Since the beginning of this year, the cement industry has experienced multiple major safety accidents during warehouse cleaning operations, resulting in multiple fatalities and injuries. This has attracted high attention and vigilance from peers in the cement industry, leading to a significant increase in the cost of safe warehouse cleaning operations throughout the industry. Due to the increasing environmental protection efforts of the country, the demand for large-scale staggered production and kiln shutdown has become increasingly prominent. The limited operational efficiency of cement warehouses in many cement enterprises has a significant impact on their value realization. People have to think about how to completely overcome the huge impact of cement warehouse cleaning.
After careful research, it was found that the actual mechanical conductivity distribution of the powder in the reservoir exhibits a skin effect similar to that of current on a conductor. The powder expands laterally in the warehouse due to gravity compression, forming parallel multi-layer weakly stable arches, also known as gravity arches. Its existence transfers the weight of each layer of material horizontally along the natural large arch bridge to the reservoir wall, and finally forms a vertical superimposed support balance, forming a hollow gravity reservoir wall external aggregation effect; And it is far from the uniform distribution of gravity that we imagine, so it is easy to produce a rigid wall hanging retention effect.
The powder material will also form a contraction arch blockage at the bottom of the usual pressure reducing cone and the storage wall. Currently, the commonly used pneumatic unloading technology is often due to the natural characteristics of the airflow being soft rather than hard. Some air flows out with the material towards the center outlet, while others must break through and escape through the middle softening area with relatively low density through the contraction arch; Due to the natural tendency of airflow to cluster and converge, the uneven development of the material path is promoted, resulting in multiple funnel flow material paths often appearing in the middle; The overall situation is that the soft materials in the middle are preferentially discharged quickly, while the supporting hard solid material area on the side wall is impossible for the gas path to enter, so it will inevitably become a dead material that flows slowly until it does not move (as shown in Figure 1). Over time, the dead zone on the storage wall is bound to continue to grow and squeeze the effective storage capacity, ultimately leading to irregular hardening, deviation, and even complete flow interruption of the circular storage (as shown in Figure 2).
Obviously, due to the severe nature of natural gas path segregation polarization in pneumatic methods, it is completely mismatched with the distribution of wall hardness and soft density caused by the gravity arch effect naturally formed by the material pressure in the reservoir. No matter how balanced the design of the air groove array at the bottom of the warehouse is, it cannot change the trend of continuous growth of dead materials on the edge walls; It can be said that the current pneumatic technology scheme essentially has serious cancerous genes, and its automatic formation of a large number of dead materials is actually the inevitable result of ineffective tumor tissue continuously self stimulating growth and deterioration.
If the hard and solid materials on the edge walls can be prioritized to flow out from the bottom of the warehouse, creating a natural equilibrium flow around the entire warehouse wall, resulting in the operation of live materials in the entire warehouse, the existence and growth of dead materials can be fundamentally eliminated; Not only can it fundamentally improve the efficiency of storage capacity utilization, but it can also ultimately completely eliminate the necessity and corresponding huge cost of clearing inventory.
We found that the shrinkage arch at the bottom outlet of the warehouse is a key obstacle to the smooth discharge of powder, and thus ingeniously invented and designed an unpowered Tai Chi cone device. The device fully utilizes the high potential energy of the powder material weight in the warehouse as the driving force, and through the targeted steel structure design of the Tai Chi cone placed above the outlet of the warehouse, it forms a natural shear force to break the arch resistance effect of powder shrinkage movement; And ensure the automatic balance arrangement of prioritizing the removal of the bottom layer of hard solid materials, so that the gravitational potential energy of thousands of tons of powder materials in the warehouse can form a front pull and back push overall effect on the warehouse wall, achieving natural overall flow discharge without power or dead zone; Moreover, its mechanical distribution and the density distribution of the storage wall precisely form a balanced feedback mechanism for automatic correction, ultimately achieving the ideal effect of self cleaning the storage wall while operating and unloading the large storage (as shown in Figure 3). Even if there is a small amount of leakage at the top of the warehouse due to rainy days, it will be quickly digested and removed by the flowing powder, completely eliminating the breeding ground for dead material formation and its malignant growth. Due to the absence of air blowing, it not only greatly saves energy and reduces noise, but also facilitates semi fluidity and subsequent mechanical flow adaptive stable discharge control. At the same time, dedicated discharge devices and high-precision punching plate flow meters were designed for complex working conditions such as different storage locations, as well as a customized intelligent feedback computer control drive system, forming a complete green intelligent cement discharge closed-loop control system powder flow control, which can be connected to the central control for digital remote quantitative control discharge (as shown in Figure 4).
