CN101476821B - Method for preventing flue gas dew-point corrosion of exhaust heat recovery apparatus - Google Patents
Method for preventing flue gas dew-point corrosion of exhaust heat recovery apparatus Download PDFInfo
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- CN101476821B CN101476821B CN2009100640882A CN200910064088A CN101476821B CN 101476821 B CN101476821 B CN 101476821B CN 2009100640882 A CN2009100640882 A CN 2009100640882A CN 200910064088 A CN200910064088 A CN 200910064088A CN 101476821 B CN101476821 B CN 101476821B
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Abstract
The invention discloses a method for preventing a waste heat recovery device from flue gas dew point corrosion, which aims to solve the problem that the prior method has a danger of making the waste heat recovery device produce the flue gas dew point corrosion. The method comprises the following steps: A, an acid dew point measurement instrument (1) is used to measure a flue gas acid dew point temperature Tm at a flue gas outlet of the waste heat recovery device and transmits the Tm to a comparator (3), and a wall surface temperature transmitter (2) is used to measure a flue gas side wall surface temperature Tgm of a heat transfer element close to the flue gas outlet, and also transmits the Tgm to the comparator; B, the comparator adds the Tm by minimum excess temperature difference dTmin(5-10 DEG C), compares the sum of the Tm and the minimum excess temperature difference dTmin (5-10 DEG C) with the Tgm to obtain regulation temperature difference delta Tgm, and transmits the delta Tgm to a temperature regulator (4); and C, the temperature regulator produces and outputs a heat exchange amount adjustment signal, controls a heat exchange amount adjustment device to actuate, and regulates the heat exchange amount of the waste heat recovery device to ensure that the Tgm is 5 to 10 DEG C higher than the Tm, therefore, the flue gas dew point corrosion is avoided.
Description
Technical field
The present invention relates to a kind of method of avoiding flue gas dew-point corrosion of exhaust heat recovery apparatus in industrial furnace waste heat recovery field.
Background technology
In industries such as petrochemical industry, electric power, iron and steel, the smog discharge temperature that reduces the industrial furnace waste-heat recovery device is a main path that improves the industrial furnace thermal efficiency.Along with riseing of energy shortage, fuel price, the smog discharge temperature of industrial furnace is more and more lower.Because of containing certain sulphur or sulfide in the fuel, when the waste-heat recovery device of industrial furnace when being less than or equal to the flue gas acid dew point temperature near the fume side wall surface temperature of the heat transfer element of exhanst gas outlet, the low-temperature flue gas dew point corrosion will take place in waste-heat recovery device (mainly be heat transfer element, for example heat-transfer pipe or heat transfer plate).The flue gas acid dew point temperature changes with the variation of fuel element and oxygen content of smoke gas, is not definite value (excursion is generally between 70～140 ℃).Consider the variation of thermic load in the actual production, fuel component and oxygen content of smoke gas and atmospheric temperature, changes of seasons, in order to prevent above-mentioned flue gas dew point corrosion, designing unit both domestic and external often fixes on the smog discharge temperature of waste-heat recovery device when design and is higher than the flue gas acid dew point temperature more than 50 ℃, makes smog discharge temperature on average more than 180 ℃; This has just caused very big fume emission heat loss.
