lp briefing - carriage of dri

7/21/2019 LP Briefing - Carriage of DRI

http://slidepdf.com/reader/full/lp-briefing-carriage-of-dri 1/7

21 January 2009

LOSS PREVENTION

BRIEFINGLoss prevention briefing for North of England Members CARGO

North of England P&I Association, The Quayside, Newcastle upon Tyne, NE1 3DU, UK

Tel: +44 191 232 5221 Fax: +44 191 261 0540 Email: [email protected] Website: www.nepia.com 1Copyright © North of England P&I Association 2009

Carriage of Direct Reduced Iron (DRI)

ContentsIntroduction .............................................................................................................................................................. 2

DRI and its derivatives ............................................................................................................................................ 2

Hazards of DRI and derivatives .............................................................................................................................. 3

Misleading descriptions of DRI .............................................................................................................................. 3

Regulatory Developments ...................................................................................................................................... 3

Safe carriage of DRI ................................................................................................................................................ 3

Safe carriage of hot briquetted iron (HBI) ............................................................................................................. 5

Safe carriage of fines .............................................................................................................................................. 6

Acknowledgements ................................................................................................................................................. 7

Disclaimer

The purpose of this publication is to provide a source of information which is additional to that available to the maritime industry fromregulatory, advisory, and consultative organisations. Whilst care is taken to ensure the accuracy of any information made available no warrantyof accuracy is given and users of that information are to be responsible for satisfying themselves that the information is relevant and suitablefor the purposes to which it is applied. In no circumstances whatsoever shall the Association be liable to any person whatsoever for any loss ordamage whensoever or howsoever arising out of or in connection with the supply (including negligent supply) or use of information.

Unless the contrary is indicated, all articles are written with reference to English Law. However it should be noted that the content of thispublication does not constitute legal advice and should not be construed as such. Members should contact the Association for specific adviceon particular matters.





Tel: +44 191 232 5221 Fax: +44 191 261 0540 Email: [email protected] Website: www.nepia.com 2

Copyright © North of England P&I Association 2009

IntroductionDirect reduced iron (DRI) is produced by passing hot reducing gases such as hydrogen and carbon monoxide over

iron ore (oxide), which is usually in the form of pellets or lumps. Although the process is conducted at hightemperature, this is still substantially below the melting point of iron. This means that the lumps and pellets retaintheir original shape, but are considerably lighter owing to the removal of oxygen from the ore. Therefore, thepellets and lumps have a very porous structure, which makes the material extremely reactive and prone to re-oxidation on contact with air and moisture.

This briefing highlights the issues, and problems, with the carriage of DRI.

DRI and its derivativesInitially, most DRI was shipped in the form of pellets. This form was found to be most at risk of heating (see below)and methods of treating DRI were tried in order to reduce the danger.

Passivated pellets

These are ordinary DRI pellets coated with a substance which is intended to protect the iron from air and moisture.Producers in different countries use different forms of coating, some of which are more effective and durable thanothers. However, no coating renders the DRI entirely safe. The coating can chip off and it will break down overtime.

Cold moulded briquettes

These are DRI pellets which have been compressed into the shape of a cake of soap, the intention being toreduce the accessible surface area of the pellets in order to reduce the area available for reacting with air andmoisture. The briquettes can also be passivated. The problem with this cargo is that the briquettes are relativelyfragile as they are compressed when cool. They can fracture during normal cargo operations, which increases the

amount of surface area available for reaction with air and moisture and the cargo becomes dangerous in a similarway to pellets.

Hot moulded briquettes or hot briquetted iron (HBI)

The pellets and lumps can be compressed at temperatures exceeding 650°C to form coherent briquettes that areless porous than the original materials. As such, the briquettes are less fragile and, therefore, less prone tobreaking up during cargo handling and have less surface area available for oxidation. They can also bepassivated. This is possibly one of the safer forms of DRI but, even so, is still prone to heating and giving offhydrogen in certain conditions.

DRI fines

The DRI production process (and the hot-briquetting process if HBI is being produced) generates copious

quantities of dust or ‘fines’.These fines are usually stored separately from the finished DRI or HBI product, but, as they have commercialvalue for steel making, there is a market for shipping them. Fines are not normally compressed into large cohesivebriquettes and remain porous like DRI pellets. As fines they also exhibit an extended surface area. Consequentlythey can exhibit self-heating qualities. They may have also generated hydrogen in sufficient quantities to formexplosive atmospheres, even in holds that have been subject to natural ventilation through conventional cargohold vents, or hatch cover openings.







