Biomass graded temperature-control slow pyrolysis process and system thereof
Technical field
The invention belongs to the biomass energy technology field, relate to the preparation of biomass pyrolytic product, refer to a kind of biomass graded temperature-control slow pyrolysis process and system thereof particularly.
Background technology
The development and use of biomass energy are the focuses that application is competitively studied in countries in the world, are that the biomass gasification technology of target has also obtained using widely to produce various synthetic gas.According to the characteristics of biogas metallization processes as can be known, the characteristic difference of gasified raw material, the granularity difference of gasified raw material, the every index in the time of all will directly having influence on the productive rate of operating load, synthetic gas and tar of vapourizing furnace and material gasification.Usually, when different raw materials reacts in different vapourizing furnaces, also different to the requirement of its granularity.Generally, require the granularity of gasified raw material to diminish gradually according to the order of fixed bed, fluidized-bed, air flow bed.But the raw material that particle is too little might be taken out of vapourizing furnace by air-flow, thereby gasification efficiency is descended, so particle grain size distribution also is an important controlling index, for example for the entrained flow bed gasification technology of shell company, require granularity in the gasified raw material will reach more than 90% less than the particle of 0.15mm.Therefore, the pulverizing pre-treatment of raw material has material impact to the performance of gasification system.
For biomass material, fibrous texture characteristics in view of biomass material, show very strong toughness, adopt traditional cutting or the extruding particulate material that disintegrating process obtained to be difficult to satisfy the requirement of vapourizing furnace reactor feed, and the expense of this mechanical workout mode is very high, and this has become the important factor in order that the restriction biomass material gasifies.
In order to solve the problem that biomass material is difficult to pulverize, the scientific research personnel has adopted pyrolytic treatment process in advance to biomass material, in the hope of obtaining to satisfy the requirement of vapourizing furnace reactor feed.This pyrolytic technique is as the pretreating scheme of gasification system raw material charging, be biomass decomposition to be become fugitive constituent and charcoal by pyrolysis, thereby be transformed into the charcoal of easy pulverizing with being difficult to the comminuted fibres element in the biomass, carry out the processing treatment of simple and regular more as required, just can satisfy the granularity requirements of biomass gasification system imported raw material.
At present, the assembled scheme to biomass material elder generation pyrolysis regasify in gasification system has demonstrated powerful superiority, does not allow very much manageable defective but prior biological matter pyrolysis pretreatment technology still exists pyrolysis product.Pyrolysis product has material impact to follow-up gasification process, and pyrolytic process especially pyrolysis temperature and pyrolysis time pyrolysis product is had a direct impact, different Heating temperatures and ultimate temperature, different pyrolysis times, resulting pyrolysis product is all different.For the high temperature fast pyrogenation stage, pyrolysis product mainly is a bio-crude oil, and at a slow speed for the pyrolysis phase, pyrolysis product mainly is charcoal and pyrolysis gas for low temperature.When pyrolysis during as pretreatment technology of biomass material gasification, the product that needs to obtain is charcoal and pyrolysis gas.In addition, for fear of influence, need to reduce CO in the pyrolysis gas to the finished product synthetic gas composition
2, component such as bio-crude oil content, increase CO and H in the pyrolysis gas
2Content, improve the quality and the quantity of charcoal in the pyrolysis product, this all requires pyrolysis temperature and pyrolysis time are carried out strict control.
