CN111495293B - Automatic switching control method of hydrolysis reactor for ammonia production system - Google Patents
Automatic switching control method of hydrolysis reactor for ammonia production system Download PDFInfo
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- CN111495293B CN111495293B CN202010321785.8A CN202010321785A CN111495293B CN 111495293 B CN111495293 B CN 111495293B CN 202010321785 A CN202010321785 A CN 202010321785A CN 111495293 B CN111495293 B CN 111495293B
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Abstract
The invention discloses an automatic switching control method of a hydrolysis reactor for an ammonia production system, which preheats a second reactor, controls the pressure of the second reactor to ensure that the pressure of the second reactor stably finishes preheating preparation before switching the second reactor; continuously adjusting the temperature of the second reactor to a first preset temperature value, controlling the urea flow by a second preset flow value matched with the minimum ammonia demand, reducing switching fluctuation, and simultaneously controlling the second reactor and the first reactor to increase and decrease loads in a preset mode when the temperature, the pressure and the urea flow of the second reactor are respectively in a preset deviation range until the urea flow of the first reactor meets the requirement, completing switching, wherein the switching fluctuation in the switching process is small, the pressure of an ammonia main pipe is effectively controlled to be stable, the ammonia yield reaches the boiler requirement, and the NOX excess discharge of a boiler system and the ammonia leakage exceed the standard are prevented; the production working condition is continuous and stable, the workload of operators is reduced, the production efficiency is improved, and the safety production is ensured.
Description
Technical Field
The invention relates to the technical field of automatic control of a hydrolysis reaction system, in particular to an automatic switching control method of a hydrolysis reactor for an ammonia production system.
Background
With the increasing awareness of the safety of the use of liquid ammonia, more and more countries begin to use urea as a source of NH3, and the us and europe have begun to use urea in large quantities as an indirect denitration reducing agent after 90 s.
The urea and water at a certain temperature and pressure can produce a mixture of ammonia and CO2, which is an endothermic reaction. The urea hydrolysis reaction can reach different chemical equilibrium states under different temperatures and pressures, and is generally carried out at 150-300 ℃. Under the temperature and normal pressure, the chemical reaction speed of urea hydrolysis is very slow, the urea hydrolysis reaction needs more than 10 hours to reach the balance, in order to improve the speed of the urea hydrolysis reaction, a urea hydrolysis process using a catalyst is developed abroad, the time for urea hydrolysis to reach the chemical balance can be shortened within 5mins under the lower temperature and pressure through the action of the catalyst, and the usability and the popularization of the urea hydrolysis reaction are greatly improved.
The specific process flow is as follows: after the urea particles are conveyed to a power plant, the urea particles are conveyed to a urea dissolving storage tank in a pneumatic conveying mode, then the urea is dissolved by adding water by utilizing steam heating, a urea solution with the concentration of 40% -50% is prepared, and then the urea solution is conveyed to the urea storage tank through a dissolving pump to be stored for later use, wherein the liquid level and the temperature of the storage solution must meet the requirements of process conveying. Before the start-up of the hydrolysis reactor, the urea solution is supplied by means of a circulation loop by means of a variable-frequency pump.
The heating and the pressure boosting of the hydrolysis reaction are realized through steam, so the steam pressure and the temperature from a power plant need to be adjusted in advance, the adjustment mode is carried out through two temperature and pressure reducing devices, and the steam is conveyed to the reactor through a buffer tank, so that the temperature and the pressure of the hydrolysis reactor are controlled more stably.
The system adopts two hydrolysis reactors to prepare ammonia gas, one is used and the other is prepared (automatic undisturbed switching can be carried out between the two hydrolysis reactors). The two reactors are pre-filled with fixed amount of catalyst, which mainly comprises MAP and DAP, and are common chemical products, under the operating condition of the reactor, the catalyst is in a molten state, the reactor is controlled to operate under constant temperature and constant pressure, such as 165 ℃ and 0.86MPa, the components of the outlet gas can be controlled, and the general concentration of NH3 is about 30%. The main function of the catalyst is to greatly accelerate the reaction speed by changing the path of chemical reaction (regeneration and recycling), and the reaction speed can be improved by 13 times compared with the traditional hydrolysis method. Due to the fact that the reaction speed is accelerated, the control time of the new hydrolysis reaction process is greatly shortened, when the denitration system has large amplitude change to the NH3 demand, the new process can stabilize the NH3 output quantity on a set value within 5mins, and when the amplitude change is small, the load tracking time can be shortened to 1min or shorter.
The automatic undisturbed switching control of the hydrolysis reactor is a key part in the reliable production process of ammonia gas, manual operation is carried out by means of manual experience all the time in China, the number of valves of the hydrolysis reactor is large, the control flow is complex, the safety coefficient is low, stable production of ammonia gas cannot be controlled by a conventional manual switching operation method, ammonia gas over-emission can be generated, NOX can be over-emitted after ammonia supply cannot be obtained by a boiler, the national environment-friendly standard for emission reduction cannot be met, and the automatic undisturbed switching control of the hydrolysis reactor becomes a short plate for reliable production of ammonia gas. Secondly, ammonia is a flammable and explosive hazardous material, and due to the difference of operation levels, if the operation is improper, ammonia leakage can occur, and even the danger of harming the safety of human bodies and equipment can occur.
Disclosure of Invention
In view of the above, the present invention provides an automatic switching control method for a hydrolysis reactor in an ammonia production system, so as to solve the problem that the switching control of the existing hydrolysis reactor is generally operated manually, and ammonia gas over-discharge caused by stable production of ammonia gas cannot be controlled.
