A liquid ammonia vaporization device with staged heating and waste heat utilization.

Abstract

This invention relates to the field of liquid ammonia vaporization and industrial waste heat utilization technology, and discloses a liquid ammonia vaporization device with staged heating and waste heat utilization. The device includes: a liquid ammonia storage tank, a liquid ammonia input pipeline, a liquid ammonia pump, a liquid ammonia flow valve, a liquid ammonia preheating device, liquid ammonia pipeline fins in the preheating device, a high-temperature hot water inlet and outlet of the preheating device, a liquid ammonia vaporization tank, a high-temperature hot water pipeline inlet, a liquid ammonia nozzle, a liquid ammonia pipeline inlet, a low-temperature hot water network inlet, a low-temperature hot water network, a gaseous ammonia outlet pipeline, a low-temperature hot water network outlet, high-temperature hot water pipeline fins, a high-temperature hot water pipeline outlet, a liquid ammonia reflux outlet, a gaseous ammonia flow valve, and a liquid ammonia reflux valve. This invention integrates multiple nozzle distribution, staged heat exchange, and deep drying functions into a single vaporization tank, resulting in a compact structure. By independently controlling the flow rates of the high and low temperature heat sources, the vaporization rate and dryness can be flexibly adjusted to adapt to different ammonia blending ratios and unit load variations.

Description

[0001] This invention relates to the field of liquid ammonia vaporization and industrial waste heat utilization technology, and particularly to a liquid ammonia vaporization device with staged heating and waste heat utilization. Background Technology

[0002] Liquid ammonia gasification is a prerequisite for key technologies in thermal power plants to achieve ammonia-blended combustion in coal-fired boilers, reduce carbon emissions, mitigate slagging corrosion, and facilitate SCR denitrification. As the proportion of ammonia blended into coal-fired boilers continues to increase, the demand for gaseous ammonia is growing several times or even dozens of times, requiring a continuous and stable supply of dry gaseous ammonia. Traditional liquid ammonia gasification technologies (such as electric heating, single-stage steam, or circulating water heating) exhibit numerous problems under extremely high loads: insufficient heat exchange capacity leads to a bottleneck in gasification volume; a single heat source cannot simultaneously meet the demands of high heat flux density gasification and deep drying, easily causing "liquid-laden ammonia," posing a serious threat to subsequent combustion safety; furthermore, the utilization of abundant but varying-grade waste heat resources in power plants is inefficient, resulting in overall low energy efficiency.

[0003] Chinese invention patent CN202322514115.X discloses a dedicated device for liquid ammonia vaporization, comprising a preheater and a heating mechanism. This technology preheats the liquid ammonia using a preheater, bringing it close to its vaporization critical point before it enters the main heating mechanism, thereby increasing the overall vaporization rate. The essence of this technology lies in enhancing the initial thermal state by adding a preheating section; however, it does not solve the problem of matching high-intensity, differentiated heat fluxes required for large-scale vaporization, and it lacks specific design for deep drying of gaseous ammonia.

[0004] Chinese invention patent CN202321368571.1 discloses an ambient temperature liquid ammonia vaporization and separation device. Its vaporization component consists of multiple vaporization tubes connected in parallel and series, achieving vaporization through natural heat exchange with ambient air, and integrates an ammonia separation component. The essence of this technology lies in…

[0005] It utilizes ambient air as a free cold source to achieve zero-energy gasification, but it is completely dependent on ambient temperature. Its gasification capacity and stability are greatly constrained by climatic conditions, making it unable to meet the continuous, stable, and high-load industrial ammonia demand. In particular, its capacity is severely insufficient during cold seasons or when the power output is high.

[0006] Chinese invention patent CN202321541435.8 discloses a liquid ammonia vaporization device employing a special U-tube heat exchanger and buffer tank structure. This design involves completely immersing the U-tube bundle in liquid ammonia, with the vapor condensing and releasing heat in the tube side, aiming to improve heat exchange efficiency and simplify the structure. Its technical essence lies in optimizing the geometry of the immersion phase change heat exchanger. However, the system still requires a separate buffer tank and cooling / depressurization structure, making the system still complex. Furthermore, it does not perform active deep drying of the gaseous ammonia generated during vaporization, limiting its adaptability to large-scale, high-quality gaseous ammonia supply scenarios.

