Effect-improving heat exchange equipment for urea preparation and urea preparation system and method

Abstract

The invention discloses efficiency-improving heat exchange equipment for urea preparation in the technical field of urea preparation, which comprises multiple stages of spray towers arranged from top to bottom, a spray device is arranged in each stage of spray tower, and the spray device of the next stage is communicated with the spray tower of the previous stage through a water pipe; the spraying tower at the lowest stage is communicated with a heat exchanger, and the heat exchanger is used for exchanging heat between air and high-temperature waste gas of the drying machine; the adjacent spray towers are communicated through an air pipe, and the spray tower at the uppermost stage is communicated with a fan; the fan is used for extracting hot air in the heat exchanger, so that the hot air exchanges heat with spray water in each stage of spray tower from bottom to top; the lowest stage of spray tower is provided with a water outlet and can be communicated with a water storage tank to store hot water.

Description

Technical Field

[0001] The present invention relates to the technical field of urea preparation, and in particular to an efficiency-enhancing heat exchange device for urea preparation, a urea preparation system and a method. Background Art

[0002] In the process of gypsum board production, for environmental protection reasons, the boiling furnace needs to be denitrated. The denitration method in the gypsum board industry is generally to use urea urea wet flue gas denitration, that is, to use urea aqueous solution to spray and absorb nitric oxide and nitrogen dioxide in the flue gas, and use urea to react with them to generate nitrogen, thereby achieving the purpose of flue gas denitration.

[0003] At present, the industry generally uses cold water to prepare urea. Since urea is easy to crystallize below 30 degrees Celsius, the crystallized urea will block the pipes and nozzles, resulting in a decrease in denitrification efficiency. To avoid this, the urea solution must be heated by a heating rod after urea preparation to increase the temperature of urea and improve the denitrification efficiency. However, the additional energy consumption generated by using a heating rod to heat urea is relatively large.

[0004] In summary, in the prior art, after using cold water to prepare urea, the urea needs to be heated by a heating rod, which consumes a lot of energy. Summary of the invention

[0005] The object of the present invention is to provide an efficient heat exchange device, a urea preparation system and a method for urea preparation, so as to solve the technical problem in the prior art that after using cold water to prepare urea, the urea needs to be heated by a heating rod, resulting in high energy consumption.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides an efficiency-enhancing heat exchange device for urea preparation, comprising a multi-stage spray tower arranged from top to bottom, each stage of the spray tower is provided with a spray device, and the spray device of the next stage is connected to the spray tower of the previous stage through a water pipe;

[0007] The spray tower at the lowest level is connected to a heat exchanger, and the heat exchanger is used to exchange heat between air and high-temperature exhaust gas from the dryer;

[0008] The adjacent spray towers are connected through air pipes, and the uppermost spray tower is connected to a fan;

[0009] The fan is used to extract the hot air in the heat exchanger, so that the hot air exchanges heat with the spray water in each level of the spray tower from bottom to top;

[0010] The spray tower at the lowest level is provided with a drain outlet, which is used to connect to a water storage tank to store high-temperature water for preparing urea.

[0011] As a preferred solution of the present invention, the spray device in each level of the spray tower is arranged close to the air inlet in the spray tower of that level, and the air outlet in each level of the spray tower is arranged away from the air inlet in the spray tower of that level, so as to prolong the contact time between the spray water and the hot air.

[0012] As a preferred solution of the present invention, the water storage tank is connected to the water inlet pipe of the lowest level spraying device through a circulation pump;

[0013] The water storage tank is equipped with a thermometer for real-time monitoring of the water temperature in the water storage tank;

[0014] When the water temperature in the water tank is lower than a predetermined temperature, the circulation pump can pump the hot water in the water tank to the spray device at the lowest level, so as to spray the hot water into the spray tower at the lowest level for reheating to maintain the water temperature in the water tank.

