Patent Application
20150273410
This invention relates to a novel apparatus for mixing fluids, especially amine and phosgene, and to a process for mixing amine and phosgene in order to obtain carbamoyl chloride and isocyanate.
Many documents disclose nozzles for mixing fluids, especially reacting fluids. One particular example is found in the phosgenation reaction in which rapid mixing is a key parameter. Hence, many designs have been proposed for such nozzles, mostly with coaxial jets, which can be impinging or not.
However, there is still a need to further improve the mixing efficiency of the nozzles, especially in the phosgenation reaction.
An object of this invention is therefore to provide an apparatus for mixing at least first and second fluid, comprising (a) a first nozzle comprising a first flow duct defining a first flow chamber, and having a first nozzle tip having a first discharge opening; and (b) a second nozzle comprising a second flow duct defining a second flow chamber, and having a second nozzle tip having a second discharge opening;
wherein said first flow duct and said second flow duct are spirally wrapped each over the other;
wherein during operation of said apparatus, the first fluid flowing in the first flow chamber and exiting through the first discharge opening forms a first fluid jet, and the second fluid flowing in the second flow chamber forms at the second discharge opening a second fluid jet, said first and second fluid jets impinging upon each other, thereby mixing the first and second fluids.
The invention especially provides a substantially round apparatus for mixing at least first and second fluid, comprising: (a) a first nozzle comprising a first flow duct defining a first flow chamber, and having a first nozzle tip having a first discharge opening; and (b) a second nozzle comprising a second flow duct defining a second flow chamber, and having a second nozzle tip having a second discharge opening;
wherein said first flow duct and said second flow duct are spirally wrapped each over the other according to an Archimedean spiral having between 1 and 20 turns, and wherein said first and second nozzles are tapered;
wherein during operation of said apparatus, the first fluid flowing in the first flow chamber and exiting through the first discharge opening forms a first fluid jet, and the second fluid flowing in the second flow chamber forms at the second discharge opening a second fluid jet, said first and second fluid jets impinging upon each other, thereby mixing the first and second fluids.
Another object of this invention is also to provide a process for mixing at least first and second fluid, comprising the steps of: (a) forming a first fluid jet, consisting of the first fluid, at a first discharge position; (b) forming a second fluid jet, consisting of the second fluid, at a second discharge position; and (c) spirally wrapping each fluid jet over the other so that the said first and second fluid jets impinge upon each other, thereby mixing the first and second fluids.
The invention especially provides a process for mixing at least first and second fluid, comprising the steps of: (a) forming a first fluid jet, consisting of the first fluid, at a first discharge position; (b) forming a second fluid jet, consisting of the second fluid, at a second discharge position; and (c) spirally wrapping each fluid jet over the other according to an Archimedean spiral having between 1 and 20 turns so that the said first and second fluid jets impinge upon each other, thereby mixing the first and second fluids.
The process of the invention is especially useful for the production of isocyanates; the invention hence also provides a process for manufacturing isocyanates, comprising the mixing process of the invention as applied to amine and phosgene, followed by the step of reacting the mixed amine and phosgene.
These processes are notably carried out in the apparatus of the invention.
Other objects, features and advantages will become more apparent after referring to the following specification.
The invention is based on the use of a spiral-like nozzle, referred to hereinafter as a spiral nozzle. The specific geometry allows thin flows impinging on each other while at the same time having high mixing energy.
Referring now to
This device, while being known for many years still requires improvement in terms of mixing efficiency.
The nozzle assembly of the present invention thus provides an apparatus for mixing at least first and second fluids, the apparatus comprising first nozzle assembly means for forming a first spiral fluid jet 206, consisting of the first fluid, and second nozzle assembly means for forming a second spiral fluid jet 207 coaxial with and wrapped around said first spiral fluid jet 206, the second spiral fluid jet consisting of the second fluid, so that second spiral fluid jet 207 impinges upon first spiral fluid jet 206, thereby mixing the first and second fluids. This part will optionally be referred to as the nozzles sub-assembly 201. It would be possible to provide further ducts for further fluids, if this is necessary.
Referring now to
In the embodiment as shown, one will notice that said first flow chamber 220 has dimensions substantially decreasing along the first flow duct towards the first discharge opening. The ratio (gap of supply end 230) to (gap of discharge opening 210) may vary from 1 to 10, preferably 2 to 4.
In the embodiment as shown, one will notice that said second flow chamber 221 has also dimensions substantially decreasing along the second flow duct towards the second discharge opening.
