CN116291809B - Control system and method for removing pollutants in tail gas by combining ammonia gas - Google Patents

Abstract

The present invention relates to the technical field of ship engine exhaust treatment, and specifically to a control system and method for removing pollutants in exhaust gas by combining ammonia. The control system for removing pollutants in exhaust gas by combining ammonia in the present application provides a reducing agent _NH3 through an ammonia supplier to react with NOx generated by an ammonia engine in an SCR reactor to remove nitrogen oxides in the engine exhaust gas. The gas after the SCR reaction enters the ammonia trap and is adsorbed in the ammonia storage material in the ammonia trap, thereby removing ammonia escaping from the ammonia engine and ammonia that has not reacted in the SCR reactor. The ammonia storage material that adsorbs a large amount of _NH3 gradually releases ammonia through heating regeneration in the ammonia supplier, and the bypass exhaust gas enters the ammonia supplier driven by a pump, driving the released ammonia to enter the SCR reactor to participate in the SCR reaction, thereby achieving full utilization of ammonia, thereby effectively removing _NH3 in the ship exhaust gas.

Description

A control system and method for removing pollutants from tail gas by combining ammonia

Technical Field

The invention relates to the technical field of ship engine exhaust gas treatment, and in particular to a control system and a method for removing pollutants in exhaust gas by combining ammonia.

Background technique

With the development of global economic globalization, shipping plays an increasingly important role in the development of the world economy. Most of the ships sailing now use carbon-containing fossil fuels, which will generate a large amount of _CO2 gas after combustion. In the field of shipping, the design concept of ammonia engines using ammonia as fuel is becoming more and more popular, and most researchers have carried out design research on ammonia engines. Ammonia engines use ammonia as fuel for combustion and work. Due to the engine cylinder structure and different workloads, there will be incomplete combustion of ammonia, causing ammonia escape. In addition, ammonia engines will inevitably generate a large amount of NOx pollutants. The main methods to reduce _NH3 and _NOX emissions are to improve the combustion strategy inside the engine and install an external removal device.

The most widely used traditional _NOx removal method outside the engine is the selective catalytic reduction technology (SCR). The ship SCR technology is that the _NH3 generated by the decomposition of urea in the urea aqueous solution reacts with the _NOx in the ship exhaust gas on the surface of the SCR system catalyst to generate _N2 , and the excess _NH3 is also oxidized to _N2 . At present, this technology is relatively mature, but there is another way to provide _NH3 , which uses solid ammonia storage materials instead of urea aqueous solution to provide the _NH3 required for the SCR reaction. At the same time, the ammonia storage material also has a strong ammonia adsorption capacity.

For example, application number CN201320618998.2 discloses a medium-pressure exhaust gas absorption system that can reduce the content in exhaust gas. It uses liquid absorption liquid to absorb ammonia in the exhaust gas. However, the absorption liquid needs to be analyzed when it is reused, which easily generates waste liquid. In addition, the tower design occupies a large space and the engine back pressure is relatively large.

Application No. CN201910189545.4 discloses a system and method for collaboratively removing sulfur trioxide, ammonia and fly ash from flue gas after SCR. For coal-fired boilers, by reducing the heat exchange area of the rotary air preheater, the flue gas outlet temperature of the rotary air preheater is increased to about the dew point temperature of NH ₄ HSO ₄ , and the NH ₃ and SO ₃ in the flue gas are used to condition the coal ash particles, so that NH ₄ HSO ₄ is generated on the surface of the ash particles. NH ₄ HSO ₄ is sticky, so that the particles are gradually generated, and finally the particles are removed, and NH ₃ and SO ₃ are removed at the same time. However, ammonia engines are different from coal-fired boilers and contain almost no sulfides. Therefore, the principle of generating NH ₄ HSO ₄ to attach particles and then remove them together does not work.

Therefore, it is very necessary to develop a control system and method for removing pollutants from tail gas by combining ammonia with small size, low cost and good effect.

Summary of the invention

The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a control system and method for removing pollutants in tail gas by combining ammonia.

To achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a control system for removing pollutants in tail gas by combining ammonia, comprising an SCR reactor and a controller, wherein an ammonia trap is connected to the gas outlet of the SCR reactor, an ammonia engine and an ammonia supplier are respectively connected to the gas inlet of the SCR reactor, a turbocharger is installed at the gas outlet of the ammonia engine, and the turbocharger is respectively connected to the SCR reactor and the ammonia supplier through pipelines; a first NOx sensor, a first NH ₃ sensor and a flow sensor are installed on the pipeline between the turbocharger and the SCR reactor, a pump is connected to the gas outlet of the ammonia trap, the gas outlet of the pump is connected to the gas inlet of the ammonia supplier through a pipeline, and the gas outlet of the ammonia supplier is connected to the gas inlet of the SCR reactor through a flow controller;

The controller is electrically connected to the first NOx sensor, the first _NH3 sensor, the flow sensor, the pump, and the flow controller respectively, and is used to control the pump and the flow controller according to the parameters obtained by the first NOx sensor, the first _NH3 sensor and the flow sensor to deliver matching ammonia-containing gas into the SCR reactor.

Furthermore, a second NOx sensor and a second NH ₃ sensor are installed on the outlet pipe of the ammonia trap, and the second NOx sensor and the second NH ₃ sensor are electrically connected to the controller respectively.

Furthermore, the SCR reactor is a cylindrical barrel structure, and the SCR reactor of the cylindrical barrel structure includes an SCR air inlet, a first rectifier plate, a first metal grid and a metal mesh, a catalyst, and an SCR air outlet which are arranged in sequence.

Furthermore, the ammonia trap is in a cylindrical barrel structure, and the ammonia trap in the cylindrical barrel structure includes a trap air inlet, a second rectifying plate, a second metal grid and a metal mesh, a first ammonia storage material, and a trap air outlet which are arranged in sequence.

Furthermore, the first ammonia storage material is a solid material having a three-layer structure and is placed horizontally.

Furthermore, the first ammonia storage material includes one or more of an inorganic salt material and a porous material; the inorganic salt material includes one or more of MgCl ₂ and CaCl ₂ ; the porous material includes one or more of zeolite, alumina, and a porous material loaded with an ionic liquid.

Furthermore, the ammonia supplier includes a first cavity layer and a second cavity layer, the second cavity layer is located in the first cavity layer, and the first cavity layer is provided with an exhaust gas bypass inlet and an exhaust gas bypass outlet; the second cavity layer is provided with an ammonia supply inlet, a third rectifier plate, a pressure sensor, a temperature sensor, a stainless steel metal mesh, a heating unit, a second ammonia storage material, and an ammonia supply outlet.

Furthermore, trumpet-shaped gas expansion areas are provided in the SCR reactor, the ammonia trap and the ammonia supplier.

Furthermore, a turbocharger is installed on the pipeline at the gas outlet end of the SCR reactor.

A control method for removing pollutants from tail gas by combining ammonia, using the above control system for removing pollutants from tail gas by combining ammonia, the method is as follows:

S1. The controller calculates the gas flow rate and NH ₃ concentration required by the SCR reactor based on the exhaust volume, NOx concentration and NH ₃ concentration of the turbocharger;

S2. The controller obtains the required amount of _NH3 according to the temperature, pressure and ammonia release spectrum of the second ammonia storage material; and automatically controls the pump, the heating unit and the flow controller according to the _NH3 amount to deliver the matching ammonia-containing gas into the SCR reactor;

S3, ammonia-containing gas and tail gas are mixed and enter the SCR reactor for SCR reaction;

S4. The tail gas after the reaction enters the ammonia trap. After the ammonia is adsorbed, the remaining gas is detected by the NOx sensor and _NH3 sensor, and is discharged into the atmosphere after meeting the Tier III emission regulations.

It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following beneficial effects:

1. The control system for removing pollutants from tail gas by combining ammonia with the present invention can remove _NH3 and NOx generated by the ammonia engine that are not completely burned and escape through the combined use of an SCR reactor and an ammonia trap, thereby meeting Tier III emission regulations.

2. The control system for removing pollutants from exhaust gas by combining ammonia of the present invention uses an ammonia supplier and an ammonia collector in combination, both of which use solid ammonia storage materials. After the ammonia storage material in the ammonia collector adsorbs ammonia, it can be placed in the ammonia supplier to act as an ammonia storage material to provide NH ₃ to the SCR reactor, thereby fully utilizing ammonia and effectively removing NH ₃ from the ship's exhaust gas.

3. The control system of the present invention for removing pollutants from tail gas by combining ammonia takes up less space and has lower equipment cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a control system for removing pollutants in tail gas in combination with ammonia in a preferred embodiment of the present invention;

FIG2 is a schematic structural diagram of an SCR reactor in a preferred embodiment of the present invention;

FIG3 is a schematic diagram of the structure of an ammonia trap in a preferred embodiment of the present invention;

FIG4 is a schematic diagram of the structure of an ammonia supplier in a preferred embodiment of the present invention;

FIG5 is a flow chart of a control method for removing pollutants from tail gas by combining ammonia with ammonia in a preferred embodiment of the present invention.