Hazards of DRI and derivativesThe principal hazards of all cargoes of DRI and its derivatives are twofold.

Reaction with air

Firstly, they will react with the oxygen present in the air, thereby producing heat. This effect can run away inspectacular fashion, leading to auto-oxidation (burning) of the iron, in which the stow becomes incandescent asthe temperatures approach 1,000

oC. This tendency is successfully prevented in most practical applications by

densifying the DRI pellets at temperatures exceeding 650oC to produce HBI.

Whereas self-heating is dangerous and alarming, it is a gradual and progressive event that can often bediagnosed early, affording masters time to obtain advice from ashore and institute suitable safety measures.

Reaction with moisture

The second hazard is again related to the reactivity of iron, this time with moisture or water. The result is thegeneration of hydrogen gas, which is explosive over a very wide range of concentrations and, in practicalsituations, displays an alarming readiness to be ignited. Explosions of hydrogen in air are extremely violent andrapid and an unfortunate master has no time in which to react to an explosion.

Misleading descriptions of DRIShippers may offer a material for bulk shipment that is clearly a DRI product, but is claimed to be safe for bulkcarriage by sea without the usual precautions. This particularly applies to DRI fines.

The most common device is to call the fines ‘HBI Fines’ or ‘Metallic HBI Fines’ and thereby claim the relaxation inprecautions afforded to HBI. Fines have also been described as ‘Iron Remet Fines’, the term ‘remet’ probablybeing a shortening of the word ‘remetalised’, signifying it is metallic rather than the ore.

Despite the foregoing, not all cargoes with ‘DRI’ in the description are hazardous. For example, Members havebeen offered cargoes described as ‘direct reduced iron ore’. By referrin g to the typical material compositionsupplied by the shippers, it could be seen that this was indeed iron ore that was destined for the direct reductionprocess, and therefore a cargo that posed no special hazards. However, this is difficult for a master to determineand expert advice should always be sought by the Member.

Regulatory DevelopmentsFollowing a number of investigations into accidents associated with the carriage of DRI, the International MaritimeOrganization (IMO) has recently revised the relevant schedules to be included in the new International MaritimeSolid Bulk Cargo (IMSBC) Code, which will replace the BC Code. The IMSBC Code was adopted at the IMOMaritime Safety Committee (MSC) meeting in November 2008 for voluntary implementation by member Statesfrom January 2009 and mandatory application from 1 January 2011.

Safe carriage of DRIThe common factor to both hazards mentioned above is the oxygen present in the atmosphere. It is clearthat the exclusion of oxygen, or its reduction to a suitably low level, will eliminate the possibilities of self-heating or of a hydrogen explosion occurring. It follows that carrying a cargo of DRI or its derivativesunder an inert gas blanket, and maintaining that blanket throughout the voyage, is an acceptable methodto carry the product safely.







BC Code, Appendix 1, Direct Reduced Iron (B)

The Code of Safe Practice for Solid Bulk Cargoes (BC Code), 2004, requires under the entry for Direct ReducedIron (B) in Appendix 1, that a competent person recognized by the national administration of the country shouldcertify to the ship’s master that the DRI, at the time of loading, is suitable for shipment. Shippers should certify that

the material conforms with the requirements of the BC Code.

The BC Code also requires a shipper to designate one of two alternative methods for the carriage of DRI

The first method is to introduce inert gas at tank top level after the cargo has been loaded so that the whole stowcan be maintained at a low oxygen level throughout the voyage. Maintenance of an inert atmosphere containingless than 5% oxygen and 1% hydrogen is required.

The second method requires the DRI to have been subjected to an oxidation-inhibiting and corrosion-inhibitingprocess approved by the competent authority as providing effective protection against dangerous reaction withseawater or air under shipping conditions. However the Association’s current advice is that no satisfactoryinhibition process is known and therefore, if this method is proposed, Members should carefully check for approvalby a competent authority.

The BC Code also permits the competent authority to waive or vary either method for a specific voyage due to

applicable conditions, but, if shippers claim to have permission not to use an inert gas blanket, Members shouldcarefully check the conditions relating to such permission.

Accordingly, a Member should be cautious if asked to carry any DRI cargo other than under an inert gasblanket, and should seek expert advice before agreeing to do so.

IMSBC Schedule for Direct Reduced Iron (B) - Lumps, pellets, cold-moulded briquettes

The International Maritime Solid Bulk Cargo (IMSBC) Code includes a recently revised schedule.

