CS241882B1 - A method of increasing hydrogen production - Google Patents

Abstract

A method for increasing hydrogen production from producer gas produced by gasification of oil and tar residues by partial oxidation with oxygen and steam by combining high-temperature and low-temperature conversion of carbon monoxide with steam and scrubbing of carbon dioxide with an aqueous solution of technical triethanolamine, in which the desulfurized producer gas is scrubbed with a potassium permanganate solution before entering the conversion and after the conversion, the carbon dioxide is scrubbed with an aqueous solution of triethanolamine with the addition of an activator.

Description

The invention relates to the gasification of oil and tar residues by partial oxidation with oxygen and steam, thereby obtaining raw producer gas, which is the starting material for the production of hydrogen and for the production of synthesis gases intended for the synthesis of ammonia, methanol, oxonation of olefins, etc.

Raw generator gas emerging from pressure generators operating at a pressure of e.g. 3.5 MPa is first freed from the contained soot by pressure water washing and in a further technological stage the contained hydrogen cyanide, hydrogen sulfide and carbonyl sulfide are removed from this gas. It is usual that the generator gas pre-purified in this way is freed from sulfur compounds to a value lower than 20 mg/m^.

From the thus treated producer gas, technical hydrogen and synthesis gases are obtained in the next stages in the required ratio. If the ratio of produced hydrogen and synthesis gases (determined by the project and established by operating ^practice ) changes, e.g. during shutdowns, when the production of a certain product, e.g. methanol and others, is discontinued, it is necessary to limit the total volume of production based on pre-purified producer gas. This is economically disadvantageous and therefore considerable efforts have been made to increase hydrogen production while limiting synthesis gas production.

However, increasing hydrogen production from additional pre-purified producer gas means a higher load on the high-temperature and low-temperature conversion section, carbon dioxide scrubbing, and methanation of residual carbon oxides to a value of less than 10 ppm vol. However, the projected and operationally adopted hydrogen production volume cannot be increased by simply increasing the throughput.

It has now been found that hydrogen production can be increased without major interventions in the existing facility and its investment-intensive modifications.

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The method of increasing hydrogen production from producer gas formed by gasification of oil and tar residues by partial oxidation with oxygen and steam, a combination of high-temperature and low-temperature conversion of carbon monoxide with steam and scrubbing of carbon dioxide in two stages using an aqueous solution of technical triethanolamine, consists, according to the invention, in that the desulfurized producer gas is scrubbed with a potassium permanganate solution before entering the conversion and after the conversion, the carbon dioxide is scrubbed with an aqueous solution of triethanolamine with the addition of an activator, e.g. 1,6 diaminohexane or/and bis(1-aminohexyl)amine in an amount of 0.1 to 15%.

The desulfurized generator gas is freed from iron and nickel carbonyls that clog the conversion catalyst before entering the conversion by washing with a native potassium permanganate solution, and in the carbon dioxide scrubbing section using a 30 to 358 aqueous solution of technical triethanolamine, the increase in working capacity is achieved by adding activators that increase the carbon dioxide scrubbing rate and at the same time increase the capacity of the scrubbing solution. For practical application, it is important that the efficiency of the added activator is such that the amount of scrubbing liquid can be reduced while maintaining approximately the same hydrodynamic load on the absorbers even with increased hydrogen production.

When selecting suitable activators, a number of substances were tested, especially amines that contain at least one primary and/or secondary and/or tertiary amino group in the molecule. For example, the following amines, their derivatives and/or mixtures thereof can be used:

n-heptylamine, n-octylamine, 2-ethylhexylamine, isononylamine, isotridecylamine, diisobutylamine, di-sec.butylamine, dipentylamine, N-ethylbutylamine, trioctylamine, N-ethylcyclohexylamine, bis-(3-aminopropyl)methylamine, 3-azohexane-1,6-diamine, 1,6-diamonohexane, bis(1-aminohexyl)amine, etc.

For practice, those amines that are available on the market and have a reasonable price are especially important.

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- 3 To improve carbon dioxide scrubbing, individual amines or their mixtures can be added to the scrubbing solution in amounts of 0.1 to 15%.

