Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L10/00—Use of additives to fuels or fires for particular purposes
  • C10L10/06—Use of additives to fuels or fires for particular purposes for facilitating soot removal
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
  • C10B43/00—Preventing or removing incrustations
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J3/00—Removing solid residues from passages or chambers beyond the fire, e.g. from flues by soot blowers

Definitions

• Process and device for loosening and removing solid coatings on the surfaces of enclosed spaces e.g. the flue gas side of a furnace or boiler
• the present invention relates to a process for loosening and removing solid coatings on the surfaces of enclosed spaces, e.g. soot and sol-id coatings formed during the operation of a furnace or boiler on the surfaces of space of the furnace forming the flue gas side, covers and flue gas ducts to the flue gas side being sealed to form a closed chamber and steam, saturated with a special cleaning composition accord ⁇ ing to the invention, is supplied to the flue gas side.
• the process according to the invention can be carried out in one or more steps, depending on the composition and thickness of the coatings.
• the invention also comprises a device for carrying out the process.
• the invention will be described in more detail below and illuminated with examples for the case where the enclosed space, the surfaces of which are to be freed of coatings and thus cleaned, is the flue gas side of a furnace or boiler, but it will be obvious that the process and the device can just as easily be applied to the cleaning of other enclosed spaces, e.g. the interior walls of tanks and large vessels.
• Soot is an extremely good insulation material, five times better as asbestos.
• the problem can also be expressed as fo.llows: an increase in the flue gas temperature of 50 C from 200 C to 250°C for example with a carbon dioxide content of 10 %, reduces the efficiency of the furnace by about 3 %. This points out the great economic importance of preventing an unnecessary rise in the flue gas temperature, e.g. as a result of reduced heat absorption because of solid coatings on the furnace surfaces.
• Factors contributing to reduced heating costs in burning fossil fuels include cleaning and soot removal in furnaces and removal of solid coatings which appreciably reduce the heat transfer capacity and thus the efficiency of the furnace, resulting in turn in higher energy consumption.
• the solid coatings on the furnace walls and the convection portions consist primarily of sulphates, which are very difficult to remove by conventional mechanical cleaning - methods or by traditional sweeping. In certain types of cast furnaces, the coatings can result in a reduction of surface area in the flue gas ducts in the convection portion making flue gas evacuation more difficult.
• combustion residues in furnaces There is no complete knowledge of the contents of combustion residues in furnaces. Analyses of coatings from oil-burning units reveal, in addition to combustion residues such as oil coke and flame soot, also high contents of ash particles silicon, asbestos, sodium, calcium, sulphur dioxide and a number of -heavy metals such as vanadium, nickel, iron, copper, cadmium, lead, zinc, mercury and chromium.
• the coatings can thus vary widely in chemical composition. This places great demands on the cleaning agent.
• the cleaning agent must not be harmful to the furnace nor to the environment, effectively removing soot and coatings on furnace walls but at the same time not producing corro- sion or brittleness of the furnace material.
• the method involves however subjecting the furnace to a certain amount of wear at each cleaning. Wear arises because of corrosion, since the steam condenses on the furnace walls and reacts with the sulphur compounds in the coatings to form sulphuric acid. This is highly corrosive also in the drainage system through which the dissolved sludge must be removed during cleaning. To ⁇ neutralize the sludge, before it runs out into the drain, caustic soda is usually used, which is placed on the bottom surface of the furnace. It is however difficult to achieve a perfect dosage of soda to prevent environmental damage, due to too high or too low pH value. Also certain risks are involved for workers handling the soda. Furthermore it is not possible to eliminate corrosion on the furnace walls with the aid of the caustic soda.
• the dissolved coatings are removed by rinsing with water. It " is possible to add a basic agent to the rinse water which can neutralize the sulphuric acid, but the amount of sulphuric acid is usually so large that too much time must be devoted to rinsing with a basic agent. After water rinsing, the cleaned furnace surfaces are treated with an approved basic agent to neutralize any remaining sulphur in pores, welding joints and the like. This method, which is designated System Vapor, is complicated and expensive in addition to having the above described problems.
