Carbon calcining flue gas heat transfer oil heating and waste heat recovery integrated device and method

Abstract

The present invention discloses an integrated device for heating carbon calcining flue gas with heat transfer oil and recovering waste heat, the device also includes a heat transfer oil regulating mechanism; the heat transfer oil regulating mechanism is composed of a first heat transfer oil heat exchanger, a second heat transfer oil heat exchanger and a heat transfer oil temperature control module; the first heat transfer oil heat exchanger is arranged between a primary economizer and a secondary economizer; the second heat transfer oil heat exchanger is arranged between the carbon calcining flue gas outlet and the superheater; the input end of the first heat transfer oil heat exchanger is connected to the cold oil process section through a first oil temperature sensor and a first regulating valve respectively; the output end of the first heat transfer oil heat exchanger is connected to the second heat transfer oil heat exchanger through a first flue gas temperature sensor and a second regulating valve respectively arranged at the front end of the primary economizer; the output end of the second heat transfer oil heat exchanger is connected to the hot oil process; the present invention realizes the two functions of heating heat transfer oil and recovering waste heat, ensuring the safe, stable and long-term operation of the waste heat boiler.

Description

Technical Field

[0001] The patent of this invention relates to the field of waste heat utilization technology, and more specifically, to an integrated device and method for heating carbon calcination flue gas with thermal oil and recovering waste heat. Background Art

[0002] Carbon products are a kind of raw material for aluminum industry, mainly used in the production of electrolytic aluminum. Petroleum coke is used as raw material and enters the carbon calcining furnace. After high-temperature calcination, calcined coke is produced. After sieving and grinding, the calcined coke is mixed with asphalt, and then kneaded and roasted to become aluminum anode.

[0003] After petroleum coke is calcined in a carbon calcining furnace, a large amount of high-temperature flue gas of 800-1050℃ is generated. At present, the industry generally divides the high-temperature flue gas into two routes. One route enters a high-temperature waste heat boiler to recover the waste heat in the high-temperature flue gas and produce steam for centralized heating, industrial steam or power generation. The other route enters a thermal oil boiler (also called a "heat medium boiler" or "organic heat carrier boiler"). After the high-temperature flue gas heats the thermal oil, the exhaust gas temperature is about 400℃ and enters a small waste heat boiler. The thermal oil is used in the carbon mixing process to meet the heat requirements for asphalt melting and insulation. The small waste heat boiler produces low-parameter steam for production or power generation.

[0004] The working principle of the thermal oil furnace in the carbon industry is to use the high-temperature flue gas at the outlet of the calcining furnace as the heat source, the thermal oil as the heat carrier, and use a circulating oil pump to force the liquid phase to circulate, and then transfer the heat energy to the heat-using equipment (mixing process), and then return to the direct-current thermal oil furnace for reheating.

[0005] The parameters of the heat transfer oil commonly used in the industry - ZD350# synthetic heat transfer oil are:

[0006]

[0007] At present, the conventional design parameters of thermal oil furnaces in the industry are:

[0008]

[0009]

[0010] Waste heat utilization boilers, whether vertical or horizontal, are currently steam-water boilers. The boiler feed water is generally 104°C after deoxygenation by an atmospheric pressure deaerator. If it is deoxygenated by a pressure deaerator, the feed water temperature is determined based on the working pressure of the deaerator. Currently, due to the limitation of the boiler exhaust temperature, the working pressure of the deaerator is generally up to 0.5MPa, and the feed water temperature does not exceed 151.9°C.

[0011] The boiler feed water is heated by the primary economizer and the secondary economizer and then enters the boiler drum. After being heated by the primary economizer and the secondary economizer, the feed water becomes high-temperature hot water or a steam-water mixture with a relatively small proportion of steam. After this hot water or steam-water mixture enters the drum, steam and water are separated, with water in the lower part of the drum and steam gathering in the upper space of the drum. On the water side of the boiler drum, the hot water passes through the downcomer to the evaporator and exchanges heat with the flue gas to become a steam-water mixture with a relatively high proportion of steam or steam that returns to the drum (the function of the evaporator is to enable the boiler working fluid (water) to become more steam). The steam on the steam side of the drum is further heated by the superheater and then collected in the superheater outlet header. This part of the steam is subsequently used for industrial steam or power generation.

