DE1917481B2 - Process for increasing and maintaining the activity of carbonaceous adsorbents used for desulphurization of exhaust gases - Google Patents

Description

^{a solid layer of 100 cm 1 of} adsorbent flowed in an amount of 80 l / h. At a layer height of 50 cm, the residence time of the exhaust gas on the adsorbent was 5 seconds. The adsorber was 120 ⁰ C. The so-called concentration was entrance and exit of the adsorber measured continuously and at all times the difference between the values of SO ₂ Wirkungs- or desulfurization of the adsorber is determined as a measure of the Entschweflungsaktivität the time is indicated, wherein that the desulphurisation level, which was initially 100%, has dropped to 90% (desulphurisation limit 90% [in hours]).

After loading with H ₂ SO ₁ up to this limit, the adsorbent was regenerated and reactivated in each case at 600 ° C. in a gentle stream of nitrogen for 2 hours.

The adsorbent was made from pre-oxidized coal by steam activation up to a burn-up of 53.3 percent by weight and had a grain size of 1 to 2 mm. The heating oil slag used contained: 19.6 percent by weight V ₂ O ₅ , 7.7 percent by weight SiO ₂ , 5.0 percent by weight Fe ₂ O ₃ , 6.4 percent by weight Al ₂ O ₃ , 2.2 percent by weight CaO, 4.5 percent by weight MgO , Total S 13.3 percent by weight, 13.3 percent by weight sulfate-S.

45.5 g of the heating oil slag were heated to boiling point for about 30 minutes in around 1250 ml of 20% sulfuric acid, the solution obtained in this way was filtered off from the residue through a glass wool filter and 1 kg of the adsorption coke dried ^{at HO 0 C through with the still hot solution} Spray impregnated.

The impregnated adsorption coke was then in a gentle nitrogen purge gas flow at 600 ° C for 2 hours annealed. A comparison sample without impregnation was also subjected to this thermal pretreatment.

The table shows that the activity, measured at the desulphurisation limit 90%, of an adsorption coke without contact addition is very low and over several adsorption-desorption cycles remain low, but after impregnation with the heating oil slag rises to about 8 to 15 times the values and is maintained.

0.6 hours
1.3 hours
1.0 hours
1.2 hours

9.2 hours 9.5 hours 7.8 hours

8.3 hours

Adsorption coke, made from pre-oxidized coal and burned up to 25.5 percent by weight activated by steam, was initially tested over 3 adsorption-desorption cycles without a catalyst.

The adsorption coke was then impregnated in the following way:

600 g of the bed were dried thoroughly. In addition, 76.5 g of those described in Example 1 were added Finely ground heating oil slag in

Suspended ία 350 ml of water and, after adding 30 ml of concentrated sulfuric acid and stirring frequently, the suspension was kept boiling for 20 to 30 minutes. The remaining residue was filtered off; there was practically no vanadium left in it. The dry adsorption coke was impregnated with the still hot solution as in Example 1 and subjected to tempering at 600 ^° C. for 2 hours. The impregnated adsorption coke now contained, among other things, 1.4 percent by weight vanadium, based on

ao to its initial weight before impregnation. A further 10 adsorption-desorption cycles were carried out with it. The regeneration was performed by heating the loaded material with a heating rate of 3 ° C / min to 500 ⁰ C in a light oil as a stream of nitrogen Desorptionsspülgas.

The present table clearly shows that without

Impregnation the desulphurisation activity is necessary and decreases to even lower values with increasing number of cycles. After the impregnation process however, it increases significantly and remains at high altitude over many cycles. (The values after the 4th and 8th adsorption-desorption cycle remain approximately the same.)

number of
Adsorption-desorption
Cycles

Reaching the desulphurisation limit 90%

* 1
2
3

8th
13th

Number of times the desulphurisation limit is reached 90%

De ^ rotationT ^{without heating oil- with heating oil}

Cycles of slag addition slag addition

(1 percent by weight vanadium)

without added heating oil slag

with added heating oil slag (1.4 percent by weight vanadium)

Example 3

5.0 hours
2.3 hours
2.0 hours

16.5 hours 25.5 hours 17.9 hours

Example 2

A flue gas from a heating oil furnace with the composition 0.12 percent by volume SO ₈ , 2.0 percent by volume O ₂ , 6.0 percent by volume H ₂ O, 15.0 percent by volume CO ₂ and the remainder to 100 percent by volume N ₂ flowed through a solid-layer adsorber with about 1, 11 bulk volume of adsorption coke with a grain size of 5 mm. The residence time of the exhaust gas was 4 seconds and the temperature of the solid layer was 120 ° C.

Under the conditions of Example 2, an _{adsorption coke impregnated with a V 2} O _e -rich heating oil slag and a comparison sample without impregnation over 5 adsorption-desorption cycles in desulfurization processes were tested in the solid layer. The adsorption coke was produced from lignite coke by steam activation up to a carbon burn-up of 30 percent by weight and used with a grain size of 4 to 6 mm.

For the test series with impregnated coke, 570 g of the ^{material dried at HO 0} C were impregnated with around 450 ml of a hot slag suspension by spraying the coke in portions with the constantly stirred suspension while being frequently circulated. So much of the finely ground heating oil slag was used that the completely impregnated adsorption coke contained 4 percent by weight of vanadium, based on its dry weight.

IS 17 481

■ ί

The heating oil slag contained: 50.0 percent by weight V ₂ O ₅ , 4.5 percent by weight SiO * 7.3 percent by weight Fe ₄ O ₃ , 7.7 percent by weight Al ₈ O ₃ , 3.2 percent by weight Na ₈ O, 24.2 percent by weight SO _S , 0.3 weight percent C.

