Flue gas treatment system and flue gas treatment process

Abstract

The invention discloses a flue gas treatment system and a flue gas treatment process, and relates to the field of flue gas treatment.The flue gas treatment system comprises (a) a cooling and washing device (2) used for cooling and washing flue gas so as to dehumidify the flue gas, and (b) a flue gas treatment device (3) used for cooling and washing the flue gas, (b) the deoxidizing device (3) is used for deoxidizing the flue gas from the cooling and washing device (2); (c) a catalytic combustion subsystem (4) for combusting carbon monoxide in the flue gas from the deoxidizing device (3); and (d) a waste heat recovery subsystem (5) for recovering the heat of the flue gas from the catalytic combustion subsystem (4). According to the system, the heat of the flue gas can be fully recovered while the emission of pollution gas is reduced, and the comprehensive utilization of the chlorinated flue gas is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flue gas treatment, in particular to a flue gas pollution emission reduction and waste heat recovery system and a pollution emission reduction and waste heat recovery process. BACKGROUND

[0002] The flue gas generated in the existing titanium tetrachloride production process still contains a low concentration of carbon monoxide after treatment, causing air pollution. Due to the presence of a large amount of N2 and CO2 in the flue gas and the low concentration of carbon monoxide, the chlorination flue gas containing carbon monoxide has a very low heat value, is difficult to ignite, and has poor combustion performance. In the prior art, the chlorination flue gas is discharged after simple treatment (such as water washing and condensation, gas-liquid separation), which not only pollutes the atmosphere, but also cannot effectively recover and utilize the heat of the chlorination flue gas.

[0003] Therefore, it is necessary to develop a flue gas pollution emission reduction and waste heat recovery system and process to effectively utilize heat energy and reduce pollution emissions. SUMMARY

[0004] An object of the present application is to provide a flue gas treatment system that can effectively reduce pollution emissions and fully recover waste heat to achieve comprehensive utilization of the heat energy of flue gas, especially chlorination flue gas.

[0005] Another object of the present application is to provide a flue gas treatment process that can effectively recover waste heat using the flue gas pollution emission reduction and waste heat recovery system of the present application.

[0006] Thus, the present application provides a flue gas treatment system, characterized in that the flue gas treatment system comprises, in series, (a) a temperature reduction and washing device for temperature reduction and washing treatment of flue gas; (b) an oxygen removal device for oxygen removal treatment of flue gas from the temperature reduction and washing device; (c) a catalytic combustion subsystem for combustion of carbon monoxide in flue gas from the oxygen removal device; and (d) a waste heat recovery subsystem for recovery of waste heat from flue gas from the catalytic combustion subsystem.

[0007] According to an exemplary embodiment of the present application, the flue gas treatment system comprises a system main path and (e) a system bypass. The system main path comprises the temperature reduction and washing device, the oxygen removal device, the catalytic combustion subsystem, and the waste heat recovery subsystem; the system bypass is in communication with a chimney, and the system bypass is parallel to the system main path, and a system bypass electric valve for opening and closing the system bypass is arranged on the system bypass.

[0008] According to an exemplary embodiment of the present application, the flue gas treatment system further comprises (f) a one-way explosion-proof valve arranged on a flue gas outlet pipeline of the temperature reduction and washing device, for avoiding explosion caused by backfire from the catalytic combustion subsystem.

[0009] According to an exemplary embodiment of the present application, the flue gas treatment system further comprises: (g) a flue gas preheater located downstream of the cooling scrubbing device and upstream of the oxygen removal device and in communication therewith, for preheating the flue gas from the cooling scrubbing device before being sent to the oxygen removal device.

[0010] According to an exemplary embodiment of the present application, the flue gas treatment system further comprises a pre-treatment subsystem and the pre-treatment subsystem comprises, in sequence: a first gas-liquid separator for gas-liquid separation of the flue gas; a water spraying device located downstream of the first gas-liquid separator and for water spraying treatment of the flue gas, for generating hydrochloric acid from chlorine in the flue gas; an alkali spraying device located downstream of the water spraying device and for alkali spraying treatment of the flue gas, for neutralizing the hydrochloric acid and removing sulfides in the flue gas; and a second gas-liquid separator located downstream of the alkali spraying device and for re-gas-liquid separation of the flue gas.

[0011] According to an exemplary embodiment of the present application, a booster fan is provided upstream of the cooling scrubbing device or downstream of the main path of the system, for increasing the pressure of the flue gas sent to the cooling scrubbing device to form a rotational cutting flow in the cooling scrubbing device, and a main path electric valve is provided on the main path of the system and upstream of the booster fan, which is linked with the system bypass electric valve to open the system bypass when the main path of the system is closed, or to close the system bypass when the main path of the system is opened.

[0012] According to an exemplary embodiment of the present application, the cooling scrubbing device comprises a cyclone, and the cyclone comprises static vanes.

[0013] According to an exemplary embodiment of the present application, the cooling scrubbing device comprises: a cooling scrubbing device body for cooling scrubbing of the flue gas inside the cooling scrubbing device body for dehumidification, dust removal and / or fire retardation; a heat exchanger in communication with the cooling scrubbing device body through an inlet water pipe and an outlet water pipe, for circulating water from the cooling scrubbing device body into the heat exchanger through the inlet water pipe, and then circulating the water into the cooling scrubbing device body through the outlet water pipe after heat exchange cooling in the heat exchanger; and a refrigerated brine system in communication with the heat exchanger through an outlet brine pipe and an inlet brine pipe, for circulating refrigerated brine from the refrigerated brine system into the heat exchanger through the outlet brine pipe, and then circulating the refrigerated brine into the refrigerated brine system through the inlet brine pipe after heat exchange in the heat exchanger, and the refrigerated brine system uses the refrigerated brine to cool the water from the cooling scrubbing device body in the heat exchanger.

[0014] According to an exemplary embodiment of the present application, the flue gas treatment system further comprises a flow detection instrument, and the cooling scrubbing device comprises: a cooling scrubbing device body for cooling and scrubbing flue gas inside the cooling scrubbing device body to remove moisture, dust and / or fire; a heat exchanger in communication with the cooling scrubbing device body through an inlet water pipe, an outlet water pipe and corresponding electromagnetic valves, when the flue gas flow to be treated is higher than a threshold value, the electromagnetic valve on the heat exchanger is opened and the electromagnetic valve on the natural heat dissipation storage tank is closed, water from the cooling scrubbing device body and entering the heat exchanger through the inlet water pipe is cooled by heat exchange with chilled brine and then circulated into the cooling scrubbing device body through the outlet water pipe; a chilled brine system in communication with the heat exchanger through an outlet brine pipe and an inlet brine pipe, chilled brine from the chilled brine system enters the heat exchanger through the outlet brine pipe for heat exchange and then is circulated into the chilled brine system through the inlet brine pipe, the chilled brine system uses the chilled brine to cool the water from the cooling scrubbing device body in the heat exchanger; and a natural heat dissipation storage tank in communication with the cooling scrubbing device body through an inlet water pipe, an outlet water pipe and corresponding electromagnetic valves, when the flue gas flow to be treated is lower than the threshold value or the chilled brine system is abnormal, the electromagnetic valve on the heat exchanger is closed and the electromagnetic valve on the natural heat dissipation storage tank is opened, water medium from the bottom of the cooling scrubbing device body falls into the natural heat dissipation storage tank, is cooled by natural heat dissipation and then is pumped into the cooling scrubbing device body.

[0015] According to an exemplary embodiment of the present application, the oxygen removal device is an adsorption oxygen removal device using porous adsorption material to remove oxygen or a catalytic oxygen removal device using catalyst to catalyze oxidation reaction to remove oxygen.

[0016] According to an exemplary embodiment of the present application, the oxygen removal device is a catalytic oxygen removal device capable of making carbon monoxide perform oxidation reaction at a temperature of 150-300 degrees Celsius.

[0017] According to an exemplary embodiment of the present application, the catalytic oxygen removal device uses catalyst with honeycomb-shaped ceramic as carrier and platinum metal as active component.

[0018] According to an exemplary embodiment of the present application, the honeycomb-shaped ceramic is cordierite.

[0019] According to an exemplary embodiment of the present application, the amount of platinum metal is controlled so that carbon monoxide can perform oxidation reaction at a temperature of 150-300 degrees Celsius and the oxygen content in flue gas is reduced to below 1% vol.

[0020] According to an exemplary embodiment of the present application, the porous adsorption material is tetracyanoquinodimethane, and the porous adsorption material is replaced after saturation or periodically replaced.

[0021] According to an exemplary embodiment of the present application, the catalytic combustion sub-system comprises: a catalytic combustion barrel for burning carbon monoxide in the flue gas from the oxygen removal device to generate carbon dioxide and release heat from the flue gas, the catalytic combustion barrel further comprises a catalytic combustion barrel body, a heat storage body and an active component, the flue gas from the oxygen removal device enters the inside of the catalytic combustion barrel body through a flue gas inlet, and after combustion, the flue gas enters the waste heat recovery sub-system through a flue gas outlet, the heat storage body is used to store heat to maintain the temperature within a suitable combustion reaction temperature range, and the active component is arranged inside the catalytic combustion barrel body to catalyze the combustion reaction between carbon monoxide and oxygen in the flue gas from the oxygen removal device; an air supply pipeline that introduces air into the inside of the catalytic combustion barrel through an air inlet of the catalytic combustion barrel to provide oxygen for the combustion reaction; and a natural gas supply pipeline that introduces natural gas into the inside of the catalytic combustion barrel body through a natural gas inlet of the catalytic combustion barrel body.

[0022] According to an exemplary embodiment of the present application, the heat storage body is a honeycomb-shaped ceramic that maintains the temperature above 600 degrees Celsius by storing heat.

[0023] According to an exemplary embodiment of the present application, an electromagnetic valve is arranged on the natural gas supply pipeline, a gas detector is arranged between the oxygen removal device and the catalytic combustion sub-system, an ignition device and a camera / observation window are arranged in the catalytic combustion sub-system, the natural gas supplied by the natural gas supply pipeline, the oxygen supplied by the air supply pipeline and the flue gas from the oxygen removal device are initially ignited by the ignition device, and after the initial ignition, the electromagnetic valve on the natural gas supply pipeline is closed; when the gas detector detects that the concentration of carbon monoxide is lower than 10%vol or the red light or flame can no longer be seen through the camera / observation window, the electromagnetic valve on the natural gas supply pipeline is reopened, the supplemental natural gas is input again, and the re-ignition is performed by the ignition device.

[0024] According to an exemplary embodiment of the present application, the active component for catalytic combustion is loaded on the heat storage body, and the active component is a noble metal or a transition metal oxide.

[0025] According to an exemplary embodiment of the present application, the active component for catalytic combustion is platinum.

[0026] According to an exemplary embodiment of the present application, the amount of the active component for catalytic combustion is controlled so that the carbon monoxide in the flue gas can still fully combust with oxygen within a temperature range of 600 to 800 degrees Celsius when the concentration of the carbon monoxide is as low as 14%vol.