However, as it turned out, for operational applications, it is not enough to simply add an activator, but it is also required that the added activator does not increase the corrosive effect of the circulating washing solution, or rather that the corrosive effect of the circulating washing solution is reduced.» Tests have shown that these two requirements are met, for example _{, by}

1,6 diaminohexane, bis (1-aminohexyl)amine, their mixtures and derivatives derived therefrom.

The effect of adding these activators is

Washing liquid % tech. TEA 70 % water % tech. TEA 65 % water % tech. TEA + 5 % activator % water % tech. TEA + 5 % activator % water e.g. the following:

added relative activator capacity speed laundry laundry solution _in C0 ₂ /l 1.02 17.5 1.0 18, 9

1,6-diaminohexane 1.26 27.1 bis(1-aminohexyl) 1.29 28.4

amine

The data were measured on laboratory equipment operating at laboratory temperature under atmospheric pressure of carbon dioxide.

The beneficial effect of the added activator on reducing the corrosion properties of the circulating washing liquid was evaluated on an operational scale. It was shown that the circulating washing liquid with the activator contained less iron compounds, less ash and less filterable fractions. During planned shutdowns and overhauls of the carbon dioxide scrubber, it was shown that the filled steel rings in the scrubbers were not or were significantly less clogged with settled sludge,

- 4,241,882 corrosion of production equipment made of grade 11 steel was not detected and a complete overhaul was facilitated and the scope of otherwise usual maintenance activities during the stop was reduced.

The properties of the circulating washing liquid after the addition of the activator and without the addition were as follows:

Washing liquid

aqueous solution of technical TEA with activator without activator 32% tech. TEA 2.6% 1,6 diaminohexane - Fe content (ppm) 0.01 0.15 content filter- % of the solids (g/l) % of the ash content (% of the mass) 26.0 294.2 0.14 0.35 content of org. acids (as formic acid) fg/1] 3.1 3.1 residual C0 ₂ content in raw hydrogen ^ά [% vol^w*/) 0.12 0.15

In the high-temperature conversion section, an increase in throughput can be achieved with unimpaired carbon monoxide conversion throughout the entire operating cycle, e.g. 18 months, if the contained iron and nickel carbonyls are removed from the incoming pre-purified generator gas.

Usually, the pre-purified producer gas contains carbonyls, e.g. Fe 3 to 5 mg/πΗ and 1 to 2 mg Ni/m^. These carbonyls decompose in the high-temperature conversion reactor and penetrate the upper layers of the packed conversion catalyst, which results in a gradually deteriorating catalyst activity, an increase in the residual carbon monoxide content and an increased pressure drop in the conversion reactor. With increased producer gas throughput, these problems appear earlier and this can lead to a shortening of the usual operating cycle. These problems can be avoided if the removal of the contained iron and nickel carbonyls is newly incorporated, preferably by washing with an aqueous solution of potassium permanganate. In order to avoid an unnecessary increase in potassium permanganate consumption, it is desirable to remove the iron and nickel carbonyls only after washing hydrogen sulfide from the producer gas. The removal of iron and nickel carbonyls is carried out with an aqueous solution of potassium permanganate at a pressure of e.g.

3.1 MPa at temperatures of e.g. 15 to 40°C. Complete or partial removal of the contained carbonyls is achieved, depending on the conditions set in the washing machine.

In the low-temperature conversion section, it is advantageous to use a partially or completely finer-grained conversion catalyst compared to the established state, and it may also be advantageous to use a conversion catalyst with a higher copper content.

The method according to the invention is described in more detail in Examples 1 to 4.

Example 1

The carbon dioxide scrubber in two absorption stages with joint desorption and regeneration of the scrubbing liquid operates at a pressure of 2.7 MPa; an aqueous 30 to 35% aqueous solution of technical triethanolamine is used as the scrubbing liquid.

