High Pressure Thermogravimetry Research Articles

Effect of pressure on the pyrolysis and gasification mechanism of corn stovers from kinetics

In the exploration of the mechanism of corn stovers pyrolysis and gasification, the kinetic parameters is of great significance for regulating the production of target products. Although the kinetic calculations of corn stovers pyrolysis gasification have been reported, the study of kinetics under high pressure and supercritical conditions is still very limited. Therefore, the effect of pressure on the kinetics of corn stovers pyrolysis and gasification reaction was investigated through experiments of atmospheric pressure, high pressure thermogravimetry and supercritical water gasification (SCWG). Different kinetic calculation models were used. It was found that an increase in pressure would increase the activation energy value and inhibit the generation of gas products, but at the same time it would also promote the interaction between gas components and samples. Through this research, this work can provide scientific and technological references for the mechanism of pyrolysis gasification under pressure and the regulation of target products.

Three-dimensional Numerical Simulation of Entrained-Flow Gasifier and Influence of Coal Distribution at the Inlet

The research object in this paper is an industrial HTL gasifier in a plant. A three-dimensional model is built. The chemical percolation devolatilization (CPD) model is used to calculate the pyrolysis reaction. Considering the gas diffusion in the inner pores of the particle and the evolution of pore structure, the random pore model (RPM) was used to simulate the chemical reaction on the particle surface, and the gasification reaction kinetic parameter of char was measured by high-pressure thermogravimetry analysis. The slag model was constructed to describe the formation process and distribution of slag. Through the coupling of the above models, a simulation method that combines several submodels for the entrained flow gasifier is built, and the results from simulation are in good agreement with the industrial data. Furthermore, the effect of the uniformity of pulverized coal injection was analyzed by this method. The simulation results reflect that the asymmetric feed of coal will affect gas-solid mixing and reduce carbon conversion, and it leads to a higher local wall temperature and a lower ratio of crude slag to fine slag.

Numerical simulation of entrained flow gasification based on properties and kinetic characteristics of pulverized coal particles

Gasification kinetic parameters of coal char based on the random pore (RPM) model are obtained with CO2 and H2O using a high-pressure thermogravimetry analysis (TGA) under atmospheric pressure and 4.0 MPa pressure, considering the influence of internal diffusion and particle structure varying with carbon conversion. The Chemical Percolation Devolatilization (CPD) model is used to modify the actual volatile content. Through the coupling of the gasification kinetic reaction model, a comprehensive numerical simulation method of the entrained flow gasification process is established. This method is used to simulate the typical gasifier of HTL (a gasification technology of Changzheng Engineering Co.) in an industrial plant. The research shows that the intrinsic reaction parameters obtained by TGA under high pressure can give a more reasonable reaction state of coal char particles in the gasifier than that measured under atmospheric pressure, and the simulation results are in good agreement with the industrial data. In addition, HTL adopts a single top-fired burner and multi-channel swirling feed type. The particles are entrained and mixed with swirling oxygen, and the combustion reaction is completed quickly in the upper part of the gasifier. In contrast, the gasification reactions are relatively slow and mostly dominate in the recirculation zone and pipe flow zone, leading to high carbon conversion.

A Case Study of Waste Scrap Tyre-Derived Carbon Black Tested for Nitrogen, Carbon Dioxide, and Cyclohexane Adsorption.

