Air Pollution from a Large Steel Factory: Toxic Contaminants from Coke-Oven Plants

Air pollution from a large steel factory: toxic contaminants from coke-oven plants

L. Liberti1, M. Notarnicola1, R. Primerano1 & G.Vitucci2 1II Engineering Faculty, Technical University of Bari, Italy 2Istituto Scientifico Breda, Valenzano (BA), Italy

Abstract

An extensive investigation has been carried out to assess air pollution caused by one of the largest European steel factories in Taranto, S. Italy. The study was aimed in particular at evaluating toxic contaminants such as TSP, PM3.5, PAHs and Benzene emitted during the coke-making process. Pollution levels largely exceeding accepted values for all toxic compounds monitored were found, causing severe health risks for workers and heavy environmental impact on the densely populated surrounding areas. Keywords: coke oven plants, polycyclic aromatic hydrocarbons (PAHs), particulate matter, air quality, speciation profile.

1 Introduction

With 250,000 inhabitants Taranto, second most populated town of Apulia Region (S. Italy), hosts a heavy industrial district unfavourably positioned toward nearby residential areas and upstream prevailing winds. The industrial district includes Europe’s largest iron and steel integrated complex (ILVA), one of the largest oil refinery in S. Italy (AGIP), a large kiln factory (CEMENTIR) and several SMEs, making actually Taranto one of the most industrialized city of S. Italy, officially listed among “Italy’s 15 areas at high risk of environmental crisis” according to laws No. 349/86 and 305/89. Although the local steel factory is blamed for being a major cause of air quality deterioration, no systematic surveys nor serious attempts to identify and quantify its diffuse (i.e., apart from chimneys and other point sources) atmospheric pollutant emissions have been carried out so far.

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Large efforts to minimise atmospheric emissions from point sources have been made during the ’80 and ’90 in many European iron and steel plants, especially towards NOx, SO2 and dust, but their overall contribution to air emissions in EU is still significant for several hazardous air pollutants as shown in Table 1 [1-3].

Table 1: Contribution of iron and steel industry to overall emission of SO2, NOx , heavy metals and PCDD/F in the EU 15 [4].

Emissions in the EU 15 Contribution of the Parameter Year [t/a] Iron and Steel Industry [%]

SO2 1994 12.088.000 ca. 1.5 NOx " 12.435.000 ca. 1.5 Cd 1990 200 19 Cd " 1.170 55 Cu " 3.040 5 Hg " 250 3 Ni " 4.900 3 Pb 1996 12.100 9 Zn 1990 11.100 35 PCDD/F 1995 5.800 g I-TEQ 19

This is presumably due to uncontrolled diffuse gaseous and dusty emissions from various sections of the plants rather than from point sources (chimneys etc.). Diffuse emissions occur in particular from coke-oven sections where coal is pyrolysed to yield coke and pyrolytic gas required from other sections of the steel-making process. Coke oven emissions are a mixture of coal tar, coal tar pitch, volatiles, creosote, polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, xylene, naphthylamine, cadmium, arsenic, beryllium and chromium, acknowledged to show sufficient evidence of carcinogenicity in humans [5-8]. A systematic investigation on major atmospheric pollutants, namely Total Suspended Particulate (TSP), Particulate Material with hydrodynamic diameter lower than 3.5 microns (PM3.5), PAHs and Benzene, emitted during coke-making process has been carried out in order to assess diffuse air pollution contribution from Taranto’s ILVA factory. To this aim atmospheric emissions and air quality around these units have been experimentally measured over a 7-months period trough continuous and discontinuous monitoring investigation.

2 Coke-oven plants

Coking plants at Taranto factory consist of 12 batteries, each made by 45 ovens. The present investigation concerned in particular the four oldest batteries (No. 3-4 and 5-6), constructed between 1964 and 1970, never submitted to revamping nor refreshing since then, with (partial) refreshing carried out on batteries No. 5-6 at the end of the 80s’.

