CN110257236A - A kind of system of photoconductive tube-raceway pond combination culture oil-producing microalgae - Google Patents

Abstract

The invention provides a system for cultivating oil-producing microalgae in combination with a light pipe and a raceway pool, which belongs to the technical field of sewage treatment. The system device includes two parts, a main part of the raceway pool and a light pipe part. The runway pool is equipped with online water quality monitoring analyzers, water pumps, water inlets and drains; the light guide is installed on the roof cover of the small runway pool device with steel structure, and the natural light is captured and redistributed by the light guide. Microalgae at different depths in the pool Accepting the same light intensity to promote the growth and reproduction of microalgae in the raceway pool has important practical value for the research progress of large-scale and high-density cultivation of microalgae and the promotion of the industrialization of microalgae biodiesel.

Description

A system for cultivating oleaginous microalgae in combination with a light pipe and a raceway pool

technical field

The invention belongs to the technical field of sewage treatment, and relates to a system for cultivating oil-producing microalgae in combination with a light pipe and a raceway pool.

Background technique

Energy is the foundation of the development of modern society and is related to national security and economic security. my country is rich in coal, poor in oil, and low in gas. Since the rapid economic development, China's energy demand has increased sharply. In 1993, 2006, and 2009, China became a net importer of oil, natural gas, and coal respectively. At present, although my country's economic growth rate is slowing down, it is still on the rise, and the dependence on fossil fuels is still higher than 50%. The energy problem has become a bottleneck restricting my country's economic development.

The shortage of energy has prompted countries to look for new clean energy. Since 2005, global solar power and wind power have grown rapidly at a rate of more than 50% and 25% respectively; and China has also begun to vigorously support the development of new energy industries in order to enhance its competitiveness. In June 2010 and 2012, respectively, Realize the world's largest installed capacity of wind power and the world's largest installed capacity of grid-connected wind power, and the total installed capacity of grid-connected wind power has exceeded 5 million kilowatts. However, the development of solar energy, nuclear power, and wind energy is limited by geographical and meteorological conditions, and cannot be widely popularized. Therefore, the research on bioenergy was born.

As early as the 1950s, microalgae began to enter people's field of vision as fuel raw materials. Since the "Aquatic Species Project" was launched in the United States in 1978 to screen oil-rich microalgae, scholars from various countries have carried out in-depth research on various links in the production process of microalgae biodiesel. At present, the common algae species in research at home and abroad are Chlorella, Isoflagellates, diatoms, and Phaeodactylum tricornutum, etc., and the oil content of these algae species is more than 20%.

At present, there are common problems in the cultivation of oil-producing microalgae, such as low light utilization rate and large-scale production area, which seriously limit the development of this industry.

CN02206967.4 provides a solar photobioreactor with a light source in a membrane-type air bag. In the culture solution tank (4), there are multiple rows of light guide groups (2) composed of membrane-type air bags, and the upper ends of the light guides communicate with each other. , a light-receiving plate (6) is arranged on the top, and a hollow partition (3) communicating with an external water source is arranged on one side and the bottom of the light pipe group. The reactor increases the light-receiving area per unit volume of the microalgae culture solution in the form of an internal light source, significantly increases the yield of the microalgae, and can cultivate microalgae products with different components. The membrane-type air bag required by the invention occupies too much volume in the culture tank. Although the output of microalgae per unit volume is increased, the growth area of microalgae is reduced, which limits the total concentration of microalgae to a certain extent.

CN201320757371.5 provides a raceway pool photobioreactor, including a raceway pool (1), a variable speed stirring system, a carbon dioxide supply system (4), and a ground temperature control system. The disadvantage of this system is that it fails to solve the problem of insufficient light for microalgae at the bottom, but only accelerates circulation, which has little effect on promoting the growth of microalgae and increases economic costs.

In response to these problems, the present invention proposes a system for cultivating oleaginous microalgae in combination with light pipes and raceway pools. By capturing and redistributing natural light, the light utilization rate is improved, and it provides a reference for the industrialization process of microalgae cultivation.

Contents of the invention

The main purpose of the present invention is to provide a system for cultivating oleaginous microalgae in combination with light pipes and raceway pools, which is used to overcome the low light utilization rate and large-scale land occupation in the process of cultivating oleaginous microalgae in sewage. question.

