Method and system for converting waste carbon in chemical wastewater

Abstract

The invention relates to the technical field of chemical industry, and discloses a method for converting waste carbon in chemical wastewater, which comprises the following steps: (1) carrying out biochemical treatment on the chemical wastewater to obtain CO2 and sludge; (2) carrying out conversion treatment on the CO2 to obtain algae mud; and (3) carrying out thermal cracking treatment on the sludge and the algae mud to obtain combustible gas and biochar. According to the method, closed-loop carbon conversion is realized, and carbon in wastewater, gas and solid in the chemical industrial wastewater process is utilized, so that the capture rate of carbon dioxide is greater than 90%, the yield of biomass charcoal is lower than 30%, and the goal of synergistic interaction of pollution reduction and carbon reduction of a chemical plant is achieved.

Description

Technical Field

[0001] The present invention relates to the field of chemical technology, and in particular to a method and system for converting waste carbon in chemical wastewater. Background Art

[0002] Since the 20th century, CO2 emissions have led to global warming, and many countries have begun to take a series of actions and measures to try to solve this global environmental problem. Wastewater treatment plants have also become one of the sources of CO2 emissions. Chemical production is a high-water-consuming and high-wastewater process, which produces a large amount of chemical wastewater that needs to be treated. When chemical wastewater enters the sewage treatment plant, the treated wastewater can be discharged after meeting the relevant regulatory requirements. The chemical wastewater treatment plant can be regarded as an open carbon emission system. On the one hand, CO2 is directly discharged into the air during the wastewater treatment process. On the other hand, in addition to CO2, a large amount of residual sludge is generated during the biochemical treatment of wastewater. Especially in chemical wastewater treatment plants, these residual sludges contain high concentrations of toxic substances, including pathogens, organic pollutants and heavy metals, and are hazardous wastes. If they are not safely and properly disposed of, they will cause secondary environmental pollution.

[0003] At present, energy optimization of sewage treatment plants mainly involves water-energy relationship. However, these methods only reduce the consumption of fossil fuels and their related carbon emissions, and few people consider using wastewater treatment to directly convert and utilize carbon in the wastewater-carbon relationship. Therefore, in view of the shortcomings of the prior art, the present invention provides a method and system for converting waste carbon in chemical wastewater to achieve the dual goals of "pollution control and emission reduction". Summary of the invention

[0004] The purpose of the present invention is to overcome the problem in the prior art that only focuses on carbon reduction in wastewater, while ignoring the conversion and utilization of gaseous carbon and solid carbon in the water treatment process in the wastewater-carbon relationship, and to provide a method and system for converting waste carbon in chemical wastewater.

[0005] In order to achieve the above object, the first aspect of the present invention provides a method for converting waste carbon in chemical wastewater, wherein the method comprises:

[0006] (1) Biochemical treatment of chemical wastewater to obtain CO2 and sludge;

[0007] (2) converting the CO2 to obtain algae mud;

[0008] (3) The sludge and the algae mud are subjected to thermal cracking to obtain combustible gas and biochar.

[0009] A second aspect of the present invention provides a system for converting waste carbon in chemical wastewater, wherein the system comprises:

[0010] Biochemical treatment unit, used to biochemically treat organic pollutants in chemical wastewater to obtain CO2 and sludge;

[0011] A gas biological capture and conversion unit, used to capture and convert the CO2 to obtain algae mud;

[0012] The biomass thermal cracking treatment unit is used to thermally crack the sludge and the algae mud to obtain combustible gas and biochar.

