FI80481B - CONTAINING CHROME LEGALING. - Google Patents

Abstract

1. The use of a molybdenum-free chromium-containing alloy consisting of 21 to 35 % by weight chromium, 30 to 70 % by weight iron, 2 to 40 % by weight nickel, 0 to 20 % by weight manganese, an typical accompanying elements, such as carbon, silicon, phosphorus, sulfur, nitrogen, aluminium, copper, vanadium, titanium, tantalum and niobium, as a material for articles which are resistant to sulfuric acid having a concentration of more than 96 %.

Description

1 80481

This invention relates to a molybdenum-free chromium alloy containing 21 to 35% by weight of chromium, 30 to 70% by weight of iron, 2 to 40% by weight of nickel, 0 to 20% by weight of manganese, and conventional impurities. the use of elements such as carbon, silicon, phosphorus, sulfur, nitrogen, aluminum, copper, vanadium, titanium, tantalum and niobium as a raw material for articles resistant to sulfuric acid with a content of more than 96%.

The production of sulfuric acid generally takes place via sulfur dioxide, which is then formed by oxidation of sulfur trioxide, which is absorbed into concentrated sulfuric acid, where it reacts with water to form more sulfuric acid.

The essential operations in the production of sulfuric acid are drying, absorption and cooling. In connection with these operations, the sulfuric acid contents are generally above 96%.

Concentrated sulfuric acid and oleum are extremely corrosive substances, especially at high temperatures. Therefore, it is highly desirable that all structural components of a sulfuric acid plant, such as contact towers, heat exchangers, put-25s, valves, pumps, manifolds, etc., be made of corrosion-resistant materials. Today, cast iron, brick, plastics and corrosion-resistant alloys are used as such materials.

The metal parts in use corrode considerably no-30. Unless special precautions are taken or the metals are highly alloyed, they have a limited service life.

High-alloy materials and cast iron are difficult to machine, which results in restrictions on the shape of the equipment, necessitates a greater number of 2 80481 flanges / fittings and costs, and increases the number of potential leaks.

One way to reduce corrosion is to use anode protection. By electrochemically forming the oxide layer, corrosion can be greatly reduced. Thus, stainless steels can also be used at acid temperatures above 120 ° C.

A weakness of anodic protection is that it can only be used with devices of simple shape. Corrosion of certain parts, such as nozzles, pipe bends, flanges, etc., can therefore not be avoided by means of anodic protection. In addition, when operating on an industrial scale, the control necessary to maintain the anode potential incurs high costs. In the event of a power failure 15, the passivation must be partially repeated.

The use of tantalum in the manufacture of corrosion-resistant materials /£>.F. Lupton, Sondermetalle is a chemical apparatus in Apparatebau, Chem. Ind. XXXV (1983) 6] prevents its high price due to poor availability.

DE Patent 2,154,126 describes the use of a molybdenum-containing austenitic nickel alloy as a material resistant to hot concentrated sulfuric acid. However, due to the difficulty of machining, its use is limited to parts such as shafts, bearings, pumps, valves, etc.

DE-A-3 320 527 describes silicon-containing steels. However, they have the disadvantage of limited usability due to the poor availability of the material.

Finally, EP-A-1 309 674 describes materials for use in hot concentrated sulfuric acid, of which, however, only Alloy 26-1 (material no. 1.4131, abbreviation X1 CrMO 26 1) has good corrosion resistance under the required conditions. 35 The disadvantage of this material is its poor machinability.

3 80481

Above all, it places particularly high demands on hit-machining.

It is therefore an object of the present invention to provide a low-cost, readily available raw material which does not have the disadvantages of the alloys described above for use as a sulfuric acid-resistant material.

It has now been found that chromium-containing alloys with a chromium content of 21 to 35% by weight and containing 30 to 70% by weight of iron and possibly nickel up to 10 to 40% by weight meet these requirements excellently.

The present invention thus relates to a chromium-containing alloy containing 21 to 35% by weight of chromium, 30 to 70% by weight of iron, 2 to 40% by weight of nickel, 0 to 20% by weight of manganese, and to conventional elements present as impurities. such as carbon, silicon, phosphorus, sulfur, nitrogen, aluminum, copper, vanadium, titanium, tantalum and niobium, 20 as a raw material for articles resistant to sulfuric acid with a content of more than 95%.

Particularly good corrosion resistance is achieved with alloys having a chromium content of 23-32% by weight.