Yet, in existing biomass pyrolytic pretreatment technology,, all only in a pyrolysis reactor, finish the pyrolytic process in above-mentioned each stage no matter be from hot mode or outer hot mode, be difficult to the homogeneity of the whole pyrolyzer internal heating speed of assurance.Therefore, the biomass material of different positions may be in different pyrolysis phase, is difficult to satisfy suitable pyrolytical condition like this, can't guarantee the quality of pyrolysis product.Particularly for pyrolytic process from hot mode, more be easy to generate following problem: at first, its combustion zone local temperature is too high, heat-up rate is too fast, make the temperature distribution in the whole pyrolysis reactor extremely inhomogeneous, heat-up rate can't strict be controlled, certainly will cause that service temperature is difficult to meet the demands in the pyrolytic process, and then make pyrolysis product undesirable, influence follow-up gasification; Secondly, adopt the partial combustion biomass from hot mode, with the CO that makes in the pyrolysis gas
2Content significantly increases, thereby has obviously reduced the gasification efficiency of gasification system.
Summary of the invention
Purpose of the present invention is exactly the biomass graded temperature-control slow pyrolysis process and the system thereof that will provide a kind of raw material wide accommodation, pyrolytic process to be convenient to regulate and pyrolysis product is convenient to control.
For achieving the above object, the biomass graded temperature-control slow pyrolysis process that the present invention is designed, adopt outer thermal source to provide heat for the biomass that are distributed in the pyrolyzer at different levels, according to of the impact analysis of biomass pyrolytic operational condition to pyrolysis product, according to the requirement of gasification system and synthetic gas product to pyrolysis product, step by step biomass material is carried out controllable drying and pyrolytic reaction at a slow speed, control pyrolytic outlet temperature is in 350~500 ℃ scope, to impel CO in the pyrolysis gas
2Lower with the content of gaseous state bio-crude oil, CO and H
2Content higher, guarantee the quality and the quantity of charcoal product simultaneously.Its technological process comprises the steps:
1) with the biomass of natural air drying, by the cutting facility of routine, it is the coarse fodder of 10~80mm that roughing becomes particle diameter;
2) above-mentioned coarse fodder is sent in the first step pyrolyzer, carried out the processing in predrying stage, keeping its interior temperature is 50~120 ℃, and a part of water evaporates in the biomass is fallen, and water content is reduced to 10~20%;
3) material after predrying is sent in the pyrolyzer of the second stage, carried out the processing in depth drying stage, keeping its interior temperature is 100~150 ℃, and the most of water evaporates in the biomass is fallen, and water content is reduced to 5~10%;
4) material behind the depth drying is sent in the third stage pyrolyzer, carry out the reaction in pre-charing stage, keeping its interior temperature is 150~250 ℃, unstable component in the biomass such as hemicellulose etc. begin to take place tangible chemical transformation at this moment, hydrocarbon component in the biomass and most oxygen and react being lower than under the situation of burning-point obtain CO, H
2O, a spot of CO
2And acetic acid, solid matter is the primary product in this stage;
5) all substances after the pre-carbonization reaction are sent in the fourth stage pyrolyzer, carry out the reaction in charing stage, the reaction in this stage mainly is weak thermopositive reaction, keeping its temperature is 250~350 ℃, make most of biomass that decomposition reaction for the first time take place, mainly generate charcoal, bio-crude oil and a small amount of gaseous product;
6) all substances after the carbonization reaction are sent in the level V pyrolyzer, carry out the reaction of calcination stage, this stage is thermo-negative reaction, keeping its temperature is 350~500 ℃, wherein part biological crude oil generation decomposition reaction for the second time, wherein a small amount of charcoal and water vapor are reacted, the final pyrolysis gas that is obtained is from the outlet output of level V pyrolyzer top, and the charcoal that is obtained is exported from level V pyrolyzer lower part outlet.
In the above-mentioned biomass graded temperature-control slow pyrolysis process, outer thermal source preferably adopts the high-temperature synthesis gas that directly causes the biomass gasifying furnace output terminal.After biomass material reacts gasification through vapourizing furnace, the temperature range of the high-temperature synthesis gas of output is at 500~900 ℃, at full capacity during steady running generally about 900 ℃, high-temperature synthesis gas has a large amount of sensible heats, effectively utilize this heat, both can save a large amount of energy, can improve the gasification efficiency of whole biomass gasification system again for pyrolytic process of the present invention.