The present invention is realized in this way, a system for cultivating oleaginous microalgae in combination with a light pipe-runway pool mainly includes:

(1) The light source is introduced, and the natural light is introduced into the parts below the water surface that cannot be directly exposed through the light guide, so that the lower part receives light, and solves the problem that the natural light cannot penetrate underwater when the water level is too deep;

(2) Assisting the growth of microalgae, by (1) allowing the deeper underwater microalgae in the runway pool to receive stronger light, thereby promoting the growth of microalgae.

Further, the system for cultivating oleaginous microalgae in combination with the light pipe-runway pool, the main structure is divided into two parts, the size of the runway pool is 2m in width, 2.5m in total length, and 1.2m in height, with 4 corridors in total; the light pipe part, the light guide is installed on the pool top cover.

Furthermore, in the system for cultivating oleaginous microalgae in combination with the light pipe and raceway pool, the structure of the raceway pool adopts a steel frame.

Further, the system for cultivating oleaginous microalgae by combining light pipe and raceway pool, the auxiliary devices include online detectors for pH, temperature, dissolved oxygen, and turbidity, and are equipped with water circulation pumps.

Furthermore, in the system for cultivating oleaginous microalgae in combination with the light pipe-runway pool, the water inlet and outlet are respectively arranged on the outermost two long sides of the runway pool, as shown in Figure 1 .

Further, the shape of the runway pool is: two small semicircles of 0.5m on one side of the runway pool are connected in parallel in parallel, and the other side is a large semicircle of 1m. There is a square structure between the two small semicircles and the large semicircle. It is separated by the steel frame extending from the connecting line of the two small semicircles to the center of the large semicircle, and the steel frame parallel to the square and the large semicircle set inside the runway pool. The width of each corridor is about 0.5m; the light pipe Evenly arranged on the internal steel frame. Specifically shown in Figure 1 and Figure 8.

Further, there are preferably 6 light pipes, which are evenly arranged on the internal steel frame, as shown in FIG. 5 .

Further, the light illuminance at the distance of 500mm from the bottom of the algae liquid should be above 2000lx, and the light illuminance on the liquid surface should be as close as possible to 27777.8lx.

Further, the distance between the light guide diffuser and the liquid surface is 50 mm.

Further, the distance between the central axes of adjacent light pipes is set at 600-1000mm.

Further, 8 fluorescent lamps are evenly added and arranged between the light pipes in the runway pool.

Further, the present invention provides a method for cultivating oleaginous microalgae in combination with a light pipe-runway pool, using the aforementioned system, the specific steps are:

(1) Pass the sewage into the runway pool in advance to provide the basic nutrients for the growth of microalgae;

(2) adding an appropriate amount of microalgae to cultivate the microalgae;

(3) Increase the irradiation depth of light through the light guide, thereby promoting the growth of microalgae in the runway pool.

Compared with the prior art, the present invention has the following advantages:

(1) The light utilization rate is high, and the natural light at the top of the reactor can be introduced into the bottom of the reactor, thereby improving the light utilization rate (measured by an illuminance meter).

(2) The growth of microalgae is good. Through the redistribution of light, the light distribution under the water surface is more uniform, which solves the disadvantage of weak light at the bottom of the reactor, thereby promoting the growth and reproduction of microalgae (measured by chlorophyll a) .

Description of drawings

Fig. 1 is a schematic diagram of the system structure of the light pipe-runway pond combined cultivation of oil-producing microalgae of the present invention;

Figure 2, a schematic diagram of the change of algae fluid turbidity during the culture period;

Figure 3, the average light intensity of the plane within the distance of 5-900mm;

Figure 4, the analysis results of illuminance on the light receiving surface when the distance is 50mm;

Figure 5, the overall layout of the light pipe;

Figure 6, the growth curve of Chlorella in the raceway pool;

Figure 7, various growth indicators of chlorella in the raceway pool;

Figure 8, schematic diagram of adding fluorescent lamps;

Figure 9, the analysis results of the liquid level of the algae liquid when there is no supplementary light;

Figure 10, the results of the illumination analysis of the liquid surface of the algae liquid after light supplementation;

Figure 11. Schematic diagram of refractive index measurement.

Detailed ways

The present invention provides a system for cultivating oleaginous microalgae in combination with light pipes and raceway pools. The present invention will be described in detail below with reference to the accompanying drawings and examples, but the present invention is not limited thereto.

As shown in Figure 1, the main structure of the device is divided into two parts. The size of the track pool is 2m wide, 2.5m long, and 1.2m high. There are 4 corridors in total; the light guide part is installed on the cover of the pool.

