CN-120947211-B - Double-machine double-stage screw type refrigeration compressor unit special for stratum freezing

CN120947211BCN 120947211 BCN120947211 BCN 120947211BCN-120947211-B

Abstract

The invention provides a special double-machine double-stage screw refrigerating compressor unit for stratum freezing, which comprises a low-pressure stage compressor, a low-pressure stage variable-frequency motor, a plate shell type heat exchanger, a high-pressure stage compressor, a high-pressure liquid storage, an evaporative condenser, a high-pressure stage power frequency motor, an oil separator, a thermosiphon oil cooler, an oil pump, a olein filter, a brine pump, a brine pond, a thermosiphon evaporator, a throttle valve and a control console. The special double-machine double-stage screw type refrigerating compressor unit for stratum freezing combines the unique characteristics of frequency conversion technology and double-machine double-stage screw type refrigerating compressor unit operation, can realize flexible adjustment of the volume ratio of the high-pressure compressor and the low-pressure compressor at different temperature points, achieves the highest efficiency, improves the refrigerating capacity at the medium temperature stage, reduces the use cost, improves the motor efficiency and the refrigerating capacity at the low temperature stage, shortens the freezing time while saving energy, and is convenient to detach, install and transport.

Inventors

Tang Ruixiong
XIONG KAN
QI WEI
LIU MENGLING
WANG YANG

Assignees

武汉新世界制冷工业有限公司

Dates

Publication Date: 20260512
Application Date: 20250725

Claims (6)

