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.
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.
Thermoregulator 4 among Fig. 1 can also link to each other with valve positioner 81 by electrical signal line 6, referring to Fig. 3; Valve positioner 81 will convert pneumatic signal to from the signal of telecommunication of thermoregulator 4, the aperture of control pneumatic control valve 8.Electropneumatic transducer 5 among Fig. 1 no longer is set this moment.Valve positioner 81 also is 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.
Frequency control motor 141 and thermal medium pump 142: by rotational speed regulation, regulate the thermal medium circular flow in the thermal medium circulation line, and regulate the heat exchange amount of waste-heat recovery device.Thermal medium pump 142 also is simultaneously the drive unit that makes the thermal medium circulation.The present invention is to frequency control motor 141 and the 142 no specific (special) requirements of thermal medium pump.
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.