Bao Min Sun

Synthesis of Carbon Nanotubes with Typical Structure from the Pyrolysis Flame

Synthesis of carbon nanotubes from V-type pyrolysis flame is a kind of new method. It has potential for carbon nanotubes preparation in mass production. Carbon monoxide was as carbon source and the acetylene/air premixed gas provides heat by combustion. Hydrogen/helium premixed gas acted as diluted and protection gas. Pentacarbonyl iron was served as catalyst. Carbon nanotubes with less impurity and high yield were captured successfully in the V-type pyrolysis flame. The diameter of carbon nanotubes was approximate between 10nm and 20nm, and its length was dozens of microns. The size of catalyst nanoparticles approximately was from 5 nm to 8nm in diameter. This study aims to examine the formation process of typical carbon nanotubes from pyrolysis flame and to characterize their morphology and structure. The morphology and structural of carbon nanotubes were characterized by scanning electron microscope and transmission electron microscopy respectively. Temperature was the key parameter in the process of synthesis carbon nanotubes. The concentration of catalyst had important influence on the synthesis of carbon nanotubes. Sampling time directly determined whether carbon nanotubes formation was completely. The carbon “dissolved-proliferation-separate out” theory can be used to explain that pentacarbonyl iron catalyses carbon monoxide in the process of carbon nanotube formation.

Flame Synthesis of Carbon Nanotubes and Nanocapsules

Flame synthesis of carbon nanotubes and nanocapsules is demonstrated via a pyramid-shaped pyrolysis flame. The mixture of CO, H2, and nebulized catalyst raw material reacts in a high temperature environment formed inside the frustum of pyramid-shaped reactor heated by premixed flame of C2H2 and air outside. A sampling substrate inserted into the incomplete combusting flame of central reacting mixtures can gain the samples of carbon nanotubes and nanocapsules. The effect of sampling time and catalyst concentration is revealed via Field emission scanning electron microscope (FE-SEM) and High-resolution transmission electron microscopy (HR-TEM). 5-mins sampling time and 0.5/50 (Fe(CO)5/C2H5OH, volume ratio) of catalyst concentration is the most appropriate for carbon nanotubes synthesis. In addition, it is to say that catalyst concentration is the most important one among all the factors that can be used to determine whether the main products are carbon nanotubes or nanocapsules, and the structures of nanocapsules are also analyzed in detail.

Carbon Nanofibers from Pyrolysis Flame and Research on the Affecting Factors

Synthesis of carbon nanofibers from the V-type pyrolysis flame is a new method and it has wide application prospects. It needs simple laboratory equipments and normal atmosphere pressure. The V-type pyrolysis flame experimental system is introduced, involving V-type pyrolysis flame burner, mass flux controllers, sampling substrate etc. The carbon nanofibers were characterized by scanning electron microscope and transmission electron microscope. Carbon nanofibers with less impurities and high quality can be captured when the temperature was from 800 to 880°C, austenitic stainless steel type304 was served as sampling substrate, nickel nitrate was served as catalyst precursor and sampling time was 5 minutes. The carbon nanofibers are from 100 to 200 nm in diameter and dozens microns in length. The average diameter of catalyst particles is approximately from 20 to 50 nm. The effects of temperature, sampling substrate materials, sampling time and catalyst were analyzed. The temperature determined the diameter and shape of carbon nanofibers. The austenitic stainless steel type304 substrate containing nickel is in favor of synthesis of carbon nanofibers. The number of carbon nanofibers got more and more while the diameter got thicker firstly and then had little change with the sampling time increased within 5 minutes. In addition, experimental results also indicated that carbon nanofibers had much impurity and worse morphology if the diameter of catalyst particles was above 50nm.

