DE2102039C3 - Process for removing mercury or mercury and oxygen from gases - Google Patents

Description

Both mercury and oxygen can be removed from the absorbent.
The absorbent according to the invention can ground _u f in a simple manner, for example, prepared by ^a, by impregnating the alumina with an aqueous solution of a copper salt, dried, optionally calcined, and transferred the copper from the F'nsatz in the metallic form. The copper content of the absorbent can for example be 05 to 40, preferably 3 to 15 percent by weight

be.

The temperature at which the absorbents according to the invention are brought to act on the mercury and / or oxygen-containing gases can be varied within wide limits. Conveniently, a temperature of 0 is maintained to 12O ⁰ C. So you can easily do the cleaning at room temperature (20 ° C). In the event that the gases to be cleaned contain oxygen, it is advantageous to carry out the cleaning at elevated temperatures, above 70.degree. C., for example from 75 to 120.degree. The reason for this is that at lower temperatures the pyrophoric absorbent forms copper oxides with the oxygen present in the gas. However, since this no longer forms Almagam with the mercury, the absorption capacity of the absorbent for mercury declines continuously as the conversion of the highly active copper surface into inactive copper oxide progresses, so that in this case frequent regeneration of the absorbent is necessary. If, on the other hand, the absorption is carried out at temperatures above about 70 ° C., at these higher temperatures the oxygen is catalytically converted to water under the influence of the highly active absorbent, so that no more CuO formation takes place, which reduces the absorption of mercury by the absorbent is affected. For these reasons, it is advantageous to carry out the cleaning, for example, at temperatures of, for example, 0 to 50 ° C. if the oxygen content of the hydrogen is less than about 20 ppm, while temperatures above 70 ° C. are more advantageous for higher oxygen contents

The cleaning according to the invention can be carried out either at normal pressure or at elevated or reduced pressure Printing can be done because the absorbency of the absorbent is not due to pressure being affected.

The pressures and temperatures under which the cleaning is carried out therefore depends depending on the given operating conditions and circumstances and on the conditions under which the purified hydrogen is to be used. Under certain circumstances it may be useful to use the Hydrogen before the cleaning according to the invention directly or indirectly, for example with water or to cool frozen brine and thus reduce its mercury and water content, in order to reduce the intervals between the required regenerations of the absorbent. Should the hydrogen can be used at elevated pressures so it is advantageous to use the in the decomposition cell in the general pressureless hydrogen to be compressed to the required pressure and through 6; Cooling already a large leii des Queocsi.uers to be deposited before the cleaning according to the invention is carried out.

The regeneration of the absorbent takes place in a simple way at temperatures of 180 to 400 ° C, preferably 200 to 220 ° C while passing a stream of hydrogen through it.

The method according to the invention is explained in more detail below with reference to the figure.

The hydrogen formed in the amalgam decomposer of a chlor-alkali electrolysis plant is fed through line 1 to a cooler 2 in which the hydrogen is cooled to a temperature below 0 ° C. It reaches the tower 6a filled with the absorbent through line 3, the opened slide 4a and line 5a. The purified hydrogen then passes through line 7a, the open slide 8a, line 9, the compressor 10 and line 11 to the consumer. This path is maintained until the analyzer 12 connected to line 7a via the opened valve 20a shows a mercury content in the gas, then the slides Ab, Sb and 20b are opened and the slides 4a, 8a and 20a are closed. The hydrogen is now cleaned in tower 6b , while the absorbent is regenerated in tower 6a. For this purpose, part of the purified hydrogen, for example 10 percent by volume, is branched off from line 11 and fed via line 13, the open slide 14, line 15 to the gas heater 15, in which the hydrogen is heated ^{to, for example, 30O 0 C.} From the gas heater 16, the gas passes through line 17, the open slide 18a, line 7a into the absorption tower 6a. After leaving the tower, it is passed through line 5a, the opened slide valve 19a and line 20 into the cooler 21, in which it is cooled to temperatures below 30.degree. The mercury which has condensed out in the process is withdrawn from line 23. The gas can then be fed back into line 1 through line 22, for example. Of course, this gas heater 16 can be omitted if, for example, the towers 6a and 6b are themselves equipped with a heater, or it is also possible to additionally heat the towers in order to accelerate the regeneration. The regeneration is carried out, for example, by heating until the gas has a temperature of 200 ° C. after leaving the absorption tower. The gas is then passed so long through the absorption tower until its temperature to, for example, 8O ⁰ C has dropped Then, the slides 14 and 18a is closed.

After the absorption medium in tower 6b has been exhausted, a switch is made again to tower 6a and the absorption medium in tower 66 is regenerated.

