Dust analysis of biomass boiler dust filter bag

Biomass boiler has a more complex fuel structure than coal-fired boiler, we will encounter a variety of problems when solving biomass boiler dust, according to Xinye Environmental Protection years of dust removal experience, for biomass boiler dust difficulties analysis, and design biomass boiler dust collector to solve the problem of difficult dust.

We will encounter the following situations when dealing with biomass boiler dust:

1. A wide variety of incoming fuels

Fuel into the plant is generally bark, straw, wheatgrass, corn stalks, branches, wood chips and so on. Because the calorific value is not the same, the combustion characteristics are not the same, and the fuel in the biomass boiler is mainly in the form of mixture, coupled with the fuel mixing personnel is not strong sense of responsibility, therefore, the fuel variety ratio of the fuel in the furnace is changing at any time, and the operation adjustment work is more complicated.

Solution:

Dust removal condition of biomass boiler

Boiler operators are required to strengthen the connection with fuel management and mixing personnel, and grasp the types of fuel into the furnace in time; Secondly, the boiler operator is required to watch the fire, observe the combustion of fuel on the grate, and adjust the combustion in time.

2, the fuel moisture is high

The deviation between the design value and the actual operation is too large. Due to the lack of experience in the design of the early biomass boiler, the moisture design of the coal boiler is less than 15%, while the moisture of the mixture in the actual operation is about 45%. Therefore, the smoke gas generated by the fuel entering the furnace is much larger than the design value, and there is the problem of insufficient output of induced draft fan. As a result, the primary and secondary air volume of the boiler can not be rationed according to demand, and the fuel combustion is insufficient. Secondly, the water in the fuel is larger, just into the furnace is not easy to fire, after a period of baking, water into steam, once the grate vibration, gathered under the material layer of water vapor instant release, easy to form positive pressure, fuel will be lifted from the grate into the slag system, at the same time a large number of hot flue gas cross-linked, by the feeder into the silo, causing silo deflation, And then cause the furnace to stop the accident phenomenon often occur.

Solve:

Do a good job of market research, master the normal moisture of fuel, in order to develop the acquisition standard, grasp the fuel purchase entrance; Secondly, according to the relationship between calorific value and moisture, make fuel quality table, determine the priority to purchase, reduce the purchase of high moisture, low calorific value fuel; If the site permits, it can be done properly before the furnace or reasonably mixed with low moisture fuel; Adopt the new process and carry out technical innovation. For example, the company adopts the drying device of wood chips for the phenomenon of high water content and easy deexplosion, and the effect is obvious after operation.

Biomass boiler dust difficulty

3, more impurities

Due to the pursuit of economic benefits, once the fuel entry control is not strict or slightly lax, the fuel will be mixed with soil and fine sand, and these fine particles will flow with the flue gas after combustion into the furnace, forming local wear at the elbow of the economizer with the faster flow rate of the boiler flue gas. As boiler designers generally believe that the hardness of grass and wood ash is far less than that of fly ash, And light texture is not easy to cause wear, so most do not set up anti-wear devices.

Solve:

Strict admission quality; Secondly, the development of anti-wear plan, in the boiler heating surface easy to wear to increase the anti-wear tile, reduce the local wear of the elbow, at the same time after each stop the furnace for the corresponding "four tube" thickness measurement work, found problems in time to deal with.

4. High ash content and high alkali metal content

Due to the influence of ash melting point of biomass fuel, it is easy to coking and ash accumulation on the heating surface of the boiler after the fuel is burned in the furnace, and the formation of ash scale affects the heat transfer of the boiler. According to the experimental data: the thermal conductivity of the ash accumulation layer is 0.0581 ~ 0.116w/m2? The thermal conductivity of metal tube wall on boiler heating surface is 46.5 ~ 58.1wm2? ℃, the thermal conductivity difference of 500 ~ 800 times, so in the operation does not take the corresponding technical measures, generally after cleaning the furnace running 20d after the main steam temperature is difficult to maintain, and the deviation from the rating is more and more large.

Solve:

Due to the steam ash blowing effect is not ideal in the operation of the biomass boiler system, so the factory in the case of many investigations, finally choose the gas pulse ash blowing and combined with coke inhibitor use method, used to remove the problem of ash and coke on the heating surface, the effect is obvious, basically can ensure that the continuous operation of more than two months main steam temperature meet the relevant requirements, And the phenomenon of ash accumulation on the heating surface has been greatly improved.

5, conveying system failure rate is high

Due to the toughness of biomass fuel is large, the proportion is small, the silo can not store a high material level, otherwise the silo jam will occur, so the transport system is normally run 24h, the rotating parts are easy to wear, high failure rate; At the same time, the length of the grass after shredding is difficult to ensure in the normal value of 8 ~ 15cm, in front of the furnace feeder is easy to jam phenomenon, and cleaning is more difficult, which has a greater impact on the load of the boiler.

Solve:

In order to reduce wear and prolong the service life of the equipment, the general motor adopts frequency conversion regulation to slow down the running speed of the equipment and control the feeding speed of the fuel, so that the material accumulation height of the silo is always within a reasonable range, the feeder can evenly feed, reduce the number of plugging; Secondly, according to the amount of feed and fuel varieties, choose the appropriate size of the feeder, fundamentally solve the problem of equipment factors brought by blocking.

We need to pay attention to the following points when designing biomass boiler dust collector:

1. Fully consider the operation problems that may be caused by large moisture content of fuel, select the appropriate induced draft fan. If the design of the induced draft output of the power plant that has been in operation is insufficient, it should be replaced from the perspective of long-term operation.

2, In the case of sufficient ventilation, reasonable distribution of a secondary wind, generally speaking, large water, light fuel such as wood chips, straw, wheat grass and so on to increase the secondary air volume; For bark, mixed wood should be used to increase the method of primary wind;

Biomass boiler dust collector

3. Increase the inspection and observation of the temperature measuring point of the ash hopper, and timely deal with abnormal findings to prevent the whole bin of the dust bag from burning out;

4. The use of higher strength dust bag base cloth, strict control of excess air coefficient and smoke exhaust temperature during operation, to prevent the oxidation and hydrolysis of dust bag.