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Coking process in each oven occurs batch wise according to the following sequence (see Figure 1: coke ovens are numbered progressively from 91 to 180 in batteries No. 3-4 and from 181 to 270 in batteries No. 5-6): coke oven # 91, 96, 101, 106 etc… until 176; then # 93, 98, 103, 108 etc… until 178; then # 95, 100, 105, 110 etc… until 180; thus # 92, 97, 102, 107 etc… until 177; finally # 94, 99, 104,109 etc… until 179. Once completed, the sequence is repeated. The sequence of five according to this pattern aims primarily at maintaining thermal asset of the batteries.

COKE SIDE

n.180 n.136 n.270 n.226 from batteries 1-2 to batteries 7-12

4 3 65

n.135 n.91 n.225 n.181

PUSHER MACHINE SIDE

Figure 1: Schematic representation of coking cycle at the plants investigated.

On the average each oven is loaded with 20,5 t (30 m3) pit-coal and produces 16,1 t coke per cycle. A total of 36,370 un/loading sessions per year (approx 100 daily) were carried out on batteries No.3-4 (approx the same productivity occurred on batteries No.5-6) treating 746,585 t pit-coal and producing 585,076 t coke and 264,749 kNm3 of pyrolytic gas. Specific productivity averaged 0,78 3 tcoke/tcoal and 355 Nm /tcoal of gas, quite acceptable figures for this type of plant. After almost 40 years of continuous operation batteries No.3-4 and 5-6 showed unbearable signs of agedness with frequent interruption, fire cases and numberless malfunctioning accidents, all producing more or less diffuse emissions of toxic gaseous and dusty compounds, as repeatedly evidenced during this study.

3 Monitoring strategy and program

Environmental monitoring at ILVA’s batteries No.3-4 and 5-6 was carried out through fixed and semi-mobile sampling stations as well as with individual samplers. Three air-sampling stations were used, one (fixed) in the Detachment Battery area and two (mobile) on the Charging and Pusher Cars respectively, monitoring alternatively batteries No. 3-4 or 5-6 (see Fig.2).

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Due to continuous movement of charging and pusher cars all along the oven front, samples collected therein are effectively representative of air characteristics all around loading and unloading areas respectively. Each station was equipped with different sampling apparatuses to collect TSP, PM3.5, Benzene and PAHs. Personal samplers were also dressed by representative workers in each shift, selected according to their tasks (employees’ caps, small tanks, loaders, scene-shifts).

Figure 2: Sketch of coke-oven batteries No.3-4 and 5-6 with monitoring points 1) Tower, 2) Charging Car*, 3) Pusher Machine*, 4) Quench Car, 5) Quench Tower, 6) Coke Discharge, 7) Chimney, 8) Detachment* *sampling point.

The monitoring program was carried out through 6 distinct sessions. Five sessions were held in 2-3, 14-15 and 21-22 November 2001 and in 5-6 and 12-13 December 2001 respectively involving both coke-oven batteries No. 3-4 and 5-6 while the 6th session (15-16 May 2002) involved just batteries No.3-4. Each monitoring session lasted approx. 12 hrs (from 9 a.m. to 8 p.m. usually) except for the last session that lasted approx. 40 continuous hrs ( from 9 a.m. 15 May to midnight 16 May 2002) in order to monitor one complete coking cycle.

4 Materials and methods

PM3.5, Benzene and PAHs were sampled and analysed accordingly respectively to met. UNICHIM 285, met. UNICHIM 565 and met. NIOSH 5506-5515 (modified to determine PAHs through PM3.5 filters) respectively.

