Diesel engine flue gas low-temperature eliminating system and operation method thereof

Abstract

The invention provides a diesel engine flue gas low-temperature eliminating system and an operation method thereof. The diesel engine flue gas low-temperature eliminating system comprises a flue gas-water pipe shell type heat exchanger, a flue gas spraying tower, an absorption type refrigerating system and a water-water plate type heat exchanger. Flue gas is cooled to 40-50 DEG C from 310-330 DEG C through the heat exchanger, then enters the spray tower, is in contact with low-temperature spray water at the temperature of 6-11 DEG C, then is cooled to 15-20 DEG C and is discharged, white smoke is eliminated, and the particulate matter removal rate is larger than or equal to 95%. The absorption refrigeration system is driven by waste heat of 80-90 DEG C, chilled water of 5-10 DEG C is prepared through refrigerant water circulation, and a closed loop is formed through plate exchange cooling spray water. The water system uses waste heat for refrigeration, heating and domestic hot water in sequence, the PH value (7-8.5), the flow and the temperature are dynamically adjusted in cooperation with the intelligent control system, waste heat utilization is achieved, and compared with a traditional system, energy is saved. According to the system, a comprehensive treatment system integrating waste heat gradient utilization, low-temperature purification and intelligent regulation and control is constructed, and the system has the characteristics of self-consistent energy, stable operation and efficient purification.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel engine exhaust gas treatment, and particularly to a low-temperature elimination system for diesel engine flue gas and its operation method. Background Art

[0002] Underground projects usually require concealed exhaust ventilation. As an important power supply equipment for underground projects, diesel generators generate a large amount of high-temperature flue gas and heat during operation, which need to be discharged outward. It is a technical problem to eliminate smoke and control the temperature of the flue gas. The commonly used treatment method at present is to use the stored water inside the project for spray smoke elimination and temperature reduction. However, the internal water temperature is usually stable throughout the year, and the temperature of the treated flue gas is also stable. But when the external air temperature changes, especially in winter when the temperature is low, the temperature difference between the treated flue gas and the external environment will become larger. This not only fails to meet the temperature discharge requirements but may also cause the "white smoke" phenomenon at the discharge port, which will affect the external environment and expose the location of the exhaust port. The heat is not effectively utilized, resulting in energy waste. Summary of the Invention

[0003] The purpose of the present invention is to provide a low-temperature elimination system for diesel engine flue gas and its operation method. By using an absorption refrigeration system, the waste heat of the diesel engine flue gas is converted into refrigeration energy, and low-temperature chilled water is prepared to deeply cool the flue gas, achieving low-temperature purification (15 - 20°C) without the white smoke phenomenon. At the same time, the waste heat is recovered for heating or domestic hot water.

[0004] According to an object of the present invention, the present invention provides a low-temperature elimination system for diesel engine flue gas, comprising:

[0005] A flue gas - water shell-and-tube heat exchanger, connected to the diesel engine exhaust port, for preliminarily cooling the 310 - 330°C high-temperature flue gas to 40 - 50°C;

[0006] A flue gas spray tower, connected to the outlet of the flue gas - water shell-and-tube heat exchanger, provided with a spray layer and a bottom water tank, and configured with 6 - 11°C low-temperature spray water;

[0007] An absorption refrigeration system, including a generator, a condenser, a throttle valve, an evaporator, an absorber, and a solution pump. The generator receives 80 - 90°C high-temperature hot water output from the flue gas - water shell-and-tube heat exchanger through a pipeline as a heat source;

[0008] A water - water plate heat exchanger, connected to the bottom water tank of the flue gas spray tower and the chilled water outlet of the evaporator, for cooling the spray water to 6 - 11°C;

[0009] A dosing device, for adjusting the pH value of the spray water;

[0010] A variable-frequency pump group, including a cooling water pump, a spray pump, and a dosing pump.

[0011] Further, the working process of the absorption refrigeration system includes:

[0012] The flow direction of the refrigerant water is as follows:

[0013] The weak solution heated by the heat source in the generator evaporates to generate refrigerant vapor. The refrigerant vapor flows through the condenser in sequence, is cooled into refrigerant water and flows out of the condenser, enters the evaporator through throttling by the throttle valve, is evaporated at low temperature again to become refrigerant vapor in the evaporator, and then flows to the absorber to be absorbed by the lithium bromide solution. The lithium bromide solution that absorbs the refrigerant vapor in the absorber comes from the concentrated lithium bromide solution in the generator;

[0014] The flow direction of the lithium bromide solution is as follows:

[0015] After the weak solution under the heating of the heat source in the generator evaporates the refrigerant vapor, it becomes a concentrated solution with a higher temperature. The concentrated solution flows out of the generator, is cooled by the solution plate heat exchanger, then enters the absorber and absorbs the refrigerant vapor from the evaporator, so that the concentration decreases and is transported back to the generator by the solution pump.