In the above-mentioned biomass graded temperature-control slow pyrolysis process, the first step to the air pressure in the level V pyrolyzer preferably all is controlled in the scope of 3.0~4.0MPa.Under high like this pressure, can effectively suppress the growing amount of bio-crude oil in the biomass pyrolysis process, impel biomass pyrolytic to become more CO and H
2, with the quality of further raising pyrolysis product.
In the above-mentioned biomass graded temperature-control slow pyrolysis process, first step residence time of material to the level V pyrolyzer is 120~400s.Like this, the total residence time of material in pyrolyzer at different levels is 600~2000s, and the heat-up rate of material is remained in the scope of 10~60 ℃/min, thereby satisfies pyrolytic intensification requirement at a slow speed.
For realizing the custom-designed biomass graded temperature-control slow pyrolysis system of above-mentioned technology, comprise system shell, one end of system shell is provided with the source import of outer hot gas, the other end of system shell is provided with the outlet of outer hot gas source, be positioned at outer hot gas source ingress in the system shell and be provided with main heat exchanger, main channel, outer hot gas source and by-pass, outer hot gas source have been arranged in parallel between the outlet of hot gas source import outside and outer hot gas source in the system shell, be respectively arranged with main channel baffle door and the by-pass baffle door that to regulate the switching degree on main channel, outer hot gas source and the by-pass, outer hot gas source, be exported to outer hot gas source importer in the main channel, outer hot gas source along outer hot gas source and the first step of being with helix transporting device arranged to the level V pyrolyzer to arranged in series successively, the first step forms the structure of pyrolyzer at different levels and at different levels interchanger staggered arrangement to spaced apart to the fourth stage time interchanger by the first step respectively between the level V pyrolyzer; Wherein: first step pyrolyzer is provided with biomass inlet and first step water vapor discharge outlet, and second stage pyrolyzer is provided with second stage water vapor discharge outlet, is respectively arranged with charcoal outlet and pyrolysis gas outlet on the level V pyrolyzer.
Further, also be provided with the by-pass interchanger in the by-pass, above-mentioned outer hot gas source.When the pyrolysis temperature in the main channel, outer hot gas source is too high, can allow part by-passing road, outer hot gas source discharge, and carry out heat exchange at the by-pass interchanger, this mode has not only realized the temperature of reaction of biomass in the flexible control pyrolyzer at different levels, and has realized making full use of of heat.
Further, above-mentioned outer hot gas source import preferably directly links to each other with the high-temperature synthesis gas output terminal of biomass gasifying furnace.Simultaneously, above-mentioned pyrolysis gas outlet directly links to each other with the pyrolysis gas input terminus of biomass gasifying furnace, and above-mentioned charcoal outlet then links to each other with the wood charcoal powder input terminus of biomass gasifying furnace by the charcoal fuel pulverizing plant, to form the benign cycle of gasifying biomass technological process.Like this, not only can make full use of the used heat of high-temperature synthesis gas, significantly save the pre-pyrolysis of biomass material and handle required energy, and, can greatly improve the gasification efficiency of whole biomass gasification system by simple circulation.
The outer hot gas of above-mentioned biomass graded temperature-control slow pyrolysis system employing source particularly high-temperature synthesis gas provides energy for pyrolyzer at different levels, by main channel, outer hot gas source and the by-pass, outer hot gas source that is arranged in parallel, and staggered arrangement multistage pyrolyzer and the interchanger in the main channel, hot gas source outside, make outer hot gas source and biomass material carry out countercurrent flow.All have the stirring puopulsion unit in each grade pyrolyzer, to guarantee that pyrolyzer endogenous substance raw materials at different levels are by even heating.Biomass are from first step pyrolyzer, in each grade pyrolyzer, heated gradually, the temperature of pyrolyzer at different levels is followed successively by 50~120 ℃, 100~150 ℃, 150~250 ℃, 250~350 ℃, 350~500 ℃, heat exchange by interchanger at different levels is regulated, guarantee that outer hot gas source enters pyrolyzer at different levels with suitable temperature, the Heating temperature and the heating rate of strict control pyrolytic processs at different levels, thus guarantee that the pyrolysis product that obtains is satisfactory pyrolysis gas and charcoal from the last step pyrolyzer.
