745results about How to "Less one-time investment" patented technology

The invention discloses a group technology for heavy oil upgrading, in which the job steps include: (1) full or moiety of heavy oil individually or mixed with catalytic clarified oil entering solvent deasphalting plant, after the solvent deasphalting treatment, obtaining a deasphalted oil and a degreasing asphalt; (2) the degreasing asphalt obtained by step (1) individually or mixed with another moiety of heavy oil entering coking plant for coking treatment, in which the obtained tar heavy oil returns to solvent deasphalting plant or enters heavy oil hydrotreating plant, or moiety of tar heavy oil returns to solvent deasphalting plant and another moiety of tar heavy oil enters heavy oil hydrotreating plant, catalytic plant or hydrocracking plant; (3) the deasphalted oil obtained by step (1) individually or mixed with vacuum residual oil, non-pressure residual oil, pressure-relief residual oil, catalytic cycle stock and one or more than one heavy oil of tar heavy oil obtained by step (2) entering heavy oil hydrotreating plant for hydrotreatment, after hydrotreatment, obtaining fractions of benzin naphtha, plane kerosene and diesel and hydrogenating heavy oil. The invention can improve the charge-in nature, alleviate the operating condition and prolong the cycle length of the heavy oil hydrotreating plant, which provides better raw oil for downstream plants including catalytic plant.

The invention discloses a comprehensive treating system for domestic wastes. Reutilizing comprehensive treatment for mixed wastes is realized by the system according to a comprehensive sorting technology and a combined anaerobic fermentation technology, wherein the advanced sorting techniques, such as, crushing, magnetic separating, sieving, air classifying, and the like, are adopted in the comprehensive sorting technology; reutilized products, such as metal, plastics, organic matters, and the like, are screened out; the screened organic matters are prepared into slurry together with sludge and excrements and are then subjected to the combined anaerobic fermentation; the reutilized products, such as methane, organic fertilizer, and the like, can be produced under the action of anaerobic fermentation; and after the methane is purified, the methane is used for generating power, domestic fuel or vehicle-mounted fuel. According to the technology, the intensified treatment for organic wastes, such as domestic wastes, sludge, excrements, kitchen wastes, and the like, can be realized. The comprehensive treating system is high in mechanical and automated degree. Compared with the prior art, the comprehensive treating system has the advantages of simplification, effectiveness, less labor power, and the like.

The invention provides a construction method for a soft rock deformation tunnel lining support dismantling-replacing arch. One-time whole section integral dismantling and replacing of a lining support is achieved. The construction method has the advantages that before dismantling and replacing, a lining which loses bearing capacity is subjected to grouting reinforcement treatment first, then a temporary cover arch is additionally arranged outside for reinforcement, and afterwards, the lining support is dismantled step by step, so that potential safety hazards caused by dismantling or removing of a temporary platform frame are avoided, and some security risks are avoided effectively. According to the construction method, the construction difficult problem of soft rock large deformation occurs during construction of a tunnel in special and complex geology is solved. Through the created novel construction method, the construction difficult problem of second lining cracking deformation needing remediation due to weak surrounding rock large deformation is solved. Through the construction method, safe, fast and economic treatment and remediation of the lining support and arch replacing construction are achieved, and the tunnel structure stability and construction safety are ensured effectively.

The invention discloses a large cross-section weak surrounding rock tunnel three-step and six-part short-distance construction method, which comprises the steps as follows: (1) annularly excavating an upper step of an upper part arc pilot tunnel, transferring excavated earthwork of the upper step to a lower step; (2) excavating a left part of a middle step about 4.5-5 meters behind the upper step, and transferring excavated earthwork to the lower step; (3) excavating a right part of the middle step about 3-4 meters behind the left part of the middle step, and transferring excavated earthwork to the lower step;(4) excavating a left part of the lower step about 6-8 meters behind the left part of the middle step or about 3-4 meters behind the right part of the middle step, and conveying excavated earthwork of the left part of the lower step out of the tunnel; (5) excavating a right part of the lower step about 3-4 meters behind the left part of the lower step, and conveying excavated earthwork of the lower step out of the tunnel; and (6) excavating the rest part of the tunnel bottom about 20-25 meters behind the right part of the lower step, excavating continuously according to the steps in a circulating and interlacing manner, and finally realizing tunnel excavating construction. The method can be used for building a large cross-section tunnel in a safe, rapid and economic manner.

