WO2021114084A1 - Energy-saving ultralow flue gas purification system for waste incineration - Google Patents

Abstract

An energy-saving ultralow flue gas purification system for waste incineration, comprising a high-speed rotary atomizer (1), a semi-dry reaction tower (2), a baghouse filter (8), an SCR reaction tower (9), a water medium type flue gas cooler (11), an induced draft fan (13), and a chimney (14). An upper portion of the semi-dry reaction tower (2) is provided with the high-speed rotary atomizer (1); a sodium bicarbonate dry powder injection device (6) and an activated carbon injection device (7) are provided on a flue between the semi-dry reaction tower (2) and the baghouse filter (8); and flue gas enters the SCR reaction tower (9) from the baghouse filter (8), and after the catalytic denitrified flue gas passes through the water medium type flue gas cooler (11) and is cooled to 130°C, the flue gas is discharged into the chimney (14) by means of the induced draft fan (13).

Description

Ultra-low purification system for energy-saving flue gas of garbage incineration Technical field

The invention relates to a waste incineration flue gas ultra-low emission system, which is a system for flue gas disposal, energy saving and consumption reduction, and low-temperature flue gas heat energy recovery and utilization.

Background technique

At present, the flue gas purification process of waste incineration power plants is mainly based on SNCR furnace denitration + semi-dry deacidification (lime slurry) + dry method (spare) + activated carbon adsorption + bag filter. The process combination is simple and fixed. The process can meet the emission requirements of GB18485-2014 and EU 2010/75/EU. However, in order to further strengthen the control of air pollutants in domestic waste incineration power plants, reduce the emission of major pollutants, improve the control of the atmospheric environment, and win the blueprint defense war, local environmental protection departments have discharged major pollutants on the basis of GB18485-2014. Put forward more stringent requirements.

Among them, the most common is the upgrading of the emission limit of nitrogen oxides. The "Control Standard for Pollutants from Domestic Waste Incineration" (GB18485-2014) requires that the emission limit of nitrogen oxides from waste incineration power plants reach 250mg/m ³ (daily average) , 300mg/m ³ (hourly average). Many provinces and cities across the country have issued more stringent standards by environmental protection departments. For example, Hainan Province requires a daily average value of 120mg/m ³ and an hourly average value of 150mg/m ³ ; comments from Fujian Province The draft requires a daily average value of 100mg/m ³ and an hourly average value of 120mg/m ³ ; Wuhan, Dongguan, and Henan Province require control below 100mg/m ³ ; some key areas in Shandong require control below 100mg/m ³ ; Nanjing and Shenzhen require control within 80mg/m ³ ; Zhejiang Ningbo, Hangzhou, Taizhou require 75mg/m ³ and so on.

In response to the improvement of the emission limit of nitrogen oxides, the company has carried out a certain combination of flue gas purification processes, which are mainly divided into two categories, one is low-temperature catalytic denitrification at 170～180℃, and the process is SNCR furnace denitrification + semi-dry Method deacidification (lime slurry) + dry method (standby) + activated carbon adsorption + bag filter + SGH+SCR (170～180℃); the other type is 230～240℃ medium temperature catalytic denitrification, the process is in SNCR furnace Denitrification + semi-dry deacidification (lime slurry) + dry method (spare) + activated carbon adsorption + bag filter + SGH + SCR (230 ~ 240 ℃) + GGH. In order to meet the reaction temperature of the catalyst, both processes need to add SGH and use steam to increase the flue gas temperature, which greatly wastes energy, increases the plant power consumption rate (the plant power consumption rate increases by about 5%), and reduces the total Plant efficiency.

Summary of the invention

The purpose of the present invention is to optimize the combined process of flue gas purification, reduce energy consumption, and improve the efficiency of the whole plant under the premise of meeting the current nitrogen oxide upgrading standard.

A waste incineration energy-saving flue gas ultra-low purification system is composed of SNCR furnace denitrification, semi-dry reaction tower deacidification, dry deacidification, activated carbon adsorption, bag filter, SCR catalytic denitrification, water medium heat exchanger, Composition of induced draft fan and chimney;

The flue gas generated by waste incineration enters the semi-dry reaction tower after denitration in the SNCR furnace and heat exchange in the waste heat boiler. The flue gas passes through the semi-dry reaction tower from top to bottom and is simultaneously atomized with the rotary atomization arranged on the top of the semi-dry reaction tower. _{The Na 2} CO ₃ droplets sprayed from the device are in full contact to cool down and remove acidic substances;

The activated carbon injection device and the dry powder injection device are arranged on the flue from the outlet of the semi-dry reaction tower to the inlet of the bag filter, and the activated carbon is injected to adsorb dioxins and heavy metals in the flue gas, and the dry powder is injected to supplement deacidification;

The reacted flue gas enters the bag filter, the tiny particles are captured, and the agent further reacts on the surface of the filter bag to improve the efficiency of deacidification and activated carbon adsorption;

The dust collected by the bag filter is transported to the ash silo by a conveyor; the flue gas at the outlet of the bag filter enters the SCR for catalytic denitrification, and the flue gas after catalytic denitrification enters the water-medium heat exchanger to cool down and then is discharged through the induced draft fan chimney.

Further, the reducing agent used for denitration in the SNCR furnace is urea or ammonia, and the reaction temperature is between 850°C and 1050°C.

Further, the temperature of the flue gas at the outlet of the waste heat boiler is not less than 220°C.

Further, the semi-dry reaction tower adopts a rotary atomizer, and the outlet temperature of the semi-dry method is controlled above 185°C.

Further, the semi-dry deacidification agent uses sodium carbonate, and is equipped with a sodium carbonate storage and slurry preparation system.

Further, the top of the semi-dry reaction tower is equipped with a cooling water system, and a two-fluid spray gun is used to atomize the cooling water. When the atomizer fails, it is used as an emergency cooling measure to protect the filter bag.

Further, the injection port of the dry deacidification is on the inlet flue of the bag filter; the dry deacidification agent is sodium bicarbonate, and the dry deacidification system is used as a backup system. Or it is activated during the maintenance of the atomizer.

Further, the activated carbon injection port is on the inlet flue of the bag filter.

Further, the bag filter adopts a 100% PTFE+PTFE film-coated filter bag and a high-pressure pulse cleaning method. The filter bag can operate stably and continuously at a temperature of 240°C.

Further, the SCR catalytic denitrification tower adopts a low-temperature catalyst, and the reaction temperature is in the range of 170-180°C.

Further, the water-medium heat exchanger is composed of a water-medium flue gas cooler and a water-medium flue gas heater, the material of the water-medium heat exchanger is 20G, and the water-medium smoke The gas cooler cools the flue gas to recover heat, reduces the flue gas temperature to 130° C. and discharges it into the chimney through an induced draft fan. The water-medium flue gas heater heats up the primary air.

When working, the ammonia or urea solution with a mass concentration of less than 5% is sprayed into the waste heat boiler flue at 850-1050°C, and under high temperature conditions, it undergoes a reduction reaction with NOx and converts to N ₂ to complete a primary denitrification. The flue gas at the outlet of the waste incineration waste heat boiler enters the semi-dry reaction tower from the upper part of the semi-dry reaction tower through the flue gas distributor. The inlet flue gas temperature of the reaction tower is controlled at 220 ℃, and the Na sprayed from the rotary atomizer arranged on the top of the tower ₂ CO ₃ droplets are in full contact to achieve the purpose of cooling down and removing acidic substances. The _{concentration of the Na 2} CO ₃ solution is controlled between 15-20%, and the amount of sprayed slurry is controlled according to the HCl/SO ₂ emission limit at the outlet of the bag filter. The temperature at the outlet of the semi-dry reaction tower is controlled at about 185°C, and the outlet temperature is controlled by adjusting the flow of cooling water. Priority is given to temperature control. When the temperature is controlled to 185°C, if the HCl/SO _{2 does} not meet the emission target, the dry process system is started to _{spray Na 2} HCO ₃ into the semi-dry reaction tower to the inlet flue of the bag filter to supplement deacidification. The top of the semi-dry reaction tower is equipped with a two-fluid atomizing spray gun cooling water system. When the atomizer fails, the water is sprayed to cool down and protect the rear filter bag.

The injection point of activated carbon powder and Na ₂ HCO ₃ powder is set in the flue duct from the semi-dry reaction tower to the inlet of the bag filter. The activated carbon powder can absorb Hg and other heavy metals in the flue gas, as well as dioxins and furans in the flue gas. Pollutants. The reacted flue gas enters the bag filter, the tiny particles are captured, and the agent further reacts on the surface of the filter bag to improve the efficiency of deacidification and activated carbon adsorption. The dust collected by the bag filter is transported to the ash silo by a conveyor. The filter material of the bag filter is made of 100% PTFE + 100% PTFE film, which has good acid resistance, alkali resistance, hydrolysis resistance, oxidation resistance, fatigue resistance, high temperature resistance and other characteristics. The coated filter material uses the formation of the primary dust layer to achieve surface filtration and achieve low emission requirements. At the same time, it also uses dust removal to maintain an ideal long-term stable operating pressure difference.

The temperature of the flue gas at the outlet of the bag filter is controlled above 180℃ to meet the reaction temperature of catalytic denitrification. It can directly enter the SCR reaction tower for secondary denitrification, and the flue gas after the denitrification reaction enters the water-based flue gas cooler for heat exchange After cooling to 130℃, it will be discharged into the chimney after the induced draft fan. The heat exchanged by the water-type flue gas heater can heat the primary air, realize the heat recovery and utilization, and improve the thermal efficiency.

Measures to save energy and reduce consumption

1. The reaction temperature of the low-temperature SCR catalyst is 170～180℃. In order to save steam, the temperature at the outlet of the semi-dry reaction tower needs to be controlled at 185℃. At this temperature, the efficiency of deacidification using slaked lime is low. The semi-dry deacidification in this invention Sodium carbonate is used as the agent, and sodium bicarbonate is used as the dry deacidification agent. The deacidification of sodium-based agents is less affected by the change of reaction temperature.

In order to meet the more stringent emission indicators when starting the furnace, replacing the atomizer or in the future, in addition to the semi-dry method of deacidification, this project also specially sets up a dry method of spraying sodium bicarbonate, so that the process will still fail. It can still meet the emission targets required by the European Union (2010/75/EU).

2. The filter bag of the bag filter is made of PTFE+PTFE coated filter bag, which has good temperature resistance and the highest temperature is 240℃.

3. The outlet temperature of the SCR reaction tower is above 175°C, and direct exhaust fumes cause a waste of heat energy. In the present invention, a water medium heat exchanger (also known as MGGH) is added after the SCR to use the waste heat of the flue gas to heat the primary air of the boiler. The primary air system of the boiler heats the primary air from ambient temperature to 220°C by saturated steam at the outlet of the steam drum. The quality of the steam parameters is high and the operating cost is high. The invention uses the waste heat of the flue gas to heat the primary air of the boiler and reduces the amount of saturated steam at the outlet of the steam drum. , Save high-grade energy, realize energy saving, and improve project efficiency.

Beneficial effect

The invention adopts a two-stage deacidification, that is, a combined process of "semi-dry method + dry method", and uses sodium-based deacidification agents to avoid the influence of reaction temperature on the deacidification system. The dry process system is a supplement to the semi-dry process system. When the atomizer fails or the semi-dry process fails to meet the standard, the supplementary deacidification is used. At the same time, the top of the semi-dry reaction tower is equipped with a two-fluid cooling water system to avoid the impact on the bag filter bag when the boiler outlet temperature exceeds 240 ℃ when the atomizer fails.

The present invention adopts a two-stage denitrification, that is, a combined process of "SNCR+SCR", injects a reducing agent into the furnace in the temperature range of 850 to 1050°C for selective non-catalytic primary denitrification, and the subsequent flue gas enters the SCR reaction tower at 180°C. Selective catalytic secondary denitrification is carried out under the reaction temperature condition. During the reaction process, by adjusting the denitration ratio of SNCR and SCR, the optimal nitrogen oxide emission index and the optimal investment and operation input are ensured.

The invention adopts a first-level dust removal, namely a bag type dust collector, and is matched with a PTFE+PTFE film-coated filter bag. The filter bag can ensure stable operation at a temperature below 240 DEG C and meet the requirements of the standard for dust removal.

The present invention adopts the secondary dioxin removal, that is, the "activated carbon injection + SCR catalysis" combined process, and the dioxin is adsorbed by spraying activated carbon into the front flue of the bag filter to complete the first dioxin removal In the present invention, a catalyst with both denitration and dioxin removal functions is selected to realize the secondary removal of dioxin in the SCR reaction tower.

The refuse incinerator flue gas of the present invention is a system for ultra-low emission power plant waste incineration flue gas purification process, the dust content of flue gas discharged 10mg / Nm ^3, chloride 10mg / Nm ^3, sulfur dioxide 35mg / Nm ³ , Nitrogen oxide 50mg/Nm ³ , Hydrogen fluoride 1mg/Nm ³ , Mercury measured average value 0.05mg/Nm ³ , Cadmium measured average value 0.03mg/Nm ³ , Lead measured average value 0.5mg/Nm ³ , Dioxins 0.05ngTEQ/m ³ . That is to meet and exceed the EU 2010 emission standards (EU flue gas emission standards (2010/75/EU)).