For sulfuric acid-resistant alloys, alloys with a molybdenum content of at least about 2% by weight are recommended in the art. In contrast, the alloys according to the invention are molybdenum-free. However, these are substantially better in corrosion resistance than known molybdenum-containing alloys. In addition, the alloys of the invention 30 are less expensive than Mo-containing ones. The good workability of the alloys according to the invention is due to their nickel content.

Materials made from these alloys have very good corrosion resistance to very concentrated sulfuric acids. Thus, one aspect of the invention is also the use according to the invention, in which use the material 4 80481 is resistant to sulfuric acid with a content of at most 100% by weight, preferably 98.0 to 99.5% by weight.

Surprisingly, it was also found that the material is also resistant to sulfuric acid with a content of 100 to 122.5% (oleum).

5 The use of the material in the oleum concentration range is also recommended due to its excellent corrosion resistance for economic and safety reasons.

In addition to the concentration-dependent corrosive behavior of the alloy 10 according to the invention, its unusual temperature behavior is particularly relevant for use as a sulfuric acid-resistant material. The materials made therefrom are resistant to sulfuric acids having a temperature of up to 350 ° C, preferably 50-250 ° C, but particularly preferably 80-190 ° C.

It is irrelevant for the purposes of this invention whether the alloy is ferritic, ferritic austenitic or austenitic in structure.

Due to the combination of these properties, the use of the alloy according to the invention is superior to other known materials. It is thus ideally suited for the manufacture of heat exchangers, pipelines, pumps, pump parts, appliances, flanges, filter baskets, smoke filters, droplet separators, SO-j-containing gas absorbers or gas dryers using sulfuric acid as a desiccant. The devices are manufactured by known methods using welding consumables similar or similar to those in the art in general.

In order to achieve the energy recovery in connection with the production of sulfuric acid, the intermediate and final absorption is aimed at a temperature of at least about 80 ° C, in which case the feed water is preheated via heat exchange or low-pressure steam is produced above 110 ° C. The materials according to the invention are also quite suitable for this purpose. A further embodiment of the use according to the invention is thus the use of devices made of said alloy in the intermediate and final absorption zones of sulfuric acid plants at temperatures of 80-190 ° C and sulfuric acid concentrations of 98.0 to 99.5% by weight.

In the following, the invention will be illustrated by means of examples 5 without limiting it.

Example 1

The corrosion behavior in 99.3% sulfuric acid / Heitz, E. and Loss, C of different materials was studied by a method using a rotating disk passing through a shaft at a speed of 2,000 min at different temperatures and using different gas treatment methods. ., Zum Mechanismus der Erosioncorrosion and Schnell Strömenden Fliissigkeiten, Werkstoffe und Korrosion, 24, No. 1, 73 /.

15 The experiment lasted seven days.

Wear rates were obtained by weighing the weight difference and converting the result to mm / a values.

The materials studied are shown in Table 1, the results of Example 1 in Table 2.

6 80481

(M

m O LO in LO LO ΙΛ in LO m O

n ro ο χτ Μ ττ -e xj · μ · χτ o m XT

οο οο Ο Ο ο ο ο ο ο ο ο ο ο α. οσ οο οο ο οοοοοοο ο ν ν | >, | ^, | - ^ | Ν ^ Ι ^ - | ν ^ | ΧΓ (M CM in ~~ eo xr «- o—> t ^ o oo o ooooooo oc - * - - * - - ------- X (\ i -. - (N) cm cm cvj n ro nnon pj cm l_j v | -x »* | n * - | x-- | -w | v |> / | n ^ | s ^ | (\ jmm in cm - .. I · - p- m oo oo o ooooooo χτ «Ί— - - - - - - - ....... - χ * LQ Γ * ί f ~" l ^ 4 «-M 4 · ^ ^ 4 ^ 4 O ** -» 0 I WI «* ✓ ('j S ^ | N * - {> ✓) N ^ j S ^ * | N ^ -j -W j N» - j N »" | «SH ··} · cnu«' 2 Αχ ^

- C

(M n r> «r xr eo m p ~. Oo n o p-. O u O— oo 00 (MO o ooooooo o u.

l — t *. «» «M» «» »» »» »X- o oo oo o oo o ooooooo o * -> ^ | n ^ | v | v | > ^ | v | v | v | v | v | x J3

E

O

m co eo> xm—- x— o in * - o ro— · in in O · - in O (M> - in in in (M (M cm eo ro cm cm - cm cm in cm - in θ 'o σ .a - - m .o in «<>> in z no zo (M e - H z - sn 2 -x

ti O O- X CM O® 3 3 - -X CO 00 3 f- -x 3 3 00 X

ti cmocmzxeuuh - ~ - u o z u c_> - a »2 in o x— o -— 3ooo H o o o X o o o · - - c n— r> x z - r r x - XXX - xxx w σ

