Among the points with dust concentration exceeding the standard, 66 exceeded the standard by less than twice, 4 exceeded it by 2 to 4 times, 14 exceeded it by 4 to 10 times, and 13 exceeded it by more than 10 times. The measurement points where the dust content exceeds the standard by more than 10 times are as follows: 2 for electric welding, 1 for grinding with a grinding wheel, 3 for the tail of the belt, 1 for bulldozer pushing soil, 5 for electrostatic precipitator ash discharge, and 1 for coal unloading at the coal yard.

From the above situation, it can be seen that the dust hazards in thermal power plants in Guangdong Province mainly come from the coal conveying system and the dry ash discharge system of the boiler dust collector.

3.2. Analysis

3.2.1 The situation of dust hazards has improved to some extent

The coal conveying system management of new power plants such as Zhanjiang Power Plant and C Plant of Shajiao Power Plant has achieved centralized automatic control. Air conditioning and sound insulation equipment have been installed in the coal transportation control room, and the working conditions of workers have been improved. Power plants with the necessary conditions have gradually abolished the duty rooms beside transfer stations, reducing the time workers are exposed to dust.

Power plants such as Shaoguan Power Plant and Meixian Power Plant use lean coal. The coal quality is poor, with high ash content, low volatile matter, difficult to burn and easy to extinguish. In the past, they often had to adopt positive pressure combustion, resulting in dust flying around the plants. After years of technological research and development, the boiler was technologically renovated by appropriately increasing the combustion belt, adjusting operating parameters, and taking measures to stabilize combustion, thus eliminating positive pressure combustion in the boiler. By controlling this dust source, the dust hazard in the power plant has been greatly reduced.

The Huangpu Power Plant carried out comprehensive utilization of dry ash a few years ago. Due to the original design of taking ash from the ash outlet of the dust collector's electric field and bagging it, the dust pollution was severe. Later, after equipment renovation, a pneumatic conveying system was adopted to transport the dry ash from each electric field to the grinding ash plant near the main plant. The high-quality ash from the third and fourth electric fields of the electrostatic precipitator was directly transported by sealed large dump trucks, while the remaining coarse ash was ground finely before being transported, reducing the dust pollution in the factory area.

In addition, during the engineering design stage of the newly-built power plant, some comprehensive measures have been taken in terms of dust prevention and removal. If the coal conveying walkway adopts a sealed method, a vacuum cleaner should be installed at the outlet of the coal guiding trough and a dust collector at the exhaust port. In addition, for coal yards and transfer stations with relatively severe dust, spray systems have been installed. Regular flushing water sources are provided in areas where people frequently walk during operation to prevent dust. Therefore, the working conditions in the thermal power plants under the jurisdiction of the Guangdong Provincial Electric Power Bureau are relatively at a good level, and the degree of dust hazard is relatively light. However, there are still positions and operation sites with seriously excessive dust.

3.2.2 The qualified rate of dust mass concentration in the workplace is not high

The National Conference on Dust Control and Pneumoconiosis Prevention in the Power Industry held in July 1996 required that within 2 to 3 years starting from 1996, the qualified rate of dust concentration in the workplace should reach over 90%. The annual physical examination rate for personnel engaged in dusty and harmful operations and the annual coverage rate of current pneumoconiosis patients should reach 100% within 2 to 3 years. By 2010, the goal of "controlling dust sources and eradicating pneumoconiosis" will be basically achieved.

The average pass rate of dust quality concentration in the operation sites of the power plants under the jurisdiction of the Guangdong Provincial Electric Power Bureau is only 64.3%, which is still a certain gap from the target of 90%.

3.2.3 There are still a few hazardous operations of Grade II or above

In accordance with the requirements of the assessment indicators and scoring regulations stipulated in the "Assessment Standards for First-Class Managed Electric Power Companies in China (Trial)", noise, toxic substances, dust and other hazards of level II or above should be completely eliminated. 5 points will be deducted for each hazard incident of level II or above that occurs. The proportion of positions at level II and above (excluding Level II) in the thermal power plants under the jurisdiction of the Guangdong Provincial Electric Power Bureau among all classified positions is as follows: physical labor intensity 3.51%, high-temperature operation 19.91%, dust operation 1.09%, noise operation 1.35%, and toxic substance operation 0. About one-third of the positions in thermal power plants across the country are at level II or above. Although the thermal power plants under the jurisdiction of the Guangdong Provincial Electric Power Bureau are better than this level, there are still a few hazardous operations at level II or above.

