RU2544993C1 - Method of removing hydrogen sulphide from decomposition gases from apparatus for atmospheric-vacuum or vacuum distillation of oil - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of removing hydrogen sulphide from decomposition gases from an apparatus for atmospheric-vacuum or vacuum distillation of oil, which includes burning decomposition gases, formed from heating mazut, in a furnace. Decomposition gases from a multi-step steam ejector-type vacuum generating system after the condenser of a cooler and (or) a first ejection step and (or) other ejection steps are fed into a barometric container and then into an absorber, into which, in order to spray contact devices, a regenerated absorbent is fed, wherein the pressure maintained in the absorber is equal to 1.01-1.05 kgf/cm², after absorption the saturated absorbent with hydrogen sulphide content of 0.1-5.0 wt % is removed from the absorber for regeneration, which is carried out either within the apparatus or on refining apparatus or apparatus for removing impurities of straight distillates or other products, the cleaned decomposition gases from the absorber are fed for burning into a mazut heating furnace before a vacuum column.

EFFECT: removing hydrogen sulphide from decomposition gases.

3 cl, 4 dwg, 2 tbl

Description

The method of purification of hydrogen sulfide decomposition gas fuel oil installation atmospheric vacuum or vacuum distillation of oil can be used in the refining industry.

A feature of the vacuum distillation of fuel oil is that the fuel oil is heated in a heating furnace and then separated in a vacuum column into straight-run vacuum distillates and tar, while in the furnace as a result of heating the fuel oil to 360-380 ° C, thermal decomposition gases of fuel oil are formed, containing, in addition to vapors hydrocarbons and inert gases, up to 30-80% of hydrogen sulfide, depending on the type of oil, which are pumped out of the vacuum column using a vacuum-generating system of a multi-stage steam ejector type and then discharged into the atmosphere causing environmental pollution. In this regard, during the processing of sulfur dioxide, hydrogen sulfide emissions into the environment for a plant with a capacity of up to 9 million tons / year reach 4 thousand tons / year.

There is a method of purification of gases from hydrogen sulfide by dissociation of hydrogen sulfide by dissolving it in distilled water by electrolysis with deposition of sulfur on the anode (Method for purifying oil gas from sulfur-containing compounds such as hydrogen sulfide or carbon disulfide: US Pat. 2287617, Russian Federation, No. 2005110307/15; . 04/08/05; publ. 11/20/06). The disadvantages of this method are:

- the frequency of the process associated with the need to clean the anode from sulfur sediment;

- high energy consumption for electrolysis;

- the need to use large quantities of distilled water, for which it is necessary to build a separate installation;

- at a gas pressure of 0.08 atm, the process of gas purification from hydrogen sulfide is complicated by the evaporation of water already at 35 ° C, while the gas temperature after the barometric capacity reaches 50 ° C.

There is a method of cleaning gases from hydrogen sulfide by irradiating a gas mixture with the addition of oxygen, ozone or atmospheric air with light radiation with photon energy exceeding the threshold for photodissociation of hydrogen sulfide and ensuring its decomposition (Method for the decomposition of hydrogen sulfide: application 94041517, Russian Federation; application. 16.11.94; publ. 09/20/96). The disadvantages of this method are:

- the need for additional input into the system of large quantities of dry air or ozone - up to 100% for hydrogen sulfide;

- low yield of photodegradation of hydrogen sulfide (not more than 60% when dry air is supplied);

- the need for a high pressure gas purification process (1.2-2.0 atm) eliminates its implementation under vacuum;

- danger of a system explosion if the insulation of the power supply to radiation sources is violated.

A known method of purification of gases from hydrogen sulfide by catalytic decomposition of hydrogen sulfide in a catalytic reactor at a temperature of about 250 ° C (US Pat. US 3962409, IPC СВВ 17/04, publ. 08.06.76). The disadvantages of this method are:

- low degree of decomposition of hydrogen sulfide (about 15%), which leads to the need for recirculation of the cleaned gas stream, increasing the size of the reactor;

- high energy costs for the implementation of the process due to the high decomposition temperature of hydrogen sulfide;

- the practical impossibility of the technical implementation of the process due to the fact that the decomposition gases have a pressure below atmospheric.

