Freeze dryer is a technical method to freeze water containing articles in advance, and then sublimate their water under vacuum to obtain dry articles. The freeze-dried articles are easy to be stored for a long time, and can be restored to the state before freeze-drying and maintain the original biochemical characteristics after adding water.

Vacuum freeze-drying technology has been widely used in bioengineering, pharmaceutical industry, food industry, material science, agricultural and sideline products deep processing and other fields, and its scale and field are still expanding. Therefore, vacuum freeze drying will become an important application technology in the 21st century.

The refrigeration dryer is composed of refrigeration system, vacuum system, heating system and electrical instrument control system. The main components are drying oven, condenser, refrigeration unit, vacuum pump, heating/cooling device, etc.

The refrigeration system is the most important part of the lyophilizer, known as the "heart of the lyophilizer". The refrigeration system is mainly composed of the following components: compressor, refrigerant, oil separator, water condenser, drying filter, intercooler, sight glass, solenoid valve, hand valve (head valve), expansion valve, evaporator (plate exchanger, rear box condenser coil), vapor liquid separator, return air filter, pressure gauge, pressure control relay, CPCE (energy regulator), safety valve, refrigeration pipeline, etc.

Freeze drying is a technology that uses the principle of sublimation to dry. It is a process that quickly freezes the dried substance at low temperature, and then directly sublimates the frozen water molecules into water vapor under an appropriate vacuum environment The product obtained by freeze-drying is called lyophilizer, and the process is called lyophilization.

The working principle of the lyophilizer (as shown in the figure below) is: after absorbing the heat of the cooled material in the evaporator, the liquid refrigerant vaporizes into low-pressure and low-temperature steam, which is sucked in by the compressor, compressed into high-temperature and high-pressure steam, and then discharged into the condenser, where heat is released to the cooling medium (water or air), condensed into high-pressure liquid, throttled into low-pressure and low-temperature liquid by the throttling device, and then enters the evaporator again for heat absorption and vaporization.

Max inlet temp	60°C	Pressure dew point	2℃~10℃
Environment temperature range	5°C-50°C	Cooling mode	water cooled
Pressure range	0.6-1.6Mpa ( 0.5-12Nm³/min )	Cryogen	0.5~2 Nm/min is R134a, 3~12Nm3/min is R410a，
	0.6-1.0 Mpa ( 15Nm³/min and above )		15~80Nm/min is R407C, 80 Nm/min and above is R22

Inlet air temperature	38°C	Working pressure	0.7Mpa
Ambient temperature	38℃	Cooling water temperature	≤32℃

Compressed refrigeration air dryer the amount of water vapor in the compressed air is determined by the temperature of the compressed air: under the condition that the pressure of the compressed air is basically unchanged, reducing the temperature of the compressed air can reduce the content of water vapor in the compressed air, and the excess water vapor will condense into liquid. According to the corresponding relationship between the saturated steam pressure and temperature of water, the freezing dryer uses the refrigeration device to cool the compressed air to a certain dew point temperature, release the contained water, and discharge the water through the steam water separator and electric drainer, so as to dry the compressed air.

● R22 refrigerant and tube heat exchanger are used for more than 80 cubic meters; the gas-liquid separator adopts a patented three-stage separation method of "direct collision separation , low-speed centrifugal separation and stainless steel wire mesh demisting separation", which will remove 99.9% of the liquid The moisture is separated from the cooled compressed air to prevent the secondary evaporation of moisture and ensure the low dew point quality of the finished gas;

● The refrigeration compressor adopts DANFOSS, FUSHENG, PANASONIC, BTZERO, COPELAND, HIGHLY, etc. fully enclosed or semi- enclosed refrigeration compressors, which have stable operation, low noise, high COP, reliable performance, and long power- saving life;

● Refrigeration control components adopt the world's advanced refrigeration components like DANFOSS, EMERSON, SPORLAN and other companies;

● Real-time display of operating parameters;

How do the air dryer and air receiver work together?

All atmospheres contain water vapor, but when air is compressed, the relative humidity of water increases to 100%. In order to avoid problems caused by water precipitation in pipelines and connected downstream equipment, compressed air must be dried.

