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成型褐煤热解特性分析_图文

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研究与开发

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商玉坤等 成型褐煤热解特性分析
成型褐煤热解特性分析

研究与开发

商玉坤 武建军 王 伟 李慧蓉 蔡志丹 (煤炭加工与高效洁净利用教育部重点实验室,江苏 徐州 221116)

摘要 分别采用热重法和差示扫描量热法对成型后褐煤的热解特性进行了分析, 并采用

Freeman-Carroll 法计算出了型煤热解动力学参数。 结果表明,300 ℃型煤开始发生激烈的

热解反应,到 431.8 ℃时,热解最为激烈。 型煤热解反应为 1 级反应;反应温度为 450 ℃左

右时,活化能为 241.94 kJ/mol;成型后褐煤的化学性质较成型前稳定。

关键词 褐煤;型煤;热重法;差示扫描量热法

中图分类号 TQ530.2

文献标识码 A

DOI 10.3969/j.issn.1006-6829.2012.01.005

煤炭在中国是主要的能源和重要的化工原料, 然而我国煤炭资源禀赋条件差, 低品质煤所占比重 较大,其中我国褐煤总资源量约为 319.438 Gt,占我 国煤炭资源总量的 5.74%; 我国已发现褐煤资源量 约 为 129.132 Gt, 占 我 国 已 发 现 煤 炭 资 源 总 量 的 12.68%[1-3]。
褐煤是支撑煤炭可持续开发的潜在能源资源。 褐煤的煤阶低、反应性高、水分含量高(质量分数 30%~50%)、热 值 低 (12.56~14.65 MJ/kg)、易 风 化 和 自燃,单位能量的运输成本高,不利于长距离输送和 贮存[4]。 褐煤直接燃烧的热效率较低,且温室气体的 排放量也很大,难以大规模开发利用。粉煤成型是最 早出现并实现工业化的褐煤提质技术, 褐煤成型提 质技术作为煤炭高效洁净利用的一种有效手段,不 但可以减少对块煤的依赖, 而且能提高低阶煤燃烧 效率,减少能源浪费和环境污染。
本研究主要采用热重法和差示扫描量热法分析 了以沥青为粘结剂成型后的蒙东白音华褐煤热解特 性和热解动力学, 对褐煤的提质利用有一定的指导 意义。
1 试验部分
1.1 物料及设备 试验物料:白音华褐煤,工业分析和元素分析结
果如表 1 所示。 试验设备:STA409C 同步热分析仪。
1.2 试验方法 将沥青和褐煤分别按适当比例混合后,进行热压
基 金 项 目 :国 家 重 点 基 础 研 究 发 展 计 划 (2012CB214900) 收 稿 日 期 :2011-12-14

表 1 原料的工业分析及元素分析 Tab 1 Proximate and ultimate analyses of coal samples

Mad

Vad

m/% 34.01 26.65

Cad

Had

N ad

m/% 50.70 3 .54 1.52

Ad 11.35
O ad 17.21

FCad 27.9 9 St,ad 0.85

成型[5]。 对成型后的褐煤进行研磨至粒径<0.2 mm, 然后在不同的升温速率(10、15、20、25 和 30 ℃/min) 下进行热重法和差示扫描量热法(DSC)分析。

2 结果与讨论

2.1 温度对热解产物量的影响 升温速率为 10 ℃/min,在试验温度范围内考察
了型煤热解产物量随温度变化情况,结果见图 1。

图 1 温度对热解产物量的影响 Fig 1 Effect of the temperature on the quantity of
pyrolysis production