Compared with prior art, the present invention has the advantage of following several respects:
One, the outer thermal source classification heat treated water content of process using of the present invention is up to the natural air drying biomass more than 20%, can get rid of of the influence of too much moisture content to follow-up pyrolytic process, guarantee not occur too much water vapor in the pyrolysis gas, thereby guarantee that pyrolysis product meets the requirement of biomass gasification reaction.
Its two, the outer thermal source classification pyrolysis of process using of the present invention is through the biomass of depth drying, can guarantee at a slow speed the pyrolytic operational condition and cross range request, makes biomass carry out controllable reaction in each pyrolysis phase, thereby obtains the pyrolysis product that needs.
They are three years old, technology of the present invention can adopt the high-temperature synthesis gas of directly drawing from biomass gasifying furnace, the sensible heat form biomass pyrolysis that makes full use of high-temperature synthesis gas provides required energy, not only reached the purpose that energy is provided for pyrolysis control, and the temperature of reduction high-temperature synthesis gas, improve the comprehensive utilization ratio of high-temperature synthesis gas waste heat, improved the working efficiency of whole biomass gasification system simultaneously.
They are four years old, system of the present invention adopts the mode of pyrolyzer at different levels and interchanger staggered arrangement at different levels, can effectively control the thermal exchange of every grade of pyrolyzer China and foreign countries thermal source, guarantee the Heating temperature and the rate of heating of pyrolytic processs at different levels, effectively control final pyrolysis temperature, the heat that interchanger at different levels exchanged simultaneously can be transported to other places that needs, and guarantees that outer thermal source has higher comprehensive utilization ratio.
Its five, system of the present invention adopts the structure of by-pass, outer hot gas source, has further improved temperature controlled validity of pyrolyzer at different levels and handiness in the main channel, outer hot gas source, can further ensure the component requirement of ultimate pyrolysis product.
This shows, pyrolytic process of the present invention and system have pyrolytic process and are convenient to regulate, the superiority that pyrolysis product is convenient to control, particularly with this pyrolytic process during as raw material handling procedure in early stage of whole biomass gasification system, the pyrolysis product that is obtained can directly be imported vapourizing furnace and carry out gasification reaction, the high-temperature synthesis gas that gasification reaction produced directly provides thermal source for the pyrolytic reaction in early stage of biomass again, both cooperation, produce benign cycle, thereby guaranteed the quality of the high-temperature synthesis gas that whole biomass gasification system is produced, also strengthened the adaptive faculty of biomass gasification system simultaneously raw material.The present invention is not only applicable to the pyrolysis processing of biomass materials such as general timber, cotton stalk, straw class, and is suitable for solid-state organic gasified raw materials such as domestic refuse, industrial refuse.
Description of drawings
Accompanying drawing is a kind of structural representation of biomass graded temperature-control slow pyrolysis system.
Embodiment
Below in conjunction with the drawings and specific embodiments biomass graded temperature-control slow pyrolysis process of the present invention and system thereof are described in further detail:
Biomass graded temperature-control slow pyrolysis system shown in the figure has a system shell 4 of vertically arranging, the bottom design of system shell 4 has outer hot gas source import 3, and outer hot gas source import 3 directly links to each other with the high-temperature synthesis gas output terminal of biomass gasifying furnace 1.The top design of system shell 4 has outer hot gas source outlet 29, delivers to subsequent processing device through the high-temperature synthesis gas of heat exchange cooling from outer hot gas source outlet 29.System shell 4 bottoms are positioned at outer hot gas source import 3 places a main heat exchanger 15 are installed, and main heat exchanger 15 at first carries out heat exchange cooling to the high-temperature synthesis gas that enters.