There is also known a method for utilizing tail gases in afterburning furnaces, in which decomposition gases from an atmospheric vacuum or vacuum distillation unit are burned in a decomposition gas furnace, while hydrogen sulfide is oxidized to sulfur oxides (Yagudin M.N. Fundamentals of calculation and design of tail gas afterburners , Ufa, Publishing House GUP INHP, 2010, 175 p.). The disadvantages of this method are:

- sulfur oxides generated during the oxidation of hydrogen sulfide are environmental pollutants;

- ejectors that provide a vacuum in the vacuum column of the primary oil refining units have a minimum excess pressure at the outlet that is insufficient for transporting the decomposition gases to the tail gas afterburner, this requires either additional compression of the decomposition gases to create excess pressure, or installation near the vacuum column additional afterburner;

- burning of hydrogen sulfide in the afterburning furnace leads to an irretrievable loss of hydrogen sulfide, which can be used as a raw material in a number of chemical processes, for example, sulfur production in the Claus process.

Closest to the claimed invention is a method implemented on the installation of purification from hydrogen sulfide decomposition gases from the installation of atmospheric vacuum or vacuum distillation of oil, comprising supplying the decomposition gases removed from the vacuum column in series for cooling to a condenser-cooler and to a vacuum-generating system of jet-injection or vapor ejector types equipped with a separator for degassing circulating working fluid or a barometric tank to remove water vapor condensate , then the decomposition gases are sent to the absorption amine purification in the absorber, on top of which the regenerated absorbent is fed to the irrigation of the contact devices, and the saturated absorbent is removed from the bottom for regeneration, which is carried out either within the installation or in a similar installation for gas purification from hydrogen sulfide of other production, removed from the absorber, the purified decomposition gases are burned in a furnace (Installation for the vacuum distillation of raw materials, mainly oil raw materials: US Pat. 2,325,207; Grew up. Federation, No. 2007103576/15 claimed 01/31/07; publ. 05/27/08; Bull. No. 15). The disadvantages of this method are:

- significant capital and operating costs for creating a vacuum in a vacuum column and for utilizing degassing and decomposition gases, since an additional ejector installation is used and purification of degassing and decomposition gases is carried out in an absorber at a pressure above atmospheric, the value of which is predetermined by the operation of the last stage of this additional installation, which reduces condensate degassing efficiency in a separator or barometric tank;

- the technological complication of this installation with an additional ejector installation is caused by the need for the separator to operate at a pressure above atmospheric for subsequent operation under increased pressure of the absorber, however, with increased pressure, dissolved gases are poorly removed from the working fluid circulating in the system and dissolved hydrogen sulfide remains, as well as the impossibility of implementing the absorption process in absorber with typical devices under vacuum;

- due to additional ejectors at the installation, the output from the system of the excess working fluid, for example, diesel fuel or vacuum gas oil containing dissolved gas components, to remove which will require further stabilization of the working fluid, for example, the stabilization of diesel fuel or vacuum gas oil, as well as dissolved hydrogen sulfide, is saved , the absorption of which at these facilities requires increasing the cost of the absorption process due to an increase in the consumption of absorbent.

It is possible to completely remove hydrogen sulfide from decomposition gases and at the same time ensure the removal of dissolved gases from the working fluid of the jet-injection vacuum pump, as well as to reduce the cost of creating a vacuum in a vacuum column only by reducing the pressure in the separator below atmospheric or very close to him, while the operation of this separator becomes close to the functioning of the barometric capacity when using a steam jet multi-stage pump.

The objective of the invention is to develop a method for purification of hydrogen sulfide from decomposition gases from an atmospheric vacuum or vacuum distillation unit, which allows one to separate hydrogen sulfide from decomposition gases and use it further in other technological processes, to increase the environmental safety of primary oil refining plants, and to use the main equipment of these plants .