In the first stage absorption, carbon dioxide is scrubbed from the gas by high-temperature conversion; the scrubbed gas, freed from the majority of carbon dioxide, is led to the low-temperature conversion and from there to the second absorption stage, in which the carbon dioxide remaining after the first stage and the newly formed carbon dioxide in the low-temperature conversion are scrubbed. The raw hydrogen thus obtained is further purified by methanization, in which the residual carbon oxide content is reduced to a value below 10 ppm CO + CO^; the technical hydrogen produced is compressed and used for the production of ammonia and for various hydrogenations.

An amount of activator 1,6-diaminohexane is gradually added to the circulating scrubbing liquid circuit such that its concentration reaches 2.5% wt/T. The addition of the activator reduces the amount of scrubbing liquid required for the first and second stage absorption while simultaneously increasing the gas throughput.

Data on carbon dioxide scrubbing without addition and with addition of activator to the scrubbing liquid are in the following table 1.

Table 1

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Carbon dioxide scrubbing without added activator with addition 2.5% activator amount of dry gas entering the first scrubber stage (m3/hj 84,272 91,560 entry to the second stage of yy feathers 60,240 65,060 total amount of washing liquid to the first stage of washing - . í ^m n ^/h ) 2,050 1,890 amount of thermally regenerated washing liquid to the first stage 110 120 amount of thermally regenerated washing liquid to the second stage 380 350 residual CO- content after the first λ stage (% vol/w/j 4.2 4 residual H-S content after the first stage * řppb vol.) 52 24 residual CO- content after the second stage * objJMmw) 0.15 0.12 steam consumption per unit ,\ scrubbed COg ^kg.kmol ) 8.4 8.15 ash content in the washing liquid mass^Moi/) 0.35 0.14 amount of filterable substances from washing liquid per year (kg) 1620 1085 dissolved iron content . in washing liquid íg/lj 0.15 0.01 solution alkalinity 8.9 9.7 The data shows that the addition of the activator allows you to increase production of raw hydrogen while reducing energy consumption

transport of washing liquid between individual apparatuses, heat consumption for regeneration of washing liquid and increase the rate of carbon dioxide scrubbing.

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Increasing the alkalinity of the washing liquid will have a positive effect in that the amount of iron in the washing liquid will be reduced and thus in less corrosion of the production equipment; the ash content in the washing liquid will be reduced, as will the amount of solid impurities that are removed by the installed filtration equipment.

Reducing corrosion of production equipment ^will result in a reduction in the amount of deposits in the equipment.

The effect of the activator on reducing the residual hydrogen sulfide content after the first stage of washing is also significant.

Example 2

In the high-temperature conversion section, 30 m of combined catalyst packing was filled into the existing reactors. Compared to the current state, the proportion of more active conversion catalysts was increased at the expense of catalysts with lower activity. A significant effect on the achieved carbon monoxide conversion parameters and the service life of the catalyst packing is the reduction of the content of iron and nickel carbonyls in the input gas; with a larger gas flow through the existing high-temperature conversion equipment, the effect of removing iron and nickel carbonyls from 50 and 90% was compared.

The conversion process and the results achieved are shown in the following table 2.

Table 2 original state reduction of Fe and Ni carbonyl content amount of dry gas to conversion fm3/iú input CO content objx**j) 46.5 water vapor content m^ per nr of input gas amount of filled. -< catalysts ¹

60,000 by 50%

65,000

46.5 by 90%

65,000

46.5

1.02-1.12 1.00-1.10 0.97-1.10

Cherox 3607 K 6 - 10 Cherox 3100 service life of the filling with respect to the shutdown cycle 1st stage reactor (months) 18 2nd stage reactor (months^ J6 price coefficient of the catalyst filling for both stages 1 price coefficient of the catalyst filling for both stages, calculated for longer cycles (months) 1 inlet gas temperature to the 1st stage reactor at the beginning of the cycle (°c) 290 at the end of the cycle (°c) 325 CO content at the outlet of the 2nd conversion stage (months) 4

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1.05

0.93

292

320

1.12

0.62

292

330

The results obtained clearly show the beneficial effect of reducing the content of iron and nickel carbonyls. More advantageous is the removal of carbonyls by 90%.

Example 3

In the low-temperature conversion section, 20 m^ of catalysts were filled into the existing reactors, as shown in the following table.

