Fundamentals of Gasification 2018-10-10

Answer: Reason: A. Low fuel supply； B. High cooling water temperature ； C. Incompatible fit between the shaft and bearing bushings ； D. The mill runs idle for a long time. Solution: A. Increase the oil supply ； B. Increase the amount of circulating cooling water or lower the temperature of the circulating water ； C. Stop the machine to inspect or replace the bearing shells ； D. Stop grinding immediately.

Answer: Reason: A. Low fuel supply； B. High cooling water temperature ； C. Incompatible fit between the shaft and bearing bushings ； D. The mill runs idle for a long time. Solution: A. Increase the oil supply ； B. Increase the amount of circulating cooling water or lower the temperature of the circulating water ； C. Stop the machine to inspect or replace the bearing shells ； D. Stop grinding immediately.

A. Low fuel supply； B. High cooling water temperature (oil temperature); C. Incompatible fit between the shaft and bearing shells ； D. The grinder runs idle for a long time

Lubricant contamination; replace the lubricant

Main reasons: 1. Insufficient supply or interruption of lubricating oil. 2. Insufficient or interrupted cooling water, and the oil level in the tank exceeding the height of the baffle results in a loss of cooling effect. 3. The bearing seal is poor, allowing dust or impurities to enter, which increases friction due to the bearing bush. 4. The viscosity of the oil leads to poor quality after long-term use. Solution: 1. Increase the oil supply ； 2. Increase the amount of circulating cooling water or lower the temperature of the circulating water ； 3. Parking for inspection or replacement of bearing shells ； 4. Stop grinding immediately. 5. Oil change ；

A. Low fuel supply； B. High cooling water temperature ； C. Incompatible fit between the shaft and bearing bushings ； D. The mill runs idle for a long time

Generally, when designing and selecting coal mills, normal operation under extreme summer temperatures is taken into account. The temperature of the mill’s shaft bearings increases to some extent during summer due to the rise in ambient temperature, but it should remain within acceptable limits. If it exceeds these limits, the main reasons are as follows: 1. The gap at the seal ring of the mill is adjusted too tightly, resulting in excessive pressure between the seal element and the mill’s shaft journal; this leads to high friction forces during rotation, which in turn generates additional heat and raises the temperature of the shaft journal. 2. The lubricating oil becomes contaminated and its quality deteriorates; the filters in the lubrication system get clogged. As a result of this contamination, the quality of the lubricating oil worsens, and frequent clogging of the filters leads to insufficient supply of oil. This prevents the lubricating oil from removing heat properly, causing heat to accumulate in the bearings. 3. The design capacity of the closed-circuit cooling water system for the coal mill bearing shells is too low, resulting in a reduced flow rate of cooling water to the heat exchangers located after the water cooling pumps. This leads to a higher inlet temperature of the cooling water for the bearing shells, thereby reducing the cooling efficiency.

The main reasons are as follows: 1. The gap at the seal ring of the coal grinder was adjusted too small, causing the seal piece to press too tightly against the shaft journal; this results in excessive friction during rotation, which increases the heat generated by the shaft journal and raises its temperature. 2. The lubricating oil becomes contaminated and its quality deteriorates; the filters in the lubrication system get clogged. As a result of this contamination, the quality of the lubricating oil worsens, and frequent clogging of the filters leads to insufficient supply of oil. This prevents the lubricating oil from removing heat properly, causing heat to accumulate in the bearings. 3. The design capacity of the closed-circuit cooling water system for the coal mill bearing shells is too low, resulting in a reduced flow rate of cooling water to the heat exchangers located after the water cooling pumps. This leads to a higher inlet temperature of the cooling water for the bearing shells, thereby reducing the cooling efficiency. Remedial measures: 1. By readjusting the sealing ring. 2. During operation, it is necessary to strengthen supervision of oil quality and promptly remove impurities and moisture from the oil to ensure effective lubrication. At the same time, take advantage of major and minor maintenance opportunities to regenerate the lubricating oil in order to reduce fuel consumption. The amount of lubricating oil used for the bearing shells should be adjusted according to operational requirements; when there are significant temperature changes, the amount of low-pressure lubricating oil should be adjusted promptly to enhance lubrication and cooling effects. It is essential to strictly prevent dust from reaching the lubricating oil at the shaft bearings during operation. During normal operation, maintain a seal air pressure of 1.5 KPa; after the initial air pressure is established before starting the mill, or during shutdowns or emergency stops, keep 1–2 burners’ shut-off valves open to prevent the cylinder pressure from exceeding the seal air pressure. 3. By checking the cooling water valves at the inlet and outlet of the coal grinder, it was found that due to long-term use, the valve cores often came loose, resulting in reduced cooling water flow. By promptly inspecting and replacing the damaged valves and pipes, smooth flow of cooling water was ensured. Additionally, to address the issue of poor return flow in the industrial water system, it was made sure that the return water was not affected by the pressure on the supply side. The return water for the coal grinder’s cooling system was changed from pressurized return to non-pressurized return via the industrial water main on the turbine side. These modifications resolved the problems with the smoothness of the coal grinder’s cooling water system, providing necessary support for the cooling of the bearing shells.

Reason: A. Low fuel supply； B. High cooling water temperature ； C. Incompatible fit between the shaft and bearing bushings ； D. The mill runs idle for a long time. Solution: A. Increase the oil supply ； B. Increase the amount of circulating cooling water or lower the temperature of the circulating water ； C. Stop the machine to inspect or replace the bearing shells ； D. Stop grinding immediately.

A. Low fuel supply； ??B、High cooling water temperature ； ??C. Incompatible fit between the shaft and bearing shells ； ??D. The mill runs idle for a long time. Solution: ??A、Increase the oil supply volume ； ??B. Increase the amount of circulating cooling water or lower the temperature of the circulating water ； C. Stop the machine to inspect or replace the bearing shells ； ? ?? ?? ? D. Stop the mill immediately.