Sulfur purification method

Abstract

The invention discloses a sulfur purification method, which comprises the following steps: carrying out centrifugation, drying dehydration and crushing on sulfur slurry to form solid sulfur particles, dissolving the sulfur particles in an extraction agent for high-temperature extraction, carrying out centrifugation and cooling crystallization after extraction to obtain purified sulfur, and recycling the extraction agent in a high-temperature vacuum distillation manner. The technology for purifying the sulfur through the extraction method is high in sulfur recovery rate, easy to operate, low in cost and free of secondary pollution hidden danger, and has feasibility in the environment and economic dual technology. According to the method disclosed by the invention, the purity and the recovery rate of the sulfur are further improved by selecting a proper extracting agent, a proper sulfur particle size, a proper material adding ratio, a proper reaction temperature and a proper reaction time, the extraction efficiency after the PCE is recycled for 8 times can still reach 90% or above, the recovery rate of the sulfur is 92.6%, and the purity of the sulfur is 95.8%.

Description

Technical Field

[0001] The invention belongs to the technical field of sulfur purification, and particularly relates to a sulfur purification method. Background Art

[0002] Sulfur oxide is an important pollutant in incinerator flue gas and the main substance that forms acid rain. Incinerator flue gas biological desulfurization technology is an emerging air pollution control technology. However, the sulfur purity in the sulfur slurry produced by the biological desulfurization device is low, has no market value, and is corrosive. Improper treatment will not only cause great pollution to the environment, but also endanger human health in serious cases, and is classified as hazardous waste. Therefore, recovering high-purity elemental sulfur from the sulfur slurry produced by the incinerator flue gas biological desulfurization device has important practical significance for my country's environmental protection and economic development.

[0003] At present, the methods of sulfur purification at home and abroad can be divided into three categories: melting method, sublimation method and extraction method. Among them, the melting method is to melt the sulfur and then filter it. The more typical ones are Frasch method and Sicilian method. The Frasch method is mainly used for the mining of special sulfur mines, and the Sicilian method is mainly used for the refining of ores; the representative of the sublimation method is vacuum distillation, which uses high vacuum to reduce the boiling point of sulfur. However, the melting method and sublimation method generally have the disadvantages of high requirements for the sealing and corrosion resistance of the equipment, high investment costs, high energy consumption, and complex operation. The extraction method uses a solvent that can dissolve sulfur to dissolve sulfur from sulfur-containing materials and then extract it to obtain a sulfur product. Patent 202110268636.4 A sulfur purification system and its purification process adopt the above method. Specifically, the liquid crude sulfur melted in the sulfur melting kettle is discharged into the stirring tank, and is sucked and transported to the separation device by a liquid sulfur pump. The crude sulfur after the solid impurities are separated enters the decomposition tank to increase the temperature. The liquid sulfur coming out of the decomposition tank enters the outside of the tube of the gas-liquid heat exchanger to exchange heat with the gaseous sulfur in the tube. The liquid sulfur exits the gas-liquid heat exchanger and enters the heater. In the heater, the liquid sulfur is heated to the boiling point and vaporized. The gaseous sulfur exits the heater and enters the tube of the gas-liquid heat exchanger to exchange heat with the liquid sulfur outside the tube. The gaseous sulfur after exiting the gas-liquid heat exchanger enters the tube of the cooler to exchange heat with the medium outside the tube whose temperature is higher than the melting point of sulfur. The sulfur exiting the cooler is liquid and enters the slicer through the separator to form refined sulfur flakes.

[0004] Compared with the first two, the extractant can be recycled after filtration, and has the potential advantages of low cost, mild reaction conditions, high recovery rate, and no secondary pollution. However, the purity and recovery rate of sulfur obtained by the extraction method are affected by many factors, such as the selection of the extractant, the material addition ratio, the reaction time, and the reaction temperature.

[0005] Based on the problems of low sulfur recovery rate and purity in the existing extraction method for purifying sulfur, an extraction process method for efficiently purifying sulfur is urgently needed, which is of great significance for protecting the environment and the resource application of sulfur. Summary of the invention

[0006] The object of the present invention is to provide a method for purifying sulfur to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for purifying sulfur, comprising the following steps:

[0008] S1: The sulfur slurry is centrifuged, dried, dehydrated and crushed to form solid sulfur particles;

[0009] S2: dissolving sulfur particles in an extractant and extracting at high temperature;

[0010] S3: After the above extraction, centrifugation and cooling and crystallization are carried out to obtain purified sulfur, wherein the extractant is recovered and reused by high-temperature vacuum distillation.

[0011] Preferably, in step S1, the moisture content of the sulfur slurry is 65-75%, preferably 68-72%.

