Self Assessment Exercise

Transcription

1 Self Assessment Exercise Read the following extract of supporting documentation for Permit Application for Galvos plc galvanising facility and the accompanying tables. Decide if the proposed control techniques for air pollution release are BAT. 1. Taking the given stack heights from Table 4, select and report the correct air pollution long-term dispersion factors, from the extract from Horizontal Guidance Note H1 shown in Table From the emission concentration information in Table 5, Delegates are to compute the long-term release rates and predicted long term concentrations (PC) for air, for each pollutant in turn. 3. Compare these concentrations with the long term Environmental Assessment (EALs) or air Air Quality Standards (AQSs), or Air Quality Objective Levels in Table 2, as appropriate. 4. Indicate which pollutants can be screened out and why. 5. Decide and report which pollutants require further more sophisticated modelling. 6. Where more detailed modelling is required, apply a dilution factor of 3.0 to the H1 predicted concentrations (PC) to gain the detailed (ADMS) modelled concentration. 7. Now decide whether BAT for air has been demonstrated and why. Extract of Supporting Documentation for Permit Application for Galvos plc Galvanising Facility 1. Plant Description A Permit Application, with supporting documentation, has been received from Galvos plc. They wish to operate a new installation, with a galvanising facility, at Anytown. The galvaniser facility will apply protective fused metal coatings (zinc/ lead alloys), to steel items with an input of

2 more than 2 tonnes of crude steel per hour, and will be covered by the PPC Regulations as an A2 process (Section 2.1 and Section 2.2 Ferrous and Non-Ferrous Metals). This facility will be subject to the limits and conditions laid down in Sector Guidance Note SG5 (06). The galvaniser plant will also contain a shot blasting surface facility for pre-cleaning the surface of the received steel items. This technically associated process will also be covered within the scope of the limits given in Sector Guidance Note SG5 (06). In addition, there will be facilities for the surface treatment of the metal by chemical processes (alkaline baths for degreasing and acid baths for the removal of surface oxidation products from the steel work items, i.e pickling). The volume of the treatment vats will be more than 30m3. These facilities will be covered by the PPC Regulations as an A2 process (Section 2.3 Surface Treating Metals and Plastic Materials). These facilities will be subject to the limits and conditions laid down in Sector Guidance Note SG5 (06). 2. Description of the Proposed Plant and Pollution Control Equipment (Refer to Fig 1) Materials Reception & Storage Areas The receiving area for powdered chemical feed-stocks will be totally enclosed. To eliminate any potential air emissions, the powdered chemical feed-stocks for the process will be delivered and stored in enclosed containers. This will include zinc / lead alloy powders (for the galvaniser baths), together with Big Bags containing zinc ammonium chloride double salt powder (for the fluxing operations). Any potential air emissions from liquid chemical feed-stocks will be eliminated by using non-fuming commercial solutions. These will be delivered by road tankers and will include deliveries of potassium hydroxide solution (for degreasing), and 28% hydrochloric acid solution (for the pickling activities). The chemical solutions will be pumped from the road tankers directly into totally enclosed receiving tanks, fitted with bunding to contain any spillages etc.

3 Shot-Blasting The incoming steel work items will be received into an enclosed storage area. As required, the steel work items will be suspended by hangers onto a continuous moving overhead line and passed to the shot-blaster for pre-cleaning. There will be a potential for air emissions of particulate matter from this activity, but these will be controlled to meet the SG5 (06) Note requirement of 20 mg/m3 by the use of a fabric filter. Any emissions passing the filter will be vented to atmosphere through a stack, with an effective height of 20 meters (Discharge Point A1). Degreasing After leaving the shot-blaster the cleaned steel work items continue, via the overhead line, to be dipped into the heated degreasing bath, which will contain an aqueous solution of potassium hydroxide. Any surface oil will be removed at this stage. The degreasing tank is covered and there are no air emissions from this activity; moreover, any potential releases to water (by spillages) will be eliminated by bunding. Rinsing After leaving the degreasing bath the cleaned work items continue, via the overhead line to be dipped into the two rinsing tanks, which will contain clean water. Any surface alkali and contaminants will be removed at this stage. There are no air emissions from this activity and any potential releases to water (by spillages) will be eliminated by bunding. Pickling Following rinsing the work items continue, via the overhead line, to be slowly dipped and passed through the solutions in any of the 3 pickling baths. These contain hydrochloric acid solution that has been diluted to range in strength from 18% to 12%. The baths can be heated and are covered by hoods. Any surface oxide (e.g. rust) and mill-scale will be removed at this stage. There is the potential for air emissions from this activity of hydrogen chloride vapour or fine droplets. The fugitive releases are contained by hoods, and the attached extract ducting transports any entrained material under suction to a wet venturi scrubber. This removes the acid mist to meet SG5 (06) HCl limit of 30 mg/m3. All three pickling baths are connected to this air pollution control equipment, which vents to

