A method for resource utilization of raw coal by flotation-electrolysis

Abstract

The invention discloses a method for resource utilization of raw coal flotation-electrolysis, which relates to the technical field of coal sorting. The method comprises the following steps: crushing raw coal and grinding it, flotation separation, and obtaining clean coal and tail coal slurry; mixing tail coal slurry with sodium hydroxide solution as anolyte, electrolyzing sodium hydroxide solution as catholyte, and reducing the cathode to obtain hydrogen; filtering and separating the anolyte, washing and drying, and obtaining inorganic salt products; mixing the filtrate and the washed solution, concentrating, acidifying to pH=3, filtering, washing and vacuum drying, and obtaining water-insoluble acid; then acidifying the filtrate to pH=1.5, extracting, concentrating and vacuum drying, and obtaining solid water-soluble acid. The method combines flotation with electrolysis, which not only improves the utilization efficiency of coal resources, simplifies the process flow, and reduces costs, but also improves the overall economic benefits through by-product high-value products, and realizes a more environmentally friendly coal sorting and utilization method.

Description

Technical Field

[0001] The invention relates to the technical field of coal sorting, and in particular to a method for resource utilization of raw coal by flotation-electrolysis. Background Art

[0002] In the coal industry, flotation technology has been widely used to extract clean coal from raw coal. Flotation is a physical and chemical method that uses the hydrophilicity and hydrophobicity of the mineral surface to achieve efficient coal sorting. It can effectively separate most of the ash and inorganic sulfur impurities in the coal, and significantly reduce the emission of harmful substances during coal combustion. However, the flotation process obtains high-value clean coal, but it also produces tail coal that still contains a large amount of carbon resources. It is often directly burned or piled up without effective treatment, and about 200 million tons of coal slime are wasted every year. This not only causes a waste of energy, but also brings serious environmental pollution problems, hindering the realization of the goal of clean and efficient use of coal. Therefore, how to efficiently utilize these tail coal resources has become an important issue that needs to be solved urgently in the coal industry, and it is also a key link in achieving deep green separation of coal.

[0003] As a by-product of the coal washing process, tailings are usually considered waste due to their low calorific value and complex composition. At present, the resource utilization of tailings mainly includes thermal power generation, building materials, soil conditioners, fuel processing, preparation of activated carbon, backfilling and other methods. However, the existing tailings utilization process still requires pretreatment of the tailings, namely filtering, dehydration, drying and other treatments, which undoubtedly increases the energy consumption cost of tailings utilization, and the combustion of tailings powder also produces greenhouse gases to pollute the environment. In summary, the existing coal sorting methods have obvious deficiencies in energy efficiency, resource utilization and environmental protection performance, and there is an urgent need for more efficient and low-energy consumption processing processes to solve this problem. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a method for raw coal flotation-electrolysis combined quality separation and resource utilization. This method combines flotation with electrolysis, which not only improves the utilization efficiency of coal resources, simplifies the process flow, and reduces costs, but also improves the overall economic benefits through the production of high-value by-products, and realizes a more environmentally friendly coal sorting and utilization method.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a method for raw coal flotation-electrolysis combined quality classification and resource utilization is provided, comprising the following steps:

[0006] Step 1: After the raw coal is crushed and ground, the coal slurry is added to the flotation tank for slurry adjustment, and then a capture agent and a frother are added for stirring, and the clean coal and tail coal slurry are obtained by flotation separation;

[0007] Step 2: Mix the tail coal slurry obtained in step 1 with a sodium hydroxide solution as an anolyte, and use the sodium hydroxide solution as a cathode electrolyte, perform electrolysis under stirring conditions, oxidize the tail coal at the anode, and reduce it at the cathode to produce hydrogen;

[0008] Step 3, filtering and separating the anolyte after electrolysis, washing the filtered solid with deionized water, and then vacuum drying to obtain an inorganic salt product;

[0009] Step 4: The filtrate of step 3 and the washing solution are mixed and concentrated, sulfuric acid solution is added to acidify to pH=3, and then filtered, washed and vacuum dried in sequence to obtain a water-insoluble acid;

[0010] Step 5: add sulfuric acid solution to the filtrate of step 4 to acidify to pH=1.5, then use butanone to extract, concentrate the extract by vacuum rotary evaporation, and finally vacuum dry to obtain water-soluble acid.

