CN100443840C - High volatile coal dust rotary drying process - Google Patents

Abstract

The invention relates to a high volatile drying technique for coal powder. Steam is thermal source and steam pipe is contacted with wet coal powder directly. Dry and hot coal powder, in which water is vaporized out by heating, is sent to revolving cooling machine by auger and is cooled in the revolving cooling machine, regular coal powder is sent into coal powder tank; water vaporized is carried out by watercarrying nitrogen. Watercarrying nitrogen is heated and sent into drier and passes through first grade fabric filter with partial coal powder; in first grade fabric filter most coal powder is settled down and residual coal powder is settled down through second grade fabric filter; almost clean nitrogen is sent into table cooler and cooled by cycle air-blower, water is eliminated by defogger and the nitrogen is sent back to nitrogen tank with closed cycle. In the whole drying process it is the nitrogen circumstance entirely so that the explosive risk is avoided and by closed cycle the cost is saved with little nitrogen amount.

Description

High volatile coal dust rotary drying process

Technical field

The present invention relates to a kind of pulverized coal drying process, specifically a kind of high volatile coal dust rotary drying process.

Background technology

We know, volatile content belongs to inflammable and explosive coal dust greater than 20% coal dust.Reach the coal dust of explosion limit, no matter at enclosure space or in open spaces, (generally greater than 15%) runs into the incendiary source burning that will set off an explosion under the suitable situation of oxygen content.Light damage equipment then, heavy then cause casualties, bring very big hidden danger to safety in production.This just requires the technology of coal dust drying will fully take into account the various possibilities that cause coal dust explosion, to greatest extent hidden danger is eliminated.

The domestic drying process that is applied to coal dust at present mainly contains: pneumatic conveying drying, fluidized bed drying and rotary drying.

Pneumatic conveying drying: pneumatic drier is used for the drying of coal dust, existing a large amount of application in engineering.When drying is handled the coal dust of fugitive constituent＞10% or more, because the air-flow band material and tube wall and acutely rubbed and be easy to generate static and bring hidden danger to safety in production in the dry run.When the moisture of coal dust was big, the easily sticking wall of material, easily blocking pipe caused system's blast of catching fire, and causes security incident.The also sticking easily wall of cyclone dust collectors blocks simultaneously, and system is difficult to the long period running.Drying medium adds the air inlet oxygen content of inert gas control pneumatic drier as main explosion precaution in the general production process.But the energy consumption of pneumatic conveying drying system is higher.The blast of a large amount of coal dust drying systems occurs now and then in document and data, illustrates that this drying process is not suitable for the drying processing of inflammable and explosive coal dust.

Fluidized bed drying: fluid bed dryer is used for dry coal dust to be had and uses but less.The little requirement that can not satisfy large-scale production of drying system unit treating capacity, and need the air distribution plate of periodic cleaning fluid bed dryer and remove the interior granule materials of bed body.Material lumps easily and causes dead bed phenomenon in the dry run.Fluidized bed drying system requires relatively stricter to charging, change such as the grade distribution of material and the moisture of material, and the too wide moisture excursion of grade distribution is the normal fluidization of big city's influence stream flower beds drying machine too, can cause channel, turbulent and dead phenomenon.Frequent startup-shutdown just brings hidden danger to safety in production.The fluidized bed drying system air intake generally uses inert gas to control the oxygen content of air intake as explosion-proof major measure when the inflammable and explosive coal dust of drying.But data and document all have this device to be applied to have explosion phenomenon to take place when high-risk inflammable and explosive coal dust is dry.

Rotary drying: whizzer is to be widely used in the drying of coal dust, coal slime and raw coal.At the oven dry fugitive constituent during less than 20% coal dust, coal slime and raw coal dry, in the general production process drying medium with combustion product gases (coal-fired flue-gas, gas from oil burning etc.) as drying medium.Typical advantage is exactly that treating capacity is big, running is stable.Shortcoming is that floor space is bigger, owing to adopt directly oven dry, the heat loss of tail gas causes system energy consumption bigger.When handling fugitive constituent greater than 20% coal dust, coal slime and raw coal dry, the air inlet oxygen content of generally gushing inert gas control drying machine is as main explosion precaution.But also there is the documents and materials report to have explosion phenomenon to take place, produces for country and cause very big loss.

Summary of the invention

The present invention is for overcoming above-mentioned the deficiencies in the prior art, provides simple, the safe and reliable fugitive constituent of a kind of technology greater than 20% high volatile coal dust rotary drying process.

