CN85103286A - The steam conversion process of the hydrocarbon of improved low severity - Google Patents

Abstract

Ammonia Process comprises one section (4) and two sections (60) catalyzed conversions, conversion (80 and 90), oxycarbide removes (115) and ammonia synthesis (110), wherein to the poor ammonia recycle of small part to the district (110), handle poor ammonia tributary (134) with partitioning cycle hydrogen rich gas (142), it is improved one's methods and is higher than under about 946 ℃ with 3 to 11 moles of excessive N of % can be provided in temperature out for (1) ₂Air-operated step (b) generate the second stage exit gas have 0.8 volume % methane at least, (2) operate (e) at least in the time can making poor ammonia contain 10 volume % stablize gas; (3) with synthetic gas that contains at least 1.2 moles of % (butt) of generating in (d) and the circulation gas (f) and (g) in the mixture of hydrogen rich gas send to synthetic, thereby make hydrogen loss minimum when separating.

Description

The steam conversion process of the hydrocarbon of improved low severity

The invention relates to the steam conversion process of improved hydrocarbon gas charging, more precisely about the steam conversion process of improved low severity.

In general, the preparation of ammonia comprises and is generally air from nitrogenous source, and hydrogen source, generally can be coal, petroleum fractions or Sweet natural gas, the preparation ammonia synthesis gas.For example, during light hydrocarbon feedstock production ammonia synthesis gas in from the Sweet natural gas to the naphtha range, at first remove gas pollutant hydrocarbon feed gases is purified, for example generate hydrogen sulfide and on the zinc oxide adsorption medium, be adsorbed and from raw material, remove desulfuration (sulphur in the unstripped gas can make downstream catalyst poison) by the sulphur compound shortening.Subsequently pollution-free gas is carried out steam reforming most of hydrogen required when hydrocarbon gas carries out ammonia synthesis will be provided.Conversion is finished by two-stage process, wherein, the mixture of the unstripped gas of steam and purification is at first transformed on the catalyzer in one section convertor, and the gas that the treating part transforms in two sections convertors is introduced two sections convertors to provide ammonia synthesis required nitrogen amount with air then.Generated reforming gas in two sections convertors, it has more substantial hydrogen and more a spot of hydrocarbon.Unstripped gas conversion reaction process resolves into methane, carbonic acid gas and carbon monoxide from hydrocarbon:

And finish i.e. conversion of methane by desired heat absorption with the conversion of these products:

And thermopositive reaction by following:

In one or more shift converters, change the carbon monoxide in the reforming gas into carbonic acid gas and other hydrogen, remove carbonic acid gas with washing method.Crude synthesis gas is further handled to remove carbonic acid gas and the carbon monoxide in the hydrogen-rich gas by methanation, generate ammonia synthesis gas then, approximately contain three parts of hydrogen and a nitrogen in the synthetic gas, be that the stoichiometric ratio of hydrogen and nitrogen is 3: 1 in the ammonia, also have a spot of stable gas in addition.For example, methane, argon and helium.Allow this gas on metallic iron (being generally magnetite) supported catalyst surface by so that make ammonia synthesis gas transform ammonification, and can use other metal oxide to make promotor.Again that ammonia is synthetic by following thermopositive reaction:

The discharging gas of ammonia reactor contains ammonia, unconverted H and N and in ammonia react stable basically gas (particularly methane and argon gas), will discharge gas and carry out the ammonia recycling and contain H with formation ₂And N ₂Cycling stream, this cycling stream can return ammonia reactor with fresh ammonia synthesis gas.

In common steam reforming ammonia process, need to reduce to greatest extent the amount of the no conversion hydrocarbon (methane output (methane slippage)) that leaves convertor.Because H ₂And N ₂Reaction also is retracted as the ammonia product, and methane will concentrate in the ammonia reactor charging, and the major portion of stable gas such as methane are with H ₂And N ₂Circulation also is retained in reactor and the circulation loop.If stable gas build and not on inspection, reactant (hydrogen and nitrogen) dividing potential drop will reduce and speed of reaction is slowed down, this considers it is unwanted from economic angle.In order to prevent this excessive accumulation, usually to remove stable gas, and deliver in the fuel and go.Regrettably, useful hydrogen (and nitrogen) has also lost in scavenging process, generally only contains 10～20% stable gas in the gas of removing.Under higher converter fuel consumption and investment, reduce convertor methane output to greatest extent and this loss can be reduced to minimum.These factors of balance can obtain common design, promptly contain 7～12%(mol, butt in one section convertor discharging gas) alkyl.

Developed the most of hydrogen in the stable air-flow that various flow processs reclaim removing in recent years.These are removed the recovery unit and are based upon on low temperature separation process, transformation absorption or the film diffusion basis.The common ground of these technology is to produce two kinds of air-flows: the hydrogen rich gas of ammonia reactor and the rich stable gas in the fuel are returned in circulation.The selectable method that reduces the hydrogen loss in the scavenging process to greatest extent is that Kellogg (Kellogg) removes the umformer flow process, and it reclaims as hydrogen and nitrogen in the part removing gas of ammonolysis product with second stage ammonia synthesis reactor.No matter use which kind of method,, increased the former conversion of expecting product, thereby make the recovery unit of removing hydrogen in the gas save energy owing to reduced the useful hydrogen that becomes fuel to greatest extent.Under the situation of high energy, remove the unitary investment of recovery this benchmark commonly used and weigh, then there is not obvious variation for the operational condition of installing transform portion.