In order to achieve the purpose, the invention provides the following technical scheme:
an automatic switching control method of a hydrolysis reactor for an ammonia production system comprises the following steps:
when the first reactor is in an ammonia production mode and the system meets a preset switching condition, respectively controlling a pressure control valve and an air outlet switch valve on an air outlet pipeline of the second reactor to open;
adjusting a first steam flow control valve assembly connected with the second reactor through a first port to bring the temperature of the second reactor to a preheating temperature set value, and preheating the second reactor;
judging whether the pressure of the second reactor is smaller than a first preset pressure value and lasts for a first preset time, if so, controlling a steam switch valve and a second steam flow control valve on a steam injection pipeline connected with the second reactor through a second port to be opened at a first preset flow value;
adjusting the first vapor flow control valve assembly such that the temperature of the second reactor is at a first preset temperature value;
respectively controlling a urea switch valve connected with the second reactor through the second port and a urea flow control valve on a urea solution supply pipeline to be opened at a second preset flow value, wherein the second preset flow value is matched with the minimum ammonia demand;
when the temperature of the second reactor is within the deviation range of the first preset temperature value, the pressure of the second reactor is within the deviation range of a second preset pressure value, and the urea flow of the second reactor is within the deviation range of the second preset flow value and lasts for a second preset time, respectively controlling the second reactor and the first reactor to increase and decrease loads in a preset mode until the urea flow of the first reactor is smaller than a third preset flow value;
and when the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, the ammonia production of the first reactor jumps to the ammonia production of the second reactor, and the ammonia production switching is completed.
Preferably, the adjusting a first steam flow control valve assembly connected with the second reactor through a first port to make the temperature of the second reactor be at a preheating temperature set value, and preheating the second reactor specifically includes:
adjusting a first main steam flow control valve connected with the second reactor through a first main port to enable the temperature of a main reaction zone of the second reactor to be at a main reaction zone preheating temperature set value, and preheating the main reaction zone of the second reactor;
adjusting a first secondary steam flow control valve connected to the second reactor via a second secondary port to bring a temperature of a secondary reaction zone of the second reactor to a secondary reaction zone preheat temperature setpoint;
the first port comprises the first main port and the second sub-port, and the first steam flow control valve assembly comprises a first main steam flow control valve connected with the main reaction zone of the second reactor and a first sub-steam flow control valve connected with the sub-reaction zone of the second reactor.
Preferably, after determining whether the pressure of the second reactor is less than a first preset pressure value for a first preset time, the method further comprises:
if not, judging whether the pressure of the second reactor is larger than or equal to the second preset pressure value and lasts for the first preset time, if so, controlling the steam switch valve and the second steam flow control valve to be closed, opening a flushing switch valve of a flushing water pipeline arranged at the steam outlet end of the steam injection pipeline and closing the flushing switch valve after the flushing switch valve lasts for a third preset time.
Preferably, before the controlling the urea switching valve connected to the second reactor via the second port and the urea flow control valve on the urea solution supply line to open at the second preset flow value, the method further comprises:
and when the current ammonia demand is greater than or equal to the sum of the minimum ammonia demands of the first reactor and the second reactor, and any one urea delivery pump connected with the urea solution supply pipeline is in an operating state and lasts for a fourth preset time, respectively controlling a urea switch valve connected with the second reactor through the second port and a urea flow control valve on the urea solution supply pipeline to be opened at a second preset flow value.
Preferably, after the urea switching valve connected to the second reactor via the second port and the urea flow control valve on the urea solution supply line are respectively controlled to be opened at a second preset flow value, the method further comprises:
counting down by a first timer, judging whether the urea flow of the second reactor is greater than the second preset flow value and continues for a fifth preset time in the counting down process, wherein the duration of the fifth preset time is less than the timing duration of the first timer, if so, the urea flow of the second reactor is in a stable state, and stopping and resetting the first timer;
if not, alarming when the urea flow of the first reactor is lower than the minimum timer, and stopping switching between the first reactor and the second reactor.
Preferably, the increasing and decreasing loads of the second reactor and the first reactor are respectively controlled in a preset manner until the urea flow rate of the first reactor is smaller than a third preset flow rate value, where the preset manner specifically includes:
step a: calculating the urea flow of the first reactor according to a formula, namely the urea flow-1.3 xn corresponding to the current ammonia demand, wherein the urea flow corresponding to the current ammonia demand is the sum of boiler ammonia demands multiplied by 60 multiplied by 1000 multiplied by 0.95/(34 multiplied by the urea concentration + the urea solution density);
step b: calculating the urea flow of the second reactor according to a formula, namely the urea flow of the second reactor is the second preset flow value +1.3 xn;
step c: waiting for a sixth preset time;
step d: judging whether the urea flow of the first reactor is smaller than a third preset flow value or not;
step e: if so, when the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, the ammonia production of the first reactor jumps to the ammonia production of the second reactor, and the ammonia production switching is completed;
step f: if not, updating n, wherein the updated n is n + 1;
step g: repeating the steps a-d;
wherein n is not less than 0 and n is an integer.
Preferably, the method further comprises:
recording the current water replenishing liquid level in the second reactor;
and when the liquid level of the second reactor is lower than the water supplementing liquid level preset liquid level difference in the operation process, opening the flushing switch valve to supplement water until the liquid level of the second reactor rises to the water supplementing liquid level, and closing the flushing switch valve.
Preferably, the stopping of the switching between the first reactor and the second reactor specifically includes:
controlling the urea flow of the first reactor to be gradually increased until the urea flow is larger than the urea flow corresponding to the current ammonia demand and lasting for a seventh preset time;
closing the urea switch valve, an injection air switch valve arranged in an injection air pipeline between the urea flow control valve and the urea switch valve, and the steam switch valve respectively;
the second steam flow control valve, the first steam flow control valve component and the urea flow control valve are respectively arranged manually, and the opening degree is 0;
after waiting for the eighth preset time, opening a flushing switch valve of a flushing water pipeline arranged at the steam outlet end of the steam injection pipeline, and after waiting for the ninth preset time, closing the flushing switch valve;
and when the pressure of the second reactor is less than a third preset pressure value and lasts for a tenth preset time, controlling the pressure control valve to be manual, wherein the opening degree is 0.
Preferably, the system meeting the preset switching condition specifically includes:
and judging whether an absorption tank switching valve connected with the second reactor is closed or not, if so, judging whether any one urea delivery pump connected with the urea solution supply pipeline is in an operating state or not, if so, judging whether the process lasts for 20 seconds or not, and if so, enabling the system to meet preset switching conditions.
