|Environmental Handbook Volume II: Agriculture, Mining/Energy, Trade/Industry (GTZ/BMZ, 1995, 736 pages)|
|Trade and industry|
|44. Nitrogenous fertilisers (raw materials, ammonia and urea production)|
In the fertiliser production plants described here, environmental impacts, in the form of emission into the atmosphere, watercourses and soil, as well as noise emissions, may be anticipated. However, there are process stages for all production plants which can be implemented to contain this impact.
In Germany, the TA-Luft [Technical Instructions on Air Quality Control] is the main instrument as regards air quality. Pollutant limit values relating to specific plants and substances are listed in the Allgemeine Verwaltungsvorschrift zum Bundesimmissionsschutzgesetz [General Administrative Regulations pertaining to the Federal Immission Control Act] of 27.02.1986. It also contains a series of Richtlinien des Vereins Deutscher Ingenieure (VDI-Richtlinien - guidelines of the Association of German Engineers) regarding process and gas purification techniques and emission measurement techniques, which must be complied with. There are similar provisions in other countries, e.g. the Clean Air Act in the USA or its Swiss equivalent, the Luftreinhalteverordnung.
In countries which do not have their own regulations, reference is frequently made to the TA-Luft or other foreign regulations at the planning stage.
Most atmospheric pollution in such plants derives from SO2 in the waste gas. Under TA-Luft, a sulphur emission level of 3% down to 0.5%, depending on plant size, must not be exceeded in sulphur extraction plants. Not all purification processes achieve this, but they are nonetheless used where less stringent regulations are in force.
In wet catalysis for sulphuric acid extraction, a minimum conversion level of 97.5% must be complied with. Sulphur trioxide emissions in the waste gas must not exceed 60 mg/m3 under constant gas conditions, and must not exceed 120 mg/m3 otherwise.
Limits which can also be adhered to are established in TA-Luft for NOx emissions in furnace flue gas streams - tube furnaces, steam generators, booster heaters.
Dust emissions from UREA fertiliser production facilities are restricted to 50 mg/m3, while the free ammonia content in waste gases must not exceed 35 mg/m3. The dust load is measured gravimetrically with filter head equipment and the free ammonia is determined by titration.
The wastewater treatment processes used are subject to local regulations. In Germany, the Wasserhaushaltsgesetz (WHG) [Federal Water Act] applies, with its associated Verwaltungsvorschrift [Administrative Regulation] relating to minimum requirements for the disposal of wastewater in drains. In fertiliser production plants, the associated 44. Verwaltungsvorschrift [44th Administrative Regulation] can be observed.
In the extreme case of wastewater treatment, no wastewater is produced, merely combustion residues which are finally disposed of on special dumps where no leaching can occur, or concentrated residual solutions which require disposal in deep wells, for example, may be formed.
The catalyst and purification mass residues, most of which are formed at intervals of two years or more, do not cause any problem in terms of quantity and, as already stated, are passed on to smelting works for metal recycling or must be dumped as special waste.
With regard to the ash and slag from solid-fuel ammonia production, the possibility of recycling or dumping has to be examined in each individual case.
The TA-Lärm [Technical Instructions on Noise Abatement] which is the comparable administrative regulation for noise protection, specifies immission values which are graded by location and time for areas, based on a variety of uses. The determining criterion is that of total impact level. Noise protection measures must be taken into account at planning stage as they are costly if implemented at a later date. In site planning, therefore, adequate distances from protected property, such as residential housing development, and a shortening of this distance must be prevented.
In Germany the TRgA 9007) for limiting the maximum pollutant concentration at the workplace (MAK/TRK values8)), the Arbeitsstättenverordnung [Ordinance on Workplaces] including workshop guidelines for workplace design and the accident prevention regulations Unfallverhütungsvorschriften of the Berufsgenossenschaften (employers' liability insurance associations), as being the body responsible for insuring accidents at work, apply to workplace conditions in terms of pollutant concentration, noise nuisance and industrial safety. Comparable regulations exist in other countries, e.g. in the USSR, with Health Standards for Industrial Concerns (SN 245-71).
7) TRgA - Technische Regeln zur Arbeitsstoffverordnung [technical regulations on the industrial substances decree]
8) MAK - Maximale Arbeitsplatzkonzentration [maximum workplace concentration]
TRK - Technische Richtkonzentration [technical approximate concentration]