Keywords: fixed bed; gasifiers; coal gasification; Chinese national standards, coal gasifiers
0 Introduction
Fixed bed coal gasifier gasification anthracite, bituminous, lignite produced by LHV producer gas is widely used in metallurgy, chemical industry, building materials, machinery and many other industrial furnaces. Before the 1980s, most of Datong bituminous coal gasification and Yangquan, Jincheng, Jiaozuo anthracite. Although coal is gasified coal gasification processes affecting key, but before 1988 no coal gasification to follow national standards. With fixed bed coal gasifier (single-stage or two-stage furnace furnace) of continuous improvement and localization of coal gasification national standard (GB9143-88), (GB9143-2001), (GB9143-2008), (GB50195-94) also will be promulgated, Table 1
Table 1 national standard for coal gasifiers
Different coal will have its own distinctive characteristics, such as: chemical reactivity of anthracite weak, and chemical reactivity of lignite is very strong, anthracite, bituminous coal, lignite chemical reactivity, see Figure 1 and Table 2; anthracite The fixed carbon content of more volatile content is less, and the fixed carbon content of lignite less volatile content of more; anthracite and lignite no significant adhesion, and has revealed the different bituminous adhesion. Therefore, the gasification of anthracite, bituminous, lignite coal gasification applied to the same standards, does have its drawbacks.
1 ash melting softening temperature
Coal gasification process in the furnace will appear slagging gasification reaction affecting the normal key factor, and the softening temperature of the molten ash, slag is to determine whether the key. However, the chemical reactivity of coal gasification and restricts the level of the reaction temperature. For example in Table 2, the gasification Jiaozuo anthracite, when the furnace temperature reached 1300 ℃ gasification, its chemical reactivity α (1300 ℃) to reach 83%, if the required chemical reactivity of α> 90% (increase of the CO2 reduction into CO chance), then the gasification furnace temperature should be> 1300 ℃. At this point, if the softening temperature of the molten ash <1300 ℃, and the ash content in coal is high, there will be slagging, affecting the normal gasification. However, when lignite gasification, gasification reaction when the furnace temperature reached 1000 ℃, its chemical reactivity can be achieved α> 90%. At this point, if the softening temperature of ash fusion 1000 ℃, even lignite ash content of more, it will not cause slagging and because of the negative impact. Therefore, gasification of lignite, it is still applied to the existing national standard coal gasification, have greater deviations. Thus, the determination of the melting ash softening temperature should be considered chemical reactivity of coal (α) factor.
In addition, there are many gas stations with the gasification of coal ash melting point lower than the national standard coal gasification (example: Shenmu weakly caking coal, Indonesian elderly lignite, bituminous coal, Australia, etc.), but in the gasification operation , not found severe slagging furnace, because of the chemical reactivity of the coal α (1300 ℃) are> 80%.
(2) the adhesion of coal
Since no adhesive anthracite and lignite, therefore, the adhesion of coal gasification, only for bituminous coal, this is because the process of bituminous coal in a specific law of heat, see Table 3. However, in different types of bituminous coal, there is a strong bond, secondary bonding and weakly caking of the points.
Caking coal, bituminous coal is means that when heated, leaving the colloid produced bonded into briquettes of coal properties. If strong bituminous adhesive is heated to 300 ℃ ~ 400 ℃ occur when bonding expanded, the smaller the coal particles of the coal agglomeration into larger clumps, which leads to uneven distribution of the furnace air, and also hinder the uniformity of the material layer down, so that the furnace gas chemical conditions deteriorate. Thus, as the bituminous coal gasification of coal caking index is important. Reflect the state of bituminous coal in the heat adhesion and expansion of the test items are: glial layer thickness Y value, bond index GR · I, Roca index R · I, free swelling number of CSN and industrial analysis cinder characteristics.
We know, when there is a certain adhesion bituminous heated to a certain temperature (350 ℃ ~ 400 ℃), gelatinous body is generated, and has a certain adhesion plastic.
