Knowledge！Application of dust removal technology in incinerators

With the current large-scale discharge of urban domestic waste, we must strengthen environmental protection awareness, and it is indispensable to strengthen dust removal technology in some factories. In recent years, with the improvement of environmental protection requirements and the need to strengthen the control of fine particles, the dust removal technology must be continuously improved. Waste incineration has been widely used abroad and has become the main means of waste treatment. Everyone is responsible for protecting the environment. For the common beautiful environment of mankind, the combination of waste incineration and dust removal technology can achieve the common development of the environment and the economy.

1. The current situation of waste incineration in China

With the rapid development of the domestic economy, the people's living standards are constantly improving, and the amount of urban waste is increasing. The total amount of urban waste has an annual growth rate of 8%. At present, 90% of urban domestic waste is landfilled, and less than 1/3 of the waste is harmlessly treated.

Domestic waste incineration projects are developing rapidly. Every province and city is building or preparing to build a waste incineration power plant. There are many reasons for the rapid expansion of domestic waste incineration projects in China, but the main reasons can be summarized as the increasing pressure on urban domestic waste treatment and the huge demand for electricity in the domestic economy.

2. Problems with waste incineration treatment technology

Most of the waste incineration plants currently in operation in China use a semi-dry method with bag dust removal for flue gas treatment. This process is between the dry method and the wet method. The process treatment effect is better than the dry method, and the investment is lower than the wet method, so it is widely used. However, with the improvement of my country's environmental requirements, the wet flue gas treatment process will surely develop rapidly in the future despite the higher investment. With the improvement and progress of dry treatment technology (such as smaller lime particle size, more advanced injection device, etc.), the application of dry flue gas treatment technology will also increase.

It is well known that the flue gas produced by the incineration of urban domestic waste contains highly toxic substances-dioxins, and its harm has attracted much attention. The application of more advanced technology and multiple methods to ensure the removal and control of its production will help eliminate social doubts about the harm caused by waste incineration and create a good external environment for the development of waste incineration technology!

3. Dust removal of incinerators

Dust collectors include cyclone dust collectors, scrubbers, granular layer dust collectors, electrostatic precipitators, bag dust collectors, electric bag composite dust collectors and other methods. Its selection has many factors to consider, such as equipment costs, operating costs, maintenance, required power, dust removal efficiency, large-scale adaptability, and the presence or absence of wastewater treatment. As dust collectors for waste incinerator exhaust, bag dust collectors and electrostatic precipitators are currently the main focus.

1. Bag filter

Block one end of a cylindrical filter cloth such as woven cloth or felt, filter the dusty gas from the outside or inside, and form a dust layer on the filter cloth. Since this layer can efficiently capture dust, the dust layer accumulated on the filter cloth is properly shaken off by back-blowing vibration or pulsating spraying.

Its characteristics are:

(1) The exhaust gas concentration is stable, ≤30mg/Nm3, and the dust removal efficiency is high;

(2) The dust removal efficiency is not affected by the characteristics of the dust;

(3) The collection of fine dust (PM10) can be achieved through filter material technology Solution;

(4) It can capture a certain amount of harmful gases such as dioxins and SO2.

Bag filter has the following shortcomings:

(1) The running resistance is relatively large, generally 1500~2000Pa, which causes large system resistance, large power of the induced draft fan after the dust collector, and high operating costs;

(2) The filter bag life is limited, the replacement cost of the filter bag is high, and the workload is large;

(3) Chemical fiber filter bags cannot withstand the passage of high-temperature flue gas, and there are also strict requirements on the moisture content and oily substance content in the flue gas.

2. Electrostatic precipitator

Electrostatic precipitator occupies the center of gravity of large dust removal devices in thermal power generation and other aspects because of its high capture rate, low pressure loss, easy maintenance and management, and is suitable for large-scale equipment. In waste incineration projects, it is still widely used. Electrostatic precipitator uses strong electric field corona discharge to ionize flue gas and charge dust, and separates dust from flue gas under the action of electric field force.

Its characteristics are:

(1) Small body pressure loss, generally <300Pa;

(2) Able to handle large-scale industrial flue gas;

(3) High temperature resistance;

(4) Long service life of main components and easy maintenance.

