Biomass coal water slurry and preparation method thereof

Abstract

According to the biomass coal water slurry and the preparation method thereof, the slurry body of the biomass coal water slurry is biochar, the calorific value of the biomass coal water slurry is 3000 kcal / kg or above, the apparent viscosity of the biomass coal water slurry is 1200 mPa.s or below, the calorific value is high, the fluidity is good, the slurry body of the biomass coal water slurry completely replaces traditional fossil fuel with biomass-sourced carbon, and the biomass coal water slurry has the advantages of environmental protection and environmental protection. The biochar can be prepared from waste biomass resources, so that the energy-saving and environment-friendly effects are achieved, and a green and environment-friendly new route is provided for waste biomass treatment.

Description

Technical Field

[0001] The invention relates to the technical field of waste biomass treatment, and in particular to a biomass water-coal slurry and a preparation method thereof. Background Art

[0002] The disposal of waste biomass has always been a major problem in my country's agricultural development, especially straw. Large-scale stacking and improper handling will not only cause environmental pollution, but also waste precious resources. At present, my country is steadily promoting the comprehensive utilization of waste biomass, especially straw as fertilizer, feed, fuel, base material and raw material, and promoting the comprehensive utilization and large-scale disposal of straw after leaving the field.

[0003] my country is a country rich in coal but short of oil and gas. As a clean coal fuel and gasification raw material, water-coal slurry is widely used in boilers, building materials, chemical industry and other fields. Especially in the field of coal chemical industry, the use of water-coal slurry has exceeded 20,000 tons / year, and chemical products such as synthetic ammonia, methanol and olefins are prepared through gasification technology. In the context of carbon neutrality, higher requirements are put forward for the clean use of coal and the substitution of renewable energy. Multiple energy sources are integrated, new and old energy sources are integrated, and new energy sources gradually replace the dominant position of fossil energy, thus achieving the goal of zero carbon.

[0004] At present, straw waste biomass has begun to be valued and used as energy, such as agricultural straw coal water slurry circulating fluidized combustion process (CN103148498B), biomass water coal slurry pulping, combustion method and integrated system (CN101639225B). The biomass used in these methods, processes and equipment can only replace part of the coal, the preparation process is complicated, the biomass conversion rate is low, direct biomass or biochar cannot meet the requirements of water coal slurry technology, it is difficult to replace coal for industrial application, and it is impossible to achieve large-scale utilization of waste and completely get rid of fossil fuels. Summary of the invention

[0005] Based on the above problems, the specific embodiment of the present invention provides a biomass water-coal slurry in which the slurry is completely replaced by carbon from biomass and a preparation method thereof. The specific scheme is as follows:

[0006] A biomass water-coal slurry, wherein the slurry of the biomass water-coal slurry is biochar, the calorific value of the biomass water-coal slurry is above 3000 kcal / kg, and the apparent viscosity is below 1200 mPa·s.

[0007] Optionally, the apparent viscosity is below 1000 mPa·s.

[0008] The method for preparing the biomass water-coal slurry as described above comprises the following steps:

[0009] Prepare straw biochar and wood biochar from straw and wood respectively, and form biochar with a calorific value of more than 4500 kcal / kg by the straw biochar and wood biochar;

[0010] The biomass water-coal slurry is prepared by mixing raw materials including the biochar, water, a surfactant and a flocculant;

[0011] The surfactant includes an ionic surfactant and a nonionic surfactant.

[0012] Optionally, based on 100 parts by weight of the biochar, the water is 60 to 75 parts by weight, the surfactant is 0.05 to 5 parts by weight, and the stabilizer is 0.05 to 5 parts by weight.

[0013] Optionally, the ionic surfactant is sodium methylenebis(methyl)naphthalene sulfonate or sodium dodecylbenzene sulfonate, and the nonionic surfactant is polyamide-modified hydrogenated castor oil and its derivatives or nonylphenol polyoxyethylene ether.

[0014] Optionally, the flocculant is polyacrylamide.

[0015] Optionally, in the biochar, the mass fraction of the straw biochar is 40 to 90 wt %, and the mass fraction of the wood biochar is 10 to 60 wt %.

[0016] Optionally, the straw biochar and wood biochar are prepared by anaerobic pyrolysis of straw and wood at a temperature of 350-450°C.

