A method for quickly checking the smoke failure of tail gas chimney in sulfuric acid production process

Abstract

A method for quickly checking the smoke failure of tail gas chimney in sulfuric acid production process, comprising the following steps: first check the outlet of the second absorption tower, if the outlet of the second absorption tower emits white smoke, then check the outlet of the first absorption tower; if the outlet of the second absorption tower does not emit white smoke, it is a desulfurization tower failure; check the outlet of the first absorption tower, if the outlet of the first absorption tower emits white smoke, then check the inlet gas temperature of the first absorption tower and the tail of the boiler; if the inlet gas temperature of the first absorption tower is stable, it indicates that the absorption efficiency of the first absorption tower is low; if the inlet gas temperature of the first absorption tower rises significantly, the vehicle should be stopped for inspection; if the outlet of the tail of the boiler emits white smoke, then detect and analyze the drying tower outlet and the drying moisture of the tail of the boiler; if the outlet of the first absorption tower does not emit white smoke, it is a coal economizer leakage or the absorption rate of the second absorption tower is low. The method of the present invention is simple and efficient, has high accuracy, does not require complex inspection, and has good effect through many years of production practice. It can quickly and accurately find the fault location and eliminate the chimney smoking failure in time.

Description

Technical Field

[0001] The invention relates to the technical field of sulfuric acid production, and in particular to a method for quickly inspecting smoke failures in a tail gas chimney in a sulfuric acid production process. Background Art

[0002] It is a common process phenomenon that tail gas chimneys of sulfuric acid plants emit a lot of smoke. Since tail gas from chimneys involves environmental protection, the emission of smoke will lead to a sharp increase in acid mist, a decrease in the absorption rate of the absorption tower, air pollution, and poor sensory perception. It is necessary to find the root cause of the problem and solve it immediately. There are many reasons for tail gas to emit a lot of smoke, and it is quite laborious to find the problem.

[0003] The emission of smoke from the tail gas of the acid unit is a common process failure. Shortening the time to find the fault and solving the problem of smoke in time can reduce environmental and economic losses. Under the increasingly stringent environmental protection requirements, in addition to the continuous improvement of process management for normal production, accurate judgment and timely emergency treatment are also required when abnormalities occur. Due to the different production process technology levels of each unit, it is usually not easy to solve the problem of smoke in time. It is very necessary to have an effective and quick method to check and judge the smoke, which is of great help to improve the level of production management and prevent environmental accidents. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned defects and provide a method for quickly checking the smoke failure of the tail gas chimney in the sulfuric acid production process.

[0005] A method for quickly checking smoke failure in a tail gas chimney in a sulfuric acid production process comprises the following steps:

[0006] If the tail gas chimney is smoking, first check the outlet of the second absorption tower. If white smoke is emitted from the outlet of the second absorption tower, check the outlet of the first absorption tower. If white smoke is not emitted from the outlet of the second absorption tower, it is a desulfurization tower failure. Check whether the desulfurization process parameters of the desulfurization tower are normal.

[0007] Check the outlet of the first absorption tower. If white smoke comes out of the outlet of the first absorption tower, check the inlet gas temperature of the first absorption tower and the tail of the boiler;

[0008] If the inlet gas temperature of the first absorption tower is stable, it indicates that the absorption efficiency of the first absorption tower is low. Check whether the acid concentration, acid temperature, acid amount, tower inlet air temperature and parameters of the acid distributor of the first absorption tower are normal.

[0009] If the inlet gas temperature of the first absorption tower rises significantly, there are three situations: if the outlet temperature of the economizer in front of the first absorption tower rises, and the outlet temperatures of the boiler and superheater are stable, the economizer in front of the first absorption tower is leaking, and the engine should be stopped for maintenance; if the outlet temperature of the superheater in front of the first absorption tower rises, and the outlet temperatures of the economizer and boiler are stable, the superheater in front of the first absorption tower is leaking, and the engine should be stopped for maintenance; if the inlet gas temperature of the second absorption tower rises, the acid concentration of the first absorption tower decreases, and the outlet temperature of the boiler decreases, it means that the boiler tube has burst, and the engine should be stopped for maintenance;

[0010] If white smoke comes out of the outlet of the boiler tail, then check and analyze the drying water content at the outlet of the drying tower and the boiler tail. If the drying water content is high, then check whether the dryer acid concentration, acid temperature, acid supply and parameters of the acid distributor are normal. If the drying water content is normal, it means that the moisture content at the outlet of the incinerator is high. At this time, check the water content of the liquid sulfur, organic matter and the leakage of the sulfonator.

