Seeking a review on the content of fermentation, as long as there is about fermentation is fine

Fermentation has evolved from the simple production of alcoholic beverages, acetic acid and fermented bread to an extremely important branch of bioengineering, a multidisciplinary project that includes microbiology, chemical engineering, genetic engineering, cell engineering, mechanical engineering and computer hardware and software engineering. Broadly speaking, fermentation engineering consists of three parts: upstream engineering, fermentation engineering and downstream engineering. Among them, downstream engineering refers to the technology of separating and purifying products from fermentation broth: including solid-liquid separation technology (centrifugation, filtration, precipitation, etc.), cell-breaking technology (ultrasonication, high-pressure shear, osmotic pressure, surfactants, and lysophospholipases, etc.), protein purification technology (sedimentation, chromatography, and ultrafiltration, etc.), and finally, the technology of product packaging and processing (vacuum drying and freezing officer Finally, there are the packaging and processing technologies (vacuum drying and freezing officer, etc.). In this paper, the principle and research progress of membrane separation technology is summarized.

Overview

Membrane separation technology is the development of high-tech in the last thirty years, is the product of multidisciplinary cross, but also the development of chemical engineering disciplines, a new growth point. Compared with the traditional separation method, it has the following obvious advantages:

1. High efficiency: due to the selectivity of the membrane, it can selectively permeate through some substances and block the permeation of some other substances. Selection of the appropriate membrane can be effective for the separation, purification and concentration of substances;

2. Energy saving: most of the membrane separation process is operated at room temperature, the separated substances do not undergo a phase change, is a low-energy, low-cost unit operation;

3. The process is simple, easy to operate and control;

4. No pollution of the environment.

Because of these advantages, membrane separation technology has developed rapidly in a short time, and has been widely and effectively used in petrochemical, biochemical and pharmaceutical, medical and health care, metallurgy, electronics, energy, light industry, textile, food, environmental protection, aerospace, shipping, people's lives and other fields, forming an independent new technology industry. At present, the world membrane market with an annual increase of 14 ~ 30% speed development, it not only formed its own annual output value of about ten billion dollars, but also strongly promote the development of social, economic and scientific and technological. In particular, its application and energy saving, environmental protection and water regeneration has a close relationship, so in today's world of energy shortages, water shortages and environmental pollution is becoming increasingly serious situation, membrane separation technology has been the world's countries pay general attention to the developed countries in Europe, the United States, Japan and other developed countries to invest huge sums of money to set up a special development and research, has achieved a leading position in this field. China in the "Sixth Five-Year Plan", "Seventh Five-Year Plan", "Eighth Five-Year Plan", "Ninth Five-Year Plan", as well as 863, 973 program In the 863, 973 program are listed as a key project, to give support.

II. Introduction to membrane separation technology

1. Types of separation membranes: membrane is the core of membrane technology, the nature of the membrane material and chemical structure of the membrane separation performance plays a decisive role in the impact. There are many types of membranes, including polymer membranes, metal membranes, inorganic membranes by material. Polymer membrane is the most widely used.

There are seven types of membranes according to their structure:

(1) Homogeneous membrane or dense membrane, a dense film with uniform structure.

(2) Symmetric microporous membranes, with an average pore size of 0.02 to 10. There are three types of microporous membranes according to the method of membrane formation, i.e., nuclear porous membranes, controlled stretching membranes, and spongy structured membranes.

(3) asymmetric membrane. The membrane section is an asymmetric structure and is the most used membrane in industry.

(4) Composite membrane. In the porous membrane surface coated with a dense composite layer of another material.

(5) Ion exchange membrane

(6) Charged membrane

(7) Liquid membranes, including the support liquid membrane and emulsion membrane

According to the shape of the flat membrane, tubular membranes and hollow fiber membrane.

2. Membrane separation equipment (components)

Plate and frame type, structure similar to plate and frame filter press.

Volume type, structure similar to the spiral plate heat exchanger.

Tubular, structure similar to the tube heat exchanger.

Hollow fiber type, structure similar to the tube heat exchanger, composed of thousands or even millions of hollow fibers.

3. Membrane separation process

Membrane separation process is a selective permeable membrane as the separation medium, when the membrane on both sides of the presence of some kind of driving force (such as pressure difference, concentration difference, potential difference, temperature difference, etc.), the raw material side of the component selectively through the membrane, in order to achieve the separation, purification purposes. Different membrane processes use different membranes, the driving force is also different. At present, the membrane separation process has been industrially applied microfiltration (MF), ultrafiltration (UF), reverse osmosis (RO), dialysis (D), electrodialysis (ED), gas separation (GS), osmotic vaporization (PV), emulsion membranes (ELM) and other eight.

