CN101556105A - Control method of liquid nitrogen supply valve of liquid nitrogen auxiliary refrigeration and freeze dryer - Google Patents

Abstract

The invention relates to a control method of a liquid nitrogen supply valve of a liquid nitrogen auxiliary refrigeration and freeze dryer, which is characterized in that the jaw opening of a control valve is K=K1*K2. The liquid nitrogen control valve adopts two parameters to control together, wherein one is an output value K2 of the difference between practical temperature and theoretic temperature, which is calculated by a PID meter, and the other one is a liquid level ratio K2; and the final jaw opening of the valve is influenced by the two factors, thus the invention can control the temperature of conducting oil and the liquid level of a liquid nitrogen heat exchanger with high control precision, good stability, economy and safety.

Description

A kind of control method of liquid nitrogen supply valve of liquid nitrogen auxiliary refrigeration and freeze dryer

Technical field

The present invention relates to a kind of control method of liquid nitrogen supply valve of liquid nitrogen auxiliary refrigeration and freeze dryer, belong to the Vacuum Freezing ﹠ Drying Technology field.

Background technology

Vacuum freeze drying (abbreviation freeze dryer) but be exactly that the hydrous matter of freeze-drying or solution are freezed in advance at low temperatures, under vacuum environment, make the material dehydration obtain dry article then.

This drying means with common dry, dry, boil dry, spray-drying is compared with vacuum drying that many outstanding advantages are arranged:

(1) do not make protein, microorganism and so on produce sex change or lose biologos;

(2) loss of the nutritional labeling of volatile ingredient in the material and heated denaturalization is little;

(3) effect of microbial growth and enzyme almost can't be carried out, and can keep the original proterties of material best;

(4) drying back form is constant substantially, is spongy open structure; Rehydration is easy, can promptly be reduced into original proterties;

(5) dry under vacuum, oxygen is few, makes the material of easy oxidation obtain protection;

(6) can remove in the material 95%～99% moisture, the goods long shelf-life;

So freeze dryer is widely used in: pharmaceuticals industry, biological products; Biological tissue, microbiology class: animals and plants; Food industry; Chemical industry; Health care products and Chinese herbal medicine etc.

The freeze dryer vacuum system comprises that freeze drying box, condenser, vavuum pump, valve, refrigeration system comprise the hydraulic system of the cold and hot matchmaker's indirect heat exchange of shelf assembly system, movable shelf.

Freezing dry process is complicated heat transfer, mass transport process.Freeze-drying process and freezing process are closely related, and the latter has determined the time of freeze-drying process and the quality of dried frozen aquatic products to a certain extent.Yet, in existing medicine freeze-drier, the freezing process of medicine is finished mostly on the shelf, the rate of temperature fall of shelf is relatively slow, be generally less than 2 ℃/min, liquid formulation is with in the shelf temperature-fall period, and ice crystal forms prior to container bottom, upper heat and lower cold, thermograde is relatively large in the preparation, and it is slow that speed is pushed ahead at the ice interface, solute migration time abundance in the solution, solution surface frozen crust solute gathers more, high concentration " top layer duricrust " phenomenon occurs easily, forms one deck fine and close " duricrust " behind the high concentration superficial drying, thereby hinders the effusion of water vapour in the freeze-drying process, prolong freeze-drying time, increase the difficulty of dried frozen aquatic products rehydration.In the actual production process, the solute Distribution inequality that the shelf slow freezing forms also can cause the difference of residual water content after the medicine preparation drying, and this solute and water content problem of uneven distribution thereof can be brought adverse influence to the storage-stable of freeze-drying process and product.So, in solution based article shelf pre-freeze process, how to control the speed of growth of ice crystal, reduce the migration from bottom to top of sample interior solute, to improve the freeze-drying sample quality, energy efficient is all significant.

In addition, the use of a large amount of organic solvents of biochemical drug production process, cause the organic solvent of drug residue under vacuum state, to enter vacuum system, and conventional cold-trap (70 ℃) can't capture these organic solvents, in a single day organic solvent enters the oil sealing rotary-vane vaccum pump, pumping fluid and sealing original paper are with destroyed, and vacuum system can't be worked normally.Thereby effectively protect vacuum system in order to make organic solvent condense, and prevent that preparation " top layer duricrust " phenomenon from taking place.Liquid nitrogen auxiliary cooling technology is developed use on freeze dryer.The liquid nitrogen auxiliary cooling system can effectively solve above-mentioned two problems.The liquid nitrogen vaporization temperature is-196 ℃, and the about 210kJ/kg of the latent heat of vaporization, and most organic solvent can be cured at-120 ℃, the auxiliary cold-trap of liquid nitrogen can guarantee that the freeze dryer vacuum system do not destroyed by organic solvent.In addition, because liquid nitrogen temperature is lower, refrigerating capacity is stronger, the automatic supply control system of liquid nitrogen can be controlled rate of temperature fall easily, liquid nitrogen refrigerating can effectively solve sample solute temperature distributing disproportionation, thereby improves the quality and the storage-stable of sample greatly, and energy savings consumption.

The liquid nitrogen auxiliary cooling system is compared with conventional compression formula refrigeration system, and following advantage is arranged:

(1) cold is regulated greater flexibility.Shelf temperature can be lower, and the faster and cold of cooling rate is more evenly distributed.