2012 年第 19 卷第 1 期

化工生产与技术

Chemical Production and Technology

· 13 ·

由图 1 可以看出, 煤热解产物释放过程可大致 分 3 个阶段,在室温~300 ℃左右,开始出现 第 1 个 热解产物快速增加阶段, 在这个阶段煤中的水分和 煤吸附的 CH4、CO2 和 N2 等气体开始析出,同时褐煤 发生轻度热解,产生 CO2 等气体,这些产物的释放共 同导致了第 1 个热解产物快速增加阶段的出现。 在 300~500 ℃左右,曲线斜率最大,说明在这个时间段 热解产物释放速度最大, 此时煤发生激烈的分解和 解 聚 反 应 ,生 成 大 量 的 CH4、H2、不 饱 和 烃 和 焦 油 蒸 汽等小分子物质[6]。 500 ℃以后,产物释放速度相对 缓和, 这个阶段主要是前一阶段生成的半焦发生分 解产生 CH4 和 H2。 2.2 热解特征参数分析
为清晰观察质量损失速率变化情况, 作微商热 损失曲线(DTG),见图 2。
图 2 10 ℃/min 升温速率下热解的 DTG 曲线 Fig 2 DTG curves of coal residue pyrolysis at the
heating rate of 10 ℃/min
由图 2 可以看出, 型煤从室温开始释放吸附的 H2O、CO2 和 N2 等气体, 在 62.2 ℃释放 速 率 达 到 峰 值;当温度达到 166.4 ℃时,吸 附 的 气 体 释 放 完 毕 。 在对应温度为 200 ℃和 300 ℃处,DTG 曲线分别出 现相对不明显的峰, 这是因为在 200~300 ℃间型煤 发生轻度热解,产生少量 CO2 气体。 300 ℃以后型煤 开始发生激烈的热解反应,到 431.8 ℃时,热解最为 激烈;当温度达到 550 ℃时,热解反应趋于缓和。
为进一步考察型煤在热解过程中的吸放热情况 和宏观物理化学变化情况,利用 DSC 对型煤进行了 分析,结果见图 3。
由图 3 可以看出, 在 20~67 ℃内型煤有一个短 暂的吸热过程, 这也进一步证实了热解初始阶段有 一个吸附气体释放过程。 67~900 ℃是 一 个 放 热 过 程,但在 400~750 ℃内出现 2 次波动,在 500 ℃左右 放热达到最大后放热能力开始减弱, 当温度达到

图 3 10 ℃/min 升温速率下热解的 DSC 曲线 Fig 3 DSC curves of coal residue pyrolysis at the
heating rate of 10 ℃/min

640 ℃左右放热能力再次变大, 到 725 ℃后放热又

达到最大并且超过 500 ℃左右时的热量, 这说明在

500 ℃和 725 ℃发生的放热反应最为激烈。

2.3 热解动力学分析

国内外研究者认为煤的热解反应为基元反应,

可用如下方程描述[7]:

dα/dt =k(1-α)n。

(1)

式 中 ,dα/dt 表 示 反 应 速 率 ,α 为 转 变 分 数 ,α=

(m0-mt)/(m0-m∞), m0、mt、m∞ 分 别 为 反 应 前 试 样 的 初 始质量、反应进行到 t 时刻的试样质量、反应结束时

残留物的质量;k 为速率常数,n 为反应级数。 k 随反

应温度变化规律可由 Arrhenius 公式表示:

k=Aexp (-E/RT)。

(2)

式中, A 指前因子,E 为表观活化能,R 为气体

常数,T 为反应绝对温度。 对于非等温热重实验升温

速率 β 可表示为:

β=dT/dt。

(3)

联立(1)~(3)式,得到:

dα/dT =A(1-α)n [exp (-E/RT)] /β。

(4)

变换得:

ln(β

da dT

)=ln

[A(1-α)n]

-

E RT



(5)

