High energy syngas production by waste tyres steam gasification in a rotary kiln pilot plant. Experimental and numerical investigations

This paper presents experimental and numerical results on steam gasification of waste tyres in a rotary kiln pilot plant. Both the process performance and the gas features have been evaluated varying the feeding ratio (FR), defined as the steam/tyres mass ratio. First, several experimental tests have been performed. Then, the obtained experimental results have been used to verify the consistency of a numerical model developed with the aid of the commercial code ChemCAD®. Once done, the effect of increasing the FR on the gas energy content has been evaluated.Numerical results showed that the gas energy content increases as the FR increases as well, achieving a maximum value for FR = 0.33 that produced a gas which composition N₂ free is (H₂ = 52.7%_vol, CO = 18.1%_vol, CO₂ = 7.0%_vol, CH₄ = 22.2%_vol) in correspondence of which the lower heating value (LHV) is equal to 29.5 MJ kg_gas⁻¹. Higher FR values do not produce a further increase of the gas energy content, rather require a greater amount of input energy for heating the steam from the atmospheric to the process temperature.     

Thermal expansion of slag and fly ash from coal gasification in IGCC power plant

Integrated gasification in combined cycle (IGCC) is an electrical power generation system which is characterized to be a clean coal technology different than conventional process in combustible treatment. IGCC process gives rise to inorganic solid wastes in the form of vitreous slag and fly ashes with singular thermal properties. The gasification of the fuel takes place at high temperature and pressure in reducing atmosphere. Under that conditions, gases such as H₂, N₂ or CO, which are the main components of the gas mixture in the gasifier, show a high solubility in the melt and during the cooling remain enclosed in the vitreous slag. When these wastes are afterward thermal treated in oxidizing conditions, two phenomena occur. The development of a crystalline phase by devitrification of the glassy matrix and the releasing of the enclosed gas, which starts at temperatures nearly to the softening point. At higher temperatures the bubbles with increasing kinetic energy tend to ascent with difficult through the viscous liquid phase and promotes an expansive reaction, giving rise to a foam glass-ceramic product. This paper has been focused on the study of thermal expansion in slag and fly ash samples from the ELCOGAS IGCC power plant located in Puertollano (Spain).     

固定床气化与气流床水煤浆气化集成的能量与经济分析

针对煤制天然气工艺中固定床气化产生大量含有焦油、酚等难处理物质的废水,提出了将固定床气化和气流床水煤浆气化相结合的气化方式解决废水问题。考察了未分离焦油煤气水直接制浆和分离焦油后酚水再制浆的两种气化集成方式,以煤制天然气项目为基础对其进行能量与经济分析。结果表明:与单一气流床相比,固定床气化和气流床水煤浆气化耦合提高了系统冷煤气效率;当固定床与气流床水煤浆气化干基煤处理量比为2,未分离焦油煤气水直接制浆和分离焦油后酚水再制浆两种气化集成方式的气化系统煤耗分别为563 kg·km^-3(CO+H₂+3.12×CH₄)和599 kg·km^-3(CO+H₂+3.12×CH₄),氧耗分别为212 m³ O₂·km^-3(CO+H₂+3.12×CH₄)和206 m³ O₂·km^-3(CO+H₂+3.12×CH₄),冷煤气效率分别为84.44%和86.74%,总热效率分别为72.53%和74.87%,且副产焦油的气化集成方案与单一固定床气化方案相比,其天然气生产成本增加不明显,经济上可行。     

Performance of an entrained-flow gasification technology of pulverized coal in pilot-scale plant

Performance of an entrained-flow gasification technology of pulverized coal in pilot-scale plant is introduced. The gasifier was operated for a throughput of 30–45 t coal per day at pressures of 1–3 MPa. Dense-phase pneumatic conveying was employed for coal's feeding to the gasifier using nitrogen and carbon dioxide as carrier gas, respectively. Effects of the operating conditions including oxygen/carbon ratio and steam/carbon ratio on gasification results were investigated, and the concentration of (CO + H₂) in gaseous products reached up to about 97% (vol., dry basis) when CO₂ was employed as carrier gas. Moreover, performances of some important instruments in the conveying system of pulverized coal, such as the level indicator and the solid mass flow meter, were also investigated. The typical operating results in this plant such as (CO + H₂) concentration, oxygen consumption, coal consumption, carbon conversion and cold gas efficiency were almost as good as those of some well-known dry-fed entrained-flow coal gasification plants.     