4 atmosphere through a single stack (Discharge Point A2). The effective height of this stack is 20 meters. Rinsing After leaving the pickling baths the work items continue, (via the overhead line), to be dipped into the two rinsing tanks, which will contain clean water. This washes off acid and prevents any carry-over of iron salts on the surface of the work-piece. Such carry-over would cause additional dross to be formed in the galvaniser bath. There are no air emissions from this activity and any potential releases to water (by spillages) will be eliminated by bunding. Fluxing Following rinsing, the work items continue, via the overhead line, to be dipped into the fluxing solution contained in the dry fluxing bath. This solution is an aqueous solution containing zinc ammonium chloride (ZAC) double salt, which can be heated to 70 Deg C. The fluxing is applied to prevent oxidation of the work-piece before it is dipped in the galvaniser bath. There are no significant air emissions from this activity and any potential releases to water (by spillages) will be eliminated by bunding. Galvanising The fluxed steel work items, still suspended on their hangers, are slowly lowered into the galvaniser kettle (bath), which contains a molten alloy of zinc and lead, heated to a temperature of about 460 Deg C. The galvanising process can last between 5 and 30 minutes and leads to an reaction between the steel work-piece and the molten alloy to create zinc alloy / iron layers, which are resistant to oxidation. Where ammonium chloride or zinc ammonium chloride fluxes are used then fume is created instantaneously at the point of dipping, as the sublimation temperature of ammonium chloride is lower than the temperature of the zinc bath. The fume is a mixture of ammonium chloride, zinc chloride, zinc oxide, lead chloride, lead and steam. A hood covers the galvanising kettle, and the metallic fume is thereby contained and taken by extraction, under suction, to a fabric filter. This removes the metallic fume to meet the SG5 (06) particulate limit of 15 mg/m3 and the lead limit of 0.25 mg/m3. This air pollution control equipment vents to atmosphere through a single stack (Discharge Point A3). The effective height of this stack is 20 meters.

5 Continuous indicative monitoring will be installed to monitor the particulate matter emissions from the shot-blaster, with annual extractive testing to BS EN 13284: Part 1. Annual extractive testing for particulate emissions will also be carried out in the galvaniser facility stacks to BS EN 13284: Part 1, together with annual testing for lead as per BS EN Annual extractive testing for hydrochloric acid emissions will also be carried out in the pickling facility stacks to BS EN Part-3.

6 3. Description of Proposed Water Treatment Plant The water releases from the air pollution control equipment installed at this installation will be collected and passed to a water treatment plant (WTP). Any liquid effluents from the various processing baths will be tankered off-site for reuse / recycling, or specialist disposal. Run-off water from roofs and surfaces will be collected by the plant drainage system. Releases of pollutants to water from these areas will be insignificant and will be direct to the sewerage system. The main pollutants concerned with the WTP, and the run-off water, will be zinc and ammonia chloride. A consent limit has not yet been agreed with Environment Agency or the Sewerage Undertaker and no further checks are required at this stage. 4. Site Description and Nearest Receptors The site covers an area of about 0.8 km 2 and the process is located near the centre and the nearest residential areas are just under 1500 meters from the installation. 5. Other Targets There are no other air pollution problems in the local area to which this process is a potential contributor. 6. Plant Design Information Air emission limit values are shown in Table 1 and are for the Worst Case scenario. Table 2 gives the appropriate Environmental Assessment Levels, Air Quality Standards and Air Quality Objectives, as taken from Appendix D of H1. Table 3 gives air pollution dispersion factors, as given in the H1 guidance document. Plant design information for the air pollution control equipment is given in Tables 4 and 5.

7 Table 1 Air Emission Limits SG 5 (06) Stack Name A1 Shot Blaster A2 Pickling Bath A3 Galvaniser & Stripper Pollutant Concentration Concentration Concentration (mg/m3 STP, wet) (mg/m3 STP, wet) (mg/m3 STP,wet) PM HCl Lead Table 2: EALs and EQS as relevant (taken from H1, Appendix D) Long Term Short Term Pollutant EAL AQS EAL AQS (µg/m 3 ) (µg/m 3 ) (µg/m 3 ) (µg/m 3 ) PM HCl Lead

8 Table 3: Air pollution dispersion factors (from H1) Effective Stack Height (m) Dispersion Factors (µg/m3/g/s) Long Term (annual) Short Term (hourly)

9 Table 4: Design parameters of air pollution control equipments Parameter Stack A1 Shot Blaster A2 Pickling Bath A3 Galvaniser & Stripper Height (m) Efflux Velocity (m/s) Gas Flow (m 3 /s STP wet) Temp o C Dispersion factor (from H1, p22 or Table 3 above)??? Note: RR = GF x C 1000 Where RR = Release rate (g/s) GF = Gas flow (m 3 /s) C = Pollutant concentration (mg/m 3 ) Table 5: Stack concentration & release, worst case design parameters Stack A1 A2 A3 A1 A2 A3 Shot Pickling Bath Galvaniser & Shot Pickling Galvaniser Blaster Stripping Blaster Bath & Stripping Concentration Concentration Concentration Release Release Release rate rate rate Pollutant (mg/m3 STP (mg/m3 STP (mg/m3 STP wet) (g/s) (g/s) (g/s) wet) wet) PM 20-15? -? HCl ? - Lead ?

10 Table 6: Quantifying air impacts, long term Notes: See below Substanc e PM HCl Lead PC PC PC PC Bkgrnd PEC A1 A2 A2 Total conce. EQS or EAL %PC total of EAL PC total >1% of EAL? Modelle d PC %PC total modelle d of EAL PC>1% of EAL? µg/m 3 µg/m 3 µg/m 3 µg/m 3 µg/m 3 µg/m 3 µg/m 3 µg/ m 3 %PEC of EAL Notes 1 Shows the calculated process contribution (PC) = RR x Dispersion Factor Where RR = release rate (g/s) Dispersion factors (µg/m 3 /s/s) are given on P22 of H1 Guidance (and Table 3 above) 2 Total process contribution of substances (two columns to the left are added) 3 Lists Environmental Quality Standard or Environmental Assessment Level of the substances in question (Appendix D, Table D4) 4 s A percentage of EAL (or EQS as relevant) 5 Whether the release of the substance is significant (i.e. if PC/EAL is >1%) 6 Process contribution of substances, obtained from ADMS modelling 7 Background of substances, where relevant 8 Predicted environmental concentration, PEC = PC + Background concentration 9 PEC as a percentage of EAL