The disclosed a kind of adjustable air preheater of Chinese patent CN2630667Y, respectively at low-temperature zone and the low-temperature zone setting of air duct and the sleeve type heat-pipe elements and the fin tube type heat exchange element of heat transfer medium transmission unit pipeline connection of exhaust gases passes, closed cycle by heat transfer medium in two heat exchange elements realizes heat exchange between exhaust gases passes low-temperature zone and air duct low-temperature zone.By regulating the flow of heat transfer medium, prevent that the heat exchange element tube wall temperature of exhaust gases passes low-temperature zone is lower than the flue gas acid dew point temperature.In an embodiment, first and second temperature sensors are set at sleeve type heat-pipe elements near the outside wall surface (fume side) of exhaust gases passes gas outlet and near the pipeline the output port respectively.Wherein, when the detected temperatures of first temperature sensor is lower than a certain setting value, show that the outside wall temperature of sleeve type heat-pipe elements has the trend that is lower than acid dew-point temperature.The control valve control device that link to each other with first temperature sensor this moment is driven greatly control valve, thereby the heat transfer medium that sleeve type heat-pipe elements flows out is distributed to delivery pump more, improve the water temperature that enters sleeve type heat-pipe elements, make tube wall temperature be higher than acid dew-point temperature.The anticorrosive air preheater of the disclosed a kind of high-performance of CN201028790Y is provided with temperature measurement and control instrument, its temperature probe and the heat transfer of endotherm section face the wall and meditate (fume side) contact, the control signal output is electrically connected with the frequency control signal input part of variable frequency pump.Temperature measurement and control instrument detects the conduct heat temperature face the wall and meditate of endotherm section can send the signal of telecommunication when low, regulate the flow velocity of thermal medium by variable frequency pump, thereby control endotherm section tube wall temperature is avoided dew point corrosion.The subject matter of avoiding the existence of flue gas dew point corroding method takes place that above-mentioned patent relates to is, the required design temperature of flue gas dew point corrosion takes place to preventing that sleeve type heat-pipe elements outer wall or endotherm section from conducting heat to face the wall and meditate, come down to set, can not accurately not determine in real time according to the true acid dew-point temperature that near discharging flue gas exhaust gases passes in the actual production process or the endotherm section exhanst gas outlet constantly changes is online according to the artificial flue gas acid dew point temperature of estimating is artificial; This design temperature is set as definite value, can not adjust in real time according to discharging flue gas acid dew point variation of temperature.Therefore, when the flue gas acid dew point temperature of reality was higher than estimated value, the temperature that sleeve type heat-pipe elements outer wall or endotherm section heat transfer are faced the wall and meditated still might be lower than the flue gas acid dew point temperature, thereby the danger that dew point corrosion takes place is arranged.Or, when actual flue gas acid dew point temperature was lower than estimated value, if control sleeve type heat-pipe elements outer wall or the endotherm section temperature of facing the wall and meditating of conducting heat higher, smog discharge temperature can be too high, to strengthen the fume emission heat loss, and make air preheater not reach best heat exchange efficiency.
Summary of the invention
The purpose of this invention is to provide a kind of method of avoiding flue gas dew-point corrosion of exhaust heat recovery apparatus, thereby can not accurately determine and can not adjust to make waste-heat recovery device that the dangerous problem of generation flue gas dew point corrosion be arranged according to discharging flue gas acid dew point variation of temperature to solve the existing design temperature of heat transfer element fume side wall generation flue gas dew point corrosion that prevents of existing method.
For addressing the above problem, the technical solution used in the present invention is: a kind of method of avoiding flue gas dew-point corrosion of exhaust heat recovery apparatus, this waste-heat recovery device is provided with heat transfer element and heat exchange quantity regulating device, it is characterized in that: described method is made up of following steps:
A, measure the flue gas acid dew point temperature T m of waste-heat recovery device smoke outlet with the acid dew point measuring instrument, and send comparator to, measure the fume side wall surface temperature Tgm of the heat transfer element of close exhanst gas outlet with the wall surface temperature transmitter, also send comparator to, wherein the acid dew point measuring instrument is online acid dew point measuring instrument;
B, comparator add a minimum margin temperature difference dTmin who sets with Tm, and compare with Tgm, and adjusted temperature difference Tgm sends Δ Tgm to thermoregulator again, and dTmin wherein is 5～10 ℃;
C, thermoregulator produce according to Δ Tgm and output heat exchange amount conditioning signal, and the heat exchange quantity regulating device of control waste-heat recovery device produces corresponding action, regulates the heat exchange amount of waste-heat recovery device, makes Tgm higher 5～10 ℃ than Tm.
