RU2307795C1 - Hydrogen sulfide and ammonia-polluted process condensate purification process - Google Patents

Abstract

FIELD: petroleum processing and petrochemical industry.

SUBSTANCE: invention is intended for deep purification of process steam condensates to produce high-purity ammonia- and hydrogen sulfide-containing gases. Process comprises supplying non-purified process condensate as a feed for a column system composed of at least two in series connected absorption-stripping and rectification columns, wherefrom purified condensate, hydrogen sulfide gas, and gaseous mixture of ammonia with residual hydrogen sulfide and water are withdrawn. A part of purified condensate is recycled into absorption-stripping column and gas mixture is passed for purification to scrubber provided with circulation reflux, upper ammonia outlet line, and bottom condensate outlet line. The latter is connected to line supplying non-purified process condensate to column system. Scrubber purification is performed in two steps: gaseous mixture is first mixed with purified condensate and then non-condensed gases are cooled and residual hydrogen sulfide contained therein is dissolved in circulating condensate, the first step being carried out in an additional section of the scrubber.

EFFECT: increased degree of purification of condensate and leaving gases (hydrogen sulfide and ammonia) on continuously operated plant without formation of ammonium hydrosulfide salts in apparatuses and lines.

4 cl, 3 dwg, 2 tbl

Description

The invention relates to the refining, petrochemical industry and is intended for deep purification of technological condensates of water vapor to produce ammonia and hydrogen sulfide-containing gases of high purity.

Known methods for cleaning process condensate from sulfide sulfur and ammonium nitrogen by the method of one-stage desorption by hydrocarbon gas or one-stage stripping with water vapor, see, for example, Refinery Handbook, ed. G.A. Lastovkina et al. L .: Chemistry, 1986, p. 569-570.

The main disadvantage of these methods is the low degree of purification of process condensate, which does not meet modern requirements for wastewater sent to biological treatment.

There are also known methods of purifying process condensate by two-stage separation by stripping and distillation methods, see Y. A. Karelin et al. "Wastewater treatment of oil refineries." M .: Stroyizdat, 1982, pp. 51-53, and purification of process condensate with a concentration block of hydrogen sulfide and ammonia, see V. G. Ponomarev et al. "Refinery wastewater treatment". M .: Chemistry, 1985, p.163-165.

The disadvantage of these methods is the low quality of the purified process condensate, hydrogen sulfide and ammonia-containing gas, as well as the formation of crystalline ammonium sulfide and hydrosulfide salts on the lower surfaces and in overflow devices of the plates of the absorption-stripping column, in the piping system and in the condenser-refrigerator of acute irrigation of the distillation column , as well as in the unit for condensation and separation of the gas mixture leaving the distillation column, which leads to the need to stop ki and clean it up.

The closest analogue selected for the prototype of the invention is a method for purifying process wastewater from sulfide sulfur and ammonium nitrogen by concentrating pure hydrogen sulfide as a top product and process condensate enriched with ammonia as the bottom residue of an absorption-stripping column, to obtain a mixture of ammonia with residual hydrogen sulfide and steam as a top product and purified condensate as a bottoms product in a distillation column, some of which grows in the absorption-stripping column, the concentration of hydrogen sulfide at the top of the absorption-stripping column is carried out in the packing layer by absorbing ammonia with a cold stream of purified condensate, the distillation column is irrigated with a circulating liquid flow on the upper plates, the mixture of ammonia with residual hydrogen sulfide and water vapor is cooled in a scrubber with formation ammonium hydrosulfide, returned to the absorption-stripping column, and ammonia is withdrawn from the top of the scrubber, see RU 2162444, С02F 1/04.

The disadvantage of this method is the relatively high residual hydrogen sulfide content in the ammonia stream, which leads to clogging of the ammonia output pipelines with ammonium hydrosulfide salts and the need for further purification of the ammonia-containing gas from the hydrogen sulfide before its use or disposal.

The problem to which the invention is directed is to ensure continuous operation of the process condensate purification unit without forming ammonium hydrosulfide salts in the apparatus and pipelines, to increase the degree of purification of the process condensate and to reduce the hydrogen sulfide content in the ammonia stream.

The solution to this problem is provided by the fact that a method for purifying process condensates from hydrogen sulfide and ammonia, including supplying an untreated process condensate as a power supply to the column system, made in the form of at least two absorption-stripping and distillation columns connected to each other in series from this system of purified condensate, gaseous hydrogen sulfide and a gas mixture of ammonia with residual hydrogen sulfide and water, the return of part of the purified condensate to absorption-steam the column and the supply of the gas mixture for cleaning in a scrubber with circulation irrigation and ammonia drain lines on top of the scrubber and condensate as its bottoms product, of which the latter is connected to the raw condensate supply line to the column system, according to the invention, the gas mixture is cleaned in the scrubber in two stages, in the first of which the gas mixture is mixed with purified condensate, and in the second, the non-condensed gases are cooled and the residue contained in them is dissolved pure hydrogen sulfide in the circulating condensate, while the scrubber is equipped with an additional section, and in the additional section, the first purification step is carried out.