System shell 4 inside have been arranged in parallel between hot gas source import 3 outside and the outer hot gas source outlet 29 and have been main channel, vertically arranged outer hot gas source 5 and by-pass, outer hot gas source 28.On main channel, outer hot gas source 5 and the by-pass, outer hot gas source 28, an end that exports 29 places near outer hot gas source is respectively arranged with main channel baffle door 6 and the by-pass baffle door 27 that can regulate the switching degree, in the by-pass, outer hot gas source 28 also design by-pass interchanger 25 arranged, flow that can be by regulating high-temperature synthesis gas and heat exchange amount are controlled the interior temperature range in main channel, outer hot gas source 5.
5 inside, main channel, outer hot gas source, snakelike successively from top to bottom series connection, horizontally disposed have the band helix transporting device the first step to level V pyrolyzer 7,9,10,12,13.Wherein: first step pyrolyzer 7 is provided with biomass inlet 26 and first step water vapor discharge outlet 20, links to each other by first step vertical channel 8 between first step pyrolyzer 7 and the second stage pyrolyzer 9; Second stage pyrolyzer 9 is provided with second stage water vapor discharge outlet 19, links to each other by second stage vertical channel 18 between second stage pyrolyzer 9 and the third stage pyrolyzer 10; Link to each other by third stage vertical channel 11 between third stage pyrolyzer 10 and the fourth stage pyrolyzer 12; Link to each other by fourth stage vertical channel 17 between fourth stage pyrolyzer 12 and the level V pyrolyzer 13, be respectively arranged with charcoal outlet 14 and pyrolysis gas outlet 16 on the level V pyrolyzer 16.Pyrolysis gas outlet 16 directly links to each other with the pyrolysis gas input terminus of biomass gasifying furnace 1, and charcoal goes out 14 and links to each other with the wood charcoal powder input terminus of biomass gasifying furnace 1 by charcoal fuel pulverizing plant 2.
To between the level V pyrolyzer 7,9,10,12,13, be respectively arranged with the first step in the first step to the fourth stage time interchanger 21,22,23,24.The first step to the fourth stage time interchanger 21,22,23,24 is the interchanger of calandria structure, be horizontally disposed state, the first step is spaced apart to level V pyrolyzer 7,9,10,12,13, form the structure of pyrolyzer at different levels and at different levels interchanger staggered arrangement, help controlling the differing temps requirement in the pyrolyzer at different levels.The first step to the fourth stage time interchanger 21,22,23,24 can independently carry out heat exchange respectively, and the back of also can connecting is unified carries out heat exchange, as long as can guarantee that the interior temperature range of pyrolyzer at different levels is in setting regions.
The principle of work of biomass graded temperature-control slow pyrolysis system of the present invention is such:
500~900 ℃ high-temperature synthesis gas from biomass gasifying furnace 1 output, by outer hot gas source import 3 input system shells 4 inside, and carry out suitable heat exchange by main heat exchanger 15 and lower the temperature, its objective is to make high-temperature synthesis gas enter main channel, outer hot gas source 5, for pyrolytic processs at different levels provide corresponding energy with suitable temperature.Enter the high-temperature synthesis gas of main channel, outer hot gas source 5, successively by level V to first step pyrolyzer 13,12,10,9,7 and the fourth stage to the first step time interchanger 24,23,22,21, because interchanger at different levels and pyrolyzer staggered arrangement at different levels have guaranteed that the temperature in the pyrolyzer at different levels reduces successively.According to the different characteristic of various concrete biomass, the temperature range in the pyrolyzer at different levels also is not quite similar, and the researchist can obtain optimum data by experiment:
For woody biomass such as timber, the temperature in the first step pyrolyzer 7 are that the temperature in 80~120 ℃, second stage pyrolyzer 9 are that temperature in 120~150 ℃, third stage pyrolyzer 10 are that temperature in 190~240 ℃, fourth stage pyrolyzer 12 are that temperature in 300~340 ℃, level V pyrolyzer 13 are 400~480 ℃.
