FI107237B - Reactor - Google Patents

Abstract

A reactor for aerating a fluid with a gas comprises a mixing tank (12) for the fluid and a centrally located vertical draft tube (13) submerged in the fluid to divide the mixing tank (12) into an inner chamber (21) and an outer chamber (23). The reactor further comprises a motor driven axial flow impeller (14) located in the draft tube (13) for circulating fluid downwardly through the inner chamber (21) and upwardly through the outer chamber (23). The reactor further comprises an external circuit for withdrawing a portion of the fluid from the mixing tank (12), aerating the fluid, and returning the aerated fluid to the mixing tank (12). The aerator is in the form of a venturi device (17).

Description

107237

Reactor

The invention relates to a reactor for a two- or three-stage rigid system.

The invention is particularly applicable to the aeration of a fluid comprising a mineral particulate slurry by air or any other suitable oxygen-containing gas, which is necessary, inter alia, for filtration of aerobic bacteria. However, the invention is not limited to this embodiment but relates to the aeration of any gas / liquid, gas / liquid / solid or gas / liquid / solid / microbial combination.

An advantage of the invention is that it aerates the liquid with gas with low energy consumption and with a high gas utilization efficiency.

The term "aeration" is understood to mean the introduction of a gas or gases into a liquid.

Reaction vessels for sludge aeration have been used in the mining industry for many years. The two main types of reaction vessels are Pachuca (or air-agitated reaction vessel) and machine-agitated reaction vessel.

15 The Pachuca reaction vessel was first favored because of its simplicity in construction and operation, but as the size of the reaction vessel has grown, it has gradually lost popularity. The loss of popularity was due to the high pressure air required for a good mineral suspension. Further, the residence time of the air in the Pachuca reaction vessel is too short for efficient mass transfer and the Pachuca reaction vessels are prone to air-chicken wellness. Compressed air mixing is generally ineffective because the effective size of the φ blend is too large for efficient bulk transfer.

The use of mechanical mixing has become more common, especially for large reaction vessels, because the impeller design has become more efficient and it has been found that the extra capital costs were well offset by the relatively low energy required for mixing.

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In order to solve efficient air mass transfer, it is necessary to provide fine bubble dispersion in a well-mixed combination as the bubbles remain in the reaction vessel for an extended period of time. In practice, this has been accomplished by passing the air through a high-slit impeller or by passing the air through a membrane or a porous slide. Both of these methods are high energy consuming because the air must be introduced at a sufficient overpressure to overcome the fluid pressure at the injection site and to overcome the pressure drop on one side of the injection port, diaphragm or diffuser. Typically, injection point 2,1072: 57 is at the bottom of the reaction vessel, and especially in the case of aeration of large vessels, the major costs are capital and operating energy costs to compress the air to the pressure required for injection. If the pools are deeper than about 10 m, it is necessary to install expensive high pressure compressors instead of air blowers 5. In addition, the use of porous diffusers or sprinklers in reaction vessels for slurry may result in loss of working time when releasing the diffusers.

In addition, mechanically stirred reaction vessels become inefficient when large amounts of compressed air are evacuated because the energy required to disperse the air in the reaction vessel becomes very high. Furthermore, in the case of biological reaction vessels, the shear forces on the blades of the blades of the high-speed impellers may damage the bacteria.

Even more so for gas / liquid / solid combinations, where it is important to keep the solid in suspension, the energy required to circulate the liquid in the aerator is a significant cost factor.

In accordance with the present invention, a reactor for introducing gas into a liquid comprises a fluid-containing mixing vessel, a baffle to divide the vessel into at least two chambers and allow fluid flow between the chambers in the lower and upper chambers. 20, and an external recirculation passage for the fluid side flow, the reactor further comprising: (a) a region of reduced cross-section in the fluid passing through it and forming a region of reduced pressure in the liquid, 25 (b) means for supplying gas to the fluid a liquid for detecting the liquid, and · '(c) means for supplying aerated liquid to the fluid stream circulating in the basin; n.

