EP0058086B1 - Method for the prevention of deposits on or the removal of deposits from heating and ancillary surfaces - Google Patents

Method for the prevention of deposits on or the removal of deposits from heating and ancillary surfaces Download PDF

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Publication number
EP0058086B1
EP0058086B1 EP82300638A EP82300638A EP0058086B1 EP 0058086 B1 EP0058086 B1 EP 0058086B1 EP 82300638 A EP82300638 A EP 82300638A EP 82300638 A EP82300638 A EP 82300638A EP 0058086 B1 EP0058086 B1 EP 0058086B1
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EP
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Prior art keywords
nitrate
additive
deposits
flue gas
equipment
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82300638A
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German (de)
French (fr)
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EP0058086A2 (en
EP0058086A3 (en
Inventor
Ulf Thore Walden
Erich Weigand
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POLARCHEM Ltd
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POLARCHEM Ltd
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Priority to AT82300638T priority Critical patent/ATE14897T1/en
Publication of EP0058086A2 publication Critical patent/EP0058086A2/en
Publication of EP0058086A3 publication Critical patent/EP0058086A3/en
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Publication of EP0058086B1 publication Critical patent/EP0058086B1/en
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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

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 riormally 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
  • GB-A-1378882 discloses a method for the removal of deposits from surfaces which comprises applying to a heated surface an agent which comprises a mixture of ammonium nitrate and at least one nitrate of an alkali metal, an alkaline earth metal, copper, zinc or an organic base, the agent not including therein an oxidisable organic material, sulphur or a sulphur compound.
  • FR-A-1357992 discloses an agent for the chemical removal of soot which comprises a nitrate of an alkali metal or an alkaline earth metal and one or more combustible materials in a proportion such that the mixture is overbalanced in favour of oxygen.
  • the combustible material may be charcoal or sugar.
  • EP-A-0042367 discloses a method for reducing the sulphur context of exit gases resulting from the combustion of sulphur bearing fuels, which method comprises the step of igniting the sulphur bearing fuel in the presence of at least one alkaline earth metal nitrate, alkali metal nitrate or ammonium nitrate.
  • EP-A-0053085 discloses a method for cleaning the surfaces of an installation in which a dispersion, for example of a mixture of potassium nitrate and ammonium nitrate, is entrained by the combustion gases whereby it reacts with the deposits of carbon and minerals which encrust the surfaces of the installation and displacing the particles resulting from the reactions by the use of sound waves so that they become entrained in the air flow or combustion gases or are deposited in the ashes of the installation.
  • a dispersion for example of a mixture of potassium nitrate and ammonium nitrate
  • 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 comprises continuously or intermittently introducing into the combustion chamber of the equipment or into the flue gas stream in atomized form by means of at least one injection device a liquid additive comprising an aqueous solution of a mixture of ammonium nitrate, at least one nitrate of an alkali metal, optionally at least one nitrate of an alkaline earth metal and an indicator, monitoring the pH value of the additive and, if necessary adjusting the pH value to within the range of from 7 to 9, monitoring the dewpoint of the flue gas stream and adjusting as necessary, the amount and composition of the additive supplied to the metering device in order to maintain the exit gas temperature of the equipment above the acid dewpoint level.
  • 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 and 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.
  • 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.

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  • 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)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Polishing Bodies And Polishing Tools (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)

Abstract

A method for preventing deposits on or removing deposits from heating and ancillary surfaces of boilers and like equipment, which method comprises continuously or intermittently introducing into the combustion chamber of the equipment or into the flue gas stream in atomized form by means of at least one injection device a liquid additive comprising an aqueous solution of a mixture of ammonium nitrate, at least one nitrate of an alkali metal, optionally at least one nitrate of an alkaline earth metal and an indicator, monitoring the pH value or the additive and, if necessary adjusting the pH value to within the range of from 7 to 9, monitoring the dewpoint of the flue gas stream and adjusting as necessary, the amount and composition of the additive supplied to the metering device in order to adjust the dew point of the flue gas stream to the desired level.