S '"? · - Z U - U - - U - Z · - · - L · Z - u 1_ - C

_ 2 'd zu ozomzuz u Z Z u i- z u u Z ro

^ 1 t g l_ o · - l> PJ U L · - l— (_) | _ l_ - O! _ · --- U * J

ti. O 'd u o Z U X U CJ Z CJ O CJ CJ Z O CJ Z Z o

ra i-ic (m— x— (M i e »oo - in · - m ro in - n N in (M

™ p- "xx xxou-xxx x x x x x x x x x m

• “l IL

w 1 (ti -H t »h

Vh «—i a> ro <U I A3 Ό D <H, iö -

T * P to t "- lo n t * -. * - ·« - · ιΛ * - · o ό ^ ^ D

74 ^ ηη so o rs. o o o n. m r? co so PJ ^ nrrj v iolo io Tr ^ LOtn ^ rioin n ti S rr * r 0 (Ό P, to w G «—I ^ ^ v-4 · - (^ 1 · —I <—I« -M < —I * -4 * H> -iwe ^ fH <0 ^.. And O <0 -V o

*: Π3 0 M

Ή Ή 3 c - (M

3 M -o -h a> λ 3 4J C> rdfl-ria) o - no o xt in o s - ® | - m 0 «· m so r ^ co —i 7 80481 3 3 · 3 3 3

U U · U O U

Olo · CJ (OTHER OOu

• * · X -XX - - X

^ * - · X (M X X CM (SI X

"*« · '- · LO CO ΙΛ CO

Π CO - ^ 1 CO Ο ΙΛ - - - - Ä · - - Λ

- OH H - Z H - - Z

on o oo lo lo ooooo lo m - o co sO ui oo sO co nhv ^ so nm co - ro - m ro ^ ^ ^ ro - ~ ro co - • -> - ^ o- ^ oo o lo ooo lo o lo o - - - - LO - - · »- ~ ~ - - - - - 2 0s co - ro - o * ro - 0s - co ττ - tt k— - · n (M Tr (M (M - χχ - - - co ro -

- LO O O LO LO LO LO LO O O LO

ro ---- - - - - - - - ro TT Tr ro ro ro ro ro lo lo ro 0 ro oooo ooo oooo X - - * - - - - - - - - - oi— »o ro ro ro ro ro ro ro ro ττ tt ro Ή

o ro OOOO o LO LO LO LO LO C LO LO

sO ^ ro O N CO O O "CO CO CO CO CO - CO CO

roro ro rj ro ro h h oj «-

r — i O CO tv O O O O O LO LO LO LOLOOLO O

«· ··.« ·. ·. ·. · * - · * · - - - *.

I U ^ “co o v v o e- ooo sO o) r ό n 0 roro ro ro ro ro ro ^ ^ -

G

• H I <T5 cu | <

% D

^ X

O

C/O

- O - z - -

L-. O O

- • I

- ro ro ro rt LO co io o o O co— o n χχ ro ro rororo ro - ro n M oo oo oo o ooo o co o o ro rt to oo oo oo o ooo o-oo o ^ U v * | s ^ l s ^ l V * »| v ^ l v ^ J - I v ^ l s ^ l O s ^ l s ^ |

tH

1 I

o (O x o λ; m o m

Λ! -H 3 G

3 M -n '»-H QJ (d j o - (M π cm H 2 3 $' ~ ™ η, ΤΛ'ΟΝ« ~ ~ ---- 8 80481

UI

3 Φ Ω.

O - g C ifl rt rt rt rt rt rt LDCOr'-rO Oj tn \ οοοοοο-Ήΐο vc go tn a

g 1 OOOOOOCMro rt rt O O O

3 ^ rt cm

B

3 C

S4 »nj

Md P CM Md tn i 2 tn

3 P t * 5 -H

3 3 1 td a w a o c • HOC <d · '0 i — I -H a; 3 P Id CM CM -H tn • H 3 a 1 '—i * —i id tn (¾ a; - ii -; i -il i' »i

1 Φ O O O O C CM

CM A (0 0) O

0 0 3 φ tn tn a: p a o c C A id C 0) C C -n o e ω <u m <u C -H C C · η • H 3 -H -H 3 SS SS -HO)

