2 PRINTING
Plant 1 Plant 2 Unit Total toluene consumption (fresh and
3 MANUFACTURE OF WINDING WIRE
3.3 Current consumption and emission levels in winding wire manufacturing
3.3.3 Emissions [80, EWWG, 2004] [128, TWG, 2005]
3.3.3.1 Emissions to air VOC, NOX and CO emissions
The values in Table 3.6 are examples of measurements in a few installations that give an indication of current emission levels of VOC, NOX and CO:
M installations1
(g/kg) F installations2 (g/kg)
VOC ~ 8 ~ 15
NOX 3 ~ 10 ~ 12.5
CO ~ 8.5 ~ 15
Note:
1. M installations: these are data from installations that produce medium sized wires (diameter of >0.1 mm).
2. F installations: these are data from installations that produce fine wires (with an average diameter of ≤ 0.10 mm).
3.There are no fine wire sites using exclusively NMP-containing materials. The higher values are derived from measurements on production lines using exclusively insulation material containing NMP (see Section 3.3.2.1 and discussion on NOx, later in this section).
(See also Table 3.3 and Table 3.4 )
Table 3.6: Examples of measurements of emissions to air [80, EWWG, 2004]
BVT-Merkblatt Oberflächenbehandlung mit Lösemitteln 111 Many attempts have been made to reach a low level of CO and NOX emissions; however, running the enamelling machine efficiently and the destruction of VOC are given priority together.
VOC emissions At an EU-25 level for the year 2000 (according to the RAINS model), NMVOC emissions were 5.4 kt, representing 0.05% of total NMVOC emissions. Total activity was 420 kt of winding wire coated, and the average emission factor is about 12.3 kg NMVOC/t of wire coated meaning that emissions from this sector are already partly treated in EU25 (based on an unabated emission factor is 17 g/kg in 1990). VOC emissions are proportionately lower from the drying processes, due to the waste gas treatment. The major remaining source of VOCs is from the application of the lubricants. In Table 3.6, fine wires are produced by applying a final wax coating with white spirit. The white spirit dries off and consequently VOC emissions are higher. However, in the case of thicker wires, new low solvent techniques can be used.
However, these techniques are not readily usable on fine wires of 0.01 - 0.1 mm (see Section 3.4.5.6) [128, TWG, 2005].
Solvent emissions from the industry have been steadily reduced for over 40 years, and a baseline figure of 13 g/kg for 1995 has been estimated (when analysis of emissions started).
The industry proposed a reduction target for emissions of 5 g/kg for wires with diameters of
>0.1 mm by 2007 and of 10 g/kg for fine wires (with an average diameter ≤0.1 mm). This was based on an industry study using best practice technologies described in this Chapter and modified by experience of the difficulty of reducing the solvents used in fine wire production (for example, see Section 3.4.5.6). This equates to a reduction of up to 60 % (and up to70 % compared with estimates of the situation in 1990). [55, Europacable, 1997]
Oxides of nitrogen (NOx.) See Section 20.11.9. [140, Tempany, 2006, 163, EWWG, 2005, 193, Tempany, et al., 2006] are produced as a result of the oxidation of VOCs in waste gases and give rise to the cross-media conflict between abating VOCs and creating NOx. One source of NOx emissions is the direct result of oxidation of the nitrogenated solvents used in the production of certain enamel systems (see Table 3.5). The concentration of NOX is proportional to the destruction of VOCs for the products that contain the nitrogenated solvents. Only a part of the nitrogen contained in NMP is converted to nitrogen oxides, at a ratio of 90 % NO and 10 % NO2. The other major source of NOx is the oxidation of atmospheric nitrogen during combustion of VOCs in the oven. When using enamels containing nitrogen, emission values of NOX can be well over 150 mg/Nm3 depending on the specific airflow conditions in the enamelling machine and the number of machines using solvents containing nitrogen. In other cases with different airflows and NMP usage on process machines, the levels are 150 mg/Nm3 and indistinguishable from satisfactory NOx levels associated with combustion (see the CWW BREF [67, EIPPCB, 2003]). This is a common problem for all installations over Europe.
Enamels based on nitrogen-free solvents, such as polyvinyl-acetal, result in wires of low heat class, and do not meet the specifications required by the customers that the polyamide-imide products attain. NOx emissions after catalytic oxidation do not currently undergo treatment.