The objective of the invention is to adopt following technical proposals to realize: a kind of high volatile coal dust rotary drying process comprises nitrogen closed cycle flow process and coal dust flow process;

When system normally moves, the low temperature and low humidity nitrogen of initial state comes out from the nitrogen storage gas tank, after the heater heating, send in the steam rotary dryer, fully mix with wet coal dust, leave drying machine with moisture evaporated and part dry coal powder, enter the primary dust removing device, most coal dusts are separated in deduster;

Then, nitrogen and moisture evaporated and micro-coal dust enter secondary ash collector, through behind the two-stage dust removal, the pulverized coal particle in the system can be considered 0, and the mist of nitrogen and moisture evaporated is through the force feed of circulating fan, in surface cooler, cool off earlier, pass through the effect of demister again, the moisture in the mist is removed, send into the nitrogen storage gas tank, get back to the primary state that rises of low temperature and low humidity, finish the closed cycle process.

Described coal dust flow process is: wet coal dust is delivered to steam rotary dryer through feeding packing auger, in steam rotary dryer inside, steam pipe coil in wet coal dust and the steam rotary dryer carries out the mass-and heat-transfer motion, moisture in the wet coal dust is heated the back evaporation, and the moisture that evaporates is carried humid gas to be taken away;

Temperature rises gradually after the coal dust drying, at rotary dryer discharging opening position, the coal dust bone dry is to rated value, surface temperature rises to the highest, falls into then in the discharging cover, falls into conveying auger A through the steam rotary dryer airlock, again in conveying auger B is delivered to dried hot coal powder the revolution cooler, under the cooling of revolution cooler, the hot coal powder is cooled to rated value gradually, and the discharging opening at the revolution cooler falls into Pulverized Coal Bin then.

Steam rotary dryer running of the present invention is stable, and the dry heat that needs is mainly provided by the tubulation in the drying machine.The drying capacity of unit volume is about 3 times of conventional indirect heat dryer, and the thermal efficiency is up to 80～90%.It is little to carry the humid gas gas usage, requires the cleaner specification of system little, simple and reliable relatively.Nitrogen in the dry occasion of handling of inflammable and explosive coal dust, provides reliable assurance to production security as the closed cycle drying process application of carrying humid gas.In whole dry run, be nitrogen environment entirely, avoided the danger of blast, adopted closed cycle to make nitrogen use level seldom save cost.

Description of drawings

Accompanying drawing is a process chart of the present invention.

Wherein 1. vapor heat exchangers, 2. buffer, 3. demister, 4. surface cooler, 5. circulating fan, 6. secondary sack cleaner, 7. one-level sack cleaner, 8. nitrogen pot, 9. revolution cooler, 10. conveying auger C, 11. conveying auger B, 12. conveying auger A, 13. steam rotary dryers, 14. feeding packing auger

The specific embodiment

The present invention is further described below in conjunction with drawings and Examples.

High-volatile bituminous coal powder, charging moisture≤10% requires dried discharging moisture≤1%.Raw material is a powdered granule.Grade distributes as follows :≤1mm, wherein 0-0.5mm (35 order) accounts for 95%.Fugitive constituent (the V of coal dust ^r) content is 36.3%, in the time of temperature 25-200 ℃, the fugitive constituent loss late is 1.41%.Volatilize the gaseous products mass percent: methane 42.8%, hydrogen 11.3%, carbon dioxide 35.5%, carbon monoxide 3.64%, free carbon 6.73%.

From oxygen concentration and coal powder density (being wind powder mixture concentration) aspect, when coal powder density reaches the blast standard and oxygen concentration fails to reach that blast standard or oxygen concentration can reach the blast standard and coal powder density when not reaching the blast standard, the danger that pulverized coal system is not blasted.Therefore, in dry run, carry a humid medium, in the processing that is applied to many inflammable and explosive materials of success with the inert gas conduct.The oxygen content of control system medium is below critical value, and system does not just have the phenomenon that fires.The critical value of oxygen content is different for different coal dusts, and this need determine by explosibility test.For the drying of inflammable and explosive coal dust, select for use nitrogen as carrying humid gas.

Steam rotary dryer is a kind of of rotary dryer, be to have settled in the tube the whole drying machine of heating tube with the difference of conventional rotary dryer, line up 1～4 circle in concentric garden mode, the dry institute calorific requirement overwhelming majority is provided by heating tube, material is subjected to the elevate a turnable ladder of heating tube and stirring action gradient and moves to low end from the higher end of drier in drier, and discharges from being located at than the discharge gate of low side.The moisture that is vaporized with is carried humid gas takes drying machine out of, carries to can be recycled after humid gas dewaters.The occasion that steam rotary dryer is specially adapted to is inflammable, explosive material is dry.