[0007] Chinese invention patent CN202411334450.4 discloses a liquid ammonia vaporization process without a gaseous ammonia buffer separator. The core of this technology lies in eliminating the traditional gaseous ammonia buffer tank. Liquid ammonia is directly heated via a liquid ammonia pump circulation and a heating medium (such as circulating cooling water), allowing gaseous ammonia to flash-separate in the liquid ammonia buffer tank before direct output. The essence of this technology is to simplify the system process and reduce the number of equipment. However, this process has extremely high requirements for the temperature of the heating medium and the system pressure control. The stability of the gaseous ammonia output quality is highly dependent on the uniformity of upstream heating and flash evaporation. When handling ultra-high flow rates or rapid load changes, the risks of liquid carryover in gaseous ammonia and pressure fluctuations increase.

[0008] Chinese invention patent CN201910108165.3 discloses an energy utilization device and method for a liquid ammonia vaporization system, employing a dual-mode approach of hot water vaporization and steam evaporation. This system switches between circulating hot water and steam as the heat source based on the season (hot / cold), aiming to balance energy efficiency and gas supply security. Its technical essence lies in switching the heat source quality according to external conditions, possessing certain advantages.

[0009] It offers flexibility. However, the system requires two heat exchange systems (hot water vaporizer and steam evaporator), resulting in high equipment redundancy, system complexity and large footprint, high investment costs, and potential response lag or operational complexity when switching between the two modes. Therefore, it is not the optimal solution for scenarios that require the simultaneous and efficient utilization of multiple stable industrial waste heat sources.

[0010] The existing technology still has the following problems:

[0011] 1. Insufficient large-scale gasification capacity: Traditional single-stage heat exchange structures have limited heat flux density, making it difficult to meet the demand for gasifying large amounts of liquid ammonia in a short time during ammonia-blended combustion.

[0012] 2. Mismatch between heat source grade and process requirements: Gasification requires high temperatures to drive rapid phase change, while drying only requires lower temperatures to remove moisture. Using a single-temperature heat source presents a contradiction of "using high-grade heat for low-grade applications" or "insufficient low-grade heat for high-grade applications," resulting in inefficient energy utilization.

[0013] 3. Low efficiency of diversified waste heat utilization in power plants: Power plants have various types of waste heat, such as high-grade (e.g., condensate from 70-80℃ low-temperature heaters) and low-grade (e.g., slag cooling water from 30-40℃). Existing equipment lacks a systematic cascade utilization scheme, and there is considerable room for improvement in the comprehensive utilization rate of waste heat resources.

[0014] 4. Difficulty in ensuring the drying of gaseous ammonia under large-scale gasification: As the gasification load increases, the risk and total amount of liquid droplets entrained in the gaseous ammonia also increase. Traditional simple separation and drying methods are difficult to ensure the dryness of the outlet gaseous ammonia, which poses a safety hazard. Summary of the Invention

[0015] The purpose of this invention is to overcome the shortcomings of the prior art and provide a liquid ammonia vaporization device with staged heating and waste heat utilization.

[0016] This invention is achieved through the following technical solution:

[0017] A liquid ammonia vaporization device with staged heating and waste heat utilization, the device comprising: a liquid ammonia storage tank, a liquid ammonia input pipeline, a liquid ammonia pump, a liquid ammonia flow valve, a liquid ammonia preheating device, finned liquid ammonia pipeline of the preheating device, a high-temperature hot water inlet of the preheating device, and a high-temperature hot water outlet of the preheating device.

[0018] Inlet, liquid ammonia vaporization tank, high-temperature hot water pipeline inlet, liquid ammonia nozzle, liquid ammonia pipeline inlet, low-temperature hot water network inlet, low-temperature hot water network, gaseous ammonia outlet pipeline, low-temperature hot water network outlet, high-temperature hot water pipeline fins, high-temperature hot water pipeline outlet, liquid ammonia reflux outlet, gaseous ammonia flow valve and liquid ammonia reflux valve.

[0019] System Composition

[0020] It includes a liquid ammonia supply unit, a staged heating and vaporization unit, and a gaseous ammonia collection and reflux unit.

[0021] The liquid ammonia supply unit includes a liquid ammonia storage tank, a liquid ammonia input pipeline, a liquid ammonia pump, and a liquid ammonia flow valve.

[0022] The core component is the staged heating and vaporization unit, which includes a liquid ammonia preheating device and a liquid ammonia vaporization tank. The tank is divided into three functional zones according to the ammonia gas path: a preheating and preliminary flash evaporation zone, located at the top of the tank, with a liquid ammonia pipeline inlet connected to the outlet of the liquid ammonia preheating device and multiple evenly distributed liquid ammonia nozzles; a high-temperature enhanced evaporation zone, located in the lower middle part of the tank, with multiple sets of series-connected high-temperature hot water pipes with gradually widening fins, each with a high-temperature hot water inlet and outlet; and a low-temperature deep drying zone, located at the top of the tank, with an independent low-temperature hot water network. This network has a low-temperature hot water network inlet and outlet, and its surface is coated with a superhydrophilic coating.