United States Patent (USP) 3081268(1963) to be about 345～1379 kPas be 3.45～13.79 to cling to so that Outlet Gas Temperature is about 732～899 ℃, pressure to use one section reforming gas of outer flame and highly excessive steam (steam is 4: 8 with the ratio of the carbon mol of unstripped gas), and make 65～85% raw material hydrocarbon change into H ₂And carbon oxides.At this moment total transformation efficiency of hydrocarbon will further be increased to 95～99% in two sections convertors.Two sections convertors discharging gas are handled in shift converter to remove CO, cooled off again and purify the synthesis gas that enters ammonia reactor with formation.

The United States Patent (USP) 3442613(1969 of C.F.Braun company) in the disclosed method, before ammonia synthesis reaction zone, remove excessive methane and argon in the methanator discharging gas by cryogenics, form highly purified synthetic gas, thereby the amount of removing gas in the ammonia synthesis loop is minimized." hydrocarbon processing " (Hydrocarbon Processing) of also having B.J.Grotz work relevant with this patent of Braun, 46 volumes, the 4th phase, " nitrogen " of 197～202 pages (in April, 1967) and B.J.Grotz work, 100 volumes, 71～75 pages (1976) and English Patent 1156002 and 1156003.

At United States Patent (USP) 3441393(1969) in, pul door (Pullman) method that discloses is wherein finished conversion, conversion and methanation step, to form ammonia synthesis gas and to make ammonia reactor discharging gas at NH ₃Middle dilution (about 9.7%NH ₃) must adopt the removing air-flow for fear of stable gas build, thereby the stable tolerance that circulation is entered in the air-flow of reactor is controlled at such limit, promptly unites body (circulation gas and fresh synthesis gas) into and contains 5～20% the stable gas of having an appointment when entering reactor.

United States Patent (USP) 3947551(1976 in Benfield company) in Xu Shu the method, one section and two sections conversion conditions should be controlled like this, even have low methane content (about 0.3%CH in two sections reforming gas discharging gas ₄), carrying out conversion, CO ₂Remove with methanation after, ammonia synthesis gas is sent to circulation gas and is carried out ammonia synthesis reaction.Disclosed UK Patent Application 2017071A(1979 in Monsanto Company) in, containing 2～15%(volume certainly) ammonia synthesis gas of methane generates ammonia, and with H ₂: N ₂Mole ratio is controlled in 2: 1～1: 4 the scope and contains 10～25%NH with generation ₃Reactor product gas.

At the laid-open U.S. Patents 4298588(1981 of Imperial Chemical Industries (ICI)) method in, one section conversion is that the ratio at total steam and carbon is to finish under 2.5～3.5: 1 the situation, be at least 10% to form methane content, but be no more than (750～850 ℃ of 30% exit gass, 30～120 crust), two sections conversions through having excess air (being higher than stoichiometry) contain 0.2～10% CH to provide again ₄And H ₂: N ₂Mole ratio is 2.0～2.9: 1 emission gases (950～1050 ℃, about 30～120 crust).Through transformationreation, remove CO ₂After methanation, the methane of the fresh synthesis gas of generation (often contain and be lower than the 1%(volume)) feed ammonia reactor with hydrogen-rich recycle stream (circulation gas: virgin gas is 4: 6) and contain 8～12%(volume with generation) NH ₃Ammonia reactor get rid of gas.After removing ammonolysis product, residual gas partly loops back reactor, and part is delivered to remove and reclaimed the unit to remove stable gas and the excessive N that comes of bringing into fresh synthesis gas ₂(being higher than stoichiometry).But, owing to reclaim H in the unit in common removing ₂Recovery incomplete, so, in remove reclaiming the unit, need to handle the gas of high flow capacity, therefore, this method will be brought higher hydrogen loss rate.At the laid-open U.S. Patents 4213954(1980 of Imperial Chemical Industries) in, conversion condition and the gas circulation situation similar adopted to United States Patent (USP) 4298588.

The disclosed European application 49967(1982 of Imperial Chemical Industries (ICI)) adopt one section convertor temperature out lower (＜750 ℃, as 550～650 ℃) one section conversion of adiabatic, rather than adopt the above-mentioned United States Patent (USP) 4298588 described practices.Make and contain 25～35%CH ₄The discharging gas of one section convertor in the temperature out of two sections convertors is lower than two sections convertors of 900 ℃, transform with excess air, form and contain 1.5～3.0%(mol) CH ₄(butt) and H ₂With N ₂Ratio be 1～2.5: 1 work off one's feeling vent one's spleen, and to generate ammonia content be the 14%(mol) ammonia reactor discharging gas (through conversion, CO ₂Remove with methanation after), then this discharging pneumatic transmission is removed to reclaim ammonia, and then part is delivered to and remove to be reclaimed the unit to form hydrogen-rich recycle stream.In addition, because in removing cycling element, need to handle a large amount of gases, so will form high hydrogen loss.

Various removings have been discussed in following document have been reclaimed the unit: English Patent 1057020; 1460681 and 1274504; UK Patent Application 2030473A; Russian patent 486667(1973); R.Banks work " chemical engineering ", 90～92 pages (on October 10th, 1977); " hydrocarbon processing " of work such as A Haslam, 103～106 pages (in January, 1976); K.S.Chari, " India's chemistry epoch ", 283～285 pages, (in April, 1978); T.Matsuoka, " India's chemistry epoch ", 30 volumes, the 2nd, the 119th～128 page (in February, 1979) and R.L.Shaner work " chemical engineering progress ", 47～52 pages (in May, 1978).

