Background technology
Along with the day by day exhausted and demand of human kind sustainable development to environmental protection of world petroleum resource, the clean coal that turns to representative with coal gas utilizes technology will in following fossil energy, play irreplaceable effect.Especially the rich coal of China is oil-poor, and coal saving amount accounts for third place in the world, and coal resources areal distribution is uneven, reasonable development and utilize Coal Gasification Technology to have long-range strategic importance to guarantee Chinese Energy Safety and Economic development.The features such as compare with existing Sweet natural gas, synthesizing methane is low with its cost, and (coal) raw material sources are abundant cause the increasing industrialization concern of people.
Current methanation technology can be divided into two kinds of two-step approach (indirect method) and single stage method (direct method) substantially.Two-step approach refers to existing mature technology (as moral formula air flow bed or lurgi gasifier technology), with oxygenants such as air or oxygens, coal or coal water slurry etc. is first gasificated into H
2with the product such as CO, product gas through cooling, acid gas removal body (as H
2s etc.), remove after the purification process such as entrained particles, by water gas shift reaction, adjust H/C ratio, finally synthesizing methane under Ni-based or other catalyst actions.The advantage of two-step approach is gasification and methanation two step process separate operation, and technology is relatively ripe, as the synthesizing methane technology (SNG) of Great Plains.Shortcoming is that cost compare is high because synthetic gas need to add costliness and complicated treating plant, and owing to introducing purified synthesis gas and water-gas shift device, technique overall thermal efficiency is lower.The two-step approach formally putting into production at present only has the technology of Great Plains, other all relatively immature.
Single stage method is that coal is gasificated into methane with water vapour direct reaction under catalyzer (being generally base metal catalysts) effect.Exxon company has carried out the research work of a large amount of catalytic coal gasifactions under the subsidy of USDOE to the eighties at twentieth century 70, the general flow of its technique is overheated steam to be carried out to catalytic gasification with the coal that is mixed with catalyzer in fluidized-bed react direct synthesizing methane.Except coal, refinery coke etc. also can adopt similar technique containing the material of high fixed carbon, as US2007/0083072 has proposed a kind of technical process of catalytic gasification petroleum slag.Compare with two-step approach, it is simple that single stage method has technique, thermo-efficiency advantages of higher.Shortcoming is need to additionally provide to prepare high temperature (800-900 ℃) overheated steam equipment and attemperator, so that gasify required heat make up the thermosteresis that system radiating causes of anaerobic to be provided.
Coal reacts generation methane with water be micro-thermo-negative reaction, as shown in reaction formula (1):
C+H
2O→CH
4+CO
2 5.4KJ/mol (1)
Only need in theory to add the power loss that a small amount of heat causes to maintain system radiating.But gasification is attended by the parallel reactors such as water vapour and coal gasification reaction (reaction formula (2)) and water gas shift reaction (reaction formula (3)) simultaneously, wherein water vapour and coal gasification reaction (reaction formula (2)) are strong endothermic reaction, and level of response is larger, so actually operating needs more heat to maintain constant temperature gasification reaction.
C+H
2O→H
2+CO 131KJ/mol (2)
CO+H
2O→CO
2+H
2 -41KJ/mol (3)
Traditional method that maintains suitable catalytic gasification temperature (~700 ℃) is the inlet air temperature (800~900 ℃) that adopts higher water vapour, as the catalytic coal gasifaction technology of Exxon, for example, referring to H.A.Marshall and F.C.R.M.Smits, " Exxon catalytic coalgasification coal gasification process and large pilot plantdevelopment program; " Pittsburgh, PA, USA, 1982,357-377 page.The overheated steam of preparing 800~900 ℃ needs sectionalized superheater and superpower boiler conventionally, causes system total energy consumption higher.In addition, the temperature-rise period at water vapour from saturated steam to overheated steam, there is the etching problem of material under High Temperature High Pressure, therefore to producing and carrying the material of the equipment of overheated steam to have higher requirement.Use the patent US4292048 of single stage method to propose the method with methane reforming, CH
4and H
2cO and H that O reaction generates
2and from the isolated CO of vapourizing furnace and H
2pass into vapourizing furnace, to improve methane yield and to make reaction approach hankering property, thereby reduce the needed heat of thermo-negative reaction (being mainly reaction formula (2)).The shortcoming of this method is required CO and H
2internal circulating load is larger, has increased system energy consumption and equipment size.