For draft biolobic material such as straw, the temperature in the first step pyrolyzer 7 are that the temperature in 50~90 ℃, second stage pyrolyzer 9 are that temperature in 100~140 ℃, third stage pyrolyzer 10 are that temperature in 150~200 ℃, fourth stage pyrolyzer 12 are that temperature in 250~310 ℃, level V pyrolyzer 13 are 350~410 ℃.
The first step to level V pyrolyzer 7,9,10,12,13 can be worked under atmospheric pressure state, but preferably gives 3.0~4.0MPa air pressure, and the growing amount with bio-crude oil in effective inhibition biomass pyrolysis process impels biomass pyrolytic to become more CO and H
2, further improve the quality of pyrolysis product.
When temperature is too high in the pyrolyzer at different levels, can suitably regulate the aperture of main channel baffle door 6 and by-pass baffle door 27, the part high-temperature synthesis gas is flow through from by-pass, outer hot gas source 28, thereby guarantee the temperature and the heating rate of pyrolytic processs at different levels.The by-pass interchanger of being arranged in the by-pass, outer hot gas source 28 25 can guarantee that outer hot gas source goes out the cooling discharge requirement of the high-temperature synthesis gas at 29 positions.
After natural air drying, open-textured biomass material tentatively are ground into the particle of granularity 10~80mm by conventional cutting mechanics, advance 26 from biomass and enter in the first step pyrolyzer 7, carry out pre-dried with the temperature and time of setting; The moisture content that evaporates is discharged from first step water vapor discharging 20, and water content is that 10~20% biomass material enters in the second stage pyrolyzer 9 by first step vertical channel 8, carries out depth drying and handle under the temperature and time of setting; The moisture content that is evaporated once more is from second stage water vapor discharging 19 dischargings, water content is that 5~10% material enters in the third stage pyrolyzer 10 by second stage vertical channel 18, carrying out charing just under the temperature and time of setting handles, control temperature at this moment is below the burning-point of raw material, make raw material carry out slow reaction, mainly obtain CO and solid matter; Allow all products in first carbonization reaction stage enter in the fourth stage pyrolyzer 12, decomposition reaction for the first time takes place under the temperature and time of setting, obtain a small amount of bio-crude oil and charcoal by third stage vertical channel 11; At last all products are sent in the level V pyrolyzer 13 by fourth stage vertical channel 17, the decomposition reaction second time of bio-crude oil is taken place under the temperature and time of setting, and the reaction of a small amount of charcoal and water vapor, thereby desired pyrolysis product obtained.
Because the temperature in the pyrolyzer at different levels evenly increases by 50~120 ℃, 100~150 ℃, 150~250 ℃, 250~350 ℃, 350~500 ℃ gradient, the residence time of biomass material in pyrolyzer at different levels remains in the scope of 120~400s, make that biomass material is heated gradually, low speed reaction has guaranteed CO lower in the pyrolysis product
2With bio oil content, suitable vapour content and more H
2With CO content.Set helix transporting device can guarantee that sticking wall, agglomeration do not take place biomass material in the pyrolyzer at different levels in conveying and pyrolytic process.Final pyrolysis product is mainly charcoal and pyrolysis gas, charcoal is by charcoal outlet 14 outputs, send in the charcoal fuel pulverizing plant 2 through piping, send into biomass gasifying furnace 1 after the fragmentation, pyrolysis gas is then by pyrolysis gas outlet 16 outputs, also deliver to biomass gasifying furnace 1 through piping, in biomass gasifying furnace 1, finish final gasification reaction, obtain needed synthetic gas.