CN107983155A - Sintering flue gas denitration and desulfurization system and application thereof - Google Patents

Abstract

The invention provides a sintering flue gas denitrification and desulfurization system and its application, which includes a gas-gas heat exchange device; a flue gas temperature raising device; an ammonia injection device; a medium-high temperature selective catalytic reduction denitrification reactor; a denitrification and heat exchange fan; Booster fan; wet desulfurization device; dust removal device; flow regulating device; flue gas discharge online monitoring system; , The main road flue is equipped with an online monitoring system for flue gas emission, which is interlocked with the flow regulating device to realize interlocking regulation. The denitrification and desulfurization system of the present invention is simple, and can avoid the complex renovation project of the flue of the original main body of the sintering machine. It can guarantee a superior denitrification efficiency of more than 90%, is safe and reliable, guarantees desulfurization efficiency, meets the emission limit value of the revised opinion sheet, greatly reduces energy consumption costs, and has considerable economic benefits.

Description

A sintering flue gas denitrification and desulfurization system and its application

technical field

The invention relates to a sintering flue gas denitrification and desulfurization system and an application thereof, belonging to the field of sintering flue gas denitrification and desulfurization.

Background technique

The "Steel Sintering and Pelletizing Industry Air Pollution Emission Standard" implemented in 2012 stipulates that the NO _x emission of new enterprises shall not exceed 300mg/Nm ³ from October 1, 2012, and the existing enterprises shall also implement the above emission from January 1, 2015 standard. In June 2017, the Ministry of Environmental Protection of the People's Republic of China issued the "Letter on Soliciting Opinions on 20 National Pollutant Emission Standards Amendments (Draft for Comments)" including <Steel Sintering and Pellet Industry Air Pollutant Emission Standards>. The sulfur dioxide limit is adjusted to 50mg/Nm ³ , and the nitrogen oxide limit is adjusted to 100mg/m ³ (the standard oxygen content is 16%).

Since the sintering flue gas must be dedusted first, the exhaust gas temperature after dedusting is between 100 and 150°C; the concentration of SO ₂ in the flue gas is between 1000 and 1500 mg/Nm ³ , and the concentration of NO _x is between 250 and 400 mg/Nm ³ During the period, its concentration exceeded the current emission standard and far exceeded the emission limit value of the standard revision opinion sheet.

In recent years, with the continuous deepening of air pollution control work, domestic people of insight have carried out research on denitrification treatment of sintering flue gas in the sintering industry, and have completed some research and engineering practice in these areas. For example, the "Sintering machine partial flue gas denitrification system and method" with the publication number CN101810999 B is to collect the flue gas in the high-concentration area and first remove the dust and then denitrify; collect the flue gas in the low-concentration area and remove the dust; common desulfurization. In this technology, the temperature of flue gas with high concentration of nitrogen oxides is ignored only at 100-120°C, which cannot meet the requirements of SCR denitrification, and a large amount of external energy is consumed to raise the temperature of flue gas; if other methods are used, it cannot be realized 100mg/Nm ³ nitrogen oxide emission requirements. At the same time, this technology requires a large-scale modification of the flue of the sintering main body, which increases the cost of the project. Another example is "a desulfurization and denitrification system and method for sintering flue gas" with publication number CN104006673 B, which adopts activated carbon adsorption method for denitrification, and the reducing agent uses excess NH ₃ produced by urea. Although this technology uses activated carbon to denitrify sintering flue gas, which can reduce nitrogen oxide emissions within a certain range, it is limited by the principle of activated carbon denitrification, and its denitrification efficiency is only in the range of 60-70%. Meet the increasingly stringent nitrogen oxide emission requirements (100mg/Nm ³ in the revised opinion in 2017); at the same time, this technology utilizes the NH ₃ produced by excessive decomposition of urea during the sintering process, and it is difficult to control the amount of NH ₃ produced, which is very easy to make the The ammonia escape at the system outlet exceeds the standard. Another example is "a sintering flue gas desulfurization and denitrification device" with the publication number CN 203437036 U, which adopts a low-temperature denitrification + semi-dry desulfurization process device, uses flue gas preheating to raise the temperature of the flue gas, and cannot avoid _SO2 below 280°C Poisoning effect on denitrification; the highest desulfurization efficiency of semi-dry desulfurization technology does not exceed 95%, which cannot meet the treatment of high _SO2 concentration sintering flue gas.

In view of the above situation, it is necessary to develop a sintering flue gas denitrification and desulfurization system and corresponding processes in this field, so as to treat sintering flue gas with high efficiency and energy saving, and meet the increasingly stringent emission requirements.

Contents of the invention

In view of the actual needs, the main purpose of the present invention is to provide a denitrification and desulfurization system for sintering flue gas, which can treat sintering flue gas with high efficiency and low energy consumption, so that the _NOx , SO ₂ and particulate matter emissions of sintering flue gas can reach or Superior to the latest national standards.

