News
Mill blockages and fires: Coal headaches continue
View(s):- Frequent capacity reductions recorded as audit reveals imported stock failed to meet basic energy standards
By Namini Wijedasa
Trident Chemphar’s coal caused serious, repetitive problems at the Lakvijaya coal power plant (LVP), including inability to generate full power capacity, severe overconsumption of coal, high pyrite (hard mineral particles that cannot be ground by the mills), leading to mill blockages and fires and restricted primary air flow due to high ash content.
The report of the National Audit Office confirms that, according to operational data, the imported South African coal’s gross calorific value (GCV) was consistently below the required standard of 6,150 kcal/kg. In some cases, it fell below the absolute rejection threshold of 5,900 kcal/kg. Due to this poor energy content, none of LVP’s three units were able to generate the full desired capacity of 300MW.
Lakvijaya coal power plant
Fire in the mills
To compensate for the coal’s low heat value, the plant had to consume significantly more fuel, causing the coal feed rates to regularly exceed the safe operational limit of 115-116MT per hour, the audit observes.
Trident’s coal contained unusually high amounts of pyrite, which are hard mineral particles that cannot be ground. Each LVP unit has grinding mills with a special mechanism to separate and discharge pyrites via a reject system into a “pyrite hopper,” from where operators periodically remove them.
When coal contains an unusually high amount of impurities, it might impede the reject system from discharging pyrites as fast as they are generated. This leads to accumulation inside the mill, causing mill blockage, overheating or fire risk. When this happens, the coal feed rate is reduced to maintain safe operation.
The mills’ reject mechanisms could not discharge the high pyrite content in Trident’s coal fast enough, causing it to accumulate inside the grinding mills, the audit says. This caused severe mill blockages, overheating, and eventually sparking a fire in the pyrite hopper of one mill on March 5, 2026. All this indicated that the equipment was physically struggling to process the new coal.
At the time the fire broke out, unit 03′s mills were operating with a coal flow rate of approximately 29 to 30MT per hour. To ensure safe operation and prevent further emergencies, the operators were forced to significantly reduce the coal feed rate to approximately 26 metric tons per hour per mill.
Furthermore, to safely manage the situation and maintain stable combustion in the boiler while the affected mills were shut down for cleaning and restoration, the operators had to temporarily use oil burners. Plant management noted that avoiding these dangerous conditions and stabilizing the unit had to take priority over maintaining maximum coal capacity.
Many other problems
Meanwhile, the coal’s ash content also exceeded the power plant’s design specifications, the audit continues. This excess ash deposited and built up inside the air preheaters (APH), restricting the “primary air flow” necessary to dry and transport pulverised coal, ultimately forcing operators to reduce the coal feed rate.
High moisture levels in the coal caused it to stick to the internal surfaces of the grinding mills. This reduced the grinding efficiency and led to material accumulation inside, significantly increasing the risk of the mills choking. Separately, the excessive feeding required to maintain power capacity caused coal particles to accumulate rapidly inside the mills, which significantly increased the internal differential pressure. To prevent the mills from completely clogging and tripping the system, operators were continually forced to lower the coal feed rate, the audit report states.
On February 16, unit 3 suffered a “cooling water intake blockage” that directly restricted its operations, reducing the unit’s available night peak capacity to 231MW (out of 300MW).
Unit 1 suffered severe capacity drops in early March, even falling to 0MW on March 7 and 9, due to mandatory maintenance required on its stator water cooling system.
Unit 2 experienced a fault in its de-superheating valve that the maintenance team could not immediately repair. Because of this malfunction, operators were restricted from using the new coal and instructed to run the unit exclusively on a previously imported stock of Russian coal from February 1 to March 1, 2026.
The auditors examined LVP’s log books. Extracts of their findings show that on January 21, operators of unit 1 recorded an “abnormal increase in steam temperature observed with new coal stock loading,” as well as abnormal increases in superheater (SH) and reheater (RH) temperatures.