In embodiments of the method, the additional section of the scrubber is made in the form of a nozzle, the purified condensate taken from the drain line of the purified condensate is used as irrigation, the condensate inlet to the scrubber located between the sections, and the input of the gas to be cleaned located below the nozzle layer of the additional section; to reduce the temperature of non-condensing gases at the first stage of purification, an additional section of the scrubber is made in the form of a tubular or plate heat exchanger, using cold purified condensate taken from the system for removing purified condensate from the system as a cooling agent; the column system further comprises a preliminary stripping column, the bottom of which is connected to the drainage line of the purified condensate, and the top to the supply line of the absorption-stripping column, while the distilled condensate is withdrawn from the bottom product of the pre-stripping column, and the aqueous concentrated condensate of hydrogen sulfide and ammonia is removed with the top product, and the power line of the preliminary stripping column is connected to the power line of the absorption-stripping column.

The technical result is to increase the degree of purification of process condensate and exhaust gases - hydrogen sulfide and ammonia.

The invention is illustrated by drawings, where:

- figure 1 shows a schematic flow diagram of the purification of technological condensate by the proposed method;

- figure 2 is the same (embodiment);

- figure 3 shows a scheme for cleaning process condensate with a preliminary stripping column (embodiment).

Implementation of the proposed method is as follows.

The feed in the form of the raw crude process condensate is fed through line 1 to the column system consisting of two sequentially connected absorption-stripping and distillation columns, respectively 2 and 3. Gaseous hydrogen sulfide is taken from line 4 from this system, and the balance amount of purified process condensate is withdrawn from line 5 , line 6 discharges ammonia. A gas mixture of water and ammonia with a residual hydrogen sulfide content, which enters a two-section scrubber 8, is discharged from the top of the distillation column through line 7, and the upper section of the scrubber is equipped with a mass-exchange section 9 with circulating irrigation, while its lower section 10 can be equipped with a nozzle or tubular heat exchanger, cm Fig. 2. In the lower section of the scrubber 10, the gas mixture is mixed with purified condensate and the hydrogen sulfide is partially dissolved with ammonia in water, which improves the conditions for the dissolution of hydrogen sulfide residues in the ammonia solution from the gas stream during the passage of the upper section 9. A liquid stream is discharged along line 11 from the scrubber 8, which is fed to line 1.

In an embodiment of the method, the column system can be made with a three-column pre-stripping column 12, the bottom of which is connected via line 13 to the clean condensate discharge line 5, and the top along line 14 to the supply line of the absorption-stripping column 2.

The use of a three-column scheme allows reducing the energy costs of separation, destroying some of the stable emulsions that fall into the purification process in a preliminary stripping column and ensuring the stable operation of the column system when emulsions get into treatment as part of technological condensates and periodic supply of technological condensates from separate sources.

Process condensate is cleaned with the following process conditions:

1. Pressure, kg / cm ² (excess):

Absorption-Stripping Column 0.2-8.0 Distillation column 0.2-3.0 Scrubber 0.2-3.0 Pre-Stripper 0.2-3.0

2. The top temperature of the apparatus, ° C:

Absorption-Stripping Column 35-90 Distillation column 35-125 Scrubber 35-100 Pre-Stripper 100-125

The degree of purification of process condensate is achieved:

from hydrogen sulfide:

- before purification 4000-10000 mg / l,

- after purification less than 1 mg / l;

from ammonia

- before purification 4000-10000 mg / l,

- after cleaning less than 10 mg / l.

As gas products receive:

hydrogen sulfide with an ammonia content of not more than 0.01 wt.%.

ammonia with a hydrogen sulfide content of not more than 0.01 wt.%.

As examples, technological condensate purification plants with a productivity of 25-80 m ³ / h are given.

The operating parameters of the main apparatus of the installation are presented in tables 1, 2.

Using the proposed method for the purification of technological condensates ensures the continuous operation of the installation, eliminates the possibility of salt formation on the working surfaces of the system, significantly reduces emissions of harmful pollution into the environment.