1. Over compression, the air is compressed to a higher pressure than the expected working pressure, which means that more water is condensed out of the system during compression. As the air cools in the compressor aftercooler, additional water is separated. Then expand the air to the working pressure and obtain a lower pressure dew point. This method is only suitable for very small air velocity because of its high energy consumption.

2. Refrigerant drying. The refrigerant drying process includes cooling the compressed air to allow a large amount of water to condense and separate. After cooling and condensation, the compressed air is reheated to room temperature so that condensation does not form outside the piping system.

3. Adsorption drying. The working principle of the adsorption dryer is very simple - moist air flows through the desiccant for drying. Once the desiccant material is absorbed by water, it will regenerate to restore its drying capacity. The adsorption dryer is usually constructed with two drying containers. The first container dries the incoming compressed air, while the second container is responsible for regeneration.

After the compressed air passes through the dryer, it will generally be equipped with an air receiver. After the compressed air reaches the air receiver, the air will stay for a certain period of time, which can precipitate impurities, moisture and other foreign matters in the air. The temperature of the compressed air will also be reduced. Even without a refrigeration dryer, it can also deliver high-quality air. In fact, the function of the air tank is just like a water reservoir. The air compressor is an air source, and the air tank is a water reservoir. The air receiver can set the air pressure balance within a certain pressure range according to the setting, buffer the fluctuation of air pressure, reduce the number of starts of the air compressor, and also play the role of settling impurities, water and other foreign matters in the air.

Compressed refrigeration air dryer (plate fin type)

Item Model	Capacity （Nm3/min）	Voltage （V）	Cooling water volume （m3/h）	Air connection pipe size	Cooling water connection pipe size	N.W （kg）	L （mm）	W （mm）	H （mm）
SDLW-8	8.5	220	1.2	G2"	R1"	140	600	600	900
SDLW-10	10.9	380/220	1.6	G2"	R1"	180	820	700	1040
SDLW-12	12.8	380/220	1.6	G2"	R1"	180	820	700	1040
SDLW-15	16	380/220	2.2	DN65	R1"	200	1170	920	1420
SDLW-20	22	380/220	2.4	DN65	R1"	270	1170	920	1420
SDLW-25	26.8	380/220	2.6	DN80	R1-1/2"	290	1170	920	1420
SDLW-30	32	380/220	3.4	DN80	R1-1/2"	410	1400	1200	1600
SDLW-40	43.5	380/220	4.6	DN100	R1-1/2"	495	1400	1200	1600
SDLW-50	53	380/220	5.8	DN100	1-1/2	850	1600	1200	1600
SDLW-60	67	380/220	7.2	DN125	1-1/2	1100	1600	1400	1650
SDLW-80	90	380/220	9.1	DN125	1-1/2	1500	1800	1500	1770

Compressed refrigeration air dryer (shell and tube type)

Item Model	Capacity （Nm3/min）	Voltage （V）	Cooling water volume （m3/h）	Air connection pipe size	Cooling water connection pipe size	N.W （Kg）	L （mm）	W （mm）	H （mm）
SDLW-100	110	380/220	14.6	DN150	R2"	2430	2410	1135	1976
SDLW-120	130	380/220	16.2	DN150	R2"	2500	2600	1355	2144
SDLW-150	160	380/220	18.6	DN200	R2-1/2"	2800	2970	1550	2374
SDLW-200	210	380/220	24.4	DN200	R2-1/2"	3500	3370	1510	2434
SDLW-250	260	380/220	30.5	DN250	R3"	3550	3660	1960	2666
SDLW-300	310	380/220	36	DN250	R3"	3900	3795	1900	2714
SDLW-350	350	380/220	43	DN300	R3"	4000	4080	2050	3009
SDLW-400	400	380/220	50	DN300	R4"	4100	4400	2050	3009
SDLW-450	450	380/220	57	DN350	R4"	4500	4600	2000	3059
SDLW-500	500	380/220	62	DN350	R4"	4700	4900	2000	3059
SDLW-550	550	380/220	68.5	DN400	DN125	5000	4900	2160	3209
SDLW-600	600	380/220	75	DN400	DN125	5300	4900	2260	3309

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