DE1467198C - Process for the recovery of NH deep 3 and H deep 2 S from these containing water - Google Patents

Description

The present invention relates to a method for purifying water, and in particular of wastewater from hydrocarbon hydrogenation processes using ammonia and hydrogen sulfide are contaminated, with the recovery of very pure ammonia and hydrogen sulfide.

The ammonia and the hydrogen sulphide are formed when hydrocarbon oils are converted with hydrogen from the nitrogen and sulfur compounds contained in the hydrocarbon oils. The ammonia and hydrogen sulfide-containing stream emerging from the reaction zone is used for the Removal of ammonia and hydrogen sulfide washed, taking the abovementioned wastewater receives.

The removal of NH ₃ and H ₂ S from such streams can be accomplished by washing with water, preferably at elevated pressure and low temperature. To achieve the desired degree of purification, however, it is often necessary to use a fairly large amount of water, so that a dilute aqueous solution of NH ₃ and H ₂ S is formed. So far, solutions have been made so dilute that they can be drained off as sewage in bays, rivers and lakes. However, due to the increasing urbanization and concentration of industrial companies, water pollution can no longer be tolerated.

High yields of very pure NH ₃ and H ₂ S cannot be obtained by simple distillation of aqueous solutions which contain H ₂ S in _{addition to NH 3.} A rectification can be carried out to remove some of the H ₂ S from the solution. As the concentration of the remaining H ₂ S decreases, however, the smallest limit ratio of H ₂ S to NH ₃ is soon reached, at which no further separation of NH ₃ and H ₂ S is achieved. The solution contains almost all of the NH ₃ and a substantial amount of H ₂ S contaminating it. B. found that even at 232 ° C, the limit value of the smallest weight ratio of H ₂ S to NH _{3 is} above 0.04.

At lower temperatures the smallest weight ratio "is greater. It does not appear that the H ₂ S and NH ₃ can be separated in this way at any applicable temperature. Such a solution has been proposed in terms of its NH ₃ content to concentrate and to form ammonium sulfate by adding sulfuric acid and then to _{strip the remaining H 2} S from the acidic solution. However, many manufacturers of chemicals and fertilizers prefer relatively pure anhydrous ammonia, ammonia water or other ammonium salts than the sulfate.

In the process according to the invention, _{high purity NH 3} and H ₂ S are obtained separately from aqueous solutions. The H ₂ S is then in an easily usable form and can e.g. B. be converted into sulfur or sulfuric acid. The NH ₃ is also in a form that is largely Absal /. finds.

The present invention relates to a process for the recovery of NH ₃ and H ₂ S from waters containing them, in particular those which are obtained in the refining of petroleum products, by rectification in several process steps, characterized in that in the first process step from a column in essentially ammonia-free H ₂ S is distilled off at overpressure up to 28 atmospheres, whereby one

_{a) either withdraws a side stream containing more NH 3} than H ₂ S on a weight basis from the column, from which essentially the main proportion of water vapor is partially condensed, whereupon a concentrated NH ₃ -haItiger vapor stream from ίο controlled by temperature adjustment, the at least the 1.5 times the H ₂ S weight is obtained and the aqueous bottom product is drained off, or where one
b) the bottom product obtained in the primal column, the more NH ₃ as H contains on a weight basis ₂ S, a second, gives up at pressure up to 28 atm operated column, from the bottom thereof practically water is removed and from which a to NH ₃ and H ₂ S enriched vapor stream is withdrawn and this is concentrated at overpressure up to 28 atm in the upper part of the second or in a third column, the water content being controlled by temperature adjustment,
25th

and in the last stage of the process, the vapor stream obtained in this way with a high NH ₃ and H ₂ S content is subjected to partial condensation, the condensate obtained, which is more NH ₃ than H ₂ S on a weight basis and essentially all of it, in the Concentrated vapor stream _{containing H 2} S present, returned to the first column and recovered as a non-condensed portion essentially H ₂ S-free ammonia.

According to one embodiment of the invention, in the case of variant b, a larger proportion of the condensate from the last process stage is given up at the top of the second column and the smaller proportion of the condensate is returned to the first column. Furthermore, in the case of variant b, the _{ammonia which has not condensed in the partial condensation and is essentially H 2} S-free, steam-containing ammonia can be partially condensed again, the pure gaseous ammonia can be drawn off and the condensate can be returned to one of the columns. Another embodiment of variant b consists in stripping off the hydrogen sulfide in the first column to such an extent that the bottom product of this column contains more NH ₃ than H ₂ S in a weight ratio between 4 and 10. The water vapor content of the concentrated _{steam stream containing H 2} S and NH ₃ is expediently adjusted to values between 30 and 75%.