超临界水中氨基乙酸的气化产氢特性

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。     

Dynamic modeling with experimental calibration for the syngas production from biomass fixed-bed gasification

In this article, a dynamic biomass gasification model was developed based on the hybrid peripheral fragmentation and shrinking-core model. To improve the accuracy of syngas generation transient prediction, the chemical kinetic model was trained using global surrogate optimization techniques. The pre-exponential corrections of kinetic reaction rates are calibrated under noncatalytic conditions, employing experimental transient data of syngas generation rate and compositions under different temperatures and gasifying agents. The Dynamic Coordinate search using Response surface model and the Gap Optimized Multi-objective Optimization using Response Surfaces framework were employed as the numerical solvers for finding the global optimum solution of the pre-exponential factors. The calibrated particle-level kinetic models based on both single-objective and multi-objective approaches have been validated by experimental data in four different biomass gasification scenarios. The calibrated model shows an over 95% decrease in terms of integrated squared error (ISE)-based model mismatch when compared with the original model.     

Polygeneration of hydrogen and power based on coal gasification integrated with a dual chemical looping process: Thermodynamic investigation

This paper assesses, from a thermodynamic perspective, the conversion of coal to power and hydrogen through gasification simultaneously with a dual chemical looping processes, namely chemical looping air separation (CLAS) and water–gas shift with calcium looping CO₂ absorption (WGS-CaL). CLAS offers an advantage over other mature technologies in that it can significantly reduce its capital cost. WGS-CaL is an efficient method for hydrogen production and CO₂ capture. The three major factors, oxygen to coal (O/C), steam to coal (S/C) and CaO to coal (Ca/C) were analyzed. Moreover, the comparisons of this suggested process and the traditional processes including integrated gasification combined cycle (IGCC), integrated gasification combined cycle with carbon capture and storage (IGCC-CCS) and integrated gasification combined cycle with calcium-based chemical looping (IGCC-CaL) were discussed. And, the exergy destruction analysis of this suggested process has also been calculated.     

Techno-economic assessment of gasification as a process step within biomass-to-liquid (BtL) fuel and chemicals production

This study investigates the gasification process step which converts a biomass derived intermediate called slurry into synthesis gas (syngas) for subsequent synthesis of fuel and chemicals. The slurry is produced by fast pyrolysis plants and is then processed in a pressurized entrained flow gasifier. The resulting syngas has to be conditioned and cleaned before it is converted in a Fischer-Tropsch or dimethyl ether synthesis in order to complete a biomass-to-liquid (BtL) production such as the considered bioliq concept. This two-stage concept allows the economic transportation of biomass over long distances, due to the relatively high energy density of the slurry produced in the first stage. In addition, reductions in specific investments and costs for further processing in the second stage are enabled by economies of scale. This paper addresses possibilities for further process development and presents an outlook for a commercial implementation of a biomass derived slurry gasification. Within the techno-economic assessment, different process configurations for the gasification facility are analysed using an Aspen Plus process model and compared from an economic and energetic point of view. The varying process parameters are operating pressure, gasification agent, syngas composition as well as feedstock composition. The techno-economic assessment concludes that it is possible to produce syngas at costs of about 23 €-Cent/Nm³ based only on biomass feedstock. The production costs can almost be cut by half when considering co-gasification of biomass and coal. Further higher operating pressures of the gasification process are identified as a major influence on production costs reduction. The potential effects of marketing by-products such as excess heat as well as excess nitrogen are also addresses in this study.     

Continuous biodiesel production using a fixed-bed Lewis-based catalytic system

It was developed a fixed bed tubular continuous reactor to produce biodiesel, using pellets of aluminum oxide doped with zinc oxide. The pellets were placed into a tubular reactor as a 30 cm long column (2.65 kg). The reactor was feed with soybean oil (168 g h⁻¹) and methanol or ethanol (89 g h⁻¹) with the temperature fixed at 100 °C. Under these conditions it was possible to convert soybean oil into biodiesel in up to 75% yield in the case of methanol and 35% for ethanol. Increasing the temperature to 180 °C, it was possible to ethanolise soybean oil with yields up to 78%. It is important to note that after a steady state is achieved the conversions remained approximately constant with time. It is also worth to mention that the fixed bed remained active for more than 120 h, showing no catalyst leaching or deactivation, and so far it was not possible to determine its overall productivity.     

