RU2531584C1 - Method of commercial triethylene glycol regeneration - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: claimed invention relates to a method of commercial triethylene glycol (TEG) regeneration by evaporation from a basic volume of moisture-containing TEG and removal of admixtures, simultaneously collected by the said TEG, and water from remaining, specially discharged from the gas drying process, volume of TEG, by extraction of admixtures by additionally added water with intensive mixing of the said mixture with the following settling, pouring out of the TEG settled from mixture, filtering and regulated dosed return of the said, poured out after settling, TEG into the basic volume, supplied to water evaporation. Before the stage of admixture extraction not less than one and a half fold volume of water and a cyclohexane mixture in their volume ratio two to one respectively is introduced into the volume of TEG, specially removed from circulation.

EFFECT: method makes it possible to separate admixtures effectively and economically with regenerated TEG settling obtaining a practically dehydrated absorbent for its return into the process of natural gas drying.

1 dwg, 1 tbl

Description

The invention relates to a technology for restoring the absorbing properties of triethylene glycol (TEG) as a desiccant, after its multiple recirculation in a system for drying natural gas before supplying the latter to the main pipeline, that is, to a technology for treating an absorbent that has practically lost its properties due to its long-term use in field conditions of the gas production industry.

The current level of technology for restoring the absorbing properties of glycols as desiccants during the drying of natural gas is reflected in a number of scientific and technical publications: Drying of natural gases. I.V. Zhdanova, A.L. Caliph - Ed. 2nd, M., Chemistry, 1984 - 192 p .; Purification of glycols from solids and hydrocarbons. O.P. Andreev, R.V. Korytnikov, D.A. Yakhontov, T.M. Farakhov - M .: OOO Gazprom Expo, 2010 - 158 p .; The effect of changes in the basic properties and characteristics of glycol in the process of gas dehydration on the efficiency of the gas treatment equipment of the Cenomanian deposit A.N. Dudov, N.I. Dubina, V.A. Stavitsky, Yu.N. Efimov, V.F. Guzov - Problems of development of deposits of the Urengoy complex, M., 1998, pp. 88-99; Comprehensive purification of diethylene glycol in absorption units for gas dehydration of the Medvezhye field. K.M. Davletov - Improving the efficiency of gas development in the Far North, M., Nauka, 1997, p. 354-362; Creation of glycol regeneration units with a complex of equipment for cleaning solutions from salts, heavy hydrocarbons, solids and ways to improve mass transfer equipment. G.K. Siebert - Problems of production and development of gas and gas condensate fields at a late stage of their development. M., 1997, p. 160-165; Methods for the purification of glycols from heavy hydrocarbons and degradation products. E.S. Klyucheva, N.P. Vein - M., VNIIEgazprom, 1990 - 40 s .; Gas dehydration: optimizing the operation of existing plants. Part 1. Determination of quality requirements for glycol and its circulation rate. D.L. Kramer, U.R. Cook - Oil, gas, petrochemicals abroad, 1981, No. 1, p.21-24; Gas dehydration: optimizing the operation of existing plants. Part 2. The effect of operational variables on the efficiency of gas dehydration. D.L. Kramer, U.R. Cook - Oil, gas, petrochemicals abroad, 1981, No. 2, p.16-21, and the main method of generating TEG is the evaporation and distillation of water. However, under the conditions of the gas field, TEG requires not only moisture removal, but also cleaning of various impurities accumulated in it, both in liquid and in solid state. Such purification of TEG as an absorbent desiccant is all the more necessary because of the negative feature of it is to selectively absorb and accumulate aromatic hydrocarbons, which significantly reduce its moisture-absorbing properties.

To comprehensively restore the properties of extremely polluted impurities and moisture, TEG is currently used in addition to adding water a significant number of additive substances (reagents, reagents, additives, surfactants, etc.) in certain dosages, such as, for example, isooctane according to the patent [EP 0211659 A2, B01D 53/26, publ. 02.25.87] or petroleum ether fraction 70 ... 100 ° C according to the patent [RU 2409407 C1, B01D 3/36, publ. 01/20/2011] or a surface-active additive of the composition Ni (C _n H _2n ) ₂ according to the patent [RU 2259861 C1, B01D 53/28, publ. 09/10/2005] or aliphatic alcohols mixed with isopropylbenzene according to the patent of [RU 2394633 C2, B01D 53/26, publ. 07/20/2010] followed by gravitational separation and separation of different density of settled layers of regenerated TEG. However, they do not remove most of the impurities of the hydrocarbon composition.

The closest technical solution is a method of restoring the properties of TEG contaminated during drying of natural gas under field conditions is the method according to the patent [RU 2446002 C1, B01D 53/26, publ. 03/27/2012], the essence of which is to add to the TEG coming from the absorber an additional amount of water, actively mixing the mixture, heating and settling until it is divided into three fractions of characteristic composition. That is, in the sump, the mixture is stratified into the upper light fraction with aromatic hydrocarbons, the middle one, which consists practically of TEG with water, and the lower heavy fraction, which contains mainly a fine suspension of solid naphthenoaromatic hydrocarbons with an admixture of asphaltenes and simply mechanical impurities carried out from the reservoir as well as corrosion products of technological equipment. The middle, the so-called “clarified” layer, consisting of TEG with a high water content, is taken from the sump, passed through a filter and fed to the main volume of TEG from the absorber to the evaporator column to distill off the water, and the upper and lower layers are periodically removed from the sump for disposal.