Theoretically, the temperature of drying medium is high more, and the heat exchange effect between medium and the material is good more.But temperature is subjected to the restriction of material characteristic and thermal source again, mainly is the restriction of material characteristic.According to the ature of coal situation of change, as coal dust combustible basis fugitive constituent V ^r=12 ~ 40% o'clock, the temperature of suitably adjusting drying machine outlet drying medium and coal dust intermixture was in 70 ~ 120 ℃ of scopes.When adopting air as drying medium, to the fuel (Vr＜10%) of non-flammable, temperature can suitably improve; To fire-hazardous fuel, during as bituminous coal, the selected of hot blast temperature should make the temperature of drying machine exit drying medium and coal dust intermixture be no more than 120 ℃; To brown coal, mixture temperature should be above 100 ℃; Can get high value with inert media temperature when carrying humid gas but can not be above 120 ℃.Special circumstances should be determined by test.

Material time of staying in rotating cylinder must could guarantee the dry requirement of product greater than the required time of dry materials.The time of staying of material in cylindrical shell is relevant with factors such as cylindrical shell length, internal diameter, rotating speed, level inclination, structure (having or not flight) and material angles of crater, and available following formula calculates.

$\mathrm{\τ}=\mathrm{mK}\frac{z}{D_{i}n\sin \mathrm{\β}};$ τ---residence time of material (min); M,---k-factor, choose by following table; D _i----cylinder internal diameter; N---rotating speed, r/min; β---material density, kg/m ³

Coefficient m, K

Embodiment: the bituminous coal to fugitive constituent 36.3% carries out following drying, as shown in Figure 1, wet coal dust is delivered to steam rotary dryer 13 through feeding packing auger 14, in steam rotary dryer 13 inside, steam pipe coil in wet coal dust and the steam rotary dryer 13 carries out the mass-and heat-transfer motion, moisture in the wet coal dust is heated the back evaporation, and the moisture that evaporates is carried humid gas to be taken away.Temperature rises gradually after the coal dust drying, at rotary dryer discharging opening position, the coal dust bone dry is to rated value, surface temperature rises to the highest, fall into then in the discharging cover, process steam rotary dryer 13 airlocks fall into conveying auger A12, conveying auger B11, conveying auger C10 is delivered to dried hot coal powder in the revolution cooler 9, under the cooling of revolution cooler 9, the hot coal powder is cooled to rated value gradually, and the discharging opening at revolution cooler 9 falls into Pulverized Coal Bin then.

When system normally moves, the low temperature and low humidity nitrogen of initial state comes out from the nitrogen storage gas tank, after vapor heat exchanger 1 heating, send in the steam rotary dryer 13, fully mix with wet coal dust, leave drying machine with moisture evaporated and part dry coal powder, enter one-level sack cleaner 7, most coal dusts are separated in deduster.Then, nitrogen and moisture evaporated and micro-coal dust enter secondary sack cleaner 6, and through behind the two-stage dust removal, the pulverized coal particle in the system can be considered 0.The mist of nitrogen and moisture evaporated cools off for 4 li at surface cooler earlier through the force feed of circulating fan 5, passes through the effect of demister 3, buffer 2 again, moisture in the mist is removed, send into nitrogen pot 8, get back to the primary state that rises of low temperature and low humidity, finish the closed cycle process.

Claims (1)

1. a high volatile coal dried bean noodles drying process is characterized in that: comprise nitrogen closed cycle flow process and coal dust flow process;

Nitrogen closed cycle flow process: when system normally moves, the low temperature and low humidity nitrogen of initial state comes out from the nitrogen storage gas tank, after the heater heating, send in the steam rotary dryer, after wet coal dust fully mixes, leave steam rotary dryer with moisture evaporated and part dry coal powder, enter the primary dust removing device, the most coal dusts in the described part dry coal powder are separated in the primary dust removing device;

Then, remaining micro-coal dust enters secondary ash collector in nitrogen and moisture evaporated and the described part dry coal powder, through behind the two-stage dust removal, the mist of nitrogen and moisture evaporated cools off in surface cooler earlier through the force feed of circulating fan, passes through the effect of demister again, moisture in the mist is removed, send into the nitrogen storage gas tank, get back to the primary state that rises of low temperature and low humidity, finish nitrogen closed cycle flow process;

The coal dust flow process: wet coal dust is delivered to steam rotary dryer through feeding packing auger, in steam rotary dryer inside, steam pipe coil in wet coal dust and the steam rotary dryer carries out the mass-and heat-transfer motion, moisture in the wet coal dust is heated the back evaporation, and the moisture that evaporates is used as the nitrogen that carries humid gas and takes away;

Temperature rises gradually after the wet coal dust drying, at steam rotary dryer discharging opening position, wet coal dust bone dry is to rated value, and surface temperature rises to the highest, becomes the hot coal powder, fall into then in the discharging cover, fall into conveying auger A through the steam rotary dryer airlock, again in conveying auger B is delivered to the hot coal powder revolution cooler, under the cooling of revolution cooler, the hot coal powder is cooled to rated value gradually, and the discharging opening at the revolution cooler falls into Pulverized Coal Bin then.

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