Self-control urea solution cabinet for ship SCR (Selective Catalytic Reduction) system

Abstract

The utility model discloses a self-control urea solution cabinet for a ship SCR (Selective Catalytic Reduction) system, which comprises a urea solution cabinet body, the top of the urea solution cabinet body is respectively provided with a liquid injection port, a pressure sensor, a stirring motor, a pressure valve and a vacuum release valve, and an output shaft of the stirring motor extends into the urea solution cabinet body and is provided with a stirrer. A steam heating pipe, a liquid level sensor and a temperature sensor are further arranged in the urea solution cabinet body, flow adjusting valves are arranged at the input end and the output end of the steam heating pipe, the urea solution cabinet body is connected with a urea pump through a pipeline, the urea pump controls flow through an air compressor, and all the components are electrically connected with a PLC control system. The urea solution cabinet is comprehensively monitored and controlled in real time, so that remote monitoring and accurate ammonia spraying of the urea solution for the ship SCR system are realized, the NOx emission reduction rate of the SCR system is improved, the ammonia escape rate is reduced, and normal and efficient operation of the SCR system is ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of ships, in particular to an automatic control type urea solution cabinet for a ship SCR system. Background Art

[0002] With the continuous development of world trade and the further integration of economic globalization, the marine transportation industry is becoming more and more developed, and the pollution of ships to the atmosphere and marine environment is also increasing. In order to reduce marine pollution and protect the earth's environment, the IMO Marine Organization officially adopted the "NOx Technical Code", an amendment to Annex VI of the MARPOL 73 / 78 Convention, in October 2008, which stipulates the emission standards and emission control areas for marine NOx, and proposes three stages of NOx emission limit requirements, among which the third stage NOx emission limit requirement is 3.4g / kWh, which means that the reduction in the third stage emission limit must reach more than 80% of the first stage. In order to cope with the increasingly stringent NOx emission standards, reducing NOx emissions has become the focus of marine diesel engine manufacturers and ship-related scientific researchers. Among various NOx emission reduction measures, SCR technology has the highest denitrification rate, which can reach more than 90%. At present, only SCR technology can meet the requirements of the third stage NOx emission limit for marine diesel engines, and is the mainstream technology for nitrogen oxide emission reduction. With increasingly stringent environmental protection requirements, it has become a general trend to equip marine diesel engines with emission after-treatment devices, namely selective catalytic reduction (hereinafter referred to as SCR).

[0003] The power of marine diesel engines is relatively large, resulting in a large consumption of urea, and a large amount of urea solution will be stored on board. Due to the unique physical and chemical properties of urea, when the SCR system of marine diesel engines is widely used, how to safely and effectively store, use and monitor the SCR urea solution to ensure the safe, stable and green operation of ships will become one of the key issues facing the shipping industry. The present invention is aimed at the reducing agent for the SCR system of marine diesel engines, and proposes a new type of automatic control urea solution cabinet, which is intended to solve the two major problems of the current conventional SCR urea solution cabinet: (1) the theoretical calculation value of the ammonia injection amount is too high or too low, and it cannot be accurately matched with the actual demand, resulting in a decrease in the SCR denitrification rate and excessive ammonia escape rate; (2) the automation degree of the urea injection system is not high. When the unit load fluctuates greatly and the operating conditions need to be adjusted frequently, the inlet and outlet NOx will also change greatly, and the instantaneous exceeding of the standard phenomenon is serious. The automatic adjustment system cannot fully play its role, resulting in the outlet NOx value exceeding the standard, affecting the normal operation of the SCR system. Utility Model Content

[0004] The utility model aims to provide an automatic control urea solution cabinet for a ship SCR system in view of the defects and shortcomings of the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the utility model is: an automatic control urea solution tank for a ship SCR system, comprising a urea solution tank body, wherein the innovation lies in that a liquid injection port, a pressure sensor, a stirring motor, a pressure valve and a vacuum release valve are respectively arranged on the top of the urea solution tank body, the output shaft of the stirring motor extends to the inside of the urea solution tank body, and a stirrer is arranged, a steam heating pipe, a plurality of liquid level sensors and a plurality of temperature sensors are also arranged inside the urea solution tank body, a flow regulating valve is arranged at both the input end and the output end of the steam heating pipe, the urea solution tank body is connected to a urea pump through a pipeline, the urea pump adopts an air compressor to control the flow, the pressure sensor, the stirring motor, the pressure valve, the vacuum release valve, the liquid level sensor, the temperature sensor, the flow regulating valve, the urea pump and the air compressor are all electrically connected to a PLC control system, and the PLC control system is also electrically connected to a host computer.

[0006] Furthermore, a gas breathing port and a filter screen are arranged inside the liquid injection port.

[0007] Furthermore, the steam heating pipes are distributed in an S-shape or a serpentine shape.

[0008] Furthermore, the liquid level sensor and the temperature sensor are arranged alternately up and down.