Reverse osmosis, ultrafiltration, microfiltration, electrodialysis, the four major processes have been technically mature, there have been large-scale industrial applications, the formation of a sizeable industry, there are a number of commercialized products available for different purposes.

Gas separation and osmosis vaporization is a developing technology. Among them, gas separation is relatively more mature. Currently there are industrial-scale gas separation system is, the separation of oxygen and nitrogen in the air; ammonia plant in the ammonia, nitrogen, methane mixture of hydrogen separation; natural gas in the separation of carbon dioxide and methane. Permeation vaporization is the only one of these membrane processes that has a phase change and is special in both component and process design. It is mainly used for organic/water, water/organic, and organic/organic separations, and is the most promising membrane process to replace some of the more energy-intensive distillation technologies. it entered industrial applications in the mid-1980s.

In addition to the above eight industrially applied membrane separation process, there are many new membrane processes are being developed and studied, they are membrane extraction, membrane distillation, bipolar membrane electrodialysis, membrane partitioning, membrane absorption, membrane reaction, membrane control release, membrane biosensors. These membrane processes are still in the small test and pilot stage.

III. Brief history of the development of membrane separation technology and the current state of research

The human phenomenon of membrane research originated in 1748, but recognized the function of the membrane and used to serve mankind, but after more than 200 years of a long process. People's scientific research on membranes is a matter of recent decades. 1950 W. Juda trial production of selective permeability of the ion exchange membrane, laid the foundation for the practical application of electrodialysis. 1960 Loeb and Souriringan first developed into the world's historical significance of the asymmetric reverse osmosis membranes, which is an important breakthrough in the development of membrane separation technology, so that membrane separation technology has entered the era of large-scale industrial application of the membrane. Membrane separation technology has entered the era of large-scale industrialized application. The history of its development is roughly as follows: microporous filtration in the 30's, dialysis in the 40's; electrodialysis in the 50's; reverse osmosis in the 60's; ultrafiltration and liquid membrane in the 70's; gas separation in the 80's; and osmotic vaporization in the 90's. In addition to other new membrane-based separation processes, as well as membrane separation and other separation processes combined with the integrated process (Integrated Membrane Process) is also increasingly important and development.

Several major membrane technology development is roughly as follows:

Microfiltration in the 30's nitrocellulose microfiltration membrane commercialization, the 60's the main development of new varieties. In recent years to tetrafluoroethylene and polyvinylidene fluoride made of microfiltration membrane has been commercialized, with high temperature resistance, solvent resistance, good chemical stability and other advantages, the use of temperature in -100 ~ 260 ℃. At present, the sales volume is in the first place.

Ultrafiltration from the 70s into the industrialized application of rapid development, has become the most widely used technology. Japan developed a pore size of 5 ~ 50nm ceramic ultrafiltration membrane, the molecular weight cut-off for 20,000, and the development of successful diameter of 1 ~ 2mm, wall thickness of 200 ~ 400 ceramic hollow fiber ultrafiltration membrane, especially suitable for the separation and purification of biological products.

Ion exchange membrane and electrodialysis technology is mainly used for desalination of brackish water, the market capacity is nearly saturated in recent years. 80's new fluorine-containing ionic membranes in the chlor-alkali industry after the success of the application, causing profound changes in the chlor-alkali industry. The ionic membrane method saves 30% of the total energy consumption and 20% of the investment than the traditional diaphragm method. 90 years, nearly 140 sets of ionic membrane electrolysis devices have been put into operation in 34 countries in the world, and 1/3 of the world's chlor-alkali production will shift to the membrane method by 2000.

In 60 years, Loeb (Loeb) and Sourirajan (Sourirajan) invented the first generation of high-performance asymmetric cellulose acetate membranes, reverse osmosis (RO) for the first time used in the sea wave and brackish water desalination. 70 years of development of high-efficiency aromatic polyamide hollow fiber reverse osmosis membranes, so that the performance of RO membranes to further improve the performance of the 90's appeared in the low-pressure reverse osmosis composite membranes, the third generation of RO membranes, membrane performance. The third generation of RO membrane, membrane performance has been greatly improved, for the development of RO technology has opened up a broad prospect. At present, RO has been widely used in many fields, for example, ultrapure water manufacturing, boiler water softening, food, pharmaceutical concentration, urban sewage treatment, chemical waste liquid recovery of useful substances.