[0015] As a preferred solution of the present invention, a cold water valve is provided on the water inlet pipe of the uppermost spray device, and a hot water valve is provided on the water outlet end of the water outlet pipe of the circulation pump;

[0016] When water is injected into the uppermost spray device, the hot water valve is closed;

[0017] When the circulation pump injects water into the spray device at the lowest level, the cold water valve is closed.

[0018] As a preferred solution of the present invention, the cold water valve and the hot water valve are both configured as electric valves, and are both communicatively connected to the processor, and the thermometer and the circulating pump are also communicatively connected to the processor;

[0019] When the water temperature in the water storage tank is lower than a predetermined temperature, the processor controls the cold water valve to close, the hot water valve to open, and starts the circulation pump.

[0020] As a preferred solution of the present invention, the water storage tank and each water pipe are covered with a thermal insulation layer.

[0021] As a preferred solution of the present invention, the outside of the air pipe between the heat exchanger and the spray tower is also covered with a thermal insulation layer.

[0022] The second aspect of the present invention provides a urea preparation system, comprising the above-mentioned efficiency-enhancing heat exchange equipment for urea preparation, and the water storage tank is connected to a urea preparation pump, and the urea preparation pump is used to pump the hot water in the water storage tank into a urea preparation device to prepare urea.

[0023] A third aspect of the present invention provides a method for preparing urea, using the above-mentioned urea preparation system, comprising the following steps:

[0024] The waste heat of the gypsum board dryer is used to exchange heat with the air through a heat exchanger to increase the air temperature;

[0025] Cold water is injected from the top spray device, and the spray water in each spray tower will enter the next spray device under the action of gravity to continue spraying, so that the water flows from top to bottom through the multi-stage spray tower and undergoes multi-stage spraying;

[0026] Start the fan to extract the hot air in the heat exchanger. The hot air flows through the multi-stage spray tower from the bottom to the top, and exchanges heat with the spray water in each stage of the spray tower, so that the water temperature in the next stage of the spray tower is higher than the water temperature in the previous stage of the spray tower;

[0027] The water temperature reaches the highest in the lowest level spray tower and enters the water storage tank through the water pipe for storage;

[0028] When urea needs to be prepared, the hot water in the water storage tank is pumped to the urea preparation device through the urea preparation pump.

[0029] As a preferred solution of the present invention, when the thermometer detects that the water temperature in the water storage tank is lower than a predetermined temperature, the processor controls the hot water valve to open and starts the circulation pump;

[0030] The circulation pump pumps the hot water in the water storage tank to the lowest level of the spray device, where it exchanges heat with the hot air with the highest temperature in the lowest level of the spray tower, quickly raising the water temperature in the water storage tank;

[0031] At the same time, the processor controls the cold water valve to close to prevent the water from the upper level from entering the lowest level spray tower, so as to improve the efficiency of raising the water temperature in the water storage tank.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This efficiency-enhancing heat exchange equipment uses the waste heat of the dryer's exhaust gas to heat the air by setting up a heat exchanger, and uses a fan to make the hot air flow from bottom to top through a multi-stage spray tower. A spray device is set in each spray tower. The hot air from bottom to top and the cold water from top to bottom perform convection heat exchange, so that the spray water is heated in multiple stages and the temperature increases step by step. The water temperature reaches the highest in the lowest spray tower, so that the thermal energy in the hot air is converted into the thermal energy of water to the maximum extent, thereby improving energy efficiency.

[0034] When urea needs to be prepared, hot water is pumped to the urea preparation device through a urea preparation pump. The urea solution prepared by hot water has a higher temperature itself and does not need to be heated by a heating rod, which makes full use of the waste heat of the exhaust gas and reduces energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0036] Figure 1 Schematic diagram of the structure of a urea preparation system in an embodiment of the present invention.