[0009] Furthermore, the urea pump is provided with a self-blowing soot device.

[0010] After adopting the above structure, the utility model has the following beneficial effects:

[0011] 1. The utility model realizes remote monitoring and precise ammonia injection of urea solution for ship SCR system by real-time monitoring and control of urea solution cabinet in all aspects, improves NOx emission reduction rate of SCR system, reduces ammonia escape rate and ensures normal and efficient operation of SCR system;

[0012] 2. The utility model designs the monitoring and control system of the urea solution cabinet through the PLC control system and the host computer. On the basis of ensuring the physical and chemical properties of the urea solution and the safe operation of the urea storage tank, it proposes the automatic control technical strategy and method of the urea solution cabinet suitable for the SCR system of the ship diesel engine, and improves the automatic control and adjustment function of the urea solution cabinet used in the ship SCR system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the utility model.

[0014] Description of reference numerals:

[0015] 1 Urea solution cabinet body, 2 liquid injection port, 3 pressure sensor, 4 stirring motor, 5 pressure valve, 6 vacuum release valve, 7 stirrer, 8 steam heating pipe, 9 liquid level sensor, 10 temperature sensor, 11 flow control valve, 12 urea pump, 13 air compressor, 14-PLC control system, 15 host computer. DETAILED DESCRIPTION

[0016] The utility model is further described below in conjunction with the accompanying drawings.

[0017] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described here are only used to explain the utility model and are not used to limit the utility model.

[0018] See also Figure 1 A self-controlled urea solution tank for a ship SCR system comprises a urea solution tank body 1. A liquid injection port 2, a pressure sensor 3, a stirring motor 4, a pressure valve 5 and a vacuum release valve 6 are respectively arranged on the top of the urea solution tank body 1. The output shaft of the stirring motor 4 extends to the inside of the urea solution tank body, and a stirrer 7 is arranged. A steam heating pipe 8, a plurality of liquid level sensors 9 and a plurality of temperature sensors 10 are also arranged inside the urea solution tank body 1. A flow regulating valve 11 is arranged at both the input end and the output end of the steam heating pipe 8. The urea solution tank body 1 is connected to a urea pump 12 through a pipeline. The urea pump 12 uses an air compressor 13 to control the flow. The pressure sensor 3, the stirring motor 4, the pressure valve 5, the vacuum release valve 6, the liquid level sensor 9, the temperature sensor 10, the flow regulating valve 11, the urea pump 12 and the air compressor 13 are all electrically connected to a PLC control system 14. The PLC control system 14 is also electrically connected to a host computer 15.

[0019] Specific:

[0020] The urea solution tank body 1 is placed in a storage compartment in the hull structure, and the compartment is treated with anti-corrosion.

[0021] The urea solution cabinet body 1 is provided with a pressure valve 5 and a vacuum release valve 6, which can always keep the urea cabinet sealed. At the same time, the pressure can be automatically released when loading or unloading urea, so that the pressure in the urea cabinet compartment is always balanced. At the same time, a pressure sensor 3 is installed on the urea solution cabinet body 1 for pressure monitoring and alarm of the urea solution cabinet, which can realize remote monitoring and precise ammonia injection of the SCR system, and improve the nitrogen oxide emission reduction rate and automatic control capability of the SCR system.

[0022] A plurality of liquid level sensors 9 are installed on the inner wall of the urea solution tank body 1, which can output the liquid level signal to the PLC control system 14, effectively monitor the liquid level and solution storage status of the ship SCR system urea solution in real time, and can realize the alarm prompt function of high liquid level, low liquid level and very low liquid level, so as to ensure the safe operation of the urea solution tank.

[0023] A steam heating pipe 8 is installed in the urea solution cabinet body 1. Steam heating is adopted. The steam used is provided by the exhaust gas boiler and the fuel oil boiler on board to heat the urea solution. A steam flow regulating valve 11 is installed on the steam heating pipe 8 and connected to the PLC control system 14. The steam heating process is controlled by the PLC.

[0024] A plurality of temperature sensors 10 are installed on the inner wall of the urea solution cabinet body 1. The temperature is controlled by the PLC control system 14 so that the storage temperature of the urea solution in the urea solution cabinet is controlled between 2-50°C to ensure the safe and effective operation of the SCR system. If the temperature of the urea solution in the urea solution cabinet is too low, the urea will precipitate and crystallize, affecting the injection and operation of the urea; if the temperature is too high, the water in the urea solution will evaporate, the ammonia concentration will change, and the precise ammonia injection will be affected.

[0025] The urea solution cabinet body 1 is equipped with a stirrer 7, which is connected to the steam heating pipe 8 system. When the steam heating pipe 8 is working, the stirring motor 4 is started to rotate the stirrer 7, and the urea solution in the cabinet is stirred at a uniform speed to ensure that the temperature of the urea solution is uniform and prevent urea crystallization.

[0026] The urea solution cabinet body 1 and all parts in direct contact with the urea solution are made of stainless steel to prevent the metal material from reacting with trace ammonia in the urea solution to generate compounds that affect the operation of the SCR.