Reference numerals: 1, ammonia engine; 2, turbocharger; 3, first NOx sensor; 4, first NH ₃ sensor; 5, flow sensor; 6, SCR reactor; 7, ammonia trap; 8, second NOx sensor; 9, second NH ₃ sensors; 10, flow controller; 11, ammonia supplier; 12, controller; 13, pump; 14, SCR air inlet; 15, first rectifier plate; 16, first metal grid and metal mesh; 17, catalyst; 18, SCR air outlet; 19, collector air inlet; 20, second rectifier plate; 21, second metal grid and metal mesh; 22, first ammonia storage material; 23, collector air outlet; 24, exhaust gas bypass inlet; 25, ammonia supply inlet; 26, third rectifier plate; 27, pressure sensor; 28, temperature sensor; 29, stainless steel metal mesh; 30, heating unit; 31, second ammonia storage material; 32, exhaust gas bypass outlet; 33, ammonia supply outlet.

Detailed ways

The technical solutions in the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

1-4, a preferred embodiment of the present invention is a control system for removing pollutants from tail gas by combining ammonia, comprising an SCR reactor 6 and a controller 12, wherein an ammonia trap 7 is connected to the outlet end of the SCR reactor 6, and an ammonia engine 1 and an ammonia supplier 11 are respectively connected to the inlet end of the SCR reactor 6, and a turbocharger 2 is installed at the outlet end of the ammonia engine 1, and the turbocharger 2 is respectively connected to the SCR reactor 6 and the ammonia supplier 11 through pipelines; a first NOx sensor 3, a first _NH3 sensor 4 and a flow sensor 5 are installed on the pipeline between the turbocharger 2 and the SCR reactor 6, a pump 13 is connected to the outlet end of the ammonia trap 7, and the outlet end of the pump 13 is connected to the inlet end of the ammonia supplier 11 through a pipeline, and the outlet end of the ammonia supplier 11 is connected to the inlet end of the SCR reactor 6 through a flow controller 10;

The controller 12 is electrically connected to the first NOx sensor 3, the first _NH3 sensor 4, the flow sensor 5, the pump 13, and the flow controller 10, respectively, and is used to control the pump 13 and the flow controller 10 according to the parameters obtained by the first NOx sensor 3, the first _NH3 sensor 4 and the flow sensor 5, and transport the matching ammonia-containing gas into the SCR reactor 6, so as to effectively remove nitrogen oxides in the ship's exhaust gas and meet the Tier III emission regulations. At the same time, it can effectively remove _NH3 in the ship's exhaust gas and realize recycling and reuse.

As a preferred embodiment of the present invention, it may also have the following additional technical features: a second NOx sensor 8 and a second NH ₃ sensor 9 are installed on the outlet pipe of the ammonia trap 7, and the second NOx sensor 8 and the second NH ₃ sensor 9 are respectively electrically connected to the controller 12. That is, the NOx sensor 8 and the NH ₃ sensor 9 are used to detect the exhaust gas after passing through the ammonia trap 7. When the concentration of NH ₃ detected is high, it means that the ammonia storage material 31 in the ammonia trap 7 may be fully adsorbed, and the second ammonia storage material 31 should be replaced layer by layer.

In this embodiment, the SCR reactor 6 is a cylindrical barrel structure, and the cylindrical barrel structure SCR reactor 6 includes an SCR air inlet 14, a first rectifying plate 15, a first metal grid and a metal mesh 16, a catalyst 17, and an SCR air outlet 18 arranged in sequence. Therefore, the reaction gas enters from the SCR air inlet 14, and a trumpet-shaped gas expansion area is set at the entrance of the inner channel to reduce the impact of the airflow on the catalyst 17. While the rectifying plate 15 is set in the inner channel to ensure the uniformity of the airflow field, a metal grid and a metal mesh 16 are also set to prevent larger ash particles from entering the catalyst 17 to cause blockage, and also reduce the accumulation of fine ash particles on the catalyst surface. NOx and NH ₃ react under the catalysis of the catalyst 17 to generate N ₂ , thereby removing the NH ₃ and the generated NOx that escape from the engine.