The technology of producing ammonia comprises: (a) carry out one section catalyzed conversion in the one section zone of transformation that is higher than under the normal atmosphere in direct flame heating, hydrocarbon feed and steam reforming are become to contain the gas mixture of oxycarbide, hydrogen and methane, (b) by bubbling air and the gas that gas mixture is tended to balance make (a) step carry out two sections catalyzed conversions, thereby produce two sections reforming gas discharging gas that contain nitrogen, oxycarbide, hydrogen and a small amount of methane, (c) under catalytic condition, make CO be transformed into CO with steam ₂And H ₂; (d) remove oxycarbide to obtain containing N ₂, H ₂Ammonia synthesis gas and with the synthesis pressure of this gas compression to ammonia, (e) in the ammonia synthesis district, make synthesis gas reaction produce ammonia, and from reactant gases, reclaim ammonia to generate the air-flow of poor ammonia, (f) airflow reflux of the above-mentioned poor ammonia of near small part is to above-mentioned ammonia synthesis district, (g) tributary of the air-flow of the above-mentioned poor ammonia of processing makes rich H again so that it is separated into the air-flow of hydrogen rich stream and rich stable gas ₂Air-flow is back to the ammonia synthesis district; Of the present invention improving one's methods comprise, (ⅰ) is not higher than under 946 ℃ the temperature and with being enough to provide 3～11%(mol in the temperature of working off one's feeling vent one's spleen) excessive N ₂Air capacity operation steps (b), work off one's feeling vent one's spleen to form two sections convertors, wherein contain the 0.8%(volume at least) methane, (ⅱ) contain the 10%(volume at least providing in the air-flow that is enough at above-mentioned poor ammonia) operation steps (e) under the condition of stable gas, (ⅲ) methane content that generates in the step (d) is at least about the 1.2%(mol) circulation gas that generates in the synthetic gas of (butt) and the step (f) and (g) in the mixture formed of the hydrogen rich stream that generates feed the ammonia synthesis district as the synthetic gas charging, thereby make in technical process by isolating the H that rich stable air-flow brings ₂Loss drops to minimum degree.

Fig. 1 is the synoptic diagram of one embodiment of the invention.

With reference to Fig. 1, directly the one-stage converter 10 of flame heating has convection zone 4 and one section conversion width of cloth section of penetrating 18, this radiation 18 is by burner (not expression, for example can be installed in the bottom of radiation section) heating, as shown in the figure, supplied burner fuel gas 14 and oxidant gas 16(such as combustion air).Flow through convection zone 4, process steam of the hot flue gases of being discharged by the width of cloth section of penetrating crossed thermal converter 21, produced air (can contain steam and air) thermal change interchanger 26, power steam over-heat-exchanger 25, feeding gas heat exchanger 24, feedwater preheater 22, discharges by chimney 2 then.So one section convertor 10 is to utilize fuel gas 14 and oxidant gas 16 to burn direct-fired therein.Will be appreciated that, not strict to the flow through requirement of the flow direction of one section convertor 10 of hot burning gas, one section convertor 10 can adopt one section convertor design of any routine, as narrating in the United States Patent (USP) 4213954, wherein burning gas is passed through downwards from the top of the width of cloth section of penetrating of convertor, and convection zone is a horizontal positioned.

Two sections method for transformation need to add four kinds of factory supplies to one section convertor respectively: feeding gas (as hydrogen source), steam, oxygen-containing gas and fuel gas.In addition, for this method being used to produce ammonia synthesis gas, generally in two sections conversions, add source nitrogen (often being air).

Feeding gas is introduced in the reaction process by pipeline 6, and the feeding gas heat exchanger 24 of flowing through, and this interchanger is arranged in general converter convection zone, makes feeding gas be preheating to about 750 °F, promptly about 399 ℃.With the accessible gas raw material 6 of method of the present invention very wide variation range is arranged.Described as United States Patent (USP) 3649558, except coal pyrolytic decomposition gas, suitable feeding gas comprises coke(oven)gas or refinery gas, and those all are suitable for from coal or the brown coal gas raw materials such as (IBG) by the medium heat (Intermediate BTU) of conventional gasification process generation.Other suitable feeding gas is Sweet natural gas, petroleum naphtha, liquefied petroleum gas (LPG) (LPG), natural gas liquids (LNG) or the like.

The feeding gas of heating flows out through pipeline 38 from interchanger 24, mixes with the gas 39 that contains H, contacts with the Hydrobon catalyst of using always under the intensification condition, makes that sulphur compound is transformed into sulphur in the unstripped gas, removes by desulfurization zone 44.Catalyzer is Co-Mo or the Ni-Mo Hydrobon catalyst on the available support for example.

If contain COS in the raw material, available another kind of scheme, promptly except hydrodesulfurizationzone zone 40, feeding gas 38 can with the vapor mixing of capacity to supply with the follow-up required water of COS hydrolysis reaction.The quantity of steam of Jia Ruing can have wide variation range like this, generally contain 2～4%(volume), this is to be benchmark with the combined feed total feed gas the pipeline 38 of discharging from heat exchanger 24, and the COS reaction can be carried out by general fashion, use hydrolyst such as active alumina commonly used.In this reactor, be about 149～177 ℃, pressure in the representative temperature scope and be about 2069～4137 kPas, promptly the COS that under the general hydrolysising conditions of 20.69～41.37 crust feeding gas is contained converts H to ₂S gas.

