CS212693B1 - Method of washing the carbon dioxide from the generator gases - Google Patents

Description

The present invention relates to the scrubbing of carbon dioxide from a generator gas, enabling the production of synthesis gas for methanol and olefin oxonation to be intensified.

A suitable feedstock for the production of synthesis gas is generator gas produced by the partial oxidation of petroleum residues, coal, tar and other fuels.

The gasification of the black oil with steam and oxygen is carried out, for example, at a pressure of about 3.5 MPa and temperatures of about 1,400 ° C. The recovered generator gas is first freed of the hydrogen sulfide and carhonyl sulfide contained therein. The selective scrubbing of hydrogen sulphide and carbonyl sulphide uses alcasic caustic with good results; in this case, the carbonyl sulphide contained is hydrolyzed after the hydrogen sulphide has been scrubbed from the generator gas in the first stage and the hydrogen sulphide formed in the second stage is again scrubbed with an alcazide lye. The residual hydrogen sulphide and carbonyl sulphide content of the scrubbed gasifier gas is generally less than 25 mg / m ³ n. The pretreated gasifier gas is de-carbonated in the scrubber using aqueous alkanolamine solutions. When using technical triethanolamine, an aqueous 30-35% triethanolamine is used as the washing solution. <£

The technical triethanolamine used usually contains about 10% diethanolamine and a small amount of monoethanolamine. In addition to triethanolamine, methyldiethanolamine, diethanolamine and isopropanolamines may be used analogously.

After carbon dioxide scrubbing, a generator gas having a residual carbon dioxide content of less than 1% by volume is obtained. The generator gas thus treated is the starting material in the synthesis gas synthesis for methanol; it is mixed with crude hydrogen in a ratio to meet the requirements of methanol synthesis.

The scrubbed generator gas can be directly used for olefin oxonation; prior to use in the oxonation apparatus, the synthesis gas is desulfurized on a fixed adsorbent and, if necessary, the carbon dioxide content is further reduced.

the production of synthesis gases for methanol and oxonation is of increasing interest and it is also desirable to increase the production of these synthesis gases to existing installed equipment without major investment requirements.

It has now been found that the production of synthesis gas for methanol production and olefin oxonation can be increased at the existing production plant by increasing the existing capacity of the installed carbon dioxide scrubber, in which a washing solution of 28-37% aqueous technol. triethanolamine.

SUMMARY OF THE INVENTION The invention is based on the fact that, in the scrubbing of carbon dioxide from a generator gas obtained by partial oxidation of petroleum and tar raw materials with an aqueous solution of technical triethanolamine, methyldiethanolamine, diethanolamine or isopropanolamines, activated by the addition of activators such as 1,6 28 to 37% technical triethanolamine solution containing 1 to 10% 1,6-diaminohexane, the scrubbing solution passes through a mechanical filter in an amount of 3 to 10 m ^ and further through an activated carbon filter with a volumetric rate of 1 to 2.5 m 2,5 / m over an anion exchange layer with a bulk rate of 1.5 to 4 m @ 2 / m @ 2. Mechanical and acidic substances, which impair the efficiency of carbon dioxide scrubbing, are regularly removed from the circulating scrubbing solution.

In circulating solution techn. In particular, the following substances of an acidic nature were found: formic acid, acetic acid, hydrochloric acid and Ν, Ν-dimethylaminoacetic acid. N, N-diemtyleminoacetic acid passes into the circulating solution from an alcasidic scrubber in which the hydrogen sulphide present is selectively scrubbed from the generator gas. The content of entrained N, N-dimethylaminoootic acid can also be inferred from the potassium content, since the potassium salt of this acid is entrained from the alcashide scrubber.

The circulating washing liquid accumulates most of the formic acid produced in the production plant from carbon monoxide and water feathers, and its formation, especially in the high and low temperature conversion sections, cannot be prevented. The presence of acetic acid was also detected; this acid is formed in the low temperature conversion region. It has been found that the circulating scrubbing solution is enriched with formic acid and other acidic ingredients over a period of several months to a value of 300 to 350 mval per liter, and this scrubbing solution scrubs carbon dioxide worse than a scrubbing solution which does not contain acidic components or e.g.

mval / 1.