It is preferable that the partition consists of a suction tube suitable for immersion in the liquid in the basin, the suction tube having an open top and an open bottom 30.

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It is particularly advantageous that the pool is cylindrical and that the suction tube is located in the center of the pool so as to divide the pool into an inner chamber and an annular outer chamber.

It is preferred that the pumping means be located in the suction pipe.

It is preferred that the pumping means comprise an axial flow pump.

It is particularly advantageous that the axial flow pump comprises an impeller located in the suction pipe.

It is very particularly advantageous that the means for introducing the aerated liquid into the recycle fluid in the basin are arranged to deliver the aerated fluid 10 into the suction pipe above the impeller.

It is preferred that the means for introducing the gas into the liquid comprise a porous membrane, orifices, or nozzles.

In the reactor of the invention, the introduction of gas into the liquid is effected by pumping the liquid through a pump in a mixing basin having at least two chambers in fluid communication with the upper and lower zones of the basin so that the fluid flows down , by introducing the gas into the liquid portion in the reduced pressure zone for aeration of the liquid and by introducing the aerated liquid into the recycle liquid in the basin.

The invention will be described with reference to the accompanying drawings, in which: • · <• <<

Figure 1 schematically shows a preferred embodiment of a reactor constructed in accordance with the invention.

Figure 2 is a detailed schematic representation of a basic design of a hopper for use in the reactor shown in Figure 1.

Figure 3 is a detailed schematic representation of a preferred embodiment of a funneling apparatus for use in the reactor shown in Figure 1, and Figure 4 is a graphical representation of oxygen uptake and oxygen utilization relative to airflow for the reactor shown in Figure 1 and a commonly known air-stirred in connection with.

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The most preferred embodiment of the reactor of the invention is described herein in connection with the aeration of mineral and aqueous slurry by air. It should be noted, however, that the invention is not limited to this application, but relates to the aeration of any liquid with or without suspended solids.

The reactor 11 shown in Fig. 1 comprises a slurry-containing mixing vessel 12, immersed in a vertical suction pipe 13, and a motor-driven axial flow impeller 14 located in the suction pipe 13 near its upper end. Below m 12 the size can be any appropriate. The suction tube 13 has an open upper and lower end 16, 18 and is located in the middle of the mixing vessel 12 dividing the mixing vessel 12 into the sieve 10 and the outer annular chamber 23. In use, chamber 23. The slurry flow is controlled so that the nine-particle particles remain in suspension.

Reactor 11 further comprises an external circulation to divert a portion of the slurry 15 from the mixing basin 12, to aerate the slurry and return the air-enriched slurry to the mixing basin 12. The external loop comprises a recirculation line 6, a pump 15 to pump slurry . The external circulation barrier is tracked to turn the slurry from the top of the mixing basin 12 and return the air-enriched slurry to a location in the suction pipe 13 above the impeller 14 to optimize mixing of the air-enriched slurry and recycle slurry in the mixing basin. The outward passage comprises at least one inlet extraction nozzle 19, which is tracked to direct the air-enriched slurry down the suction pipe 13.

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Figure 2 illustrates the basic construction features of a hopper 17. Referring to Figure 25, the funnel apparatus 17 comprises a tubular body 25 having an inlet end 41, an outlet end 43 and an intermediate neck 3 defining a region of reduced cross-section with openings 2 for introducing air into the slurry for mixing. When the slurry flows of the tubular body 25 in the arrow A direction indicated by the flow rate increases, "when the slurry enters the throat 3 thereby creating a region of reduced according Bemoullin equation 30 a pressure zone. As a result, no air pressure in the reduced pressure zone for introducing necessarily have to be high, but the air can be When the slurry flows from the neck 3, it enters the area 5 of the extension where the fluid velocity decreases and the pressure increases.

