Discuss the advantages and disadvantages of self-returning alkali calcining furnace and external returning alkali calcining furnace

It's hard to compare different models. Our factory is a self-returning calciner. I personally think it is relatively convenient in terms of operation. As long as you control the amount of entry, you basically don’t have to worry about anything else. The amount of alkaline return has been determined during the design. One less variable, easier to operate. However, if the alkaline is returned externally, it is more flexible to add more, depending on the operation. But it is more troublesome for operators.

This post was last edited by 9067jxhuas on 2009-11-20 09:16 Here is an excerpt from Baidu about the transformation of its own back-to-alkali calcining furnace http://liuhuizhong99.blog.163.co ... 907920091029395727/ March 30, 2005 08:40 China Science and Technology Daily's own back-alkali steam calcining furnace is used in larger-scale soda ash plants. The furnace adopts new technologies for furnace head back-alkali feeding, discharging and sealing. The basic structure of the furnace head consists of a gas outlet square box, alkali outlet cover, material throwing machine, light gray reamer, dynamic and static rings, reverse pushing material spiral, floating ring, mechanical compression wheel seal, etc. The combination seal of the burner head's reverse thrust spiral and floating ring prevents back alkali from escaping into the finished product, and the mechanical seal is used to seal gas and alkali dust leakage and other technical structures. Although the furnace's own back-alkali technology is mature and relatively advanced, it has the advantages of short process flow, less equipment, low overall machine power, low infrastructure investment, low operating costs, simple operation, and good environmental sanitation. It has been unanimously praised by many experts in the soda ash industry across the country. However, there are still many imperfections exposed during the operation of the equipment... Brief technical introduction: The self-returning steam calcining furnace is used in larger-scale soda ash plants. The furnace adopts new technologies for the furnace head returning to alkali feeding, discharging, and sealing. The basic structure of the furnace head consists of a gas outlet square box, alkali outlet cover, material throwing machine, light gray reamer, dynamic and static rings, reverse pushing material spiral, floating ring, mechanical compression wheel seal, etc. The combination seal of the burner head's reverse thrust spiral and floating ring prevents back alkali from escaping into the finished product, and the mechanical seal is used to seal gas and alkali dust leakage and other technical structures. It has been running continuously for five years so far. The production practice in the past few years has proved that although the furnace's own back-alkali technology is mature and relatively advanced, it has the advantages of short process flow, less equipment, low power of the whole machine, low investment in infrastructure, low operating costs, simple operation, and environmental sanitation. It has been unanimously praised by many experts in the soda ash industry across the country. However, there are still many imperfections exposed in the operation of the equipment. 　　 Technical transformation of the calciner 1. Transformation of the alkali feeding equipment at the furnace head to reduce unreasonable equipment in the furnace head. The alkali dust in the original furnace gas is separated by the separator and transported into the furnace by two spiral reamers. Due to the long transportation pipeline and numerous equipment, it is easy to cause the equipment to stop and have a greater impact on production. Now directly remove the six-meter-high steel platform on the second floor and the alkali dust reamer with a power of 5.5kW and a specification of φ273. At the same time, remove the heavy alkali conveying system with a power of 15kW and a specification of φ600. * The 580 high-speed material throwing machine directly uses the original heavy alkali reamer to feed the material. The medium-heavy alkali material is fed directly into the furnace head from the throwing port diagonally above the front of an 18.5kW reamer. The two sets of conveying equipment are reduced to one, and the alkali dust reamer is reduced from the original design of two sets to a single set, and the feed port is separated from the side and fed directly. 　　 2. Improve the process flow and redistribute the separator positions and pipelines. The original light ash alkali dust system is separated by a separator on the fifth floor. It needs to go through a straight pipe more than 5 meters long to the alkali dust reamer on the steel platform on the second floor. The alkali dust reamer then passes through a slide of about 3 meters. The pipe is transported to the burner head and the light ash reamer is transported to the furnace. This not only takes a long process, but also because the pipeline is long and cumbersome. When the amount of alkali dust is large, it is easy to cause the alkali dust reamer to stop and the separator to be clogged, which will affect and fluctuate production. In this transformation, while removing the alkali dust reamer equipment, the separator on the fifth floor was moved to the third floor, and the light ash reamer, which was originally located at the left end of the furnace (viewed from the direction of the furnace head) and was moved to the right side of the furnace, to the lower center of the original furnace head, was moved to the right side of the furnace, and the separator material legs were directly connected to it for a short distance. This layout has been proven by production practice to be very reliable in operation without any stoppage, blockage or alkali leakage. The environmental sanitation has been greatly improved compared to before. 　　 