What is the prospect of the application of microchemical technology?

First of all, the conclusion of the micro-chemical wind mouth has been hidden, especially in April this year, Shandong Haomai launched a 120,000 yuan of micro-reverse device has greatly reduced the threshold of micro-chemical process research, resulting in more production units are willing to invest in micro-chemical research.

Before we talk about this issue, let's review the history and technical characteristics of microchemicals.

The concept of microchemistry was first proposed by a German in the 1970s, the name of which I forget, but it should still be alive now. Its main principle is that when the fluid channel is reduced can produce a series of process enhancement effects.

First of all, it is the enhancement of the transfer effect

Any chemical transfer process has to pass through the so-called boundary layer, and the speed of the transfer process can be approximated as inversely proportional to the thickness of the boundary layer. The thickness of the boundary layer is currently a difficult concept to explain clearly, it is difficult to calculate and simulate, but there is a qualitative conclusion is that the boundary layer thickness can never be greater than the size of the runner, so the smaller the runner, the thinner the thickness of the boundary layer, the faster the transfer process. Therefore, reducing the runner size has a mass transfer enhancement effect on all transfer processes, such as heat transfer (heat exchange), liquid-liquid mass transfer (extraction), and gas-liquid mass transfer (gas absorption). This is the reason that reaction rates in microreactors can often be significantly faster than in conventional reactors.

Secondly, the heat transfer interface increases due to the microfluidic channel

There is a so-called specific surface area concept for any device, especially when it comes to heat transfer processes. For example, how much heat is given off by a reaction within a device is related to how much material is loaded inside the reactor, and the heat given off by the reaction is proportional to the volume of the reactor. However, the removal of this heat is related to the area of the reactor, because heat transfer relies on heat exchange surfaces, and the larger the heat exchange area, the more heat is transferred. In order to maintain a constant temperature inside a reactor, the exothermic reaction and heat removal must be conserved. The larger the specific surface area, the better the ability of the reactor to dissipate heat, and the more stable the reactor temperature can be maintained. If we assume that the reactor is a cylinder, the specific surface area of the reactor is inversely proportional to the diameter. Conventional reactor, the general diameter of about 1000mm, the experimental reaction bottle diameter of 80-100mm, while the maximum diameter of the micro-reactor is not more than 1-3mm, that is to say, the micro-reactor's ability to move heat is 1000 times that of the conventional reactor. Some of the reactions in the reactor are very dangerous as they heat up very quickly, but they can be carried out successfully in the microreactor.

Third is push flow

The flow state in a conventional stirred kettle is full mixing, which is an inefficient form of flow from a reaction engineering point of view. Why? Because for most reactions, the higher the substrate concentration, the faster the reaction. Under the full-mixed state, the substrate concentration in the reactor is always equal to the outlet concentration, and for general process requirements, the outlet concentration of the reactor is very low, resulting in the reactor running at a low overall concentration, and the reaction efficiency is very low. And in the tubular reactor and micro reactor total, the fluid inside the reactor is approximately flat push flow, that is to say, the concentration in the reactor along the reactor axial distribution, the import high export low, and the export concentration for the reaction process requirements, in this case, the average concentration in the reactor is higher than the stirred reactor, which further improves the efficiency of the reaction.

Lastly, it can be quantitatively scaled up

That is, in the process of microreactor research and development can be quantitatively scaled up to achieve industrial production, so that the industrial production conditions and the experimental conditions are almost exactly the same, avoiding the amplification of various amplification effects in the process of amplification, and the overall research and development process becomes shorter.

From the above point of view, the microreactor is mainly used for some intense chemical reactions, because intense chemical reactions are very obvious exothermic, so the need to quickly remove the reaction heat, and intense chemical reactions are generally easy to generate by-products and in the state of advection to maximize the inhibition of the occurrence of side reactions. In addition, for the non-homogeneous gas-liquid, liquid-liquid, liquid-solid process, due to its process strengthening effect can effectively improve the reaction efficiency.

Of course, as a microchannel reactor also has many shortcomings, mainly reflected in the following points.

1. Can not use solids, this is well understood, both catalyst particles or reaction produced by the solid, will clog the pore. At present, it is generally accepted that the size of particles in the microchannel tens of microns is the upper limit.

2. Large pressure drop, liquid through the microchannel pressure drop is very large. Of course, this is almost unavoidable, because any mass transfer enhancement process is the use of energy for efficiency.

3. Difficulty in large-scale equipment. Now the microreactor if the corning route single plate flux should be in the thousands of tons / year or so, or difficult to meet the production requirements of bulk products, microreactor applications are currently still limited to high value-added products.