[0037] The numbers in the figure represent the following:

[0038] 1-heat exchanger, 2-spray tower, 3-fan, 4-spray device, 5-water storage tank, 6-urea preparation pump, 7-urea preparation device, 8-circulation pump, 9-cold water valve, 10-hot water valve, 11-gas pipe. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The first aspect of the present invention provides an efficiency-enhancing heat exchange device for urea preparation, comprising a multi-stage spray tower 2 arranged from top to bottom, each stage of the spray tower 2 is provided with a spray device 4, and the spray device 4 of the next stage is connected to the spray tower 2 of the previous stage through a water pipe;

[0041] The lowest level spray tower 2 is connected to the heat exchanger 1, and the heat exchanger 1 is used to exchange heat between air and high temperature exhaust gas of the dryer;

[0042] Adjacent spray towers 2 are connected via air pipes 11, and the top spray tower 2 is connected to a fan 12;

[0043] The fan 12 is used to extract the hot air in the heat exchanger 1, so that the hot air exchanges heat with the spray water in each level of the spray tower 2 from bottom to top;

[0044] The spray tower 2 at the lowest level is provided with a drain port which can be connected to the water storage tank 5 . The drain port is used to be connected to the water storage tank 5 to store hot water for preparing urea.

[0045] The efficiency-enhancing heat exchange equipment for urea preparation utilizes the waste heat of the exhaust gas of the gypsum board dryer to exchange heat with air through the heat exchanger 1, thereby increasing the air temperature.

[0046] Cold water is injected from the top spray device 4, and the spray water in each spray tower 2 enters the next spray device 4 under the action of gravity to continue spraying, so that the water flows from top to bottom through the multi-stage spray tower 2 and undergoes multi-stage spraying.

[0047] The fan 12 is started to extract the hot air in the heat exchanger 1. The hot air flows from bottom to top through the multi-stage spray tower 2 and exchanges heat with the spray water in each stage of the spray tower 2, that is, the hot air exchanges heat from bottom to top with the cold water from top to bottom.

[0048] In this way, the spray water is heated in multiple stages from top to bottom, the temperature increases step by step, and the temperature of the hot air decreases step by step from bottom to top. The water temperature reaches the highest in the lowest spray tower 2 and enters the water storage tank 5 through the water pipe for storage.

[0049] This efficiency-enhancing heat exchange equipment can use the hot air after heat exchange in the next-stage spray tower 2 to preheat the spray water of the previous stage, so that the thermal energy in the hot air can be converted into the thermal energy of water to maximize the energy efficiency.

[0050] When urea needs to be prepared, the hot water in the water storage tank 5 is pumped to the urea preparation device 7 by the urea preparation pump 6 .

[0051] In summary, the efficiency-enhancing heat exchange equipment uses the waste heat of the dryer's exhaust gas to heat the air by setting a heat exchanger 1, and uses the fan 12 to make the hot air flow from bottom to top through the multi-stage spray tower 2. A spray device 4 is set in each spray tower 2, and the hot air from bottom to top and the cold water from top to bottom are convectively exchanged, so that the spray water is heated in multiple stages, and the temperature increases step by step. The water temperature reaches the highest in the lowest spray tower 2, so that the heat energy in the hot air is converted into the heat energy of water to the maximum extent, thereby improving energy efficiency. And it enters the water storage tank 5 through the water pipe for storage. When urea needs to be prepared, the hot water is pumped to the urea preparation device 7 by the urea preparation pump 6. The urea solution prepared by hot water has a high temperature itself, and there is no need to use a heating rod for heating, which makes full use of the waste heat of the exhaust gas and reduces energy consumption.

[0052] Furthermore, the spray device 4 in each stage of the spray tower 2 is arranged close to the air inlet in the spray tower 2 of this stage, and the air outlet in each stage of the spray tower 2 is arranged away from the air inlet in the spray tower 2 of this stage.

[0053] The time from the hot air entering the spray tower 2 to leaving the spray tower 2 can be extended, that is, the residence time of the hot air in each stage of the spray tower 2 can be extended to extend the contact time between the spray water and the hot air, so that the thermal energy of the air can be converted into the thermal energy of the water to the maximum extent.

