3 solutions to the red color of acidic steam condensate

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3 solutions to the red color of acidic steam condensed water Source of acidity in steam condensed water Steam condensed water is equivalent to distilled water, and its pH value is generally close to 7, which is neutral. Boilers whose supplementary water is demineralized water usually add ammonia to increase the pH value of the demineralized water. The ammonia enters the boiler with the supplementary water and is heated and volatilizes with the steam entering the heat exchanger. The ammonia condenses with the steam and dissolves into the condensate water, which can increase the pH value of the condensate water to 8 or above. In addition, under normal circumstances, the pH value of the steam condensate water is about 5.5-6.5, and is usually acidic if it is lower than 7. ▲On July 2, 2022, the acidic steam condensation return water of a certain unit turned red in color, causing the steam condensation water to have a low pH value and become acidic. The main reason is that CO2 is dissolved in the water, and CO2 dissolves in water to form weak carbonic acid. Also, because the steam condensation water is very pure and has poor buffering properties, tests have shown that at 25°C, when 1 mg of carbon dioxide is dissolved in 1 liter of pure water, the pH value of the pure water drops from 7.0 to 5.5. ▲On July 2, 2022, the acidic steam condensation return water of a certain unit turned red in color and had a pH value of 6. Sources of carbon dioxide in steam condensation water There are two sources of carbon dioxide in steam condensation water. One is dissolved in the air. 0.03% of carbon dioxide in the air dissolves into the steam condensation water through raw water or an open steam condensation water recovery system, causing the PH value in the steam condensation water to decrease and become acidic. The second source of carbon dioxide in steam condensate water comes from a large amount of carbonate ions or bicarbonate ions in the boiler feed water. After the feed water is softened by sodium ion exchange, carbonates and bicarbonates (such as sodium carbonate, sodium bicarbonate) will be left in the water. Carbonate and bicarbonate enter the boiler with the make-up water and are heated and concentrated. Carbonate and bicarbonate in the make-up water are decomposed by heat, and CO2 escapes and enters the steam system with the steam. At this time, sodium hydroxide is formed in the boiler water, and the boiler water becomes alkaline. As the temperature and pressure decrease, CO2 dissolves into the condensed water to form carbonic acid, causing the PH value of the steam and condensed water to decrease and become acidic. НСΟ3-→СΟ2↑+Н2Ο+СΟ32- СΟ32-+Н2Ο→СΟ2↑+ΟН-The hazards of acidic steam condensation water and the reason why acidic steam condensation water turns red. CO2 dissolves into the condensation water to form carbonic acid, causing the PH value of the steam condensation water to decrease and become acidic to produce Н +, at this time, if the boiler system does not have deaerator or the deaerator efficiency is not high, or the steam condensate recovery system is open, 21% oxygen content in the air will dissolve into the air, and Н+ and dissolved oxygen are both cathode depolarizers in the corrosive battery, which means * * Accelerates the corrosion of anode metals in steam and condensate system equipment and pipe networks. High-temperature acidic steam condensate can quickly cause corrosion to steam and condensate system equipment and pipe networks, so acidic steam condensate cannot be directly reused in the boiler without treatment. Because corrosion causes iron ions in steam condensate to exceed the standard, colorless ferrous iron ions are oxidized into ferric ions. As the concentration of ferric ions increases, the colors of yellow steam condensate, pink steam condensate, orange steam condensate, red steam condensate, dark red steam condensate, and soy sauce-colored steam condensate change in color. This is also the reason why some newly installed boiler steam and condensate water pipe networks are corroded, perforated, and leaked within 4 to 5 years. According to the requirements of the national standard GB1576-200 "Industrial Boiler Water Quality", water with an iron ion content exceeding 0.3mg/L cannot enter the boiler for use. The appearance of pure and transparent steam condensate water with excessive ferrous iron ions exceeding the standard is directly reused in the boiler without treatment. The ferrous iron ions enter the boiler with the steam condensate water and are heated and concentrated and oxidized into colored ferric iron, which will cause the boiler water to turn red. Among the situations where the author encountered steam boiler users whose boiler water turns red, more than 85% are caused by steam boiler users whose steam condensate water has excessive iron and is directly returned to the boiler for use without treatment. Ferric ions are the catalyst for oxygen corrosion inside the boiler. They