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Technical Measures for Preventing Coking of 80t / h Circulating Fluidized Bed Boiler

Circulating fluidized bed boiler combustion Coking is a common situation, both in the ignition start, the ignition start and run may occur. In the event of coking, the spread rate is very fast. Improper handling will cause more and more serious coking, eventually leading to shutdown and cause great impact on security and economic operation.In order to prevent the coking of the fluidized bed boiler, ensure the safe, continuous and economical operation of the fluidized bed boiler, now specially formulated measures are as follows:

1. Start the process to ensure a good and stable into the furnace quality

1) calorific value of not less than 17000KJ / KG, volatile not less than 12%;

2) particle size qualified: 8mm pass rate of not less than 85%;

3) ash melting temperature> 1500 ℃;

4) sulfur content of not more than 1.2%.

2. Before the ignition must be a good fluidization test

1) Determine the critical flow rate. Critical flow of air flow should be 16-18 million Nm3 / h or so, such as;

Too large should find the reason 

2) the amount of wind blowing on the furnace for 10 minutes, blowing air volume (primary air) of not less than 250,000 Nm3 / h;

3) do cloth wind board uniformity test. In the critical flow of air at the emergency stop all the fans, into the furnace bed material inspection

Fluidization, to ensure fluidization.

3. After the boiler burst, be sure to clean the bed and check the hood to ensure that the bed without knot and hood no clogging.

4. Control bed pressure riser bed material added to 1-1.2 meters, start bed pressure 13-13.5KPA; furnace furnace bed pressure should be maintained within the normal range, such as greater than 20.8 or below 8.7KPA should report the relevant leadership And ask for a shutdown.

5. In strict accordance with the provisions of the coal

1) after the coal should ensure that the primary air volume is not less than the critical flow of air flow;

2) bed temperature to reach the specified temperature and then try to vote coal (in the row of bed temperature> 510 ℃), such as poor quality, should be

Bed temperature increased 50-100 ℃ and then re-put coal

3) the initial start should be strictly in accordance with the "pulsating" form of coal, coal should be based on changes in oxygen and bed temperature to determine whether the coal has been burning, such as unburned is to immediately stop the coal, to be properly raised bed temperature, and then in the same form to re-coal. To prevent excessive coal after the occurrence of deflagration, resulting in bed temperature is too high, resulting in high temperature coking.

6. Control bed temperature

1) closely monitor the bed temperature distribution, as follows, the average bed temperature difference> 100 ℃, or a little and more bed temperature and average bed temperature> 100 ℃, should be carefully analyzed to strengthen the inspection, Low temperature coking;

2) When the bed temperature is too high, measures should be taken immediately to increase the amount of air or reduce fuel to reduce bed temperature. Especially the coal particles become thicker or the deterioration of coal and other reasons caused by bed temperature fluctuations, should be appropriate as appropriate to increase the amount of air flow to the bed, flat bed temperature, or prone to large particles deposition, bed stratification, resulting in local Or the overall over-temperature coking phenomenon.

3) according to the bed temperature rise, timely fine-tuning, fine-tuning air volume and the amount of coal to maintain good fluidization, control bed temperature rise should not be too fast to avoid significant changes in bed temperature, resulting in a vicious cycle

7. Establish a recycling cycle as soon as possible, while close observation of the return of the legs temperature, pressure changes. To avoid the return material due to poor material recovery or local dead zone and slagging phenomenon

8. In the furnace process should try to shorten the start-up time, otherwise the oil and coal co-firing time is too long, improper adjustment prone to coking, especially coal into the initial kerosene burning stage, a lot of coal into the furnace can not burn completely Easy and unburned oil stick together to form a local high temperature coking.

9. Or slightly coke, bed material can be replaced by bed material method to remove the coke (as soon as possible to restore the sand system); if the coke is serious, you should immediately stop the coal, and increase the amount of air flow to the furnace, The coke is blown away and the furnace is cooled to reduce the severity of coking and shorten the time to focus.