The method of gas purification from hydrogen sulfide and mercaptans

 

(57) Abstract:

The invention relates to processes for cleaning of gases from sulfur compounds, which can be used in gas, oil, chemical, petrochemical industries. The method of gas purification from hydrogen sulfide and mercaptans by introducing into the pipeline in a stream of sulfur dioxide 10-50% aqueous solution of formaldehyde containing water-soluble organic base. As the water-soluble organic bases use a water-soluble primary organic amine in an amount to provide achievement of the initial pH of the solution is greater than 7, and partially purified gas optionally in contact with a water-soluble primary organic amine in the absorption apparatus at elevated temperatures. This invention improves the efficiency of the process. 1 S. and 2 C.p. f-crystals.

The invention relates to processes for cleaning of gases from sulfur compounds by liquid media and can be used in gas, oil, refining, chemical and other industries for selective treatment of low-sulphur hydrocarbon exhaust gases from hydrogen sulfide and/or mercaptans, aerovodochody by contacting the oxide alkylene, for example ethylene oxide or propylene with simultaneous achievement of dioxideequivalent (see and. C. N 288219, 1970, Pat. France N 2031726, Pat. Germany N 1669322 and N 1912054).

The main disadvantages of known methods of preventing the use in industry, are low-tech and complexity for practical implementation, due to the physico-chemical properties of the used oxide alkylene and the necessity of carrying out the process at elevated temperatures. Thus, the low boiling point of ethylene oxide and propylene and high volatility lead to large losses with purified gas contamination gone oxide alkylene and to the need for additional purification of the gas is gone oxide alkylene. In addition, high pozarovzryvobezopasnost requires compliance with special safety measures.

There are also known methods of gas purification from sulfur compounds by contacting with aldehyde or dialdehyde, for example, 15-50% aqueous solution of glyoxal (oxalic acid aldehyde) at pH 5-11 (see U.S. Pat. USA N 5085842, Z. Germany N 4002132 and N 3927763, Z. EPO N 438812, Pat. USSR N 1447267 and others).

The main disadvantages of these methods are the low degree of gas purification from mercaptans because of the formation of solid stubborn reaction product.

The technical essence and the achieved result closest to the proposed invention is a method of purification of natural gas from hydrogen sulphide by introducing into the pipeline in a stream of sulfur dioxide obeserver solution containing 10-50 wt.% low molecular weight aldehyde or ketone; 20-80% water; 10-50% methanol; 1-25% amine corrosion inhibitor; 0-5% sodium hydroxide or potassium; 2-5% isopropanol and having a pH 6-14. The aldehyde used formaldehyde, acetaldehyde, Propionaldehyde or Butyraldehyde, and as amine corrosion inhibitors and oxidation of water - soluble Quaternary ammonium salts or organic bases. In addition, obeserve solution is injected (injected through a nozzle in the pipe in the flow of sulfurous gas in an amount to provide virtually complete reaction between the aldehyde and hydrogen sulfide. Thus preferably used obeserve solution containing 30 wt.% formaldehyde; 30% water, 30% methanol; 5% imidazoline; 2% sodium hydroxide and 3% isopropanol, taken in an amount of 20-300 hours every 100 hours neutralizing of hydrogen sulfide, i.e. 0,68-of 1.02 mol of formaldehyde per 1 mol neutralizing of hydrogen sulfide is this method are the contamination of the purified gas produced by volatile mercaptans (mercaptoethanol and others) and gone (unreacted) a low molecular weight aldehyde (formaldehyde), and education trudnootdelyaemogo spent solution containing the easily polymerizing the reaction products leading to clogging of pipelines, equipment stubborn hard water-insoluble sulfur-containing polymers-titiana and others (see W. "Oil and Gas J, 1989, T. 87, No. 4, 51-53 C. and N 8 S. 46-48). Other major drawbacks of this method are the lack of opportunities for gas purification from mercaptans and complexity (complexity) used obeserver solution (6 component).

These deficiencies significantly reduce the efficiency of the process as a whole and prevent its widespread use in industry for cleaning various serovodorodom and mercaptoundecanoic gases.

The aim of the invention is to increase the efficiency of the process by ensuring a high degree of gas purification from mercaptans (while maintaining the degree of purification from hydrogen sulfide at a high level), prevent the formation of solid serosoderjaschei polymers (Tatiana) and clogging of pipelines, equipment stubborn solid reaction products, reduce carryover and contamination clean gas used volatile aldehyde and formed mercaptide described by way of gas purification from hydrogen sulfide and mercaptans by introducing into the pipeline in a stream of sulfur dioxide 10-50% aqueous solution of formaldehyde, containing water-soluble organic base, in which as a final use of water-soluble primary organic amine in an amount to provide achievement of the initial pH of the solution is greater than 7, and partially purified gas optionally in contact with a water-soluble primary organic amine in the absorption apparatus at an elevated temperature.

