However, if we do not operate and use the biomass boiler properly and do not carry out proper maintenance, then the best boiler will not be able to withstand the frustrations of years, and the consequent constant maintenance costs will haunt you. Spending money on another new machine will still fall into the endless cycle of maintenance—new machine—maintenance—new machine!
Therefore, when the biomass boiler is suspended, it is necessary to carry out good maintenance. Regarding these, our equipment manufacturers must tell users that they not only help customers but also reduce their own after-sales costs. Why not? ?
Hazards due to improper maintenance or improper maintenance during the shutdown of the biomass boiler 1. Wide corrosion surface, large amount of corrosion products (iron oxide) After the boiler is discharged and the boiler water is discharged, the humidity in the boiler or furnace is very high, and the ventilation is poor. Being in a humid state, due to the large amount of air entering, corrosion may occur in all parts in contact with the air, and because the corrosion forms are mainly ulcerated and spotted, the amount of Fe2O3 and Fe (OH) 3 rust produced is also large. Therefore, corrosion during the shutdown period will thin the metal wall, reduce the strength and shorten the boiler service life.
2. Aggravate the corrosion during boiler operation, causing a corrosive vicious cycle. Iron is oxidized to Fe2O3 and Fe (OH) 3 when the boiler is stopped. It is a cathode depolarizer for corrosive batteries (analytical battery discharge detection), that is, the reaction occurs at the cathode : Fe (OH) 3 + e → Fe (OH) 2 + OH- and Fe2O3 + 2e + H2O → FeO + 2OH-, so that high-priced iron can be reduced to low-priced iron again at the cost of iron as anode being corroded. At the same time, high-valent iron oxide also emits oxygen when it is reduced to magnetic iron oxide, that is, 6Fe2O3 → 4Fe3O4 + O2 ↑, which increases the oxygen content in water. Due to the large amount of iron oxide and the wide range of corrosion caused by the boiler outage corrosion, the iron corrosion is also very serious when the boiler is running. When the boiler is deactivated again, the reduced low-priced iron is oxidized again to high-priced iron, and a strong oxygen concentration difference (uneven distribution of oxygen concentration) is generated under the rust, which further corrodes the iron under the rust. A large amount of new iron oxide was generated. When the boiler is re-operated, the iron oxides mentioned above all react with the cathode, causing the boiler to have more severe corrosion.
Maintenance methods during biomass boiler shutdown 1. Alkali solution method Fill the boiler with a certain concentration of lye and keep the pH above 10. The specific method is as follows: remove scale and sediment, ensure that each valve is tight, and install a blind plate on the pipeline connected to the operating system. A small lye tank can be installed at the highest position of the boiler to ensure the replenishment of lye when the lye is lost. The alkali agent used is Na2CO4, NaOH, Na3PO4 or a mixture thereof. Use soft water instead of raw water when preparing. The dosage of the agent is: Na2CO4 is added 20kg per t pot of water; NaOH is added 5 to 6kg per t pot of water; Na3PO4 is added 10 to 12kg per t pot of water. The lye is sent into the pot by a special pump until the water from the air The valve pops up and ensures that the water pressure in the pot is greater than atmospheric pressure. At the beginning of protection, the system's tightness inspection should be strengthened. After normal, the alkali concentration should be monitored once a month. When the lye concentration is lower than 5% of the original injection concentration, the alkali should be replenished.
2. Hydrazine method Fill the pot with hydrazine (a mixture of H2N2 and ammonia (NH3)). The anticorrosive principle is to use the strong reducing ability of hydrazine to remove oxygen in water and polarize the cathode. At the same time, ammonia is alkaline in the aqueous solution, which can increase the pH value, passivate the metal surface, and cause anodic polarization to achieve the purpose of anticorrosion. Use of hydrazine is restricted due to its toxicity.