Another object of the present invention is to provide a method for denitrification and desulfurization of sintering flue gas, which uses the above-mentioned denitrification and desulfurization system for sintering flue gas.

In order to achieve the above object, the present invention provides a sintering flue gas denitrification and desulfurization system, which includes:

A gas-gas heat exchange device for exchanging heat between the flue gas before denitrification and the flue gas after denitrification, which is equipped with a flue gas inlet before denitration, a flue gas outlet before denitrification, a flue gas inlet after denitrification, and a flue gas outlet after denitrification ;

A flue gas temperature raising device used to raise the temperature of the flue gas before denitrification;

Ammonia injection device, medium and high temperature selective catalytic reduction denitrification reactor, denitrification and heat exchange fan, booster fan, wet desulfurization device, dust removal device, flow adjustment device for chain adjustment of sintering flue gas distribution and real-time monitoring outlet Flue gas emission online monitoring system (CEMS) for NO _x and SO ₂ concentrations in flue gas;

The flow regulating device includes a flow meter and a baffle door capable of electrically adjusting its opening;

The total flue gas channel from the sintering machine is divided into a main flue and a bypass flue, and the baffle door and the flow meter are on the bypass flue; the main flue is sequentially connected with the flue gas before denitration Inlet, outlet of flue gas before denitration, inlet and outlet of flue gas temperature raising device, inlet and outlet of medium-high temperature selective catalytic reduction denitration reactor, inlet of flue gas after denitration, flue gas after denitration The outlet, the inlet and outlet of the denitrification and heat exchange fan are connected, the main flue then merges with the bypass flue to form a total flue gas channel, and then the total flue gas channel is sequentially connected with the inlet of the booster fan The outlet, the inlet and outlet of the wet desulfurization device are connected to the inlet of the dust removal device, the outlet of the dust removal device is used as the outlet of the purified flue gas, and the online monitoring system for flue gas emission is set on the flue gas outlet, The flue gas emission on-line monitoring system is interlocked with the flow meter and the baffle door, so as to feed back the _NOx and _SO2 concentrations detected in real time to the flow meter and the baffle door, so as to timely adjust the The baffle door is used to adjust the flow of sintering flue gas distributed to the main flue and bypass flue, so that the NO _x and SO ₂ at the flue gas outlet meet the requirements; the ammonia injection device and the medium-high temperature selective catalytic A reduction denitrification reactor is connected to supply ammonia thereto.

The sintering flue gas denitrification and desulfurization system provided by the present invention is an integrated system for sintering flue gas denitrification and desulfurization. The application of this system has good operability, system stability and economy. The energy consumption during the process is too large, and it cannot be matched with the existing desulfurization device or process. When the low-temperature denitrification system or process is used, the SO ₂ is too high and affects the low-temperature denitrification efficiency. At the same time, how to comprehensively save energy and reduce consumption, reduce the difficulty of actual project implementation and investment costs To solve the problem, a new system and process are provided.

The flue gas emission online monitoring system, the flow meter and the baffle door in the present invention are all commonly used equipment or devices in the field. Regarding the flue gas emission online monitoring system and the flow meter and the The interlock adjustment of the panel door can be realized by automatic conventional means. Usually, the CEMS monitoring value is fed back to the control system in real time: the control system calculates the maximum flow rate of the flue gas B that meets the standard emission through the CEMS monitoring data, and can input the flow signal to participate in the adjustment of the baffle door opening; if the CEMS value at the outlet exceeds 100mg/ Nm ³ (can be set), then output an analog signal to adjust the baffle door, reduce the opening to reduce the flow of flue gas B; if the outlet CEMS value is far less than 100mg/Nm ³ (can be set), then output The analog signal is used to adjust the baffle door, increase the opening to increase the flow of flue gas B, and reduce the flow of flue gas A that needs to be heated to reduce the heating consumption.

The main function of the gas-gas heat exchange device in the system of the present invention is to exchange heat between flue gas before denitration and flue gas after denitration. The temperature of the flue gas before denitrification is usually only 100-150°C, and the flue gas after denitrification is high-temperature flue gas. On the one hand, it can significantly increase the temperature of the flue gas before denitration and reduce the temperature rise of the flue gas by exchanging heat with the low-temperature flue gas before denitrification. The load of the device can reduce energy consumption. On the other hand, the temperature of the high-temperature flue gas after heat exchange can meet the requirements of the subsequent wet desulfurization device.