[0027] The PLC control system 14 performs all-round monitoring and management of the storage state, circulation and injection process of the urea solution and the steam-assisted heating process. The PLC control program calculates the theoretical ammonia injection amount according to the NOx concentration at the flue outlet and the required denitration rate, adjusts the ammonia injection system in real time through dynamic working conditions, and finds the optimal ammonia injection amount through the feedforward PID closed-loop control strategy to ensure the flue gas denitration rate and enhance the reliability, continuity and economy of the denitration system.

[0028] In view of the problem of low automation of traditional urea solution storage tanks, the utility model uses a PLC control system to monitor and automatically control key parameters such as temperature, pressure, and liquid level of the urea solution storage tank in real time, and combines the PLC control system, the host computer and the entire SCR system to perform closed-loop control and adjustment according to the ammonia injection demand and the actual ammonia injection amount, thereby realizing comprehensive regulation and precise ammonia injection, improving the nitrogen oxide emission reduction rate of the SCR system, and enhancing the automatic control and regulation capabilities of the urea solution cabinet.

[0029] Aiming at the hysteresis of traditional closed-loop control, the utility model adopts closed-loop PID control plus feedback control technology to carry out comprehensive control design for the monitoring and control of urea solution cabinets. Based on PLC control system and LabVIEW software, an automatic control urea cabinet and a monitoring and testing platform of a host computer are developed, and an automatic control technology of urea solution cabinet suitable for the SCR system of ship diesel engines is proposed, which improves the automatic control and adjustment function of urea solution used in the ship SCR system and ensures the normal operation of the SCR system.

[0030] In this embodiment, a gas breathing port and a filter are provided inside the liquid injection port 2. The breathing port is kept sealed to prevent too low a vacuum degree from being generated, thereby reducing the evaporation rate or crystallization rate of the urea solution; the filter prevents impurities from entering the urea solution tank, thereby affecting the quality of urea and the normal operation of the urea injection system.

[0031] In this embodiment, the steam heating pipe 8 is distributed in an S-shape or a serpentine shape, which increases the contact area with the solution and prolongs the retention time of the steam, thereby improving the heating efficiency.

[0032] In this embodiment, the liquid level sensor 9 and the temperature sensor 10 are arranged alternately up and down, so as to realize real-time monitoring of the solution.

[0033] In this embodiment, the urea pump 12 is provided with a self-blowing device. The self-blowing device is a blower, which can blow soot to the urea pump 12.

[0034] The working principle of this utility model:

[0035] The urea solution cabinet stores 40% urea solution for ammonia spraying in the SCR system. Depending on the distance of the voyage, the corresponding demand and surplus urea solution are equipped. The PLC control system accurately controls the unit load and urea injection. When the unit is running at normal load and the SCR inlet flue gas temperature exceeds 295°C, the device is started to spray ammonia into the SCR reactor; when the unit load is too low and the SCR inlet flue gas temperature is lower than 295°C, the urea injection is stopped to prevent the catalyst activity from decreasing and a large amount of ammonium salts from being generated, and to prevent the SCR catalyst from fouling.

[0036] The above description is only used to illustrate the technical solution of the utility model rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the utility model by ordinary technicians in this field should be included in the scope of the claims of the utility model as long as they do not depart from the spirit and scope of the technical solution of the utility model.

Claims

1. An automatic control urea solution tank for a ship SCR system, comprising a urea solution tank body, characterized in that: A liquid injection port, a pressure sensor, a stirring motor, a pressure valve and a vacuum release valve are respectively arranged on the top of the urea solution cabinet body. The output shaft of the stirring motor extends to the interior of the urea solution cabinet body, and a stirrer is arranged. A steam heating pipe, a plurality of liquid level sensors and a plurality of temperature sensors are also arranged inside the urea solution cabinet body. A flow regulating valve is arranged at both the input end and the output end of the steam heating pipe. The urea solution cabinet body is connected to a urea pump through a pipeline. The urea pump uses an air compressor to control the flow. The pressure sensor, the stirring motor, the pressure valve, the vacuum release valve, the liquid level sensor, the temperature sensor, the flow regulating valve, the urea pump and the air compressor are all electrically connected to a PLC control system, and the PLC control system is also electrically connected to a host computer.

2. The automatic urea solution cabinet for a ship SCR system according to claim 1, characterized in that: A gas breathing port and a filter screen are arranged inside the liquid injection port.

3. The automatic urea solution cabinet for a ship SCR system according to claim 1, characterized in that: The steam heating pipes are distributed in an S-shape or a serpentine shape.

4. The automatic urea solution cabinet for a ship SCR system according to claim 1, characterized in that: The liquid level sensor and the temperature sensor are arranged alternately up and down.

5. The automatic control urea solution cabinet for a ship SCR system according to claim 1, characterized in that: The urea pump is provided with a self-blowing soot device.

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