EP0253324A2 — Method and apparatus for reducing sulphur dioxide…

Claim 1

Independent Claim 211 words

In the combusting of a sulfur-containing fuel, a method for reducing the sulfur dioxide (SO₂) content of the combustion reaction gases, said method comprising the steps of: introducing a sulfur-containing fuel into a first zone in an enclosed combustion chamber; introducing a first portion of air into said first zone at least closely adjacent said fuel to at least partially combust said fuel and produce combustion reaction gases containing sulfur dioxide; introducing a second portion of air into said combustion chamber at a second zone spaced relatively remotely from said first zone; flowing the contents of said first zone downstream through said second zone; controlling the location at which said second portion of air is introduced, and the velocity thereof, to buffer the peak flame temperature and provide a relatively uniform flame front in said second zone; providing finely divided particles of a material which forms lime upon exposure to the heat in said second zone; introducing said particles into said second zone together with and under the urging of said second portion of air, without premixing said particles and said second portion of air before they enter said second zone; and employing said second portion of air to distribute said particles throughout the gases flowing downstream through the second zone.

Claim 2

Dependent Claim 211 words

In the combusting of a sulfur-containing fuel, a method for reducing the sulfur dioxide (SO₂) content of the combustion reaction gases, said method comprising the steps of: introducing a sulfur-containing fuel into a first zone in an enclosed combustion chamber; introducing a first portion of air into said first zone at least closely adjacent said fuel to at least partially combust said fuel and produce combustion reaction gases containing sulfur dioxide; introducing a second portion of air into said combustion chamber at a second zone spaced relatively remotely from said first zone; flowing the contents of said first zone downstream through said second zone; controlling the location at which said second portion of air is introduced, and the velocity thereof, to buffer the peak flame temperature and provide a relatively uniform flame front in said second zone; providing finely divided particles of a material which forms lime upon exposure to the heat in said second zone; introducing said particles into said second zone together with and under the urging of said second portion of air, without premixing said particles and said second portion of air before they enter said second zone; and employing said second portion of air to distribute said particles throughout the gases flowing downstream through the second zone.

Claim 3

Dependent Claim 64 words

A method as recited in claim 1 and comprising: flowing the contents of said second zone in a downstream direction away from said first and second zones; and flash calcining said particles of material downstream of said first zone to produce particles of lime (CaO) which reacts with at least part of any SO₂ present to produce calcium sulfate (CaSO₄) in said combustion chamber.

Claim 4

Dependent Claim 110 words

A method as recited in claim 2 wherein: the average temperature in said first zone exceeds the sintering temperature of lime; and said controlling step provides an average processing temperature range, downstream of said first zone, which is below the sintering temperature for said lime particles and below the temperature at which said calcium sulfate decomposes into lime and gaseous oxides of sulfur; said average processing temperature range being high enough and prevailing long enough to react the lime produced downstream of said first zone with the desired amount of SO₂ gas during the time in which said lime and said SO₂ gas are subjected to said average processing temperature.

Claim 5

Dependent Claim 17 words

A method as recited in claim 3 wherein: said average processing temperature range is about 1600°-2400°F (871-1316°C).

Claim 6

Dependent Claim 27 words

A method as recited in claim 4 wherein: said lime and said SO₂ gas are subjected to said average processing temperature range for more than 0.5 second.

Claim 7

Dependent Claim 28 words

A method as recited in claim 5 wherein said lime and said SO₂ gas are subjected to said average processing temperature range for at least about 1.5 seconds.

Claim 8

Independent Claim 34 words

A method as recited in any one of claims 1 to 6 wherein: said sulfer-containing fuel is at least one of the group comprising finely divided coal particles, coke oven gas and fuel oil.

Claim 9

Independent Claim 65 words

A method as recited in any one of claims 1 to 7 wherein said step of introducing said particles of material into the second zone comprises: transporting said particles of material up to said second zone; and aspirating said particles of material into said s econd zone by the action of the second portion of air as the latter is introduced into the second zone.