In 1979, Monsanto used for H2/N2 separation Prism system was established, the gas separation to industrial applications. 1985 Dow Chemical Company to the market to provide rich N2 for the purpose of air separator "Generon" gas separation for petroleum, chemical industry, natural gas production and other fields, greatly improving the efficiency of gas separation, gas production, greatly improving the economic efficiency of the process.

In the late 80's into the industrial application of membrane separation technology is used to permeate the vaporization of alcohols and other constant-boiling dehydration, due to the energy consumption of the process is only constant boiling distillation 1 / 3 ~ 1/2, and does not use benzene and other hostage agent, in place of constant boiling distillation and other dehydration technology has a great economic advantage. Germany's GFT company is the first to develop the only successful commercial GFT membrane company. the early 1990s to Brazil, Germany, France, the United States, Britain and other countries sold more than 100 sets of production units, the largest for the annual output of 40,000 tons of anhydrous ethanol industrial plant, built in France. In addition, the PV method for the removal of small amounts of organic matter in water and the separation of certain organic / organic mixtures, such as the separation of trace chlorine-containing organics in water, MTBE / methanol separation, in recent years, there are also pilot-scale research reports.

In China, the development of membrane technology from 1958, ion exchange membrane research began. 65 years to reverse osmosis membrane exploration, 66 years Shanghai Chemical Plant polyethylene heterogeneous ion exchange membrane formally put into operation for the industrial application of electrodialysis laid the foundation for the 67 years of desalination of seawater in China's membrane science and technology progress has played a positive role in promoting the progress of the 70's on electrodialysis, Reverse osmosis, ultrafiltration and microfiltration membranes and components for research and development in the 80's into the promotion and application of the stage. 80's China's gas separation membrane research has made great progress in the mid-80's, in 1985, the Chinese Academy of Sciences, Dalian Institute of Chemical Physics for the first time developed a successful hollow fiber N2 / H2 separator, the main performance indicators close to the indicators of similar products abroad, has been put into mass production, the cost of each set of imported devices for only 1 / 3.

China's permeation vaporization (PV) process research began in 1984, into the 90's, the preparation of composite membranes has made greater progress, in 1992, the Department of modified PVA/PAN composite membranes through the technical appraisal, in 98 years, the establishment of China's first 1,000-ton Benzene dewatering demonstration project in Yanhua, China's PV technology has laid the foundation for the industrial application of PV technology.

Four. Membrane separation discipline development of the main disciplines to support the system

Selective separation of membranes as the center of the membrane science research since the 1950s to form a discipline, has made rapid development, mainly around several directions of in-depth research, which are: membrane materials and membrane structure; membrane preparation and membrane formation mechanism; membrane performance and structure of the relationship between the membrane process and the transfer mechanism; process and equipment design and optimization; membrane application research. Optimization; membrane application research. Membrane separation technology is able to stand out in the rapid development in just 30 years, first of all, because it has a solid theoretical foundation, such as chemical osmotic pressure theory, gas membrane permeability theory, membrane aperture theory, membrane equilibrium concepts, fixed potential theory, double layer theory and so on. Secondly, the development of modern science and technology for the separation of membrane materials research provides good conditions, polymer science progress for membrane separation provides a variety of characteristics of synthetic polymer membrane materials; electron microscopy and other modern analytical techniques for the separation of the structure of the membrane analysis and separation mechanism provides an effective means of research. The third is the development of modern industry urgently needs energy saving, the reuse of low-grade raw materials and the elimination of environmental pollution of the new technology, and membrane separation is just can meet these needs of the new technology.

V. Currently the frontier of basic research

1. water treatment-based membrane materials and membrane research

Large flux, high surface area of the reverse osmosis membrane research

The molecular weight of the molecular weight of less than 1,000, more than 1 million ultrafiltration membrane and the mechanism of transmission; anti-pollution membrane manufacturing

Pore size from 0.1m to 75m microporous membrane serialization research

Interfacial condensation method to prepare active layer of nanofiltration membrane

2. High flux and high selectivity gas separation membrane research

Carbon dioxide separation

Organic waste gas (VOCS) treatment

3. Osmotic vaporization membrane

High selectivity membrane research on separating organics from water

Research on organic/organic separation membrane

4.

4. Inorganic membranes

Ultra-thin, ultra-microporous composite membranes; multi-component composite membranes

Electrically conductive mobile membranes

Grafted membranes of inorganic and organic materials

5. Models of mass and heat transfer in membrane-catalyzed reactors

6. Theory and application of membrane processes in environmental protection and governance, water resource regeneration, and fuel cell membranes

7. Applied Research

7. Molecular Modeling in Membranes