RU2113403C1 - Method of isolating sulfur from sulfur concentrate - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: invention relates to sulfur concentrates and sulfur sludges formed in hydrogen sulfide-containing gas treatment processes. Sulfur-containing raw material is melted in calcium chloride aqueous solution with boiling temperature exceeding melting point of sulfur by 5-15 C, while 1-3 ml of solution is taken per 1 g of sulfur concentrate. EFFECT: facilitated sulfur isolation process.

Description

 The invention relates to methods for the extraction of sulfur from sulfur concentrates, in particular from sulfur sludge generated during interfacial oxidative treatment of hydrogen sulfide-containing gases in the oil industry.

 Known extraction methods for the extraction of sulfur from native ores [1]. They are based on its high solubility in many organic and inorganic solvents and the inertness of these solvents with respect to rock-forming materials. The crushed ore is treated with a solvent, and the sulfur is transferred into a solution, which is separated from the waste rock, and then sulfur is extracted from it in various ways.

 However, the high cost of sulfur produced, mainly due to significant losses of solvent, as well as toxicity, explosion and fire hazard of solvents are an obstacle to the application of extraction methods in industry.

Closest to the proposed is an autoclave method for extracting sulfur from sulfur concentrate, in particular from sulfur sludge [2]. The essence of the method consists in heating an aqueous suspension of sulfur sludge to the melting point of sulfur. This leads to the coalescence of sulfur droplets, the separation of sulfur from minerals of waste rock and the deposition of liquid sulfur in the lower part of the reactor. To achieve the melting point of sulfur (≈ 120 ^o C), heating of sulfur sludge is carried out in an autoclave at elevated pressure (10 atm). In order to increase the selectivity of the process, a number of reagents are added to sulfuric sludge: surfactants, Trilon B, hydrochloric acid, gasoline, etc.

 The disadvantage of this method is the non-standard production of sulfur, the need to use expensive reagents, as well as the complexity of the equipment operating in high pressure mode.

 The aim of the invention is to improve the quality of sulfur and simplify the method.

 This goal is achieved by the described method for the extraction of sulfur from sulfur concentrate by heating it to the melting point of sulfur.

New in the method is that the melting of sulfur is carried out in an aqueous solution of calcium chloride with a boiling point 5-10 ^o C higher than the melting temperature of sulfur at a ratio of sulfur concentrate and a solution of calcium chloride from 1: 1 to 1: 3 g / ml.

 It is known that to increase the boiling point of water, one can either increase the pressure or introduce the corresponding salts into the solution.

The maximum temperature that is achieved by heating in normal conditions an aqueous suspension of sulfur sludge does not exceed 100 ^o C, which is significantly lower than the melting temperature of sulfur. The addition of calcium chloride salt to this suspension (to a density of 1.45-1.46 g / cm ³ ) increases the boiling point of the aqueous suspension of sulfur sludge to a temperature of 5-10 ^o C higher than the melting temperature of sulfur. Thus, without bringing the mixture to a boil (which excludes its spraying), the melting point of sulfur is reached. Further, in this mixture, all those transformations occur as in the autoclave process. However, unlike the prototype, this is achieved without creating high pressure. In addition, part of the impurities contained in the sulfur sludge is transferred to a solution of calcium chloride, which provides increased, in comparison with the prototype, the purity of the sulfur obtained. Thus, we experimentally discovered that more than 80% of the iron contained in the sludge passes into a solution of calcium chloride.

Thus, the use of a solution of calcium chloride (CaCl ₂ ) during the melting of sulfur sludge helps to achieve a melting point of sulfur at normal atmospheric pressure, as well as a cleaner sulfur.

The ratio of sulfur sludge (g) to a solution of CaCl ₂ (ml) in the range from 1: 1 to 1: 3 ensures the production of sulfur from sulfur sludge.

The technological scheme of the method is shown in the drawing and includes a container 1 for dissolving CaCl ₂ in water, a filter 2 for removing mechanical impurities from a CaCl ₂ solution, a reactor 3, a coolant 4, supply pipelines 5, 6, 7, respectively, for water, unfiltered and filtered solution CaCl ₂ , pipe 8 for introducing sulfuric sludge, discharge pipes: 9 - for the finished product, 10 - for the secondary suspension.

 The method is as follows.

