Water injection optimization method and control system for reaction effluent of hydrogenation device
By establishing a process model and DCS system in the hydrogenation unit, the distribution and quantity of water injection points can be monitored and optimized in real time, solving the problems of fixed water injection volume and substandard water quality. This enables precise control of ammonium salt corrosion and improves the safety and stability of the unit.
Patent Information
- Application Number
- CN202511730192.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-24
- Publication Date
- 2026-02-03
AI Technical Summary
In existing hydrogenation units, the fixed water injection volume and location cannot be dynamically adjusted according to changes in ammonium salt production, resulting in poor corrosion prevention. Furthermore, substandard water quality may exacerbate equipment corrosion. The lack of real-time monitoring means leads to unstable corrosion prevention.
A process model was established using Aspen Plus process simulation software. Combined with the DCS system, the distribution of water injection points and the amount of water injected were monitored and adjusted in real time. The ammonium salt corrosion rate and water quality were monitored by an online detection device. The amount of water injected was dynamically optimized, and a water purification device was set up to ensure that the water quality of the injected water meets the standards.
It enables precise control of ammonium salt corrosion in hydrogenation units, reduces water waste, lowers the load on subsequent wastewater treatment, improves the safety and reliability of unit operation, and prevents equipment corrosion caused by poor water quality.
Smart Images
Figure CN121446409A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of corrosion protection technology for chemical equipment, specifically to a method and control system for optimizing water injection into the effluent from a hydrogenation unit. Background Technology
[0002] During operation, in hydrogenation units (such as hydrocracking and hydrorefining units), nitrogen compounds in the feedstock are converted into ammonia (NH3) during the hydrogenation reaction. Ammonia combines with hydrogen sulfide (H2S) generated in the reaction to form ammonium salts such as ammonium chloride (NH4Cl) and ammonium hydrosulfide (NH4HS). These ammonium salts, in a gaseous state at high temperatures, flow sequentially through the high-pressure heat exchanger and high-pressure air cooler with the reaction effluent. When the temperature drops below the crystallization temperature, the ammonium salts crystallize and precipitate in the high-pressure heat exchanger, air cooler, and their pipelines. The precipitated ammonium salts not only cause blockages in equipment and pipelines, leading to increased pressure drop and decreased heat exchange efficiency, but more seriously, they absorb moisture to form highly corrosive ammonium salt solutions, causing severe electrochemical corrosion of equipment and pipelines. This results in thinning of the equipment and pipeline walls, leaks, and even ruptures, seriously threatening the safe and stable operation of the hydrogenation unit.
[0003] Currently, the common industrial solution is to inject water into the salt-prone areas of the hydrogenation unit. This dissolves and carries away the precipitated ammonium salts, preventing corrosion. However, existing water injection methods have several shortcomings: First, the injection volume is often fixed, failing to dynamically adjust according to changes in ammonium salt formation. This leads to insufficient water injection and poor corrosion prevention in some operating conditions; or excessive water injection wastes water resources and increases the load on subsequent wastewater treatment. Second, the fixed injection location makes it impossible to accurately replenish water based on changes in the ammonium salt crystallization area, easily resulting in localized salt corrosion. Third, there is a lack of precise control over the injection water quality; some injections, due to high chloride ion content and unsuitable pH values, actually exacerbate equipment corrosion. Fourth, outdated monitoring methods prevent real-time monitoring of corrosion and timely adjustment of the injection volume, leading to unstable corrosion prevention effects. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a method and control system for optimizing water injection into the effluent from a hydrogenation unit reaction.
