Reasons for the burnout of brick plate flanges
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The gasification furnace in our facility uses Texaco gasification technology, with a pressure of 6.5 MP; it produces 200,000 tons of methanol per year. During this maintenance period, when we inspected the bricks at the bottom of the furnace, we found that the flanges supporting those bricks were almost completely worn out. What could be the reason for this? We have three furnaces, with two in use and one as a backup. This is the one that is used most frequently. This kind of situation has never occurred before, but recently, due to issues with the quality of coal, the temperature of the furnace rose to 1300 degrees, and it operated at that temperature for some time.
1. Is it due to a long operating cycle and severe wear? 2. Has the quality of the coal changed, with a high ash content that causes severe erosion of the furnace bricks?
In my opinion, the first issue is the load problem, and the second is the oxygen-coal ratio problem! ! !
The refractory bricks at the bottom of the cone have become thinner or there is air leakage; a operating temperature of 1300 isn’t that high. Was no abnormal temperature increase in the tray observed during operation? This phenomenon is already very dangerous.
Has it been a long time since the tuyere bricks were replaced? With a sudden change in coal quality and an increase in furnace temperature, erosion will surely occur rapidly
The high temperature causes severe erosion of the bricks at the bottom of the cone.
It’s possible; I think the second factor is the main one. Every time we carry out maintenance, we check the quenching ring and the cone bottom bricks, and after two shutdowns, we replace the cone bottom bricks once. However, there were a few times in between when operations stopped to ensure production levels, and work resumed after that. I’ve made multiple attempts to submit it – could that also have an impact?
The load remained around 70, and the oxygen-coal ratio was kept high due to the high ash content in the coal.
The temperature of the brick slabs during operation was fairly normal; this issue was not detected until we went in for maintenance this time to replace the cone-bottom bricks. That swivel flange is now down to a quarter of an inch in thickness. Due to the tight schedule, we used fireclay for pouring this time, without adding any support flanges. Who would have known about this situation before?
It doesn’t seem to be a problem with the slag outlet bricks; we replace them quite frequently.
The cooling ring is equipped with a baffle layer that is connected to the supporting brick plates; this component is itself prone to damage. Its primary function is to support the bricks at the base of the cone and protect the cooling ring. Modern cooling rings utilize a concealed design, in which the size of the slag outlet at the base of the cone is smaller than the diameter of the cooling ring. To install bricks at the base of the cone on top of the cooling ring, it is necessary to increase the size of the supporting brick plates. When these bricks at the base of the cone wear down, the additional supporting brick plates become exposed and are subject to attack by hot slag, making them susceptible to damage. The cooling ring concealment technique takes advantage of the fact that the size of the cone-bottom slag outlet in Texaco gasifiers is smaller than the diameter of the cooling ring; by positioning the semi-circular ring tube facing the flame and hiding it beneath the furnace bricks, direct contact between the high-temperature, rapidly flowing raw syngas and the molten ash and slag can be avoided. The heating mechanism changes from direct scouring to radiation, allowing the surface temperature to drop to around 600°C. This reduces the thermal ablation and scouring corrosion on the cooling ring, thereby effectively extending its service life. When the slag discharge opening at the base of the cone becomes abraded and enlarged, the furnace should be shut down promptly for replacement in order to protect the quenching ring. Therefore, extending the service life of the cone bottom bricks can increase the operating cycle of the quenching ring.