[0027] According to an exemplary embodiment of the present application, the waste heat recovery subsystem comprises: a waste heat boiler and a steam drum in communication with the interior of the waste heat boiler, wherein the steam drum is capable of receiving feed water and discharging steam, the feed water in the steam drum is circulated to the interior of the waste heat boiler to exchange heat with flue gas from the catalytic combustion subsystem, and the steam drum discharges steam; an air preheater downstream of the waste heat boiler, for preheating air using heat from the flue gas from the waste heat recovery subsystem and feeding the preheated air into the catalytic combustion subsystem; a feed water preheater downstream of the waste heat boiler, for preheating demineralized water using heat from the flue gas from the waste heat recovery subsystem and feeding the preheated demineralized water into the waste heat recovery subsystem; and a flue gas circulation branch provided between the waste heat boiler and the flue gas preheater, for feeding a portion of the flue gas from the waste heat boiler into the flue gas preheater and circulating to the waste heat boiler, and preheating flue gas from upstream in the flue gas preheater using heat from the portion of the flue gas. The air preheater and the feed water preheater are provided in series or in parallel.

[0028] According to an exemplary embodiment of the present application, the waste heat recovery subsystem comprises the flue gas circulation branch, the air preheater and the feed water preheater provided in series.

[0029] According to an exemplary embodiment of the present application, the flue gas treatment system further comprises a dust collector and a booster fan, and the chlorinated flue gas from the feed water preheater is fed into the dust collector after passing through the booster fan and then discharged into a chimney after passing through the dust collector.

[0030] According to an exemplary embodiment of the present application, the flue gas treatment system further comprises a control module, which can automatically control the opening and closing of each electromagnetic valve / electrically operated valve according to the detection results of various detectors, and / or the control module can control the opening and closing of each electromagnetic valve / electrically operated valve in response to the instructions / button actions input by a user / operator.

[0031] According to an exemplary embodiment of the present application, a flue gas treatment process is provided, comprising the steps of using the flue gas treatment system as described above to reduce pollution and recover waste heat from flue gas.

[0032] According to an exemplary embodiment of the present application, the flue gas from the feed water preheater is fed into a dust collector after passing through the dust collector and then discharged into a chimney, and a flue gas detection device is installed at the chimney discharge port to monitor the treatment effect of the system.

[0033] The present application also provides a flue gas treatment process, comprising the steps of using the flue gas treatment system of the present application as described above to treat flue gas.

[0034] According to certain embodiments, the flue gas treatment process according to the exemplary embodiments of the present application is used for treating chlorinated flue gas, which comprises the following steps in sequence: (1) pre-treating the flue gas from the titanium tetrachloride production process to remove most of the chlorine and titanium tetrachloride; (2) cooling and washing treatment of the chlorinated flue gas; (3) oxygen removal treatment of the chlorinated flue gas; (4) catalytic combustion treatment of the chlorinated flue gas; and (5) waste heat recovery step.

[0035] The pre-treatment of the aforementioned step (1) can comprise the following sub-steps in sequence: condensation cooling with chilled water to precipitate titanium tetrachloride droplets; first gas-liquid separation to separate out the titanium tetrachloride droplets and solid impurities; spraying with water to make the chlorine in the flue gas generate hydrochloric acid; spraying with alkali to neutralize the hydrochloric acid to remove hydrochloric acid droplets and sulfides; second gas-liquid separation to further condense the droplets from the spraying device and collect again.

[0036] In order to ensure the safety of the titanium tetrachloride production system, and at the same time to facilitate emergency disposal, a system bypass as described above can be provided on the pipeline between step (1) and step (2).

[0037] The chlorinated flue gas from step (1) is passed through a pressure detection instrument and a booster fan to enter the cooling and washing device (as described above) of step (2) for heat exchange cooling (condensation and dehumidification) to reduce the moisture content of the flue gas.

[0038] In order to further ensure safety, especially the safety of the main titanium tetrachloride production system, a one-way explosion-proof valve can be provided on the pipeline between step (2) and step (3).

[0039] The chlorinated flue gas from step (2) can be preheated with a flue gas preheater (as described above) before entering step (3). For example, the waste heat of the chlorinated flue gas from step (5) can be used to preheat the chlorinated flue gas from step (2), the preheated flue gas enters step (3), and the chlorinated flue gas whose temperature is reduced by the flue gas preheater can be circulated to step (5) or discharged into the chimney.

[0040] The oxygen removal of step (3) can be adsorption oxygen removal or catalytic oxygen removal as described above.

[0041] The catalytic combustion of step (4) is carried out in a catalytic combustion subsystem as described above.

[0042] The chlorinated flue gas from step (4) enters step (5) for waste heat recovery. Step (5) is carried out in a waste heat recovery subsystem as described above.

[0043] A small part of the chlorinated flue gas from the waste heat boiler in step (5) can be used as a circulating medium to preheat the flue gas before entering step (3) in a flue gas preheater (a gas phase heat exchanger can be used) and circulate into the waste heat boiler, and the remaining majority can preheat the fresh air entering the catalytic combustion barrel in step (4) in an air preheater (a gas phase heat exchanger can be used) and the desalted water entering the waste heat boiler as boiler makeup water in a feed water preheater. For the waste heat boiler with a steam drum, the preheated boiler makeup water is fed into the steam drum, and the steam generated by the steam drum is delivered outward for power generation. The cooled flue gas is discharged through a chimney, and a flue gas detection device can be installed at the chimney outlet to monitor the treatment effect of the system.

[0044] The present application can achieve the following beneficial effects: The flue gas treatment system and the flue gas treatment process of the present application can effectively reduce pollution emissions and safely and fully recover the waste heat of the chlorinated flue gas, realizing safe and efficient comprehensive utilization of the chlorinated flue gas. The heat generated by the catalytic combustion sub-system is recovered and utilized by the waste heat recovery sub-system, most of which is used to generate steam and deliver the steam outward through the steam drum, thereby achieving the purpose of waste heat recovery and utilization, and the remaining heat is further recovered and utilized through the flue gas preheater, the air preheater and the feed water preheater, thereby greatly improving the comprehensive utilization rate. At the same time, by burning low-calorific-value carbon monoxide, the concentration of low-concentration carbon monoxide is reduced again, thereby greatly reducing air pollution. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a schematic diagram of the connection relationship of each part in the overall structure of the flue gas treatment system according to an embodiment of the present application; Figure 2 is a schematic diagram of the flue gas treatment process flow according to an embodiment of the present application; Figure 3 is a more specific schematic diagram of the chlorinated flue gas treatment process according to an embodiment of the present application; Figure 4 is a schematic diagram of the overall structure of the cooling and washing device used in embodiment 4 of the present application; Figure 5 is a schematic diagram of the internal structure of the cooling and washing device body used in embodiment 4 of the present application; Figure 6 is a more specific schematic diagram of the internal structure of the cooling and washing device body used in embodiment 4 of the present application; Figure 7 is a schematic diagram of the structure of the cyclone of the cooling and washing device used in embodiment 4 of the present application; Figure 8 is a schematic diagram of the cross-sectional structure of the gas equalizing chamber of the cooling and washing device used in embodiment 4 of the present application. DETAILED DESCRIPTION

[0046] Unless otherwise specified, the "content" of a gas in the present application refers to the volume percentage content.

[0047] The present application will be described in more detail below.

[0048] As previously mentioned and with reference to Figure 1 The present application provides a flue gas treatment system, which comprises in series: (a) a temperature reduction and washing device 2 for reducing the temperature, removing dust and removing moisture from the flue gas; (b) an oxygen removal device 3 for removing oxygen from the flue gas from the temperature reduction and washing device; (c) a catalytic combustion sub-system 4 for burning carbon monoxide in the flue gas from the oxygen removal device; and (d) a waste heat recovery sub-system 5 for recovering heat from the high-temperature flue gas from the catalytic combustion sub-system.

[0049] The components of the present application will be described in further detail below. According to another embodiment of the present application, the present application can further comprise a pre-treatment sub-system 1.

[0050] Pre-treatment sub-system The present application does not have any particular limitation on the pre-treatment sub-system, and any device capable of pre-treating flue gas, especially chlorinated flue gas, can be used in the flue gas treatment system of the present application. Those conventional devices that treat chlorinated flue gas before discharging can be used as the pre-treatment sub-system of the flue gas treatment system of the present application.

[0051] As Figure 2 shown, the pre-treatment sub-system can comprise in series: a first gas-liquid separator 101 for gas-liquid separation of the flue gas; a spraying device 102 downstream of the gas-liquid separator and for spraying treatment of the flue gas; and a second gas-liquid separator 103 downstream of the spraying device and for re-gas-liquid separation of the flue gas. Further, according to yet another embodiment of the present application, as Figure 3As shown, the spraying device 102 comprises water spraying device 1021 and alkali spraying device 1022 connected in series. Both the water spraying device 1021 and the alkali spraying device 1022 are preferably composed of multiple stages of spraying devices connected in series. The chlorination flue gas is subjected to water spraying to obtain by-product hydrochloric acid (chlorine reacts with water to obtain hydrochloric acid) and alkali spraying (for example, spraying with sodium hydroxide solution) to remove hydrochloric acid droplets and sulfides. Further, a water washing condensing device is provided upstream of the first gas-liquid separator 101, which uses chilled water to wash and condense the chlorination flue gas to precipitate titanium tetrachloride droplets. The first gas-liquid separator 101 separates the titanium tetrachloride droplets in the chlorination flue gas, and the remaining chlorination flue gas mainly comprises chlorine, carbon monoxide, oxygen, nitrogen and a small amount of titanium tetrachloride, and the temperature of the chlorination flue gas is also significantly reduced (for example, to about minus ten degrees). The second gas-liquid separator 103 can further condense and collect the droplets from the spraying device.

[0052] It should be understood that the chlorination flue gas from the titanium tetrachloride production process can also be directly introduced into the cooling and washing device for cooling and washing treatment without the pretreatment subsystem in some cases (for example, when the impurity content is low). However, preferably, the flue gas treatment system of the present application comprises a pretreatment subsystem.

[0053] System main path and system bypass According to an embodiment of the present application, the flue gas treatment system comprises a system main path and a system bypass. The system main path comprises a cooling and washing device (2), an oxygen removal device (3), a catalytic combustion subsystem (4) and a waste heat recovery subsystem (5). The system bypass is connected between the induced draft fan 104 and the main path electric valve 105, and is connected to the chimney. An induced draft fan 104, a main path electric valve 105, a pressure detection instrument (not shown in the figure) and a booster fan 107 are connected in series between the flue gas pipeline between the pretreatment subsystem and the cooling and washing device. The pressure detection instrument is used to detect the flue gas pressure in the main path. The booster fan 107 is used to increase the flue gas pressure to form a high-speed airflow in the cyclone when passing through the inside of the cooling and washing device. The system bypass electric valve 106 is used to open and close the system bypass to directly discharge the flue gas from the chimney when the main path components of the flue gas treatment system need to be repaired, replaced or maintained, or in case of emergency. The main path electric valve and the system bypass electric valve are linked to cut off the main path when the system bypass is started.