[0017] Optionally, the straw is at least one of reed, wheat straw, rice straw, corn straw and sorghum straw.

[0018] Optionally, the wood is at least one of bark, branches and trunks.

[0019] The biomass water-coal slurry and its preparation method according to the specific embodiment of the present invention, the slurry of the biomass water-coal slurry is biochar, the calorific value of the biomass water-coal slurry is above 3000kcal / kg, the apparent viscosity is below 1200mPa·s, the slurry of the biomass water-coal slurry is completely replaced by charcoal from biomass instead of traditional fossil fuels, the biochar can be prepared from waste biomass resources, plays a role in energy conservation and environmental protection, and provides a new green and environmentally friendly route for the treatment of waste biomass. The preparation method of the biomass water-coal slurry according to the specific embodiment of the present invention can reduce the emission of nitrogen oxides and sulfur, realize the large-scale application and consumption of biomass in the chemical industry, the heavy metals in the biochar will be enriched in ash or glass, realize the efficient recycling of biomass, and reduce the emission of pollutants. DETAILED DESCRIPTION

[0020] A specific embodiment of the present invention provides a biomass water-coal slurry, wherein the slurry of the biomass water-coal slurry is biochar, the calorific value of the biomass water-coal slurry is above 3000 kcal / kg, and the apparent viscosity is below 1200 mPa·s.

[0021] The biomass water-coal slurry of the specific embodiment of the present invention does not require traditional petrochemical raw materials, is completely prepared from biomass charcoal, has high calorific value, good fluidity, and can replace traditional water-coal slurry. In some specific embodiments, the calorific value of the water-coal slurry is above 3200 kcal / kg, in some specific embodiments, the calorific value of the water-coal slurry is below 4500 kcal / kg, and in some specific embodiments, the calorific value of the water-coal slurry is below 4000 kcal / kg. The specific calorific value of the water-coal slurry can be, for example, 3300 kcal / kg, 3400 kcal / kg, 3500 kcal / kg, 3600 kcal / kg, 3700 kcal / kg, 3800 kcal / kg or 3900 kcal / kg, etc. In some specific embodiments, the apparent viscosity of the biomass water-coal slurry is below 1000 mPa·s, in some specific embodiments, the apparent viscosity of the biomass water-coal slurry is above 800 mPa·s, and in some specific embodiments, the apparent viscosity of the biomass water-coal slurry is above 900 mPa·s.

[0022] The inventors of the present invention found that the straw biochar has the disadvantages of low calorific value and high ash content when studying the application of straw biochar as water-coal slurry. In addition, since straw is a highly fibrous material and has strong water absorption, after pyrolysis, the biochar has many surface voids, which will cause a large amount of free water to be absorbed into the pores, weakening the effect of the surfactant, and failing to form a water-enclosed biochar structure, thereby causing the increase of the apparent viscosity of the slurry, poor fluidity, and failure to meet the use requirements. Wood biochar has the characteristics of high calorific value and low ash content. By adding a certain amount of wood biochar to the straw biochar, the shortcomings of low calorific value and high ash content of the straw biochar can be effectively compensated. Furthermore, by adding an ionic surfactant and a non-ionic surfactant, the ionic surfactant is beneficial to covering the large pores of the biomass and effectively preventing the biomass from absorbing water, while the non-ionic surfactant is beneficial to being absorbed into the interior of the biomass and eliminating the entry of some free water. After the two are combined, the apparent viscosity of the slurry can be effectively reduced, the flow stability can be improved, and the use requirements can be met. Based on this, a specific embodiment of the present invention provides a method for preparing the above-mentioned biomass water-coal slurry, comprising the following steps:

[0023] Prepare straw biochar and wood biochar from straw and wood respectively, and form biochar with a calorific value of more than 4500 kcal / kg by the straw biochar and wood biochar;

[0024] The biomass water-coal slurry is prepared by mixing raw materials including the biochar, water, a surfactant and a flocculant;

[0025] The surfactant includes an ionic surfactant and a nonionic surfactant.

[0026] The preparation method of biomass water-coal slurry according to the specific embodiment of the present invention, in some specific embodiments, the biochar is calculated based on 100 parts by weight, water is 60-75 parts by weight, further 65-70 parts by weight, and specific examples include 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight or 70 parts by weight, the surfactant is 0.05-5 parts by weight, further 0.5-2 parts by weight, and specific examples include 0.5 parts by weight, 1 part by weight, 1.5 parts by weight or 2 parts by weight, the flocculant is 0.05-5 parts by weight, further 0.1-1 parts by weight, and specific examples include 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight or 1 part by weight.