[0005] The technical solution adopted in this invention is: A method for optimizing water injection of the reaction effluent from a hydrogenation unit includes the following steps: (1) Based on the historical operating parameters of the hydrogenation unit reaction effluent, a process model of the hydrogenation reaction effluent was established using Aspen Plus process simulation software and ENRTL-RK method; (2) Determine the initial distribution location of the water injection points of the reaction effluent through the process model; and install a detection device at each water injection point to detect the ammonium salt corrosion rate, water injection volume and material temperature at each water injection point; (3) The operating parameters of the reaction effluent of the hydrogenation unit are collected in real time through the DCS system, and the operating parameters are input into the process model established in step (1). The real-time distribution of water injection points, as well as the ammonium salt crystallization rate and crystallization temperature of each water injection point, are determined according to the process model. The reference water injection volume of each water injection point is determined according to the ammonium salt crystallization rate. (4) The DCS system compares the real-time distribution of water injection points obtained in step (3) with the initial distribution of water injection points obtained in step (2), and shuts down all other water injection points except for the real-time distribution points; the detection device transmits the ammonium salt corrosion rate, water injection volume and material temperature of each water injection point collected in real time to the DCS system; when the ammonium salt corrosion rate of a certain water injection point exceeds its ammonium salt crystallization rate, the DCS system turns on the water injection system to inject water into the water injection point; and when the material temperature of a certain water injection point is lower than its ammonium salt crystallization temperature or its ammonium salt corrosion rate exceeds its critical corrosion rate, the water injection volume of that point is increased by a certain value based on the benchmark water injection volume; when the material temperature of a certain water injection point is higher than its initial ammonium salt crystallization temperature, the water injection volume of that water injection point is decreased by a certain value based on the benchmark water injection volume.
[0006] Furthermore, step (4) also includes: when the ammonium salt corrosion rate at a certain water injection point exceeds its critical corrosion rate, the DCS system issues an early warning signal.
[0007] Furthermore, the upward adjustment value of the water injection volume is 10-15%, and the downward adjustment value of the water injection volume is 5-10%.
[0008] Furthermore, in steps (1) and (3), the operating parameters include the sulfur, nitrogen, and chlorine content of the hydrogenation reaction feedstock, the temperature and pressure of each hydrogenation reaction unit, and the circulating hydrogen flow rate.
[0009] Furthermore, in step (3), the baseline water injection volume and the initial ammonium salt crystallization rate satisfy the following relationship: H0 = k1 * V0; Where H0 is the baseline water injection volume, m³ / h; V0 is the initial ammonium salt crystallization rate, kg / h; and k1 is the proportionality coefficient, k1 = 8~12 m³ / kg.
[0010] Furthermore, the method for optimizing water injection of the reaction effluent from a hydrogenation unit further includes: (5) Connect each water injection point to the water purification device through an online water quality analyzer. The conductivity, pH value and chloride ion content of the injected water are collected in real time by the online water quality analyzer. When the conductivity, pH value and chloride ion content are higher than their set values, the DCS system starts the water purification device to purify the injected water.
[0011] Furthermore, the conductivity was set to 5 μS / cm, the pH value to 7.5, and the chloride ion content to 1 mg / L.
[0012] A control system for optimizing the water injection of the effluent from any of the above-mentioned hydrogenation units is a DCS system, comprising a data acquisition module, a core calculation module, an execution module, and a monitoring module. The data acquisition module collects the sulfur, nitrogen, and chlorine content of the hydrogenation feedstock, the temperature and pressure of each hydrogenation reaction unit, and the circulating hydrogen flow rate, and transmits this data to the core calculation module. The monitoring module monitors the ammonium salt corrosion rate, water injection volume, stream temperature, and water quality at each water injection point in real time, and transmits this data to the core calculation module. The core calculation module generates instructions based on the process model of the hydrogenation reaction effluent and sends these instructions to the execution module. The execution module performs the switching of each water injection point, adjustment of the water injection volume, and water purification.
[0013] The beneficial effects of this invention are: 1. By constructing a process model of the hydrogenation reaction effluent and combining it with a DCS system, the distribution of water injection points and the optimized regulation of water injection volume at each point are dynamically controlled. This achieves precise prevention and control of ammonium salt corrosion in the hydrogenation unit, significantly improving the safety and reliability of the unit's operation. The dynamic water injection mechanism can adjust the water injection points and volume according to real-time operating conditions, effectively avoiding the excessive water injection problem that occurs with traditional fixed water injection methods. This saves water resources and reduces the load on subsequent wastewater treatment.
[0014] 2. By setting strict water quality indicators and implementing real-time monitoring, equipment corrosion caused by poor water quality is effectively prevented, further enhancing the overall anti-corrosion effect.
[0015] 3. The control system integrates intelligent monitoring functions, which can collect corrosion status and water injection parameters in real time, and realize automatic adjustment based on feedback, reducing the need for manual intervention and comprehensively improving the stability of the control process and the engineering applicability of the method. Attached Figure Description
[0016] Figure 1 This is a control system framework diagram of the present invention.
[0017] Figure 2 This is a flowchart of the hydrogenation process in Example 1.
