Thread Content
Practice of relocating the upward gas duct of the gas generator to the top of the furnace / Author/Source: Luo Lin (Jinling Chemical Co., Ltd., Yibin, Sichuan 645150) Date: 19-1-2009. Problems existing: In order to increase the production capacity of each gas generator, the company’s fertilizer plant carried out technical upgrades in various areas such as air and steam handling as well as waste heat recovery; subsequently, 4 of these gas generators were upgraded from φ2400 mm to φ2650 mm. The gas production volume of the gas generator after technical upgrades has increased significantly, achieving certain results. After operating for a period of time, it was found that although the gas production increased significantly, the amount of material carried away through the upper airway increased markedly compared to before the modification, and the furnace operation was highly unstable with high energy consumption. 2 Cause analysis: (1) The gas generation furnace in our company’s fertilizer plant was expanded multiple times to reach its current diameter of φ2,650 mm, with the expansions being carried out one by one under the conditions of the existing old factory building. Due to the limitations imposed by the factory building and floor height, it is difficult to adjust the height of the gas generator vessel during its expansion retrofitting, which results in inherent shortcomings from the start of the renovation process. (2) When the gas generator furnace was expanded from φ2400mm to φ2650mm, the diameter of the upper gas passage was appropriately increased in order to reduce the resistance to blowing air and generating gas upward. Since the air inlet duct on the original gas generation furnace is designed on the side of the furnace body, it cannot be moved upward due to limitations imposed by the height of the furnace body and the factory beams. This results in a reduced actual distance between the surface of the carbon layer and the lower edge of the inner opening of the air inlet duct. Moreover, as the inner diameter of the air inlet duct increases, the resistance to air blowing and gas generation upward is significantly reduced, leading to an increase in the amount of material carried away during these processes. (3) After the gas generation furnace was expanded from φ2,400 mm to φ2,650 mm, although its furnace chamber cross-sectional area increased by 20% compared to that of the φ2,400 mm furnace, the height of the furnace body did not increase, and the carbon layer remained at roughly the same level; as a result, the heat storage conditions inside the furnace were not improved accordingly. (4) During downward gas supply, since the furnace chamber area of the φ2 650mm furnace is 20% larger than that of the φ2 400mm furnace, and the upper gas inlet is located on the side of the furnace body, the actual distance between the lower edge of the enlarged inner diameter of this upper gas inlet and the surface of the carbon layer is quite small. As a result, steam entering the furnace through the upper gas inlet is distributed unevenly, which has a certain impact on the stability of the gas composition and the furnace conditions. 3 Solutions: After thorough analysis of the aforementioned situation and a careful examination of the structure and dimensions of the gas generation furnace, it was concluded that it is feasible to move the upper air inlet of the gas generation furnace from the side of its body to the top of the furnace, without altering the structure of the building or the dimensions of the furnace itself. Based on an analysis of the drawing dimensions, it does not affect the position of the carbon feeding port on the furnace top nor the carbon feeding operation; furthermore, the position of the horizontal pipe in the upper gas duct after the rerouting is actually more than 1,000 mm higher than when it was located on the side of the gas generator furnace body. If the gas generator is upgraded according to this plan, it will be possible to increase the carbon layer thickness and the blowing intensity, which will play a very positive role in resolving the aforementioned problems. Therefore, it was decided to adopt and implement a design that moves the upper air duct of the gas generator from the side of its body to the top of the body, without changing the structure of the factory building or the dimensions of the gas generator itself. 4. Effects of the modification: After moving the upper air duct of the gas generator to the top of the furnace, good results were achieved after a period of operation. The desired goals of increasing production while reducing consumption were met, and the following advantages were observed. (1) Operation to increase the carbon layer height by about 200–300 mm. Appropriately increase the thickness of the gasification layer to boost the heat storage capacity in the furnace, thereby prolonging the contact time between steam and the gasification layer and further improving the steam decomposition rate. (2) The carry-away during blowing and top blowing is **reduced**. (3) Appropriately increase the blowing intensity. (4) When blowing gas from below, the steam distribution is more even, and the furnace operation is more stable. (5) Operating by appropriately lowering the furnace surface temperature reduces the loss of sensible heat in the gas generator furnace.