A cement company in Sichuan has 6 large-scale cement production lines and 36 cement warehouses with a capacity of 10000 tons. It has been plagued by various malfunctions in the cement warehouses for many years. They learned about the new powder flow control technology through the Kunming Cement Technology Exchange Conference in April 2017. After several rounds of discussion, research, and negotiation, they decided to first carry out powder flow control transformation from the severely damaged No. 5 warehouse of Plant 2, in order to verify whether the powder flow control technology has met theoretical expectations and find a way to completely overcome the huge operational and repair pain caused by the use of traditional pneumatic technology in a large number of 10000 ton cement depots.
The diameter of the warehouse is 18 meters and the height is 39 meters. The warehouse is filled with about 10000 tons of cement. Originally, a pressure reducing cone with a circular pneumatic inclined groove array Roots blower was used for blowing at the bottom of the warehouse. At that time, during the cleaning inspection, it was found that the pressure reducing cone had been severely damaged, and the cost of repairing it alone was far higher than the cost of replacing the powder flow control. Although the powder flow control has been successfully applied in 3000 ton and 5000 ton cement warehouses, whether the design effect of the powder flow control can be achieved in such a tall cement warehouse is still strongly doubted by technical leaders at all levels. However, with the spirit of being a dead horse and a living horse doctor, everyone has decided to give it a try.
In January 2018, the original concrete pressure reducing cone (as shown in Figure 5) was completely dismantled and replaced with a powder flow controlled Tai Chi cone. Starting with a 5-meter material level of 2000 tons of cement and a 9-meter material level of 4000 tons of cement, until the warehouse was filled with 10000 tons of cement, trial production gradually began, and the results fully achieved the expected goals (as shown in Figure 6); After two months of normal operation, a full storage emptying verification was conducted again in March, as evidenced by the fact (as shown in Figure 7). The powder flow control has always been used for natural overall discharge, ensuring that the hard material on the wall of the storage is always in a dynamic and automatic updating state. Moreover, the huge material pressure acts on the cleaning effect of the storage wall, which is very smooth and clean, truly achieving the ideal situation of automatic cleaning while operating the discharge. Finally, there is very little naturally released tailings, with a depth of 37 meters. The height range of naturally accumulated residual materials around it fully conforms to the theoretical description.
Dismantle the original reinforced concrete large pressure reducing cone and replace it with a small Tai Chi cone.
It was officially put into use in January 2018 and can flexibly set the feeding flow rate and operate in a closed loop.
After 2 months of normal operation until March 23, 2018, the full emptying verification test confirmed that the automatic cleaning effect of the storage wall was excellent, and the emptying rate met the expected requirements.
The successful application of powder flow control in a 10000 ton cement warehouse has shown that it can completely bid farewell to the headache inducing cement cleaning operation, specifically manifested in:
1、Implement priority unloading of hard materials on the overall flow warehouse wall, and simultaneously discharge and clean the warehouse, fundamentally eliminating the conditions in the dead material area and thus completely eliminating the necessity of periodic cleaning. In addition, the operation of the entire warehouse with live materials can eliminate the cumulative harm caused by a small amount of rainwater leakage entering the warehouse to the maximum extent. Moreover, the Taiji cone in the warehouse is an unpowered steel structure device, with a simple force design balance and no need for wear and tear maintenance. Its operating and maintenance costs are almost zero.
2、The two warehouses use unpowered natural balance discharge, and the external power of the warehouse is two 5.5kW variable frequency speed discharge motors, which are quiet and environmentally friendly, and significantly energy-saving; And originally it was a 45 kW Roots blower, operating with high decibel noise.
3、Adopting closed-loop intelligent feedback control, it has the function of digital remote central control and arbitrary quantitative operation control, which can stably achieve maximum efficiency of process flow matching or multi library matching equalization control.
4、The cement in the warehouse has a natural accumulation angle and circulating tailings in the ultra-low material level, which can run at various storage heights and fully release storage capacity efficiency; And fully realize the reasonable order of first in, first out, and fully realize the maximization and natural homogenization of cement products.
5、The structure is simple and exquisite, with an economical cost, making it convenient for low-cost and rapid construction of new warehouses.
It has been proven that the application of powder flow control in cement storage can not only completely eliminate various drawbacks caused by traditional pneumatic technology, but also completely eliminate the headache inducing periodic cleaning operations from the source, and significantly save energy and reduce consumption; And promote on-site operation management from the popular open-loop extensive manual operation to the advanced state of unmanned intelligent quantitative optimization unloading, opening up a new upgrade and replacement path for cement enterprises.
