Method and mixer apparatus for mixing gas into slurry in a closed reactor

Abstract

The mixer apparatus accordant with the invention includes a closed reactor, at least two mixers at different heights, which are on the same shaft, a gas feed pipe below the lower mixer and baffles. The blades of the mixers are mostly rectangular in shape and a minimum of six in number. The angle of inclination of the blades of the lower mixer is around 50-70° and that of the upper mixer around 25-35°. The number of baffles is at least six and their range around 20% of the reactor diameter. The invention is focused also the corresponding method.

1 - 21 . (canceled) 
     
     
         22 . A mixer apparatus for mixing gas into a slurry formed of a liquid and solids, where the apparatus consists of a closed cylindrical vertical reactor provided with a bottom and a cover, with an effective slurry height of around 1.5-2 times the diameter of the reactor, a mixer member located inside the reactor consisting of two mixers connected above each other on the same shaft, at least six, preferably eight flow baffles, directed inwards with a range from the reactor wall that is about ⅕ of the reactor diameter, and a gas feed pipe located in the bottom of the reactor, wherein
 a) the reactor is equipped with a mixer member, which consists an upper mixer and a lower mixer, whereby the straight-bladed upper mixer is equipped with at least six, preferably eight, blades, which are inclined from the horizontal at an angle of 25-35°, and the straight-bladed lower mixer is equipped with at least six, preferably eight, blades, which are inclined from the horizontal at an angle of 60-70°   
     
     
         23 . A mixer apparatus according to  claim 22 , wherein the power taken by the lower mixer is at least three times, preferably at least five times that taken by the upper mixer. 
     
     
         24 . A mixer apparatus according to  claim 22 , wherein the blades of the upper mixer are inclined from the horizontal at an angle of 30°. 
     
     
         25 . A mixer apparatus according to  claim 22 , wherein the blades of the lower mixer are inclined from the horizontal at an angle of 62°. 
     
     
         26 . A mixer apparatus according to  claim 22 , wherein the height of the lower mixer is in the region of ¼ of the mixer diameter. 
     
     
         27 . A mixer apparatus according to  claim 22 , wherein the height of the upper mixer is in the region of ⅙ of the mixer diameter. 
     
     
         28 . A mixer apparatus according to  claim 22 , wherein the height of the lower mixer is in the region of 1.5 times the height of the upper mixer. 
     
     
         29 . A mixer apparatus according to  claim 22 , wherein the diameter of the mixers is over 0.4, but a maximum of 0.5 times the reactor diameter. 
     
     
         30 . A mixer apparatus according to  claim 22 , wherein the distance of the mixers from each other is in the region of 50-70% of the effective slurry height of the reactor. 
     
     
         31 . A mixer apparatus according to  claim 22 , wherein the distance of the lower mixer from the bottom of the reactor is in the region of the diameter of the mixer. 
     
     
         32 . A mixer apparatus according to  claim 22 , wherein the width of the baffles is 12-15% of the diameter of the reactor. 
     
     
         33 . A mixer apparatus according to  claim 22 , wherein the distance between the baffles and the reactor wall is in the region of 6-8% of the reactor diameter. 
     
     
         34 . A mixer apparatus according to  claim 22 , wherein the baffle forms a heat transfer member. 
     
     
         35 . A mixer apparatus according to  claim 34 , wherein the baffle consists of tubes attached to each other by means of plate-like components. 
     
     
         36 . A mixer apparatus according to  claim 22 , wherein the reactor bottom is curved. 
     
     
         37 . A method for dispersing gas fed into the bottom section of a closed reaction space into a slurry formed of a liquid and solids by means of flow baffles and a mixer member located in the reaction space, whereby the effective slurry height of the reaction space is in the region of 1.5-2 times the diameter of the reaction space, the mixer member consisting of two mixers located on the same shaft, whereby the gas is fed below the lower mixer into the slurry flow characterised in the slurry flow is directed by means of the said mixer is directed to the lower part of the reaction space wall and is made to discharge there into two separate streams, one of which is made to turn via the wall towards the centre of the reaction space bottom in the form of a toroidal flow and the other to rise in the zone formed by the reaction space wall and the baffles up towards the surface, where the flow is deflected by means of the upper mixer towards the centre of the reaction space and is made to form at the same time horizontal and vertical vortexes carrying gas bubbles; the direction of the slurry flow in the centre of the reaction space is deflected by means of the upper mixer to flow downwards as a uniform tubular flow towards the lower mixer. 
     
     
         38 . A method according to  claim 37 , wherein the solids content of the slurry is in the region of 500 g/l. 
     
     
         39 . A method according to  claim 37 , wherein the flow rate of the rising stream in the zone of the reaction space wall and baffles is 0.5-1.5 m/s, preferably 0.8-1.2 m/s. 
     
     
         40 . A method according to  claim 37 , wherein the cross-sectional area of the slurry flow directed downwards in the centre of the reaction space is in the region of 30-40% of the reactor cross-sectional area. 
     
     
         41 . A method according to  claim 37 , wherein the gas bubbles in the downward-directed slurry flow in the centre of the reaction space are put into oscillating motion. 
     
     
         42 . A method according to  claim 37 , wherein the infeed of slurry into the reaction space and its removal from there occur as an overflow.