[0054] The system bypass is not necessary for the flue gas treatment system of the present application. However, in order to ensure the safety of the titanium tetrachloride main production system, and to facilitate emergency disposal, the flue gas treatment system of the present application preferably comprises a system bypass, which is preferably located downstream of the pretreatment subsystem and parallel to the system main line. An electric valve can be provided in the system bypass, which can be opened to shut off the process and let the chlorination flue gas not enter the subsequent process, but be directly discharged from the chimney when needed (for example, in an emergency).

[0055] Cooling and washing device The cooling and washing device of the present application is not particularly limited, and any device capable of cooling and washing chlorination flue gas can be used in the flue gas treatment system of the present application. The cooling and washing device with fireproof function is preferred. For example, the cooling and washing device can comprise a cooling and washing device and a fireproof device respectively, or a cooling and washing device with cooling and fireproof functions can be used, such as a cooling and washing device with a cyclone with static blades inside to form a cyclone water seal to achieve the fireproof function.

[0056] According to some embodiments, with reference to Figures 1-4 The cooling and washing device 2 is provided with a heat exchanger 2015 communicating with the cooling and washing device body 201 thereof, for heat exchange between the water medium from the bottom of the cooling and washing device body and the chilled brine from the chilled brine system 2016 to achieve cooling (for example, from 40 degrees Celsius to about 20 degrees Celsius, and correspondingly the chilled brine can be raised from 0 degrees Celsius to about 20 degrees Celsius), and then circulate into the cooling and washing device body 201. In this case, the heat exchanger 2015 is used as a liquid storage mechanism, for example, the heat exchanger 2015 can be multiple, for example, two. According to the embodiment of the present application, the cooling and washing device can directly use the circulating chilled brine for washing, and the chilled brine is drawn from the heat exchanger 2015 into the cooling and washing device body 201 and then circulates into the heat exchanger 2015.

[0057] According to another embodiment of the present application, the cooling and washing device can also use the original flue gas (about minus 10 degrees Celsius to 0 degrees Celsius) from the titanium tetrachloride production process to cool the circulating water (for example, about 40 degrees Celsius) from the bottom of the cooling and washing device body 201 by setting a cooling tower (not shown in the figure). The heat-exchanged original chlorination flue gas then enters the cooling and washing device 2 through the pretreatment subsystem 1 (including the water spraying device 1021 and the alkali spraying device 1022). The outlet temperature of the heat-exchanged original chlorination flue gas and the temperature of the circulating water medium can be controlled at the same lower temperature, for example, both are 20 degrees Celsius.

[0058] According to another exemplary embodiment of the present application, a natural heat dissipation tank can be used instead of one of the two heat exchangers 2015, and the refrigerated brine system 2016 is connected to the heat exchanger but not to the natural heat dissipation tank. A flow detection instrument (not shown in the figure) is also arranged in the chlorination flue gas pipeline. When the flow of titanium tetrachloride flue gas to be treated is the normal flow (about 6000 cubic meters / hour), the electromagnetic valves (2018, 2019) on the heat exchanger are opened and the electromagnetic valves (2018, 2019) on the natural heat dissipation tank are closed, and the water medium from the bottom of the cooling scrubbing device body falls into the heat exchanger, is cooled by the refrigerated brine, and is then pumped into the warm scrubbing device body 201. When the flow of titanium tetrachloride flue gas to be treated is less than 30% of the normal flow, or when the refrigerated brine system is abnormal (the refrigerated brine from the main production system of titanium tetrachloride is not enough, the refrigerated brine system is faulty, etc.), the electromagnetic valves (2018, 2019) on the heat exchanger are closed and the electromagnetic valves (2018, 2019) on the natural heat dissipation tank are opened, and the water medium from the bottom of the cooling scrubbing device body falls into the natural heat dissipation tank, is cooled by natural heat dissipation, and is then pumped into the cooling scrubbing device body 201.

[0059] Deoxidizing device According to certain embodiments, with reference to Figures 1-3 , the deoxidizing device 3 is an adsorption deoxidizing device using a porous adsorption material (for example, tetracyanoquinodimethane) to adsorb oxygen and / or a catalytic deoxidizing device using a catalyst to catalyze the oxidation reaction, preferably a catalytic deoxidizing device. The adsorption deoxidizing device needs to be replaced regularly, for example, once every three months. Preferably, the deoxidizing device is a catalytic deoxidizing device capable of catalytic deoxidization at a low temperature of 150-300 degrees Celsius, at which the carbon monoxide in the flue gas reacts with the oxygen in the flue gas. More preferably, the catalyst used by the catalytic deoxidizing device is a catalyst using honeycomb-shaped ceramic (preferably cordierite) as a carrier and a noble metal as an active component, and platinum metal is particularly preferred as the active component. Further, the amount of platinum metal is controlled so that the carbon monoxide can react at a low temperature of 150-300 degrees Celsius and the oxygen content in the flue gas is reduced to 1% vol or less. This ingenious design of the present application can prevent the downstream tempering from igniting the upstream, thereby avoiding a tragic explosion accident.

[0060] One-way explosion-proof valve See Figure 3The one-way explosion-proof valve 8 is not necessary for the flue gas treatment system of the present application. However, in order to further ensure safety, especially the safety of the titanium tetrachloride main production system, the flue gas treatment system of the present application preferably comprises a one-way explosion-proof valve, which is preferably arranged downstream of the cooling scrubbing device 2, more specifically between the cooling scrubbing device 2 and the oxygen removal device 3, and between the cooling scrubbing device 2 and the flue gas preheater 7 when the flue gas preheater is arranged. The one-way explosion-proof valve can be used to prevent the cooling scrubbing device and the system upstream thereof from exploding due to backfire, so that the process can be reliably shut down in case of accidental explosion, avoiding the impact of the accident on the operation of the titanium tetrachloride main production system.

[0061] Flue gas preheater Referring to Figure 3 The flue gas preheater 7 is not necessary for the flue gas treatment system of the present application. However, in order to bring the chlorinated flue gas entering the oxygen removal device to a suitable temperature, the flue gas treatment system of the present application preferably further comprises a flue gas preheater arranged downstream of the cooling scrubbing device 2 and upstream of the oxygen removal device 3 and in communication therewith. When the one-way explosion-proof valve 8 is arranged, the flue gas preheater 7 is arranged between the one-way explosion-proof valve 8 and the oxygen removal device 3.

[0062] The flue gas preheater 7 can use various suitable means to preheat the chlorinated flue gas. However, it is preferable to use the waste heat of the chlorinated flue gas from the waste heat recovery subsystem 5 to preheat the chlorinated flue gas. For example, most of the chlorinated flue gas from the waste heat boiler of the waste heat recovery subsystem 5 enters the downstream device, but a small part of the flue gas can be circulated (e.g. by a high-temperature fan) into the flue gas preheater 7 to further utilize the waste heat of the chlorinated flue gas. This part of the recycled flue gas can be directly discharged into the chimney after exiting the flue gas preheater, but is preferably recycled to the waste heat boiler. More specifically, the chlorinated flue gas from the cooling scrubbing device has a relatively low temperature (e.g. generally about 20°C), and preheating the flue gas from the cooling scrubbing device using the heat of a part of the flue gas from the waste heat recovery subsystem involved in internal circulation can provide heat in advance to the subsequent processes (e.g. oxygen removal, catalytic combustion, etc.), thereby further improving the oxygen removal efficiency.

[0063] Oxygen removal device Referring to Figures 1-3 The oxygen removal device 3 of the present application is not particularly limited, and any device capable of removing oxygen from chlorinated flue gas can be used in the flue gas treatment system of the present application, such as adsorption oxygen removal devices and catalytic oxygen removal devices, preferably low-temperature (i.e. below the normal reaction temperature, e.g. 150 to 300°C) catalytic oxygen removal devices.

[0064] The oxygen-removing device directly uses some porous adsorbing material to adsorb oxygen, and the distance between the oxygen-removing device and the catalytic combustion sub-system is set to be long, so that the oxygen concentration near the fire source is extremely low and it is impossible to transmit back to the fire to cause explosion, thus ensuring the safety of the upstream. For example, porous adsorbing material such as tetracyanoquinodimethane (TCNQ) can be used. Since the material only reacts with the electrons of oxygen in the air, only oxygen molecules can be adsorbed into the material through the small pores of the material, so that the oxygen in the air can be easily separated. Of course, other materials that can reduce the oxygen content can also be selected. However, the cost of such an oxygen-removing device is relatively high compared with the catalytic oxygen-removing device.

[0065] The catalytic oxygen-removing device preferably uses honeycomb-shaped ceramic as a carrier (preferably honeycomb-shaped cordierite), and then coats a noble metal (preferably platinum) as an active component catalyst. The amount of noble metal is controlled to enable the oxidation reaction of carbon monoxide and oxygen at a lower temperature (for example, one hundred to three hundred degrees Celsius) that is lower than the ignition point of carbon monoxide (about 650 degrees Celsius under normal pressure and normal concentration of carbon monoxide), so as to consume oxygen. Since there is no combustion, backfire explosion will not occur. In order to improve the oxygen-removing efficiency, it is required that the gas can be in full contact with the catalyst, and the contact area is increased.

[0066] The oxygen-removing device 3 can operate at a low temperature. Even if the catalytic combustion sub-system 4 mentioned below accidentally has a flame when burning, since the oxygen-removing device 3 reduces the oxygen concentration to a very low level (for example, below 1% VOL), the flame does not have the condition to transmit back, and can block backfire to avoid explosion. The low-temperature catalyst suitable for the oxygen-removing device is, for example, those mentioned above.

[0067] Catalytic combustion sub-system Referring to Figure 3 The catalytic combustion sub-system 4 of the present application is not particularly limited, and any device capable of catalytic combustion treatment of chlorinated flue gas can be used in the catalytic combustion sub-system of the present application. When the carbon monoxide content in the chlorinated flue gas is 20% VOL or less, it is usually not ignitable because its heat value is not enough, and the ignition temperature will be very high (at 850 to 950 degrees Celsius). The flue gas needs to be ignited by the catalyst in the catalytic combustion sub-system, and the ignition temperature after catalysis can be controlled at more than 600 degrees Celsius. The catalytic combustion sub-system of the present application can make the carbon monoxide in the flue gas, even if the concentration is very low, fully combust and oxidize with oxygen in the air under the action of the catalyst, and then be discharged after being combined into carbon dioxide.

[0068] According to some embodiments, the catalytic combustion sub-system 4 suitable for the present application includes: A catalytic combustion barrel for burning carbon monoxide in flue gas from the oxygen removal device to produce carbon dioxide to release the heat of the flue gas, the catalytic combustion barrel further comprising a catalytic combustion barrel body, an active component and a heat accumulator, the flue gas from the oxygen removal device enters the catalytic combustion barrel body through a flue gas inlet, burns inside the catalytic combustion barrel body and exits through a flue gas outlet to enter the waste heat recovery subsystem, the active component is arranged inside the catalytic combustion barrel body to catalyze the combustion reaction (preferably flameless combustion) between carbon monoxide in the flue gas and oxygen, the heat accumulator is used to accumulate and maintain heat at a suitable temperature for the combustion reaction (preferably, the heat accumulator is a honeycomb-shaped ceramic which maintains the temperature above 600 degrees Celsius by accumulating heat), an air supply pipeline which introduces fresh air into the catalytic combustion barrel through an air inlet of the catalytic combustion barrel to provide oxygen for the combustion reaction, and a natural gas supply pipeline which introduces natural gas into the catalytic combustion barrel body through a natural gas inlet of the catalytic combustion barrel body for initial ignition or for supplementary combustion in the case that the carbon monoxide content in the flue gas is too low to sustain combustion.