Adopt the present invention, have following beneficial effect: the present invention has set up flue gas acid dew point temperature detection link on the basis that has the waste-heat recovery device that can regulate the heat exchange amount now, constitutes a servo regulation system that changes with the flue gas acid dew point temperature near the fume side wall surface temperature of the heat transfer element of exhanst gas outlet.Flue gas acid dew point temperature T m with the online real-time measurement waste-heat recovery device smoke outlet of acid dew point measuring instrument, according to surveying flue gas acid dew point temperature T m and variation thereof accurately, dynamically change fume side wall surface temperature desired value (Tm+dTmin) near the heat transfer element of exhanst gas outlet, and according to the fume side wall surface temperature of the heat transfer element of the close exhanst gas outlet of measuring and the difference (promptly regulating temperature difference Tgm) of this desired value, heat exchange amount by automatic adjusting waste-heat recovery device, all the time will be controlled at exactly in the temperature range that is higher than 5～10 ℃ of flue gas acid dew point temperature near the fume side wall surface temperature Tgm of the heat transfer element of exhanst gas outlet, thereby avoid flue gas dew-point corrosion of exhaust heat recovery apparatus effectively.The inventive method is the servo-actuated pursuit gain with flue gas acid dew point temperature T m, and the fume side wall surface temperature Tgm of the heat transfer element of close exhanst gas outlet is a controlled variable, and the heat exchange amount of waste-heat recovery device is for regulating parameter.Simultaneously, the inventive method can make waste-heat recovery device move under minimum, most economical smog discharge temperature, realization is to the optimization control of smog discharge temperature, prevent that smog discharge temperature is too high and cause the increase of fume emission heat loss, the waste heat recovery efficient of waste-heat recovery device is improved, the thermal efficiency of industrial furnace operation is improved.When the flue gas acid dew point variation of temperature is comparatively frequent or big, adopt effect of the present invention particularly outstanding.
The present invention can fundamentally overcome the existing existing variety of issue of method that prevents flue gas dew-point corrosion of exhaust heat recovery apparatus, the waste-heat recovery device of industrial furnace is being moved under the smog discharge temperature in the best under the prerequisite that the flue gas dew point corrosion does not take place, to obtain maximum waste heat recovery efficient, reach best energy-saving effect.Be higher than the method for flue gas acid dew point temperature more than 50 ℃ and compare with in the prior art smog discharge temperature of waste-heat recovery device being fixed on, adopt the present invention, the thermal efficiency of industrial furnace approximately can improve 2～2.5%, and fuel approximately can reduce 2～2.5%, obtains energy-saving effect and economic benefit preferably.
The present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.The drawings and specific embodiments do not limit the scope of protection of present invention.
Description of drawings
Fig. 1 is the schematic diagram of system applies on the waste-heat recovery device of a kind of flue gas and cold medium direct heat transfer formula that the present invention avoids flue gas dew-point corrosion of exhaust heat recovery apparatus.
Fig. 2 is the schematic diagram of system applies on a kind of waste-heat recovery device of middle heating agent formula that the present invention avoids flue gas dew-point corrosion of exhaust heat recovery apparatus.
Fig. 3 is the schematic diagram that the thermoregulator among Fig. 1 links to each other with valve positioner.
Fig. 4 is the schematic diagram that the thermoregulator among Fig. 2 links to each other with valve positioner through output alternative selector.
Among Fig. 1 to Fig. 4, same reference numerals is represented identical technical characterictic.
The specific embodiment
Referring to Fig. 1, the present invention avoids the system applies of flue gas dew-point corrosion of exhaust heat recovery apparatus on a kind of waste-heat recovery device 9.This kind waste-heat recovery device is the waste-heat recovery device (being also referred to as the waste-heat recovery device that does not have middle heating agent) of a kind of flue gas and cold medium direct heat transfer formula, mainly be meant heat pipe preheater, turbolator air preheater, the plate-fin air preheater that to regulate the heat exchange amount in the industries such as petrochemical industry, electric power, iron and steel and the economizer that can regulate the heat exchange amount etc., be equipped with heat transfer element (for example heat-transfer pipe or heat transfer plate) and heat exchange quantity regulating device.Waste-heat recovery device 9 shown in Figure 1 enters pipe 93, smoke discharge tube 94, cold medium with flue gas respectively and enters pipe 95 and link to each other with cold medium discharge pipe 96.Waste-heat recovery device 9 is provided with cold medium shunt valve 97, and its two ends are connected to cold medium and enter on pipe 95 and the cold medium discharge pipe 96.The heat exchange quantity regulating device is a pneumatic control valve 8, is located on the cold medium shunt valve 97.Among Fig. 1, cold medium is represented its flow direction with Reference numeral 11 expressions with big hollow arrow; Cold medium 11 is an air.Flue gas is represented its flow direction with Reference numeral 10 expressions with big filled arrows.