As a primary organic amine, preferably using N, N-dimethylpropanediamine, monoethanolamine or mixtures thereof, and further contacting the gas with the primary amine in the absorber is carried out at a temperature of 25-50oC. in Addition, the original solution of formaldehyde to the magnitude of the pH > 7 is injected into a stream of sulfur dioxide at a rate of not less than 1.5 mol of formaldehyde per 1 mol of hydrogen sulfide and at least 1 mole of formaldehyde to 1 mol of mercaptan sulfur.

Distinctive features of the proposed method are used as the organic base it is a primary organic amine, preferably N,N-dimethylpropanediamine (DMPD), monoethanolamine (MEA) or a mixture thereof, with a new technical feature of the second reactive component of the solution and at the same time the school is sterowanie gas with the primary amine (DMPD, The IEA, or their mixture) in the absorption apparatus at elevated temperatures (25-50oC).

These distinctive features of the proposed technical solutions determine its novelty and inventive step in comparison with the prior art in the field of desulfurization of gases liquid chemical absorbers, because the process of gas purification from hydrogen sulfide and mercaptans two-stage contacting of the sulfur gas stream first with a solution of formaldehyde at a pH > 7 in the pipeline, and then with a primary amine in the absorption apparatus when found above the optimal quantities and temperatures are not described in literature, and improves the efficiency of the process by increasing the degree of gas purification from mercaptans (while maintaining the degree of purification from hydrogen sulfide at a high level), to prevent the formation of solid reaction products and driving their gas-cleaning equipment, reduce carryover and contamination of cleaned gas formaldehyde and formed mercaptans, as well as simplifying the structure of the applied solution (eliminating the use of sodium hydroxide, potassium and isopropanol).

The need and feasibility of use in CA ability in the reaction of interaction with the applied formaldehyde and mercaptans to form a liquid, non-volatile, stable and non-corrosive nitrogen and serosoderjaschei organic compounds-amidosulfuron and a relatively high basicity to achieve the pH of the original solution of formaldehyde greater than 7 (without additional application of the hydroxide into three, potassium). The expediency of use as a primary amine it DMPD, the IEA, or their mixtures due to their higher reactivity and adaptability and accessibility for practical application. The primary amine is most appropriate to use DND or a mixture DND and the IEA, because DND also has the properties of an effective corrosion inhibitor and high sorption capacity for mercaptans (see, for example, and.with. N 782212 and N 1089799). It should be stated that in the proposed method, in principle, can be used and other water-soluble primary amines, in particular monoisopropanolamine, methylamine, ethylamine, Propylamine, however, they are relatively less reactive and not technologically advanced products for practical application in industry.

The necessity and expediency of use of a primary amine in an amount to provide a pH of the solution formaldeh outstay primary amine at pH > 7 avoid the formation of solid serosoderjaschei reaction products (Tatiana and others) and thus eliminates the possibility of driving their gas-cleaning equipment. The most appropriate use of primary amines in an amount to provide a pH of the original solution in the range from 7.5 to 8.5.

Additional contacting the partially purified gas with the primary amine in the absorption apparatus (absorber) at elevated temperatures is also necessary and reasonable, because otherwise not attained a high degree of gas purification from mercaptans, reducing carryover and contamination of cleaned gas formaldehyde and formed with mercaptans. The primary amine can be used in the absorber as in pure (concentrated) form and in the form of water or odnopetlevykh solutions (if necessary simultaneous dehydration). Taking into account the physico-chemical and technological properties of the IEA and DMPD (viscosity, TDeputyvolatility , and others) most appropriate to use them as 50-80% of the energy of aqueous solutions. As absorption apparatus for an extra contact of the gas with the primary amine can be used a known standard gasify absorbers. Additional shielding gas with a primary amine in the proposed temperature range (25-50oC) is optimal, since at temperatures below the 25oC decreases the velocity of the flowing of neutralization reactions and not achieved a high degree of gas purification from mercaptans, as the temperature increases above the 50oC is not economically feasible (due to increased energy costs, losses used reagents with purified gas). The most appropriate process when 30-45oC.

We offer you input the amount of formaldehyde solution with pH > 7 is connected with the stoichiometry of the flowing neutralization reactions of hydrogen sulfide and mercaptans:

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< / BR>
< / BR>
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From the above equations it is seen that to neutralize 1 mole of hydrogen sulfide to the introduction of a stream of sulfur dioxide to 1.5 mol of formaldehyde, and to neutralize 1 mole of mercaptan - 1 mole of formaldehyde. Taking into account possible fluctuations in the concentrations of hydrogen sulfide and mercaptans in the source of the cleaned gas to ensure a consistently high level of cleaning gas, it is expedient introduction of a solution of formaldehyde in an amount to provide a slight excess formaldeh the l of formaldehyde to 1 mol of mercaptan sulfur. Should indicate that the reactions (1) and (2) occurs mainly in the pipeline, and reactions (3) and (4) absorption apparatus with a primary amine at elevated temperatures (25-50oC).

