BG66997B1 - Method for separation of hydrogen sulphide and sulphur dioxide from fluids - Google Patents

Abstract

The invention represents a method for separation of hydrogen sulphide and sulphur dioxide from fluids, which comprises contacting of simultaneously fed two purified fluids with salt composition 18 g/l through a catalytic mass, consisting of teflonized high-dispersion coals and/or soot as a padding with coated catalyst, which represents chelate of the transition-metal series of iron, cobalt, vanadium or manganese and so forth. The process is conducted in a single-step at room temperature and normal atmospheric pressure, with values of pH in the range of 2 to 13.5. The quantitative ratio between the catalysts: teflonized coals/soot is within limits of 1:10 to 6:4. The used catalytic mass represents 10-60% teflonized coal/soot and the applied catalysts, which represents 2-40% chelate of transition metal ( such as iron, cobalt, vanadium or manganese,etc.). The catalytic mass is used, whereby the catalyst is applied on top of specially prepared through high-energy agitated pad, representing high-dispersion coal and/or soot with coated Teflon.

Description

Field of technology

The invention relates to a method for separating hydrogen sulfide and sulfur dioxide from fluids, applicable to the treatment of wastewater, industrial waste gases, harmful pollutants in the atmosphere and natural sources of pollution.

BACKGROUND OF THE INVENTION

The presence of sulfur compounds causes serious damage to the balance of the environment. Sulfur compounds such as sulfur dioxide (SO ₂ ) and hydrogen sulfide (H ₂ S) in the atmosphere or wastewater, in gas mixtures and other fluid streams are considered undesirable compounds. In addition to natural gas, which may contain unwanted sulfur compounds such as carbonyl sulfide, carbon disulfide, mono and dialkyl sulfides, thiophenes, harmful pollutants in gas streams emitted from stationary and mobile sources such as power plants, cars, ships, trains and others are well known. Sulfur oxides with water vapor form highly corrosive vapors, causing irritation of the eyes and mucous membranes, damage to metal-containing structures, etc. damage to the environment - incl. and for agriculture due to acid rain. Carbonyl sulfide (COS) is another toxic pollutant formed as a reaction product between sulfur-containing compounds and carbon monoxide in gas streams or wastewater. Hydrogen sulfide (H ₂ S) is a corrosive and extremely toxic gas that is found in natural gas with concentrations ranging from a few ppm to 50% or even higher. Hydrotreating of fuel oil and bitumen and gasification of coal also produce gas streams containing hydrogen sulfide as an unwanted by-product. Hydrogen sulfide is a by-product or is present as an impurity in raw materials on a large scale in a number of important industrial industries, such as petroleum, electricity generation or chemical synthesis, and must be removed from streams before they can be released into the atmosphere or rivers and canals. .

The rules for controlling these pollutants in the atmosphere are becoming more stringent and the production of sulfur and polysulphides from SO ₂ and H ₂ S is considered a desirable product in their purification.

A number of methods are known for removing H ₂ S from natural gas and from the process gas stream to make it useful or at least harmless products. Most of these methods are multi-step processes that begin with the chemical or physical absorption of H ₂ S.

In many cases, H ₂ S is removed by contacting the process gas with a thin film of organic solvent. The solvent was recovered by heating, then reacted with additional stoichiometric amounts of H ₂ S over an alumina catalyst based to produce elemental sulfur, water and heat. The chemical reaction takes place at 525-700 ° C.

There are different methods for purification of sulfur dioxide gases and they can be classified into the following several groups: neutralization - conversion of SO ₂ to CaSO ₄ [1]; liquefaction of SO ₂ by adsorption in sulfite solution [2]; catalytic - oxidation of SO ₂ on Pt, V ₂ O ₅ at t = 400-600 ° С to SO ₃ and its dissolution in water to H ₂ SO ₄ [3].