The present invention shown in Figure 1 avoids the system of flue gas dew-point corrosion of exhaust heat recovery apparatus, is provided with acid dew point measuring instrument 1, wall surface temperature transmitter 2, comparator 3, thermoregulator 4 and electropneumatic transducer 5.The sensor 101 of acid dew point measuring instrument 1 is located near the space the waste-heat recovery device exhanst gas outlet 92, unsettled setting.Because flue gas does not carry out heat exchange near exhanst gas outlet 92, temperature does not change basically, all is fine so the sensor 101 of acid dew point measuring instrument 1 is located near exhanst gas outlet 92 any spaces.Shown in Figure 1, sensor 101 is located at the smoke discharge tube 94 interior (sleeve pipe through being located on the smoke discharge tube 94 inserts) in exhanst gas outlet 92 outsides.Sensor 101 also can be located at the inboard of exhanst gas outlet 92, and figure slightly.The output of acid dew point measuring instrument 1 links to each other with the input of comparator 3.The temperature sensor 201 of wall surface temperature transmitter 2 is welded on the fume side wall 91 (outside wall surface) near the heat transfer element of exhanst gas outlet 92, and its output also links to each other with the input of comparator 3.The output of comparator 3 links to each other with the input of thermoregulator 4, and the output of thermoregulator 4 links to each other with the input of electropneumatic transducer 5.Connection between above-mentioned acid dew point measuring instrument 1, wall surface temperature transmitter 2, comparator 3, thermoregulator 4 and the electropneumatic transducer 5 all connects by electrical signal line 6.The output of electropneumatic transducer 5 links to each other with pneumatic control valve 8 by pneumatic signal line 7.
Each above-mentioned unit component is existing universal control module or parts, is commercially available.Wherein:
Acid dew point measuring instrument 1: be used to measure the flue gas acid dew point temperature T m at waste-heat recovery device exhanst gas outlet 92 places, and send comparator 3 to.The present invention requires online acid dew point measuring instrument or the transmitter of acid dew point measuring instrument 1 for 250～400 ℃ of heatproofs; As using the acid dew point measuring instrument of the Britain S-680 of LAND company type.
Wall surface temperature transmitter 2: be used to measure fume side wall surface temperature Tgm, and send comparator 3 near the heat transfer element of exhanst gas outlet 92.Wall surface temperature transmitter 2 is general unit component, and its temperature sensor 201 can be surface heat resistance or surface thermocouple.The present invention requires online surface heat resistance or the surface thermocouple of the temperature sensor 201 of wall surface temperature transmitter 2 for 250～500 ℃ of heatproofs; As using the temperature sensor of homemade WZPM-201 type, WREM type, WRNM-203A type.
Comparator 3: be used for the Tm of input is added the minimum margin temperature difference dTmin of setting, compare with Tgm again, adjusted temperature difference Tgm, and send thermoregulator 4 to.Comparator 3 is conventional addition and subtraction arithmetic unit or configuration software module, and the present invention does not have specific (special) requirements.
Comparator 3 needs to set the positive-negative polarity of each input signal and the scope of dTmin.For the present invention, Tm and dTmin are set at positive pole, and Tgm is set at negative pole; Δ Tgm=Tm+dTmin-Tgm.DTmin is generally 5～10 ℃.
Thermoregulator 4: the Δ Tgm according to input produces and output heat exchange amount conditioning signal, and the heat exchange quantity regulating device of control waste-heat recovery device produces corresponding action, regulates the heat exchange amount of waste-heat recovery device.Thermoregulator 4 is control modules that the present invention avoids the system of flue gas dew-point corrosion of exhaust heat recovery apparatus, adopts conventional PID (proportional-integral-differential) thermoregulator or configuration software module, no specific (special) requirements.
