CN111560035A - A kind of method that utilizes dimethyl ether to extract phosphoric acid ester in algal mud - Google Patents

Abstract

The invention relates to a method for extracting phosphate ester from algae mud by using dimethyl ether, which comprises the steps of placing algae mud formed after blue algae are fished in a reaction kettle, converting DME into liquid by an air pressure pump, and adjusting the polarity of the DME to be consistent with that of phosphate ester by adjusting reaction parameters of the reaction kettle, so as to dissolve the phosphate ester. Performing solid-liquid separation on the mixture, wherein the solid phase is dehydrated algae mud, the water content is reduced to 40 percent, and the subsequent landfill incineration requirement is met; separating the obtained liquid phase product, converting liquid DME into a gas state through normal temperature and reduced pressure, collecting and recycling, wherein the residual liquid phase product is rich in phosphate, and further extracting phosphorus element, thereby achieving the purposes of algae mud reduction and resource utilization.

Description

A kind of method that utilizes dimethyl ether to extract phosphoric acid ester in algal mud

technical field

The invention belongs to the field of resources and environment, and in particular relates to a method for extracting phosphorus elements by dissolving phosphate ester in algal slime by utilizing the dissolving properties of dimethyl ether (DME) for organic matter.

Background technique

Cyanobacteria are aquatic organisms that are divided into four categories: Basketballalgae; Oscillatoriasp; Nostoc; Seaweed. When the lake water is seriously polluted by organic pollutants, and the nitrogen and phosphorus content exceeds the standard and is in a state of heavy eutrophication, and then encounters suitable temperature (the temperature is around 18 °C) and other conditions, cyanobacteria may explode and grow wildly. Spirulina is actually green in color, and a large number of floating algae cover the water surface like a sticky "green paint". Experts have given it a beautiful name - cyanobacteria bloom. When cyanobacteria erupt, the dissolved oxygen in the water is consumed by cyanobacteria, and other aquatic organisms such as fish die due to lack of oxygen, and the water body not only changes its color, but also smells bad. For a long time, the lake lost its function and became a dead lake. The basic guiding ideology of cyanobacteria management is: control the input of exogenous nutrients as much as possible; reduce the load of endogenous nutrients; emergency algae removal before and after hydration outbreaks. At present, the main emergency treatment method for cyanobacteria in my country is cyanobacteria salvage. The salvaged cyanobacteria enter the algal water separation station, and form algal sludge after flocculation and dehydration. nutrients such as phosphorus. At present, the commonly used algal sludge disposal methods are landfill, composting, fermentation and drying.

In my country, if 5000t of algae are obtained from the lake every year, it is equivalent to 525t of nitrogen and 62t of phosphorus from the lake. Therefore, for cyanobacteria, it is also a natural resource in itself. Among them, the recovery of phosphorus element is the direction that is more concerned in China at present. DME stripping technology is an emerging technology. Currently, there are preliminary attempts in the fields of coal and sludge dewatering. For example, Simple extraction method of green crude from natural blue-greenmicroalgae by dimethyl ether by Hideki Kanda et al. 1266" provides a simple extraction method for green crude oil from blue-green microalgae with dimethyl ether. The use of dimethyl ether asan organic extraction solvent for biomass applications in future biorefineries: A user-oriented review by Manuel C. Bauer et al. provides the application of dimethyl ether as an organic extraction solvent for biomass in biorefineries.

However, there is no published literature on the method for extracting phosphorus from algal mud using DME.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a method for utilizing dimethyl ether to extract phosphate ester in algal mud, and adjust the polarity of liquid DME by adjusting the reaction parameters, so as to realize the phosphate ester in the algal mud. The selective dissolution of algal sludge allows it to exist in the extraction liquid phase mixture, and then further extract phosphorus elements, so as to achieve the purpose of reducing the amount of algal mud and utilizing it as a resource. The DME in the liquid phase mixture is converted into a gaseous state after decompression, and can be recycled after being liquefied under pressure again, which greatly reduces the use loss of the dimethyl ether solvent.

The present invention is achieved through the following technical solutions:

A method for utilizing dimethyl ether to extract phosphoric acid ester in algal mud, comprising the following steps:

Step (1), place the algal mud in the reactor, after the DME is converted into a liquid state by an air pressure pump, press into the reactor to mix with the algal mud, and use DME to dissolve the phosphate ester of the algal mud;

The chemical formula of dimethyl ether (DME) is: H ₃ COCH ₃ , melting point -138.5 ℃, boiling point -23 ℃, water-soluble 328 g/100 mL (20 ℃), has excellent miscibility, can be with most polar and non-polar Miscible with polar organic solvents. It is a colorless, tasteless and odorless gas under normal temperature and pressure, and a liquid under pressure. In this step, an air pressure pump is used to convert the gaseous DME into a liquid state.

The amount of liquid DME used is 15 to 30 times the water content of the algal mud, the reaction pressure is 0.5 to 2 MPa, the reaction temperature is 15 to 30°C, and the reaction time is 20 to 40 minutes.

