CN115074208B - Stirring type airlift fermentation tank and system - Google Patents

Abstract

The invention discloses a stirring type airlift fermentation tank and a stirring type airlift fermentation system. The stirring type airlift fermentation tank comprises an outer wall component, a guide cylinder component, a rotary jetting device and the like, wherein the stirring type airlift fermentation tank is an airlift inner circulation reactor, and the air inlet mode is a central air inlet mode. When fermentation is carried out, the low stirring rotation speed is started, so that bubbles are further broken up, and gas-liquid mass transfer is promoted; in addition, the rotary cutting four nozzles are matched with the forced circulation of the first-stage propelling stirring paddle in the guide cylinder, so that the gas-liquid mixing effect can be further fully improved, biomass synthesis gas is fully utilized by thalli, and the yield of ethanol is improved. The whole device can simultaneously realize the separation, purification and collection of ethanol produced by continuous fermentation of biomass synthesis gas, and has good application prospect in the industry of producing ethanol by fermentation of synthesis gas by a biological method.

Description

A stirred gas lift fermentation tank and system

Technical Field

The invention relates to the field of preparing fuel ethanol from biomass synthesis gas, and in particular to a system for producing ethanol from biomass synthesis gas by fermentation.

Background Art

Biomass syngas mainly uses agricultural and forestry waste as raw materials. Through high-temperature baking, the biomass raw materials are pyrolyzed or gasified to produce a variety of combustible gases (crude syngas), the main components of which are hydrogen and carbon monoxide, and usually also contain carbon dioxide, nitrogen, water, tar and particulate matter. High-quality syngas can be obtained by high-temperature dust removal, tar cracking, component adjustment and other steps.

At present, there are two main methods for preparing fuel ethanol from biomass synthesis gas: one is chemical catalysis, and the other is microbial anaerobic fermentation. Microbial anaerobic fermentation to produce fuel ethanol has many advantages. First, the reaction conditions of the microbial conversion method are mild, and it can be carried out under normal temperature and pressure conditions, which can reduce three major costs (energy costs, equipment costs and production costs). Secondly, microbial fermentation to produce ethanol has a higher selectivity. Compared with the chemical catalysis method, the yield of fermentation products is high and there are fewer by-products, which can reduce the purification cost. Third, the proportion of each component in the synthesis gas has little effect on the process of microbial fermentation to produce ethanol. Fourth, sulfide poisoning will not occur during the fermentation process.

At present, the reactors commonly used for syngas fermentation include: mechanical stirring reactor, tower reactor, fixed bed reactor, membrane reactor, airlift reactor, etc. However, these reactors generally have the problems of poor gas-liquid mass transfer and low mixed gas recycling efficiency. How to improve gas-liquid mass transfer and recycling efficiency is one of the main bottlenecks in syngas fermentation to produce ethanol.

Summary of the invention

In view of the shortcomings of poor gas-liquid mass transfer effect and low efficiency of existing reactors, the present invention provides a stirred gaslift fermentation tank and system to improve the gas-liquid mass transfer effect and recycling efficiency of syngas fermentation to produce ethanol.

In order to achieve the above object, the present invention solves it through the following technical solutions.

A stirring type airlift fermentation tank, the fermentation tank comprises an outer wall component, the outer wall component is a fluid containing and supporting cavity for the fermentation tank, wherein the fermentation tank also comprises a guide tube component and a rotary injection device, the outer wall component comprises a jacket, a defoaming electrode, a manhole, a feeding port, a tank body, a pH electrode, and a dissolved oxygen electrode; the guide tube component comprises a flow tube bracket, a guide tube, a first-stage propulsion impeller and a motor; the rotary injection device comprises a first gas cylinder, a first valve, a second valve, an air compressor, a filter, a flow meter, a second gas cylinder, an exhaust port, a rotary cutting four-nozzle and a rotating shaft driving the rotary cutting four-nozzle; the first-stage propulsion impeller and the rotary cutting four-nozzle are fixed by the same rotating shaft, the same rotating shaft extends upward from the bottom of the tank body into the guide tube, the first-stage propulsion impeller is arranged in the middle position of the guide tube, and the rotary cutting four-nozzle is arranged on the outer side of the lower end of the guide tube.

