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1.
Australian coal loaded with a mixed catalyst of K2SO4+Ni(NO3)2 has been gasified with steam in a fluidized bed reactor of 0.1 m inside diameter at atmospheric pressure. The effects of
gas velocity (2-5 Ug/Umf), reaction temperature (750-900 °C), air/coal ratio (1.6-3.2), and steam/coal ratio (0.63-1.26) on gas compositions, gas
yield and gas calorific value of the product gas and carbon conversion have been determined. The product gas quality and carbon
conversion can be greatly improved by applying the catalyst; they can also be enhanced by increasing gas velocity and temperature.
Up to 31% of the catalytic increment in gas calorific value could be obtained at higher temperatures. In the experimental
runs with variation of steam/coal ratio, the catalytic increments were 16-38% in gas calorific value, 14-57% in carbon conversion,
5-46% in gas yield, and 7-44% in cold gas efficiency. With increasing fluidization gas velocity and reaction temperature,
the unburned carbon fraction of cyclone fine for catalytic gasification decreased 4-18% and 13-16%, respectively, compared
to that for non-catalytic gasification.
Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his
retirement from Korea University. 相似文献
2.
《Fuel》2007,86(10-11):1631-1640
The advanced high efficiency cycles are all based on gas turbine technology, so coal gasification is the heart of the process. A 2 MWth spout-fluid bed gasifier has been constructed to study the partial gasification performance of a high ash Chinese coal. This paper presents the results of pilot plant partial gasification tests carried out at 0.5 MPa pressure and temperatures within the range of 950–980 °C in order to assess the technical feasibility of the raw gas and residual char generated from the gasifiier for use in the gas turbine based power plant. The results indicate that the gasification process at a higher temperature is better as far as carbon conversion, gas yield and cold gas efficiency are concerned. Increasing steam to coal ratio from 0.32 to 0.45 favors the water–gas and water–gas shift reactions that causes hydrogen content in the raw gas to rise. Coal gasification at a higher bed height shows advantages in gas quality, carbon conversion, gas yield and cold gas efficiency. The gas heating value data obtained from the deep-bed-height displays only 6–12% lower than the calculated value on the basis of Gibbs free energy minimization. The char residue shows high combustion reactivity and more than 99% combustion efficiency can be achieved. 相似文献
3.
Coal gasification has been internationally accepted as one of the most viable and effective clean coal technology for power
generation. Presently, the coal being produced in India is having high ash content and it is a major constraint for most of
the commercial applications in process industries. The present paper deals with the variation of higher heating value (HHV)
of the product gas and carbon conversion with different inherent properties under different operating conditions in fluidized
bed gasification. It has been observed that HHV of product gas increases with volatile mater, fixed carbon and temperature,
whereas, mineral matter, air and steam show decreasing effect on HHV. On the other hand, carbon conversion increases with
volatile matter, air, steam and temperature. It has also been observed that mineral matter provides catalytic effect to a
certain level for carbon conversion, whilst, decreasing trend has been observed with the fixed carbon. 相似文献
4.
Results are presented for gasification of coal and char by means of air or air-steam mixtures in fluidised bed reactors of three different volumes. Two sizes of coal feedstock particles, 0.5-1.0 mm and 1.0-1.5 mm, and one size of char particles, 0.5-1.5 mm, were used. The calorific value of generated gas and the carbon conversion are presented as a function of particle residence time. For coal gasification higher carbon conversion has been obtained at the same particle residence time than for char gasification. For the steam gasification, a lower gas heating value of about 4 MJ/m3 (S.T.P.) was obtained. 相似文献
5.