[0012] At present, the conventional design parameters of small waste heat boilers in the industry are:

[0013]

[0014] At present, the flue gas of carbon calcining furnace is affected by the quality of raw material petroleum coke. The SO2 content in the calcining flue gas is relatively high, generally reaching 1500-6000mg / Nm 3 . When a waste heat boiler is set up behind the thermal oil boiler to recover waste heat, due to the presence of sulfur, sulfur corrosion is easily generated after the flue gas temperature drops, thus affecting the life of the boiler. At present, the industry has also set up a desulfurization system for calcination flue gas, but it is all set up behind the waste heat boiler, so the high sulfur content in the flue gas must be considered when designing the waste heat boiler. At present, the exhaust temperature of the waste heat boiler is generally set at 180-200℃. If it is too high, firstly, the waste heat is not fully recovered, and secondly, the subsequent desulfurization system cannot withstand the temperature resistance; if the flue gas temperature is too low, the temperature of the heat exchange surface at the rear of the boiler may be lower than the sulfur dew point temperature of the flue gas, causing the corrosion of the heat exchange surface at the rear of the boiler to intensify.

[0015] At present, the thermal oil boiler and waste heat boiler are built separately, which takes up a large area and requires a large investment, and the flue gas acid corrosion problem is borne by the waste heat boiler alone. Therefore, there is an urgent need for a thermal oil heating and waste heat recovery integrated equipment with high technical and economic efficiency, which can jointly deal with sulfur corrosion and has multiple adjustment means.

[0016] Invention patent content

[0017] In view of the deficiencies of the above-mentioned prior art, the patent of the present invention provides an integrated device for heating the thermal oil and recovering the waste heat from the flue gas of carbon calcination. The device ensures that the two functions of heating the thermal oil and recovering the waste heat are met, reduces the footprint, and increases the resistance of the heat exchange surface of the low-temperature section at the rear of the waste heat boiler (mainly the first-level economizer) to sulfur corrosion, thereby ensuring the safe, stable and long-term operation of the waste heat boiler.

[0018] To achieve the above purpose, the present invention is implemented through the following technical solutions:

[0019] A device for heating carbon calcining flue gas with heat transfer oil and recovering waste heat is provided between the carbon calcining flue gas outlet and the induced draft fan, and comprises: a primary economizer, a secondary economizer, an evaporator, a superheater, a drum, and a superheater header; the device is characterized in that the device also comprises a heat transfer oil control mechanism for controlling flue gas by heating and recovering the heat transfer oil temperature; the heat transfer oil control mechanism is composed of a first heat transfer oil heat exchanger, a second heat transfer oil heat exchanger, and a heat transfer oil temperature control module; wherein:

[0020] The first heat transfer oil heat exchanger is arranged between the secondary economizer and the primary economizer; the second heat transfer oil heat exchanger is arranged between the carbon calcination flue gas outlet and the superheater; the input end of the first heat transfer oil heat exchanger is connected to the cold oil process section through the first oil temperature sensor and the first regulating valve respectively; the output end of the first heat transfer oil heat exchanger is connected to the second heat transfer oil heat exchanger through the first flue gas temperature sensor and the second regulating valve arranged at the front end of the primary economizer respectively; the output end of the second heat transfer oil heat exchanger is connected to the hot oil process;

[0021] Wherein: the heat transfer oil temperature control module monitors the temperature values ​​of the first oil temperature sensor and the first smoke temperature sensor in real time; and adjusts the first control valve and the second control valve.

[0022] Furthermore, the first-level economizer input end is connected to the deaerator, and the first-level economizer output end is connected to the second-level economizer input end; the second-level economizer output end is connected to the evaporator input end through the water side space at the bottom of the boiler drum, and the evaporator input end is connected to the superheater input end after being temporarily stored in the steam space at the top of the boiler drum; the superheater output end collects steam through the superheater header and increases industrial steam to the factory or uses it for power generation; the boiler drum is connected to the second-level economizer output end, the evaporator input end, the evaporator output end, and the superheater input end to realize the storage and separation of steam and water.

