Control method for reducing pulling amount in photovoltaic glass production

After a slight rebound in photovoltaic glass prices in early 2024, on May 16th, the China Trade Remedy Information Network announced that in response to an application submitted by the American Alliance for Solar Manufacturing Trade Committee on April 24, 2024, the US Department of Commerce has launched anti-dumping and countervailing investigations on crystalline silicon photovoltaic cells (whether assembled into modules or not) imported from Cambodia, Malaysia, Thailand, and Vietnam. The market has taken a sharp turn for the worse, and the entire photovoltaic industry has entered a loss making phase. As of now, the price of 2.0mm glass is 12.5 yuan/square meter, a decline of over 23%. Along with the narrowing of profits, some enterprises are operating at a loss. Small and medium-sized production capacity and long service life production capacity are accelerating cold repair, and the industry has reduced production by more than 13000 tons due to cold repair.

After the completion of cold repair for small tonnage and long service life, further measures to reduce the pulling and pulling capacity will be taken by stopping the branch line operation on the rolling photovoltaic kiln. The pulling volume of a single kiln will decrease by about 20% after stopping a branch line, and in severe cases, it will stop at branch line 4, with a pulling reduction of up to 80%.

Because it is passive, sudden high-level notices to shut down branch lines usually do not have specific plans for production reduction, and the gate is lowered after receiving the notice. Then come up with solutions and solve each problem one by one. On the rolling line, there is a significant fluctuation in the pulling amount in a short period of time, such as the replacement of lip tiles, and the pulling amount fluctuates within about 3 hours. The reduction of furnace heat load is a result of being familiar with the process.

 In terms of melting:

1. Calculation method for reducing the pulling amount by about 20%: ① Oil flow rate of each small furnace=Original oil flow rate of each small furnace - Difference in pulling amount before and after/Original pulling amount * 0.8 * Original oil flow rate of each small furnace; ② Automatic conversion of combustion air volume, timely measurement of residual oxygen and fine adjustment In order to ensure the stability of the material mountain location and production safety, after reducing the pulling amount, the wind oil volume of each small furnace is appropriately reduced. Then, as the pulling amount decreases, the wind oil volume of each small furnace slowly decreases to the desired level.

2. To ensure the safety of the kiln, the hot spot temperature can be appropriately lowered by 10 degrees (cooling can reduce the pulling amount by one hour, so that the temperature fluctuation will be smaller). The burner in front of kiln 1 can be removed.

3. Maintain the temperature of the forming flow and increase the heat load in the rear area appropriately (install the burner in a timely manner if the last team is stopped in the early stage). If the temperature continues to decrease, it is necessary to raise the neck water bag in a timely manner.

4. If the pulling amount exceeds 40%, the No.1 small furnace burner can be shut down. The production line using thick layer feeding needs to pay attention to the changes in feeding frequency, which cannot be too low, causing motor overcurrent and low-speed vibration (timely reduce the thickness of the material layer to maintain the feeding cycle).

5. The highest temperature point on the kiln further decreases, the heat load is appropriately shifted back, and the clarification temperature is maintained to avoid rapid temperature drop and microbubbles falling off the plate.

6. Attention should be paid to whether there is negative pressure in the pathway and if the molding temperature is not high enough to lift the neck water bag in a timely manner when the pulling amount drops by more than 30%. It can be done in small quantities multiple times; Strengthen insulation after the passage, do a good job of sealing, and pay special attention to insulation of water bag holes and arch surfaces.

7. Continuous reduction, the molding temperature cannot be maintained, and a burner can be added to the pathway; During the first 24 hours of activating the burner,

In terms of molding

1. Prioritize intermediate production lines when stopping branch lines.

2. Seal off and ensure proper insulation of pathways and overflow outlets, with special support for low arches at the exits of pathways.

3. When the thickness of the production line with low molding temperature is difficult to press down, timely feedback should be given to the process engineer, and the process temperature should be stabilized first.

4. The sealed overflow outlet should be inspected over the first 8 hours; After the overflow outlet is completely frozen, all cooling measures such as side air ducts should be turned off.

5. It is recommended to cool down slowly during annealing and check the operation of the rollers in a timely manner; When stopping the line for a long time to reduce speed and save energy, the speed should not be too low and there should be no shaking; When restarting the guide plate, the annealing kiln should also not run at low speed for a long time to avoid the roller from shaking and coming to a stop.

6. The cleaning of broken glass in the annealing kiln is a good opportunity.

Other high attention matters

1. The reduction in pull volume exceeds 50%, and the daily warehouse material level for easy to consolidate raw materials and small materials is evaluated.

2. The crystallization situation of the shutdown line is that after one week of blockage, the upper layer of the glass liquid below the overflow outlet is basically crystallized; Stopping only one branch for a long time has little impact, and the further expansion rate of crystallization is slower. But if there are more than three branch lines, the crystallization area will further expand, and the subsequent recovery of bubbles will have a long impact time.

3. It is not recommended to reduce the pulling amount by more than 100 tons for all production lines. Currently, the cooling design of rolling rolls in various companies is strong, and it is very difficult to control various cooling defects and thickness.

4. Is it necessary to stop a branch line in turns? There's no need, when activated, the head of the burner will cause fluctuations in the temperature of the entire pathway. For a single branch, the temperature drop in the rear area of the entire pathway is limited, so there's no need to worry about the crystallization spreading too far into the pathway.

5. The cost continues to rise, and the short-term trade-off is a better option than releasing water. The loss is further expanded, which reduces some cash flow pressure.