3. Notes on the analysis and evaluation of environmental impacts

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3.1 General

Any evaluation of the detrimental effects of coking plant emissions must allow for numerous factors, some of which are difficult to quantify, e.g.:
baseline pollution by other emitters,
- climatic influences, particularly of wind, on propagation behavior,
- accumulative capacity of surrounding ecosystems.

It has been qualitatively determined that some such emissions, BTX and benzo(a)pyrene in particular, have carcinogenic effects on humans and animals and that particulate emissions and some gases can cause diseases of the respiratory tract.

The fact that coking plants, most notably in the near vicinity of the coke oven batteries, have both definite and diffuse sources of emissions complicates the stipulation of tolerable emission levels, e.g., in the form of emission factors. This problem is evidenced in pertinent German directives and regulations such as TA-Luft, which states allowable concentrations in the exhaust gases/air from definite points, but also applies qualitative technical measures to the erection of numerous different systems and types of plant.

Hence, only a narrow selection of emission limits/factors is available for reference.

That information, however, is supplemented by MAK/TRK-values which define limits for airborne workplace pollution and allow for the registration and monitoring of emissions from diffuse sources.

3.2 Summary of limit values and standards

Proceeding on the basis of Germany's Federal Immission Control Act Bundesimmissionschutzgesetz), the following directives and regulations apply in essence to the design and planning of coal processing in the Federal Republic of Germany:

- Technical Instructions on Air Quality Control (TA-Luft) dated February 27, 1986,
- Limit values for pollutants in coking plant wastewater according to the Federal Water Act, section 7a,
- Limit values according to the Technical Instructions on Noise Abatement (TA-Lärm) dating from July 1984 (5th update),
- Hazardous Substances Ordinance.

Additional directives and regulations to be heeded for planning purposes are listed in section 6 (References).

The following tables (1.1, 1.2, 2, 3 and 4) survey the presently valid limit values for emissions, pollutant concentrations and MAK/TRK-values according to German standards.

It must, of course, be kept in mind that more stringent requirements may apply, depending on the baseline pollution level (initial load) at the location in question.

The tables compare the emission limits imposed by various industrialized countries of Europe with those reflected in German standards. With few exceptions, as quickly becomes apparent, the German standards impose the most stringent environmental protection requirements.

Table 1.1 - Emission limits according to TA-Luft (general exhaust emissions)

Component Definition of mass-flow range German emission limits European comparative values Remarks
Dust > 0.5 kg/h
< 0.5 kg/h
50 mg/m³
150 mg/m³
50 - 115 mg/m³, Æ 94 mg/m³
150 mg/m³
(as NO2)
> 5 kg/h 0.5 g/m³ 0.35 - 0.8 g/m³, Æ 0.55 g/m³ 0.35: Belgian outlier
SO2 > 5 kg/h 0.5 g/m³ 0.5 - 0.8 g/m³, Æ 0.6 g/m³
alternative: limitation of annual load to 10 000 - 12 000 t
H2S > 50 g/h 5 mg/m³ 5 mg/m³  
HCN > 50 g/h 5 mg/m³ 5 mg/m³  
C6H6 > 25 g/h 5 mg/m³ 5 mg/m³  
Benzo(a)pyrene > 0.5 g/h 0.1 mg/m³ no emission limit defined  

1) The comparative values derive from the Netherlands, England, Belgium, France, Spain, Austria, Sweden and Finland; the Æ -values represent the arithmetic mean of the respective limit values.