[0011] If there is no white smoke at the outlet of the first absorption tower, it means that the economizer is leaking or the absorption rate of the second absorption tower is low. Check the inlet temperature of the second absorption tower. If the temperature rises significantly, the economizer in front of the second absorption tower is leaking. At this time, the machine should be stopped for inspection and maintenance. If the temperature is stable, it means that the absorption efficiency of the second absorption tower is low. Check whether the acid concentration, acid temperature, acid supply amount, tower inlet temperature and acid distributor parameters of the second absorption tower are normal.

[0012] The process flow of the sulfuric acid production process is as follows:

[0013] Granular solid sulfur is used as the production raw material, which is sent to the rapid sulfur melting tank via a belt conveyor. The solid sulfur is melted into liquid by steam heating, and then sent to the liquid sulfur storage tank for storage after clarification and filtration.

[0014] Liquid sulfur passes through the refined sulfur tank, and is atomized by a sulfur pump through a sulfur gun and sent into the sulfur incinerator. It burns and reacts with the air dried by the drying tower sent by the main fan in the sulfur incinerator to generate SO2 furnace gas, and at the same time releases a large amount of heat energy. The heat energy is recovered by the boiler to produce saturated steam. The SO2 furnace gas passes through the gas filter and enters the first stage of the conversion reaction. The high-temperature furnace gas of the first reaction exchanges heat with the superheated steam from the low-temperature superheater in the superheater to generate superheated medium-pressure steam that is sent to the steam turbine unit for power generation. After the high-temperature furnace gas is cooled, it enters the second and third stages of the converter. After the heat is recovered by the economizer, it enters the first absorption tower (high-temperature absorption tower) to absorb and produce product sulfuric acid. The furnace gas coming out of the first absorption tower (high-temperature absorption tower) is heated by the cold and hot heat exchangers and then enters the fourth stage of the converter. The reaction furnace gas first recovers heat energy through the low-temperature superheater, and then enters the second absorption tower after further recovering heat energy through the economizer, and then is desulfurized by the tail gas desulfurization tower and discharged from the chimney.

[0015] When the organic matter content in liquid sulfur is high, water is produced during combustion. The moisture content at the outlet of the sulfur incinerator is 20-50 times higher than that at the import. Adjust the sulfur supplier and origin according to the export moisture content to reduce the organic matter content in the sulfur. If the liquid sulfur has a high water content, increase the stirring time of the molten sulfur and the clarification time of the liquid sulfur to allow the water to fully evaporate.

[0016] If the drying effect of the drying tower is poor and the moisture content of the furnace gas is high, adjust the amount of acid in the upper tower or increase the concentration of drying acid based on the drying moisture analysis data; clean the packing of the drying tower to reduce resistance and increase surface area.

[0017] The normal temperature difference between the upper and lower towers of the first absorption tower and the second absorption tower is between 20-30℃, and the acid concentration in the lower tower is 0.3%-0.5% higher than that in the upper tower.

[0018] When the absorption acid concentration is 98%-98.5%, the equilibrium partial pressure of water and sulfur trioxide in sulfuric acid is the lowest and the absorption efficiency is the highest.

[0019] During the start-up process, the absorbed acid temperature is controlled between 60-80℃.

[0020] The normal temperature difference between the upper and lower towers of the drying tower is between 8-15℃, and the acid concentration in the lower tower is 0.3%-0.5% lower than that in the upper tower.

[0021] The following abnormal phenomena occur when a boiler tube bursts:

[0022] ①The furnace gas temperature at the tail of the furnace continues to drop;

[0023] ② The boiler feed water volume increases;

[0024] ③The tail gas chimney emits a lot of smoke;

[0025] ④ The inlet temperature of the first absorption tower continues to rise, and the temperature rise exceeds 15℃;

[0026] ⑤ When the concentration of the first-stage acid in low-temperature waste heat recovery decreases, the injection water decreases, and the boiler leaks a lot, the concentration of the first-stage acid cannot be maintained, and a low limit alarm is issued;

[0027] ⑥ There is obvious smoke at the smoke emission inspection port at the outlets of the first and second absorption towers;

[0028] ⑦ The temperature of each section of the converter is out of control, rising or falling abnormally. When the leakage is small, the conversion temperature rises, and when the leakage is large, the conversion temperature will drop seriously;

[0029] ⑧ Check if there is condensed acid discharged from the valve at the bottom of the economizer;

[0030] When ①, ③, ④, and ⑤ of the above phenomena occur simultaneously, it can be determined that a tube burst has occurred in the boiler.