The gaseous mixture of handling (or from such COS hydrolysis) generation from hydrogenating desulfurization can contain H ₂S sends into desulfurization zone 44 through pipeline 42, and gas temperature wherein is about 316～399 ℃ usually, and hydrogen sulfide impurities wherein can remove from air-flow with general technology, for example available zinc oxide adsorption bed technology.Be substantially free of the gas of sulphur impurity, for example contain and be lower than 0.2ppm(weight) sulphur compound (in elementary sulfur), discharge also and vapor mixing through pipeline 54, this can be by finishing steam through pipeline 12 flow in pipes 54, this steam contains the waste gas that some steam turbine 50 is discharged at least.Usually, both can also can mix the reheat gas mixture earlier with the latter, and send to then and carry out one section conversion earlier with mixing with desulfurization material gas again after 12 heating of turbine steam waste gas.Between the carbon in the quantity of steam of this place's adding is everlasting 2.5～5.0 mol steam/mol processed gas charging.Provide the required water of follow-up conversion reaction in this effect that adds steam.Then steam/processed gas mixture is added in the pipeline 56 of direct flame convertor 10, in pipeline 56, under conversion condition, unstripped gas is contacted with the conversion catalyst of using always, transform thereby make unstripped gas carry out part at least.Resemble any a section of conversion catalyst commonly used of nickel, nickel oxide, chromic oxide, molybdenum and composition thereof or the like and all can use, and with the nickel on the calcium aluminate carrier or the nickel on the alumina supporter for well.Temperature in the pipeline 56 generally is about 427～816 ℃, preferably is about 538～788 ℃; Pressure generally is about 2069～6900 kPas, and promptly 20.69～69 crust preferably are about 3100～4137 kPas, promptly is about 31～41.37 crust, and total gas hourly space velocity is 5000～15,000 hour in the pipeline 56 ^-1(V/V/hr), be preferably 6000～10000 hours ^-1

After the conversion reaction in the pipeline 56 in one section convertor 10, hydrocarbon components (except that methane) all in the feeding gas all transform into CH basically ₄, CO, CO ₂And H ₂, a part of original methane component changes into CO, CO similarly ₂And H ₂, temperature of gas mixture generally rises to about 677～802 ℃, preferably is about 732～788 ℃.The technology according to the present invention contains remaining methane content in the gas 58 that part transforms and is at least the 13%(volume) methane, preferably be about 15～20%(volume) CH ₄(butt).

Hot combustion gas is sent radiation section 18 through piping 56 outsides, delivers to convection zone 4 again, and hot gas and heat exchanger 21,26,25,24 contact with 22 there, with various air-flow heat exchanges to reclaim heat.Available common technology selects the accurate number of convection zone heat exchanger and recovered energy is maximum so that invest minimum in proper order.(for example, one or more above-mentioned heat exchangers can be divided into several independent unit to reach more favourable temperature distribution in convection zone 4).(not shown) the dry drum is discharged and fed to oiler feed 8 heat exchanger 22 of flowing through from pipeline 30 again, exhaust vapour thus, and make it overheated by carrying out heat exchange with two sections convertors discharging gas 62, high-temperature shift converters discharging gas 82 or ammonia reactors discharging gas 112, pipeline 20 preferably flow through then again with further overheated in convection zone heat exchanger 25, be about 482 ℃ thereby vapor temperature is reached.This steam is flowed through pipeline 36 again to turbine 50 actings, discharge through pipeline 28 from the vapor portion of turbine vent line 52, rest part feeds heat exchanger 21 so that the steam of discharging reheats to about 649 ℃ by indirect heat exchange in convection zone 4, delivers to pipeline 12 then.The steam of this heat again combines in the back reformer tube 56 that adds in the radiation section 18 of having filled catalyzer with the feeding gas after the desulfurization.In " carrying out the steam reforming of hydrocarbon " with the series connection vapor superheater, proxy Docket and this application No.cs-307 that awaits the reply that fills in together narrated the desirable especially method that forms superheated vapour 38, the reference during of all the other disclosures only for enforcement method of the present invention.

The production that will obtain from any general source feeds convection zone heat exchanger 26 preheatings of one section convertor with air, and Re one section convertor indirect and its heat exchange to gas there generally makes it to be heated to 482～704 ℃.Before heating process or intermediate point, produce with air and can mix with part turbine exhaust vapour 13.This production of heating feeds two sections convertors 60 with air (no matter whether with vapor mixing) through pipeline 34 and the gaseous mixture that the part of sending into through pipeline 58 transforms.

Regulate with general setting device (not shown) through the air capacity that pipeline 34 is sent into, so that provide the air and the ratio of charging be about 2.7: 1～2.9: 1, this ratio is to produce the ratio of hydrocarbon and nitrogen in the methanator emission gases 99, promptly about 3～11%(mol) excessive N ₂In general, the H in two sections convertor escapers 62 ₂With N ₂Mole ratio be about 2.0: 1～2.8: 1, preferably be about 2.2: 1～2.6: 1.

