Method for co-producing lignite wax, fulvic acid and humic acid

Abstract

The invention provides a method for co-production of lignite wax, fulvic acid and humic acid, and the method comprises the following steps: step S1, mixing lignite with an extraction agent for extraction, carrying out solid-liquid separation to obtain a lignite wax liquid and a first solid-phase residue, and carrying out extraction to make the mass ratio of the residual lignite wax in the obtained first solid-phase residue less than 1%; s2, the first solid-phase residue reacts with strong acid, and fulvic acid and a second solid-phase residue are obtained through separation after the reaction is finished; and S3, dissolving the second solid-phase residue by using an alkaline solution, and reacting the solution obtained by dissolving with an acidic solution to separate out humic acid. According to the method for co-producing the lignite wax, the fulvic acid and the humic acid, high-value development of Baoqing lignite is achieved, a traditional extraction agent can be replaced, the extraction rate of the lignite wax is guaranteed, and then the extraction rate of the fulvic acid and the extraction rate of the humic acid are increased.

Description

Technical Field

[0001] The invention relates to the field of coal chemical industry, and in particular to a method for co-producing lignite wax, fulvic acid and humic acid. Background Art

[0002] Baoqing lignite has a short geological period of formation and a shallow degree of metamorphism, and contains high contents of effective ingredients such as moisture, humic acid, lignite wax, and fulvic acid. How to extract humic acid, lignite wax, and fulvic acid and realize the co-production of the three is the key to improving economic benefits.

[0003] At present, there are few studies on the co-production of the three, which is a blank area in technical research. The extraction of lignite wax, humic acid and fulvic acid mainly has the following problems:

[0004] ① The lignite wax is viscous and wrapped on the surface of lignite, inhibiting the extraction of fulvic acid and humic acid;

[0005] ② The proportion of lignite wax in the overall mass of lignite is relatively low, and the extraction is difficult;

[0006] ③ The extraction rate of lignite wax and humic acid is low, which restricts the development of the industry;

[0007] ④The extraction agent has toxicity problems or low extraction rate problems.

[0008] Patent CN112625745B proposes a microwave extraction process for lignite wax, which includes the following steps: (1) lignite wax extraction: lignite is passed through a wet pulverizer, water is added for pulverization, and then the pulverization is classified. The fine slurry is used for standby use, and the coarse slurry is adjusted with tap water for pulp concentration, and then ammonium chloride is added for stirring and dissolving. The flow rate is adjusted and microwave extraction is performed. The extracted slurry is hot filtered, the filter residue is dried, and the filtrate is used for wax and liquid separation. The lignite wax is completely solidified and floats on the liquid to obtain a lignite wax product, and the liquid is recycled; (2) humic acid extraction: the fine slurry of the step is adjusted for its solid-liquid ratio, and then sodium hydroxide is added for stirring and dissolving to adjust the pH value. The flow rate is adjusted and humic acid is extracted by microwave. After extraction, it is filtered, and the filter residue is reused. The filtrate is acidified and precipitated. The solution is yellow humic acid, and the precipitate is brown-black humic acid. The filtrate is filtered, concentrated, dried, and pulverized to obtain a yellow humic acid product, and the filter residue is dried to obtain brown-black humic acid. That is, the patent proposes to first extract lignite wax by microwave hydrolysis, and then extract humic acid by alkali dissolution and adjusting pH in combination with microwave. This method requires adding multiple microwave extractors, which increases equipment investment.

[0009] Patent CN108384578A discloses the use of a mixed solution of alcohol and benzene as an extractant to extract lignite wax, wherein lignite is screened, crushed, and placed in a fermentation device, residual sludge and a sugar solution are added to the fermentation device, stirred evenly, the pH is adjusted to 7.2-8.0, and the fermentation is sealed. After the fermentation is completed, the lignite is taken out, dried and crushed, and added to a mixed solution of alcohol solution and benzene for extraction, and then the obtained extract is centrifuged, the extract after centrifugation is evaporated, the residue is obtained, and dried to prepare lignite wax.

[0010] The prior art does not provide a solution to the above technical problems.

[0011] In view of the above technical problems, the present invention is specially introduced. Summary of the invention

[0012] The main purpose of the present invention is to provide a method for co-producing lignite wax, fulvic acid and humic acid, which greatly reduces the influence of lignite wax in lignite on the extraction of fulvic acid and humic acid, and realizes efficient co-production and extraction of three high value-added products.