[0031] The advantages of the present invention are as follows: the method for quickly checking the process fault of smoke emission from the chimney of sulfuric acid production tail gas of the present invention is simple, efficient, highly accurate, very practical, does not require complicated inspections, and has been used in production practice for many years with good results. The fault location can be found quickly and accurately every time, and the chimney smoking fault can be eliminated in time.

[0032] Instruction Manual

[0033] Figure 1 The present invention is a flow chart of the inspection method.

[0034] Figure 2 This is the process flow chart of sulfuric acid production process. DETAILED DESCRIPTION

[0035] The present invention will be described in further detail below in conjunction with embodiments of the present invention:

[0036] A method for quickly checking smoke failure in a tail gas chimney in a sulfuric acid production process comprises the following steps:

[0037] If the tail gas chimney is smoking, first check the outlet of the second absorption tower. If white smoke is emitted from the outlet of the second absorption tower, check the outlet of the first absorption tower. If white smoke is not emitted from the outlet of the second absorption tower, it is a desulfurization tower failure. Check whether the desulfurization process parameters of the desulfurization tower are normal.

[0038] Check the outlet of the first absorption tower. If white smoke comes out of the outlet of the first absorption tower, check the inlet gas temperature of the first absorption tower and the tail of the boiler;

[0039] If the inlet gas temperature of the first absorption tower is stable, it indicates that the absorption efficiency of the first absorption tower is low. Check whether the acid concentration, acid temperature, acid amount, tower inlet air temperature and parameters of the acid distributor of the first absorption tower are normal.

[0040] If the inlet gas temperature of the first absorption tower rises significantly, there are three situations: if the outlet temperature of the economizer in front of the first absorption tower rises, and the outlet temperatures of the boiler and superheater are stable, the economizer in front of the first absorption tower is leaking, and the engine should be stopped for maintenance; if the outlet temperature of the superheater in front of the first absorption tower rises, and the outlet temperatures of the economizer and boiler are stable, the superheater in front of the first absorption tower is leaking, and the engine should be stopped for maintenance; if the inlet gas temperature of the second absorption tower rises, the acid concentration of the first absorption tower decreases, and the outlet temperature of the boiler decreases, it means that the boiler tube has burst, and the engine should be stopped for maintenance;

[0041] If white smoke comes out of the outlet of the boiler tail, then check and analyze the drying water content at the outlet of the drying tower and the boiler tail. If the drying water content is high, then check whether the dryer acid concentration, acid temperature, acid supply and parameters of the acid distributor are normal. If the drying water content is normal, it means that the moisture content at the outlet of the incinerator is high. At this time, check the water content of the liquid sulfur, organic matter and the leakage of the sulfonator.

[0042] If there is no white smoke at the outlet of the first absorption tower, it means that the economizer is leaking or the absorption rate of the second absorption tower is low. Check the inlet temperature of the second absorption tower. If the temperature rises significantly, the economizer in front of the second absorption tower is leaking. At this time, the machine should be stopped for inspection and maintenance. If the temperature is stable, it means that the absorption efficiency of the second absorption tower is low. Check whether the acid concentration, acid temperature, acid supply amount, tower inlet temperature and acid distributor parameters of the second absorption tower are normal.

[0043] As attached Figure 2 As shown in the figure, the process flow of sulfuric acid production is as follows:

[0044] Granular solid sulfur is used as the production raw material, which is sent to the rapid sulfur melting tank via a belt conveyor. The solid sulfur is melted into liquid by steam heating, and then sent to the liquid sulfur storage tank for storage after clarification and filtration.

[0045] Liquid sulfur passes through the refined sulfur tank, and is atomized by a sulfur pump through a sulfur gun and sent into the sulfur incinerator. It burns and reacts with the air dried by the drying tower sent by the main fan in the sulfur incinerator to generate SO2 furnace gas, and at the same time releases a large amount of heat energy. The heat energy is recovered by the boiler to produce saturated steam. The SO2 furnace gas passes through the gas filter and enters the first stage of the conversion reaction. The high-temperature furnace gas of the first reaction exchanges heat with the superheated steam from the low-temperature superheater in the superheater to generate superheated medium-pressure steam that is sent to the steam turbine unit for power generation. After the high-temperature furnace gas is cooled, it enters the second and third stages of the converter. After the heat is recovered by the economizer, it enters the first absorption tower (high-temperature absorption tower) to absorb and produce product sulfuric acid. The furnace gas coming out of the first absorption tower (high-temperature absorption tower) is heated by the cold and hot heat exchangers and then enters the fourth stage of the converter. The reaction furnace gas first recovers heat energy through the low-temperature superheater, and then enters the second absorption tower after further recovering heat energy through the economizer, and then is desulfurized by the tail gas desulfurization tower and discharged from the chimney.