Two sections convertors can be usually the adiabatic convertors of design, and the heat that the thermopositive reaction that utilizes oxygen and part to transform raw material under steady state operation condition discharges makes it further conversion.The type of the catalyzer in the convertor 60 and consumption also are general, are typically with the Ni catalyzer on the alumina carrier.In the method for the invention, two sections convertor temperature outs are lower than about 946 ℃, preferably be about 882～938 ℃, two sections convertor top hole pressures are generally 2069～6900 kPas, promptly 20.69～69 crust preferably are about 3100～4137 kPas, promptly are about 31～41.37 crust, the total gas hourly space velocity of general employing is 6000～10,000 hour ^-1

Two sections transform emission gases 62 and generally contain remaining CH ₄Amount is at least the 0.8%(volume) CH ₄, be preferably volume at least about 1%() and to about 2%(volume) CH ₄(butt), discharging gas are discharged and are led to from two sections convertors 60 and wherein can comprise saturated high pressure steam producer heat recovery area 70, steam superheating interchanger or one or more this producer and vapor superheater coupling.The part refrigerative that generates transforms discharging gas for two sections and feeds then in the high-temperature shift converter 80 from pipeline 72 discharges, makes the CO in the convertor discharging gas become CO at catalyzer up conversion commonly used with usual method and equipment here ₂With other H ₂

Usually, the temperature that adopts in the shift converter 80 is about 316～482 ℃, and pressure is about 2069～6900 kPas, promptly 20.69～69 clings to, and catalyzer generally helps catalytic iron catalyst to form by the chromium on the carrier.Then, the exit gas of high-temperature shift converter is discharged through pipeline 82, delivers to heat recovery area 84,84 and can comprise the second steam producer, and the part refrigerative high temperature shift discharging gas in Jiang Zi district 84 adds low temperature shift converter 90, or preferably delivers to guard bed 88 earlier.

Guard bed 88 can choose wantonly, preferably are used for handling in low temperature shift converter 90 air-flow 86 to the upper reaches, thereby so that remove in the plain and sulphur impurity protection low temperature shift converter 90 of fontanel catalyzer to fontanel element and sulfur sensitive.Guard bed 88 the operational condition and the type of catalyst system therefor are (for example, help catalytic zinc oxide with cupric oxide) all be general, this step is operated under the temperature and pressure condition of low temperature shift converter as described below 90 usually, removes the guard bed 88 used solids that contain fontanel and sulfur-containing impurities by forming with the same catalyzer of low temperature shift converter 90.

In shift converter 90, the low temperature permutoid reaction is to use method and apparatus commonly used to carry out on common catalyzer, to generate more substantial H ₂And CO ₂Usually, the temperature of shift converter 90 is 204～260 ℃, and pressure is 2069～6900 kPas, promptly 20.69～69 clings to, and catalyzer often is the mixture of zinc oxide and cupric oxide.The discharging gas of low temperature shift converter 90 cools off (can comprise one or more heat exchangers) in the 3rd heat recovery area 94, refrigerative low temperature shift converter discharging gas at the calorific value that has consumed it after pipeline 113 feeds CO ₂Remove district 115, and adopt general technology (as CO ₂The solvent adsorption of gas) removes CO through pipeline 111 ₂With the essentially no CO that generates ₂Gas add in the general methanator 98 (often comprising one or more heat exchangers) to remove unnecessary CO and CO through pipeline 96 ₂, discharge through pipeline 99 then, form air-flow 101 with hydrogen-rich recycle stream 142, and in compressor 100, be compressed to the required pressure of ammonia synthesis.Contain synthetic gas fresh or that replenish in the method for the present invention in the methanator discharging gas 99, it is characterized by and introduce circulating current 142 CH before ₄Concentration be at least about 1.2%(volume, butt), preferably be about 1.4～2.2%(volume, butt).

The synthetic gas 102 of compression mixes with recycle stream 132 and is incorporated in preheating in the heating zone 104, and the heating zone is made up of indirect heat exchanger, and wherein hot ammonia reactor emission gases or the gas that comes from one or more catalytic section are used as thermal medium.Preheated feed gas feeds ammonia reactors 110 through pipeline 106, and adopt general technology (as on iron catalyst, at 316～538 ℃) to make generally to reach stoichiometric ratio in the synthetic gas air inlet 106 (be H ₂: N ₂Be about 3: the H 1(mol) ₂/ N ₂Gas generates NH ₃Ammonia reactor discharging gas is discharged and cooling in recovery zone 114 through pipeline 112, recovery zone 114 can be made up of interchanger, boiler etc., refrigerative ammonia reactor discharging gas is fed ammonia recovery zone 120 for example to reclaim ammonolysis product 112(, with cold method condensation ammonia wherein), will contain unreacted N ₂, H ₂, remaining NH ₃With stable gas (as CH ₄, Ar and He) air-flow 124 deliver in the ammonia react and in heating zone 126, be heated, deliver to circulator 130 through pipeline 128, be recycled in the charging of ammonia synthesis reactor preheater 104 upstreams through pipeline 132.If desired, refrigeration cycle gas 124 can discharge gas 112 indirect heating with ammonia reactor, and in this case, well heater 126 comprises an interchanger at least in recovery zone 114.Usually, with liquefied ammonia logistics 122 flash distillations (i.e. decompression) so that soluble gas (H ₂, CH ₄, N ₂, Ar and He) remove as flash steam, flash steam can be sent to the gas that acts as a fuel and use.