[0023] The present invention can also adopt the following technical solutions:

[0024] The production method of heating carbon calcination flue gas with heat transfer oil and recovering waste heat by means of a heat transfer oil control mechanism comprises the following steps:

[0025] The first flue gas temperature sensor 12 sends a signal to the thermal oil temperature control module when it detects that the outlet flue gas temperature of the first thermal oil heat exchanger (that is, the inlet flue gas temperature of the first economizer) is higher than 270°C; the thermal oil temperature control module adjusts the first regulating valve 9 to increase the temperature, reduces or completely closes the second regulating valve 10, and allows all or part of the thermal oil at 260°C to flow through the first thermal oil heat exchanger, allowing the heat in the flue gas to release heat to the thermal oil, thereby heating the thermal oil;

[0026] The first flue gas temperature sensor 12 detects that the flue gas temperature at the outlet of the first thermal oil heat exchanger (that is, the flue gas temperature at the inlet of the first economizer) is lower than 250°C and sends a signal to the thermal oil temperature control module, and the thermal oil temperature control module starts the first regulating valve; at the same time, the thermal oil temperature control module weakens the second regulating valve 10, so that the thermal oil at 260°C flows through the first thermal oil heat exchanger, and the heat in the thermal oil is released to heat the flue gas;

[0027] The first flue gas temperature sensor 12 sends a temperature signal of 250-270°C of the flue gas temperature at the outlet of the first thermal oil heat exchanger to the thermal oil temperature control module, and the thermal oil temperature control module starts the second regulating valve signal to fully open the second regulating valve; at the same time, the first regulating valve signal is closed, the first thermal oil heat exchanger is decoupled, and the thermal oil is directly supplied to the second thermal oil heat exchanger.

[0028] Beneficial Effects

[0029] 1. The present invention changes the technical problem of the heat transfer process of the heat transfer oil furnace in the traditional process into full heat absorption heating through the heat transfer oil regulating mechanism, and the first heat transfer oil heat exchanger in the heat transfer oil regulating mechanism realizes the dual functions of absorbing and releasing heat to the oil temperature and smoke temperature in the heat transfer process, thereby solving the technical problem of the complex function of the temperature control program of the tail smoke exhaust of the heat transfer furnace and the waste heat boiler in the prior art.

[0030] 2. The second heat transfer oil heat exchanger in the present invention is placed in front of the flue gas of the waste heat recovery system to exchange heat with the high-temperature flue gas at the outlet of the calcining furnace to ensure that a stable and reliable heat medium heat source is provided for the kneading process of carbon production.

[0031] 3. The heat transfer oil regulating mechanism of the present invention has a reasonable structure and advanced production technology, which ensures the effect of recycling the flue gas from carbon calcination and complies with the production concept of energy saving and consumption reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure of the integrated device for heating the flue gas heat transfer oil and recovering the waste heat from carbon calcination.

[0033] 1-first-stage economizer; 2-second-stage economizer; 3-evaporator; 4-superheater; 5-boiler drum; 6-superheater header; 7-first thermal oil heat exchanger; 8-second thermal oil heat exchanger; 9-first regulating valve; 10-second regulating valve; 11-first oil temperature sensor; 12-first smoke temperature sensor; 13-second smoke temperature sensor. DETAILED DESCRIPTION

[0034] The present invention will be further described below based on specific implementation methods.

[0035] like Figure 1As shown, the high-temperature flue gas at the outlet of the calcining furnace of the present invention at 800-1050°C passes through the second thermal oil heat exchanger 8, the superheater 4, the evaporator 3, the secondary economizer 2, the first thermal oil heat exchanger 7, and the primary economizer 1 respectively. After heat exchange with the thermal oil and steam-water, the exhaust gas temperature is about 180-200°C (detected by the second flue gas temperature sensor 13), and then discharged to the subsequent desulfurization system through the induced draft fan.

[0036] The boiler feed water process is as follows: the outlet water temperature of the deaerator is 104~151.9℃, and it enters the first-level economizer 1, the second-level economizer 2, the boiler drum 5, the evaporator 3, the boiler drum 5, and the superheater 4 respectively. The qualified steam is collected by the superheater header 6 and subsequently provides industrial steam or power generation for the factory.