The gas-gas heat exchange device of the present invention is a conventional heat exchanger. Those skilled in the art can determine according to heat exchange requirements. In some embodiments of the present invention, the gas-gas heat exchange device seals the flue gas inlet and outlet and uses a fan-shaped plate regulating device. This gas-gas heat exchange device can strictly control the leakage rate < 2%, which not only improves the heat exchange efficiency, but also ensures that the _NOx concentration of the clean flue gas reaches the standard. This is mainly because the gas-gas heat exchanger is used to remove The high temperature of the purified flue gas after NO _x is used to exchange the heat of the original flue gas. The lower the leakage rate of the gas-gas heat exchanger, it can ensure that the purified flue gas after removing NO _x will not be polluted by the original flue gas, and ensure that the NO _x reaches the standard .

The main function of the flue gas temperature raising device of the present invention is to increase the temperature of the flue gas before denitrification, and the medium-high temperature selective catalytic reduction denitrification reactor needs to raise the temperature of the flue gas to 300-320°C for effective removal. The temperature of the sintering flue gas is only 100-150°C, so it needs to be heated. The flue gas temperature raising device of the present invention is a conventional temperature raising device, and those skilled in the art can choose it reasonably according to the needs of on-site operating conditions. In some embodiments of the present invention, the flue gas temperature raising device is composed of a burner, a valve group, a control system, a combustion chamber, a mixing chamber and an auxiliary pipeline system, etc. The ability to reach the temperature required for medium and high temperature denitrification reaction. The heating raw material of the flue gas temperature raising device of the present invention can adopt coal gas, natural gas, electricity, etc.; because the present invention is applicable to the sintering plant of iron and steel enterprises, the coal gas in the plant is abundant, and the cost is relatively low, so the present invention chooses to use coal gas as the temperature raising of raw material device as an example, of course other heating materials can also be selected.

The function of the ammonia injection device in the system of the present invention is to provide the reductant ammonia to the medium-high temperature selective catalytic reduction and denitration reactor to make it perform selective reduction and denitration reaction. It can use liquid ammonia or waste ammonia water as raw material to provide the ammonia needed for denitrification reaction.

The medium-high temperature selective catalytic reduction denitrification reactor described in the system of the present invention is an existing mature reactor, and a medium-high temperature selective catalytic reduction denitrification catalyst is used in the reactor. Catalyze the _NOx in it with a denitrification efficiency of not less than 90% to undergo a selective catalytic reduction denitrification reaction, thereby removing _NOx . These catalysts are conventional catalysts in this field, and they are commercially available, for example, they can be purchased from Shell Corporation, Corning Corporation Wait. In some medium and high temperature selective catalytic reduction and denitrification reactors, two layers of medium and high temperature selective reduction and denitrification catalysts and one spare catalytic layer can be installed. In addition, the reactor can also be equipped with diversion, ammonia injection, soot blowing And other auxiliary systems to ensure that the flue gas flow field in the device, the dynamic control of the reducing agent, and the pressure loss meet the actual needs. These components are conventional, and their connection relationship can be determined after flow field simulation according to actual operating conditions. Flow field simulation is a routine and essential step in reactor design.

The main function of the denitrification and heat exchange fan in the system of the present invention is to provide a solution to prevent the sintering flue gas from passing through the medium-high temperature selective catalytic reduction denitrification reactor, the gas-gas heat exchanger, and the flue gas temperature raising device. The power required for resistance. In addition, the denitrification and heat exchange fan can also assist the flow regulating device to adjust the flow of the sintering flue gas distributed to the main flue and the bypass flue.

The main function of the booster fan in the present invention is to provide power to overcome the resistance of flue gas passing through the desulfurization device and dust removal device.

The wet desulfurization device described in the present invention is an existing device, which can ensure desulfurization efficiency >98%. In some embodiments, the wet desulfurization device is a calcium desulfurization device or a magnesium desulfurization device.

The dust removal device of the present invention is an existing device, and in some embodiments, the dust removal device is a wet electrostatic precipitator. According to the actual situation of different enterprises, it can be arranged on the top of the desulfurization tower, or it can be arranged separately outside the desulfurization device. Generally speaking, the dust removal device is composed of corona wire (cathode wire), sedimentation electrode (anode tube), insulator chamber, power supply and flushing system, which are all conventional settings.

In another aspect, the present invention provides a method for denitrification and desulfurization of sintering flue gas, which uses the above-mentioned denitrification and desulfurization system for sintering flue gas, and includes the following steps:

All the sintering flue gas from the sintering machine after dust removal first enters the main flue, and when the temperature of the sintering flue gas is raised to the temperature required by the medium-high temperature selective catalytic reduction denitrification reactor, the flue gas is discharged online The monitoring system works, and feeds back the real-time monitored _NOx and _SO2 concentrations to the flow meter and the baffle door, so as to adjust the baffle door in time to adjust the distribution to the main flue and bypass flue The flow rate of the sintering flue gas, so that the _NOx and _SO2 at the flue gas outlet meet the emission requirements. During the working process of the sintering flue gas denitrification and desulfurization system, relying on the flow adjustment device and the denitrification and heat exchange fan, After dust removal from the sintering machine, the sintering flue gas is divided into two parts, flue gas A and flue gas B, wherein the flue gas A enters the main flue, and the flue gas B enters the bypass flue; the flue gas Gas A enters the gas-gas heat exchanger and heats up to the temperature required for the medium-high temperature selective reduction and denitrification reaction. If the flue gas A has not reached the required temperature after heat exchange through the gas-gas heat exchanger, The flue gas temperature raising device continues to raise the temperature, and the flue gas A undergoes a selective reduction reaction to remove _NOx in the medium-high temperature selective catalytic reduction denitrification reactor. During this process, the ammonia injection device The medium-high temperature selective catalytic reduction denitrification reactor is sprayed with reducing agent ammonia, and the high-temperature flue gas after denitrification is discharged from the outlet of the medium-high temperature selective catalytic reduction denitrification reactor and enters the gas-gas heat exchanger for heat exchange. , the flue gas after heat exchange passes through the denitrification and heat exchange fan and merges with the flue gas B entering the bypass flue, and the merged flue gas passes through the wet desulfurization device for desulfurization and the dust removal device for dedusting After the purified sintering flue gas is obtained, the flue gas emission online monitoring system monitors the concentration of NO _x and SO ₂ in the sintering flue gas in real time, and feeds it back to the flow meter and the baffle door to The baffle door is adjusted in time to adjust the flow of sintering flue gas distributed to the main flue and bypass flue, so that the _NOx and _SO2 at the flue gas outlet meet the emission requirements.

In the initial stage of the method of the present invention, since the medium-high temperature selective catalytic reduction denitrification reactor has not yet completed its function, the high-temperature flue gas after denitration cannot be produced, so the gas-gas heat exchanger cannot make the flue gas A before denitrification At this time, the temperature of the flue gas A needs to be raised by using the flue gas temperature raising device so that it reaches the temperature required by the medium-high temperature selective catalytic reduction denitrification reactor, but the process time is very short and will not consume Excessive energy consumption. After the high-temperature selective catalytic reduction denitrification reactor produces denitrification high-temperature flue gas, the temperature of the flue gas A before denitrification can be raised through the gas-gas heat exchanger. The flue gas A is raised to 270-290 °C, and the subsequent flue gas temperature raising device only needs to raise the temperature slightly, and consumes little energy to raise the temperature of the flue gas A to the level required by the usual medium-high temperature selective catalytic reduction denitrification reactor. 300 ~ 320 ℃, according to which can save a lot of energy consumption.

In some embodiments, the temperature of the sintering flue gas after dedusting in the present invention is 100-150°C, the concentration of SO ₂ in the sintering flue gas is 1000-1500 mg/Nm ³ , and the concentration of NO _x is 250-400 mg/Nm ³ . SO ₂ <50 mg/Nm ³ and NO _x <100 mg/Nm ³ in the sintering flue gas purified by the method of the present invention.

In some embodiments, the temperature required for the medium-high temperature selective catalytic reduction denitrification reactor is 300-320°C.

In some embodiments, the temperature of the denitrated flue gas after heat exchange is 140-150°C, and the temperature at which it merges with the flue gas B is 140-145°C.

In some embodiments, the temperature of the flue gas before denitrification is raised to 270-290° C. by the gas-gas heat exchanger, and then the temperature of the flue gas is raised to 300-320° C. by the flue gas temperature raising device.

Beneficial effect

The sintering flue gas denitrification and desulfurization system of the present invention is simple and newly built after the sintering flue, which can avoid the complex reconstruction project of the original main body flue of the sintering machine. The medium-high temperature selective catalytic reduction denitrification reactor and method can ensure a superior denitrification efficiency of more than 90%, which is safe and reliable, and is not affected by SO ₂ poisoning in the flue gas; the selected wet desulfurization process can ensure desulfurization efficiency. This makes the denitrification and denitrification rate of the present invention meet the emission limit value of the revised opinion list. At the same time, through the process design of the system content and the coordinated work of auxiliary equipment, while ensuring efficient denitrification conditions, the cost of energy consumption is greatly reduced, and the economic benefits are considerable. Therefore, with lower investment and operating costs, the operation stability of the entire system is improved, and the emission of NO _x and particulate matter in the sintering flue gas reaches or exceeds the latest national standards.

Description of drawings

Figure 1 is a schematic diagram of the sintering flue gas denitrification and desulfurization system in Embodiment 1 and Embodiment 2 of the present invention, and the symbols in the figure have the following meanings:

1: Gas-gas heat exchanger; 101: Flue gas inlet before denitration; 102: Flue gas outlet before denitration; 103: Flue gas inlet after denitration; 104: Flue gas outlet after denitration; 2: Flue gas temperature raising device; 3 : Ammonia injection device; 4: Medium-high temperature selective catalytic reduction denitrification reactor; 5: Denitrification and heat exchange fan; 6: Booster fan; 7: Wet desulfurization device; 8: Dust removal device; 9: Flow adjustment device; 10 : main flue; 11: bypass flue; 12: main flue; 13: online monitoring system for flue gas discharge.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, now in conjunction with specific embodiments and the technical solutions of the present invention are described in detail below, it should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention scope. In the examples, each original reagent material can be obtained commercially, and the experimental methods without specific conditions are conventional methods and conventional conditions well known in the art, or according to the conditions suggested by the instrument manufacturer.

Example 1

This embodiment provides a sintering flue gas denitrification and desulfurization system and its application. The schematic diagram of the sintering flue gas denitrification and desulfurization system is shown in Figure 1, which includes:

A gas-gas heat exchange device 1 for exchanging heat between flue gas before denitration and flue gas after denitration, which is provided with a flue gas inlet 101 before denitration, a flue gas outlet 102 before denitration, a flue gas inlet 103 after denitrification, and a flue gas inlet 103 after denitration Rear flue gas outlet 104;

A flue gas temperature raising device 2 for raising the temperature of the flue gas before denitrification;

Ammonia injection device 3, medium and high temperature selective catalytic reduction denitrification reactor 4, denitrification and heat exchange fan 5, booster fan 6, wet desulfurization device 7, dust removal device 8, flow adjustment device for chain adjustment of sintering flue gas distribution 9 and an online flue gas emission monitoring system 13 for real-time monitoring of NO _x and SO ₂ concentrations in the outlet flue gas;

The flow regulating device 9 includes a flow meter and a baffle door (not shown separately) that can electrically adjust its opening;

The total flue gas duct 12 from the sintering machine is divided into a main flue 10 and a bypass flue 11, and the baffle door and the flow meter are arranged on the bypass flue 11; the main flue 10 is in turn With the flue gas inlet 101 before denitration, the flue gas outlet 102 before denitration, the inlet and outlet of the flue gas temperature raising device 2, the inlet and outlet of the medium-high temperature selective catalytic reduction denitration reactor 3, the denitrification The rear flue gas inlet 103, the flue gas outlet 104 after the denitrification, and the inlet and outlet of the denitrification and heat exchange fan 5 are connected, and the main flue 10 then merges with the bypass flue 11 to form a main flue gas duct 12, and then the total flue gas channel 12 is connected with the inlet and outlet of the booster fan 6, the inlet and outlet of the wet desulfurization device 7 and the inlet of the dust removal device 8 in sequence, and the outlet of the dust removal device 8 is used as the purified The flue gas outlet, the flue gas discharge online monitoring system 13 is set on the flue gas outlet, and the flue gas discharge online monitoring system 13 is interlocked with the flow meter and the baffle door to monitor it in real time The NO _x and SO ₂ concentrations are fed back to the flow meter and the baffle door to adjust the baffle door in time to adjust the flow rate of the sintering flue gas distributed to the main flue and bypass flue, so that the flue gas The NO _x and SO ₂ at the outlet meet the requirements; the ammonia injection device 3 is connected to the medium-high temperature selective catalytic reduction denitrification reactor 4 to provide ammonia thereto.

In addition, this embodiment provides a method for denitrification and desulfurization of sintering flue gas, which applies the above-mentioned denitrification and desulfurization system for sintering flue gas, specifically, it includes the following steps:

All the sintering flue gas from the sintering machine after dust removal first enters the main flue, and when the temperature of the sintering flue gas is raised to the temperature required by the medium-high temperature selective catalytic reduction denitrification reactor, the flue gas is discharged online The monitoring system 13 works, and feeds back the _NOx and _SO2 concentrations monitored in real time to the flow meter and the baffle door, so as to adjust the baffle door in time to adjust the distribution to the main flue and bypass flue. The flow rate of the sintering flue gas in the duct, so that the _NOx and _SO2 at the flue gas outlet meet the requirements. During the work of the sintering flue gas denitrification and desulfurization system, rely on the flow regulating device 9 and the denitrification and heat exchange fan 5 , so that the sintering flue gas from the sintering machine after dust removal is divided into two parts, flue gas A and flue gas B, wherein the flue gas A enters the main flue 10, and the flue gas B enters the bypass flue 11; The flue gas A enters the gas-gas heat exchanger 1 and heats up to the temperature required by the medium-high temperature selective catalytic reduction denitrification reactor. If the flue gas A has not yet After reaching the required temperature, the flue gas temperature is continued to be raised through the flue gas temperature raising device 2, and the flue gas A undergoes a selective reduction reaction to remove _NOx in the middle-high temperature selective catalytic reduction denitrification reactor 4. During the process, the ammonia injection device 3 sprays the reducing agent ammonia to the medium-high temperature selective catalytic reduction denitrification reactor 4, and the high-temperature flue gas after denitration is discharged from the outlet of the medium-high temperature selective catalytic reduction denitrification reactor. Entering the gas-gas heat exchanger 1 for heat exchange, the flue gas after heat exchange passes through the denitrification and heat exchange fan 5 and merges with the flue gas B entering the bypass flue 11, and the merged flue gas The purified sintering flue gas is obtained after desulfurization by the wet desulfurization device 7 and dedusting by the dust removal device 8 in sequence, and the online monitoring system for flue gas emission monitors the concentrations of _NOx and _SO2 in the sintering flue gas in real time, And feed it back to the flow meter and the baffle door to adjust the baffle door in time to adjust the flow of sintering flue gas distributed to the main flue and bypass flue, so that the NO at the flue gas outlet _x and _SO2 fit the bill.

Specifically, the method of the present invention includes the following steps:

(a) After the sintering flue gas is dust-removed, the dust-removed sintering flue gas is obtained. The temperature of the flue gas is 100-150°C. First, all of it enters the main flue. When the required temperature of the catalytic reduction denitrification reactor is reached, the flue gas emission online monitoring system 13 works, and the _NOx and SO _{concentrations} detected by it in real time are fed back to the flow meter and the damper door, so as to Timely adjust the baffle door to adjust the flow of sintering flue gas distributed to the main flue and bypass flue, so that the NO _x and SO ₂ at the flue gas outlet meet the requirements, and the sintering flue gas denitrification and desulfurization system works In the process, the flue gas enters the main flue 10 and the bypass flue 11 by starting the flow regulating device 9 and the denitrification and heat exchange fan 5; part of the flue gas entering the main flue 10 is called flue gas A, and the flue gas entering the bypass flue The rest of the flue gas in the channel 11 is called flue gas B; the flue gas A flows through the gas-gas heat exchanger 1, the flue gas temperature raising device 2, and the medium-high temperature selective catalytic reduction denitrification reactor device 4 , the flue gas B enters the bypass flue 11.

(b) Feed in the coal gas, start the flue gas temperature raising device 2, at this time, the temperature of the sintering flue gas A is raised to 300-320°C by continuously raising the temperature, satisfying the requirement in the medium-high temperature selective catalytic reduction denitrification reactor 4 Temperature requirements for high temperature denitration catalysts.

(c) After flue gas A is heated by the flue gas temperature raising device, when the temperature before the inlet of the denitrification reactor exceeds 160°C, the gas-gas heat exchanger 1 is started, and the low-temperature flue gas and high-temperature flue gas flow countercurrently The way of heat exchange is that low-temperature flue gas flows from top to bottom, and high-temperature flue gas flows from bottom to top, so that the lower part of the gas-gas heat exchanger 1 becomes the hot end and the upper part becomes the cold end. The rotor is supported by support bearings at the cold end, which are connected to the central cylinder by trunnions.

(d) Open the ammonia injection device 3 before the denitrification reactor 4, the reductant _NH3 from the ammonia injection device 3 is sprayed into the denitrification reaction device 4, and the flue gas is discharged under the action of the medium-high temperature selective catalytic reductant NO _x removal in A.

(e) At this time, after the low-temperature flue gas passes through the gas-gas heat exchanger 1, the temperature rises to 270-290°C; reduce the gas supply of the flue gas heating device 2, and reduce the The working load of the heating device 2; after the high-temperature flue gas passes through the gas-gas heat exchanger 1, the temperature drops to 130-150°C, and the flue gas A and flue gas B are mixed and sent to the desulfurization device 7.

(f) The desulfurization device 7 is a wet desulfurization device suitable for this process route, and a calcium desulfurization device or a magnesium desulfurization device can be selected according to the actual situation, which can ensure a desulfurization efficiency >98%. The flue gas enters the wet absorption tower of the desulfurization device 7, and is in countercurrent contact with the alkaline slurry droplets sprayed from top to bottom, wherein the acidic oxide SO ₂ is absorbed and the flue gas is fully purified.

(g) The denitrification and heat exchange fan 5 and the booster fan 6 provide a boost for the flue gas to overcome the pressure loss of the system device. They are all equipped with frequency conversion motors, and the fan speed can be adjusted according to the actual production conditions of sintering to ensure normal production.

(h) Ammonia injection device 3 can use liquid ammonia or ammonia water as raw material, after being evaporated by ammonia evaporator, mixed with air and diluted to below 5%, sprayed into the medium-high temperature selective catalytic reduction denitrification reaction by ammonia injection grid The flue in front of device 4 provides the ammonia needed for the denitrification reaction.

