高灰熔点煤气化特性研究及数值模拟

VIP免费

3.0 侯斌 2024-11-19 4 4 5.66MB 142 页 15积分

侵权投诉

高灰熔点煤气化特性研究及数值模拟

摘要

本文以新型固态排渣气化技术为研究对象，采用实验与模拟相结合的方法，

研究了高灰熔点煤种的气化特性和新型气化炉内的冷态流场，并以此为基础，结

合煤焦气化反应动力学，建立了新型气化炉的一维综合模型，考察了不同工况下

温度、气体浓度及碳转化率随停留时间的变化规律。具体总结如下：

1. 在随机孔模型的基础上，考虑了内、外扩散对气化反应速率的影响，建立

了经过修正的气化反应动力学模型。在经过改造的 Thermax 500 加压热重分析仪

上，选取我国典型高灰熔点煤种-淮南精煤，在气化温度为 850～950℃、压力在

0.1～2Mpa 的工况范围内采用等温热重法考察了温度、分压、总压对高灰熔点煤

焦与水蒸汽的加压气化反应速率的影响，根据实验结果对高灰熔点煤的动力学参

数进行分析计算，最后用建立的动力学模型模拟分析了煤种在高温高压下的气化

反应速率，研究结果表明：不同工况下，减小外扩散影响所需的气流大小也不相

同，压力越大，所需的气流量越大；温度越高，加压下气化反应速率越快；在反

应气体浓度一定的情况下，气化反应速率随着系统压力的增加，先增加后趋于平

缓。活性较高的煤种较快进入外扩散控制，而活性较低的煤种较慢进入外扩散控

制。在模型的基础上综合考察压力、温度的影响后得到淮南精煤煤焦与水蒸气的

气化反

应速率表达式为，外扩散的

速率表达式为。

2. 选取典型高灰熔点煤种淮南精煤，通过在柱塞流中实验的方法，对其进行

气化特性研究，分析了 O/C 摩尔比和气化温度对气化特性的影响，并根据实验气

化炉的边界条件，在经过内、外扩散修正的随机孔模型的基础上，建立了相应的

一维柱塞流气化炉小室模型。结果表明：在相同反应温度下，随 O/C 摩尔比的增

加，CO2含量和碳转化率增加，CO 和H2的含量减小，结合碳转化率与合成气组

分两个因素，本实验条件下，最佳的氧碳摩尔比为 0.9~1.1；温度是影响高灰熔点

煤气化特性的最重要因素，随着气化温度的升高，合成气中 CO 和H2含量升高，

CO2含量不断降低，CH4的体积分数逐渐减少并趋向于零，同时碳转化率也逐渐

升高。使用模型对水煤浆在柱塞流反应中的气化特性进行计算，得出与干煤粉气

化相比，水煤浆气化的出口合成气有效组分降低 7%，但是碳转化率增加 4~5%，

煤浆浓度提高 10%，碳转化率高 1~2%，H2含量降低 2%，CO 含量升高 2%。

3.以某厂 500T/D 耗煤量的气化炉为原型，搭建新型两段供氧气流床气化炉冷

模实验台进行冷态实验，使用 Fluent 软件对其冷态流场进行模拟，将实验结果与

模拟结果进行对比及分析，结果表明：传统气流床气化炉膛内部流场分布并非简

单的管流（平推流）；由于主气流的高速喷出，引起的射流流场在主气流周围形

成大回流区。炉膛内正反向速度并存，反向速度的流体构成回流；炉内存在“短

路”现象，部分颗粒随着主气流直接离开炉膛，部分颗粒随着回流再次来到炉膛

顶部。随着喷嘴位置的逐渐下移，在二次气流上部逐渐形成一个新的回流区，并

随着位置的下降，回流区面积不断增大，炉膛内部的回流强度得到加强。同时部

分回流颗粒会回流至炉膛顶端，在新产生的回流区内运动，部分颗粒在二次气流

下部的回流区内进行运动，加强了整个炉膛内的混合程度，这在一定程度上延长

了炉内颗粒的停留时间，有利于气化效率的提高。

4. 以实际750T/D 的水煤浆加压气流床气化炉为背景，采用一维的动力学模

型分别对传统加压气流床气化炉和新型的两段供氧加压气流床气化炉进行模拟，

研究并分析典型高灰熔点煤在其内部的工作过程，对新型的气化炉进行工程设计

结果表明：模型的计算结果与实际工业结果相接近；煤的热解和燃烧进行的非常

快，O2在0.2 秒内即消耗完毕；气化炉内温度的最大值出现在O2消耗完毕的同时，

传统气流床气化炉内可以达到 2200K；氧碳比对气化炉内工作过程起决定性的影

响，氧碳比越高，气化炉内的温度和出口的碳转化率越高；负荷的改变带来的影

响非常小，在一定范围内可以忽略不计；针对不同的煤种，必须设计相应的气化

工艺和工况；要保证固态排渣的顺利进行，调节炉膛内温度，在合适位置加入一

定量的 H2O和O2，发现氧碳比为 0.8，二段喷嘴给 H2O80%，给O220%的工况下，

炉内温度可以保证淮南精煤固态排渣顺利进行。但是由于温度的降低，导致出口

处碳转化率只有75%，应采取措施来提高碳转化率。

关键词：高灰熔点煤气流床气化炉气化反应动力学冷

态流场一维模型

ABSTRACT

This paper takes the new dry-slagging gasification technology as the research

object ,using experimental and simulation methods to study the gasification

characteristics of coal with high ash fusion temperature and cold flow field inside the

new gasifier, and creats a one-dimensional kinetics model of it, investigates the

relationship between temperature, gas concentration, carbon conversion rate and the

residence time under different conditions.Specific summarizes as follows:

On the basis of the random pore model, considering the impact of internal and

external diffusion on the gasification reaction rate, establishes a revised gasification

kinetics model. Takes the Chinese typical coal with high ash fusion temperature -

Huainan Coal as the object to do the experiment on the condition of 850 ~ 950 ℃,0.1

~ 2Mpa by using the Thermax 500 pressurized thermal gravimetric analyzer, studies

The effects of temperature, partial pressure, total pressure on the gasification reaction

rate between the coal with high ash fusion temperature and water vapor. According to

the experimental results, calculates thes Kinetic parameters of coal with high ash

fusion temperature, at last simulates and analyzes the reaction rate of coal gasification

at high temperature and pressure by using the established dynamic model. The results

show that, the desired gas flow to reduce the impact of external diffusion is different

in different conditions, the higher pressure, the greater required gas flow; The higher

temperature, the faster reaction rate of gasification under pressure; in the case of a

certain concentration of the reaction gas, gasification reaction rate first increases and