[0054] Furthermore, when the hot water in the water storage tank 5 is not used for a period of time, the temperature of the hot water stored in the water storage tank 5 will decrease. In order to maintain the temperature of the hot water in the water storage tank 5, the water storage tank 5 is connected to the water inlet pipe of the lowest level spray device 4 through the circulation pump 8;

[0055] A thermometer is installed on the water storage tank 5 to monitor the water temperature in the water storage tank 5 in real time;

[0056] When the water temperature in the water tank 5 is lower than the predetermined temperature, the circulation pump 8 can pump the hot water in the water tank 5 to the lowest-level spray device 4 to spray the hot water into the lowest-level spray tower 2 for reheating to maintain the water temperature in the water tank 5.

[0057] The reason why the hot water in the water storage tank 5 is pumped to the lowest level of the spray device 4 is that the hot air in the lowest spray tower 2 has the highest temperature and the temperature difference with the hot water is the largest, which can quickly increase the temperature of the hot water. The temperature of the hot air in the spray tower 2 of the upper level may be very different from the hot water temperature, or even lower than the hot water temperature, so it is chosen to pump the hot water in the water storage tank 5 to the lowest level of the spray device 4.

[0058] Furthermore, a cold water valve 9 is provided on the water inlet pipe of the uppermost spray device 4 , and a hot water valve 10 is provided on the water outlet end of the water outlet pipe of the circulation pump 8 .

[0059] When water is injected into the uppermost spray device 4 , the hot water valve 10 is closed to prevent cold water from entering the water storage tank 5 of the circulation pump 8 .

[0060] When the circulation pump 8 injects water into the lowest-level spray device 4, the cold water valve 9 is closed, which can prevent the hot water heated for the first time from mixing with the hot water heated again, thereby increasing the water temperature increase rate in the water storage tank 5 to a certain extent.

[0061] The reason why the cold water valve 9 and the hot water valve 10 are provided and only one can be opened at the same time is:

[0062] If the first heated hot water and the reheated hot water pumped out of the water storage tank 5 enter the lowest level spray device 4 at the same time, the amount of hot water pumped out of the water storage tank 5 per unit time will be reduced due to the limited spraying amount of the spray device 4 per unit time, delaying the time for the water temperature in the water storage tank 5 to return to the predetermined temperature. If it is close to the water fetching time or there is a sudden demand for water fetching, production will be delayed.

[0063] If the reheated hot water pumped out of the water storage tank 5 enters the lowest-level spray tower 2 through a separate pipeline, although the water intake per unit time in the spray tower 2 of this level can be increased, since the total amount of hot air entering the spray tower 2 of this level per unit time is limited, the limited heat energy is distributed to a larger amount of water, which will cause the water temperature to fall short of expectations.

[0064] Furthermore, in order to improve the automation level of the system, the cold water valve 9 and the hot water valve 10 are both configured as electric valves and are both communicatively connected to the processor, and the thermometer and the circulation pump 8 are also communicatively connected to the processor;

[0065] When the water temperature in the water storage tank 5 is lower than a predetermined temperature, the processor controls the cold water valve 9 to close, the hot water valve 10 to open, and the circulation pump 8 to start.

[0066] Furthermore, in order to prolong the time required for the water temperature in the water storage tank 5 to drop to a predetermined temperature, the water storage tank 5 and each water pipe are coated with a thermal insulation layer, which can weaken the intensity of heat exchange between hot water and the outside air.

[0067] Furthermore, the air pipe 11 between the heat exchanger 1 and the spray tower 2 is also covered with an insulation layer, which can reduce the heat loss of the hot air before entering the spray tower 2, make the air flow temperature entering the spray tower 2 higher, and increase the water temperature of the hot water while ensuring the contact time between the air and the spray water.