Detailed Description Of The Invention
Method of the present invention is carried out in the two-stage vapourizing furnace being connected in series.Below in conjunction with Fig. 1, elaborate the present invention.
In step a of the present invention, coal and oxygen-containing gas are reacted in one-level vapourizing furnace, generate and comprise CO, CO
2, H
2, H
2the gasification gaseous product of O.Wherein coal can pass into the form of coal water slurry or dry coal dust in one-level vapourizing furnace, and apparatus for feeding is that the slurry feed equipment of this area routine is if high pressure water coal slurry transferpump (as surge pump) and coal-water slurry nozzle or feeding-in solid body equipment are as lock hopper charging and pressurization air blowing equipment.Meanwhile, from pass into oxygen-containing gas to one-level vapourizing furnace, described oxygen-containing gas can be air, oxygen-rich air or purity oxygen.Coal and oxygen, in the temperature of 900-1600 ℃ of one-level vapourizing furnace and the lower generating gasification reaction of the pressure of 20-70atm (referring to absolute pressure, lower same), generate and comprise CO, CO
2, H
2, H
2the gasification gaseous product of O, if use air or oxygen-rich air, this gasification gaseous product also comprises nitrogen and rare gas element.The gasification reaction of coal and oxygen is emitted amount of heat, and this heat part is for maintaining the high temperature of one-level vapourizing furnace, and another part is contained in gasification gaseous product for future use.Gasification gaseous product moves upward along one-level vapourizing furnace, and the lime-ash producing after gasification is discharged from one-level vapourizing furnace bottom.
In step b of the present invention, to passing into refrigerant in described gasification gaseous product, lower the temperature, obtain one-level gaseous product.The object that passes into refrigerant cooling is that the temperature of gas is adjusted to the temperature that is applicable to performance katalysis a little more than the catalyzer of secondary vapourizing furnace.Wherein refrigerant is that liquid water or temperature are that the water vapour of 200~350 ℃ or the gas separating technology after two-stage vapourizing furnace technique of the present invention are separated and CO and the H of recirculation
2, or their mixture.In the embodiment operating at the mixture that uses them, refrigerant be take water or water vapour as main, the CO of recirculation and H
2play auxiliary cooling effect, circulation CO and H
2main purpose be the CH improving in secondary vapourizing furnace
4yield.As its name suggests, the temperature of these refrigerants should be lower than the temperature of gasification gaseous product.When refrigerant is liquid water or water at low temperature steam, due to the existence of water gas shift reaction (seeing aforesaid equation 3), the gas phase composition of gasification gaseous product can change; When refrigerant is CO and the H of recirculation
2time, the gas phase of gasification gaseous product forms also and can therefore change.To make the gaseous product after gas phase composition changes be called one-level gaseous product because mixing coolant cools.Wherein refrigerant can pass into any position between the outlet of one-level vapourizing furnace at the middle part of one-level vapourizing furnace, for example, by the middle part at one-level vapourizing furnace at least one pair of between the outlet of one-level vapourizing furnace, be preferably the nozzle that contraposition lays and pass in one-level vapourizing furnace.Or refrigerant also can be passed in the connecting tube between one-level vapourizing furnace and secondary vapourizing furnace.Or, in any position between can exporting by the middle part at one-level vapourizing furnace to one-level vapourizing furnace and the connecting tube between one-level vapourizing furnace and secondary vapourizing furnace, all pass into refrigerant and carry out performing step b.The temperature of the one-level gaseous product of cooling rear formation is 800-900 ℃.
