A kind of Fischer-Tropsch synthesis process being applicable to fixed-bed reactor
Technical field
The present invention relates to a kind of Fischer-Tropsch synthesis process being applicable to fixed-bed reactor.
Technical background
Coal produces oil fuel through F-T synthesis and chemical is one of the important content in clean coal technology field.Now, fluidized-bed, slurry bed system and fixed-bed reactor are main reactor of Fischer-Tropsch synthesis.Although fluidized-bed reactor heat transfer coefficient is high, heat-transfer effect good, be easy to automatic production, its fluid mapper process is restive, and catalyst utilization is low, back-mixing, serious wear; Although paste state bed reactor temperature of reaction is even, productive rate is high, also there is serious back-mixing, and the separation of catalyzer is also an insoluble problem; There is the poor feature of bed temperature skewness even bed thermal conductivity in fixed-bed reactor, but fixed-bed reactor volume is little, and catalyzer loading amount is little, is suitable for High Temperature High Pressure operation, is thus usually used in Fischer-Tropsch synthesis process.Particularly cobalt-base catalyst, it has high reactivity, high stability, low water gas shift reaction, low methane selectively, high C
5 +the advantages such as selectivity.But cobalt catalyst cost is higher, to be separated and the problem that runs off causes it not to be suitable for slurry bed system and fluidized-bed reactor, and to be preferablyly applied to fixed-bed reactor.But cobalt catalyst is used for fixed bed to be existed two problems and causes it can not industrial applications, and first is that reaction bed temperature is uneven, very easily temperature runaway; Second is that temperature inequality causes bed utilization ratio low, and productive rate is low.
The original intention of fixed-bed reactor design is exactly mainly take away with the form of the evaporation of water latent heat of vaporization amount of heat produced in reaction tubes.Boiled water is by heat exchange between pipe, and by-product high-pressure steam, enhances heat transfer process.But existing technique still effectively cannot remove the large calorimetric that fischer-tropsch reaction is released, and still there is the problem of beds temperature runaway.Since fixed bed can by the latent heat of vaporization heat radiation between pipe, so also it can strengthen heat transfer by the latent heat of vaporization effect in pipe, just urgently develops a kind of like this Fischer-Tropsch synthesis process that effectively can move heat in pipe at present.
Summary of the invention
The invention provides that a kind of heat exchange efficiency is high, bed temperature evenly, the fixed bed reaction technique for Fischer-Tropsch synthesis that controls of stable operation being easy to.
Fischer-Tropsch synthesis process of the present invention adopts ferrum-based catalyst or cobalt-base catalyst, the cobalt-base catalyst that preferably life-span is longer.Described beds can be unanimous between the higher and lower levels, also can be according to bed hotspot's distribution, presses different ratios dilution filling, can realize the homogeneous temperature of whole reaction bed so better, make advantage of the present invention more outstanding with thinner.
The present invention realizes especially by following steps:
(1) bed is divided into upper, middle and lower segment, three bed sections is needed to the catalyzer of filling, fill out than for 0-1:1 dilutes laggard luggage by thinner and catalyst volume;
(2), after circulatory mediator is preheated to the temperature of supercritical state under reaction pressure, beds is entered from the top of fixed-bed reactor;
(3) beds is entered from fixed-bed reactor upper feeding mouth separately after fresh synthesis gas and circulation gas are mixed to form unstripped gas preheating, or enter beds from fixed-bed reactor top after mixing with circulatory mediator, carry out Fischer-Tropsch synthesis, all products flow out bottom fixed-bed reactor; Or unstripped gas enters from the lower opening for feed of fixed-bed reactor bottom, and liquid product flows out from reactor bottom, and gaseous product flows out from top;
(4) reaction product is all collected and is then carried out oil gas water three phase separation, the synthetic water separated enters wastewater treatment equipment, the gas separated enters circular buffering tank, after entering stable state, a part makes other purposes as periodic off-gases, and another part and fresh synthesis gas converge as unstripped gas; The liquid separated enters rectifying tower and is further separated, and will be separated the C obtained
5-C
8a part use as circulatory mediator, all the other make other purposes.