The aqueous solution treated according to the invention can contain more than 15 percent by weight of NH ₃ and more than 30 percent by weight of H ₂ S. Usually, however, the solution is considerably more dilute and contains only a little less percent NH ₃ and H ₂ S each, usually about 1 percent by weight or more of both compounds. The original ratio of So NH ₃ to H ₂ S in the aqueous solution is primarily determined by the origin of the solution. The aqueous solution preferably contains 1 to 5 mol percent and advantageously up to 2 mol percent each of NH ₃ and H ₂ S.

Ammonia and H ₂ S react in the solution, ie they are at least partially in the form of dissolved, partially or fully ionized salts. For simplicity, the concentrations of nitrogen are shown

3 4

and sulfur in the various streams of des and H ₂ S in the aqueous bottoms product can be relatively large.

However, the method as NH ₃ - and H ₂ S total equi- The concentrations of NH ₃ and H ₂ S must

valente specified. be low enough to get the absorption you want

The bisulfide equilibrium appears to be reached upon reaching. Usually, at least about 75 ° / ₀ mood of absorption in water and of the possible 5 of the NH ₃ and H ₂ S from the whole to be treated loan separation of NH ₃ and H ₂ S from aqueous aqueous solution and removed as a NH ₃ - and H ₂ S solutions play an important role. The NH ₃ streams of high purity are recovered so that the aqueous and H ₂ S are easily absorbed in water with the formation of product _{containing substantially less NH 3} and H ₂ S than ammonium bisulfide (NH ₄ HS). After that, the initial aqueous solution becomes. An object of the invention to dissolve further amounts of NH ₃ more easily than further io is the recovery of .NH ₃ and H ₂ S in high out amounts of H ₂ S. As a result, the aqueous bags contain what is not affected by the fact that solutions usually either Almost equimolar amounts of NH ₃ and H ₂ S, or even more NH ₃ than H ₂ S, are allowed in the aqueous sump, which are recovered in the feed, namely up to 2 moles of NH ₃ per mole of H ₂ S seem accordingly. The net yield of NH ₃ and H ₂ S of the compound (NH ₁ J ₂ S or more in some cases. 15 each is at least 90% based on that in the

Since H ₂ S absorbs a particularly undesirable contaminant in aqueous solutions, net amounts

represents supply in NH _3, to the invention, the vapor pressure of H ₂ S to aqueous solutions

Process is an NH ₃ product of high purity produced from NH ₃ and H ₂ S at low temperatures

which is substantially free of H ₃ S, quite low when the ratio of ammonia

in which the H ₂ S concentration is below 0.5% by weight - 20 to H ₂ S high. If the solution is a relatively high

percent lies. The NH ₃ preferably does not contain any concentration of NH ₃ that consists of a

"7 more than about 1000 parts / million H ₂ S, still advantageous such a solution in equilibrium

~ Less than about 100 parts / million H ₂ S. It vapors from NH _{3 of} high purity.

but also NH ₃ can be produced, which no or accordingly it is the aim of the invention

contains only traces of H ₂ S. . 25 according to the method, from the feed solution

The NH ₃ in high purity can be obtained as a dry gas - a solution (condensate), the N Hastrom of which can be obtained, but it can also be obtained as a concentration and its ratio of NH ₃ to the wet NH ₃ production stream, the H ₂ S is high, so that the solution in the same 'is then used as ammonia water and z. B. _{high-purity NH 3} vapors by weight contains about 25 percent by weight of NH _3. Preferably 30 can be obtained. In the solution, however, dry gaseous ammonia must be obtained. The ratio of NH ₃ to H ₂ S, based on weight, is obtained. which is no more than about 2 percent by weight greater than 2 to 1. Significantly higher proportions of water and preferably no more than 0.5 percent by weight in the range between 4 to 1 and 10 to 1 are contained before percent water. admitted. Furthermore, the NH ₃ concentration in the

According to the process according to the invention, 35 solution of at least 20 percent by weight is obtained, one H ₂ S in high purity, which is essentially free, with higher concentrations of 30 to 50 weight percent of NH ₃ . If it is preferred to produce sulfur percent or higher to be used, the NH ₃ content is not _{critical to that of the H 2} O content in equilibrium with the solution. However, it is usually limited to limit the vapors that are present. If to prevent the NH ₃ formation of solid substances. At low concentrations in the preferred higher ranges pressures, e.g. B. at about 7 atmospheres, which could be, the H ₂ S concentration can make up to 2% of the H _{2 S in ammonia content.} However, for depending on the concentration in the original, sulfuric acid production and most other initial feed solution 20 percent by weight for uses, the NH ₃ content is approaching. For dilute feed solutions is no more than about 100 parts per million and the purity of the H ₂ S concentration in the solution, in general, the H ₂ S is at least about 95 percent, with less than 10 percent by weight. The “desired solution” consists of the rest of the water. The H ₂ S is preferred and the equilibrium vapors are thus also obtained in a relatively dry form, which keep a concentrated vapor stream no more than 1% H ₂ O, advantageously no more than partially condensed, which necessarily has one 0.2 percent by weight H ₂ O contains. 50 higher NH ₃ concentration and a higher ratio

After the NH ₃ and H ₂ S have been separated off, the NH ₃ must also have H ₂ S as the condensate

Obtained water, the only non-polluting ("desired solution") and which also has a controlled

Contains amounts of NH ₃ and H _{2 S.} If the process must have th water content. The concentrated one

Primarily used for the purification of waste water, steam flow cannot, however, be achieved by distillation

is used to obtain their discharge in sea bays, 55 of the aqueous feed solution.