[0013] Through the above technical solution, the present invention achieves the following beneficial technical effects:

[0014] By adopting the waste carbon conversion method in chemical wastewater provided by the present invention, the chemical wastewater is subjected to a comprehensive treatment of biochemical treatment, conversion treatment and thermal cracking treatment, so that the carbon dioxide capture rate is greater than 90% and the biomass charcoal yield is less than 40%; in addition, through closed-loop carbon conversion and utilization of carbon in wastewater, gas and solid in the process of chemical production wastewater, the goal of synergistic efficiency improvement of "pollution reduction and carbon reduction" in chemical plants is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a process flow chart for the conversion of waste carbon in chemical wastewater. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] A first aspect of the present invention provides a method for converting waste carbon in chemical wastewater, wherein the method comprises:

[0018] (1) Biochemical treatment of chemical wastewater to obtain CO2 and sludge;

[0019] (2) converting the CO2 to obtain algae mud;

[0020] (3) The sludge and the algae mud are subjected to thermal cracking to obtain combustible gas and biochar.

[0021] In the present invention, the source of the chemical wastewater is not particularly limited, for example, it can be petrochemical wastewater. More specifically, the CODcr concentration in the chemical wastewater is 3900-4100 mg / L, and the pH value is 4.1-5.8.

[0022] According to some embodiments of the present invention, in step (1), the biochemical treatment method includes oxidizing the chemical wastewater using aerobic activated sludge.

[0023] In order to ensure the purification efficiency of the biochemical treatment reactor, a certain amount of sludge concentration must be maintained in the reactor. Preferably, the concentration of the aerobic activated sludge is 4-5 g / L.

[0024] In the present invention, when the concentration and dosage of the well-cultivated activated sludge treatment meet the above-mentioned limited range, the concentration of organic wastewater can be significantly reduced, and the COD value measured at the outlet is <300 mg / L, the COD removal rate is >90%, and the pH value is 6-9, thereby meeting the requirements for access to the pipeline network.

[0025] Preferably, the conditions of the biochemical treatment include: dissolved oxygen content of 2-3 g / L, temperature of 20-30° C., pH of 6-9, C / N ratio of (20-100): 1, and time of 24-48 h.

[0026] In order to further process the CO2 collected in the biochemical treatment, it is preferred to subject the CO2 to biological conversion treatment.

[0027] According to some embodiments of the present invention, the conversion method includes biochemically treating the CO2 using green algae.

[0028] Preferably, the green algae is Chlorella pyrenoidosa.

[0029] Preferably, the conditions for the green algae biochemical treatment include: a green algae concentration of 0.5-0.6 g / L, a light intensity of 2500-3000 lux, and a temperature of 25-30°C.

[0030] In the present invention, when the type of green algae and the conditions of biochemical treatment meet the above-mentioned limited range, a higher CO2 capture effect can be achieved.

[0031] According to some embodiments of the present invention, the moisture content of the sludge is 70-90wt%, preferably 75-80wt%.

[0032] In the present invention, if the water content of the sludge is too low, the fluidity is poor and the biochemical treatment time is long; if the water content is too high, the gasification of water requires more energy, resulting in energy waste.

[0033] In order to achieve deep conversion and utilization of waste carbon in chemical wastewater, the present invention further performs thermal cracking treatment on the sludge and algae mud, so that the waste carbon is converted into combustible gas and biochar, thereby improving the utilization efficiency of chemical wastewater.

[0034] According to some embodiments of the present invention, the conditions of the thermal cracking treatment include: a temperature of 500-900° C. and a heating rate of 10-30° C. / min.

[0035] Preferably, the conditions of the thermal cracking treatment include: a temperature of 600-700°C and a heating rate of 20-25°C / min.

[0036] In the present invention, when the conditions of the thermal cracking treatment meet the above-defined range, the thermal decomposition of the residual sludge and the residual algae mud is more complete, more pyrolysis gas is generated, and the biomass charcoal yield is lower.

[0037] A second aspect of the present invention provides a system for converting waste carbon in chemical wastewater, wherein the system comprises:

[0038] Biochemical treatment unit, used to biochemically treat organic pollutants in chemical wastewater to obtain CO2 and sludge;

[0039] A gas biological capture and conversion unit, used to capture and convert the CO2 to obtain algae mud;

[0040] The biomass thermal cracking treatment unit is used to thermally crack the sludge and the algae mud to obtain combustible gas and biochar.