3. Organic corrosion and scale inhibitor method Organic corrosion and scale inhibitor is a water treatment agent that integrates various functions such as anticorrosion, scale prevention, and scale removal. Its main components are polyphosphate, organic phosphate, BTA copper corrosion inhibitor and inorganic base. The agent is a brown-red liquid with a pH value of 13 or higher. The anti-corrosion mechanism is that the agent can dissolve negatively charged polyphosphate anions and positively charged cations after dissolving in water. The polyphosphate anions are in the anode region of the metal corrosion battery with Fe2 + phase. Combined, it is extremely difficult to dissolve water polyferric phosphate, and it covers the metal surface of the anode area to form anodic polarization. The hydrolyzed pharmaceutical cations take electrons in the cathode area of the metal and become atoms with strong affinity to the metal. It is adsorbed on the surface of the metal in the cathode area and forms cathodic polarization. As a result, metal corrosion is stopped and it acts as an anticorrosive. The organic corrosion inhibitor and scale inhibitor have a pH value of ≥13, and the treatment of 4 to 5t of water according to 1L of medicament can guarantee the pH value of ≥10, which can effectively prevent the acid corrosion caused by CO2 gas, and also has the function of anticorrosion. When the organic corrosion inhibitor and scale inhibitor is used as a maintenance and deactivation agent, the organophosphorus component in the agent can also dissolve some components in the scales and iron scales of the boiler and soda water system, so that the hard scales become loose and porous. Thing. At the same time, the agent can penetrate the scale to form a protective film, which destroys the combination of the metal surface layer and the scale and causes the scale to fall off.
4. Biomass boiler dry maintenance This method is to drain the water and keep the metal surface dry after the boiler is deactivated, or fill some gas to prevent the intrusion of air, so as to achieve the purpose of deactivation and maintenance.
The inflation method generally uses nitrogen or ammonia in a steel cylinder to fill it from the height of the boiler and maintain a pressure of 0.05 to 0.1 MPa, forcing the denser air to be discharged from the lowest point of the boiler, so that the metal does not come into contact with oxygen. This method has good maintenance effect, but the requirements are strict, and the operation process is complicated, which limits its use.
Desiccant method This method uses the characteristics of moisture absorption of the desiccant to fully dry the metal surface in the pot to achieve the purpose of anticorrosion.
The operation method is as follows: release all the pot water, remove the scale, silt and rust, block each pipeline with a blind plate, open the manhole and hand hole, and dry the furnace. The desiccant is then placed in the drum and the header respectively according to the predetermined distribution points, the drum and the header are closed, and the valves are closed tightly to isolate the inside of the boiler from the outside and keep the surface of the boiler dry for a long time. Quick lime or anhydrous calcium chloride should be placed in an iron pan, and silica gel can be put in a cloth bag. The amount of desiccant is generally: 2 ~ 3kg per m3 of boiler volume; anhydrous calcium chloride 1 ~ 2kg per m3 boiler volume; silica gel 1 ~ 2kg per m3 boiler volume (120 ~ 140 ° C drying). At the same time, the desiccant should be checked regularly at intervals of 7 to 10 days for the first time; half a month for the second time; monthly checks thereafter. If using silica gel, it should be taken out, dried and put back, and quicklime should be replaced regularly.
5. Biomass boiler gas phase maintenance Traditional water system maintenance is complicated in practice, and small and medium boiler rooms are not fully equipped, so the actual anticorrosive effect is not satisfactory. Vapor phase corrosion inhibitors are new-type agents applied to boiler corrosion protection in recent years. They mainly include inorganic ammonium salts and organic amines, such as ammonium carbonate, ammonium bicarbonate, urea, and cyclohexyl carbonate. These agents are highly volatile and condensed on the metal surface, so they can fully exert their anticorrosive effect. Its anticorrosive mechanism is the decomposition of inorganic ammonium salt into ammonia gas, which acts as a corrosion inhibitor on metals. Organic amine dissociates and metals are combined by coordination bonds, which are adsorbed on the metal surface to form anodic polarization, which reduces the metal's reaction ability.
At present, the widely used TH2901 semi-dry protection agent is a gas phase corrosion inhibitor protection agent. Compared with traditional dry and wet methods, TH2901 gas phase corrosion inhibitor maintenance method has a corrosion rate of only 1/7 of dry maintenance and 1/105 of wet maintenance, and has comprehensive protection performance, not only protecting metals in the gas phase. , And protect the metal in a wet state; not only protect the non-scale metal, but also the metal under the scale. This medicine has achieved good anticorrosive effect during the outage and maintenance of steam boilers and hot water boilers. The corrosion rate of steel plates of boilers tested using this agent is only 0.036mg / a, which is better than traditional maintenance methods. The method of use is: first empty the pot water, remove the dirt in the pot, add medicine in the header and the boiler, store the medicine in a tray, and also spray the protective agent into the pot. The dosage is 1 ～ 2kg per m3 of water capacity of the boiler, and the dosage of the header and drum is calculated according to 1: 6 or 1: 7. The medicine is not harmful to the boiler. When the boiler is restarted, it is not necessary to remove the medicine, and only the container can be taken out. It should be noted that when there is too much water in the pot after drainage, the amount of medicine can be increased by 0.5 to 1 times. Compared with traditional maintenance, this method is simple in operation, one-time dosing, no drug addition in the middle, no personnel supervision, labor saving, time saving, and good effect, even if there is residual water in the pot or the seal is not tight, it will not affect the antiseptic effect. .