[0069] According to certain embodiments, the active component for catalytic combustion is loaded on the heat accumulator. The active component lowers the activation energy of the reaction, allowing the reaction to proceed rapidly under relatively mild conditions. The active component for catalytic combustion is preferably a noble metal active component, more preferably a platinum active component. The amount of the active component for catalytic combustion is controlled to be within a range that allows carbon monoxide in the flue gas and oxygen in the air to burn (preferably flameless combustion) sufficiently at a temperature ranging from 600 to 800 degrees Celsius.

[0070] According to more specific certain embodiments of the present application, the present application promotes combustion by using a honeycomb-shaped ceramic as a carrier and coating it with a catalyst (i.e. a so-called COC catalyst) capable of catalyzing the oxidation reaction of carbon monoxide to produce carbon dioxide (preferably a platinum active component), for treating carbon monoxide produced by incomplete combustion, at a reaction temperature interval of 600 to 800 degrees Celsius, to improve the efficiency of flue gas combustion. The honeycomb-shaped ceramic carrier of the catalyst itself functions as a heat accumulator. After the flue gas flows through the heat accumulator, a portion of the heat is left in the heat accumulator, allowing the heat accumulator to maintain a high temperature (such as about 600 to 800 degrees Celsius) at all times. Even if the temperature of the flue gas before entering the catalytic combustion barrel is low, it can be ignited after flowing through the high-temperature heat accumulator, allowing the carbon monoxide to burn to produce carbon dioxide.

[0071] The catalysts used in the catalytic combustion sub-system and the catalysts used in the oxygen removal device can use substantially the same material, but the amount of active component used in the oxygen removal device is significantly higher than the amount of active component used in the catalytic combustion sub-system to ensure that the oxidation reaction effect (reducing the oxygen content in the flue gas to below 1% vol, and not a combustion reaction) is achieved in the oxygen removal device at low temperature (for example, about 150-300 degrees Celsius), while the amount of active component used in the catalytic combustion sub-system is correspondingly lower, preferably controlled in the amount range that can catalyze the flameless combustion reaction of low concentration carbon monoxide and oxygen at a temperature range of 600-800 degrees Celsius. In actual operation, although most of the time is flameless combustion, red light can be seen through the observation window or monitoring camera, and even small flames may appear when the temperature is higher than 800 degrees Celsius.

[0072] According to some embodiments, the catalytic combustion sub-system includes a supplemental natural gas inlet for supplementing natural gas. At the moment when the system initially starts to work, the supplemental natural gas inlet is needed to introduce natural gas, and the initial ignition of flue gas and natural gas is carried out by an electric arc high-voltage pack or similar device. The carbon monoxide content in chlorinated flue gas normally fluctuates between 8-20% vol, but is basically around 14-16% vol, at which point additional natural gas for accompanying combustion is not needed, so after the initial ignition, the electromagnetic valve on the supplemental natural gas pipeline can be closed to cut off the supplemental natural gas. However, once the carbon monoxide content in the chlorinated flue gas fluctuates to a low level (such as below 14% vol or even below 10% vol), the combustion may be interrupted due to insufficient heat value, at which point the red light can no longer be seen. In the case of combustion interruption, since carbon monoxide and oxygen are not consumed by combustion, they will accumulate, and when they exceed the critical concentration, the catalytic combustion barrel of the catalytic combustion sub-system will explode, causing a serious safety accident. Therefore, it is necessary to monitor the situation in the catalytic combustion barrel at all times, and after combustion interruption, it is beneficial to maintain combustion by adding a portion of natural gas for accompanying combustion and re-igniting. In addition, in theory, for chlorinated flue gas with a carbon monoxide content of 16% vol or less, supplementing natural gas for accompanying combustion is beneficial to the complete combustion of carbon monoxide. Therefore, it is preferred in the present system to provide a supplemental natural gas inlet in the catalytic combustion sub-system.

[0073] According to some embodiments, the catalytic combustion barrel further contains honeycomb ceramic inside, which can store the residual heat of the last round of combustion. The honeycomb ceramic acts as a heat accumulator, which can maintain a high temperature, so that the combustion can be carried out under the action of the temperature of the heat accumulator which is higher than the inlet temperature of the combustor (i.e. high-temperature heat-accumulating catalytic combustion). In this case, the catalytic combustion barrel is a high-temperature heat-accumulating catalytic combustion barrel with a heat accumulator (honeycomb ceramic), which is more conducive to dealing with the situation where the heat value of the chlorinated flue gas is unstable. Specifically, the carbon monoxide content in the chlorinated flue gas normally fluctuates between 8% and 20% vol. For the case where the carbon monoxide content in the chlorinated flue gas is relatively high (such as 14% vol or more), it can still be basically combusted even without a heat accumulator. However, for the case where the carbon monoxide content in the chlorinated flue gas is relatively low, it is difficult to combust due to the low heat value, and therefore the heat accumulator can be used to warm up the chlorinated flue gas to facilitate its combustion (after adding the heat accumulator and the catalyst mentioned later, the carbon monoxide concentration in the flue gas can still be combusted in the range of 12% vol-14% vol, or even 10% vol or more).

[0074] In addition, since the normal fluctuation range of the carbon monoxide content in the chlorinated flue gas is about 8% vol to 20% vol, and the heat value is not enough when the carbon monoxide content in the flue gas is 14% vol or less, the ignition temperature is very high (about 850 to 950 degrees Celsius). Therefore, a catalyst needs to be used to reduce the ignition temperature to ignite the flue gas. For example, the ignition temperature of the flue gas with low-concentration carbon monoxide can be controlled to about 600 to 800 degrees Celsius under the action of the catalyst. The particularly suitable catalyst is as described above.

[0075] The high-temperature heat-accumulating catalytic combustion barrel can be arranged next to the waste heat boiler, so that the flue gas is directly introduced into the waste heat boiler.

[0076] Waste heat recovery subsystem The present application does not have special restrictions on the waste heat recovery subsystem 5.

[0077] According to some embodiments, referring to Figures 1-3 The waste heat recovery subsystem 5 suitable for the flue gas treatment system of the present application includes a waste heat boiler 501. When the flue gas treatment system of the present application uses a flue gas preheater, most of the chlorinated flue gas from the waste heat boiler 501 enters the downstream device, and a small part is circulated into the flue gas preheater to further utilize the waste heat of the chlorinated flue gas. Further, the waste heat recovery subsystem further includes a steam drum in communication with the waste heat boiler, and steam is delivered outward from the steam drum, thereby achieving the recycling of heat energy. The catalytic combustion barrel is arranged next to the waste heat boiler 501 and introduces the flue gas into the waste heat boiler 501 through a plurality of flue gas outlet pipes, so that the flue gas is introduced into the waste heat boiler 501 as soon as possible.

[0078] If the chlorination flue gas still has a high temperature after being treated by the waste heat recovery subsystem, in order to further recover and utilize the waste heat of the chlorination flue gas, an air preheater 404 and / or a feed water preheater 503 can be arranged downstream of the waste heat recovery subsystem. The air preheater 404 can utilize the heat of the flue gas from the waste heat recovery subsystem 5 to preheat air and pass the preheated air into the catalytic combustion subsystem 4. The feed water preheater 503 can utilize the heat of the flue gas from the waste heat recovery subsystem to preheat desalted water and pass the preheated desalted water into the waste heat recovery subsystem 5, for example, into the steam drum 502 which is in communication with the waste heat boiler 501.

[0079] Further, the system simultaneously comprises the air preheater 404 and the feed water preheater 503. Still further, the feed water preheater 503 is arranged downstream of the air preheater 404. When the waste heat recovery subsystem applicable to the present application comprises a waste heat boiler 501 and a steam drum 502 which is in communication with the waste heat boiler, the desalted water from the feed water preheater is passed into the steam drum, and the steam drum converts the desalted water into steam which is delivered outwards. The high-temperature flue gas after combustion in the catalytic combustion barrel is discharged into the waste heat boiler through a plurality of flue gas outlet pipes, for example, two flue gas outlet pipes. The waste heat boiler has a plurality of serpentine heat exchange pipes therein, and the heat exchange pipes are filled with water which flows down from the steam drum. The heat exchange pipes are heated by the high-temperature flue gas, thereby converting the desalted water into water vapor which evaporates into the steam drum 502 and is delivered outwards through an upper pipeline to generate power or do work. The delivery of the steam reduces the water amount in the steam drum, and the desalted water from the pipeline of the feed water preheater continues to supplement the water in the steam drum.

[0080] Generally, the flue gas from the waste heat recovery subsystem (such as the waste heat boiler) still has a temperature of more than 200 degrees Celsius. After the outdoor air is heated by the air preheater 404, the temperature of the flue gas continues to decrease, for example, to about 150 degrees Celsius, and then the flue gas enters the feed water preheater 503 to heat the desalted water (for example, to about 40 to 70 degrees Celsius) using the residual heat of the flue gas, and then the heated desalted water is sent to the steam drum 502 through a pipeline to supplement the hot water.

[0081] The flue gas from the feed water preheater 503 is passed into a dust collector 504 after being dedusted and is discharged into a chimney. A flue gas detection device is arranged at the discharge opening of the chimney to ensure that the flue gas meets the relevant emission standards and to monitor the treatment effect of the system.

[0082] The present application also provides a flue gas treatment process, which comprises the step of treating flue gas, especially chlorination flue gas, by using the flue gas treatment system of the present application.

[0083] According to certain embodiments, the flue gas treatment process of the present application for treating chlorinated flue gas can comprise the following steps in sequence: (1) pre-treating the flue gas from the titanium tetrachloride production process to remove most of the titanium tetrachloride; (2) cooling and washing the chlorinated flue gas; (3) removing oxygen from the chlorinated flue gas; (4) catalytically combusting the chlorinated flue gas; and (5) recovering waste heat.

[0084] The pre-treatment of step (1) can comprise the following sub-steps in sequence: condensing and cooling with chilled water to precipitate titanium tetrachloride droplets; first gas-liquid separation to separate out the droplets and solid impurities; spraying water to generate hydrochloric acid from chlorine in the flue gas; spraying alkali to neutralize the hydrochloric acid and remove hydrochloric acid droplets and sulfides; and second gas-liquid separation to further condense and collect the droplets from the spraying device.

[0085] To ensure the safety of the titanium tetrachloride production system and to facilitate emergency disposal, a system bypass as described above can be provided between the corresponding pipeline of step (1) and the corresponding pipeline of step (2).

[0086] The chlorinated flue gas from step (1) is passed through a pressure detection instrument and a booster fan 107 into the cooling and washing device 2 (as described above) of step (2) for heat exchange and cooling (condensation and dehumidification) to reduce the moisture content of the flue gas.