In the embodiment as shown (as will be further indicated on
Here the various dimensions of the respective discharge openings (i.e. width or gap) are chosen so as to impart the required velocities. Typically, the (superficial) velocity of the jet 206 will be 5-90 ft/sec, preferably 20-70 ft/sec, Typically, the (superficial) velocity of the jet 207 will be 5-70 ft/sec, preferably 10-40 ft/sec. The gap at nozzle tip 204 is typically 0.04″-0.20″, preferably 0.05″-0.10″. The gap at nozzle tip 205 is 0.04″-0.20″, preferably 0.05″-0.10″. These gaps may be constant or may be varied along the spiral. The wall thickness, or separating gap, is generally less than each of the gap for the discharges openings and will typically be 0.03″-0.10″, preferably 0.03″-0.06″. If one considers each discharge opening, one may measure an approximate length for the discharge (considered as a deployed line). The discharge openings have typically a length L such that the ratio L on gap is from 20 to 200, preferably 60 to 150. The discharge gap 210 can be smaller, equal or larger than the discharge gap 211. The discharge gap 211 can also vary from the outer to the inner, and e.g. 211 on outer is half 211 on inner. The discharge gap 210 can also vary the same way, if need be.
Referring now to
Referring now to
Referring now to
As can be derived from the preceding drawings, the nozzle assembly of the invention is spirally wound or wrapped on itself. The term “ducts spirally wrapped each over the other” is intended to cover those cases where one duct will wrap the other over more than one turn. It will be generally considered, for the purpose of the instant invention, that a curve will form a turn if there exits a straight line that intersects said curve in at least 3 different locations. One may count the number of turns by counting the number of intersections of said straight line with the curve.
One way of expressing this is to count the number of intersections as 2n+1, where n is the number of turns. Spiral is here intended to cover any substantially continuous curve drawn at ever increasing distance from fixed point. Wrapped is here to denote that there is more than one turn, resulting in an overlap of ducts. The “turn” need not necessarily mean round, although this is the preferred embodiment, and this covers also spiral-like squared wrapped ducts. Asymmetry resulting from this design enhances mixing of the two fluids. The number of turns is not critical, and may vary between broad limits such as between 1 and 20 turns. In one embodiment, this number is quite high, for example for the first embodiment depicted, which may be depicted as the “tight spiral” embodiment. The number of turns may vary here between 3 and 10. In another embodiment, this number is quite low, and may be depicted as the “open spiral” embodiment.
The number of turns may vary then between 1.05 and 1.5. The case where double ducts are wrapped is also foreseen.
The first and second flow ducts are preferably spirally wrapped each over the other according to an Archimedean spiral, and more preferably according to an Archimedes' spiral.
An Archimedean spiral is a spiral with polar equation r=aθ1/y, where r is the radial distance, θ is the polar angle, and y is a constant which determines how tightly the spiral is “wrapped”. An Archimedes' spiral is the spiral for which y is one.
The surfaces of the nozzle assembly of the invention can also be treated and/or finished with conventional surface treatments including coatings, polishing, adding ridges or grooves, if need be.
The invention provides several advantages over prior art nozzle assemblies. One advantage is a substantial gain in mixing efficiency, compared to prior nozzle assemblies. The specific geometry of the nozzle does not require impingement on other surfaces, and this avoids erosion and expensive alignment.
The present invention may also provide for adjustment of the nozzles sub-assembly 201 (including the cover plate 251 and associated carriages, if any) with respect to the lower housing 250. Axial movement of nozzles sub-assembly 201 with relation to lower housing 250 is achieved by mechanical means (not shown) for adjustment of the axial position of sub-assembly 201. These mechanical means may typically comprise a shaft on which the sub-assembly is mounted and means for displacement of this shaft. By adjusting the sub-assembly with respect to the lower housing, one may then vary the dimensions of the outer duct 203 proximate the lower housing 250 and thus the flow rate through this duct. This will provides adjustment means for the reaction that will take place. An advantage of the embodiment with movable sub-assembly is the on-line adjustability of the cross-sectional area for flow of the extreme outer jet. On-line adjustability denotes the ability to make adjustments without undue interference with an ongoing process. In commercial scale processes, on-line adjustability allows for frequent adjustment of the nozzles for, e.g., maximum pressure drop or flow rate at the extreme outer discharge point of the nozzle. Another advantage is improved turn-down capability of commercial processes. The adjustability may allow a wider range of operating rates for some processes. Another advantage is the ability to stroke sub-assembly relative to lower housing 250 through its full travel path with the nozzle assembly installed. Commercial scale mixer assemblies can become plugged with debris or solid deposits. Stroking sub-assembly 201 on lower housing 250 can scrape debris and deposits lodged in extreme outer duct, in case no tine is present at this duct location. The nozzle assembly is simple to manufacture and install, where one process for its manufacture is electrical wire discharge machining, which is a technology widely available. A process for manufacturing the nozzles sub-assembly of the apparatus of the invention will typically comprise the steps of (a) providing a preform; and (b) wire electrical discharge machining said preform. The housing may be manufactured using conventional machining. One further advantage is that there are no continuously moving or rotating parts, avoiding thus any mechanical wear of the system.