[0012] Preferably in any of the above schemes, in step S1, the moisture content of the sulfur slurry after drying and dehydration is 1-3%, preferably 1.5-2.5%.

[0013] Preferably, in any of the above schemes, in step S1, the particle size of the crushed sulfur particles is 0.05-0.15 mm, preferably 0.08-0.12 mm, and the mass fraction of sulfur in the sulfur particles is 40-55%, preferably 45-50%.

[0014] Preferably in any of the above schemes, in step S2, the extractant is tetrachloroethylene.

[0015] In any of the above schemes, it is preferred that the concentration of tetrachloroethylene is 85-95%, preferably 88-92%, and the density is 1.622 g / cm 3 The solubility in water at 25°C is 0.015g, the boiling point is 121.1°C, and the solubility of elemental sulfur in tetrachloroethylene is 1.507%.

[0016] In any of the above schemes, preferably, in step S2, the addition ratio of the extractant to the sulfur slurry is 1-9 mL / g, preferably 3-7 mL / g.

[0017] In any of the above schemes, preferably, in step S2, the conditions of the extraction reaction are a reaction temperature of 80-120° C., preferably 90-110° C., and a reaction time of 5-25 min, preferably 10-20 min.

[0018] Preferably in any of the above schemes, in step S3, the temperature of the sulfur particles crystallizing is below 25°C.

[0019] Preferably, in any of the above schemes, in steps S1 and S3, the centrifugal rotation speed is 8000-12000 rpm, preferably 9500-10500 rpm.

[0020] Technical effects and advantages of the present invention:

[0021] 1. The present invention uses tetrachloroethylene (PCE) as an extractant and adopts a high-temperature extraction + low-temperature crystallization process to purify sulfur. Compared with the traditional extraction method, the sulfur slurry in the present invention is centrifuged, dried and dehydrated, and crushed to increase the contact area with PCE, and PCE has a high sulfur solubility rate at high temperature and a high sulfur precipitation rate at low temperature, all of which are conducive to the recovery of sulfur components. The extraction method for purifying sulfur provided by the present invention has a high sulfur recovery rate, simple operation, low cost, no secondary pollution risk, and has both environmental and economic technical feasibility.

[0022] 2. The present invention further improves the purity and recovery rate of sulfur by selecting a suitable extractant, sulfur particle size, material addition ratio, and selecting a suitable reaction temperature and reaction time. The extraction efficiency of PCE can still reach more than 90% after 8 cycles, the sulfur recovery rate is 92.6%, and the purity is 95.8%.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the extraction process in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] In the following examples and comparative examples, unless otherwise specified, conventional methods are used; the reagents and materials used, unless otherwise specified, can be obtained from commercial sources. The determination methods and raw materials involved in each example and comparative example are as follows:

[0027] Moisture content determination method: Gravimetric method, determination conditions: 105℃ vacuum drying, drying for 6h;

[0028] Sulfur mass fraction determination method: Determined in accordance with standard GB / T 2499.1-2014;

[0029] Sulfur purity determination method: high performance liquid chromatography;

[0030] Sulfur recovery rate calculation formula: recovery rate (Q) = (m 前 -m 后 ) / m 前 .

[0031] Where: Q is sulfur recovery rate, %, m 前 is the mass of sulfur before extraction, g; m 后 is the mass of sulfur after extraction, g.

[0032] Sulfur slurry: The sulfur slurry used in the test was taken from the microbial desulfurization side-line test device.

[0033] Embodiment 1:

[0034] A method for purifying sulfur is as follows:

[0035] The sulfur slurry taken from the biodesulfurization side line test device was separated into solid and liquid by a centrifuge at a rotation speed of 10,000 rpm, and then entered the subsequent oven for drying and dehydration at 105°C for 6 hours. The moisture content of the sulfur particles after drying in the oven was about 2%, and the sulfur particles were crushed to 0.1 mm with a pulverizer.

[0036] According to the material addition ratio of 5mL / g (i.e. 500mL 90% concentration PCE + 100g sulfur granules), high-temperature extraction is carried out in an extraction reactor, the reaction temperature is 100°C, the reaction time is 15min, so that the sulfur in the sulfur granules is fully dissolved in the PCE, and after the reaction, it enters a heat-insulated centrifuge with a rotation speed of 10000rpm for solid-liquid separation again; the PCE dissolved with sulfur enters a subsequent cooling reactor and is cooled to below 25°C. In the cooling reactor, the sulfur crystallizes and precipitates as the temperature decreases, and flows into the centrifuge for separation by gravity. The sulfur is retained on the filter cloth, and the PCE extractant is recovered and reused by high-temperature vacuum distillation.