1. The double-machine double-stage screw refrigerating compressor unit special for stratum freezing is characterized by comprising a low-pressure stage compressor (1), a low-pressure stage variable frequency motor (2), a plate shell type heat exchanger (3), a high-pressure stage compressor (4), a high-pressure liquid storage (5), an evaporative condenser (6), a high-pressure stage power frequency motor (7), an oil separator (8), a thermosiphon oil cooler (9), an oil pump (10), a refined oil filter (11), a brine pump (12), a brine tank (14), a thermosiphon evaporator (15), a throttle valve (16) and a control console (17); The low-pressure stage compressor (1) and the high-pressure stage compressor (4) are both open screw compressors, and the low-pressure stage compressor (1) adopts a non-energy slide valve mechanism or a compressor always in a full-load state; The low-pressure-stage compressor (1) is driven to operate by a low-pressure-stage variable-frequency motor (2), the high-pressure-stage compressor (4) is driven to operate by a high-pressure-stage power-frequency motor (7), the exhaust end of the low-pressure-stage compressor (1) is connected with the air suction end of the high-pressure-stage compressor (4), the high-pressure-stage compressor (4) is connected with the inlet of an oil separator (8), the exhaust end of the oil separator (8) is connected with the inlet of an evaporative condenser (6), the refrigerant output end of the evaporative condenser (6) is connected with the inlet of a high-pressure liquid reservoir (5), the refrigerant in the high-pressure liquid reservoir (5) is connected with the input end of a thermosiphon evaporator (15) sequentially through a plate-shell heat exchanger (3) and a throttle valve (16), and the output end of the thermosiphon evaporator (15) is connected with the air suction port of the low-pressure-stage compressor (1); The lubricating oil outlet of the oil separator (8) is connected with the oil inlet of the thermosiphon oil cooler (9), and the oil outlet of the thermosiphon oil cooler (9) is connected with the oil injection ports of the low-pressure stage compressor (1) and the high-pressure stage compressor (4) sequentially through an oil pump (10) and an oil fine filter (11); An inlet of the brine pump (12) is connected with a secondary refrigerant outlet of the thermosiphon evaporator (15), and an outlet of the brine pump (12) sequentially passes through the brine pond (14) and the stratum (13) and is connected with a secondary refrigerant inlet of the thermosiphon evaporator (15); When the variable frequency operation is performed, the high-voltage power frequency motor (7) is started, the high-voltage level compressor (4) is driven to operate by the high-voltage level coupler, the high-voltage level compressor is gradually and automatically loaded to 100% full load through the energy regulating slide valve, after the starting condition of the low-voltage level compressor (1) is met, the low-voltage level variable frequency motor (2) is started in a variable frequency mode, the low-voltage level compressor (1) is driven to operate by the low-voltage level coupler, and then a liquid supply valve of the plate shell type heat exchanger (3) is opened, so that the secondary supercooling of the refrigerant from the high-voltage liquid reservoir (5) is realized; The plate-shell type heat exchanger (3) is integrated by an economizer and an intercooler, and heat exchange cores of the economizer and the intercooler are integrated in the same shell, wherein the plate-shell type heat exchanger (3) is provided with a liquid supply valve which is opened immediately after the low-pressure stage compressor (1) is started, so that the refrigerant from the high-pressure liquid reservoir (5) firstly passes through the plate-shell type heat exchanger (3) to be supercooled, and then enters the throttle valve (16) to be secondarily expanded; The working frequency of the low-voltage-stage variable-frequency motor (2) is automatically adjusted in a segmented mode according to the evaporation temperature change of the thermosiphon evaporator (15) during the running period of the unit, when the evaporation temperature is reduced, the frequency of the low-voltage-stage variable-frequency motor is reduced to 40-45Hz to adapt to a partial load state, and then the frequency is gradually increased to be not more than 60Hz.
2. The double-machine double-stage screw type refrigeration compressor unit special for stratum freezing according to claim 1 is characterized in that in refrigeration cycle, low-pressure refrigerant steam generated by a thermosiphon evaporator (15) is sucked and compressed by a low-pressure stage compressor (1) and then enters a high-pressure stage compressor (4) for secondary compression, compressed high-pressure refrigerant gas is deoiled by an oil separator (8) and then flows into an evaporative condenser (6) to be condensed into liquid under the action of cooling water, the condensed high-pressure refrigerant sequentially flows through a plate-shell type heat exchanger (3) for secondary supercooling, the refrigerant throttled and depressurized by a throttle valve (16) enters the thermosiphon evaporator (15) for heat absorption and evaporation, and the generated low-pressure steam returns to the low-pressure stage compressor (1) to complete refrigeration cycle.
3. The double-machine double-stage screw type refrigeration compressor unit special for stratum freezing according to claim 1 or 2 is characterized in that lubricating oil separated by the oil separator (8) enters a unit lubricating oil path, is conveyed by the oil pump (10) and flows through the thermosiphon oil cooler (9) to be cooled, then flows back to the low-pressure stage compressor (1) and the high-pressure stage compressor (4) to be lubricated after passing through the olein filter (11), and the olein filter (11) adopts a double-parallel structure, wherein when one olein filter works, the other is in a standby state and is used for replacing a filter element under the condition of no shutdown.
4. The double-machine double-stage screw type refrigeration compressor unit special for stratum freezing according to claim 1 or 2, wherein on the side of the secondary refrigerant, brine enters a brine pond (14) after exchanging heat with the refrigerant in a thermosiphon evaporator (15), is pumped into a mine digging hole and a pipeline beside the stratum (13) through a brine pump (12) to absorb heat of soil, and returns to the thermosiphon evaporator (15) to release heat to complete circulation.
5. The double-machine double-stage screw type refrigeration compressor unit special for stratum freezing according to claim 1 or 2 is characterized in that the low-pressure stage compressor (1) and the low-pressure stage variable frequency motor (2) are arranged on the top of a thermosiphon oil cooler (9), the high-pressure stage compressor (4) and the high-pressure stage power frequency motor (7) are arranged on a common base, the plate shell type heat exchanger (3) is arranged on the base behind the low-pressure stage compressor (1) in the form of an integrated module, and the control console (17) is arranged behind the high-pressure stage power frequency motor (7) and connected with a power cable.
6. The double-machine double-stage screw type refrigeration compressor unit special for stratum freezing according to claim 1 or 2 is characterized in that the low-voltage-stage variable-frequency motor (2) is a 20-60Hz variable-frequency motor, and the high-voltage-stage power frequency motor (7) is a motor with rated frequency of 50Hz and is used for driving the high-voltage-stage compressor (4) to run at full load under a high-temperature working condition.