[0013] In order to achieve the above object, the present invention provides a method for co-producing lignite wax, fulvic acid and humic acid, characterized in that it comprises the following steps:

[0014] Step S1, mixing lignite with an extractant for extraction, and obtaining lignite wax liquid and a first solid phase residue by solid-liquid separation, wherein the weight percentage of the residual lignite wax in the first solid phase residue obtained by extraction is less than 1%;

[0015] Step S2, reacting the first solid phase residue with a strong acid, and separating and obtaining fulvic acid and a second solid phase residue after the reaction is completed;

[0016] Step S3, dissolving the second solid phase residue with an alkaline solution, and reacting the dissolved solution with an acidic solution to precipitate humic acid.

[0017] Preferably, the extractant used in step S1 includes 1,4-dioxane and methanol, and the mass ratio of 1,4-dioxane to methanol is 1:4 to 1:8.

[0018] Preferably, in step S1, the mass ratio of the extractant to the lignite is 2 to 3:1, the extraction temperature is 30 to 60° C., and the extraction time is 2 to 4 hours.

[0019] Preferably, step S1 includes step S11, separating the lignite wax liquid by negative pressure distillation to obtain methanol and 1,4-dioxane aqueous solution respectively.

[0020] Preferably, the separated 1,4-dioxane aqueous solution is added to the reaction solution of step S2.

[0021] Preferably, in step S2, the strong acid is a nitric acid solution, the concentration of the nitric acid solution is 20-30%, and the mass ratio of nitric acid to the first solid phase residue is 1:0.8-1.2.

[0022] Preferably, in step S2, the mass ratio of the 1,4-dioxane aqueous solution to the nitric acid solution is 1:1 to 1:4.

[0023] Preferably, in step S3, the alkaline solution is selected from sodium hydroxide and potassium hydroxide, and the molar concentration range of the alkaline solution is 2 to 4 mol·L-1.

[0024] Preferably, in step S3, the acidic solution is selected from nitric acid, hydrochloric acid, and phosphoric acid, and the concentration of the acidic solution is in the range of 10 to 30 wt%.

[0025] Preferably, the lignite needs to be dried and crushed before step S1, so that the moisture content in the lignite is 10-20wt% and the particle size of the lignite is 0.2-2mm.

[0026] Preferably, the mass proportion of lignite wax in the lignite raw material is 5-12wt%, the mass proportion of humic acid is 30-50wt%, and the mass proportion of fulvic acid is 4-10wt%.

[0027] The method for co-producing lignite wax, fulvic acid and humic acid proposed in the present invention achieves the following technical effects:

[0028] 1. This application proposes a method for co-producing lignite wax, fulvic acid and humic acid, which realizes the high-value development of Baoqing lignite with a simple process route.

[0029] 2. The present application realizes efficient extraction of lignite wax from lignite by selecting a reasonable extractant, limiting the residual lignite wax in lignite to 1%. Since the inclusion of lignite wax is reduced, the subsequent extraction rate of fulvic acid and humic acid from lignite is increased.

[0030] 3. The present application uses 1,4-dioxane and methanol as extractants, which improves the extraction rate of lignite wax and can reduce the restriction on the water content in lignite; the extract is further recovered, and 1,4-dioxane is added as an additive to the extraction step of fulvic acid and humic acid, which improves the extraction rate of fulvic acid and humic acid and reduces the process cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] In the attached picture:

[0033] Figure 1The process flow chart of the method for co-producing lignite wax, fulvic acid and humic acid is shown. DETAILED DESCRIPTION

[0034] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] The present invention is further described in detail below in conjunction with specific embodiments, and these embodiments cannot be understood as limiting the scope of protection claimed by the present invention. The term "including" when used indicates the existence of a feature, but does not exclude the existence or addition of one or more other features; the orientation or position relationship indicated by the terms "lateral", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention; in addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

[0036] In the description, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0037] The Baoqing lignite used in this application has lignite wax accounting for 5-12% by mass, humic acid accounting for 30-50% by mass, and fulvic acid accounting for 4-10% by mass. This application proposes a method for co-producing lignite wax, fulvic acid and humic acid, which can achieve efficient utilization of Baoqing lignite and improve the industrial economic value.