As has been found, the scrubbing ability of the scrubbing liquid affects the addition of a suitable activator; the scrubbing capacity of the scrubbing solution, i.e. its capacity, as well as the scrubbing speed of the carbon dioxide increases.

Thus, the addition of an activator has a similar effect to installing another washing machine or installing a new washing machine with a larger working volume. To improve the carbon dioxide scrubbing, up to 20% of the individual amines or mixtures thereof can be added to the circulating scrubbing solution.

Amines having at least one primary or secondary or tertiary amino group have suitable properties. In preparing suitable amines, consideration is given to their boiling point; for scrubbing carbon dioxide, those having a low vapor pressure under scrubbing conditions are preferable so that they do not pass into the scrubbed gas or only to a minimal extent. It is also desirable that the added amines dissolve well in the wash liquid. From a practical point of view, especially those amines whose production is well established or easy to obtain will be used. Suitable properties have aliphatic amines and derivatives thereof, such as C 8, C 8, C 8, C 8, C 8 diamines such as 1,6-diaminohexane, 3- (2-aminoethyl) aminopropylamine, N, N-bis (3-aminopropyne) £) ethylene-3-amine, aminoalkanols such as 2-amino-2-methyl-3-pentanol, piperidine substituted in the 2-position (e.g. 2-piperidinmethanol), aminoethyldiethanolamine, aminoethylethanolamine, 1- (2-hydroxylethepiperidine and other amines) .

Alkanolamines such as triethanolamine, diethanolamine, methyldiethanolamine and the like isopropanolamines are also suitable raw materials for the preparation of carbon dioxide scrubbing activators.

The above list does not limit the choice and use of other amines as activators.

The effect of added activator and acid components on the absorbency of the scrubbing solution and on the rate of absorption of carbon dioxide in the scrubbing solution is apparent from these data obtained by measuring at 75 kPa carbon dioxide partial pressure and at 70 ° C.

Washing solution used Content of acidic fractions as HCOOH g / 1 Content activator g / 1 Absorbency 1 _n CO _2/1 Absorption rate (relative, calculated on the original 35 # triethanolamine) 1. Aqueous solution containing 35 # techn. triethanolamine 0 0 12.80 100 ALIGN! 2. Aqueous solution containing 35 # techn. triethanolamine after 24 months of operation 13 0 7.56 46 3. Aqueous solution 32 # techn. triethanolamine 0 30 36.27 283 4. Aqueous solution 32 # techn. triethanolamine 13 30 21, 99 181

after 24 months of operation

32 # techn. triethanolamine after 24 months of operation and after removal of acidic fractions

0.8

32.81

242

In the scrubbing of carbon dioxide, not only the amount of generated generator gas is important, but also the rate of carbon dioxide removal.

During scrubbing of desulphurized generator gas of composition

CO ₂ 3,9 # vol.

CO 45,80 # vol.

H ₂ 48,70 # obj.

CH ₄ 0,30 # vol.

Ng + Ar 1.30 # vol.

the residual content of the scrubbed gas is dependent on the characteristics of the circulating scrubbing liquid in Table 1. It is evident that the removal of acidic constituents from the circulating scrubbing liquid and the concomitant addition of activator have a significant effect on improvement and allow increased performance at a satisfactory degree of scrubbing. carbon dioxide

Table I

Quantity enforced Quantity of washing liquid per m ^ n of scrubbed gas Residual content of ₂ % vol. Washing liquid gene. gas m ^ n / h Aqueous solution techn. triethanolamine 32%, content. 13 g / l acid fractions (as HCOOH) 23 500 2.76 1.1 Aqueous solution techn. triethanolamine 32%, content. 3 wt. activator (1,6-diaminohexane or aminoethyldiethanolamine), acid-free to 0,8 g / l (as HCOOH) 30 500 2.28 0.8

The addition of an activator and the regular removal of acidic components from the circulating scrubbing solution by means of a newly incorporated filter and anion exchange station will allow the production of synthesis gas for methanol and oxonation to be increased without major investment costs and without increasing the number of plant operators.

The extent to which the synthesis gas production for methanol and oxonation is expanded can be inferred from the following Examples 1 and 2.

Example 1 describes the synthesis gas production according to the procedure established so far, and Example 2 describes the increased synthesis gas production made possible by the addition of an activator and the regular removal of acidic substances from the circulating scrubbing solution.

