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 OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • 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

Definitions

• the present invention relates to a method for the prevention or removal of soot and other deposits from heating and ancillary surfaces, which deposits are formed as a result of the combustion of gaseous, liquid and solid fuels, and also to the reduction of corrosion of these surfaces by the lowering of the acid dewpoint of the combustion gases.
• the invention relates to the removal of deposits from and the prevention of corrosion of heating and ancillary surfaces such as boiler and economiser tubes, in turbo-compressors, turbo-chargers, exhaust- .boilers, gas turbines, process furnaces and other equipment.
• deposits as used herein is meant the deposits formed from the products resulting from the combustion of gaseous, liquid and solid fuels.
• the deposits may consist of carbon, in the form of soot, or may comprise sulphur and/or sulphur compounds or the ash of fuels, which are generally argillaceous compounds when the fuel is coal or a product thereof, and vanadium compounds when the fuel is an oil.
• the deposits are.generally hard and adherent. When deposits are formed on steel or other metals, then because the thermal conductivity of the deposits is low compared with that of the steel or other metal, the rate of heat transmission from the flame or hot gases to the water or other fluid which is being heated is reduced, thereby reducing the efficiency of the equipment.
• the deposits may also increase the corrosion of metal surfaces by trapping corrosive agents, such as acid sulphates, therein. At high temperatures, in the absence of liquid water, these sulphur compounds do not normally cause corrosion and it is usual to maintain the combustion gases at a temperature above that temperature (the "dew point") at which liquid can form. However, when there is a deposit on a metal surface the temperature at the metal surface itself may be below the “dew point” whilst the temperature of the gases is above the “dew point". The deposit thus increases the risk of corrosion.
• corrosive agents such as acid sulphates
• the present invention provides a method for preventing deposits on or removing deposits from heating and ancillary surfaces of boilers and like equipment, which method comprise:
• the additive which is used in the present invention may be composed as follows:
• the preferred alkali metal nitrate for use in the additive is potassium nitrate and the preferred alkaline earth metal nitrate is magnesium nitrate.
• the indicator may be any suitable indicator which will indicate the pH of the additive, thereby indicating whether or not the pH is within the range of from 7 to 9.
• the pH of the additive is preferably in the range of from 8 to 9 and thymol blue or bromothymol blue may be used to give an indication of a pH within this range.
• the pH may be adjusted as necessary by the addition of-a base, e.g. potassium hydroxide.
• the dewpoint of the flue gas may be monitored by any conventional dewpoint meter.
• the nitrogen oxides produced as a result of the decomposition of the nitrates affect the reactions occurring.
• the nitrogen oxides thus react with the sulphur oxides to form the anhydride of nitrosylsulphuric acid.
• This is a stable compound excluding water or up to a sulphuric acid concentration of 80%. Even at:.a 70% sulphuric acid concentration (corresponding to a flue gas temperature of about 100°C) decomposition is slight. The compound leaves the combustion chamber undecomposed and does not cause any corrosion.
• the additive is fed into the combustion chamber or flue gas stream, the composition of the additive and the volume thereof being adjusted to suit the plant being treated and the problems associated with the particular fuel being burnt.
• the additive is effective both at high temperatures, i.e. >1000°C, and at low temperatures, i.e. >100°C.
• aqueous solutions of the nitrates are provided in separate tanks.
• the required amounts.of each of these ingredients is then supplied in the desired amount to a common tank for mixing prior to introduction into the combustion chamber or flue gas..
• a STEINMULLER water-tube boiler was treated with the aim of decreasing the heating-surface contamination and thus keeping the flue-gas temperature almost constant during a 3-month seasonal operation.
• the heating an ancillary surfaces were free of solid deposits, and the surfaces could be dry cleaned using compressed air.
• a MAN water-tube boiler was treated with the aim of keeping the heating and ancillary surface deposit rate as low as possible over a 12 month period and of reducing the dew point from 134°C to about 105°C.
• Addition continuous, i.e. 0.4 litres of the additive per ton of fuel oil.
• Injection point combustion chamber 1 injection lance Injection appliance: semi-automatic; pump operation Results: The heating and ancillary surfaces were up to 85% free of solid deposits. The surfaces could be dry cleaned by means of compressed air and no wet cleaning was required in the combustion chamber.
• the acid dew point was reduced to 102°C accordingly, the steam-operated air-preheater could be used without-fear of corrosion.
• the flue-gas temperature of initially 172°C adjusted itself to 145°C; i.e. the flue-gas heat loss was reduced by about 1.5%, equivalent to a fuel saving of about the same order and, additionally, a steam saving in the air-preheater, so that an improvement in efficiency of about 2.5% overall was achieved.
• Addition of the additive took place continuously at a rate of 4.9 litre by means of injection lances securely installed in the combustion chamber.
• Pump units fed the additive from the storage containers to the injection lancers. It was thus possible to match the output of the pump units to the desired reduction in acid dew point.
• the additive was used over a relatively long period of time.
• the acid dew point was lowered to 60-62°C and the flue gas temperature was set at 147°C. It was possible to blow or dust off the residues on the heating and ancillary surfaces with compressed air when the boiler was taken out of operation.
• the lowering of the sulphuric acid dew point by about 60°C enabled an economy to be made in the steam required for the air preheater, without any fear of corrosion.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Treating Waste Gases (AREA)
• Heat Treatment Of Articles (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

Family

ID=10519544

Family Applications (1)

Country Status (4)

Cited By (5)

Families Citing this family (2)

Family Cites Families (4)

• 1981
  • 1981-02-09 GB GB8103859A patent/GB2095283B/en not_active Expired
• 1982
  • 1982-02-09 EP EP82300638A patent/EP0058086B1/de not_active Expired
  • 1982-02-09 DE DE8282300638T patent/DE3265325D1/de not_active Expired
  • 1982-02-09 AT AT82300638T patent/ATE14897T1/de not_active IP Right Cessation

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