To enable currents and the like are attempted under the method according to the invention

"Non-polluting amounts" low concentration, the H ₂ S content in the concentrated NH ₃ -containing

tions understood that the local regulations steam flow and in the condensate on a low

correspond. With the method according to the invention to keep concentration, but lets the H ₂ S-Kon-

Wastewater can be cleaned to such an extent that it is concentrated to between about 5 and 10 percent by weight

only contain traces of NH ₃ and H _{2 S.} Typical for zent or, as mentioned, in some cases up to

: such purified wastewater has a content of 20 percent by weight increase. This can be achieved through

: about 0.03 percent by weight of H ₂ S and 0.1 percent by weight of incomplete stripping of H ₂ S from the aqueous

percent NH ₃ . Solution so that, based on weight, the H ₂ S-

The aqueous bottom product can, however, also have a concentration below the NH ₃ concentration.

led to further amounts of NH ₃ and H ₂ S, more precisely, the weight ratio of NH ₃ to

to absorb from the electricity to be cleaned. In H ₂ S in the bottom product of the first column according to the

In this case, the maximum permissible amount of NH ₃ can be in one column or in the side stream of a single column

5 6

According to the other variant of the feed according to the invention, the pre-process should be between 4 and 10 in a heat exchanger 16. 'heated and at a central point in the distillery essentially consists of the treatment of the sump column 17 introduced. The portion in line 14 of product from a first column or the side stream is introduced at a higher point into the distillation of a single column to form the concentrated column 17. The part in line 15 is triated steam flow in the controlled lowering, preferably in heat exchanger 18, and cooling of the amount of water. In general, treatment near the top of the distillation column involves distillation or partial con-introduction. The temperature at the top of the densation at a controlled temperature so that column 17 is kept as low as the uncondensed portion of concentrated NH ₃ - and io that essentially NH ₂ -free H ₂ S vapors as Pro-H ₂ S-containing steam with a water content of 30 ducts can be withdrawn through line 19, and 75 percent by weight is obtained. The temperature is preferably so low that the

The higher the NH ₃ concentration in the concentrated vapors in line 19 contain less than l ° / ₀ H ₂ O.

The NH ₃ -containing vapor stream, the lower the aqueous bottom product, the NH ₃ and, based

and will be the H ₂ O concentration. The water 15 by weight, H ₂ S in a lower concentration

However, it must always be present in a higher concentration than NH ₃ , is from the bottom of the column 17

than the H ₂ S, based on the withdrawn through line 20. So on the ground

Weight, at least about 1.5 times as much H ₂ O as H ₂ S, the column is at a high temperature and

so that when the concentrated NH ₃ -containing vapor- upflowing vapors are generated, a

stream is partially condensed, the condensate easily 20 part of the bottom products through line 21 and

essentially all of the H ₂ S dissolves. It follows that the heater 22 is passed and to the bottom of the column

that the H ₂ S concentration in the concentrated vapor is returned. The aqueous bottom product (line

flow barely exceed about 20 percent by weight 20) is cooled in the heat exchanger 16 and in 23

is and fed _{at NH 3} concentrations below 40% and a second distillation column 24a. The

more than 50% is less than 20 ° / o. 25 aqueous bottom product is in the column 24a

The condensate, which is further stripped off by partial condensation, so that one enters line25.

of the concentrated NH ₃ -containing steam obtained aqueous bottom product can decrease, the essential

must therefore contain less NH ₃ and H ₂ S than the original

H ₂ S and NH _{3 are} treated further, otherwise the liehe aqueous solution in line 11. Part of the

Process objective is not achieved. This becomes 30 water through the line 26 and the heater 27

achieved- that the condensate is conducted in the same way to a high temperature at the bottom of the

treated like the loading, d. H. to generate by return column 24a and rising vapors,

guidance in the process. In this way, an amount of NH ₃ and H ₂ S rise at the top of the column 24a

obtain the NH ₃ and H ₂ S concentrations in the side-enriched vapor stream 28 leading to

current to the high concentrations that the formation of 35 weight basis more NH ₃ than H ₂ S in a ratio

facilitate the enriched steam flow. This contains that usually not very different from

that is, the higher the H ₂ S and NH ₃ concentrations that prevailing in line 23. This NH ₃ -H ₂ S-