[0041] According to some embodiments of the present invention, the CO2 outlet of the biochemical treatment unit is connected to the inlet of the gas biological capture and conversion unit, and the sludge outlet of the biochemical treatment unit is connected to the inlet of the thermal cracking treatment unit.

[0042] According to some embodiments of the present invention, the biochar outlet of the thermal cracking treatment unit is connected to the inlet of the biochemical treatment unit, and the algae mud outlet of the gas biological capture and conversion unit is connected to the inlet of the thermal cracking treatment unit.

[0043] According to some embodiments of the present invention, the system further comprises a boiler for supplying heat to the system.

[0044] According to some embodiments of the present invention, the combustible gas is used to provide a heat source for the gas biological capture and conversion unit and the boiler.

[0045] According to a particularly preferred embodiment of the present invention, the method for converting waste carbon in chemical wastewater provided by the present invention is described, and the specific steps are as follows:

[0046] The wastewater is pumped into the biochemical treatment unit, the concentration of aerobic activated sludge is 4-5g / L, and the conditions of biochemical treatment include: dissolved oxygen content is 2-3g / L, temperature is 20-30℃, pH is 6-9, C / N ratio is (20-100):1, and time is 24-48h. The water content of the residual sludge generated by the biochemical treatment unit is 75-80wt%, which is introduced into the gas biological capture and conversion unit. In the unit, Chlorella pyrenoidosa and / or Microcystis aeruginosa are selected, and the concentration of green algae is 0.5-0.6g / L. The light intensity is maintained at 2500-3000lux and the temperature is 25-30℃. The residual sludge and the residual algae mud are mixed and pumped into the thermal cracking treatment unit. The treatment temperature is 600-700℃, and the heating rate is 20-25℃ / min. The biomass charcoal and pyrolysis gas obtained after thermal cracking at the slag discharge outlet are hydrogen, methane, carbon monoxide and other hydrocarbon-containing gases. The biomass charcoal is used as a water treatment carrier material and is put into the biochemical treatment unit.

[0047] The present invention will be described in detail below through examples.

[0048] The CODcr value is determined in accordance with GB / T 11914-1989 Determination of Chemical Oxygen Demand of Water - Dichromate Method.

[0049] Method for determining the volume concentration of carbon dioxide: The carbon dioxide concentration at the inlet and outlet of the gas biocapture conversion unit is measured using an infrared gas analyzer (GXH-3010E1).

[0050]

[0051] C0 is the inlet carbon dioxide concentration (%); C i is the outlet carbon dioxide concentration (%).

[0052] Biochar yield (%) = 100% × (biochar mass / sludge mass).

[0053] The contents of hydrogen, methane, carbon monoxide and hydrocarbon gases are in accordance with GB / T 27885-2011 H2, N2, CO, CO2 and C1-C 18 Determination of hydrocarbons by gas chromatography.

[0054] The following examples and comparative examples are according to Figure 1 The process of waste carbon conversion is carried out.

[0055] Example 1

[0056] This example is used to illustrate the method for converting waste carbon in chemical wastewater provided by the present invention.

[0057] Take a chemical organic wastewater, CODcr concentration is 3900mg / L, pH value is 4.1, water inflow is 10000m 3 / d, adjust the pH of the wastewater to 7.0. First, pump the wastewater into the biochemical treatment unit, the concentration of aerobic activated sludge is 4g / L, the conditions of biochemical treatment include: dissolved oxygen content is 2g / L, temperature is 20℃, pH is 6.5, C / N ratio is 100:1, after 48h of treatment time, the CODcr value measured at the outlet is 240mg / L, COD removal rate is 93.85%, pH value is 8.1, meeting the requirements of connecting to the pipe network, the biochemical treatment unit produces 2010kg / d of residual sludge, the water content is 80%, the volume concentration of carbon dioxide generated during the biochemical treatment process is 2.1%, which is introduced into the gas biological capture and conversion unit, in which protein core chlorella and green algae concentration are selected The carbon dioxide capture rate is 91%, the residual algae mud is 100 kg / d, the water content is 83%, the residual sludge and the residual algae mud are mixed and pumped into the thermal cracking treatment unit, the treatment temperature is 700 ° C, the heating rate is 20 ° C / min, and the biomass charcoal after thermal cracking is obtained at the slag outlet. The biomass charcoal yield is 31.58%, and the content of the pyrolysis gas (in volume fraction) is 1.13% hydrogen, 2.77% carbon dioxide, 0.25% methane, and 95.8% other volatile carbon compounds. The biomass charcoal is put into the biochemical treatment unit as a water treatment carrier material.