[0038] The process mainly includes the following steps:

[0039] Step S1, mixing lignite with an extractant, and obtaining lignite wax liquid and a first solid phase residue by solid-liquid separation, wherein the lignite wax content in the first solid phase residue is less than 1%.

[0040] The lignite used in step S1 needs to be pre-treated, including drying and crushing. The moisture content in the lignite is reduced to 10-20% by drying, and the particle size of the lignite after grinding is 0.2-2 mm.

[0041] By extracting the lignite wax from lignite in step S1, the added value of lignite is increased, and the lignite wax is removed by subsequent separation to prevent the lignite wax from encapsulating humic acid and fulvic acid, thereby increasing the conversion rate and extraction efficiency of humic acid and fulvic acid. The lignite wax liquid obtained in step S1 is evaporated and separated, and the solvent is recovered to obtain lignite wax and an extraction solvent.

[0042] Experiments have found that by maximizing the extraction and separation of montan wax, the extraction rate of fulvic acid and humic acid can be effectively improved. Taking into account the process cost of separating montan wax and the yield of humic acid and fulvic acid, the content of montan wax retained in the solid phase residue after extraction is limited to less than 1%, and the preferred content is 0.06-0.08%.

[0043] In order to improve the extraction rate of lignite wax and reduce the content of lignite wax in the solid phase residue, the present application adopts a 1,4-dioxane and methanol composition as an extractant, the mass ratio of 1,4-dioxane and methanol is 1:3 to 1:8, the preferred mass ratio of 1,4-dioxane and methanol is 2.5:10, and the extraction temperature is 30 to 60°C. Methanol is used as the main extractant component to reduce the amount of 1,4-dioxane, which is a low-toxic liquid and can also reduce the cost of the extraction process. 1,4-dioxane is miscible with methanol and the water in lignite, which is different from the currently commonly used benzene, ether, and normal alkane extractants. Therefore, 1,4-dioxane is used as an extractant to reduce the limit on the water content in lignite. The water content can be controlled at 10 to 20 wt% by simple drying. The water content in lignite does not require complicated procedures, reducing process costs.

[0044] The experimental results show that the extraction rate of montan wax can be guaranteed by using 1,4-dioxane and methanol as mixed extractants.

[0045] In step S2 of the present application, the first solid phase residue is reacted with a strong acid, and after the reaction is completed, fulvic acid and a second solid phase residue are separated and obtained; the strong acid is nitric acid, the concentration of nitric acid is 20-30%, and the mass ratio of nitric acid to the first solid phase residue is 1:0.8-1.2. In step S2, in addition to generating fulvic acid, lignite is also activated to generate humic acid, which exists in the second solid phase residue in a solid form.

[0046] Furthermore, the present application also found that the separated 1,4-dioxane and water can be used as additives for extracting fulvic acid and humic acid. By adding the mixed solution of 1,4-dioxane and water to the nitric acid reaction solution, the extraction rate of fulvic acid and humic acid can be significantly improved. 1,4-dioxane, as an active agent, can dissolve the wax or resinous substances remaining in the first solid phase residue, which is beneficial for nitric acid to enter the particles of the first solid phase residue, improve the conversion rate of fulvic acid and humic acid, and shorten the oxidation time. In the present application, the feed ratio of 1,4-dioxane solution to nitric acid solution is 1:1 to 1:4.

[0047] The present application adopts the traditional alkaline dissolution and acid precipitation method to extract the humic acid from the second solid phase residue, that is, the humic acid is firstly dissolved in an alkaline solution and then sent into an acidic solution to realize the precipitation of the humic acid.

[0048] The alkaline solution is potassium hydroxide or sodium hydroxide solution with a molar concentration of 2-4 mol·L-1, and the amount of the alkaline solution added is 2-8 wt% of the second solid phase residue. The acidic solution is 10-30 wt% nitric acid, the reaction temperature of acid precipitation is 60-80°C, and the reaction time is 1 hour.

[0049] The solution of the present application is further described below in conjunction with specific embodiments.