Md «β Md Md Md Md 3 M 3 3 PO) + j4j + jppPrH (ts ι-t a tn Ai tntntntntntn3tt) 33 <go

H -H -H -H -H -H a; C Ai A C C A

S S s S S S C 0) 01 C

R? I> i> i> i> itninti) tncncc brings aftaaaottdtöcnjrtj-H-H φ a O> 0 Ό Ό Ό ‘0 A! Ai -H X X g g tn Ai ω 0) 0) o tntncntntntngspgeaO) φ a a -h -h a a a ό so p a! 3 a a a a a a o O 3 O O> i> i tn H αια) (υα> α> α >>> Αί >> ιηιη a c a Md tn «o

I,> i P

P PO) a * »tj tn id« o a: to a aa A <d a 3 p rtrtCMrororororo rt cm cm * h>, td U)> i A! -n id a td Φ tö td A p m tn ω tn <d td - oooooooo oooo aa O cMiricMtntor ^ tnto cm cm ui uo 3 aa O »H t— <iH H» H I »H H iH ^ 4 ^ 4 ^

^ P iOO

g φ aa <c <<< gpgs a «d 110 OOOOOOOO O O O OCNj-iaa XXXXXXXX x x x x 3

AAAAAAAA A A A A tn CC

φφφφφφφφ ΦΦΦΦ3ΰΦΦ Φ a a a a a a a a a a a a 3 a φ φ

a AAAAAAAA AAAAtnaCC

Id A! ο O O

a 'td «d« d Md Md Md Md Md Md Md Md: <d id 3 3 3 id td a >>>>>>>> >>>> aax; Äca id a a a a a a a a a a aa aa a a! PPPPMPPP p P p P * C CM CMa ··

φ O '0 Ό' O '0' 0 '0 O' 0 ΙΟ '0' 0 g a O O U CM

O> l> l> i> lBSWCMfdZ

a aaaciiaaaa a a a & s 2 o φ c c c ro a id id id Md O o id id a Md

CU T & gPPOP

cm a c φ φ a φ

a ·· ·· Ό Ό P P

Oidid c cd ji Λ O a A! id> O O a φ a a φ rt ro n · o o h> a a 3 P tn A! a φ a A 11 11 n 3 P O 0) 3 id 3 a rt cm co EM s -ro A * 9 80481

Example 2

In a double contact plant based on sulfur combustion with a capacity of 500 t / day SO 2, various alloys were used in the acid cycle of the intermediate absorber at temperatures of 125 to 135 ° C and a sulfuric acid content of 98.5 to 99.5%.

The flow velocity was about 1 m / s and the duration of the experiment was 42-60 3 days. The amount of circulating acid was about 250 m / H.

The dimensions of the rectangular specimens were 50 x 15 x 3 mm.

10 Separate test pieces (welded joint) were superimposed on each other, separated by a Teflon spacer and insulated from the pipe wall.

Corrosion resistance (mm / a) was determined by weighing and performing the necessary calculations.

15 The results are given in Table 3 below.

ίο 8Q481

Table 3

Material Time Wear Rate Result

Iin running (day) seva no mm / a 5 'la) 45 0.01 matt surface b) 42 0.02 matt surface

Comparison 10 3 42 0.10 / 0.24 corroded surface, deep cavities 4 42 0.17 / 0.13 scratched corrosion 5 42 2.00 / 0.96 severe scratched corrosion, deep cavities 6 42 0.32 / 0.64 / 0.90 scratched corrosion 7 60 0.12 / 0.18 matt surface, here and there scratches 20 “8 42 0.81 / 0.69 scratched corrosion and deep cavities 9 42 0.41 clear surface; upper half strong. naarra.

25 10 42 1.92 severe corrosion 11 42 0.90 rough granular surface 12 42 «dissolved 13 42 * dissolved 14 42 ® dissolved 30 15 60 0.40 scratched surface

Tantalum 42 0.05 corroded 11 80481

Example 3

In a double contact plant based on sulfur combustion with a capacity of 500 t / day SC ^, an 80 cm long piece of pipe 5 (other dimensions 44.5 x 1.6 mm) made of 1.4335 material was placed in the bypass branch of the heat absorber of the intermediate heat absorber stationary for 56 days at a temperature of 125-135 ° C and a sulfuric acid content of 98.5-99.5%. The flow velocity was adjusted to about 1 m / s.

10 No significant corrosion was visible on the inner surface in contact with the product, including the weld.

Example 4

The rotating disc method described in Example 1 examined various materials in oleum. The results of the experiments are given in Table 4.

