【Learning from Others: HaiChuan】Guohua Ninghai Power Plant achieves zero emissions violations through full-process denitration

**Guohua Ninghai Power Plant, which belongs to the energy sector, is located in the eastern coastal area of Zhejiang. It is a key area for **energy conservation, emission reduction, and the control of air pollutants. In recent years, technological advancements in this industry have continued, and policies related to energy conservation and environmental protection have become increasingly stringent. To adapt to the fierce competition in the power industry and secure greater benefits for the enterprise, it is essential to seize opportunities and take the lead. “Denitration throughout the entire production process – we must take action now! ”Zhu Jienan, the chief engineer of the factory, was the first to propose this idea. Achieving \"denitration throughout the entire production process\" is no longer something new in the thermal power industry. With investment amounts ranging from 5 million to 40 million, there are four or five different large-scale renovation options available; however, the technical staff at this plant chose not to opt for the cheaper solution that involves spending money to expedite the process. Through comparisons and research on several common types of modifications in the industry, they found that large-scale equipment modifications require the reorganization of the space and the rearrangement of equipment, which has a significant impact on the safe operation of other systems in the unit. This leads to an increase in defect rates and instability in system operation, among other safety hazards.

“I will never pursue a plan with high costs, low returns, and high risks, no matter how easy it might seem! To achieve denitration throughout the entire production process in a safer manner and with higher returns, it is necessary to overturn the existing approaches and forge a path of transformation of one’s own. ”——The Party branch is the basic unit of Party organizations, while the work team is the basic unit of production departments. With the same role and the same frontline experience, they share the same spirit to take on challenging tasks. To enable the early commissioning of denitration equipment through refined adjustment during operation, close coordination among various specialties and equipment is required. The feedwater system, boiler water system, flue gas system, combustion system, high and low pressure heaters of the steam turbine, etc.–affected by factors such as the environment, temperature, and equipment condition–result in numerous possible combinations of various equipment systems and dozens of parameter values during operation. Even the slightest difference can lead to outcomes that are contrary to those intended. For the parameter of only the water temperature at the economizer inlet, the influencing factors include the boiler’s feedwater volume, evaporation rate, drainage volume, and the amount of water recycled within the furnace. These parameters interact with one another; to keep the water temperature at the economizer inlet above 230°C, it is necessary to conduct a comprehensive assessment and carry out precise operations in order to identify stable equilibrium points.

On August 27, 2018, Unit 6 was started up, marking the beginning of the first experiment on denitration during full-scale operation. This is the opportunity for the task force to verify the plan after waiting for days. Based on the pre-set parameter values, after startup, the flue gas temperature at the inlet of the denitrification unit rises rapidly to above 280°C, causing the unit to begin operating immediately. This enables the NOx emission levels to drop below the specified limits as quickly as possible after startup, thus achieving denitrification throughout the entire production process. However, this is not the case; after a brief rise, the flue gas temperature drops rapidly, preventing the denitration device from reaching its operational conditions. The first attempt failed, and reality seemed to remind them once again just how difficult this path was; everyone felt a bit disheartened. It is the department’s responsibility to identify the causes of failure and overcome technical challenges ； It is the undeniable responsibility of the party branch to rebuild people’s confidence and boost collective morale. With their respective missions, a project analysis and summary meeting was promptly held. Thanks to their extensive operational experience, the problem-solving team and the operators on duty realized what the issue was – their calculations were incorrect. They had assumed that an increase in coal supply would lead to a higher combustion rate and higher temperatures, but in reality the opposite happened: once the coal supply reached a certain limit, the parameters of the water system caused the amount of water supplied at low temperature to increase significantly, thereby reducing the flue gas temperature. As long as the coal volume is kept within an appropriate range, combined with precise adjustment of the circulating water system on the turbine side, we still have every hope of achieving the target value!

As research becomes more detailed, the number of parameters involved increases, and the team working on it grows larger as well. Technical experts from various fields, such as those involved in boiler operations, turbine operations, and sulfidation, all participated in the modification of the plan. The calculations became increasingly smooth, and the processes were refined to ever greater detail – down to the opening degree of each small valve and the flow control at each outlet. The task force worked day and night to meticulously tailor every parameter of the startup plan, treating it like a work of art with a perfect balance of elements. The extensive experience of the technical experts and their thorough understanding of the equipment gave confidence to the task force as well as to all members of the department; everyone was eagerly waiting for Unit 5 to be brought online, looking forward to the next opportunity to put these skills into practice. On October 24, the company’s leadership, party branch secretary, and department managers were all present, ready to take action. Due to the close involvement of the operators in the initial design phase, once Unit 5 was brought online, the operators were able to quickly become familiar with the operating procedures and carry out precise operations despite their complexity. As various parameters related to the unit changed, adjustments were made to each parameter in a timely manner. The steadily rising flue gas temperature enabled the denitrification system to operate properly, resulting in NOx emission levels falling below the **specified standards.

In 2019, the plant achieved a record of zero excess NOx emissions throughout the year from its million-unit facility. Thus, the research on “complete denitration throughout the entire production process” for million-unit plants can be considered temporarily concluded. One success did not stop them from continuing their research; this ideal partnership of \"integration\" and \"combination\" will continue to work together to face more and greater challenges. Today, the **\"full-process denitrification\" project for the four 600,000-kilowatt units at Guohua Ninghai Power Plant, which belongs to an energy group, has been fully implemented. Compared to units with a capacity of one million kilowatts, the combustion rate of these 600,000-kilowatt units is lower, making it more difficult to increase the flue gas temperature. Party branch staff and department technical personnel need to put in more effort. Properly carrying out environmental protection efforts is not only related to the future survival and development of a company, but also represents the political and social responsibilities of a state-owned enterprise. The path to reducing emissions is long and arduous; only by adhering strictly to the benchmarks and limits related to safety and environmental protection, and by continuing to strive forward in difficult circumstances and breaking through obstacles amid adversity, can progress be achieved.