Electropneumatic transducer 5: be used for converting the signal of telecommunication (heat exchange amount conditioning signal) of thermoregulator 4 inputs to pneumatic signal, and send pneumatic signal to pneumatic control valve 8 by pneumatic signal line 7, with the aperture of control pneumatic control valve 8.Electropneumatic transducer 5 belongs to conventional unit component, and the present invention does not have specific (special) requirements.
Pneumatic control valve 8: change cold rate-of flow and then the heat exchange amount of regulating waste-heat recovery device of regulating by its aperture.Pneumatic control valve 8 is butterfly valves, gate valve of pneumatic type that can adjustments of gas (air) flow etc., belongs to conventional unit component, and the present invention does not have specific (special) requirements.
Acid dew point measuring instrument 1, wall surface temperature transmitter 2, comparator 3 and thermoregulator 4 are all exported the standard electric signal of 4～20mA (milliampere).The modular, pneumatically powered signal of electropneumatic transducer 5 or valve positioner 81 outputs 20～100kPa.
Shown in Figure 2, the system applies of avoiding flue gas dew-point corrosion of exhaust heat recovery apparatus for the present invention is on another waste-heat recovery device 9.This kind waste-heat recovery device 9 is the waste-heat recovery device of middle heating agent formula, mainly be meant hot oil carrier air preheater, the hydro-thermal matchmaker's regenerative air heater that to regulate the heat exchange amount in the industries such as petrochemical industry, electric power, iron and steel, can regulate the economizer and the waste heat boiler of heat exchange amount in addition.Waste-heat recovery device 9 shown in Figure 2 is provided with the thermal medium pump 142, the thermal medium that are driven by frequency control motor 141 and enters pipe 991, thermal medium heat absorption coil pipe, thermal medium heat release coil pipe, thermal medium discharge pipe 992.Thermal medium heat absorption coil pipe and thermal medium heat release coil pipe are heat transfer element, are located at respectively in exhaust gases passes 98 and the cold medium channel 99.Thermal medium discharge pipe 992 is provided with pneumatic control valve 8, and pneumatic control valve 8 also can be located at thermal medium and enter (figure slightly) on the pipe 991.Select a ground as the heat exchange quantity regulating device by thermal medium pump 142 and pneumatic control valve 8 that frequency control motor 141 drives, thermal medium pump 142 also is the drive unit that thermal medium is circulated in pipeline simultaneously.Among Fig. 2, the flow direction of thermal medium is shown with little filled arrows; Thermal medium is generally water or conduction oil.Cold medium 11 can be the various gas, liquid process mediums that need heating, for example air, hydro carbons, industrial chemicals etc.
The present invention shown in Figure 2 avoids the system of flue gas dew-point corrosion of exhaust heat recovery apparatus, is provided with acid dew point measuring instrument 1 (comprising sensor 101), wall surface temperature transmitter 2 (comprising temperature sensor 201), comparator 3, thermoregulator 4 equally; Each above unit component and set-up mode thereof, connection each other, all with Fig. 1 in identical.Be that the output of thermoregulator 4 links to each other by the input of electrical signal line 6 with output alternative selector 12 with the difference of system shown in Figure 1.Output alternative selector 12 has two outputs, and first output links to each other with the input of variable-frequency governor 13 by electrical signal line 6, and the output of variable-frequency governor 13 links to each other with frequency control motor 141 by electrical signal line 6 again.Second output of output alternative selector 12 links to each other with the input of electropneumatic transducer 5 by electrical signal line 6, and the output of electropneumatic transducer 5 links to each other with pneumatic control valve 8 by pneumatic signal line 7 again.
Above-mentioned each unit component also is existing universal control module or parts, is commercially available.Wherein:
Output alternative selector 12: by the switching of two outputs, the thermal medium pump of selecting to be driven by frequency control motor 141 142 is as the heat exchange quantity regulating device, or selection pneumatic control valve 8 is as the heat exchange quantity regulating device.Output alternative selector 12 belongs to conventional selector or configuration software module, and the present invention does not have specific (special) requirements.