12 80481 I Ίβ o \ a g m g m.

H - · 1— is T- ro -.

g "· * V c 3 M O r- T- fS 3 i — I d β

3 0) <H

a ft O

β CO I - β d -p <#> β d d i -h tn (¾ o ·· • rt O C <#>

0 Ή -rl O O O O I

P> β CN (N (N <N O

H β ft β ft Q) - -r | 1 o ta my B) ft o o d β β β to y -p β β β · r "β β β d <ν rt -Η -Η Ρ>

<0 Egg -Ρ II

-ρ> ι> ι> ι α »- · β ft ft ft -Ρ • H: 0: 0: 0 -rl at>

ft> ι> ι ϊ> ί M

to tn to d vo β o β 01 η η β τ- 0) β ttj β · Η η »eyyy rH ra to β β β β β o tn o ft ggggd« i rH ft S -rl -rl -H ft dd β -HOOO Ή eh λ; χ; >>> ββ

•B

g β

Il g 0) P * -rl β β • rl Q) H y to β ft 0 0

: β ft GM

Μ β β d -Ρ rH> i =: = β '-rl

10> 1 rH pl O g rH

β rH ·· -Ρ M ti Ο β ο) <ν φ λ: a -Ρ ζ -Ρ o <ν m • h d to d o o o o d tn

υ CJ N tN N: β d ‘H

μ O r- T- r- r-: β tfl O

-> y p • Ρ β -rl ·

Sh ft ft β O: 0 I -Ρ H CQ>, - ^ -Ρ β ft god ft: β β g C0 β ft> rH β (M y β -H β = Ϊ Ϊ -hoao λ: p ft · η m ρ β --ο ft Ρ »β o ο> ι β + J ®t -hda ft λ: β g> I -Ρ ·· dom> ι o β r-

β Ρ: β: β p) rH <N

-Ρ β P M O O

rH β d -H

Οββ Pi H β 6 β Pi y β> β H tO> i 10 py-Ηβ r-H K 10 β p> β

d P m · Η · Η Ο β M

Γ-ΗβΜ · Ρ> ι β, * pl dpio ρ>?> Py β> ι o β β d * - ββ Ο · Η: β ο ΐ- <s · γ-> 1- τ— a γ-η aaaa 13 80481

Example 5

The following materials were stored for seven days in 99% CH 2 Cl 2 at various temperatures. The following wear rate values (mm / a) were obtained.

5 Material Test piece Temperature (° C) running 1 = Welding rod 170 190 210 3 No. 2 = 50x15x3 mm Wear rate mm / a 1 2 0.02 0.02 0.03 2 1 0.01 0.01 0.03 10 Example 6

The following materials were stored for seven days in 99.5% I 2 SO 4 at various temperatures.

The following wear rate figures (mm / a) were obtained. Material Test piece Temperature (° C) 3 15 running 1 = 50x15x4 mm 150 170 No. Wear rate mm / a 3 1 0.03 0.04

Claims (7)

1. Use of a molybdenum-free, chromium-containing alloy containing 21-35 wt.% Chromium, 30-70 wt.% Iron, 2-40 wt.% Nickel, 0-20 wt.% Raw material and customary elements present as impurities. Such as koi, silicon, phosphorus, sulfur, nitrogen, aluminum, copper, vanadium, titanium, tantalum and niobium, as raw materials for articles resistant to sulfuric acid levels above 96%. Use according to claim 1, characterized in that the chromium content is 23-32% by weight. Use according to claim 1 or 2, characterized in that the raw material is resistant to sulfuric acid content of not more than 100, preferably 98.0-99.5% by weight. Use according to any one of claims 1-3, characterized in that the raw material is resistant to sulfuric acid content of 100-122.5% by weight (oleum). Use according to any of claims 1-4, characterized in that the raw material is resistant to sulfuric acid having a temperature not exceeding 350 ° C, preferably 50-250 ° C, in particular 80-190 ° C. Use according to any one of claims 1-5, characterized in that the alloy is used for the manufacture of heat exchangers, pipelines, pumps, pump parts, instruments, flanges, filter baskets, smoke filters, drip separators, containers, absorption devices for SO3-containing gases and drying devices for gases in which the desiccant is sulfuric acid. Use according to any of claims 1-6, characterized in that devices made by the alloy are used in sulfuric acid producing factories for intermediate and final absorption at a temperature of 80-190 ° C and where sulfuric acid content is 98.0-99. , 5 wt% H2SO4.