[0058] Example 2

[0059] This example is used to illustrate the method for converting waste carbon in chemical wastewater provided by the present invention.

[0060] Take a chemical organic wastewater, CODcr concentration is 4100mg / L, pH value is 5.8, water inflow is 15000m 3 / d, adjust the pH of the wastewater to 7.0. First, pump the wastewater into the biochemical treatment unit, the concentration of aerobic activated sludge is 5g / L, the conditions of biochemical treatment include: dissolved oxygen content of 3g / L, temperature of 30℃, pH of 8, C / N ratio of 20:1, after 48h of treatment, the outlet CODcr is 256mg / L, COD removal rate is 93.76%, pH value is 7.9, which meets the requirements of connecting to the pipe network, the biochemical treatment unit produces 2915kg / d of residual sludge, the water content is 82%, the volume concentration of carbon dioxide generated in the biochemical treatment process is 2.5%, which is introduced into the gas biological capture and conversion unit, in which protein core chlorella is selected, the concentration of green algae is 0.5g / L, and the light is maintained. The illumination intensity is 3000 lux, the temperature is 20℃, the capture rate of carbon dioxide reaches 93%, the residual algae mud produced is 185kg / d, the water content is 84%, the residual sludge and residual algae mud are mixed and pumped into the thermal cracking treatment unit, the treatment temperature is 800℃, the heating rate is 20℃ / min, and the biomass charcoal after thermal cracking is obtained at the slag outlet. The biomass charcoal yield is 30.57%, and the content of the pyrolysis gas (in volume fraction) is 10.89% hydrogen, 8.33% carbon dioxide, 6.27% methane, 7.14% carbon monoxide, and 67.37% other volatile carbon compounds. The biomass charcoal is put into the biochemical treatment unit as a water treatment carrier material.

[0061] Comparative Example 1

[0062] According to the method of Example 1, the difference is that anaerobic activated sludge is used in the biochemical treatment unit, the biochemical treatment time is 48h, the CODcr at the outlet is 2120mg / L, the COD removal rate is 45.64%, the pH value is 6.5, which does not meet the requirements of connecting to the pipe network, and the biochemical treatment unit produces 267kg / d of residual sludge with a moisture content of 80%. The residual sludge is pumped into the thermal cracking treatment unit, and the slag outlet outlet obtains the biomass charcoal after thermal cracking, the biomass charcoal yield is 32.75%, and the content of the pyrolysis gas (in volume fraction) is 1.14% of hydrogen, 2.65% of carbon dioxide, 0.26% of methane, and 95.95% of other volatile carbon compounds. The biomass charcoal is returned to the biochemical treatment unit as a water treatment carrier material.

[0063] Comparative Example 2

[0064] According to the method of Example 1, the difference is that Microcystis aeruginosa is selected in the gas biological capture conversion unit. The treatment time of the biochemical treatment unit is 48h, the CODcr measured at the outlet is 226mg / L, the COD removal rate is 94.21%, and the pH value is 8.0, which meets the requirements of access to the pipe network. The biochemical treatment unit produces 1989kg / d of residual sludge with a water content of 81%. The volume concentration of carbon dioxide produced during the biochemical treatment process is 2.4%. When introduced into the gas biological capture conversion unit, the capture rate of carbon dioxide is only 65%, and the residual algae mud produced is 86kg / d, with a water content of 89%. The residual sludge and the residual algae mud are mixed and pumped into the thermal cracking treatment unit, and the slag outlet is obtained. The biomass charcoal after thermal cracking has a biomass charcoal yield of 32.61%, and the content of the pyrolysis gas (in volume fraction) is 1.21% of hydrogen, 2.79% of carbon dioxide, 0.26% of methane, and 95.74% of other volatile carbon-containing compounds. Biochar is put into the biochemical treatment unit as a water treatment carrier material.