The calculated amount of CaCl _{2 is} loaded into the tank 1 and technical water is fed through the pipe 5, stirred until CaCl _{2 is} completely dissolved, the density and pH of the resulting solution are measured. If the density is less than 1.45-1.46 g / cm ³ add an additional amount of CaCl ₂ ; at pH> 6.5, the solution is acidified with hydrochloric acid. Next, the solution through line 6 is fed to the filter 2 to free from mechanical impurities, the purified CaCl ₂ solution through line 7 enters the reactor 3, where it is heated to a temperature of 120 ^o C; then, through the pipe 8, the calculated amount of sulfur sludge is fed in small portions with stirring in small portions to the reactor 3. The resulting suspension is brought to the melting point of sulfur and maintained at this temperature for 0.5-1.5 hours with gentle stirring. When this occurs, the coalescence of sulfur droplets and their deposition to the bottom of the reactor 3 in the form of liquid sulfur, which through the pipe 9 is allocated to molding and the consumer.

In the reactor 3, a secondary (spent) suspension remains, which is a suspension of insoluble sulfur sludge constituents in a CaCl ₂ solution enriched with soluble impurities from sulfur sludge.

 Secondary suspension can be used in two ways.

1. With the initial ratio of sulfur sludge and a solution of CaCl ₂ 1: 1, a rather thick suspension is obtained. Precipitation of insoluble constituents of sulfur sludge in it is difficult. Such a suspension can be used as a filling fluid in oil production or in a thickening compound in the development of heterogeneous oil reservoirs, i.e., pumped directly into the reservoir. To do this, it is removed from the reactor 3 through a pipeline 10 and sent to the well.

2. When the ratio of sulfuric sludge and a solution of CaCl ₂ > 1: 1, a less saturated suspension is obtained, from which sedimentation separates insoluble impurities of sulfuric sludge and purifies the CaCl ₂ solution more easily.

Such a solution can be reused in the process of extracting sulfur from sulfur sludge by mixing it with a new portion of CaCl ₂ to achieve the desired density. Technologically, this is done as follows: measure the density of the used CaCl ₂ solution after precipitation of insoluble impurities and add an additional CaCl ₂ solution _of such a density to the reactor 3 so that after mixing with the used CaCl ₂ solution, a solution with a density of 1.45-1.46 g / cm ^{3 is} obtained; further operate according to the above scheme. In this case, the sludge remaining in the reactor also enters the sulfur recovery reaction together with a new portion of sulfur sludge. As laboratory tests have shown, another 4% sulfur can be additionally extracted from it.

 The effectiveness of the proposed method was determined in laboratory conditions. The following materials were used.

 1. Sulfur sludge from a gas desulfurization unit. Composition (wt.%): Sulfur 86.2; Trilon B-0.1; trisodium phosphate - 0.9; thiosulfate and sodium sulfate - 0.1; iron compounds - 1.2; moisture - 11.5.

 2. Technical calcium chloride, processed, produced in Sterlitamak, Republic of Bashkortostan (GOST 450-77).

 3. Technical water.

 4. As a reactor, a three-necked round-bottom flask equipped with a reflux condenser and a thermometer was used.

 The results of the studies are presented in table. one.

As can be seen from the table. 1, the highest sulfur yield is obtained when the ratio of sulfur sludge and a solution of CaCl ₂ 1: 1 (87.4%). A further decrease in the proportion of CaCl ₂ solution leads to a strong thickening of the obtained system, which complicates the process of coalescence and deposition of sulfur droplets. An increase in the proportion of CaCl ₂ solution in the ratio of sulfur sludge: CaCl ₂ solution facilitates the process of coalescence of sulfur droplets by reducing the viscosity of the suspension, however, the reagent costs (CaCl ₂ ) increase significantly. Thus, the optimal ratio is from 1: 1 to 1: 3.

 Sulfur obtained by the proposed method was analyzed according to GOST 127-76 for grade 9900 "Technical Sulfur", approved and put into effect on 06/01/90, table. 2 shows the data obtained.

 Obtained by autoclave melting (according to the prototype), sulfur did not comply with GOST, the iron content in it was 0.75%.

 The advantage of the proposed method compared with the prototype is that it allows you to get sulfur of higher quality using affordable and cheap reagent and simple equipment.

Claims (2)

1. The method of extraction of sulfur from sulfur concentrate, including the use of a solution of calcium chloride, melting sulfur at a temperature exceeding its melting point by 5 - 15 ^o C, characterized in that the melting of sulfur is carried out in a medium of calcium chloride at a ratio of sulfur concentrate and calcium chloride solution equal to 1 g of concentrate 1 - 3 ml of solution.  2. The method according to claim 1, characterized in that the feedstock use sulfur slurry generated during the purification of hydrogen sulfide-containing gases in the oil industry.

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