A kind of air preheater system of anti-low-temperature corrosion
Technical field
The present invention relates to a kind of waste heat recovery system of heating furnace heat transmission equipment, relate in particular to a kind of for recycling flue gas waste heat and air preheater system that can anti-low-temperature corrosion.
Background technology
Air preheater is to utilize the heat heating fuel burning required air of boiler tail flue gas to improve the heat-exchange apparatus of boiler thermal output.Generally, referred to as air preheater, can be divided into two kinds of box type, swingings; Bobbin carriage preheater operation principle is comparatively simple, and flue gas is from bobbin carriage outer flow warp, and air passes through from bobbin carriage inside, by temperature difference different heat transfer, identical with the principle such as economizer, superheater.
The operation principle of rotary preheater is: preheater rotor part is made up of the heat transfer element of tens thousand of meters, and when air preheater slow circumvolve, the reverse alternating current of flue gas and air is through air preheater.Heat accumulating element absorbs heat in fume side, in air side heat release, thereby reaches reduction exhaust gas temperature, improves the pre-heat effect of hot blast temperature.
Existing air preheater easily produces cold end corrosion, has affected the service life of air preheater, has further affected the service life of boiler.Cold end corrosion is exactly when heated surface at the end of boiler (economizer, air preheater etc.) tube wall temperature is during lower than flue gas dew point, and the steam that contains sulfuric acid in flue gas is in wall the caused corrosion of condensing.
The formation of cold end corrosion: the combustion of sulfur in fuel generates sulfur dioxide (S+O
2=SO
2), sulfur dioxide is further oxidized and generates sulfur trioxide (2SO under the effect of catalyst
2+ O
2=2SO
3), SO
3generate sulfuric acid vapor (SO with the water vapour in flue gas
3+ H
2o=H
2sO
4), the existence of sulfuric acid vapor significantly raises the dew point of flue gas, because the temperature of air in air preheater is lower, the flue-gas temperature of preheater section is not high, wall temperature is often lower than flue gas dew point, and sulfuric acid vapor will condense on air preheater heating surface like this, causes sulfuric acid corrosion.
Cold end corrosion often occurs on air preheater, but when in fuel, sulfur content is higher, excess air coefficient is larger, SO in flue gas
3content is higher, and dew point raises, and when feed temperature lower (steam turbine high add inactive), cold end corrosion also likely occurs in economizer tube.
In recent years, along with the rising of petroleum chemical enterprise's processing sulfur content in crude oil, the SO in flue gas of heating furnace
xincrease, flue gas acid dew point temperature is raise, cause waste heat recovery system of heating furnace heat transmission equipment corrosion aggravation, had a strong impact on heating furnace long-period stable operation.
Air preheater anti-low-temperature corrosion technology adopts at present: heat pipe preheater, ND steel tubular air heater, enamel pipe regenerative air heater, Pyrex tubular air preheater etc., these several technology all have pluses and minuses separately, but they have a problem that cannot overcome is exactly all to realize air preheater long period on-line operation, long periods of time in order is no more than 3 years, will there is serious cold end corrosion or device damage in five, six months in the shortest on-line operation, cause air preheater to be scrapped.
Wherein, the operation principle of heat pipe preheater is: by the vaporizable liquid that injects 1/3 in pipe, then sealing is evacuated, pipe divides, lower two sections, use tube sheet spaced apart, the hypomere of the pipe flue gas that becomes popular, utilize flue gas heat to carry out the liquid in heating tube, make its evaporation and rise to pipe epimere and heated air conducts heat, emitting gas after the latent heat of vaporization is condensed into the hypomere that drops to again pipe after liquid and continues and hot flue gas heat exchange, after evaporation, rise to epimere again and heated air conducts heat, thereby circulation realizes the heating of flue gas to air and so forth.Because cold air does not directly carry out heat exchange with hot flue gas, thereby avoid the generation of cold end corrosion phenomenon, but thereby its air in long-term operation is inhaled in heat exchanger tube and causes the vacuum in pipe destroyed, the steam latent heat of managing interior vaporization can not be passed on tube wall, thereby air can not, by continuation heating, cause this heat pipe preheater to lose efficacy.