恩德粉煤气化炉的气化工艺及应用

煤气化技术对于促进煤炭的综合利用、改善当前资源紧缺状况并减少环境污染具有重要的意义。对恩德粉煤气化炉的特点和气化工艺流程、工艺操作进行了分析,并以景德镇市焦化煤气总厂应用恩德粉煤气化炉实现煤气化的工程实例,分析了恩德粉煤气化技术的运行指标和投资效益。     

煤催化气化催化剂发展现状及研究展望

煤与气化剂(如水蒸气、CO2、H2和O2)之间的气化反应最有效的催化剂主要为碱金属、碱土金属以及过渡金属的盐类,根据其组成,详细论述了煤催化气化催化剂的特性。据研究,在气化反应中碱金属催化剂如Na、K等易与煤中矿物质如Si或Al反应致使催化剂失活,同时过渡金属易被煤中S毒化,这在一定程度上制约了煤催化气化工业化进程。论述了煤催化气化催化剂的研究方向,认为开发新型高效、低廉且易回收催化剂是有必要的。     

The characteristics of inorganic elements in ashes from a 1 MW CFB biomass gasification power generation plant

This paper investigated the characteristics of inorganic elements in ashes from biomass gasification power generation (BGPG) plant. The ash samples of the gasifier ash, separator ash and wet scrubber ash were collected in a 1 MW circulating fluidized bed (CFB) wood gasification power generation plant. Particle size distribution of ashes was determined by gravimetric measurement and super probe analyzer. The concentrations of trace elements and major ash-forming elements, such as As, Al, Ca, Cd, Cr, Cu, K, Mg, Na, Ni, Pb, Ti in different ashes as a function of particle size were determined by Inductive Coupled Plasma Spectrometer. The concentrations and distribution coefficient and enrichment factors of the inorganic elements in ashes were studied. X-ray fluorescence spectrometer and X-ray powder diffraction were used to provide information on the characteristics of the ashes. The results showed that most of the trace elements had an enrichment tendency in the finer size particles. A considerable amount of the ashes was residual carbon. Most of the volatile e.g. halogen elements and alkali elements existed mainly in wet scrubber ash and enriched in fly ash. Most of the Si, Ni, Pb, Zn, Cr, Cd were found in separator ash, indicating an enrichment of heavy metal elements in separator ash. K, S, Mn, Cu mainly existed in gasifier ash.     

Steam gasification of coal char catalyzed by K2CO3 for enhanced production of hydrogen without formation of methane

Steam gasification of coal char catalyzed by potassium carbonate was investigated on a laboratory fixed-bed reactor to examine the catalytic effects not only on the reaction rate but also on the reaction selectivity, and non-catalytic gasification of coal char was performed by way of contrast. It was observed that the catalytic gasification of coal char with steam occurred significantly in a temperature range of 700-750 °C, producing a hydrogen-rich gas with slight formation of carbon monoxide and virtually no formation of methane. An oxygen transfer and intermediate hybrid mechanism of the catalytic char gasification with steam is proposed for understanding of the experimental data regarding both the kinetic behaviors and reaction selectivity. The study has highlighted the advantages of the catalytic gasification of coal char over the conventional coal gasification with respect to the reaction selectivity. The catalytic steam gasification of coal char makes it possible to eliminate or simplify the methane reforming and water-gas shift processes in the traditional gas-to-hydrogen purification system.     

Production of hydrogen and syngas via gasification of the corn and wheat dry distiller grains (DDGS) in a fixed-bed micro reactor

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%).     

Lower emission plant using processed low-rank coals

Low-rank coals can be processed into non-fouling coal, ultra-low ash coal, and coals containing catalysts. Systematic studies of the action of acid to reduce ash in a number of low-rank coals have shown total ash reduction varied from 96% to 30%; the extent of ash reduction was limited by the nature of minerals, which may be removed using various acids, including HF, to produce ultra-low ash coal. A commercial process must operate at elevated temperatures, but this must not produce toxic wastewater; data are provided to show that wastewater may be treated and water recycled without polluting the environment. The addition of effective catalysts results in enhanced reactivity of the coal to oxygen and steam; experimental data show high yield of H₂ from char and steam, and accompanying post-gasification chemistry. Development of catalytic steam gasification requires an understanding of aqua-chemistry and the thermal transformations of inorganics as the coal is heated. The scientific basis exists for processing low-rank coals, but commercial application requires: (i) high production rates, (ii) treating wastewater produced from coal treatment plant, (iii) catalysts that increase the yield of H₂ from steam gasification, and (iv) plant that achieves high power and thermal efficiencies. Modelling studies for super-critical plant, and for direct coal-fuelled turbine in combined cycle, illustrate the potential for lower-emission technology; catalytic steam gasification offers the cleanest option for future coal-fuelled plant.     

