Methanol Vapor Information Applicable to the BioPro 190
In order to prevent pressurization of the BioPro, the lid (about 10lbs for the BioPro 190) which covers the reaction chamber, is not locked down but is rather held down by its own weight. This lid seals the reaction chamber up to a pressure of about 0.11 psi. The lid seal will allow any pressure above this level to bleed off, should it develop.
Assuming that the BioPro is loaded cold (there has been no preheating of the oil), during the 8 hour reaction processes, due to thermal expansion of the gas in the vacant space above the fluid in the BioPro, as well as the partial pressure exerted by methanol as it dissolves in free air inside the vessel, there is typically some venting that occurs.
Worst case, as much as 1 cubic foot of methanol gas may be vented during this eight hour period. (In reality, this is probably closer to 0.50 cubic feet. The effects of the methanol under partial pressure cause the bulk of the initial venting to be composed almost entirely of just air.) But we’ll stick with 1 cubic foot for worst case.
To put this in perspective, the relatively small exhaust fan which cools the electronics in the top of the BioPro is rated at 250 cubic feet of gas moved per minute.
Does this venting pose a flammability issue? See analysis of Methanol Vapor Volume
Methanol’s lower flammability limit is 6.7% concentration in air. To achieve this concentration, using the maximum amount of vapors that can escape (1 cubic foot), you need to confine all of these in sealed volume of about 16 cubic feet.
This, however, is impossible with a BioPro. If you designed a rectangular space (like a coffin) to enclose the BioPro on all sides so that it just fit inside, the total volume of that space would be about 50 cubic feet. The volume of the BioPro itself is about 11 cubic feet. This means that the minimum free space that you could achieve in this sealed volume would be about 39 cubic feet, well over two times the maximum allowable volume to reach the lower flammability limit for methanol.
If you stuck the BioPro in a 36” x 40” broom closet, and it was completely sealed, you’d have over five times the maximum allowable volume to reach the lower flammability limit for methanol.
And if it was in a typical one-car garage, completely sealed, you’d have about 100 times the maximum allowable volume to reach the lower flammability limit for methanol.
How about breathing this air? Is it hazardous?
When it comes to methanol concentration in the air, OSHA designated 200ppm methanol in the air as the limit for continuous workplace exposure (all day long, every day). For non-continuous exposure, the related agency NIOSH (National Institute of Occupational Safety and Health) rates 6,000 ppm as a level immediately dangerous to health.
At www.cdc.gov/niosh, this rating is discussed and described as a conservative value. References are cited which place the actual value at around 30,000 ppm.
If a BioPro operated in a completely sealed shop, it would need to be 23’ x 23’ with 10’ ceilings (5280 cubic feet) to keep the worst case concentration in the air below 200ppm. (Although if there truly was no ventilation, you might eventually die from suffocation as you consumed all of the available oxygen due to breathing.)
So, the bottom line is: If you’ve got a large garage, and no ventilation whatsoever, you can live out there with your BioPro™ processing and have:
- no flame hazard (~1/300th of the lower flammability limit for methanol)
- no health hazard (per OSHA’s limits)
If you’ve got a one-car garage, and no ventilation whatsoever, you still have nowhere near any flame hazard (~1/100th of the lower flammability limit for methanol).
With no ventilation, the methanol levels may exceed OSHA’s limit for continuous workplace exposure. They will, however, only reach about 1/10th of NIOSH’s classification of an immediate health hazard.
With the minimum ventilation required by ANSI/ASHRAE for an occupied room, (17 CFM) you will be well under OSHA’s limit for continuous workplace exposure as well.
Frequently asked questions
How much methanol vapor does a BioPro 190 release during a batch?
Very little. In the worst case, about 1 cubic foot of methanol vapor may vent during the 8-hour reaction when the BioPro is loaded with cold oil, and the real figure is probably closer to 0.5 cubic feet because early venting is mostly air.
The roughly 10-pound lid is held down only by its own weight and seals up to about 0.11 psi, so pressure cannot build while the slight pressure limits methanol escape. For scale, the fan that cools the electronics moves 250 cubic feet per minute.
Is there a fire risk from BioPro methanol vapors in a closed garage?
No realistic one. Methanol's lower flammability limit is 6.7% in air, so the worst-case 1 cubic foot of vapor would need to be confined in a sealed space of about 16 cubic feet to become flammable.
Even a tight box built around the BioPro would leave about 39 cubic feet of free space, more than twice that amount. In a completely sealed one-car garage, vapor would reach only about 1/100th of the flammability limit, and in a large garage about 1/300th. Still keep flames and sparks away from methanol storage and handling.
Is it safe to breathe the air around a running BioPro?
Yes, with normal ventilation. OSHA's continuous workplace exposure limit for methanol is 200 ppm, and a completely sealed room of about 5,280 cubic feet (23 by 23 feet with 10-foot ceilings) would keep worst-case BioPro emissions below it.
In a small, completely unventilated one-car garage, levels could exceed the OSHA continuous limit but would reach only about one-tenth of NIOSH's 6,000 ppm immediately-dangerous level. The minimum ventilation required for an occupied room (17 CFM) keeps levels well under OSHA's limit.
Does a BioPro need ventilation or an exhaust hood to operate?
Ventilation is recommended but not required. Worst-case methanol venting from a BioPro is small enough that the minimum ventilation required by ANSI/ASHRAE for an occupied room, 17 CFM, keeps methanol in the air well below OSHA's 200 ppm continuous exposure limit.
Good airflow is still sensible, since methanol is also handled when loading the machine and during cleanup. Springboard also recommends an operating space of at least 10 by 8 feet with an 8-foot ceiling.
How does the BioPro keep methanol vapor away from its electrical components?
The BioPro separates methanol from its electronics and constantly purges the component housing. Whenever the machine has power, a 250 CFM exhaust fan ventilates the area under the lid so vapors can never reach a flammable concentration there, even if a leak occurs.
Internal hoses are stainless steel, lid ports are sealed, the methanol pumps are diaphragm style with no shaft seal, and the pump and mixing motors are rated explosion proof (Class 1, Division 2). Heat is applied indirectly through the tank walls.
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