Refer to the current trend of microreactor promotion.

According to the analysis of technical characteristics, I tend to divide the microreactor into two categories:

1. Corning route: through the plate etched or machined out of ultra-fine channels as a microreactor, Corning's original is also the Corning Glass Works, the work done is in the plate carved out a variety of shapes of micro-channels and to test these channels on the reaction of the adaptability. The main problem with the Corning route is the small throughput of the device, and even Corning themselves are not confident in the industrialization of the device, and in terms of market orientation, they define their reactors as being suitable for laboratory process screening. As for industrialized production, as far as I know the production capacity of single-plate Corning route reactors is just around a thousand tons/year. And the only way to achieve mass production is to sell hundreds of reactors in parallel. The price of a reactor system is now seen as sky-high and unaffordable for the average factory.

2. Bayer route: The Bayer route is a very different microreactor route from the Corning reactor, and its outstanding feature is that the flux can be made very large, and there is hope to achieve industrial-grade production. However, the microreactor structure of the Bayer route has a major flaw: insufficient heat transfer capacity. Due to structural problems, the heat transfer efficiency of the Bayer microreactor is about 1/10 of that of the Corning route, which is of course sufficient under many conditions. But once a strong exothermic reaction occurs, it must be made into a multi-stage adiabatic reaction system, which is very demanding for process research.

From the point of view of the promotion of microreactors in China, there are several companies that have already started work in this area. From my exchanges with them, those who have taken the Corning route include: Haomai, Shen, and Dalian Microtek. These units, Howe and Shen's processing capacity is no problem at all. Dalian Microtek's equipment processing capacity is the worst, the core experimental equipment is to buy Siemens. Haomai in the micro-reverse started earlier, basically to do the equipment and technology go hand in hand, publicity is also doing a good job, recently launched a micro-reverse of 120,000 small test device is likely to significantly reduce the investment in research and development equipment, resulting in a series of new processes. Shen's side of the late start, equipment processing no problem, but the process has not kept up. As for the Bayer route, I respect Tsinghua University, has done a lot of work in this area, there have been industrialized production cases of calcium carbonate nanoparticles.

Lastly, let's talk about the development trend of microreactor, which can be summarized as follows:

1. Demand is definitely there

Actually, there are already many production units that mean the value of microreactor, and even spend a lot of money to buy the foreign pilot equipment before the domestic processors start. But until now I have not seen any enterprise based on such small pilot equipment independent research and development of industrialized production process case, only a few cases of industrialized micro-reaction are with Tsinghua University and even Bayer cooperation. The rest of the enterprises spent money to buy the equipment, found that can not be done, the equipment in the plant thrown into a scrap metal.

2. Equipment can be processed

Preliminary contact with the microstructure of the people will think that the processing of microstructures for domestic enterprises is a very difficult thing, for a long time in a variety of publicity that the current domestic machining capacity is far behind Europe and the United States. But in fact at present, whether it is the Corning route or the Bayer route. As far as equipment processing is concerned, the domestic processing capacity can be done, many companies claiming to be doing micro-reverse can indeed carry out equipment processing, there is no problem.

3. The process is problematic

But now the key problem is still in the process research and development, at present can do micro-reversal of the enterprise is at best the equipment factory, does not have the ability to combine the process and equipment. Even for Corning's genre of microreactors, how to go from the existing process package over to the microreactor conditions for the current microreactor R & D companies are a difficult thing, not to mention the process development is more difficult Bayer microreactor. And the Bayer microreactor is the right route for possible industrialization. Now our problem lies in this: the process package is available, the equipment is available, but the combination of process and equipment cannot be done. The process is in the hands of the manufacturer and the equipment is in the hands of the microreactor processing unit, and for reasons of technological monopoly and commercial considerations, there will be no adequate technological exchanges between these two parties.

4. Prospects are bright

Of course, with the development of technology, these are not problems, from now on, the status quo does have a gradual trend to break, and now a set of micro-reactor pilot plant cost has been reduced to hundreds of thousands of dollars, the general production organizations have the ability to afford, more and more enterprises will have the ability to micro-reactor research, combined with their process capabilities, even if only a small part of the process package is suitable for the use of micro-reactor, the micro-reactor is the most important part of the process. There will be more and more enterprises with microreactor research capability, combined with their process capability, even if only a small part of the process package is suitable to use microreactor, there should be projects that can be processed and produced soon. In addition, microreactor manufacturers are investing more in process R&D personnel. All it takes is for one of these two sides to tip the balance, and the microreactor windfall will occur.

