DE1948427B2 - PROCESS FOR THE SEPARATE RECOVERY OF HYDROGEN SULFUR AND AMMONIA FROM AQUATIC SOLUTIONS - Google Patents

Description

rnd which separates from the wastewater streams, eat the strippers are kept cleaner. Enthaiü Feed streams dirty water from liquid * "catalytic cracking units, <o enables one -ιΓ j: about 24 hours or more, plus one

table cracks, g

_for about 24 hours or longer also one of hydrocyanic acids, which in the tö liht d id

? MINATION of Cyanwasse, V "* ⁸ _Sc hmutzwasserströmen easily are present, ^iftl thiocyanate The conversion of Cyanwasse ··. -

r thiocyanate helps prevent corrosion

* 'To reduce the number of participants to a minimum in the vv

A can ¹⁶⁰ h in recycling of NH ₃ -Überkopf-

Hnsats large amounts of H ₂ S in the circuit

Stir feed streams without excessive

c Vriust * in light hydrocarbons

Y / nder the hydrogen from the degassing stage

'"ι! delt be. Under most conditions it is

ι? ς content of the gases from the emission stage very high

^{& tX} A The degasser levy can be used as a refinery

f «can be used as there is only one very

• The amount of SO is reduced by burning the gases

^gen Ü ⁸ ? "irH" Air pollution is therefore essential

^llC i Tonn a plurality of H ₂ S and / or NH ₃ ent-H η currents according to the invention behaving a _he d _s however, it is expedient to provide rrRnHer a device which ensure ί ^η Since, and mixing the NH ₃ - enough y ^ sats and allow the net feedstock for the vor process. For example, einchenbehälter can without extracting the light SäSSff "or a degassing Fntfernen the light hydrocarbons used from GurgleGuts one of the feed streams n Früner ^ ar a degassing necessary η Sten λ cases to loss of H" S EZausgab n ".to removing H ₂ S resulted from outlawing hydrocarbons. the H ₂ S r hit the net feed streams may be at the new I _n the drawing the scheme of a preferred embodiment is shown of the method, wherein two degassing stages are shown.

An aqueous feed stream containing H ₂ S and NH ₃ is fed to the device via line 1. This stream is particularly expediently obtained by mixing or contacting the material flowing out of a hydrocracking reactor at a pressure of about 140 atmospheres with water. This contact is therefore carried out in order to remove ammonia and H ₂ S from the material flowing out of the hydrocracking reactor. Since the latter contains substantial amounts of hydrogen and light hydrocarbons, the aqueous solution that forms is composed of hydrogen and light hydrocarbons _{, in addition to H 2} S and NH _3. · 1 f

The aqueous solution is combined with the recirculated NH ₃ -rich aqueous stream, u which flows from the overhead material of the ΝΗ, -Stnppers. The NH ₃ -rich aqueous solution is fed into line 26 in the circuit.

An H ₂ S-rich stream obtained from the overheads of one of the stripping distillation columns used to remove light hydrocarbons from the product exiting the hydrocracker is fed via line 2. Among the many H ₂ S-rich streams that can be processed are streams derived from liquid steam stripping hydrocarbon streams from hydrotreating or hydrofining processes. These liquid hydrocarbons contain H ₂ S and light hydrocarbons, which are removed or distilled off. These overhead vapors from stripping or distillation columns obtained from the stopping process contain substantial amounts of H ₂ S, which dissolve to a significant extent in the water that b. det, when the JUbertapp material is partially condensed. Often this will be

H.S i

is then an H ^

-Gasun ^ keeps _{the H drotreating} -

ι, Dr'ocke, for example 0.7 to 7 a.ü in ^

Solution are dissolved, one leads advantageously to the Vu K "in such a way that these currents with the watered through the low-pressure degasser

Between 0.07 and 0.7 atm.

after An κ u "s de; Krj

Ken onernaiL. ,. stripper

Konc ensa-ren des Übujcop ^^ tena ^ _{mk rfen}

b ¹ ^ ¹ ^^^ f ^ _be , lower HS-Partial-Ä Ätam I ** »». ^ reic, to ^{be able to} -