[0011] Furthermore, in step one, the raw coal is at least one of lignite, bituminous coal and anthracite, that is, the method is applicable to all types of coal.

[0012] Furthermore, in step one, the raw coal is crushed to a particle size less than 2 mm and then ground to a particle size less than 0.5 mm.

[0013] Further, in step one, the coal slurry concentration is 80 g / L.

[0014] Furthermore, in step 1, the capture agent is undecane, and the amount used is 1300-1700 g / t; the foaming agent is octanol, and the amount used is 300-700 g / t.

[0015] Further, in step 1, at an air flow rate of 0.1-0.2 m 3 / h and the scraper speed is 30-40 r / min, and flotation takes 2-4 min.

[0016] Furthermore, in step 2, the concentration of the sodium hydroxide solution is 0.8-1.2 mol / L; the volume ratio of the tail coal slurry to the sodium hydroxide solution is 800-1200:1.

[0017] Furthermore, in step 2, the electrolysis electrode is a platinum sheet electrode; the electrolysis is carried out under the conditions of voltage ≥1.2 V and temperature of 40-80°C. The platinum sheet electrode can also be replaced by an electrode of other materials that undergo hydrogen evolution reaction; the temperature is controlled by water bath heating, heat tracing heating, oil bath heating or platform contact heating; the electrolyzer is one of an intermittent proton exchange membrane electrolyzer, a continuous proton exchange membrane electrolyzer, an intermittent membraneless electrolyzer and a continuous membraneless electrolyzer.

[0018] Further, in step 3 and step 4, vacuum drying is performed at a temperature of 100-110°C.

[0019] Further, in step five, vacuum drying is performed at 60-95° C. for 10-15 h.

[0020] Further, in step 5, butanone is used for extraction 4-6 times. The amount of the extractant is gradually reduced.

[0021] The present invention has the following beneficial effects:

[0022] 1. The present invention maximizes the recovery of carbon resources in tail coal and achieves more efficient material separation. Compared with the traditional single flotation process, this method can more thoroughly separate coal and gangue, significantly improve the overall utilization rate of coal resources, and reduce resource waste.

[0023] 2. Tailings are rich in metal ions such as iron and manganese. These elements act as catalysts in the electrolysis process, significantly improving the electrolysis efficiency while reducing the overall processing cost.

[0024] 3. The method of the present invention not only recovers carbon resources in tail coal through electrochemical oxidation process, but also obtains a variety of high value-added products. The byproducts of the electrolysis process are high-purity hydrogen, water-insoluble acid (such as humic acid) and water-soluble acid (such as coal acid). Water-insoluble acid can be used as agricultural fertilizer and is a good soil conditioner. It can be used as an expander, coal binder and water treatment agent in industry, and has a wide range of applications. After separation, processing and purification, water-soluble acid can produce pure terephthalic acid and pyromellitic acid products, which are used to produce polyester resins, polyester fibers, dye intermediates and plastic films, etc., and are expected to replace the route of terephthalic acid production by oxidation of petroleum fractions.

[0025] 4. A large amount of carbon resources remain in the tail coal after separation by the traditional flotation process, which is usually filtered, dehydrated and dried, and the process is complicated and energy-intensive. The method of the present invention combines flotation with electrolysis technology to directly electrolyze and oxidize the tail coal, thereby simplifying the process flow, reducing unnecessary processing steps and energy consumption, and achieving efficient utilization of tail coal, reducing greenhouse gas emissions and the generation of other pollutants. In addition, the high-value-added by-products can replace some traditional petroleum products, thereby further reducing the negative impact on the environment, and has obvious environmental advantages.