The expanded cross-sectional area 5 is shaped to provide maximum recovery of energy 35 as the air-enriched slurry expands as it flows from neck 3.

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Further, the design and operation parameters of the hopper device 17 are selected so that air bubbles are formed which are optimally sized for efficient transfer of oxygen mass from the bubbles to the slurry. As a result, minimal airflow is required, which reduces operating costs. The design and operating parameters include the flow rate of the slurry 5, air pressure and means for injecting air into the instant.

Figure 3 illustrates a preferred embodiment of the hopper device 17 for use with a 3000 liter mixing tank 12 and a 75 mm recirculation line 6. The neck 3 of the funnel device 17 comprises an inlet cone of 25 ° and an outlet cone 47 of 7 °. The neck 3 has a diameter of 25 mm and a si-10 has a diameter of 75 mm of the inlet and outlet ends 41, 43. The apertures 2 are located in the outlet cone 47 of the neck 3 and are arranged in three rows of circumference 5 mm apart, each row comprising 24 x 1 mm apertures.

It is to be understood that the invention is not generally limited to the specific details mentioned above.

The invention will now be illustrated by reference to the following example.

A test set was performed on a conventional reactor comprising a 3000 liter mixing tank stirred by means of an axial flow impeller and air injection tracked through a 1 mm hole spray ring below the impeller, and a preferred embodiment of the reactor of the invention with a flow impeller and having a funnel that returned the aeration to the point above the axial flow impeller.

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The wells contained 8% w / v slurry of pyrite / pyrhoththis precipitated with Thiobacil-lus ferrooxidans.

The aeration efficiency of each pool was expressed in figures and the results are shown in Figure 4.

Figure 4 illustrates the relationships between the aha mentioned; (a) oxygen uptake and air flow to the conventional reactor and to the most preferred embodiment of the reactor; and 30 (b) use of oxygen and air flow to the conventional reactor and to the most preferred embodiment of the reactor.

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The term "oxygen uptake" refers to the amount of oxygen introduced into the solution and thus is a direct measurement of the degree of aeration. The term "oxygen utilization" refers to the amount of oxygen introduced into the solution as a percentage of the total amount of oxygen introduced into the reactor, and is thus a direct measurement of the aeration efficiency.

5, the term "air jet" refers to a conventional reactor and the term "hopper" refers to the most preferred embodiment of the reactor.

The results shown in Fig. 4 show that the most favorable reactor throughput level was the aeration efficiency of the conventional reactor, which was substantially better than the conventional reactor air efficiency. As a detailed example, the mucous-10a reactor of the most preferred embodiment was able to aerate the slurry with 150 mg O2 / liter slurry per hour with an air flow of 60 l / min and 50% oxygen utilization, while a conventional reactor slurry / hour only with a significantly higher airflow of 150 rpm and significantly lower oxygen uptake of 20%.

15 For each type of reaction vessel, the aeration capacity required for aeration shall be applied to the recording equipment and increased to a scale representing the foreseeable aeration requirement at 1000 m in the evening. The results are shown in Table 1.

Table 1: Comparison of aeration power requirements

Structure of the basin Aeration capacity 20 (Wh / m3 air)

The reactor 80 is generally known

Ilmanpirskottimella

Reactor of the invention 20 * 25 suction tube with funnel device

The results show significant energy savings in the most favorable sucritas form of the reactor compared to the commonly known reactor. In particular, the results show * Λ that the energy required or the air supplied per m was four times lower in the most preferred embodiment of the reactor than in the case of the well known reactor. Based on the results of energy use, the energy required to carry out the above O 2 at 150 mg O 2 / liter ointment / tant per liter of oxygen delivered was nine times lower in the most preferred embodiment of the reactor than in the generally known reactor.

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The most preferred embodiment of the reactor of the invention has the following advantages over a generally known reactor: (i) The gas is supplied by low pressure or natural suction, thus avoiding the use of expensive high pressure gas compressors and reducing the reactor power requirement.

