Method for rapidly mixing different kinds of gas

Abstract

A method for rapidly mixing two kinds of gas which comprises introducing one kind of gas having a higher density than the other kind of gas into the upper part of a cyclone-type gas mixing chamber through an upper gas inlet pipe communicating with a hole bored in the mixing chamber in a tangential direction, and simultaneously introducing the other kind of gas into the lower part of said gas mixing chamber through another gas inlet pipe communicating with a hole formed in the mixing chamber and disposed in the opposite tangential direction to that in which said upper gas is swirled in the gas mixing chamber, wherein the vertical distance between the two gas inlet pipes is 1.5 to 3.0 times the diameter of the upper gas inlet pipe, the lower gas enters the mixing chamber at a linear velocity 1.15 to 20.0 times that of the upper gas, and the upper gas has a vortical flow at a swirling linear velocity 1.0 to 3.5 times the vertical velocity at which said gas is gradually brought downward while spirally flowing.

Description

This invention relates to a method for mixing different kinds of gas, and more particularly to a method for rapidly mixing different kinds of gas to promote reaction therebetween.

Where two kinds of gas are mixed, there has heretofore been used a cyclone-type gas mixing chamber illustrated in FIGS. 1 and 2 in order to carry out mixing with higher efficiency. As apparent from these figures, there is introduced one kind of gas 3 into a cylindrical mixing chamber 1 through a vertical gas inlet pipe 2 communicating with a hole bored at the top center of said chamber 1 to be dispersed therein, whereas the other kind of gas 5 is brought into the chamber 1 through a tangential gas inlet pipe 4 communicating with a hole formed in the upper periphery of the cylindrical mixing chamber 1 for a vortical flow. The gas mixture 8 in the chamber 1 is drawn off through a vertical gas outlet pipe 7 communicating with the bottom opening of a funnel section 6 integrally fitted to the underside of the mixing chamber 1.

Even a cyclone-type gas mixing chamber of the above-mentioned construction fails to effect the rapid mixing of two kinds of gas. For uniform mixing, the mixing chamber 1 would have to be considerably elongated. Further, if the two kinds of gas widely vary in temperature or density, then there will generally be presented greater difficulties in attaining homogeneous mixing.

It is accordingly an object of this invention to provide a method for rapidly mixing different kinds of gas by improving the prior art cyclone method, using a mixing chamber having even a small capacity.

Another object of the invention is to provide a method for attaining the rapid homogeneous mixing of different kinds of gas widely varying in temperature or density.

These objects can be attained by the method of this invention for rapidly mixing different kinds of gas, which comprises introducing one kind of gas having a higher density than another kind of gas into the upper part of a cyclone-type gas mixing chamber through an upper gas inlet pipe communicating with a hole bored in said chamber in a tangential direction; and simultaneously conducting another kind of gas into the lower part of said chamber through another lower gas inlet pipe communicating with a hole formed in said mixing chamber and disposed in a tangential and opposite gas swirling direction to that of the gas introduced in the chamber through the upper gas inlet pipe, wherein the vertical distance between the two gas inlet pipes is from 1.5 to 3.0 times the diameter of the upper gas inlet pipe; the lighter gas is conducted through the lower gas inlet pipe at a linear velocity 1.15 to 20.0 times that at which the denser gas is brought into the mixing chamber through the upper gas inlet pipe; and the denser gas supplied to the mixing chamber through the upper inlet pipe makes a vortical flow at a swirling linear velocity 1.0 to 3.5 times the vertical velocity at which said gas is gradually brought downward while spirally flowing.

Other important objects and advantageous features of this invention will be apparent from the following description and accompanying drawings, wherein, for the present purpose of illustration only, specific embodiments of this invention are set forth in detail.

In the drawings:

FIG. 1 is an elevational view of a cyclone-type gas mixing chamber of the prior art;

FIG. 2 is a plan view of FIG. 1;

FIG. 3 is an elevational view of a cyclone-type gas mixing chamber according to the present invention;

FIG. 4 is a plan view of FIG. 3;

FIG. 5 is an elevational view of a cyclone-type gas mixing chamber according to another embodiment of the invention;

FIG. 6 is a plan view of FIG. 5;

FIG. 7 is an elevational view of a cyclone-type gas mixing chamber according to still another embodiment of the invention; and

FIG. 8 is a plan view of FIG. 7.