[0046] There are generally three reasons why the tail gas chimney emits a lot of smoke. The first reason is that the sulfur trioxide flue gas entering the absorption tower contains water, and the acid mist cannot be absorbed. The acid mist that is not absorbed is discharged from the tail gas chimney and emits a lot of smoke; the second reason is that the absorption tower itself does not meet the process indicators, resulting in a decrease in the absorption rate, and the acid mist that is not absorbed is discharged from the tail gas chimney and emits a lot of smoke. The third reason is that the tail gas absorption tower itself does not meet the process indicators. For example, the tail gas absorption tower using the ammonia desulfurization process has a high pH value of the desulfurization liquid and excessive ammonia is added, resulting in ammonia escape. When encountering an external environment with high water content and low temperature, the ammonia in the tail gas combines with water to form ammonia mist. Ammonia mist, like sulfur trioxide acid mist, can cause tail gas to emit a lot of smoke.

[0047] The first reason is that the sulfur trioxide flue gas entering the absorption tower contains water, and the acid mist cannot be absorbed. There are mainly the following situations:

[0048] 1. Water entering the flue gas is caused by organic matter and water brought in by raw materials. For example, liquid sulfur contains organic matter, and organic matter contains hydrocarbons. Water is produced by combustion, and water combines with sulfur trioxide to produce acid mist. The evaporation time of water in liquid sulfur is short, and there is no time to evaporate completely, or the steam coil leaks steam. In this case, the dry moisture can be detected at the inlet and outlet of the sulfur incinerator. Generally, when the organic content of liquid sulfur is high, the organic matter contains C and H compounds, and water is produced during combustion. The moisture at the outlet of the sulfur incinerator is about 20-50 times higher than that at the inlet. Adjust the sulfur supplier and origin according to the outlet moisture to reduce the organic content in sulfur as much as possible. If the water content of liquid sulfur is high, the stirring time of molten sulfur and the clarification time of liquid sulfur can be increased to allow the moisture to fully evaporate.

[0049] 2. The drying effect of the drying tower is poor and the moisture content of the furnace gas is high. According to the drying moisture analysis data, adjust the amount of acid in the upper tower or appropriately increase the drying acid concentration; clean the packing of the drying tower to reduce resistance and increase the surface area.

[0050] 3. Water or steam leaks from the boiler system and enters the furnace gas, which has a high water content. The fire tube boiler of the sulfuric acid plant bursts, causing a large amount of boiler water to enter the furnace gas. When the boiler bursts, the water side pressure of the fire tube boiler is about 3.8MPa, and the furnace gas side pressure is about 30KPa. Once the boiler bursts, a large amount of boiler water enters the furnace gas, causing serious corrosion to subsequent equipment, and the furnace gas and water combine to produce a large amount of acid mist. The chimney exhaust emits a lot of smoke, which has a great impact on safety and environmental protection. The following abnormal phenomena occur when the boiler bursts:

[0051] ①The furnace gas temperature at the tail of the furnace continues to drop;

[0052] ② The boiler feed water volume increases;

[0053] ③The tail gas chimney emits a lot of smoke;

[0054] ④ The inlet temperature of the first absorption tower or high-temperature absorption tower (low-temperature waste heat recovery system) continues to rise, and the temperature rise exceeds 15°C;

[0055] ⑤ When the concentration of the first-stage acid in low-temperature waste heat recovery decreases, the injection water decreases, and the boiler leaks a lot, the concentration of the first-stage acid cannot be maintained, and a low limit alarm is issued;

[0056] ⑥ There is obvious smoke at the flue gas discharge inspection port at the outlet of the first absorption tower or high temperature tower and the outlet of the second absorption tower;

[0057] ⑦ The temperature of each section of the converter is out of control, rising or falling abnormally. When the leakage is small, the conversion temperature rises, and when the leakage is large, the conversion temperature will drop seriously;

[0058] ⑧ Check if there is condensed acid discharged from the valve at the bottom of the economizer;

[0059] When ①, ③, ④, and ⑤ of the above phenomena occur simultaneously, it can be determined that a tube burst has occurred in the boiler.

