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For integrated kraft pulp and paper mills, the process-specific BAT conclusions for papermaking given in Section 1.6 apply, in addition to the BAT conclusions in this section.
Technique | Description | Applicability | |
---|---|---|---|
a | Modified cooking before bleaching | See Section 1.7.2.1 | Generally applicable |
b | Oxygen delignification before bleaching | ||
c | Closed brown stock screening and efficient brown stock washing | ||
d | Partial process water recycling in the bleach plant | Water recycling may be limited due to incrustation in bleaching | |
e | Effective spill monitoring and containment with a suitable recovery system | Generally applicable | |
f | Maintaining sufficient black liquor evaporation and recovery boiler capacity to cope with peak loads | Generally applicable | |
g | Stripping the contaminated (foul) condensates and reusing the condensates in the process |
See Table 1 and Table 2. These BAT-associated emission levels are not applicable to dissolving kraft pulp mills.
The reference waste water flow for kraft mills is set out in BAT 5.
BAT-associated emission levels for the direct waste water discharge to receiving waters from a bleached kraft pulp mill
a The BAT-AEL ranges refer to market pulp production and the pulp production part of integrated mills (emissions from papermaking are not included). | |
b A compact biological waste water treatment plant can result in slightly higher emission levels. | |
c The upper end of the range refers to mills using eucalyptus from regions with higher levels of phosphorus (e.g. Iberian eucalyptus). | |
d Applicable for mills using chlorine containing bleaching chemicals. | |
e For mills producing pulp with high strength, stiffness and high purity properties (e.g. for liquid packaging board and LWC), emissions level of AOX up to 0,25 kg/ADt may occur. | |
Parameter | Yearly averagekg/ADta |
---|---|
Chemical oxygen demand (COD) | 7 – 20 |
Total suspended solids (TSS) | 0,3 – 1,5 |
Total nitrogen | 0,05 – 0,25b |
Total phosphorus | 0,01 – 0,03b Eucalyptus: 0,02 – 0,11 kg/ADtc |
Adsorbable organically bound halogens (AOX)d e | 0 – 0,2 |
BAT-associated emission levels for the direct waste water discharge to receiving waters from an unbleached kraft pulp mill
a The BAT-AEL ranges refer to market pulp production and the pulp production part of integrated mills (emissions from papermaking are not included). | |
b A compact biological waste water treatment plant can result in slightly higher emission levels. | |
Parameter | Yearly averagekg/ADta |
---|---|
Chemical oxygen demand (COD) | 2,5 – 8 |
Total suspended solids (TSS) | 0,3 – 1,0 |
Total nitrogen | 0,1 – 0,2b |
Total phosphorus | 0,01 – 0,02b |
The BOD concentration in the treated effluents is expected to be low (around 25 mg/l as a 24-hour composite sample).
a The SOx emission levels of the lime kiln increase significantly when strong non-condensable gases (NCG) are fed to the kiln and no alkaline scrubber is used. | ||
b Applicable for the treatment of weak odorous gases. | ||
c Applicable for the treatment of strong odorous gases. | ||
Technique | Description | |
---|---|---|
a | Collection systems for strong and weak odorous gases, comprising the following features:
| |
b | Incineration of strong and weak non-condensable gases | Incineration can be carried out using:
To ensure the constant availability of incineration for odorous strong gases, back-up systems are installed. Lime kilns can serve as back-up for recovery boilers; further back-up equipment are flares and package boiler |
c | Recording unavailability of the incineration system and any resulting emissionsc |
Generally applicable for new plants and for major refurbishments of existing plants. The installation of necessary equipment may be difficult for existing plants due to layout and space restrictions. The applicability of incineration might be limited for safety reasons, and in this case wet scrubbers could be used.
BAT-associated emission level of total reduced sulphur (TRS) in residual weak gases emitted is 0,05 – 0,2 kg S/ADt.
Technique | Description | |
---|---|---|
a | Increasing the dry solids (DS) content of black liquor | The black liquor can be concentrated by an evaporation process before burning |
b | Optimised firing | Firing conditions can be improved e.g. by good mixing of air and fuel, control of furnace load etc. |
c | Wet scrubber | See Section 1.7.1.3 |
See Table 3.