It should also specify that the resulting end products of reactions - aminosulfonyl (secondary and tertiary Mannich bases) are non-volatile (high-boiling), stable organic compounds with a number of useful properties, and can then be recycled in the economy, for example, as an adsorbent for purification of exhaust gases from sulfur dioxide, corrosion inhibitor in various aggressive environments, and so on (see and. C. N 1060210; U.S. Pat. USA NN 4332967, 4393026, 4450138, 4981609; kN. Rachinsky F. Yu , Slavonska N. M. Chemistry aminothiols, M.-L., Chemistry, 1965, S. 3-6 and 146, and others).

The proposed method has been tested in laboratory conditions. Examples and experimental results.

Example 1. The gas purification from hydrogen sulfide and mercaptan carried out using a temperature-controlled glass Packed absorber height of 500 mm and a diameter of 20 mm as a nozzle use glass ring process size HH mm absorber load 50 ml of the primary amine, the quality is second pressure is passed through the absorber at a rate of 12 l/h of nitrogen, containing 2.5% vol. of hydrogen sulfide, 0,5% vol. ethyl mercaptan and 5 vol.% of carbon dioxide. In the pipeline (line Gasometer-absorber) in the original thread sulfur dioxide simultaneously injected (injected) 10% solution of formaldehyde containing 8 wt.% DMPD and ensuring the achievement of pH 8.5, at the rate of 1.5 formaldehyde to 1 mol of hydrogen sulfide and 1.1 mol of formaldehyde per 1 mol of ethyl mercaptan. Exhaust from the top of absorber purified gas is passed through the flask Drexel with 10% aqueous sodium hydroxide solution (lye) to absorb the residual amount of hydrogen sulfide and mercaptan. At the end of the experiment the solution of alkali analyze the content of sulfide and mercaptan sulfur by potentiometric titration and calculate the residual concentration of hydrogen sulfide and mercaptan in the purified gas and the degree of gas purification. While conducting the analysis of the purified gas for formaldehyde by well-known methods and conduct visual observation of the condition of the pipeline and absorber.

The degree of gas purification from hydrogen sulfide is 100% and from mercaptan - 99,3%, ash of formaldehyde with purified gas in trace quantities (not quantitatively defined), the formation of a gas from hydrogen sulphide and mercaptan carried out analogously to example 1 using as the primary amine of monoethanolamine (on THE 6-02-915-84). In the absorber load 50 ml of 80% aqueous solution of the IEA and at a temperature of 50oC is passed through it at a rate of 12 l/h nitrogen containing 2.5% vol. of hydrogen sulfide, 0,5% vol. ethyl mercaptan and about 5. % of carbon dioxide. This in the pipeline into the flow of the source of sulfur dioxide at the same time impose a 30% solution of formaldehyde containing 27,3 wt, % IEA and ensuring the achievement of pH 8, the rate of 1.6 mol of formaldehyde per 1 mol of hydrogen sulfide and 1 mol of formaldehyde per 1 mol of ethyl mercaptan.

The degree of gas purification from hydrogen sulfide is 100% and from mercaptan - 98,5%, ash of formaldehyde with purified gas in trace quantities (not quantitatively defined), the formation and deposition of solid products of the reactions are not observed.

Example 3. The cleaning gas from ethyl mercaptan is carried out analogously to example 1 using as the primary amine mixture DMPD and IEA. In the absorber load 50 ml of a mixture of DMPD and IEA (4:1) and at a temperature of 35oC is passed at a rate of 12 l/h of nitrogen, containing 1.5 vol.% ethyl mercaptan. In the pipeline in the original thread mercaptoacetate gas is introduced simultaneously with 37% solution of formaldehyde containing 7.6 wt.% the mixture DMPD and IEA and providing DOS the TCI gas from ethyl mercaptan is 99,8%, ablation of formaldehyde with purified gas in trace quantities, the formation and deposition of solid products of the reactions are not observed.

The data presented in examples 1-3 show that the proposed method, in contrast to the known, provides a high degree of gas purification from mercaptans while maintaining the degree of gas purification from hydrogen sulfide at a high level. In addition, the process of the proposed method, in comparison with the known, can significantly reduce the entrainment of formaldehyde with purified gas and its contamination with gone with formaldehyde and formed mercaptans to eliminate stubborn solid reaction products, and driving their gas purifying apparatus, and also to simplify the structure used obeserver solution (by eliminating the use of sodium hydroxide and isopropanol) and to receive liquid recyclable products of reactions - aminosulfonyl.

The above advantages of the proposed method allows to increase the efficiency of the process as a whole in comparison with the known.

1. The method of gas purification from hydrogen sulfide and mercaptans by introducing into the pipeline in a stream of sulfur dioxide 10 - 50%-aqueous solution of formaldehyde, with doraswamy primary organic amine in a quantity ensuring the achievement of the initial pH of the solution is greater than 7, and partially purified gas optionally in contact with a water-soluble primary organic amine in the absorption apparatus at an elevated temperature.

2. The method according to p. 1, characterized in that the primary amine used is N,N-dimethylpropanediamine, monoethanolamine or mixtures thereof.

3. The method according to PP.1 and 2, characterized in that the additional contacting the gas with a primary organic amine in the absorption tower is carried out at 25 - 50oC.

 

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2 dwg, 6 tbl, 2 ex

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