[0027] In the method for preparing biomass water-coal slurry according to a specific embodiment of the present invention, in some specific embodiments, in the biochar, the mass fraction of straw biochar is 40-90wt%, the mass fraction of wood biochar is 10-60wt%, and the mass ratio of straw biochar to wood biochar can be, for example, 40:60, 50:50, 60:40, 70:30, 80:20 or 90:10, etc.

[0028] In the method for preparing biomass water-coal slurry according to a specific embodiment of the present invention, in some specific embodiments, the ash mass content in the biochar is 10-20wt%, for example, it can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%, etc.

[0029] The preparation method of biomass water-coal slurry of the specific embodiment of the present invention, in some specific embodiments, the straw biochar and wood biochar are prepared by the straw and wood through an anaerobic pyrolysis process, in some specific embodiments, the reaction temperature of the anaerobic pyrolysis is 350-450°C, and specifically, for example, it can be 350°C, 360°C, 370°C, 380°C, 390°C, 410°C, 420°C, 430°C, 440°C or 450°C, etc. At this reaction temperature, during the pyrolysis process, the pyrolysis temperature can be maintained by the combustion of pyrolysis gas generated by its own pyrolysis to maintain the temperature of the pyrolysis furnace, without adding additional fuel, the pyrolysis furnace can operate normally, and at the same time, the biochar prepared at the reaction temperature has low ash content and high charcoal yield. In some specific embodiments, the pyrolysis reaction time is 15-30min.

[0030] In the preparation method of biomass water-coal slurry in a specific embodiment of the present invention, the anaerobic pyrolysis also produces 30-40wt% of pyrolysis gas and 30-40wt% of pyrolysis liquid, and the components of the pyrolysis liquid are wood vinegar and tar. In some specific embodiments, the preparation method also includes further separating and purifying the pyrolysis liquid produced during the anaerobic pyrolysis process into wood vinegar and tar, and sending the pyrolysis gas produced during the anaerobic pyrolysis process to a gas boiler for high-temperature combustion, and sending the generated high-temperature flue gas to a pyrolysis furnace to maintain the reaction temperature of the pyrolysis furnace.

[0031] In the method for preparing biomass water-coal slurry according to a specific embodiment of the present invention, in some specific embodiments, the ionic surfactant is sodium methylenebismethylnaphthalene sulfonate or sodium dodecylbenzene sulfonate.

[0032] The preparation method of the biomass water-coal slurry of the specific embodiment of the present invention, in some specific embodiments, the non-ionic surfactant is nonylphenol polyoxyethylene ether, in some specific embodiments, the non-ionic surfactant is polyamide-modified hydrogenated castor oil and its derivatives, polyamide-modified hydrogenated castor oil and its derivatives have a suitable molecular structure, and have a better viscosity reduction effect on the biomass water-coal slurry. In some specific embodiments, the mass ratio of the ionic surfactant to the non-ionic surfactant is 1:10 to 10:1, in some specific embodiments, the mass ratio of the ionic surfactant to the non-ionic surfactant is 1:5 to 5:1, for example, it can be 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1 or 5:1, etc., which can be adjusted according to the apparent viscosity requirements of the water-coal slurry.

[0033] In the method for preparing biomass water-coal slurry according to a specific embodiment of the present invention, in some specific embodiments, the flocculant is polyacrylamide.

[0034] The preparation method of biomass water-coal slurry according to the specific embodiment of the present invention, in some specific embodiments, the straw biochar and the wood biochar are composed of biochar with a calorific value of more than 5000 kcal / kg, in some specific embodiments, the calorific value of the biochar is below 6000 kcal / kg, and in some specific embodiments, the calorific value of the biochar is below 5500 kcal / kg. The specific calorific value of the biochar can be, for example, 5000 kcal / kg, 5100 kcal / kg, 5200 kcal / kg, 5300 kcal / kg, 5400 kcal / kg or 5500 kcal / kg, etc.