• the patent specification discloses that the process can be amplified by temporary heating. This pressure increase achieved thereby is said to be the cause of the powerful bursting effect.
• the patent specification also discloses that according to one embodiment of the process, the desired effect is achieved in a more advantageous manner by alter ⁇ natingly cooling and heating the waterside, the heating being done by steam for example, hot water or the like, and the cooling being effected in various ways which require more work, time and expense. According to one embodiment, it is disclosed that cooling is effected by means of softened water and salt solution is recommended for cooling other parts of the flue gas space.
• German Auslegeschrift 27 02 716 describes a process which is divided into several steps.
• ammonia- water is introduced into the flue gas space in the furnace by means of steam for a period of 1-2 hours.
• the ammonia used is not mixed into the steam before it is introduced into the flue gas space. Rather, ammonia vapours are intro- pokerd into the upper portion of the flue gas duct to be cleaned through openings designed therefor, and the ammonia is finally divided by means of a spray device for water, also in the upper portion of the flue gas space.
• steam is introduced into the lower portion of the flue gas duct through steam jets, whereby the steam produces an additional fine division of the ammonia vapouis.
• the Auslegeschrift discloses that it is advantageous to arrange the spray device for water as high as possible in the flue gas space and the injectors as low as possible in the space, so that the water can effect a cleaning process from top to bottom while the steam flows from bottom to top.
• the a moniawater used suitably has a 25 % content of ammonia, the rest being water.
• Danish Lay-open Print 122 969 describes an agent for cleaning the flue gas side of furnaces.
• the agent consists in principle of two components, namely a . ordinary anionic, amphoteric or non-ionic tensides and b) chemical compounds which to a far reaching degree are subjected to thermal decomposition with heavy generation of gases,. preferably ammonia and carbon dioxide.
• gases preferably ammonia and carbon dioxide.
• the Lay-open print the following demands are placed on the means used: 1. it must have a high wetting and penetrating effect, 2. it must have a good neutralizing effect, 3. it must produce a heavy generation of gas at elevated tempera- ture and finally, the medium must have minimal tendency to form coatings.
• the inventive idea can be said to lie in point 3, i.e.
• the means must produce a heavy gas generation at elevated temperature.
• components having this characteristic of producing heavy gas genera- tion preferably ammonia and carbondioxide, are ammonium carbonate, ammonium bicarbonate, ammonium carbamate or carbamide.
• gas generating compounds which do not split the ammonia i.e. compounds which have been used as blowing agent in the manufacture of foamed plastic articles. It is stated that we are dealing with compounds which at elevated temperature split off nitrogen, e.g. azodicarbonamide with several compounds.
• oxygen generating compounds e.g. carbamide peroxide adducts and finally it is also possible to use a combination of substances, which are thermally decomposed with gas generation.
• the cleaning agent in question can be used: a solution in water or possibly partially a dispersion of the means being sprayed as such into the flue gas space of the furnace, using for this purpose a spray .
• a spray . device commonly available on the market with sufficient capacity, e.g. those available for spraying of gardens against harmful insects.
• the present invention relates to a process, according to which steam, prior to being supplied to the flue gas side for example of the furnace, is saturated with a com ⁇ position which, if the process is carried out in only one step, or alternatively in the first step of a multistep process, i.a. produces an increase in the pH value of the steam to a level which is sufficient and necessary for creating a basic environment, in which the components of the composition during the cleaning process transform all harmful sulphur compounds in the coatings and environmental ly harmful heavy metals into harmless salts which can be easily removed from the bottom of the furnace.
• the composition used in the process according to the inven ⁇ tion consists of a mixture, which primarily and in principl comprises synthetic tensides, organic complexing agents, alkali which in addition to the above mentioned effects (i.e. achieving a basic environment and neutralizing any sulphuric acid formed) also have a direct grease dissolving and cleaning effect, environmentally safe solvents and solvent vehicles, corrosion inhibitor, passivating additive, surfactants and water.