[0016] Further, the circulating path of the water system is as follows:

[0017] The cooling water conveyed by the cooling water pump flows through the evaporator in sequence to prepare chilled water;

[0018] The chilled water is heated up by the water-water plate heat exchanger and then enters the absorber to absorb the condensation heat and is heated up; after flowing out of the absorber, it enters the condenser for secondary heating; finally, the cooling water enters the flue gas-water shell-and-tube heat exchanger for heating, and the high-temperature water flowing out of the flue gas-water shell-and-tube heat exchanger enters the generator and finally outputs waste heat hot water after cooling down.

[0019] Further, the dosing device includes:

[0020] The pH meter monitors the pH value of the sprayed water in real time;

[0021] The lye storage tank is connected to the dosing pump;

[0022] When it is detected that the pH value is lower than 7, the PLC controller starts the dosing pump to inject NaOH solution until pH = 8.5.

[0023] Further, it further includes an intelligent control system. The intelligent control system includes a PLC controller, a temperature sensor, a pressure sensor and a pH meter, and the PLC controller is connected to each sensor and actuator.

[0024] Further, the intelligent control system executes:

[0025] The temperature sensor monitors the temperature of the sprayed water, the flue gas emission temperature and the cooling water temperature in real time;

[0026] Dynamically adjust the flow rate of the cooling water pump according to the change of the diesel engine power;

[0027] When the flue gas temperature exceeds 20 °C, increase the rotational speed and spray volume of the spray pump.

[0028] Furthermore, the solution heat exchanger is a plate heat exchanger, which cools the concentrated solution at 80 - 85 °C at the outlet of the generator to 40 - 45 °C and then sends it to the absorber.

[0029] Furthermore, the flue gas spray tower is provided with:

[0030] Multiple layers of swirl spray layers with a spray density of 8 - 12 m3 / (m 2 ·h);

[0031] The packing layer uses porous ceramic packing with a porosity ≥ 85%;

[0032] The demister is a two-stage baffle structure and is arranged at the outlet of the tower top.

[0033] Furthermore, the control strategy of the variable frequency pump group includes:

[0034] The frequency of the cooling water pump is controlled in linkage with the water temperature at the outlet of the evaporator;

[0035] The frequency of the spray pump is PID-regulated according to the flue gas emission temperature;

[0036] The chemical dosing pump adopts a pulsed chemical dosing method, and the single chemical dosing duration does not exceed 30 seconds.

[0037] According to another object of the present invention, the present invention provides an operation method for the above-mentioned diesel engine flue gas low-temperature elimination system, which is characterized by including:

[0038] Step 1: Cool the high-temperature flue gas to 40 - 50 °C through a shell-and-tube heat exchanger;

[0039] Step 2: Treat the medium-temperature flue gas with spray water at 6 - 11 °C in the spray tower and discharge it at 15 - 20 °C;

[0040] Step 3: The absorption refrigeration system uses hot water at 80 - 90 °C to prepare chilled water at 5 - 10 °C;

[0041] Step 4: The PLC controller adjusts the pH value of the spray water to 7 - 8.5 and the water temperature to 6 - 11 °C in real time;

[0042] Step 5: The 50 - 60 °C waste heat hot water output by the system is shunted to the heating, domestic hot water or cooling tower system.

[0043] The technical solution of the present invention realizes efficient energy recovery through multi-stage cascade utilization of waste heat. The high-temperature flue gas is gradually cooled to a certain temperature by a flue gas-water shell-and-tube heat exchanger, and combined with the ultra-low temperature spray water prepared by the absorption refrigeration system to achieve deep purification of the flue gas. The particulate matter removal rate is ≥95% and the "white smoke" phenomenon is eliminated; the waste heat is successively used to drive refrigeration, heating and domestic hot water through a closed-loop water system circulation, forming a self-balancing energy network. Cooperating with the intelligent control system to dynamically adjust the pH value, water temperature and flow rate, while realizing low-temperature emission of the flue gas, the waste heat utilization rate is improved, the operation energy consumption is reduced compared with the traditional system, and a comprehensive treatment system with self-consistent energy, high purification efficiency and stable operation is constructed. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0045] Figure 1 It is the system schematic diagram of the embodiment of the present invention; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined. In addition, the terms "installed", "connected", and "joined" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] Embodiment 1