It is worth noting that, except for the major overhaul of Unit 9 at Shaoguan Power Plant, the test results of the labor condition classification this time were mainly conducted under the normal operating conditions of the units. When a boiler undergoes major overhauls, the classification result of the boiler maintenance position should be slightly higher than that under normal operating conditions.

4. Countermeasures, measures and suggestions for preventing and controlling dust hazards

To improve the working environment, measures must be taken to eliminate dust sources, control workers' exposure to dust containing silica, reduce dust hazards, and protect workers' physical and mental health.

4.1. Implement relevant laws, standards and regulations

According to the "Code for Design of Labor Safety and Industrial Hygiene in Thermal Power Plants" and the "Hygienic Standards for Design of Industrial Enterprises", labor safety and industrial hygiene facilities must be designed, approved, completed, accepted and put into operation simultaneously with the main project. Facilities to prevent dust from flying should be included in the design of power plants. Appropriate processes should be adopted to avoid the generation of dust, and various engineering and technical measures for dust removal should be taken to ensure that the dust mass concentration in the workplace meets the standards.

4.2. Strengthen the maintenance and management of dust-proof equipment

Improve the maintenance quality of the ash removal system and the powder-making system to prevent ash and powder leakage. Regularly test the dust mass concentration. If it is found to exceed the standard, measures should be taken. Invest funds to carry out technological transformation and increase the investment rate and dust prevention efficiency of dust prevention equipment. Maintain and manage the existing dust-proof equipment well to ensure its normal operation and play its dust-proof role.

4.3. Enhance the level of operation automation

For places with significant dust hazards, mechanical arms or automatic control should be adopted to achieve unmanned or minimally manned duty, reducing the exposure time of workers to dust.

4.4. Enhance self-protection awareness

Strengthen safety education and training on dust prevention for workers, enhance their awareness of the hazards of dust and prevention knowledge, and strengthen their self-protection consciousness.

Power plants should purchase qualified, practical and convenient dust-proof personal items for workers. When workers are working in workplaces with dust hazards, they should wear personal dust-proof equipment correctly as required and develop good habits just like wearing safety helmets.

4.5. Arrange work procedures reasonably. For instance, during boiler maintenance, it is necessary to fully implement dust-proof measures before entering the furnace and pipelines for work.

4.6. Do a good job in the technical transformation of the fly ash dry ash discharge system

If there is any leakage in the dry ash collection system of the electrostatic precipitator, it is all silicon dust, which is very harmful to human health. Measures should be taken to gradually transform simple ash removal into mechanized and automated operations. When designing the new factory, the comprehensive utilization project of fly ash should be taken into consideration. Necessary conditions should be created for the supply and use of fly ash in terms of investment, equipment purchase, and site utilization, such as separate packaging of coarse and fine fly ash, equipping with a well-sealed conveying, storage and transportation system and transport vehicles, and building roads for the transportation of fly ash outside.

4.7 Do a good job in the management of coal yards and ash yards

Do a good job in the sprinkling and compaction of dry ash storage areas. For areas that are full of ash, soil should be covered and greened in a timely manner. Do a good job in the greening of the factory area (including the area around the coal yard), carry out civilized production and reduce dust.

4.8. Strengthen the dust prevention work of the desulfurization system

With the launch of the desulfurization project, the dust prevention issues of the pulverizing system, gypsum or waste residue treatment system of the desulfurization project should be taken into consideration. The limestone powder silo should be equipped with a dust collector, and the valves of the conveying pipeline should be tightly sealed without leakage. If the process of grinding limestone slurry by wet ball milling is adopted, large pieces of limestone materials smaller than 200mm can be directly ground into limestone slurry through wet grinding, reducing dust pollution.