Description of the drawings

Figure 1 is a flow chart of an energy-saving ultra-low flue gas purification system for waste incineration according to the present invention.

Detailed ways

The present invention will be further described below through the embodiments and in conjunction with the drawings, but the present invention is not limited.

Example 1

The present invention is a waste incineration energy-saving flue gas ultra-low emission system. The system flow chart is shown in Fig. 1, including an SNCR denitrification device (not shown in the schematic diagram, which belongs to furnace denitrification), a semi-dry reaction tower 2, sodium carbonate Slurry system 4, atomizer cooling water system 3, two-fluid atomization cooling water system 5, sodium bicarbonate dry powder injection device 6, activated carbon injection device 7, bag filter 8, SCR reactor 9, ammonia water storage and injection device 10. Water-based flue gas cooler 11 (also known as MGGH11), water-based flue gas heater 12 (also known as MGGH12), induced draft fan 13, and chimney 14. The upper part of the semi-dry reaction tower 2 is provided with a high-speed rotary atomizer 1, the rotary atomizer 1 is connected with a sodium carbonate slurry system 4 and an atomizer cooling water system 3, and the top of the semi-dry reaction tower 2 is equipped with a two-fluid atomized cooling water system 5. The flue between the semi-dry reaction tower 2 and the bag filter 8 is equipped with a sodium bicarbonate dry powder injection device 6 and an activated carbon injection device 7; the flue gas enters the SCR reaction tower 9 from the bag filter 8, and the two are connected to the flue. The ammonia injection grid is connected to the ammonia water storage and injection device 10; the SCR reaction tower 9 is provided with a bypass flue, and the bypass flue is opened so that the bag dust removal 8 can be connected with the water-medium flue gas cooler 11, and the main purpose is to When the type dust collector has a leaky bag, the bypass will be activated to protect the SCR catalyst; the flue gas purification SCR reaction tower 9 after catalytic denitrification, the exhaust gas temperature is about 175℃, enters the water-based flue gas cooler 11 and is cooled to 130℃, and then passes through the induced draft fan 13 Discharge into the chimney 14. The water-type flue gas heater 12 uses the recovered heat to heat the primary air to realize the waste heat utilization of the flue gas, reduce the amount of saturated steam at the outlet of the steam drum, save high-grade energy, realize energy saving, and improve project benefits.

The flue gas treatment of Example 1:

The waste incineration flue gas energy-saving ultra-low emission system described in Example 1 is used to process the flue gas generated in the waste incineration process. The working route is as follows:

After denitration in the furnace, the flue gas discharged from the garbage incineration boiler enters the semi-dry reaction tower 2, and then passes through the high-speed rotary atomizer 1, the atomizer cooling water system 3, and the sodium carbonate slurry system 4, and then passes through the sodium bicarbonate dry powder injection After the device 6 and the activated carbon injection device 7, enter the bag filter 8.

Sodium bicarbonate spray dry method is used as a backup system to supplement deacidification, and the spray of activated carbon powder can adsorb dioxins and heavy metals. The reactants and products of the sodium bicarbonate spraying dry powder device 6 and the activated carbon spraying device 7 enter the bag filter 8 together with the flue gas, and form a filter cake layer on the surface of the filter bag of the bag filter 8 to further react and remove the flue gas Residual acidic substances, dioxins, heavy metals and other pollutants. The flue gas from the outlet of the bag filter 8 enters the SCR reaction tower 9, and the reducing agent ammonia is sprayed into the inlet flue of the SCR reaction tower 9, and enters the SCR reaction tower together with the flue gas, where it is catalyzed with NOx under the action of the catalyst Reduction reaction and catalytic removal of dioxins at the same time. The 175°C flue gas is cooled to 130°C by the water-medium flue gas cooler 11 and then discharged into the chimney 14 through the induced draft fan 13. The heat recovered by the water-medium flue gas cooler 11 is used to heat the primary air, which realizes energy saving and improves project benefits.

After being treated by the above-mentioned waste incineration flue gas ultra-low emission system, the discharged flue gas contains 10mg/Nm ³ of dust, hydrogen chloride 10mg/Nm ³ , sulfur dioxide 35mg/Nm ³ , nitrogen oxides 50mg/Nm ³ , hydrogen fluoride 1mg/Nm ³ , the average measured value of mercury is 0.05mg/Nm ³ , the average measured value of cadmium is 0.03mg/Nm ³ , the average measured value of lead is 0.5mg/Nm ³ , and the dioxins are 0.05ngTEQ/m ³ . That is, it meets and is lower than the EU flue gas emission standards (2010/75/EU).

