CN105498535A - A method and device for removing nitrogen oxides in marine diesel engine exhaust gas using sodium chlorite seawater solution - Google Patents

Abstract

The invention discloses a method for removing nitrogen oxides in marine diesel engine exhaust gas by using a sodium chlorite seawater solution, which comprises the following steps: 1. desulfurizing and dedusting; 2. carrying out denitration treatment; 3. waste liquid treatment: performing solid-liquid separation on the waste liquid obtained after desulfurization and dust removal treatment, mixing the obtained waste liquid with the waste liquid obtained after denitration treatment for reaction, wherein the pH value of the obtained mixed liquid is more than 6.5, and NO is₃ ^2-When the content of (B) meets the discharge requirement, the sewage is discharged into the sea. The invention also discloses a device for removing nitrogen oxides in the exhaust gas of the marine diesel engine by using the sodium chlorite seawater solution, which comprises a sodium chlorite solution water tank, a denitration spray tower, a desulfurization spray tower, a separation device, a mixed water tank and a seawater inlet pipe. The method has good denitration effect by utilizing the sodium chlorite seawater solution, can meet relevant emission requirements, ensures that the waste liquid after denitration treatment does not pollute the seawater, is favorable for reducing equipment cost and medicine cost, and is convenient for flexible arrangement of equipment and convenient to operate.

Description

A method and device for removing nitrogen oxides in marine diesel engine exhaust gas using sodium chlorite seawater solution

technical field

The invention relates to the fields of air pollution control and ship tail gas emission control, in particular to a method and a device for removing nitrogen oxides in ship diesel engine exhaust gas by using sodium chlorite seawater solution.

Background technique

With the development of international trade, the economy of ship transportation has become more and more obvious, resulting in more and more goods being transported by ship. However, many ships use low-quality fuel oil as fuel, and the pollution of marine diesel engine exhaust to the environment is becoming more and more serious. According to the data provided by Norway to the International Maritime Organization, the total amount of particle pollutants emitted by ships at sea every year is equivalent to half of the particle pollutants emitted by global automobiles, and the total amount of nitrogen oxides emitted by ships accounts for the total amount of nitrogen oxides emitted globally. The total amount of sulfur oxide gas emitted by ships accounts for about 4% of the world's total emissions. The air pollution caused by ship exhaust gas cannot be ignored, especially in port cities and dense waterway areas. The international community is paying more and more attention to the environmental pollution caused by ships.

At the 40th session of MEPC in September 1997, IMO passed the MARPOL73/78 1997 Protocol (including Annex VI - Rules for the Prevention of Air Pollution from Ships) and 8 resolutions. my country's "Comprehensive Emission Standards of Air Pollutants" was also implemented in 1997. In October 2008, the fifty-eighth meeting of MEPC adopted Resolution MEPC.176(58)—Amendment to the Annex of the 1997 Protocol to the "1973 International Convention for the Prevention of Pollution from Ships" as Amended by the 1978 Protocol (Revised MAPOL73/78 Annex VI), the amendment was deemed accepted on January 1, 2010, and entered into force by default on July 1, 2010. Regarding the requirements for nitrogen oxides, except for emergency devices, on ships built on or after January 1, 2000, the emission of nitrogen oxides for each marine diesel engine with an output power exceeding 130kW shall be within the following limit values: (1) Class I, ships constructed on or after January 1, 2000 and before January 1, 2011: ①17.0g/(kW·h), when n<130r/min; ②45.0×n ^{( -0.2)} g/(kW·h), when 130r/min≤n<2000r/min; ③9.8g/(kW·h), when n≥2000r/min. Where n is the rated speed of the diesel engine. (2) Class II, ships constructed on or after January 1, 2011: ①14.4g/(kW·h), when n<130r/min; ②44.0×n ^(-0.2) g/(kW·h) h), when 130r/min≤n<2000r/min; ③7.7g/(kW·h), when n≥2000r/min. (3) Class III, ships built on or after January 1, 2016: ①3.4g/(kW·h), when n<130r/min; ②9.0×n ^(-0.2) g/(kW·h) h), when 130r/min≤n<2000r/min; ③2.0g/(kW·h), when n≥2000r/min. For the requirements of sulfur oxides, the sulfur content of any fuel oil used on board shall not exceed the following limits: (1) before January 1, 2012, 4.5% m/m; (2) on and after January 1, 2012 , 3.5% m/m; (3) On and after January 1, 2020, 0.5% m/m. When a ship is operating in a sulfur emission control area (SECA), the sulfur content of the fuel used on board shall not exceed the following limits: (1) before July 1, 2012, 1.5% m/m; (2) July 1, 2012 On and after January 1, 2015, 1.0% m/m; (3) On and after January 1, 2015, 0.1% m/m. ECAs include the Baltic Sea area, the North Sea area and other areas designated by the MEPC, including port areas. Governments and shipping companies are seeking new solutions to the increasingly stringent requirements for exhaust emissions from ships.