[0023] The ammonia collection and reflux unit includes an ammonia outlet pipe located at the top of the tank and an ammonia flow valve thereon, a liquid ammonia reflux outlet located at the bottom of the tank and a liquid ammonia reflux pipe and a liquid ammonia reflux valve connected thereto.

[0024] A method for vaporizing liquid ammonia using a liquid ammonia vaporization device with staged heating and waste heat utilization is achieved through the following technical solution:

[0025] S1: Pump the liquid ammonia to the preheating device and preheat it using the high-temperature waste heat (70-80℃);

[0026] S2: The preheated liquid ammonia is atomized and sprayed into the vaporization tank through multiple nozzles for preliminary flash evaporation;

[0027] S3: The high-temperature waste heat (70-80℃) at the preheater outlet is introduced into the enhanced heat exchange pipe in the high-temperature evaporation zone inside the tank to heat the atomized liquid ammonia with high intensity, so as to achieve rapid vaporization of the main body;

[0028] S4: Utilize another low-temperature waste heat (30-40℃) to enter the drying pipeline network at the top of the tank to cool and deeply dry the rising gaseous ammonia and remove entrained droplets;

[0029] S5: Collect and output dry ammonia gas, while returning the residual liquid accumulated at the bottom of the tank to the storage tank.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. This invention employs a staged heating mode of "high-temperature evaporation + low-temperature drying," overcoming the technical bottleneck of large-flow gasification. This is because the invention decomposes the gasification process into two stages: "evaporation," requiring high heat density, and "drying," requiring low-temperature fine processing. These stages are respectively matched with high-temperature waste heat of 70-80℃ and low-temperature waste heat of 30-40℃. The high-temperature stage uses a preheater to enhance the flash evaporation effect of liquid ammonia at the nozzle. The design of multiple sets of series-connected pipes with gradually widening fins within the gasification tank greatly enhances the heat exchange capacity per unit volume, thus solving the problem that traditional single-stage heating cannot meet the demand for massive amounts of gaseous ammonia in scenarios such as ammonia-blended combustion.

[0032] 2. This invention enables refined, tiered utilization of diversified waste heat from power plants, significantly improving system energy efficiency. It creatively allocates waste heat resources of different grades (condensate from low-temperature heaters and slag cooling water) precisely: high-quality waste heat is used for preheating and the main gasification load, while low-quality waste heat is used for deep drying. This "temperature-matched, tiered utilization" approach overcomes the low efficiency of single heat sources, maximizing the overall waste heat utilization rate and minimizing operating energy consumption.

[0033] 3. An innovative low-temperature drying pipeline network with a super-hydrophilic coating was designed to ensure high-load drying.

[0034] The quality and safety of the gaseous ammonia under load are ensured. This invention features a dedicated low-temperature drying pipeline network before the final outlet of the gaseous ammonia. The superhydrophilic coating on its surface effectively intercepts and spreads minute droplets, and combined with the cooling effect of the low-temperature heat source, achieves deep drying of the gaseous ammonia. This design fundamentally solves the problem of "liquid-laden gaseous ammonia" that easily occurs during large-scale gasification, providing a guarantee for the safe and stable operation of subsequent ammonia-blended combustion.

[0035] 4. High system integration and strong adaptability. This invention integrates multi-nozzle distribution, staged heat exchange, and deep drying functions into a single gasification tank, resulting in a compact structure. By independently controlling the flow rates of high and low temperature heat sources, the gasification rate and dryness can be flexibly adjusted to adapt to different ammonia blending ratios and unit load variations, thus improving the system's operational flexibility and adaptability. Attached Figure Description

[0036] Figure 1 is a schematic diagram of the structure of the present invention.

[0037] Figure 2 is a schematic diagram of the low-temperature hot water pipe network used for drying ammonia gas according to the present invention.

[0038] Labeling Explanation: 1. Liquid ammonia storage tank; 2. Liquid ammonia input pipeline; 3. Liquid ammonia pump; 4. Liquid ammonia flow valve; 5. Liquid ammonia preheating device; 51. Fins of liquid ammonia pipeline in the preheating device; 52. High-temperature hot water inlet of the preheating device; 53. High-temperature hot water outlet of the preheating device; 6. Liquid ammonia vaporization tank; 61. High-temperature hot water pipeline inlet; 62. Liquid ammonia nozzle; 63. Liquid ammonia pipeline inlet; 64. Low-temperature hot water network inlet; 65. Low-temperature hot water network; 66. Gaseous ammonia outlet pipeline; 67. Low-temperature hot water network outlet; 68. Fins of high-temperature hot water pipeline; 69. High-temperature hot water pipeline outlet; 610. Liquid ammonia reflux outlet; 7. Gaseous ammonia flow valve; 8. Liquid ammonia reflux valve. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, those skilled in the art...