串行流化床煤气化试验 总被引:3,自引:3,他引:0
针对串行流化床煤气化技术特点,以水蒸气为气化剂,在串行流化床试验装置上进行煤气化特性的试验研究,考察了气化反应器温度、蒸汽煤比对煤气组成、热值、冷煤气效率和碳转化率的影响。结果表明,燃烧反应器内燃烧烟气不会串混至气化反应器,该煤气化技术能够稳定连续地从气化反应器获得不含N2的高品质合成气。随着气化反应器温度的升高、蒸汽煤比的增加,煤气热值和冷煤气效率均会提高,但对碳转化率影响有所不同。在试验阶段获得的最高煤气热值为6.9 MJ8226;m-3,冷煤气效率为68%,碳转化率为92%。 相似文献
6.
Changsui Zhao Liangsheng Lin Keliang Pang Wenguo Xiang Xiaoping Chen 《Fuel Processing Technology》2010,91(8):805-809
The gasification characteristics of natural coke from Peicheng mine with steam were investigated in a fluidized bed reactor. The effects of catalyst type, composition and dosage of catalyst on the yield, components and heating value of product gas, and carbon conversion rate were examined. The results show that fluidized bed gasification technology is an effective way to gasify natural coke. Also the results indicate that individual addition of K-, Ca-, Fe-, Ni-based catalyst effectively increases the gasification reaction rate of the natural coke samples. With the increase in catalyst dosage, the yield and heating value of product gas per hour increase obviously, and carbon conversion rate is improved substantially. Each of aforementioned catalysts has similar catalytic effect and trend, among which the effect of Ca-based catalyst is a little weaker. The optimum metal atom ratio of mixed catalyst is Fe/Ni/others = 35/55/10, and the mixed catalyst displays maximum catalytic performance when the catalyst dosage in the natural coke is about 4%. The experimental findings provide an interesting reference for large-scale development and utilization of natural coke. 相似文献
7.
Production of hydrogen and syngas via gasification of the corn and wheat dry distiller grains (DDGS) with oxygen in a continuous downflow fixed bed micro reactor are studied in this paper. A series of experiments have been performed to investigate the effects of reaction time (15–45 min), reactor temperature (700–900 °C) and oxygen to nitrogen ratio (0.08–0.2 vol./vol.) on product gas composition, gas yield, low heating value (LHV) and carbon conversion efficiency. Over the ranges of the experimental conditions used, the results obtained seemed to suggest that for both biomasses the operating conditions were optimized for a gasification temperature around 900 °C, an oxygen to nitrogen ratio of 0.08 and a reaction time of 30 min, because a gas richer in hydrogen and carbon monoxide and poorer in carbon dioxide and hydrocarbons. The results showed that the product gas of corn DDGS gasification has higher H2 and CO concentrations (11 and 56.5%) than that of wheat DDGS gasification (10.5 and 51.5%). In addition gasification of corn DDGS resulted to higher gas yield (0.42 m3/kg), LHV (10.65 MJ/m3) and carbon conversion efficiency (44.2%). 相似文献
8.
Duan Feng Bao-Sheng Jin Ya-Ji Huang Bin Li Yu Sun Yiming Wu Ming-Yao Zhang 《Korean Journal of Chemical Engineering》2010,27(6):1707-1714
High temperature preheated air and steam as gasifying agent and coal gasification was performed in a pressurized turbulent
circulating fluidized bed (CFB) gasification pilot plant to investigate the pressurized gasification process and estimate
its potential. Within the scope of this paper this test facility as well as its operation behavior was described. Furthermore,
the parameter pressure has been investigated regarding its influence on the syngas composition and was presented and discussed
in the following. The results show that the gasification quality is improved at higher pressure because of the better fluidization
in the reactor. Coal gasification at a higher pressure shows advantages in lower heat value and carbon conversion. With the
gasifier pressure increased from 0.1MPa to 0.3MPa, the gas heating value is increased by 15%. Increasing the gasifier pressure
would increase the carbon conversion from 57.52% to 76.76%. Also, the dry gas yield and efficiency of cold gas increase little
with the increase of the gasifier pressure. The operating parameter of pressure exists at optimum operating range for this
specific CFB coal gasification process. 相似文献
9.