will not only accelerate the occurrence of oxygen corrosion in the boiler, but also form iron oxide scale. At the same time, they will also cause corrosion under the scale. Iron oxide scale will greatly reduce the heat transfer efficiency of the furnace tube. The heat transfer efficiency will drop significantly, resulting in a large amount of waste of fuel energy and high exhaust temperature. ； Iron oxide scale will not only shorten the service life of the boiler, but a large amount of iron oxide scale accumulated in the furnace tube will also cause the furnace tube to creep up due to overheating, causing the danger of tube explosion, posing a great hidden danger to the safe operation of the boiler. ▲On July 11, 2022, the acidic steam condensation return water of a certain unit was treated. The color and appearance are transparent and pure. ▲ On July 11, 2022, the acidic steam condensation return water of a certain unit was treated. The pH value was 8. The color of the acidic steam condensation water turned red. 3 solutions for the color of the acidic steam condensation water turning red. One of the solutions for the redness of the acidic steam condensation water - Add ammonia to the boiler feed water. Add ammonia to the boiler feed water. Ammonia is weakly alkaline. Ammonia escapes when heated in the boiler and enters the steam system with steam. The steam carrying ammonia passes through the heat exchanger or heat exchange equipment and condenses into water as the temperature and pressure decrease. Ammonia dissolves into the condensate water, causing the pH value in the steam condensate water to rise to alkaline. When the pH value is greater than 8, ammonia can completely neutralize carbon dioxide in the water to generate NH4HCO3. NH3+H2O→NH4OH (reversible) NH4OH+CO2→NH4HCO3 (reversible) NH4OH+NH4HCO3→(NH4)2CO3+H2O (reversible) The advantage of adding ammonia to boiler feed water to solve the red color of acidic steam condensate water. Ammonia is economical and cheap. It is a common PH regulator. Add ammonia to boiler feed water. Ammonia dissolves in water and is weakly alkaline, which can increase the PH value of the boiler water. After the ammonia is heated in the boiler water and escapes with the steam into the heat exchange equipment, the ammonia dissolves into the condensate water due to the drop in temperature and pressure. Adding ammonia to the boiler feed water can increase the PH value of the boiler water, steam and condensate water, neutralize the corrosion of system equipment and pipe networks caused by CO2 in acidic steam and acidic condensate water, and reduce the iron ion content in the condensate water. Adding ammonia to boiler feed water solves the shortcomings of the red color of acidic steam condensate. Adding ammonia to boiler feed water solves the red color of acidic steam condensate. Problems that need attention: 1. Adding ammonia can only control weak acid corrosion caused by CO2, but cannot control oxygen corrosion. Feed water ammonia boiler systems often suffer from steam pipeline corrosion, heat exchanger corrosion, steam condensate pipeline corrosion, and steam condensate water turning red and having iron ions exceeding the standard. ； Adding ammonia to boiler feed water solves the problem of red color of acidic steam condensate. 2. Ammonia has a certain corrosive effect and is easy to volatilize ammonia gas. The storage and use of liquid ammonia is a source of danger. ； Adding ammonia to boiler feed water solves the problem of red color of acidic steam condensate water. 3. The pH value of ammonia is not maintained for a long time, and the amount of ammonia added is relatively large. Ammonia is easily volatile and unstable when heated. Among the two phases of steam boiler vapor and liquid, the gas phase is more abundant and the liquid phase is less. To maintain the PH value of the steam condensate return water to prevent corrosion of the return water pipeline and excessive iron, the amount of ammonia added must be large. This is also the reason why the smell of ammonia is sometimes smelled when the steam condensate return water is collected or discharged. ； Adding ammonia to boiler feed water solves the problem of red color of acidic steam condensate. 4. When the amount of ammonia added to the feed water is too large, with the participation of dissolved oxygen, the corrosion of copper is relatively strong. Copper metal heat exchangers, copper pipes and instrument accessories are prone to corrosion. ； Adding ammonia to boiler feed water solves the problem of red color of acidic steam condensate water that needs attention. 5. Adding ammonia water in high doses for a long time is detrimental to boiler operation. Adding too much ammonia water to the boiler will cause corrosion. Ammonia is alkaline and will accelerate the precipitation of calcium, magnesium, etc., causing boiler scaling and corrosion under scale. ； Long-term use may cause corrosion to valves, pipelines, etc., so the amount added should be strictly controlled and adjusted appropriately while adding continuously. ； Adding ammonia to boiler feed water solves the reddening color of acidic steam condensate. Problems that need attention. 