Furthermore, the jacket is arranged at the lower middle part of the tank body; the defoaming electrode, the exhaust port, the manhole and the feeding port are located on the top closed structure of the tank body.

Furthermore, the fermentation tank completes the defoaming operation in the tank body through the cooperation of the defoaming electrode and the defoaming agent, and the defoaming agent is fed into the tank body through the feed port.

Furthermore, the pH electrode and the dissolved oxygen electrode are located on the side lower wall of the tank body, and the controller obtains the pH and oxygen content in the fermentation liquid through the two electrodes.

Furthermore, the guide tube is supported on the side wall of the tank body by the guide tube bracket, and the guide tube bracket is divided into two groups, an upper bracket is fixedly connected to the upper edge of the guide tube, and a lower bracket is fixedly connected to the lower edge of the guide tube.

Furthermore, the rotation speed of the same rotating shaft is controlled by a controller, thereby controlling the fermentation speed of ethanol in the fermenter; during fermentation, a low stirring speed is turned on, and the speed is controlled to be 200 rpm.

Furthermore, after cooling and purification, the biomass synthesis gas is collected in the first gas cylinder, and the synthesis gas passes through the valve and pipeline and enters the air compressor. After passing through the gas filter, the synthesis gas passes through the flow meter and the rotary cutting four-nozzle into the stirred gas lift fermentation tank filled with culture medium.

Furthermore, the fermentation tail gas is collected into the second gas cylinder through the exhaust port, and the controller determines the second valve according to the collected signal, and circulates the fermentation tail gas into the air compressor and then circulates it to the rotary cutting four nozzles.

Furthermore, the four rotary cutting nozzles are hollow cylindrical structures, and each nozzle consists of two parts, namely a top bending part and a base supporting part. The inner diameter of the hollow cylinder is preferably 1.2-2.4mm, more preferably 1.84mm; there is a certain angle between the top bending part and the base supporting part, and the angle is preferably 40-50°, more preferably 45°.

A system for producing ethanol by fermenting biomass syngas comprises the stirred gas lift fermentation tank and an ethanol collecting device; the ethanol collecting device comprises a first pump, a sterile membrane filtration device, a distillation tower device, a molecular sieve dehydration device, an ethanol container, a concentrated fermentation liquid container and a second pump.

Specifically, the first pump is used to remove the fermentation liquid of ethanol fermentation from the stirred gaslift fermenter, the sterile membrane filtration device is used to concentrate the fermentation liquid; the distillation tower device is used to distill the concentrated fermentation liquid, the molecular sieve dehydration device is used for dehydration, the ethanol container is used to collect the dehydrated ethanol, and the concentrated fermentation residue container is used to collect the fermentation liquid residue after filtration; the second pump is used to return the fermentation liquid residue from the concentrated fermentation residue container to the stirred gaslift fermenter for continued cultivation.

The whole device can realize the continuous fermentation of biomass syngas to produce ethanol and the separation, purification and collection of ethanol at the same time, and has good application prospects in the industry of syngas biological fermentation to produce ethanol. At the same time, the system can significantly improve the gas-liquid mass transfer effect of the reactor and the utilization efficiency of the circulating fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of the present invention.

Explanation of the reference numerals: 1-first gas cylinder (synthesis gas after purification and cooling), 2-first valve, 3-second valve, 4-air compressor, 5-filter, 6-flow meter, 7-jacket, 8-defoaming electrode, 9-second gas cylinder (fermentation tank tail gas), 10-exhaust port, 11-manhole, 12-feeding port (acid, alkali, defoaming agent, culture medium, etc.), 13-tank body, 14-bracket of guide tube, 15-guide tube, 16-agitation impeller (first-stage propulsion impeller), 17-pH electrode, 18-dissolved oxygen electrode, 19-gas nozzle (rotary cutting four-nozzle), 20-discharge port, 21-motor, 22-support seat, 23-first pump, 24-sterile membrane filtration device, 25-distillation tower device, 26-molecular sieve dehydration device, 27-ethanol container, 28-concentrated fermentation residual liquid container, 29-second pump.