In a system operated according to this scheme, the absorption towers are equipped with an absorbent filled which consists of 5 χ 5 mm aluminum oxide strands, to which 13.5 percent by weight copper is applied The aluminum oxide has an inner surface of 130 mVg, a total pore volume of 06cmVg and a mean pore diameter of 70 A. At a pressure of 200 to 300 mm The water column in this system is 7000 m per hour

directly ^{precooled to -10 0} C and then brought back to room temperature. The pre-cleaned hydrogen contains. 0.8 mg / m ³ Hg and 12 to 20 ppm O ₂ . The purified hydrogen contains 1 Hg / m ³ and 1 to 3 ppm O ₂ . Within 6.5 years of uninterrupted operation and after 62 regenerations, the absorbent shows no decrease in its activity.

example 1

Through a glass tube with a diameter of 40 mm and a height of 2 m, which is filled to a height of 1.50 m with an absorbent, hydrogen at room temperature is 0.8 to 1 mg Hg / m ³ and 10 to 12 ppm O2 passed through from below in an amount of 1 mVh. The absorbent consists of 4 x 4 mm strands of aluminum oxide with an inner surface of 220 nmVg, a total pore volume of 0.7 cm ³ / g and an average pore diameter of 65 Å and has a copper content of 2 percent by weight. After passing through the pipe, a recording UV absorption analyzer, which has a display sensitivity of 1 γ Hg / m ³ , shows no display. After 670 hours, the analyzer begins to register a slow breakthrough from Hg from 0 to 25 y / m ^3. The supply of hydrogen is then switched off, and the absorbent is ^{regenerated by passing 0.1 m 3 of} hydrogen / h through it from top to bottom at a temperature of 350 ^° C. for 5 hours. After loading and regeneration three times, the absorption capacity of the absorbent is still unchanged.

Example 2

Through a glass tube as described in Example 1, but which is filled with an absorbent consisting of 5x5mm strands of aluminum oxide activated with 13.2 percent by weight Cu, hydrogen with 0.8 to 1 mg Hg and 10 to 12 ppm O2 is in a Amount of 1 m ³ / h passed through at room temperature. The aluminum oxide has a surface area of 150 mVg, a total pore volume of 0.7 cm ³ / g and an average pore diameter of 70 Å. After 1080 hours, the analyzer shows the breakthrough in Hg. The absorption capacity of the absorbent is _{still unchanged after regeneration with H 2} at 250 ° C. 7 times.

Example 3

^{Hydrogen with an Hg content of 15 mg / m 3} and an O 2 content of 15 to 18 ppm at room temperature in an amount of 1 m ³ / h is passed through a glass tube with a filling as described in Example 2. The analyzer shows a breakthrough of Hg after 184 hours.

Example 4

Through a glass tube with a filling as described in Example 2, hydrogen with 0.8 to

1 mg Hg / m ³ and 10 to 20 ppm O2 in an amount of

However, passed 2 mVh at a temperature of 8O ⁰ C. The analyzer shows a breakthrough of Hg after 2880 hours.

Example 5

^{1 m 3 of} hydrogen / h with 0.5 to 1 mg Hg / m ³ and an O2 content of 0.1 percent by volume, which was obtained by mixing in 1 102 / h, through a glass tube with a filling as described in Example 2 , passed through at a temperature of 80 to 85 ° C. The analyzer shows a breakthrough of Hg after 6150 hours. After passing through the pipe, the oxygen device is approx. 2 to 3 ppm.

1 sheet of drawings

Claims (1)