Description

  • 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. In particular 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.
  • By the term "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 riormally 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.
  • GB-A-1378882 discloses a method for the removal of deposits from surfaces which comprises applying to a heated surface an agent which comprises a mixture of ammonium nitrate and at least one nitrate of an alkali metal, an alkaline earth metal, copper, zinc or an organic base, the agent not including therein an oxidisable organic material, sulphur or a sulphur compound.
  • FR-A-1357992 discloses an agent for the chemical removal of soot which comprises a nitrate of an alkali metal or an alkaline earth metal and one or more combustible materials in a proportion such that the mixture is overbalanced in favour of oxygen. The combustible material may be charcoal or sugar.
  • EP-A-0042367 discloses a method for reducing the sulphur context of exit gases resulting from the combustion of sulphur bearing fuels, which method comprises the step of igniting the sulphur bearing fuel in the presence of at least one alkaline earth metal nitrate, alkali metal nitrate or ammonium nitrate.
  • EP-A-0053085 discloses a method for cleaning the surfaces of an installation in which a dispersion, for example of a mixture of potassium nitrate and ammonium nitrate, is entrained by the combustion gases whereby it reacts with the deposits of carbon and minerals which encrust the surfaces of the installation and displacing the particles resulting from the reactions by the use of sound waves so that they become entrained in the air flow or combustion gases or are deposited in the ashes of the installation.
  • 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 comprises continuously or intermittently introducing into the combustion chamber of the equipment or into the flue gas stream in atomized form by means of at least one injection device a liquid additive comprising an aqueous solution of a mixture of ammonium nitrate, at least one nitrate of an alkali metal, optionally at least one nitrate of an alkaline earth metal and an indicator, monitoring the pH value of the additive and, if necessary adjusting the pH value to within the range of from 7 to 9, monitoring the dewpoint of the flue gas stream and adjusting as necessary, the amount and composition of the additive supplied to the metering device in order to maintain the exit gas temperature of the equipment above the acid dewpoint level.
  • The additive which is used in the present invention may be composed as follows:
    Figure imgb0001
  • 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 reactions will occur in the neutralization of gases containing sulfur oxides are as follows:-
    Figure imgb0002
    Figure imgb0003
    Figure imgb0004
    Figure imgb0005
    Figure imgb0006
    Figure imgb0007
    Figure imgb0008
    Figure imgb0009
  • In addition, 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.
  • During the operation of the method of the invention 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.
  • In a preferred mode of operating the present invention 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.
  • In operating the method of the invention a reduction in the temperature of the flue gases usually occurs and this leads to a reduction in flue-gas heat loss with a concurrent fuel saving.
  • The present invention will be further described with reference to the following Examples.
    • Example 1
  • 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.
    Figure imgb0010
    • Addition: 02 litres of the additive per ton of fuel
    • Injection point: combustion chamber 1 injection lance
    • Injection appliance: fully automatic, time-controlled pneumatic operation
    Results
  • The heating and ancillary surfaces were free of solid deposits, and the surfaces could be dry cleaned using compressed air.
  • The flue-gas temperature rise during the operation was only 6°C as compared with 35°C according to the previous operating records.
  • A reduction in flue-gas heat loss of 2%, was achieved which was equivalent to a fuel saving of about the same order.
    • Example 2
  • 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.
    Figure imgb0011
    • 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.
    • Example 3
  • A VKW-Lentjes Benson boiler was treated.
    Figure imgb0012
    • Addition
  • 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.
    • Results
  • 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.

Claims (8)