[0050] As Figure 1 shown, a diesel engine flue gas low-temperature elimination system includes:

[0051] An absorption refrigeration system, including a generator, a condenser, an evaporator, an absorber, and a solution pump;

[0052] A flue gas spray tower for low-temperature spray purification of flue gas;

[0053] A flue gas - water shell-and-tube heat exchanger, connected to the diesel engine exhaust port, for preliminary cooling of flue gas;

[0054] A water - water plate heat exchanger, connected to the delay spray tower and the absorption refrigeration system, for cooling the spray water;

[0055] A dosing device for adjusting the pH value of the spray water;

[0056] A variable frequency pump group, including a cooling water pump (Pump 2), a spray pump (Pump 3), and a dosing pump (Pump 4);

[0057] A control cabinet, with a PLC controller built-in, for monitoring and adjusting the system operation parameters.

[0058] In this embodiment, the heat source of the absorption refrigeration system is the high-temperature hot water (80 - 90 °C) output by the flue gas - water shell-and-tube heat exchanger, which is used to heat the lithium bromide dilute solution to generate refrigerant vapor.

[0059] The temperature of the spray water in the flue gas spray tower is reduced to 6 - 11 °C through the water - water plate heat exchanger, and the temperature of the flue gas after spraying is reduced to 15 - 20 °C.

[0060] The dosing device includes a pH meter and a dosing pump, and automatically supplements alkaline liquid when the pH value of the spray water is lower than the set threshold.

[0061] The PLC controller dynamically adjusts the cooling water flow according to the temperature and pressure sensor data to match the change in diesel engine power.

[0062] The waste heat hot water (50 - 60 °C) output by the system is used for heating or domestic hot water, or is circulated and cooled through a cooling tower.

[0063] The diesel engine flue gas low-temperature elimination system of the present invention mainly includes the control processes of the following 5 parts:

[0064] 1. Flue gas treatment process: The high-temperature flue gas is cooled to 40 - 50 °C by a flue gas - water shell-and-tube heat exchanger, and then enters the flue gas spray tower, where it is further purified and cooled to 15 - 20 °C by low-temperature spray water (6 - 11 °C) and then discharged.

[0065] 2. Absorption refrigeration cycle:

[0066] Refrigerant water circulation: The generator uses the high-temperature hot water (80 - 90 °C) output by the heat exchanger to heat the lithium bromide dilute solution to generate refrigerant steam; the steam is liquefied by the condenser and then enters the evaporator to evaporate and absorb heat, forming low-temperature chilled water (5 - 10 °C).

[0067] 3. Solution circulation: The concentrated solution is cooled and then returned to the absorber to absorb the refrigerant steam, and after dilution, it is pumped back to the generator by the solution pump.

[0068] Specifically, as Figure 1 shown:

[0069] The flow direction of the refrigerant water (refrigerant steam) is:

[0070] The dilute solution heated by the heat source in the generator (the high-temperature hot water from the flue gas - water shell-and-tube heat exchanger) evaporates to generate refrigerant steam. The refrigerant steam flows through the condenser in sequence, is cooled into refrigerant water and flows out of the condenser, passes through the throttle valve and enters the evaporator, where it is evaporated at low temperature again to become refrigerant steam, and then flows to the absorber to be absorbed by the lithium bromide solution. The lithium bromide solution that absorbs the refrigerant steam in the absorber comes from the lithium bromide concentrated solution in the generator.

[0071] The flow direction of the lithium bromide solution is:

[0072] After the dilute solution heated by the heat source in the generator (the high-temperature hot water from the flue gas - water shell-and-tube heat exchanger) evaporates the refrigerant steam, it becomes a concentrated solution with a higher temperature. The concentrated solution flows out of the generator, is cooled by the solution plate heat exchanger, then enters the absorber and absorbs the refrigerant steam from the evaporator, thereby reducing the concentration and being transported back to the generator by the solution pump (pump 1).

[0073] The continuous circulation of the two flow directions enables the absorption refrigeration to proceed continuously.

[0074] 4. Water system circulation: The chilled water is cooled and sprayed by the water-water plate and then heated to 14-19°C. It then enters the absorber and condenser to absorb heat and finally returns to the flue gas-water shell and tube heat exchanger to complete the cycle.