[0087] To further ensure safety, especially the safety of the main titanium tetrachloride production system, a one-way explosion-proof valve 8 (as described above) can be provided between the corresponding pipeline of step (2) and the corresponding pipeline of step (3).

[0088] The chlorinated flue gas from step (2) can be preheated with a flue gas preheater 7 (as described above) before entering step (3). For example, the waste heat of the chlorinated flue gas from step (5) can be used to preheat the chlorinated flue gas from step (2), and the preheated flue gas enters step (3), while the chlorinated flue gas whose temperature is reduced by the flue gas preheater 7 can be recycled to step (5) or discharged into a chimney.

[0089] The oxygen removal of step (3) can be adsorption oxygen removal or catalytic oxygen removal as described above.

[0090] The catalytic combustion of step (4) is carried out in a catalytic combustion subsystem as described above.

[0091] The chlorinated flue gas from step (4) enters step (5) for waste heat recovery. Step (5) is carried out in a waste heat recovery subsystem as described above.

[0092] A small portion of the chlorinated flue gas from the waste heat boiler in step (5) can be used as a circulating medium to preheat the flue gas before entering step (3) in a flue gas preheater 7 (a gas phase heat exchanger can be used) and circulate into the waste heat boiler, and the rest can be used to preheat the fresh air into the catalytic combustion barrel in step (4) in an air preheater 404 (a gas phase heat exchanger can be used) and the desalinated water into the waste heat boiler as boiler makeup water in a feed water preheater. For the waste heat boiler with a steam drum, the preheated boiler makeup water is fed into the steam drum 502, and the steam drum delivers the generated steam outward. The cooled flue gas is discharged through a chimney, and a flue gas detection device can be installed at the chimney outlet to monitor the treatment effect of the system.

[0093] It should be understood that the orientation words such as "upper", "lower", "front", "back", etc. and the shape words such as "rod", "box" and "sheet" used herein are only for the convenience of explaining the application in conjunction with the drawings, and do not constitute or be used to limit the application. All directional indications in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between the components in a certain posture, and if the posture changes, the directional indications also change accordingly. In the present application, unless otherwise explicitly specified and limited, the terms "communication", "connection", "fixation" and the like should be understood in a broad sense, for example, "fixation" can be fixed connection, or detachable connection, or integral; can be direct connection, or indirect connection through an intermediate medium; can be the communication or interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, the description such as "first", "second" and the like in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical features of each embodiment can be combined with each other, but it must be based on the realization of those skilled in the art, and when the combination of technical features appears contradictory or unachievable, it should be considered that the combination does not exist and is not within the scope of protection claimed in the present application.

[0094] In order to make the technical solutions of the present application clearer, the present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0095] Embodiment 1 of the flue gas treatment system: As Figure 1As shown, the flue gas treatment system of the present application comprises, in sequence, a pretreatment subsystem 1 (for a pretreatment process), a cooling and washing device 2 (for a pneumatic emulsification process), an oxygen removal device 3 (for a catalytic oxygen removal process), a catalytic combustion subsystem 4 (for a catalytic combustion process), and a waste heat recovery subsystem 5 (for waste heat recovery).

[0096] As shown in Figure 2 and Figure 3 chlorinated flue gas from a titanium tetrachloride production process is pretreated by passing through a first gas-liquid separator 101, a spraying device 102, and a second gas-liquid separator 103 of the pretreatment subsystem 1 in sequence, and then is cooled, dehumidified, and fireproofed by passing through the cooling and washing device 2 (a cyclone water seal fireproofing device). The heat exchanger 2015 enables heat exchange between the water medium from the bottom of the cooling and washing device and the chilled brine from the chilled brine system 2016 to achieve cooling. The cooling and washing device 2 uses the cooled water medium to cool the chlorinated flue gas and remove water vapor. The chlorinated flue gas after cooling and dehumidification is preheated by passing through the flue gas preheater 7 via the one-way explosion-proof valve 8, and then is subjected to oxygen removal treatment by passing through the oxygen removal device 3 (a catalytic oxygen removal device). The chlorinated flue gas after oxygen removal is introduced into the catalytic combustion subsystem 4 and reacts with air (and natural gas as needed) from the outside to generate carbon dioxide by combustion. The chlorinated flue gas is then introduced into the waste heat boiler 501 of the waste heat recovery subsystem 5 and uses the heat to generate steam from boiler water. The steam is sent out after passing through the steam drum 502. A small part of the chlorinated flue gas from the waste heat boiler 501 is sent to the flue gas preheater 7 by the fan 507 (a high-pressure fan) to preheat the main stream of flue gas in the flue gas preheater 7 and circulate into the waste heat boiler 501. The rest of the chlorinated flue gas continues to be introduced into the air preheater 404 and exchanges heat to preheat the air from the outside. The air preheated by the air preheater 404 is introduced into the catalytic combustion subsystem 4. The chlorinated flue gas from the air preheater 404 continues to be introduced into the feedwater preheater 503 and exchanges heat to preheat the demineralized water. The demineralized water is pumped into the feedwater preheater 503 by two parallel boiler feedwater pumps 505, and the demineralized water preheated by the feedwater preheater 503 is introduced into the steam drum 502. The chlorinated flue gas from the feedwater preheater 503 is introduced into the dust collector 504 and then into the chimney 6 for discharge. A system bypass is provided before the cooling and washing device to discharge the chlorinated flue gas into the chimney 6 in case of emergency. The flue gas treatment system of the present embodiment can fully recover and utilize the heat value of the chlorinated flue gas and ensure the safety of the main system.

[0097] Embodiment 2 of the flue gas treatment system The flue gas treatment system of Example 2 is basically the same as that of Example 1, except that the oxygen removal device 2 is not a catalytic oxygen removal device, but an adsorption oxygen removal device, in which tetracyanoquinodimethane (TCNQ) is used as a porous adsorption material. Accordingly, the length of the pipeline between the oxygen removal device and the catalytic combustion subsystem is significantly extended, so that the oxygen concentration near the fire source position is extremely low, which makes it impossible to pass back to the fire to cause an explosion, ensuring the safety of the upstream. The flue gas treatment system of this embodiment can fully recover the heat value of the chlorinated flue gas and ensure the safety of the main system, but the oxygen removal cost of the adsorption oxygen removal device is relatively high, and the extension of the pipeline length to ensure safety will also increase the cost.

[0098] Example 3 of the flue gas treatment system As shown in Figure 3 chlorinated flue gas (temperature -10 to 0 degrees Celsius) from the titanium tetrachloride production process passes through the first gas-liquid separator 101 (valve is provided after the first gas-liquid separator 101) and then through the three-stage series water spray device 1021 and the two-stage series alkali spray device 1022 in sequence, and then passes through the second gas-liquid separator 103, and then is introduced into the cooling scrubbing device 2 by the induced draft fan 104, the main road electric valve 105, the pressure detection instrument (not shown in the figure) and the booster fan 107 (boosted to 1500 Pa) in sequence. The first gas-liquid separation can separate out liquid droplets and solid impurities, the water spray can make chlorine in the flue gas generate hydrochloric acid, the alkali spray can neutralize the hydrochloric acid and remove the hydrochloric acid and sulfides, and the second gas-liquid separation can further separate out liquid droplets.

[0099] A system bypass directly leading to the chimney is connected between the induced draft fan 104 and the main road electric valve 105, and a system bypass electric valve 106 is provided in the system bypass. The system bypass electric valve 106 is normally closed, and can be opened to shut off the process when needed (such as during parking or in an emergency), so that the chlorinated flue gas is not introduced into the subsequent process, but is directly discharged from the chimney 6.

[0100] The cooling scrubbing device 2 includes a cyclone (cyclone explosion-proof valve, 1500 Pa), which can cool and scrub the flue gas in a gas dynamic emulsification manner and achieve water sealing and fire blocking, thereby playing the role of an explosion-proof valve. The cooling scrubbing device 2 uses water as the heat exchange medium, and the water enters the inlet of the cooling scrubbing device 2 body at a temperature of 20 degrees Celsius and exits at a temperature of 40 degrees Celsius. The 40 degrees Celsius water from the cooling scrubbing device 2 body is circulated through the heat exchanger circulating pump 2017 (3m 3The hot water medium from the heat exchanger 2015 exchanges heat with chilled brine (about 0 degree Celsius) from a chilled brine system 2016. After the heat exchange, the outlet temperature of both the chilled brine and the water medium from the heat exchanger 2015 is about 20 degrees Celsius. The chilled brine is circulated to the chilled brine system 2016, and the water medium is circulated to the quenching scrubber 2. The flue gas (oxygen content: 2-3%vol) from the quenching scrubber 2 enters the oxygen removal device 2 (specifically, a catalytic oxygen removal device) in sequence through a one-way explosion-proof valve 8 and a flue gas preheater 7. If backfire occurs when ignition or combustion, the one-way explosion-proof valve 8 can prevent the quenching scrubber 2 and the upstream system from exploding due to backfire, thereby cutting off the process and avoiding the impact of backfire on the operation of the titanium tetrachloride main production system. The flue gas preheater 7 uses a small part (for example, 10%) of the high-temperature flue gas from the waste heat boiler 501 (a control valve is arranged in the pipeline) to preheat the flue gas in the main flow path. The preheated flue gas enters the oxygen removal device 2, and the flue gas from the waste heat boiler 501 for preheating is circulated to the waste heat boiler 501 by a high-temperature fan. After being preheated, the flue gas is deoxidized by the oxygen removal device 2, and the oxygen content is reduced from 2-3%vol to less than 1%vol.

[0101] The flue gas from the oxygen removal device 2 enters the catalytic combustion barrel with a regenerator in the catalytic combustion subsystem 4 for catalytic combustion. The carbon monoxide in the flue gas reacts with oxygen in the fresh high-temperature air (120 degrees Celsius) from the air preheater 404 to generate carbon dioxide and release heat. The catalytic combustion barrel has a honeycomb-shaped ceramic as a regenerator, which can store the waste heat of the previous round of combustion. This device is beneficial to deal with the situation where the heat value of the chlorination flue gas is unstable (for example, the temperature of the flue gas is low due to fluctuations). After flowing through the regenerator, the flue gas leaves part of the heat in the regenerator, so that the regenerator is always maintained at a high temperature (more than 600 degrees Celsius). Even if the temperature of the flue gas before entering the catalytic combustion barrel is low, it can be ignited when flowing through the high-temperature regenerator, so that the carbon monoxide is burned to generate carbon dioxide. The catalyst used in the high-temperature regenerative catalytic combustion barrel can lower the ignition temperature to ignite the flue gas. The catalyst uses a honeycomb-shaped ceramic as a carrier, and a active component (Pt) is coated on the carrier at high temperature. It can treat the carbon monoxide produced by incomplete combustion at a reaction temperature range of 600-800 degrees Celsius to make it burn to generate carbon dioxide. The honeycomb-shaped ceramic carrier of the active component can also act as a regenerator.

[0102] In order to deal with the situation where the carbon monoxide content in the flue gas is too low, the catalytic combustion barrel is provided with a supplementary natural gas inlet and a corresponding pipeline (supplementary natural gas flow: 125 Nm 3 / h). If necessary, supplementary natural gas can be used for combustion.