Preferably, the method further comprises, prior to adjusting a first steam flow control valve assembly connected to the second reactor via a first port to bring the temperature of the second reactor to a preheat temperature setpoint, preheating the second reactor:
closing the air outlet switch valve, setting the pressure control valve to be manual and the opening degree to be 15%, and waiting for 20 seconds;
judging whether the feedback value of the pressure control valve is less than 10%, if so, setting the pressure control valve to be manual and the opening to be 0, and respectively carrying out the pressure control valve opening test failure of the second reactor and the switching preparation alarm of the reactor quitting;
if not, waiting for 5 seconds, setting the pressure control valve to be manual, setting the opening degree of the pressure control valve to be 0, waiting for 20 seconds, judging whether the feedback value of the pressure control valve is greater than 5%, and if so, respectively carrying out pressure control valve closing test failure of the second reactor and exiting reactor switching preparation alarm; if not, waiting for 5 seconds, setting the pressure control valve to be automatic, and opening the air outlet switch valve.
The invention provides an automatic switching control method of a hydrolysis reactor for an ammonia production system, which comprises the following steps: when the first reactor is in an ammonia production mode and the system meets a preset switching condition, respectively controlling a pressure control valve and an air outlet switch valve on an air outlet pipeline of the second reactor to open; adjusting a first steam flow control valve assembly connected with the second reactor through the first port to enable the temperature of the second reactor to be at a preheating temperature set value, and preheating the second reactor; judging whether the pressure of the second reactor is smaller than a first preset pressure value and lasts for a first preset time, if so, controlling a steam switch valve and a second steam flow control valve on a steam injection pipeline connected with the second reactor through a second port to be opened at a first preset flow value; adjusting the first steam flow control valve assembly so that the temperature of the second reactor is at a first preset temperature value; respectively controlling a urea switch valve connected with the second reactor through a second port and a urea flow control valve on a urea solution supply pipeline to be opened at a second preset flow value, wherein the second preset flow value is matched with the minimum ammonia demand; when the temperature of the second reactor is within the deviation range of a first preset temperature value, the pressure of the second reactor is within the deviation range of a second preset pressure value, and the urea flow of the second reactor is within the deviation range of a second preset flow value for a second preset time, respectively controlling the second reactor and the first reactor to increase and decrease loads in a preset mode until the urea flow of the first reactor is smaller than a third preset flow value; and when the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, the ammonia production of the first reactor jumps to the ammonia production of the second reactor, and the ammonia production switching is completed.
When the automatic switching control method for the hydrolysis reactor for the ammonia production system is applied, provided by the invention, when the hydrolysis reactor needs to be switched, the first steam flow control valve assembly is adjusted to preheat the second reactor, the pressure of the second reactor is controlled to be smaller than a first preset pressure value and lasts for a first preset time, the pressure of the second reactor is ensured to be stable, and the preheating preparation before the switching of the second reactor is finished; and continuously adjusting the temperature value of the second reactor to a first preset temperature value, and opening a urea switch valve and a urea flow control valve by a second preset flow value matched with the minimum ammonia demand to reduce switching fluctuation, meanwhile, when the temperature, the pressure and the urea flow of the second reactor are respectively in the preset deviation ranges, respectively controlling the second reactor and the first reactor to increase and decrease the load in a preset mode until the urea flow of the first reactor is smaller than a third preset flow value, the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, completing the switching from the ammonia production of the first reactor to the ammonia production of the second reactor, the switching fluctuation in the switching process is small, the pressure of the ammonia gas main pipe is effectively controlled to be stable, the ammonia gas output meets the requirement of a boiler, and the excessive discharge of NOX in a boiler system and the excessive ammonia gas leakage are prevented; the production working condition is continuous and stable, the workload of operators is reduced, the production efficiency is improved, and the safety production is ensured.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic flow chart of a method for automatically switching and controlling hydrolysis reactors in an ammonia production system according to an embodiment of the present invention;
FIG. 2 is a schematic process flow diagram of an ammonia production system provided by an embodiment of the present invention;
fig. 3 is a schematic system structure diagram of an ammonia production system according to an embodiment of the present invention.
The drawings are numbered as follows:
a first reactor 1 and a second reactor 2;
urea flow control valve 21, injection air on-off valve 22, urea on-off valve 23, steam on-off valve 24, second steam flow control valve 25, flush water on-off valve 26, first steam flow control valve assembly 27, first main steam flow control valve 271, first sub-steam flow control valve 272, ammonia removal absorption valve 28, pressure control valve 29, and outlet on-off valve 210.
Detailed Description
The embodiment of the invention discloses an automatic switching control method for a hydrolysis reactor for an ammonia production system, which aims to solve the problems that the switching control of the existing hydrolysis reactor is generally operated manually, and the ammonia gas is over-discharged due to the fact that the stable production of the ammonia gas cannot be controlled.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In a specific embodiment, the automatic switching control method for the hydrolysis reactor of the ammonia production system provided by the invention is based on an ammonia production system, as shown in fig. 2-3, and fig. 2 is a schematic process flow diagram of the ammonia production system provided by the embodiment of the invention; fig. 2 is a schematic system structure diagram of an ammonia production system according to an embodiment of the present invention. The system comprises a first reactor and a second reactor, wherein the gas outlet pipelines of the first reactor and the second reactor are respectively connected with a denitration pipeline and an ammonia removal absorption tank pipeline. The first reactor and the second reactor are connected with the same pipeline, the second reactor is used for explanation, the second reactor comprises a main reaction area and a side reaction area, the main reaction area and the side reaction area are respectively connected with a heating steam pipeline and a condensate water recovery pipeline, a first steam flow control valve assembly is arranged on the heating steam pipeline, and the first steam flow control valve assembly is connected with the second reactor through a first port; the second reactor is also connected with an injection steam pipeline, a urea solution supply pipeline, an injection air pipeline and a flushing water pipeline through the first port, wherein the urea solution supply pipeline and the injection air pipeline are communicated with the second port through a urea switch valve, the flushing water pipeline is arranged at the steam outlet end of the injection steam pipeline, and the pressure reduction and other operations are carried out through flushing water. The denitration pipeline is provided with a pressure control valve and an air outlet switch valve, and the ammonia absorption tank pipeline is provided with an ammonia absorption valve.
As shown in fig. 1, fig. 1 is a schematic flow chart of an automatic switching control method for a hydrolysis reactor of an ammonia production system according to an embodiment of the present invention; the method comprises the following steps:
s11: when the first reactor is in an ammonia production mode and the system meets a preset switching condition, respectively controlling a pressure control valve and an air outlet switch valve on an air outlet pipeline of the second reactor to open;
here and hereinafter, the system, i.e. the ammonia production system described above, performs the switching between the first reactor and the second reactor when the system meets the preset switching condition, such as at least one urea solution delivery pump is in an operating state, at least one superheat attemperation pump is in an operating state, and the like, so as to ensure the stability of the system during the switching between the two reactors, such as when the above state lasts for more than 20 seconds, and then performs the next step S12.
