The application of fully enclosed filtering, washing and drying three-in-one equipment in the automatic production line of gold powder and silver powder

2023/04/09

In order to meet the increasingly stringent environmental protection requirements for gold powder post-processing production, Wuxi ZhangHua Machinery developed and designed a new type of fully enclosed filtration, washing and drying three-in-one equipment, which replaces the existing plate and frame filter press for coarse silver powder filtration, washing, and drying. . After a period of trial operation, the application practice in actual production has proved that the new three-in-one equipment can significantly reduce the concentration of ammonia gas on site, and achieved good results.

Fully enclosed filter washing and drying three-in-one equipment structure principle

Wuxi ZhangHua Machinery has designed a filter, washing and drying machine, which is mainly composed of transmission device, lifting device, mechanical seal, manhole, tank body, mixing system, discharge valve device, outriggers, etc.

Its working principle is to use high-pressure nitrogen to generate positive pressure in the tank to achieve solid-liquid separation. The continuous operation of the whole process from feeding to filtering, washing, drying, and finally to discharging can be completed in the same container.


Since the new three-in-one fully enclosed filtering, washing and drying equipment was first used in the post-processing production of metallurgical coarse silver powder, there is no ready-made experience to refer to when designing, and the use of this equipment in the metallurgical industry is extremely rare. For the later purchase and installation, there are certain defects in the design due to the limitation of the site and other aspects. At the same time, after a period of trial operation, some existing problems have been exposed. The practical process of the trial operation is briefly described as follows:
The first stage: After feeding and filtering the materials in the first reaction kettle, the silver powder in the first reaction kettle was observed, and the silver powder accounted for about one-third of the volume. Add the materials in the kettle and continue the follow-up steps. When the material is discharged, it is found that the resistance of the stirring paddle is relatively large, and the ammonia smell is strong after the discharge, indicating that the washing effect is poor. , into a reaction kettle each time after sinking silver solution, and then into the second pot after treatment.


The second stage: After several test runs, it was found that the feeding speed was getting slower and slower. After checking the reactor, it was found that silver powder was deposited at the bottom of the immersion silver reactor, which caused the discharge port of the reactor to be blocked and a large amount of subsequent silver powder accumulated. An integrated machine, so a compressed air pipeline was added to the reactor to raise the pressure inside the reactor to 0.2MPa and then open the opening valve to feed the material, so as to prevent the occurrence of silver powder deposition, and at the same time, the liquid in the reactor can be deposited once After the permanent filtration is completed, the number of repeated operations of the feeding filtration step is greatly reduced, and the cumbersome operation and feeding operation time are reduced, with an average reduction of 20 minutes per pot.
Three stages: Since the all-in-one machine is mostly used in the pharmaceutical industry, the main function of the designed water pipe is to reduce dust and wash the bearing of the stirring paddle. The water output of the nozzle does not meet the actual production needs of our factory, and the water replenishment time is too long, which increases the processing time of the single reactor. The original replenishing water pipeline on the reactor is used as the water replenishing pipeline of the all-in-one machine. While reducing the operation time, replenishing clean water through the reactor can play a dual role of washing away a small amount of residual silver powder at the bottom of the reactor and the residual silver powder in the feed metal hose of the all-in-one machine.
Four stages: The thickness of the silver powder above the sintered plate of the integrated machine increases continuously with the progress of the test run, resulting in an increase in the load on the stirring paddle, which exceeds the normal range and affects production safety, resulting in the need to frequently clean the dense silver powder layer, which is labor-intensive and difficult to operate. High, affecting normal production. After observation, it was found that the function of the agitator of the all-in-one machine to reverse and level the material made the silver powder above the sintering plate gradually dense, resulting in a gradual increase in the thickness of the silver powder layer. After entering the all-in-one machine to remove the dense silver powder layer, Re-run the test run and no longer use the function of leveling the material. With the progress of the test run, the silver powder layer is always kept at the lowest point of the stirring paddle and does not increase, and remains stable. At the same time, the silver powder layer and the sintered plate form a pre-filter→secondary filter The advanced filter structure not only ensures the filter effect, but also protects the sintered plate.

Thereby prolonging the cleaning period of the sintered plate, which is conducive to normal production.
After a period of trial production, the silver powder filtered by the integrated machine is more stable than the silver powder filtered by the traditional filter press, and the water content index is generally reduced by 7% to 8%, and the production site environment has improved significantly, and the ammonia concentration in the workshop has been greatly improved. , there is no obvious ammonia gas, and the labor intensity of workers is reduced, but the requirements for operation precision are increased, and the operation time is prolonged compared with before.

Existing problems and improvement ideas of a new type of fully enclosed filter washing and drying three-in-one equipment for gold powder and silver powder
In addition to the problems that have been discovered and solved in the course of practice, there are some unresolved problems that are briefly described as follows:
Problem 1: The shaft seal of the reactor is not tightly sealed. Because the all-in-one machine is purchased and installed in the later stage, the pressure design of the reactor was not carried out in the early design stage. After the later transformation, the dynamic seal of the reactor is not tightly sealed, which affects the pressure of the reactor. process, and has a certain influence on the normal operation of the reactor stirring paddle.


Problem 2: The discharge pipe of the all-in-one machine is long, the vertical drop between the inlet and outlet of the pipe is large, and the liquid outlet of the all-in-one machine is at a low position. Under the action of the filtrate in the pipeline, the resistance of the liquid outlet of the all-in-one machine increases, which is not conducive to filtration. Prolonging the filtration time will affect the smooth progress of production, and at the same time, it will easily cause extremely fine particles to deposit at the liquid outlet of the all-in-one machine and block the pipeline.
Question 3: The manual discharge valve of the all-in-one machine must be opened and cleaned after each pot of all-in-one machine is finished, otherwise the silver powder will adhere to the inner wall and the valve cannot be strictly sealed, and there is a risk of liquid leakage. This step has a large amount of operation and a small amount of ammonia gas will escape during the operation process, and the local ammonia gas concentration is high, which will cause environmental pollution and have a certain impact on the on-site operators.

The future improvement direction of the new fully-sealed filter, washing and drying three-in-one equipment
After basically solving the problems of ammonia gas emission and silver powder water content, the improvement direction mainly has the following two points.
(1) Compress the working time as much as possible. At present, according to the different materials, the all-in-one machine takes 1.2 to 1.6 hours to process the material of 1 reactor, and the time for the existing plate and frame filter press to process the material of 2 reactors is about 1.5 to 2 hours. According to The current work and rest time of our factory, the processing capacity of the integrated machine is slightly insufficient, so it is particularly important to compress the operating time of the integrated machine to process 1 reactor material to 0.6 to 0.8 hours to make it more in line with actual production needs.
(2) The whole process of operation is automatically controlled. The all-in-one machine itself can be automatically controlled by setting, but in order to solve the practical problems encountered in production, the control steps of the valves related to the reactor are added to the operation process, because the related valves on the reactor Most of the valves are manually controlled valves, so they cannot be directly linked with the integrated machine to achieve automatic control.

At the same time, the operation process of the all-in-one machine itself is more complicated than that of the traditional plate-and-frame filter press, and it has higher requirements for refined operations. If the entire process can be automatically controlled, it will reduce human errors and reduce production costs. If it goes smoothly, it will be very helpful and beneficial.


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