[0065] Comparative Example 3

[0066] According to the method of Example 1, the difference is that the illumination intensity of the gas biological capture conversion unit is 1000 lux. The biochemical treatment unit is treated for 48 hours, the outlet CODcr is 241 mg / L, and the COD removal rate is 93.82%. The pH value is 8.2, which meets the requirements of access to the pipeline network. The biochemical treatment unit produces 2019 kg / d of residual sludge, with a water content of 84%. The volume concentration of carbon dioxide produced during the biochemical treatment process is 2.1%. When introduced into the gas biological capture conversion unit, the capture rate of carbon dioxide is only 45%, and the residual algae mud produced is 41 kg / d, with a water content of 88%. The residual sludge and the residual algae mud are mixed and pumped into the thermal cracking treatment unit, and the slag outlet is obtained. The biomass charcoal after thermal cracking has a biomass charcoal yield of 31.43%, and the content of the pyrolysis gas (in volume fraction) is 1.15% of hydrogen, 2.67% of carbon dioxide, 0.23% of methane, and 95.95% of other volatile carbon-containing compounds. Biochar is put into the biochemical treatment unit as a water treatment carrier material.

[0067] Comparative Example 4

[0068] According to the method of Example 1, the difference is that the temperature set in the gas biological capture conversion unit is 35°C. The biochemical treatment unit is treated for 48 hours, the CODcr at the outlet is 198mg / L, the COD removal rate is 94.92%, and the pH value is 8.2, which meets the requirements for access to the pipe network. The biochemical treatment unit produces 1990kg / d of residual sludge with a water content of 82%. The volume concentration of carbon dioxide produced during the biochemical treatment process is 2.2%. When introduced into the gas biological capture conversion unit, the capture rate of carbon dioxide is only 31%, and the residual algae mud produced is 12kg / d with a water content of 87%. The residual sludge and the residual algae mud are mixed and pumped into the thermal cracking treatment unit, and the slag outlet is obtained. The biomass charcoal after thermal cracking has a biomass charcoal yield of 32.13%, and the content of the pyrolysis gas (in volume fraction) is 1.16% for hydrogen, 2.69% for carbon dioxide, 0.23% for methane, and 95.92% for other volatile carbon-containing compounds. Biochar is put into the biochemical treatment unit as a water treatment carrier material.

[0069] Comparative Example 5

[0070] According to the method of Example 2, the difference is that the thermal cracking treatment unit has a treatment temperature of 400°C. The biochemical treatment unit is treated for 48 hours, and the CODcr value measured at the outlet is 275mg / L, the COD removal rate is 93.29%, and the pH value is 8.2, which meets the requirements of access to the pipe network. The biochemical treatment unit produces 3020kg / d of residual sludge with a water content of 82%. The volume concentration of carbon dioxide produced during the biochemical treatment process is 2.1%, which is introduced into the gas biological capture and conversion unit. The capture rate of carbon dioxide reaches 92%, and the residual algae mud produced is 210kg / d, with a water content of 87%. The residual sludge and the residual algae mud are mixed and pumped into the thermal cracking treatment unit, and the slag outlet outlet obtains the biomass charcoal after thermal cracking, and the biomass charcoal yield is 42.5%. The content of the pyrolysis gas (in volume fraction) is 0.03% for hydrogen, 0.01% for carbon dioxide, 0.01% for methane, and 99.95% for other volatile carbon-containing compounds. Biochar is put into the biochemical treatment unit as a water treatment carrier material.