The purification of hydrogen sulfide is carried out mainly by the so-called "Claus process", which is the oxidation of H ₂ S with oxygen from the air, which takes place in the following stages:

Stage I: thermal oxidation of hydrogen sulfide to sulfur dioxide

H _; S + 3 / 2O _; ^ SO _; + H _; Oh

Stage II: catalytic oxidation of hydrogen sulfide and sulfur dioxide to sulfur 2H ₂ S + SO ₂ - + 3 / nS _n + 2H ₂ O + (0,087-0,154) MJ / mol.

Widespread is the so-called. process Supsrklaus -99.

Thermal conversion - three stages of catalytic oxidation with intermediate removal of sulfur obtained in the process. A method is known for the purification of waste gases from sulfur dioxide by its direct electrocatalytic oxidation from oxygen in the air in the presence of water to sulfuric acid at ordinary temperature [4-6].

Small amounts are adsorbed, usually on activated carbon. Sulfur is thermally reduced

Descriptions of issued patents for inventions № 01.1 / 15.01.2020 sulfur dioxide [7-9]. There are various methods for improving the Klaus process by controlling the concentration over time and / or reducing the temperature in the catalyst sections [10, 11]. The Klaus process can also be combined with microbiological processes to reduce sulfur dioxide and hydrogen sulfide [12].

The methods listed above are performed at high temperatures and high concentrations. It is known that chemical kinetics do not work well at reagent concentrations below 1.0% (vol.), And chemical reactions are very slow. Special catalysts and technologies are being sought to overcome this problem.

A method is known which includes a material for absorbing sulfur compounds such as hydrogen sulfide or sulfur oxides from a fluid stream and decomposing them to sulfur. It is applicable for the removal of hydrogen sulfide and other sulfur compounds from acidic natural gas, or liquid streams, and the conversion of sulfur to elemental sulfur. The same method can be used to remove some nitrogen and carbon oxides from gas streams, as well as compounds such as carbonyl sulfide, sulfur carbon, mono and dialkyl sulfides, alkyl-type disulfides, and thiophenes. The process is carried out at room temperature. The adsorbent material is regenerated by applying heat at elevated temperature (in the range of 250 ° C to 600 ° C).

Biological purification is known in which sulphate, sulphite and other sulfur compounds are transformed by sulphate-reducing bacteria under anaerobic conditions to give a sulphide which in turn can be oxidised to elemental sulfur. The advantage of this method is the possibility of processing small and low-concentrated waste streams. However, its disadvantage is that when wastewater does not contain organic matter, electronic donors must be added. The most important electron donors are methanol, ethanol, glucose, hydrogen and carbon monoxide. The use of these or other electron donors significantly increases the cost of the method of removing sulfur from waste streams.

Elevated temperature can be used continuously or almost continuously, for example when a cheap source of energy is available, as in the case of hot flue gases and / or hot flushing fluid. Preferably, the anaerobic treatment is carried out at an elevated temperature of 55 ° C-100 ° C, preferably 60 ° C-100 ° C. In general, a higher temperature has a better effect. The fever can be maintained for a period of several minutes or hours to several days. The level of this maximum, and the time for which this maximum temperature is maintained, can be selected depending on the nature of the wastewater to be treated, the microorganisms used and the desired degree and rate of treatment.

Chemical / electrochemical processes are known and are generally a galvanic cell consisting of a parent metal and an impurity of another metal, most often nobler than the parent. The two electrodes are electronically connected through the metal and make an electrolytic connection through the solution. These impurities can be a separate phase or create one in the corrosion process. Therefore, the surface of the metal is considered as a system of anodes (base metal) and microscopic cathodes. The nobler cathodes and the parent metal are a series of numerous galvanically connected elements. There is a certain potential difference between the cathodes and the anodes, which causes an electric current to flow. The greater the potential difference between the anodes and the cathodes, the greater the current flowing in the local elements and therefore the speed of the process. Only two types of anodes and cathodes do not have to exist on the electrode surface. The simultaneous presence of several impurities leads to the formation of a system of many electrode elements, characterized by the presence of several types of cathodes and anodes with different potentials and polarization characteristics [13].