《Fuel》2006,85(12-13):1935-1943
This paper presents modeling of a coal gasification reaction, and prediction of gasification performance for an entrained flow coal gasifier. The purposes of this study are to develop an evaluation technique for design and performance optimization of coal gasifiers using a numerical simulation technique, and to confirm the validity of the model. The coal gasification model suggested in this paper is composed of a pyrolysis model, char gasification model, and gas phase reaction model. A numerical simulation with the coal gasification model is performed on the CRIEPI 2 tons/day (T/D) research scale coal gasifier. Influence of the air ratio on gasification performance, such as a per pass carbon conversion efficiency, amount of product char, a heating value of the product gas, and cold gas efficiency is presented with regard to the 2 T/D gasifier. Gas temperature distribution and product gas composition are also presented. A comparison between the calculation and experimental data shows that most features of the gasification performance were identified accurately by the numerical simulation, confirming the validity of the current model. 相似文献
10.
鉴于湿生物质如食品加工工业残余物和城市污泥中含有大量蛋白质的情况,以氨基乙酸作为蛋白质的模型化合物进行超临界水气化实验,研究了反应温度和反应时间耦合条件下Na2CO3的催化特性以及氨基乙酸气化产物特性。结果表明:添加Na2CO3会增大氨基乙酸的气化效率、氢气的体积分数和产率以及反应后液体化学需氧量(COD)的去除率,且添加质量分数为0.1%时的催化效果优于0.2%;Na2CO3主要是对H2产率产生影响,其催化机理与已有碱性化合物的催化机理不同,可能是通过促进氨基乙酸的水解产物(甲酸)的脱羧反应来提高H2的产率;氨基乙酸气化效率可达99.4%,生成物包括H2、CO2、N2、CH4和C2~C3气体,其中H2的体积分数可超过50%,产率可达1.8 L·g-1,且超过一半的份额来源于水,反应后液体清澈透明,COD和pH值指标均可以达到《生活杂用水水质标准》,可以进行回收利用。 相似文献
11.
流化床作为生物质气化反应器试验研究 总被引:13,自引:1,他引:13
在流化床生物质气化炉内 ,用空气进行气化生物质 (花生壳 )的试验研究 ,分析的参数是当量比ER 0 .2— 0 .4 5 ,气化床的温度 75 0— 85 0℃和加入二次风。当ER在 0 .2 5— 0 .33,气化燃气热值为 6 .2— 6 .8MJ/m3 ,气体产量在 2 6 0— 390m3 /h ,生物质燃烧时比气化产量在 1.2 8— 2 .0 3m3 /kg之间 ,炭转化率在 5 3%— 80 %。并对 7种农、林废弃物进行了初步气化试验研究 ,生成的燃气体积分数 :CO为 14 %— 18% ,H2 一般低于 6 % ,甲烷 4 %— 12 %。燃气热值在 4 70 0— 710 0kJ/m3 。试验结果表明 ,在流化床生物质气化炉中 ,通过在悬浮空间加入二次风 ,可使燃气热值得到提高。 相似文献
12.
《Fuel》1987,66(4):568-571
The effects of eleven catalysts on the steam gasification of Datong coal char were studied. The catalysts were oxides and chlorides of alkali and alkaline earth metals, separately or in combination. The catalytic effects of the NaCa composite on the reaction rate, methane conversion, steam decomposition and product gas composition and heating value were studied at reaction temperatures of 700–900 °C and pressures of 0.1, 1.1, 3.1 and 5.1 MPa. A kinetic equation of catalytic gasification was derived and the reaction rate constants and the activation energy at elevated pressure were determined. 相似文献
13.
Ammonia present in the product gas from coal gasification may increase NOx emissions from IGCC systems. A fixed bed reactor was used to study the effect of calcined limestone (CaO) on NH3 decomposition and reaction of NH3 and NO. Reactions at temperatures to 900°C in helium and in gas compositions typical of air-blown gasifiers were studied. Although CaO enhanced ammonia decomposition in helium, reaction in the gasification atmosphere resulted in the loss of this catalytic activity. Increasing the total pressure further reduced the rate of NH3 decomposition. CaO enhanced conversion of NO to NH3 in gasification atmospheres. 相似文献
14.