Hydrogen generation by catalytic gasification of motor oils in an integrated fuel processor

Catalytic gasification of waste motor oil (MO) for the generation of high purity of hydrogen and then integrated to a proton exchange membrane fuel cell (PEMFC) is economically and environmentally attractive. Thus, the objective of the present work was to investigate a MO catalytic gasification for generating high-purity hydrogen with 15 wt.% NiO/Al₂O₃ catalysts. In a lab-scale fixed-bed downdraft experimental approach, catalytic gasification of MO was accompanied by a substantial production of syngas at 760–900 K. From the XANES spectra, most of the Ni(II) reduced to Ni(0) was found in the MO catalytic gasification process. The EXAFS data also showed that the central Ni atoms have a Ni–O and a Ni–Ni with bond distances of 2.04 ± 0.05 Å and 2.48 ± 0.05 Å, respectively. In addition to over 85% of syngas generation, approximately 8.35 × 10⁵ kcal h⁻¹ of thermal energy was recovered and cold gas efficiency (CGE) was 77–84% when the catalytic gasifier was operated at O/C atomic ratios between 1.1 and 1.3. The proposed syngas production unit can be integrated in a fuel processor (e.g. PEMFC), in order to separate and purify the syngas to yield a 99.99% hydrogen stream. Moreover, cost or benefit analyses of MO catalytic gasifiers of 10- and 20-TPD (tons per day) were also performed.     

A pre-heating vaporization technology of coal-water-slurry for the gasification process

A pre-heating vaporization technology of coal water slurry, CWS, was developed to increase the efficiency of coal gasification with the reduction of oxygen consumption. A CWS pre-heating experimental unit having a capacity of 2.0 tons-coal/day was manufactured. After the CWS was heated to 573 K at about 10 MPa, water in CWS was continuously vaporized in a tube of which the diameter increased gradually (2–10 mm I.D.), and dry coal particles with steam were atomized and fed to a vessel. No aggregation of coal particles was observed in the atomized samples. The temperature and the pressure distributions of the fluid were calculated with empirical heat transfer and pressure drop correlations. The calculated results well corresponded to the experimental data measured in some test points. Using the calculation model, a large scale apparatus of 100 tons-coal/day was designed using KNO₃ + NaNO₂ + NaNO₃ molten salt as a heating medium.     

Two-stage equilibrium model for a coal gasifier to predict the accurate carbon conversion in hydrogen production

The performance of the Texaco gasifier in hydrogen production was studied numerically. To estimate the accurate carbon conversion, a two-stage equilibrium model was proposed. In the proposed model, the two reactions which determined the carbon conversion were separated from other vapor–vapor reactions. The governing equations of the proposed model were derived and a self-consistent method was developed to solve the governing equations. The %AAD of the calculated carbon conversions from the measured values was 2.89 and that of the calculated gas production rate was 0.64. Calculated gas compositions showed a fairly good agreement with the experimental ones for commercial scale plants. It was found that the chemical reactions that occurred in the Texaco gasifier possess a mechanism for keeping the carbon conversion close to unity against a wide variation in the H₂O to coal ratios.     

炼油厂制氢技术路线选择

为确定适合我国炼油厂的制氢工艺路线,以低成本获得高品质氢气,对比分析了可供炼油厂采用的各种制氢技术,包括轻烃蒸汽转化、重质油气化、煤/石油焦气化和焦炉气制氢等的工艺流程、投资、消耗等,并对各种技术进行综合技术经济评价及成本分析。结果表明,煤/石油焦制氢的总成本最低为0.74元/m~3,重质油制氢成本最高为1.42元/m~3,天然气制氢在当前低迷的市场行情下成本仍高于煤制氢,为0.87元/m~3。煤/石油焦制氢不仅具备成本优势,而且可以优化炼油厂的物料平衡,是我国炼油厂补充氢源的主要发展方向。     

Fate of the chlorine and fluorine in a sub-bituminous coal during pyrolysis and gasification

The fate of the chlorine and fluorine present in a sub-bituminous coal from Indonesia during pyrolysis and gasification has been studied with fixed and entrained bed reactors. The rate profile for HCl evolved in the temperature programmed pyrolysis exhibits the main and shoulder peaks at 480 and 600 °C, respectively. Model experiments and subsequent Cl 2p XPS measurements show that HCl reacts with metal impurities and carbon active sites at 500 °C to be retained as inorganic and organic chlorine forms, from which HCl evolves again at elevated temperatures. It is suggested that the HCl observed in the coal pyrolysis may originate from the above-mentioned chlorine functionalities formed by secondary reactions involving the nascent char. In the CO₂ gasification of the 900 °C char at 1000 °C and 2.5 MPa, any measurable amounts of HCl and HF could not be detected even at a high conversion of 75 wt% (daf), suggesting the accumulation of these halogens in the residual char. When the coal is injected into an O₂-blown, entrained bed gasifier at 1200-1400 °C under 2.6 MPa, the partial oxidation proceeds to a larger extent at a higher O₂/coal ratio, whereas the chlorine and fluorine are enriched in the remaining char, and the extent of the enrichment at the latter stage of gasification is larger with the fluorine. The XPS measurements of the chars reveal the presence of the broad F 1 s peak, which can cover a wide range of binding energies attributable to inorganic and organic fluorine. The halogen enrichment during gasification is discussed in terms of secondary reactions of HCl and HF with char.