Claim 10

Dependent Claim 46 words

A method as recited in claim 8 wherein said particle-transporting step comprises: imparting to said particles of material, before the second zone, a velocity sufficient to flow the particles of material up to the second zone but insufficient to distribute the particles across the second zone.

Claim 11

Dependent Claim 26 words

A method as recited in claim 9 wherein said particle-transporting step comprises: flowing the particles of material up to said second zone under dense phase transport.

Claim 12

Dependent Claim 29 words

A method as recited in claim 10 wherein said particle-transporting step comprises: mixing said particles of material with transporting air in an amount which will provide dense phase transport.

Claim 13

Dependent Claim 29 words

A method as recited in claim 8 wherein: said particles of material have a flow velocity up to said second zone of at least about 300 ft/min. (91 m/min).

Claim 14

Dependent Claim 42 words

A method as recited in claim 12 wherein: said second portion of air is introduced into said second zone at a veloctiy of at least about 2,500 ft/min (1762 m/min.) so as to aspirate the particles of material into the second zone.

Claim 15

Independent Claim 43 words

A method as recited in any one of claims 1 to 13 and comprising: causing tubulence by the introduction of said second portion of air into the second zone to aid in the distribution of the particles of material throughout the second zone.

Claim 16

Independent Claim 52 words

A method as rcited in any one of claims 1 to 14 wherein: the velocity of the second portion of air as it enters the second zone is at least about 2,500 ft/min. (762 m/min.); and said particles of material are introduced into the second zone without the use of extraneous air.

Claim 17

Independent Claim 27 words

A method as recited in any one of claims 1 to 15 wherein: said particles of material are smaller than 100 mesh on a wet screen basis.

Claim 18

Dependent Claim 45 words

A method as recited in claim 16 wherein: said particles of material have a size, in the range between about 5 microns and minus 100 mesh, on a wet screen basis, sufficient to provide the reaction required to eliminate SO₂ gas to the extent desired.

Claim 19

Independent Claim 85 words

A method as recited in any one of claims 1 to 17 wherein: said fuel is particulate coal; said first portion of air is divided into two parts, one of which is mixed with said coal for injection with the coal into said first zone: the other of said two parts of air being injected into said first zone alongside said mixture of particulate coal and the one part of air; and said method comprises preheating essentially all of said air entering said combustion chamber.

Claim 20

Independent Claim 58 words

A method as recited in any one of claims 1 to 18 wherein: said second portion of air enters said second zone initially as a stream of air which is relatively cool compared to the temperature in said second zone; and said particles of material enter said second zone within said stream of air constituting said second portion.

Claim 21

Dependent Claim 54 words

A method as recited in claim 19 wherein: there are peak temperatures, in the contents of said first zone flowing downstream through said second sone, which are high enough to cause sintering of said particles; and said second portion of air cushions said particles from said peak temperature to prevent sintering of the particles.

Claim 22

Independent Claim 111 words

A method as recited in any one of claims 1 to 20 wherein: said combustion chamber has inside wall surfaces, deposits form on said inside wall surfaces in said second zone during the combustion operation, lime formed from said particles of material is incorporated into said deposits, soot blowing is employed to remove said deposits, and lime from said deposits is introduced into said combustion chamber as a result of said soot blowing: said method comprising the step of reducing the amount of said lime-forming material introduced into said second zone, during said soot blowing step, without reducing substantially the decrease, in sulphur dioxide content, obtained before the soot blowing step.

Claim 23

Independent Claim 66 words

A method as recited in any one of claims 1 to 21 wherein: said combustion chamber is part of a combustion system. acids are formed in said combustion system as a result of the comusting of said fuel; said acids are neutralised by said lime; and said combustion reaction gases are exhausted from the combustion system at a temperature below the dew point of said acids.