[0068] The second aspect of the present invention provides a urea preparation system, comprising the above-mentioned efficiency-enhancing heat exchange equipment for urea preparation, and the water storage tank 5 is connected to a urea preparation pump 6, which is used to pump the hot water in the water storage tank 5 to a urea preparation device 7 to prepare urea.

[0069] The urea preparation system fully utilizes the waste heat of the dryer exhaust gas to heat the air through the heat exchanger 1. When the hot air is extracted by the fan 12, it fully contacts the spray water in the spray tower 2 to heat the spray water, and the hot water is collected and stored in the water storage tank 5. When urea needs to be prepared, the hot water is pumped to the urea preparation device 7 through the urea preparation pump 6. The urea solution prepared by the hot water has a high temperature itself, and does not need to be heated by a heating rod, so the waste heat of the exhaust gas is fully utilized, which reduces energy consumption.

[0070] A third aspect of the present invention provides a method for preparing urea, using the above-mentioned urea preparation system, comprising the following steps:

[0071] The heat exchanger 1 utilizes the waste heat of the gypsum board dryer's exhaust gas to exchange heat with the air to increase the air temperature;

[0072] Cold water is injected from the top spray device 4, and the spray water in each spray tower 2 enters the next spray device 4 under the action of gravity to continue spraying, so that the water flows from top to bottom through the multi-stage spray tower 2 and undergoes multi-stage spraying;

[0073] The fan 12 is started to extract the hot air in the heat exchanger 1. The hot air flows through the multi-stage spray tower 2 from the bottom to the top, and exchanges heat with the spray water in each stage of the spray tower 2, so that the water temperature in the next stage of the spray tower 2 is higher than the water temperature in the previous stage of the spray tower 2;

[0074] The water temperature reaches the highest in the lowest level spray tower 2 and enters the water storage tank 5 through the water pipe for storage;

[0075] When urea needs to be prepared, the hot water in the water storage tank 5 is pumped to the urea preparation device 7 by the urea preparation pump 6 .

[0076] Further, when the thermometer detects that the water temperature in the water storage tank 5 is lower than a predetermined temperature, the processor controls the hot water valve 10 to open and starts the circulation pump 8;

[0077] The circulating pump 8 pumps the hot water in the water storage tank 5 to the spray device 4 at the lowest level, and exchanges heat with the hot air with the highest temperature in the spray tower 2 at the lowest level, thereby quickly raising the water temperature in the water storage tank 5;

[0078] At the same time, the processor controls the cold water valve 9 to close to prevent the water from the upper level from entering the spray tower 2 of the lowest level, so as to improve the efficiency of raising the water temperature in the water storage tank 5.

[0079] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. A heat exchange device for improving the efficiency of urea preparation, characterized in that: It comprises a multi-stage spray tower (2) arranged from top to bottom, each stage of the spray tower (2) is provided with a spray device (4), and the spray device (4) of the next stage is connected to the spray tower (2) of the previous stage through a water pipe; The spray tower (2) at the lowest level is connected to a heat exchanger (1), and the heat exchanger (1) is used to exchange heat between air and high-temperature exhaust gas from a dryer; The adjacent spray towers (2) are connected via an air pipe (11), and the uppermost spray tower (2) is connected to a fan (12); The fan (12) is used to extract the hot air in the heat exchanger (1), so that the hot air exchanges heat with the spray water in each level of the spray tower (2) from bottom to top; The spray tower (2) at the lowest level is provided with a drain outlet, which is used to communicate with a water storage tank (5) to store hot water for preparing urea.

2. The heat exchange equipment for improving the efficiency of urea preparation according to claim 1, characterized in that: The spray device (4) in each stage of the spray tower (2) is arranged close to the air inlet of the spray tower (2) of that stage, and the air outlet in each stage of the spray tower (2) is arranged away from the air inlet of the spray tower (2) of that stage, so as to prolong the contact time between the spray water and the hot air.