[0075] Specifically, the cooling water delivered by the cooling water pump (pump 2) enters the evaporator of the absorption refrigeration system and is heat exchanged to prepare low-temperature chilled water of 5-10°C. The chilled water is first sent to the water-water plate exchanger to heat exchange and cool the hot water sprayed at the bottom of the flue gas spray tower. After the temperature is raised to 14-19°C, it becomes cooling water. The hot water sprayed at the bottom of the flue gas spray tower is cooled to 6-11°C and then lifted to the top of the spray tower by the spray pump (pump 3) and then used for flue gas spraying. The cooling water exchanged from the water-water plate is sent to the absorber to absorb the condensation heat of the refrigerant steam. After the temperature rises to 25-35℃, it enters the cooler and absorbs the condensation heat of the refrigerant steam in the condenser again. After the temperature rises to 40-50℃ again, it enters the flue gas-water shell and tube heat exchanger to cool the high-temperature flue gas output by the diesel engine. After the water temperature further rises to 80-90℃, it enters the generator to heat and evaporate the lithium bromide solution. After the temperature drops to 50-60℃, it flows out of the system as hot water. This hot water can be used for heating, domestic hot water or for circulating cooling in the cooling tower. The water system completes a cooling and heating cycle.

[0076] 5. Intelligent control: PLC dynamically adjusts the water volume and dosage according to the sensor data to ensure the stability of the pH value of the spray water (by replenishing the alkali solution through the dosing device) and optimize the energy efficiency of the system.

[0077] Specifically, the pH meter of the flue gas spray tower monitors the pH value of the spray water at the bottom of the tower in real time. When the pH value drops to a specified range, the dosing process is started, and the dosing device automatically adds alkaline solution into the tower through the dosing pump (pump 4) until the pH value of the spray water meets the requirements.

[0078] The PLC controller in the control cabinet senses the cooling (freezing) water temperature fluctuations caused by changes in the diesel engine's operating power in real time based on the pressure (temperature) sensor of the pump group, and further improves the system's operating efficiency and controls the final purification treatment temperature of the flue gas by changing the water volume of the cooling (freezing) water system.

[0079] The diesel engine smoke low temperature elimination system of the present invention comprises the following steps when in use:

[0080] S1. System assembly:

[0081] Connect the flue gas-water shell and tube heat exchanger to the diesel engine exhaust pipe, and connect the outlet to the flue gas spray tower;

[0082] The generator of the absorption refrigeration system receives the high-temperature hot water output from the flue gas-water shell and tube heat exchanger through a pipeline;

[0083] The water-water plate heat exchanger connects the bottom water tank of the spray tower with the chilled water outlet of the evaporator.

[0084] S2. Operating process:

[0085] The diesel engine flue gas (310 - 330 °C) enters the flue gas-water shell-and-tube heat exchanger and is cooled to 40 - 45 °C by the cooling water.

[0086] The medium-temperature flue gas enters the flue gas spray tower, contacts with the spray water at 6 - 11 °C, is cooled to 15 - 20 °C, and then discharged into the external ambient air, with the particulate matter removed; the high-temperature flue gas generated by the diesel engine has completed the low-temperature elimination treatment.

[0087] The absorption refrigeration system is driven by hot water at 80 - 90 °C to prepare chilled water at 5 - 10 °C, and the spray water is cooled to 6 - 11 °C through the water-water plate heat exchanger.

[0088] The PLC monitors the pH value of the spray water in real time. When pH < 7, the dosing pump (pump 4) is started to inject NaOH solution until pH = 8.5.

[0089] S3. Waste heat utilization:

[0090] The hot water at 50 - 60 °C output by the system is supplied to the underground engineering heating system, and the remaining part enters the cooling tower for circulation.

[0091] The present invention can effectively eliminate flue gas particles and achieve low-temperature emission, avoiding the "white smoke" phenomenon. The waste heat recovery is used for refrigeration, heating and domestic hot water, improving the energy utilization rate, with full automatic control, adapting to the power fluctuation of the diesel engine, and operating stably and efficiently.

[0092] The system of the present invention utilizes one kind of water source to undertake multiple functions, comprehensively allocate various heats in the system. It can not only use the heat in the diesel engine flue gas as the heat source of the absorption refrigeration system, but also use the low-temperature chilled water prepared by the refrigeration system to purify the diesel engine flue gas at low temperature. At the same time, this water source can undertake the function of secondary cooling water in the absorption refrigeration system. The hot water finally transformed by the water source can also be used for heating, domestic hot water functions, or enter the cooling tower for circulation cooling to meet the water-saving requirements, further improving the utilization efficiency of the water source.

