Proposals for new NFM BAT conclusions for Ferro-Alloys production

Transcription

1 EUROPEAN COMMISSION JOINT RESEARCH CENTRE Institute for Prospective Technological Studies Sustainable Production and Consumption Unit European IPPC Bureau Seville, 26 May 2011 Proposals for new NFM BAT conclusions for Ferro-Alloys production 9.4 Best available techniques for Ferro-Alloys Key environmental issues for the production of ferro-alloys are: dust and fume, CO and CO 2 gas, SO 2, energy recovery, waste water, residues such as filter dust, sludge and slag. Air BAT Process control: see Sections 2.5.1, 2.5.2, Raw materials storage and handling Transport of raw materials such as char coal, coke and coal < 3 mg dust/nm 3 measured, always < 20 mg dust/nm 3. (Where are these data from?) Displaced air cleaning Handling, storage and transport of very fine powders can create problems The BAT-AEL for dust is < 1 to 20 mg/nm 3. Burden preparation (crushing,weighing, mixing, blending) and conveying BAT is to minimise dust emissions by appropriate measures and, where relevant, to extract emissions with subsequent purification by means of dry dedusting. I. Wet grinding, filtering, pelletising (measured at the homogenization of charge mix for themetallothermic reduction process showed emissions concentration values of 0.2 mg dust/nm3. [255]) The BAT-AEL for dust is < 1 to 20 mg/nm 3. Pretreatment stages such as coke and raw material drying, prereduction and preheating, drying and degreasing of secondary raw materials Raw material drying in rotary drums or kiln furnaces Shaft furnace for coke drying BAT-AEL for FF 5 mg/nm3 Rotary kiln??? DC Plasma process

2 BAT for the drying and degreasing of raw materials is to apply a rotary kiln, afterburner for VOC BAT-AEL for dust 5 mg/nm 3 and VOC 20 mg/nm 3? Sintering plant BAT for sinter plants is to reduce dust emissions by applying the following techniques individually: I. wet scrubber II. FF The BAT-AEL for dust is <4 to 10 mg/nm3, determined as daily mean value. Smelting processes BAT for process gas cleaning from closed EAFs is to apply individually or in combination I. wet scrubber II. dry cleaning systems III. any other technique with the same removal efficiency For cleaned process gas, the residual dust concentration associated with BAT is mg/nm 3, determined as the average over the sampling period (spot measurement, for at least half an hour). BAT for charging, open EAFs, is to prevent or reduce diffuse emissions by applying the following techniques I. Fume collection enclosure What about the preference of semi-continuous charging over batch charging? [526] II. hoods Optimising the capture efficiency for diffuse dust emissions and fumes with subsequent cleaning The BAT-AEL is??? BAT for the off-gas from semi-closed or open EAFs, ladles, oxygen blown converters, crucibles, or other furnaces is optimising the capture efficiency, and applying fine dust abatement by means of FF or other techniques with the same removal efficiency. The BAT-AEL for dust is < 1 5 mg/nm3, determined as a daily mean value. BAT for SO 2 emissions from molybdenite roasting is to apply desulphurisation in single or double contact plants. The BAT-AEL is a conversion efficiency of 98 99%. (Crosscheck with SO 2 section in chapter 2)