DRI lumps, pellets and briquettes moulded at less than 650°C remain very porous and therefore very reactive.Their fragility means that they can break during loading leading to increased surface area and reactivity. Thisschedule has been amended to only allow carriage of such cargo under inert conditions.

Practical precautions

It should be noted that certificates are required at the time of shipment from both the shipper and a "competentperson". The Master should be assured by the "competent person" that, in certifying the stability and suitabilityof the cargo for shipment, he has had specific regard to the period and conditions of storage of the cargobefore loading, and its temperature.

The ship should be equipped with systems for continuous monitoring of the temperature, and of oxygen andhydrogen concentrations during the voyage.

Only certified safe electrical equipment and associated wiring should be installed in any cargo space oradjacent closed spaces or deck houses where flammable gases may accumulate.

The temperature of the cargo should be monitored during loading and, if more than 10°C above ambienttemperature, the Master should call for the assistance of the local P&I correspondent and the "competent

person" providing the certificate of suitability for shipment. During loading or discharging no smoking, burning,cutting, chipping or other source of ignition should be allowed in the vicinity of the holds.

As far as is reasonably practical the DRI should not be dropped from a height into the hold.

During loading the DRI must ether be protected from exposure to rain or snow or else loading should bestopped and hatches covered. DRI which has been exposed to wetting on an open conveyor or elsewhereshould be rejected.

The ship should be fitted with means of introducing inert gas immediately after completion of loading and becapable of maintaining an inert atmosphere during the voyage. The preferred inert gas is nitrogen.

Piping should be arranged so that the inert gas may be put in at the bottom of the stow at several points in thehold so as to force out effectively the air within the stow.

The amount of inert gas put in should be such as to keep the oxygen concentration below 5% by volume.







If water enters the hold hydrogen is likely to be evolved with the development of heat. The effect ofcondensation on the cargo may have similar results. The heat may be sufficient to cause ignition. For thisreason every precaution should be taken to exclude water. Particular attention should be paid to bilges,adjacent ballast tanks and the water-tightness of the hatches and other openings on the weather deck.Inspection of these openings should be made regularly throughout the voyage, particularly after heavy

weather, and any defects be remedied.

Hydrogen gas is liable to escape even through small openings. Care should be taken to guard against itspossible accumulation in adjacent enclosed spaces. The ship should carry a suitable portable meter formeasuring hydrogen concentrations.

A meter to measure Lower Explosive Limit (LEL) is also acceptable but it should be remembered that this doesnot directly measure hydrogen concentration but the amount of hydrogen present in terms of the explosiveconcentration. In all cases the meters should be able to function in reduced oxygen concentrationatmospheres.

During the voyage monitoring of the oxygen concentration will indicate whether air has entered the hold andwhether more inert gas is required to maintain the oxygen concentration below 5% by volume. If monitoringshows a continuing increase in hydrogen and/or rise in temperature a fire situation may be developing.

If a fire situation develops the ship should make for the nearest suitable port and neither water, steam oradditional carbon dioxide should be used at this stage to counteract the fire as a reaction with the cargo mayresult. If, however, nitrogen gas is available the use of this gas to keep the oxygen concentration down willcontain the fire.

Should heavy weather severely damage the hatches so that they cannot be repaired and water enters the holda fire situation is likely to develop. The ship should make for the nearest suitable port and seek assistance.

Entering the hold without breathing apparatus must be prohibited at any time unless the hatch covers arecompletely open and the holds effectively ventilated. If entry of the hold with breathing apparatus is required,this should only be done with full back-up assistance.

If hydrogen is developing opening of hatches may result in a spark induced fire or explosion. In suchcircumstances hatches should not be opened without expert advice which may be obtained through the local

P&I correspondents.

During discharge the DRI should be kept dry.

Any dust accumulated on decks or elsewhere during loading or discharge should be washed off as soon aspossible to prevent adhesion.

Safe carriage of hot briquetted iron (HBI)BC Code 2004, Appendix 1, Direct Reduced Iron (A)

Hot moulded briquettes compressed at temperatures in excess of 650°C are less porous than those of DRI (B)

with a more robust construction and reduced surface area. However, hot moulded briquettes may still self-heatand emit hydrogen when brought into contact with water and should therefore be kept under close supervision.

With HBI, because of its greater stability and resistance to auto-oxidation, carriage under an inert atmosphere isnot required in the BC Code under the entry for Direct Reduced Iron (A) in Appendix 1. As a precaution theamount of fines under 4 mm in the shipment should not exceed 5% and should be distributed throughout the cargorather than allowed to accumulate in any portion.

