A Method for Evaluating Coal and Biomass Coke Reactivity Using Thermogravimetric Analyzer

Abstract

The invention relates to a method of utilizing a thermogravimetric analyzer to evaluate coal and biomass coke reactivity. The method mainly solves the problems that comprehensiveness and accuracy of existing coke combustion / gasification reactivity evaluation indexes are insufficient and can better achieve reasonable representation of coal and biomass coke combustion / gasification reaction activity.The method comprises the steps: firstly, obtaining a specific reaction rate curve capable of effectively reflecting sample activity; then choosing a plurality of feature points on the curve; finally,constructing reaction comprehensive indexes capable of comprehensively and accurately representing sample reaction activity through organic combination of corresponding parameters of the feature points. The reaction comprehensive indexes are combined with a plurality of parameters capable of reflecting all aspects of sample combustion / gasification behaviors, difficulty and an intensity degree ofsample intrinsic combustion / gasification reaction occurrence can be comprehensively represented, and the reaction comprehensive indexes are more ideal indexes for comprehensively evaluating coal and biomass coke intrinsic reaction activity.

Description

technical field [0001] The invention belongs to the technical field of energy and environment, and relates to the improvement of a method for evaluating the combustion / gasification reactivity of coal and biomass coke, in particular to a method for evaluating the reactivity of coal and biomass coke by using a thermogravimetric analyzer. Background technique [0002] In all combustion and gasification process systems that use coal or biomass as raw materials and thermochemical conversion as the basic principle, the raw materials have undergone drying, volatile precipitation (pyrolysis) and reforming, and coke combustion / gasification three processes. Many related studies have shown that compared with drying and pyrolysis, the rate of char combustion / gasification reaction is very low, and it is the slowest step in the entire thermal conversion process, thus determining the efficiency of the entire process system. Taking the entrained bed coal gasification process as an example,...

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Problems solved by technology

However, the above-mentioned test and evaluation methods have the following defects: (1) The particle size of the coal char sample is required to be on the order of mm, and the accumulation in the reactor reaches a certain thickness, which increases the internal and external diffusion of particles during the reaction process. resistance, which reduces the contribution of the intrinsic chemical reaction rate to the reaction rate of the total package process, thereby weakening the characterization significance of the final reactivity data to the intrinsic reactivity of the sample; (2) the reactivity evaluation indexes adopted are all It is a description of the cumulative amount of samples participating in the reaction within a specified time, but cannot reflect the difficulty and intensity of the reaction of the sample within this period of time, so it cannot fully characterize the reactivity of the sample; (3) the required sample The usage is large (tens to hundreds of grams), the test equipment is complicated, and the operation steps are cumbersome, thus limiting the promotion and application of the method

However, there are still some problems in the application of the above indicators: (1) Some indicators are measured at higher temperatures (such as τ 0.5 ), at this time, the rate of the intrinsic chemical reaction is relatively fast, so the contribution of the internal and external diffusion of the sample particles to the reaction rate of the total package process is relatively increased, and the characterization significance of the index on the intrinsic reactivity of the sample is weakened

(2) When the test temperature is higher than the coke preparation temperature, the thermal effect of the reactivity test process will introduce additional changes in the chemical structure of the sample, so that the obtained data cannot well reflect the real reactivity of the sample

(3) The above indicators only one-sidedly reflect the difficulty of coke combustion / gasification reaction (such as ignition temperature, temperature corresponding to the maximum weight loss rate, apparent activation energy, T 0.5 , τ 0.5 , 0.5 / τ 0.5 , 0.38 / τ 0.5 and 2 / τ 0.5 ) or intensity (such as maximum weight loss rate, initial reaction rate, average reaction rate, specific reaction rate, and half-life reaction rate), but cannot fully characterize the reactivity of the sample

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