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 3.
2. 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
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.
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
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.
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 14385. Annual extractive testing for hydrochloric acid emissions will also be carried out in the pickling facility stacks to BS EN 1911. Part-3.
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 km2 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.
Table 1 – Air Emission Limits SG 5 (06)
Stack Name Pollutant
A1 Shot Blaster
A2 Pickling Bath
A3
Galvaniser & Stripper
Concentration (mg/m3 STP, wet)
Concentration (mg/m3 STP, wet)
Concentration (mg/m3 STP,wet)
PM 20 - 15
HCl - 30 -
Lead - - 0.25
Table 2: EALs and EQS as relevant (taken from H1, Appendix D)
Long Term Short Term
Pollutant EAL AQS EAL AQS
(µµµµg/m3) (µµµµg/m3) (µµµµg/m3) (µµµµg/m3)
PM 40 50
HCl 20 800
Lead 0.50 0.50 - -
Table 3: Air pollution dispersion factors (from H1)
Dispersion Factors (µµµµg/m3/g/s) Effective Stack Height
(m)
Long Term (annual) Short Term (hourly)
0 148 3900
10 32 580
20 4.6 161
30 1.7 77
50 0.52 31
70 0.24 16
100 0.11 8.6 150 0.048 4.0 200 0.023 2.3
Parameter Stack A1 – Shot Blaster A2 – Pickling Bath
A3 – Galvaniser &
Stripper Height (m) 20 20 20 Efflux Velocity (m/s) 15 15 15 Gas Flow (m3/s STP wet) 3.0 5.0 5.0
Temp oC 15 15 100 Dispersion factor (from H1, p22
or Table 3 above)
? ? ?
Table 5: Stack concentration & release, ‘worst case’ design parameters
Stack A1 A2 A3 A1 A2 A3
Shot Blaster
Pickling Bath Galvaniser &
Stripping
Shot Blaster
Pickling Bath
Galvaniser
&
Stripping Concentration Concentration Concentration Release
rate
Release rate
Release rate Pollutant (mg/m3STP
wet)
(mg/m3STP wet)
(mg/m3STP wet) (g/s) (g/s) (g/s)
PM 20 - 15 ? - ? HCl - 30 - - ? - Lead - - 0.25 - - ?
Note:
RR = GF x C ÷÷÷÷ 1000 Where
RR = Release rate (g/s) GF = Gas flow (m3/s)
C = Pollutant concentration (mg/m3)
1 1 1 2 3 4 5 6 4 5 7 8 9 Notes:
See below PC
A1
PC A2
PC A2
PC Total
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?
Bkgrnd conce.
PEC %PEC of EAL
Substanc e
µµµµg/m3 µµµµg/m3 µµµµg/m3 µµµµg/m3 µµµµg/m3 µµµµg/m3 µµµµg/m3 µµµµg/
m3 PM
HCl Lead
Notes 1 Shows the calculated process contribution (PC) = RR x Dispersion Factor Where RR = release rate (g/s)
Dispersion factors (µg/m3/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