[0103] The catalytic combustion barrel is next to the waste heat boiler 501 and is connected with the waste heat boiler 501 through two flue gas outlet pipes of the catalytic combustion barrel, so that the heat generated by the combustion of the flue gas in the catalytic combustion barrel can be immediately used for heating the waste heat boiler 501. The waste heat boiler 501 converts the water in the steam drum 502 connected therewith into steam through the heat exchange between the water and the high-temperature flue gas in the serpentine pipe inside the boiler, and the steam is delivered outward, and the rated evaporation capacity is about 4 tons / hour (i.e. 4 t / h), so as to realize the recycling of the heat.

[0104] The flue gas from the outlet of the waste heat boiler 502 is divided into two parts. A small part (for example, 10%) of the flue gas is introduced into the flue gas preheater 7 and circulated to the waste heat boiler, and the remaining flue gas (11500 Nm 3 / h) is introduced into the downstream air preheater 404 and the feed water preheater 503 in sequence. The air preheater 404 can preheat the fresh air (20 degrees Celsius, 5500 m 3 / h) sent from the outdoor through the air blower 506 to 120 degrees Celsius and send the fresh air into the catalytic combustion barrel. The feed water preheater 503 can preheat the demineralized water pumped from the demineralized water pipe network through two parallel boiler feed water pumps 505, and the preheated demineralized water is used as boiler makeup water and introduced into the steam drum 502 connected with the waste heat boiler 501.

[0105] The flue gas from the feed water preheater is introduced into the dust collector 504 for dust removal, and the dust-removed flue gas (100 degrees Celsius, 15700 m 3 / h) is introduced into the chimney 6 for emission. The flue gas detection equipment is installed at the outlet of the chimney 6 to ensure that the flue gas meets the relevant emission standards and to monitor the treatment effect of the system.

[0106] The process of the embodiment has been proved to be able to output steam at an average flow rate of 4 t / h, and can ensure the safety of the flue gas treatment system and the titanium tetrachloride main production system. In addition, since the system bypass is provided, even if the flue gas treatment system needs to be shut down for maintenance, the normal operation of the titanium tetrachloride main production system will not be affected.

[0107] The flue gas treatment system of the present application realizes the efficient and safe comprehensive utilization of the chlorination flue gas, and effectively improves the safety, stability and effectiveness of the whole system through system design.

[0108] Embodiment 4 of the flue gas treatment system As Figures 1 to 3 shown, the flue gas treatment system of the embodiment includes a pretreatment subsystem 1 (for a pretreatment process), a cooling and washing device 2 (for a pneumatic emulsification process), an oxygen removal device 3 (for an oxygen removal process), a catalytic combustion subsystem 4 (for a catalytic combustion process), and a waste heat recovery subsystem 5 (for a waste heat recovery process) connected in sequence. The processes and corresponding devices are as follows: Pretreatment process: Chlorinated flue gas from the titanium tetrachloride production process is passed into a pretreatment subsystem 1 for pretreatment. The pretreatment subsystem 1 includes, in series, a first gas-liquid separator 101 for performing gas-liquid separation on the flue gas to remove most solid impurities; a plurality of water spray devices 1021 connected in series for spraying the flue gas with water to precipitate titanium tetrachloride droplets and generate hydrochloric acid as a byproduct; a plurality of alkali spray devices 1022 (sodium hydroxide solution) connected in series for spraying the flue gas with alkali to remove hydrochloric acid droplets and sulfides; and a second gas-liquid separator 103 for performing further gas-liquid separation on the flue gas to remove droplets. The pretreatment subsystem 1 also includes a water washing and condensing device arranged upstream of the first gas-liquid separator 101. The water washing and condensing device uses chilled water to wash the chlorinated flue gas to condense and cool it to precipitate titanium tetrachloride droplets. The first gas-liquid separator 101 then separates the titanium tetrachloride droplets from the chlorinated flue gas. The remaining chlorinated flue gas mainly includes chlorine, carbon monoxide and other flue gases, as well as a small amount of titanium tetrachloride. The temperature of the chlorinated flue gas is also significantly reduced (to about minus ten degrees Celsius).

[0109] A system bypass is installed downstream of the second gas-liquid separator 103 and upstream of the cooling and scrubbing device 2. This bypass is equipped with an emergency interlocking device (system bypass electric valve 106). When necessary (e.g., in an emergency such as a sudden shutdown), the system bypass electric valve 106 can be opened to shut down the process, preventing the chlorinated flue gas from entering subsequent processes and discharging it directly through the chimney. Simultaneously, the subsequent flue gas treatment system enters an automatic shutdown sequence. To ensure positive pressure operation of the flue gas treatment system, a pressure meter and a booster fan 107 (blower) located downstream of and interlocked with the pressure meter are installed in the flue gas flow path before the cooling and scrubbing device 2. According to another exemplary embodiment of the present invention, the booster fan 107 can also be set at a position between the feed water preheater 503 and the dust collector 504. Because when the booster fan 107 is located at the front end of the system main road (close to the position of the system main road electric valve 105), there is a certain concentration of sulfide and chlorine there, which has a corrosive effect on the booster fan components, so the booster fan 107 can be placed at the rear end of the system main road (i.e., the downstream end).

[0110] Cooling washing process: The chlorinated flue gas (40-43°C) at the outlet of the alkali spraying device 1022 is separated by the second gas-liquid separator 103 and then passed into the cooling and washing device 2 through the induced draft fan 104 and the booster fan 107. Figures 4 to 8 The detailed structure of the cooling and scrubbing device 2 used in this embodiment is shown. This device is a pneumatic emulsification device that utilizes a pneumatic suspension cavitation mechanism and a cyclonic water seal fire arrester. As the flue gas flows through the cooling and scrubbing device 2, it exchanges heat with the water medium in the water seal formed by the internal cyclone 204, reducing the moisture content of the flue gas and achieving condensation and dehumidification.

[0111] As Figure 4 and Figure 5 shown, the cooling washing device adopted in the embodiment comprises a cooling washing device body 201, a uniform gas chamber 202 is arranged below the inside of the cooling washing device body 201, a demisting chamber 203 is arranged above the inside of the cooling washing device body 201, and two cyclones 204 (specifically, emulsion layer cyclones) are arranged between the uniform gas chamber 202 and the demisting chamber 203 in the inside of the cooling washing device body 201. A flue gas inlet 2011 is integrally formed below the outer side wall of the cooling washing device body 201; a flue gas outlet 2012 is integrally formed at the top of the cooling washing device body 201, and a fan 2013 is fixedly installed at the right end of the flue gas outlet 2012. The upper part of the cyclone 204 and the heat exchanger 2015 are connected and communicated through a circulating pipe 206. The circulating pipe 206 can include one or two or even more transverse circulating pipe branch pipes 205, the left end of the circulating pipe branch pipe 205 is connected and communicated with the inside of the cooling washing device body 201, the number of the circulating pipe branch pipe 205 can correspond to the number of the cyclone 204, and each circulating pipe branch pipe 205 is connected with the cooling washing device body 201 above the corresponding cyclone 204. The bottom end of the circulating pipe 206 is provided with a circulating pump 207, the output end of the circulating pump 207 is fixedly connected and communicated with the bottom end of the circulating pipe 206, and the input end of the circulating pump 207 and the bottom end of the cooling washing device body 201 are both fixedly connected and communicated with a shunt pipe 2010 (specifically, a U-shaped shunt pipe).

[0112] As Figure 4 shown: the bottom ends of the two shunt pipes 2010 are fixedly connected and communicated with two heat exchangers 2015. Each shunt pipe 2010 comprises a longitudinal (vertical) shunt pipe main pipe and at least two shunt pipe branch pipes equal in number to the at least two heat exchangers, and each shunt pipe branch pipe is connected with the corresponding heat exchanger 2015 through an outlet electromagnetic valve / electric valve 2018 and an inlet electromagnetic valve / electric valve 2019. The electromagnetic valve 2018 is controlled so that when one heat exchanger 2015 needs to be repaired and maintained, the corresponding outlet electromagnetic valve 2018 and the corresponding inlet electromagnetic valve 2019 are closed, while the corresponding inlet and outlet electromagnetic valves of the other heat exchanger 2015 are kept open.

[0113] In use, flue gas enters the inside of the cooling and washing device body 201 through the flue gas inlet 2011, is uniformly distributed to the middle part of the cooling and washing device body 201 through the air equalizing chamber 202, and is then extracted by the fan 2013 after passing through the cyclone 204 and the mist eliminator 203 and is discharged from the flue gas outlet 2012; the circulating pump 207 extracts cooling medium from the lower heat exchanger 2015 and enters the inside of the cooling and washing device body 201 through the left end of the circulating pipe branch 205, and the cooling medium from top to bottom cools and washes the flue gas from bottom to top, and then falls into the heat exchanger 2015 through the shunt pipe 2010 at the bottom of the cooling and washing device body 201.

[0114] Figure 6 A more specific structure of the cooling and washing device body 201 is shown, in which the mist eliminator 203 comprises a wire mesh mist eliminator, and a buffer mesh plate 2014 is arranged above the cyclone 204. The wire mesh mist eliminator is composed of multiple layers of wire mesh, and the mist droplets are captured and adsorbed when passing through the wire mesh. The buffer mesh plate 2014 is arranged obliquely towards the inlet of the circulating pipe branch 205, and has a buffering effect on the introduced cooling medium liquid, avoiding direct concentrated impact on the inner wall of the cooling and washing device body 201. Figure 6 Only one buffer mesh plate 2014 and one circulating pipe branch 205 are shown; in another embodiment (not shown in the figure), there can be two buffer mesh plates 2014 and two circulating pipe branches 205, and each buffer mesh plate 2014 is located above each cyclone 204; in yet another embodiment (not shown in the figure), there can be only one buffer mesh plate 2014 and two circulating pipe branches 205, and each circulating pipe branch 205 is located on the sidewall of the device body 201 above each cyclone 204. As shown, Figure 7 The cyclone 204 of the cooling and washing device is of a modular structure, comprising a sleeve 20401 and multiple obliquely placed static rotary vanes 20402 arranged inside the sleeve 20401. As shown, Figure 6 and Figure 8As shown, the inner part of the equalizing chamber 202 includes a conical guide vane 20201, and the lower surface of the equalizing chamber is provided with a through-type equalizing chamber through slot 20202, and the flue gas inlet 2011 is arranged adjacent to the lower surface of the equalizing chamber 202, and the inner lower surface of the equalizing chamber 202 is integrally formed with a guide slope surface 20203. A plurality of conical guide vanes 20201 are sequentially and fixedly connected in the inner part of the equalizing chamber 202 from top to bottom, and the number of the conical guide vanes 20201 decreases sequentially from top to bottom. After the flue gas enters from the flue gas inlet 2011 and then enters the inner part of the equalizing chamber 202 from bottom to top through the equalizing chamber through slot 20202, the flue gas can enter the inner part of the device body 201 uniformly after being guided by the multiple layers of conical guide vanes 20201. In addition, when the liquid falls from top to bottom, the guide slope surface 20203 can be arranged to facilitate the circulation and falling of the liquid to be discharged from the inner part of the equalizing chamber 202. When the flue gas flow passes through the static spiral vane of the cyclone 204, it will undergo strong planar centripetal rotation, and the rotating flue gas impacts the liquid in the cyclone 204 into a rotating foam area, and then the flue gas supports the foam area, so that the entire rotating foam area is in a suspended state to form a pneumatic suspended bubble area, and the flue gas passes through the foam area and the rotating downward liquid from bottom to top to be fully cooled and washed.