The combined streams 1, 2 and 26 are fed into the high-pressure degasser 4 via line 3. _{In order to achieve low H 2} S contents in the exhaust gases, the high pressure degasser is preferably kept at a pressure of about 13 atmospheres and a temperature of about 27 ° C. _{The H 2} S content in the exhaust gases increases as a result of lower pressures and higher temperatures. Light hydrocarbons and hydrogen are removed through line 5 from the top of the high pressure degasser vessel. If a pressure of about 7 to 14 atmospheres and a temperature of 27 to 38 ° C. is used, the H ₂ S content of stream S is generally below 3 percent by volume. If the process according to the invention is carried out at high pressure and low temperature in the high-pressure degasser, the H ₂ S content can be kept between about 0.1 and 2.0 percent by volume. In this way, stream 5 has a very low H ₂ S content and is generally suitable as a refinery fuel gas. The partially degassed aqueous solution is withdrawn through line 6 from the bottom of the high pressure degasser.

An aqueous solution of H ₂ S, NH ₃ and small amounts of dissolved hydrocarbons, obtained as overhead condensate from a hydrocarbon stripper operating at an overhead pressure of about 3.5 atmospheres, is introduced through line 7. The combined aqueous streams in lines 6 and 7 are passed through line 8 to the low pressure degasser 9. The low pressure degasser is preferably maintained at a pressure of about 0.14 atmospheres. Light hydrocarbons are withdrawn from the low pressure degasser in line 10 and an aqueous solution of H ₂ S and NH ₃ is withdrawn from the bottom of the degasser via line 11. The H ₂ S content of stream 10 is generally less than about 4 percent by volume when the process according to the invention is used. The percentage of H ₂ S in the low pressure degasser exhaust gases can be further reduced, for example to a range for the high pressure degasser, by increasing the amount of NH ₃ -rich condensate, decreasing the temperature and increasing the pressure. In most cases, most of the exhaust gases, mainly hydrogen and methane, are vented into the high pressure degasser. Typically, about 80 to 90 percent by volume of the dissolved gases will drain into the high pressure degasser. Only a relatively small amount of H ₂ S is therefore withdrawn from the low-pressure degasser with the exhaust gases. As a result, almost all of the hydrogen sulfide remains in the aqueous phase so that it can be recovered _{as an overhead stream from the H 2 S stripper.}

The aqueous solution from the low pressure degasser is introduced into the expansion tank 12, where a Residence time of preferably 3 to 24 hours is provided. The container 12 should have a floating layer or Have an inert gas cover. If air is allowed to come into contact with the aqueous solution come, the hydrogen sulfide oxidizes and forms free sulfur.

The aqueous solution is drawn off from the expansion tank through line 13 and introduced into the H ₂ S stripper 14. As a result of the supply of heat to the bottom of the H ₂ S stripper, hot, upward-flowing vapors develop, which serve to strip the hydrogen sulfide from the aqueous solution. A cold water stream is introduced through line 16 into the top of the H ₂ S stripper to create a downward flowing aqueous stream which serves to fractionate the ammonia from the hydrogen sulfide. A relatively pure H ₂ S stream is withdrawn through line 15 from the top of the H ₂ S stripper. The NH ₃ content in this H ₂ S stream is usually less than 2 percent by weight, usually as low as a few tenths of a percent; preferably the HgS stripper conditions are maintained such that an NH ₃ content of less than 100 parts / million, for example 10 to 30 parts / million, is obtained.

An aqueous solution rich in NH ₃ but still containing substantial amounts of H ₂ S is withdrawn through line 17 from the bottom of the H ₂ S stripper. This stream is directed to the NH ₃ stripper 18. By supplying heat to the bottom of the NH ₃ stripper, hot gases flowing upwards are generated. These serve to remove NH ₃ and H ₂ S from the

ao to strip aqueous solution passed to the NH _{3 stripper.} A purified water stream is withdrawn from the bottom of the NH ₃ stripper through line 19.