[0026] In summary, the present invention combines flotation with electrolysis, which not only improves the utilization efficiency of coal resources, simplifies the process flow, and reduces costs, but also improves the overall economic benefits by producing high-value by-products, and realizes a more environmentally friendly coal sorting and utilization method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the process of raw coal flotation-electrolysis combined with quality separation and resource utilization in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0029] Example 1

[0030] A method for raw coal flotation-electrolysis combined quality classification and resource utilization, the flow diagram is as follows Figure 1 As shown, the method comprises the following steps:

[0031] Step 1: crush the raw coal with a crusher, screen it through a 2 mm sieve, grind it in a ball mill, screen it through a 0.5 mm sieve, add the coal slurry with a concentration of 80 g / L into the flotation tank for slurry preparation, then add the capture agent undecane (1500 g / t) and the foaming agent octanol (500 g / t) for stirring, and stir at an air flow rate of 0.15 m 3 / h and scraper speed 36 r / min, flotation for 3 min, clean coal and tail coal slurry were obtained;

[0032] Step 2: Mix the tail coal slurry obtained in step 1 with 1 mol / L sodium hydroxide solution in a volume ratio of 1000:1 as an anode electrolyte, and use 1 mol / L sodium hydroxide solution as a cathode electrolyte, use platinum electrodes as anodes and cathodes, and electrolyze at a voltage of ≥1.2 V, a temperature of 60°C, and stirring conditions to oxidize the tail coal at the anode and reduce it at the cathode to produce hydrogen;

[0033] Step 3, filtering and separating the anolyte after electrolysis, washing the filtered solid with deionized water, and then vacuum drying at 105° C. to obtain an inorganic salt product;

[0034] Step 4: The filtrate of step 3 and the washing solution are mixed and concentrated, sulfuric acid solution is added to acidify to pH=3, and then filtered and washed, and then vacuum dried at 105°C to obtain a water-insoluble acid;

[0035] Step 5: Add sulfuric acid solution to the filtrate of step 4 to acidify it to pH = 1.5, then use butanone to extract 5 times with gradually decreasing amount, concentrate the extract by vacuum rotary evaporation, and finally vacuum dry at 80°C for 12 h to obtain water-soluble acid.

[0036] According to the method of this embodiment, 80 g of raw coal was processed, and 49.99 g of clean coal was obtained after flotation, with a clean coal yield of 62.49%; the hydrogen output was 1.006 L, and the yield of the anodic oxidation product was 71.63%.

[0037] Example 2

[0038] A method for raw coal flotation-electrolysis combined quality classification and resource utilization, the flow diagram is as follows Figure 1 As shown, the method comprises the following steps:

[0039] Step 1: crush the raw coal to a particle size of less than 2 mm and then grind it to a particle size of less than 0.5 mm. Add the coal slurry with a concentration of 70 g / L into the flotation tank for slurry preparation. Then, add the capture agent undecane (1300 g / t) and the foaming agent octanol (300 g / t) and stir. 3 / h and scraper speed 30 r / min, flotation for 2 min, clean coal and tail coal slurry were obtained;

[0040] Step 2: Mix the tail coal slurry obtained in step 1 with 0.8 mol / L sodium hydroxide solution at a volume ratio of 800:1 as an anode electrolyte, and use 0.8 mol / L sodium hydroxide solution as a cathode electrolyte, use platinum electrodes as anodes and cathodes, and electrolyze at a voltage of ≥1.2 V, a temperature of 40°C, and stirring conditions to oxidize the tail coal at the anode and reduce it at the cathode to produce hydrogen;

[0041] Step 3, filtering and separating the anolyte after electrolysis, washing the filtered solid with deionized water, and then vacuum drying at 100° C. to obtain an inorganic salt product;

[0042] Step 4: The filtrate of step 3 and the washing solution are mixed and concentrated, and sulfuric acid solution is added to acidify to pH=3, and then filtered and washed, and then vacuum dried at 100° C. to obtain a water-insoluble acid;

[0043] Step 5: add sulfuric acid solution to the filtrate of step 4 to acidify it to pH=1.5, then use butanone to extract 4 times with gradually decreasing amount, concentrate the extract by vacuum rotary evaporation, and finally vacuum dry at 60°C for 10 h to obtain water-soluble acid.