After adding the activator to the scrubbing liquid during carbon dioxide scrubbing, the hydrogen sulfide content in the outlet gas from the first scrubbing stage decreased from the original 52 ppb to 23 ppb, which had a positive effect on reducing the irreversible deactivation of the packed copper-based low-temperature catalyst.

When selecting the catalyst filling, the availability and price ranges of individual catalysts were taken into account.

Contrary to the usual situation, catalysts were filled, which can be expected to have a three-year operating cycle with sufficient operational reliability throughout the entire operating period.

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In the first case of intensified production, the catalyst was filled with NTK 4, which, due to the lower zinc oxide content, has lower resistance to catalyst poisons. After 18 months of operation, 40% of the catalyst charge was replaced with the same amount of ICI 52-1 catalyst and, after its reduction, the plant was operated with this combined charge for another 18 months.

In the second case of intensified production, the ICI 52-1 catalyst was loaded, which allowed operation for 36 months.

The conversion process and the results achieved are shown in the following table 3.

Table 3 original state of dry matter to conversion input CO content

water foam content, among others, per m3 of input gas

60,240

5.42

0.28

C 18 HC

NTK 4 ICI 52-1 catalyst cartridge

filling life ^months^ catalyst filling price coefficient catalyst filling price coefficient calculated per working cycle output CO content at the beginning and end of the cycle (% ob 0.37-0.41

intensified traffic case 1 case 2 65,060 65,060 5.42 5.42 0.30 0.26 20 (12) - - ( 8) 20 36 36 0.9 1.17 0.65 0.78 0.38-046 0.36-0.41

Better results were achieved in case 2

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Example 4

As mentioned in Example 3, the removal of iron and nickel carbonyls from the feed gas to the high temperature conversion has beneficial consequences.

An aqueous solution of potassium permanganate can be used to partially or completely remove the carbonyls contained in the pre-purified generator gas. In this case, it is necessary to ensure intensive contact between the aqueous solution and the gas; the rate of carbonyl removal can be regulated by the ratio of the dosed potassium permanganate in the form of its diluted solution to the generator gas.

From the verified arrangements, i.e.

- dosing of an aqueous solution into the producer gas pipeline with subsequent separation of the aqueous phase and integrated water washing

- introducing producer gas into the scrubber and circulating aqueous solution

- introducing the generator gas into a non-circulating vessel filled with a potassium permanganate solution, the most easily secure arrangement was chosen for the operational test.

A washing vessel with a useful capacity of 15 m ^J is filled with 5 m of an aqueous solution of potassium permanganate with a concentration of 6%. The generator gas is introduced below the surface of the solution and distributed evenly.

perforated ring. It works at 25 C and a pressure of 3.1 MPa. The course of the whole the cycle is obvious from the following data: input quantity gas (m^j 70,000 carbonyl content in gas Fe input (mg/m;5) 3.2 None (mg/mJ) 1.2 output concentration fmg/m^j duty cycle hours in 0 100 200 300 400 Fe 0.03 0.03 0.06 0.5 2.5 None 0.01 0.01 0.03 0.2 0.8

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After a working cycle of e.g. 380 - 445 hours, the scrubber was taken out of service and the scrubbing liquid was drained; it was then rinsed with water and refilled with fresh potassium permanganate solution. The entire exchange could be carried out in 28 hours; during this time, the producer gas was fed into a high-temperature conversion with the usual content of Fe and Ni carbonyls.

After the installation of a continuously operating device, it will be possible to remove the carbonyls contained in the producer gas without interruption and without downtime of the operating equipment.

Claims (1)

OBJECT OF THE INVENTION Process for increasing hydrogen production from gasifier gas produced by gasification of petroleum and tar residues by partial oxidation with oxygen and steam by combining high temperature and low temperature carbon monoxide conversion with water and carbon dioxide scrubbing in two stages using an aqueous solution of technical triethanolamine characterized in it is washed with an aqueous potassium permanganate solution prior to conversion and after conversion the carbon dioxide is washed with an aqueous solution of triethanolamine with the addition of an activator such as 1,6-diaminohexane and / or bis (1-aminohexyl) amine in an amount of 0,1 to 15