The reactor is equipped with a stirrer to ensure that the DME and the algal mud are mixed evenly. The parameters of the agitator are set: the stirring rate is 60rpm-120rpm/min, and the stirring time is 20-40min.

In step (2), after the DME is dissolved, the mixture is subjected to solid-liquid separation, wherein the solid phase is dehydrated algal mud, and the moisture content is reduced to 40%, which meets the requirements of subsequent treatment such as landfill and incineration.

The solid-liquid two-phase is filtered and separated by setting the separation pressure difference, the separation pressure difference is set to 0.5-2MPa, and the separation time is 1-2min.

In step (3), the obtained liquid-phase product is separated, and the liquid DME is converted into a gaseous state by normal temperature and reduced pressure, and then collected and reused. The remaining liquid-phase product is rich in phosphate ester, and the phosphorus element can be further recycled and utilized.

The beneficial effects of the present invention are as follows:

(1) The algal mud has the disadvantages of high water content, difficult dehydration and low disposal efficiency. Generally, solvent extraction requires a dry and anhydrous environment. The present invention adopts DME to wet-extract the phosphate in the algal mud, which is easy to separate and has high efficiency, and provides a new idea for the reduction of the algal mud.

(2) By changing the reaction conditions and adjusting the polarity of DME to be consistent with the phosphate ester, the complete dissolution of the phosphate ester in the algal mud is achieved. Therefore, it has a high phosphate ester extraction rate, which can be as high as 70%.

(3) DME is gaseous at normal temperature and pressure, and turns into liquid after pressurization. After dissolving the phosphate in the algal mud, it exists in the liquid-phase product.

(4) The DME separated from the liquid-phase product can be recovered and recycled after being pressurized and liquefied again, saving costs and improving energy utilization efficiency.

Description of drawings

FIG. 1 is a flow chart of the present invention.

FIG. 2 is a schematic diagram of the connection relationship of the device used in the present invention.

In Figure 2: 1: DME gas tank; 2: Flow regulating valve; 3, 17: Air pressure pump; 4: Storage tank inlet valve; 5: Liquid DME temporary storage tank; 6: Storage tank outlet valve; 7: Reactor Inlet valve; 8: Reactor; 9: Reactor operating parameter regulator; 10: Pressure regulating valve; 11: Gas-liquid separation tank; 12: Liquid flow valve; 13: Gas flow valve; 14: Gas inlet valve; 15: Gas drying tank; 16: Gas outlet valve; 18: Recovery tank inlet valve; 19: Recovery tank; 20: Pressure control gauge; 21: DME recycling inlet valve.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

The algal mud adopted in the following examples is taken from the algal water separation station of Taihu Huangnitian Port, the moisture content is 95%, and the phosphate ester content is 27% of the dry weight of the algal mud. The phosphoric acid ester of the present invention is a polar organic compound, including phosphoric acid monoester, diester and triester, is liquid at room temperature, and has a specific gravity (20°C) of 1.165.

Fig. 1 is the flow chart of the present invention, as shown in Fig. 1, a kind of method utilizing dimethyl ether to extract phosphoric acid ester in algal mud, the steps are as follows:

Step 1: the algal mud is placed in the reactor 8, the DME in the DME gas tank 1 is converted into a liquid state by the air pressure pump 3, from the gas tank, the liquid DME temporary storage tank 5 is entered through the output pipeline, and then injected into the reactor, Dissolve the phosphate ester in the algal mud, adjust the amount of DME used by the reactor operating parameter regulator 9 to be 15 to 30 times the water content of the algal mud, the reaction pressure is 0.5 to 2 MPa, the reaction temperature is 15 to 30 ° C, and the reaction time is 20 to 20 times. 40min, the stirring speed of the reaction kettle is 60rpm～120rpm/min, and the stirring time is 20～40min.

Step 2: After the DME dissolves the algal slime, the pressure is reduced by the pressure regulating valve 10 of the reaction kettle, and the product is separated into two phases of solid and liquid, the separation pressure difference is set to 0.5～2MPa, and the separation time is 1～2min. After the solid-liquid separation, the solid phase remains in the reactor, which is dehydrated algal mud, and the moisture content is reduced from 95% to 40%, which can meet the requirements of subsequent treatment and disposal such as landfill and incineration; the solid phase can be taken out by opening the reactor 8 The product undergoes subsequent processing.

Step 3: the liquid-phase product after the solid-liquid separation is input into the gas-liquid separation tank 11, and the DME in the liquid-phase product is converted into gaseous separation at normal temperature, and the gas flow valve 13 and the gas inlet valve 14 are opened successively, and the DME is separated by gas-liquid separation. The second output pipeline of the tank 11 enters the drying tank 15. After drying, the DME is pressurized and liquefied again through the air pressure pump 17 and enters the recovery tank 20 from the output pipeline of the drying tank. After the liquid DME in the recovery tank 20 is collected, the DME can be opened. The inlet valve 21 is recycled and injected into the output pipeline of the DME gas tank 1 to realize the recycling of DME. The liquid phase product after DME separation is a mixture of water, phosphate ester and other water-soluble products. Because phosphate ester is liquid at room temperature and its specific gravity is greater than that of water, phosphate ester can be separated after standing for stratification.