[0037] The heat transfer oil process starts from the aluminum product kneading process, the heat transfer oil temperature is 260°C, and it passes through the first heat transfer oil heat exchanger 7 and the second heat transfer oil heat exchanger 8 respectively, and after being heated to 280°C, it returns to the kneading section of the roasting workshop. Among them: a bypass pipeline is set between the inlet of the first heat transfer oil heat exchanger 7 and the inlet of the second heat transfer oil heat exchanger 8. When the first heat transfer oil heat exchanger 7 is disconnected, the heat transfer oil can be directly heated in the second heat transfer oil heat exchanger 8. The specific structure is:

[0038] A device for heating carbon calcining flue gas with heat transfer oil and recovering waste heat is arranged between the carbon calcining flue gas outlet and the waste heat furnace, the device comprising: a primary economizer 1, a secondary economizer 2, an evaporator 3, a superheater 4, a drum 5, and a superheater header 6; the device also comprises a heat transfer oil control mechanism for controlling flue gas by heating and recovering the heat transfer oil temperature; the heat transfer oil control mechanism is composed of a first heat transfer oil heat exchanger 7, a second heat transfer oil heat exchanger 8 and a heat transfer oil temperature control module; wherein:

[0039] The first heat-conducting oil heat exchanger 7 is arranged between the secondary economizer 2 and the primary economizer 1; the second heat-conducting oil heat exchanger 8 is arranged between the carbon calcining flue gas outlet and the superheater 4; the input end of the first heat-conducting oil heat exchanger 7 is connected to the cold oil process section through the first oil temperature sensor 11 and the first regulating valve 9 respectively; the output end of the first heat-conducting oil heat exchanger 7 is connected to the second heat-conducting oil heat exchanger 8 through the first flue gas temperature sensor 12 and the second regulating valve 10 arranged at the front end of the primary economizer respectively; the output end of the second heat-conducting oil heat exchanger 8 is connected to the hot oil process;

[0040] in:

[0041] The thermal oil temperature control module monitors the temperature values ​​of the first smoke temperature sensor 12 and the first oil temperature sensor 11 in real time; and adjusts the first control valve 9 and the second control valve 10;

[0042] The input end of the first-stage economizer 1 is connected to the deaerator, and the output end of the first-stage economizer 1 is connected to the input end of the second-stage economizer 2;

[0043] The output end of the secondary economizer 2 is connected to the input end of the evaporator 3 through the water side space at the bottom of the drum 5;

[0044] The input end of the evaporator 4 is connected to the input end of the superheater 4 after being temporarily stored in the steam space above the drum 5;

[0045] The output end of the superheater 4 collects steam through the superheater header 6 and supplies it to the factory to increase industrial steam or to generate electricity;

[0046] The boiler drum is connected with the secondary economizer output end, the evaporator input end, the evaporator output end, and the superheater input end to achieve the function of steam and water storage and separation.

[0047] The present invention adopts the following design concepts in carbon calcination flue gas heat transfer oil heating and waste heat recovery:

[0048] A flue gas temperature measuring point, i.e., the first flue gas temperature sensor 12, is set at the outlet of the first economizer 1. When the flue gas temperature is higher than a certain value (e.g., 200°C), the first thermal oil heat exchanger 7 is put into operation to heat the thermal oil with the heat in the flue gas. The flow rate of the first thermal oil is adjusted according to the flue gas temperature at the outlet of the first economizer. By increasing the amount of thermal oil, the amount of heat absorbed from the flue gas is increased, and the flue gas temperature is reduced.

[0049] Specific technical solutions adopted:

[0050] The production method of heating carbon calcination flue gas with heat transfer oil and recovering waste heat by means of a heat transfer oil control mechanism comprises the following steps:

[0051] The first flue gas temperature sensor 12 sends a signal to the thermal oil temperature control module when it detects that the outlet flue gas temperature of the first thermal oil heat exchanger (that is, the inlet flue gas temperature of the first economizer) is higher than 270°C; the thermal oil temperature control module adjusts the first regulating valve 9 to make all or part of the thermal oil at 260°C flow through the first thermal oil heat exchanger 7, so that the heat in the flue gas is released to the thermal oil to heat the thermal oil;

[0052] The first flue gas temperature sensor 12 sends a signal to the thermal oil temperature control module when it detects that the outlet flue gas temperature of the first thermal oil heat exchanger (that is, the inlet flue gas temperature of the first economizer) is lower than 250°C. The thermal oil temperature control module starts the first regulating valve 9. At the same time, the thermal oil temperature control module weakens the second regulating valve 10 to allow the thermal oil at 260°C to flow through the first thermal oil heat exchanger 7, so that the heat of the thermal oil is released to the flue gas to heat the flue gas.