6. Adding ammonia to control excessive iron ions in steam condensate return water is a false proposition. Adding ammonia can only control the weak acid corrosion caused by CO2, but cannot control oxygen corrosion. Since ammonia is easily volatile and unstable when heated, with a large amount of gas phase and small liquid phase, and it cannot be added in high doses for a long time, adding ammonia can only partially alleviate the corrosion of the steam system and reduce the limited iron ion content in the steam condensate return water. Dear colleagues, has your unit's steam boiler ever experienced a situation where the pH value of the steam condensate water is low and acidic? Has the color of the steam condensation water turned red or yellow, or has the iron content of the steam condensation water exceeded the standard? How did you solve it? What methods are you using for boiler scale inhibition, descaling, and corrosion inhibition? Regarding the adjustment of PH value of boiler feed water, redness of boiler water, hardness of return water, boiler corrosion and scale explosion, corrosion of steam system, excessive iron content of steam condensate water, red color of acidic steam condensate water, boiler water quality detection and treatment, etc., Yan Hui of Beijing University of Chemical Technology l86OO47538 6. Colleagues in the industry are always welcome to discuss issues and exchange experience and insights. Colleagues are always welcome to communicate about new technologies related to boilers. Colleagues are always welcome to share experience in boiler equipment management and use. Boiler-related workers are always welcome to learn from each other on solving various practical problems of boilers. * . Three solutions to the red color of acidic steam condensate. The second solution to the red color of acidic steam condensate - high-temperature steam condensate iron removal equipment filters high-temperature steam condensate water iron removal equipment to filter out excess iron ions in the condensate, so that the color of the steam condensate water and the iron ions in the steam condensate water reach the standard can be directly and safely reused in the boiler. Disadvantages of high temperature steam condensate iron removal equipment: High-temperature steam condensate water iron removal equipment requires a large one-time investment ； The high-temperature steam condensate iron removal equipment occupies a large area, and the operation and maintenance costs of the high-temperature steam condensate iron removal equipment are not worth the cost. ； The filter material of high-temperature steam condensate iron removal equipment needs to be replaced once every 2-3 years, and the cost of replacing the filter material accounts for about one-third of the equipment cost. ； High temperature steam condensate water iron removal equipment cannot increase the PH value of steam condensate water ； High-temperature steam condensate iron removal equipment cannot solve the corrosion of acidic steam and condensate water on boiler steam system and condensate recovery system equipment and pipelines. System corrosion has always been a source of iron ions, and high-temperature steam condensate iron removal equipment can only treat the symptoms but not the root cause. ▲In July 2022, the third solution to the red color of the acidic steam condensate return water in a certain unit was to treat the redness of the acidic steam condensate water. Add BF-31T steam condensate water protective agent to target the oxygen corrosion and weak carbonic acid corrosion of the boiler steam system and condensate recovery system equipment and pipelines caused by acidic steam and condensate water. Usually, BF-31T condensate system protection technology is added, and BF-31T condensate system protective agent, an exclusive product of Beijing University of Chemical Technology, is added to prevent the occurrence of corrosion. BF-31T condensate system protective agent is the core technology in the "Zero Emission Steam Generation Technology" project of the Ministry of Science and Technology Innovation Fund undertaken by our unit. BF-31T condensate system protective agent product has passed the "China Boiler Water Treatment Association Registration" project in 2003. Technical advantages of BF-31T steam condensate water protection agent to solve the red color of acidic steam condensate water Technical advantages of BF-31T steam condensate water protective agent to solve the red color of acidic steam condensate water 1BF-31T condensate water system protective agent is an alkaline emulsion liquid agent and is volatile. Boiler feed water addition BF-31T condensate system protective agent. BF-31T condensate system protective agent dissolves in water and is weakly alkaline. BF-31T condensate system protective agent is heated in the boiler water and escapes with steam entering the heat exchange equipment. Due to the drop in temperature and