[0115] In the present application, the cyclone 204 utilizes the pneumatic suspended bubble technology reaction mechanism, which is composed of multiple groups of modular static spiral vanes 20402, and the static spiral vanes 20402 are arranged in the inner part of the sleeve 20401 (as shown). Figure 7 As shown), the accelerated flue gas enters the container at a certain angle from the lower end of the container, collides with the unstable cooling liquid flowing downward from the upper end of the container, and the flue gas high-speed rotary cuts the downward cooling liquid, the cooling liquid is cut into pieces, and the gas-liquid phase continuously collides and rotary cuts, the liquid particles are crushed more and more finely, the gas and liquid are fully mixed to form a stable reaction liquid layer. During the continuous flow of the flue gas, the reaction liquid layer gradually thickens, and when the upward pneumatic supporting force balances with the gravity of the emulsion, the earliest formed reaction liquid will be replaced by the newly formed reaction liquid, so that a relatively stable emulsion layer is always maintained, and a continuous, stable and efficient flue gas washing model is finally formed.

[0116] In the module reaction space of the pneumatic suspended bubble generation mechanism, as long as there is sufficient flue gas flow, a relatively stable reaction liquid layer (emulsion layer) will always be maintained. The emulsion layer is located above the cyclone 204, and multiple cyclones will have multiple corresponding emulsion layers. The flue gas passes through the foam area and the rotating downward cooling water from bottom to top to be fully mixed and cooled. Unlike the traditional multi-stage spraying, the pneumatic suspended bubble technology reaction mechanism is a dynamic liquid film wrapped around a small flue gas group reaction, which has higher cooling efficiency, and the flue gas passes through the pneumatic suspended bubble device, and the gas-liquid in the reaction liquid layer undergoes high-speed rotary cutting and collision, and there is almost no dead zone.

[0117] Because the mechanism of the aerodynamic suspension bubble is strong mass transfer cooling, the liquid-gas ratio of the device is 1 / 2 of the existing air tower spray for treating the same amount of flue gas and the same temperature flue gas.

[0118] Unlike the traditional multi-stage spray washing, the cyclone of the device utilizes the aerodynamic suspension bubble technology reaction mechanism, so that the dynamic liquid film wraps the small flue gas group for cooling and washing, the cooling efficiency is higher, the flue gas can pass through the aerodynamic suspension bubble zone formed by the cyclone, and there is almost no dead zone, so that the chlorinated flue gas can be cooled and washed efficiently.

[0119] In addition, the cyclone water seal formed by the cyclone of the device can achieve the purpose of effective fire prevention. Specifically, the cyclone 204 can make the flue gas flow form a rotating flow, and the water entering the inside of the cooling and washing device body 201 through the circulating pump 207 and the circulating pipe 206 also forms a rotating flow, achieving the effect of cyclone water seal and achieving the purpose of fire prevention.

[0120] According to the embodiment of the present application, the heat exchanger 2015 has a refrigerated brine inlet and a refrigerated brine outlet and corresponding heat exchange pipes, and the refrigerated brine from the refrigerated brine system flows in the heat exchange pipes to circulate and cool the cooling medium (such as water) from the bottom end of the device body 1 by using the refrigerated brine from the refrigerated brine system.

[0121] In yet another embodiment, one of the two heat exchangers 2015 has a refrigerated brine inlet and a refrigerated brine outlet and corresponding heat exchange pipes, and the cooling medium (such as water) from the bottom end of the cooling and washing device body 201 is circulated and cooled by using the refrigerated brine from the refrigerated brine system, while the other heat exchanger 2015 is replaced by a liquid storage mechanism, which is not connected to the refrigerated brine system, and the liquid storage mechanism can be made of copper and mainly utilizes natural heat dissipation, and a plurality of slowly rotating stirring rods can be arranged inside.

[0122] Deoxidation process The chlorinated flue gas treated by the aerodynamic emulsification (cooling and dehumidification) passes through the one-way explosion-proof valve 8 and the flue gas preheater 7 in sequence. The one-way explosion-proof valve 8 can be used to prevent the cooling and washing device 2 and the system further upstream from exploding due to backfire, so that it can be reliably cut off in case of accidental explosion to avoid the accident affecting the operation of the main production system. The flue gas preheater 7 can warm up the chlorinated flue gas. The warmed chlorinated flue gas is introduced into the deoxidation device 3 for catalytic deoxidation treatment, so that the oxygen content (generally 2-3%vol) of the chlorinated flue gas is reduced to less than 1%vol. If the oxygen content exceeds 2%, backfire may occur under the condition of backfire, which will cause safety failure of the system. Therefore, the oxygen content is reduced to below 1% as much as possible to block the backfire. The deoxidation device 3 suitable for the present application preferably adopts a catalytic deoxidation device capable of removing oxygen by catalyst, more preferably a low-temperature catalytic deoxidation device, to reduce the cost.

[0123] The chlorinated flue gas after the heat storage body of the catalytic combustion barrel is heated enters the waste heat boiler 501 to produce steam (low heat value combustion process + auxiliary partial natural gas blending combustion if necessary), and the heat exchanger is used to extract the waste heat of the flue gas at the outlet of the waste heat boiler 501, the original flue gas is preheated in the flue gas preheater 7, and the boiler fresh air is heated in the air preheater 404, and the cooled flue gas is discharged through the chimney 6, and the chimney 6 is provided with a flue gas detection device. The specific process is as follows: The catalytic combustion barrel with high-temperature heat storage body is arranged next to the waste heat boiler 501. The high-temperature flue gas in the catalytic combustion barrel enters the waste heat boiler 501 through two flue gas outlet pipes, the waste heat boiler 501 is provided with a steam drum 502, and the steam drum 502 recycles the heat energy from the flue gas in the waste heat boiler 501 by generating and sending out steam (for example, generating electricity by steam). The waste heat boiler 501 heats the desalted water in the heat exchange pipes in the form of serpentine pipes arranged in the waste heat boiler 501 into steam through heat exchange and sends the steam into the steam drum 502.

[0124] As mentioned above, in the case that the concentration of carbon monoxide in the flue gas is low, the combustion may be interrupted, and in the case of combustion interruption, since the carbon monoxide and oxygen are not consumed by combustion, they will accumulate, and when they exceed the critical concentration, the catalytic combustion barrel of the catalytic combustion subsystem will explode, causing serious safety accidents. Therefore, it is necessary to keep the combustion, according to the embodiment of the present application, a gas detector is arranged between the oxygen removal device 3 and the catalytic combustion subsystem 4, and a camera / observation window is arranged in the catalytic combustion subsystem 4 (the camera can transmit image data to the monitoring screen in the monitoring room, which is safer for remote monitoring; it is simple and direct to observe through the glass observation window opened on the catalytic combustion barrel, but the safety is slightly worse), when the gas detector detects that the concentration of carbon monoxide is lower than 10%vol or the red light or flame can no longer be seen through the camera, the electromagnetic valve on the natural gas supply pipeline is reopened, the supplementary combustion natural gas is input again, and the ignition action is performed through the arc high-voltage pack or similar device.

[0125] The chlorinated flue gas (mainly carbon dioxide) from the waste heat boiler 501, which emits most of the heat energy, still has a relatively high temperature (for example, it can be as high as more than 200 degrees Celsius), most of which enters the air preheater 404 to heat the air from the outside, so that the temperature of the chlorinated flue gas continues to drop (for example, to about 150 degrees Celsius). The air preheated by the air preheater 404 is introduced into the catalytic combustion barrel for catalytic combustion treatment of the chlorinated flue gas. The chlorinated flue gas from the air preheater 404 is introduced into the feed water preheater 503 to preheat the demineralized water from the demineralized water pipe network and pumped by the boiler feed water pump 505 (for example, from room temperature to about 40 to 70 degrees Celsius). The demineralized water preheated by the feed water preheater 503 is sent to the steam drum 502 of the waste heat boiler 501 to supplement the hot water in the steam drum 502 and supply water to the waste heat boiler 501 through the steam drum 502. The water in the steam drum 502 is heated into steam by the waste heat boiler 501. The chlorinated flue gas from the feed water preheater 404 is introduced into the dust remover 504 for dust removal and then discharged through the chimney. The steam drum 502 continuously outputs steam, and the boiler feed water pump 505 continuously supplies water, which is equivalent to the waste heat boiler 501 directly heating the water in the steam drum 502 into steam.

[0126] A small part of the chlorinated flue gas passing through the waste heat boiler 501 can be introduced (for example, by means of a fan 507 such as a high-temperature fan) into a flue gas preheater 7 located upstream of the deoxidizing device 3 to heat the chlorinated flue gas from the upstream of the flue gas preheater 7 (referred to as "original flue gas" relative to the flue gas participating in the circulation).

[0127] The system of the present application adds a pressure detection instrument and a booster fan before the cooling and washing device. The booster fan is interlocked with the pressure detection instrument upstream of it to ensure the positive pressure operation of the system. The booster fan can also be arranged at the rear end to avoid damage by corrosive gas at the front end.

[0128] The flue gas treatment system of the present application also includes a system bypass and corresponding emergency interlocking devices such as a system bypass electric valve arranged in parallel with the main path of the system. When needed (for example, in an emergency such as sudden stop), the chlorinated flue gas from the second gas-liquid separator can pass through the induced draft fan without entering the downstream booster fan and cooling and washing device, but the system bypass electric valve is opened to directly discharge the chlorinated flue gas from the chimney, and the main path of the downstream flue gas treatment system enters the automatic stop program.

[0129] The system of the embodiment can safely and effectively recover waste heat. The waste heat recovery subsystem effectively comprehensively recovers heat of the chlorination flue gas, wherein the waste heat boiler generates steam to be delivered from a steam drum outward, thereby achieving the purpose of waste heat recovery and utilization, and the flue gas preheater, the air preheater and the feed water preheater further utilize the residual heat, thereby improving the comprehensive utilization rate. In addition, since the low-temperature catalytic deoxidizing device, the cooling and washing device and other devices are adopted, backfire explosion is avoided, and the safety of the system is ensured; the catalytic combustion subsystem can still perform flameless combustion in the case of low carbon monoxide concentration, thereby not only absorbing the heat energy of the flue gas through heat exchange but also absorbing the heat energy of the flue gas through combustion; the arrangement of the entire flue gas treatment system effectively absorbs toxic gases and simultaneously efficiently recovers flue gas heat, and good technical effects are achieved.

[0130] The flue gas treatment system according to the exemplary embodiment of the present application further comprises a control module, which can automatically control the opening and closing of each electromagnetic valve according to the detection results of various detectors, and / or which can control the opening and closing of each electromagnetic valve in response to the instructions / button actions input by a user / operator.