由(5)式 可 以 看 出 ,1/T 与 ln (β dα/dT)呈 线 性 关

系,由不同升温速率(10、15、20、25 和 30 ℃/min)下,

反应最为激烈温度 450 ℃附*的热重数据, 作 1/T

与 ln (β dα/dT)关系图,见图 4。

图 4 的线性关系为 ln (β dα/dT)=62.71-29 060 K/T,

ρ=-0.999 2。 求得活化能为 241.9 kJ/mol。

由 ln A(1-α)n=lnA+nln (1-α)可以看出,ln A(1-α)n

与 ln (1-α)呈直线关系,由直线斜率可求得 A 和 n。

取若干 α,在 DTG 曲线上分别找出对应的 da/dT 和 T,

· 14 ·

商玉坤等 成型褐煤热解特性分析

研究与开发

图 4 1/T~ln (β dα/dT)关系 Fig 4 Relationship between 1/T~(β dα/dT)
再根据图 4 曲线计算出 ln A(1-α)n,然后与 ln (1-α) 作图,见图 5。
图 5 ln A(1-α)n~ln (1-α)关系 Fig 5 Relationship between ln A(1-α)n ~ln (1-α)
图 5 的线性关系为 ln A(1-α)n=63.41+0.94 ln (1-α), ρ=0.999 3,直线斜率为反应级数 ,等于 0.94,因此型 煤热解反应*似为 1 级反应。 求得指前因子为 3.5× 1027 s-1。
由图 4 和图 5 可以看出, 曲线拟合相关系数比 较高, 这表明用基元反应来描述型煤热解反应是正 确的,根据基元反应求得的反应级数和活化能可取。 求得煤热解反应*似为 1 级反应,与文献报道接*, 进一步证明了所求数据的准确性 。 [8-9] 褐煤成型后热 解活化能明显高于成型前热解活化能, 表明褐煤成 型后,化学性质稳定,不容易变质[10]。

3 结论
通过对成型后褐煤热解特性的分析, 得出如下 结论:
1)型煤热解出现 3 个特征阶段,其中在 300~500 ℃ 阶段,热解产物释放速度最大。
2)温度达到 62.2 ℃时,释放吸附的气体速率达 到 峰 值 ;300 ℃型 煤 开 始 发 生 激 烈 的 热 解 反 应 , 到 431.8 ℃时,热解最为激烈。
3)在 20~67 ℃内型煤有一个短暂 的 吸 热 过 程 ; 67~900 ℃是一个放热过程,其中在 500 ℃和 725 ℃ 发生的放热反应最为激烈。
4)型煤热解反应为 1 级反应;反应温度为 450 ℃ 左右时,活化能为 241.94 kJ/mol;成型后褐煤的化学 性质较成型前稳定。
参考文献
[1] 宋贝,周江红. 我国褐煤煤化工技术现状及发展前景[J]. 科 技论坛, 2010,26(9): 34.
[2] 董洪峰,云增杰,曹勇飞. 我 国 褐 煤 的 综 合 利 用 途 径 及 前 景 展望[J]. 煤炭技术, 2008,27(9): 122-124.
[3] 陈冰冰,池海. 谈对褐煤的加工利用[J].煤炭技术, 2005,24 (11): 113-114.
[4] 屈 进 州,陶 秀 祥,刘 金 艳,等. 褐 煤 提 质 技 术 研 究 进 展[J]. 煤 炭科学技术, 2011,39(11): 121-125.
[5] 张传祥,谌伦建,王永建,等. 工业型煤热稳定性形成机理的 实验研究[J]. 煤炭学报, 2002,27(2): 184-187.
[6] Maki T, Takatsuno A, Iura K. Analysis of pyrolysis reactions of various coals including Argonne Premium coals using a new distributed activation energy model [J]. Energy& Fuels, 1997,11(5): 972-977.
[7] 杨景标,张彦文,蔡宁生. 煤 热 解 动 力 学 的 单 一 反 应 模 型 和 分 布 活 化 能 模 型 比 较[J]. 热 能 动 力 工 程, 2010,25(3): 301305.
[8] 朱 学 栋,朱 子 彬,张 成 芳. 煤 热 失 重 动 力 学 的 研 究[J]. 高 校 化学工程学报, 1999,13(3): 223-228.
[9] 孙 庆 雷,李 文,陈 皓 侃,等. DAEM 和 Coats-Redfern 积 分 法 研 究 煤 半 焦 燃 烧 动 力 学 的 比 较[J]. 化 工 学 报, 2003,54(11): 1598-1602.
[10] 姚 昭 章,韩 永 霞. 不 同 煤 化 度 煤 的 热 解 动 力 学 参 数[J]. 煤 化工, 1994,(2): 34-40.