then remains steady with the increase of the total pressure. Coal with high activity

enters external diffusion control quicker than the coal with low activity. On the basis

of the model, comprehensive study the impact of pressure, temperature, then we can

got reaction rate of Huainan coal and steam coal gasification can be expressed as

, the rate of out-diffusion of

expression is . At last, calculates the influence of temperature and

pressure on the rate of reaction.

Study on gasification characteristics of coal with high ash fusion temperature is

carried out during pulg flow. A corresponding gasification model which is based on

the kinetic model which was built in the second chapter, has been built, in accordance

with the boundary conditions of the experimental gasifier to calculate the influence of

O/C and temperature on the characteristics of gasification. The results show that, the

higher O/C, the higher content of CO2 and carbon conversion, the lower content of H2

and CO at the same temperature, considering the two factors of syngas components

and carbon conversion, identifies the best O/C is 0.9~1.1 in this experiment.

Temperature is the most important factor to impact the characteristice of coal, the

higher temperature, the higher content of CO and H2, the lower content of CO2 and

CH4, the carbon conversion will rise too. Calculates the gasification characteristics of

coal water slurry during pulg flow by using the established model, the results show

that the sysgas component decreases 7%, but carbon conversion rises 4~5% compared

with dry pulverized coal. The concertration of coal water slurry increases 10%, the

carbon conversion will increase 1~2%, the content of CO will rise 2%, and the content

of H2 will decrease 2%.

Does a cold state experiment to study cold flow field on a test-bed of two-stage

dry slagging gasifier which is built as an entrained flow gasifier of 500 tons daily coal

consumption in a factory, And campares with the calculated results which is simulated

by the sofyware fluent. The results show that, the cold flow field in the gasifier is not

a simple pulg flow, because of the high speed of the main flow, a large backflow field

formed around the main flow. Some particles just leave the gasifier with part of main

flow, and other particles back to the upper part of the furnace with the back flow.

With the decrease of the height of the second nozzles, a new backflow field forms on

top of the second flow from the second nozzles, the lower height, the bigger backflow

field. At the same time, some particles which is back to the top of the furnace will

move in the new backflow field, these mean that the residence time of the particles

will increase. It is good for the gasification.

To study the differences between the Texaco gasifier and the new two-stage

gasifier, calculates the working process of coal with high ash fusion temperature in

them with a 750t/d entrain flow gasifier in the background by using the model which

is built in chapter 3. The results show that, the calculated results are close to the actual

results. The pyrolysis and combustion of coal are very fast, O2 is consumed in 2s.

When the O2 is burn out, the highest temperature appears, in the Texcao gasifier, it

could be more than 2000k.O/C determines the working process of gasification

furnace. Influence of load is very small, can be neglected. The condition of

gasification must change if the coal changes. When the O/C is 0.8, the second nozzles

give 80% H2O and 20% O2 could ensure the highest temperature in the gasifier is

lower than the ash fusion temperature. Because the temperature is lower, the carbon

conversion is only 75%, measures should be taken to increase the gasification

efficiency.