In step c of the present invention, described one-level gaseous product is passed in secondary vapourizing furnace and with coal and catalyst reaction, obtain the secondary gas product that comprises methane.Wherein, the temperature in secondary vapourizing furnace is 650-750 ℃, and pressure is 20-40atm, and the required heat of temperature maintaining in secondary vapourizing furnace can completely or partially be provided by one-level gaseous product.The catalyzer using in this step c is selected from alkaline carbonate or alkali metal hydroxide or their mixture.Coal and catalyzer can pass into respectively in secondary vapourizing furnace or pass in secondary vapourizing furnace with the form of mixture, preferably the form with mixture passes in secondary vapourizing furnace, wherein by this area conventional means, coal and aqueous catalyst solution are mixed, after being dried, obtain the mixture of coal and catalyzer.The apparatus for feeding adopting is also the conventional apparatus for feeding of this area, such as lock hopper feeding unit etc.The requirement of reacting required water coal ratio according to fluidization and catalytic gasification in secondary vapourizing furnace can preferably additionally pass into overheated steam in secondary vapourizing furnace, for the auxiliary transformation efficiency that maintains fluidized state and improve gasification.The temperature of described overheated steam is 800~900 ℃, pressure is 20~40atm, it can directly pass in secondary vapourizing furnace or pass in the connecting tube between one-level vapourizing furnace and secondary vapourizing furnace, preferably directly pass in secondary vapourizing furnace, for example, by being arranged in the conical distribution plate of secondary vapourizing furnace bottom, enter secondary vapourizing furnace.Under the effect of catalyzer, there is reacting as shown in following equation with one-level gaseous product in coal dust, generation comprises the secondary gas product of methane, this secondary gas product leaves secondary vapourizing furnace, enter follow-up gas delivery operation, the lime-ash producing in secondary vapourizing furnace is discharged from secondary vapourizing furnace bottom.
C+H
2O→H
2+CO (4)
CO+H
2O→CO
2+H
2 (3)
3H
2+CO→CH
4+H
2O (5)
Secondary gas product adopts the conventional separation means in this area to isolate CO, H in follow-up gas delivery operation
2, CO
2deng, finally obtaining highly purified methane gas, these separation means are that technician is known, do not repeat them here.The CO separating in separation circuit and H
2can be separately as refrigerant Deng gas, or, as other refrigerant as the fill-in of liquid water or water at low temperature steam, with implementation step b.
The lime-ash of discharging from secondary vapourizing furnace, contain the materials such as semicoke, lime-ash and catalyzer.Can pass through therefrom Separation and Recovery catalyzer of the conventional separation means in this area, and the catalyst recirculation reclaiming is used, these are all that technician is known, repeat no more.
The one-level vapourizing furnace adopting in method of the present invention can be air flow bed, fluidized-bed or carry bed.The example of air flow bed can be the several types such as egas air flow bed of Shell, GEHuo ConocoPhilips company; The example of fluidized-bed can be ugas fluidized-bed, can be also that KRW is gray melting poly-fluid bed; Carrying the example of bed is the conveying vapourizing furnace of KBR, etc.When these vapourizing furnaces of direct use do not carry out any transformation to it, need in the connecting tube between one-level vapourizing furnace and secondary vapourizing furnace, pass into refrigerant.As the preferred embodiments of the invention, can transform above-mentioned various vapourizing furnaces, described transformation referred to before the outlet of these vapourizing furnaces sets up coolant jet, preferably set up at least one pair of and be the nozzle that contraposition is laid, by these nozzles, refrigerant is passed in one-level vapourizing furnace, for gasification gaseous product is carried out to chilling.Wherein without Shell, the GE of transformation or the concrete structure of the egas air flow bed of ConocoPhilips respectively referring to below with reference to document:
Schuurman, the United States Patent (USP) 4202672 that is entitled as " Apparatus for gasification of finelydivided fuel " of P.J;
Schlinger, W.G. " Coal gasification development andcommercialization of the Texaco coal gasification process ", International Journal of Energy Research, 2007, vol 4 (2), 127-136; With
Rotter, the United States Patent (USP) 4306506 that is entitled as " Gasification apparatus " of Franz;
Carry the example of bed to see below with reference to document:
Brandon M.Davis,Roxann Leonard,P.Vimalchand,Guohai Liu,Peter V.Smith,Ron Breault,“Operation of the PSDF transportgasifier”,Twenty-second Annual Pittsburgh Coal Conference,Pittsburgh,PA,September 12-15,2005。
Gray melting poly-fluid bed about uga s fluidized-bed and KRW, referring to below with reference to document:
Jequier, J., Longchambon, L., and Van De Putte, G., " Thegasification of coal fines ", and J.Inst.Fuel, 1960,33584-591, and
Hartman,H.F.,Belk,J.P.,Reagan,E.E.,Low Btu coalgasification processes,vol 2,Selected Process Descriptions,1978,11,A-139-151;
By reference the content of these patents or paper is incorporated to herein.