[0060] The second reason is that the absorption tower itself does not meet the process indicators, resulting in a decrease in absorption rate. According to production practice, when the absorption tower absorption rate is higher than 99.7%, no smoke can be seen at the outlet of the second absorption tower; when it is 99.5%, a small amount of smoke can be seen at the outlet of the second absorption tower; when it is lower than 99.0%, thick smoke can be seen at the outlet of the second absorption tower. The main reasons for the decrease in absorption rate are as follows:

[0061] 1. The acid concentration is too high or too low. When the concentration of the absorbed acid reaches more than 99.3% to form fuming acid, the equilibrium partial pressure of sulfur trioxide gas gradually increases, and sulfur trioxide gas volatilizes from the acid into the furnace gas. Not only can it not absorb sulfur trioxide, but it increases the concentration of sulfur trioxide, and the absorption rate is greatly reduced. The chimney emits a lot of smoke, and the tail of this smoke is getting bigger and bigger. The reason is that after sulfur trioxide comes out of the chimney, it combines with moisture in the air to produce acid mist; when the concentration of the absorbed acid is below 96%, the equilibrium partial pressure of water vapor gradually increases, and moisture volatilizes from the acid, enters the furnace gas and combines with sulfur trioxide to form acid mist, causing the chimney to emit a lot of smoke. The tail of this smoke is basically the same before and after, and the amount of moisture combined with the air is not high. Studies have shown that when the concentration of the absorbed acid is 98.3%, the equilibrium partial pressure of water and sulfur trioxide in sulfuric acid is the lowest, and the absorption efficiency is the highest. Therefore, the concentration of the absorbed acid should be controlled at around 98.3%, not too high or too low.

[0062] 2. The acid temperature is too high or too low; the absorption acid temperature has a great influence on the absorption rate. Through production practice, the absorption effect is better when the absorption acid temperature is above 60℃, and the lower the temperature is below 50℃, the worse the absorption effect is. If the acid temperature is too low, the viscosity of the acid increases, the mass transfer is slow, the fluidity is poor, the wetting effect of the filler surface is poor, the absorption rate slows down, resulting in poor absorption, and sulfur trioxide comes out of the chimney. The absorption effect will become worse and worse when the absorption acid temperature is above 90℃, because as the temperature rises, the water in the sulfuric acid will evaporate, enter the furnace gas and combine with sulfur trioxide to form acid mist. Therefore, the absorption acid temperature should be controlled within an appropriate range. Low acid temperature is more serious than high acid temperature, so the absorption acid temperature should be controlled during the start-up process, preferably between 60℃-80℃.

[0063] 3. Insufficient acid in the upper tower. Insufficient acid in the upper tower will result in insufficient wetting of the filler, short-circuiting of the gas, and failure to absorb sulfur trioxide. Insufficient acid in the upper tower will result in a large increase in the acid concentration in the lower tower and a large temperature difference between the upper and lower towers. The appropriate measurement indicators of the acid amount in the upper tower can be evaluated by the temperature difference between the upper and lower towers and the acid concentration difference between the upper and lower towers. Generally, the normal temperature difference between the upper and lower towers of the absorption tower is between 20-30℃ and the acid concentration of the lower tower is about 0.3%-0.5% higher than that of the upper tower. The normal temperature difference between the upper and lower towers of the drying tower is between 8-15℃ and the acid concentration of the lower tower is about 0.3%-0.5% lower than that of the upper tower. If the acid amount in the upper tower is too large, the acid pump will be overloaded, the gas-liquid convection resistance will increase, the tower resistance will increase, which will be unfavorable for absorption and mass transfer, restrict the production load, and may also increase the probability of flooding accidents. Therefore, it is necessary to control the appropriate acid amount in the upper tower, and formulate the best acid amount in the upper tower based on the acid temperature of 20-30℃ and the acid concentration difference of 0.3%-0.5% in the upper and lower towers. Acid pump tripping can also be classified as insufficient acid, which is a serious shortage.

[0064] 4. The flue gas temperature entering the tower is too high or too low; when the flue gas temperature entering the tower contacts the sulfuric acid at the bottom of the tower, if the temperature is too high and the flue gas temperature is more than 100°C higher than the acid temperature leaving the tower, during the gas-liquid contact process at the bottom of the tower, the water in the sulfuric acid is evaporated by the high-temperature flue gas, and the rate at which sulfur trioxide combines with water to generate acid mist increases. The generated acid mist cannot be absorbed when passing through the packing layer, causing the acid mist to emerge. The flue gas temperature entering the tower is too low, below 140°C, reaching the dew point of sulfur trioxide, and sulfur trioxide will condense into acid mist. The generated acid mist cannot be absorbed when passing through the packing layer, causing the acid mist to emerge.