The impregnated adsorption coke was then poured into a gentle stream of nitrogen gas at 500 ° C. for 2 hours annealed; the same treatment was also applied to the non-impregnated control sample subject.

The loaded materials were regenerated as in Example 2.

Number of adsorption-desorption cycles

1 2 3 4 5

Reaching the desulphurisation limit 90

without heating oil with heating oil slag addition slag addition

(4 percent by weight vanadium)

2.8 hours
2.3 hours
2.1 hours

1.9 hours
1.8 hours

8.9 hours 9.2 hours 9.5 hours

9.1 hours

9.2 hours

Claims (2)

the carbonaceous adsorbents for a Claim: Use in the temperature range from about 100 to 200 ⁰ C very effective, and they show despite many Modification of the process for increasing and charging with sulfuric acid and subsequent thermal maintenance of the activity of for the demixer regeneration at temperatures of 400 to sulfurization of SO ₂ -containing exhaust gases at temperatures of 600 ° C, no or only a slight decrease in the ventilation Sulphurizing activity used between 100 and 200 ° C In addition, inactive carbon-containing adsorbents, the adsorbents that have been attached can regain or even increase their effectiveness with oxygen exclusion at temperatures between io by impregnation and thermal regeneration using mixed vanadium catalysts.
400 and 600 ⁰ C are subjected to by Auf- The invention is based on the object of producing metal oxide and / or metal carbide position of the catalysts for the process according to the patent, consisting of compounds of the carbon-containing Adsorp vanadium and used 1619 840 Simplify connections of the elements K, Li, tion agent with high desulfurization activity to and / or Ba and / or the elements Al, Cr, Si 15. or Ti according to patent 1619 840, thereby This object is achieved according to the invention characterized in that the catalysts are dissolved in that the catalysts are in the form of fuel oil of heating oil slag or heating oil slag slag or constituents of heating oil slag be applied. be brought. ao heating oil slags fall as deposits on the walls, on the superheater surfaces and in the flue gas flues oil-fired boiler on. It is worthless and undesirable products that essentially cause high temperature corrosion cause in the boilers. In the desulphurisation of SO ₂ -containing exhaust gases as they mainly contain Na ₂ SO ₄ , V ₂ O ₅ and SiO _{2 in} addition to carbon-containing adsorbents, FeO ₃ , AJ ₂ O ₃ , VaO and other high-temperature SO _{2 are} not as such adsorbed, but it takes place on permanent constituents, in particular those of the surface of the adsorbent with the participation of sodium and vanadium compounds with each other of the usually present in the exhaust gas or slightly chemical compounds of the type of sodium to be added oxygen form a catalytic oxidation 30 vanadylvanadate. It is therefore extremely over SO ₂ instead of SO _3. With the fact that these compounds are a good source of water vapor, the SO _{3 is hydrated to H 2} SO ₄ immediately after the formation of desulphurisation stones has been increased and maintained and retained in the pore spaces of the adsorbent in the activity of carbon-containing adsorbents. have as a consequence. It is therefore a significant advantage after saturation of the adsorbent with H ₂ SO ₄ , the 35 of the process according to the invention, that worthless waste products in a concentration of 60 to 80 percent by weight instead of the expensive waste products in the pores, the sulfuric acid must again from technical pure compounds of vanadium and removed from the adsorbent. Mixed catalysts produced by the accompanying elements In addition to activated carbon to impregnate the adsorbents, so-called semi-cokes made from peat, brown, are used as adsorbents. The heating oil slag used should be around and hard coal or pre-oxidized hard coal in question. 5 to 70 percent by weight of V ₂ O ₅ .
With these materials, characteristic characteristics can be used. B. medium pore size and inner upper first finely ground and then varied with water or area within wide limits. Since extracts are produced with these dilute mineral acids, the exhaust gas desulphurization, the relatively poorly volatile sulfur, is produced by spraying on or by vacuum impregnation acid, it is possible to bring the process to temperatures between 100 and 200 ⁰ C on the adsorbent when the pre-dried adsorbent is activated. But you can also operate from the fine medium. In this way, ground heating oil slag avoids aqueous Aufschlämmunman the disadvantage of excessive cooling of the gene or suspensions and these on the steam laden smoke plume. Apply 50 adsorbent, however, preference should be given to the first after desulfurization and thus loading with working method. In the case of impregnating sulfuric acid, about 1 to 5 percent by weight of vanadium-containing adsorbent, based on the weight of the pure carbon-containing adsorbent, should be applied to regenerate the carbonation, with the exclusion of oxygen between 400 and 400% by weight. The imprä-600 ⁰ C carried out. In this case, according to the 55 gnated materials are then ^{dried at approximately equation HO 0} C and can immediately thereafter in used the first adsorption-desorption cycle 2 H ₂ SO ₄ + C - 2 SO ₂ + CO ₂ + 2 H ₂ O. Are used for impregnation with a high SO ₄ content Slags used in large quantity so recommends the sulfuric acid is _{reduced to SO 2} and an SO ₂ -rich 60 is also a thermal one after the impregnation Desorption gas obtained, which also CO ₂ , N ₂ , treatment of the adsorbent at temperatures Contains water vapor and possibly some CO. Runs from about 500 to 600 ⁰ C with inert gas purging.
one with the adsorbent in this way several Adsorption-desorption cycles through, so the B is ρ ie 1 1
initially found desulfurization activity of the 65th Materials strongly after. A flue gas with the composition 0.3 vol- With the addition of Vanadm mixed catalysts, volume percent SO ₂ , 3.0 volume percent O ₂ , 6.0 volume according to the method according to patent 16 19 840 percent H ₂ O vapor and 90.7 percent by volume N ₂ through-