Help with practical Dust Explosion assessment 1

[DoctorBond]

Dear All,

I need some help regarding dust explosions. I have to assess wheather we can blow Titanium Oxide (TiO2)to atmosphere (about 2.5 Kg/day) or collect it in a dust collector (I am still working through the UK environmental legislation).

Assuming a dust collector is used however, how can I determine the dust explosion hazard??? Is there still a hazard in collectors??? As you can see I am quite new to the dust explosion subject, and all help is much appreciated.

I understand that dust explosions are related to temperature, any Idea where I can find out the minimum concnetratio at a given temperature for a dust explosion of Titanium Oxide (Ti02)????

 

[SAFTENG]

Yes there remains a dust explosion hazard in dust collectors, as several hundred blow up annually. You need to reference NFPA 481 - Standard for the Production, Processing, Handling, and Storage of Titanium.

Here's some of what NFPA 481 says about titanium dusts and dust collection systems:

Industry experience has clearly demonstrated that an eventual explosion can be expected where a bag- or media-type collector is used to collect titanium fines. Seldom, if ever, can the source of ignition be positively identified. In those unusual instances where it becomes necessary to collect very small fines for a specific commercial product, it is customary for the producer to employ a bag- or media-type collector. Since this presents a strong explosion potential, the bag- or media-type collector should be located a safe distance from buildings and personnel.

If a bag- or media-type collector is used, the shaking system or dust removal system can be such as to minimize sparking due to frictional contact or impact. Pneumatic or pulse-type shaking is more desirable than systems that use mechanical moving parts such as fan-driven systems because no mechanical moving parts are involved in the dusty atmosphere. If the bags are provided with grounding wires, they can be positively grounded through a low-resistance path to ground. Where bags are used, it is customary that the baghouse be protected by an alarm that indicates excessive pressure drop across the bags. An excess air temperature alarm is also frequently used. A bag- or media-type collector is customarily located at least 50 ft (15 m) from any other building or operation. It is not customary to permit personnel to be within 50 ft (15 m) of the collector during operation or when shaking bags. Explosion vents are usually built into the system, as described in NFPA 68, Guide for Venting of Deflagrations. Care is customarily exercised in locating the vents because of the possibility of blast damage to personnel or adjacent structures.

Hope this leads you in the right direction. You can subscribe to NFPA at

http://www.NFPA.org

Bryan

http://www.SAFTENG.net

 

[JEBoone]

TiO2 will not react with air and is not a dust hazard. Ti metal would be.

Jim

 

[DoctorBond]

Dear All, many thanks for your replies, the engineering department, that designs the projects was unaware of dust hazards in general. Armed with your replies, and a bit more information from other sources, I have at least provided them with enough information (now they know there are cetain standards/code of practice) they should follow. I am still reading up on the subject, so to gain a better understanding, but many thanks for furthering my education and providing me enough insight to make a point to the design engineers!!

 

[butelja]

The TiO2 itself is not combustible, as mentioned earlier. However, if the conveying lines are not properly bonded and grounded, conveying any bulk solid pneumatically can generate large voltages and potential arcing. This could be a problem if the line runs through a classified area, or personnel may touch the line. I've seen arcs jump 4-5" across a clear plastic sight glass in a railcar lime unloading system.