To solve this problem, a method for cleaning decomposition gas from hydrogen sulfide from an atmospheric vacuum or vacuum distillation unit of oil is proposed, which includes supplying decomposition gases removed from a vacuum column for cooling to a condenser-cooler and to a vacuum-generating system of jet-injection or steam-ejector types equipped with a separator for degassing of circulating working fluid or a barometric tank to remove water vapor condensate, then the decomposition gases are sent for absorption amine purification into an absorber, on top of which a regenerated absorbent is supplied for irrigation of contact devices, and a saturated absorbent is removed from below for regeneration, which is carried out either within the installation or at a similar gas purification plant from hydrogen sulfide of another production, the purified decomposition gases removed from the absorber are burned in a heating furnace for fuel oil, in which the absorption amine purification of decomposition gases is carried out under a pressure below or close to atmospheric in the range of 1.01-1.05 kgf / cm ² , ensuring This can be achieved by minimizing the pressure drop across the contact devices of the absorber and the reduced pressure in the gas path in the furnace, if this is not possible, an additional vacuum system is connected to discharge the gas into the furnace. The supply of decomposition gases after the barometric capacity to the absorber under vacuum or minimal overpressure improves the selectivity of the pre-regenerated absorbent, which under reduced pressure practically does not absorb the hydrocarbon vapor in the decomposition gases, but only selectively dissolves hydrogen sulfide. The decomposition gases purified from hydrogen sulfide but retaining hydrocarbons are transported by gravity to the fuel oil heating furnace in front of the vacuum column as additional fuel to one of the furnace burners due to rarefaction in the furnace furnace space. The saturated absorbent removed from the absorber can be regenerated either in the apparatus — desorber — optionally installed on the installation, or at any technological installation where this absorbent is also used and regenerated. As a result of regeneration of the absorbent, hydrogen sulfide is released, which can be used as a raw material in a number of chemical processes, for example, sulfur production in the Claus process. The creation of even an insignificant (several mmHg) vacuum at the last stage of pumping out the decomposition gases allows one to indirectly reduce the pressure in the vacuum column by the same amount and thereby reduce energy consumption in the main technological process.

It is advisable to use cross-flow nozzles in the absorber as contact devices, providing a pressure drop of not more than 0.005 kgf / cm ² , with a range of gas load changes from zero to 200% of the nominal, which allows the absorber to work at a pressure below atmospheric at different load of the vacuum column technological plant for raw materials and with a significant change in its composition.

It is also advisable as a regenerated absorbent to use an aqueous solution of methyldiethanolamine with a concentration of the latter of 20-50% and a residual hydrogen sulfide content of not more than 0.07% of the mass. The high quality of the regeneration of the absorbent provides an increase in the depth of purification of decomposition gases from hydrogen sulfide, and an increase in the concentration of the reagent in the absorbent leads to a decrease in its consumption and a reduction in energy consumption for the regeneration of the absorbent.

Since it is impossible to exclude the situation when the vacuum in the gas path of the furnace created by the chimney is insufficient to pump decomposition gases from the barometric container through the absorber, it is advisable to connect an additional vacuum system to the discharge line of decomposition gases into the fuel oil heating furnace.

The invention is illustrated by drawings, where Figures 1-4 are schematic diagrams of a unit for purifying decomposition gas from hydrogen sulfide, implementing a method for purifying decomposition gas from hydrogen sulfide and including the following positions of apparatuses and pipelines:

2 - oven;

5 - vacuum column;

11 - the first condenser-refrigerator;

13 - multi-stage steam-jet evacuation;

16 - second condenser-refrigerator;

21 - barometric capacity;

25 - an absorber;

28 - pump;

30 is an amine regeneration unit;

32 - additional vacuum system;

1, 3, 4, 6-10, 12, 14, 15, 17-20, 22-24, 26, 27, 29, 31, 33 - pipelines.

Shown in figures 1-4 options schematic diagrams of a unit for purification of decomposition gas from hydrogen sulfide are determined by the technology of vacuum rectification of fuel oil:

a) during vacuum distillation of fuel oil in the presence of water vapor and a significant content of decomposition gases according to Figure 1, the decomposition gases with steam come after the vacuum column 5 into the first condenser-cooler 11 with the release of mainly water condensate sent to the barometric tank 21, and non-condensed gases, coming after multi-stage steam-jet evacuation 13 to the second condenser-cooler 16 with condensate supply to the barometric tank 21, and non-condensed gases decompose eniya directly to the absorber 25;

b) with a “dry” vacuum rectification of fuel oil and a significant content of decomposition gases according to FIG. 2, decomposition gases enter after a multi-stage steam-jet evacuation 13 into the second condenser cooler 16 with condensate supplied to the barometric tank 21 and non-condensed decomposition gases directly to the absorber;

c) during vacuum distillation of fuel oil in the presence of water vapor and a small content of decomposition gases according to figure 3, decomposition gases with steam come after the vacuum column 5 into the first condenser-cooler 11 with the release of mainly water condensate sent to the barometric tank 21, and non-condensed gases come after multi-stage steam-jet evacuation 13 in the form of a vapor-liquid mixture directly into the barometric tank 21;

g) with a "dry" vacuum rectification of fuel oil and a small content of decomposition gases according to figure 4, decomposition gases come after a multi-stage steam-jet evacuation 13 in the form of a vapor-liquid mixture directly into the barometric tank 21.