[0050] Example 1

[0051] The lignite is dried and crushed to make the moisture content 10-20wt% and the particle size less than 2mm. 100g of lignite and 300g of extractant are taken, wherein the extractant includes 60g of 1,4-dioxane and 240g of methanol. The lignite and the extractant are mixed and extracted at 60°C for 4h. The stirring rate during the extraction process is 200r / min. After the extraction is completed, the lignite wax liquid and the first solid phase residue are obtained after standing and filtering.

[0052] The lignite wax liquid is first sent to a cooling device, the temperature in the cooling device is set to 10°C, the lignite wax in the lignite wax liquid solidifies, and the lignite wax and the extraction solvent are separated by a filtering device. The extraction solvent is sent to a distillation device for staged distillation, and the process conditions are: the distillation temperature in the first stage is 60°C and the pressure is 0.08MPa; the distillation temperature in the second stage is 90°C and the pressure is 0.08MPa. In the first stage of distillation, methanol is distilled out, and in the second stage of distillation, 1,4-dioxane and water are distilled out at the same time. Furthermore, methanol, 1,4-dioxane and water can also be recovered by condensation. The obtained lignite wax is dried at 80°C and weighed to calculate the yield.

[0053] Example 2

[0054] The lignite was crushed to a particle size of less than 2 mm, 100 g of lignite and 300 g of an extractant were taken, wherein the extractant included 60 g of toluene and 240 g of methanol, the lignite and the extractant were mixed, and the extraction time was 4 h at a temperature of 60° C. The stirring rate during the extraction process was 200 r / min. After the extraction was completed, the lignite wax liquid and the first solid phase residue were obtained after standing and filtering.

[0055] The lignite wax liquid is first sent to a cooling device, the temperature of which is set at 10°C, the lignite wax in the lignite wax liquid solidifies, and the lignite wax and the extraction solvent are separated by a filtering device. The obtained lignite wax is dried at 80°C and weighed, and the yield is calculated.

[0056] Example 3

[0057] The lignite was crushed to a particle size of less than 2 mm, 100 g of lignite and 300 g of an extractant were taken, wherein the extractant included 40 g of 1,4-dioxane and 260 g of methanol, the lignite and the extractant were mixed, and the extraction time was 4 h at a temperature of 60°C, and the stirring rate during the extraction process was 200 r / min. After the extraction was completed, the lignite wax liquid and the first solid phase residue were obtained after standing and filtering.

[0058] The lignite wax liquid is first sent to a cooling device, the temperature of which is set at 10°C, the lignite wax in the lignite wax liquid solidifies, and the lignite wax and the extraction solvent are separated by a filtering device. The obtained lignite wax is dried at 80°C and weighed, and the yield is calculated.

[0059] Example 4

[0060] The lignite was crushed to a particle size of less than 2 mm, 100 g of lignite and 300 g of an extractant were taken, wherein the extractant included 30 g of 1,4-dioxane and 270 g of methanol, the lignite and the extractant were mixed, and the extraction time was 4 h at a temperature of 60°C, and the stirring rate during the extraction process was 200 r / min. After the extraction was completed, the lignite wax liquid and the first solid phase residue were obtained after standing and filtering.

[0061] The lignite wax liquid is first sent to a cooling device, the temperature in the cooling device is set to 10°C, the lignite wax in the lignite wax liquid is solidified, and the lignite wax and the extraction solvent are separated by a filtering device. The obtained lignite wax is dried at 80°C and weighed, and the lignite wax yield is calculated.

[0062] Table 1. The yield and component proportion of lignite wax in different embodiments

[0063]

[0064]

[0065] Combining the lignite wax yield and component ratio of Example 1 and Example 2, the lignite wax yield and pure wax component ratio of the extraction solvent of 1,4-dioxane and methanol are higher than that of the combination of toluene and methanol. Combining Examples 1, 3, and 4, the lignite wax yield and pure wax component ratio can be improved by optimizing the component ratio of 1,4-dioxane and methanol. When the ratio of methanol to 1,4-dioxane exceeds 1:8, the extraction rate will decrease due to the decrease in the ratio of 1,4-dioxane. In addition, considering safety and process costs, the mass of 1,4-dioxane and methanol is limited to 1:8.