The BC Code requires that a competent person recognized by the national administration of the country shouldcertify to the ship’s master that the DRI, at the time of loading, is suitable for shipment and does not contain finesmore than 5%.

Unfortunately, whereas auto-oxidation might not be a realistic hazard, the material will still produce hydrogen andthe BC Code requires provision of adequate ventilation to address the potential hazard. As the generation ofhydrogen is slow with correctly produced HBI, the BC Code does not require monitoring of hydrogen quantities.







However, the Association has become aware of hydrogen being generated more rapidly with certain HBI cargoesand therefore monitoring the gas concentrations in the holds with a detector that is suitable for hydrogen is a wiseadditional precaution with all HBI cargoes.

Moreover, the Code permits open storage and accepts that the cargo may therefore be wet prior to loading,

although loading and transfer during rain is prohibited.

IMSBC Schedule for Direct Reduced Iron (A) - Briquettes, hot moulded

The International Maritime Solid Bulk Cargo (IMSBC) Code includes a recently revised schedule.

IMSBC amendments to this schedule are of a minor nature.

Practical precautions

The main hazard arises from the evolution of hydrogen if water enters the stow. For this reason, effectiveventilation should be carried out whenever possible. The equipment used for forced ventilation should be suchas to avoid the possibility of ignition of gas/air mixtures.

Prior to loading the briquettes may have been stored uncovered, exposed to rain. This is not necessarily

objectionable provided that the cargo is not obviously wet at the time of loading. However, loading shouldcease during periods of rain and the holds be covered.

The Master should be assured by the "competent person" that all practical steps have been taken to ensurethat the cargo delivered to the ship does not contain more than 5% fines. As far as is practical dropping from aheight into the hold should be avoided to prevent disintegration of the briquettes.

On completion of loading and prior to sailing if weather and circumstances permit, the hold should be left openas long as possible to allow the dissipation of any hydrogen evolved.

The temperature of the stow should be taken. If it is in excess of 65°C (150°F) sailing should be postponeduntil it is clear that it is falling.

If it continues to rise, the Master should call for the assistance of the local P&I correspondent.

Should the Master suspect a serious abnormality in the temperature of the cargo during the voyage he shouldmake for a port of refuge and seek assistance. Ventilation should continue in the meantime.

Any dust accumulated on decks or elsewhere during loading or discharge should be washed off as soon aspossible to prevent adhesion.

Safe carriage of finesIMSBC Schedule for Direct Reduced Iron (C) - By-products

A new schedule is being introduced for the carriage of fines and small particles that are the by-products of DRI (A)and DRI (B). This schedule is drafted in a similar manner to the schedule for DRI (B) and such cargo must becarried under an inert gas blanket.

The allowable moisture content for the carriage of DRI under an inert blanket is a maximum of 0.3%. Intercargohas reported that current DRI (C) cargoes are considered to have moisture content in excess of this value.

Tests currently being carried out by the Venezuelan authorities on DRI (C) cargoes with moisture content inexcess of 0.3% are expected to be submitted to the IMO Sub-Committee on Dangerous Goods, Solid Cargoesand Containers (DSC) meeting in 2009.

It is expert opinion that if the fines are produced from any form of direct reduced iron then the finelydivided form renders the fines reactive to air and moisture.

Accordingly, a Member should be cautious if asked to carry any DRI fines cargo or HBI fines cargo otherthan under an inert gas blanket, and should seek expert advice before agreeing to do so.







AcknowledgementsThe Association is very grateful to Dr Alan Mitcheson, Dr J H Burgoyne & Partners LLP, for providing articles forNorth of England’s Signals newsletter on which this briefing is based, and for providing further assistance with thebriefing. The Association is also very grateful to Cliff Mullins, Minton, Treharne & Davies Ltd, for providingassistance with the briefing.

Dr J H Burgoyne & Partners LLP Burgoyne HouseChantry DriveIlkleyWest YorkshireLS29 9HUUK

Telephone: +44 (0) 1943 609251Website: www.burgoynes.com

Minton, Treharne & Davies Ltd Bankside House107-112 Leadenhall StreetLondonEC3A 4DJUK

Telephone: +44 (0) 20 7626 8626

Website: www.minton.co.uk

http://www.burgoynes.com/

http://www.burgoynes.com/

lp briefing - carriage of dri

Documents