Writing here in fact, I also want to explain a problem, is the necessity of microchannel reactor, microchannel reactor many advantages, will be reactive, exothermic are strengthened. But in fact these advantages of ordinary tubular reactor also has, of course, the effect is not as obvious as the micro reactor. For example, a DN15 reaction pipe, its heat transfer effect will be dozens of times more than the mixing kettle, at the same time has the characteristics of flat push flow, reactor pressure drop is also far less than the micro-reverse. These advantages are enough to be accepted by many enterprises in the renewal of products. In fact, I think that if we want to give the reactor like a weapon to divide the generation difference. Ordinary stirred kettle is counted as one generation, tubular reactor and other traditional strengthening equipment is counted as the second generation, and micro reactor is counted as the third generation. In fact, the second generation of reactors than the first generation of reactors have a lot of obvious advantages, but in fact most of China's chemical production is still stuck in the first generation of the level. At this stage of technological transformation, as long as the second generation of reactors to replace the first generation of reactors will be able to see the benefits. But favoring this step we have not even done, I have always said that our production process and the ability to combine equipment is poor. For example, an ammonia reaction, flammable and explosive, the Germans in the 40's with a tubular reactor to do, the effect is very good, but we are still in the kettle until now, stirring around, almost every plant to do this product has blown up. At the bottom of the story, the reaction engineering capability is not up to scratch. From the first generation of reactors to the second generation of reactors, how to carry out the combination of process and equipment, this lesson we must make up. Of course microreactors have the potential to give us a leapfrog development program, we can step over other reaction equipment such as tubular reactors, and directly interface with the most advanced international reactors, which is indeed a good time.

First on the conclusion, the micro-chemical wind mouth has been hidden, especially in April this year, Shandong Haomai launched 120,000 yuan of micro-reaction device greatly reduced the micro-chemical process research threshold, resulting in more production units are willing to invest in micro-chemical research.

Before we talk about this issue, let's review the history and technical characteristics of microchemicals.

The concept of microchemistry was first proposed by a German in the 1970s, the name of which I forget, but it should still be alive now. Its main principle is that when the fluid channel is reduced can produce a series of process enhancement effects.

First of all, it is the enhancement of the transfer effect

Any chemical transfer process has to pass through the so-called boundary layer, and the speed of the transfer process can be approximated as inversely proportional to the thickness of the boundary layer. The thickness of the boundary layer is currently a difficult concept to explain clearly, it is difficult to calculate and simulate, but there is a qualitative conclusion is that the boundary layer thickness can never be greater than the size of the runner, so the smaller the runner, the thinner the thickness of the boundary layer, the faster the transfer process. Therefore, reducing the runner size has a mass transfer enhancement effect on all transfer processes, such as heat transfer (heat exchange), liquid-liquid mass transfer (extraction), and gas-liquid mass transfer (gas absorption). This is the reason that reaction rates in microreactors can often be significantly faster than in conventional reactors.

Secondly, the heat transfer interface increases due to the microfluidic channel

There is a so-called specific surface area concept for any device, especially when it comes to heat transfer processes. For example, how much heat is given off by a reaction within a device is related to how much material is loaded inside the reactor, and the heat given off by the reaction is proportional to the volume of the reactor. However, the removal of this heat is related to the area of the reactor, because heat transfer relies on heat exchange surfaces, and the larger the heat exchange area, the more heat is transferred. In order to maintain a constant temperature inside a reactor, the exothermic reaction and heat removal must be conserved. The larger the specific surface area, the better the ability of the reactor to dissipate heat, and the more stable the reactor temperature can be maintained. If we assume that the reactor is a cylinder, the specific surface area of the reactor is inversely proportional to the diameter. Conventional reactor, the general diameter of about 1000mm, the experimental reaction bottle diameter of 80-100mm, while the maximum diameter of the micro-reactor is not more than 1-3mm, that is to say, the micro-reactor's ability to move heat is 1000 times that of the conventional reactor. Some of the reactions in the reactor are very dangerous as they heat up very quickly, but they can be carried out successfully in the microreactor.