All that flue gas and air pass through heat exchange between tube wall for now conventional ND steel tubular air heater, enamel pipe regenerative air heater, Pyrex tubular air preheater, flue gas is from managing interior flowing, air through the above lateral flow of secondary, is realized the heat exchange between air and flue gas outside pipe.
Wherein, the main raw material(s) of ND steel tubular air heater is ND steel, a kind of material of resisting sulfide corrosion of ND Gang Shi steel mill exploitation, but ND steel steel pipe is expensive, and this material actual on-line operation time under cold end corrosion environment can not exceed 3 years yet and will low-temperature dew point corrosion occur and damage.
And enamel pipe regenerative air heater is to plate one deck enamel in the pipe side of flue gas contact to prevent low-temperature dew point corrosion, but be subject in actual applications the cause influences such as coating became uneven, pipe postwelding coating be destroyed, after a period of time that actual on-line operation is not grown, also in succession low-temperature dew point corrosion occur and damage.
Pyrex tubular air preheater often occur in actual applications tube sheet and borosilicate glass tube poorly sealed, leak cigarette, leak out and the glass tube former thereby on-line operation for a long time such as frangible.
Summary of the invention
The object of the invention is to solve following technical problem:
One, conventional box type air preheater because of the temperature of air to be heated lower, sometimes even lower than sulfur-containing smoke gas dew-point temperature, thereby make fume side tube wall easily because cold end corrosion is destroyed, thereby cause shutdown maintenance, the problem that even air preheater is scrapped;
Two, adopt heat pipe preheater in long-term operation, thereby air is easily inhaled in heat exchanger tube and causes the vacuum in pipe destroyed, the steam latent heat of managing interior vaporization can not be passed on tube wall, and air can not be continued heating, the problem that causes this heat pipe preheater to lose efficacy;
Three, adopt ND steel tubular air heater easily to make its manufacturing cost raise, and after length, low-temperature dew point corrosion also can occur running time, thus the problem that causes air preheater to damage;
Four, adopt enamel pipe regenerative air heater to be subject in actual applications the easy became uneven of coating, pipe postwelding coating easily destroyed, after a period of time that causes actual on-line operation not grown, also in succession low-temperature dew point corrosion occurs and the problem damaged;
Five, adopt Pyrex tubular air preheaters, often occur in actual applications that tube sheet and borosilicate glass tube are poorly sealed, leakage cigarette, leak out and the glass tube former thereby problem of on-line operation for a long time such as frangible;
Six, existing air preheater can not effectively solve cold end corrosion problem, makes troubles to the use of air preheater and boiler, has increased use, the maintenance cost of air preheater and boiler.
For solving the problems of the technologies described above, the invention provides a kind of air preheater system of anti-low-temperature corrosion, it can effectively prevent cold end corrosion, so that air preheater on-line operation for a long time, reduce the cost that air preheater and boiler use, keep in repair, improved the reliability of boiler operatiopn.
For reaching this object, the present invention by the following technical solutions:
An air preheater system for anti-low-temperature corrosion, comprises heat-exchange system, heat medium system;
Described heat-exchange system comprises flue gas-air heat exchanger, flue gas-heating-medium heat exchanger, heating agent-air heat exchanger, described flue gas-air heat exchanger, described flue gas-heating-medium heat exchanger are successively set in hot stove flue along flue gas flow direction, and described heating agent-air heat exchanger is arranged on outside hot stove flue;
Described flue gas-heating-medium heat exchanger, heating agent-air heat exchanger and heat medium system compose in series the circulatory system, by described flue gas-heating-medium heat exchanger, flue gas heat is passed to heating agent, the air intake connecting fan of described heating agent-air heat exchanger, extraneous air enters flue gas-air heat exchanger after heating agent-air heat exchanger once heats, after high-temperature flue gas post bake for combustion-supporting.
Described heat medium system comprises circulating pump, expansion drum, holding vessel, and wherein circulating pump, expansion drum compose in series closed circuit by pipeline and flue gas-heating-medium heat exchanger, heating agent-air heat exchanger; Described holding vessel connects expansion drum and closed circuit by valve group.