Variable-frequency governor 13: [the frequency control signal is the standard electric signal of 4～20mA to be used for converting the signal of telecommunication (heat exchange amount conditioning signal) that thermoregulator 4 is imported through output alternative selector 12 to the frequency control signal, or the normal voltage signal of 1～5V (volt)], and send the frequency control signal to frequency control motor 141 by electrical signal line 6, with control frequency control motor 141 with by the rotating speed of the thermal medium pump 142 of its driving.
Pneumatic control valve 8: change the heat exchange amount that the thermal medium circular flow is regulated waste-heat recovery device of regulating by its aperture.Pneumatic control valve 8 is the butterfly valve that can regulate the pneumatic type of liquid (for example water or conduction oil) flow, gate valve etc., belongs to conventional unit component, and the present invention does not have specific (special) requirements.
The effect of unaccounted other each unit component among Fig. 2, type, running parameter scope etc., all with Fig. 1 in identical.
Second output of output alternative selector 12 can also link to each other with valve positioner 81 by electrical signal line 6 among Fig. 2, referring to Fig. 4.Valve positioner 81 converts thermoregulator 4 to pneumatic signal, the aperture of control pneumatic control valve 8 through the signal of telecommunication (heat exchange amount conditioning signal) of output alternative selector 12 inputs.Electropneumatic transducer 5 among Fig. 2 no longer is set this moment.About valve positioner 81, can be referring to explanation to Fig. 3 did.
Avoid the method for flue gas dew-point corrosion of exhaust heat recovery apparatus below in conjunction with description of drawings the present invention.At first referring to Fig. 1, described method is made up of following steps:
A, measure the flue gas acid dew point temperature T m at waste-heat recovery device exhanst gas outlet 92 places, and send comparator 3 to acid dew point measuring instrument 1; Measure fume side wall surface temperature Tgm with wall surface temperature transmitter 2, also send comparator 3 near the heat transfer element of exhanst gas outlet 92;
B, comparator 3 add a minimum margin temperature difference dTmin who sets with Tm, and compare with Tgm, and adjusted temperature difference Tgm sends Δ Tgm to thermoregulator 4 again.DTmin wherein is generally 5～10 ℃;
C, thermoregulator 4 produce according to Δ Tgm and output heat exchange amount conditioning signal, and the heat exchange quantity regulating device of control waste-heat recovery device produces corresponding action, regulates the heat exchange amount of waste-heat recovery device, makes Tgm higher 5～10 ℃ than Tm.
As mentioned before, waste-heat recovery device shown in Figure 1 is the waste-heat recovery device of flue gas and cold medium direct heat transfer formula, and the heat exchange quantity regulating device is the pneumatic control valve of being located on the cold medium shunt valve 97 8.Among the step C, thermoregulator 4 produces and the heat exchange amount conditioning signal of output sends electropneumatic transducer 5 to, electropneumatic transducer 5 produces and output pneumatic signal, and send pneumatic signal to pneumatic control valve 8 by pneumatic signal line 7, produce corresponding action (finer opening changes) with control pneumatic control valve 8, by the heat exchange amount that the flow of regulating cold medium 11 (air) is regulated waste-heat recovery device, regulate the fume side wall surface temperature Tgm of the heat transfer element of close exhanst gas outlet 92 with this.Specifically, when the aperture of pneumatic control valve 8 increases, the flow of cold medium 11 increases (more cold medium by-passing) in the cold medium shunt valve 97, and the heat exchange amount of waste-heat recovery device 9 reduces thereupon, and the fume side wall surface temperature Tgm of the heat transfer element of close exhanst gas outlet 92 will raise.Otherwise, when the aperture of pneumatic control valve 8 reduces, the flow of cold medium 11 reduces (less cold medium by-passing) in the cold medium shunt valve 97, and the heat exchange amount of waste-heat recovery device 9 increases thereupon, and the fume side wall surface temperature Tgm of the heat transfer element of close exhanst gas outlet 92 will reduce.Finally, Tgm is reached than in high 5～10 ℃ temperature range of Tm.
If the thermoregulator among Fig. 14 links to each other (referring to Fig. 3) with valve positioner 81 by electrical signal line 6, then in step C (steps A, step B constant), the heat exchange amount conditioning signal that thermoregulator 4 produces and exports sends valve positioner 81 to.Valve positioner 81 produces and output pneumatic signal, and the aperture of control pneumatic control valve 8 is regulated the heat exchange amount of waste-heat recovery device by regulating cold rate-of flow.