Claim 24

Dependent Claim 24 words

A method as recited in claim 22 wherein: said fuel gases are exhausted from the combustion system at a temperature below 250°F (121° C).

Claim 25

Independent Claim 110 words

A method as recited in any one of claims 1 to 23 wherein: said combustion chamber has inside wall surfaces, deposits form on said inside wall surfaces in said second zone during the combustion operation, and lime formed from said particles of material is incorporated into said deposits; said step of introducing said lime forming material is temporarily suspended for a period of time, after it has been performed for awhile; at least some of said SO₂ is absorbed by the lime in said deposits during at least the early part of said temporary suspension period; and soot blowing is deferred while said SO₂ is being absorbed into said deposits.

Claim 26

Dependent Claim 45 words

A method as recited in claim 24 wherein: after deferring said soot blowing for a period of time, soot blowing is then only partially performed, to remove only an outer layer of said deposits and expose a new deposit outer layer for absorption of SO₂.

Claim 27

Dependent Claim 176 words

In the combusting of a sulfur-containing fuel, a method for reducing the sulfur dioxide (SO₂) content of the combustion reaction gases, said method comprising the steps of: combusting a sulfur-containing fuel with air in a combustion chamber, having inside wall surfaces, to produce combustion reaction gases containing sulfur dioxide (SO₂); introducing, into said combustion chamber, finely divided particles of a material which forms lime upon exposure to the heat in said combustion chamber; reacting said lime with said sulfur dioxide in the combustion reaction gases, in said combustion chamber, to decrease the sulfur dioxide content of said gases; forming deposits on the inside wall surfaces of said combustion chamber during the combustion operation; incorporating lime from said particles of material into said deposits; soot blowing, after there has been an accumulation of said deposits, to remove said deposits from said inside wall surfaces; and reducing the amount of said lime-forming material introduced into the combustion chamber, during said soot blowing step, without reducing substantially the decrease in sulfur dioxide content obtained before the soot blowing step.

Claim 28

Dependent Claim 176 words

In the combusting of a sulfur-containing fuel, a method for reducing the sulfur dioxide (SO₂) content of the combustion reaction gases, said method comprising the steps of: combusting a sulfur-containing fuel with air in a combustion chamber, having inside wall surfaces, to produce combustion reaction gases containing sulfur dioxide (SO₂); introducing, into said combustion chamber, finely divided particles of a material which forms lime upon exposure to the heat in said combustion chamber; reacting said lime with said sulfur dioxide in the combustion reaction gases, in said combustion chamber, to decrease the sulfur dioxide content of said gases; forming deposits on the inside wall surfaces of said combustion chamber during the combustion operation; incorporating lime from said particles of material into said deposits; soot blowing, after there has been an accumulation of said deposits, to remove said deposits from said inside wall surfaces; and reducing the amount of said lime-forming material introduced into the combustion chamber, during said soot blowing step, without reducing substantially the decrease in sulfur dioxide content obtained before the soot blowing step.

Claim 29

Dependent Claim 119 words

In the combusting of a sulfur-containing fuel in a combustion chamber which is part of a combustion system, a method for reducing the sulfur dioxide (SO₂) content of the combustion reaction gases, said method comprising the steps of: combusting a sulfur-containing fuel with air in said combustion chamber to produce combustion reaction gases containing sulfur dioxide (SO₂); introducing, into said combustion chamber, finely divided particles of a material which forms lime upon exposure to the heat in said combustion chamber; forming acids in said combustion system as a result of said combusting step; neutralizing said acids with said lime; and exhausting said combustion reaction gases from said combustion system at a temperature below the dew point of said acids.