In these streams are, the smaller the amount 'enriched stream will concentrate its

of the returning condensate. Ammonia content in the distillation section 24b in

The invention will now be based on the drawings 4 ° countercurrent contact with the at the top of the

explained in more detail. Section 24b introduced through line 30

F i g. 1 show a flow diagram for the implementation of the liquid brought. A flows in through the line 30

method according to the invention. In this embodiment, the larger part of the section 24b to section

form is the process with two distillation columns- 24a downward flowing liquid. This part in

NEN carried out (variant b); 45 line 30 is through the heat exchanger 32

F i g. 2 shows a flow diagram and explains a cooled one. The degree of cooling and the speed

Execution of the invention, in which a single distillation of the liquid circulating through the line 30

tion column used and from the speed in the middle part are controlled so that in line 29 a concentrated

side stream withdrawn by partially condensed steam stream with high NH ₃ and H ₂ S content

A concentrated NH _{; 1} -containing vapor stream 50 is formed. In particular, the steam in line contains 29

is formed (variant a); into the NH ₃ and H ₂ S in a ratio that is usual

F i g. Figure 3 is a two column flow sheet of that not very reproduced in lines 28 and 23; after that, a greater part of the divorce will be. The water content in line 29 is, however, by partial condensation of a concentrated by regulating the temperature at the top vapor stream with high NH ₃ - and H ₂ S content ER- 55 end of the portion 24b in a controlled concentrator detainee cold condensate is reduced to form the concen- tration . The NH ₃ -concentrated vapor is used in trated vapor in the second column, line 29 is then partially condensed in the condenser 33 while the smaller part of the condensate is condensed in the first. A condensate is formed in line 34, which is led to the column; that on a weight basis more NH ₃ than H ._> S and im

F i g. 4 gives an embodiment example for the essential 60 the entire, originally in the stream 29

drive with a column again. contained H ₂ S contains; as uncondensed parts

The figures are explained below. go in line 35 NH ₃ vapors, which are essentially

According to FIG. 1 is borrowed _{containing NH 3} and H ₂ S which are free of H ₂ S. In the embodiment shown

aqueous solution in line 11 divided into three parts approximately form the NH ₃ vapors further thereby

and fed into lines 12, 14 and 15. The part 65 cleaned that one could reduce the pressure by means of the compressor

in line 12 is increased with recirculated condensate 41 36 and the vapors through under high pressure

combined, which has a much higher content of NH ₃ and the line 37 to a partial condenser 38

H ₂ S has. The combined lead led in line 13, in which a large part of the remaining water

7 8

is condensed. The condensate obtained in lei column 17, z. B. through line 42, withdraws, in device 39 contains more NH ₃ than H ₂ S on a weight basis, a heat exchanger 43 cools and passes into one and the greater part of the remaining H ₂ S in settling tank 44. The oil will then concentrate on the vapors in line 35, causing NH ₃ vapors to concentrate at that point. High fineness separated can be obtained in line 40. The 5 and through line 46 can be removed. The oil-free condensates 34 and 39, the NH ₃ and essentially aqueous solution are returned through line 45 into the entire, previously in the aqueous bottom product of the distillation column. The place at column 17 and through line 25 to which the oil separation system is attached, does not _{contain removed H 2} S, are combined and depends on the type of oil. If, as in Fig. 1 im form the reflux condensate 41. As above, the upper part of the column is attached, it has been described, this reflux condensate is combined with the additional purpose of regulating the top temperature of the fresh feed and supporting it in the distillation temperature.

tion column 17 introduced. In the case of the in FIG. 2 illustrated embodiment

In the case of the in FIG. 1 shown embodiment is an aqueous _{solution containing NH 3} and H ₂ S, the section 24b can be placed directly on the Ab- 15 through the line 51 in a single distillation section 24a and with this a single column 52 is introduced, the distillation column operated under excess pressure form. In this case it would. At the top of this column 52, a _{stream 28 essentially enriched with NH 3} —H ₂ S is drawn off, not actually borrowed NH ₃ -free, steam-containing sulfur, but rather forms the vapors which are drawn off through line 56. The temperature rise in the bottom of section 24b , 20 temperature at the top of column 52 is so low from the liquid, e.g. B. through line 30 to maintain that the steam has the desired purity. Cooling and recycling to the upper end of the A wash water stream is withdrawn through line 57 in the column. The section 24Z> acts at the upper end of the column introduced, essentially as a partial condenser, in which the removal of NH ₃ is supported and in order to be controlled to conditions so that an NH ₃ 25 cool. From the bottom of the column is formed by the concentrated vapor and a condensate, which is withdrawn in line 53 an aqueous bottom product, section 24a is returned, the only non-contaminating amounts of H ₂ S and NH ₃ so that the uncondensed NH _{Contains 3} concentrated. The column is heated in that a vapor in line 29 contains essentially the entire portion of the _{bottom products via line 54 by means of H 2} S, which previously leads a heater 55 in the bottom product of the first 30. A side stream is included from column 17 (lines 20 and 23) and the column was withdrawn through line 58 at such a point that the aqueous bottoms product in line 25 does not. he was removed more on a weight basis. The steam in line 29 contains an NH ₃ as H ₂ S contains. This side stream becomes the amount of water controlled _{with respect to the NH 3.} Formation of a concentrated NH ₃ -containing vapor