The present invention is former hot blast and latter vacuum microwave combining drying process of producing fruit and vegetable grains, and belongs to the field of fruit and vegetable food processing technology. The drying process includes the steps of: washing fruit and vegetable material, dicing, scalding to killing enzyme, cooling in flow water, draining, optional fast freezing and defrosting, soaking with seasoning, draining, pre-dewatering with hot blast to obtain semi-finished product with water content of 40-60 %, and final vacuum microwave drying to obtain product with water content of 2-5 %. The said process has the nutritious components and color well maintained, crisp product, short production period, low cost, high product quality and other features.

The invention discloses a spatial soilless vegetable planting method. The method is characterized by comprising the following steps: a. selecting two or more raw substrate materials such as biogas residue, furnace slag, grass carbon, decomposed fermentative crushed crop straw, decomposed fermentative crushed wood shavings, decomposed fermentative sawdust, decomposed fermentative lees and decomposed fermentative spent mushroom, and mixing the selected raw substrate materials to prepare a culture substrate; b. erecting a spatial cultivation groove in the existing facility space; c. installing a drip irrigation system, d. planting vegetable crops on a suitable upper layer and a suitable lower layer of the cultivation groove; and e. cultivation management. In the method, the vegetable cultivation is realized by carrying the culture substrate in a certain frame groove to artificially make an 'artificial land' in the limited facility space, the soilless vegetable cultivation is convenient as land cultivation and needs no nutrient solution, and the organic substrate and solid fertilizers provide nutrients necessary for growth and development of the vegetables, which can be accepted by vegetable growers, can improve utilization ratio of the facility by 50-200%, reduce cost by 30-60% and increase yield by 50-100%.

The invention discloses a distributed type power supply zone branch circuit three-phase load current balance monitoring method and device and belongs to the field of power supply and distribution devices. At least one three-phase load current balance main controller is arranged, load current signals of each phase circuit in each branch loop are collected, according to the obtained load current signals of each phase circuit, the three-phase current unbalance rate or the mean value of the three-phase current unbalance rate of each branch loop is computed, and the unbalance situation of three-phase load current of each branch loop is judged. The magnitude of load current in each unit meter box of each branch loop is collected, and the phase of unit meter box load which needs to be adjusted is determined. According to the three-phase load current unbalance situation of a certain branch, a control instruction is issued to an automatic phase-changing switch in a unit meter box corresponding to the branch loop, converting of load phases is carried out, adjusting of three-phase load current balance of each branch loop on the low-voltage side of a distribution transformer is achieved, and the real balance of distribution transformer low-voltage side main loop three-phase load current is guaranteed.

The invention relates to a deep treatment process of oily wastewater, which is characterized in that an absorption system and a regeneration system are provided in the process, wherein the absorption system is formed by a series of absorption tower groups with columns in series used for realizing parallel operation, the absorption tower groups are used for alternately performing deep treatment on oily yielding water with a low concentration of 30-50 mg / L of a traditional process, the absorption operation is carried out at normal temperature, the oil content in the yielding water is controlled to be lower than 1 mg / L through the treatment of a group of the absorption towers with columns in series, and an absorbing agent is made of modified fly ash, activated carbon and an expanded graphite absorbing material; when the yielding water in a group of the absorption towers exceeds a treatment requirement, the group of the absorption towers is switched to a biological regeneration system, and other absorption tower groups are simultaneously switched to the absorption system for continuous absorption; and saturated absorption towers are used for performing in-situ regeneration on the saturated absorbing agent by utilizing degradation ability of high temperature-resistant and efficient petroleum hydrocarbon for degrading bacteria.

A preparing method for a crystallite wear-resistant ceramic ball belongs to a technical field of abrasive media, which is characterized in that: firstly preparing a superfine material adopting wet ball milling, spraying and prilling; then rolling moulding; finally the crystallite wear-resistant ceramic ball with a diameter of 0.5-50mm after drying, firing and polishing. The inventive method has lots of advantages such as little equipment, low cost, large output and easy expansion; meanwhile, the ceramic ball is high-density, wear-resistant and stable.