In recent years, major marine equipment companies and scientific research institutes at home and abroad have increased their investment in ship exhaust gas denitrification and desulfurization technologies. Many patents on exhaust gas denitration technology have emerged. For example, in the patent "A Method and Device for Flue Gas Denitration" (Patent No. CN104258701A), an oxidant is used to oxidize NO into NO ₂ , and then an alkaline absorbent and water are used to absorb NO _2. Complete the denitrification process. The method of using oxidant and absorbent separately will increase the initial investment cost of the equipment, the cost of medicine will also increase accordingly, and the economy will be reduced. Moreover, the use of two sets of reaction devices will increase the floor area of the equipment, which is not conducive to flexible layout. In the patent "A device and method for desulfurizing and dust-removing ship exhaust by using seawater" (Patent No. CN102274682A), the desulfurized solution is mixed with seawater and discharged into the sea directly, and the pH value of the solution is difficult to meet the discharge requirement of greater than 6.5 . At the same time, the desulfurized solution contains a large amount of SO ₃ ^2- , which will be decomposed into SO ₂ again when directly discharged into seawater, causing secondary pollution.

Contents of the invention

According to the technical problems raised above, a method and device for removing nitrogen oxides in marine diesel engine exhaust gas using sodium chlorite seawater solution are provided.

The technical means adopted in the present invention are as follows:

A method of using sodium chlorite seawater solution to remove nitrogen oxides in marine diesel engine exhaust gas has the following steps:

S1. Desulfurization and dust removal treatment: pump seawater into the desulfurization spray tower, and perform desulfurization and dust removal treatment on the exhaust gas from the diesel engine;

S2. Denitrification treatment: mix sodium chlorite aqueous solution with a solute mass fraction of 10%-40% with seawater to obtain sodium chlorite seawater solution, and then treat the obtained sodium chlorite seawater solution with desulfurization and dust removal to obtain The mixed reaction of exhaust gas, the _NOx content in the obtained exhaust gas is discharged when it is lower than 2.0g/(kW·h);

S3. Waste liquid treatment: The waste liquid obtained after desulfurization and dust removal treatment is subjected to solid-liquid separation treatment, particles and other impurities are separated, and the obtained waste liquid is mixed with the waste liquid obtained after denitrification treatment, and SO ₃ ^2- is oxidized to SO ₄ ^{2 -} , and increase the pH value at the same time. When the pH value of the obtained mixed liquid is greater than 6.5 and the content of NO ₃ ^2- meets the discharge requirements, it can be directly discharged into the sea.

The _NOx content in the waste gas obtained after denitrification treatment is monitored by a gas monitoring device, and according to the monitoring results, the amount of sodium chlorite aqueous solution with a solute mass fraction of 10%-40% is controlled when mixed with seawater, and the amount of NO x obtained after denitrification treatment is controlled. Whether the exhaust gas is discharged.

In the step S3, the pH value of the mixed liquid and the content of NO ₃ ^2- are monitored by a liquid monitoring device, and the mixing ratio of the waste liquid obtained after the solid-liquid separation treatment and the waste liquid obtained after the denitrification treatment is controlled according to the monitoring results, and the control Whether the mixed liquid is directly discharged into the sea.

The content of NO ₃ ^2- meeting the discharge requirement in step S3 is less than 60 mg/L.

The invention also discloses a device for removing nitrogen oxides in marine diesel engine exhaust gas by using sodium chlorite seawater solution, including sodium chlorite solution water tank, denitrification spray tower, desulfurization spray tower, separation device, mixed water cabinets, sludge tanks, seawater inlet pipes and seawater discharge pipes,

The seawater inlet pipe communicates with the spraying device of the denitrification spray tower through the filter and the seawater pump I sequentially,

The seawater inlet pipe communicates with the spray device of the desulfurization spray tower through the filter and seawater pump II in sequence,

A dosing pump is provided between the seawater pump I and the denitrification spray tower, and the dosing pump communicates with the sodium chlorite solution tank,

The top of the denitration spray tower is provided with a waste gas outlet, the waste gas outlet is provided with a gas monitoring device, the bottom of the denitration spray tower communicates with the mixing water tank, and the bottom of the side wall of the denitration spray tower It communicates with the top of the desulfurization spray tower, the bottom of the side wall of the desulfurization spray tower is provided with a waste gas inlet, the bottom of the desulfurization spray tower communicates with the separation device, and the separation device is respectively connected to the mixing The water tank is in communication with the sludge tank, the mixing water tank is provided with a stirring device and a liquid monitoring device, and the mixing water tank is in communication with the seawater drainage pipe through the seawater pump III.

The seawater pump I, the seawater pump II and the seawater pump III are all centrifugal pumps.

The dosing pump is a liquid dosing metering pump.

The spray device of the denitrification spray tower has one or more spray layers; the spray device of the desulfurization spray tower has one or more spray layers.

The separation device is a hydrocyclone.

The working principle of the device for removing nitrogen oxides in marine diesel engine exhaust gas using sodium chlorite seawater solution is that seawater enters the desulfurization spray tower through the filter and the seawater pump II, and is combined with the The exhaust gas of the diesel engine is mixed and reacted, the exhaust gas obtained enters the denitration spray tower, and the waste liquid obtained enters the separation device,

The sodium chlorite solution in the sodium chlorite solution water tank is mixed with the seawater pumped through the filter and the seawater pump I through the dosing pump, and enters into the denitrification spray tower to be mixed with The exhaust gas entering the denitrification spray tower is mixed and reacted, and the _NOx content in the obtained exhaust gas is monitored by a gas monitoring device. According to the monitoring results, the amount of sodium chlorite aqueous solution mixed with seawater is controlled, and whether the obtained exhaust gas is discharged , The waste liquid obtained enters in the mixing water tank.

The waste liquid in the separation device is treated by solid-liquid separation, and the obtained particles and other impurities enter the sludge tank, and the obtained waste liquid enters the mixed water tank, and enters the denitrification spray tower together with the denitrification spray tower. The waste liquid in the mixing water tank is mixed by the stirring device, the pH value of the obtained mixed liquid and the content of NO ₃ ^2- are monitored by the liquid monitoring device, and the waste liquid obtained after the solid-liquid separation treatment is controlled according to the monitoring results. The mixing ratio of the waste liquid entering the mixing water tank in the denitrification spray tower is controlled, and the seawater pump III is controlled to control whether the mixed liquid is directly discharged into the sea.

The present invention has the following advantages:

1) The denitrification effect of sodium chlorite seawater solution is better, which can meet the relevant discharge requirements, and it is easier for ships to obtain seawater, and the waste liquid after denitrification treatment has no pollution to seawater;

2) Both the oxidation of NO and the absorption of NO _X can be completed by sodium chlorite seawater washing liquid, which is beneficial to reduce equipment costs and drug costs, and is convenient for flexible arrangement of equipment;

3) The waste liquid obtained after the desulfurization and dust removal treatment is subjected to solid-liquid separation treatment, and the waste liquid obtained after the denitration treatment is mixed with the waste liquid obtained after the denitrification treatment, and the unexhausted sodium chlorite can be used to oxidize the SO ₃ ^2- in the mixed solution , to replace the aeration process, prevent secondary pollution caused by SO ₃ ^2- escaping from SO ₂ after discharge, and at the same time help to improve the pH value of the waste liquid obtained after solid-liquid separation treatment, simplify the experimental device and process, and efficiently Realize simultaneous desulfurization and denitrification;

4) According to the monitoring results of the gas monitoring device, the addition amount of the sodium chlorite aqueous solution with a solute mass fraction of 10%-40% can be controlled when mixed with seawater, and whether the exhaust gas obtained after the denitrification treatment is discharged;

According to the monitoring results of the liquid monitoring device, the mixing ratio of the waste liquid obtained after the solid-liquid separation treatment and the waste liquid obtained after the denitrification treatment can be controlled, and whether the mixed liquid is directly discharged into the sea;

5) The spray method is used, which has fast reaction speed and large gas _- liquid contact surface, which is beneficial to the absorption and reaction of _NOx and SO2. At the same time, the flue gas velocity is high and the resistance is small. The cross-sectional area of the spray scrubber is small and the space occupied Small;

6) The method has simple equipment and convenient operation, and can be widely used.

Based on the above reasons, the present invention can be widely promoted in the fields of air pollution control and ship tail gas emission control.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a kind of structural representation of the device that uses sodium chlorite seawater solution to remove nitrogen oxides in marine diesel engine exhaust gas in the specific embodiment of the present invention.

Wherein, the direction of the arrow in Fig. 1 is the flow direction of the medium.

detailed description

Example 1

A method of using sodium chlorite seawater solution to remove nitrogen oxides in marine diesel engine exhaust gas has the following steps:

S1. Desulfurization and dust removal treatment: pump seawater into the desulfurization spray tower, and perform desulfurization and dust removal treatment on the exhaust gas from the diesel engine;

S2. Denitrification treatment: mix sodium chlorite aqueous solution with a solute mass fraction of 10%-40% with seawater to obtain sodium chlorite seawater solution, and then treat the obtained sodium chlorite seawater solution with desulfurization and dust removal to obtain The mixed reaction of exhaust gas, the _NOx content in the obtained exhaust gas is discharged when it is lower than 2.0g/(kW·h);

S3. Waste liquid treatment: The waste liquid obtained after desulfurization and dust removal treatment is subjected to solid-liquid separation treatment, and the obtained waste liquid is mixed with the waste liquid obtained after denitrification treatment. The pH value of the obtained mixed liquid is greater than 6.5, and NO ₃ ^2- When the content meets the discharge requirements, it is directly discharged into the sea.

The _NOx content in the waste gas obtained after denitrification treatment is monitored by a gas monitoring device, and according to the monitoring results, the amount of sodium chlorite aqueous solution with a solute mass fraction of 10%-40% is controlled when mixed with seawater, and the amount of NO x obtained after denitrification treatment is controlled. Whether the exhaust gas is discharged.

In the step S3, the pH value of the mixed liquid and the content of NO ₃ ^2- are monitored by a liquid monitoring device, and the mixing ratio of the waste liquid obtained after the solid-liquid separation treatment and the waste liquid obtained after the denitrification treatment is controlled according to the monitoring results, and the control Whether the mixed liquid is directly discharged into the sea.

The content of NO ₃ ^2- meeting the discharge requirement in step S3 is less than 60 mg/L.

Example 2

As shown in Figure 1, a device for removing nitrogen oxides in marine diesel engine exhaust gas using sodium chlorite seawater solution, including sodium chlorite solution water tank 1, denitrification spray tower 2, desulfurization spray tower 3, hydraulic Cyclone 4, mixing water tank 5, sludge tank 6, seawater inlet pipe 7 and seawater drain pipe 8, the seawater inlet pipe 7 passes through the filter 9, seawater pump I10 and the spraying of the denitrification spray tower 2 in turn The device is connected, the seawater inlet pipe 7 is connected with the spraying device of the desulfurization spray tower 3 through the filter 9 and the seawater pump II11 in turn, and the seawater pump I10 and the denitrification spray tower 2 are provided with Liquid-adding metering pump 12, the liquid-adding metering pump 12 communicates with the sodium chlorite solution water tank 1, the top of the denitrification spray tower 2 is provided with a waste gas outlet 13, and the waste gas outlet 13 is provided with a gas Monitoring device 14, the bottom of the denitrification spray tower 2 communicates with the mixing tank 5, the bottom of the side wall of the denitrification spray tower 2 communicates with the top of the desulfurization spray tower 3, and the desulfurization spray tower 2 communicates with the top of the desulfurization spray tower 3. The bottom of the side wall of the tower 3 is provided with a waste gas inlet 15, and the bottom of the desulfurization spray tower 3 communicates with the hydrocyclone 4, and the hydrocyclone 4 is connected with the mixing water tank 5 and the waste water tank respectively. The mud tank 6 is connected, and the mixing water tank 5 is provided with a stirring device 16 and a liquid monitoring device 17 , and the mixing water tank 5 is connected to the seawater drain pipe 8 through a seawater pump III18.