Typical and preferred process conditions in the current in the condenser 59 under such conditions referring to the embodiment according to FIG. 1 include gen partially condensed that the concentrated steam the application of overpressures in the columns 17, flow in line 61 a controlled water content 24a and 24b, which is preferably in the range between and the condensate in line 60 more NH ₃ than H ₂ S about 1, 4 and 10.5 atmospheres and rarely contains more than 28 atmospheres. The concentrated steam flow in line 61 will be. The temperature at the upper end of 40 is then partially condensed in the condenser 62. Column 17 is below about 38 ° C and preferably and yields NH ₃ vapor as the uncondensed portion at about 15.5 ° C. The temperature at the bottom, which is essentially free of H ₂ S and through the column 17, is essentially withdrawn through the conduit 63, and is determined as the condensed pressure and is between about part water, the NH ₃ and essentially that is 100 and 230 ° C, preferably between about 135 and 45 total H ₂ S of the concentrated stream in line 61 185 ° C. In general, the pressures are contained in column 24a. The condensate (line 64) is mixed with the and the temperature at the bottom of this column some condensate of the line 60 and forms.ein lower than in column 17, but are in the reflux condensate in line 65, the same order of magnitude for recovery. Higher pressures in that of the H ₂ S and NH _{3 contained} in it in the distilla column 24a are indeed to achieve very pure 50 tion column is recycled. Streams 64 and NH _{3 are} advantageous with less recirculation. It can be operated at various points in the distilla but under conditions in which the ionic column is recycled or combined in the manner shown in the low pressure steam applied in the heater and preferably above. that can be. The partial condensations are returned to the column at the point at which the condensers 33 and 38 are preferably carried out at 55 at which the side stream 58 is withdrawn.
Temperatures from 15.5 to 65.5 ⁰ C to a case in F i g. 3 illustrated embodiment

Allow cooling with water. The previously prepared an aqueous solution of NH ₃ and H ₂ S is broken down into its given preferred ratios of NH ₃ to H ₂ S constituents by referring to the _{distillation column 85 operated under pressure and NH 3} concentrations in concentrated vapor overpressure on the condensation in this temperature 60 H ₂ S strips off. At the top of the column there is a low temperature range. Maintain temperature to essentially

If the aqueous solution can be obtained by washing a pure H ₂ S vapors while the temperature is high at the bottom of _{the column 85 containing hydrocarbons containing NH 3} and H ₂ S, so that the tio'nsstromes can be obtained some dissolved aqueous bottom product containing more or entrained oil on a weight basis. To prevent 65 NH ₃ containing as H ₂ S is formed. The stripped aqueous that this oil appears in the product, it can be in the bottom product near the top of F i g. 1 can be removed by feeding a second distillation column 92. The one liquid stream from the first distillation second column 92 is also under excess pressure

operated at a high temperature at the bottom, so that the bottom product obtained is water which is essentially free of NH ₃ - and H ₂ S. The vapor stream 100 with a high NH ₃ - and H ₂ S content is in the second column 92 by partial condensation (condenser 101) of the above-mentioned vapors at a temperature which is considerably below the temperature of the vapors withdrawn above, and by recirculation of the Most of the condensate obtained (line 105) received as reflux in the upper end of the column 92. In this way, upwardly flowing vapors are _{concentrated in NH 3} below the top of the column 92, the vapor withdrawn at the top, when it is partially condensed, yielding an uncondensed portion which consists _{predominantly of NH 3.} The other smaller part of the condensate (line 81) is returned to the distillation column 85 . In the embodiment shown, the non-condensed portion is again partially condensed in order to separate off _{essentially pure NH 3 vapors.}