The invention discloses a single-phase and three-phase combined in-phase power supply and transformation device which comprises a single-phase traction transformer, a three-phase YNd11 grounding compensation transformer and a single-phase in-phase compensation device thereof; the in-phase compensation device comprises an alternating current-direct current-alternating current (AC-DC-AC) converter; the traction transformer and the compensation transformer have equal effect to a three-phase and two-phase balance transformer with the phase of secondary side voltage being vertical; when in a normal state, the traction transformer, the compensation transformer and the in-phase compensation device jointly supply power for a transaction load by a specified proportion; when the compensation transformer or the in-phase compensation device exit the operation, the traction transformer can work independently in a short time; and a backup traction transformer can replace the traction transformer to work and can work on linear voltage different from that of the traction transformer. According to the device, the electric phase at the exit of a traction transformer substation can be canceled, so that the electric energy quality requirements mainly comprising the unbalance of three-phase voltage can be met, and the optimal configuration of traction power supply resources can be realized.

The invention discloses a construction method of a circular reinforced concrete chimney cylinder wall, and a hydraulic sliding mould device, wherein a hydraulic sliding mould construction method is a rapid construction method of dynamically and continuously molding concrete; loads such as an operation platform and a template are completely supported on a support rod which is stabilized by low-age concrete and has small rigidity; the operation platform and the template are driven to climb along the cylinder wall by a hydraulic jack; and the hydraulic jack climbs on the support rod by an oil path system. The hydraulic sliding mould construction employing the sliding mould as an external cylinder wall and building a lining adopts an ''outside sliding and inside building'' construction process featured by synchronously constructing the external cylinder wall and the lining. The hydraulic sliding mould construction is featured by dynamic continuous construction, having fast construction speed in comparison with mould reverse, symmetrically distributing the hydraulic jack on the circumference of the chimney cylinder wall, forming the template by combining a fixed template with a moveable plate and a contracting and separating template, convenient to assemble and dismount as well as regulate the diameter and the circumference of the combined template structure, capable of gradually decreasing the diameter and the circumference of the combined template structure along with the diameter change of the chimney diameter. The hydraulic sliding mould construction is advantaged in few invested construction operators and convenient management.

The invention relates to a technology for deeply processing coking wastewater through combining catalytic oxidation method and membrane separation technique. Preprocessed coking wastewater is processed through pretreatment, A / O biochemical treatment, catalytic oxidation, coagulating sedimentation, ultrafiltration and reverse osmosis treatment. The invention has the advantages that the technology can greatly reduce the amount of COD, suspended substance and pollutant and the like, and has the advantages of low investment once, stable treatment effect and high water yield. Water from catalytic oxidation is separated through a coagulative precipitation tank, and clean water can be used for production, daily use or slag washing in iron works. Water from reverse osmosis can be directly reused as make-up water in water circulating systems, thereby realizing reutilization of water sources and zero discharge of coking wastewater. The technology has remarkable social benefits.

The invention relates to a membrane treatment process for oilfield reinjection water, which comprises the specific steps of: firstly introducing oil-containing wastewater into a settling tank for naturally settling to remove part of large suspended solid granules and waste oil; directly introducing the settled water into a ceramic membrane ultrafiltration device for internal circulating filtration, directly using the liquid penetrating through the membrane for reinjection, introducing the circulating liquid containing large amounts of suspended solid granules and waste oil which do not penetrate through the membrane into the settling tank for continuing settlement, mixing with inflow water and introducing into the ceramic membrane ultrafiltration device for filtration again; automatically discharging pollutants when the wastewater in a circulation tank reaches a certain concentration ratio; and automatically adjusting the membrane surface flow rate of an online detection device according to the inflow water quality conditions, so as to achieve the purpose of energy conservation. The membrane treatment process provided by the invention has the advantages of simple process, low investment cost, high filtering precision, no need for the introduction of any reagents during the treatment process, no secondary pollution, etc.

This invention discloses a vacuum deep well water-lowering device including a vacuum pump, a deep wall filter pipe, a pipe cover, a vacuum total main, a vacuum branch water pipe and a discharging pipe, in which, the filter pipe cover is set at the top of a filter pipe and connected with it in seal, the body of the filter pipe is distributed uniformly with many small holes, the discharging pipe and the water main are connected at both ends of the pump, the branch pipe and the main are connected and enter into the filter pipe via the cover set with small holes and the branch pipe is set with small holes.