[0053] The first flue gas temperature sensor 12 sends a temperature signal of 250-270°C of the flue gas temperature at the outlet of the first thermal oil heat exchanger 7 to the thermal oil temperature control module, and the thermal oil temperature control module starts the second regulating valve 10; at the same time, the first regulating valve 9 is closed, the first thermal oil heat exchanger 7 is decoupled, and the thermal oil is directly supplied to the second thermal oil heat exchanger 8.

[0054] The actual production and application process of the present invention is as follows:

[0055] Control method 1 for whether the low-temperature heat transfer oil (first heat transfer oil heat exchanger) is put into operation: The return oil temperature from the carbon product kneading process is relatively stable, generally 260°C. Whether the first heat transfer oil heat exchanger is working depends on the flue gas temperature 12 at the outlet of the first heat transfer oil heat exchanger (that is, the flue gas temperature at the inlet of the first economizer). When the flue gas temperature at the outlet of the first heat transfer oil heat exchanger is lower than 250°C, open the first heat transfer oil heat exchanger oil supply valve, that is, the first regulating valve 9, and at the same time close or reduce the first heat transfer oil heat exchanger bypass valve second regulating valve 10, so that all or part of the 260°C heat transfer oil flows through the first heat transfer oil heat exchanger, and the heat contained in the heat transfer oil is released to the flue gas, and the flue gas is heated as much as possible (the flue gas temperature 13 at the outlet of the first economizer shall not be lower than 180°C). The opening of the first heat transfer oil heat exchanger bypass valve, that is, the second regulating valve 10, is adjusted according to the flue gas temperature at the outlet of the first economizer not lower than 180°C. Ensure that the first economizer is not affected by sulfur corrosion.

[0056] 2: When the flue gas temperature at the outlet of the first thermal oil heat exchanger (that is, the flue gas temperature at the inlet of the first economizer) is higher than 270°C, fully open or increase the opening of the first thermal oil heat exchanger bypass valve, that is, the second control valve 10, so that all or part of the 260°C thermal oil flows through the first thermal oil heat exchanger, allowing the heat in the flue gas to release heat to the thermal oil, and heating the thermal oil as much as possible (and the flue gas temperature 13 at the outlet of the first economizer shall not be higher than 200°C). The opening of the second control valve of the thermal oil heat exchanger bypass valve is adjusted according to the flue gas temperature at the first economizer outlet not exceeding 200°C, which ensures that the first economizer is not corroded by sulfur and ensures the safe operation of the subsequent desulfurization process.

[0057] 3: When the outlet flue gas temperature of the first thermal oil heat exchanger (that is, the inlet flue gas temperature of the first economizer) is between 250 and 270°C, fully open the bypass valve of the first thermal oil heat exchanger, i.e., the second regulating valve 10; and fully close the oil supply valve of the first thermal oil heat exchanger, i.e., the first regulating valve 9, to decouple the first thermal oil heat exchanger, and directly supply the thermal oil to the second thermal oil heat exchanger.

[0058] The heat exchange area of ​​the first-stage economizer is calculated based on the inlet flue gas temperature of 250℃ and the outlet flue gas temperature of 180℃.

[0059] The heat exchange area of ​​the first heat transfer oil heat exchanger is calculated by comprehensively considering the heat transfer oil return temperature (generally 260°C), the fluctuation range of the sulfur content in the flue gas and the flue gas dew point temperature, the first-level economizer feed water temperature, the heat exchange area of ​​the first-level economizer, and the actual situation of the calcined coke mixing and kneading process.

[0060] The heat exchange area of ​​the second thermal oil heat exchanger is calculated on the basis of the original calculation, taking into account the heat release of the first thermal oil heat exchanger. This part of the lost heat needs to be compensated by increasing the heat exchange area in the second thermal oil heat exchanger for heating.