Example 1

The hydrogen sulphide and carbonyl sulphide-free generator gas to a residual value of about 25 mg / nAi on a two-stage alcasside scrubber incorporating carbonyl sulphide hydrolysis contains 4.1 mol% at the inlet of the absorption column. C0 ₂ · The amount of generator gas entering is 23,500 m ^ / N. Carbon dioxide It is washed with a circulating scrubbing solution containing 32% technical triethanolamine at 55 ° C and 2.7 MPa; the content of acidic components, such as formic acid, is up to 13 g / l.

Washed generator gas in an amount of 22,706 m6 / h with a content of 1.2 mol. % Carbon dioxide was mixed with 11,794 m ^J n / h of crude hydrogen to give 34,500 mN / h of a synthesis gas intended for the production of methanol.

62.67 m @ 3 of the circulating solution, i.e. 2.76 l per m @ 2 of scrubbed gas, are fed to the absorption column.

The saturated circulating solution is freed of carbon dioxide upon release from the operating pressure of 110 kPa at the top of the recovery column and at 100 ° C at the bottom of the recovery column.

Example 2

The prior art carbon dioxide scrubber is supplemented with a continuous working filter in which about 5% of the circulating solution is freed from the suspended matter contained therein and thus the mechanical impurity content is maintained at about 0.1 g / l. Furthermore, the carbon dioxide scrubber is supplemented with a device in which the acidic substances are removed from the circulating wash solution.

This device consists of a mechanical filter, an activated carbon filter and an anion exchange filter. The anion exchange resin Wofatit SBW was filled; this anion exchanger has a capacity of 0.85 val / l and is regenerated in the usual manner with 4% sodium hydroxide solution.

In order for the anion exchange filter to function properly, it is desirable that no solids are present in the inlet wash solution: therefore, good function of the pre-filters is ensured.

A portion of the circulating scrubbing solution is passed through a filter device and an anion exchange filter in an amount of 15 m ^ / h, for example for 3 hours once a week. It has been verified that the concentration of acidic fractions (such as formic acid) in the circulation solution can be kept below 1 g / l at this dosage. In this case, work is carried out on filled activated carbon with a volumetric io3 of 3 at a rate of 2 ar / nr. ha on an anion exchange filter with a flow rate of 3 m ^J / m ^J / h.

The carbon dioxide is washed with a circulating wash solution containing 32% lech. % of triethanolamine, activated by 3 wt. 1,6-diaminohexane and containing usually below 1 g / l of acidic fractions (such as formic acid).

30 350 m m / h of desulfurized generator gas containing 4.1 mol% are passed through the absorption column. carbon dioxide.

The scrubbed gas is obtained at 29,000 πΑ / h containing 0.8 mol%. carbon dioxide.

Of this amount, 3,500 m ^ / h are separated, desulfurized on a solid adsorbent, e.g. ZnO, and fed to a propylene oxonation plant.

To the remaining 25,500 m ^ / h of scrubbed gas, 13,500 m ^ / h of crude hydrogen was added to give 39,000 nPn / h of synthesis gas for methanol production.

66.12 mAh of the circulating solution, i.e. 2.28 L per mA of scrubbed gas, is fed into the absorption column.

The saturated circulating solution is freed from the carbon dioxide upon release from the working pressure to 130 kPa at the top of the recovery column and at a temperature of 106 ° C at the bottom of the recovery column.

Claims (2)

A process for scrubbing carbon dioxide from a generator gas obtained by the partial oxidation of petroleum and tar feedstocks, enabling the intensified production of synthesis gases for the production of methanol and the oxonation of olefins to be introduced or to increase the production of these gases on an existing plant where carbon dioxide is scrubbed with an aqueous solution of technical triethanolamine , methyldiethanolamine, diethanolamine or isopropanolamines, activated by the addition of an activator such as 1,6-diaminohexane or aminoethylethanolamine, in particular an aqueous 28 to 37% technical triethanolamine solution to which 1 to 10% 1,6-diaminohexane has been added, characterized in that the scrubbing solution passes through a mechanical filter in the amount of 3 3 3 3 to 10 m &^lt; 3 &gt; and further through an activated carbon filter having a flow rate of 1 to 2.5 m ^{&lt; 3 &gt;} / m &^lt; 3 &gt;