• the make up of the composition is directed in each individual cleaning case to the type of pollutants occurring and the coatings in the spaces to be cleaned and to the thickness of the coating. In practice, several steps must often be combined to achieve a satis ⁇ factory clean result. Thus it is not possible to recommend a uniform composition for all types of furnace units and coatings.
• the first step is suitably carried out in a basic environment as mentioned above, while the second
• I step for removing for example hard to remove burned on residue on furnace walls, such as oil coke and flame soot as well as iron sulphate coatings, is performed in an acid environment.
• the scope of the invention encompasses the use of a number of special cleaning agents which best fulfil the requirements.
• the invention f lfils even present high environmental standards. This is especially true with regard to acid components in coatings such as sulphur compounds and harmful heavy metals such as vanadium, nickel, iron, copper, cadmium, lead, zinc, mercury and other metal ions. These are neutralized and converted into harmless compounds or salts in the cleaning process in one or more steps, i.e. before the waste products enter the drainage system. Our tests have shown that waste products from the cleaning process contain only half or one fourth of the amount of environmentally hazardous substances permissible by the environmental authorities.
• compositions used in the process according to the invention are in the form of premixed additives, either viscous liquids or powders, which are mixed with water before use.
• a composition in liquid form appears to be advantageous.
• a powder composition has the advantage that it need not be protected from frost, which can be important in certain cases.
• the process according to the invention in combination with the special cleaning compositions can be used in closed tanks for example and all types of combustion systems with fossil fuels for achieving a particularly effective cleaning, soot removal and removal of coatings by means of a non- damaging treatment, which i.a. eliminates the danger of corrosion damage to the metal surfaces.
• the process is considerably more simple and less time-consuming than methods used up to now and the treatment result is decidedly better, thus providing economic advantages over traditional methods.
• the process according to the invention also provides an effective corrosion protection of furnace walls for example.
• the compositions used according to the inven ⁇ tion are environmentally safe and do not damage hands or clothings. Nor are they poisonous, thus_making handling thereof completely safe.
• ⁇ ⁇ U £_ Said anticorrosion effect and the formation of a passivating layer on the furnace wall is suitably achieved by performing the passivation in a separate step, after the primary clean ⁇ ing process.
• a surface-passivating -layer By formation of " a surface-passivating -layer, the life of the furnace can be appreciably extended.
• the passivating,layer formed on the furnace wall consists of iron or zinc phosphate and iron oxide and has a weight of 200-1000 mg m . Examples of passivating agents will be given below.
• the process according to the invention has the following characteristics for furnace cleaning:
• the furnace is turned off. 2.
• the furnace is sealed to form a closed space.
• the process is similar when applied to other enclosed spaces than furnaces.
• the cleaning composition used together with water produces a steam which is then introduced in a pressureless state into the space to be cleaned, e.g. the flue gas space of a furnace.
• the steam made up of water and cleaning composition can be made according to two different embodiments within the scope of the invention: A) The initially viscous or powder cleaning composition is dissolved in water of normal pH value and this aqueous solution together with other steam forming water is vapour- ized together in a device which also falls within the scope of the invention and will be described below. The mixed steam is then introduced without pressure into the space to be cleaned, e.g. the flue gas side of a furnace.
• the aqueous solution of the cleaning composition is introduced into the pressureless steam already formed in the device according to the invention or provided from another source at the site (in that case being first de- pressurizedl.
• the vapourization temperature of the composi ⁇ tion lies sufficiently below the temperature of the steam so that vapourization of the composition takes place immediately upon introduction of the steam.
• the introduction of the aqueous solution of the composition into the steam presents no problem since the steam is in-'a "pressureless state", i.e. is at approximately ambient pressure.
• Introduc- tion can be done by means of a pump for example.
• the furnace 1 is provided with a burner 2 which generates flue gas. These rise -upwards in the furnace past a hotwater heater 3 and leave the furnace through a flue duct 4. ⁇ nter normal operation of the furnace, soot and solid coatings 5 are formed, which lower the efficiency of the hotwater heater 3. Also, the coatings increase the flue gas tempera ⁇ ture significantly, which means both poor use of the fuel supply and increased wear on the flue gas ducts and chimney.