Thus, in figures 1 and 3, technological solutions are presented regarding the purification of decomposition gases from hydrogen sulfide according to the claimed invention for the process of vacuum distillation of fuel oil with the supply of water vapor directly to the column and transfer line, and in figures 2 and 4 it is similar for the dry process ′ ′ Vacuum distillation of fuel oil.

Block purification from hydrogen sulfide decomposition gases according to figure 1 works as follows.

Raw materials (fuel oil) through pipeline 1 enters furnace 2, to the nozzles of which fuel gas is fed through pipeline 3. The fuel oil heated in the furnace 2 is sent via pipeline 4 to the vacuum column 5 for fractionation. Water vapor is supplied to the bottom of the vacuum column 5 through line 8. The vacuum column is equipped with nozzle and plate type contact devices. Tar is discharged from the lower part of the vacuum column 5 through pipeline 9. The upper side shoulder of the vacuum column 5 discharges through the pipeline 7 a fraction of light vacuum gas oil, while part of it, after cooling in the heat exchangers, returns to the top of the column as the upper circulation irrigation. The second lateral overhead pipe 6 is used to discharge a wide gas oil (oil) fraction, and part of it after cooling is used as the average circulation irrigation of the vacuum column. From the top of the vacuum column 5 through line 10, the mixture of oil and water vapor and decomposition gases enters the first condenser-cooler 11, where the condensation of vapors and cooling of the decomposition gases takes place, partially separated condensate enters the barometric tank 21 through line 18, and non-condensed vapors and gases decompositions through pipeline 12 are directed to multi-stage steam-jet evacuation 13, to which water vapor is supplied through pipeline 14. Partially separated condensate flows through pipeline 19 to a barometric pressure th container 21, and via line 15 and uncondensed vapors decomposition gases fed to the next stage of compression and condensation. From the last stage of ejection, the vapors and decomposition gases enter the second condenser-cooler 16, from where the separated condensate flows into the barometric tank 21, and the decomposition gases through the pipe 17 are combined with the decomposition gases discharged through the pipe 24 from the barometric tank 21, and enter the absorber 25 . In the barometric tank 21 is the separation of hydrocarbons from water condensate, while hydrocarbons are discharged through a pipe 22, and a water condenser through a pipe 23.

The decomposition gases enter the absorber 25, into which the regenerated absorbent is supplied by irrigation of the contact devices through the pipe 31. The absorber is equipped with nozzle type contact devices. From the bottom of the absorber, a saturated absorbent with a hydrogen sulfide content of 0.1-5.0% of the mass. through the pipe 27 it is received by the pump 28, after which it is sent through the pipe 29 to the amine regeneration unit 30. The amine is regenerated either within the installation or at the facilities for the refinement or purification of impurities of straight-run distillates or other products. From the top of the absorber 25, through the pipe 26, decomposition gas purified from hydrogen sulfide is fed to the furnace 2, in which the fuel oil is heated in front of the vacuum column 5. The circuit also provides for insufficient vacuum in the furnace gas path to connect an additional vacuum system to discharge gases through the pipe 33 to oven 2.

Unlike figure 1, the decomposition gas purification block from the decomposition gases shown in figure 2 does not require the use of the first condenser 11, since the vacuum column 5 operates according to the “dry” technology, that is, without supplying water vapor to the lower part of the vacuum column 5.

In figures 3 and 4, respectively, presents a block diagram of the purification of hydrogen sulfide decomposition gases in relation to the technology of vacuum distillation with the supply of water vapor and “dry” distillation. The difference from figures 1 and 2 is the use of a second condenser-cooler 16, which allows to increase the degree of removal of hydrogen sulfide from the condensate by supplying a hot stream of condensate mixed with decomposition gases to the barometric tank 21. This solution allows you to maintain the temperature in the barometric tank 21 95 ° C, which reduces the proportion of hydrogen sulfide in the condensate. A feature of the technologies presented in figures 3 and 4 is the operation of the unit at a higher concentration of hydrogen sulfide, as well as inert gases, moisture and light hydrocarbons in the decomposition gases entering the absorber 25.

Example. According to the claimed invention, the implementation of the testing unit for the purification of decomposition gas from hydrogen sulfide was tested at the AVT-1 unit with a capacity of 1.5 million tons / year of Bashneft-Ufaneftekhim OAO. In this case, the scheme shown in figure 3 was implemented. The purpose of testing was to achieve a concentration of hydrogen sulfide in the decomposition gas of fuel oil after amine purification of not more than 20 mg / m ³ , which corresponds to the quality of commercial commodity natural gas. The parameters of the technological mode of the unit are shown in table 1.