Principles for the selection of maintenance methods for biomass boilers <br /> According to the time of deactivation, you can refer to the following methods: choose the lye method for 1 to 3 months; choose the desiccant method, organic scale inhibitor and gas phase for more than 3 months Corrosion inhibitor method (TH2901), coating method.
According to the maintenance object, you can refer to the following methods: For long-term maintenance of steam boilers, you can choose the desiccant method, vapor phase inhibitor method (TH2901), lye method, organic corrosion and scale inhibitor method; hot water boiler and water circulation system maintenance can choose Liquid method and organic corrosion inhibitor method, desiccant method should not be used for hot water boilers.
Biomass boiler maintenance requirements <br /> In principle, immediately after the boiler is stopped, the ash and slag should be cleaned and descaled, and the inspection time should be submitted to the technical supervision department in time to strive for early inspection, early repair, and early maintenance. If conditions permit, the boiler should be maintained immediately after its shutdown. Its advantages are: it can use water resources in the system and perfect operating facilities to save manpower and material resources; good water quality and a perfect operating system can make maintenance measures fall In practice, it achieves the purpose of small dosage, uniform medicament, wide covering surface, no dead angle, and easy monitoring and adjustment; the maintenance effect is guaranteed, no water is prevented to prevent air from entering, and the addition of medicament improves the metal anticorrosive ability. In addition, maintenance inspections should be strengthened, especially during the rainy season.
When fouling occurs inside the biomass boiler, the heating surface in the boiler cannot effectively transfer heat, and the transfer effect is reduced. As a result, when the boiler is exhausting smoke, all the internal heat is discharged with the smoke, and the thermal energy is reduced.
When dirt occurs in the internal pipeline, it will cause the circulation area of the pipeline to become smaller, the water circulation will be blocked, and normal circulation will not be possible. When the dirt falls off, it may cause the pipeline to be blocked, which will cause expansion of some pressure-bearing equipment in the long term. , Deformation and other dangerous situations.
The appearance of fouling will cause the heating efficiency of biomass boilers to decrease, the working life of equipment to be shortened, and the cost of boiler maintenance to increase. Let's listen carefully to the experts of Green Probe HVAC to introduce how to solve the dirt inside the boiler.
1. Try to use water with low scale, or reduce the salt content of the existing water.
2. Add a treatment agent to the water circulation system in the biomass boiler, and perform drug treatment on the fouling-prone water slag to prevent it from depositing and scaling, and then regularly discharge the water slag.
3. Use special descaling agent to regularly remove the dirt on the inner wall of the boiler and the inner wall of the pipeline. After the removal, rinse with clean water until the clean water is discharged from the pipeline.
Analysis of the reasons for black smoke from biomass boilers Biomass particles, bituminous coal, and wood are not treated like anthracite. After treatment, the fixed carbon content is high, and the volatile matter yield is low. No smoke will be generated when burning. Good quality biomass particles have something in common with anthracite, that is, they both have high density and high hardness, but on volatiles and fixed carbon, biomass wood pellets are pressed from wood with less carbon content and more volatiles.
Biomass particulate fuel has high purity and does not contain other sundries that do not generate heat. Its carbon content is 75-85%, ash content is 3-6%, and water content is 1-3%.
When the biomass particulate fuel is ignited, the particles are slowly carbonized, and the combustion is incomplete, which produces water vapor, carbon monoxide, carbon dioxide, and other hydrocarbons and nitrogen oxides mixed flue gas. These flue gases are blown under the action of blast and phoenix It is discharged into the atmosphere through the boiler flue and chimney, so we will see black smoke from the boiler.
When the biomass particles in the boiler are completely burned, the temperature in the furnace is as high as 800-1000 degrees, or even higher, and the volatiles such as water and ash contained in the biomass particles are rapidly carbonized and combusted at high temperatures to produce combustible carbon such as carbon monoxide. Hydrogen compounds, nitrogen oxides, and oxygen are fully converted into non-combustible gases on time. Impurities in the black smoke have been burned out at high temperatures, so that no black smoke can be seen, which is what everyone says is no smoke.