pressure, BF-31T condensate system protective agent dissolves into the condensate water. The performance mechanism of BF-31T steam condensate protective agent is to film the entire boiler system to isolate O2 and CO2, and to increase the pH value of boiler water, steam, and return water to completely solve the common oxygen corrosion and weak acid corrosion of steam condensate and eradicate it from the root cause The source of iron ions in steam condensate water fundamentally solves the problem of red color of steam condensate water. This corrosion inhibition mechanism treats both the symptoms and root causes of excessive condensate iron. It not only makes the condensate iron meet the standard, but also completely protects the entire boiler system equipment and pipelines from corrosion, perforation, and leakage. * * Extends the service life of system equipment. BF-31T steam condensate protective agent solves the red color of acidic steam condensate. Technical advantages: 2BF-31T condensate system protective agent has simple on-site working conditions and has no requirements for condensate temperature and iron content. Some equipment has requirements for condensate temperature and iron content for iron removal. BF-31T steam condensate water protective agent solves the red color of acidic steam condensate water. Technical advantages: 3BF-31T condensate water system protective agent is not affected by production load fluctuations and has good buffering performance. It will not affect the index performance of water quality treatment. BF-31T steam condensate protective agent solves the red color of acidic steam condensate. Technical advantages: 4. The cost of BF-31T steam condensate protective agent will decrease with the cumulative use of the agent in the system. There is no wastewater discharge problem of backwashing of other equipment. BF-31T steam condensate protective agent solves the red color of acidic steam condensate. Technical advantage 5BF-31T steam condensate protective agent is more effective than adding ammonia. Adding ammonia can increase the PH value of furnace water and steam, and can solve weak acid corrosion. Ammonia is volatile, has more gas phase and less liquid phase, and its dosage is large, so it cannot solve oxygen corrosion. The technology of adding BF-31T steam condensate water protective agent to boiler feed water to control the pH value has all the advantages of the ammonia adding process.: Affordable price ； Will not increase salt content in boiler water ； It is volatile and can protect the overall equipment and pipelines of the boiler steam and water system. The main components of BF-31T condensate protective agent are neutralizer, film-forming agent and other additives. It has film-forming neutralization function, good stability, and reasonable vapor-liquid phase distribution ratio, which can quickly control system corrosion. Neutralizing amines can neutralize and increase the pH of boiler feed water, boiler water, steam and condensate, and neutralize the weak acid corrosion caused by carbon dioxide in the water. ； The film-forming agent forms a monomolecular layer of hydrophobic protective film on the metal surface. The gaps between the film molecules are smaller than the cross-sections of carbon dioxide and oxygen, preventing the corrosive gas molecules O2 and CO2 from contacting the metal, thereby preventing corrosion of the metal. ； A reasonable vapor-liquid phase distribution ratio can effectively distribute the agent into the vapor-liquid phase in the metal pipeline, which can effectively solve the metal corrosion of the vapor-liquid two-phase system. It is especially suitable for the protection and anti-corrosion of intermittent steam equipment. BF-31T steam condensate protective agent solves the red color of acidic steam condensate. Technical advantage 6BF-31T steam condensate protective agent has a fast coating speed, and the condensate water quality iron ion (full iron index) quickly reaches the standard within 72 hours. The reddened acidic steam condensate normally reaches the standard pure and transparent state within 72 hours, which provides convenience for pharmaceutical trial experiments. It can completely replace the deaerator and deoxidizer. Compared with common equipment iron removal processes and other measures on the market, BF-31T condensate system protective agent does not require huge investment in fixed equipment, does not require equipment operation and maintenance costs, and does not require expensive filter material replacement (the service life is about 3 years, the total cost is 20-30%) , not only protects system equipment and pipelines, prolongs the service life of the boiler system, but also completely cuts off the source of iron ions, completely solves the problem of red color of acidic steam condensate, and allows high-temperature and pure steam condensate to be recycled for safe use of the boiler, achieving condensate iron removal and treating both the root cause and the root cause. 3 solutions to the red color of acidic steam condensate (Yan Hui)