Controlling SO ₂ emissions and ensuring the purification of H ₂ S implies creating a process for simultaneous purification of H ₂ S and SO ₂ . It is desirable to provide a method for removing hydrogen sulfide and sulfur dioxide contained in various fluids at moderate temperatures and subsequently converting the sulfur compounds into other environmentally friendly conversion products.

Descriptions of issued patents for inventions № 01.1 / 15.01.2020

Technical essence of the invention

The invention is a method for separating hydrogen sulfide and sulfur dioxide from fluids, which comprises contacting simultaneously fed two purified fluids with a salt composition of 18 g / l through a catalytic mass consisting of Teflon-coated fine carbons and / or carbon black as a support. is a chelate of transition metals of the order of iron, cobalt, vanadium or manganese, etc. The process is carried out in one step at room temperature and normal atmospheric pressure, at pH values in the range from 2 to 13.5. The quantitative ratio between catalyst: Teflon carbon / carbon black is in the range of 1:10 to 6: 4. The catalyst mass used is 10-60% Teflon-coated carbon / carbon black and supported catalyst, which is 2-40% transition metal chelates (such as iron, cobalt, vanadium or manganese, etc.).

A catalytic mass is used in which the catalyst is applied on a substrate specially prepared by high-energy stirring, representing highly dispersed charcoal and / or carbon black, Teflon is applied.

This invention represents a substantially new method is in fact a chemical / electrochemical reaction mechanism and a catalyst for the simultaneous separation of sulfur dioxide and hydrogen sulfide from fluids and their conversion to obtain harmless compounds.

The method we developed is based on the Klaus reaction, but using a special catalyst and technology, which does not result in sulfur, but polysulfides, sulfites and sulfates that do not poison the catalysts. Sulphates are environmentally friendly. The mechanism of the reactions is electrochemical / chemical and is performed on scattered chemical microgalvanic elements by the following exemplary reactions:

HS ~ —S + H + 2c ~ E = - 0.065 V (1)

SO ₂ (g) + 4H ++ 4e-θ 2H ₂ O + SE = + 0.451V (2)

As a result of the ongoing reactions, H ₂ S and SO ₂ are purified to concentrations C _H2S = 0 and C _SO2 = 0.

The method allows the treatment of fluids in a batch as well as a continuous catalytic process in the reaction zone.

A minimum amount of catalyst in the catalytic mass is required to catalyze the processes of conversion of sulfur compounds into environmentally friendly products. Depending on whether they are only coal / soot or we have a catalyst applied to them, the efficiency of the processes changes significantly. When the two fluids are mixed on the catalyst mass under the reaction conditions chosen by us, microgalvanic elements are formed spontaneously, on which reactions 1 and 2 take place. This is due both to the difference between the electrochemical potentials of the reactions and to the numerous places created for the three-phase gas-liquid-solid interface (catalyst) in the originally developed catalytic mass.

The velocity of the fluids is determined by the content of sulfur compounds in the purified fluids. The pH value is not maintained in a certain range, as the method works in both acidic and alkaline environments depending on the purified fluid. Approximately 99% purification is achieved. The ratio of catalyst (catalytic mass) to concentrations of sulfur compounds obtained was 6: 1 mg / mg / h. For 24 h the ratio is 1: 4. The ratio of the amount of catalyst (cobalt phthalocyanine), well distributed in the coal, respectively - in the soot and the amount of converted sulfides and sulfites to a harmless product is approximately 1: 3 mg / mg / h. For 24 h it is approximately 1:80. Since the developed method does not reach elemental sulfur, but sulfates, the catalyst can be used for a long time.

The developed method has the following advantages:

- applicable for both alkaline, neutral and acidic environments;

- provides complete separation of sulfur dioxide and hydrogen sulfide from the purified fluids;

- works at low concentrations below 0.1% - (1000 ppm), at which concentrations the chemical kinetics do not work;

- works at room temperature;

operates in acidic and alkaline environments at pH values ranging from approximately 2 to 13.5 and

Descriptions of issued patents for inventions № 01.1 / 15.01.2020 leads to complete conversion (purification) of the starting materials.