[0035] In the preparation method of biomass water-coal slurry according to a specific embodiment of the present invention, in some specific embodiments, the calorific value of the straw biochar is 4200-5200 kcal / kg, for example, 4200 kcal / kg, 4300 kcal / kg, 4400 kcal / kg, 4500 kcal / kg, 4600 kcal / kg, 4700 kcal / kg, 4800 kcal / kg, 4900 kcal / kg, 5000 kcal / kg, 5100 kcal / kg or 5200 kcal / kg, and the calorific value of the wood biochar is 5500-6000 kcal / kg, for example, 5500 kcal / kg, 5600 kcal / kg, 5700 kcal / kg, 5800 kcal / kg, 5900 kcal / kg or 6000 kcal / kg, and the like.

[0036] In the method for preparing biomass water-coal slurry according to a specific embodiment of the present invention, in some specific embodiments, before the straw and wood are used to prepare the straw biochar and wood biochar through an anaerobic pyrolysis process, the straw and wood / waste wood are collected, crushed into straw particles and wood particles with a length of 5 to 8 mm by a crusher, dried, and sent to a briquetting machine, where they are pressed and molded at a high temperature of about 100°C and cooled to form straw biomass blocks and wood biomass blocks, which are then sent to a pyrolysis device for adiabatic pyrolysis.

[0037] The preparation method of biomass water-coal slurry in a specific embodiment of the present invention, due to the small burner diameter during the utilization of water-coal slurry, the large coal particle size is easy to clog the burner, the particle size is required to be small, the coal grindability index is low, and the energy consumption and life of the pulverizer are comprehensively considered. The coal is crushed to 120 meshes, and the water-coal slurry concentration can be controlled at 60wt% through grading technology and a better mixer. The grindability index of biochar is high and can be crushed into powder finer than 120 meshes, so that a biomass water-coal slurry with a slurry concentration of 60%-65% can be prepared, reducing process energy consumption and equipment investment. Therefore, in some specific embodiments, the biochar in the biomass water-coal slurry is crushed to finer than 120 meshes, in some specific embodiments, the biochar in the biomass water-coal slurry is crushed to finer than 130 meshes, in some specific embodiments, the biochar in the biomass water-coal slurry is crushed to finer than 140 meshes, and in some specific embodiments, the biochar in the biomass water-coal slurry is crushed to finer than 150 meshes or finer.

[0038] In the method for preparing biomass water-coal slurry according to a specific embodiment of the present invention, in some specific embodiments, the straw is at least one of reed, wheat straw, rice straw, corn straw and sorghum straw.

[0039] In the method for preparing biomass water-coal slurry according to a specific embodiment of the present invention, in some specific embodiments, the wood is at least one of bark, branches and trunks.

[0040] Example

[0041] Performance test description The calorific value and ash content of biochar are determined according to the method specified in GB / T 30732-2014 "Industrial analysis method of coal", and the calorific value and apparent viscosity of water-coal slurry are determined according to the method specified in GB / T18856 "Test method for water-coal slurry".

[0042] Example 1

[0043] Reed biochar preparation:

[0044] The collected reeds are sent to the feeding device, enter the double-shaft crusher through the conveyor belt, and then enter the fine crusher through the belt conveyor. After passing through the bag dust collector, they reach the belt conveyor and are transferred to the feeding conveyor. The briquetting machine is used to compress them into reed biomass blocks. The cross-sectional area of ​​the biomass blocks is 3cm*3cm and the length is less than 10cm.

[0045] The reed biomass blocks enter the feeder through the silo and are sent to the anaerobic pyrolysis device for pyrolysis. The pyrolysis temperatures are controlled at 400°C, 500°C, 600°C and 700°C, respectively. Continuous sampling is adopted. The reed biomass blocks stay in the pyrolysis furnace for 40 minutes. They are cooled to 40°C by a water cooler and reed biochar is obtained. The ash content, calorific value and charcoal yield of the reed biochar at different pyrolysis temperatures are tested. The results are shown in Table 1.

[0046] Table 1 Ash content, calorific value and charcoal yield of reed biochar at different pyrolysis temperatures

[0047] 400℃ 500℃ 600℃ 700℃ Ash wt% 18.9 20.4 21.3 22.0 Calorific value kcal / kg 4948 5163 5297 5319 Carbon yield% 36 33 32 29

[0048] As shown in the results in Table 1 above, as the pyrolysis temperature increases, although the calorific value of reed biochar increases, the charcoal yield decreases and the ash content increases.