example 1

According to FIG. 3 is z. B. used an aqueous solution containing 4.4 percent by weight H ₂ S and 3.1 percent by weight NH ₃ , which was obtained by washing a product stream obtained in a hydrogenation process and containing hydrocarbons, hydrogen, ammonia and hydrogen sulfide. The solution is passed via line 75 to degassing and oil settling drum 76 . The dissolved, released gases are removed via line 77. The entrained separated oil is removed through line 78. The aqueous solution is withdrawn through line 79 and a major portion of it is combined with the recycled condensate (line 81) in line 82 to form a feed. This is preheated in the heat exchangers 83 and 84 and then introduced into the H ₂ S stripping column 85 at about 127 ° C. The condensate (line 81) consists of about 50 percent by weight of NH ₃ and 16.5 percent by weight of H ₂ S. The remainder is water. It Maecht about 8 ° / ₀ of the in line 82 (-sensitive feed from. As b shown, a smaller portion, ie approximately one quarter of the aqueous solution in line 79 via line 80 at a low temperature in the column 85th Column 85 is operated at about 8.4 atmospheres and a bottom temperature of about 160 ° C., which is maintained by introducing part of the bottom product drawn in via line 86 and heated in heater 87. The bottom product from column 85, which passes through line 88 is withdrawn, contains about 1 percent by weight H ₂ S and 6 percent by weight NH _3. The vapors withdrawn at the top of column 85 consist essentially of H ₂ S, which is only 0.1 percent by weight H ₂ O and less than ICO parts / million NH _3. They are withdrawn through line 89 at about 15.5 ° C. The lower temperature is maintained with chilled water at about 7 ° C. introduced into the top of the column through line 90. The bottom product in L Zeitung 88 is cooled in heat exchanger 84 and then introduced at about 13O ⁰ C in the Ammoniakabslreifkolonne 92nd As shown, a minor portion of this stream can be withdrawn through line 91 which can be used as a scrubbing solution to absorb additional H ₂ S from a stream exiting a reactor, not shown, and flows back through line 75 into the process. The column 92 is operated at a pressure of about 4.2 atmospheres and a ^{bottom temperature of about 153 0} C, which is maintained by leading part of the bottom products through the line 95 and the heater 94 and then at the bottom of the column in this returns. As a bottom product, water is withdrawn through line 95 , which is not

ίο contains more than 0.01 percent by weight H ₂ S and not more than 0.03 percent by weight NH ₃ . As indicated, the hot bottom product in line 95 is used to preheat the feed solution in heat exchanger 83 and then passed through cooler 97 by pump 96. Part of the chilled water. is passed through line 90 and further cooled in heat exchanger 117 in order to generate the low temperature at the top of the column and to prevent the transfer of water and ammonia.

The remainder of the water in line 95, which is essentially the net amount of the input through line 75. led water is deducted for reuse or removal, as the case may be.
A concentrated steam stream consisting of about 57 percent by weight of NH ₃ , 14 percent by weight of H ₂ S and 19 percent by weight of H ₂ O is thus obtained as the top product in line 100 at about 115.degree. When cooled to about 38 ° C at 3.5 atm by passing through heat exchanger 101, 85% of this vapor stream condenses and is collected in drum 102 . The condensate is withdrawn through line 103 and returned by pump 104 partially through line 81 (about one third) and 82 into column 85 and partially through line 105 (about two thirds) as reflux for column 92. The not The condensed portion consists predominantly of NH ₃ and contains about 1.6 percent by weight H ₂ O and about 0.8 percent by weight H ₂ S. It is drawn off through line 106 . For further cleaning, the uncondensed part is introduced into the washer 108 via the line 107. In the scrubber 108 , a low temperature of about 7 ° C. is maintained by supplying essentially pure NH ₃ at a temperature of about "-1 ° C. from line 109 _{to the steam. The NH 3} in line 109 has partially evaporated, but essentially Its low temperature is obtained by expanding higher pressure liquid NH ₃ through valve 110. A strong liquid circulation is maintained in scrubber 108 by drawing liquid from the bottom through line 111 and by pump 112 into line 113 into the The net amount of condensate obtained by cooling the steam in line 106 to the lower temperature of scrubber 108 is withdrawn through line 114 and returned to one of the distillation columns, e.g., as shown. to the top of column 92. Under the conditions of the example, this stream in line 114 consists of 73% NH ₃ , 10 _{% H 2} S and de The remainder is water and is less than 10% of the steam in line 106. The steam emerging from the scrubber in line 115 thus consists essentially of pure NH _a , which is about 0.24 percent by weight of H ₂ O and less than 100 parts / million Contains H _{2 S.} This ammonia vapor is in line 119 with part of the ammonia vapor

from the line 116 combined. The mixture in line 119 is brought to a pressure of approximately 14.0 atmospheres in compressor 120 , condensed in heat exchanger 121 at approximately 38 ° C., and the condensed liquid ammonia is recovered in drum 122. The ammonia is continuously drawn off from this drum 122 through line 123. As previously described, a part is depressurized through the valve 110 into the line 109 . Another portion is depressurized through valve 118 to produce cooling ammonia in line 116 which is used in heat exchanger 117 to cool the water in line 90. The net recovery of NH ₃ takes place through line 124. Thus the NH ₃ , H ₂ S and H ₂ O are obtained separately in really quantitative amounts and essentially free of the other constituents.