Fig. 2 has provided improved egas air flow bed as the example of one-level vapourizing furnace, has only provided the charging situation of each material, and omitted concrete vapourizing furnace internal structure in Fig. 2.After coal water slurry and oxygen mix, enter the bottom of one-level vapourizing furnace, in the generating gasification reaction of high temperature (1400-1500 ℃) district of one-level vapourizing furnace bottom.Different from the coal water slurry swirling flow feeding manner at original egas bis-fragment position places, any position before the outlet of one-level vapourizing furnace, be provided with at least one pair of and be the nozzle that contraposition is laid, by this nozzle, refrigerant is passed in one-level vapourizing furnace, the mode that this contraposition is laid has been strengthened mixing of gasification gaseous product and refrigerant, thereby has realized rapid cooling.
The secondary vapourizing furnace adopting in method of the present invention can be jet-flow bed or circulating fluidized bed, but preferred jet-flow bed.Because gasification gaseous product and one-level gaseous product are all without dust removal process, therefore enter and usually carry coal ash or unreacted Coal Char Particles completely in the one-level gaseous product of secondary vapourizing furnace secretly, for the gas distribution grid of the particle plugging secondary vapourizing furnace that prevents from carrying secretly, secondary vapourizing furnace preferably adopts the operating method of jet-flow bed.Jet-flow bed, is named again jet fluidized-bedly, is to spray into by (vertical, level or inclination) jet at a high speed the bed type that the fluidized-bed of a finite space forms.In practical application, commonly the flat spout of high speed vertical fluid fluid by bottom conical distribution plate or flat grid distributor center or insertion nozzle enter bed and form jet and the coexistent two kinds of flow states of fluidisation.About structure and the operating method of jet-flow bed, can be referring to following two reference:
Jequier, J., Longchambon, L., and Van De Putte, G., " Thegasification of coal fines ", and J.Inst.Fuel, 1960,33584-591, and
Hartman,H.F.,Belk,J.P.,Reagan,E.E.,Low Btu coalgasification processes,vol 2,Selected Process Descriptions,1978,11,A-139-151;
By reference the full text of these reference is incorporated to herein.Fig. 3 has provided a kind of diagram of jet-flow bed: one-level gaseous product injects bed from jet-flow bed pipe core, not only avoided entrained particles to stop up gas distribution grid, and can be by adjusting caliber and the charge flow rate of pipe core, realize the separated of ash that density is different and Jiao.Fluidisation passes into from bottom with water vapour, and coal and catalyzer pass into from certain position, secondary vapourizing furnace middle part.
It will be appreciated by those skilled in the art that the present invention is applicable to coal incessantly, but can expand to multiple carbonaceous material, such as refinery coke etc.Wherein refinery coke refers to that crude oil is after distillation is separated with mink cell focus by lightweight oil, the product that mink cell focus changes into through the process of hot tearing again, and its main component is carbon, more than occupying 80wt%, remaining is hydrogen, oxygen, nitrogen, sulphur and metallic element.
Advantage of the present invention is as follows:
(1) after regulating by temperature, the high-temperature gas that in this technique, one-level vapourizing furnace produces can be directly used in secondary vapourizing furnace, for secondary vapourizing furnace provides reaction required reaction heat, the load that has alleviated secondary catalytic gasification overheated steam boiler, overall thermal efficiency is higher than conventional two-step methane technology method processed.
(2) gas enters before secondary vapourizing furnace without adding independent treating plant to remove CO
2, H
2s or entrained particles, reduced facility investment.
(3) one-level vapourizing furnace produces is rich in CO and H
2the synthetic gas of (60-80 volume %), can improve the methane yield of secondary vapourizing furnace catalytic gasification effectively, has relatively alleviated CO and H with a ground beetle alkylation process
2internal circulating load, thus energy consumption reduced.