S12: adjusting a first steam flow control valve assembly connected with the second reactor through the first port to enable the temperature of the second reactor to be at a preheating temperature set value, and preheating the second reactor;
the preheating temperature setting value is 155 ℃, which is realized by adjusting the opening degree and the control flow of the first steam flow control valve assembly, preferably, when the temperature of the second reactor is at the preheating temperature setting value and lasts for a certain time, such as 3-5 seconds, the temperature of the second reactor is considered to tend to be stable, and in other embodiments, the preheating temperature setting value and the preheating time duration can be set as required.
S13: judging whether the pressure of the second reactor is smaller than a first preset pressure value and lasts for a first preset time, if so, controlling a steam switch valve and a second steam flow control valve on a steam injection pipeline connected with the second reactor through a second port to be opened at a first preset flow value;
after the second reactor is preheated, whether the pressure of the second reactor meets the requirement or not is judged to reduce the pressure disturbance to the ammonia gas main pipe in the switching process, the first preset pressure value can be set to be 0.84Mpa in one embodiment, the first preset time can be set to be 10 seconds, and the first preset flow value is 80 kg/h.
When the pressure of the second reactor is greater than or equal to a first preset pressure value and lasts for a first preset time, setting the second steam flow control valve to be manual by using the optical ratio steam switch valve, wherein the opening degree is 0; opening a flushing water switch valve to reduce the pressure, and setting the temperature of the solution in the alarm reactor B to be 158 ℃ lower for use; the alarm reactor B can be used when the temperature of the solution is low 138 ℃.
S14: adjusting the first steam flow control valve assembly so that the temperature of the second reactor is at a first preset temperature value; it will be appreciated that the first predetermined temperature value is greater than the pre-heat temperature set point, which is typically set at 162 c, and the pressure of the injected air is greater than 0.9 Mpa. When the pressure of the jet air is less than 0.9Mpa in the process, the jet air switch valve of the second reactor is closed to give an alarm, the jet air switch valve is opened, 5 seconds are waited, and an alarm that the temperature of the blowdown area of the first reactor is low and the deviation is 10 ℃ is available is set; the '24-hour low deviation of the temperature of a sewage discharge area' can be used at 5 ℃; the "second reactor demister differential pressure high" 7KPa was available;
setting a urea flow control valve to be manual, opening the urea flow control valve to be 0, opening the urea switch valve, and waiting for 15 seconds; and judging whether the pressure of the injected air is less than 0.9Mpa, if not, closing the injection air switch valve, so that the pressure of the injected air is increased to ensure the injection pressure of the urea pipeline.
S15: respectively controlling a urea switch valve connected with the second reactor through a second port and a urea flow control valve on a urea solution supply pipeline to be opened at a second preset flow value, wherein the second preset flow value is matched with the minimum ammonia demand;
the minimum ammonia demand is set according to the requirement, generally 25kg/h, and the second preset flow value is calculated according to the minimum ammonia demand. It can be understood that the current ammonia gas demand is equal to or greater than the sum of the minimum ammonia demands of the first reactor and the second reactor, so that the ammonia demand of the system is ensured to be smooth and not to generate large fluctuation during the switching process. As in one embodiment, the minimum ammonia demand of the first reactor and the second reactor is set the same. When the current ammonia demand is less than 2 times of the minimum ammonia demand and lasts for 5 seconds and the timer does not count time, starting the timer, setting the time to be 100 seconds, and alarming that the ammonia demand is lower than the minimum demand in the switching transition mode of the reactor;
when the current ammonia gas demand is more than or equal to 2 times of the minimum ammonia demand and lasts for 5 seconds and the timer is timing, stopping and resetting the timer, and alarming to switch the transition mode that the ammonia gas demand is more than the minimum demand;
when the timer expires for 100 seconds, the ammonia demand is lower than the minimum demand in the alarm reactor switching process, the timer expires, the timer is reset, the alarm forced switching stop mode is carried out, and the first reactor and the second reactor stop switching.
S16: when the temperature of the second reactor is within the deviation range of the first preset temperature value, the pressure of the second reactor is within the deviation range of the second preset pressure value, and the urea flow of the second reactor is within the deviation range of the second preset flow value for a second preset time, the second reactor and the first reactor are respectively controlled to increase and decrease loads in a preset mode until the urea flow of the first reactor is smaller than the third preset flow value.
The first preset temperature value, the second preset pressure value and the second preset flow value are preset values set according to requirements, in one embodiment, the first preset temperature value is 162 ℃ and the deviation range is 1 ℃; the second preset pressure value is 0.88Mpa, and the deviation range is 0.01 Mpa; the urea flow rate of the second reactor was 78L/h with a deviation of 2L/h. When the temperature of the second reactor is less than 161 ℃, the pressure of the second reactor is less than 163 ℃, the pressure of the second reactor is less than 0.89Mpa, the pressure of the second reactor is less than 0.87Mpa, the urea flow of the second reactor is less than 80L/h, and the process lasts for 1 minute, the second preset time can be set by self in other embodiments, and the preset mode such as timing and quantitative mode simultaneously increases and decreases the same value for the two reactors; or slightly increasing or decreasing the load for the first time, such as simultaneously increasing or decreasing 1-1.5L/h for the first time and 1.5-3L/h for the second time, thereby gradually increasing the load until the urea flow rate of the first reactor is less than a third preset flow rate value and exceeds a preset time, such as 9 seconds, so as to ensure the flow rate to be stable, wherein the third preset flow rate value is equal to the second preset flow rate value +1.