In this embodiment, the ammonia trap 7 is a cylindrical barrel structure, and the ammonia trap 7 of the cylindrical barrel structure includes a trap air inlet 19, a second rectifier 20, a second metal grid and a metal mesh 21, a first ammonia storage material 22, and a trap air outlet 23 arranged in sequence. That is, the trumpet-shaped gas expansion area, the second rectifier 20, the metal grid and the metal mesh 21 are arranged in the ammonia trap, and the functions are the same as those in the SCR reactor 6. The ammonia storage material 22 is a solid material, divided into three layers, and placed horizontally. The ammonia storage material 22 can be an inorganic salt material such as _MgCl2 , _CaCl2 , or a porous material such as zeolite, alumina, or a porous material loaded with ionic liquid.

In this embodiment, the ammonia supplier 11 includes a first cavity layer and a second cavity layer. The second cavity layer is located in the first cavity layer. The first cavity layer is provided with an exhaust gas bypass inlet 24 and an exhaust gas bypass outlet 32; the second cavity layer is provided with an ammonia supply inlet 25, a third rectifier plate 26, a pressure sensor 27, a temperature sensor 28, a stainless steel metal mesh 29, a heating unit 30, a second ammonia storage material 31, and an ammonia supply outlet 33. Therefore, the outer first cavity layer is used to heat the bypassed exhaust gas, increase the overall exhaust gas temperature, and promote the SCR reaction. The second ammonia storage material 31 is placed in the inner second cavity layer. The ammonia release rate of the second ammonia storage material 31 is different at different temperatures and pressures. Therefore, by controlling the temperature, pressure and gas flow rate of the second ammonia storage material 31, ammonia-containing gas with different _NH3 concentrations and different flow rates can be obtained. The relevant second ammonia storage material 31 pulse spectrum diagram regarding temperature, pressure and ammonia release amount is input into the controller 12, and the required _NH3 amount is known from the readings measured by the NOx sensor 3 and the _NH3 sensor 4 and the gas flow rate under the corresponding engine load. Then the controller 12 controls the pump 13, the heating unit 30 and the flow controller 10 to deliver matching ammonia-containing gas to the SCR reaction unit.

In this embodiment, trumpet-shaped gas expansion areas are provided in the SCR reactor 6, the ammonia trap 7 and the ammonia supplier, so as to ensure uniform gas field, reduce the impact and accumulation of ash particles on the filler, and extend the service life of the filler. At the same time, the SCR reactor 6 and the ammonia trap 7 have the same structure. In extremely special environments, the function of the device can be changed by simply changing the internal filling material.

In this embodiment, the turbocharger is installed on the pipeline at the outlet end of the SCR reactor. That is, the SCR reactor 6 of the present invention is not limited to being placed behind the turbocharger 2, but can also be placed in front of the turbocharger according to needs.

As shown in FIG5 , a control method for removing pollutants from tail gas by combining ammonia is provided. The control system for removing pollutants from tail gas by combining ammonia is as follows:

S1. The controller calculates the gas flow rate and NH ₃ concentration required by the SCR reactor based on the exhaust volume, NOx concentration and NH ₃ concentration of the turbocharger;

S2. The controller obtains the required amount of _NH3 according to the temperature, pressure and ammonia release spectrum of the second ammonia storage material; and automatically controls the pump, the heating unit and the flow controller according to the _NH3 amount to deliver the matching ammonia-containing gas into the SCR reactor;

S3, ammonia-containing gas and tail gas are mixed and enter the SCR reactor for SCR reaction;

S4. The tail gas after the reaction enters the ammonia trap. After the ammonia is adsorbed, the remaining gas is detected by the NOx sensor and _NH3 sensor, and is discharged into the atmosphere after meeting the Tier III emission regulations.

Thus, the combined use of the SCR reactor and the ammonia trap can remove the _NH3 and NOx generated by the incomplete combustion of the ammonia engine, meeting the Tier III emission regulations; and the combined use of the ammonia supplier and the ammonia trap, both of which use solid ammonia storage materials. After the ammonia storage material in the ammonia trap adsorbs ammonia, it can be placed in the ammonia supplier to act as an ammonia storage material to provide _NH3 to the SCR reactor, thereby fully utilizing the ammonia, thereby effectively removing _NH3 in the ship's exhaust gas.

Under the premise that no conflict occurs, those skilled in the art may freely combine and superimpose the above-mentioned additional technical features.

