RU2307700C2 - Method of regeneration of the saturated solution of the absorbent - diethyleneglycol - Google Patents

Abstract

FIELD: natural gas industry; chemical industry; methods of regeneration of the saturated solution of the absorbent- diethyleneglycol.

SUBSTANCE: the invention is pertaining to natural gas industry and is intended for usage in the installations of the field preparation of the natural gas for transportation through the main pipeline. The saturated solution of diethyleneglycol is fed into the regeneration installation. In the tubular furnace it is heated up to the temperature of 165÷185°C with preservation of its single-phase state and provision of its recirculation through the furnace. No more than 30 % of the regenerated solution of the diethyleneglycol is fed for purification of the impurities and heated up in the furnace of the installation of purification from the of impurities up to the temperature of 165÷210°C. The purified from the impurities solution of diethyleneglycol is directed into the installation of the gas drying. The invention increases the concentration of diethyleneglycol at regeneration above 99 mass %, reduces the corrosive effect of the absorbent on the regeneration equipment at preservation of the materials consumption for the installation.

EFFECT: the invention ensures the increase of the concentration of the diethyleneglycol at the regeneration process exceeding 99 mass percent, the decrease of the corrosive effect of the absorbent on the regeneration equipment, preservation of the materials consumption for the installation.

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Description

The invention relates to the gas industry and is intended for use in installations for field preparation of natural and associated petroleum gases to the main transport.

The closest analogue to this invention is a method of regeneration of an absorbent - diethylene glycol (DEG), including its output from the absorber of a drying unit for natural and petroleum gases, supplying the latter to a stripper separated by a half-deaf plate, heating in a tube furnace with maintaining the single-phase state of DEG in the amount necessary to obtain a given concentration of the regenerated absorbent solution and determined by the frequency of recirculation of the DEG solution through the furnace, determined according to the mathematical calculation (see Patent RU No. 2023484, IPC B01D 53/26, publ. 30.11.94).

When the installation is operating according to the known method of solution regeneration using a water-glycol mixture supplied to the furnace, complete purification of the DEG solution from light impurities, including acids, which contribute to the decomposition of glycols and increase corrosion activity, is not achieved.

When creating the invention, the technical problems were solved to increase the concentration of diethylene glycol during regeneration above 99 wt.%, Reduce the corrosive effects of the absorbent on the regeneration equipment while maintaining the material consumption of the installation.

The stated technical problems are solved in a method for regenerating absorbent DEG, including supplying a saturated DEG solution to a regeneration unit, heating it in a tubular furnace of a unit while maintaining a single-phase state and ensuring recirculation through the furnace, supplying a regenerated DEG solution to a gas dehydration unit, while regenerating DEG heated to a temperature of 165 ° C ÷ 185 ° C, and not more than 30% of the regenerated DEG solution is fed for purification from impurities and heated in a furnace of a purification plant from impurities to a temperature of 165 ° C ÷ 210 ° C, and the DEG solution purified from impurities is sent to a gas dehydration unit.

The invention is illustrated by a flow chart of a method for regenerating a saturated absorbent.

The technological scheme consists of a unit for vacuum regeneration of DEG-1 and a unit for cleaning impurities of DEG-2.

Installation 1 consists of a weathering device 3, a regenerative heat exchanger 4, a column 5, a pump 6, a furnace 7, a regulator 8, a tank 9 and a pump 10. Installation 2 consists of a regenerative heat exchanger 11, an evaporator 12, a furnace 13, a pump 14, a regulator 15, refrigerators 16 and 17, containers 18 and 19 and pump 20.

The method is as follows.

The concentration of the saturated DEG solution is restored at the vacuum regeneration unit of DEG 1. The saturated DEG solution from the drying unit (not shown in the diagram) is sent to the weathering device 3 and then enters the column 5 through the regenerative heat exchanger 4, where the concentration is restored by rectification. From the bottom of the column 5, the partially regenerated DEG is pumped into the tube furnace 7, where the solution is heated in the liquid-phase state at an excess pressure exceeding the vapor pressure of the solution at the maximum temperature in the furnace, that is, without evaporation in the furnace, followed by a decrease in pressure by the entrance to the column 5. This solution provides uniform controlled heating of the DEG solution and eliminates the ingress of oxygen due to air leakage. If necessary, recycle DEG solutions through the furnace. To prevent deposits on the surface of the furnace tubes and, accordingly, increase the temperature of the wall, the circulation velocity of the DEG solution is taken no lower than 1 ... 2 m / s. The DEG solution heated in the furnace 7 to a temperature of 165 ° C ÷ 185 ° C is fed into the column 5 through a regulator 8, which maintains the necessary pressure in the furnace. The operating mode of the regeneration unit 1 is determined by the necessary concentration of the regenerated DEG. The regenerated DEG solution passes through the heat exchanger 4 and enters the tank 9, from where it is sent to the gas dehydration unit (not shown in the diagram).