S17: and when the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, the ammonia production of the first reactor jumps to the ammonia production of the second reactor, and the ammonia production switching is completed. The urea flow converted from the current ammonia demand is equal to the sum of ammonia demand from a boiler, namely x 60 x 1000 x 0.95/(34 x urea concentration (normally 45-50%) × urea solution density (normally 1100kg/m3-1150kg/m 3)). The 'ammonia demand from the boiler' is generally between 25m3/h and 35m3/h, and the current ammonia demand changes along with the change of the boiler load. The deviation range may be set to ± 2L/h. The third duration may be set to 1 minute. Above ammonia output accords with the switching in-process, and the ammonia rate of two steerable reactors production guarantees the smooth transition of system, and the main pipe pressure of ammonia keeps steady, satisfies the boiler side demand to ammonia.
When the automatic switching control method for the hydrolysis reactor for the ammonia production system is applied, provided by the invention, when the hydrolysis reactor needs to be switched, the first steam flow control valve assembly is adjusted to preheat the second reactor, the pressure of the second reactor is controlled to be smaller than a first preset pressure value and lasts for a first preset time, the pressure of the second reactor is ensured to be stable, and the preheating preparation before the switching of the second reactor is finished; and continuously adjusting the temperature value of the second reactor to a first preset temperature value, and opening a urea switch valve and a urea flow control valve by a second preset flow value matched with the minimum ammonia demand to reduce switching fluctuation, meanwhile, when the temperature, the pressure and the urea flow of the second reactor are respectively in the preset deviation ranges, respectively controlling the second reactor and the first reactor to increase and decrease the load in a preset mode until the urea flow of the first reactor is smaller than a third preset flow value, the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, completing the switching from the ammonia production of the first reactor to the ammonia production of the second reactor, the switching fluctuation in the switching process is small, the pressure of the ammonia gas main pipe is effectively controlled to be stable, the ammonia gas output meets the requirement of a boiler, and the excessive discharge of NOX in a boiler system and the excessive ammonia gas leakage are prevented; the production working condition is continuous and stable, the workload of operators is reduced, the production efficiency is improved, and the safety production is ensured.
When the second reactor comprises a main reactor and a secondary reaction zone, adjusting a first steam flow control valve assembly connected with the second reactor through a first port to enable the temperature of the second reactor to be at a preheating temperature set value, and preheating the second reactor, specifically comprising:
adjusting a first main steam flow control valve connected with the second reactor through the first main port to enable the temperature of a main reaction zone of the second reactor to be at a main reaction zone preheating temperature set value, and preheating the main reaction zone of the second reactor;
adjusting a first secondary steam flow control valve connected to the second reactor via a second secondary port to bring the temperature of the secondary reaction zone of the second reactor to a secondary reaction zone preheat temperature setpoint;
the first port includes a first primary port and a second secondary port, and the first vapor flow control valve assembly includes a first primary vapor flow control valve connected to the primary reaction zone of the second reactor and a first secondary vapor flow control valve connected to the secondary reaction zone of the second reactor.
If the flow of the first main steam flow control valve is adjusted to be 200kg/h, when the temperature of the main reaction zone is more than or equal to the preset temperature set value of the main reaction zone for more than 3 seconds, the first main steam flow control valve is set to be automatic, the temperature of the main reaction zone is controlled to be the preset temperature set value of the main reaction zone, and the preset temperature set value of the main reaction zone is 155 ℃;
the opening of the first secondary steam flow control valve is adjusted to be 7%, when the temperature of the secondary reaction zone is greater than or equal to the pre-heating temperature set value of the secondary reaction zone for more than 5 seconds, the first secondary steam flow control valve is set to automatically set the temperature of the secondary reaction zone, the pre-heating temperature set value of the secondary reaction zone is preferably 152 ℃, and in other embodiments, the temperature and the steam flow can be set according to needs.
Preferably, after determining whether the pressure of the second reactor is less than a first preset pressure value for a first preset time, the method further comprises:
if not, judging whether the pressure of the second reactor is larger than or equal to a second preset pressure value and lasts for a first preset time, if so, controlling the steam switch valve and the second steam flow control valve to be closed, opening a flushing switch valve of a flushing water pipeline arranged at the steam outlet end of the steam injection pipeline and closing the flushing switch valve after the flushing switch valve lasts for a third preset time.
And explaining that the first preset pressure value is 0.84Mpa and the second preset time is 10 seconds, judging whether the pressure of the second reactor is less than 0.84 and lasts for 10 seconds, if not, judging whether the pressure of the second reactor is more than 0.84 and lasts for 10 seconds, if so, indicating that the current pressure of the second reactor is higher, controlling a flushing switch valve to flush, and setting the third preset time to be 10-15 seconds.
Further, before controlling the urea on-off valve connected to the second reactor via the second port and the urea flow control valve on the urea solution supply line to open at a second preset flow value, the method further comprises:
and when the current ammonia demand is more than or equal to the sum of the minimum ammonia demands of the first reactor and the second reactor, and any one urea delivery pump connected with the urea solution supply pipeline is in an operating state and lasts for a fourth preset time, respectively controlling a urea switch valve connected with the second reactor through the second port and a urea flow control valve on the urea solution supply pipeline to be opened at a second preset flow value.
Preferably, the minimum ammonia demands of the first reactor and the second reactor are set to be equal, any one urea delivery pump is in a running state, and the process lasts for 15 seconds, so that the follow-up operation is carried out after the ammonia demand is stable.
Furthermore, after controlling the urea on-off valve connected to the second reactor via the second port and the urea flow control valve on the urea solution supply line to open at a second preset flow value, the method further comprises:
counting down by a first timer, judging whether the urea flow of the second reactor is greater than a second preset flow value and continues for a fifth preset time in the counting down process, wherein the duration of the fifth preset time is less than the timing duration of the first timer, if so, the urea flow of the second reactor is in a stable state, and stopping and resetting the first timer; therefore, the current ammonia demand is prevented from being reduced, and the reactor switching cannot be carried out.
If not, alarming when the urea flow of the first reactor is lower than the minimum timer, and stopping switching the first reactor and the second reactor. The fifth preset time may be set to 30 seconds.
After the steps are finished, timing is carried out, the reactor is subjected to increase and decrease switching operation after the timing is finished, and an alarm that the flow deviation of the urea solution in the second reactor is too high is available (the deviation is more than 100L/h, and the alarm is delayed for 2 minutes);
the alarm of the 'the flow deviation of the urea solution in the second reactor is too high' is made available (the deviation is more than 100L/H, and the alarm is delayed for 2 minutes);
making an alarm "the deviation of the density of the urea solution in the second reactor is too high" available, and the deviation of the density of the urea solution in the second reactor from 1120kg/m3 (the density of the urea solution at 50 ℃) is more than 100 kg/m;
making the alarm 'the flow of the urea solution in the second reactor is high' 1100L/h available;
the alarm "the pressure of the second reactor is low" 0.7MPa can be used.