[0093] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diesel engine smoke low temperature elimination system, characterized in that: include: The flue gas-water shell and tube heat exchanger is connected to the exhaust port of the diesel engine and is used to initially cool down the high-temperature flue gas; A flue gas spray tower, connected to the outlet of the flue gas-water shell and tube heat exchanger, provided with a spray layer and a bottom water tank, and equipped with low-temperature spray water; An absorption refrigeration system comprises a generator, a condenser, a throttle valve, an evaporator, an absorber and a solution pump, wherein the generator receives high-temperature hot water outputted from a flue gas-water shell and tube heat exchanger as a heat source through a pipeline; A water-water plate heat exchanger is connected to the water tank at the bottom of the flue gas spray tower and the chilled water outlet of the evaporator to cool the spray water; Dosing device, used to adjust the pH value of spray water; Variable frequency pump set, including cooling water pump, spray pump and dosing pump.

2. The system according to claim 1, characterized in that The working process of the absorption refrigeration system includes: The flow direction of refrigerant water is: The dilute solution heated by the heat source in the generator evaporates to generate refrigerant steam, which flows through the condenser in turn to be cooled into refrigerant water and flows out of the condenser, throttled by the throttle valve into the evaporator, evaporated at low temperature in the evaporator to become refrigerant steam again, and then flows to the absorber to be absorbed by the lithium bromide solution. The lithium bromide solution that absorbs the refrigerant steam in the absorber comes from the lithium bromide concentrated solution in the generator; The flow direction of lithium bromide solution is: The dilute solution heated by the heat source in the generator is evaporated to produce refrigerant vapor, becoming a concentrated solution with a higher temperature. After the concentrated solution flows out of the generator, it is cooled by the solution plate exchanger, then enters the absorber and absorbs the refrigerant vapor from the evaporator, thereby reducing the concentration and being transported back to the generator by the solution pump.

3. The system according to claim 1, characterized in that In the system, the water system circulation path is: The cooling water delivered by the cooling water pump flows through the evaporator in sequence to prepare chilled water; The chilled water is heated by the water-water plate exchanger and then enters the absorber to absorb the condensation heat and heat up; after flowing out of the absorber, it enters the condenser for secondary heating; finally, the cooling water enters the flue gas-water shell and tube heat exchanger for heating, and the high-temperature water flowing out of the flue gas-water shell and tube heat exchanger enters the generator, and finally outputs waste heat hot water after cooling.

4. The system according to claim 1, characterized in that The dosing device comprises: The pH meter monitors the pH value of the spray water in real time; The alkali solution storage tank is connected to the dosing pump; When the pH value is detected to be lower than 7, the PLC controller starts the dosing pump to inject NaOH solution until the pH is 8.

5.

5. The system according to claim 1, characterized in that It also includes an intelligent control system, which includes a PLC controller, a temperature sensor, a pressure sensor and a pH meter. The PLC controller is connected to each sensor and an actuator.

6. The system according to claim 5, characterized in that The execution strategy of the intelligent control system is: Real-time monitoring of spray water temperature, flue gas emission temperature and cooling water temperature through temperature sensors; Dynamically adjust the cooling water pump flow rate according to the change of diesel engine power; When the flue gas temperature exceeds 20°C, increase the spray pump speed and spray volume.

7. The system according to claim 2, characterized in that The solution heat exchanger is a plate heat exchanger, which cools the concentrated solution at the generator outlet and then sends it to the absorber.

8. The system according to claim 1, characterized in that The arrangement of the flue gas spray tower includes: Multi-layer swirl spray layer, spray density is 8-12m3 / (m 2 h); The packing layer uses porous ceramic packing with a porosity of ≥85%; The demister is a two-stage baffle structure and is arranged at the tower top outlet.

9. The system according to claim 1, characterized in that The control strategy of the variable frequency pump group includes: The cooling water pump frequency is linked to the evaporator outlet water temperature; The frequency of the spray pump is PID-regulated according to the flue gas emission temperature; The dosing pump adopts pulse dosing method, and the single dosing time does not exceed 30 seconds.

10. The method for operating the system according to any one of claims 1 to 9, characterized in that include: Step 1: The high-temperature flue gas is cooled to 40-50°C through a shell and tube heat exchanger; Step 2: The medium-temperature flue gas is treated in a spray tower with 6-11℃ spray water until it is discharged at 15-20℃; Step 3: The absorption refrigeration system uses 80-90℃ hot water to prepare 5-10℃ chilled water; Step 4: The PLC controller adjusts the spray water pH value to 7-8.5 and the water temperature to 6-11℃ in real time; Step 5: The 50-60℃ waste heat hot water output by the system is diverted to the heating, domestic hot water or cooling tower system.

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