A vapor stream of H ₂ O, NH _3, and H ₂ S is withdrawn from the top of the NH ₃ stripper through line 20. The process conditions in the NH ₃ stripper are controlled in such a way that the _{amount of H 2} O in the vapor stream in line 20 is regulated so that when this vapor stream partially condenses in the condenser 21, the liquid condensate that is formed is discharged withdrawn from the condenser through line 22, contains a very large fraction of the H ₂ S present in the overhead system. In this way, the ammonia withdrawn as a gas in line 24 is essentially freed _{from H 2 S.} The H ₂ S content in the NH ₃ gas is generally less than about 1 to 2% and can be reduced to 0.1 to 0.5 percent by volume H ₂ S. The condensate formed by cooling the NH ₃ stripper overhead gases in the condenser 21 is rich in NH ₃ . Typically the ratio of NH ₃ to H ₂ S in the condensate withdrawn from reflux drum 23 through line 25 is between 10: 1 and 2: 1. The ratio of NH ₃ to H ₂ S is preferably 3: 1

♦ 5 to 6: 1 on a molar basis. A portion of this NH ₃ -rich condensate is allowed to flow back through line 27 to the NH ₃ stripper in order to obtain a cool, downwardly flowing liquid in the upper part of the NH ₃ stripper. After the process according to the invention, a second amount of the NH ₃ -rich condensate! recirculated through line 26 to remove the net charge material passed through lines 1 and 2 to the process. to be united.

According to the invention it is considered expedient _{to regulate the amount of NH 3} -rich condensate that is recycled in the circuit and the ratio of NH to H ₂ S in the circuit so that the ratio of NH ₃ to H ₂ S is the united currents, di

fed to the high pressure degasser is at least 1.1: 1.0 on a molar basis. For streams containing more than 1 or 2% dissolved H ₂ S and NH ₃ , it is advisable to use more NH ₃ -rich circulating condensate, so that the ratio

from NH ₃ to H ₂ S (calculated as separate species is at least 1.2: 1.0. In many cases, it may be correct to have one and a half to about five times as much NH as WS .

example 1

This example has illustrated the advantages obtained when the temptation of the present invention is applied to the treatment of aqueous streams containing large amounts of H ₂ S relative to NH _{1 in} addition to light hydrocarbons and odor hydrogen, in 1 olpc of high pressure contained in the aqueous stream dissolved.

a) Fine solution of about 446 kg of H ₂ S, 234 kg of NH, and about 21.5 liters of hydrogen plus light hydrocarbons. dissolved in 126 kg of H ₂ O was obtained by washing a material emanating from a hydrocracking actuator with water. The stream emerging from the hydrocracking reactor had a temperature of about 121 ° C. and a pressure of 87.9 atmospheres. This aqueous stream was fed into the apparatus via line 1, with no ammonia-rich circulating condensate from the NH ₃ stripper 18 being fed into the high-pressure gas gasifier 4. However, some of the NH.j-rich overhead material from 18 became the H _{2 directly} S-stripper recirculated.

An aqueous solution of 12,700 kg H ₂ O, 198 kg H ₂ S and only trace amounts of NH ₃ is obtained as an overhead indentate from a fractionation column in the fractionation section of the hydrocracking unit. This stream is introduced into the process through line 2. At this first stage the NH _; , -richc condensate from the upper part of the Nfi _r stripper circulated directly to the H ₂ S stripper. The above streams and the streams obtained, which correspond to the numbered streams shown in the drawing, are summarized in the table below:

Table 1

Si rom no. H ₂ O (kg / h) H ₁ S (kg / h) NH ₃ (kg ^; h) 1 ! 2614 446 234 2 12700 198 0 3 25 320 644 234 5 0.90 177 0 8th 25 319 467 234 10 0.45 4.54 0 Il 25318 463 234 15th 2.72 458 0 24 1.36 2.27 226