On the basis of the above embodiments, the load increase and decrease of the second reactor and the first reactor are respectively controlled in a preset manner until the urea flow rate of the first reactor is smaller than a third preset flow rate value, and the preset manner specifically includes:
step a: calculating to obtain the urea flow of the first reactor according to a formula, wherein the urea flow of the first reactor is equal to the urea flow-1.3 xn corresponding to the current ammonia demand, and the urea flow corresponding to the current ammonia demand is equal to the sum of the boiler ammonia demands, namely x 60 x 1000 x 0.95/(34 x urea concentration + urea solution density);
step b: calculating the urea flow of the second reactor according to the formula, wherein the urea flow of the second reactor is a second preset flow value plus 1.3 xn;
step c: waiting for a sixth preset time;
step d: judging whether the urea flow of the first reactor is smaller than a third preset flow value or not;
step e: if so, when the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, the ammonia production of the first reactor jumps to the ammonia production of the second reactor, and the ammonia production switching is completed;
step f: if not, updating n, wherein the updated n is n + 1;
step g: repeating the steps a-d;
wherein n is not less than 0 and n is an integer.
The steps are adopted to realize the operation of increasing and decreasing the loads of the first reactor and the second reactor in a timing and quantitative mode. The sixth time is set to 10 seconds, the third preset flow value is equal to the minimum ammonia demand +1, and when the urea flow rate of the first reactor is less than the third preset flow value and lasts for 9 seconds, the next step is executed. Wherein, the concentration of the urea is generally 45-50%, and the density of the urea solution is 1100kg/m3-1150kg/m 3.
In one embodiment, the method further comprises:
recording the current water replenishing liquid level in the second reactor;
and when the liquid level of the second reactor is lower than the water supplementing liquid level preset liquid level difference in the operation process, opening the flushing switch valve to supplement water until the liquid level of the second reactor rises to the water supplementing liquid level, and closing the flushing switch valve.
Therefore, under the ammonia production mode of the second reactor, the liquid level is supplemented, and the preset liquid level difference can be set to be 10 mm.
In one embodiment, stopping the switching between the first reactor and the second reactor specifically comprises:
controlling the urea flow of the first reactor to be gradually increased until the urea flow is larger than the urea flow corresponding to the current ammonia demand and continuing for a seventh preset time; wherein the same urea flow rate or different urea flow rates can be increased in series, or in one embodiment a): calculating the urea flow of the first reactor according to the formula, namely the urea flow corresponding to the current ammonia demand and 1.3 to obtain the urea flow of the first reactor;
b) the method comprises the following steps Waiting for 10 s;
c) the method comprises the following steps Judging whether the urea flow of the first reactor is larger than the urea flow corresponding to the current ammonia demand by + 1;
d) the method comprises the following steps If not, continuing to execute the steps a) to c);
e) the method comprises the following steps If yes, closing the urea switch valve, an injection air switch valve of an injection air pipeline arranged between the urea flow control valve and the urea switch valve and a steam switch valve respectively; the second steam flow control valve, the first steam flow control valve component and the urea flow control valve are respectively arranged manually, and the opening degree is 0; after waiting for the eighth preset time, opening a flushing switch valve of a flushing water pipeline arranged at the steam outlet end of the steam injection pipeline, and after waiting for the ninth preset time, closing the flushing switch valve; and when the pressure of the second reactor is less than the third preset pressure value and lasts for the tenth preset time, controlling the pressure control valve to be manual, and controlling the opening degree to be 0.
Wherein the first steam flow control valve assembly includes a first primary steam flow control valve and a first secondary steam flow control valve. The eighth preset time is set to be 1 minute, the ninth preset time is set to be 5 minutes, the tenth preset time is 100 seconds, the third preset pressure value is 0.79Mpa, the actions are quitted from the switching of the reactors, and ammonia is generated only through the first reactor.
The pressure control valve of the ammonia gas main pipe is arranged automatically, and the pressure control valve of the first reactor is arranged automatically to regulate the pressure. Setting the alarm that the flow of the urea solution in the second reactor is high to be unavailable; making the alarm that the flow deviation of the urea solution in the second reactor is too high unavailable; making the alarm that the flow deviation of the urea solution in the second reactor is too high unavailable; making the alarm that the urea solution density deviation of the second reactor is too high unavailable; making an alarm "second reactor solution temperature low" unusable; the alarm "the second reactor solution temperature is low" is made unusable; making an alarm "low deviation of temperature in blowdown zone of second reactor" unavailable; making an alarm "the temperature of the blowdown area of the second reactor is low for 24 hours" unavailable; the valves of the first reactor were closed.
When any one of the following alarm signals is received, stopping switching between the first reactor and the second reactor, if all the urea delivery pumps do not confirm operation; the second reactor discharges the fault of the switch valve to the absorption tank; the liquid level of the second reactor is higher than 1.2 m; the height of the liquid level of the blowdown area of the second reactor is more than 1.2 m; "second reactor solution temperature high" greater than 185 ℃; the temperature of the blowdown area of the second reactor is higher than 185 ℃; the pressure of the safety valve pipeline of the second reactor is higher than 0.67 MPa; a second reactor steam injection switch valve off failure; the second reactor urea switch valve open failure; a second reactor urea switch valve off failure; a second reactor steam switch valve open failure; a second reactor steam switch valve off failure; the "second reactor pressure high" is greater than 1.02 MPa; the flow height of the heating steam of the second reactor is more than 1350 kg/h; the flow height of the urea solution in the second reactor is more than 1100L/h; the' second reactor solution temperature is lower than 138 ℃; the first reactor exits the ammonia production mode of operation.
Specifically, the system meeting the preset switching condition specifically includes:
and judging whether an absorption tank switching valve connected with the second reactor is closed or not, if so, judging whether any one urea delivery pump connected with the urea solution supply pipeline is in an operating state or not, if so, judging whether the process lasts for 20 seconds or not, and if so, enabling the system to meet a preset switching condition.