Key Word: Coal with high temperature, entrained flow gasifier,

gasification reaction kinetics, cold flow field, one-dimensional model

中文摘要

ABSTRACT

第一章绪论.....................................................................................................................1

§1.1 课题研究背景...........................................................................................................1

§1.2 国内外煤气化技术研究发展现状与分析...............................................................2

§1.3 煤气化理论与气化特性研究现状...........................................................................6

§1.3.1 煤气化理论的研究现状........................................................................................6

§1.3.2 煤气化反应动力学的研究现状..........................................................................10

§1.3.3 煤气化特性的研究现状......................................................................................11

§1.3.4 高灰熔点煤的气化利用研究现状......................................................................11

§1.4 气流床气化炉数值模拟研究现状.........................................................................13

§1.4.1 气流床气化炉内冷态流场研究现状..................................................................13

§1.4.2 气流床气化炉内气化过程研究现状..................................................................14

§1.5 本课题主要研究内容及意义.................................................................................18

§1.6 本章小结.................................................................................................................19

第二章高灰熔点煤焦气化反应动力学研究.................................................................20

§2.1 引言.........................................................................................................................20

§2.2 加压高灰熔点煤焦气化模型的建立.....................................................................21

§2.2.1 反应控制区域的划分..........................................................................................21

§2.2.2 动力扩散的动力学方程......................................................................................21

§2.2.3 内扩散的动力学方程..........................................................................................22

§2.2.4 外扩散的动力学方程..........................................................................................23

§2.2.5 高温下气化模型的分析讨论..............................................................................24

§2.3 高灰熔点煤焦气化反应实验工况.........................................................................26

§2.3.1 高灰熔点煤制焦实验系统..................................................................................26

§2.3.2 高灰熔点煤焦加压热重实验系统......................................................................28

§2.3.3 高灰熔点煤样特性及气化实验工况..................................................................31

§2.4 结果与分析.............................................................................................................32

§2.4.1 加压条件下高灰熔点煤焦气化反应实验结果分析与模型验证......................32

§2.4.2 高温条件下高灰熔点煤焦气化反应动力学模型验证......................................37

§2.4.3 高温加压条件下煤焦气化动力学模型预报......................................................38

§2.5 本章小结.................................................................................................................41

第三章高灰熔点煤在柱塞流反应器中气化实验研究与数值模拟.............................43

§3.1 引言.........................................................................................................................43

§3.2 煤气化柱塞流反应实验系统、测试方法及实验工况.........................................43

§3.2.1 煤气化柱塞流反应实验系统及测试方法..........................................................44

§3.2.2 煤气化柱塞流反应实验工况..............................................................................45

§3.3 柱塞流反应中的气化过程及模型的建立.............................................................46

§3.3.1 柱塞流反应中的气化过程..................................................................................46

§3.3.2 柱塞流煤气化反应模型的建立..........................................................................48

§3.4 气化实验数据处理.................................................................................................54

§3.5 结果与分析.............................................................................................................55

§3.5.1 柱塞流煤气化实验结果分析与模型验证..........................................................55

§3.5.2 柱塞流煤气化模型计算预报..............................................................................60

§3.6 本章小结.................................................................................................................63

第四章 500T/D 二段供氧气流床气化炉冷态流动实验与数值模拟...........................65

§4.1 引言.........................................................................................................................65

§4.2 二段供氧气流床气化炉实验工况的确定.............................................................66

§4.2.1 二段供氧气流床气化炉系统冷态模型结构......................................................66

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

15 积分 4人已下载

立即下载 VIP免费下载

摘要：

高灰熔点煤气化特性研究及数值模拟摘要本文以新型固态排渣气化技术为研究对象，采用实验与模拟相结合的方法，研究了高灰熔点煤种的气化特性和新型气化炉内的冷态流场，并以此为基础，结合煤焦气化反应动力学，建立了新型气化炉的一维综合模型，考察了不同工况下温度、气体浓度及碳转化率随停留时间的变化规律。具体总结如下：1.在随机孔模型的基础上，考虑了内、外扩散对气化反应速率的影响，建立了经过修正的气化反应动力学模型。在经过改造的Thermax500加压热重分析仪上，选取我国典型高灰熔点煤种-淮南精煤，在气化温度为850～950℃、压力在0.1～2Mpa的工况范围内采用等温热重法考察了温度、分压、总压对高灰熔点煤...

展开>> 收起<<

高灰熔点煤气化特性研究及数值模拟.doc

共142页,预览10页

还剩页未读，继续阅读

高灰熔点煤气化特性研究及数值模拟

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

推荐作者

热门标签

举报选择: