A few questions about the process
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I currently work at a small factory in the silicone downstream industry. Since this factory is about to launch a new project and has encountered several issues, I would like to discuss them with you all: 1. Can diaphragm pumps be used to transport carbon black? (Pigment carbon black, with particle sizes of 20–50 microns, similar to silica gel); due to the low usage amount (approximately 200–300 kg/h), it is not convenient to use pneumatic conveying, and the investment required for such a system is relatively high; therefore, the possibility of using diaphragm pumps for transportation is being explored. 2. Currently, the removal of low-molecular-weight components from silicone oils is mostly carried out in reaction vessels; those with lower requirements for volatile matter require less processing time, while those with higher requirements need more time, resulting in a relatively long processing period. The book mentions the use of an internal circulation falling film evaporation system, but both the investment and operating costs seem to be high. Is there any cheaper and more economical method? At the moment, I have considered two options: one is to use a low-molecular-weight removal unit (the kind used in raw rubber production lines), and the other is to use a scraper-type thin-film evaporator. Both of these should be feasible in theory, but they require some modifications. Do any of you sea friends have any other better methods? 3. A type of adhesive with a consistency of 5 (Consistency: After the material is shaped in a fixed manner using a mold on a flat surface, a glass plate of a specified weight is placed on top of the material to apply uniform pressure in all directions; after 1 minute, the average outer diameter of the material under pressure is measured, and this outer diameter represents the consistency.) In my estimation, for materials with a viscosity of less than 100,000, their fluidity is so high that their consistency is likely to be above 10. ), it comes out of the twin-screw extruder (with a diameter of around 80 mm), at a temperature of approximately 100–110°C; it needs to be cooled down to below 60°C. I thought of some solutions, but none of them worked well. We conducted an experiment in which the freshly extruded glue was directly immersed in water; after 5 minutes, it was taken out – its surface was cold, but its interior temperature was still above 100°C. I’m not sure if a shell-and-tube heat exchanger can be used? 4. It is said that pneumatic diaphragm pumps have relatively low energy consumption, but looking at the parameters of many such pumps, something seems off. Taking a case of 20 m3/h and H=50m as an example, the amount of compressed air required is approximately 1 m3/min. Are these figures based on standard conditions or actual operating conditions? Is there anyone who has used a pneumatic diaphragm pump who can explain it? Additionally, there is a significant price difference between domestically produced diaphragm pumps and imported ones; domestic ones can be found for less than 2000, while imported ones cost 7000–8000. Is the difference really that large? What’s the problem with using domestic and imported ones?
My personal understanding: (1) Diaphragm pumps can be used to transport carbon black. For transporting such fine powders, apart from pneumatic conveying, diaphragm pumps seem to be a good option. However, diaphragm pumps also require compressed gas to operate; you should compare their investment costs with those of pneumatic conveying. Especially if it’s a continuous process, does the diaphragm pump need to run continuously? Continuous operation is also very important when choosing diaphragm pumps; the lifespan of the diaphragm is limited, and I believe this is a key reason for the significant price variations among diaphragm pumps. Additionally, the compressed air volume is 1 m3/min, which refers to standard conditions, that is, 1 Nm3/min. (2) The issue of removing low-component substances – I’m not quite sure what that means. From a process perspective, is it possible to reduce the pressure? What about the vacuum system? (3) For the selection of the heat exchanger, based on your description, a shell-and-tube type seems inappropriate, right? The viscosity is too high, so the flowability isn’t good, right? I’ll help you @a few influencers: @arpcd @DesertFish @ljtjbx @ShineOfRunningWater
Perhaps it wasn’t made clear enough earlier, so let me add the following: 1. Generally, small manufacturers in the silicone downstream industry operate on an intermittent basis; many of them process materials batch by batch, so there is no issue of continuous operation for long periods. If something breaks, they can stop operations immediately to make repairs, and then resume production once the repairs are complete. The main considerations for pneumatic diaphragm pumps at that time were their ability to transport powders, their relatively simple maintenance requirements – as they lack complex transmission mechanisms – and their low energy consumption. In general, small factories do not have their own maintenance teams; they can only use equipment with simple structures and replace parts when it breaks down. (Small factories have relatively few pieces of equipment – just one or two – and it’s possible that they might never get another order, so equipment repairs are usually carried out by the factory itself or by someone found in the vicinity; suppliers are rarely turned to, unless things really can’t be fixed on their own.) I just don’t know whether there is a very large difference between domestic diaphragm pumps and imported ones at the moment. If domestic products last for one year while imported ones last for one and a half years, then it’s better to use domestic products; the price of imported products is probably twice that of domestic ones. 2. The particles of carbon black are very small, with a very high specific surface area, around 350. Moreover, a binder is added to the carbon black during granulation; as a result, when the carbon black powder is held in the hand and then released, it forms a clump. However, with just a slight touch, the entire clump disperses instantly. I also talked to Wilton’s agent at that time; they said it might be worth trying, but they didn’t explicitly state that it would work, only saying that many carbon black manufacturers use diaphragm pumps for transportation. Additionally, I have learned that vapor-phase silica black (with a specific surface area of around 300–400 as well) can be transported using diaphragm pumps. It’s just that I’m not sure about this type of silica black; I wonder if anyone has heard of diaphragm pumps being used for transporting silica black. 3. For the removal of low-molecular-weight components in the downstream processes of silicone products, vacuum is also generally used; however, the vacuum level does not need to be as high as in large-scale chemical manufacturing – a level of 90 kPa or higher is usually sufficient. For materials with a viscosity of 300–500 mPa.s, I can only think of these two options. They are relatively simple, require little initial investment, and their operating costs should also be low; it’s just unclear what the performance will be like. (Because it is batch production, if one attempt at removal fails, it can be tried again.) ) 4. As for heat exchange with materials that have high viscosity, it’s a real problem at the moment; with my skills, I’m no longer able to find a solution, not even the simplest ones.
The knowledge in this area is really limited. Hehe, but I can share some information on diaphragm pumps: 1. Transporting powdered materials through closed pipelines helps to minimize contact between operators and the powder, which is especially important when dealing with toxic or harmful powders, thereby ensuring personal safety ； 2. Prevent dust from floating around in the production workshop, thereby reducing air pollution and raw material waste (by using specialized air release components) ； 3. It is equipped with an air flow induction system; 4. The fluidizing gas and the motor-driven gas for the pump can be separated, thereby preventing oxidation and deliquescence of the material due to contact with air ； The fluidized gas can be subjected to further purification and drying treatments on its own (in contact with the powder), and other gases such as inert gases like nitrogen can also be used; 5. The system is cost-effective and simple to use – unlike expensive, traditional large-scale and complex pre-installed powder transfer systems ； 6. Lightweight and easy to move around for use anywhere (it can be installed on a trolley, which can be customized). Ready to use out of the box, no installation or debugging required ； 7. The bore sizes are 1.5 inches, 2 inches, 3 inches, and 4 inches; the pump body materials include cast iron, aluminum alloy, and stainless steel. Powder pumps can successfully transport powders that are granular, lightweight, dry, and flowable, with a bulk density of 80~880 kg/m3. It is widely used in industries such as carbon, silica, powdered activated carbon, fine graphite powder, lithium iron phosphate, nano-calcium carbonate, aluminum hydroxide, titanium dioxide, starch, globulin powder, activated clay, resin powder, pigment powder, flame retardants, solid sodium methoxide, as well as in the production of fine chemicals and pharmaceutical raw materials and intermediates. It is also employed for the transportation of various lightweight powders, offering a wide range of applications.