(2) refrigeration system is more reliable.Because traditional compressor formula refrigeration system often operates in underload or approximate zero load condition, so refrigeration system is very unreliable, then there is not this type of problem in the liquid nitrogen auxiliary cooling.

(3) reduce electricity needs.Because liquid nitrogen auxiliary cooling technology adopts the liquid nitrogen vaporization refrigeration, therefore dispense the electricity needs of conventional compression formula refrigeration.

(4) noise is low.Omit the compressor noise of conventional compression formula refrigeration.

(5) floor space is little.Reduce the water system in the conventional compression formula refrigeration, floor space approximately reduces 50%.

(6) frosting of cold-trap coil pipe is even.

The control method of traditional liquid nitrogen auxiliary refrigeration and freeze dryer is: the open degree of valve is according to the comparison actual value of PID instrument demonstration and the difference K between the setting value ₂Come the by-pass valve control aperture, so the control of valve is not very accurate, and the liquid level of liquid nitrogen heat exchanger can not be controlled effectively.For the liquid nitrogen heat exchanger, the control of liquid nitrogen liquid level also is very important, in case liquid level is too high, some liquid nitrogen with regard to not through pervaporation and directly along with the nitrogen discharge tube drainage to the outside, be breakneck like this, and the consumption of liquid nitrogen also can increase.

Summary of the invention

The control method that the purpose of this invention is to provide the high liquid nitrogen supply valve of liquid nitrogen auxiliary refrigeration and freeze dryer of a kind of control accuracy.

For realizing above purpose, technical scheme of the present invention provides a kind of control method of liquid nitrogen supply valve of liquid nitrogen auxiliary refrigeration and freeze dryer, it is characterized in that, the aperture of by-pass valve control is K=K ₁* K ₂

K ₂Be the output valve that the difference of actual temperature and theoretical temperatures is calculated by the PID instrument, K ₁Be the control parameter of liquid nitrogen heat exchanger liquid level ratio, its computing formula:

$K_1=\frac{L\max -L}{L\max -\mathrm{LLAH}}$

Wherein:

K ₁: represent the liquid level ratio of liquid nitrogen heat exchanger,

Lmax: represent the highest liquid level of liquid nitrogen heat exchanger permission, mm;

L: the liquid nitrogen liquid level of actual measurement, mm;

LLAH: the minimum liquid nitrogen liquid level that the liquid nitrogen heat exchanger requires, mm;

The aperture K=K of valve ₁* K ₂, the aperture K according to the valve that calculates removes to open valve at last.

The present invention takes two parameters to control together for the control of liquid nitrogen control valve, an output valve K who is the difference of actual temperature and theoretical temperatures by the calculating of PID instrument ₂, another one control parameter is the liquid level ratio K ₁, the final aperture of employing valve is subjected to the influence of two big factors, so, not only can control the temperature of conduction oil, can also control the liquid level of liquid nitrogen heat exchanger, and control accuracy is very high, good stability, not only economy but also safety.

Advantage of the present invention is that control accuracy is very high, and security is good.

The specific embodiment

The invention will be further described below in conjunction with embodiment.

Embodiment

Below the liquid nitrogen supply valve of liquid nitrogen auxiliary refrigeration and freeze dryer that only manufactures and designs with our company is controlled to be embodiment the invention will be further described:

A kind of control method of liquid nitrogen supply valve of liquid nitrogen auxiliary refrigeration and freeze dryer is:

The aperture of by-pass valve control is K=K ₁* K ₂

K ₂Be the output valve that the difference of actual temperature and theoretical temperatures is calculated by the PID instrument, the K of PID instrument demonstration at present ₂Be 80%

K ₁Be the control parameter of liquid level ratio, its computing formula:

$K_1=\frac{L\max -L}{L\max -\mathrm{LLAH}}$

Wherein:

K ₁: represent the liquid level ratio of liquid nitrogen heat exchanger,

Lmax: represent the highest liquid level of liquid nitrogen heat exchanger permission, the highest liquid level of liquid nitrogen heat exchanger permission is 840mm;

L: the liquid nitrogen liquid level of actual measurement is 600mm;

LLAH: the minimum liquid nitrogen liquid level that the liquid nitrogen heat exchanger requires is 420mm;

K ₁Calculate K ₁=(840-600)/(840-420)=57.1%

The aperture K=K of valve ₁* K ₂=80%*57.1%=45.7%, the aperture K according to the valve that calculates removes to open valve at last.

Claims (1)

1. the control method of a liquid nitrogen supply valve of liquid nitrogen auxiliary refrigeration and freeze dryer is characterized in that, the aperture of by-pass valve control is K=K ₁* K ₂

K ₂Be the output valve that the difference of actual temperature and theoretical temperatures is calculated by the PID instrument, K ₁Be the control parameter of liquid level ratio, its computing formula:

$K_1=\frac{L\max -L}{L\max -\mathrm{LLAH}}$

Wherein:

K ₁: represent the liquid level ratio of liquid nitrogen heat exchanger,

Lmax: represent the highest liquid level of liquid nitrogen heat exchanger permission, mm;

L: the liquid nitrogen liquid level of actual measurement, mm;

LLAH: the minimum liquid nitrogen liquid level that the liquid nitrogen heat exchanger requires, mm;

The aperture K=K of valve ₁* K ₂, the aperture K according to the valve that calculates removes to open valve at last.