On January 27, when system control requested LVP operators for the full capacity of 300MW from unit one, they replied that “the maximum capacity available due to new South African coal is 290MW”.
On February 6, LVP operators noted that “the capacity of the unit (unit 2) has been reduced to 270MW as the coal rate cannot be maintained at a value of about 115 tons per hour at the current capacity of 275MW from South African coal”.
Meanwhile, daily power system reports prepared by the system control division frequently and explicitly recorded capacity reductions “due to a coal quality issue”. For example, throughout January and February 2026, these reports cited a “coal quality issue” as the reason unit 1, unit 2 and unit 3 were limited to capacities such as 236MW, 240MW, 246MW and 262MW during critical night peak hours.
Unit 1 suffered continuous capacity reductions on almost every recorded date from late January through mid-march—for example, dropping to 256MW on January 27; 233MW on February 6; 231MW on February 16; and regularly down to 214 to 257MW between March 4 and March 16. The reason: “restricted mill operation”.
The 2020 to 2025 period
The NAO also reviewed the plant’s records for the six years from 2020 to 2025 and found that there were no explicitly recorded problems attributed to poor-quality coal. An analysis of coal imported during this period (from the 262nd to the 455th shipment) showed that GCV exceeded the required standard of 6,150 kcal/kg in 72 percent of shipments, while the remaining 28 percent remained safely about the rejection threshold.
The log books maintained by the operating officers for all three units contained no entries indicating that the quality of imported coal stocks had decreased or that the units could not operate their full 300MW capacity due to coal quality issues.
Across thousands of daily power system reports prepared by the system control division from 2020 to 2025, there was only one recorded instance explicitly citing a coal quality issue—on November 3, 2025, unit 1’s capacity dropped to 260MW during the night peak due to “wet coal”. No such notes were found for units 2 and 3 during this entire period.
However, there were other operational problems recorded including operating units at partial capacity, which significantly reduced thermal efficiency and increases the coal consumption rate; using wet coal on rainy days which lowers the coal’s effective heating value, increases latent heat loss, and adds water weight, requiring more coal to be burned; and ignition and stabilization processes which require high coal consumption, oil support firing and auxiliary steam, which spikes consumption rates.
Also cited are ash buildup on heat exchange surfaces that reduced heat transfer efficiency; equipment issues such as steam leaks, bypassing of high-pressure feedwater heaters, reduced vacuum in the condenser and leaks or blockages in air preheaters.
| Overlapping consignments and shortfalls Trident Chemphar’s 15th coal shipment is currently being unloaded at Norochcholai, its 16th shipment is in the queue at Puttalam, and its 17th shipment is on the way, likely to arrive this weekend. Meanwhile, with the first emergency coal consignment from Taranjot Resources also having landed five days ahead of schedule, authorities will struggle to prioritise which gets to use the jetty first, official sources warned. The Taranjot consignment was scheduled to land on April 20th, but reached on April 15. Its second shipment should arrive on April 27, according to the schedule. Every delay at the jetty incurs demurrages, informed sources pointed out, adding that the coal Taranjot is supplying through its first shipment is of Indonesian origin. It won the emergency tender for five coal shipments (300,000MT). It remains unclear how many shipments short Trident’s supply will be. The contract was awarded for 25 shipments or 1.5mn MT of coal. Official sources said, however, that they expect around 18 consignments to be completed, leaving seven shipments short from the 2025-26 term tender. With the addition of five shipments from the emergency tender—purchased at a significantly higher price of US$ 142 per metric ton (Trident was at US$ 98.5 per MT)—the total number of shipments for the season will be 23. That is still two less than the required quantity. Trident’s 15th shipment, which arrived on April 8, is still unloading (unloading started on April 13). The significant delay has been attributed to rough seas caused by high winds that online weather reports indicate could last up to five more days. | |
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