According to the molecular structure of coal and coal colloid science theories, bituminous, although its molecular structure is very complicated, but can be seen as the bituminous very irregular molecular structure of the polymer space, the basic molecular structure unit is condensed with an aromatic ring as the mainstay of many side chains and functional groups of macromolecules. When bituminous coal is rapidly heated to a certain temperature, increased cleavage of macromolecules in the coal, this time a large number of side chains and functional groups on the aromatic ring condensed from breakage, while the functional groups in its side chain can be further cleaved at its moment, These unstable side chains and functional groups will focus on the large number of both fracture and fragmentation, in which gaseous small molecular weight, molecular weight in liquid medium, and large molecular weight cut off those side-chain functional groups and aromatic ring condensed with non-combustible collection of solid state components. Thus, gas, liquid, and solid states coexist, namely the formation of a certain bond plasticity gelatinous body. Colloid quantity and quality, the process determines heated bituminous strong and weak adhesion. If bituminous slow heat. These highly unstable side chains and functional groups will be cleaved off and gaseous escape, that affect the process of heating bituminous binder to form a certain plasticity gelatinous body. In summary, it is easy to see the adhesion of bituminous coal is its moment in the fast process formed.
Bituminous adhesion testing, (GB9143-88) and (GB9143-2001) standard coal gasification, coal represents the adhesion strength of Y values gelatinous layer thickness (mm), glial layer index is based on bituminous coal Determination (GB497-87) to detect, that is, to the measured coal into coal cup is detected, 8 ℃ per minute temperature rose from 250 ℃, 3 ℃ per minute and then gradually heated to 620 sequence ℃, in this case the measured Y value gelatinous layer thickness (mm) size, determine the bituminous strong and weak adhesion, using this method detects the strength of adhesion of bituminous coal, bituminous coal in a furnace in accordance with the cryogenic distillation The heating process, there are certain guiding significance.
(GB9143-2008) standard coal gasification, coal represents the strength of the adhesion bond index GR · I, is based on bituminous coal caking index measurement method (GB5447-85) detected, that is, will be equipped with the measured coal sample crucible, placed in a temperature of 850 ℃ ± 10 ℃ in a muffle furnace; (GB50195-94) two coal gasification furnace standards, which means that the strength of adhesion bituminous Roca index R · I and that freedom of bituminous adhesive swelling swelling number of CSN, is respectively bituminous Roca index measurement method (GB5449-85) and bituminous free expansion ordinal measurement method (GB5448-85) detection. That is, coal samples were tested will be equipped with a crucible, placed in 850 ℃ ± 5 ℃ for measuring the electric furnace. Another is by observing method by analysis of coal (GB212-9) Determination of time-volatile coal coke residue inside the crucible characteristics (1-8), to determine the adhesion of bituminous strong and weak, and the determination of coal volatile sharing, but also will be equipped with the tested coal samples crucible placed in a heating temperature control at 900 ℃ ± 5 ℃ under isothermal conditions detected.
Therefore, CR-I, RI, CSN, coke residue characteristics (1-8) method of detecting the coal sample to be tested are placed in an oven controlled at the heating temperature> 800 ℃ under the conditions, are coal samples to be tested heating temperature is momentarily exceeded 600 ℃, which does not comply with bituminous coal gas furnace in order gradually when heated in the temperature range cryogenic distillation process. Therefore, CR-I, RI, CSN, cinder characteristics (1-8) to determine the adhesion of coal debatable.
For example: a glass factory has used the moderate adhesion of bituminous coal, coke residue characteristics (1-8) 5, in φ3.0cm single-stage gas furnace, not only to normal gasification and gas will be produced for melting glass.
3 The thermal stability of coal
Thermal stability is a hot strength of coal, which means the coal under high temperature is easily cracked into small particles, but also affect the normal coal gasification furnace important indicator. In coal thermal stability factors are: the process by heating or evaporation of water within the coal and crack coal volatiles escape leaving; or because of large temperature difference between inside and outside of lump coal, as the different components of the coal material expansion coefficient caused by the different coal fragmentation; or because of thermal decomposition of carbonates in coal into CO2, leaving the lump broken. Generally, anthracite and bituminous poor thermal stability as compared, because the internal structure of anthracite closely with its fixed carbon are more brittle, while the thermal conductivity of the coal are relatively low, so that the temperature difference than lump Large; lignite and bituminous poor thermal stability as compared, because the moisture lignite and bituminous more volatile than the other, the internal structure of lignite are more loosely.