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合理利用资源 保护生态*衡

促进经济持续发展

2012,19(1)

Chemical Production and Technology

ABSTRACTS

Reaction Mechanism in Liquid Phase Fluorinated Catalyed Synthesizing Difluoromethane and the Corrosivity
Ouyang Hao1, He Huilong2, Zhou Liyang2, Zhong Yijun1 (1. Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004;
2. Quhua Fluor-chemistry Company Limited, Quzhou, Zhejiang 324004) Abstract: This paper expounded the influence of catalyst, reaction temperature, reaction pressure, the mass ratio of dichloromethane to hydrofluoric acid and the phasestate of HF to the corrosive of reactor materials in the liquid phase fluorinated catalytic synthesizing difluoromethane. Combination of the two kinds of metal corrosion mechanism, several techniques were proposed to reduce reactors corrosion effectively including adding weak Lewis acids, augmenting the mass ratio of dichloromethane to hydrofluoric acid, employing strong corrosion-resisting alloys, using fluoropolymers as the reactor lined, controlling HF in gaseous phase by means of the coupling low temperature and the suitable pressure. Pointed out that reducing highly reactive proton concentration ionized out by coordination acid H[SbClxF6-x] could solve corrosive problems fundamentally from the perspective of reactive mechanism. Keywords: liquid phase fluorinated catalyzed; difluoromethane; reaction mechanism; reactor materials; corrosive
Synthesis Progress of Hydrofluoroethers
Geng Weili, Wang Zongling, Lei Zhigang (National Engineering Technology Research Center of Fluoro Materials, Quzhou, Zhejiang 324004) Abstract: The physical properties and applications of hydrofluoroethers(HFEs) were introduced, described the preparation methods of HFEs domestic and abroad such as: fluorination of ethers, intermolecular eliminated of fluorinated alcohol (or phenol) and halogenated hydrocarbons, addition reaction of fluorinated alcohol and olefins, alkylation of fluorinated carbonyl compounds, addition reaction of fluorinated alcohol with paraformaldehyde , reaction of tert-butyl alcohol salt with alkyl sulfate and synthesis methods of HFEs with hydroxyl and double bond. Through comparing the synthetic routes, the base -catalyzed addition of unsaturated hydrocarbons and alcohols was simple, relatively mild reaction conditions; the product was easy to separation and purification, which has industrial prospect. Keywords: hydrofluoroethers(HFEs); fluorinated alcohols; olefin; synthesis
Research on the Synthesis Process of Methoxyphenamine Hydrochloride
Yao Yi, Liu Yanbin, Tang Qian, Zhong Weihui (College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou 310014) Abstract: A new process for the preparation of methoxyphenamine hydrochloride was designed. Methoxyphenamine hydrochloride was obtained through methylation, Dakin -West reaction, condensation with methylamine and salification starting from 2 hydroxyphenylacetic acid, the effects of catalyst, the ratio of materials and the solvent of recrystallization on the yields were discussed. The optimal molar ratio of 2-hydroxyphenylacetic acid, methyl sulfate, sodium hydroxide, acid anhydride, N-methylimidazole was 1: 2.5:4.0:2.5:0.2 in the intermediate preparation of 2-methoxyphenylacetone, the optimal mass ratio of 2-methoxyphenylacetone, 33% methylamine in ethanol and Pt/C was 1:0.6:0.01 in the preparation of methoxyphenamine, the optimal mass ratio of toluene and ethanol was 5:1 in recrystallization , the total yield was 46.5% (calculated from 2 -hydroxyphenylacetic acid). The process has industrialization prospect. Keywords: methoxyphenamine hydrochloride; 2-hydroxyphenylacetic acid; Dakin-West reaction; catalyst
Extracting of Total Polyphenols in Longjing Tea
Hu Xinyi, Li Chao, Gao Jianlong, Gu Huiyue, Zang Chao, Li Hongsen, Zhao Linjing (Shanghai University of Engineering Chemistry and Chemical Engineering, Shanghai 201620) Abstract: Extracted total polyphenols in Longjing tea by hot water extract method, used ferrous tartrate spectrophotometric method to determine the content, and examined the total polyphenols extraction rate on temperature, time and material ratio. Results showed that suitable conditions: temperature 85 ℃, 40 min, materials mass ratio 1:24. Keywords: Longjing tea, polyphenols, extraction, content determination
Analysis of Pyrolysis Characteristics in Briquetted Lignite
Shang Yukun, Wu Jianjun, Wang Wei, Li Huirong, Cai Zhidan (Key Lab of Coal Processing and Efficient Utilization of Ministry of Education,
China University of Mining and Technology, Xuzhou, Jiangsu 221116) Abstract: Pyrolysis characteristics of briquetted lignite were analyzed by thermogravimetry and differential scanning calorimetry, the