As mentioned above, thinner be without detrimental impurity, do not participate in reacting, the one of resistant to elevated temperatures porcelain ring, aluminium ball, silicon ball etc.
As mentioned above, the catalyzer that Fischer-Tropsch synthesis process adopts comprises all cobalt-base catalysts that can be used for Fischer-Tropsch synthesis.
The method preparation that catalyzer can describe by Chinese patent CN102962077A: prepare a certain amount of sodium aluminate aqueous solution, instillation ammoniacal liquor, water-bath keeps for some time, then adds peptizing agent HNO
3, stirring and refluxing, to transparent colloidal sol, keeps for some time, then at room temperature aging obtained gel.Gel is put in loft drier dry, then by xerogel in microwave oven Program intensification roasting, obtained support of the catalyst.Form by final catalyzer, the Co (NO of preparation
3)
26H
2o-LaCl
37H
2o-IrCl
33H
2the O aqueous solution, impregnated in above-mentioned carrier, dry, roasting, and obtained Co/La/Ir/Al catalyzer, its weight consists of Co
3o
4: LaO
2: IrO
2: Al
2o
3=100:5-15:2-3:300-500.
Or the method preparation that can describe by patent CN101269328: by final catalyzer a certain amount of for 9.06g Jing Ti/Bao Pian COBALT NITRATE CRYSTALS/FLAKES is dissolved in butanols and stirs evenly, add a certain amount of stearylamine, abundant dissolving, add a certain amount of water and butyl (tetra) titanate again, stir, decompression rotary evaporation is dry, roasting, obtained Co/TiO
2catalyzer, catalyst weight consists of Co:TiO
2=15-40:100.
Or the method preparation that can describe by patent CN101269336: with porous-starch gel for template, take a certain amount of potato starch to be added to the water, heated and stirred, place in the refrigerating chamber of-20 DEG C after room temperature leaves standstill, and then dry under room temperature, the obtained porous-starch gel with ordered structure.Form by final catalyzer, obtain solution TEOS-EtOH-NH
3-Co-Re the aqueous solution, by this solution in stirred at ambient temperature, then three steps are impregnated in the duct of starch template, dry, roasting removing starch template under air atmosphere, obtained Co-Re-SiO
2catalyzer, its catalyst weight consists of Co:Re:SiO
2=100:0.1-1.0:300-600.
As mentioned above, in Fischer-Tropsch synthesis, catalyzer reduces in pure hydrogen atmosphere, and reductive condition is: 350-450 DEG C, 0.5-1.0MPa, 500-1500h
-1(v/v), 6-12h; Reaction conditions is: 170-250 DEG C, and synthetic gas consists of H
2: CO(v/v)=1.5-3:1, synthetic gas dividing potential drop is 2.0-3.0MPa, and volume space velocity is 500-2500h
-1(v/v), the volume ratio of circulation gas and fresh synthesis gas is 1-5:1.In view of the volatilization of circulatory mediator part occupies system dividing potential drop, need suitable raising system stagnation pressure, to ensure effective dividing potential drop of synthetic gas.
Above method for preparing catalyst only for explaining the present invention, and does not limit the method for preparing catalyst that the present invention relates to.
As mentioned above, circulatory mediator is C
5-C
8liquid state list alkane or C
5-C
8liquid alkane mixture, it derives from system and adds outward or product separation in system.
As mentioned above, circulatory mediator can be that reactor is entered in independent preheating, can also with the laggard reactor of unstripped gas mixing preheating.
As mentioned above, circulatory mediator can soak beds in advance, also can not soak in advance.
As mentioned above, the weight ratio of circulatory mediator and unstripped gas is 1-20:1, initially needs out-of-bounds to provide corresponding circulatory mediator in reaction.