It is significant that the agitator is only used for slurrying the mineral particles and for circulating the aerated slurry.

(ii) The gas is naturally injected or aspirated into the hopper at a location where the liquid velocity is high. This produces very small bubbles, which improves the mass transfer of oxygen to the solution. As a result, operating costs are reduced because the air required for the reactor is minimized.

(iii) The aerated slurry is returned to the mixing tank above the impeller at low pressure in the central suction pipe. As a result, operating costs are reduced because the pumping force required for sludge recycling is minimized.

(iv) The capital cost of the reaction vessel is minimized because the mixing pool has 15 fewer internal parts. In addition, economies of scale can be achieved in the construction of large reactors.

(v) Maintenance costs and downtime are minimized because there are few defective parts inside the mixing basin. Maintenance of the external components is simple because the operation of the aeration unit alone can be shut down for maintenance without affecting the overall reactor performance. A blocked air conditioner can be replaced quickly with minimal disruption to the process.

(vi) The invention is suitable for efficient gas supply and suspension of solids in a gas-liquid solid system or for efficient gas supply to a gas-liquid ice system. One example of the practice of the invention is the suspension of a reactive mineral particulate slurry and aeration in bacterial filtration. Other uses include biological methanisation of synthetic gases, digestion of sewage or other sludges, and production of synthetic rutile by Becher. method. However, its use is not restricted to these areas.

In the most preferred embodiment of the reactor described above, several modifications can be made without departing from the spirit and scope of the invention.

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For example, although in the most preferred embodiment, the impeller 14 is located near the top of the suction tube 13, but the invention is not limited to this arrangement, and the impeller 14 may be located at any convenient position along the length of the suction tube 13.

Claims (9)

Reactor (11) for introducing a gas into a liquid, characterized in that it comprises a mixing tank (12) for the liquid, an intermediate wall (13) for dividing the tank into at least two chambers (21, 23). and to enable the liquid to flow between the chambers in a lower and an upper part of the tank, a pumping device (14) located in the lower end of the chambers for circulating the liquid downstream in one of the cannulas (21) and then heated up. in the second chamber (23), and an outer circuit (6) within a lateral flow of the liquid from the tank (12), the reactor also comprising: a) a region of high-cross section (3) to provide venturi effect for the liquid passing therethrough and to create an area (3) of reduced pressure in the liquid; B) means (2) for introducing the gas into the liquid in the region (3) of reduced pressure to vent the liquid, and c) means (19) for introducing the aerated liquid into the liquid circulating in the tank (12). Reactor according to claim 1, characterized in that the intermediate wall consists of a draw tube (13) arranged to be immersed in the liquid in the tank (12) and provided with an upper upper end (16) and an open lower end (18). • · • 3. Reactor according to claim 2, characterized in that the tank (12) is cylindrical c and the draw tube (13) is placed centrally in the tank to divide the tank into an inner chamber (21) and an outer annular chamber (23). 4. Reactor according to any of the preceding claims, characterized in that the pumping device comprises an axial flow pump (14). 107237 11 Reactor according to claim 4, characterized in that the axial flow pump (14) is located in the draw tube (13). 6. Reactor according to claim 4 or 5, characterized in that the axial flow pump comprises a stirrer. 7. Reactor according to claim 6, characterized in that said means (19) for introducing the aerated liquid into the liquid circulating in the tank is arranged to introduce the aerated liquid into the draw tube (13) upstream of the stirrer (14). Reactor according to any of the preceding claims, characterized in that said means for introducing gas into the liquid in the area (3) of reduced pressure comprises a porous membrane, shark or nozzles. 9. A reactor according to any preceding claim, characterized in that said means for generating the area of reduced pressure in the liquid comprises a tubular element having a region of limited cross-section to provide venturi effect to the liquid passing therethrough, thereby increasing the velocity of the liquid. the pressure 15. the liquid decreases in the region of limited cross-section. • <%> · · • · <