Comparative implementation example 1

Taking a waste incineration power plant as an example, with the existing technology of "semi-dry deacidification + dry deacidification + activated carbon adsorption + bag filter + SGH + SCR" flue gas combined treatment process, pollutant emissions meet The comparison shall be conducted under the premise of the same standard requirements. The basic design parameters are shown in the table below.

When the emission index meets the environmental protection requirements, the energy-saving combined process of "SNCR + semi-dry method (sodium carbonate) + dry method (sodium bicarbonate) + activated carbon adsorption + bag filter + SCR + MGGH" of the present invention is adopted, which guarantees both The flue gas emission reaches the standard, and energy consumption can be reduced. The thermal efficiency of the whole plant can be increased by 0.75%.

Claims (10)

1. A waste incineration energy-saving flue gas ultra-low purification system is composed of SNCR furnace denitrification, semi-dry reaction tower deacidification, dry deacidification, activated carbon adsorption, bag filter, SCR catalytic denitrification, water medium heat exchanger, Composition of induced draft fan and chimney;

   The flue gas generated by waste incineration enters the semi-dry reaction tower after denitration in the SNCR furnace and heat exchange in the waste heat boiler. The flue gas passes through the semi-dry reaction tower from top to bottom and is simultaneously atomized with the rotary atomization arranged on the top of the semi-dry reaction tower. _{The Na 2} CO ₃ droplets sprayed from the device are in full contact to cool down and remove acidic substances;

   The activated carbon injection device and the dry powder injection device are arranged on the flue from the outlet of the semi-dry reaction tower to the inlet of the bag filter, and the activated carbon is injected to adsorb dioxins and heavy metals in the flue gas, and the dry powder is injected to supplement deacidification;

   The reacted flue gas enters the bag filter, the tiny particles are captured, and the agent further reacts on the surface of the filter bag to improve the efficiency of deacidification and activated carbon adsorption;

   The dust collected by the bag filter is transported to the ash silo by a conveyor; the flue gas at the outlet of the bag filter enters the SCR for catalytic denitrification, and the flue gas after catalytic denitrification enters the water-medium heat exchanger to cool down and then is discharged through the induced draft fan chimney.
2. The energy-saving waste incineration flue gas ultra-low purification system according to claim 1, wherein the reducing agent used for denitration in the SNCR furnace is urea or ammonia, and the reaction temperature is between 850°C and 1050°C.
3. An energy-saving waste incineration flue gas ultra-low purification system according to claim 1, wherein the temperature of the flue gas at the outlet of the waste heat boiler is not less than 220°C; the semi-dry reaction tower adopts a rotary atomizer, and the semi-dry reaction tower adopts a rotary atomizer. The outlet temperature of the dry process is controlled above 185°C.
4. The energy-saving waste incineration flue gas ultra-low purification system according to claim 1, wherein the semi-dry deacidification agent uses sodium carbonate, and is equipped with a sodium carbonate storage and slurry preparation system.
5. The energy-saving waste incineration flue gas ultra-low purification system according to claim 1, wherein the top of the semi-dry reaction tower is equipped with a cooling water system, and a two-fluid spray gun is used to atomize the cooling water.
6. The energy-saving waste incineration flue gas ultra-low purification system according to claim 1, wherein the spray inlet of the dry deacidification is on the inlet flue of the bag filter; the dry deacidification agent Sodium bicarbonate is selected, and the dry deacidification system is used as a backup system.
7. The energy-saving waste incineration flue gas ultra-low purification system according to claim 1, wherein the activated carbon injection port is on the inlet flue of the bag filter.
8. The waste incineration energy-saving flue gas ultra-low purification system according to claim 1, wherein the bag filter adopts a 100% PTFE+PTFE membrane filter bag and a high-pressure pulse cleaning method.
9. The energy-saving waste incineration flue gas ultra-low purification system according to claim 1, wherein the SCR catalytic denitrification tower adopts a low-temperature catalyst with a reaction temperature range of 170-180°C.
10. The energy-saving waste incineration flue gas ultra-low purification system according to claim 1, wherein the water-medium heat exchanger is composed of a water-medium flue gas cooler and a water-medium flue gas heater The water-based flue gas cooler cools the flue gas to recover heat, reduces the temperature of the flue gas to 130° C. and discharges it into the chimney through an induced draft fan, and the water-based flue gas heater heats up the primary air.

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