3 Do we have example plants? What are the residual SO 2 concentrations? We have SADACI, Ghent, Belgium with conversion rate between 99 and 99.4 % BAT for Dioxins, HCN, vaporised metals such as Hg, Cd, Pb?? PAH? If dusts from steel mills are recovered it is quite likely that HM can be emitted. Two stage bag filter with injection of activated carbon or a 3 stage venture scrubber or wet ESP with subsequent mercury removal with selenium filter can be applied. Try to get further information. SO 2 : Depends on the sulphur content of the input materials. Are any requirements necessary? Dioxins: very low concentration values are reported. Nevertheless industry proposes very high values (see Excel spread sheet). Is there any BAT for dioxins or only prevention? Decide if something is needed in the material selection and pretreatment stage for dioxins and Hg in particular. Post furnace operations BAT for tapping (oxygen lancing, drilling, vaporised slugs if tapping guns are used), melt refining and casting from all exposed metal and slag furnaces is to prevent or reduce diffuse emissions by applying the following techniques I. complete fume collection enclosures II. casting spout capture hoods III. cast house canopy hoods IV. vortex capture hood if applicable Optimising the capture efficiency for diffuse dust emisissions and fumes with subsequent cleaning. The BAT-AEL for dust is < 1 10 mg/nm 3, determined as a daily mean value. BAT is to minimise dust emissions from size reduction, screening and packaging of alloys to extract emissions by applying one of the following techniques with subsequent purification by means of dry dedusting. I. totally enclosed systems II. crushers with capture hoods The BAT-AEL for dust is < 1 10 mg/nm 3, determined as a daily mean value. (values < 3 mg/nm 3 have been measured. [255] enclosed systems!) Handling, storage and transport of very fine powders can create problems: Densification of silica powder Water Water consumption and discharge BAT is to minimise the water consumption from the smelting process by the use of closed loop water cooling systems for the cooling of furnace devices and by the use of treated waste water for metal and slag granulation and cooling. (Quenching of off-gas?) BAT is to minimise the waste water discharge from wet scrubbers, cooling systems and granulation processes by applying the following techniques in combination:

4 I II. III. IV. the removal of cyanide and fluoride the reduction of Cr 6 + to Cr 3 +, precipitation of metal hydroxides together with oxidation of cyanides removal of solids by sedimentation, flocculation and/or filtration in the case of molybdenite roasting ion exchangers The BAT AELs for waste water after treatment is: Suspended solids < mg/l In Section are no data for waste water after treatment. Only emission factors for the treated scrubbing water from plasma dust process and the roasting of molybdenite. Where are the data from Section from? Production residues such as wastes and by-products Minimising slag treatment emissions Slag granulation and water spraying to reduce dust emissions See tables 9.31 and 9.32 in Section of the draft of the NFM BREF. BAT is to prevent waste generation by applying the following techniques individually or in combination (see Sections..): I. appropriate collection and storage to facilitate a specific treatment II. on-site recycling of dust and sludge from gas treatment and pretreatment processes, dust from crushing, raw material and product transport and handling, secondary dedusting and mill scale from continuous casting back to the ferro-alloy making processes with due regard for the effect of emissions from the plant where they are recycled III. on-site recycling of ferro-alloy slag and ferro alloy fines in various IV. applications use of MnO rich slag as raw material for the production of silicomaganese or other metallurgical applications, use of FeV and FeCr-slags i.e. in the steel industry V. slag treatment where market conditions allow for the external use of slag (e.g. as an aggregate in materials or for construction, sandblasting, production of refractory castables or refractories) VI. use of filter dusts and sludge for external recovery of alloys in the nonferrous metals industry, e.g. ISP or waelz kiln VII. use of a settling tank for sludge with the subsequent recycling of coarse fraction in the sinter/blast furnace or cement industry when grain size distribution allows for a reasonable separation. Ferro-alloy production residues which can neither be avoided nor recycled should be managed in a controlled manner. Energy BAT for the production of HC FeCr, HC FeMn and SiMn is to apply closed furnaces and to collect, clean and buffer CO rich off gas for subsequent use as a fuel or raw material where prerequisites are given individually or in combination for I. coke drying II. sintering III. preheating of burden

5 IV. heating of ladles V. production of electrical energy VI. heat and steam production VII. use as a raw material in the chemical industry BAT for the production of FeSi, Si-metal, and FeNi is to apply semi-closed electric arc furnaces where prerequisites are given and reduce/minimise thermal energy consumption by applying the following techniques individually or in combination: I. process integrated re-use of sensible heat as far as possible from the off-gas II. using sensible heat for internal and external heating networks if there is a demand from a third party (the cooperation and agreement of a third party may not be within the control of the operator, and therefore not be within the scope of an IPPC permit). (What about oxygen blowing converters, crucibles, plasma dust process or other furnaces? Is there any energy recovery, or CO recovery??) BAT is to reduce energy consumption by covering ladles with a lid during transport where prerequisites are given. Noise?? EAF can be quite loud, see iron and steel BREF requirements