'J "" Rhiedene procedures known. A chemical, τ kt by washing with solutions that are active SÄe. of course. Ei »e ₈ ,» nd, iche NacW _äK „e Patent claims: 1. Process for removing mercury or mercury and oxygen from gases by Treating these gases with an absorbent made from copper applied to a carrier denotes that the docking aui _{w rspibllll r} is applied to a carrier made of aluminum oxide. Water ^^ _{Q p lh} , _em the inner surface of 100 to 300 m '/ g. a .o it ^ ^ ^. ^ _{that one d} mercury at Pore volume of 0.5 to 0.8 cmVg and a housing _{would be impregnated} Average pore diameter of 40 to 80 _{Å can be reduced, for} example with od I ·, rhlor are also known alkali polysulfur "! Ve drive according to claim 1, characterized by marked- ^ _{kaBsuinde or} alkali hydrogen sulfides as impregnation draws that the copper content of the absorpt.onsm.t- .5 je. α _{aS 10 75 953)} According to the US patent Ξ05 to 40 percent by weight. S ^ 31 93987 is used for fine cleaning of the gases 3. A process according to claim 1 or 2, characterized _yerwendet longs _{which m,} t e.nem metal mprägekennzeichnet that the treatment at a ^nude ^ _{is the miUem} Quecks.lber e, _n ,, image amalgam femperaturvon0bisl20 ° Cerfolgt. ₂₀ f for example copper or S.lberD.e regeneration of 4 A method according to any one of claims to 3, 20 _aparie to> P rten activated carbon is characterized by its in that in the case of water £ mercury au if at all, only material _{possibilities} feasible as mercury and oxygen-containing Be £ · wherein the Aktmtat _. ". j, .._ .. i. ":";"". T ^ mnpratur voiiO to mil ^ 'rf _energy decreases, so that such Soles so far on an industrial scale for the fine-tuning of gases from their mercury housing "have not yet been used. Finally, it is also known, for the purpose of removing mercury from gases, these with e.nem Absorp. _ · .. "■;" Rpriihriine that is made of metallic stott ais yuecKMiuci uuu ^ - . Gas the treatment is carried out at a temperature vo, 0 ^ b 50 ⁰ C if the oxygen content is less than 20 ppm. 5. The method according to any one of claims 1 to J. characterized in that in the case of hydrogen as a gas containing mercury and oxygen, treatment at a temperature of KJb.s. 120 ⁰ C is carried out when the amount of hydrogen is more than 20 ppm. mercury as mercury and oxygen contain mercury from gases, this rn.te.nem absorption Gas treatment at a temperature of 70 ° C. * _Ule , _{to bring into} contact that is carried out from metalli-120 ⁰ C if the oxygen content 3 u ^^ _{that precipitated on gravel} earth, st, d Wtffs is more than 20 ppm. _{However, this} absorbent has Disadvantage is that it is broken down and pulverized in a shorter time due to the water content of the gases, V _{and the applied flow rates.} In order to eliminate this steepness, according to DAS 12 44 721 Na ^ ^. ^ _{F the meta nical} silver ⁸ ^ _{iumoxid to be} used, which in order to produce a sufficient α _d strength, in the form of ^u J ^u _{enem A,} to be emgesetzt _to i _n iurnox.d With chlor-alkali electrolysis, chlorine becomes alkali-hydroxide and hydrogen in equivalent amounts generated. In the amalgam process, the passport _strength arises, in the form of material in the decomposer, in which the m of Pnmarzele ^ü J ^u, _{zenem A,} is to be emgesetzt _to i _n iurnox.d alkali metal amalgam formed at temperatures of 60 to 4 * scluno ^ ^ _{n 634 patent} is a method 16 over 120 ⁰ C with water on a catalyst, _effective removal of paramagnetic gases, Mercury, alkali hydroxide and hydrogen decompose oxygen, described from gas mixtures that will. When leaving the decomposer, the · ■ ^^ is _{that the gas is} finely divided Hydrogen of the lye in the decomposer _{ejtet dgs on y} . Aluminum oxide as a carrier temperature corresponding to water and mercury above 45 P _{ht is;. The} aluminum oxide is said to have a surface saturated steam. Usually de: hot 8 will now _{have at least 10 m} Vg and by adding Hydrogen cooled directly or indirectly. While one ..J _{15 wt} .-% sodium oxide be activated, formerly the hydrogen of all cells in a geme.nsa-. ^^ ^ _{gefundeili that one} mercury or The collective cooler is preferably cooled in the last few _{minutes, and} oxygen is advantageously cooled off Years usually a cooling right after each ν ^^ _{treatment with} on a carrier _{Decomposer to} remove the condensed mercury directly from the copper, if that back into the mercury circuit of the cell ™ "« ™ - « _{ff a} carrier made of alum.n.umox.d- to lead. At temperatures of hydrogen from + lO to Mip ^ ^. ^^ surface from 100 to + 30 ° C, which is usually dm. Pore volume of 0.5 to 0.8 cmVg and obtained from 5 to 25 ° C, de, -55 ³ is f ^ ^0m _{tleren Porend} urch _m eater of 40 to 80Ä Mercury content of the water that has been cooled in this _way but still 5 to 30 mg / m ^. In principle, according to the invention _Proceed n any gases that do not contain mercury _6o ^V _{ming ver} may be cleaned. With particular RESPOND ^ ^ ^ _{Rejnigung of Wasserstoffi} by j ^. ^ _chlor- alkali after ctrolysis J ^ * _β ^μ _{ΓίβΗΓβη} is applicable. ^dem * ™ ^lga _rt j _onsm i _lte | is characterized by a long uas α μ service _life . The activity <"QJ ^Iv ^ _h ^a" _{bi annual} r _a NGEM use and also after Mercury content of the so g
but still 5 to 30 mg / m ^. Although electrolysis hydrogen is "in Igewohnlich 99.9" / o) much of this Q "^ makes him ⁸¹ ^ salary for many applications unusable, for example, for the hydrogenation of fats for human consumption, and also for all those hydrogenation in which the The hydrogenation catalyst is often poisoned by traces of mercury. In addition, the high mercury losses for additional reasons require it to be loose the high mercury losses from w.r and hygienic reasons one possible. it loose QJ ^Iv ^ _h ^a "r _a NGEM _{years in} use and also after, practically regenerations not yield. Of particular advantage is that by means of