ABSTRACTS

Chemical Production and Technology

2012,19(1)

parameters of reaction dynamics were obtained based on Freeman-Carroll method. The violent pyrolysis of briquetted lignite started at 300 ℃, and reached the most at 431.8 ℃. The pyrolysis reaction of briquetted lignite was first order reaction; Activation energy was 241.94 kJ/mol when reaction temperature at the vicinity of 450 ℃; Chemical properties became more stable after briquetted. Keywords: lignite; briquetted coal; thermogravimetry; differential scanning calorimetry
Research on the Influence of the Compatibility between Adhesive and Pigment on the Infrared Coatings Emissivity
Shao Chunming1, 2, Wang Shuhua2, Xu Guoyue1 (1. College of Material Science and Technology, Nanjing University of Aeronautics & Astronautics, Nanjing 210016;
2. Technology Center of Juhua Group, Quzhou, Zhejiang 324004) Abstract: Through adding Cu powder in EPDM and EPDM-g-MAH which used as adhesive, infrared coatings with different infrared emissivity (8~14μm) were obtained. The infrared spectra of the adhesive, the interface between adhesion and pigment, the emissivity and microcosmic configuration of the coatings were analyzed. The results showed that, infrared transparency was essentially the same after graft modification of EPDM. The XPS analysis showed that the polar groups of EPDM-g-MAH could form coordination bonds with the metal, significantly improve the compatibility between adhesive and metallic pigment and the emissivity of coatings was decreasing. The reasons were analyzed in detail. Keywords: infrared emissivity; adhesive; pigment; compatibility; coating
Error Analysis and Measurement of Sodium Bentonite Thermal Conductivity
Liang Dong1, Yang Zhongtian1, Yang Weibing1, Liu Wei1,2 (1. Waste Disposal Technology Lab, Institute for Three Waste Management, China Institute for Radiation Protection, Taiyuan 030006;
2. The School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000) Abstract: Using LFA447 -type laser thermal conductivity to measure instrument for measuring thermal conductivity in different moisture content, different compaction density of sodium bentonite at different temperature, obtained the curves of thermal conductivity on moisture, temperature, molding pressure and wet density; Analyzed the accuracy and error of the measurements, then made improvements program according to the cause of the error. Keywords: thermal conductivity; sodium bentonite; moisture; error analysis
Research on CO2 Absorption of Flue Gas in the Mixed Alcohol Amine Solutions
Zhang Yaping1, Jiang Jinzheng2, Ji Qinqin1, Luo Hongqing1 (1. School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, JiangSu 221116;
2. Zhengzhou Coal Industry (Group) Co.Ltd. ZhengZhou 450042) Abstract: In this paper, the influence of temperature, CO2 content and absorption liquid concentration on the performance of alcohol amine solution absorbing CO2 was studied, also the effects of MDEA activation by different complex systems were compared, and the results showed that CO2 absorption rate of alcohol amine solution decreased with the increasing of reaction time and enhanced with the increasing of absorption temperature, the appropriate temperature was 40 ℃ ; Absorption reaction rate enhanced with the increasing of gas and liquid phase reagent content; The effects of MDEA activation by different complex systems was DETA the best and MEA the worst. Keywords: alcohol amine; CO2; absorption rate
New Removal Methods of the Ferric Iron as Impurities in Titanium Dioxide Production Process using Sulfuric Acid
Lihuaquan1, 2 (1. Shandong Dong Jia Group Technology Center, 255200; 2. Institute of Chemical Technology, Shandong University of Technology, Zibo, Shandong: 255100) Abstract: Adopted new reductant to removal the ferric iron in metatitanic acid after the first wash of sulfuric acid method titanium dioxide production process, investigated the influence of new reductant adding quantity, pulp content and temperature on deironing and titanium dioxide color. The results showed that when the new reductant dosage was 0.4% mass of titanium dioxide, TiO2 mass concentration was 300 g/L in pulp and temperature was 50 ℃ , the iron removal efficiency was best which reached 99.52% ; Investigated the color after calcination, the color of titanium dioxide obtained from new reductant method and traditional sulfuric acid bleaching close. The production practice application proved that product indexes such as Hunter Whiteness, Blue-ray Whiteness and




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