[0066] Example 5

[0067] 40 g of the first solid phase residue obtained by Example 1 was sent to a fulvic acid extraction device, and 30 g of 1,4-dioxane and water were recovered by condensation, wherein 4 g of water and 26 g of 1,4-dioxane were contained, and mixed with 40 g of nitric acid with a concentration of 25 wt%. The mixed solution was sent to a fulvic acid extraction device, and the reaction temperature was 80°C for 2 hours. A solution containing fulvic acid and a second solid phase residue were further obtained by solid-liquid separation. The fulvic acid was concentrated and dried, and the weight of the fulvic acid was weighed.

[0068] Further, 20 g of the second solid phase residue is added to a sodium hydroxide solution with a molar concentration of 2 mol·L-1, the amount of alkaline solution added is 40 g, the reaction temperature is set to 60°C, the reaction is carried out for 1 hour, and the mixture is allowed to stand and then centrifuged or filtered to obtain a supernatant.

[0069] The obtained supernatant was sent to an acid precipitation device, a nitric acid solution was added to the acid precipitation device, and the nitric acid concentration was 20wt%, and the humic acid precipitate was allowed to stand for 1 hour to precipitate all the humic acid precipitate. The precipitate was dried at 50°C to obtain humic acid solid, and the humic acid solid was weighed.

[0070] Example 6

[0071] 40 g of the first solid phase residue obtained by Example 1 was sent to a fulvic acid extraction device, and 30 g of 1,4-dioxane and water were recovered by condensation, including 4 g of water and 26 g of 1,4-dioxane, and mixed with 40 g of nitric acid with a concentration of 25 wt%. The mixed solution was sent to a fulvic acid extraction device, the reaction temperature was 80 ° C, and the reaction was carried out for 1 hour. A solution containing fulvic acid and a second solid phase residue were further obtained by solid-liquid separation. The fulvic acid was concentrated and dried, and the weight of the fulvic acid was weighed.

[0072] Further, 20 g of the second solid phase residue is added to a sodium hydroxide solution with a molar concentration of 2 mol·L-1, the amount of alkaline solution added is 40 g, the reaction temperature is set to 60°C, the reaction is carried out for 1 hour, and the mixture is allowed to stand and then centrifuged or filtered to obtain a supernatant.

[0073] The obtained supernatant was sent to an acid precipitation device, a nitric acid solution was added to the acid precipitation device, and the nitric acid concentration was 20%, and the solution was allowed to stand for 1 hour to allow all humic acid precipitates to precipitate. The precipitate was dried at 50° C. to obtain humic acid solids, and the humic acid solids were weighed.

[0074] Example 7

[0075] 40 g of the first solid phase residue obtained by Example 1 was sent to a fulvic acid extraction device, and 30 g of 1,4-dioxane and water were recovered by condensation, wherein 4 g of water and 26 g of 1,4-dioxane were contained, and mixed with 40 g of nitric acid with a concentration of 20 wt%. The mixed solution was sent to a fulvic acid extraction device, the reaction temperature was 80°C, and the reaction was carried out for 1 hour. A solution containing fulvic acid and a second solid phase residue were further obtained by solid-liquid separation. The fulvic acid was concentrated and dried, and the weight of the fulvic acid was weighed.

[0076] Further, 20 g of the second solid phase residue is added to a sodium hydroxide solution with a molar concentration of 2 mol·L-1, the amount of alkaline solution added is 40 g, the reaction temperature is set to 60°C, the reaction is carried out for 1 hour, and the mixture is allowed to stand and then centrifuged or filtered to obtain a supernatant.

[0077] The obtained supernatant was sent to an acid precipitation device, a nitric acid solution was added to the acid precipitation device, and the nitric acid concentration was 20wt%, and the humic acid precipitate was allowed to stand for 1 hour to precipitate all the humic acid precipitate. The precipitate was dried at 50°C to obtain humic acid solid, and the humic acid solid was weighed.

[0078] Example 8

[0079] As a comparative example, 1,4-dioxane and water were not added for condensation recovery. 40 g of the first solid phase residue obtained by Example 1 was sent to a fulvic acid extraction device and mixed with 40 g of nitric acid with a concentration of 25 wt%. The mixed solution was sent to a fulvic acid extraction device, the reaction temperature was 80°C, and the reaction was carried out for 2 hours. A solution containing fulvic acid and a second solid phase residue were further obtained by solid-liquid separation. The fulvic acid was concentrated and dried, and the weight of the fulvic acid was weighed.