(i) The flue gas emission online monitoring system monitors the concentration of _NOx and _SO2 in the sintering flue gas in real time, and feeds it back to the flow meter and the baffle door, so as to adjust the baffle in time The door thus regulates the flow of sintering flue gas distributed to the main flue and bypass flue, so that the NO _x and SO ₂ at the flue gas outlet meet the requirements.

Example 2

This embodiment provides more detailed step descriptions based on actual cases if the sintering flue gas denitrification and desulfurization system and method provided in Embodiment 1 are applied.

The existing 180m ² sintering machine with an annual output of 2 million tons, the flue gas volume is 1,260,000m ³ /h, the flue gas temperature is 100-120°C, the SO ₂ concentration is 1000-1500mg/Nm ³ , and the _NOx concentration is 300mg/Nm 3 Nm ³ . The method includes the following steps:

(a) All of them enter the main flue at first, and when the temperature of the sintering flue gas is raised to the temperature required by the medium-high temperature selective catalytic reduction denitrification reactor, the online monitoring system 13 for flue gas emission will work, Feedback the real-time monitored _NOx and _SO2 concentrations to the flow meter and the baffle door, so as to adjust the baffle door in time to adjust the sintering flue gas distributed to the main flue and bypass flue flow, so that the _NOx and _SO2 at the outlet of the flue gas meet the requirements. During the operation of the sintering flue gas denitrification and desulfurization system, relying on the coordinated adjustment of the flue gas regulating device 9 and the denitrification and heat exchange fan 5, In a certain period of time, the flow rate of flue gas A passing through the main flue 10 is 945000m ³ /h, and the flow rate of flue gas B passing through the bypass flue 11 is 315000m ³ /h;

(b) feed gas, start the flue gas temperature raising device 2, and raise the temperature of flue gas A; the present embodiment uses blast furnace gas as fuel;

(c) When the flue gas temperature rises to 160°C, start the gas-gas heat exchanger 1 to start heat exchange. This step is to ensure that the flue gas at the desulfurization inlet does not exceed 160°C, and reduce gas consumption at the same time;

(d) After _about 5 hours, the flue gas temperature at the denitrification inlet rises to 320°C, and the valve of the ammonia injection device 3 is opened to spray ammonia, and nitrogen oxides in the flue gas react with NH under the action of a catalyst; The catalyst can be a medium-high temperature denitration catalyst produced by Shell, Corning, etc. The amount of the denitration catalyst is about 181m ³ , and the denitration efficiency of the denitration treatment is >90%;

(e) The flue gas A after denitrification passes through the gas-gas heat exchanger 1 to reduce the temperature to 150°C, and after mixing with the flue gas B, the flue gas temperature is about 140°C, and then it is sent to the desulfurization device 7, sprayed Desulfurization agent is added to carry out desulfurization reaction; the obtained net flue gas is sent to the chimney for discharge; SO ₂ in the purified sintering flue gas is <50mg/Nm ³ , and NO _x <100mg/Nm ³ .

(f) In this embodiment, the blast furnace gas consumption is not more than 6300Nm ³ /h, the annual operating cost of the denitrification part is about 6.84 million yuan, and the denitrification cost per ton of sintered ore is only 3.39 yuan (excluding booster fan, desulfurization and dust removal ).

Although the present invention has been described in detail with general descriptions and specific embodiments above, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (8)