It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims (6)

1. A control method for removing pollutants from tail gas by combining ammonia, which is applied to a control system for removing pollutants from tail gas by combining ammonia, and is characterized by: The control system for removing pollutants in tail gas by combining ammonia comprises: an SCR reactor and a controller, wherein the outlet end of the SCR reactor is connected with an ammonia trap, the inlet end of the SCR reactor is respectively connected with an ammonia engine and an ammonia supplier, the outlet end of the ammonia engine is equipped with a turbocharger, and the turbocharger is respectively connected with the SCR reactor and the ammonia supplier through pipelines; a first NOx sensor, a first NH3 sensor and a flow sensor are installed on the pipeline between the turbocharger and the SCR reactor, a pump is connected with the outlet end of the ammonia trap, the outlet end of the pump is connected with the inlet end of the ammonia supplier through a pipeline, and the outlet end of the ammonia supplier is connected with the inlet end of the SCR reactor through a flow controller; The controller is electrically connected to the first NOx sensor, the first NH3 sensor, the flow sensor, the pump, and the flow controller, respectively, and is used to control the pump and the flow controller according to the parameters obtained by the first NOx sensor, the first NH3 sensor, and the flow sensor, so as to deliver the matching ammonia-containing gas into the SCR reactor; The ammonia trap is a cylindrical barrel structure, and the ammonia trap of the cylindrical barrel structure comprises an ammonia trap air inlet, a second rectifying plate, a second metal grid and a metal mesh, a first ammonia storage material, and a trap air outlet which are arranged in sequence; The ammonia supplier comprises a first cavity layer and a second cavity layer, wherein the second cavity layer is located in the first cavity layer, and the first cavity layer is provided with an exhaust gas bypass inlet and an exhaust gas bypass outlet; the second cavity layer is provided with an ammonia supply inlet, a third rectifier plate, a pressure sensor, a temperature sensor, a stainless steel metal mesh, a heating unit, a second ammonia storage material, and an ammonia supply outlet; wherein the heating unit is located in the first cavity layer, and the heating unit is arranged on the outer surface of the second cavity layer, the first cavity layer is used for heating the bypassed exhaust gas to increase the exhaust gas temperature, and the bypassed exhaust gas enters the SCR reactor through the exhaust gas bypass outlet to promote the SCR reaction; The turbocharger is installed on the pipeline at the air inlet end of the SCR reactor, that is, the SCR reactor is placed behind the turbocharger; Both the ammonia supplier and the ammonia collector use solid ammonia storage materials. After the ammonia storage material in the ammonia collector absorbs ammonia, it is placed in the ammonia supplier to act as an ammonia storage material to provide NH3 to the SCR reactor; A second NOx sensor and a second NH3 sensor are installed on the outlet pipe of the ammonia trap; The method of removing pollutants from tail gas by combining ammonia is as follows: S1. The controller calculates the ammonia-containing gas flow rate and NH3 concentration required by the SCR reactor according to the exhaust volume, NOx concentration and NH3 concentration of the turbocharger; S2. The controller obtains the required amount of NH3 according to the temperature, pressure and ammonia release spectrum of the second ammonia storage material; and automatically controls the pump, the heating unit and the flow controller according to the NH3 amount to deliver the matching ammonia-containing gas into the SCR reactor; S3, ammonia-containing gas and tail gas are mixed and enter the SCR reactor for SCR reaction; S4. The tail gas after the reaction enters the ammonia trap. After the ammonia is adsorbed, the remaining gas is detected by the second NOx sensor and the second NH3 sensor, and is discharged into the atmosphere after meeting the Tier III emission regulations. 2. The control method for removing pollutants from tail gas by combined ammonia according to claim 1 is characterized in that: the SCR reactor is a cylindrical barrel structure, and the SCR reactor of the cylindrical barrel structure comprises an SCR air inlet, a first rectifier plate, a first metal grid and a metal mesh, a catalyst, and an SCR air outlet arranged in sequence. 3. The control method for removing pollutants from tail gas by combined ammonia according to claim 2 is characterized in that: the first ammonia storage material has a three-layer structure and is placed horizontally. 4. The control method for removing pollutants from tail gas by combined ammonia according to claim 2 is characterized in that: the first ammonia storage material includes one or more of an inorganic salt material and a porous material; the inorganic salt material includes one or more of MgCl2 and CaCl2; the porous material includes one or more of zeolite, alumina, and a porous material loaded with ionic liquid. 5. The control method for removing pollutants in tail gas by combined ammonia according to claim 1, characterized in that: a trumpet-shaped gas expansion area is provided in the SCR reactor, the ammonia trap and the ammonia supplier. 6. The control method for removing pollutants in tail gas by combining ammonia as claimed in claim 1, characterized in that the second NOx sensor and the second NH3 sensor are electrically connected to the controller respectively.