• a steam unit 6 is- connected via a steam line 7 to the flue gas side of the furnace.
• the furnace de ⁇ scribed above can instead be another closed space which is to be cleaned of coatings on the walls.
• the steam unit 6 is provided with a chamber 8, in which, according to the embodiment shown, an electrode 9 is arranged. This part can be made differently from that shown in the drawing.
• the heating unit can be made as immersion electrode, using process variant B ⁇ .
• the composition is thus introduced in this case in aqueous solution into the steam via an introduction unit (not shown) in the steam line 7 after the vapourization chamber 8, by means of which line, the chamber is connected to the closed space, e.g. the furnace.
• An inlet line 10 for water is connected to the lower end of the chamber 8.
• a reduction valve 11 is included in the inlet line 10, by means of which the water flow through the inlet line 10 can be regulated.
• the reduction valve 11 is also provided with a branch 12 for a feeder line 13 for the cleaning composition 14, which is stored in a container 15.
• the composition in liquid form which is produced by dissolving the initially viscous or powdered composition in water, is drawn by the flow of water through the reduc ⁇ tion valve into the chamber 8 in the steam unit 6.
• a pump (not shown) in the feeder line 13 can press the composition into the branch 12, when a large amount of composition is to be mixed into the steam.
• the flow of liquid composition 14 into the inlet line 10 can be regulated by a valve 16.
• the flow of the mixture of composition 14 and water into the chamber 8 can be regulated by means (not shown) i.n the steam unit 6 for sensing the liquid level in the chamber together with a throttle valve 17.
• a liquid level sensor device should suitably be included in the device even when using immersion electrodes for heating in variant Bl-
• the reduction valve 11 is provided with a nonreturn valve (not shownI , which prevents water from penetrating into the feeder line 13 for the composition, when the flow to the chamber 8 is cut off by the valve 17.
• the device can be adapted to closed spaces, e.g. furnaces of various dimensions by setting the reduction valve 11 for small flows of water and composition 14 when a small space is to be cleaned, and for greater flows when a large space, e.g. an industrial furnace is to be cleaned.
• the steam formation in the unit 6 has automatically the correct admixture of cleaning ' composition.
• the steam saturated with the composition according to the invention usually has, in a one step process, a pH value of between 8 and 14.
• the steam is condensed in a known manner on the metal walls of the flue gas side of a furnace for example.
• Surfactants in the composition facilitate penetra- tion of the composition into layers of soot for example and into the solid coatings; and tensides and complexing agents in the composition break down the coatings.
• Corrosion inhibitors in the cleaning composition prevent corrosion when the metal surfaces after the steam treatment are rinsed clean in a known manner with plain water.
• the process described according to the invention eliminates the problem of neutralizing the coatings removed from a furnace, for example by caustic soda, as is done according to the prior art.
• caustic soda is eliminated and thereby the risk of corrosion damage to the furnace and drainage system.
• furnaces can be cleaned, for maintaining a high efficiency, more often than previously at the same cost as previously.
• the process according to the invention is adapted to the nature of the coatings to be removed, by suitable selection of the cleaning composition.
• the process can be divided into for example the following reaction types:
• CuCO ⁇ l which reacts with damaging sulphur compounds while forming insoluble copper sulphide (CuS) .
• tensides which can be in ⁇ cluded in the cleaning composition: Hydroxy alkyl- ethyl alkyl amino ethyl glycine, which is an amphoteric tenside, which is effective in both strongly alkaline and acidic cleaning agents. It is biodegradable and non-toxic. Lauryl dimethyl carboxymethyl ammonium betaine, which is an amphoteric tenside, which is- effective and stable in both alkaline and acidic environment. It is biodegradable and non-toxic.
• Alkylphenylpolyglycol ether with 10 ethylene oxide groups in the molecule which is a non-ionic tenside with especially good cleaning and emulsifying properties. It is partially biodegradable and non-toxic.
• An example of a combined corrosion inhibitor and emulsifier in the cleaning composition is 1—hydroxyethyl-2-alkyl- imidazoline, which has good adhesion to all types of metal
• An example ' of a complexing agent in the composition for heavy metals in the combustion residue and coatings, such as copper, cadmium, silver, mercury, lead, nickel and several other metal ions, is 2-mercaptobenzo-l,3,5-triazine.