(GB9143-88), (GB9143-2001), (GB9143-2008), (GB50195-94) standard coal, coal thermal stability is determined by method (GB1573-89) for detection. Determination of thermal stability of coal is to be detected with coal into the crucible temperature to 900 ℃ in a muffle furnace for detecting. Although suitable for the non-caking anthracite and lignite, but not suitable for a certain adhesion bituminous. This is because the lump coal into the furnace after the order to go through the gradual heating up of dry, dry lutetium process, and appeared broken into fine particles of coal thermal cracking, often appear in the <600 ℃ heating heating process, while bituminous coal in an instant under high temperature (> 800 ℃), will produce a certain bond plasticity gelatinous body, and thus be detected coal samples (6 ~ 13mm) without drying, dry lutetium bonding process has been gathered into a mass, and that and can not show the coal at low temperature drying process is cracked into a dry lutetium fine particles. Therefore, using (GB1573-89) Determination of the thermal stability of coal to bituminous coal testing to determine the thermal stability is something wrong.
4 lignite gasification
China is not only storage of coal, coal-producing countries, but also very complete coal varieties. Before the twentieth century, multi-use anthracite coal gasification, weakly caking coal, long flame coal and coke, and lignite gasification rarely, only a variety of gasified fuel used 1.0%. Thus, in (GB9143-88), (GB9143-2001), (GB50195-94) standard coal gasification, were not included in the lignite.
On China's coal reserves, which accounts for about 14% of lignite. In recent years, large lignite reserves in Inner Mongolia, Yunnan, Jilin and other remote areas, using local produce lignite replace expensive imported bituminous coal gasification growing to do, therefore, in (GB9143-2008) standard coal gasification, for the first time included in the lignite. The coal gasification previously promulgated standards, only for anthracite and bituminous coal. Considering lignite and anthracite and bituminous coal, compared to the lignite coal's shallow, and thus more vulnerable lignite texture, its cold and hot strength are adversely affected. In addition, because the moisture lignite and ash content is high, and thus its low heat. However, we should also see the strong chemical reactivity of lignite, which helps in the furnace while the gasification reaction. In addition, because of the volatile content of lignite is high, but also conducive to CH4 and CmHn gas in the generation of the calorific value of the gas produced is not low, but the gasification gas yield strength and low.
As with lignite coal gasification, early in the last century and four fifties, the former Soviet Union, and in recent years the gasification of lignite and Indonesia, there are many successful examples. Therefore, since the different characteristics of anthracite and bituminous coal gasification of lignite are listed in, then it should be based on the characteristics of lignite, re-enacted for the gasification of lignite coal criteria and corresponding detection methods.
5 Coal particle size, moisture, ash and sulfur
Coal particle size and size distribution, related to the lump coal into the furnace is able to achieve normal after complete gasification of the important factors, many of our gas stations have not been running seriously. Practice shows that if we can according to different characteristics of the identified coal into the furnace with coal particle size and grade of coal, it will be a good multiplier effect. Therefore, it is recommended should be (GB9143-88), (GB9143-2001) standard coal gasification in the "granularity" (particle size classification) execution.
In (GB9143-2008) standard coal gasification, coal refined according to different water requirements in the coal, sulfur and ash merits of grading, which will help to develop appropriate according to the characteristics of the coal of the gas of indicators is to develop standards for coal gasification significant progress.
6 Other
On coal gasification, in the (GB9143-88), (GB9143-2001), (GB9143-2008), (GB50195-94) of the respective use of the "coal quality standards", "coal standards" "coal gasification technology requirements and test methods", "coal gasification technology indicators." Whether it can be considered a "coal gasification quality requirements and testing methods," such as: "fixed bed coal gasifier coal gasification quality requirements and test methods"; "two-stage gas furnace coal gasification quality requirements Detection Methods ";" fixed bed coal gasifier gasification of lignite quality requirements and testing methods. "
7 Conclusion
Amend or add a professional performance standards, which is to show the continuous progress of science and technology. Atmospheric fixed bed coal gasification technology, after half a century of exploration and practice, has made considerable progress. Based on the maturity of the technology, energy conservation and environmental awareness should be injected in order to maintain its long-term vitality. Therefore, the gasification of coal has issued standards, careful analysis, and proposed is consistent with the theoretical basis and practical experience to consider new coal gasification standards, gas workers have any. The author of standard coal gasification superficial analysis, peer reference purposes only.