[0131] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A flue gas treatment system, characterized in that: The flue gas treatment system includes: (a) a cooling and scrubbing device (2), which is used to cool and scrub the flue gas; (b) a deoxygenation device (3) for deoxygenating the flue gas from the cooling and scrubbing device (2); (c) a catalytic combustion subsystem (4) for burning carbon monoxide in the flue gas from the deaerator (3); and (d) A waste heat recovery subsystem (5) for recovering waste heat from the flue gas from the catalytic combustion subsystem (4).

2. The flue gas treatment system according to claim 1, characterized in that: The flue gas treatment system includes a system main path and (e) a system bypass, The main circuit of the system includes a cooling and washing device (2), a deoxidizing device (3), a catalytic combustion subsystem (4) and a waste heat recovery subsystem (5). The system bypass is in communication with the chimney (6), the system bypass is parallel to the system main line, and a system bypass electric valve (106) for opening and closing the system bypass is provided on the system bypass.

3. The flue gas treatment system according to claim 1, characterized in that: The flue gas treatment system further comprises: (f) a one-way explosion-proof valve (8), which is provided on the flue gas outlet pipeline of the cooling and washing device (2) and is used to prevent explosion caused by backfire from the catalytic combustion subsystem (4).

4. The flue gas treatment system according to claim 2, characterized in that: The flue gas treatment system further comprises: (g) a flue gas preheater (7), the flue gas preheater (7) being located downstream of the cooling and scrubbing device (2) and upstream of the deoxidation device (3) and being in communication with the two, and being used for preheating the flue gas from the cooling and scrubbing device (2) and then sending the flue gas to the deoxidation device (3).

5. The flue gas treatment system according to claim 1 or 2, characterized in that: The flue gas treatment system further comprises a pretreatment subsystem (1), and the pretreatment subsystem (1) comprises: a first gas-liquid separator (101), used for performing gas-liquid separation on the flue gas; a water spraying device (1021), located downstream of the first gas-liquid separator (101) and performing water spraying treatment on the flue gas, for converting chlorine in the flue gas into hydrochloric acid; an alkali spraying device (1022), which is located downstream of the water spraying device (1021) and performs alkali spraying treatment on the flue gas to neutralize the hydrochloric acid and remove sulfides in the hydrochloric acid and the flue gas; and The second gas-liquid separator (103) is located downstream of the alkali spraying device (1022) and performs gas-liquid separation on the flue gas again.

6. The flue gas treatment system according to claim 2, characterized in that: A booster fan (107) is provided upstream of the cooling and scrubbing device (2) or at the downstream end of the main path of the system, for increasing the pressure of the flue gas fed into the cooling and scrubbing device (2) to form a rotary shear flow in the cooling and scrubbing device (2). A main circuit electric valve (105) is provided at the upstream end of the system main circuit. The main circuit electric valve is linked to a system bypass electric valve (106) to open the system bypass when the system main circuit is closed, or to close the system bypass when the system main circuit is opened.

7. The flue gas treatment system according to claim 6, characterized in that: The cooling and washing device (2) comprises a cyclone (204), and the cyclone (204) comprises static rotating blades (20402).

8. The flue gas treatment system according to claim 1, characterized in that: The cooling and washing device (2) comprises: A cooling and washing device body (201) utilizes water to cool and wash the flue gas therein for dehumidification, dust removal and / or fire prevention; a heat exchanger (2015) connected to the cooling washing device body (201) via an inlet water pipe and an outlet water pipe, for cooling water from the cooling washing device body (201) and entering the heat exchanger (2015) via the inlet water pipe through heat exchange and then circulating the water back to the cooling washing device body (201) via the outlet water pipe; and The chilled brine system (2016) is connected to the heat exchanger (2015) through an outlet brine pipe and an inlet brine pipe. The chilled brine from the chilled brine system (2016) enters the heat exchanger (2015) through the outlet brine pipe for heat exchange and then circulates to the chilled brine system (2016) through the inlet brine pipe. The chilled brine system (2016) uses the chilled brine to cool the water from the cooling washing device body (201) in the heat exchanger (2015).

9. The flue gas treatment system according to claim 1, characterized in that: The flue gas treatment system further includes a flow detection instrument, and the cooling and washing device (2) includes: A cooling and washing device body (201) utilizes water to cool and wash the flue gas therein for dehumidification, dust removal and / or fire prevention; The heat exchanger (2015) is connected to the cooling and washing device body (201) through an inlet water pipe, an outlet water pipe and a corresponding solenoid valve. When the flow rate of the flue gas to be treated is higher than a threshold value, the solenoid valve on the heat exchanger opens and the solenoid valve on the natural heat dissipation storage tank closes. Water from the cooling and washing device body (201) and entering the heat exchanger (2015) through the inlet water pipe is cooled by heat exchange with the chilled brine and then circulates to the cooling and washing device body (201) through the outlet water pipe. A chilled brine system (2016) is connected to the heat exchanger (2015) via an outlet brine pipe and an inlet brine pipe. The chilled brine from the chilled brine system (2016) enters the heat exchanger (2015) via the outlet brine pipe, undergoes heat exchange, and then circulates back to the chilled brine system (2016) via the inlet brine pipe. The chilled brine system (2016) uses the chilled brine to cool the water from the cooling washing device body (201) in the heat exchanger (2015); and The natural heat dissipation liquid storage tank is connected to the cooling and washing device body (201) through an inlet water pipe, an outlet water pipe and a corresponding electromagnetic valve. When the flow rate of the flue gas to be treated is lower than a threshold value or an abnormality occurs in the refrigerated brine system, the electromagnetic valve on the heat exchanger is closed and the electromagnetic valve on the natural heat dissipation liquid storage tank is opened. The water medium from the bottom of the cooling and washing device body (201) falls into the natural heat dissipation liquid storage tank, is cooled by natural heat dissipation, and is then pumped into the cooling and washing device body (201).

10. The flue gas treatment system according to claim 1, characterized in that: The deoxygenation device (3) is an adsorption deoxygenation device that removes oxygen using a porous adsorption material and / or a catalytic deoxygenation device that removes oxygen using a catalytic oxidation reaction.

11. The flue gas treatment system according to claim 10, characterized in that: The catalytic deoxidation device uses a catalyst with honeycomb-shaped ceramics as a carrier and platinum metal as an active component.

12. The flue gas treatment system according to claim 11, characterized in that: The honeycomb-shaped ceramic is cordierite.

13. The flue gas treatment system according to claim 11, wherein: The amount of platinum metal in the catalytic deoxidation device is controlled so that carbon monoxide can undergo oxidation reaction at a temperature of 150-300 degrees Celsius and reduce the oxygen content in the flue gas to below 1% vol.

14. The flue gas treatment system according to claim 10, characterized in that: The porous adsorption material is tetracyano-p-benzoquinodimethane, and the porous adsorption material is replaced after being saturated or replaced regularly.

15. The flue gas treatment system according to claim 1, characterized in that: The catalytic combustion subsystem (4) includes: A catalytic combustion barrel, which is used to burn carbon monoxide in the flue gas from the deoxygenation device (3) to generate carbon dioxide, thereby releasing heat from the flue gas. The catalytic combustion barrel further includes a catalytic combustion barrel body, a heat storage body, and an active component. The flue gas from the deoxygenation device (3) enters the interior of the catalytic combustion barrel body through the flue gas inlet, and after combustion, enters the waste heat recovery subsystem (5) through the flue gas outlet. The heat storage body is used to accumulate heat to maintain the temperature within a temperature range suitable for the combustion reaction. The active component is arranged inside the catalytic combustion barrel body and is used to catalyze the combustion reaction between carbon monoxide and oxygen in the flue gas from the deoxygenation device (3); an air supply line, which passes air into the interior of the catalytic combustion barrel through the air inlet of the catalytic combustion barrel to provide oxygen for the reaction; and The natural gas supply pipeline introduces natural gas into the interior of the catalytic combustion barrel body through the natural gas inlet of the catalytic combustion barrel body.

16. The flue gas treatment system according to claim 15, characterized in that: The heat storage body is a honeycomb-shaped ceramic, which maintains the temperature above 600 degrees Celsius by accumulating heat.

17. The flue gas treatment system according to claim 15, characterized in that: A solenoid valve is provided on the natural gas supply pipeline, a gas detector is provided between the deoxidation device (3) and the catalytic combustion subsystem (4), and an ignition device and a camera / observation window are provided in the catalytic combustion subsystem (4). The natural gas supplied by the natural gas supply pipeline, the oxygen supplied by the air supply pipeline and the flue gas from the deoxygenation device (3) are initially ignited by the ignition device, and the solenoid valve on the natural gas supply pipeline is closed after the initial ignition. When the gas detector detects that the concentration of carbon monoxide is lower than 10%vol or the red light or flame is no longer visible through the camera / observation window, the solenoid valve on the natural gas supply pipeline is reopened, the supplementary natural gas is input again, and the ignition device is used to re-ignite.

18. The flue gas treatment system according to claim 15, characterized in that: The active component for catalytic combustion is loaded on the heat storage body, and the active component is a noble metal or a transition metal oxide.

19. The flue gas treatment system according to claim 18, characterized in that: The active component for catalytic combustion is platinum.

20. The flue gas treatment system according to claim 15, characterized in that: The amount of the active component used for catalytic combustion is controlled so that the carbon monoxide in the flue gas can still fully undergo a combustion reaction with oxygen in a temperature range of 600 to 800 degrees Celsius when the concentration is as low as 14% vol.

21. The flue gas treatment system according to claim 1, characterized in that: The waste heat recovery subsystem (5) includes: A waste heat boiler (501) and a steam drum (502) connected to the interior of the waste heat boiler (501), wherein the steam drum (502) is capable of receiving feed water and transmitting steam to the outside. The feed water in the steam drum enters the interior of the waste heat boiler (501), exchanges heat with the flue gas from the catalytic combustion subsystem (4), and then circulates to the steam drum (502). The steam drum (502) transmits the steam to the outside. an air preheater (404), located downstream of the waste heat boiler (501), for preheating air using the heat of the flue gas from the waste heat recovery subsystem (5) and passing the preheated air into the catalytic combustion subsystem (4); a feedwater preheater (503), located downstream of the waste heat boiler (501), utilizing the heat of the flue gas from the waste heat recovery subsystem (5) to preheat the desalted water and passing the preheated desalted water into the waste heat recovery subsystem (5); and a flue gas circulation branch, which is arranged between the waste heat boiler (501) and the flue gas preheater (7), and is used to send a portion of the flue gas from the waste heat boiler (501) into the flue gas preheater (7) and circulate it to the waste heat boiler (501), and use the heat of the portion of the flue gas to preheat the flue gas from upstream in the flue gas preheater (7); The air preheater (404) and the feed water preheater (503) are arranged in series or in parallel.

22. The flue gas treatment system according to claim 21, characterized in that: The flue gas treatment system further includes a dust collector (504) and a booster fan (107). The chlorinated flue gas from the feed water preheater (503) passes through the booster fan (107) and then passes through the dust collector (504) for dust removal before being discharged into a chimney.

23. A flue gas treatment process, comprising the steps of reducing pollution emissions and recovering waste heat from flue gas using the flue gas treatment system according to any one of claims 1 to 22.

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