[0061] As mentioned above: a bypass system is set for the first heat exchanger of the thermal oil system, that is, in actual production operation, the first thermal oil heat exchanger can be decoupled for operation, that is, by fully opening the bypass valve of the first thermal oil heat exchanger, that is, the second regulating valve, and fully closing the oil supply valve of the first thermal oil heat exchanger, that is, the first regulating valve.

[0062] As mentioned above: the flow rate of the first thermal oil heat exchanger can be adjusted, and the flow rate control is performed as described above, that is, it is achieved by adjusting the opening of the bypass valve of the first thermal oil heat exchanger.

[0063] The above is only the preferred implementation of the patent of the present invention, but the patent of the present invention is not limited to the above specific implementation. For ordinary technicians in this field, several modifications and improvements can be made without departing from the creative concept, which all belong to the protection scope of the patent of the present invention.

Claims

1. A method for heating carbon calcining flue gas with heat transfer oil and recovering waste heat, the method is based on an integrated device for heating carbon calcining flue gas with heat transfer oil and recovering waste heat, which is arranged between the carbon calcining flue gas outlet and the induced draft fan, and the device comprises: A primary economizer, a secondary economizer, an evaporator, a superheater, a boiler drum, and a superheater header; characterized in that the device also includes a heat transfer oil control mechanism for controlling flue gas by heating and recovering the heat transfer oil temperature; the heat transfer oil control mechanism is composed of a first heat transfer oil heat exchanger, a second heat transfer oil heat exchanger, and a heat transfer oil temperature control module; the first heat transfer oil heat exchanger is arranged between the primary economizer and the secondary economizer; the second heat transfer oil heat exchanger is arranged between the carbon calcining flue gas outlet and the superheater; the input end of the first heat transfer oil heat exchanger is connected to the cold oil process section through the first oil temperature sensor and the first control valve respectively; the output end of the first heat transfer oil heat exchanger is connected to the second heat transfer oil heat exchanger through the first flue gas temperature sensor and the second control valve respectively arranged at the front end of the primary economizer; the output end of the second heat transfer oil heat exchanger is connected to the hot oil process; the heat transfer oil temperature control module monitors the temperature values ​​of the first oil temperature sensor and the first flue gas temperature sensor in real time; adjusts the first control valve and the second control valve; including the following steps: The first smoke temperature sensor sends a signal to the heat transfer oil temperature control module when it detects that the smoke temperature at the outlet of the first heat transfer oil heat exchanger is higher than 270°C; the heat transfer oil temperature control module adjusts the first regulating valve to make all or part of the heat transfer oil at 260°C flow through the first heat transfer oil heat exchanger, so that the heat in the smoke is released to the heat transfer oil to heat the heat transfer oil; The first flue gas temperature sensor sends a signal to the thermal oil temperature control module when it detects that the flue gas temperature at the outlet of the first thermal oil heat exchanger is lower than 250°C, and the thermal oil temperature control module starts the first regulating valve; at the same time, the thermal oil temperature control module weakens the second regulating valve to allow the thermal oil at 260°C to flow through the first thermal oil heat exchanger to heat the flue gas; The first flue gas temperature sensor sends a temperature signal of 250-270°C of the flue gas temperature at the outlet of the first thermal oil heat exchanger to the thermal oil temperature control module, and the thermal oil temperature control module starts the second regulating valve signal; at the same time, the first regulating valve signal is closed, the first thermal oil heat exchanger is decoupled, and the thermal oil is directly supplied to the second thermal oil heat exchanger.

2. The method for heating carbon calcining flue gas with thermal oil and recovering waste heat according to claim 1, characterized in that: The input end of the first-level economizer is connected to the deaerator, and the output end of the first-level economizer is connected to the input end of the second-level economizer; the output end of the second-level economizer is connected to the input end of the evaporator through the water side space at the bottom of the boiler drum, and the output end of the evaporator is connected to the input end of the superheater after being temporarily stored in the steam space at the top of the boiler drum; the output end of the superheater collects steam through the superheater header and increases industrial steam to the factory or uses it for power generation; the boiler drum is connected to the output end of the second-level economizer, the input end of the evaporator, the output end of the evaporator, and the input end of the superheater to realize the storage and separation of steam and water.

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