System optimization and selection of lignite coal drying pro

Solutions for Coal Drying

System optimization and selection of lignite coal drying process for coal mines

Lignite Coal Misture and Ash

Lignite Coal ProductionCountry or area United States China Germany Australia Russian Poland Turkey Greece Serbia Czech Republic Romania Year 2011 2011 2011 2012 2011 2011 2011 2011 2011 2011 2011 Quantity,thousand ton Country or area 503890 450000 160210 109730 75410 Estonia 61800 60670 59860 39480 39260 36920 Other Asia Bosnia and Herzegovina Philippines Hungary Indonesia 2011 2011 2011 2011 2011 2011 14390 13080 11790 10960 9500 8000 Canada Bulgaria Year 2011 2011 Quantity,thousand ton 36660 35230

IndiaThailand Mexico

20112011 2011

3206017160 15590

1801650

Lignite coal for power generationCountry or area United States Germany Year 2011 2011 Quantity,thousand ton 503890 160210 Country or area Canada Bulgaria Year 2011 2011 Quantity,thousand ton 36660 35230

AustraliaChina Russian Poland Turkey Greece Serbia Czech Republic Romania

20112012 2011 2011 2011 2011 2011 2011 2011

109730100000

IndiaThailand Mexico

20112011 2011 2011 2011 2011 2011 2011 2011

3206017160 15590 14390 13080 11790 10960 9500 8000

75410 61800 60670 59860 39480 39260

Estonia Other Asia Bosnia and Herzegovina Philippines Hungary Indonesia

145171036920

Benefits and issue with lignite coal drying Benefits with lignite coal drying Reduce moisture Reduce ash Increase heating value Reduce transportation cost Issues with lignite coal drying Spontaneous combustion Coal dust during handling

Benefits and issue with lignite coal drying Spontaneous combustion of lignite coal Mechanism of spontaneous combustion of lignite coal Lignite coal has a large surface area and therefore has a strong ability to absorb oxygen due to its porous structure; When lignite coal contacting with air, oxygen physisorption of coal occurs first, and physisorption heat is released; Chemical absorption and chemical reaction happens and chemical reaction and chemical adsorption heat are released afterwards; It will cause self-heating if heat produced cannot be carried away immediately and coal temperature rises constantly with heat buildup inside coal; Coal temperature rising causes the oxidation reaction more intensive; intensive reaction would release more heat; and speed of coal temperature rising accelerates further and vicious circle accelerates, spontaneous combustion occurs when coal temperature reaches its ignition temperature. Coal dust issue during handling According to study, coal dust problem is mainly caused by fine coal less than 0.6mm. Solution: Selecting grinding equipment with minimum fine coal Separation of fine coal from coarse coal: fine coal can be used as fuel for drying process; the remaining fine coal can be sold nearby; and fine coal briquetting.

Benefits and issue with lignite coal drying Mechanism of inhi

bition of spontaneous combustion of lignite By destroying or reducing the structure with lower activation energy; Coal surface is inerted by covering with binders to reduce contacting chance between coal and oxygen; By water spraying on the surface of coal pile to absorb heat and reduce heating speed; Measures of inhibition of spontaneous combustion of lignite Dried lignite coal briquetting can destroy or reduce structure with lower activation energy. Many attempts, but no successive story in industry; Coal pile surface inerted treatment by covering with airtight cloth or scaring formed by binder spraying to prevent contacting between coal and oxygen; Water spraying on surface of coal pile to cool down. This is widely used in industry;

Benefits and issue with lignite coal drying Fine coal briquetting (Binderless Coal Briquetting, BCB process; Hot briquetting process, HBP): (1), Fine coal collection fine coal is collected by cyclone after dryer. Fine coal dusting issue is mainly caused by fines 150 mesh or less; 150 mesh or less fines only accounts for 35% or so from cyclone; (2), Fine heating Fined coal is heated close to its softening point with vertical indirect heating (3), Fines screening Fine coal is then screened after heating. According to the mechanism of pressing granulation, occupied state and void ratio of fines are determined by its size distribution; larger bonding interface between fines are necessary for fine briquetting and finer coal would have higher strength of product. Screening before briquetting is necessary: the amount of fines to briquetting process is reduced; strength of product is increased, which is particularly important for lignite coal as it will experience multi loading and unloading for long distance transportation; (4), Fine briquetting: Fine coal passed screen is briquetted after screening with roll compactor; Features of BCB/ Hot briquetting Binderless and low cost Fines are heated up to close its softening temperature and therefore power consumption for briquetting can be reduced to minimum;

Selection of lignite coal pre-drying technologiesAvailable drying technologies for lignite coal

Flue gas fluidized bed dryer Size mm Heating source Energy consumption kw Drying& de-ashing integrated Water evaporation/ unit Investment 0-50 Flue gas 1 Y 500 1

Flue gas rotary dryer 0-50 Flue gas 1.25 N 30 1,5

Flue gas flash dryer 0-6 Flue gas 1.25 N 30 1.5

Superheated steam fluidized bed dryer 0-6 Steam 1.5 N 100 2

Steam rotary dryer 0-6 Steam 0.8 N 30 2

Microwave dryer 0-50 Electricity 2 N NA NA

Selection of lignite coal pre-drying technologiesDDT high temperature flue gas fluidized bed dryer process High temp flue gas fluidized bed dryer has been developed based on conventional low to medium temp (650 C and below ) to utilize high temp flue gas (900 C to 1000 C ); The inlet flue gas temp was only about 450 C in the original …… 此处隐藏：8167字，全部文档内容请下载后查看。喜欢就下载吧 ……