FIG. 2 is a schematic diagram of the structure of the rotary cutting four-nozzle in the present invention.

FIG. 3 is a schematic diagram showing the dimensions of a stirred gaslift fermenter according to the present invention.

Explanation of the reference numerals: D-reactor diameter, H-reactor height, H/D-reactor height-to-diameter ratio, _DE -diameter of the draft tube of the reactor, _HE -height of the draft tube of the reactor, _d1 -height of the bottom clarification zone of the reactor, _d2 -height of the upper gas-liquid separation zone of the reactor, Φ-nozzle diameter of the rotary cutting four-nozzle, _Dp -diameter of the gas nozzle, _d3 -distance between the stirring impeller and the bottom edge of the draft tube, _Dy -diameter of the stirring impeller.

DETAILED DESCRIPTION

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a system for producing ethanol from biomass syngas fermentation of the present invention is shown. The system device for producing ethanol from biomass syngas fermentation is mainly composed of a stirred gas lift fermentation tank (which is composed of multiple components), ethanol collection devices and the like. Through the system device, the fermented ethanol is concentrated, and at the same time, the recyclable fluid flows back to the stirred gas lift fermentation tank through other passages. In the entire system, the circulation of the fluid is powered by a pump, and the container in the circulation system provides an overall intermediate storage space. The following describes the entire system structure for producing ethanol in a corresponding manner.

Embodiment 1

The present embodiment relates to a stirred gas lift fermentation tank. The stirred gas lift fermentation tank is the main structure for producing ethanol, and mainly comprises an outer wall component, a guide tube component, and a rotary injection device. The outer wall component provides a accommodating cavity for the fermentation tank and provides support for the components on the cavity, mainly including a jacket 7, a defoaming electrode 8, a manhole 11, a feeding port 12, a tank body 13, a pH electrode 17, and a dissolved oxygen electrode 18. The jacket 7 provides a fluid accommodating cavity for heating or cooling the container, so as to facilitate the control of the temperature of the entire tank body and the interior. The fluid that can be used for heating in the jacket can be water, oil or other media. The jacket is arranged in the middle and lower part of the tank body according to the heating and cooling needs. The defoaming in the fermentation tank is mainly to sense the foam in the tank by providing a certain voltage to the defoaming electrode 8, and then the defoaming agent is added through the feeding port 12, which effectively reduces the foam generated in the tank during the fermentation process. In order to provide a device maintenance and replacement channel, a manhole is arranged just above the center of the tank body, and maintenance personnel or equipment replacement personnel can enter and exit the tank body through the manhole 11. During the fermentation process, the manhole is closed by a cover structure or other sealing structure. In addition to replenishing the above-mentioned defoaming agent, the feed port 12 also replenishes the acid, alkali and corresponding culture medium required for controlling and adjusting the pH of the fermentation process. The defoaming electrode 8, the exhaust port 10, the manhole 11 and the feed port 12 are located on the top closed structure of the tank body. Such an arrangement ensures that the defoaming electrode 8, the exhaust port 10, the manhole 11 and the feed port 12 are at a certain height from the fermentation liquid surface to achieve the structural function. The pH electrode 17 and the dissolved oxygen electrode 18 are located on the side wall of the tank body 13. The pH and oxygen content of the fermentation liquid in the tank body are collected through the pH electrode 17 and the dissolved oxygen electrode 18, and the pH and oxygen content electrical signals are input into the controller. The controller controls the pump structure and the related feeding and discharging devices according to the above parameters to realize the recycling of the device. The pH electrode 17 and the dissolved oxygen electrode 18 are located at the lower part of the tank body 13 to ensure that the fermentation liquid can completely cover the electrode detection device.