The method developed by us and the ongoing process of removal of sulfur dioxide and hydrogen sulfide can be presented in the following way and scheme (Scheme 1, Annex), which presents the conditions for spontaneous formation of microgalvanic elements (2 and 3, 4), on which the reactions take place in the three-phase boundary gas - liquid (electrolyte-4) - solid (2-hydrophobic material carbon / soot catalytic mass (catalyst) is applied) in the process of simultaneous purification of fluids from sulfur dioxide and hydrogen sulfide in periodic operation.

The invention is illustrated by the following examples with respect to the novelty, the mode of operation and the possibilities of the method developed by us, which are not limiting.

Example 1 for alkaline medium.

Two fluids were fed to the reactor as described above, representing the above catalytic mass (25% cobalt phthalocyanine and 40% Teflon carbon / carbon black in a ratio of 1: 3.5), each with a salt content of 18 g / / - fluid 1 containing sulfide ions is a concentration of 400 mg / l and fluid 2 - sulfites is a concentration of 200 mg / l and pH of the solution pH = 11.3. After 4 hours the content of sulfide ions is depleted, ie. not detected, and the sulfite is 145 mg / l.

The obtained products are polysulphides and sulphates, the presence of which is determined qualitatively. The content of sulphides is determined photometrically and that of sulphites iodometrically. When mixing the two fluids, the concentrations are 200 mg / l sulfide and, respectively, 100 mg / l sulfite. Their total concentration after mixing and during the experiment is determined iodometrically, and only the sulfide by masking the sulfite is formalin. An indication for obtaining polysulfides is the change of the color of the solution to yellow-greenish. When hydrochloric acid is added, it clarifies and a precipitate of sulfur appears (qualitative reaction for polysulphides). The presence of opalescence with the addition of barium chloride indicates the presence of sulfates (qualitative reaction for sulfates), with a decrease in pH to 10.90, which also determines the presence of sulfates. The content of polysulphides and sulphates in balance is equivalent to 82 mg / l sulphide. The remaining amount of sulfide was oxidized to sulfites and it was equivalent to 18 mg / l, which explains the increased concentration of sulfite relative to the initial amount when mixed.

From the obtained products it can be seen that we have a complete conversion of hydrogen sulfide (up to 100%) and a subsequent continuation of the conversion of the products of sulfites to sulfates.

Example 2 for alkaline medium.

The reactor is the catalytic mass described above (10% cobalt phthalocyanine and 30% Teflon carbon / carbon black in a ratio of 1:10), the two fluids are fed, which have a salinity of 18 g / Ι. Fluid 1 contains sulfide ions is a concentration of 400 mg / 1, and fluid 2 - sulfites is a concentration of 3250 mg / 1, pH = 12.7 After 4 hours the content of sulfide ions is depleted and sulfite is 1470 mg / 1.The content of sulfides is determined photometrically, and that of sulfites The resultant concentration and pH of the solution when mixing the two fluids is 200 mg / l sulfide, 1625 mg / l sulfite, respectively.Their total concentration after mixing and during the experiment is determined iodometrically, and only the sulfide by masking the sulfite is formalin.The products obtained are polysulphides and sulphates, the presence of which is determined qualitatively.Indication for the production of polysulphides is the change in color of the solution to yellow-greenish.When adding hydrochloric acid it clarifies and a precipitate of sulfur appears (qualitative reaction for polysulphides). The presence of opalescence when adding barium chloride indicates the presence of sulfates (qualitative reaction for sulfates).

The resulting pH decreases to 11.80, which also determines the presence of sulfates. The balance of polysulphides and sulphates in balance is equivalent to the depletion of 200 mg / l sulphides and 155 mg / l sulphites.