[0065] The third is that the tail gas absorption tower itself does not meet the standard of process indicators. The tail gas absorption tower has different processes, and the size of the tail gas smoke is also different. The tail gas is smaller when washing with hydrogen peroxide and alkali. When ammonia water is used as a desulfurizer, if the pH value is controlled at a high level, ammonia will escape. When ammonia encounters an external environment with high water content and low temperature, the ammonia in the tail gas combines with water in the atmosphere to form ammonia mist, which will also cause heavy smoke.

[0066] Through the above three smoking situations, when the chimney emits heavy smoke, there are many reasons for analysis, and it is difficult to find the problem. If there is no clear and fast judgment method, it will prolong the processing time, leading to increased environmental pollution and production losses. Therefore, it is very important to quickly and accurately judge the cause of heavy smoke. A set of effective, simple and fast judgment method flow chart is summarized as shown in the attached figure Figure 1 shown.

[0067] Except for the tripping of the concentrated acid circulation pump, no matter what the reason for the chimney to emit heavy smoke, quickly check the color of the flue gas at the outlet of the absorption tower, determine the smoking tower, and then check the process parameters of the upstream equipment to determine whether it is a problem with the absorption tower itself or the upstream equipment. Through this method, the cause of the smoking can be quickly found, the smoking time can be shortened, and environmental pollution can be reduced. Especially for the device with low-temperature waste heat recovery of sulfuric acid, the upstream boiler or economizer leaks, causing heavy smoke to come out of the chimney. If it cannot be quickly judged and handled, it will cause serious corrosion of the subsequent low-temperature waste heat recovery equipment, or even scrapped, resulting in heavy losses.

[0068] The factory where I work has had smoke coming out of chimneys many times. Some of the causes were due to too high or too low acid concentration in the absorption tower, some were due to insufficient acid circulation in the upper tower, some were due to economizer leakage, and some were due to boiler tube bursting. With this method, the cause of the smoke can be determined in a few minutes if it is discovered and handled in a timely manner. The leaking equipment or abnormal process indicators can be found and handled in a timely manner, resulting in minimal economic losses and a short chimney smoking time. I have encountered three chimney smoking accidents caused by sulfuric acid boiler tube bursts. One of them was a sulfuric acid-making unit equipped with sulfuric acid low-temperature waste heat recovery. The boiler leakage caused smoke treatment cases. The sulfuric acid-making process flow is as shown in the attached figure. Figure 2 shown.

[0069] The chimney smoke incident happened as follows:

[0070] ①At 21:07, the flue gas temperature at the boiler outlet began to slowly drop from 370.5℃.

[0071] ②21:13 The flue gas temperature at the inlet of the low-temperature waste heat recovery high-temperature absorption tower (first absorption tower) began to rise from 197°C, and the tower outlet temperature was 76°C, which was relatively stable. The flue gas temperature at the inlet of the second absorption tower began to rise slowly from 207.8°C. The first-level acid concentration of the high-temperature absorption tower began to decrease from the normal value of 99.09% (the process indicator requirement range is 99.0-99.1%).

[0072] ③21:17 The sulfuric acid low temperature waste heat recovery station found that the concentration of the first-level acid decreased, and began to adjust the amount of water injected to dilute the concentrated acid, from a flow rate of 4.12m 3 / h reduced to 3.7m 3 / h.

[0073] ④21:32 The first-stage acid concentration reached a minimum of 98.61%, and the injection water was reduced to 3.0m at 21:38 3 / h, the primary acid concentration stabilizes to above 98.6%. During this process, the chimney begins to smoke and gradually becomes larger and larger.

[0074] ⑤Arrived at the production site at 21:58 and checked that there was a small amount of white smoke at the outlet of the high-temperature tower, white smoke at the outlet of the second suction tower, and heavy smoke coming out of the chimney. The flue gas temperature at the tail end of the boiler dropped, while the flue gas temperature at the inlet of the high-temperature tower rose. It was determined that the boiler had burst, and the production post was notified immediately to stop the operation urgently.

[0075] ⑥ At 22:00, the main fan of the sulfuric acid system is stopped.