The guide tube component is mainly composed of a guide tube bracket 14, a guide tube 15, a first-stage propulsion impeller 16 and a motor 21. The guide tube 15 is supported on the side wall of the tank body 13 by the guide tube bracket 14. The guide tube bracket 14 is divided into two groups, an upper and a lower group. The upper bracket is fixedly connected to the upper edge of the guide tube 15, and the lower bracket is fixedly connected to the lower edge of the guide tube 15. The cylindrical guide tube 15 is entirely arranged in the fermentation liquid, and the first-stage propulsion impeller 16 and the rotary cutting four-nozzle 19 provide power for the fluid to flow in and out of the guide tube 15. The first-stage propulsion impeller 16 rotates to drive the fluid to flow upward from the lower end of the guide tube 15. The first-stage propulsion impeller 16 is arranged in the middle position of the guide tube. The motor drives the impeller 16 to rotate through the rotating shaft, and the rotating shaft passes through the bottom of the tank body and extends upward from the lower end surface of the guide tube 15. Compared with the conventional mechanical stirring tank, this device has only one stirring blade. Since the diameter of the airlift reactor and the diameter of the draft tube are usually not too large, if an upper mechanical stirring system is used, the manhole is also opened from the top of the reactor, which is not very convenient due to limited space. Therefore, this design adopts a lower mechanical stirring system, and the motor 21 is located at the bottom of the reactor. In this way, a manhole 11 can be opened from the top of the reactor, effectively solving this problem.

The rotary jet device includes a first gas cylinder 1 (syngas after purification and cooling), a first valve 2, a second valve 3, an air compressor 4, a filter 5, a flow meter 6, a second gas cylinder 9 (fermentation tank tail gas), an exhaust port 10, a rotary cutting four-nozzle 19 and a rotating shaft driving the rotary cutting four-nozzle 19. The rotary cutting four-nozzle 19 is fixed on the rotating shaft. The rotating shaft drives the first-stage propulsion impeller 16 and the rotary cutting four-nozzle 19 to rotate at the same time. The controller controls the rotation speed of the rotating shaft based on the feedback signal, thereby controlling the flow speed of the fluid inside and outside the guide tube 15 and controlling the overall fermentation speed. After cooling and purification, the biomass syngas is collected in the first gas cylinder 1. The syngas passes through the valve 2 and the pipeline and enters the air compressor 4. After passing through the gas filter 5, the syngas enters the stirring type gas lift fermentation tank filled with culture medium through the rotary cutting four-nozzle 19 through the flow meter 6. During fermentation, turning on a low stirring speed (within 200rpm) helps to further break up the bubbles and promote gas-liquid mass transfer; in addition, the forced circulation of the first-stage propulsion stirring paddle in the guide tube with the rotary cutting four-nozzle 19 can also further improve the gas-liquid mixing effect, allowing the bacteria to fully utilize the biomass synthesis gas, thereby increasing the ethanol production. The fermentation tail gas, containing gases such as CO, is first collected in the second gas cylinder 9 through the exhaust port 10. The controller determines the second valve 3 according to the collected signal, and opens the valve 3 when necessary, so that the fermentation tail gas is circulated into the air compressor 4, and then circulated to the rotary cutting four-nozzle 19 part, further improving the utilization rate of the synthesis gas.

The planar structure of the rotary cutting four-nozzle 19 is shown in Figure 2. The rotary cutting four-nozzle 19 is composed of four independent nozzle structures. The nozzle structure is a hollow cylindrical structure. Each nozzle is composed of two parts, namely the top bending part and the base end support part. The base end support part has the same cross-sectional structure as the top bending part, both of which are hollow cylinders. The inner diameter of the cylinder is 1.84mm, and the flow channel of the biomass synthesis gas is provided through the inner diameter part. There is a certain angle between the top bending part and the base end support part. By setting such an angle, the mixing effect of the biomass synthesis gas and the liquid in the container is increased, ensuring that the biomass gas merges with the liquid faster, and promoting the upward movement of the fluid outside the guide tube 15. According to many experiments, considering the fluid resistance and mixing effect, setting the angle to 45° is the best choice.

