of fuel) typically include sulphur, sulphur compounds, soot and metal ash. The thermal performance of a domestic oil-fired pressure-jet boiler depends on efficient heat transfer from hot burner gasses through the metal surfaces. Such deposits can adversely affect such heat transfer; they can also cause gas flow passages to become obstructed or restricted.

Such problems lead to heat wastage because much of the heat generated by combustion of the oil is lost, resulting merely in disadvantageous raising of the flue gas temperature. Conventional brushing and scraping during maintenance cycles do not fully remove such deposits.

Furthermore, when a boiler is not adequately cleaned, and is then brought back into service after such inadequate cleaning, residual deposit not cleaned away acts as a base for the formation of new deposits. These new deposits therefore form much faster than would be the case with properly cleaned boiler tubes.

Finally, largely because of the sulphur content of the fuel, the usual environment within a domestic oil-fired pressure jet boiler is acidic, which tends to accelerate corrosion of metal parts within the boiler. This is particularly true when the fuel is diesel or mazut.

The present invention provides an improved method for removing of sulphide combustion deposit from at least one heated metal surface in the interior of a boiler, which surface in use is exposed to combustion gases and heated thereby.

IEO 80 52: 83 The method according to the invention comprises: (a) opening a port in the boiler to permit access to the heated metal surface in the interior of the boiler, and (b) directing a spray of non-acidic cleaning agent to the heated metal surface via the access port so as to at least loosen the combustion deposit, the cleaning agent comprising an ammonium-free non-effervescent solution of sodium bicarbonate, and a wetting agent for the solution; and (c) permitting the loosened combustion deposit to exhaust from the boiler via an exhaust flue.

The heated metal surface from which the sulphide combustion deposit is to be removed is typically of a thermally resistant metal such as is conventionally employed in domestic boilers.

The method according to the invention results in loosening of the sulphide combustion deposit on the metal surface before it is exhausted through the exhaust flue. Optionally, the loosened deposit may be removed from the surface mechanically, prior to exhausting in gas phase through the flue, together with exhaust combustion gases arising in the boiler.

The cleaning agent comprising the solution of the sodium bicarbonate and the wetting agent is preferably made up immediately before use, because protracted storage of an aqueous solution of sodium bicarbonate results in deterioration and degradation of the sodium bicarbonate.

In one embodiment of the invention, the cleaning agent may contain a zirconium salt, such as a zirconium carbonate, in a catalytic amount (an amount to catalyse breakdown of sulphide combustion deposits).

Preferably, the cleaning agent used in the method according to the invention contains no further active cleaning ingredients, which results in the advantage that the cleaning agent need only employ economically produced bulk ingredients. These ingredients are preferably of food grade such that there are no inherently harmful chemicals used, and the ingredients are safe to transport and use. lEoeo4a3 3 The cleaning agent may contain additional non-deleterious ingredients; an example of such an ingredient is a dye or pigment (which is preferably intimately mixed with sodium bicarbonate powder before the latter is dissolved in water to produce the cleaning agent used in the method according to the invention). Such a dye or pigment, which is preferably of food grade, offers the advantage that it is easier for the user to identify the cleaning agent before or after mixing with the detergent.

The cleaning agent is preferably applied to the heated metal surface in the form of droplets (especially atomised droplets) by spraying, typically by the use of manually operable spraying apparatus. Such spraying apparatus should be under relatively low pressure, so as to avoid impacting the deposit with the spray.

As indicated above, the solution used according to the invention is typically made up immediately before use; the solution should be mixed rapidly and used promptly, and not exposed to temperatures in excess of 50°C before application to the heated surface(s). Such rapid mixing and use is generally only suitable for professional use.

It is particularly preferred that the method according to the invention be carried out in a maintenance cycle, preferably when at least part of a domestic oil-fired pressure jet boiler has been removed to permit access and maintenance. Such a maintenance cycle preferably includes an inspection step before and/or after application of the cleaning agent. It is preferred to mechanically remove large and/or loose deposits from the surfaces to be cleaned, before application of the cleaning agent according to the invention.

The method according to the invention provides the further advantage that the sodium bicarbonate present in the cleaning agent results in at least partial neutralization of the acidic environment present in the boiler, thereby helping to combat corrosion caused by acid gases. it is preferred that the cleaning agent used in the method according to the invention contains from 5 to 15 grams of sodium bicarbonate per litre of water and/or 1 to 5 grams of food-grade detergent as wetting agent. The detergent is preferably supplied in the form of an aqueous concentrate, to be diluted with water prior to use.

E0 80 4 33 Examples of suitable food-grade detergents include anionic and non—ionic surfactants. it is particularly preferred that the major surface active ingredient of the detergent (in proportions by weight) is an anionic surfactant, such as fatty acid soap, or an alkylsulphonic acid salt.