[0080] Further, 20 g of the second solid phase residue is added to a sodium hydroxide solution with a molar concentration of 2 mol·L-1, the amount of alkaline solution added is 40 g, the reaction temperature is set to 60°C, the reaction is carried out for 1 hour, and the mixture is allowed to stand and then centrifuged or filtered to obtain a supernatant.

[0081] The obtained supernatant was sent to an acid precipitation device, a nitric acid solution was added to the acid precipitation device, and the nitric acid concentration was 20%, and the solution was allowed to stand for 1 hour to allow all humic acid precipitates to precipitate. The precipitate was dried at 50° C. to obtain humic acid solids, and the humic acid solids were weighed.

[0082] Example 9

[0083] The Baoqing lignite wax is dried and crushed to make the moisture content between 10% and 20% and the particle size less than 2 mm. As a comparative example, the lignite was not extracted in this embodiment, and more than 4% of lignite wax was retained in the lignite. Take 20g of lignite, condense and recover 30g of 1,4-dioxane and water, which contains 4g of water and 26g of 1,4-dioxane, and mix with 40g of nitric acid with a concentration of 25wt%. The mixed solution is sent to the fulvic acid extraction device, the reaction temperature is 80°C, and the reaction is carried out for 2 hours. A solution containing fulvic acid and a solid phase residue are further obtained by solid-liquid separation. The fulvic acid is concentrated and dried, and the weight of the fulvic acid is weighed.

[0084] Further, 20 g of the solid residue is added to a sodium hydroxide solution with a molar concentration of 2 mol·L-1, the amount of alkaline solution added is 40 g, the reaction temperature is set to 60°C, the reaction is carried out for 1 hour, and the mixture is allowed to stand and then centrifuged or filtered to obtain a supernatant.

[0085] The obtained supernatant was sent to an acid precipitation device, a nitric acid solution was added to the acid precipitation device, and the nitric acid concentration was 20wt%, and the humic acid precipitate was allowed to stand for 1 hour to precipitate all the humic acid precipitate. The precipitate was dried at 50°C to obtain humic acid solid, and the humic acid solid was weighed.

[0086] Example 10

[0087] 40 g of the first solid phase residue obtained in Example 4 was sent to a fulvic acid extraction device. About 1 wt% of lignite was retained in the first solid phase residue obtained in Example 4. 30 g of 1,4-dioxane and water were recovered by condensation, which contained 4 g of water and 26 g of 1,4-dioxane, and mixed with 40 g of nitric acid with a concentration of 25 wt%. The mixed solution was sent to a fulvic acid extraction device, the reaction temperature was 80°C, and the reaction was carried out for 2 hours. A solution containing fulvic acid and a second solid phase residue were further obtained by solid-liquid separation. The fulvic acid was concentrated and dried, and the weight of the fulvic acid was weighed.

[0088] Further, 20 g of the second solid phase residue is added to a sodium hydroxide solution with a molar concentration of 2 mol·L-1, the amount of alkaline solution added is 40 g, the reaction temperature is set to 60°C, the reaction is carried out for 1 hour, and the mixture is allowed to stand and then centrifuged or filtered to obtain a supernatant.

[0089] The obtained supernatant was sent to an acid precipitation device, a nitric acid solution was added to the acid precipitation device, and the nitric acid concentration was 20wt%, and the humic acid precipitate was allowed to stand for 1 hour to precipitate all the humic acid precipitate. The precipitate was dried at 50°C to obtain humic acid solid, and the humic acid solid was weighed.

[0090] Table 2 Extraction amount of fulvic acid and humic acid in different examples

[0091]

[0092] Referring to Example 5 and Example 8, it can be seen that the addition of 1,4-dioxane can improve the extraction rate of fulvic acid and humic acid; in combination with Example 5 and Example 6, it can be seen that the addition of 1,4-dioxane can also shorten the extraction time of fulvic acid and humic acid. In combination with Example 5 and Example 7, under the condition of adding 1,4-dioxane, using 25wt% and 20wt% nitric acid solutions can ensure a high extraction rate of fulvic acid and humic acid.

[0093] Combining Examples 5, 9 and 10, it can be seen that by extracting lignite wax in lignite and reducing the lignite wax content in lignite, the extraction rate of humic acid and fulvic acid can be significantly improved. By using a mixed extractant of 1,4-dioxane and methanol at a suitable concentration, the lignite wax residue after extraction can be ensured to be less than 1%, thereby improving the extraction rate of humic acid and fulvic acid.