3. Further adjust the structure and size of the combined seal of the furnace head to eliminate internal leakage of mixed alkali. The original furnace head seal was a single-channel floating ring mechanical seal. Due to the serious wear of the furnace head shell, and the floating ring stopped with the alkali and deformed and failed with the operation of the furnace body, it could not function as a seal. The leakage of wet and heavy alkali in the equipment often occurred, resulting in unqualified product quality. The original floating ring is now being modified, and the equipment is The design is installed as a combined sealing structure, and the floating ring is fixed so that it does not rotate with the furnace body. That is, a hole is made from the top of the furnace head floating ring, a fixed round steel and a circumferential displacement plate are welded, a sealing cover is installed, and a sealing tongue is added behind the floating ring sealing device to form a new double sealing area. From the operational conditions, the effect is very ideal, no internal leakage occurs, and the product quality is satisfactory. 　　 4. Add a combined sealing structure on the discharge side of the finished product to reduce the number of flexible connections to ensure CO2 concentration. There are three rings of flexible connections between the furnace head shell and the static ring of the original furnace, which are directly sealed. During production, due to improper operation or sudden self-stopping of the compressor, the furnace head is under positive pressure for a long time, which can easily cause the flexible section to be filled with alkali. At this time, the furnace body is running very fast, which can easily lead to damage or rupture of the flexible section. Therefore, long cracks and holes have appeared in many places in the flexible section. Due to tight production tasks, it is impossible to completely repair, and one replacement is complicated. There are only nearly 200 pre-tightened bolts in one set. Now we will make a simple modification. Add a steel sleeve to the lining of the flexible section, and reduce a circle of flexible sections. The steel sleeve is fixed and does not rotate. This not only ensures that the flexible section is not worn out, improves the sealing performance, extends the service life of the flexible section, but also increases the CO2 concentration. 　　 5. Modify the structure of the end face of the furnace to ensure the long-term operation of the furnace. The original furnace design was not very perfect. The distance between the top of the furnace body and the furnace shell is long, which is easy to form a dead zone. Especially when the throwing point of the throwing machine reaches the furnace head area, part of the wet heavy alkali is directly scattered in this area. After a period of time, the scars accumulate, and the furnace must be shut down for cleaning every half a month or so (except when unplanned). Now the ring plate at the top of the furnace body is lengthened and strengthened. When the furnace body is running, the ring plate will stir up the alkali scab at any time and fully premix it with the returned alkali, so that the current will not run out due to serious scabbing and affect the operation cycle of the calciner. After the transformation, it used to be cleaned once every half a month. Now it has been running continuously for at least three months, and the amount of scarring on the furnace head is very small every time it is inspected and cleaned. Therefore, * * The calcining furnace operation cycle is improved. 　　 6. Modify the internal structure of the furnace head, rearrange the structure of the mixing section and use a heavy alkali auger to replace the feed of the throwing machine. Compared with the throwing machine, the amount of alkali balls increased. Therefore, the internal structure of the furnace must be modified accordingly. Now, not only the ash ring of the furnace head is increased by 200MM, but also the last five lifting plates are changed from forward to reverse to increase the premixing effect of the furnace head. The crushing chain in the furnace head is rearranged and increased in quantity to enhance the crushing effect and prevent the increase of alkali balls and flakes. 　　 7. Add three new alkali return valves. Each of the return alkali pipes has a new alkali return valve in front of the original alkali return valve. Its function is that when the furnace production capacity increases, the return alkali valve can be fully utilized to return to alkali in advance. This not only increases the return alkali amount of the furnace, but also leaves as much heating space as possible to promote further drying of the finished product and ensure product quality.

I think the external alkaline return calcining furnace should be adjusted according to the discharging situation, and manual operation is convenient but laborious. I once participated in the work of adding alkali and danghua alkali.

This post was last edited by wal5980729 on 2009-11-20 23:02. Comparison of external back-alkali and self-back alkaline steam calcining furnaces: http://bbs.hcbbs.com/viewthread.php?tid=576268&extra=

The biggest disadvantage of the calcining furnace with external alkali return is that leakage will be serious in the later period. The furnace body cannot be insulated, and the insulation layer is full of alkali. Safety hazards increase. Personally, I think it's better to return to alkalinity.

The calciner's own alkali return and external alkali return have their own advantages. Simply put, the external alkali return has large capacity, poor sealing, and is easy to operate.； The self-returning boiler has relatively small capacity, good sealing performance, and difficult operation.

Is the design of the furnace body not very good and the stress is too great?