Current is 26.?: the total mol / ahl for H., S is 7. so that a molar ratio of NIi ₁ 7ii HoS of about 3.0! results. _{There is a sufficient amount of MI in the NH 2} cycle through line 26 so that the resulting combined syrups in line 3 have a ratio of NH 3 / uH, S on a molar basis greater than 1.0. Preferably the ratio of NH., ? \\ H., S in stream 3 is kept above 1.1. In this example, the ratio of NH to H ₂ S is L? " ¹ The feed streams and the streams obtained are summarized below:

labe! Ic II H-O (kg'hl H ₁ S (kg / m NH, (kg'M Stream no 12614 446 234 1 12 700 19S 0 2 258 67 202 26th 25600 711 435 3 0.45 0.90 0 5 25602 710 436 8th 0.45 0.90 0 10 25600 70S 436 11th 2.72 638 0 15th 1.36 2.27 226 24

40

45

50

The combined streams 5 and 10 contain approximately 21,523 liters of hydrogen plus light hydrocarbons. K) When using the method according to the invention, identical streams 1 and 2 are conducted in accordance with the method explained schematically in the drawing. A portion of the condensed overhead material from the NH ₃ stripper 18 is recirculated through line 26 to the high-pressure degasser. This cycle stream is rich in NH ₃ relative to H ₂ S. The number of moles for NH ₃ in the cycle - The combined streams 5 and 10 contain about 21,523 liters of hydrogen plus light hydrocarbon gases.

As can be seen from the comparison of streams 5 and 10 in Table II with streams 5 and 10 in Table 1. the H _s S losses are drastically reduced. When using the process according to the invention, the H..S losses are reduced from 181 kg h (Table 1) to 1.81 kg / h (Table 11). The method according to the invention thus brings about a reduction in the Vi ₂ S present in the withdrawn gases by a factor of 100 in this example. The recirculation of the ΝΗ, - straight overhead condensate from the NH ₃ stripper is therefore of particular advantage if feed streams are supplied which have relatively large amounts of H ₁ , S in comparison to NH 3. If the HoS concentrations in the net feed streams are lower, the benefit is correspondingly reduced, but in general the H ₅ S loss is reduced by a factor of at least five. Furthermore, the recirculation in the circuit of the NH ₃ -rich condensate still serves to a certain extent for this purpose. Retain hydrogen sulfide in the aqueous phase so that it can be recovered through line 15 as a single product stream. Furthermore, the recirculation of the NH ₃ -rich condensate to the degassing section instead of the direct route to the H «S stripper has the very significant advantage that the control _{resistance of the H 2} S stripper and the NH ₃ stripper is improved .

1 sheet of drawings

Claims (1)

