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Begrænsning af luftformig emission af tetrachlorethylen fra renserier SummaryToday, dry-cleaning shops primarily use perchloroethylene as cleaning fluid. The annual consumption of perchloroethylene in the dry-cleaning business in Denmark was approximately 150 t in 2000 and has been decreasing gradually with the years. It is still believed that the consumption can be reduced and, consequently, the emission of perchloroethylene will decrease. Perchloroethylene is on the Danish Environmental Protection Agency's list over undesirable substances as it has been classified as being carcinogenic. The dry-cleaning shops have been in focus during the last year because it was been registered that the air quality criterion is exceeded in apartments next to dry-cleaning shops. It is a general problem as most dry-cleaning shops are located in residential buildings. Perchloroethylene can spread from a dry-cleaning shop to an apartment via diffuse emission through open windows and doors, untight exhaust from the dry-cleaning shops and not least via transport through floors or walls to neighbouring apartments. At the request of the Danish Environmental Protection Agency various municipalities have conducted measurements regarding the concentration of perchloroethylene in apartments located above dry-cleaning shops, of the air outside the shops and in the shop itself. The results show high levels in the apartments located above dry-cleaning shops. The Danish Environmental Protection Agency has set an air quality criterion for neighbouring apartments of 0.006mg/m3, which has been exceeded in all measurements. Typically, the criterion has been exceeded 100-1000 times. Consequently, the Danish Environmental Protection Agency has started this investigative project to find out whether it is possible to comply with the air quality criterion in neighbouring apartments. It will also be examined whether the requirements to the contribution value and the future VOC directive can be met. The project is based on an investigation of different dry-cleaning shops, especially including two selected model dry-cleaning shops, where a number of emission measurements have been made together with data collection, literature search, and calculations. A theoretical review of the cleaning process has been made to identify the most important sources of perchloroethylene emission. This review has led to a division of the perchloroethylene dry-cleaning machines in the Danish dry-cleaning business into 3 groups, which differ from each other according to their principle and emission levels. The three main groups are defined in the following way in accordance with the business (suppliers, service men and dry-cleaning shops):
The emissions are theoretically calculated and evaluated for a dry-cleaning machine, which works satisfactorily in main group 2 and estimated for the main groups 1 and 3. The theoretical considerations have shown that the most important contributions to gaseous emissions for the 3 main groups are: Main group 1: Emission from the cleaned clothes during ironing pressing and storage and emission when opening the dry-cleaning machine. Main group 2: Fugitive emission, exhaust to the stack when opening the dry-cleaning machine, emission when opening the machine and emission from the dry-cleaned clothes during pressing and storage. Main group 3: Exhaust from airing, emission from fugitive emission, exhaust when opening the dry-cleaning machine, emission when opening the dry-cleaning machine and emission from the dry-cleaned clothes during pressing and storage. To reduce the mentioned emissions it is provided that the necessary measures are established at all dry-clean shops so that breathing from the dry-cleaning machine, exhaust when opening the dry-cleaning machine and exhaust from fugitive emission is led to the stack. On the basis of theoretical assessments key figures are set up for the emissions per kg of clean clothes. In practice the emissions may be considerably higher than suggested by the key figures, especially for the main groups 2 and 3. In order to estimate the possibilities of improvement, the consumption of each dry-cleaning machine must be controlled. In the above-mentioned emissions are disregarded leakage, accidents and other emissions due to bad maintenance of the dry-cleaning machine. Moreover, small and short emissions happen in connection with the daily operation and maintenance such as the cleaning of filters, emptying of sludge, distillation, and the refilling of cleaning fluid. Some of them can be eliminated by establishing emission free systems for filling and emptying. An evaluation has been made according to a stepless model as to whether it is realistic to comply with the air quality criterion in the neighbour apartment. The first condition is that the dry-cleaning machine work satisfactorily and that the emissions mentioned in the main groups 2 and 3 are exhausted through the stack. Furthermore, it is expected that all leakage be sealed in order to establish a constant low pressure in the dry-cleaning shop by means of a ventilation system. This to secure that, among other things, transport through floors is limited to diffusion and that convection can be disregarded. It has been examined how high a concentration is allowed if only due to diffusion through floors. Calculations of the diffusion show that the concentration must be no higher than approximately 5 mg/m3 in the dry-cleaning shop if the floors are made of solid concrete. If the decks are wood and clay insulation or concrete element deck the concentration must be no higher than 1 mg/m3. The maximum concentrations in the dry-cleaning shop that are the basis for the calculation regarding the need for ventilation are conservative, and they correspond to reduction factors of 833 and 166, respectively. In order to reach this level in the dry-cleaning shop the need for ventilation for the three main groups has been calculated. The ventilation need also depends on the amount of dry-cleaned clothes (tonnage). In consideration of the air speed in the room the ventilated amount of air should not exceed 1500 m3 per hour. On the basis of the above-mentioned requirements it is expected that most dry-cleaning shops must make the following improvements:
Once these initiatives are implemented it is expected that, theoretically, the dry-cleaning shops in main group 1 will be able to meet the air quality criterion. However, depending on the floor type it may be necessary to seal ceilings and maybe walls too. For dry-cleaning shops with dry-cleaning machines in main groups 2 and 3 it is required that the necessary measures are taken to avoid the fugitive emission from the dry-cleaning machine. The exhaust from the drying cabinet is led to the stack when opening the machine and exhaust from drying for main group 3 are exhausted through the stack. At the same time the need for ventilation is bigger regarding both the room and local exhaust. For the dry-cleaning shops in main groups 2 and 3 it is expected that the following improvements be made:
For dry-cleaning shops in main group 3 it is expected that further improvements are made, such as:
Emissions from the dry-cleaning machines in main group 3 may be considerable and essential improvements must be made in order to meet the air quality criterion. As the dry-cleaning machines belonging to this group are estimated to be rather old and that they use a lot of perchloroethylene, it should be discussed whether they should be changed instead of making investments in redressing initiatives. One alternative could be to move the dry-cleaning section and to change the existing section to a handing-in place. It is expected that some of the dry-cleaning shops in this main group cannot meet the air quality criterion without investing in a new dry-cleaning machine with the newest technology. This may also apply for some of the dry-cleaning machines in main group 2. It must be emphasised that the assessment of evaluation whether the dry-cleaning machines in main groups 1, 2, and 3 can meet the air quality criterion is based on theoretical calculations and estimates, etc. For the time being the examples of actions do not seem to be carried out and documented. In connection with later supplementary measurements it has not been possible neither to confirm nor to disprove the calculated reduction factors. Even though the calculations theoretically show that it is possible to meet the air quality criterion it may not be so in reality. A few undiscovered cracks and leaks in the ceiling may imply that perchloroethylene is transported faster than shown by the theoretical calculations. The diffusion calculations are based on an air exchange of 0.5 times per hour in the neighbouring apartments, which is believed to be conservative as the inspection has shown that, in general, air exchange in apartments take place 0.7 times per hour, (Gunnarsen, 2000). The problem about perchloroethylene should be considered as a whole so that the stipulated solutions and estimates include compliance with the contribution value for perchloroethylene. From calculations it seems that the main part of dry-cleaning shops in the main group 1 can comply with the contribution value without having to establish cleaning measures on the stack, e.g. such as a carbon absorber. In all dry-cleaning shops the stack must be placed at least 1 metre above the roof and in some cases even higher up. However, in some cases it may be difficult to obtain a construction license. For the dry-cleaning shops in main group 2, and especially those in main group 3, it may not be possible to comply with the contribution value without establishing a carbon absorber in the stack. In these cases a financial feasibility study should be made in order to find out whether it pays, or whether a new dry-cleaning machine should be bought shortly. The report contains a description of the initiatives that may be necessary to meet the air quality and the contribution value. The initiatives are briefly described and a financial estimate made for each initiative. The total costs will vary depending on the state of the dry-cleaning machine and the building. The cost level will probably be between 100,000 and 600,000 DKK. In the last mentioned case, a new dry-cleaning machine is included. Section 8 and appendix 9 of the report contain tools for an action plan to be made by the dry-cleaning shops. It is important that the dry-cleaning shops take a stand regarding the future use of perchloroethylene in the dry-cleaning business, including considerations about investing in a new dry-cleaning machine. Finally, the report lists different methods to control/document the compliance with the limits for perchloroethylene including the making of an annual report, operation journals, service inspections, consultancy, diffusion calculations, emission measurements in indoor rooms and emission calculations for the outdoor air (OML-calculations).
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