As previously described, the prior art cyclone-type gas mixing chamber illustrated in FIGS. 1 and 2 presents difficulties in effecting the easy homogeneous mixing of two kinds of gas. Unlike FIGS. 1 and 2, the gas mixing chamber according to the method of this invention is characterized in that two gas inlet pipes are fitted to the upper and lower parts of the periphery of a gas mixing chamber in opposite tangential directions so as to cause the two kinds of gas brought into the mixing chamber to flow vortically in opposite directions. In this case, it is required that the vertical distance between both gas inlet pipes be 1.5 to 3.0 times the diameter of the upper inlet pipe, and that the denser gas be carried through the upper pipe. If the distance between both inlet pipes departs from the above-mentioned range or the lighter gas is ejected into the chamber through the upper inlet pipe, then the desired object will not be obtained. Further, it has been experimentally found that the following two conditions should be fully met. Namely, the lighter gas should be carried through the lower gas inlet pipe at a velocity 1.15 to 20.0 times that at which the denser gas is conducted through the upper gas inlet pipe, and further said denser gas should make a vortical flow in the mixing chamber at a swirling linear velocity 1.0 to 3.5 times the vertical linear velocity at which said gas is gradually brought downward while spirally flowing. (The ratio of the vortical linear velocity of the denser gas to its descending velocity is generally referred to as the swirl ratio.) Unless these two conditions are fully satisfied, the two kinds of gas could not be homogeneously mixed.

There will now be described the operation of the cyclone-type mixing chamber of this invention shown in FIGS. 3 and 4 with all the aforesaid conditions fully met. Both sides of a cylindrical gas mixing chamber 11 are fitted with an upper gas inlet pipe 12 and a lower gas inlet pipe 14 disposed in parallel and in opposite tangential directions, with the vertical distance between both pipes 12 and 14 chosen to be 1.5 to 3.0 times the diameter of the upper gas inlet pipe 12. when introduced into the gas mixing chamber 11 through the upper inlet pipe 12, the denser gas 13 is gradually brought downward while making a vortical flow along the inner wall of the mixing chamber 11. On the other hand, the lighter gas 15 conducted into the gas mixing chamber 11 through the lower inlet pipe 14 makes an opposite vortical flow to the denser gas 13 and vigorously strikes against said denser gas 13 descending from above while spirally flowing, thus effecting rapid mixing.

In FIGS. 3 and 4, the two gas inlet pipes 12 and 14 are fitted to the mixing chamber 11 in opposite tangential directions. However, provided the two kinds of gas brought into the mixing chamber 11 flow vortically in opposite directions, the two horizontal gas inlet pipes may define any desired angle. This condition is exemplified in FIGS. 5 and 6. Namely, the two horizontal gas inlet pipes 22 and 24 are fitted to the same side of the gas mixing chamber in the same vertical plane and in opposite tangential directions, defining an angle of 180.degree.. Where there are rapidly mixed three or more kinds of gas, the densest kind of gas is introduced into the mixing chamber through the upper inlet pipe, and the remaining lighter kinds of gas may be conducted into the mixing chamber through a lower inlet pipe system consisting of a plurality of component pipes which are fitted to the mixing chamber in the same level and in such tangential direction as causes the lighter kinds of gas carried therethrough to make an opposite vortical flow to the descent kinds of gas.

FIGS. 7 and 8 show a gas mixing chamber for mixing five kinds of gas. The densest kind of gas is carried into the mixing chamber through an upper gas inlet pipe 32. The other four lighter kinds of gas are brought into the mixing chamber through lower gas inlet pipes 34a, 34b, 34c and 34d respectively so as to make an opposite vortical flow to the densest kind of gas taken into the mixing chamber through the upper inlet pipe 32. In this case, too, the previously mentioned conditions should be followed, excepting that said four lighter kinds of gas introduced into the mixing chamber through the lower inlet pipes 34a, 34b, 34c and 34d should make a vortical flow at a mean velocity 1.15 to 20.0 times that at which the densest kind of gas brought into the mixing chamber through the upper inlet pipe 32 makes an opposite vortical flow. This modified process attains the rapid mixing of several kinds of gas.

The gas mixing chamber of FIGS. 7 and 8 provided with a plurality of gas inlet pipes is not only adapted to mix several kinds of gas, but also has the advantage of facilitating the quick mixing of two kinds of gas widely varying in density which has heretofore been considered appreciably difficult, by introducing the lighter gas into the mixing chamber uniformly through a plurality of lower gas inlet pipes.

The method of the invention not only attains the rapid mixing of two or more kinds of gas independently of their temperature, but also quickly completes the chemical reactions which would accompany said mixing in a mixing chamber having even a small capacity.

There will now be described, for example, the case where there is prepared reducing gas used in the operation of a blast furnace by mixing blast furnace gas at a temperature of 1250.degree.C with coke oven gas at 700.degree.C.

Mixing of both kinds of gas gives rise to the following reactions:

CH.sub.4 .fwdarw. 2H.sub.2 + C

C + CO.sub.2 .fwdarw. 2CO

When mixed by the method of this invention, both kinds of gas quickly react with each other, decreasing the content of free carbon and increasing that of CO in the produced gas. Imperfect mixing of both kinds of gas would cause unreacted CH.sub.4 and CO.sub.2 to remain in the gas mixture, probably giving rise to larger carbon loss in attaining the reducing effect for blast furnace operation.