• EDTA ethylene diamino-tetra acetic acid
• NTA nitrilo-triacetate
• DTPE diethylene triamino-penta acetic acid
• HEEDTE hydroxy- ethyl-ethylene diamino-triacetic acid
• An example of a solvent vehicle in aqueous solutions of the composition is sodium cumol sulfonate, which has good dispersion properties.
• An example of an environmentally safe solvent for grease and fuel oils is 1,2-propylene glycol and iso-propanol.
• waste products from the cleaning and treatment of furnaces for example fall to the bottom of the furnace in the form of a slurry which is removed therefrom.
• No special instructions for handling the waste slurry are required and as was mentioned above, there is no toxic discharge, and therefore no separate discharge purification or detoxification is required.
• Neutralization of steam condensate and removal of soot, heavy metals and lighter coatings from furnace walls is carried out in an alkaline environment in a one step process by using for example the above mentioned zinc carbonate * method, iron(IIIhydroxide method, iron(III)oxide method, copper carbonate method or the hydrogen peroxide method.
• cleaning agents for example, can be used with advantage:
• lauryl dimethyl carboxymethyl ammonium- betaine dimethyl lauryl aminobetaine, about 39 % active substance
• alkyl phenyl polyglycol ether with 10 ethylene oxide groups in the molecule about 100 % active substancel 1-2 % by weight 1-hydroxy ethyl-2-alkyl-imidazoline 2-3 % by weight l-mercapto-benzo-l,3,5-triazine 5-10 % by weight potassium hydroxide solution (about 40 %) 5-8 % by weight tetra-potassium pyrophosphate 3-5 % by weight zinc carbonate, basic 2-3 % by weight iso-propanol 3-5 % by weight 1,2-pro ⁇ ylene glycol 1-2 % by weight ethylene diamine tetra-acetic acid (EDTA) The rest water nap to 100 % by weight.
• active substancel 1-2 % by weight 1-hydroxy ethyl-2-alkyl-imidazoline 2-3 % by weight l-mercapto-benzo-l,3,5-triazine 5-10 % by weight potassium hydroxide solution (about 40 %)
• a specially composed cleaning agent in powder form designed for neutralization of the drop water and for removing soot and light coatings in furnaces. It provides a non-corrosive treatment of furnaces by effective desulphurization of furnace walls. Damaging sulphur compounds are transformed in alkaline environment into completely harmless salts which end up in the bot _tom of the furnace, where they are removed.
• triammonium dodecylbenzene sulfonate (about 92 % active 'substance).
• trisodium phosphate (tertially sodium phosphate) 8-10 % by weight sodium percarbonate (Na 2 CO.- • 1.5 H.-0)
• sodium silicate powder 35-40 % by weight sodium disilicate powder (sodium silicate powder"!
• ethylene diamine tetra-acetic acid EDTA
• the rest water up to 100 % by weight.
• triammonium dodecylbenzene sulfonate (about 92.% active substance)
• Cleaning and removal of strongly adhering combustion residue for example on furnace walls, such as oil coke and flame soot as well as iron-sulphate coatings of a thickness of 10 mm on furnace walls or in other enclosed spaces is suit ⁇ ably done in two steps, the first of which is carried out in an alkaline environment using the above mentioned means for example, the second supplementary step for removing the strongly adhering coatings being carried out in an acid environment.
• the cleaning steps are then suitably followed by a passivation step for the metal surface.
• cleaning agents for example, can be used with advantage:
• alkylphenyl polyglycolether with 10 ethylene oxide groups in the molecule (about 100 % active substance)
• activator AD 5 % by weight activator AD 10 % by weight potassium hydroxide solution, about 40 %
• the rest water up to 100 % by weight.
• alkylphenyl polyglycolether 8 % by weight alkylphenyl polyglycolether with 10 ethylene oxide groups in the molecule 5 % by weight alpha-olefine sulphonate 2 % by weight diethylene glycol The rest water up to 100 % by weight.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Combustion & Propulsion (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Incineration Of Waste (AREA)
• Processing Of Solid Wastes (AREA)

Priority Applications (5)

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Family Applications (1)

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Cited By (4)

Citations (7)

• 1981
  • 1981-05-20 SE SE8103177A patent/SE437032B/sv not_active IP Right Cessation
  • 1981-10-27 SE SE8106333A patent/SE8106333L/ not_active Application Discontinuation
• 1982
  • 1982-04-19 WO PCT/SE1982/000125 patent/WO1982004065A1/en active IP Right Grant
  • 1982-04-19 DE DE8282901377T patent/DE3264872D1/de not_active Expired
  • 1982-04-19 EP EP19820901377 patent/EP0079338B1/en not_active Expired
  • 1982-05-03 CA CA000402177A patent/CA1211345A/en not_active Expired
• 1983
  • 1983-01-13 DK DK011583A patent/DK156677C/da active
  • 1983-01-17 FI FI830144A patent/FI75594C/fi not_active IP Right Cessation

Patent Citations (7)

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