Below with adopting the specific embodiment that the present invention carries out sewage culture to Chlorella, the present invention is further introduced:

Example 1:

The research of the present invention finds that when Chlorella grows under natural conditions, the solar effective radiation at the light saturation point of photosynthesis is 500 μmol·m ^-2 ·s ^-1 , and the corresponding illuminance is 27777.8 lx.

According to the light attenuation curve experiment, it is found that the incident light of 2 000lx can meet the growth requirements of Chlorella with a depth of 500mm.

Therefore, the light illuminance at the distance of 500mm from the bottom of the algae liquid should be above 2000lx, and the light illuminance on the liquid surface should be as close as possible to 2 7777.8lx.

Example 2:

In actual situations, light will be refracted when it enters the algae liquid from the air, causing the irradiation range of the light pipe to exit the algae liquid to change when it enters the algae liquid. Therefore, it is necessary to measure the refractive index of the algae liquid and calculate The irradiation range is corrected. The refractive index (n) of the chlorella algae liquid and domestic sewage were measured respectively, and the experimental data and results are shown in Table 2-1.

Table 1 Domestic sewage and chlorella algae liquid refractive index measurement results (see Figure 11)

For the same incident angle of light, the larger the refractive index, the smaller the exit angle (the angle between the exit light and the normal), and the smaller the illuminated area of the light guide in the water. In order to ensure the normal growth of Chlorella under harsh conditions, the minimum illuminated area should be considered when designing the light guide lighting scheme. Therefore, the refractive index of the liquid is designed with the refractive index n=1.50 of the chlorella liquid.

Example 3:

In order to make the designed lighting scheme meet the lighting requirements in the whole cultivation period, the change of turbidity of algae fluid during the cultivation period was studied, and the change of turbidity of algae fluid in one cultivation period was sorted into a graph, as shown in Figure 2.

It can be seen from Figure 2 that at the initial stage of cultivation, the turbidity of the algae liquid of Chlorella is about 190NTU. Therefore, when designing the lighting scheme, the turbidity of the algae liquid is 190NTU as a reference value.

Example 4:

Through previous experiments, it was found that when the diffuser is at a certain distance from the water surface, the area where the light is scattered is larger than when the diffuser is in contact with the algae liquid. By adjusting the distance between the light guide diffuser and the liquid surface, the light intensity of the incident algae liquid and the irradiation range of the imported light on the water surface can be changed. When the diffuser is 50mm away from the liquid surface of the algae liquid, the change of the average light intensity in the range of 50-900mm below the diffuser is shown in Figure 3. According to the experimental results, the average light intensity on the plane 50mm away from the diffuser is 2 134.1 lx, which can meet the growth needs of Chlorella.

Therefore, considering factors such as equipment installation and equipment maintenance, and factors such as the light utilization rate of chlorella, it is more appropriate to set the distance between the light guide diffuser and the liquid surface at 50 mm.

Example 5:

Adjust the distance between the light guide diffuser and the liquid surface to be 50mm, the light receiving surface is set at 49mm below the liquid surface, and the radius is 500mm. The results of illuminance analysis after ray tracing are shown in Figure 4. In order to maximize the light receiving range in the chlorella algae liquid and ensure that the algae liquid meets the basic light conditions for the growth of chlorella, the distance between the central axes of adjacent light pipes is set at 600-1000mm.

Embodiment 6:

According to the design parameters determined above, the arrangement of the light guide is carried out, as shown in Fig. 5 . The growth curve of microalgae in the raceway pool is shown in Figure 6, and its biomass is indirectly expressed by the content of chlorophyll a. The trend of the growth curve of Chlorella shown in the figure is similar to the situation in the outdoor sufficient light culture, indicating that the lighting environment provided by the light guide is similar to that under outdoor conditions, and can be used for the normal growth of Chlorella.

On the 5th day of the culture period, the dry weight and oil content of the chlorella were measured. Various growth indicators are shown in Figure 2, a schematic diagram of the change of algae fluid turbidity during the culture period;

Figure 3, the average light intensity of the plane within the distance of 5-900mm;

Figure 4, the analysis results of illuminance on the light receiving surface when the distance is 50mm;

Figure 5, the overall layout of the light pipe;

Figure 6, the growth curve of Chlorella in the raceway pool;

Figure, wherein the dry weight reaches 0.31g/L, and the oil content reaches 49.3% of the dry weight, indicating that Chlorella grows well in the raceway pool.