Such an anionic surfactant is typically present in aqueous solution in a concentration of 5 to 25% by weight (prior to mixing with the sodium bicarbonate solution).

The detergent may also contain a relatively minor amount of one or more non—ionic surfactants, such as carboxymethyl cellulose, a starch or a polyethoxylated wetting agent. Such a non—ionic surfactant is typically present in aqueous solution in a concentration of up to 10% (such as up to 5%) by weight (prior to mixing with the sodium bicarbonate solution). The detergent is preferably substantially free of cationic surfactants, but may contain relatively minor amounts of amphoterio surfactants.

The sodium bicarbonate may be provided in solid form (typically in the form of powder) for solution in water (and mixing with detergent) prior to use; such solid sodium bicarbonate is preferably dyed or pigmented as described above.

The present invention therefore comprises a pack for use in a method according to the invention, the pack comprising a first container containing solid (such as powdered) sodium bicarbonate, optionally a dye or pigment as described above, and optionally a zirconium salt, and a second container containing aqueous wetting agent. The contents of the first container are to be dissolved in water and mixed with the contents of the second container immediately prior to use in the method according to the invention.

The present invention further extends to the combination of sodium bicarbonate, a dye or pigment for the sodium bicarbonate, and optionally a zirconium salt, and a wetting agent, for use in forming an aqueous solution for removal of combustion products from heated metal surfaces in domestic oil-fired pressure jet boilers (including condensing boilers). lE0 80430 The present invention will now be illustrated in the following examples, in which reference is made to the accompanying drawings.

Example 1 This example illustrates schematically the removal of deposit from a conventionally flued domestic oil fired pressure jet boiler; reference is made to Figure 1 of the accompanying drawings which illustrates schematically how the process according to the invention can be put into operation. grams of dyed powdered sodium bicarbonate and 15 ml of ammonium-free liquid detergent concentrate were dissolved in 2.5 litres of cold or warm water. The resulting solution was charged into a standard garden pressure sprayer 1 A conventionally flued domestic oil fired pressure jet boiler 2 is first prepared for cleaning. The door cover 3 is removed and then the baffles 4 are removed. Any loose deposits within the boiler 2 are removed by vacuuming or the like.

The door cover 3 is then loosely replaced and the burner 5 fired on domestic hot water mode for about 5 to 7 minutes until the flue 6 is hot. The door cover 3 is then again removed and with the burner still firing, solution from sprayer 1 is economically sprayed into the boiler 2 until deposits within the boiler have been satisfactorily removed. The service of the boiler should then be completed as normal, and the baffles 4 and door 2 replaced before the boiler is put back into service.

The solution from sprayer 1 should be sprayed as soon as practicable after the solution has been made up.

Example 2 This example illustrates schematically the removal of deposit from a balanced flue domestic oil fired boiler; reference is made to Figures 2 and 3 of the accompanying drawings which illustrate schematically how the process according to the invention can be put into operation.

IE080433 grams of dyed powdered sodium bicarbonate and 15 ml of ammonium-free liquid The resulting cleaning solution was charged into a standard garden pressure sprayer 1. detergent concentrate were dissolved in 2.5 litres of cold or warm water.

As flue products will always spill from low level or balanced flues (see Figs 2 and 3), the boiler 11 is heated to 55 to 70°C with the flue cover in place, but with baffles 13 removed. The flue cover 12 is then removed and the solution sprayed from sprayer 1 as described above with reference to Figure 1. The flue cover is then replaced and the burner again fired. Further cleaning solution is sprayed from sprayer 1.

The service of the boiler should then be completed as normal, and the baffles 13 and flue cover replaced before the boiler is put back into service.

Claims (1)

1. A method of removing sulphide combustion deposit from at least one heated metal surface located in the interior of a boiler, which metal surface in use is exposed to and heated by combustion gases and is in communication with an exhaust flue, which method comprises: (a) opening a port in said boiler to permit access to said heated metal surface in the interior of the boiler, (bl surface via the access port so as to at least loosen said combustion deposit, directing a spray of non-acidic cleaning agent to said heated metal the cleaning agent comprising an ammonium-free non-effervescent solution of sodium bicarbonate, and a wetting agent for the solution; and (c) permitting said loosened .combustion deposit to exhaust from said boiler via said exhaust flue. A method according to claim 1, wherein baffles are taken out from the interior of the boiler prior to step (b). A method according to claim 1 or 2, further comprising at least partial mechanical removal of said combustion deposit from the heated metal surface after step (b). A method according to any of claims 1 to 3, wherein the cleaning agent further comprises at least one zirconium salt and/or a dye or pigment. A method according to any of claims 1 to 4, wherein the cleaning agent contains no further active cleaning ingredients.