The main disadvantages of electrostatic precipitator: dust removal performance is greatly affected by the physical and chemical properties of dust, and the application effect is not ideal for high resistivity dust, fine dust and high viscosity dust. Therefore, in order to improve the dust removal efficiency, the dust collection area has to be greatly increased, which makes the investment uneconomical and even cannot be used normally in some special working conditions. When operating at around 300℃, there is a possibility of dioxin generation in the electrostatic precipitator. The recent increase in the use of bag dust collectors has the following reasons:

(1) Due to changes in garbage quality and the reduction in water vapor concentration in exhaust gas, in order to suppress the generation of dioxins, the dust collection temperature is promoted to be lowered;

(2) The high-temperature durability of bag dust collectors is improved;

(3) The dust collection performance of bag dust collectors is extremely high, which is very effective in controlling the discharge of dioxins contained in dust;

(4) In front of the dust collector, a water spray cooling tower is set up and the desulfurizer slurry is sprayed. Even in abnormal combustion, there is little possibility of high-temperature fire reaching the dust collector.

3. Comparison of the characteristics of bag filter and electrostatic precipitator

(1) The bag filter has a higher performance in capturing submicron particles;

(2) The dust concentration at the outlet of the bag filter is not greatly affected by the inlet concentration, but the electrostatic precipitator is greatly affected by the inlet concentration. If the inlet concentration exceeds the design value, the outlet concentration cannot reach the required value;

(3) The resistivity of the dust has a great influence on the dust collection performance of the electrostatic precipitator. The resistivity varies with the operating temperature of the dust composition;

(4) When dry scrubbing is set up upstream, it can correspond to the absorption reaction in the dust layer in the bag filter. Therefore, when using an electrostatic precipitator, in order to remove the same degree of acidic gas, the amount of absorbent increases by about 30%. As mentioned above, in recent years, the use of bag filters for dust treatment in waste incineration facilities has increased.

4. Electrostatic bag composite dust collector

The electrostatic bag composite dust collector is a new dust removal technology proposed based on two mature dust removal theories: electrostatic dust removal and bag dust removal. It combines the advantages of both, has high dust removal efficiency, can meet the new environmental protection standards, and increase operational reliability. Therefore, the electric bag composite dust collector gives full play to the respective advantages of the electrostatic precipitator and the bag dust collector.

(1) Scientific mechanism, reliable technology, and high efficiency. The first electric field of a conventional electrostatic precipitator can usually remove 80%-90% of the dust in the flue gas, and the remaining electric field is used to remove the remaining 10%-20% of the dust. The composite dust collector makes full use of this characteristic of the electrostatic precipitator, only using the first electric field, and the remaining fine dust is filtered out by the bag dust removal unit, giving full play to the high efficiency of the bag dust collector in removing ultrafine dust. At the same time, the electric bag dust collector uses two mature dust removal technologies, electrostatic and bag, and the dust removal efficiency can reach more than 99.9%, and the mass concentration of the outlet dust is less than 30mg/m3.

(2) Not affected by dust characteristics, high dust removal efficiency. Conventional electrostatic precipitators are greatly affected by dust characteristics, making the dust removal efficiency extremely unstable. The electrostatic bag composite dust collector takes advantage of the wide adaptability of the bag dust collector to dust characteristics, so that dust characteristics no longer become a factor restricting dust removal efficiency, and improves dust removal efficiency overall.

(3) Small filtration resistance, long filter bag life, low operation and maintenance costs. As the primary dust removal system of the bag dust collector, the electrostatic precipitator can significantly reduce the dust concentration of the inlet flue gas of the bag dust collector. Compared with the ordinary bag dust collector, the bag unit load of the electrostatic bag composite dust collector is greatly reduced, so a longer cleaning cycle and lower blowing pressure can be selected, thereby extending the service life of the filter bag.

(4) Small footprint and low investment. Compared with the bag dust collector, the electrostatic precipitator has removed most of the dust and greatly reduced the filter bag load. Therefore, a higher filtration wind speed can be selected, requiring fewer filter bags, with a compact structure and reduced floor space. At the same time, a larger filter bag spacing can be selected, which solves the problem of secondary dust caused by the dense filter bags of the pulse bag dust collector during cleaning.

In recent years, with the development of cities in my country, the amount of urban garbage generated has increased year by year. How to properly dispose of garbage and reduce environmental pollution has become the key to restricting urban development. At present, garbage incineration is an effective measure for solid waste treatment. Most cities in China use stacking and sanitary landfill methods to deal with garbage, and the research, development and application of garbage incineration technology started late. It is particularly important to be familiar with the development trend of garbage incinerator combustion technology and equipment, and to master advanced garbage incinerator design and manufacturing technology.