If z. B. 26195 hl heavy California gas oils, which contain nitrogen and sulfur compounds, are converted into lower-boiling fuels by combined catalytic hydrofining and catalytic hydrocracking per day, become about 25.58 t / day H ₂ S and about 11.8 t / day Generates NH _3. The bulk of this NH ₃ and H ₂ S is obtained atm by hydrogenation of nitrogen and sulfur compounds in the Hydrofinierungsstufe at temperatures 315-480 ⁰ C and pressures from 70 to 210, which is used for preparing a purified oil feed to the hydrocracking stage. It is desirable to _{quantitatively remove the NH 3} from the purified oil because the NH _{3 has} an adverse effect on the hydrocracking catalyst. It is also desirable _{to remove the NH 3} and H ₂ S in order to increase the purity of the hydrogen recycled to the hydrofining stage and the hydrocracking stage.

Example 2

The stream emerging from the hydrofining reactor, which is about 85,000 to 113,000 m ³ / hour. Comprises hydrogen and 26195 hl / day of hydrogenated oil, is cooled to about 55 ° C. at a reactor pressure of about 105 to 140 atü and at 38556 kg / h. Washed water containing 0.034 ° / ₀ H ₂ S and 0.12 ° / ₀ NH ₃ . In this way, an aqueous solution is obtained which contains 2.3 percent by weight of H ₂ S and 1.2 percent by weight of NH ₃ . The aqueous solution is separated from the oil and gas and then contains only traces of NH ₃ . It is then fed into a distillation column in which there is a pressure of about 6 atmospheres. At the bottom of the column a temperature of 154.5 ° C and at the top of the column a temperature of. Maintain 15.5 ° C. A larger portion of the aqueous solution is preheated to about 115.5 ⁰ C below the center in the column inserted, a smaller part above the center with a temperature of about 38 ° C and an even smaller part, about 2 ° / o "with a temperature of 7 ° C at the top. A recycle stream (condensate) in an amount of 5V4 ° / ^he od feed is with the preheated to 115.5 ° C part: of the feed introduced into the column. This reflux stream consists of the condensate obtained by the partial condensation of the concentrated vapor stream formed in the manner described below with a high NH ₃ and H ₂ S content, and contains 38 percent by weight of NH ₃ and 7.4 percent by weight of H ₂ S. Vigorous stripping in the distillation column gives an aqueous bottom product which contains 3 percent by weight of NH ₃ and 0.4 percent by weight of H ₂ S. At the top of the column are 907 kg / hour. Stripped H ₂ S vapors containing only about 0.15 weight percent H ₀ O and less than 100 parts / million NH ₃ .

The aqueous bottom product obtained at 154.5 ° C the first column is cooled to 115.5 ° C and fed to a second distillation column, which at

ίο about 2.1 atü is operated. This column contains 25 trays. The temperature at the bottom of the second column is 134.4 ⁰ C, and under vigorous boiling is obtained at the bottom of an aqueous product containing 0.12 weight percent of NH ₃ and 0.034 percent by weight H ₂ S contains. It is recycled and used to wash the stream exiting the reaction zone.

At one point in the second column above the feed, an H ₂ S- and NHa-enriched vapor stream is obtained which consists of 40 percent by weight of NH ₃ , 5 percent by weight of H ₂ S and the remainder of water. Liquid is drawn off from the plate above this steam flow at a rate of about 13.45 hl / min, at a temperature of 115 ° C. This liquid stream is cooled to 65.5 ° C. and returned to the upper end of the second distillation column, namely three to five trays above the withdrawal product. Since this liquid flows downwards in countercurrent to the upwardly flowing H ₂ S and NH ₃ -enriched vapor stream, the vapor stream, based on the H ₂ O, is concentrated in the ascending vapor of NH ₃ and H ₂ S, so that at the head end the second distillation column a vapor stream is obtained which contains 49 percent by weight of NH ₃ and 6 percent by weight of H ₂ S at a temperature of 107 ⁰ C and a pressure of 1.7 atm. This concentrated steam stream is cooled to 38 ° C at 1.4 atm in order to achieve partial condensation of the steam. The condensate obtained contains 38 percent by weight of NH ₃ and 7.4 percent by weight of H ₂ S in H ₂ O. The uncondensed part consists of 96.8 percent by weight of NH ₃ , 2.9 percent by weight of H ₂ O and 0.3 percent by weight of N ₂ S. The NH ₃ vapor stream is then brought to a pressure of 5.3 atmospheres and again cooled to 38 ° C. in order to achieve a further partial condensation. A small amount of condensate containing 52 percent by weight of NH ₃ and 4.3 percent by weight of H ₂ S is obtained. The condensates are combined and passed into the first column as the aforementioned reflux stream. The 444.5 kg / hour obtained. uncondensed vapor from this partial condensation consist essentially of. NH ₃ and are composed specifically of 99 percent by weight NH ₃ , about 1 percent by weight H ₂ O and less than 0.1 percent by weight H ₂ S. Although this NH ₃ vapor product is suitable for almost all purposes, it is further washed by washing with 113.5 l / day sodium hydroxide solution at 25 ° Be in order _{to remove the small amount of H 2} S as sodium sulfide and also to partially dry it to achieve the NH _3. This gives 422 kg / hour. NH _? -Product that, consisting of 99.5% NH ₃ , contains only a trace amount of sulfur. ■