The experiments were carried out in order to remove hydrogen sulfide from the decomposition gases of fuel oil, the concentration of which in the decomposition gases reached 18% vol. As the absorbent was used 20% of the mass. a solution of methyldiethanolamine in water, containing after regeneration not more than 0.07% of the mass. hydrogen sulfide. Amine regeneration was carried out beyond the boundaries of this installation. Cross-flow type contact devices were installed in the absorber, providing a pressure drop of about 0.005 kgf / cm ² with a consumption of 240 nm ³ / h of decomposition gases and 6 t / h of regenerated absorbent in the absorber. The absorber successfully operated at a pressure of 1.01-1.05 kgf / cm ² , which was provided by natural draft in the gas path of the furnace without the inclusion of an additional vacuum system on the line connecting the absorber to the furnace.

Table 2 shows the results of testing the block for cleaning gas of decomposition of fuel oil at the AVT-1 installation on the quality of decomposition gases before and after purification, which ensured the complete removal of hydrogen sulfide from decomposition gases.

Analysis showed (table 2) that in the decomposition gases discharged from the top of the absorber 25, there is practically no hydrogen sulfide and carbon dioxide. The content of combustible components and hydrogen in the decomposition gases after the absorber 25 reaches 97.0% vol., Which allows the use of purified gases as an environmentally friendly fuel with high calorific value up to 13700 kcal / m ³ for heating fuel oil in the furnace. Calculations showed that during the experimental run 67.1 kg / h of hydrogen sulfide was extracted from the decomposition gases by the absorption method, while the concentration of hydrogen sulfide in the saturated absorbent reached 1.19% of the mass. These indicators correspond to the concentration of H ₂ S in a saturated absorbent 2 mol of H ₂ S per 1 mol of pure amine, then when in most cases with amine purification of gases from hydrogen sulfide the degree of saturation of the absorbent at the level of 0.4 mol of H ₂ S per 1 mol of pure amine is achieved .

When the performance of the gas purification unit of decomposition gases from hydrogen sulfide 240 nm ³ / h in the source gas, its operation allowed:

1) to separate acid gas during the regeneration of the amine absorbent, from which up to 67 kg / h of elemental sulfur (587 t / year) is produced at the Claus production. Previously, this amount of sulfur was discharged into the atmosphere, polluting the environment;

2) use purified decomposition gases in an amount of up to 230 nm ³ / h for heating fuel oil in the furnace, which will save fuel gas consumption up to 2.1 million nm ³ / year with an annual period of operation.

Thus, the claimed invention developed and tested a method for purification of hydrogen sulfide from decomposition gases of fuel oil from an atmospheric vacuum or vacuum distillation unit, which makes it possible to recover almost completely hydrogen sulfide from decomposition gases and use it further in other technological processes, to increase the level of environmental safety of primary processing plants oil and save fuel gas stoves for heating fuel oil.

Claims (3)

1. A method of purification of hydrogen sulfide from decomposition gases from an atmospheric vacuum or vacuum distillation unit, including burning decomposition gases generated from heating fuel oil in a furnace, characterized in that the decomposition gases from a vacuum-generating system of a multi-stage steam ejector type after the condenser of the refrigerator and (or) the first the stages of ejection and (or) other stages of ejection enter the barometric container and then into the absorber, into which the regenerated absorbent is fed to irrigate the contact devices, etc. and this in the absorber maintain a pressure of 1.01-1.05 kgf / cm ² , after absorption, a saturated absorbent with a hydrogen sulfide content of 0.1-5.0% of the mass. It is removed from the absorber for regeneration, which is carried out either within the installation, or at the plants for the refinement or purification of straight-run distillates or other products from impurities, the purified decomposition gases from the absorber are fed to the fuel oil heating furnace to be burned in front of the vacuum column. 2. A method for purifying decomposition gases from hydrogen sulfide from an atmospheric vacuum or vacuum distillation unit according to claim 1, characterized in that cross-flow nozzles are used as contact devices in the absorber, capable of providing an extremely low pressure drop of not more than 0.005 kg / cm ² with a range of gas load changes from zero to 200% of the nominal. 3. The method of purification of decomposition gases from hydrogen sulfide from an atmospheric vacuum or vacuum distillation unit according to claim 1, characterized in that an aqueous solution of methyldiethanolamine with a concentration of the latter of 20-50% and a residual hydrogen sulfide content of not more than 0.07 is used as a regenerated absorbent. % of the mass.

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