Table 1 An example of the parameters of the main apparatus of the installation without a preliminary stripping column Absorption-Stripping Column Parameter Appliance Pressure (g.) kg / cm ² 6.01 Cold Power Consumption m ³ / h 12.3 Hot Food Consumption m ³ / h 19.2 Consumption of purified technol. condensate m ³ / h 0.6 Temperature: - cold power input ° C 41 - input hot food ° C 126 - input purified technol. condensate ° C 39 - top of the device ° C 46 - bottom of the device ° C 152 Distillation column Parameter Appliance Pressure (g.) kg / cm ² 1.47 Circulation Irrigation Consumption m ³ / h 26.1 Temperature: - power input ° C 74 - top of the device ° C 102 - bottom of the device ° C 128 Scrubber Parameter Appliance Pressure (g.) kg / cm ² 0.98 Consumption of purified technol. condensate m ³ / h 2.1 Circulation Irrigation Consumption m ³ / h 11.2 Temperature: - top of the device ° C 45 - bottom of the device ° C 78 The content of hydrogen sulfide and ammonia in raw materials and products Parameter Content, wt.% (Mg / l) hydrogen sulfide ammonia water Untreated process condensate (4867) (3920) Purified Process Condensate (one) (8) Hydrogen sulfide gas 99.25 0.74 0.01 Ammonia-containing gas 0.01 95.40 3,59

table 2 An example of the parameters of the main apparatus of the installation with a preliminary stripping column Pre-Stripper Parameter Appliance Pressure (g.) kg / cm ² 0.35 Raw material consumption m ³ / h 27.3 Temperature: - top of the device ° C 102 - bottom of the device ° C 106 Absorption-Stripping Column Parameter Appliance Pressure (g.) kg / cm ² 6.1 Cold Power Consumption m ³ / h 7.1 Hot Food Consumption m ³ / h 18.2 Consumption of purified technol. condensate m ³ / h 0.5 Temperature: - cold power input ° C 38 - input hot food ° C 120 - input purified technol. condensate ° C 44 - top of the device ° C 57 - bottom of the device ° C 154 Distillation column Parameter Appliance Pressure (g.) kg / cm ² 1,54 Circulation Irrigation Consumption m ³ / h 34.2 Temperature: - power input ° C 77 - top of the device ° C 81 - bottom of the device ° C 129 Scrubber Parameter Appliance Pressure (g.) kg / cm ² 0.24 Consumption of purified technol. condensate m ³ / h 2,8 Circulation Irrigation Consumption m ³ / h 8.3 Temperature: - top of the device ° C 51 - bottom of the device ° C 84 The content of hydrogen sulfide and ammonia in raw materials and products Parameter Content, wt.% (Mg / l) hydrogen sulfide ammonia water Crude Process Codesate (5337) (6432) Purified Process Condensate (0) (7) Hydrogen sulfide gas 98.76 1.23 0.01 Ammonia-containing gas 0.01 95.33 3.66

Claims (4)

1. A method for purifying process condensates from hydrogen sulfide and ammonia, comprising supplying a crude process condensate as a power supply to the column system, made in the form of at least two sequentially connected absorption-stripping and distillation columns, with the removal of purified condensate and gaseous hydrogen sulfide from this system and a gas mixture of ammonia with residual hydrogen sulfide and water, returning part of the purified condensate to the absorption-stripping column and supplying the gas mixture for cleaning to a scrubber with by circulating irrigation and ammonia drain lines on top of the scrubber and condensate as its bottom product, of which the latter is connected to the feed line of the crude process condensate into the column system, characterized in that the gas mixture is cleaned in a scrubber in two stages, the first of which mixes gas mixture with purified condensate, and on the second, non-condensing gases are cooled and the residual hydrogen sulfide contained in them is dissolved in the circulating condensate, while the scrubber is equipped with dissolved auxiliary section, the auxiliary section is carried out in the first stage of purification. 2. The method according to claim 1, characterized in that the additional section of the scrubber is made in the form of a nozzle, the refined condensate taken from the drain line of the purified condensate is used as an irrigation, the condensate input to the scrubber located between the sections, and the input of the cleaned gas-vapor mixture located below the nozzle layer of the additional section. 3. The method according to claim 1, characterized in that in order to reduce the temperature of non-condensing gases at the first stage of cleaning, the additional section of the scrubber is made in the form of a tubular or plate heat exchanger, using cold purified condensate taken as a cooling agent taken from the clean condensate outlet line from the system . 4. The method according to claim 1, characterized in that the column system further comprises a preliminary stripping column, the bottom of which is connected to the drain line of the purified condensate, and the top to the supply line of the absorption-stripping column, while the purified condensate is withdrawn from the bottom product of the preliminary stripping column and the concentrated condensate water of hydrogen sulfide and ammonia is removed as the upper product, the feed line of the preliminary stripping column being connected to the supply line of the absorption stripping column.

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