Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Organic component
Reexamination Certificate
1994-09-22
2001-09-18
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Organic component
Reexamination Certificate
active
06290923
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a stack emission control system, preferably for use in removing organic pollutants from air present in polyurethane foam processing plants. More specifically, the stack emission control system includes a packed tower scrubber containing inert material as the packing and pH-adjusted water as the wash fluid. The pH-adjusted water serves to separate and remove the organic pollutants as water-soluble solids from the air prior to exhaust of the air from a plant into the surrounding atmosphere.
BACKGROUND OF THE INVENTION
It is known in the art to use a scrubber unit to remove impurities from air. It is recognized that the scrubber unit will contain a packing or filter material through which the polluted air will move and which is wet by a scrub or wash fluid. The type of filter and wash fluid used depends on the type of impurities which are to be separated and removed from the air. Generally, for effective removal of impurities from air, however, specific filter structures and/or specialty chemicals are required. Such filters normally require regeneration and use of specialty chemicals can result in high cost.
For example, U.S. Pat. No. 4,460,552 discloses a process for separating and removing impurities from air. The impurity-containing air is fed into a scrubber unit and passed through a filter material having an absorbent medium sprayed thereon. The filter pack is described as being one or more packs of stratified filter mats having a specified structure for removing the impurities from the air. The absorbent medium which is sprayed over the filter mats is stated to depend on the particular impurity to be removed, i.e., when an alkaline-reacting impurity is to be absorbed, an acidic absorbent is utilized and when an acid-reacting impurity is to be absorbed, an alkaline absorbent medium is utilized. If the impurity is soluble in water, acidic or alkaline-reacting aqueous solutions can be utilized in the filter process. In columns 6-7 of the patent, scrubber operations using the filter mats of the patent are compared with the operation of conventional packed columns, with each scrubber using the same absorbent medium. Improved results, as shown by the increased recovery over the conventional scrubbers, are attributed to the use of the specified filter mat structure.
U.S. Pat. No. 4,172,880 states that it is recognized in the art to remove pollutants from the air prior to exhaust of the air from an industrial production area through the use of a scrubbing tower. A scrubbing tower suitable for use includes inert material as packing which is wet by a downward spray of fluid. The patent states that in the metal casing industry where the air contains contaminants such as triethylamine, dimethylethylamine, ammonia, or the like, in trace quantities that an acid solution can be used as a scrubbing liquid.
U.S. Pat. No. 2,560,635 discloses a scrubbing apparatus wherein a gas passes upward through a scrubbing or baffle means, such as touching balls. A wash fluid flows downward over the baffle means from a spray outlet positioned above the baffle means as the gas flows upward through the baffle means. The wash fluid utilized can be water alone, an aqueous solution, or any other suitable fluid. The only specific gas referred to for removal is S
2
which when contacted with wash water is changed to H
2
SO
3
.
Accordingly, the art does not disclose the use of a pH-adjusted water as a wash fluid in a packed scrubber unit utilizing only an inert material as packing to remove essentially all of the organic impurities from air present in foam processing plants where the organics to be removed include toluene diisocyanate (TDI). More particularly, the art does not disclose the removal of one or more organic pollutants, which are neither acid nor basic, from air as water-soluble solids using a pH-adjusted wash water with only inert packing. Even more specifically, the removal of toluene diisocyanate from air utilizing acidic water is not taught in the art.
OBJECTS OF THE INVENTION
A primary object of the present invention is to provide for the removal as water-soluble solids of organic pollutants or impurities from air present in polyurethane foam processing plants utilizing pH-adjusted water as a wash fluid in a packed tower scrubber utilizing only inert packing material, particularly where the organic pollutants are neither acidic nor basic in nature, resulting in substantially contaminant-free air.
A further primary object of the present invention is to provide for the removal as water-soluble solids of organic impurities which are neither acidic nor basic from air utilizing water as a wash fluid in a packed tower scrubber wherein the pH of the water has been adjusted so that the water is either alkaline or acidic, and preferably is acidic, resulting in substantially contaminant-free air.
A further primary object of the present invention is to provide for the removal, as a water-soluble solid, of toluene diisocyanate from air prior to exhaust of the air into the surrounding atmosphere through the use of acidic water as a wash fluid in a packed tower scrubber which utilizes only an inert packing material and which results in substantially contaminant-free air.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is directed to a stack emission control system for removing organic pollutants or impurities as water-soluble solids from air, which enter the air from a polyurethane foam processing operation, prior to exhaust of the air into the surrounding atmosphere. In particular, the emission control system is useful in processing lines which involve the thermal treatment of polyurethane foam, since there is the possibility of generating organic pollutants, such as toluene diisocyanate, upon the thermal decomposition of foam, such as polyether or polyester based polyurethane foams. It is desirable to remove the organic pollutants from the work area and to prevent their discharge into the surrounding atmosphere.
To remove organic pollutant-containing air from the vicinity of a foam processing line which can be either a line where the polyurethane foam is initially manufactured or where the finished polyurethane foam is subsequently treated, for example, laminated by heat treatment to textile. a canopy-type fume hood is positioned in relation to the processing line so that the hood can be utilized to take up the air containing the organic pollutants, such as toluene diisocyanate, from the line area. A duct is connected to the hood and serves as a means of conveying the impure air to a packed scrubber unit.
The scrubber apparatus can be of a conventional packed tower scrubber structure. A suitable scrubber unit contains a wash fluid reservoir in the base of the unit. The air conveyed to the scrubber is received into the scrubber unit through the duct which is connected to the scrubber unit at a point just above the wash fluid reservoir in the base of the scrubber unit. The scrubber unit has a packed column of inert packing material, such as balls or the like, to provide a torturous path through which the air will travel as the air passes upward through the scrubber unit. A pH-adjusted water wash fluid is sprayed down from one or more sprayheads which are positioned over the packing through which the air is moving. The water has had its pH adjusted so that the water has either an alkaline or acidic pH. The addition of an acid compound in a quantity sufficient to give the water an acidic pH is highly preferred and has been found to provide surprising results in the substantial complete removal of toluene diisocyanate (TDI) from air. The acidic water reacts with the substantial portion of TDI, which is the major organic contaminant present upon the thermal decomposition of polyether or polyester based polyurethane foam. The pH-adjusted water serves to separate and remove the impurities, i.e., TDI and toluene diamine (TDA) from the air as water-soluble solids. The contaminant-free air is then drawn out of the scrubber unit into an exhaust condu
Fracalossi Roland N.
Greenhouse Walter V. V.
Sollers Joseph S.
Tolen George J.
Breiner & Breiner L.L.C.
Griffin Steven P.
Wm. T. Burnett & Co.
LandOfFree
Stack emission control system for removing organic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stack emission control system for removing organic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stack emission control system for removing organic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2543493