The above-mentioned two kinds of gas were mixed in a cyclone-type gas mixing chamber shown in FIGS. 5 and 6. In this case, the denser blast furnace gas was taken into a cyclone-type gas mixing chamber through the upper gas inlet pipe 22 and the lighter coke oven gas into said mixing chamber through the lower inlet pipe 24. The blast furnace gas had a density 2.75 times that of the coke oven gas. The value of swirl ratio of the introduced denser gas was 1.8. Table 1 below presents the compositions of gas mixtures obtained from the mixing chamber by varying the ratio of the velocity Vc at which the coke oven gas was ejected from the lower inlet pipe 24 to the velocity Vb at which the blast furnace gas was supplied from the upper inlet pipe 22.

Table 1 ______________________________________ Composition of gas mixture obtained from the gas mixing chamber (% by volume) ______________________________________ Value of Vc/Vb Component 1.0 1.2 1.5 2.0 ______________________________________ CO.sub.2 12 9 1 <1 CO 28 31 39 41 H.sub.2 26 39 37 38 N.sub.2 21 21 21 21 CH.sub.4 13 10 2 0 ______________________________________

As clearly seen from Table 1 above, where the value of Vc/Vb was 1.0, mixing was carried out insufficiently, leaving a large amount of CH.sub.4 and CO.sub.2, and where said value was larger than 1.2, content of CH.sub.4 and CO.sub.2 prominently decreased. When the value of Vc/Vb reached 2.0, mixing and reaction were fully effected, substantially eliminating CH.sub.4 and CO.sub.2.

Further, the blast furnace gas and the coke oven gas were mixed in the present mixing apparatus by varying the swirl ratio in the range of from 0.8 to 3.8 with the value of the aforesaid Vc to Vb ratio kept at 1.5, the compositions of the resulting gas mixtures are presented in Table 2 below.

Table 2 ______________________________________ Composition of gas mixture obtained from the mixing chamber (% by volume) ______________________________________ Value of swirl ratio Component 0.8 1.0 2.6 3.5 3.8 ______________________________________ CO.sub.2 3 <1 <1 1 1 CO 36 39 40 40 40 H.sub.2 30 37 38 37 36 N.sub.2 21 21 21 21 21 CH.sub.4 10 2 <1 1 2 ______________________________________

As apparent from Table 2 above, where the value of swirl ratio was smaller than 1.0, the content of CH.sub.4 and CO.sub.2 in the gas mixture noticeably increased. Where the value of swirl ratio was in the range of from 1.0 to 3.5, there was almost no CH.sub.4 and CO.sub.2, and when the value exceeding 3.5, the content of CH.sub.4 rather tended to rise.

Claims

1. A method for rapidly mixing at least two different kinds of gases which comprises introducing a first gas into the upper part of a cyclone-type gas mixing chamber having a longitudinal axis through an upper gas inlet pipe disposed in a tangential direction to the periphery of said chamber; and simultaneously introducing a second gas having a lower density than said first gas into the lower part of said mixing chamber through a lower gas inlet pipe disposed in a tangential direction to said periphery and in an opposite gas swirling direction to that of said first gas, both gases swirling vortically about said longitudinal axis, the vertical distance between said gas inlets being from 1.5 to 3.0 times the diameter of said upper gas inlet pipe; said second gas entering said mixing chamber at a linear velocity 1.15 to 20.0 times that at which said first gas enters said mixing chamber; said first gas supplied to the mixing chamber through the upper gas inlet pipe having a vortical flow at a swirling linear velocity 1.0 to 3.5 times the vertical velocity at which said gas is gradually brought downward while spirally flowing; whereby said gases are mixed, and withdrawing said mixed gas through an outlet positioned in said

2. A method for rapidly mixing and reacting blast furnace gas with coke oven gas which comprises introducing blast furnace gas into the upper part of a cyclone-type gas mixing chamber having a longitudinal axis through an upper gas inlet pipe in a tangential direction to the periphery of said chamber; and simultaneously introducing coke oven gas into the lower part of said mixing chamber through a lower gas inlet pipe disposed in a tangential direction to said periphery and in an opposite gas swirling direction to that of said blast furnace gas; both gases swirling vortically about said longitudinal axis; the vertical distance between both gas inlet pipes being from 1.5 to 3.0 times the diameter of said upper gas inlet pipe; the coke oven gas entering said mixing chamber at a linear veloctiy 1.15 to 20.0 times that at which said blast furnace gas enters said mixing chamber; said blast furnace gas entering said mixing chamber to cause vortical flow at a swirling linear velocity 1.0 to 3.5 times the vertical velocity at which said gas is gradually brought downward while spirally flowing, whereby said gases are mixed, and withdrawing said mixed gas through an outlet positioned in said mixing chamber below said lower gas inlet pipe.