Present invention process has that heat exchange efficiency is high, bed temperature evenly, the advantage that controls of stable operation being easy to, and there is C
5 +the outstanding advantages that selectivity is high, methane selectively is low and operation air speed is large, product yield is high.
Accompanying drawing explanation
Fig. 1 is process flow sheet of the present invention.
Fig. 2 is embodiment 1 bed temperature scatter chart.
Fig. 3 is embodiment 2 bed temperature scatter chart.
Fig. 4 is embodiment 3 bed temperature scatter chart.
As shown in the figure: 1-spraying gun, 2-reactor, 3-three phases separator, 4-unstripped gas, 5-interchanger, 6-fresh synthesis gas, 7-circulation gas, 8-periodic off-gases, 9-circular buffering tank, 10-synthetic water, 11-rectifying tower, 12-liquor pump, 13-C
5-C
8cut, 14-heavy oil, 15-soft wax, 16-hard wax, 17-interchanger, 18-circulatory mediator.
Embodiment
For a better understanding of the present invention, provide below several illustrative but be not restrictive embodiment.
Embodiment 1:
Method Kaolinite Preparation of Catalyst Co/La/Ir/Al by Chinese patent CN102962077A describes: the sodium aluminate aqueous solution preparing a certain amount of 0.5mol/L, instillation 2ml ammoniacal liquor, keeping temperature to be 65 DEG C, hold-time 60min, is then that 0.1:1 adds peptizing agent HNO by sol and sodium aluminate mol ratio
3, stirring and refluxing is to transparent colloidal sol, and keep 3h, then aged at room temperature 12h obtains gel.Gel is put in 105 DEG C of dry 6h in loft drier, then xerogel is placed in temperature programming microwave oven, temperature rise rate 2 DEG C/min, roasting 10h at 350 DEG C, obtained support of the catalyst.22 (wt) %, 3 (wt) % and 0.5% that account for final catalyzer by tricobalt tetroxide, lanthanum trioxide and iridium dioxide respectively take Co (NO
3)
26H
2o, LaCl
37H
2o and IrCl
33H
2o, measures deionized water according to equi-volume impregnating, is mixed with mixing salt solution and impregnated in above-mentioned carrier, and dipping time is 5h, then dry 6h at 100 DEG C, and finally at 250 DEG C of roasting 15h, temperature rise rate 3 DEG C/min, obtained catalyzer, compressing tablet screening is for subsequent use.Final catalyst weight is Co
3o
4: LaO
2: IrO
2: Al
2o
3=22:2.5:0.5:75.
Get this catalyzer of 20-40 object 100ml and be loaded on fixed-bed reactor, internal diameter 14mm, bed height is about 900mm.On bed, 1/3 section is diluted with porcelain ring/catalyzer (v/v)=1:3, and in the middle of bed, 1/3 section is diluted with porcelain ring/catalyzer (v/v)=1:5, and lower 1/3 section of bed dilutes with porcelain ring/catalyzer (v/v)=1:10.Catalyzer reduces in pure hydrogen, and reductive condition is 410 DEG C, 0.8MPa, 500h
-1(v/v), 20h.After reduction, cooling switching and merging gas reacts, and reacts to temperature 220 DEG C, synthetic gas dividing potential drop 2.2MPa, H
2: CO(v/v)=1.5:1, feed gas volume air speed 2000h
-1under carry out, the volume ratio of circulation gas and fresh synthesis gas is 1.Fresh synthesis gas 6 (240L/h) is preheated to 180 DEG C through preheater 5, with the C being preheated to 170 DEG C through preheater 17
5-C
8beds is entered from fixed-bed reactor 2 top after cut 13 (4.9L/h) mixing.All products flow out from reactor bottom, reaction product is all collected and is then separated at three phases separator 3, the synthetic water 10 separated enters wastewater treatment equipment, the gas separated enters circular buffering tank 9, after entering stable state, a part (45L/h), as periodic off-gases 8, makes other purposes, a part (240L/h) makes circulation gas 7, converges as unstripped gas 4 with fresh synthesis gas (240L/h); The liquid separated enters rectifying tower 11 and carries out further cutting and separating, will be separated the C obtained
5-C
8a part (4.9L/h) for cut (boiling range is 28 DEG C to 126 DEG C) uses as circulatory mediator, and oil gas weight ratio is about 15:1, and all the other make other purposes.Under this operating mode, CO per pass conversion is 81.3%, and methane selectively is 3.23%, C
5 +space-time yield is 0.35g/ml
cath.This operating mode lower bed layer temperature distributing curve diagram is shown in curve a in Fig. 2, curve b is without bed temperature distribution curve time oil circulation, correlation curve a, b are visible, without time oil circulation, the bed temperature difference can reach 21 DEG C, and time oil circulation, the bed temperature difference is only 5.5 DEG C, and whole bed temperature is homogeneous very gently, reactor utilization ratio is high, and throughput is large, and bed is without focus.Final product distribution is as shown in table 1.