[0071] Comparative Example 6

[0072] According to the method of Example 2, the difference is that the heating rate of the thermal cracking treatment unit is 5°C / min. The biochemical treatment unit is treated for 48 hours, the CODcr value measured at the outlet is 243mg / L, the COD removal rate is 94.07%, and the pH value is 8.3, which meets the requirements of access to the pipeline network. The biochemical treatment unit produces 2980kg / d of residual sludge with a water content of 82%. The volume concentration of carbon dioxide produced during the biochemical treatment process is 1.9%, which is introduced into the gas biological capture and conversion unit. The capture rate of carbon dioxide reaches 94%, and the residual algae mud produced is 265kg / d, with a water content of 87%. The residual sludge and the residual algae mud are mixed and pumped into the thermal cracking treatment unit, and the slag outlet outlet obtains the biomass charcoal after thermal cracking, and the biomass charcoal yield is 44.41%. The content of the pyrolysis gas (in volume fraction) is 0.98% of hydrogen, 2.41% of carbon dioxide, 0.28% of methane, and 96.33% of other volatile carbon-containing compounds. Biochar is put into the biochemical treatment unit as a water treatment carrier material.

[0073] Comparative Example 7

[0074] The method of Example 2 is followed, except that before the thermal cracking treatment unit, the remaining sludge and the remaining algae mud are mixed and dehydrated, and the moisture content is reduced to 60%. After 48 hours of treatment in the biochemical treatment unit, the CODcr value measured at the outlet was 221 mg / L, the COD removal rate was 94.61%, and the pH value was 8.2, which met the requirements for access to the pipeline network. The biochemical treatment unit produced 3098 kg / d of residual sludge with a water content of 82%. The volume concentration of carbon dioxide produced during the biochemical treatment process was 2.0%. It was introduced into the gas biological capture and conversion unit, and the capture rate of carbon dioxide reached 92.8%. The residual algae mud produced was 245 kg / d with a water content of 87%. The residual sludge and residual algae mud were mixed and pumped into the thermal cracking treatment unit. The pyrolysis biochar was obtained at the slag outlet. The biochar yield was 43.31%. The content of the pyrolysis gas (in volume fraction) was 1.16% hydrogen, 2.73% carbon dioxide, 0.28% methane, and 95.83% other volatile carbon compounds. The biochar was put into the biochemical treatment unit as a water treatment carrier material.

[0075] According to the data of Examples 1-2 and Comparative Examples 1-7, it can be seen that the waste carbon conversion method in chemical wastewater provided by the present invention is used to comprehensively treat the chemical wastewater with biochemical treatment, conversion treatment and pyrolysis treatment, and the process conditions of each treatment are controlled so that the capture rate of carbon dioxide is greater than 90%, the biomass charcoal yield is less than 40%, and more pyrolysis gas is obtained at the same time; Comparative Example 1 uses anaerobic activated sludge in the biochemical treatment unit. Due to the low treatment efficiency of anaerobic activated sludge, the removal capacity of the COD value of wastewater is limited, so that the wastewater at the outlet of the biochemical treatment does not meet the requirements of the pipe network, and anaerobic fermentation gases such as methane are generated during the biochemical treatment process, and carbon-containing gases such as methane are generated during the anaerobic biological decomposition process. Can not be captured and utilized by microalgae; Comparative Example 2 uses Microcystis aeruginosa in the gas biological capture and conversion unit. Since Microcystis aeruginosa has a better capture effect on carbon dioxide than green algae, the capture rate of carbon dioxide is significantly reduced, and the amount of residual algae mud produced is significantly reduced; Comparative Example 3 reduces the illumination intensity of the gas biological capture and conversion unit. Due to the light intensity Insufficient, the microalgae capture effect is not ideal, resulting in a significant decrease in the capture rate of carbon dioxide, and a significant decrease in the amount of residual algae mud produced; in comparative example 4, the temperature of the gas biological capture and conversion unit is increased. Due to the high temperature, the microalgae capture effect is not ideal, the capture rate of carbon dioxide is significantly reduced, and the amount of residual algae mud produced is significantly reduced; in comparative example 5, the temperature of the thermal cracking treatment unit is reduced, resulting in low decomposition efficiency of biological sludge and biological algae mud, and more biomass charcoal is produced, which needs to be temporarily stored and put into the biochemical treatment unit in batches, increasing the operating cost; in comparative example 6, the heating rate of the thermal cracking treatment unit is reduced, resulting in low decomposition efficiency of biological sludge and biological algae mud, and more biomass charcoal is produced, which needs to be temporarily stored and put into the biochemical treatment unit in batches, increasing the operating cost; in comparative example 7, the residual sludge and the residual algae mud are mixed and dehydrated to reduce the water content and poor fluidity. Due to the reduction in the water content of the residual sludge and the residual algae mud treated by thermal cracking, on the one hand, more biomass charcoal is produced, which needs to be temporarily stored and put into the biochemical treatment unit in batches, increasing the operating cost. On the other hand, dehydration prior to treatment also increases operating costs.