[0044] Example 3

[0045] A method for raw coal flotation-electrolysis combined quality classification and resource utilization, the flow diagram is as follows Figure 1 As shown, the method comprises the following steps:

[0046] Step 1: Crush the raw coal to a particle size of less than 2 mm and then grind it to a particle size of less than 0.5 mm. Add the coal slurry with a concentration of 90 g / L into the flotation tank for slurry preparation. Then, add the capture agent undecane (1700 g / t) and the foaming agent octanol (700 g / t) and stir. 3 / h and scraper speed 40 r / min, flotation for 4 min, clean coal and tail coal slurry were obtained;

[0047] Step 2: Mix the tail coal slurry obtained in step 1 with 1.2 mol / L sodium hydroxide solution at a volume ratio of 1200:1 as an anode electrolyte, and use 1.2 mol / L sodium hydroxide solution as a cathode electrolyte, use platinum electrodes as anodes and cathodes, and electrolyze at a voltage of ≥1.2 V, a temperature of 80°C, and stirring conditions to oxidize the tail coal at the anode and reduce it at the cathode to produce hydrogen;

[0048] Step 3, filtering and separating the anolyte after electrolysis, washing the filtered solid with deionized water, and then vacuum drying at 110° C. to obtain an inorganic salt product;

[0049] Step 4: The filtrate of step 3 and the washing solution are mixed and concentrated, sulfuric acid solution is added to acidify to pH=3, and then filtered and washed, and then vacuum dried at 110°C to obtain a water-insoluble acid;

[0050] Step 5: Add sulfuric acid solution to the filtrate of step 4 to acidify it to pH = 1.5, then use butanone to extract 6 times with gradually decreasing amount, concentrate the extract by vacuum rotary evaporation, and finally vacuum dry at 95°C for 15 h to obtain water-soluble acid.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement 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 raw coal flotation-electrolysis combined quality separation and resource utilization, characterized in that: The following steps are involved: Step 1: After the raw coal is crushed and ground, the coal slurry is added to the flotation tank for slurry adjustment, and then a capture agent and a frother are added for stirring, and the clean coal and tail coal slurry are obtained by flotation separation; the raw coal is at least one of bituminous coal and anthracite; Step 2: Mix the tail coal slurry obtained in step 1 with a sodium hydroxide solution as an anolyte, and use the sodium hydroxide solution as a cathode electrolyte. The electrolytic electrode is a platinum sheet electrode. The electrolysis is carried out under a voltage of ≥1.2 V, a temperature of 40-80°C and stirring conditions. The tail coal is oxidized at the anode and reduced at the cathode to produce hydrogen. The concentration of the sodium hydroxide solution is 0.8-1.2 mol / L. The volume ratio of the tail coal slurry to the sodium hydroxide solution is 800-1200:

1. Step 3, filtering and separating the anolyte after electrolysis, washing the filtered solid with deionized water, and then vacuum drying to obtain an inorganic salt product; Step 4: The filtrate of step 3 and the washing solution are mixed and concentrated, sulfuric acid solution is added to acidify to pH=3, and then filtered, washed and vacuum dried in sequence to obtain a water-insoluble acid; Step 5: add sulfuric acid solution to the filtrate of step 4 to acidify to pH=1.5, then use butanone to extract, concentrate the extract by vacuum rotary evaporation, and finally vacuum dry to obtain water-soluble acid.

2. The method for raw coal flotation-electrolysis separation and resource utilization as claimed in claim 1, characterized in that: In step 1, the raw coal is crushed to a particle size less than 2 mm and then ground to a particle size less than 0.5 mm.

3. The method for raw coal flotation-electrolysis separation and resource utilization as claimed in claim 1, characterized in that: In step 1, the coal slurry concentration is 80 g / L.

4. The method for raw coal flotation-electrolysis separation and resource utilization as claimed in claim 1, characterized in that: In step 1, the capture agent is undecane, and the amount used is 1300-1700 g / t; the foaming agent is octanol, and the amount used is 300-700 g / t.

5. The method for raw coal flotation-electrolysis separation and resource utilization as claimed in claim 1, characterized in that: In step 1, at an airflow rate of 0.1-0.2 m 3 / h and the scraper speed is 30-40 r / min, and flotation takes 2-4 min.

6. The method for raw coal flotation-electrolysis separation and resource utilization as claimed in claim 1, characterized in that: In step 3 and step 4, vacuum drying is performed at a temperature of 100-110°C.

7. The method for raw coal flotation-electrolysis separation and resource utilization as claimed in claim 1, characterized in that: In step 5, vacuum drying is performed at 60-95° C. for 10-15 h.

8. The method for raw coal flotation-electrolysis separation and resource utilization as claimed in claim 1, characterized in that: In step 5, butanone is used for extraction 4-6 times.

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