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Liquefaction system

In the starch sugar production industry, there is no doubt that enzyme method is the most ideal sugar production method at present.

1     technological process of enzyme method
The important purpose of lique faction process is to create good conditions for the saccharification process, because the amylase used in the saccharification process is exonuclease, and the hydrolysis is carried out from the non reducing end of the substrate molecule. Liquefying will make starch in the feed liquid hydrolyze to many small chain molecular products, increasing the action chance of enzyme, and accelerate the speed of saccharification reaction.
In production, there are many methods of enzymatic liquefaction, but jet liquefaction is the most popular one because of its many advantages. For example, compared with α-amylase, thermostable α-amylase can spray and liquefy at high temperature, which has good protein flocculation effect and no insoluble starchparticles. What’s more, it does not cause aging phenomenon, and the liquefying liquid is clear and transparent. Moreover, spray and liquefy in high temperaturecan also prevent the formation of small molecules precursor substances, such as maltose, trisaccharide, etc., which will be of benefit to the improving of glucose yield. Last but not least, the cost of using thermostable α-amylase is lower than that of α-enzyme.
2     Brief description of the process
In the batching tank, adjust the Be’ of liquid to 17-25, and the pH to 5.0-7.0 with Na2CO3 or NaOH . Add thermostable α-amylase,then pump into the jet liquefier after stirring evenly. In the ejector, the feedliquid and steam meet directly, and the discharge temperature is controlled at 95-110 ℃. The feed liquid enters the laminar flow tank from the ejector for 30-90 minutes, and the temperature is maintained at 95-97 ℃. In the second ejector, the temperature rises above 120-145 ℃ for about 5-10 minutes, so as to thermostable α-amylase is completely killed, the starch will be further broken, and the protein will be further solidified. Finally,the feed liquid passes through the second flash cooling system, and the temperature drops to 95-97℃for about 30 minutes. The liquefying is over.
3     Process control plan
The effect of liquefaction has a crucial impact on subsequent processes and even product quality. In the process o f liquefaction, the viscosity of starch paste should be low enough, and the size and uniformity of hydrolysate should be controlled within a certain range. That is to say, liquefaction requires high operating conditions. Automatic control will contribute to liquefaction effect.
In order to optimize the starch liquefaction process, Oumingzhuang has conducted many investigations and tests on the process problems. As for the critical points control of starchliquefaction process, we put forward our automatic control plan, and solved the problem pertinently.

1)  Calculation the dry basis
The dry basis content of starch is an important parameter of starch production and sugar making process, and it is also the core of automatic control of liquefaction process. In the past, the calculation of starch dry basis was measured by pycnometer or Baume meter, and then calculated manually. In fact, there are errors in the data. Because the inaccuracy of the instrument,the deviation of the manual measurement, and the inaccuracy of the empirical formula of the dry base calculation.
Oumingzhuang summarized the comparison table of starch milk density,pomme and dry base. What’s more, we compiled them into a database. In the production line, the mass flowmeter collects the density of starch, and at the same time the temperature sensor collects the temperature of starch milk. After data index, formula conversion and data modification, the accurate value of starch dry base content is obtained, and it is transport to the control screen in real time. This technology has been widely used in the saccharification projects in which our company participates, and has also been recognized by local technical personnel.
2)  Adjust concentration and pH
The concentration of starch milk must be controlled within a certain range. If it is too high, it will not only affect the effect of enzyme preparation, but also make the operation of equipment difficult. If the concentration is too low, it will increase the steam consumption in the evaporation process. To solve this problem, Oumingzhuang designed a solution. Amass flowmeter is installed at the pump outlet of the starch milk tank to detect the density of the feed liquid, and then the flow of the added water is adjusted through the DCS system calculation and control valve, so as to ensure the starch milk concentration within the set range.
pH is an important factor affecting the effect of enzyme preparation.At present, the best pH range of high temperature amylase is 5.6-6.0, so the pH should be strictly controlled in production.
We install online pH detector at the outlet of the pump, and the regulating valve controls the amount of alkali added to ensure that the pH is within the set range. The chemical used for adjusting pH is NaOH solution. The ions brought into the system are removed in the ion exchange process.
3)  Adding enzyme preparation online
It is difficult to control the amount of enzyme added manually. If the enzyme is added too little, there will be many adverse consequences. For example, it may cause poor liquefaction effect and lead to unqualified products, or block the pipeline and affect the normal operation of production.If too much enzyme is added, it will cause waste and can not meet the sugar yield requirements of the saccharification process.
We need to set the operation parameters correctly and supply sufficient enzyme, so as to add enzyme on line automatically in high accuracy.
According to the real-time data of starch milk flow and dry basis,CPU will adjust quantity by controlling metering pump. At present, the system to control the quantity of enzyme addition is relatively mature. For different starch sugars, process engineers only need to adjust the coefficient. The control system will measure the amount of starch milk enzyme at any time, and display the historical data record on the control screen.


FIG3-1  Operation control screen of liquefaction system

4     Liquefaction system operated by one-button start
Click one button and all equipment on the liquefaction site will start and run automatically. From starch milk receiving tank to saccharification tank, all operations are controlled by CPU through feedback data of field instrument. All liquefaction parameters can be adjusted and modified flexibly in the host computer.
In the past, when the ejector was operated manually, it was necessary to control the steam flow and feed flow at the same time. Improper operation will cause excessive temperature fluctuation and unstable feed flow,which will cause starch aging, incomplete liquefaction effect, pipe blockage,large vibration and affect the service life of the equipment. The one-button start system of Oumingzhuang ensures that starch milk is fully mixed with steam in the liquefying ejector to complete the gelatinization process, with low vibration and noise. It ensures the stability of production process and good product quality.
The key of the system is automatic control without artificial intervention.The enzyme is added automatically. The starch milk concentration is adjusted automatically. The pH is adjusted automatically. And the liquid level of all tanks in the liquefaction process is adjusted automatically according to the flow of the first injector.
In addition, no additional factory equipment is needed for one-button start of liquefaction. Our program is completely modular, which shortens the software design cycle. It has strong portability and can save much time in the design, testing and debugging phases,providing ‘formulaic’ solutions for all automation services.
In terms of hardware, we use SIMATIC S7-300 / 400 series programmable controller. This series of PLC runs stably and reliably with low failure rate. It integrates the latest development of advanced control thought,modern communication technology and IT technology. All components of totally integrated automation have high performance and good interoperability. A lot of time in the design, testing and commissioning phase can be saved, so that the cost of plant operation is reduced. Totally integrated automation can also provide many conveniences in rapidly transforming plant equipment. What’s more, high speed CPU and powerful process function can bring higher productivity.
One-button start system is the highlight of liquefying control in our company. It has been used in the sodium gluconate production line of Heilongjiang Longfeng Corn Development Co., Ltd. It is also used in the production lines of sodium lactate and ethyl lactate of Shandong Baisheng Biotechnology Co., Ltd. No matter the control process or the automation programming has been quite mature. It can be said that the liquefaction of one-button startup is not only a big step in the development process of Oumingzhuang, but also a small step in the automation control of starch and sugar industry in China.