Frequently asked questions about Met Coke

A carbon residual-materia

The BIMCO Marine department has been asked many times by members whether Met Coke is a clean or a dirty bulk cargo under the International Maritime Solid Bulk Cargoes (IMSBC ) Code.

In order to answer that, we need to know what sort of cargo Met Coke isin the first place.

What is Met Coke ?
“Met Coke” or “Metallurgical coke” is a carbon residual-material made or manufactured by the “destructive distillation” or “carbonization” of various blends of bituminous coal; a type of coal which is a soft, medium grade containing a high percentage of volatile components. The coal is often referred to as coking coal or metallurgical coal, that is, coal processed to be become Met Coke. Metallurgical coal is found in large quantities in Asian and Far Eastern countries like India and China. Large reserves have also been found in Turkey with small quantities in United States too.

How is Met Coke manufactured?
The destructive distillation or carbonization process is performed by heating the bituminous coal in an oxygen-free environment inside a coke oven. This process is also called coking and is conducted so that coal can be purified from its volatile components.

The coke ovens used are special high-temperature “beehive coke ovens” or “coke batteries” and are actually banks of large enclosed kilns. Once the kilns are loaded, they are heated to approximately 1,000 C for more than 22 hours in the absence of air until a great part of the volatile components is driven off.

During the heating process, the volatile components of the coal are released and the remaining coal goes through a partial melting and subsequent re-solidification into a non-melting hard carbon. Volatile components include coal tar, ammonia, and dozens of other “products of decomposition” or waste products. The volatile components released from the coke oven gas are disposed of either by venting into the atmosphere or are directed to a separate chemical recovery plant where they are refined into by-products; a process conveniently called by-product coke-making.

At the time of writing, China is the largestMet Coke producer, followed by Japan.

Properties of Met Coke
The resulting or finalised product is a stable non-melting carbon solid called metallurgical coke or Met Coke , comprising mainly of carbon. Due to the loss of volatile gases and partial melting process, Met Coke has an open, porous structure and may appear glassy in some varieties. It has also a low volatile content or rather low waste product content due to the heat treatment process received. However, the “ash” constituents, that were part of the original bituminous coal feedstock, remain intact in the finished product. Met Coke is available in a wide range of sizes; from fine powder (30 mm) to basketball-sized lumps (20 cm). The purity ranges from 88-92% of fixed carbon. One ton of coal yields approximately 0.7 ton of coke.

Uses of Met Coke
Because Met Coke has a stable burning temperature, producing little or no smoke, it is used as one of the main ingredients for steel production. It is used primarily for the reduction of iron ore in blast furnaces, fuelling blast furnaces that smelt or reduce iron ore and other bearing materials , acting both as a source of heat and as a chemical reducing agent to produce pig iron ( also known as hot metal). Pig iron is then used to produce steel. More than 90% of the metcoke produced is used in the iron and steel industries.

In addition, it is used in many applications which require carbon that is strong, robust and resilient and of high quality and performance. Some applications that use metcoke are foundry coatings, drilling applications, friction materials, corrosion materials, reducing agents, ceramic packing media and oxygen exclusion and electrolytic processes.

Met Coke in the IMSBC Code
Met Coke is not the proper Bulk Cargo Shipping Name (BCSN) in the IMSBC Code,i.e., you will not be able to findthe carriage requirements of”Met Coke” by looking for that name in the Code.Its properBCSN is “Coke” and itis classified as a Group C cargo, i.e. one that neither liquefies nor possesses chemical hazards. Members should note that the use of BCSNs is a mandatory requirement under the IMSBC Code and hence are duly advised to use the rightBCSN forbulk shipments of Met Coke.

Is Met Coke a clean or dirty cargo?
The IMSBC Code does not classify solid bulk cargoes as clean or dirty nor does it have definitions of what constitutes a clean or dirty cargo. It is well known in the tanker industry, there is somewhat a clear definition of dirty cargoes in terms of the commercial distinction between “dirty petroleum products” and “clean petroleum products”. However in the dry bulk industry, no such definitions exist.

To the best of the BIMCO Marine Department’s knowledge, dirty cargoes have so far been interpreted as dirty in terms of cleaning the holds after discharge or in terms of what the next cargo shipment is and the level of hold cleanliness required for the next cargo. The BIMCO Marine Department is inclined to consider a dirty cargo as one that is capable of soiling the cargo holds, i.e. dirtying the cargo holds by leaving stubborn or greasy stains to the extent of contaminating the holds or even the next cargo to be carried. One good example which seems to be commercially accepted and classified as a dirty cargo would be Petcoke. Petcoke is well known for its obnoxious properties particularly in the context of cleaning since Petcoke tends to have a high oil content, leaving greasy/oily stains behind. This results is the need to wash the holds thoroughly clean after discharge, a difficult task perhaps requiring special cleaning methods. Coals are also generally considered to be “dirty” cargoes, again looking at it from the cleaning-of-holds perspective.

Met Coke maynot be considered a dirty cargo compared to Petcoke in that respect, but on the other hand, it could be dirty in terms of it being a dusty cargo depending on the type and grade of Met Coke, e.g., if it contains fines (breeze), where it spreads dust and dirt over a wide area.

Therefore, whether Met Coke is a clean or dirty cargo, it would depend on your interpretation based on the above scenarios.The BIMCO Marine deparment urges members to obtain exact cargo information required for the type of Met Coke to be shipped from the shipper; in particular, the standard of hold cleanliness and/or cleaning after discharge requirements. Members should also note that it is the statutory obligation of the shipper under SOLAS and the IMSBC Code, to furnish appropriate information of the cargo in advance of loading so that preparations and precautions can be made for safe stowage and safe carriage to be put into effect.

The following is taken from the Standard P&I Club giving a short write-up on Met Coke in respect of hold preparation, cleanliness and cleaning required after discharge for members’ guidance :

Metcoke
Metallurgical coke, or Met Coke, is manufactured from blends of bituminous coal in a heated distillation process resulting in a non-melting carbon used mainly in the manufacture of steel.

Before loading
Remove all solid residues, sweep clean and flush with seawater.
Paint protection is not usually required.

After discharge

• remove all solid residues, sweep clean; the application of chemicals diluted with
• freshwater may be required to dry bulkheads
• seawater cleaning before the application of chemicals may reduce the effect of the chemicals and should only be done if heavy cargo deposits are present
• cleaning is completed by flushing with freshwater, working from the top down

Source: BIMCO