Woon-Jae Lee Sang-Done Kim Byung-Ho Song 《Korean Journal of Chemical Engineering》2002,19(6):1091-1096
To produce low calorific value gas, Australian coal has been gasified with air and steam in a fluidized bed reactor (0.1 m-I.Dx1.6
m-high) at atmospheric pressure. The effects of fluidizing gas velocity (2–5 Uf/Umf), reaction temperature (750–900 °C), air/coal ratio (1.6-3.2), and steam/coal ratio (0.63–1.26) on gas composition, gas yield,
gas calorific value of the product gas and carbon conversion have been determined. The calorific value and yield of the product
gas, cold gas efficiency, and carbon conversion increase with increasing fluidization gas velocity and reaction temperature.
With increasing air/coal ratio, carbon conversion, cold gas efficiency and yield of the product gas increase, but the calorific
value of the product gas decreases. When steam/coal ratio is increased, cold gas efficiency, yield and calorific value of
the product gas increase, but carbon conversion is little changed. Unburned carbon fraction of cyclone fine decreases with
increasing fluidization gas velocity, reaction temperature and air/coal ratio, but is nearly constant with increasing steam/coal
ratio. Overall carbon conversion decreases with increasing fluidization velocity and air/ coal ratio, but increases with increasing
reaction temperature. The particle entrainment rate increases with increasing fluidization velocity, but decreases with increasing
reaction temperature.
This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University. 相似文献
15.
The kinetics and catalysis of the reaction between steam and two different coal chars were investigated in a small fixed-bed reactor. Atmospheric pressure and temperatures between 600 and 850 °C were used. Various possible catalysts were tested, and the effect of catalyst concentration was examined. Of the catalysts used, potassium carbonate was the most effective. It was followed in order of decreasing effectiveness by sodium carbonate, lithium carbonate, potassium chloride, sodium chloride, and copper (II) oxide. Calcium oxide and iron (III) oxide were totally ineffective. The catalysts were more effective at higher concentration. Also, addition of 10% potassium carbonate to the coal char lowered the apparent activation energy of the reaction from 254.2 to 144.5 kJ/mol and the frequency factor from 2.41 × 108 to 1.32 × 104 s?1. The water-gas shift reaction reached equilibrium during gasification in the presence of alkali-metal carbonates and the product gas was primarily carbon dioxide and hydrogen. Without catalyst present, the water-gas shift reaction was far from equilibrium. 相似文献
16.
《Fuel》2005,84(12-13):1612-1621
Steam gasification of nascent char from rapid or slow pyrolysis of a Victorian brown coal was performed at 1073–1173 K in a novel drop-tube/fixed-bed reactor, in which steam-containing gas was forced to pass through an extremely thin bed of nascent char particles at sufficiently high velocity and large flux. The nascent char underwent parallel reactions consisting of non-catalytic gasification and catalytic one. The non-catalytic gasification followed first-order kinetics with respect to the fraction of unconverted carbon, and the rate constant was hardly influenced by operating variables such as heating rate for the pyrolysis, total pressure and even period of isothermal heating between the pyrolysis and gasification. The overall activity of inherent catalysts, alkali and alkaline earth metallic species, diminished due to volatilization and intra-particle deactivation, both of which were induced by the gasification. As a result, the catalytic gasification took place within a limited range of the char conversion up to 60–80%. The initial catalyst activity and the kinetics of activity loss largely depended on the operating variables as above and also partial pressure of steam. 相似文献
17.