The invention relates to a method for removing aldehydes in an epoxypropane reaction mixture. The method comprises carrying out primary aldehyde removal on an epoxypropane reaction mixture through an aldehyde-free resin tank so that aldehyde content is reduced and epoxypropane product purity is guaranteed, orderly removing water and unreacted propylene, feeding the materials containing epoxypropane and methanol into an epoxypropane refining tower, carrying out extraction on methanol in the middle section of the tower through desalinized water containing ethanolamine or hydrazine hydrate, simultaneously removing residual aldehyde in the epoxypropane product, separating the separated aqueous solution through a methanol tower, feeding the aqueous solution into a membrane separation device, further removing residual aldehydes and impurities, returning the methanol as circulation methanol at a penetration side to a reaction system and returning aldehyde-containing methanol at a retentate side to a collection tank. The method utilizes less devices, reduces a disposable investment, does not need hydrogen in a separation and recovery process, does not increase a safety risk, is safe and reliable in use and reduces later waste water treatment energy consumption.

An ecological fish-culturing system by use of the water drained from factory features that the reverse filter is used for the deposition pool to remove solid substance, the natural ore is used as the adsorbing, filtering and bio-membrane-attaching material, the novel artificial nunja and the appreciative plant growing in said nunja are used to degrade NH4, Cl and nitrate, the microbes are inoculated for biochemical reaction, and the resultant water is aerated for enriching oxygen gas.

An organic environment-protecting soilless culture novel method comprises the following content: in certain protection facilities, to build planting groove and drip irrigation facilities, then to add the medium by high temperature fermentation into 25 percent solid organic fertilizer mixing fully and filling in the groove, and to increase fertilizer and water control management of planting crops. The present invention is based on our soilless culture practical experience, after numerous exploration and improvement, selected an organic new environment-protecting soilless cultivation method. The method utilizes cotton seed hulls, barks, sawdusts, parings, sunflower stalks, corn stalks, sands, slags, pot ales and mushroom residus cheapness material as culture medium, utilizes getting easily organic fertilizer and inorganic fertilizer as fertilizer, it not only has traditional soilless culture features, but also lump sum investment of soilless culture system decreases 60 percent compared with nutrient solution in soilless culture, fertilizer cost decreases 60 percent, yield improves 10 percent to 20 percent, and its operating management is simple, discharging liquid of this system is no pollution, and the product quality is good.

The invention relates to a method for recycling carrene of waste gas, wherein the invention uses condense-adsorption method to recycle the carrene of organic waste gas; uses water as cooling medium to condense the waste gas; then uses dimethyl formamide in the stuff adsorption tower as absorber to absorb the carrene; the absorber is analyzed in passive pressure in degrade vaporizer, to regenerate the absorber and form loop-close circulation. The invention has low cost and high efficiency.

The invention relates to an oil-containing sludge pyrolysis and its resource treatment method, and belongs to the field of environmental protection and energy saving technologies. The oil-containing sludge pyrolysis and its resource treatment method comprises the following steps of: adding a gangue powder and Fe3O4 into an oil-containing sludge; respectively carrying out mixing, granulation, preheated drying (using a pyrolysis gas as a heat source) and pyrolysis on the mixture; cooling the pyrolysis gas discharged out from a pre-drier by the use of circulating water such that steam and hydrocarbons in the pyrolysis gas are condensed respectively in the forms of oil-containing sewage and liquid hydrocarbon; allowing the oil-containing sewage to enter a sewage treatment plant so as to reach the standard, recovering and utilizing liquid hydrocarbon, and activating sludge to prepare a magnetic carbonaceous adsorbent. According to the invention, resource of the oil-containing sludge can be completely realized, and the carbonaceous adsorbent with large pore volume and specific surface area can be prepared. The invention is especially suitable for pyrolysis treatment of oil-containing sludge (such as oil tank bottom mud, oil-field oil extraction sludge, tank car or oil tanker bottom mud and the like) with high oil content.

The invention relates to a method for producing AZ31 magnesium alloy sheet, at 300MPa level and isotropic property, wherein the invention uses magnesium alloy electromagnetic low-temperature semi-casting method to produce blank to be uniformly annealed, milled and compressed at 200-400Deg. C into sheet band, while the compress ratio is 8-15 and the thickness of compressed sheet is 5-20mm; then cutting the compressed sheet into the sheets whose width is 10-30mm, to be heated to 300-400Deg. C; then preheating the roller of rolling machine, vertically to the former extrusion direction, to obtain the sheet whose width is not higher than 500mm and thickness is 0.3-1.0mm; via combining the extruding temperature and rolling temperature, obtaining the sheet with high plasticity or high strength; then cutting edge, coating protective film and packing. The invention has simple process, low cost, and high property, while the anti-drawing strength is 300MPa level.