[0018] Figure 3This is a process model diagram of the hydrogenation reaction effluent from Example 1.
[0019] Figure 4 This is a map showing the distribution of water injection points predicted based on the process model. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and preferred embodiments.
[0021] This application provides a control system for a water injection optimization method for the reaction effluent of a hydrogenation unit.
[0022] like Figure 1 As shown, the control system is a DCS system, which includes a data acquisition module, a core computing module, an execution module, and a monitoring module. The data acquisition module is used to collect the sulfur, nitrogen, and chlorine content of the hydrogenation feedstock, the temperature and pressure of each hydrogenation reaction unit, and the circulating hydrogen flow rate of the hydrogenation system, and transmit them to the core computing module. The monitoring module is used to monitor the ammonium salt corrosion rate, water injection volume, material temperature, and water quality at each water injection point in real time, and transmit them to the core computing module. The core computing module is used to generate instructions based on the process model of the hydrogenation reaction effluent and send the instructions to the execution module. The execution module performs the switching of each water injection point, the adjustment of the water injection volume, and the water purification.
[0023] The monitoring module includes a corrosion probe, a flow sensor, a temperature sensor, and an online water quality analyzer. The online water quality analyzer is used to collect the conductivity, pH value, and chloride ion content of the injected water in real time. The execution module includes a water purification device and a water injection device. The water injection device is connected to each water injection point through water injection pipelines and control valves. The online water quality analyzer is installed on the water injection pipelines. The water purification device is connected to the water injection device. The water purification device is existing technology; for example, a reverse osmosis system can be selected. The water injection device is existing technology; for example, it can be a water pump or a water tank.
[0024] In this embodiment, a resistance corrosion probe is used, with a measurement accuracy of ±0.001 mm / a.
[0025] Both the water purification device and the water injection device are existing technologies, and their structure and working principle will not be described in detail here.
[0026] The following practical application case illustrates in detail the water injection optimization method and its effects of the present invention. Example
[0027] Figure 2This is a process flow diagram of the residue hydrocracking process at Maoming Petrochemical. In the diagram: R-101 is the reactor, E-101, E-102, and E-103 are high-pressure heat exchangers, A-101 is the air cooler, V-101 is the hot high-pressure separator, V-102 is the cold high-pressure separator, V-108 is the water tank, and P-105 is the water pump. Figure 3 The diagram shows the process model of the hydrogenation reaction effluent. In the diagram, R-102, R-103, and R-104 are mixers. Figure 4 This is a distribution map of water injection points predicted by the process model. In the map: Z is a corrosion probe, F is a flow sensor, T is a temperature sensor, and H is an online water quality analyzer.
[0028] like Figure 2 As shown, the feedstock oil for the hydrotreating process is heated and mixed with hydrogen before entering reactor R-101. After the reaction is complete, it exchanges heat with E-101 and enters the hot high-pressure separator V-101 for gas-liquid two-phase separation. The hot high-pressure gas at the top exchanges heat again before entering the cold high-pressure separator V-102. It is cooled from 377°C at the inlet of separator V-101 to 42°C at the outlet of air cooler A-101. During the reaction, the corrosive gas reacts continuously during the cooling and heat exchange stages, continuously forming corrosive ammonium salt crystals.
[0029] The original water injection scheme for this device was as follows: water was injected at a single point before the air cooler A-101 (temperature 280℃, pressure 16MPa), with a water injection rate of 15t / h. The water quality was deoxygenated water (pH=7.0~7.5, conductivity ≤100μS / cm), without online monitoring or dynamic adjustment mechanism.
[0030] Since its commissioning, the unit has exhibited significant ammonium salt crystallization and corrosion issues in high-pressure heat exchangers E-102 and E-103 and air cooler A-101. During maintenance in 2024, it was discovered that white ammonium salt crystals with a thickness of 2-5 mm were present in the inlet sections of the high-pressure heat exchangers and air coolers, corresponding to pitting corrosion on the inner walls of the pipelines. The maximum corrosion depth reached 0.8 mm, and the corrosion rate reached 0.12 mm / a. The analysis of the corrosion causes was as follows: insufficient water injection, excessively high water injection point temperature, which caused some water to vaporize and fail to effectively dissolve the ammonium salts. Furthermore, the lack of water injection in the low-temperature section exacerbated the ammonium salt crystallization blockage and corrosion in the inlet area of the air cooler.