The invention is especially useful for very fast chemical reactions where fast mixing is crucial. Hence, the invention is useful as a pre-phosgenation reactor for the preparation of isocyanates. In this embodiment, the fluid flowing through the inner path is a primary amine, optionally dissolved in a solvent. In this embodiment, the fluid flowing through the outer path is phosgene, optionally dissolved in a solvent. Hence, the invention is useful for the manufacture of various isocyanates, and may e.g. be selected from aromatic, aliphatic, cycloaliphatic and araliphatic polyisocyanates.
The nozzle assembly allows for minimizing the excess phosgene used in the reaction, or having higher blend strength or higher output. Blend strength refers to the concentration of amine within the solvent and amine mixture that comprises the amine feed to the nozzle. It is possible, as in the known techniques, to recycle a solution of solvent, phosgene, and isocyanate singly or in combination back into the phosgene flow. In one embodiment, it is preferred not to recycle this solution.
In particular are produced the aromatic polyisocyanates such as methylene diphenyl diisocyanate (MDI) (e.g. in the form of its 2,4′-, 2,2′- and 4,4′-isomers and mixtures thereof), and mixtures of methylene diphenyl diisocyanates (MDI) and oligomers thereof known in the art as “crude” or polymeric MDI (polymethylene polyphenylene polyisocyanates) having an isocyanate functionality of greater than 2, toluene diisocyanate (TDI) (e.g. in the form of its 2,4- and 2,6-isomers and mixtures thereof), 1,5-naphthalene diisocyanate and 1,4-diisocyanatobenzene (PPDI). Other organic polyisocyanates which may be obtained include the aliphatic diisocyanates such as isophorone diisocyanate (IPDI), 1,6-diisocyanatohexane and 4,4′-diisocyanatodicyclohexylmethane (HMDI). Still other isocyanates that can be produced are xylene diisocyanates, phenyl isocyanates.
If need be, the geometry of the nozzle assembly of the invention can be adapted to the specific isocyanate to be manufactured. Routine tests will enable one skilled in the art to define the optimum values for the gaps and lengths, as well as operative conditions.
The nozzle assembly of the invention can be used in a classical continuously stirred tank reactor (with or without baffles). The nozzle assembly can be in the vapor space or submerged. The nozzle assembly of the invention can be used in all existing equipment with minimal adaptation, thus saving costs. Also, the nozzle assembly of the invention can be used in any type of reactor; for example the nozzle assembly can be mounted at the bottom of a rotary reactor equipped with impellers and baffles or the nozzle assembly can be used as an injection device in a rotor/stator type reactor.
The process conditions are those typically used. The phosgene:amine molar ratio is generally in excess and ranges from 1.1:1 to 10:1, preferably from 1.3:1 to 5:1. A solvent is generally used for the amine and the phosgene. Exemplary solvents are chlorinated aryl and alkylaryl such as monchlorobenzene (MCB), o- and p-dichlorobenzene, trichlorobenzene and the corresponding toluene, xylene, methylbenzene, naphthalene, and many others known in the art such as toluene, xylenes, nitrobenzene, ketones, and esters. The amine blend strength can be from 5 to 40 wt % while the phosgene concentration can be from 40 to 100 wt %. The temperature of the amine flow is generally comprised from 40 to 80° C. while the temperature of the phosgene flow is generally comprised from −20 to 0° C. The process is conducted at a pressure (at the mixing zone) generally from atmospheric to 100 psig.
It is also possible to use one or more further reactors (esp. CSTRs) to complete the reaction. In the process for manufacturing isocyanates, it is also possible to use typical units for recycling solvent and/or excess phosgene, for removing HCl and recycling HCl to chlorine, etc. The depicted and described preferred embodiments of the invention are exemplary only and are not exhaustive of the scope of the invention.
This application is a divisional of U.S. patent application Ser. No. 11/910,945, pending, which is the National Phase of International Application PCT/EP2006/060488 filed Mar. 6, 2006 which designated the U.S. and which claims priority to provisional U.S. Pat. App. No. 60/669,545 filed Apr. 8, 2005. The noted applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60669545 | Apr 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11910945 | Feb 2010 | US |
| Child | 14468363 | US |
