Hole jet reactor and a process for the preparation of an isocyanate using the reactor
The present invention relates to a hole-jetting type reactor and its applications, in particular to a process for the production of isocyanates by the phosgenation of aliphatic or aromatic diamines or triamines in the gas phase using this reactor. The present invention achieves a good mixing and reacting result of the gas-phase phosgenation reaction at a high temperature by improving the mixing of reactants in the reactor to reduce the possibility of forming swirls and eliminate negative pressure produced at a local jet area, which can finally reduce back-mixing and formation of solid by-products.
1. A hole-jetting type reactor, comprising:
an internal feed tube;
an external feed tube coaxial with the internal feed tube, the external feed tube having two ends, wherein the internal feed tube and the external feed tube define an annular space therebetween, and wherein the two ends of the external feed tube are closed;
a convergent channel coaxially connected to a downstream part of the internal feed tube;
a necking tube coaxially connected with the convergent channel, wherein the cross sectional area of the necking tube is less than that of the internal feed tube;
a divergent channel coaxially connected to the downstream part of the necking tube;
a reaction tube coaxially connected with the divergent channel, wherein the cross sectional area of the reaction tube is greater than that of the necking tube; and
2 to 20 holes in the wall of the downstream part of the internal feed tube or in the wall of the convergent channel,
wherein part or all of the holes are arranged at the same cross section of the internal feed tube or the convergent channel, and
wherein the cross section is perpendicular to the flow direction of a reactant in the internal feed tube, and distributed symmetrically, and
wherein the cross sectional area of the holes totals 2% to 30% of the cross sectional area of the internal feed tube.
2. The hole-jetting type reactor according to claim 1 , wherein the reactor comprises 4 to 10 holes, and the total cross sectional area of the holes is 5% to 15% of the cross sectional area of the internal feed tube.
3. The hole-jetting type reactor according to claim 2 , wherein the holes are arranged in the wall of the downstream part of the internal feed tube and the distance from the plane of the holes to the beginning of the convergent channel is in the range of about 0 to 5 cm, with the plane of the holes being perpendicular to the flow direction of reactant in the internal feed tube; or
wherein the holes are arranged in the wall of the convergent channel and distributed in the region from the beginning to the central cross section of the convergent channel.
4. The hole-jetting type reactor according to claim 1 , wherein an angle α between the wall of the convergent channel and the flow direction of reactant in the internal feed tube is 30 to 60 degrees, and an angle β between the wall of the divergent channel and the flow direction of reaction materials in the reaction tube is 30 to 60 degrees; and the ratio of length to diameter of the necking tube is 1:1 to 15:1.
5. The hole-jetting type reactor according to claim 4 , wherein the ratio of length to diameter of the necking tube is 3:1 to 10:1, and the inner diameter of the necking tube is 0.2 to 0.8 times the inner diameter of the internal feed tube.
6. The hole-jetting type reactor according to claim 5 , wherein the inner diameter of the necking tube is 0.4 to 0.7 times the inner diameter of the internal feed tube, and the inner diameter of the reaction tube is equal to that of the internal feed tube.