Table 1.2 - Emission limits for coking-plant waste gas/purified exhaust air

Component Definition of mass-flow range German emission limits European comparative values Remarks
Coal plant Dust 50 mg/m³ 100 mg/m³  
Coal drying and preheating Dust 100 mg/m³ 115 mg/m³  
Coke screening Dust 50 mg/m³    
Coal charging (filling process) Dust
PAH for mass flows > 0.5 g/h
25 mg/m³
0.1 mg/m³
15 - 230 mg/m³, Æ 92 mg/m³
0.1 mg/m³, alternative: limitation of daily load to 2 kg
15: Dutch outlier
Coke pushing (operation) Dust 5 g/t coke 5 - 115 mg/m³, Æ 46 mg/m³ or 5 g/t coke  
Dry coke cooling Dust 20 mg/m³ 20 mg/m³  
Wet coke quenching Dust 50 g/t coke 50 - 800 mg/m³, Æ 330 mg/m³ or 80 g/t coke  
Exhaust stack, coke oven batteries (new facilities) NOx as NO2

0.5 g/m³
0.8 g sulfur in UF gas

0.2 g/m³
10 mg/m³
0.2 - 0.8 g/m³, Æ 0.53 mg/m³
0.5 - 1.7 g sulfur in UF gas
Æ 9 g sulfur in UF gas or 0.5 g H2S in UF gas
100 - 200 mg/m³, Æ 130 mg/m³
0.2: Dutch outlier
0.5: Spanish outlier
Exhaust stack of by-product plants (new facilities) Dust
SO3 (H2SO4 systems)
SO2 (H2SO4 systems)
H2S (Claus systems)
Sulfur (tolerable emission level)
Production capacity: < 20 t S/d
Production capacity: 20 - 50 t S/d
Production capacity: > 50 t S/d

60 mg/m³
SO2-to-SO2 conversion rate: > 97.5 % or 2500 mg/m³
10 mg/m³

3 %
2 %
0.5 %
50 mg/m³
200 mg/m³
0.1-0.35mg/m³,Æ 0.225 g/m³
60 - 10 mg/m³, Æ 70 mg/m³
500 - 3000 mg/m³,
Æ 1750 mg/m³
10 mg/m³

3 %
2 %
0.5 %

Austrian outlier

2) cf. table 1.1 footnote

Table 2 - General administrative framework regulation (Rahmen-Abwasser VwV) on minimum requirements for the discharge of wastewater from coking plants, Appendix 46 (draft dated August 1990), valid for direct discharge

NO2 40 mg/l
Phosphorus 2 mg/l
BOD5 30 mg/l
Filterable substances 50 mg/l
COD 200 mg/l
Phenol index 0.5 mg/l
PAH 0.1 mg/l
BTX 0.1 mg/l
CN (volatile) 0.1 mg/l
Sulfide 0.1 mg/l
Fish toxicity 4 (dilution factor)

Note: The above emission limits apply to undiluted coking plant wastewater occurring at the rate of 0.3 m³/t of coal.

Coking plants equipped for HP gas treatment and with installations for collecting and recycling contaminated rainwater, or with appropriate supplementary process stages, can increase the specific wastewater discharge to as high as 0.42 m³/t of coal.

Table 3 - Standard immission values for noise emissions (July 1984)

The noise immission levels are specified for:

a) areas containing only commercial or industrial facilities and living quarters for supervisory and standby personnel, to:  

70 dB(A)
b) areas containing primarily non-residential buildings, to: (daytime)
65 dB(A)
50 dB(A)
c) areas containing nonresidential and residential buildings accommodating neither mostly nonresidential occupants nor primarily residential occupants, to:


60 dB(A)
45 dB(A)
d) areas containing primarily residential buildings, to: (daytime)
50 dB(A)
40 dB(A)
e) areas containing exclusively residential buildings, to: (daytime)
50 dB(A)
35 dB(A)
f) areas containing health resorts, hospitals, nursing homes, to: (daytime)
45 dB(A)
35 dB(A)
g) residential buildings attached to industrial/business premises, to: (daytime)
40 dB(A)
30 dB(A)

· Comments

- The acoustic engineering of industrial facilities and the requisite prognostical calculations rely heavily on the algorithms elucidated in VDI (Association of German Engineers) guideline 2714 (E) "Outdoor Sound Propagation" and VDI guideline 2571 "Sound Radiation from Industrial Buildings".
- If the above guideline values are exceeded and/or adulterated by superimposed extraneous noise to such an extent that accurate measuring becomes impossible, appropriate correction factors must be allowed for, as generally laid down in TA-Lärm (technical instructions on noise abatement). If measurements cannot be conducted, sound propagation calculations must be performed.
- "Nighttime" is understood as the eight hours between 10:00 p.m. and 6:00 a.m.
- In supplementation of the workplace ordinance Verordnung über Arbeitsstätten (section 15: protection against noise), the following provisions shall apply to workplace noise nuisance:

(1) The workplace noise level must be kept as low as possible for the type of operation in question. The workplace reference intensity, inclusive or exclusive of extraneous noise, shall not exceed:

· 55 dB(A) for primarily intellectual work
· 70 dB(A) for simple or mostly mechanized office work and comparable activities
· 85 dB(A) for all other activities; to the extent that the prescribed sound intensity level cannot be adhered to by available, reasonable means, it may be exceeded by 5 dB(A).

(2) The sound intensity level prevailing in breakrooms, duty rooms, rest rooms and first-aid rooms shall not exceed 55 dB(A). The reference sound intensity level shall be set by taking into account only the noise generated by installations inside the rooms plus the extraneous sounds entering the rooms in question.

Table 4 - MAK-values (occupational exposure limits) and TRK-values (technical concentration guideline values)

Component Limit values in Germany Comparative values in Europe* Remarks
Dust 6 mg/m³ 10 - 15 mg/m³,
Æ 11 mg/m³
NOx (as NO2) 9 mg/m³ 4 - 6 mg/m³,
Æ 5.3 mg/m³
30 mg/m³ NO
SO2 5 mg/m³ 1.5 - 5 mg/m³
Æ 4.7 mg/m³
1.5: Spanish outlier
CO 33 mg/m³ 29 - 57 mg/m³
Æ 45 mg/m³
29: Dutch outlier
Benzene 164) mg/m³ 3 - 32 mg/m³ 3: Swedish outlier
Toluene 375 mg/m³ 375 mg/m³  
Xylene 440 mg/m³ 425 - 435 mg/m³,
Æ 430 mg/m³
Benzo(a)pyrene 2-5 mg/m³ 2 - 5 µg/m³  
H2S 15 mg/m³ 14 - 15 mg/m³  
HCN 11 mg/m³ 10 - 11 mg/m³  
NH3 35 mg/m³ 17 - 18 mg/m³  
Phenol 19 mg/m³ 19 mg/m³  
Mercaptans 1 mg/m³ 1 mg/m³  
Biphenyl 1 mg/m³ 1 - 1.5 mg/m³  
Carbon disulfide 30 mg/m³ 30 mg/m³  
Naphthalene 50 mg/m³ 50 mg/m³  

3) cf. table-1.1 footnote
4) TRK-values
5) In the direct vicinity of the batteries, higher levels (measured in µg/m³) can be tolerated but then call for supplementary organizational and/or hygienic measures in addition to personal protective equipment, e.g., breathing masks.

Adherence to the permissible emission levels and the efficiency of the airborne emission control equipment must be monitored by measurements.

Subsequent to commissioning of facilities, it shall be determined by measurements whether or not the numerical data assumed at the planning stage correspond to the actual operating conditions. The measurements shall be conducted by neutral institutions, authorities or the like with due consideration of pertinent guidelines.

The TA-Luft and relevant VDI guidelines describe in detail the conduct of emission and ground-level pollution measurements.

3.3 Evaluation of environmental impacts

The aforementioned emission limits can be complied with by implementing the protective measures described in section 2.2.

Compared to existing facilities, the following reductions in emission levels (referred to a complete coking plant, including so-called diffuse sources) are foreseeable:

SO2 by 20 - 40 %
NOx by 20 - 40 %
CO by 30 - 35 %
BTX by > 95 %
Dust by approx. 50 %
PAH by approx. 90 %
BaP by approx. 90 %

The following emissions can be completely avoided by replacing wet quenching facilities with dry coke cooling systems:

H2S up to 80 g/t of coke, amounting to 160 t/a of H2S for an annual coke output of 2 million tons;
NH3 up to 15 g/t of coke, amounting to 30 t of NH3 per year.


