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Chromatographic separation system

1     Introduce

Chromatographic separation is carried out in a column with a stationary phase. And this kind of stationary phase must have enough different retention effect on the separated components, so as to use their flow rate difference to separate components.
For example, to use this principle to separate a mixture including two main components, thefollowing conditions need to be met
①  A road with different resistance to the two components, and the stationary phase in the system is equivalent to the"road" here.
②  The driving force to push the feed liquid forward. Here is provided by the mobile phase.
So if these two conditions are satisfied, we can get the mixture of each component and mobile phase by waiting at the end point. The mobile phase can be separated by a simple method, such as distillation.
After one cycle, if it is necessary to separate again, feed repeatedly. When using this method to separate materials, as long as there is "speed difference" and "the road is long enough", the perfect separation can be achieved. But in the production, not only the concentration and purity of the extract, but also the investment cost should be considered. The simulated moving bed separation technology developed in 1960s is the most widely used separation and purification technology in the fields of petrochemical industry and pharmaceutical industry. There are many types of simulated moving bed, such as traditional simulated moving bed (SMB),sequential simulated moving bed (SSMB), variable length simulated moving bed and so on.
At present, the chromatography designed and built by Oumingzhuang is the sequential simulated moving bed. Its principle is the same as that of the traditional simulated moving bed. The differences are as follows.
①  The number of chromatographic columns is small(4-6 columns), but the effect of separation and purification is equivalent to that of multiple columns.
②    It divides one step of traditional simulated moving bed into two or more steps.
③    Feed and discharge and circulation are intermittent rather than continuous.
④    Because fewer columns are used, its one-off investment is relatively small

2     The practical application 

Separation of glucose mother liquor by six column chromatography


FIG 2-1   Process flow chart

 1)   Process description

The whole system including not only the filtration and degasification of feed and water but 6 chromatographic resin columns. In the preparation part, the material and water are respectively filtered to avoid the insoluble impurities polluting the resin in the chromatographic column. After flash evaporation gas removal, the dissolved oxygen in the solution and water is removed to reduce the oxidation of the resin. At the same time, the temperature of material and water is controlled to 60 ℃ to ensure the stable operation of the system. After degasification, the feed liquid is fed to the chromatographic column through the feed pump and the circulating pipeline, and the pressure of the ring pipe is maintained at 2.0 bar.After degassing, the eluate water is supplied to the chromatographic column through the inlet pump and circulation pipeline. The outlet of the chromatographic system is connected with the extraction liquid tank and the extraction residual liquid tank, which are respectively responsible for receiving the extraction liquid rich in glucose and the extraction residual liquid rich in other impurities separated from the chromatographic system. A set of chromatographic column consists of 6 resin silos, which are connected in series with each other, and are connected in parallel to the public water inlet, feed, extraction and residual liquid pipelines. Each resin silo has 5 valves with different functions to perform different functions.
For example, the valves on 3168CT101

3168XV1      water  inlet  valve
3168XV2          feed         valve
3168XV3   residual liquid valve
3168XV4        extraction  valve
3168XV5           series     valve

2)   The production principle

Chromatographic separation is to use the difference of the binding force between the two substances and the resin. When the two substances flow through the space filled with resin, the moving speed is different and they are separated.
In this system, glucose moves slowly and flows behind. The polysaccharide moves fast and runs to the front.
We usually divide six resin columns into six role areas: Z1, Z2, Z2, Z3, Z3, Z4. Through the opening and closing of the valve and the start and stop of the circulating pump among the resin silos, the roles of the six resin columns can be switched orderly. Each time the switch is completed, we call it a short cycle. The process shall be carried out in the following steps for each short cycle.
①   Step A is to circulate.


The feed liquid enters into the system and forms a dry matter band in the resin layer, which is mainly distributed in Z1, Z2 and Z3 areas. In step A, all valves are closed, that is to say, the system is closed and circulates, and the materials in the system move down a column space in sequence.
Then the various components in the dry matter zone are partially separated due to the difference of movement speed in the resin layer. Finally, the Z1 area is rich in glucose components with relatively small molecular weight. The second Z3 region is rich in polysaccharides with large molecular weight.
②   Step B is to take in water and residual liquid out.


The eluant water enters into the system through the water inlet valve of resin column in Z1 area. At the same time, the material liquid reaches the Z3 column through the inter column pump, and the material is discharged from the residual liquid valve of the column. The concentration of the residual liquid is increased slowly. At this time, materials in zone Z1 are further separated and glucose content is further increased.
③   Step C is to take in water and extracting liquid out.

When the elution water enters the system through the water inlet valve of resin column in Z1 area, the extraction liquid of resin column in this area is discharged from the extraction valve.
④   Step D is to take in feed liquid and residual liquid out.

  

Feed transfer to the second Z3 column from the first Z3 column through the circulation pump, and the residual liquid out. Generally, step C and step D are carried out at the same time, and the time of these two steps is basically equal by setting the instantaneous flow rate of the two steps, so as to savetime. When step C and step d are completed, a short cycle ends. In the next cycle, the outlet of the extract and residual will switch one column forward,and the injection point of the raw material and eluent will also switch one column forward. When the entrances and exits move to the last column 3168CT106, a long cycle ends. Continue from the first column 3168CT101 at the next operation.

3     Technology development and service

In 2018, the multi-unit high efficiency chromatographic system with array valves invested by Oumingzhuang was completed, and it was first presented at the 6th Shanghai International bio fermentation products and technical equipment exhibition in 2018, and then participated in the 14th Shanghai International Starch and starch derivatives exhibition in 2019.The system consists of 20 chromatographic columns and 400 automatic on-off valves. It offers a subtle blend of high performance chromatography with ion exchange system, and realizes the switching between chromatographic system and separation system by using different resin and valve groups.
So far, this pilot plant has successively made experiments on site, such as HFCS separation,mother liquor separation and glucose refining, etc. The experiment not only optimizes the operation parameters, but provides convenience for the customer's technical development.
In addition, other small test equipment of Oumingzhuang has also been built and transported to various sites for test. We strive to develop high-quality products and provide the best service for new and old customers.

 

FIG  3-1  the multi-unit high efficiency chromatographic system with array valves

 

 

 

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