112 BVT-Merkblatt Oberflächenbehandlung mit Lösemitteln Installation(s)
Group of 34 enamelling
ovens
Group of 165
enamelling ovens Installation 1
enamelling Installation 2
Short
description of the
installation
Exhaust gases collected in three tubes leading to one stack (flue) Special local conditions:
industrial area, close to a power station
Exhaust gases collected by hoods over single sources in four stacks (flues), 35 - 50 m high In order to avoid odour emissions (olfactory trouble with
neighbourhood), a large amount of air from the production hall is extracted together with the gas from the oven Sources are spread over an area of about 10000 m²
Special local conditions:
mixed industrial and residential zone (climatic spa)
80 % of all product lines used NMP during measuring period Dilution of the exhaust gas in the hood: 1/10 from oven, 9/10 from hall Estimation: 2/3 of the NOx is caused by nitrogen input (NMP), 1/3 caused by thermal process
Measurement on ventilator on the roof (ventilation of production hall and air from the cooling of the enamelling oven) NOx emissions caused by small, uncontrollable process source.
Number of fans:
more than 100, spread over the production area of 10000 m²
Volume flow (Nm3/h)
3700, 7000, 34500
53600 – 98000 in each of the stacks average mean value:
68480
60 - 810
Temperature (°C)
~ 80 gas
temperature at the entrance of the stack
70 - 110
gas temperature at the entrance of the stack
250 - 550 temperature of undiluted exhaust gas at the source
30 - 45
temperature of air
Concentration (mg
NOx/Nm³)
19 60 34
Average: 51.3 550 – 1500 Average: 615
Average value: 12
Mass flow NOx (kg NOx/h)
Total: 14.07 Average: 0.0835 from a single source
Total: 4 mean single sources: <0.040 Table 3.7: Winding wires: Further examples of NOx emissions
[193, Tempany, et al., 2006]
The total amount of NOx emitted by the industry is estimated to be between 1 and 2.7 ktonnes a year (based on 2000 EUROSTAT figures).
Carbon monoxide is formed by the partial combustion of the enamel components during catalytic incineration in the enamelling machine. Carbon monoxide is a consequence of the destruction of solvent rather than of the burner efficiency. The concentration of carbon monoxide is dependent on the dwell time within the burner rather than the burner being incorrectly set. If the combustion efficiency is increased, the CO emissions would be reduced, but with a corresponding increase in CO2 and NOX emissions.
BVT-Merkblatt Oberflächenbehandlung mit Lösemitteln 113 An enamelling machine is not controlled according to CO emissions but under completely different conditions, and these are:
• ensuring the correct temperature within the enamelling machine in order to achieve the optimum properties from the enamel film. Increasing the burner temperature would require dilution air to reduce the temperature in the enamelling chamber overall. This would require a greater amount of energy and is not considered to be the best environmental option
• using excess air to prevent the lower explosive limit from being exceeded and so preventing explosions within the machine. Reducing the airflow to increase the residence time is, therefore, not an option.
Attempts have been made to limit the emission of carbon monoxide by using secondary catalysts; however, meeting the emission limits will remain an issue because of the relatively short life of the catalysts and the corresponding financial implications.
Dust emissions
As the films applied to the wire are extremely thin (in the order of 10 µm) any dust present in the enamelling process would cause very serious surface quality problems. As any emission to the air is only a portion of the recirculated air, there will be no dust emissions expected.
With respect to the current consumption and emission values, there are no major differences in all the European countries because of the same machinery and the fully integrated abatement technique in all kind of enamelling machines.
3.3.3.2 Emissions to water
The water used in a winding wire plant normally is used in closed circuits. Emissions to water from the enamelling process are low; however water use should be kept as low as possible and this is commonly done by:
• minimising the flow through cooling baths and recycling the water through filters and de-ionisers when practicable
• using conductivity meters to optimise the treatment and conserve water in cooling towers
• prolonging the life of waterborne wire drawing lubricant emulsions by using filtration, centrifugation where practicable and ensuring efficient management of the lubricant to prevent premature ageing by stagnation and bacterial degradation.
3.3.3.3 Waste
The main sources of waste are from the drawing process and in the enamelling stage of the winding wire production [128, TWG, 2005].
Drawing:
• the drawing emulsion is used in a closed loop system, it is continuously cleaned using a paper filter or a hydrocyclone separator. In order to reduce waste amounts, emulsion treatment (reconditioning) is carried out with demineralised water; water is evaporated during the process and waste amounts are minimised
• the filters of the drawing emulsion circuit contain a certain amount of copper particles from the drawing process. They are recycled externally for the copper content.
114 BVT-Merkblatt Oberflächenbehandlung mit Lösemitteln Enamelling:
• varnish application. In order to reduce varnish losses, the varnish is applied in varnish baths, during die stripping using the varnish circuit and by dosed varnish using felt application
• recycling of bare or enamelled wires. The production scrap (bare and enamelled wires) is recycled to 100 %
• used solvents, residual enamels and cleaning wipes containing solvent are collected and disposed of (usually by incineration).
3.4