Direct reduced iron/HBI/DRI/Sponge iron is the result of the reduction of iron oxide to iron (Fe203 to Fe). In its natural state it is highly porous and has an affinity for oxygen in any form. Reoxidation of reduced iron can take place at ambient conditions especially in the presence of any atmospheric moisture, faster with salt air. The reoxidation of reduced iron will be exothermic generating heat which will increase the speed of reoxidation and further the rate. In all DRI free carbon graphite is present and this also will enhance the reoxidation rate at some elevated temperatures. During reoxidation some of the reactions will be; Fe>FeO + CO, Fe>FeO + H2, etc., etc., From the availability of CO and H2 is where the fires and potential explosions will come from.

Firstly, it is imperative to keep the reduced iron dry, preferrably in a storage facility. If it is a silo then nitrogen should be applied or at least available to ensure that the atmosphere will be inert. If it is in a warehouse and piled up then a border should surround the pile so that any water in the area cannot get near the pile (concrete barrier). Additionally, the pile should not exceed 1/2 meter in height, therefore if there is any reoxidation taking place, the heat should dissipate rather than heat up the surrounding materials. If reoxidation starts, spread out the material and let it reoxidize on its own and protect the area. I would not suggest you use water to cool as this will generate H2 resulting in some interesting fireworks.

Remember that anyone working in the area should have protective clothing like is used in steel mills and breathing air should be available with masks.

Once the material has started to reoxidize it will return to its oxide state Fe2O3. You should be able to reuse it.

The reason we developed HBI and then RBI was to densify DRI enough so that the material porosity was reduced to a level that would prevent reoxidation. (HBI>hot briquetted iron, after reduction before cooling),(RBI>ram briquetted iron, after reduction after cooling). Both produce the same level of densified materials.

Sincerely,

T.C.Inc. (an independent engineering consulting firm in Direct Reduced Iron, agglomeration, pelletizing, briquetting and materials preparation for the iron and steel industry)

tcinc002@aol.com ■

Originally Posted by sganesh

Dear Experts,

How to avoid fire in cold DRI ( Direct reduced Iron ) storage & handling?

Thanks a lot & high regards,

simple enough if you are a Midrex unit , make sure the discharge temperature is as low as possible , les than 90 C preferably less than 65ºc then make sure the inert gas irrigation of the bottom sel is operating check the composition of the inlet gas , allow a minimun amount of oxygen , less than 1% if possible , but not cero..

do the sme with the seals of the blending bin (so called passivation bin) make sure the inerted bin has enhanced flow , and that your solids flow pattern does not segregate the fine material , then take samples of the out flow from the reactor and from the passivation bin , check re-activity ratio calculate the temperature rise in your secondary storage to insure that it cannot reach more than 120ºc or so , eliminate the paralleled skirts from your belt feeders en bottom of your bins , give them an angle . check your overall material hanf+dling system for ignition sources, change your Ir sensor to cover the whole belt area , with no more than 8 inches diemeter spots , redundant self checking coverage , use two station with a transfer station between them , and gates, a double and a single , tripped at 120, and 90ºc , 90c . check your patio storage with IR scanners , , embed termocouples in the floor level and if posisble a floor cooling circuit .

remember remove the very fine fraction as soon as possible .

if in doubt drop me a line .

marco ■

Originally Posted by Marco A. Flores

simple enough if you are a Midrex unit , make sure the discharge temperature is as low as possible , les than 90 C preferably less than 65ºc then make sure the inert gas irrigation of the bottom sel is operating check the composition of the inlet gas , allow a minimun amount of oxygen , less than 1% if possible , but not cero..

do the sme with the seals of the blending bin (so called passivation bin) make sure the inerted bin has enhanced flow , and that your solids flow pattern does not segregate the fine material , then take samples of the out flow from the reactor and from the passivation bin , check re-activity ratio calculate the temperature rise in your secondary storage to insure that it cannot reach more than 120ºc or so , eliminate the paralleled skirts from your belt feeders en bottom of your bins , give them an angle . check your overall material hanf+dling system for ignition sources, change your Ir sensor to cover the whole belt area , with no more than 8 inches diemeter spots , redundant self checking coverage , use two station with a transfer station between them , and gates, a double and a single , tripped at 120, and 90ºc , 90c . check your patio storage with IR scanners , , embed termocouples in the floor level and if posisble a floor cooling circuit .

remember remove the very fine fraction as soon as possible .

if in doubt drop me a line .

marco

Marco,

It sounds as though you have first hand experience in DRI fires. I'm not in agreement that discharge temperature can be up to 90C as reox can take place with atmosphere moisture well below that. I also do no like passivation bins, but prefer storage buildings and separate storage blocks or areas to pile DRI and let it passivate (surface reox) on its own. A pass bin will force the passivation faster but will also generate combustible gases if it gets away from you. And I don't like using seal gas (by products of combustion with O2 and CO2 as components which add to reoxidation. Also the friction from these gases will cause added heat. All these cases are worse in areas next to salt water and marine air.

Many of the areas you mention are valid but there is much more to it than storage and passivation.

My email is: tcinc002@aol.com, attn: Thomas j Coyne jr, T.C.Inc. ■

I am sorry you do not agree ... If you have a real case we can discuss it ....

Marco

Regarding storage temperature , the storage bin geometry will affect the max temp in storage , flat floor storage upp to 2000 tons in one pile HYL 1 fresh Dri separated at 90º had experienced temps up to 150 without runaway reox and HYL 1 DRI is a mix of high temperature and low temperature reduced Iron , I do not believe you can get worse than that .

Open storage up to 200 tons single pile sepperated at 65ºc had experienced rain pouring rain without runaway reox, with pile temps up to 110 after storage when properly screened In pile oxigen content near cero. , temperture will normally rise during storage, oxygen in pile will normally drop , some companies have the practice of reshuffling the storage to dissipate heat , in PTKrakatao they call it jalan jalan...and they claim success every time .

this is not a simple matter at all , reactivity measurements can give you data for decision making regarding open storage , rain or no rain , salt water or not ..MIdrex or HYL ...

regards

Marco ■