Waste scrap tyres were thermally decomposed at the temperature of 600 °C and heating rate of 10 °C·min−1. Decomposition was followed by the TG analysis. The resulting pyrolytic carbon black was chemically activated by a KOH solution at 800 °C. Activated and non-activated carbon black were investigated using high pressure thermogravimetry, where adsorption isotherms of N2, CO2, and cyclohexane were determined. Isotherms were determined over a wide range of pressure, 0.03–4.5 MPa for N2 and 0.03–2 MPa for CO2. In non-activated carbon black, for the same pressure and temperature, a five times greater gas uptake of CO2 than N2 was determined. Contrary to non-activated carbon black, activated carbon black showed improved textural properties with a well-developed irregular mesoporous-macroporous structure with a significant amount of micropores. The sorption capacity of pyrolytic carbon black was also increased by activation. The uptake of CO2 was three times and for cyclohexane ten times higher in activated carbon black than in the non-activated one. Specific surface areas evaluated from linearized forms of Langmuir isotherm and the BET isotherm revealed that for both methods, the values are comparable for non-activated carbon black measured by CO2 and for activated carbon black measured by cyclohexane. It was found out that the N2 sorption capacity of carbon black depends only on its specific surface area size, contrary to CO2 sorption capacity, which is affected by both the size of specific surface area and the nature of carbon black.

Computer processing of thermogravimetric-mass spectrometric and high pressure thermogravimetric data. Part 1. Smoothing and differentiation

High quality data smoothing is frequently required in the thermal analysis. Though the mathematical methods for smoothing are well known, the selection of the proper smoothing parameters cannot be based on statistical checks alone in thermal analysis. Many times a compromise must be found between the effective removal of the various experimental error components and the distortion of the curves by too strong smoothing. The following topics are discussed from a practical point of view: (i) the determination of the derivative thermogravimetric (DTG) curves at low sample masses; (ii) the elimination of the noise and flutter from the results of high-pressure TG experiments; (iii) the evaluation of the noisy, low intensity mass spectrometric signals arising from the minor volatile products of decomposition or oxidation. The performance of the methods is shown in two applications: (1) Evaluation 0.25–0.5 mg mass loss steps in high-pressure thermogravimetry; (2) Study of NO x formation by atmospheric pressure thermogravimetry-mass spectrometry during the temperature programmed combustion of 0.4 mg coal char.

Comparison of Temperature-Programmed Char Combustion in CO2−O2 and Ar−O2 Mixtures at Elevated Pressure

A pressurized thermobalance (TGA) system was built. The role of CO2 was studied in the controlled temperature combustion under pressurized conditions. Particular care was taken to employ low sample masses in thin layers, to avoid self-heating phenomena and ensure kinetic control. It was found that a CO2 partial pressure of 0.57MPa at a 0.6 MPa total pressure had no effect on the overall reaction rate of a temperature programmed combustion. KEYWORDS: High pressure thermogravimetry, char, combustion, effect of carbon dioxide

Thermal analysis of Beypazari lignite

Beypazari lignite was investigated by differential scanning calorimetry (DSC), thermogravimetry (TG), high pressure thermogravimetry (HPTG) and combustion cell experiments. All the experiments were conducted at non-isothermal heating conditions with a heating rate of 10°C min−1, in the temperature range of 20–700°C. DSC-TG data were analysed using an Arrhenius-type reaction model assuming a first-order reaction. For the HPTG data the Coats and Redfern equation was used for kinetic analysis. In the combustion cell experiments the Fassihi and Brigham approach was used in order to calculate kinetic data. Finally a comparison is made between the kinetic results.

Catalytic reactions in waste plastics, HDPE and coal studied by high-pressure thermogravimetry with on-line GC/MS