1. A sintering flue gas denitrification and desulfurization system, comprising: A gas-gas heat exchange device (1) for exchanging heat between flue gas before denitration and flue gas after denitration, which is provided with a flue gas inlet before denitration (101), a flue gas outlet before denitration (102), and a flue gas outlet after denitration Flue gas inlet (103) and denitrated flue gas outlet (104); A flue gas temperature raising device (2) for raising the temperature of the flue gas before denitrification; Ammonia injection device (3), medium-high temperature selective catalytic reduction denitrification reactor (4), denitrification and heat exchange fan (5), booster fan (6), wet desulfurization device (7), dust removal device (8), A flow regulating device (9) for chain adjustment of sintering flue gas distribution and an online flue gas emission monitoring system (13) for real-time monitoring of NO _x and SO ₂ concentrations in outlet flue gas; The flow regulating device (9) includes a flow meter and a baffle door capable of electrically adjusting its opening; The total flue gas passage (12) from the sintering machine is divided into a main flue (10) and a bypass flue (11), and the baffle door and the flow meter are arranged on the bypass flue (11) ; The main flue (10) is successively connected with the flue gas inlet (101) before the denitration, the flue gas outlet (102) before the denitration, the inlet and outlet of the flue gas temperature raising device (2), the middle The inlet and outlet of the high-temperature selective catalytic reduction denitration reactor (4), the inlet of the denitrated flue gas (103), the outlet of the flue gas after denitration (104), the inlet and outlet of the denitrification and heat exchange fan (5) connected, the main flue (10) then merges with the bypass flue (11) to form a total flue gas duct (12), and then the total flue gas duct (12) is sequentially connected with the booster fan (6 ), the inlet and outlet of the wet desulfurization device (7) and the inlet of the dedusting device (8) are connected, and the outlet of the dedusting device (8) is used as the outlet of the purified flue gas. The flue gas emission online monitoring system (13) is set on the outlet, and the flue gas emission online monitoring system (13) is interlocked with the flow meter and the baffle door, so that the _NOx and _SO2 that it monitors in real time The concentration is fed back to the flow meter and the baffle door to adjust the baffle door in time to adjust the flow of sintering flue gas distributed to the main flue (10) and bypass flue (11), so that the flue gas The _NOx and _SO2 at the gas outlet meet emission requirements; the ammonia injection device (3) is connected to the medium-high temperature selective catalytic reduction denitrification reactor (4) to provide ammonia thereto. 2. The sintering flue gas denitrification and desulfurization system according to claim 1, wherein the wet desulfurization device (7) is a calcium desulfurization device or a magnesium desulfurization device. 3. The sintering flue gas denitrification and desulfurization system according to claim 1, wherein the dust removal device (8) is a wet electrostatic precipitator. 4. A sintering flue gas denitrification and desulfurization method, which uses the sintering flue gas denitrification and desulfurization system described in any one of claims 1 to 3, and comprises the following steps: All the sintering flue gas after dedusting from the sintering machine enters the main flue (10), and when the temperature of the sintering flue gas is raised to the temperature required by the medium-high temperature selective catalytic reduction denitrification reactor (4), The flue gas emission on-line monitoring system (13) works, and feeds back the _NOx and _SO2 concentrations monitored in real time to the flow meter and the damper door, so as to adjust the damper gate in time to adjust the distribution To the flow of the sintering flue gas in the main flue (10) and the bypass flue (11), the NO _x and _SO at the flue gas outlet meet the emission requirements, and in the sintering flue gas denitrification and desulfurization system (13) During the working process, relying on the flow regulating device (9) and the denitrification and heat exchange fan (5), the sintering flue gas from the sintering machine after dedusting is divided into two parts, flue gas A and flue gas B, wherein the flue gas Gas A enters the main flue (10), and the flue gas B enters the bypass flue (11); the flue gas A enters the gas-gas heat exchanger (1) and heats up to a medium-high temperature selection The temperature required by the catalytic reduction denitrification reactor (4), if the flue gas A has not yet reached the required temperature after heat exchange through the gas-gas heat exchanger (1), through the flue gas temperature raising device ( 2) Continue to raise the temperature, the flue gas A undergoes a selective reduction reaction to remove _NOx in the medium-high temperature selective catalytic reduction denitrification reactor (4), during this process, the ammonia injection device (3) Spray the reductant ammonia to the medium-high temperature selective catalytic reduction denitrification reactor (4), and the flue gas after denitrification is discharged from the outlet of the medium-high temperature selective catalytic reduction denitrification reactor (4) and enters the gas- The gas heat exchanger exchanges heat, and the denitrification flue gas after heat exchange passes through the denitrification and heat exchange fan (5) and merges with the flue gas B entering the bypass flue (11), and the flue gas after confluence is sequentially After desulfurization by the wet desulfurization device (7) and dedusting by the dust removal device (8), the purified sintering flue gas is obtained, and the online monitoring system for flue gas emission (13) monitors the NO _x in the sintering flue gas in real time and the concentration of SO ₂ , and feed it back to the flow meter and the baffle door, so as to adjust the baffle door in time to adjust the amount of gas distributed to the main flue (10) and the bypass flue (11) The flow rate of sintering flue gas, so that the NO _x and SO ₂ at the flue gas outlet meet the emission requirements. 5. The method for denitrification and desulfurization of sintering flue gas according to claim 4, wherein the temperature required for the medium-high temperature selective catalytic reduction denitrification reactor (4) is 300-320°C. 6. The method for denitrification and desulfurization of sintering flue gas according to claim 4, wherein the temperature of the sintering flue gas after dust removal is 100-150°C, the concentration of SO ₂ in the sintering flue gas is 1000-1500 mg/Nm ³ , NO _{The x} concentration is 250-400 mg/Nm ³ . 7. The method for denitrification and desulfurization of sintering flue gas according to claim 4, wherein the temperature of the denitrification flue gas after the heat exchange is 140-150°C, and the temperature at which it merges with the flue gas B is 140-145°C . 8. The method for denitrification and desulfurization of sintering flue gas according to claim 4, wherein the temperature of the flue gas before denitrification after being heated by the gas-gas heat exchanger (1) is 270-290°C, and then the flue gas The temperature raising device (2) raises its temperature to 300～320°C.