Further, adjusting a first vapor flow control valve assembly connected to the second reactor via the first port to bring the temperature of the second reactor to a preheat temperature setpoint, prior to preheating the second reactor, the method further comprises:
closing the air outlet switch valve, setting the pressure control valve to be manual, setting the opening degree to be 15%, and waiting for 20 seconds;
judging whether the feedback value of the pressure control valve is less than 10%, if so, setting the pressure control valve to be manual and the opening to be 0, and respectively carrying out the switching preparation alarm of the pressure control valve of the second reactor when the opening test fails and the reactor exits;
if not, waiting for 5 seconds, setting the pressure control valve to be manual, setting the opening degree to be 0, after waiting for 20 seconds, judging whether the feedback value of the pressure control valve is greater than 5%, if so, respectively carrying out pressure control valve closing test failure of the second reactor and exiting reactor switching preparation alarm; if not, waiting for 5 seconds, setting the pressure control valve to be automatic, and opening the air outlet switch valve. And testing the switch of the pressure control valve through the valve pulling test.
After the step of S1, when an alarm signal is received, the switching between the first reactor and the second reactor is stopped, and the alarm is given, namely the liquid level of the blowdown area of the second reactor is high; "high second reactor solution temperature"; "high temperature of blowdown zone of second reactor"; "high second reactor heating steam flow"; "second reactor heating steam switch valve open failure"; "second reactor heating steam switch valve off failure"; "second reactor blowdown zone heating steam switch valve open failure"; "second reactor pressure high"; the pipeline pressure of the safety valve of the second reactor is high; "second reactor jet steam switch valve open failure"; "high steam injection flow rate in the second reactor"; "second reactor jet steam switch valve off failure"; initializing again, closing a steam switch valve of a second reactor, setting a second steam flow control valve, a first main steam flow control valve and a first auxiliary steam flow control valve to be manual, setting the opening degree to be 0, and setting an alarm that the solution temperature of the second reactor is low to be unavailable; setting the 'second reactor solution temperature low' to be unavailable; and when the fault of the double-pressure transmitter of the second reactor is not reported, setting the pressure control valve to be automatic, setting the pressure of the second reactor to be a preset value, waiting for 1 minute, judging whether the pressure of the second reactor is greater than the preset value of-0.02 Mpa and lasting for 5 seconds, if so, opening a flushing water switch valve, and closing after waiting for 3 minutes.
And when the fault of the double pressure transmitters of the second reactor is alarmed, judging whether the pressure of the second reactor is less than a preset value of-0.1 Mpa for 100 seconds, and if so, exiting the reactor switching mode.
The ammonia yield load switching can control the ammonia production rate of the two reactors to be 2.5kg/min, can ensure the stable transition of the system, and basically keeps the pressure of the ammonia main pipe stable, thereby meeting the requirement of SCR (boiler side) on ammonia. Under the condition of failure or alarm, the reactor equipment can still ensure the normal and stable operation of the system through automatic undisturbed switching, and ensure that NOX and ammonia escape of a boiler system do not exceed standards. The production is safe and reliable, and the environmental protection reaches the standard. The method can adapt to each production scale controlled by one reactor and one standby reactor in the catalytic hydrolysis ammonia production; and the environmental pollution is reduced. Plays a key role in preventing NOX from being excessively exhausted for the thermal power plant boiler, and indirectly protects the environment. The labor intensity of operators is reduced, the engineering debugging and the operation maintenance work in the complex control process are simplified, the workload of maintenance personnel is reduced, the human-computer interface is friendly, and better automatic control is realized
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. A method for automatically switching and controlling a hydrolysis reactor for an ammonia production system is characterized by comprising the following steps:
when the first reactor is in an ammonia production mode and the system meets a preset switching condition, respectively controlling a pressure control valve and an air outlet switch valve on an air outlet pipeline of the second reactor to open;
adjusting a first steam flow control valve assembly connected with the second reactor through a first port to bring the temperature of the second reactor to a preheating temperature set value, and preheating the second reactor;
judging whether the pressure of the second reactor is smaller than a first preset pressure value and lasts for a first preset time, if so, controlling a steam switch valve and a second steam flow control valve on a steam injection pipeline connected with the second reactor through a second port to be opened at a first preset flow value;
adjusting the first vapor flow control valve assembly such that the temperature of the second reactor is at a first preset temperature value;
respectively controlling a urea switch valve connected with the second reactor through the second port and a urea flow control valve on a urea solution supply pipeline to be opened at a second preset flow value, wherein the second preset flow value is matched with the minimum ammonia demand;
when the temperature of the second reactor is within the deviation range of the first preset temperature value, the pressure of the second reactor is within the deviation range of a second preset pressure value, and the urea flow of the second reactor is within the deviation range of the second preset flow value and lasts for a second preset time, respectively controlling the second reactor and the first reactor to increase and decrease loads in a preset mode until the urea flow of the first reactor is smaller than a third preset flow value;
when the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, the ammonia production of the first reactor jumps to the ammonia production of the second reactor, and the ammonia production switching is completed;
wherein, the system meeting the preset switching condition specifically comprises:
judging whether an absorption tank switching valve connected with the second reactor is closed or not, if so, judging whether any one urea delivery pump connected with the urea solution supply pipeline is in an operating state or not, if so, judging whether the process lasts for 20 seconds or not, and if so, enabling the system to meet a preset switching condition;
the load increase and decrease of the second reactor and the first reactor are respectively controlled in a preset mode until the urea flow of the first reactor is smaller than a third preset flow value, and the preset mode specifically comprises the following steps:
step a: calculating the urea flow of the first reactor according to a formula, namely the urea flow of the first reactor = urea flow-1.3 xn corresponding to the current ammonia demand, wherein the urea flow corresponding to the current ammonia demand = the sum of boiler ammonia demands × 60 × 1000 × 0.95/(34 × urea concentration + urea solution density);
step b: calculating the urea flow of the second reactor according to the formula of the urea flow of the second reactor = the second preset flow value +1.3 xn;
step c: waiting for a sixth preset time;
step d: judging whether the urea flow of the first reactor is smaller than a third preset flow value or not;
step e: if so, when the urea flow of the second reactor is within the deviation range of the urea flow corresponding to the current ammonia demand and lasts for a third preset time, the ammonia production of the first reactor jumps to the ammonia production of the second reactor, and the ammonia production switching is completed;
step f: if not, updating n, wherein the updated n = n + 1;
step g: repeating the steps a-d;
wherein n is not less than 0 and n is an integer.