High-pressure thermogravimetry (TG) with rapid on-line gas chromatography/mass spectrometry (GC/MS) has been used to investigate the effects of different catalysts on decomposition reactions of commingled waste plastics (predominantly PE), high-density polyethylene (HDPE) and mixtures of DECS-6 coal with waste plastics in H 2 at 900 psig. This permits direct evaluation of relative decomposition and residual char amounts as well as yield and composition of the evolved products. Catalysts evaluated for the conversion of waste plastics include solid superacids such as Fe 2O 3 SO 4 2− , Al 2O 3 SO 4 2− , Al 2O 3 SO 4 2− promoted by 0.5% Pt, and ZrO 2 SO 4 2− (all added at 10 wt%), as well as a conventional cracking catalyst of SiO 2Al 2O 3 in a 4:1 ratio, a hydrocracking catalyst of NiMo Al 2O 3 mixed with SiO 2 Al 2O 3 (both added at 50%), and an HZSM-5 zeolite catalyst (added at 10%). Under these conditions cracking activity for waste plastics reveals the following order: SiO 2 Al 2O 3 , HZSM-5 > NiMo Al 2O 3 mixed with SiO 2Al 2O 3 > solid superacids. Of the solid superacids studied, the ZrO 2 SO 4 2− catalyst possesses the highest cracking activity and the approximate order of cracking activity is ZrO 2 SO 4 2− > Al 2O 3 SO 4 2− > Pt/Al 2O 3/SO 4 2− > Fe 2O 3 SO 4 2− no catalyst. The stronger the cracking catalyst, the lighter the aliphatic products and the more abundant the isomeric constituents. Similar results are found for HDPE with these catalysts. For co-processing of coal with commingled waste plastic the HZSM-5 zeolite catalyst shows the most promising results by increasing the rate of the decomposition reactions at 420°C nearly tenfold. Hydrocracking catalysts, such as NiMo Al 2O 3 mixed with SiO 2 Al 2O 3 , show potential promise for co-processing of coal with commingled waste plastic due to their combined hydrogenation and cracking ability. By contrast, a superacid such as ZrO 2 SO 4 2− or a cracking catalyst such as SiO 2 Al 2O 3 appears to have little effect on the decomposition rate of the mixture. To what extent these findings are influenced by transport limitations (e.g. due to incomplete mixing or degree of crystallinity) and/or catalyst pretreatments is being studied further.

95/06248 Catalytic reactions in waste plastics and coal studies by high pressure thermogravimetry with on line GC/MS

95/06248 Catalytic reactions in waste plastics and coal studies by high pressure thermogravimetry with on line GC/MS

95/00241 Studies of thermal and catalytic hydroliquefaction of model compounds, waste polymers and coal by high pressure TG/GC/MS

A recently developed on-line high pressure thermogravimetry (TG)/gas chromatography (GC)/mass spectrometry (MS) system provides certain advantages over other on-line analysis techniques for high pressure reactors reported previously. The high pressure TG/GC/MS system enables the simulation of solvent-free thermal and catalytic reactions for polymers and coal. During the reactions the total weight change is monitored and the volatile intermediate products are identified. It requires only very small amounts (10-100 mg) of sample and can be operated at high pressure under different atmospheres (N, He, H, etc.). Current efforts to recycle lower grade postconsumer polymers such as colored polyethylene and polystyrene or used rubber tires, are concentrated on co-processing with coal. Purely thermal degradation processes involve both decomposition and condensation (recombination) reactions and the resulting product is highly olefinic and often aromatic. In order to improve the yield and selectivity of the process, a great deal of effort has been spent on finding the proper catalysts. Catalysts selected for the present studies include ZrO{sub 2}/SO{sub 4}{sup =}, (NH{sub 4}),MoS{sub 4} and carbon black. Carbon black present in waste rubber tires has been reported to be very selective for the cleavage of specific alkylaryl bonds. (NH{sub 4}){sub 2}MoS{sub 4} has been shown tomore » improve the liquid yields in coal liquefaction. The superacid catalyst ZrO{sub 2}/SO{sub 4}{sup =} possesses markedly higher hydrogenolytic activity compared to that of conventional SiO{sub 2}-supported soluble Fe salts.« less

石炭急速熱分解技術の研究

Coal flash pyrolysis is one of the most interesting future coal utilization technology, because the flash pyrolysis has tendency to volatilize more coal substance than that from conventional slow heating.Coal pyrolysis has been studied under various conditions by high pressure thermogravimetry and estimation model of products from coal pyrolysis.Authers proposed the conditions of coal pyrolysis from controlling products and economic points.Small scale reacters with these conditions have been constructed for getting basic and engineering data of the pilot plant.