[0037] Embodiment 2-9:

[0038] The method for purifying sulfur in sulfur slurry is the same as that in Example 1, except that the material addition ratio or reaction conditions in the extraction process are different. The data of material addition ratio, reaction temperature and reaction time are specifically shown in Table 1:

[0039] Table 1

[0040]

[0041] Embodiment 10:

[0042] The method for purifying sulfur in sulfur slurry is the same as that in Example 1, except that the PCE concentration is changed from 90% to 70%.

[0043] Embodiment 11:

[0044] The method for purifying sulfur in sulfur slurry is the same as that in Example 1, except that the moisture content of the sulfur particles after drying and dehydration is changed from 2% to 10%.

[0045] Embodiment 12:

[0046] The method for purifying sulfur in sulfur slurry is the same as that in Example 1, except that the particle size of the sulfur particles after drying, dehydration and crushing is changed from 0.1 mm to 1 mm.

[0047] Comparative Example 1

[0048] Sulfur was purified according to the process of Example 1, except that the extractant was replaced from 90% tetrachloroethylene (PCE) to 90% carbon disulfide.

[0049] After the extraction reaction was completed, the mass fraction of sulfur in the sulfur particles of each embodiment and the comparative example was measured to analyze and investigate the sulfur purification and recovery in each embodiment and the comparative example, and the sulfur purity and sulfur recovery rate of each embodiment and the comparative example were calculated according to the formula. The results are shown in Table 2:

[0050] Table 2

[0051]

[0052]

[0053] From the results in Table 2, it can be seen that Examples 1-12 use the extraction process of the present invention to purify sulfur in sulfur slurry, and have higher sulfur purity and sulfur recovery rate. The extractant in Comparative Example 1 is replaced with carbon disulfide, and the sulfur purity and sulfur recovery rate are significantly reduced compared with Examples 1-12. This indicates that the extractant (PCE) used in the present invention has a strong sulfur recovery capacity.

[0054] In addition, Examples 4-5 changed the material addition ratio during the extraction process, Examples 6-7 changed the reaction temperature during the extraction process, Examples 8-9 changed the reaction time during the extraction process, and Examples 10-12 changed the PCE concentration, the moisture content of the sulfur particles, and the sulfur particle size, respectively. Compared with Example 1, the sulfur purity and sulfur recovery rate were both reduced.

[0055] It is thus shown that the extraction process provided by the present invention has a strong sulfur purification and recovery capacity; the selection of a specific extractant can fully dissolve sulfur, with a high sulfur dissolution rate at high temperature and a high sulfur precipitation rate at low temperature, which is convenient for sulfur separation and recovery; the PCE extractant is recycled and reused by high-temperature vacuum distillation, and the extraction efficiency can still reach more than 90% after 8 cycles. In addition, by selecting a suitable PCE concentration, the moisture content of the sulfur particles after drying and dehydration, and the sulfur particle size after crushing, and strictly controlling the material addition ratio, reaction temperature and reaction time in the extraction process, the sulfur purity and sulfur recovery rate can be further improved.

[0056] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A sulfur purification method, characterized in that: The following steps are involved: S1: The sulfur slurry is centrifuged, dried, dehydrated and crushed to form solid sulfur particles; S2: dissolving sulfur particles in an extractant and extracting at high temperature; S3: After the above extraction, centrifuge, cool and crystallize to obtain purified sulfur.

2. A sulfur purification method according to claim 1, characterized in that: In step S1, the moisture content of the sulfur slurry is 65-75%.

3. A sulfur purification method according to claim 1, characterized in that: In step S1, the moisture content of the sulfur slurry after drying and dehydration is 1-3%.

4. A sulfur purification method according to claim 1, characterized in that: In step S1, the particle size of the crushed sulfur particles is 0.05-0.15 mm, and the mass fraction of sulfur in the sulfur particles is 40-55%.

5. A sulfur purification method according to claim 1, characterized in that: In step S2, the extractant is tetrachloroethylene.

6. A sulfur purification method according to claim 3, characterized in that: The concentration of tetrachloroethylene is 85-95%, and the density is 1.622 g / cm 3 The solubility in water at 25°C is 0.015g, the boiling point is 121.1°C, and the solubility of elemental sulfur in tetrachloroethylene is 1.507%.

7. A sulfur purification method according to claim 1, characterized in that: In step S2, the addition ratio of the extractant to the sulfur slurry is 1-9 mL / g.

8. A sulfur purification method according to claim 1, characterized in that: In step S2, the extraction reaction is carried out at a temperature of 80-120°C and a reaction time of 5-25 min.

9. A sulfur purification method according to claim 1, characterized in that: In step S3, the temperature of the sulfur particles crystallization is below 25°C.

10. A sulfur purification method according to claim 1, characterized in that: In steps S1 and S3, the centrifugal rotation speed is 8000-12000 rpm.

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