1. A method for preventing deposits on or removing deposits from heating and ancillary surfaces of boilers and like equipment, which method comprises continuously or intermittently introducing into the combustion chamber of the equipment or into the flue gas stream in atomized form by means of at least one injection device a liquid additive comprising an aqueous solution of a mixture of ammonium nitrate, at least one nitrate of an alkali metal and optionally at least one nitrate of an alkaline earth metal characterized in that the additive also contains an indicator and the pH value of the additive is monitored and, if necessary, adjusted to within the range of from 7 to 9, and in that the acid dewpoint of the flue gas stream is monitored and the amount and composition of the additive supplied to the metering device is adjusted as necessary in order to maintain the exit gas temperature of the equipment above the acid dewpoint level.
2. A method as claimed in Claim 1 wherein the alkali metal nitrate is potassium nitrate.
3. A method as claimed in Claim 1 or Claim 2 wherein the alkaline earth metal nitrate is magnesium nitrate.
4. A method as claimed in any one of the preceding claims wherein the indicator is thymol blue or bromothymol blue.
5. A method as claimed in any one of the preceding claims wherein the pH value of the additive is adjusted to within the range of from 7 to 9 by the addition of an alkali.
6. A method as claimed in any one of the preceding claims wherein the injection device is an injection lance.
7. A method as claimed in any one of the preceding claims wherein aqueous solutions of the nitrates are provided in separate tanks.
8. A method as claimed in claim 7 wherein the aqueous solutions of the nitrates are supplied in the desired amounts to a common tank for mixing prior to their introduction into the combustion chamber or flue Qas.
EP82300638A 1981-02-09 1982-02-09 Method for the prevention of deposits on or the removal of deposits from heating and ancillary surfaces Expired EP0058086B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82300638T ATE14897T1 (en) 1981-02-09 1982-02-09 DEPOSIT PREVENTION AND/OR DEPOSIT REMOVAL PROCEDURES FROM HEATED OR SIMILAR SURFACES.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8103859A GB2095283B (en) 1981-02-09 1981-02-09 Method for the prevention of deposits on or the removal ofdeposits from heating and ancillary surfaces
GB8103859 1981-02-09

Publications (3)

Publication Number Publication Date
EP0058086A2 EP0058086A2 (en) 1982-08-18
EP0058086A3 EP0058086A3 (en) 1982-09-08
EP0058086B1 true EP0058086B1 (en) 1985-08-14

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EP82300638A Expired EP0058086B1 (en) 1981-02-09 1982-02-09 Method for the prevention of deposits on or the removal of deposits from heating and ancillary surfaces

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AT (1) ATE14897T1 (en)
DE (1) DE3265325D1 (en)
GB (1) GB2095283B (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3530276A1 (en) * 1985-08-24 1987-02-26 Hoelter Heinz Environment-friendly fuel
JP2977569B2 (en) * 1988-03-10 1999-11-15 シーメンス、アクチエンゲゼルシヤフト Method and apparatus for operating a gas turbine by introducing additives
AT391873B (en) * 1988-10-03 1990-12-10 Lang Chem Tech Prod AQUEOUS CATALYST SOLUTION AND FUELS
GB9311070D0 (en) * 1993-05-28 1993-07-14 Gb Thermaxhem Ltd Compound
GB2395722A (en) * 2002-11-27 2004-06-02 Polarchem Internat Ltd The prevention or removal of deposits from heating and ancillary surfaces
CN109504405A (en) * 2018-11-02 2019-03-22 石首市博锐德生物科技有限公司 The system and method for handling corn stover
GB202205074D0 (en) 2022-04-06 2022-05-18 Brookes Jonathan Pneumatic liquid injection device/method

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0053085A1 (en) * 1980-11-26 1982-06-02 Etablissements SOMALOR - FERRARI "SOMAFER" S.A. Method of cleaning surfaces soiled by deposits accrued during conbustion of carbon materials

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL293035A (en) * 1962-05-24 1900-01-01
GB1378882A (en) * 1972-05-16 1974-12-27 Polar Chemicals Ltd Method for the removal of soot and other deposits formed as a result of the combustion of gaseous liquid and solid fuels
SE8006781L (en) * 1980-06-16 1981-12-17 Peter M Scocca PRESENT INVENTION ALL OVER THE ENVIRONMENT AREA AND SPECIFIC REDUCTION OF SULFUR DIOXIDE AND SULFUR TRIOXIDE EMISSIONS COGASES FROM COMBUSTION

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0053085A1 (en) * 1980-11-26 1982-06-02 Etablissements SOMALOR - FERRARI "SOMAFER" S.A. Method of cleaning surfaces soiled by deposits accrued during conbustion of carbon materials

Also Published As

Publication number Publication date
DE3265325D1 (en) 1985-09-19
ATE14897T1 (en) 1985-08-15
GB2095283B (en) 1984-08-01
EP0058086A2 (en) 1982-08-18
GB2095283A (en) 1982-09-29
EP0058086A3 (en) 1982-09-08

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