Claim 30

Dependent Claim 119 words

In the combusting of a sulfur-containing fuel in a combustion chamber which is part of a combustion system, a method for reducing the sulfur dioxide (SO₂) content of the combustion reaction gases, said method comprising the steps of: combusting a sulfur-containing fuel with air in said combustion chamber to produce combustion reaction gases containing sulfur dioxide (SO₂); introducing, into said combustion chamber, finely divided particles of a material which forms lime upon exposure to the heat in said combustion chamber; forming acids in said combustion system as a result of said combusting step; neutralizing said acids with said lime; and exhausting said combustion reaction gases from said combustion system at a temperature below the dew point of said acids.

Claim 31

Dependent Claim 23 words

A method as recited in claim 27 wherein: said flue gases are exhausted from the combustion system at a temperature below 250°F (121°C).

Claim 32

Dependent Claim 152 words

In the combusting of a sulfur-containing fuel, a method for reducing the sulfur dioxide (SO 2 )content of the combustion reaction gases, said method comprising the steps of: combusting a sulfur-containing fuel with air in a combustion chamber, having inside wall surfaces, to produce combustion reaction gases containing sulfur dioxide; introducing, into said combustion chamber, finely divided particles of a material which forms lime upon exposure to the heat in said combustion chamber; forming deposits on the inside wall surfaces of said combustion chamber during the combustion operation; incorporating lime from said particles of material into said deposits; temporarily suspending said introducing step for a period of time, after it has been performed for awhile; absorbing at least some of said SO₂ by the lime in said deposits during at least the early part of said temporary suspension period; and deferring soot blowing while said SO₂ is being absorbed into said deposits.

Claim 33

Dependent Claim 152 words

In the combusting of a sulfur-containing fuel, a method for reducing the sulfur dioxide (SO 2 )content of the combustion reaction gases, said method comprising the steps of: combusting a sulfur-containing fuel with air in a combustion chamber, having inside wall surfaces, to produce combustion reaction gases containing sulfur dioxide; introducing, into said combustion chamber, finely divided particles of a material which forms lime upon exposure to the heat in said combustion chamber; forming deposits on the inside wall surfaces of said combustion chamber during the combustion operation; incorporating lime from said particles of material into said deposits; temporarily suspending said introducing step for a period of time, after it has been performed for awhile; absorbing at least some of said SO₂ by the lime in said deposits during at least the early part of said temporary suspension period; and deferring soot blowing while said SO₂ is being absorbed into said deposits.

Claim 34

Dependent Claim 45 words

A method as recited in claim 28 wherein: after deferring said soot blowing for a period of time, soot blowing is then only partially performed, to remove only an outer layer of said deposits and expose a new deposit outer layer for absorption of SO₂.

Claim 35

Dependent Claim 134 words

In a combustion chamber: a nozzle for introducing fuel and primary air into said chamber; means for introducing fuel into said nozzle; means for introducing primary air into said nozzle; means, located adjacent said fuel nozzle, for introducing secondary air into said chamber; tubular means for introducing a stream of tertiary air into said chamber at a location spaced relatively remotely from said nozzle; and pipe means for injecting finely divided particles of material into said stream of tertiary air as the stream enters said chamber, without premixing said particles and said stream before they enter said chamber; said pipe means being disposed substantially coaxially within said tubular means and terminating at an open downstream end, there being no communication between said pipe means and said tubular means upstream of said open downstream end.

Claim 36

Dependent Claim 134 words

In a combustion chamber: a nozzle for introducing fuel and primary air into said chamber; means for introducing fuel into said nozzle; means for introducing primary air into said nozzle; means, located adjacent said fuel nozzle, for introducing secondary air into said chamber; tubular means for introducing a stream of tertiary air into said chamber at a location spaced relatively remotely from said nozzle; and pipe means for injecting finely divided particles of material into said stream of tertiary air as the stream enters said chamber, without premixing said particles and said stream before they enter said chamber; said pipe means being disposed substantially coaxially within said tubular means and terminating at an open downstream end, there being no communication between said pipe means and said tubular means upstream of said open downstream end.

Method and apparatus for reducing sulphur dioxide content in flue gases

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