[0040] All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] Please refer to Figures 1-2. This invention provides a technical solution:

[0042] A liquid ammonia vaporization device with staged heating and waste heat utilization is characterized by comprising: a liquid ammonia supply unit, a staged heating and vaporization unit, and a gaseous ammonia collection and reflux unit; the liquid ammonia supply unit includes a liquid ammonia storage tank 1, a liquid ammonia pump 3, and a liquid ammonia flow valve 4 connected in sequence; the staged heating and vaporization unit includes a liquid ammonia preheating device 5 and a liquid ammonia vaporization tank 6; the liquid ammonia preheating device 5 is provided with a liquid ammonia channel and a high-temperature hot water channel, the inlet of which is connected to the outlet of the liquid ammonia flow valve 4, and the high-temperature hot water channel is provided with a high-temperature hot water inlet 52 and a high-temperature hot water outlet 53 of the preheating device; the liquid ammonia vaporization tank 6 is internally divided into a low-temperature deep drying zone, a preheating and preliminary flash evaporation zone, and a high-temperature enhanced evaporation zone from top to bottom; the preheating and preliminary flash evaporation zone is provided with a liquid ammonia pipeline inlet 63 and multiple liquid ammonia nozzles 62, the liquid ammonia pipeline inlet 63 being connected to the liquid ammonia channel outlet of the liquid ammonia preheating device 5; the high-temperature enhanced evaporation zone is provided with multiple sets of fins 68. The system includes a high-temperature hot water pipeline, which has a high-temperature hot water pipeline inlet 61 and a high-temperature hot water pipeline outlet 69. The high-temperature hot water pipeline inlet 61 is used to receive high-temperature waste heat from the high-temperature hot water outlet 53 of the preheating device. The low-temperature deep drying zone is provided with a low-temperature hot water pipeline network 65 with a super-hydrophilic coating on its surface. The pipeline network has a low-temperature hot water pipeline network inlet 64 and a low-temperature hot water pipeline network outlet 67 for receiving low-temperature waste heat. The gaseous ammonia collection and reflux unit includes a gaseous ammonia outlet pipeline 66 located at the top of the liquid ammonia vaporization tank 6, a gaseous ammonia flow valve 7 located on the gaseous ammonia outlet pipeline 66, a liquid ammonia reflux outlet 610 located at the bottom of the liquid ammonia vaporization tank 6, and a liquid ammonia reflux valve 8 connected to the liquid ammonia reflux outlet 610.

[0043] Taking the application of this invention to a 600MW anthracite coal-fired unit for 20% ammonia blending combustion retrofit as an example, the specific implementation process is explained as follows:

[0044] Liquid ammonia process: Liquid ammonia is pressurized to 1.5 MPa from storage tank 1 via pump 3, and the total flow rate is adjusted to the design value (e.g., 6 kg / h) via flow valve 4. The liquid ammonia first enters preheater 5, where it exchanges heat with 80°C condensate generated by the cryogenic heater. After the temperature rises from -10°C to -5°C, it is atomized and sprayed into vaporization tank 6 at a pressure of 1.2 MPa through multiple nozzles 62.

[0045] High-temperature evaporation section: 75°C hot water from the preheating device outlet 53 is introduced into the high-temperature evaporation zone inside the tank through inlet 61. Liquid ammonia droplets come into full contact with these finned high-temperature pipes 68, rapidly absorbing heat and vaporizing.

[0046] Low-temperature drying section: Cooling water from the 45°C slag exiting the high-temperature slag cooler is diverted and pumped from inlet 64 into the low-temperature drying pipeline network 65 at the top of the tank. The rising moist ammonia is cooled and dried as it passes through this pipeline network.

[0047] Heat recovery and product output: High-temperature hot water is discharged from outlet 69 after cooling and can be reused in the deaerator. Low-temperature hot water is returned to the cooling tower after being cooled in the preheater and drying network. Dried ammonia gas is delivered to the boiler burner via outlet 66 and flow regulating valve 7.

[0048] Residual liquid treatment: The system periodically (e.g., once per shift) opens the reflux valve 8 to return any small amount of liquid ammonia that may have accumulated at the bottom of the tank to the storage tank.