The invention relates to a liquid electrode surface discharge plasma reactor which is used for water treatment and consists of a flume, a discharge electrode system and a wastewater region, wherein, the discharge electrode system is positioned at the center of the flume, wastewater exists around the insulating medium tube of the discharge electrode system, the discharge electrode system is connected with the high pressure terminal of an alternating current high voltage source, the wastewater is taken as the liquid electrode which is connected with the low pressure terminal of the alternating current high voltage source, or the liquid electrode and the low pressure terminal of the alternating current high voltage source are simultaneously connected with ground wires, and aeration gas enters from the upper end of the insulating medium tube of the discharge electrode system, is ejected out from an aeration head at the lower end and then flows into the wastewater. When electricity is supplied by power, surface discharge plasma is produced on the inner wall of the medium tube, active materials are generated when the aeration gas passes through, and the active materials degrade pollutants in water and then treat the water. The liquid electrode surface discharge plasma reactor has the advantages of simple structure, high water treatment effect, low initial investment and small operation cost.

The invention discloses an active organic bacterial fertilizer and a preparation method of the active organic bacterial fertilizer. The active organic bacterial fertilizer takes plant ash, industrial and agricultural wastes containing organic matters, and an inorganic fertilizer as raw materials, and is prepared by once continuously fermenting, pelletizing, drying and screening bacterial strains bred from the raw materials. The preparation method of the active organic bacterial fertilizer can consume a large amount of wasted industrial and agricultural wastes containing the organic matters, reduce the environmental pollution, and also solve the problems of soil hardening, fertilizer efficiency reduction and environmental pollution caused by long-term fertilizer application in the crops cultivation and urban landscaping processes. The preparation method of the active organic bacterial fertilizer can provide the novel fertilizer source for the agricultural production.

The invention discloses a construction method for one-time formation of a concrete pool wall. The method includes the steps of erection of a pool wall reinforced frame, mounting of pool wall forms, mounting of a support system, and casting of the concrete pool wall. The method has the advantages that the problems of large pool wall height and large form side pressure are solved by the use of the solid side forms and a reinforcing support system; the pool wall forms are erected to the top once, and the appearance quality of the pool wall is easily guaranteed; pool concrete is cast once, structure integrity is good, and the potential water leakage problem of the pool wall caused by reservation of multiple horizontal construction joints; construction process is greatly quickened, construction period is shortened, labor cost and materials cost are saved, and engineering cost is lowered; the method is especially applicable to construction of concrete pool walls 9m in height and 300mm-1100mm in thickness.

The invention discloses a system for remotely monitoring and controlling an internet of things on the basis of a GPRS (General Packet Radio Service) network, relating to a monitoring system. A center server with coexistence of two modes such as B / S and C / S is adopted for carrying out data conversion with monitoring terminal equipment and a monitoring center client side by a TCP / IP (Transmission Control Protocol / Internet Protocol) mode so as to realize distributed remote monitoring and controlling. In the system, the operation does not need to create a local area network by self, so that the network creating cost is saved and the reliability is high; and the equipment is general and simple, the cost is low, the one-time investment is less, the use cost is low, the installation and maintenance are convenient, and the operation is safe, no limitation can be caused by the terrain, the landform and the environment, and even no pollution can be caused. The system can be widely applicable to streetlamps, railways, gas, running water, power, environment, petroleum and machines and the like. The system has the advantages of high network access speed, advanced technology, safety, reliability, economy, reasonability, energy conservation, simpleness and convenience in maintenance and strong practicability, and conforms to the trend for development of the conservation-minded society.

The invention provides a technology for treating dilute emulsified oiliness wastewater comprising the steps of uniform aeration adjustment, one-stage pH regulation, two-stage pH regulation, coagulation, air floatation, cooling, biological contact oxidation, flocculation deposition, part sludge reflux, after the above steps, the effluent reaches the discharge standard or the recycling standard. The technology of the invention effectively overcomes the problems of weak safety, high requirement for operation running and daily management and secondary pollution and the like, furthermore has the advantages of low once investment, stable treatment effect, low production operation running cost and simple operation running.