2. The automatic switching control method for the hydrolysis reactor of the ammonia production system according to claim 1, wherein the adjusting the first steam flow control valve assembly connected to the second reactor through the first port to make the temperature of the second reactor at the preheating temperature set point for preheating the second reactor comprises:
adjusting a first main steam flow control valve connected with the second reactor through a first main port to enable the temperature of a main reaction zone of the second reactor to be at a main reaction zone preheating temperature set value, and preheating the main reaction zone of the second reactor;
adjusting a first secondary steam flow control valve connected to the second reactor via a second secondary port to bring a temperature of a secondary reaction zone of the second reactor to a secondary reaction zone preheat temperature setpoint;
the first port comprises the first main port and the second sub-port, and the first steam flow control valve assembly comprises a first main steam flow control valve connected with the main reaction zone of the second reactor and a first sub-steam flow control valve connected with the sub-reaction zone of the second reactor.
3. The automatic switching control method for the hydrolysis reactor in the ammonia production system according to claim 1, wherein the determining whether the pressure of the second reactor is less than a first preset pressure value for a first preset time period further comprises:
if not, judging whether the pressure of the second reactor is larger than or equal to the second preset pressure value and lasts for the first preset time, if so, controlling the steam switch valve and the second steam flow control valve to be closed, opening a flushing switch valve of a flushing water pipeline arranged at the steam outlet end of the steam injection pipeline and closing the flushing switch valve after the flushing switch valve lasts for a third preset time.
4. The automatic switching control method for the hydrolysis reactor in the ammonia production system according to claim 1, wherein before the urea switching valve connected to the second reactor via the second port and the urea flow control valve on the urea solution supply line are respectively controlled to be opened at a second preset flow value, the method further comprises:
and when the current ammonia demand is greater than or equal to the sum of the minimum ammonia demands of the first reactor and the second reactor, and any one urea delivery pump connected with the urea solution supply pipeline is in an operating state and lasts for a fourth preset time, respectively controlling a urea switch valve connected with the second reactor through the second port and a urea flow control valve on the urea solution supply pipeline to be opened at a second preset flow value.
5. The automatic switching control method for the hydrolysis reactor in the ammonia production system according to claim 1, wherein after the urea switching valve connected to the second reactor via the second port and the urea flow control valve on the urea solution supply line are respectively controlled to be opened at a second preset flow value, the method further comprises:
counting down by a first timer, judging whether the urea flow of the second reactor is greater than the second preset flow value and continues for a fifth preset time in the counting down process, wherein the duration of the fifth preset time is less than the timing duration of the first timer, if so, the urea flow of the second reactor is in a stable state, and stopping and resetting the first timer;
if not, alarming when the urea flow of the first reactor is lower than the minimum timer, and stopping switching between the first reactor and the second reactor.
6. The automatic switching control method for the hydrolysis reactor in the ammonia production system according to claim 3, further comprising:
recording the current water replenishing liquid level in the second reactor;
and when the liquid level of the second reactor is lower than the water supplementing liquid level preset liquid level difference in the operation process, opening the flushing switch valve to supplement water until the liquid level of the second reactor rises to the water supplementing liquid level, and closing the flushing switch valve.
7. The automatic switching control method for the hydrolysis reactor of the ammonia production system according to claim 5, wherein the stopping of the switching of the first reactor and the second reactor specifically comprises:
controlling the urea flow of the first reactor to be gradually increased until the urea flow is larger than the urea flow corresponding to the current ammonia demand and lasting for a seventh preset time;
closing the urea switch valve, an injection air switch valve arranged in an injection air pipeline between the urea flow control valve and the urea switch valve, and the steam switch valve respectively;
the second steam flow control valve, the first steam flow control valve component and the urea flow control valve are respectively arranged manually, and the opening degree is 0;
after waiting for the eighth preset time, opening a flushing switch valve of a flushing water pipeline arranged at the steam outlet end of the steam injection pipeline, and after waiting for the ninth preset time, closing the flushing switch valve;
and when the pressure of the second reactor is less than a third preset pressure value and lasts for a tenth preset time, controlling the pressure control valve to be manual, wherein the opening degree is 0.
8. The automatic shift control method for a hydrolysis reactor in an ammonia production system of claim 1, wherein the adjusting a first vapor flow control valve assembly connected to the second reactor via a first port to bring the temperature of the second reactor to a preheat temperature setpoint further comprises, prior to preheating the second reactor:
closing the air outlet switch valve, setting the pressure control valve to be manual and the opening degree to be 15%, and waiting for 20 seconds;
judging whether the feedback value of the pressure control valve is less than 10%, if so, setting the pressure control valve to be manual and the opening to be 0, and respectively carrying out the pressure control valve opening test failure of the second reactor and the switching preparation alarm of the reactor quitting;
if not, waiting for 5 seconds, setting the pressure control valve to be manual, setting the opening degree of the pressure control valve to be 0, waiting for 20 seconds, judging whether the feedback value of the pressure control valve is greater than 5%, and if so, respectively carrying out pressure control valve closing test failure of the second reactor and exiting reactor switching preparation alarm; if not, waiting for 5 seconds, setting the pressure control valve to be automatic, and opening the air outlet switch valve.
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| CN201458752U (en) * | 2009-06-24 | 2010-05-12 | 成都锐思环保技术有限责任公司 | Urea hydrolysis system for preparing reducing agent needed by flue gas denitrification |
| EP2354092A1 (en) * | 2010-01-29 | 2011-08-10 | Ammonia Casale S.A. | A method for modernizing the synthesis loop of an ammonia plant |
| US9849444B2 (en) * | 2014-09-15 | 2017-12-26 | Paccar Inc | Urea hydrolysis reactor for selective catalytic reduction |
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| CN107721799A (en) * | 2017-10-20 | 2018-02-23 | 中石化上海工程有限公司 | The method that parallel reactor pattern automatically switches |
| CN207950685U (en) * | 2017-12-29 | 2018-10-12 | 安徽六国化工股份有限公司 | The circulatory system is cut in a kind of evaporation of urea melting liquid |
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