The disadvantages of the prototype method include uneconomical process management (additional heating and long sludge), the difficulty of controlling two interfaces of three layers in the sump during the selection of the middle layer for TEG regeneration, as well as the low quality of TEG cleaning from pollutants that affect the drying ability of TEG.

The required technical result (otherwise, the task and purpose of the claimed invention) is to provide higher rates of restoration of the drying properties of TEG in comparison with the prototype with greater efficiency of the process as a whole.

The claimed invention solves the task of commercial regeneration of TEG in accordance with the fact that in the prototype method by evaporating water from the main volume of moisture-containing TEG and removing impurities and water incidentally accumulated by this TEG from the rest of the TEG volume specially removed from the gas drying process, extracting the impurities of the additionally added water with vigorous stirring of this mixture, followed by sedimentation, drainage of the TEG that has settled from the mixture, filtration and controlled dosed return of this, with cast after settling, TEG is introduced into the bulk supplied to the evaporation of water, before the stage of extraction of impurities, at least 1.5 times the volume of the mixture of water and cyclohexanone in a volumetric ratio of two to one, respectively, is introduced into the volume of TEG specially removed from circulation.

A search in the patent documentation and in the scientific and technical literature showed that the given set of essential features was not found in it. Thus, the given set of features ensures compliance with the criteria of patentability, namely: novelty, inventive blood stock, industrial applicability, and also provides a technical result, expressed in a decrease in energy consumption, quality of TEG cleaning (regeneration) during implementation.

This technical solution is illustrated by the drawing, which shows a schematic flow diagram of the field regeneration of contaminated TEG, where positions 1 and 2 show the absorption unit and the TEG regeneration unit of the complex gas treatment unit (UKPG). Positions 3 and 4 show the settling apparatus and evaporator, respectively, of the TEG purification unit. The flow of raw gas 101 enters the absorption unit 1. The flow of dry gas 102 from the absorption unit 1 is directed to the gas pipeline. The saturated TEG stream (NTEG) 202 from the absorption unit 1 is supplied to the TEG regeneration unit 2, where water is evaporated from the NTEG (stream 203). The flow of regenerated TEG (RTEG) 201 is returned to the absorption unit 1.

The method is implemented as follows. From a stream of NTEG 202 or RTEG 201 a stream 301 of TEG with pollutants is taken and fed to the TEG purification unit. Water (stream 302) and cyclohexanone (stream 303) are dosed into stream 301 during the purification of the first portion of TEG. When cleaning subsequent portions of TEG, azeotropic water-cyclohexanone mixture (stream 306) is fed to stream 301, streams 302 and 303 are fed with the missing quantities of water and cyclohexanone to fulfill the following ratio: 1 volume of triethylene glycol with pollutants; 1 volume of water; 0.5 volume cyclohexanone. The presence of cyclohexanone in a TEG diluted with water allows 2 phases to be obtained in a settling apparatus: the upper one, which consists mainly of pollutants, which is disposed of for disposal (stream 304); the lower one, consisting of TEG, water and cyclohexanone, which is sent by stream 305 to the evaporator, where the azeotropic water - cyclohexanone mixture (stream 306) is distilled off from the mixture at a temperature of 97 ÷ 107 ° C and sent to the stream of purified TEG 301. Purified TEG by stream 307 fed into the stream of NTEG 202 or RTEG 201.

Table 1 shows the balance of TEG purification by dilution with water in the presence of cyclohesanone (specific example).

Table 1 Flow NTEG RTEG entrance to cleaning, m ³ exit from cleaning, m ³ entrance to cleaning, m ³ exit from cleaning, m ³ TEG + pollutants 5 5 Pollutants 1,2 1,1 TEG purified 5 4.9 Water 5 4.8 5 4.6 Cyclohexanone 2,5 1,5 2,5 1.9

In the presence of cyclohexanone in diluted with water TEG is achieved:

- reduction of sludge time during TEG cleaning;

- simplification of control over the process (in the settling apparatus 2 phases are formed, and not 3, as in the prototype);

- improving the quality of purification of TEG from pollutants, including hydrocarbons, osmols, thermal decomposition products of TEG.

In addition, TEG purified from contaminants with a minimum water content is sent to the TEG regeneration process, which will not cause an increase in the load on the evaporator column of the TEG regeneration unit and will not require an increase in the number of technological equipment of the TEG regeneration unit or the number of blocks.

Thus, the present invention provides the desired technical result by available technical means without the use of complex specialized equipment using an insignificant amount of such an additive substance as the widely used and inexpensive cyclohexanone according to GOST 24619-81 (formerly ST SEV 1681-79) and is subject to protection document (patent) of the Russian Federation.

Claims (1)

The method of commercial regeneration of triethylene glycol by evaporation of water from the main volume of a moisture-containing TEG and removal of impurities and water incidentally accumulated by this TEG from the rest of the TEG volume specially removed from the gas drying process, extraction of impurities by additionally added water with vigorous stirring of this mixture, followed by settling from the mixture, which settled out TEG, filtration and controlled dosed return of this fused after settling, TEG to the main volume supplied to the evaporation water, characterized in that before the stage of extraction of impurities in a specially withdrawn from circulation TEG volume is introduced not less than one and a half times the volume of a mixture of water and cyclohexanone in a volume ratio of two to one, respectively.

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