《Fuel Processing Technology》2006,87(4):343-353
Biomass is a promising sustainable energy source. A tar-free fuel gas can be obtained in a properly designed biomass gasification process. In the current study, a tar-free biomass gasification process by air was proposed. This concept was demonstrated on a lab-scale fluidized bed using sawdust under autothermic conditions. This lab-scale model gasifier combined two individual regions of pyrolysis, gasification, and combustion of biomass in one reactor, in which the primary air stream and the biomass feedstock were introduced into the gasifier from the bottom and the top of the gasifier respectively to prevent the biomass pyrolysis product from burning out. The biomass was initially pyrolyzed and the produced char was partially gasified in the upper reduction region of the reactor, and further, char residue was combusted at the bottom region of the reactor in an oxidization atmosphere. An assisting fuel gas and second air were injected into the upper region of the reactor to maintain elevated temperature. The tar in the flue gas entered the upper region of the reactor and was decomposed under the elevated temperature and certain residence time. This study indicated that under the optimum operating conditions, a fuel gas could be produced with a production rate of about 3.0 Nm3/kg biomass and heating value of about 5000 kJ/Nm3. The concentration of hydrogen, carbon monoxide and methane in the fuel gas produced were 9.27%, 9.25% and 4.21%, respectively. The tar formation could be efficiently controlled below 10 mg/Nm3. The system carbon conversion and cold gasification efficiency reached above 87.1% and 56.9%, respectively. In addition, the investigation of energy balance for the scale-up of the proposed biomass gasification process showed that the heat loss could be recovered by approximately 23% of total energy input. Thus, partial fuel gas that was produced could be re-circulated and used to meet need of energy input to maintain the elevated temperature at the upper region of reactor for tar decomposition. It was predicted the heating value of product fuel gas would be 8000 kJ/Nm3 if the system was scaled up. 相似文献
18.
With increasing environmental considerations and stricter regulations, coal gasification, especially partial coal gasification,
is considered to be a more attractive technology than conventional combustion. Partial coal gasification was conducted in
detail under various experimental conditions in a lab-scale fluidized bed to study the factors that affected gas components
and heating value, including fluidized air flow rate, coal feed rate, and steam feed rate, gasification temperature, static
bed height, coal type and catalyst type. The experiment results indicate that gasification temperature is the key factor that
affects components and the heating value of gas is in direct proportion to gasification temperature. There exists a suitable
range of fluidized air flow rate, coal feed rate, steam feed rate and static bed height, which show more complex effect on
gas components. High rank bitumite coal is much more suitable for gasification than low rank bitumite coal. The concentrations
of H2, CO and CH4 of bitumite coal are more than those of anthracite coal. Compounds of alkali/alkaline-earth metals, such as Ca, Na, K etc.,
enhance the gasification rate considerably. The catalytical effects of Na2CO3 and K2CO3 are more efficient than that of CaCO3.
This work was presented at the 6
th
Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006. 相似文献
19.
Toshimitsu Suzuki Masaru Mishima Junji Kitaguchi Maki Itoh Yoshihisa Watanabe 《Fuel Processing Technology》1984,8(3):205-212
The catalytic steam gasification of four different coals using potassium and sodium carbonates as catalysts was carried out in a semi-flow type fixed-bed reactor. The coal was gasified with or without the catalyst under a steam—argon atmosphere at a heating rate of 50°C/s at 700–800°C. The catalytic activity of carbonates for gasification was remarkable for Japanese high-volatile coals (Miike and Takashima coals), and moderate for Australian medium-volatile coal (New Lithgow coal); however, the carbonates had little effect on gasification of Japanese lignite (Taiheiyo coal). It is assumed that Miike and Takashima coals soften and melt during the heating process to make the contact between char and catalyst better. New Lithgow and Taiheiyo coals do not have this property. Gasification was promoted significantly at lower temperatures when the catalyst was used. In both catalyzed and uncatalyzed runs the main products were hydrogen and carbon dioxide; the reaction temperature did not affect the composition of the gases much. A water—gas shift reaction occurred during gasification resulting in a large amount of carbon dioxide under a large excess of steam flow. 相似文献