BAT-associated emission levels for SO2 and TRS emissions from a recovery boiler
a Increasing the DS content of the black liquor results in lower SO2 emissions and higher NOx emissions. Due to this, a recovery boiler with low emission levels for SO2, may be on the higher end of the range for NOx and vice versa. | ||||
b BAT-AELs do not cover periods during which the recovery boiler is run on a DS content much lower than the normal DS content due to shut down or maintenance of the black liquor concentration plant. | ||||
c If a recovery boiler were to burn black liquor with a DS > 83 %, then SO2 and gaseous S emission levels should be reconsidered on a case-by-case basis. | ||||
d The range is applicable without the incineration of odorous strong gases. | ||||
DS = dry solid content of the black liquor. | ||||
Parameter | Daily averagea bmg/Nm3 at 6 % O2 | Yearly averageamg/Nm3 at 6 % O2 | Yearly averageakg S/ADt | |
---|---|---|---|---|
SO2 | DS < 75 % | 10 – 70 | 5 – 50 | — |
DS 75 – 83 %c | 10 – 50 | 5 – 25 | — | |
Total reduced sulphur (TRS) | 1 – 10d | 1 – 5 | — | |
Gaseous S (TRS-S + SO2-S) | DS < 75 % | — | — | 0,03 – 0,17 |
DS 75 – 83 %c | 0,03 – 0,13 |
Technique | |
---|---|
a | Computerised combustion control |
b | Good mixing of fuel and air |
c | Staged air feed systems, e.g. by using different air registers and air inlet ports |
Technique (c)is applicable to new recovery boilers and in the case of a major refurbishment of recovery boilers, as this technique requires considerable changes to the air feed systems and the furnace.
See Table 4.
BAT-associated emission levels for NOx emissions from a recovery boiler
a Increasing the DS content of the black liquor results in lower SO2 emissions and higher NOx emissions. Due to this, a recovery boiler with low emission levels for SO2, may be on the higher end of the range for NOx and vice versa. | |||
b The actual NOx emission level of a recovery boiler depends on the DS content and the nitrogen content of the black liquor, and the amount and combination of NCG and other nitrogen containing flows (e.g. dissolving tank vent gas, methanol separated from the condensate, biosludge) burnt. The higher the DS content, the nitrogen content in the black liquor, and the amount of NCG and other nitrogen containing flows burnt, the closer the emissions will be to the upper end of the BAT-AEL range. | |||
c If a recovery boiler were to burn black liquor with a DS > 83 %, then NOx emission levels should be reconsidered on a case-by-case basis. | |||
DS = dry solid content of black liquor. | |||
Parameter | Yearly averageamg/Nm3 at 6 % O2 | Yearly averageakg NOx/ADt | |
---|---|---|---|
NOx | Softwood | 120 – 200b | DS < 75 %: 0,8 – 1,4 DS 75 – 83 %c: 1,0 – 1,6 |
Hardwood | 120 – 200b | DS < 75 %: 0,8 – 1,4 DS 75 – 83 %c: 1,0 – 1,7 |
SeeSection 1.7.1.1.
See Table 5.
BAT-associated emission levels for dust emissions from a recovery boiler
a For an existing recovery boiler equipped with an ESP approaching the end of its operational life, emission levels may increase over time up to 50 mg/Nm3 (corresponding to 0,4 kg/ADt). | |||
Parameter | Dust abatement system | Yearly averagemg/Nm3 at 6 % O2 | Yearly averagekg dust/ADt |
---|---|---|---|
Dust | New or major refurbishment | 10 – 25 | 0,02 – 0,20 |
Existing | 10 – 40a | 0,02 — 0,3a |
Technique | Description | |
---|---|---|
a | Fuel selection/low sulphur fuel | See Section 1.7.1.3 |
b | Limit incineration of sulphur-containing odorous strong gases in the lime kiln | |
c | Control of Na2S content in lime mud feed | |
d | Alkaline scrubber |
See Table 6.
BAT-associated emission levels for SO2 and sulphur emissions from a lime kiln
a ‘strong gases’ includes methanol and turpentine | ||
Parametera | Yearly averagemg SO2/Nm3 at 6 % O2 | Yearly averagekg S/ADt |
---|---|---|
SO2 when strong gases are not burnt in the lime kiln | 5 – 70 | — |
SO2 when strong gases are burnt in the lime kiln | 55 – 120 | — |
Gaseous S (TRS-S + SO2-S) when strong gases are not burnt in the lime kiln | — | 0,005 – 0,07 |
Gaseous S (TRS-S + SO2-S) when strong gases are burnt in the lime kiln | — | 0,055 – 0,12 |
Technique | Description | |
---|---|---|
a | Control of the excess oxygen | See Section 1.7.1.3 |
b | Control of Na2S content in lime mud feed | |
c | Combination of ESP and alkaline scrubber | See Section 1.7.1.1 |
See Table 7.