[0031] The method used in this invention is as follows: (1) First, the key operating parameters of the device over the past 6 months were collected through the DCS system, including: sulfur, nitrogen, and chlorine content of the feedstock oil, reaction temperature and pressure of the high-pressure heat exchanger and air cooler, and circulating hydrogen flow rate of the hydrogenation system. The control range of each parameter is: nitrogen content 0.1-1.5 wt%, sulfur content 1.8-2.5 wt%, chlorine content 0.5-1.5 ppm, reaction temperature 180-350℃, reaction pressure 8-18 MPa, and circulating hydrogen flow rate 1000-5000 Nm³ / h; (2) Based on the above data, a process model of the hydrogenation reaction effluent system was established using Aspen Plus process simulation software and the ENRTL-RK method, such as Figure 3 As shown. The method for establishing the process model of the hydrogenation reaction effluent system is existing technology, and its principle will not be elaborated here; (3) Based on the above process model, determine the original distribution location of the water injection points of the device, such as... Figure 4 As shown in the figure. The simulation results indicate that the high-risk locations for ammonium salt crystallization corrosion in the hydrogenation unit coincide with the corrosion locations discovered during maintenance.
[0032] (4) Modify the original device according to the original distribution of water injection points obtained from the simulation and add water injection points; for example, add candidate water injection points 1m-2m before the inlet of high pressure heat exchangers E-102 and E-103 respectively to form three-point water injection for the initial dissolution of some ammonium salts generated in the high temperature section. Upgrade the water injection point before the original air cooler A-101 and set a distribution pipe at the inlet of the air cooler tube bundle to directly act on the key area of ammonium salt crystallization. Install a detection device at each water injection point. The detection device is a corrosion probe, a flow sensor and a temperature sensor. Connect the water injection device to each water injection point through pipelines. Connect the water purification device to the outlet pipeline of the water injection device. Set an online water quality analyzer on the outlet pipeline of the water injection device.
[0033] (5) During operation, the improved device collects hydrogenation process parameters in real time through the DCS system and inputs them into the process model to simulate the chemical reaction process of sulfur, nitrogen, and chlorine components being converted into intermediates such as NH3, H2S, and HCl, and then generating ammonium salts. The real-time distribution of water injection points is obtained, and the crystallization rate and temperature of ammonium salts in the tube bundles of high-pressure heat exchangers E-102 and E-103, and the crystallization rate and temperature of ammonium salts in the tube bundles of air cooler A-101 are calculated to determine the crystallization rate, crystallization temperature, reference water injection volume, and water volume adjustment coefficient of each water injection point. The ammonium salt corrosion rate, water injection volume, and material temperature of each water injection point are collected through the detection device. The conductivity, pH value, and chloride ion content of the injected water are collected in real time through the online water quality analyzer. (6) The DCS system compares the real-time distribution of water injection points obtained in step (3) with the initial distribution of water injection points obtained in step (2) and shuts down all other water injection points except those at the real-time distribution locations. When the ammonium salt corrosion rate of a certain water injection point exceeds its ammonium salt crystallization rate, the DCS system starts the water injection system to inject water into that water injection point. When the material temperature of a certain water injection point is lower than its ammonium salt crystallization temperature or its ammonium salt corrosion rate exceeds its critical corrosion rate, the water injection volume of that point is increased by 10-15% based on the benchmark water injection volume. When the material temperature of a certain water injection point is higher than its initial ammonium salt crystallization temperature, the water injection volume of that water injection point is decreased by 5-10% based on the benchmark water injection volume. During this process, the conductivity, pH value and chloride ion content of the injected water are collected in real time by an online water quality analyzer. When the conductivity, pH value and chloride ion content are higher than their set values, the DCS system starts the water purification device to purify the injected water.
[0034] In this embodiment, the conductivity is set to 5 μS / cm, the pH value is set to 7.5, and the chloride ion content is set to 1 mg / L.
[0035] After a period of actual operation, according to statistical data, the method of the present invention can reduce water consumption by 5-15%. Within one and a half years of operation, the ammonium salt crystallization rate in the tubes of the high-pressure heat exchanger and air cooler is significantly reduced, and no corrosion or perforation of equipment and pipelines is found.
[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.