Both the NH ₃ and the H ₂ S are thus obtained separately in quantitative yield with purities of 99% or more. The quantitative extraction is possible because the soil product is made from

the second column, which contains non-contaminating amounts of NH ₃ and H ₂ S, is recycled to absorb further amounts of NH ₃ and H ₂ S and is then worked up. There is no sewage that is drained. If the bottoms were discharged as non-polluting waste water, the NH ₃ and H ₂ S yields were 90 and 99%, respectively, under the conditions used in the previous example. A more complete recovery of the NH ₃ would be possible because the aqueous product leaving the process could be purified more completely by applying a more vigorous stripping treatment in the second column.

Example 3

An aqueous stream of about 45000 kg of water with more than 1800 kg of hydrogen sulfide and more than 2000 kg of ammonia is introduced into the process at a temperature of 66 ° C. This aqueous solution is with reflux condensate of about 5300 kg / hour. ao combined, which consists of about 50% ammonia, 14% hydrogen sulfide and 36% water. The combined feed is brought into heat exchange with the bottom product of the single distillation column and is thereby heated to about 116.degree. In the as distillation column, hydrogen sulfide is then stripped from this stream, the heat being supplied at the foot of the column; A cooled portion of the aqueous solution (7 ^° C.) is fed in at the top of the column. _{In this way, an H 2} S stream of high purity can be drawn off at the top of the distillation column. A vapor side stream is withdrawn from the middle part of the column at about 143 ⁰ C. This contains about 34% ammonia, 6.5% hydrogen sulfide, the rest water. The side stream is partially condensed, giving a liquid stream of about 4800 kg of water per hour, together with about 0.6% ammonia and 0.2% hydrogen sulfide. The vapor stream obtained in this partial condensation consists of about 3800 kg of ammonia, 1950 kg of water, and 725 kg of hydrogen sulfide. This concentrated, NH ₃ -containing stream is partially condensed, giving an NH ₃ vapor stream of relatively high purity and a condensate , which contains ammonia and a substantial amount of hydrogen sulfide. The condensate is returned to the distillation column. The aqueous bottom product of the column contains 2 percent by weight ammonia and 0.25 percent by weight hydrogen sulfide. Fig. 4 illustrates this example.

Claims (5)

Patent claims: 1. A process for the recovery of NH ₃ and H ₂ S from these containing waters, in particular those which are obtained in the refining of petroleum products, by rectification in several process steps, characterized in that in the first process step from a column essentially ammonia-free H ₂ S distilled off at overpressure up to 28 atmospheres, whereby one _{a) either withdraws a side stream containing more NH 3} than H ₂ S on a weight basis from the column, from which essentially the main proportion of water vapor is partially condensed, whereupon a concentrated NH ₃ -containing vapor stream of water content controlled by temperature adjustment, which at least the l , 5 times the H ₂ S weight is obtained and the aqueous bottom product is drained off, or one b) the bottom product obtained in the first column, which _{contains more NH 3} than H ₂ S on a weight basis, is fed to a second column operated at overpressure up to 28 atmospheres, from the bottom of which water is practically withdrawn, and from which one of NH ₃ and H ₂ S-enriched vapor stream is withdrawn and this is concentrated at an overpressure of up to 28 atm in the upper part of the second or in a third column (the water content being controlled by adjusting the temperature, and in the last process stage the vapor stream obtained in this way with a high NH ₃ and H ₂ S content is a partial. Subjects to condensation, the resulting condensate, which on a weight basis contains more NH ₃ than H _{2 S and essentially all of the H 2} S present in the concentrated vapor stream, returns to the first column and, as a non-condensed portion, is essentially H ₂ S-free Ammonia wins. 2. The method according to claim 1, characterized in that in the case of variant b one gives up larger proportion of the condensate of the last stage of the process at the top of the second column and returns the smaller portion of the condensate to the first column. 3. The method according to claim 1, characterized in that in the case of variant b, the non-condensed in the partial condensation, ₂ S-free, water vapor-containing ammonia is again partially condensed in \ substantially H, pure gaseous ammonia evaporated and the condensate in one of the columns is recycled. 4. The method according to claim 4, characterized in that in the case of variant b hydrogen sulfide is stripped so far in the first column that the bottom product of this column contains more NH ₃ than H ₂ S in a weight ratio between 4 and 10. 5. The method according to claim 1, characterized in that in the case of variant b, the water vapor content of the concentrated H ₂ S and NH ₃ -halligen steam flow is set to values between 30 and 75%. 1 sheet of drawings