Table 1 embodiment 1 final product distribution table
Embodiment 2:
By the method Kaolinite Preparation of Catalyst Co/TiO that patent CN101269328 describes
2, 9.06g Jing Ti/Bao Pian COBALT NITRATE CRYSTALS/FLAKES is dissolved in 350ml butanols and stirs evenly, add a certain amount of stearylamine (mol ratio C
18-NH
3/ Co=3), fully dissolve, then add the water of 6.8ml, finally add 24ml butyl (tetra) titanate, adopt decompression rotary evaporation dry after continuing to stir 24h, 100 DEG C of dryings, last 500 DEG C of roasting 6h, obtained catalyzer, its weight consists of Co:TiO
2=25.5:100, compressing tablet screening is for subsequent use.
Get this catalyzer of 20-40 object 100ml and be loaded on fixed-bed reactor, internal diameter 14mm, bed height is about 900mm.On bed, 1/3 section is diluted with aluminium ball/catalyzer (v/v)=1:2, and in the middle of bed, 1/3 section is diluted with aluminium ball/catalyzer (v/v)=1:9, and lower 1/3 section of bed does not dilute.Catalyzer reduces in pure hydrogen, and reductive condition is 380 DEG C, 0.6MPa, 1200h
-1(v/v), 18h.After reduction, cooling switching and merging gas reacts, and reacts to temperature 200 DEG C, synthetic gas dividing potential drop 2.5MPa, H
2: CO(v/v)=2:1, feed gas volume air speed 1000h
-1under carry out, the volume ratio of circulation gas and fresh synthesis gas is 2.Fresh synthesis gas 6 (120L/h) is preheated to 200 DEG C through preheater 4 and enters reactor 2, C from lower opening for feed
5-C
8cut 13 (1.2L/h) enters reactor 2 from upper feeding mouth after preheater 17 is preheated to 170 DEG C.All products flow out from reactor bottom, reaction product is all collected and is then separated at three phases separator 3, the synthetic water 10 separated enters wastewater treatment equipment, the gas separated enters circular buffering tank 9, after entering stable state, a part (45L/h), as periodic off-gases 8, makes other purposes, a part (240L/h) makes circulation 7 gas, converges as unstripped gas 4 with fresh synthesis gas (120L/h); The liquid separated enters rectifying tower 11 and carries out further cutting and separating, will be separated the C obtained
5-C
8a part (1.2L/h) for cut (boiling range is 28 DEG C to 126 DEG C) uses as circulatory mediator, and oil gas weight ratio is about 5:1, and all the other make other purposes.Under this operating mode, CO per pass conversion is 70.8%, and methane selectively is 4.73%, C
5 +space-time yield is 0.15g/ml
cath.This operating mode lower bed layer temperature distributing curve diagram is shown in curve a in Fig. 3, and curve b is without bed temperature distribution curve time oil circulation.Correlation curve a, b are visible, and can reach 14.5 DEG C without bed temperature difference time oil circulation, bed focus is fairly obvious, very easily temperature runaway, and when having oil circulation, the bed temperature difference is only 5.5 DEG C, and bed, without obvious focus, is not easy temperature runaway, and whole bed utilization ratio is high, and reactor efficiency is high.Final product distribution is as shown in table 2.