The patent proprietor has the problem solved here in Claim: two earlier inventions, their USA patents 33 35 071 and 33 65 374, edited. Neither of the two Process for the separate extraction of sulfur patents shows the proposed here recirculation of hydrogen sulfide and ammonia from aqueous solutions of part of the ammonia stream to a point which is located in front of the degassing _{vessel at superatmospheric pressure H 2 O.} In this, however, lies the H ₂ S and NH ₃ and light hydrocarbons being the essence of the new invention, which do not hold any of the listed, by degassing the light hydrocarbons shows disadvantages. Pressurized water-containing substances. If the method according to the invention is used, it is avoided _{A direct return of the NH 3} stripper stripping of H ₂ S from the no light coal overhead condensate in the circuit to the aqueous solution containing H, S stripping hydrogen is achieved by reducing the pressure and / or achieving improved control and Be-NH ₃ and H ₂ S in a first distillation column, stability of the H, S stripper. In addition, stripping of NH ₃ from the aqueous bottom _{enables the recirculation of the NH 3} -rich overproduct of the first distillation column in an overhead condensate from the NH ₃ stripper to the split distillation column and partial congassing zone H ₂ S in the aqueous phase to withhold the resulting NH ₃ -rich th, while light hydrocarbons and / or overhead gases, with an NH ₃ -rich gas and hydrogen from the aqueous, H ₂ S and NH ₃ containing an NH ₃ -rich overhead condensate, since - the charge is removed in gaseous form,
indicates that one ao the subject of the invention is now a process for part of the NH ₃ -rich overhead condensate of the separate recovery of hydrogen sulfide and the second distillation column in the aqueous ammonia from aqueous solutions, which is recycled in the case of excess solution. atmospheric pressure H ₂ O, H ₂ S and NH ₃ and slightly »· Contain hydrocarbons, through degassing 25 of the light hydrocarbons containing, under Pressurized, aqueous solution by reducing the pressure and / or stripping off H ₂ S from the aqueous solution which does not contain any light hydrocarbons The invention relates to an improved method for dissolving NH ₃ and H ₂ S in a first distillation recovery of H ₂ S and NH ₃ from aqueous solutions 30 column, stripping of NH ₃ from the aqueous of H ₂ S, NH ₃ and light Hydrocarbons below the bottom product of the first distillation column at a pressure above atmospheric, in which the H ₂ S and NH _{3 of the} second distillation column and partial condensate separated from an H ₂ S stripper or an NH ₃ sizing of the resulting NH ₃ -rich overhead stripper are obtained . _{gaseSi WODe} i _an NH ₃ -rich gas and an NH ₃ -rich one In many hydroconversion processes, which occur with overhead condensate, which is characterized by hydrocarbon oils, shale oils, heavy oil _{sands, that part of the NH 3} -rich overhead is used, for which catalytic hydrogenation, condensates of the second distillation column in the hydrofinement process or hydrodesulphurisation and recycling aqueous feed solution.
Hydrocracking are typical examples, will H ₂ S The improved resistance of the H ₂ S stripper will and NH ₃ as a result of a conversion of water largely achieved by the fact that the direct return material with sulfur and nitrogen compounds, which are contained in the circuit of the NH ₃ -rich condensate verdem oil, are obtained. This typical is avoided. Processes are usually liquid coal The NH ₃ -rich condensate instead becomes the hydrogen, the nitrogen and sulfur compounds returned to the degassing zone in the circuit, where it contains a gene, and returned hydrogen-rich gas 45 reaches equilibrium with the net amount of H ₂ S and additional hydrogen at increased temperature stripper or approaches it very closely, temperature and At elevated pressure through a reaction zone, fluctuations in the feed composition, which usually contains a catalyst, are attenuated by an additional residence time, with at least some of the hydrocarbons being vaporized using a residence time of at least five. This gives a mixture of 50 minutes after combining the aqueous streams and evaporated hydrocarbons, hydrogen, H ₂ S before introduction into the H ₂ S stripper. Much; nehr yet ^Un iv tX ^{au 'the reaction zone} escaping gas. The processes and apparatuses used to date for the combined gross feed streams of the recirculation condensate rich in _{NH 3 for the separate recovery of hydrogen sulfide from the NH 3} - and ammonia, which in the listed processes 55 stripper and the aqueous H ₂ S-NH ₃ net feed solution arise, show considerable disadvantages, the elimination of which is achieved. A dwell time of around 3 will be even more. Thus, after the up to 24 hours or longer for the combined, ie gross previously known processes, considerable _{amounts of H 2} S input streams are aimed for. from the aqueous solution, which is necessary for a separate process A residence time for the NH ₃ -rich recirculation recovery of H ₂ S and NH ₃ is to be treated, 60 condensate is lost before the introduction into the H ₂ S-Strippei when the pressure on the aqueous solution is in contrast to the previous process; will struggle to light hydrocarbons and / or those in the circuit of the NH ₃ -rich condensate, the hydrogen, which are dissolved in the aqueous solution of H ₂ S and H ₂ S stripper directly with the NH ₃ stripper connected to NH ₃ remove. Further arise in so that adverse effects in any of these stripper pull the previously for the separate recovery of H ₂ S and 65 ft _o the other stripper affected NH ₃ used methods difficulties could wherein. Attempt to work evenly and consistently. It is also advantageous that the oil to achieve the H ₂ S and NH _{3 stoppers.} Dwell time of about 24 hours or essentially longer