Description

Double-machine double-stage screw type refrigeration compressor unit special for stratum freezing Technical Field The invention relates to the technical field of refrigeration compressor sets, in particular to a double-machine and double-stage screw type refrigeration compressor set special for stratum freezing. Background The artificial freezing method is a cooling technology for realizing stratum freezing through a refrigerant heat transfer process, after the saline solution is cooled by a refrigerator, the saline solution is used as a secondary refrigerant to circulate in a freezing pipe buried in rock soil, the low-temperature saline solution exchanges heat with the rock soil body, the heat of the rock soil is absorbed, the sensible heat of the rock soil is increased, most of water in the surrounding rock soil body is made into ice, and therefore the strength and stability of the rock soil body are effectively enhanced, deformation is reduced, underground water is isolated, and shaft digging and construction are carried out under the protection of a freezing wall until the shaft construction of a freezing section is completed. The refrigeration compressor selected in the cooling technology is a double-machine double-stage screw type refrigeration compressor unit, the refrigeration cycle of the unit is an improved two-stage compression one-stage throttling intermediate incomplete cooling cycle, two-stage supercooling is adopted, and the cooling technology has the characteristics of compact structure, low cost, small occupied area, simplicity and convenience in operation, simplicity in system, high refrigeration efficiency, large coverage range of the refrigeration capacity of a low-temperature system and the like. The freezing of the artificial stratum can be divided into three stages of high temperature, medium temperature and low temperature, in which, in the high temperature stage, single stage compression is generally used, the evaporating temperature of this stage is 10 ℃ to-10 ℃, the salt water is reduced from 25 ℃ to-5 ℃ at normal temperature for about 10 to 20 days, the evaporating temperature of the medium temperature stage is-10 ℃ to-30 ℃, the evaporating temperature of the salt water is-5 ℃ to-25 ℃ for about 10 to 20 days, the evaporating temperature of the low temperature stage is-30 ℃ to-45 ℃, and the evaporating temperature of the salt water is-25 ℃ to-40 ℃ for about 90 percent of the total time. According to the difference of well depth, from the excavation to the preset depth, more than 1 year is needed, the refrigerator continuously runs in the whole process, the running cost is more than 60% of the total engineering cost, the photoelectric cost is up to tens of millions, so that the energy saving of the refrigerator set is extremely important, and huge cost can be saved for engineering. The existing conventional two-stage compressor unit faces the following problems: the evaporation temperature and load are continuously changed in the whole stratum freezing process, when the evaporation temperature is lower, the unit is more energy-saving, but the volume ratio of the high-pressure level compressor and the low-pressure level compressor of the conventional double-machine double-stage unit is certain, and the energy efficiency is lower due to the fact that the volume ratio of the high-pressure level compressor and the low-pressure level compressor cannot be changed along with different working conditions; And (II) the higher refrigerating capacity is needed for rapid cooling in the freezing medium-temperature stage, because the temperature point is broken through for a longer time, but the cooling speed is increased once the point is broken through. In this case, the economizer needs to be started to provide higher refrigerating capacity, but in the middle temperature stage, the low-pressure stage compressor can only be loaded at partial load through the energy slide valve, and a leakage channel exists between the energy slide valve and the machine body of the low-pressure stage compressor at partial load, so that the economizer cannot be started. On the other hand, the low-pressure stage compressor has longer partial load operation time in the freezing process, but the motor still operates at full speed, so that energy waste is caused; (III) in the freezing low-temperature stage, as the pressure ratio of the low-pressure stage compressor is continuously increased, the exhaust gas quantity is greatly reduced, the shaft power is also reduced, the shaft power required by the full load of the compressor is lower than 50% of the capacity of the motor, the stage accounts for 90% of the total running time, and the motor is low in low-load running efficiency and poor in power factor for a long time and possibly penalized by a power supply department; and (IV) after one project is finished, the equipment for freezing the artificial stratum is moved to another mine reconstruction system. The conven