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1. Requirements for the environment when the gasifier is working
Gasifier production is carried out at 1300-1400°C high temperature and high pressure (8.34MPa for large furnaces). Raw oil (heavy oil, residual oil, or crude oil) and oxidants such as oxygen and steam are sprayed into the furnace through nozzles for an incomplete oxidation (that is, combustion) reaction. The surface temperature of the gasifier is 80-120°C, and the maximum temperature shall not exceed 200°C. Generally, a surface temperature measuring device (thermistor) or color-changing paint is used. The inner shell is lined with refractory materials. In addition to the influence of changes in furnace pressure, operating temperature, and process gas on the life of refractory bricks, trace metals such as vanadium and nickel in raw oil have a great impact.
The nozzle is the core component of the gasifier, which sprays raw material oil, oxygen, steam, and other oxidants into the furnace for reaction. There are many types, and the commonly used ones are two-casing external mixing type, three-casing type, and secondary airflow atomization double-casing nozzle.
The structure of the gasifier itself is simple, but because the process gas contains hydrogen and carbon monoxide. Hydrogen has hydrogenation corrosion to the furnace body; carbon monoxide is harmful to the human body, so pay attention to production.
The quenching chamber is in the lower part of the combustion chamber, where the temperature of the process gas is lowered (about 262 ° C), and the entrained carbon black is washed away. After gas-liquid separation, it leaves the gasifier at the upper part of the quenching chamber, but the liquid left in the quenching chamber contains formic acid and carbonic acid. , hydrogen sulfide, etc., also have a corrosive effect on the quenching chamber shell.
2. Reduction reaction to ablation reaction of corundum bricks for gasifier
Inside the furnace is a strong reducing gas H2, CO, C ratio, etc., with a high temperature of 1350°C and a high pressure of 8.53MPa.
The SiO2 content in the corundum brick is 0.2%, and the Fe3O4 content is 0.15%. Under high temperatures and high pressure, the gas in the furnace reacts with the silicon oxide and iron oxide in the brick as follows: the reduction of silicon oxide and iron oxide when the furnace is stopped to cool down, and the oxidation reaction is accompanied by The large volume expansion effect causes the internal stress of the corundum brick to change continuously, destroys the original gutter of the corundum brick, increases the porosity of the corundum brick, reduces its strength, and causes damage and peeling.
3. Special-shaped refractory bricks for coal-water slurry gasifier
In the coal-water slurry gasification furnace, the installation of refractory bricks in the furnace is a key technology, especially around the nozzle with complex structure and large curvature change and the arched part of the furnace roof. Poor installation of refractory bricks may lead to high-temperature gas channeling if ordinary block refractory bricks are used. It is very difficult to drag the 9 warehouses. Therefore, in order to better prevent the problem of high-temperature blow-by, the author designed several special-shaped refractory bricks, which are mainly used to install around the nozzle. The special-shaped refractory brick can not only bring convenience to the construction but also effectively prevent the problem of high-temperature blow-by gas. The main idea is to ensure that the whole refractory brick is used around the nozzle and the arched part of the furnace roof. Reduce the difficulty of construction and eliminate the gaps that may arise due to construction difficulties when using block refractory bricks.
4. Specific use of clay refractory bricks in gasifiers
The specific use of clay refractory bricks in gasifiers. As an important refractory material, clay refractory bricks are used in gasifiers. How to avoid some problems? Clay refractory bricks also experienced oxygen load fluctuations during the operation of the gasifier. Sometimes the oxygen regulating valve will cause the oxygen load to fluctuate. Sometimes large particles will suddenly block the high-pressure coal slurry pump valve, and the coal slurry flow rate will suddenly drop. Relatively excess oxygen. Oxygen fluctuations directly cause fluctuations in furnace temperature, and the range of oxygen fluctuations is sometimes 500m3 to 600m3, and the maximum reaches about 1000m3. After the oxygen suddenly rises, the furnace temperature will suddenly rise, and the high-temperature thermocouple will be burned out suddenly. This situation has a great impact on the clay refractory bricks and should be avoided as much as possible. We all know that the temperature in the furnace is very important to the life of the refractory lining, so it should be strictly controlled not to exceed the temperature. Under normal production conditions, there is a layer of cinder layer on the surface of clay refractory bricks. In fact, the slag layer is dynamic. The slag layer is thicker at low temperatures and thinner at high temperatures. An appropriately thick slag layer can slow down the high-temperature gas and slag. scour.
5. Precautions for each sub-project of refractory brick masonry in the gasifier combustion chamber
The masonry quality of refractory bricks in the gasifier combustion chamber directly affects the normal operation of the equipment, so the construction must be carefully organized in strict accordance with the construction plan and construction specifications. Due to the large workload of masonry refractory bricks and many factors to be controlled, it is necessary to pay attention to the details of each project. According to these details, the overall construction quality of the furnace refractory brick masonry will be ensured. Before the construction of each sub-project, it is required to conduct an appearance inspection on the hot-faced refractory bricks, high-alumina refractory bricks, and heat-insulating refractory bricks in accordance with the current relevant refractory brick standards and the size deviation of the refractory bricks in the technical conditions agreed in the contract. , remove all unqualified bricks.
In summary, the above is the refractory materials and masonry-related content for gasifiers compiled by the editor. Welcome to follow Xinhongji Refractory.
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