Taking into account the mutual interference and correlation of the main components, the dimensions of each component are designed as follows (see Figure 3 for the corresponding component positions of the dimensions): the appropriate range of the ratio of the height to the diameter (H/D) of the stirred airlift fermenter is 5 to 9; the appropriate range of the ratio of the diameter of the draft tube to the diameter of the fermenter (D _E /D) of the stirred airlift fermenter is 0.6 to 0.8; the appropriate range of the ratio of the height of the clarification zone at the bottom of the stirred airlift fermenter to the diameter of the fermenter (d ₁ /D) of the stirred airlift fermenter is 1/6 to 1/3; the height of the gas-liquid separation zone at the top of the fermenter of the stirred airlift fermenter, that is, the distance d ₂ from the upper edge of the draft tube to the liquid surface, generally the liquid level in the tank should not be higher than 1.5m from the outlet of the draft tube; the stirring impeller of the stirred airlift fermenter is a first-stage propulsion impeller, the appropriate range of the ratio of the diameter of the stirring impeller to the diameter of the fermenter (d _y /D) is 0.33 to 0.45, and the installation height of the stirring impeller is the middle height position of the draft tube, that is, d ₃ =0.5×H _E The gas nozzle of the stirring type gas lift fermenter is a rotary cut four-nozzle, specifically, each nozzle is bent downward 45 degrees, and then each nozzle is twisted 45 degrees clockwise. The ratio of the diameter of the gas nozzle to the diameter of the fermenter is 0.4, and the diameter of the nozzle is 1.84mm.

Example 2

This embodiment is a system for producing ethanol by fermentation of biomass synthesis gas, which contains an ethanol collection device in addition to the stirred gas lift fermentation tank of embodiment 1. The ethanol collection device includes a first pump 23, a sterile membrane filter device 24, a rectifying tower device 25, a molecular sieve dehydration device 26, an ethanol container 27, a concentrated fermentation residual liquid container 28, and a second pump 29. During the fermentation and cultivation process, the ethanol content index in the fermentation liquid is monitored in real time. According to the ethanol content index, part of the fermentation liquid is regularly transferred out by the first pump 23 and concentrated by the sterile membrane filter device 24. After being concentrated by about 10 times, the filtrate is rectified by the rectifying tower device 25 and dehydrated by the molecular sieve dehydration device 26, and then ethanol can be separated and collected, and the ethanol is collected in the ethanol container 27; at the same time, the concentrated fermentation residual liquid concentrated by the sterile membrane filter device 24 enters the concentrated fermentation residual liquid container 28, and the remaining fermentation residual liquid containing bacteria is returned from the concentrated fermentation residual liquid container 28 to the stirred gas lift fermentation tank for continued cultivation by the second pump 29, so as to realize the reuse and regeneration of the biocatalyst. The whole device can realize the continuous fermentation of biomass synthesis gas to produce ethanol and the separation, purification and collection of ethanol at the same time. In addition, it can also realize the reuse and regeneration of biocatalysts and the recycling of fermentation tail gas. It has good application prospects in the industry of ethanol production by synthesis gas biological fermentation.

The above-described embodiments are only for illustration and therefore cannot be used to limit the patent protection scope of the present invention. That is, equivalent changes and modifications made according to the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims (11)

1. The stirring type airlift fermentation tank comprises an outer wall component, wherein the outer wall component is a fluid accommodating and supporting cavity for the fermentation tank, and is characterized by further comprising a guide cylinder component and a rotary spraying device, and the outer wall component comprises a jacket (7), a defoaming electrode (8), a manhole (11), a feed supplementing port (12), a tank body (13), a pH electrode (17) and an oxygen dissolving electrode (18); the guide cylinder component comprises a guide cylinder bracket (14), a guide cylinder (15), a primary propelling impeller (16) and a motor (21); the rotary jetting device comprises a first air bottle (1), a first valve (2), a second valve (3), an air compressor (4), a filter (5), a flowmeter (6), a second air bottle (9), an exhaust port (10), rotary-cut four nozzles (19) and a rotating shaft for driving the rotary-cut four nozzles (19); the primary propulsion type impeller (16) and the rotary-cut four nozzles (19) are fixed through the same rotating shaft, the same rotating shaft extends upwards from the bottom of the tank body (13) to enter the guide cylinder (15), the primary propulsion type impeller (16) is arranged at the middle position of the guide cylinder (15), and the rotary-cut four nozzles (19) are arranged at the outer side of the lower end of the guide cylinder (15).