[0094] In summary, the method for co-producing lignite wax, fulvic acid and humic acid proposed in this embodiment achieves the following technical effects:

[0095] 1. This application proposes a method for co-producing lignite wax, fulvic acid and humic acid, which realizes the high-value development of Baoqing lignite with a simple process route.

[0096] 2. The present application realizes efficient extraction of lignite wax from lignite by selecting a reasonable extractant, limiting the residual lignite wax in lignite to 1%. Since the inclusion of lignite wax is reduced, the subsequent extraction rate of fulvic acid and humic acid from lignite is increased.

[0097] 3. The present application uses 1,4-dioxane and methanol as extractants, which improves the extraction rate of lignite wax and can reduce the restriction on the water content in lignite; the extract is further recovered, and 1,4-dioxane is added as an additive to the extraction step of fulvic acid and humic acid, which improves the extraction rate of fulvic acid and humic acid and reduces the process cost.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for co-producing lignite wax, fulvic acid and humic acid, characterized in that: The following steps are involved: Step S1, mixing lignite with an extractant for extraction, and obtaining lignite wax liquid and a first solid phase residue by solid-liquid separation, wherein the weight percentage of residual lignite wax in the first solid phase residue obtained by extraction is less than 1%; Step S2, reacting the first solid phase residue with a strong acid, and separating and obtaining fulvic acid and a second solid phase residue after the reaction is completed; Step S3, dissolving the second solid phase residue with an alkaline solution, and reacting the dissolved solution with an acidic solution to precipitate humic acid.

2. The method for co-producing lignite wax, fulvic acid and humic acid according to claim 1, characterized in that: The extractant used in step S1 includes 1,4-dioxane and methanol, and the mass ratio of the 1,4-dioxane to the methanol is 1:4 to 1:

8.

3. The method for co-producing lignite wax, fulvic acid and humic acid according to claim 2, characterized in that: In step S1, the mass ratio of the extractant to the lignite is 2-3:1, the extraction temperature is 30-60° C., and the extraction time is 2-4 hours.

4. The method for co-producing lignite wax, fulvic acid and humic acid according to claim 3, characterized in that: Step S1 includes step S11, performing negative pressure distillation separation on the lignite wax liquid to obtain methanol and 1,4-dioxane aqueous solution respectively.

5. The method for co-producing lignite wax, fulvic acid and humic acid according to claim 4, characterized in that: The separated 1,4-dioxane aqueous solution is added to the reaction solution of step S2.

6. The method for co-producing lignite wax, fulvic acid and humic acid according to claim 5, characterized in that: In step S2, the strong acid is a nitric acid solution, the concentration of the nitric acid solution is 20-30wt%, and the mass ratio of the nitric acid to the first solid phase residue is 1:0.8-1.

2.

7. The method for co-producing lignite wax, fulvic acid and humic acid according to claim 5, characterized in that: The mass ratio of the 1,4-dioxane aqueous solution to the nitric acid solution in step S2 is 1:1 to 1:

4.

8. The method for co-producing montan wax, fulvic acid and humic acid according to any one of claims 1 to 7, characterized in that: In step S3, the alkaline solution is selected from sodium hydroxide and potassium hydroxide, and the molar concentration range of the alkaline solution is 2 to 4 mol·L-1.

9. The method for co-producing montan wax, fulvic acid and humic acid according to any one of claims 1 to 7, characterized in that: In step S3, the acidic solution is selected from nitric acid, hydrochloric acid, and phosphoric acid, and the concentration of the acidic solution is in the range of 10 to 30 wt%.

10. The method for co-producing montan wax, fulvic acid and humic acid according to any one of claims 1 to 7, characterized in that: Before step S1, the lignite needs to be dried and crushed so that the moisture content of the lignite is 10-20wt% and the particle size of the lignite is 0.2-2mm.

11. The method for co-producing montan wax, fulvic acid and humic acid according to any one of claims 1 to 7, characterized in that: The weight percentage of lignite wax in the lignite raw material is 5-12%, the weight percentage of humic acid is 30-50wt%, and the weight percentage of fulvic acid is 4-10wt%.

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