Methanol segment: Weekly topic – Knowledge related to water in drum boilers? 2016.05.30--06.5
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This post was last edited by TH373637 on 2016-5-31 16:19. Answer: Adding trisodium phosphate to the boiler water not only serves to prevent scaling, but it also has the adverse effect of increasing the conductivity of the boiler water as well as the Na+ content in the steam. If an excessive amount is added, it will cause a significant increase in the conductivity of the boiler water, as well as elevated levels of Na+ in the steam. In severe cases, this can lead to a steam-water azeotrope phenomenon. Over time, it can also result in problems such as deterioration of the convective tube bundles, phosphorus deposition at the tube ends, and aggressive corrosion of the aqueous phase. Therefore, as long as there is a certain residual amount of phosphate in the furnace water (above 10 ppm), it is better to keep its level low. Answer: To prevent the concentration ratio of the boiler water from becoming too high, various parameters of the boiler water and steam are kept within the specified limit ranges. Therefore, control and adjustment must be achieved through waste discharge. Answer: There are two ways of draining waste water from a boiler: periodic drainage and continuous drainage. Answer: The control of the drum water level relies primarily on balanced and proactive operation. Whether it is automatic or manual control, it is important to maintain relative stability in the feedwater pressure and drum pressure, as well as to ensure that the ratio of feedwater flow to steam flow is appropriate. Changes in feedwater flow should be gradual, avoiding sudden increases or decreases that could affect the water level. It is essential to be aware of the operations that can influence the water level, in order to keep its fluctuations to a minimum. Answer: 1) The operators were careless, failed to monitor the water level properly, made untimely adjustments, or performed incorrect operations. 2) The water level gauge shows an incorrect water level, and the steam flow meter or feedwater flow meter provides inaccurate readings, leading to misjudgments by the operators. 3) Failure of the water supply automatic regulator or malfunction of the control valve. 4) The feed water pressure decreases, resulting in less water entering the steam drum. 5) Fault in the boiler feed water pump. 6) Improper waste discharge or severe leakage in the discharge valves. 7) Excessive steam output. Answer: A full boiler is the opposite of a low-water boiler; the main reasons are as follows: 1) The water level in the steam drum is higher than the normal level. 2) False indication of the level gauge. 3) The steam output is too low, resulting in high pressure in the steam pipeline network. 4) The water supply flow rate is abnormal, being greater than the steam flow rate. 5) The salt content in the steam increases. 6) The inlet valve is faulty and cannot function properly for regulation.
1 Equipment protection: Drum boilers provide protection for components such as the drum, water wall, economizer, superheater, and reheater during startup. Protection of the steam drum: (1) Strictly control the water supply temperature and water supply rate ； ⑵Strictly control the temperature difference between the upper and lower walls of the drum, as well as the temperature difference between the inner and outer walls, to keep them within specified limits ； ⑷Strictly control the rate of temperature and pressure increase. Protection of the water wall: Proper selection and appropriate rotation of the ignition oil nozzles or burners to ensure even heating of the water wall ； ⑵Ensure uniform expansion across all sections of the water wall; drain an appropriate amount of water from the water wall lower header where expansion is less ； ⑶At the beginning of ignition, steam from an adjacent furnace is introduced into the lower header for heating, to accelerate the establishment of water circulation. Protection of the superheater: The increase rate of fuel supply during ignition should not be too fast ； ⑵Keep the flame center from drifting, ensuring good fill level ； ⑶Open the water drainage valve to drain water promptly ； ⑷Lower the flame center and control the flue gas temperature at the furnace outlet ； ⑸Regularly switch the burners to reduce thermal deviation ； ⑹Use the spray water cooler properly. Protection of the economizer: Close the recirculation valve when water is being supplied, and open it when the water supply is stopped; or drain water through the fixed-drain or continuous-drain system to maintain a steady flow of water supply. 2 Load adjustment: Since drum boilers consume 10% to 15% more metal than once-through boilers and have a larger water volume, they possess a higher heat storage capacity; moreover, the steam space in the drum can store a certain amount of steam. When the fuel amount remains constant and the load changes, the steam pressure in the boiler changes relatively slowly. As the load increases, before any adjustments are made, since the amount of fuel remains unchanged, the steam generated is less than the amount of steam consumed, so the steam pressure inevitably drops. The saturation temperature of the boiler water also decreases; part of the heat stored in the boiler water and the metal causes some of the boiler water to vaporize, generating a small amount of steam to compensate for the increased load. The steam stored in the drum space expands when the steam pressure drops, thereby slowing down the rate of pressure decline before additional fuel is added. Conversely, when the steam generation rate exceeds the load, on one hand, the excess steam is stored in the steam space of the drum in a compressed form, and on the other hand, the excess heat is stored by raising the saturation temperature of the boiler water and the temperature of the metal, thereby slowing down the rate of increase in steam pressure. One of the advantages of drum boilers is their high heat storage capacity, which gives them a strong ability to automatically adapt to changes in load. When the steam pressure is actively adjusted, for the same reason, the speed at which the steam pressure returns to normal is also slower, which is a disadvantage. Understanding this characteristic of drum boilers is very useful for properly adjusting the load and maintaining stable steam pressure. For example, when manually adjusting the steam pressure, if a decrease in steam pressure is observed, it indicates that the boiler’s steam production is insufficient to meet the load, and fuel should be added promptly. If the steam pressure stops falling, it indicates that the steam generation rate and the load have reached equilibrium on a new basis. To restore the original steam pressure, more fuel needs to be added. By the same logic, when the steam pressure rises, fuel should be reduced promptly until the steam pressure stops rising and returns to normal. Due to the high heat storage capacity of drum boilers, the steam pressure changes slowly when the amount of fuel is adjusted. Therefore, adjustments should be made promptly as the steam pressure changes, rather than waiting until the pressure exceeds the specified limits, in order to maintain a relatively stable steam pressure in the boiler.
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Water analysis in drum boilers is really important.
What causes the high electrical conductivity of boiler water? Waste discharge small i?
Introducing desalinated water, adding salts and phosphates, continuously removing suspended solids from the water, and intermittently removing sediments and sand through bottom discharge – all these measures are taken to prevent scale formation, as steam is generated continuously and the desalinated water becomes increasingly concentrated. The analysis generally involves measuring the pH value, phosphate concentration, and silica concentration.