[0076] In summary, by adopting the waste carbon conversion method in chemical wastewater provided by the present invention, the chemical wastewater is subjected to a comprehensive treatment of biochemical treatment, conversion treatment and thermal cracking treatment, so that the carbon dioxide capture rate is greater than 90% and the biochar yield is less than 40%.

[0077] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for converting waste carbon in chemical wastewater, characterized in that: The method includes: (1) Biochemical treatment of chemical wastewater to obtain CO2 and sludge; (2) converting the CO2 to obtain algae mud; (3) The sludge and the algae mud are subjected to thermal cracking to obtain combustible gas and biochar.

2. The method according to claim 1, wherein: In step (1), the biochemical treatment method includes using aerobic activated sludge to oxidize the chemical wastewater; Preferably, the concentration of the aerobic activated sludge is 4-5 g / L; Preferably, the conditions of the biochemical treatment include: dissolved oxygen content of 2-3 g / L, temperature of 20-30° C., pH of 6-9, C / N ratio of (20-100):1, and time of 24-48 h.

3. The method according to claim 1, wherein: The conversion treatment method includes biochemically treating the CO2 using green algae; Preferably, the green algae is Chlorella pyrenoidosa; Preferably, the conditions for the green algae biochemical treatment include: a green algae concentration of 0.5-0.6 g / L, a light intensity of 2500-3000 lux, and a temperature of 25-30°C.

4. The method according to any one of claims 1 to 3, wherein: The water content of the sludge is 70-90wt%, preferably 75-80wt%.

5. The method according to any one of claims 1 to 4, wherein: The conditions of the thermal cracking treatment include: a temperature of 500-900°C and a heating rate of 10-30°C / min; Preferably, the conditions of the thermal cracking treatment include: a temperature of 600-700°C and a heating rate of 20-25°C / min.

6. A system for converting waste carbon in chemical wastewater, characterized in that: The system includes: Biochemical treatment unit, used to biochemically treat organic pollutants in chemical wastewater to obtain CO2 and sludge; A gas biological capture and conversion unit, used to capture and convert the CO2 to obtain algae mud; The biomass thermal cracking treatment unit is used to thermally crack the sludge and the algae mud to obtain combustible gas and biochar.

7. The system according to claim 1, wherein: The CO2 outlet of the biochemical treatment unit is connected to the inlet of the gas biological capture and conversion unit, and the sludge outlet of the biochemical treatment unit is connected to the inlet of the thermal cracking treatment unit.

8. The system according to claim 6 or 7, wherein: The biochar outlet of the thermal cracking treatment unit is connected to the inlet of the biochemical treatment unit, and the algae mud outlet of the gas biological capture and conversion unit is connected to the inlet of the thermal cracking treatment unit.

9. The system according to any one of claims 6 to 8, wherein: The system further comprises a boiler for supplying heat to the system.

10. The system according to any one of claims 6 to 9, wherein: The combustible gas is used to provide a heat source for the gas biological capture and conversion unit and the boiler.

Images