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Air samples were collected by a sampling train made by a cassette (47/12 mm) equipped with a Teflon filter (2 µm) followed by short (10-200 cm) PVC tubes containing 100 mg/50 mg of Amberlite XAD-2 adsorbent by Rohm and Haas. Sampling pumps (Zambelli mod. ZB2 - PLUS 6000 and Tecora mod. Bravo R/PRG equipped with dry volume meter, flow rate meter, rotary pump with linear flow forced circulation and cooling circuit with heat exchange serpentine) were set at proper flow rate, i.e., 8-10 l/min for particulate and 0,2 l/min for Benzene. All samples were protected from sunlight and frozen immediately. Before sampling, all filters were cleaned and washed with a solvent solution (mixture of n-hexane and dichloromethane, v:v = 1:1) for 24 h in a Soxhlet extractor. Dust collected was weighed on an electrical balance (± 0.01 mg), then sent to the lab, together with the sorbent trap, to determine both particle-bound and gaseous PAH concentrations. To this aim each sample was placed in 1,000 ml of the above mentioned solvent solution and extracted with a Soxhlet extractor for 24 h. The extract was then concentrated, cleaned-up and re-concentrated to 1.0 or 0.5 ml. PAH content was determined with a high resolution gas chromatograph (HRGC) by Hewlett-Packard equipped with flame ionisation detector (FID) and computer workstation The mass of PAHs primary and secondary ions was determined in the scan mode for pure PAH standards. PAH recovery efficiencies were determined by processing a solution with known PAH concentration through the same experimental procedure used for sampling. Samples for Benzene were collected by 70 × 4 (i.d.) × 6 (o.d.) mm glass sampling tubes packed with two sections of coconut shell charcoal containing 100 mg (front) and 50 mg (back section) of charcoal respectively. The sections were held in place with glass wool and polyurethane plugs. For this evaluation, commercially prepared charcoal tubes by SKC Inc. were used. The samples were then extracted with carbon disulfide and analysed with the FID-HRGC previously mentioned.

5 Results and discussion

It must be pointed out that the 6 sampling sessions lasted cumulatively approx 110 hr and were spread over a 7-months period with different meteorological conditions (Fall, Winter and Spring) and varying operation performance of the coking plants considered. In order to state that the results of the study may be reasonably assumed representative of average air quality at ILVA’s plants investigated, experimental measurements of TSP, PM3.5, Benzene and PAHs were preliminarily evaluated trough the well-know Statistical Inference Analysis (SIA) procedure [9]. According to SIA if n measurements of a given pollutant are repeated in m 2 2 sessions, the expressions for variations (σT ; σR ) and respective degree of freedom (νT; νR) are:

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m 2 ∑ i − xxn )( σ 2 = i=1 T m −1 n m 2 ∑∑ − xx iij )( σ 2 = j==11i R nm − )1(

T mv −= 1

R nmv −= )1( 2 σ T F = 2 σ R where xij = argument values (the single measurements) xi = average per session x = general average F = Fisher’s Distribution accidental variable.

The analysis consisted of confronting the variance of all n experimental 2 2 measurements (σT ) with the variance within the m classifications (σR ) for each pollutant considered. If σT is significantly larger than σR, each classification represents different populations. A 5% level of significance was assumed. In this case it resulted:

m n νT νR F5%(νT; νR) Batteries 5 6 4 25 2,76 N.o. 3-4 Batteries 5 10 4 45 2,57 No. 5-6

The corresponding experimental Fexp for the various pollutants resulted always lower than F5%(νT; νR) as reported below:

Fexp Batteries No. 3-4 Batteries No. 5-6 TSP 2,3 1,7 PM3.5 2,1 1,5 PAH - 1,3 Benzene 1,6 2,1

According to SIA this confirms that, except for PAHs sampled near batteries No.3-4, no systematic component of unacceptable entity existed among all experimental data collected. It is conceptually correct hence to calculate the arithmetic average from measurements carried out on samples taken in different sampling stations for TSP, PM3.5, Benzene and Total PAHs as reported in Tab.2. According to Italian regulation (Ministerial Decree 20/08/1999), measured concentration of pollutants investigated were compared with air standards in workplace based on TLV (Threshold Limit Value) by the ACGIH (American

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Conference of Governmental Industrial Hygienists) [10]. Two TLVs were considered in particular for each pollutant as reported in Table 3:

• TLV–TWA (Time–Weighted Average concentration for a conventional 8-hr workday) worker exposure levels that may be exceeded up to 3 times for no more than total 30’ during a workday (under no circumstances it should be exceeded by 5 times) • TLV-STEL (Short Term Exposure Level), a 15’ exposure that should not be exceeded at any time during the workday.

Table 2: Summary of TSP, PM3.5, Benzene and Total PAHs average concentration at batteries No. 3-4 and 5-6 for each station.