Embodiment 1-6 is the investigation effect to phosphoric acid ester extraction rate under different reaction conditions, and the results are shown in Table 1:

Table 1

From Examples 1, 2, and 3, it can be concluded that the greater the mass ratio of water content in DME to algal mud, the higher the dehydration rate of algal mud and the higher the extraction rate of phosphate ester. From Examples 1 and 4, it can be concluded that the longer the reaction time, the higher the dehydration rate and the phosphate extraction rate of the algal sludge. From Examples 3 and 5, it can be concluded that the greater the stirring speed, the higher the dehydration rate of algal sludge and the extraction rate of phosphate ester. The viscosity of DME increases with pressure, and in general low solvent viscosity has a beneficial effect on many extraction systems, as it aids solvent mixing and penetration into the sample matrix. Therefore, the increase of pressure will reduce the extraction effect of DME, but the change of pressure cannot change the polarity of DME. In order to balance the conversion of gaseous DME into liquid and the extraction effect, the inventors set the pressure to 0.5 MPa.

Example 7 Investigation on the extraction rate of phosphate ester at reaction temperature

Polarity is the key to determining solubility, because phosphate ester is a polar organic compound . According to the principle of similar compatibility, it is necessary to adjust DME to be a polar solvent, and the larger the dielectric constant, the stronger the polarity, and vice versa. less polar.

Dielectric constant between 0-5: non-polar

Dielectric constant between 5-30: medium (or semi-polar)

Dielectric constant >30: strong polarity

The inventors evaluated the parameters affecting the extraction rate of phosphate ester (relative dielectric constant of DME) at different temperatures, as shown in Table 2. It can be seen that the temperature increases, the dielectric constant decreases, and the extraction rate of phosphate ester decreases. (The extraction rate of phosphate ester was measured at a mass ratio of DME:H ₂ O of 30 times, the reaction time was 35 min, and the stirring speed was 60 rpm).

Table 2

Example 8

FIG. 2 is a schematic diagram of the connection relationship of the device used in the present invention. As shown in Figure 2, the output pipeline of the DME gas tank 1 is connected to the liquid DME temporary storage tank 5 through the flow regulating valve 2; the output pipeline of the liquid DME temporary storage tank 5 is connected with the storage tank outlet valve 6 and the reactor inlet valve 7 in turn. The input pipeline of the reactor 8 is connected; the output pipeline of the reactor 8 is connected with the input pipeline of the gas-liquid separation tank 11 through the pressure regulating valve 10; The liquid can further extract the phosphorus element in it.

The second output pipeline of the gas-liquid separation tank 11 is connected to the input pipeline of the drying tank 15 through the gas flow valve 13 and the gas inlet valve 14 in turn; the output pipeline of the drying tank 15 is connected to the recovery tank through the gas outlet valve 16 and the recovery tank inlet valve 18. Tank 19; the output pipeline of the recovery tank is connected to the output pipeline of the DME gas tank through the DME recycling inlet valve 21.

Claims (6)

1. A method for extracting phosphate from algae mud by using dimethyl ether is characterized by comprising the following steps:

placing the algae mud into a reaction kettle, converting DME into liquid by an air pressure pump, pressing the liquid into the reaction kettle, uniformly mixing the liquid with the algae mud, and dissolving phosphate ester of the algae mud by using the DME;

step (2), after dissolving phosphate ester by DME, carrying out solid-liquid separation on the mixture, wherein the solid phase is dehydrated algae mud, the water content is reduced to 40%, and the requirement of subsequent landfill incineration is met;

and (3) separating the obtained liquid-phase product, converting the liquid DME into a gas state at normal temperature and under reduced pressure, collecting the gas-phase product for reuse, and further extracting the residual liquid-phase product rich in phosphate to obtain the phosphorus element.

2. The method for extracting phosphate from algal mud by using dimethyl ether according to claim 1, wherein in the step (1), the amount of the liquid DME is 15-30 times of the water content of the algal mud.

3. The method for extracting phosphate from algal mud by using dimethyl ether according to claim 1, wherein in the step (2), the pressure of a reaction kettle for dissolving phosphate by DME is 0.5-2 MPa, the temperature is 15-30 ℃, and the reaction time is 20-40 min.

4. The method for extracting phosphate from algal mud by using dimethyl ether according to claim 1, wherein in the step (2), the solid-liquid two phases are separated by filtration by setting a separation pressure difference, the separation pressure difference is set to be 0.5-2 MPa, and the separation time is 1-2 min.

5. The method for extracting phosphate from algal mud by using dimethyl ether according to claim 3, wherein in the step (2), the polarity of DME is adjusted to be consistent with that of phosphate by adjusting the pressure and temperature of the reaction kettle, so as to dissolve the phosphate.

6. The method for extracting phosphate from algae mud by using dimethyl ether as claimed in claim 1, wherein in the step (1), the algae mud is waste biomass formed by flocculating and dewatering through an algae-water separation station after the blue algae is salvaged, and is rich in phosphorus element, and the water content is 89% -95%.

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