1, the service life of the old chimney after the renovation of thermal power generation
The equipment generally has an economic operation period of about 25 years.
Design life Usually 35 years.
building structure The design has a service life of 50 years. Chimney is
Generator set The last link in the operation, due to the current
Environmental standards The chimney is gradually being treated as a device in a thermal power generation system. Old unit desulfurization transformation brought
Chimney anticorrosion Transforming the problem. First of all, it should be clear how many years the modified unit may be operated to determine the standard of anti-corrosion of the chimney and the anti-corrosion design life. It is expected that the chimney will be operated for 30 years and the chimney that may run for 10 years. The anti-corrosion modification of the lining of the exhaust pipe should obviously be treated differently, and it should not be simply treated according to the design standard of the new generator set wet chimney anti-corrosion.
2, the original chimney structure form A few years ago, China's non-desulfurization units (including GGH after desulfurization) supporting chimneys are generally single-tube chimneys or sleeve chimneys. What were the original chimneys considered in the design?
Anti-corrosion measures , which places can not meet the requirements of the wet chimney? The inner wall of a single-tube chimney has brickwork or double-slip
Cement mortar Mosquito. The inner tube of the sleeve chimney has
Brickwork And steel. Before the anti-corrosion transformation, it is necessary to find out the structural form of the original chimney lining. The anti-corrosion requirements of the wet chimney are generally not considered, and suitable anti-corrosion materials are selected for different lining surfaces. For the sleeve chimney, the inner wall of the steel exhaust pipe only needs to add acid-resistant clay or paint as
Water barrier Just fine.
For the past, the glazed acid-resistant brick exhaust pipe, due to the domestic purchase of acid-resistant bricks
Water absorption rate At 12-20%, far from solving the problem of wet chimney anti-corrosion, it is necessary to add another water-repellent layer and anti-corrosion layer, or after removing the original lining, refer to the experience of Jinzhushan and Xiangtan Power Plant.
Foam ceramic Brick brick building. For single-tube chimneys, whether the lining is brick or double-slip, it is necessary to apply 2-3cm acid-resistant mortar to form a water-proof and anti-corrosion layer.
3, the inner wall of the exhaust pipe is generally cleaned of brickwork, mortar and steel inner cylinder. The old chimney transformation must first clean up the ash and defects on the surface of the inner cylinder. Because the surface of the brick lining is not flat, and some bricks are damaged, it must be cleaned by sand blasting or high-pressure water spray, and then the defects are filled. If the coating is used for anti-corrosion, it should not be washed by water. After the water is rinsed, the surface of the lining must be cooled to be sprayed, so the construction time will be long.
4, applicable operating conditions
At present, many operating desulfurization units have bypasses for flue gas, and the working conditions of chimney exhaust are relatively complicated, and the anti-corrosion design of the exhaust pipe is difficult. The owner generally proposes that the anti-corrosion coating should be suitable for the conditions of alternating operation of desulfurization conditions (wet flue gas, 45-50 ° C) and non-desulfurization conditions (dry flue gas, 145 ° C). It should be ensured that the expansion is reversible and maintains good elasticity in the long-running operating temperature of 145 ° C of the chimney; and it should be able to withstand high temperatures of 180 ° C for a short period of time (three times a year, three times a year). Many organic-based coatings are difficult to meet these requirements. If the desulfurization unit can be bypassed in the near future, the flue gas of the chimney will not appear mixed discharge, and the anti-corrosion design of the exhaust pipe will be simpler.
5, schedule
The 200-300 MW unit is generally a chimney of two furnaces. When the two furnaces are scheduled to be shut down and overhauled by the power dispatching plan, the chimney lining anti-corrosion transformation can be carried out. Generally, all the renovation works can be completed within 45 days. Therefore, the impact of winter severe cold and summer rain on the construction of anti-corrosion engineering should be considered, and if necessary, heating or adding rain canopy during the construction process. [China High-altitude Engineering Network (Business Line)]
6, anti-corrosion renovation costs
The old 210-240M high-strength slab-tube chimneys cost about 12 to 14 million yuan per project in the 1980s. In the 1990s, it was 1600 to 18 million yuan, and after 2000, it was 2200 to 25 million yuan. If the cost of anti-corrosion modification exceeds 25~30% of the original project cost, the possibility of modification is not appropriate. At this time, a reasonable plan should be sought from the system design of the desulfurization reform. For example, Huaneng Shandong Xindian Power Plant considers that the old chimney is not retrofitted, and is used for the discharge of high-temperature flue gas. Another chimney of the FRP inner cylinder is dedicated to the wet flue gas after desulfurization. The first phase of Ligang Power Plant is 42m high
Desulfurization tower On the top, an anti-corrosion steel chimney with a total height of 120 meters was built to discharge the wet flue gas. The original chimney was not used for anti-corrosion modification, but only for bypassing flue gas. The two power plants have calculated that the economic effect of this scheme is still relatively good.
7, on-site construction conditions
Due to the production transformation, the construction site is relatively small. During the construction of the renovation project, the stacking and transportation of engineering materials and tools inside the chimney will be restricted. If a steel row tube is added to the old chimney, the implementation conditions of the steel inner tube on-site processing site, chimney installation, welding, and lifting platform should be considered.
8, performance and engineering performance of anti-corrosion materials
Many new anti-corrosion materials often appear in the bidding of chimney anti-corrosion projects, and some are wholly foreign-owned or joint venture manufacturers. Their anti-corrosion material standards are held one by one, and the test methods and test results of performance and indicators are also different, and the performance indicators provided are very poor. The performance provided by some manufacturers mainly reflects foreign projects and is difficult to understand and verify.
In fact, the engineering performance of the wet chimney anti-corrosion has only begun in the past few years due to the anti-corrosion of the wet chimney. Each anti-corrosion company has no typical performance that has been tested. At present, it can only verify its characteristics mainly through the detection and review of anti-corrosion materials. Therefore, we recommend that the anti-corrosion materials introduced by domestic and foreign manufacturers should have the opinions of domestic peer experts for review. The test and research units that are qualified in the domestic and familiar with the thermal power generation system are evaluated according to the performance indicators measured by the unified test method.