Feature of the present invention is that circulating current 128 and circulating current 132 contain stable gas (CH ₄, Ar and He), its content is at least about the 10%(volume), preferably be about 12～20%(volume), simultaneously, the H that generally contains ₂And N ₂Mole ratio be 2.5～3.5.Usually contain 65～85%(volume of having an appointment in the circulating current 132) total compression air-flow 106, so the mole ratio of circulation gas (air-flow 132) and fresh feed gas (air-flow 102) was at least 2: 1, preferably was about 2.5～3.9: 1.At least a portion generally is about 2.5～6%(volume), preferably be about 3～4.5%(volume) warm circulation gas 128 discharge and deliver to and remove recovery zone 140 through pipeline 134, handle gas there to isolate rich CH ₄Can make fuel gas with Ar(such as needs) stable gas clean-up air-flow 138, and formation hydrogen rich gas 142, it is looped back in the ammonia react, as mixes with methanator discharging gas 99 (this can be in advance when compressor 100 compresses or finish afterwards).H in the circulating current 142 ₂With N ₂Mole ratio generally be about 5～20: 1, preferably be about 7～15: 1.The volume of circulating current 142 generally is about fresh synthesis gas and flows 5～12% of 99 volumes.

CO ₂The operating method that removes the synthetic district 110 of district 115, methane conversion district 98, compressor 100 and NH can be come by those skilled in the art in the art to determine at an easy rate, thereby achieve the above object, therefore, need not to do explanation more completely and understand method of the present invention fully.And the accurate operating parameters of each processing step and equipment also is easy to be understood by the those skilled in the art in present technique field, and each step can comprise that prior art thinks useful internal recycle logistics and stage commonly used.Therefore, CO ₂Remove district 115 and can comprise common CO ₂Absorption and CO ₂Desorption procedure makes rich CO ₂Air-flow 113 with contain the solvent that can react with it or soluble compound (as K ₂CO ₃) liquid contact, discharge no CO ₂The CO of gas (general＜0.3%(volume) ₂).Handle solvent again and make it desorb CO ₂Gas 111, and with solvent cycle resorption adnexa.District 115 also can use common pressure swing adsorption process to remove CO ₂In " encyclopedia of chemical technology " (the 3rd edition, the 2nd volume, 492～494 pages, 1978) of Kirk-Othmer, suitable CO commonly used has been discussed ₂Remove the test of system.Equally, methanator 98 general use temperatures are about 260～482 ℃, and pressure is about 2069～6900 kPas, promptly 20.69～69 cling to, and the Ni catalyzer on the carrier (as the Ni on alumina carrier) makes CO and the CO of any remnants in the air-flow 96 ₂Be transformed into methane, consequent discharging gas 99 contains and is less than 10Vppm(is per 1,000,000/umber (volume)) total CO and CO ₂And H ₂And N ₂And H ₂: N ₂Mole ratio be 2.7: 1～2.9: 1.As required, the compression in the zone 100 can divide several sections to carry out, so that methanator discharging air pressure shortens the pressure of synthesis reactor into, is about 10,340～34,470 kPas usually, promptly is about 103.4～344.7 crust.(if desired, compressor 100 can be installed in the upstream in district 115, makes gas compression before the 115 li processing in district).At last, as required, available general dryer unit (not shown) is removed the water of trace in the fresh synthesis gas 99.If desired, this dryer unit commonly used can be installed with flow of process air 101 or be installed in the mid point in gas compression district 100.）

In zone 140, can adopt various art breading air-flows 134 to remove stable gas and excessive N as removing qi exhaustion ₂(being higher than stoichiometry), removing gas and discharge through pipeline 138.The operation of removing recovery zone 140 is easy to determine that the present invention no longer describes in detail to persons skilled in the art.Therefore, suitable removing is reclaimed technology and is comprised cryogenic method, is about to the air-flow cooling and removes stable gas, as methane and argon; Pressure swing absorption process and film diffusion technique are to reclaim rich H air-flow and segregational stability gas.English Patent 1057020,1460681 and 1274504; UK Patent Application 2,030,973A; Russian patent 486,667(1973); " chemical engineering " 90～92 pages (1977.10.10) of R.Banks work; " hydrocarbon processing " of people such as A.Haslam work, 103～106 pages (1976.1); " the India's chemistry epoch " of K.S.Chari, 283～285 pages (1978.4); In " India's chemistry epoch " of T.Matsuoka work, 30 the 2nd phases of volume, " chemical engineering progress " of 119～128 pages (1979.2) and R.L.Shaner all discussed suitable removing and reclaimed technology in 47～52 pages (1978.5).

The synthetic gas 102 of improving one's methods and producing of the present invention has H ₂With N ₂Mole ratio is about 3: 1, promptly be about 2.6: 1～3.2: 1, about 1～3%(the volume of remaining methane concentration (butt)), preferably be about 1.2～2.2%(volume), and suitable especially be combine back formation to contain 7～13%(volume with circulating current 132) CH ₄The synthesis gas reaction device incoming flow 106 of (butt) can be used as the direct charging in ammonia synthesis reactor district 110.So, in the method for the invention needn't be with cryogenic purification step process air-flow 99,101 or 102 before adding ammonia synthesis reaction, to remove excessive methane and N ₂(still, if desired, can make synthetic gas 101 carry out cryogenic purification before adding ammonia synthesis reactor district 110, as adopting cryogenic purification method in the United States Patent (USP) 3442613, its disclosed method is only for referencial use for implementing the present invention.

Of the present invention improving one's methods can be further described with reference to the following example.