Table 2 embodiment 2 final product distribution table
Embodiment 3:
By the method Kaolinite Preparation of Catalyst Co/Re/Si that Chinese patent CN101269336 describes, with porous-starch gel for template, taking 10g potato starch joins in 100g water, being heated to 90 DEG C stirs after 10min. room temperatures leave standstill 12h, places 12h and then dry 24h must have the porous-starch gel of ordered structure under room temperature in the refrigerating chambers of-20 DEG C.Obtain solution TEOS:EtOH:NH
3: H
2o:Co:Re=1:30:0.15:0.45:0.02, by this solution in stirred at ambient temperature 8h, then three steps are impregnated into (starch gel/starch gel+solution=20 (wt%)) in the duct of starch template.Often walk dipping 12 hours, 120 DEG C of dry 24h.Last under 550 DEG C of air atmospheres roasting 8 hours removing starch templates, obtained be 7.5wt%, Re containing Co is 2wt%, SiO
2for the catalyzer of 70.5wt%, compressing tablet screening is for subsequent use.
Get this catalyzer of 20-40 object 100ml and be loaded on fixed-bed reactor, internal diameter 14mm, bed height is about 900mm.On bed, 1/3 section is diluted with silicon ball/catalyzer (v/v)=1:5, and in the middle of bed, 1/3 section is diluted with silicon ball/catalyzer (v/v)=1:4, and lower 1/3 section of bed dilutes with silicon ball/catalyzer (v/v)=1:5.Catalyzer reduces in pure hydrogen, and reductive condition is 350 DEG C, 0.7MPa, 1500h
-1(v/v), 10h.After reduction, cooling switching and merging gas reacts, and reacts to temperature 210 DEG C, synthetic gas dividing potential drop 2.0MPa, H
2: CO(v/v)=2.5:1, unstripped gas air speed 2000h
-1under carry out, the volume ratio of circulation gas and fresh synthesis gas is 3.Fresh synthesis gas 6 (240L/h) is preheated to 180 DEG C through preheater 4, with the C being preheated to 170 DEG C through preheater 17
5-C
8beds is entered from fixed-bed reactor 2 top after cut 13 (6.5L/h) mixing.All products flow out from reactor bottom, reaction product is all collected and is then separated at three phases separator 3, the gas separated enters circular buffering tank 9, after entering stable state, a part (88L/h) is as periodic off-gases 8, make other purposes, a part (720L/h) makes circulation gas 7, converges as unstripped gas 4 with fresh synthesis gas (240L/h); The liquid separated enters rectifying tower 11 and carries out further cutting and separating, will be separated the C obtained
5-C
8a part (6.5L/h) for cut (boiling range is 28 DEG C to 126 DEG C) uses as circulatory mediator, and oil gas weight ratio is about 10:1, and all the other make other purposes.Under this operating mode, CO per pass conversion is 63.3%, and methane selectively is 5.75%, C
5 +space-time yield is 0.27g/ml
cath.This operating mode lower bed layer temperature distributing curve diagram is shown in curve a in Fig. 4, and curve b is without bed temperature distribution curve time oil circulation.Correlation curve a, b are visible, and can reach 14 DEG C without bed temperature difference time oil circulation, time oil circulation, the bed temperature difference is only 7 DEG C, without bed temperature fluctuation time oil circulation, amplitude is very large, when having oil circulation and bed temperature only has fuctuation within a narrow range, bed temperature is comparatively mild, and bed is without obvious focus.Final product distribution is as shown in table 3.
Table 3 embodiment 3 final product distribution table