The seawater pump I10, the seawater pump II11 and the seawater pump III18 are all centrifugal pumps.

The spray device of the denitrification spray tower 2 has a secondary spray layer; the spray device of the desulfurization spray tower 3 has a secondary spray layer.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (9)

1. use sodium chlorite sea water solution to remove a method for boat diesel engine nitrogen oxides of exhaust gas, it is characterized in that there are following steps:

S1, desulfurization and dedusting process: seawater is pumped in desulfuration spray tower, and desulfurization and dedusting process is carried out to the waste gas from diesel engine;

S2, denitration process: the sodium chlorite aqueous solution and the sea water mixing that by Solute mass fraction are 10%-40%, obtain sodium chlorite sea water solution, afterwards, by the waste gas hybrid reaction obtained after the sodium chlorite sea water solution obtained and desulfurization and dedusting process, NO in the waste gas obtained _xcontent is discharged lower than time 2.0g/ (kWh);

S3, liquid waste processing: the waste liquid obtained after desulfurization and dedusting process is through Separation of Solid and Liquid process, and the waste liquid hybrid reaction obtained after the waste liquid obtained and denitration process, the pH value of the mixing material obtained is greater than 6.5 and NO ₃ ^2-content when meeting emission request, directly enter marine.

2. method according to claim 1, is characterized in that: NO in the waste gas obtained after denitration process _xcontent is monitored by gas controlling device, addition when being sodium chlorite aqueous solution and the sea water mixing of 10%-40% according to monitoring result control Solute mass fraction, and whether the waste gas obtained after controlling denitration process discharges.

3. method according to claim 1, is characterized in that: the pH value of mixing material and NO in described step S3 ₃ ^2-content monitored by gas controlling device, the mixing ratio of the waste liquid obtained after the waste liquid obtained after controlling Separation of Solid and Liquid process according to monitoring result and denitration process, and control described mixing material and whether directly enter marine.

4. method according to claim 1, is characterized in that: the NO meeting emission request in described step S3 ₃ ^2-content for being less than 60mg/L.

5. the device using sodium chlorite sea water solution to remove boat diesel engine nitrogen oxides of exhaust gas, it is characterized in that: comprise sodium chlorite solution's water tank, denitration spray column, desulfuration spray tower, separator, mixing water tank, sludge tank, seawater water inlet pipe and seawater drainpipe

Described seawater water inlet pipe is communicated with the spray equipment of sea water pump I with described denitration spray column by filter successively,

Described seawater water inlet pipe is communicated with the spray equipment of sea water pump II with described desulfuration spray tower by described filter successively,

Be provided with dosing pump between described sea water pump I and described denitration spray column, described dosing pump is communicated with described sodium chlorite solution's water tank,

The top of described denitration spray column is provided with waste gas outlet, described waste gas outlet is provided with gas controlling device, the bottom of described denitration spray column is communicated with described mixing water tank, the sidewall bottom of described denitration spray column is communicated with the top of described desulfuration spray tower, the sidewall bottom of described desulfuration spray tower is provided with exhaust gas inlet, the bottom of described desulfuration spray tower is communicated with described separator, described separator is communicated with described sludge tank with described mixing water tank respectively, agitating device and liquid monitoring device is provided with in described mixing water tank, described mixing water tank is communicated with described seawater drainpipe by sea water pump III.

6. device according to claim 5, is characterized in that: described sea water pump I, described sea water pump II and described sea water pump III are centrifugal pump.

7. device according to claim 5, is characterized in that: described dosing pump is liquid feeding measuring pump.

8. device according to claim 5, is characterized in that: the spray equipment of described denitration spray column has one or more levels spraying layer; The spray equipment of described desulfuration spray tower has one or more levels spraying layer.

9. device according to claim 5, is characterized in that: described separator is hydrocyclone.