Embodiment 1

Method of the present invention, indicated as Fig. 1, be used for producing 1000 tonnes of ammonia of daily output, used feeding gas and processing condition are listed in the table 1.

The condition of embodiment 1 obtains from following basis, be typically the used design of industrialized ammonia factory: the spill losses of permission is the 1%(mol by the air-flow of synthesic gas compressor 100), the desulfurization hydrogen stream 39 in 29 kilograms of molecule/times is comprising the tributary (not shown) from hydrogen-rich recycle stream 142; Send the H in 14.5 kilograms of molecule/times in the flashed vapour of fuel _-Hydrogen with 7 kilograms of molecule/times.(flashed vapour is to be relaxed from the liquefied ammonia 122 that 116 condensations of ammonia synthesis reactor discharging gas go out to discharge the H that is dissolved in wherein ₂, N ₂, CH ₄, the gas that discharges when Ar and helium).Hydrogen recovery unit 140 also is a low temperature form during removing, and the clean recovery (clean component reclaims the percentage ratio of the given component that is defined as the removing gas 134 that reclaims in the air-flow 142) of following various charging compositions is arranged:

H ₂87.64 mol %

N ₂25.61

CH ₄3.66

Ar????15.70

He????99.00

It should be noted that these clean 1%(mol that comprises the removing gas that is added to unit 140 that reclaims) the permission spillage.

The table I

Comparative example 2 and 3

Still with reference to technical process shown in Figure 1, table 2 illustrated certain situation, in table 2, Fig. 1 indicated method of the present invention and comparative example 2 and 3 are compared, it further specify owing to use extra air deliver to two sections convertors as improve that two sections convertor temperature outs are higher than that means that 946 ℃ of whiles correspondingly reduce methane content in the methanator vent gas obtain away from the opposite effect of the present invention.It is all the same to every kind of situation remove to reclaim unit component recovery part supposition, as the compressor leakage loss, send to the flash steam of making fuel and the demand of desulfurization hydrogen all is the same.

At first see comparative example 2, table 2 shows that two sections convertor temperature outs increase to 950 ℃ (among the embodiment 1 being 921.5 ℃), can increase by 9.1% with the dry air flow velocity by exsiccant production and reach (from 1712 kilograms of kilogram molecule/times in molecule/time to 1868).This also can make, and methane content drops to 0.63%(butt, mol from 1.05% in two sections convertor vent gas), methanator is discharged methane content and is dropped to the 1.26%(butt from 1.78%, mol), make H in the methanator discharging gas owing to added extra nitrogen with additional air ₂With N ₂Ratio reduce to 2.60 from 2.82.

In comparative example 2, charging methane conversion degree big (promptly two sections convertor vent gas methane contents are lower) can make H in the methanator vent gas ₂Flow increase 0.7%(from 3814 kilograms of molecule/times to 3841 kilogram/time.It is misleading that but comparative example 2 is better than the tangible result of embodiment 1, because the H of lower methanator ₂/ N ₂Than needing the ammonia synthesis district to use higher clearance rate so that the ratio of ammonia synthesis reactor 110 ingresss is high to stoichiometrical ratio, promptly about 3.0.Higher clearance rate has increased the H that enters fuel again in fact ₂Loss, this is because removing H ₂Recovery unit 140 in H ₂Reclaim and not exclusively cause.Although the hydrogen richness in the methanator vent gas is higher, comparative example 2 and embodiment 1 net result relatively are H ₂The amount of actual conversion ammonification is lower, and promptly comparative example 2 is 3631 kilograms of molecule/times, and embodiment 1 is 3675 kilograms of molecule/times.Therefore after the ammonia loss of having estimated to enter flash steam in the fuel and embodiment 1 have under same input rate and the converter flame, comparative example 2 is only produced the 988 tonnes/pure ammonolysis product produced day, and embodiment 1 can produce 1000 tonnes/produce day clean ammonia.

Particularly with respect to 684 kilograms of molecule/times (no ammonia) of embodiment 1, example 2 has been used 1388 kilograms of molecule/times of higher clearance rate, reclaims unit product logistics 142 and can mix with air-flow 99 to reach the H in the air-flow 101 in each example so contain the percentile removing of high hydrogen ₂With N ₂Ratio be 3.0.Higher clearance rate can reduce the content of removing stable gas in the air-flow greatly, and is just as shown in table 2, and comparative example 2 is removed in the gas and only contained 6.6% stable gas, and embodiment 1 contains under the situation of 15.9%(both based on no ammonia more frequently).The low-down content (as being lower than 10%) that stable gas in the gas is removed in this explanation is the high feature of hydrogen loss of sending to fuel.

See comparative example 3 again, table 2 explanation is produced by extra increase and can be made two sections convertor temperature outs increase to 1000 ℃ with air speed 15.4%, compares with embodiment 1, and the production of passing through has increased by 24.5% with the total speed of air.Owing to produce the further increase with air speed, two sections convertor discharging gas methane contents drop to 0.23%(butt, mol), methane content drops to 0.80%(butt, mol in the methanator vent gas), H in the corresponding methanator discharging gas ₂And N ₂Ratio only be 2.29.