Carbon Nanotubes Preparation Using Carbon Monoxide from the Pyrolysis Flame

Carbon nanotube is a new kind of carbon material. Synthesis of carbon nanotubes from V-type pyrolysis flame is a kind of novel technique. It needs simple laboratory equipments and normal atmosphere pressure. The V-type pyrolysis flame experimental system is introduced. Carbon source is the carbon monoxide which is carried to the middle pipe of V-type pyrolysis flame combustor. Heat source is from acetylene /air premixed flame. Pentacarbonyl iron, served as catalyst, is transported by spray- pyrolysis method into the burner. The carbon nanotubes were characterized by scanning electron microscope and transmission electron microscope. The diameter of carbon nanotubes is approximate 20nm and its length is dozens of microns. The impact of the temperature, reactant composition and catalyst was analyzed to reveal the rule of carbon nanotube growth. Carbon nanotubes with good form and less impurity can be captured when the temperature was from 800°C to 1000°C and carbon monoxide/hydrogen/helium mixed gas flow was supplied. The effective diameter of pentacarbonyl iron nanoparticles is approximate from 5nm to 20nm in the process of carbon nanotube formation. Mechanism of carbon nanotube base on the V-type pyrolysis flame method was proposed. The carbon “dissolved-proliferation-separate out” theory can be used to explain how the pentacarbonyl iron catalyses carbon monoxide to form carbon nanotubes.

Prediction Model for the Boiler NOx Emission with Material Properties Based on the Artificial Neural Network

This paper establishes the prediction model for the NOx emission with Material Properties based on the artificial neural network,and predicts the NOx emission before and after the borler’s combustion reform .First, this paper analyzes the NOx formation mechanism. Then,this paper establishes the prediction model for the NOx emission with Material Properties based on the artificial neural network,which uses the main factors of influencing NOx formation as input variable. At last , this paper trains new samples again,and predicts the boiler NOx emission after the boiler’s low NOx combustion reform.This paper demonstrates that the model is effective for predicting boiler NOx emission before and after the boiler’s low NOx combustion reform.

Study on Computational Methods for the Refractory Belt Area of Coal Fired Boilers

The worse coal quality cause low center flame temperature in furnace, low combustion stability, high carbon content in fly ash and slag. The refractory belt installed in primary combustion zone can reduce the heat absorption capacity of water wall and improve the average temperature to steady ignition and high efficient combustion. For conforming the area of refractory belt better, the equation was founded by thermal computational methods and analyzing the different influence to the area of refractory belt.

Experimental Investigation of Biomass Slag Deposit on the Surface of Super-Heaters

Growing attention had been drawn to the use of biomass as fuel for electricity generation in China. However, as a fairly new imported technology in localization, it had met serious problems with slagging and fouling of the super-heaters. The slag deposit on the first super-heaters in a biomass boiler was characterized by XRD, SEM-EDS and XRF to make clear the reason for the slag deposit. According to the results, alkali metal such as K, Na and Ca were predominant in the slag deposit. NaCl and KCl in the form of halite and sylvite were confirmed by XRD.

Design and Implementation of Experimental System for Comprehensive Utilization of Oil Shale

The single model of oil shale development, which is, burning in boiler for power generation and distillation for shale oil, may cause enormous waste of oil-gas resources and semi-coke. For energy conservation and efficiency improvement, it is necessary to realize the comprehensive utilization of oil shale. The development of experimental system is foundation of further studying. In the paper, an experimental system for comprehensive utilization of oil shale is designed and realized. These includes: spouted bed combustor and shale ash collection system, oil shale retort with solid heat carrier and shale oil recovery system. With the system, the realistic simulation under different condition such as different kinds of oil shale, operation condition can be studied. This work lays an experimental foundation for the further study of comprehensive utilization of oil shale.

A Preliminary Study on DeNOx Technologies for Biomass Power Plant

The aim of this paper is to discuss and find proper technologies to meet the new deNOX demand for biomass power plants in China. One of the outstanding features of these power plants is the emission of NOX at times which fails to meet the new standard. However, even if it’s above the emission standard, the value is not too high due to its low combustion temperature. Another feature is the large alkali content in the straw which forms fly-ash with vapour in flue gas. The traditional methods of SNCR and SCR will not fit bio-fuel boilers because of their low combustion temperature, small volume of furnace, high humidity and alkali metal in bio-fuel. Active coke adsorption maybe fit the installed boilers for its simple system and high efficiency. The recirculation of flue gas through a char layer needs to change the design of the boiler combustion system, which can cut immensely the deNOX operation cost of the biomass power plants.

Influence of Mo Content of Fe/Mo/Al2O3 on Flame Synthesis of Carbon Nanotubes

Catalysts play a critical role in the synthesis of carbon nanotubes. In this paper, we design a series of experiments to explore the impact of contents of Mo on the products. Analysis show, when the molar ratio of Fe: Mo: Al is 1: 0.2: 16, the carbon nanotubes show the best yields and quality.