When wall surface temperature transmitter 2 was measured fume side wall surface temperature Tgm near the heat transfer element of exhanst gas outlet 92 and reached the temperature range of Tm+dTmin (5～10 ℃), the present invention avoided the system of flue gas dew-point corrosion of exhaust heat recovery apparatus out of service; Otherwise, proceed the operation of next or a plurality of circulations to the order of step C by above-mentioned steps A.
When adopting the present invention to avoid the method for flue gas dew-point corrosion of exhaust heat recovery apparatus, still carry out to the order of step C generally, referring to 1 explanation of being carried out in conjunction with the accompanying drawings by above-mentioned steps A to the waste-heat recovery device of heating agent formula in the middle of shown in Figure 2.Steps A, step B are constant; In step C, thermoregulator 4 produces and the heat exchange amount conditioning signal of output sends output alternative selector 12 to, switching by two outputs, the thermal medium pump 142 that can select to be driven by frequency control motor 141 is as the heat exchange quantity regulating device, or selection pneumatic control valve 8 is as the heat exchange quantity regulating device.
When 1. selecting the thermal medium pump 142 that drives by frequency control motor 141 as the heat exchange quantity regulating device, the heat exchange amount conditioning signal that thermoregulator 4 produces and exports among the step C sends variable-frequency governor 13 to through output alternative selector 12, variable-frequency governor 13 produces the frequency control signal, and send frequency control motor 141 to, regulate the circular flow of thermal medium, the heat exchange amount of regulating waste-heat recovery device by the rotation speed change of the thermal medium pump 142 that drives by frequency control motor 141.The rotating speed of thermal medium pump 142 changes, and is meant that promptly it has produced corresponding action as the heat exchange quantity regulating device.
When 2. selecting pneumatic control valve 8 as the heat exchange quantity regulating device, the heat exchange amount conditioning signal that thermoregulator 4 produces and exports among the step C sends electropneumatic transducer 5 to through output alternative selector 12, electropneumatic transducer 5 produces the also aperture of output pneumatic signal control pneumatic control valve 8, by regulating the heat exchange amount that the thermal medium circular flow is regulated waste-heat recovery device.If second output of output alternative selector 12 is by electrical signal line 6 link to each other with valve positioner 81 (referring to Fig. 4) among Fig. 2, then in step C (steps A, step B constant), thermoregulator 4 produce and the heat exchange amount conditioning signal of output sends valve positioner 81 to through output alternative selector 12.Valve positioner 81 produces the also aperture of output pneumatic signal control pneumatic control valve 8, by regulating the heat exchange amount that the thermal medium circular flow is regulated waste-heat recovery device.
In general, under the little situation of heat exchange quantitative changeization, just select pneumatic control valve 8 as the heat exchange quantity regulating device.This moment, the rotating speed of frequency control motor 141 and thermal medium pump 142 can be fixed, and also can use the thermal medium pump 142 of fixed rotating speed; 142 of thermal medium pumps play the effect that thermal medium is circulated in pipeline.
Thermal medium is generally water or conduction oil.When the thermal medium circular flow in the thermal medium circulation line increased, the heat exchange amount of waste-heat recovery device increased thereupon; Thermal medium heat absorption coil pipe in the middle of shown in Figure 2 in the heating agent formula waste-heat recovery device exhaust gases passes 98 will reduce at the fume side wall surface temperature Tgm near exhanst gas outlet 92.Otherwise when the thermal medium circular flow in the thermal medium circulation line reduced, the heat exchange amount of waste-heat recovery device reduced thereupon, and the thermal medium heat absorption coil pipe in the exhaust gases passes 98 will raise at the fume side wall surface temperature Tgm near exhanst gas outlet 92.Waste-heat recovery device for heating agent formula in the middle of shown in Figure 2 adopts the present invention to avoid the method for flue gas dew-point corrosion of exhaust heat recovery apparatus, by the heat exchange amount that the flow of regulating thermal medium is regulated waste-heat recovery device, finally can be in the fume side wall surface temperature Tgm near exhanst gas outlet 92 be controlled at than high 5～10 ℃ temperature range of the flue gas acid dew point temperature T m at exhanst gas outlet 92 places with the heat absorption of the thermal medium in the exhaust gases passes 98 coil pipe.