2. The stirred gas-lift fermenter according to claim 1, wherein: the jacket (7) is arranged at the middle and lower part of the tank body (13); the defoaming electrode (8), the exhaust port (10), the manhole (11) and the feed supplement port (12) are positioned on the top closed structure of the tank body (13).

3. The stirred gas-lift fermenter according to claim 2, wherein: the fermentation tank is characterized in that the defoaming agent is fed into the tank body (13) through the defoaming electrode (8) through the feeding port (12), and the defoaming agent is matched with the defoaming electrode (8) to complete defoaming operation in the tank body (13).

4. A stirred gas-lift fermenter according to claim 3, wherein: the pH electrode (17) and the dissolved oxygen electrode (18) are positioned on the side lower wall of the tank body (13), and the controller obtains the pH value and the oxygen content in the fermentation liquor through the two electrodes.

5. The stirred gas-lift fermenter according to claim 1, wherein: the guide cylinder (15) is supported on the side wall of the tank body (13) through the guide cylinder support (14), the guide cylinder support (14) is divided into an upper group and a lower group, the upper support is fixedly connected with the upper edge of the guide cylinder (15), and the lower support is fixedly connected with the lower edge of the guide cylinder (15).

6. The stirred gas-lift fermenter according to claim 1, wherein: the rotating speed of the same rotating shaft is controlled by the controller, so that the fermentation speed of the ethanol in the fermentation tank is controlled; the low stirring speed was turned on during fermentation, and the speed was controlled at 200rpm.

7. The stirred tank air-lift fermenter according to claim 6, wherein: after cooling and purifying, biomass synthesis gas is collected to the first gas bottle (1), the synthesis gas passes through the first valve (2) and a pipeline, enters the air compressor (4), passes through the filter (5), and then enters the stirring type airlift fermentation tank body filled with culture medium through the flowmeter (6) by the rotary-cut four nozzles (19).

8. The stirred tank air-lift fermenter according to claim 7, wherein: the fermentation tail gas passes through the exhaust port (10), is firstly collected into the second gas cylinder (9), the controller judges the second valve (3) according to the collected signal, and the fermentation tail gas is circularly fed into the air compressor (4) and is recycled to the rotary-cut four nozzles (19).

9. The stirred gas-lift fermenter according to claim 1, wherein: the rotary-cut four nozzles (19) are of hollow cylindrical structures, and each nozzle consists of two parts, namely a top end bending part and a base end supporting part.

10. The stirred gas-lift fermenter according to claim 9, wherein: the inner diameter of the hollow cylinder is 1.2-2.4mm; the angle between the top end bending part and the base end supporting part is 40-50 degrees.

11. A system for producing ethanol by fermenting biomass synthesis gas, which is characterized by comprising the stirring type airlift fermentation tank as claimed in any one of claims 1-10 and an ethanol collecting device; the ethanol collecting device comprises a first pump (23), a sterile membrane filtering device (24), a rectifying tower device (25), a molecular sieve dehydration device (26), an ethanol container (27), a concentrated fermentation residual liquid container (28) and a second pump (29);

The first pump (23) is used for removing fermentation liquor of ethanol-producing fermentation from the stirring type airlift fermentation tank, and the sterile membrane filtration device (24) is used for concentrating the fermentation liquor; the rectifying tower device (25) is used for rectifying the concentrated fermentation liquor, the molecular sieve dehydration device (26) is used for dehydration, the ethanol container (27) is used for collecting dehydrated ethanol, and the concentrated fermentation residual liquid container (28) is used for collecting fermentation liquor residual liquid after filtration and concentration; the second pump (29) is used for returning the fermentation liquor raffinate from the concentrated fermentation raffinate container (28) to the stirring type airlift fermentation tank for continuous culture.