Third is push flow

The flow state in a conventional stirred kettle is full mixing, which is an inefficient form of flow from a reaction engineering point of view. Why? Because for most reactions, the higher the substrate concentration, the faster the reaction. Under the full-mixed state, the substrate concentration in the reactor is always equal to the outlet concentration, and for general process requirements, the outlet concentration of the reactor is very low, resulting in the reactor running at a low overall concentration, and the reaction efficiency is very low. And in the tubular reactor and micro reactor total, the fluid inside the reactor is approximately flat push flow, that is to say, the concentration in the reactor along the reactor axial distribution, the import high export low, and the export concentration for the reaction process requirements, in this case, the average concentration in the reactor is higher than the stirred reactor, which further improves the efficiency of the reaction.

Lastly, it can be quantitatively scaled up

That is, in the process of microreactor research and development can be quantitatively scaled up to achieve industrial production, so that the industrial production conditions and the experimental conditions are almost exactly the same, avoiding the amplification of various amplification effects in the process of amplification, and the overall research and development process becomes shorter.

From the above point of view, the microreactor is mainly used for some intense chemical reactions, because intense chemical reactions are very obvious exothermic, so the need to quickly remove the reaction heat, and intense chemical reactions are generally easy to generate by-products and in the state of advection to maximize the inhibition of the occurrence of side reactions. In addition, for the non-homogeneous gas-liquid, liquid-liquid, liquid-solid process, due to its process strengthening effect can effectively improve the reaction efficiency.

Of course, as a microchannel reactor also has many shortcomings, mainly reflected in the following points.

1. Can not use solids, this is well understood, both catalyst particles or reaction produced by the solid, will clog the pore. At present, it is generally accepted that the size of particles in the microchannel tens of microns is the upper limit.

2. Large pressure drop, liquid through the microchannel pressure drop is very large. Of course, this is almost unavoidable, because any mass transfer enhancement process is the use of energy for efficiency.

3. Difficulty in large-scale equipment. Now the microreactor if the corning route single plate flux should be in the thousands of tons / year or so, or difficult to meet the production requirements of bulk products, microreactor applications are currently still limited to high value-added products.

Refer to the current trend of microreactor promotion.

According to the analysis of technical characteristics, I tend to divide the microreactor into two categories:

1. Corning route: through the plate etched or machined out of ultra-fine channels as a microreactor, Corning's original is also the Corning Glass Works, the work done is in the plate carved out a variety of shapes of micro-channels and to test these channels on the reaction of the adaptability. The main problem with the Corning route is the small throughput of the device, and even Corning themselves are not confident in the industrialization of the device, and in terms of market orientation, they define their reactors as being suitable for laboratory process screening. As for industrialized production, as far as I know the production capacity of single-plate Corning route reactors is just around a thousand tons/year. And the only way to achieve mass production is to sell hundreds of reactors in parallel. The price of a reactor system is now seen as sky-high and unaffordable for the average factory.

2. Bayer route: The Bayer route is a very different microreactor route from the Corning reactor, and its outstanding feature is that the flux can be made very large, and there is hope to achieve industrial-grade production. However, the microreactor structure of the Bayer route has a major flaw: insufficient heat transfer capacity. Due to structural problems, the heat transfer efficiency of the Bayer microreactor is about 1/10 of that of the Corning route, which is of course sufficient under many conditions. But once a strong exothermic reaction occurs, it must be made into a multi-stage adiabatic reaction system, which is very demanding for process research.

From the point of view of the promotion of microreactors in China, there are several companies that have already started work in this area. From my exchanges with them, those who have taken the Corning route include: Haomai, Shen, and Dalian Microtek. These units, Howe and Shen's processing capacity is no problem at all. Dalian Microtek's equipment processing capacity is the worst, the core experimental equipment is to buy Siemens. Haomai in the micro-reverse started earlier, basically to do the equipment and technology go hand in hand, publicity is also doing a good job, recently launched a micro-reverse of 120,000 small test device is likely to significantly reduce the investment in research and development equipment, resulting in a series of new processes. Shen's side of the late start, equipment processing no problem, but the process has not kept up. As for the Bayer route, I respect Tsinghua University, has done a lot of work in this area, there have been industrialized production cases of calcium carbonate nanoparticles.

Lastly, let's talk about the development trend of microreactor, which can be summarized as follows:

1. Demand is definitely there

Actually, there are already many production units that mean the value of microreactor, and even spend a lot of money to buy the foreign pilot equipment before the domestic processors start. But until now I have not seen any enterprise based on such small pilot equipment independent research and development of industrialized production process case, only a few cases of industrialized micro-reaction are with Tsinghua University and even Bayer cooperation. The rest of the enterprises spent money to buy the equipment, found that can not be done, the equipment in the plant thrown into a scrap metal.