Claims (3)
1. method of avoiding flue gas dew-point corrosion of exhaust heat recovery apparatus, this waste-heat recovery device (9) is provided with heat transfer element and heat exchange quantity regulating device, it is characterized in that: described method is made up of following steps:
A, measure the flue gas acid dew point temperature T m that waste-heat recovery device exhanst gas outlet (92) is located with acid dew point measuring instrument (1), and send comparator (3) to, measure the fume side wall surface temperature Tgm of the heat transfer element of close exhanst gas outlet (92) with wall surface temperature transmitter (2), also send comparator (3) to, wherein acid dew point measuring instrument (1) is online acid dew point measuring instrument;
B, comparator (3) add a minimum margin temperature difference dTmin who sets with Tm, and compare with Tgm, and adjusted temperature difference Tgm sends Δ Tgm to thermoregulator (4) again, and dTmin wherein is 5～10 ℃;
C, thermoregulator (4) produce according to Δ Tgm and output heat exchange amount conditioning signal, and the heat exchange quantity regulating device of control waste-heat recovery device produces corresponding action, regulates the heat exchange amount of waste-heat recovery device, makes Tgm higher 5～10 ℃ than Tm.
2. according to the described method of avoiding flue gas dew-point corrosion of exhaust heat recovery apparatus of claim 1, it is characterized in that: waste-heat recovery device is the waste-heat recovery device of flue gas and cold medium direct heat transfer formula, the heat exchange quantity regulating device is for being located at the pneumatic control valve (8) on the cold medium shunt valve (97), among the step C, thermoregulator (4) produces and the heat exchange amount conditioning signal of output sends electropneumatic transducer (5) or valve positioner (81) to, electropneumatic transducer (5) or valve positioner (81) produce the also aperture of output pneumatic signal control pneumatic control valve (8), regulate the heat exchange amount of waste-heat recovery device by regulating cold rate-of flow.
3. according to the described method of avoiding flue gas dew-point corrosion of exhaust heat recovery apparatus of claim 1, it is characterized in that: waste-heat recovery device is the waste-heat recovery device of middle heating agent formula, the heat exchange quantity regulating device is the thermal medium pump (142) that is driven by frequency control motor (141), among the step C, thermoregulator (4) produces and the heat exchange amount conditioning signal of output sends variable-frequency governor (13) to through output alternative selector (12), variable-frequency governor (13) produces the frequency control signal, and send frequency control motor (141) to, regulate the circular flow of thermal medium, the heat exchange amount of regulating waste-heat recovery device by the rotation speed change of the thermal medium pump (142) that drives by frequency control motor (141);
Or, the heat exchange quantity regulating device enters pneumatic control valve (8) on the pipe (991) for being located at thermal medium discharge pipe (992) or thermal medium, among the step C, thermoregulator (4) produces and the heat exchange amount conditioning signal of output sends electropneumatic transducer (5) or valve positioner (81) to through output alternative selector (12), electropneumatic transducer (5) or valve positioner (81) produce the also aperture of output pneumatic signal control pneumatic control valve (8), by regulating the heat exchange amount that the thermal medium circular flow is regulated waste-heat recovery device.
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| CN2009100640882A CN101476821B (en) | 2009-01-16 | 2009-01-16 | Method for preventing flue gas dew-point corrosion of exhaust heat recovery apparatus |
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| CN108926859A (en) * | 2017-05-27 | 2018-12-04 | 中国石化工程建设有限公司 | The tower top control system of fractionating column |
| CN107120976B (en) * | 2017-06-15 | 2018-02-16 | 龙游县金怡热电有限公司 | A kind of gas cleaning and residual neat recovering system |
| CN107883392B (en) * | 2017-10-27 | 2019-10-29 | 北京中电联节能技术有限公司 | Feedforward neural network control method and system suitable for flue gas waste heat recovery apparatus |
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