[0049] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A liquid ammonia vaporization device with staged heating and waste heat utilization, characterized in that, include: The system comprises a liquid ammonia supply unit, a staged heating and vaporization unit, and a gaseous ammonia collection and reflux unit; the liquid ammonia supply unit includes a liquid ammonia storage tank (1), a liquid ammonia pump (3), and a liquid ammonia flow valve (4) connected in sequence; the staged heating and vaporization unit includes a liquid ammonia preheating device (5) and a liquid ammonia vaporization tank (6); the liquid ammonia preheating device (5) is provided with a liquid ammonia channel and a high-temperature hot water channel, the inlet of which is connected to the outlet of the liquid ammonia flow valve (4), and the high-temperature hot water channel is provided with a high-temperature hot water inlet (52) and a high-temperature hot water outlet (53); the liquid ammonia vaporization tank (6) is divided into a low-temperature deep drying zone, a preheating and preliminary flash evaporation zone, and a high-temperature enhanced evaporation zone from top to bottom; the preheating and preliminary flash evaporation zone... The flash evaporation zone is provided with a liquid ammonia pipeline inlet (63) and multiple liquid ammonia nozzles (62). The liquid ammonia pipeline inlet (63) is connected to the liquid ammonia channel outlet of the liquid ammonia preheating device (5). The high-temperature enhanced evaporation zone is provided with multiple sets of high-temperature hot water pipelines with gradually widening fins (68). The pipeline sets are provided with high-temperature hot water pipeline inlets (61) and high-temperature hot water pipeline outlets (69). The high-temperature hot water pipeline inlets (61) are used to receive high-temperature waste heat from the high-temperature hot water outlet (53) of the preheating device. The low-temperature deep drying zone is provided with a low-temperature hot water pipe network (65) with a super-hydrophilic coating on the surface. The pipe network is provided with a low-temperature hot water pipe network inlet (64) and a low-temperature hot water pipe network outlet (67) for receiving low-temperature waste heat. The ammonia collection and reflux unit includes an ammonia outlet pipe (66) located at the top of the liquid ammonia vaporization tank (6), an ammonia flow valve (7) located on the ammonia outlet pipe (66), a liquid ammonia reflux outlet (610) located at the bottom of the liquid ammonia vaporization tank (6), and a liquid ammonia reflux valve (8) connected to the liquid ammonia reflux outlet (610).

2. The liquid ammonia vaporization device according to claim 1, characterized in that, The high The hot and warm water pipes are arranged in multiple sets in series.

3. The liquid ammonia vaporization device according to claim 1, characterized in that, The high-temperature waste heat received at the inlet (61) of the high-temperature hot water pipe is 70-80℃.

4. The liquid ammonia vaporization device according to claim 1, characterized in that, The low-temperature waste heat received at the inlet (64) of the low-temperature hot water pipeline is 30-40℃.

5. The liquid ammonia vaporization device according to claim 1, characterized in that, The liquid ammonia preheating device (5) is equipped with liquid ammonia pipe fins (51) in the liquid ammonia channel.

6. A method for vaporizing liquid ammonia using the apparatus according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Pump the liquid ammonia to the liquid ammonia preheating device (5) to preheat the liquid ammonia using high-temperature waste heat; S2: The preheated liquid ammonia is atomized and sprayed into the preheating and preliminary flash evaporation zone of the liquid ammonia vaporization tank (6) through multiple liquid ammonia nozzles (62) for preliminary flash evaporation; S3: Utilize the high-temperature residual heat after preheating the liquid ammonia in step S1, and pass it into the enhanced heat exchange pipe of the high-temperature enhanced evaporation zone in the liquid ammonia vaporization tank (6) to heat the atomized liquid ammonia in a high intensity, so as to achieve rapid vaporization of the main body. S4: Use a low-temperature waste heat to enter the low-temperature hot water pipe network (65) at the top of the liquid ammonia vaporization tank (6) to cool and deeply dry the rising gaseous ammonia and remove entrained droplets; S5: Collect and output dried gaseous ammonia from the gaseous ammonia outlet pipe (66), and at the same time return the residual liquid accumulated at the bottom of the tank to the liquid ammonia storage tank (1) through the liquid ammonia return outlet (610).

7. The method according to claim 6, characterized in that, In step S1, the high-temperature waste heat is condensate from a low-temperature heater at 70-80°C.

8. The method according to claim 6, characterized in that, In step S4, the low-temperature waste heat is slag cooling water at 30-40°C.

Images