BAT-associated emission levels for TRS emissions from a lime kiln
a For lime kilns burning strong gases (including methanol and turpentine), the upper end of the AEL range may be up to 40 mg/Nm3. | |
Parameter | Yearly averagemg S/Nm3 at 6 % O2 |
---|---|
Total reduced sulphur (TRS) | < 1 – 10a |
Technique | Description | |
---|---|---|
a | Optimised combustion and combustion control | See Section 1.7.1.2 |
b | Good mixing of fuel and air | |
c | Low-NOx burner | |
d | Fuel selection/low-N fuel |
See Table 8.
BAT-associated emission levels for NOx emissions from a lime kiln
a When using liquid fuels originating from vegetable matter (e.g. turpentine, methanol, tall-oil), including those obtained as by-products of the pulping process, emission levels up to 350 mg/Nm3 (corresponding to 0,35 kg NOx/ADt) may occur. | |||
b When using gaseous fuels originating from vegetable matter (e.g. non-condensable gases), including those obtained as by-products of the pulping process, emission levels up to 450 mg/Nm3 (corresponding to 0,45 kg NOx/ADt) may occur. | |||
Parameter | Yearly averagemg/Nm3 at 6 % O2 | Yearly averagekg NOx/ADt | |
---|---|---|---|
NOx | Liquid fuels | 100 – 200a | 0,1 – 0,2a |
Gaseous fuels | 100 – 350b | 0,1 – 0,3b |
See Section 1.7.1.1.
See Table 9.
BAT-associated emission levels for dust emissions from a lime kiln
a For an existing lime kiln equipped with an ESP approaching the end of its operational life, emission levels may increase over time up to 50 mg/Nm3 (corresponding to 0,05 kg/ADt). | |||
Parameter | Dust abatement system | Yearly averagemg/Nm3 at 6 % O2 | Yearly averagekg dust/ADt |
---|---|---|---|
Dust | New or major refurbishments | 10 – 25 | 0,005 – 0,02 |
Existing | 10 – 30a | 0,005 – 0,03a |
See Table 10.
BAT-associated emission levels for SO2 and TRS emissions from the incineration of strong gases in a dedicated TRS burner
a This BAT-AEL is based on a gas flow in the range of 100-200 Nm3/ADt. | ||
Parameter | Yearly averagemg/Nm3 at 9 % O2 | Yearly averagekg S/ADt |
---|---|---|
SO2 | 20 – 120 | — |
TRS | 1 – 5 | |
Gaseous S (TRS-S + SO2-S) | — | 0,002 – 0,05a |
Technique | Description | Applicability | |
---|---|---|---|
a | Burner/firing optimisation | See Section 1.7.1.2 | Generally applicable |
b | Staged incineration | See Section 1.7.1.2 | Generally applicable for new plants and for major refurbishments. For existing mills, applicable only if space allows for the insertion of equipment |
See Table 11.
BAT-associated emission levels for NOx emissions from the incineration of strong gases in a dedicated TRS burner
Recirculation of dust may be limited due to non-process elements in the dust.
Technique | |
---|---|
a | High dry solid content of bark, by use of efficient presses or drying |
b | High efficiency steam boilers, e.g. low flue-gas temperatures |
c | Effective secondary heating systems |
d | Closing water systems, including bleach plant |
e | High pulp concentration (middle or high consistency technique) |
f | High efficiency evaporation plant |
g | Recovery of heat from dissolving tanks e.g. by vent scrubbers |
h | Recovery and use of the low temperature streams from effluents and other waste heat sources to heat buildings, boiler feedwater and process water |
i | Appropriate use of secondary heat and secondary condensate |
j | Monitoring and control of processes, using advanced control systems |
k | Optimise integrated heat exchanger network |
l | Heat recovery from the flue-gas from the recovery boiler between the ESP and the fan |
m | Ensuring as high a pulp consistency as possible in screening and cleaning |
n | Use of speed control of various large motors |
o | Use of efficient vacuum pumps |
p | Proper sizing of pipes, pumps and fans |
q | Optimised tank levels |
Technique | |
---|---|
a | High black liquor dry solid content (increases boiler efficiency, steam generation and thus electricity generation) |
b | High recovery boiler pressure and temperature; in new recovery boilers the pressure can be at least 100 bars and the temperature 510 °C |
c | Outlet steam pressure in the back-pressure turbine as low as technically feasible |
d | Condensing turbine for power production from excess steam |
e | High turbine efficiency |
f | Preheating feedwater to a temperature close to the boiling temperature |
g | Preheating the combustion air and fuel charged to the boilers |