[0076] Afterwards, by checking the DCS process parameter history, it was found that when the system was shut down at 22:00, the flue gas temperature at the inlet of the high-temperature tower was 228.4℃, which had risen by 31℃ from 197℃; the flue gas temperature at the inlet of the second absorption tower was 217.1℃, which had risen by 10℃ from 207.8℃; the flue gas temperature at the outlet of the boiler was 354.49℃, which had slowly dropped by 16℃ from 370.5℃. At 21:41, the inlet temperature of the first section of the conversion system was 423.49℃, which began to rise slowly, reaching a maximum of 425.6℃, with no obvious increase. There was no obvious change in other conversion temperatures. After opening the boiler for inspection, it was found that one of the evaporation tube bundles of the boiler had burst, and boiler water was sprayed from the burst tube into the high-temperature sulfur dioxide gas at about 1000℃, which had a cooling effect, causing the flue gas temperature at the outlet of the boiler to slowly drop. The reason why the inlet temperature of the high-temperature absorption tower rises instead of falls is that the sulfur trioxide concentration at the inlet of the high-temperature tower is as high as about 10%, which combines with water to produce sulfuric acid, which is an exothermic reaction, resulting in a high temperature rise of the flue gas entering the tower. After cooling by the economizer, the amount of acid mist will also increase. The sulfur trioxide concentration of the second absorption tower is low, and the temperature rise of the flue gas entering the tower is smaller than that of the first absorption tower.

[0077] Through this case, we can see that when the boiler tube bursts and leaks, the flue gas temperature at the boiler outlet drops, and the trend is slow. The flue gas temperature at the inlet of the first absorption tower (or high-temperature absorption tower) rises fastest and with the largest amplitude. The rising trend of the flue gas temperature at the inlet of the second absorption tower is slower than that of the boiler, and the amplitude is small; the temperature of the converter catalyst rises slightly, with the smallest amplitude, and the temperature rise is not obvious. Due to timely discovery, one boiler tube bursts, the primary acid concentration of the high-temperature absorption tower drops, and the tail gas chimney emits a lot of smoke. If it is not discovered in time, the boiler tube burst will cause the evaporation tube bundle around the burst tube mouth to suffer high-temperature corrosion and scouring, and more tube bundles will burst successively, with more serious consequences. A large amount of boiler water enters the sulfur dioxide flue gas to form water vapor, causing great corrosion to subsequent low-temperature equipment. A large amount of water enters the low-temperature waste heat recovery high-temperature absorption tower, and the primary high-temperature circulating acid concentration is lower than the safe value, resulting in corrosion and perforation of low-temperature waste heat recovery sulfuric acid evaporator, heater and other equipment in a short time. At the same time, the moisture content of the converter catalyst increases, which has a great impact on the activity of the catalyst. The tail of the chimney emits a lot of smoke, polluting the surrounding atmospheric environment, which will cause great economic losses.

[0078] In this case, through the quick judgment method of chimney smoke, it was discovered in time that the boiler tube burst was the cause of the chimney smoke, and the vehicle was stopped and handled in time to minimize the losses.

[0079] Heavy smoke from tail gas in sulfuric acid plants is a common process failure. Shortening the time to find the failure and solving the problem of heavy smoke in time can reduce environmental and economic losses. With increasingly high environmental protection requirements, in addition to the continuous improvement of process management for normal production, accurate judgment and timely emergency disposal are also required when abnormalities occur. Due to the different production process technology levels of each set of equipment, it is usually not an easy task to solve the problem of heavy smoke in time. It is very necessary to have an effective and quick method to check and judge heavy smoke, which is of great help to improve the level of production management and prevent environmental accidents. The rapid inspection method for the process failure of heavy smoke from the chimney of sulfuric acid tail gas introduced in this article is simple and efficient, with high accuracy, very practical, and does not require complicated inspections. After years of production practice, the effect is good. The fault location can be found quickly and accurately every time, and the chimney smoke failure can be eliminated in time.

[0080] The above are only preferred feasible embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Various modifications or applications made according to the above embodiments are within the protection scope of this technical solution.