TSP PM3.5 Benzene Total PAHs Location of Sampling 3 3 3 3 TYPE mg/m mg/m mg/m mg/m Station No. 3-4 No. 5-6 No. 3-4 No. 5-6 No. 3-4 No. 5-6 No. 3-4 No. 5-6 Charging Car MOBILE 3.6 2.0 1.9 1.3 4.6 22.5 - 0.5 Top (Pusher Machine) FIXED 2.1 1.7 1.1 0.4 1.2 4.0 - 1.0 Top (Coke side) FIXED 2.1 - 0.6 - 0.3 - - - Pusher Machine MOBILE 1.9 1.6 0.9 0.5 3.3 4.0 - 0.2 Pusher Machine side FIXED 1.7 2.3 0.8 0.6 0.4 0.2 - 1.4 Batteries Detachment FIXED 1.6 1.2 0.7 0.4 2.5 6.5 - 0.4 AVERAGE 2.1 1.7 1.0 0.6 2.2 7.4 - 0.5

Table 3: ACGIH Threshold Limit Values for the pollutants investigated.

TWA STEL (mg/m3) TSP 0.4 2.0

PM3.5 0.4 2.0 Benzene 1.6 8.1 PAHs 0.2 1.0

Figs. 3 to 6 reports all experimental data for the pollutants considered during this investigation together with corresponding TLVs. As for TSP, from Figs.3a and 5a it appears that approx. 90% of samples (94/104) exceeded the reference TWA, 67% (70/104) exceeded it also by 3 times and 34% (35/104) by over 5 times. Similar discouraging results were recorded for PM3.5. As shown in Figs.3b and 5b, indeed, the corresponding TWA was exceeded by 80% of samples (82/104), with 22% and 8% of values exceeding it by 3 and 5 times respectively. TWA and STEL for Benzene were similarly exceeded in 22% (18/82) and 16% (13/82) of samples respectively (see Figs. 4 and 6a). Finally TWA for PAHs was exceeded in 44% of cases (36/82), 23% and 13% of which exceeded it by 3 and 5 times respectively (see Fig.6b).

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Figure 3: TSP (a) and PM3.5 (b) near batteries no. 3-4.

Figure 4: Benzene near batteries no. 3-4.

(a) (b)

Figure 5: TSP (a) and PM3.5 (b) near batteries no. 5-6.

(a) (b)

Figure 6: Benzene (a) and PAHs (b) near batteries no. 5-6.

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All toxic compounds considered resulted to largely exceed, even by order of magnitude, particularly at the upper plant desk (coal loading area), the allowed limits in Italy. These results confirmed unambiguously the relevant contribution of Taranto’s steel factory, namely its coke-oven plants, to the deterioration of air environment around with special concern for the densely populated residential areas actually surrounding factory boundaries. Parallel sanitary controls carried out by personal samplers as well by biological sampling showed clear evidence of high accumulation of typical PAHs and benzene biomarkers in excreta (blood, urine) from coking workers, confirming unacceptable health risks in their working place, as described elsewhere [11].

6 Conclusions

It may be clearly concluded that air pollution caused by atmospheric emission of total and fine particulate, PAHs and benzene from some coke-oven batteries of Taranto’s steel factory are not acceptable accordingly to ACGIH guidelines and recommendations. This poses serious health risks not only to workplaces, but also to residential areas nearby. Following the results of this investigation, coke-oven batteries No. 3-4 and 5- 6 have been shut off.

References

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[8] Tsai, J.H., Jenq, F.T., Lee, C.C., PAH characteristics in ambient air within a steel industrial complex. Toxicol. Environ. Chem. 53, 127–136 (1996) [9] Harold J. Larson, Introduction to Probability Theory and Statistical Inference, Wiley Text Books; 3rd edition (1982) [10] ACGIH (1998) Documentation of TLVs and BEI, 1993 with updates 1997 and 1998. ACGIH, Cincinnati, OH [11] Assennato, G., Bisceglia. L., de Nichilo, G., Assessment of occupational exposure to PAHs in a coke plant by biological monitoring, 12th Int. Conf. Air Pollution 2004, Rhodes, GR, 30 June – 2 July 2004