3. The heat exchange equipment for improving the efficiency of urea preparation according to claim 1, characterized in that: The water storage tank (5) is connected to the water inlet pipe of the lowest level spraying device (4) through a circulation pump (8); The water storage tank (5) is provided with a thermometer for real-time monitoring of the water temperature in the water storage tank (5); When the water temperature in the water storage tank (5) is lower than a predetermined temperature, the circulation pump (8) can pump the hot water in the water storage tank (5) to the spray device (4) at the lowest level, so as to spray the hot water into the spray tower (2) at the lowest level for reheating, thereby maintaining the water temperature in the water storage tank (5).

4. The heat exchange equipment for improving the efficiency of urea preparation according to claim 3, characterized in that: A cold water valve (9) is provided on the water inlet pipe of the uppermost spray device (4), and a hot water valve (10) is provided on the water outlet end of the water outlet pipe of the circulation pump (8); When water is injected into the uppermost spray device (4), the hot water valve (10) is closed; When the circulation pump (8) injects water into the spray device (4) at the lowest level, the cold water valve (9) is closed to increase the rate of increase of the water temperature in the water storage tank (5).

5. The heat exchange equipment for improving the efficiency of urea preparation according to claim 4, characterized in that: The cold water valve (9) and the hot water valve (10) are both configured as electric valves and are both connected to the processor for communication, and the thermometer and the circulation pump (8) are also connected to the processor for communication; When the water temperature in the water storage tank (5) is lower than a predetermined temperature, the processor controls the cold water valve (9) to close, the hot water valve (10) to open, and starts the circulation pump (8).

6. The heat exchange equipment for improving the efficiency of urea preparation according to claim 5, characterized in that: The water storage tank (5) and each water pipe are coated with a thermal insulation layer.

7. The heat exchange equipment for improving the efficiency of urea preparation according to claim 6, characterized in that: The air pipe (11) between the heat exchanger (1) and the spray tower (2) is also coated with a thermal insulation layer.

8. A urea preparation system, characterized in that: The invention comprises a heat exchange device for improving the efficiency of urea preparation as described in any one of claims 1 to 7, and the water storage tank (5) is connected to a urea preparation pump (6), and the urea preparation pump (6) is used to pump the hot water in the water storage tank (5) to a urea preparation device (7) to prepare urea.

9. A method for preparing urea, characterized in that: The urea preparation system according to claim 8 comprises the following steps: The waste heat of the exhaust gas from the gypsum board dryer is used to exchange heat with the air through a heat exchanger (1) to increase the air temperature; Cold water is injected from the top spray device (4), and the spray water in each spray tower (2) enters the next spray device (4) under the action of gravity to continue spraying, so that the water flows from top to bottom through the multi-stage spray tower (2) and undergoes multi-stage spraying; The fan (12) is started to extract the hot air in the heat exchanger (1), and the hot air flows from the bottom to the top through the multi-stage spray tower (2), and exchanges heat with the spray water in each stage of the spray tower (2), so that the water temperature in the next stage of the spray tower (2) is higher than the water temperature in the previous stage of the spray tower (2); The water temperature reaches the highest in the lowest level spray tower (2) and enters the water storage tank (5) through the water pipe for storage; When urea needs to be prepared, the hot water in the water storage tank (5) is pumped to the urea preparation device (7) via the urea preparation pump (6).

10. The heat exchange equipment for improving the efficiency of urea preparation according to claim 9, characterized in that: When the thermometer detects that the water temperature in the water storage tank (5) is lower than a predetermined temperature, the processor controls the hot water valve (10) to open and starts the circulation pump (8); The circulating pump (8) pumps the hot water in the water storage tank (5) to the spray device (4) at the lowest level, and exchanges heat with the hot air with the highest temperature in the spray tower (2) at the lowest level, thereby quickly raising the water temperature in the water storage tank (5); At the same time, the processor controls the cold water valve (9) to close to prevent the water from the upper level from entering the spray tower (2) at the lowest level, so as to improve the efficiency of raising the water temperature in the water storage tank (5).

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