Purification of DEG from non-volatile, low-volatile and volatile impurities is carried out in installation 2.

Not more than 30% of the regenerated DEG is pumped through the recuperative heat exchanger 11 to the evaporator 12 through the recuperative heat exchanger 12. The necessary temperature is maintained in the evaporator by controlling the heating of the circulating solution at the outlet of the furnace 13. The addition of more than 30% of the regenerated DEG to the impurities purifier will lead to a sharp increase material consumption, installation costs and operating costs.

In the furnace 13, the DEG solution is supplied from the evaporator 12 by the pump 14. The heating is carried out under excess pressure, which is maintained by the regulator 15 0.2 ... 0.3 MPa higher than the boiling pressure of the solution at the exit temperature of the heat exchanger 11. The heated DEG solution to the temperature 165 ° C ÷ 210 ° C through the regulator 15 enters the evaporator 12, where the pressure decreases and part of the solution boils.

A mixture of non-volatile and non-volatile impurities and partially DEG from the bottom of the evaporator 12 is taken out for disposal. The distillate (a mixture of DEG vapors and volatile impurities) is removed from the evaporator for cooling and condensation to the refrigerator 16 and fed to the first collecting tank 18. From the tank 18, the purified DEG solution, which contains a small amount of volatile impurities, is returned to the gas dehydration unit. The vapor phase from the collector 18 is fed into the refrigerator 17, and the condensate formed, which contains volatile impurities (water, methanol, acid, aldehydes) and a small amount of DEG, is fed into the second collection tank 19, from where it is sent for disposal by the pump 20. Non-condensed vapors from the tank 19 are disposed of.

The method was tested at one of the gas treatment plant of the Tyumen region., Russia.

The table below compares the performance of the gas treatment plant according to the known and proposed methods under comparable process conditions during the compressor operation period. From a comparison of indicators, it follows that the proposed method, by increasing the regeneration temperature, provides a higher concentration of DEG and, accordingly, a higher quality of the dried gas at the outlet of the installation (gas dew point in water). Achieved high-quality cleaning of glycol from harmful impurities, which provides less ablation of the drip absorbent, reduction of the corrosive effect of the absorbent on the regeneration equipment and an increase in the overhaul period of the main equipment. An increase in the heating temperature during cleaning is short-term and will not lead to an increase in destruction. Due to the increase in the heating temperature during glycol purification, the energy consumption and metal consumption of the installation are reduced. The proposed method provides a reduction in operating costs for the installation of field gas treatment with a productivity of 70 million m ² / day. about 300 thousand US dollars per year.

In terms of the totality of the parameters, the proposed method has technological and economic advantages over the known method when using natural gas for the main transport in field processing plants.

Table. Indicators Known method The proposed method Productivity of gas treatment plant, mln.m ³ / day. 70 70 DEG temperature during regeneration, ° С at the exit of the furnace 164 185 in the cube of the column 156 174 DEG temperature during cleaning, ° С heating 164 210 cubed 160 195 The achieved concentration of regenerated DEG,% wt. (at a pressure in the cube of the column 26.7 kPa) 98.8 99.7 Achievable dew point (water) at the outlet of the unit, ° С (Р = 4 MPa) minus 20 minus 27 Loss of absorbent with dried gas specific, mg / m ³ to 10 up to 7 full, t / year 250 185 Overhaul period of the main equipment, months eighteen 24 The degree of purification of diethylene glycol from volatile components,% 68 98 Thermal load when cleaning glycol, MJ / t 5300 3500

Claims (1)

A method of regenerating a saturated solution of absorbent - diethylene glycol, comprising supplying a saturated solution of absorbent to a regeneration unit, heating it in a tube furnace while maintaining a single-phase state and ensuring recirculation through the furnace, supplying regenerated diethylene glycol to a gas drying unit, characterized in that the diethylene glycol is heated to a temperature during regeneration 165 ÷ 185 ° C, and not more than 30% of the regenerated diethylene glycol solution is fed for purification from impurities and heated in the furnace of the s to a temperature of 165 ÷ 210 ° C and purged of impurities diethylene glycol solution is routed to the gas drying unit.