4. Interaction with other sectors

Coking plants are closely allied with the iron-producing industry (cf. environmental brief Iron and Steel). However, some coking plants are located near mines (see briefs on mining), with a coal processing facility (coal washing plant) operating at the mine.

New developments in the steel-making industry such as those enabling the use of both oil and coal in the blast furnace process can help reduce the specific coal requirement of blast furnace operation. At present, however, there is no sign of coke becoming dispensable as a fuel and mainstay medium (reducing agent) for blast furnaces.

References to other adjacent sectors are to be found at the appropriate text passages.


5. Summary assessment of environmental relevance

Without the safe and sure operation of comprehensive antipollution devices, coking plants can cause substantial pollution of the air, soil and water.

In addition to emission reduction measures to avoid pollution from definite sources, the avoidance of emissions from diffuse sources is also important. Moreover, the maximum allowable workplace concentrations (occupational exposure limits) must be observed.

Systematic implementation of well-tested modern environmental protection measures, in combination with the observance of pertinent rules and regulations, can ensure that coking plants, like other coal processing facilities such as carbonization systems, need not be classified as environmentally hazardous.

With due regard to local circumstances, official ordinances must ensure that environmental protection measures are properly executed.

To that end, it is advisable to designate environmental protection and environmental safety officers, who, with proper training and technical support, are in a position to assume supervisory functions and attend to the interests of environmental protection and occupational safety in connection with all relevant industrial activities.

Early involvement of affected groups (women in particular) in the planning and decision-making processes enables consideration of their interests and helps alleviate environmental problems, e.g., in connection with the contamination of foodstuffs and/or health impairment in the vicinity of such undertakings.


6. References

Laws, Regulations, Directives


Bergverordnung zum gesundheitlichen Schutz der Beschäftigten (Gesundheitsschutz - Bergverordnung - GesBergV) dated 31.07.1991.

Druckbehälterverordnung (pressure vessel code), Bundesarbeitsblatt Nr. 3, Teil Arbeitsschutz, March 1990.

Hinweise für das Ableiten von Abwasser in öffentliche Kläranlagen, ATV Arbeitsblatt 115.

MAK-Liste, Liste maximaler Arbeitsplatzkonzentrationen, 1990, Mitteilung XXVI, Bundesarbeitsblatt 12/1990.

Richtlinie für Rohrleitungsanlagen zum Befördern wassergefährdender Stoffe, Gemeinsames Ministerialblatt GMBL (joint ministerial circular) Nr. 8, 02.04.1987.

Technische Regeln zum Umgang mit brennbaren Flüssigkeiten, TRbF, BGBL III (Federal Law Gazette III).

Unfallverhütungsvorschriften UVV, Hauptverband der gewerbliche Berufsgenossenschaften, Bonn.

VDI-Richtlinie 2058, Blatt 1, Beurteilung von Arbeitslärm in der Nachbarschaft, September 1985.

VDI-Richtlinie 2058, Blatt 3, Beurteilung von Lärm am Arbeitsplatz unter Berücksichtigung unterschiedlicher Tätigkeiten, April 1981.

VDI-Richtlinie 2560, Persönlicher Schallschutz, December 1987.


Verordnung über Arbeitsstätten (Arbeitsstättenverordnung), Ausgabe 1983, Bundesminister für Arbeit und Sozialordnung (German Federal Minister of Labour and Social Affairs).

Verordnung über gefährliche Stoffe (Gefahrstoffverordnung), BGBL (Federal Law Gazette), Aug. 26, 1986.

Wasserhaushaltsgesetz, insbesondere mit dem § 7a, Mindestanforderungen an Kokereiabwässer, BGBL I (Federal Law Gazette I) (1986)

Other applicable provisions cited in diverse rules and regulations.


Mitteilungen des Europäischen Kokereiausschusses zu Emissionsgrenzwerten und MAK-/TRK-Werten (unveröffentlicht).

Bernd Schärer, Article "US Clean Air Act" in Staub - Reinhaltung der Luft 52 (1992) 1 - 2, Springer Verlag.

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