Further, heating agent arrival end and the port of export of described flue gas-heating-medium heat exchanger are provided with bypass regulator valve.Adjusting enters the heat medium temperature of heating agent-air heat exchanger, makes it higher than flue gas dew point temperature.
Further, described valve group is connected with gear pump, supplementing and deriving for heating agent in heat medium system.
Especially, described heat medium system heating agent adopts conduction oil.
Especially, described heat medium system heating agent adopts glycol water.
A kind of method that air preheat is provided simultaneously, passes to heating agent by flue gas-heating-medium heat exchanger by flue gas heat; Utilize heat medium system through heating agent-air heat exchanger, introducing air once to be heated, make air themperature be heated to above flue gas dew point temperature, then enter into flue gas-air heat exchanger and utilize high-temperature flue gas to be further heated to needed hot air temperature.
By by heating agent with waste heat flue gas until temperature higher than dew-point temperature in sulfur-containing smoke gas, again with the heating medium for heating cold air after heating, make air themperature after heated higher than dew-point temperature in sulfur-containing smoke gas, and then be sent to and in waste heat flue gas, be further heated to again needed hot air temperature, because enter the temperature of air of flue gas-air heat exchanger higher than dew-point temperature in sulfur-containing smoke gas, so just there will not be the phenomenon of cold end corrosion, so just extend the service life of equipment, and by flue gas-heating-medium heat exchanger, waste heat flue gas is further lowered the temperature, make like this flue-gas temperature that is drained into atmosphere reduce, not only save the energy, also protect environment.
Preferably, described heating agent adopts conduction oil, conduction oil is a kind of Transfer Medium of heat, and because it has homogeneous heating, temperature adjustment control temperature is accurate, can under low-steam pressure, produce high temperature, heat-transfer effect is good, energy-conservation, carries and the feature such as easy to operate, be widely used in recent years various occasions, and its purposes and consumption are more and more.
Preferably, described heating agent adopts glycol water.
Beneficial effect of the present invention is: by by the waste heat flue gas of the heating agent in flue gas-heating-medium heat exchanger, until temperature is higher than dew-point temperature in sulfur-containing smoke gas, again with the heating medium for heating cold air after heating, make air themperature after heated higher than dew-point temperature in sulfur-containing smoke gas, and then be sent to and in waste heat flue gas, be further heated to again needed hot air temperature, enter like this temperature of air of flue gas-air heat exchanger higher than dew-point temperature in sulfur-containing smoke gas, the phenomenon that has effectively prevented cold end corrosion occurs, realize macrocyclic on-line operation, avoided equipment damage and damage after because of maintenance need blowing out to bring economic loss, also saved because often changing the expense of buying new air preheater, by flue gas-heating-medium heat exchanger, waste heat flue gas is further lowered the temperature, make like this flue-gas temperature that is drained into atmosphere reduce, not only saved the energy, also protected environment, by connecting bypass control valve between the entrance at flue gas-heating-medium heat exchanger and the outlet of flue gas-heating-medium heat exchanger, can make the heating agent in flue gas-heating-medium heat exchanger repeatedly carry out heat exchange with waste heat flue gas, thereby make the temperature of the heating agent that enters heating agent-air heat exchanger always higher than dew-point temperature in sulfur-containing smoke gas, further strengthen the heat exchange of the air in watertight aircase, guarantee enters the air themperature of flue gas-air heat exchanger higher than dew-point temperature in sulfur-containing smoke gas, contrast prior art, this air preheater system can effectively prevent cold end corrosion, so that air preheater on-line operation for a long time, having reduced air preheater and boiler uses, the cost of maintenance, improve the reliability of boiler operatiopn.
Brief description of the drawings
Fig. 1 is the structural representation of air preheater system that can anti-low-temperature corrosion shown in the present.