From the obtained products it can be seen that we have a complete conversion of hydrogen sulfide (up to 100%) and a subsequent continuation of the conversion of the products of sulfites to sulfates.

Example 3 for an acidic environment.

In the reactor is the catalytic mass described above (40% cobalt phthalocyanine and 20% Teflon carbon / carbon black in a ratio of 6: 4 are fed the two fluids, which have a salinity of 18 g / Ι. Fluid

Descriptions of issued patents for inventions № 01.1 / 15.01.2020 contains sulfide ions with a concentration of 194 mg / Ι and fluid 2 - sulfites with a concentration of 2560 mg / l. pH = 4.3. After 4 hours the content of sulfide ions was depleted and of sulfite ions was 1430 mg / Ι. The content of sulfides is determined photometrically, and that of sulfites iodometrically. The resulting concentration of the solution when mixing the two fluids is 97 mg / Ι sulfide and 1260 mg / Ι sulfite, respectively. Their total concentration after mixing and during the experiment is determined iodometrically, but only on the sulfide by masking the sulfite with formalin. The products obtained are sulfur and sulphates, the presence of which is determined qualitatively. Sulfur production is determined visually, of sulfates by the presence of opalescence with the addition of barium chloride (qualitative reaction for sulfates). The resulting pH reaches 6.5. Quantitatively, the sulfide has been oxidized to sulfites, which explains the increased concentration of sulfite relative to the initial amount of mixing.

From the obtained products it can be seen that we have a complete conversion of hydrogen sulfide (up to 100%) and a subsequent continuation of the conversion of the products of sulfites to sulfates.

Example 4 for a neutral medium.

In a reactor with the catalytic mass described above (30% cobalt phthalocyanine and 60% Teflon carbon / carbon black in a ratio of 1: 3.5), the two fluids with a salinity of 18 g / l are fed. Fluid 1 contains sulfide ions with a concentration of 160 mg / Ι, and fluid 2 - sulfites with a concentration of 1500 mg / Ι pH = 7.4 After 4 hours the content of sulfide ions is depleted and sulfite is 850 mg / Ι The content of sulfides is determined photometrically and that of sulfites iodometrically. The resulting concentration of the solution when mixing the two fluids is 80 mg / Ι sulfide, 750 mg / Ι sulfite, respectively, and their total concentration after mixing and during the experiment is determined iodometrically, and only of the sulfide by masking the sulfite with formalin. Polysulphides and sulphates, the presence of which is qualitatively determined.Indication for the production of polysulphides is the change in color of the solution to yellow-greenish.When adding hydrochloric acid it clarifies and a precipitate of sulfur appears (qualitative reaction for poly sulphides) and sulphates in the presence of opalescence with the addition of barium chloride (qualitative reaction for sulphates). Some of the sulphides have been oxidised to sulphites equivalent to half of the sulphides (40 mg / l) and the other part has been converted to polysulphides and sulphates, the pH reaching 7.1.

In alkaline environments we have polysulfides and sulfates.

From the obtained products it can be seen that we have a complete conversion of hydrogen sulfide (up to 100%) and a subsequent continuation of the conversion of the products of sulfites to sulfates.

In many cases, the separation of fluids was done using catalysts included in the catalytic mass of chelates of iron, manganese and others. transition metals.

The results showed similar results in the evolution of hydrogen sulfide and sulfur dioxide.

Claims (2)

Patent claims Method for separating hydrogen sulfide and sulfur dioxide from fluids, characterized by the simultaneous feeding of two purified fluids through a catalytic mass consisting of 10-60% Teflon-coated fine coal and / or carbon black, as a support with 2-40% catalyst applied. , which represents chelates of transition metals such as Fe, Co, Μη, at room temperature and normal atmospheric pressure, pH values in the range from 2 to 13.5 and with a quantitative ratio between catalyst: Teflon-coated / carbon black in the range 1:10 to 6: 4. Process for separating hydrogen sulfide and sulfur dioxide from fluids according to claim 1, characterized in that the transition metal chelate is cobalt phthalocyanine.