[0049] Preparation of tree branch biochar:

[0050] The collected poplar branches are sent to the feeding device and then enter the double-shaft crusher through a conveyor belt to obtain branch segments of 5 to 8 cm in length. The branches are then sent to the dryer through a conveyor belt for drying. The dried branch segments are sent to an anaerobic pyrolysis device for pyrolysis. The pyrolysis temperature is controlled at 400°C and a continuous sampling method is adopted. The branch biomass blocks stay in the pyrolysis furnace for 40 minutes and are cooled to 40°C by a water cooler to obtain branch biochar. The ash content of the branch biochar is 5.8 (wt%), the calorific value is 6042 (kcal / kg), and the charcoal yield is 35%.

[0051] Biochar preparation:

[0052] The reed biochar prepared at the 400° C. pyrolysis temperature and the tree branch biochar were conveyed to a crusher at a mass ratio of 70:30 for the reed biochar and the tree branch biochar. After crushing, the carbon powder was sieved to a particle size of 150 mesh to obtain biochar powder.

[0053] Preparation of biomass water-coal slurry:

[0054] By weight, 65 parts of the above-mentioned biochar powder, 35 parts of water, 0.4 parts of sodium methylene bis(methyl naphthalene sulfonate), 0.1 parts of polyamide-modified hydrogenated castor oil, and 0.1 parts of polyacrylamide flocculant were added into a stirring tank and stirred into a biomass water-coal slurry. The calorific value of the biomass water-coal slurry was measured to be 3429 kcal / kg, and the apparent viscosity was 973 mPa·s.

[0055] Example 2

[0056] Rice straw biochar preparation:

[0057] The collected rice straw is sent to the feeding device, enters the double-shaft crusher through the conveyor belt, and then enters the fine crusher through the belt conveyor. After passing through the bag dust collector, it reaches the belt conveyor and is transferred to the feeding conveyor. The briquetting machine is used to compress it into rice straw biomass blocks. The cross-sectional area of ​​the biomass blocks is 3cm*3cm and the length is less than 10cm.

[0058] The rice straw biomass block enters the feeder through the silo and is sent to the anaerobic pyrolysis device for pyrolysis. The pyrolysis temperature is controlled at 400°C. Continuous sampling is adopted. The rice straw biomass block stays in the pyrolysis furnace for 40 minutes. It is cooled to 40°C by a water cooler and the rice straw biochar is obtained. The ash content of the rice straw biochar is tested to be 24.9 (wt%), the calorific value is 4311 (kcal / kg), and the charcoal yield is 35%.

[0059] Bark biochar preparation:

[0060] The collected bark is sent to the feeding device and then enters the double-shaft crusher through a conveyor belt to obtain bark blocks of 5 to 8 cm in length. The blocks are then sent to the dryer through a conveyor belt for drying. The dried bark blocks are sent to an anaerobic pyrolysis device for pyrolysis. The pyrolysis temperature is controlled at 400°C and a continuous sampling method is adopted. The bark biomass blocks stay in the pyrolysis furnace for 40 minutes and are cooled to 40°C by a water cooler to obtain bark biochar. The ash content of the bark biochar is tested to be 6.3 (wt%), the calorific value is 5984 (kcal / kg), and the charcoal yield is 41%.

[0061] Biochar preparation:

[0062] The rice straw biochar and the bark biochar were conveyed to a crusher at a ratio of 47:53 by mass of the rice straw biochar and the bark biochar. After crushing, the carbon powder particle size was sieved to 150 mesh to obtain biochar powder.

[0063] Preparation of biomass water-coal slurry:

[0064] By weight, 65 parts of the above-mentioned biochar powder, 35 parts of water, 0.4 parts of sodium methylene bis(methyl naphthalene sulfonate), 0.1 parts of polyamide-modified hydrogenated castor oil, and 0.1 parts of polyacrylamide flocculant were added into a stirring tank and stirred into a biomass water-coal slurry. The calorific value of the biomass water-coal slurry was measured to be 3429 kcal / kg, and the apparent viscosity was 973 mPa·s.

[0065] Example 3

[0066] Biomass water-coal slurry was prepared. Except that sodium methylenebismethylnaphthalene sulfonate was replaced by sodium dodecylbenzene sulfonate and polyamide-modified hydrogenated castor oil was replaced by nonylphenol polyoxyethylene ether during the preparation of the biomass water-coal slurry, the other steps were the same as those in Example 1. The calorific value of the biomass water-coal slurry was measured to be 3429 kcal / kg, and the apparent viscosity was 1181 mPa·s.