From this point of view, the lighting scheme of the track pool designed in this study is reasonable and can meet the growth needs of chlorella in the track-type microalgae cultivation system.

Embodiment 7:

According to the light compensation point for the growth of chlorella, the outdoor natural light intensity is less than 1 000 lx in cloudy or rainy weather in Shenzhen, which cannot satisfy the growth of microalgae. In order to meet the growth needs of Chlorella, the average light intensity on the liquid surface of the algae should be at least 2 000 lx. In order to ensure the normal growth of microalgae, additional light must be added. Add another 8 fluorescent lamps to the runway pool model (as shown in Figure 8), assuming that the average light introduced into the model through the light guide is 800 lx in rainy days, then the illuminance analysis results on the surface of the algae liquid without light supplement and with light supplement Don't show it in Figure 9 and Figure 10.

The above examples illustrate that the present invention, through the capture and redistribution of natural light, allows the bottom of the reactor with poor illumination to be fully exposed to light, which satisfies the conditions for the growth of microalgae, thereby promoting the growth and reproduction of microalgae. Large-scale, high-density cultivation provides a reference and advances the process of microalgae bioenergy.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (10)

1. A system for cultivating oleaginous microalgae in combination with a light pipe-runway pond, characterized in that: (1) The light source is introduced. Through this system, natural light is introduced into the parts below the water surface that cannot be directly exposed, so that the lower part receives light, and solves the problem that natural light cannot penetrate underwater when the water level is too deep; (2) The growth of microalgae, by (1) making the deeper underwater microalgae in the runway pool receive stronger light, thereby promoting the growth of microalgae. 2. The system for cultivating oleaginous microalgae in combination with a light pipe-runway pool according to claim 1, characterized in that: the main structure of the system is divided into two parts, and the size of the runway pool part is 2m in width and 2.5m in total length. The height is 1.2m, and there are 4 corridors in total; for the light pipe part, the light pipe is installed on the cover of the pool roof. 3. The system for cultivating oleaginous microalgae in combination with a light pipe-runway pool according to claim 1, wherein the structure of the runway pool adopts a steel frame. 4. The system for cultivating oleaginous microalgae in combination with a light pipe-runway pool according to claim 1, characterized in that the accessory device includes online detectors for pH, temperature, dissolved oxygen, and turbidity, and is equipped with a water circulation pump. 5. The system for cultivating oleaginous microalgae in combination with a light pipe-runway pool according to claim 1, characterized in that: the water inlet and outlet are respectively arranged on the outermost two long sides of the runway pool. 6. The system for cultivating oleaginous microalgae in combination with a light pipe-runway pool according to claim 1, characterized in that: the shape of the runway pool is: two 0.5m small semicircles on one side of the runway pool are connected in parallel in parallel, and the other A large semicircle with a side of 1m, and a square structure between the two small semicircles and the large semicircle. The 4 corridors are steel frames extending from the connecting lines of the two small semicircles to the center of the large semicircle, and the inside of the runway pool. Parallel to the square and semi-circular steel frames, the width of each corridor is about 0.5m; the light pipes are evenly arranged on the internal steel frames. 7. The system for cultivating oleaginous microalgae in combination with light pipes and raceway pools according to claim 6, characterized in that there are 6 light pipes, which are evenly arranged on the internal steel frame. 8. The system for cultivating oleaginous microalgae in combination with light guide-runway pool according to claim 6 or 7, characterized in that: the light illuminance at the place where the algae liquid is 500 mm away from the bottom should be above 2000 lx, and the light illuminance on the liquid surface should be more than 2000 lx. It should be as close as possible to 27777.8lx; the distance between the light pipe diffuser and the liquid surface is 50mm; the distance between the central axes of adjacent light pipes is set at 600-1000mm. 9. The system for cultivating oil-producing microalgae in combination with light pipes and raceway pools according to claim 6 or 7, in addition, 8 fluorescent lamps are evenly added and arranged between the light pipes in the raceway pools. 10. A method for the combined use of a light pipe-runway pond to cultivate the algae of oleaginous microalgae, adopting the system described in any one of the preceding claims 1-9, the specific steps are: (1) Pass the sewage into the runway pool in advance to provide the basic nutrients for the growth of microalgae; (2) adding an appropriate amount of microalgae to cultivate the microalgae; (3) Increase the irradiation depth of light through the light guide, thereby promoting the growth of microalgae in the runway pool.