The invention relates to a continued ironmaking device based on melting reduction of iron oxide containing carbon iron oxide balling (blocks). In the invention, the device is a continued ironmaking device based on melting reduction and can carry out continual tapping by pre-reducing furnace burden (3) through continually adding the furnace burden (3), extracting air, preheating, blasting and carrying out downstream roasting, and directly conveying the pre-reduced furnace burden (3) into a smelting-separating furnace (B) for continuous smelting-separation; a preheat area (4), a roasting area (5) and the smelting-separation areas behind the preheat area and the roasting area form a connected hearth; a combustion-supporting burner (8) and a secondary tuyere (7) are arranged also; preferably, the high-temperature coat gas generated in the smelting-separation area is subjected to secondary combustion in a pre-reduced furnace (A) for preheating and roasting the furnace burden (3); then the furnace burden (3) is discharged into the smelting-separation area for the further reduction, carburization and melting to separate the slag and iron; in the preheated area (4), the fuse passes through a bed of material to directly heat the furnace burden (3), and then the fuse enters a heat exchanging device (9) and a fuse process system; and a fan blasts the cool air below the bed into a hearth bottom (2) through the heat exchange device (9). The device has the advantages of short flow, reduced energy consumption, low carbon emission, low production cost, simple equipment, less occupied space, less investment and short building period.

The invention relates to a method for cleaning mercury and nitrogen oxide in fire coal smoke gas, employing specific chemical matter as additive to be added into high-heat smoke gas in furnace, said chemical matter selectively reducing nitrogen oxide and oxiding mercury into bivalent mercury. Said chemical matter comprises compound containing ammonium and halogen atom absorption, and lower carbon number hydrocarbons containing halogen atom and it's derivant; it can be used separately or together with urea, ammonia gas and natural gas. The matter is degraded under high temperature, and then they can oxide mercury and selectively reduce nitrogen oxide into innocuous nitrogen; smoke gas is treated in desulfurization unit to absorb bivalent mercury and sulfur dioxide. The invention controls nitrogen oxide, mercury and sulfur dioxide in smoke gas without increasing main device and using no catalyst.

The invention relates to a method for preparing a microcrystal wear-resisting zirconia ball, and belongs to the technical field of grinding mediums. The method is characterized by comprising the following steps of: preparing superfine powder raw materials first by adopting wet-process ballmilling and spray granulation; rolling for forming; and drying, sintering and polishing to prepare a microcrystal wear-resisting ceramic ball with the grain diameter between 0.5 to 50 millimeters. The method has the advantages of less used equipment, small investment, high yield, easy production expansion and the like; moreover, the ceramic ball prepared by the method has the advantages of large density, wear resistance and stable performance.

The invention discloses a method for overlaying a wear-resistant layer of a blade shroud of a turbine working blade. In the method, manual tungsten electrode argon arc welding is used, and the specific process parameters meet the requirements that: welding wires are selected from a T800 cobalt-based wear-resistant alloy welding wire which is researched according to a B50TF193 standard of AmericanGeneral Electric Company and an S-6 cobalt-based wear-resistant alloy welding wire which is researched according to an American metal society standard AMS5788; the diameters are phi 1.6mm and phi 1.2mm respectively; a mark and the diameter of a tungsten electrode are WCe20 and phi 2.0mm; the diameter of a nozzle is phi 12mm; welding current is between 20 and 25A; and the flow rate of protective gas is between 10L / min and 12L / min. By the method, the condition of incomplete penetration or over-melting of a Z-shaped gear switching part R is avoided, the problem of overheating of welding is also solved, and the occurrence probability of welding cracks is greatly reduced or avoided. The method completely meets the requirements of the wear-resistant layer in a high-temperature working state after welding.

The invention discloses a two-stage compression refrigerating system. The two-stage compression refrigerating system is easy for energy regulation and can realize switch between a high-pressure refrigerating compressor and a low-pressure refrigerating compressor so as to improve the efficiency of the refrigerating system. The air exhaust end of each refrigerating compressor is respectively connected with a first electromagnetic valve and a second electromagnetic valve, and the air suction end of each refrigerating compressor is respectively connected with a third electromagnetic valve and a fourth electromagnetic valve. After the parallel connection, all the first electromagnetic valves connected on the refrigerating compressors are connected with an inlet of a condenser. After the parallel connection, all the second electromagnetic valves connected on the refrigerating compressors are connected with an outlet at the shell side of an intercooler. After the parallel connection, all the third electromagnetic valves connected on the refrigerating compressors are connected with the outlet at the shell side of the intercooler. After the parallel connection, all the fourth electromagnetic valves connected on the refrigerating compressors are connected with an outlet of an evaporimeter. Through the opening or closing of the electromagnetic valves connected with the refrigerating compressors, the switch between the high-pressure stage and the low-pressure stage can be realized.