Claims

1. A method for quickly checking smoke failure in tail gas chimney in sulfuric acid production process, characterized in that: The following steps are involved: If the tail gas chimney is smoking, first check the outlet of the second absorption tower. If white smoke is emitted from the outlet of the second absorption tower, check the outlet of the first absorption tower. If white smoke is not emitted from the outlet of the second absorption tower, it is a desulfurization tower failure. Check whether the desulfurization process parameters of the desulfurization tower are normal. Check the outlet of the first absorption tower. If white smoke comes out of the outlet of the first absorption tower, check the inlet gas temperature of the first absorption tower and the tail of the boiler; If the inlet gas temperature of the first absorption tower is stable, it indicates that the absorption efficiency of the first absorption tower is low. Check whether the acid concentration, acid temperature, acid amount, tower inlet air temperature and parameters of the acid distributor of the first absorption tower are normal. If the inlet gas temperature of the first absorption tower rises significantly, there are three situations: if the outlet temperature of the economizer in front of the first absorption tower rises, and the outlet temperatures of the boiler and superheater are stable, the economizer in front of the first absorption tower is leaking, and the engine should be stopped for maintenance; if the outlet temperature of the superheater in front of the first absorption tower rises, and the outlet temperatures of the economizer and boiler are stable, the superheater in front of the first absorption tower is leaking, and the engine should be stopped for maintenance; if the inlet gas temperature of the second absorption tower rises, the acid concentration of the first absorption tower decreases, and the outlet temperature of the boiler decreases, it means that the boiler tube has burst, and the engine should be stopped for maintenance; If white smoke comes out of the outlet of the boiler tail, then check and analyze the drying water content at the outlet of the drying tower and the boiler tail. If the drying water content is high, then check whether the dryer acid concentration, acid temperature, acid supply and parameters of the acid distributor are normal. If the drying water content is normal, it means that the moisture content at the outlet of the incinerator is high. At this time, check the water content of the liquid sulfur, organic matter and the leakage of the sulfonator. If there is no white smoke at the outlet of the first absorption tower, it means that the economizer is leaking or the absorption rate of the second absorption tower is low. Check the inlet temperature of the second absorption tower. If the temperature rises significantly, the economizer in front of the second absorption tower is leaking. At this time, the machine should be stopped for maintenance. If the temperature is stable, it indicates that the absorption efficiency of the second absorption tower is low. Check whether the acid concentration, acid temperature, acid amount, tower inlet temperature and acid distributor parameters of the second absorption tower are normal. The process flow of the sulfuric acid production process is as follows: Granular solid sulfur is used as the production raw material, which is sent to the rapid sulfur melting tank via a belt conveyor. The solid sulfur is melted into liquid by steam heating, and then sent to the liquid sulfur storage tank for storage after clarification and filtration. Liquid sulfur passes through the refined sulfur tank, and is atomized by a sulfur pump through a sulfur gun and sent to the sulfur incinerator. It burns with the air sent by the main fan and dried by the drying tower in the sulfur incinerator to generate SO2 furnace gas, while releasing a large amount of heat energy. The heat energy is recovered by the boiler to produce saturated steam. The SO2 furnace gas passes through the gas filter and enters the first stage of the conversion reaction. The high-temperature furnace gas of the first reaction exchanges heat with the superheated steam from the low-temperature superheater in the superheater to generate superheated medium-pressure steam to send to the steam turbine unit for power generation. After the high-temperature furnace gas is cooled, it enters the second and third stages of the converter. After the heat is recovered by the economizer, it enters the first absorption tower for absorption to produce product sulfuric acid. The furnace gas from the first absorption tower is heated by the cold and hot heat exchangers and then enters the fourth stage of the converter. The reaction furnace gas first recovers heat energy through the low-temperature superheater, and then enters the second absorption tower after further recovering heat energy through the economizer, and then enters the tail gas desulfurization tower for desulfurization and is discharged from the chimney; When the organic matter content in liquid sulfur is high, water is produced during combustion. The moisture content at the outlet of the sulfur incinerator is 20-50 times higher than that at the import. Adjust the sulfur supplier and origin according to the moisture content at the outlet to reduce the organic matter content in the sulfur. If the water content of liquid sulfur is high, increase the stirring time of the molten sulfur and the clarifying time of the liquid sulfur to allow the moisture to fully evaporate. If the drying effect of the drying tower is poor and the moisture content of the furnace gas is high, adjust the amount of acid in the upper tower or increase the concentration of drying acid based on the drying moisture analysis data; clean the packing of the drying tower to reduce resistance and increase surface area.

2. A method for quickly checking smoke failure of tail gas chimney in a sulfuric acid production process according to claim 1, characterized in that The normal temperature difference between the upper and lower towers of the first absorption tower and the second absorption tower is between 20-30℃, and the acid concentration in the lower tower is 0.3%-0.5% higher than that in the upper tower.

3. A method for quickly checking smoke failure of tail gas chimney in a sulfuric acid production process according to claim 1, characterized in that When the absorption acid concentration is 98%-98.5%, the equilibrium partial pressure of water and sulfur trioxide in sulfuric acid is the lowest and the absorption efficiency is the highest.

4. A method for quickly checking smoke failure of tail gas chimney in a sulfuric acid production process according to claim 1, characterized in that During the start-up process, the absorbed acid temperature is controlled between 60-80℃.

5. The method for quickly checking smoke failure of tail gas chimney in a sulfuric acid production process according to claim 1, characterized in that The normal temperature difference between the upper and lower towers of the drying tower is between 8-15℃, and the acid concentration in the lower tower is 0.3%-0.5% lower than that in the upper tower.

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