2. Equipment can be processed

Preliminary contact with the microstructure of the people will think that the processing of microstructures for domestic enterprises is a very difficult thing, for a long time in a variety of publicity that the current domestic machining capacity is far behind Europe and the United States. But in fact at present, whether it is the Corning route or the Bayer route. As far as equipment processing is concerned, the domestic processing capacity can be done, many companies claiming to be doing micro-reverse can indeed carry out equipment processing, there is no problem.

3. The process is problematic

But now the key problem is still in the process research and development, at present can do micro-reversal of the enterprise is at best the equipment factory, does not have the ability to combine the process and equipment. Even for Corning's genre of microreactors, how to go from the existing process package over to the microreactor conditions for the current microreactor R & D companies are a difficult thing, not to mention the process development is more difficult Bayer microreactor. And the Bayer microreactor is the right route for possible industrialization. Now our problem lies in this: the process package is available, the equipment is available, but the combination of process and equipment cannot be done. The process is in the hands of the manufacturer and the equipment is in the hands of the microreactor processing unit, and for reasons of technological monopoly and commercial considerations, there will be no adequate technological exchanges between these two parties.

4. Prospects are bright

Of course, with the development of technology, these are not problems, from now on, the status quo does have a gradual trend to break, and now a set of micro-reactor pilot plant cost has been reduced to hundreds of thousands of dollars, the general production organizations have the ability to afford, more and more enterprises will have the ability to micro-reactor research, combined with their process capabilities, even if only a small part of the process package is suitable for the use of micro-reactor, the micro-reactor is the most important part of the process. There will be more and more enterprises with microreactor research capability, combined with their process capability, even if only a small part of the process package is suitable to use microreactor, there should be projects that can be processed and produced soon. In addition, microreactor manufacturers are investing more in process R&D personnel. All it takes is for one of these two sides to tip the balance, and the microreactor windfall will occur.

Writing here in fact, I also want to explain a problem, is the necessity of microchannel reactor, microchannel reactor many advantages, will be reactive, exothermic are strengthened. But in fact these advantages of ordinary tubular reactor also has, of course, the effect is not as obvious as the micro reactor. For example, a DN15 reaction pipe, its heat transfer effect will be dozens of times more than the mixing kettle, at the same time has the characteristics of flat push flow, reactor pressure drop is also far less than the micro-reverse. These advantages are enough to be accepted by many enterprises in the renewal of products. In fact, I think that if we want to give the reactor like a weapon to divide the generation difference. Ordinary stirred kettle is counted as one generation, tubular reactor and other traditional strengthening equipment is counted as the second generation, and micro reactor is counted as the third generation. In fact, the second generation of reactors than the first generation of reactors have a lot of obvious advantages, but in fact most of China's chemical production is still stuck in the first generation of the level. At this stage of technological transformation, as long as the second generation of reactors to replace the first generation of reactors will be able to see the benefits. But favoring this step we have not even done, I have always said that our production process and the ability to combine equipment is poor. For example, an ammonia reaction, flammable and explosive, the Germans in the 40's with a tubular reactor to do, the effect is very good, but we are still in the kettle until now, stirring around, almost every plant to do this product has blown up. At the bottom of the story, the reaction engineering capability is not up to scratch. From the first generation of reactors to the second generation of reactors, how to carry out the combination of process and equipment, this lesson we must make up. Of course the microreactor has the potential to give us a leapfrog development program, we can step over other reaction equipment such as tubular reactors, direct access to the most advanced international reactors, this is really a good time.

Lastly, I would like to bring you some personal information, don't think that it is difficult to process the microreactor, and think the microreactor is very far away, the following picture is the microreactor cold molding device that I made by myself, and it has already had the characteristics of the Bayer microreactor, the diameter of the orifice has been up to 0.2mm, and the flux has been up to 1,400 tons/year. Of course, because of the limitations of the processing capacity, the pressure drop is larger than the general microreactor, material problems can only do extraction. The whole set of equipment processing does not use any high-end equipment, a set down within 2000 to get it done. So micro reactor is really around us.

Lastly, I would like to bring a little bit of private goods, don't think that it is difficult to process the micro-reactor, the micro-reactor is very far away, the following picture is my own micro-reactor cold mold device, already has the characteristics of the Bayer micro-reactor, the diameter of the pore has been up to 0.2mm, the flux has reached 1400 tons/year. Of course, because of the limitations of the processing capacity, the pressure drop is larger than the general microreactor, material problems can only do extraction. The whole set of equipment processing does not use any high-end equipment, a set down within 2000 to get it done. So the micro reactor is really on our side.