Claims
1. A method for optimizing water injection into the effluent from a hydrogenation unit, characterized in that, Includes the following steps: (1) Based on the historical operating parameters of the hydrogenation unit reaction effluent, a process model of the hydrogenation reaction effluent was established using Aspen Plus process simulation software and the ERTL-RK method; (2) Determine the initial distribution location of the water injection points of the reaction effluent through the process model; and install a detection device at each water injection point to detect the ammonium salt corrosion rate, water injection volume and material temperature at each water injection point; (3) The operating parameters of the reaction effluent of the hydrogenation unit are collected in real time through the DCS system, and the operating parameters are input into the process model established in step (1). The real-time distribution of water injection points, as well as the ammonium salt crystallization rate and crystallization temperature of each water injection point, are determined according to the process model. The baseline water injection volume for each injection point is determined based on the ammonium salt crystallization rate. (4) The DCS system compares the real-time distribution of water injection points obtained in step (3) with the initial distribution of water injection points obtained in step (2), and shuts down all other water injection points except for the real-time distribution points; the detection device transmits the ammonium salt corrosion rate, water injection volume and material temperature of each water injection point collected in real time to the DCS system; when the ammonium salt corrosion rate of a certain water injection point exceeds its ammonium salt crystallization rate, the DCS system turns on the water injection system to inject water into the water injection point; and when the material temperature of a certain water injection point is lower than its ammonium salt crystallization temperature or its ammonium salt corrosion rate exceeds its critical corrosion rate, the water injection volume of that point is increased by a certain value based on the benchmark water injection volume; when the material temperature of a certain water injection point is higher than its initial ammonium salt crystallization temperature, the water injection volume of that water injection point is decreased by a certain value based on the benchmark water injection volume.
2. The method for optimizing water injection of the reaction effluent from a hydrogenation unit according to claim 1, characterized in that, Step (4) also includes: when the ammonium salt corrosion rate at a certain water injection point exceeds its critical corrosion rate, the DCS system issues an early warning signal.
3. The method for optimizing water injection of the reaction effluent from a hydrogenation unit according to claim 1, characterized in that, The water injection volume can be increased by 10-15% and decreased by 5-10%.
4. The method for optimizing water injection of the reaction effluent from a hydrogenation unit according to claim 1, characterized in that, In steps (1) and (3), the operating parameters include the sulfur, nitrogen, and chlorine content of the hydrogenation reaction feedstock, the temperature and pressure of each hydrogenation reaction unit, and the circulating hydrogen flow rate.
5. The method for optimizing water injection of the reaction effluent from a hydrogenation unit according to claim 1, characterized in that, In step (3), the baseline water injection volume and the initial ammonium salt crystallization rate satisfy the following relationship: H0 = k1 * V0; Where H0 is the baseline water injection volume, m³ / h; V0 is the initial ammonium salt crystallization rate, kg / h; and k1 is the proportionality coefficient, k1 = 8~12 m³ / kg.
6. The method for optimizing water injection of the reaction effluent from a hydrogenation unit according to claim 1, characterized in that, Also includes: (5) Connect each water injection point to the water purification device through an online water quality analyzer. The conductivity, pH value and chloride ion content of the injected water are collected in real time by the online water quality analyzer. When the conductivity, pH value and chloride ion content are higher than their set values, the DCS system starts the water purification device to purify the injected water.
7. The method for optimizing water injection of the reaction effluent from a hydrogenation unit according to claim 6, characterized in that, The conductivity was set to 5 μS / cm, the pH value to 7.5, and the chloride ion content to 1 mg / L.
8. A control system for a water injection optimization method for the reaction effluent of a hydrogenation unit as described in any one of claims 1 to 7, characterized in that, The control system is a DCS system, which includes a data acquisition module, a core computing module, an execution module, and a monitoring module. The data acquisition module is used to collect the sulfur, nitrogen, and chlorine content of the hydrogenation feedstock, the temperature and pressure of each hydrogenation reaction unit, and the circulating hydrogen flow rate; and transmits it to the core computing module. The monitoring module is used to monitor the ammonium salt corrosion rate, water injection volume, material temperature, and water quality at each water injection point in real time, and transmit it to the core computing module. The core calculation module is used to generate instructions based on the process model of the hydrogenation reaction effluent and send the instructions to the execution module. The execution module performs the switching of each water injection point, the adjustment of water injection volume, and water purification.