Comparative example 3 makes the H flow velocity that leaves methanator increase 0.2%(to 3849 kilogram of molecule/time a little).But the same with comparative example 2, net result is born, H ₂To the actual inversion quantity of ammonia drop to only be 7736 pound molecules/time, pure hydrazine yield drop to 955 tonnes/produce day.Low H in the methanator vent gas ₂/ N ₂Ratio and low pure H ₂The characteristics that are transformed into ammonia make clearance rate height (2678 kilograms of molecule/times are in no ammonia), and remove stable gas content also low (2.8%, in no ammonia) in the gas

In addition, comparative example 2 and 3 higher productions have increased the energy expenditure that air compresses with air speed, and this is considerable production cost concerning synthesis ammonia plant.

The note of table 2

Annotate: the carbon in (1) steam and the feeding gas in the hydrocarbon (does not comprise CO ₂) mole ratio.

(2) for making H in the methanator exhaust jet stream ₂With N ₂Mole ratio be the 3.0(stoichiometry) required excess air.

(3) the stable gas % of clearance rate and removing is all in no ammonia.Stability gas is CH ₄, Ar and He.

(4) comprise the H of spillage that synthesic gas compressor 100 allows, desulfurization hydrogen 39, flash steam ₂, remove and reclaim monopropellant gas product 138 and remove the spillage that the recovery unit allows.

(5) steam flow of 34 li of logistics keeps constant identical with speed in the example 1.

(6) supposition logistics 122 is relaxed stable gas is removed as flash steam.

(7) flash stream 122 is removed the ammonia in the liquid product flow behind the stable gas.

(8) go the temperature of the air gas mixture 34 of two sections convertors to be held constant at 649 ℃.

Therefore, illustrated and illustrated the preferred embodiment of my invention when me, and with complete, clear, succinct and accurate language the present invention and enforcement have been described, use it mode and technology so that in the art those skilled in the art implement and when using it, each technician can determine essential characteristic of the present invention at an easy rate, and under situation without departing from the spirit and scope of the present invention, for adapt to various uses and condition can to the present invention make various changes and (or) improve.Therefore, this change and (or) improve in the desired same range as of following claim.

The pressure unit that the present invention uses is kPa (gauge pressure).

Claims (8)

1, the method for production ammonia comprises:

(a) in direct one section zone of transformation of flame, be higher than and carrying out one section catalyzed conversion under the normal atmosphere, making hydrocarbon feed and steam reforming generate the gas mixture that contains oxycarbide, hydrogen and methane,

(b) carry out two sections catalyzed conversions by sending into air and gas mixture is tended to balance the gas that (a) step is come, contain two sections convertor discharging gas that nitrogen, oxycarbide, hydrogen and methane content reduce thereby produce,

(c) carry out catalyzed conversion with steam, make CO change into CO ₂And H ₂,

(d) remove oxycarbide to obtain containing N ₂, H ₂Ammonia synthesis gas and with the pressure of this gas compression to ammonia synthesis,

(e) in the ammonia synthesis district, make synthesis gas reaction produce ammonia and from reactant gases, reclaim ammonia and generate poor ammonia (ammonia-depleted) air-flow,

(f) reflux the above-mentioned poor ammonia flow of part at least again to above-mentioned ammonia synthesis district,

(g) tributary of handling above-mentioned poor ammonia makes rich H again to separate rich hydrogen and rich stable air-flow ₂Air-flow returns the ammonia synthesis district, and of the present invention improving one's methods comprises:

(1) is not higher than under 946 ℃ the temperature and in the temperature of working off one's feeling vent one's spleen with being enough to provide 3～11% (mol) excessive N ₂Air capacity operation steps (b), generate two sections convertors containing at least 0.8% (volume) methane and work off one's feeling vent one's spleen,

(2) be enough to make operation steps (e) under the condition that contains the stable gas of at least 10% (volume) in the above-mentioned poor ammonia flow,

(3) methane content that generates in the step (d) is at least about the synthesis gas of 1.2 (mol) % (butt) and the circulation gas of the middle generation of step (f) and the mixture that the middle hydrogen rich stream that generates of step (g) is formed and feeds the ammonia synthesis district, thereby make in technical process by isolating the H that rich stable air-flow brings as the synthetic gas charging ₂Loss drops to minimum degree.

2, according to claim 1 described improving one's methods, wherein, step (b) is to operate in the temperature of working off one's feeling vent one's spleen is 882～938 ℃ scope.

3, according to claim 2 described improving one's methods, wherein, step (b) is about 2758 to 4137 kPas at the pressure of working off one's feeling vent one's spleen, and promptly operates under the conditions of 27.58～41.37 crust, and contains 1～2%(volume of having an appointment in the working off one's feeling vent one's spleen of step (b)) methane (in butt).

4, above-mentioned poor ammonia according to claim 1 described improving one's methods, wherein, about 2.5～6%(volume) is delivered to step (g) with the tributary.

5, according to claim 4 described improving one's methods, wherein, above-mentioned poor ammonia flow contains 10～20%(volume of having an appointment) stable gas.

6,, it is characterized in that to the above-mentioned synthetic gas charging in ammonia synthesis district, containing 7～13%(volume of having an appointment according to claim 5 described improving one's methods) methane.

7, according to claim 1 described improving one's methods, wherein, above-mentioned poor ammonia flow contains about 10～20% stable gas, and is to be feature at 2.5～3.5: 1 with the mole ratio of hydrogen and nitrogen.

8, according to claim 1 described improving one's methods, wherein, step (a) is about 677～802 ℃ in the temperature of working off one's feeling vent one's spleen, and the mole ratio of steam and carbon is to operate under 2.5～5.0: 1 the condition, and makes the methane content of working off one's feeling vent one's spleen be at least about 13%(volume) (butt).

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