In figure:
1, flue; 2, heating agent-air heat exchanger; 3, flue gas-air heat exchanger; 4, flue gas-heating-medium heat exchanger; 5, chimney; 6, bypass regulator valve; 7, centrifugal blower;
8, expansion drum; 81, the first entrance; 82, the second entrance; 83, the first outlet; 84, the second outlet;
9, holding vessel; 10, centrifugal pump; 11, storage barrel; 12, gear pump.
Detailed description of the invention
As shown in Figure 1, the air preheater system of a kind of anti-low-temperature corrosion of the present invention comprises heat-exchange system, heat medium system;
Heat-exchange system comprises flue gas-air heat exchanger 3, flue gas-heating-medium heat exchanger 4, heating agent-air heat exchanger 2, flue gas-air heat exchanger 3, flue gas-heating-medium heat exchanger 4 are arranged in hot stove flue 1, and set gradually along flue gas flow direction, heating agent-air heat exchanger 2 is arranged on outside hot stove flue 1;
The entrance of flue gas-heating-medium heat exchanger 4 connects centrifugal pump 10 outputs, and the outlet of flue gas-heating-medium heat exchanger 4 connects the heating agent entrance of heating agent-air heat exchanger 2, and the heating agent outlet of heating agent-air heat exchanger 2 connects the input of described centrifugal pump 10;
The air intake of heating agent-air heat exchanger 2 connects centrifugal blower 7, and the air outlet slit of heating agent-air heat exchanger 2 connects the entrance of flue gas-air heat exchanger 3, and the outlet of flue gas-air heat exchanger 3 connects hot burner.By will be first with overheated flue gas by heating medium for heating; make the temperature of heating agent higher than dew-point temperature in sulfur-containing smoke gas; again with the heating medium for heating cold air after heating; make air themperature after heated higher than dew-point temperature in sulfur-containing smoke gas; and then be sent to and in waste heat flue gas, be further heated to again needed hot air temperature; enter like this temperature of air of flue gas-air heat exchanger 3 higher than dew-point temperature in sulfur-containing smoke gas; also just there will not be the phenomenon of cold end corrosion; extend the service life of equipment; reduce exhaust gas temperature; save the energy, protected environment.
In the specific implementation, for the heat medium temperature that ensures to go out from flue gas-heating-medium heat exchanger 4 also conveniently carries out temperature control higher than dew-point temperature sulfur-containing smoke gas, so a bypass regulator valve 6 is installed between the preferred outlet at flue gas-heating-medium heat exchanger 4 and entrance.
Heat medium system comprises expansion drum 8, expansion drum 8 comprises the first entrance 81, the second entrance 82, the first outlet 83 and the second outlet 84, the first entrance 81 of expansion drum 8 connects the heating agent outlet of heating agent-air heat exchanger 2, with the heating agent of absorption portion expanded by heating, the first outlet 83 of expansion drum 8 connects the input of centrifugal pump 10, to supplement the heating agent of absorbed part expanded by heating.
Heat medium system also comprises heating agent storage barrel 11, and heating agent storage barrel 11 is by the input of pipeline connection teeth wheel pump 12, and the output of gear pump 12 connects the second entrance 82 of expansion drum 8 by pipeline.By storage barrel 11 is set, in the time that the heating agent of system lacks, can carry out heating agent to whole system in time and supplement, to ensure the normal operation of system.
The second outlet 84 of expansion drum 8 is connected with holding vessel 9, and holding vessel 9 is by the input of pipeline connection teeth wheel pump 12, and the output of gear pump 12 connects the second entrance 82 of expansion drum 8 by pipeline.Not only can supplement to closed circuit heating agent by expansion drum 8 is set, can also solve the volumetric expansion problem producing because of heating medium for heating.
Heating agent in the present embodiment is selected conduction oil, because conduction oil is a kind of Transfer Medium of heat, and it has homogeneous heating, and temperature adjustment control temperature is accurate, can under low-steam pressure, produce high temperature, and heat-transfer effect is good, energy-conservation, the feature such as carries and easy to operate.
Heating agent is not limited only to conduction oil, as long as have homogeneous heating, heat-transfer effect is good, and conveying and easy to operate material all can be selected, such as heating agent can also be selected glycol water.