[0067] Comparative Example 1

[0068] Biomass water-coal slurry was prepared. Except that polyamide-modified hydrogenated castor oil was not added during the preparation of the biomass water-coal slurry, other steps were the same as those in Example 1. The calorific value of the biomass water-coal slurry was measured to be 3429 kcal / kg, and the apparent viscosity was 1201 mPa·s.

[0069] Comparative Example 2

[0070] Biomass water-coal slurry was prepared. Except that sodium methylene bis(methyl naphthalene)sulfonate was not added during the preparation of the biomass water-coal slurry, the other steps were the same as those in Example 1. The calorific value of the biomass water-coal slurry was measured to be 3430 kcal / kg, and the apparent viscosity was 1324 mPa·s.

[0071] Comparative Example 3

[0072] Biomass water-coal slurry was prepared. Except that polyamide-modified hydrogenated castor oil and sodium methylenebismethylnaphthalene sulfonate were not added during the preparation of the biomass water-coal slurry, other steps were the same as those in Example 1. The calorific value of the biomass water-coal slurry was measured to be 3430 kcal / kg, and the apparent viscosity was 1764 mPa·s.

[0073] From the results of Example 1 and Comparative Examples 1 to 3, it can be seen that the apparent viscosity of biochar can be well reduced by the ionic surfactant sodium methylenebis(methyl)naphthalene sulfonate and the non-ionic surfactant polyamide-modified hydrogenated castor oil, ensuring the fluidity and stability of the biomass water-coal slurry. From the results of Example 1 and Example 3, polyamide-modified hydrogenated castor oil may be more conducive to being absorbed into the biomass to prevent water from entering because of its molecular structure being larger than that of nonylphenol polyoxyethylene ether and having better binding ability with biochar, and is more conducive to forming a thicker adsorption layer on the surface with sodium methylenebis(methyl)naphthalene sulfonate, thereby reducing the apparent viscosity of the final biomass water-coal slurry and improving performance.

[0074] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A biomass water-coal slurry, characterized in that: The slurry of the biomass water-coal slurry is biochar, the calorific value of the biomass water-coal slurry is above 3000 kcal / kg, and the apparent viscosity is below 1200 mPa·s.

2. The biomass water-coal slurry according to claim 1, characterized in that: The apparent viscosity is below 1000 mPa·s.

3. A method for preparing biomass water-coal slurry according to any one of claims 1 to 2, characterized in that: The following steps are involved: Prepare straw biochar and wood biochar from straw and wood respectively, and form biochar with a calorific value of more than 4500 kcal / kg by the straw biochar and wood biochar; The biomass water-coal slurry is prepared by mixing raw materials including the biochar, water, a surfactant and a flocculant; The surfactant includes an ionic surfactant and a nonionic surfactant.

4. The method for preparing biomass water-coal slurry according to claim 3, characterized in that: Based on 100 parts by weight of the biochar, the water comprises 60 to 75 parts by weight, the surfactant comprises 0.05 to 5 parts by weight, and the stabilizer comprises 0.05 to 5 parts by weight.

5. The method for preparing biomass water-coal slurry according to claim 3, characterized in that: The ionic surfactant is sodium methylenebis(methyl)naphthalene sulfonate or sodium dodecylbenzene sulfonate, and the nonionic surfactant is polyamide-modified hydrogenated castor oil and its derivatives or nonylphenol polyoxyethylene ether.

6. The method for preparing biomass water-coal slurry according to claim 3, characterized in that: The flocculant is polyacrylamide.

7. The preparation method according to claim 3, characterized in that: In the biochar, the mass fraction of the straw biochar is 40-90wt%, and the mass fraction of the wood biochar is 10-60wt%.

8. The preparation method according to claim 3, characterized in that: The straw biochar and wood biochar are prepared by anaerobic pyrolysis of straw and wood at a temperature of 350-450°C.

9. The preparation method according to claim 3, characterized in that: The straw is at least one of reed, wheat straw, rice straw, corn straw and sorghum straw.

10. The preparation method according to claim 3, characterized in that: The wood is at least one of bark, branches and trunks.