In the present embodiment can anti-low-temperature corrosion the method for anti-low-temperature corrosion of air preheater system, first utilize the heating agent of flue gas from heat medium system, then utilize the heating medium for heating cold air after heating, make air themperature after heated higher than dew-point temperature in sulfur-containing smoke gas, so that heat exchange manifold does not produce cold end corrosion, then the air after heating is sent to and in waste heat flue gas, is further heated to needed hot air temperature.By by the waste heat flue gas of the heating agent in flue gas-heating-medium heat exchanger, until temperature is higher than dew-point temperature in sulfur-containing smoke gas, again with the heating medium for heating cold air after heating, make air themperature after heated higher than dew-point temperature in sulfur-containing smoke gas, and then be sent to and in waste heat flue gas, be further heated to again needed hot air temperature, enter like this temperature of air of flue gas-air heat exchanger higher than dew-point temperature in sulfur-containing smoke gas, the phenomenon that has effectively prevented cold end corrosion occurs, realize macrocyclic on-line operation, avoided equipment damage and damage after because of maintenance need blowing out to bring economic loss, also saved because often changing the expense of buying new air preheater,
Specific works process is as follows:
One, heating agent:
First heating agent enters in flue gas-heating-medium heat exchanger 4 by centrifugal pump 10, carry out heat exchange with waste heat flue gas, and then enter by the heating agent entrance of heating agent-air heat exchanger 2 and enter into heating agent-air heat exchanger 2, carry out heat exchange with cold air, the complete heating agent part of heat exchange enters centrifugal pump 10 by the heating agent outlet from heating agent-air heat exchanger 2 and recycles, in order to ensure that heating furnace enters air themperature in flue gas-air heat exchanger 3 all higher than the dew-point temperature of sulfur-containing smoke gas under various operating modes, between the outlet of flue gas-heating-medium heat exchanger 4 and entrance, bypass regulator valve 6 is set.
The complete heating agent another part of heat exchange enters expansion drum 8 from heating agent-air heat exchanger 2, now due to heating agent in heat exchanging process because heating causes heating agent volumetric expansion, if being put into expansion drum 8, heating agent can reduce heating agent expansion, part heating agent flows out from the second outlet 84 again, entering centrifugal pump 10 circulates, another part heating agent enters in holding vessel 9, by gear pump 12 inject expansion drum 8 carry out closed circuit heating agent supplement.
A pipeline of directly linking gear pump 12 inputs in addition between the second outlet 84 of expansion drum 8 and centrifugal pump 10, this is in the heating agent amount that enters centrifugal pump 10 during higher than requirement, and heating agent is injected in expansion drum 8 and is regulated by gear pump 12 by this pipeline.
If the heating agent amount of whole system during lower than normal operation use amount, is at this moment injected new heating agent by storage barrel 11, ensure the normal operation of whole system.
Two, air
First cold air enters in heating agent-air heat exchanger 2 by centrifugal blower 7, in heating agent-air heat exchanger 2 cold air with carry out heat exchange from the high temperature heating agent of flue gas-heating-medium heat exchanger 4, make the temperature of air higher than the dew-point temperature of sulfur-containing smoke gas, and then entered in flue gas-air heat exchanger 3 by the air outlet slit of heating agent-air heat exchanger 2, carry out heat exchange with the waste heat flue gas in flue 1, make the air in flue gas-air heat exchanger 3 reach the needed air themperature of hot stove.
Three, flue gas
Flue gas washes away successively from top to bottom flue gas-air heat exchanger 3 and flue gas-heating-medium heat exchanger 4 in heating furnace convection cell exhaust pass 1, by the heat exchange of two-stage heat exchanger, the temperature of flue gas is declined, then flue gas is discharged in atmosphere (before atmosphere, also can carry out the operations such as dedusting, herein just not explanation in detail entering) along chimney 13.
Know-why of the present invention has below been described in conjunction with specific embodiments.These are described is in order to explain principle of the present invention, and can not be interpreted as by any way limiting the scope of the invention.Based on explanation herein, those skilled in the art does not need to pay performing creative labour can associate other detailed description of the invention of the present invention, within these modes all will fall into protection scope of the present invention.