A Brief Discussion on the Selection and Application of Roots Blowers

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When selecting a three-blade Roots blower, it is first necessary to choose the model and material composition of the blower based on performance parameters, application purposes, process requirements, and operating environment, in order to meet the required working conditions. The goal is to ensure that the inlet flow rate and pressure rise of the blower are as close as possible to those specified by the process, so that the blower operates within its high-efficiency range. Otherwise, this can lead to accidents and waste of energy. The selection of a triple-lobe Roots blower should be determined based on the properties of the medium to be transported, as well as the flow rate and pressure required by the process. When determining these values, it is necessary to take into account the pressure losses caused by pipeline resistance and the flow rate losses resulting from system leaks. The selected three-lobe Roots blower should take into account the full utilization of existing equipment, as well as suitability for on-site fabrication and installation and safe operation. When selecting, specify the conveying medium, inlet gas conditions, inlet flow rate, exhaust pressure, and environmental conditions. Explain special usage requirements such as corrosion resistance, explosion protection, installation layout, sealing, adjustment, and control methods. Major domestic fan manufacturers have developed a series of three-blade Roots blowers: these blowers are characterized by their small size, light weight, low noise level, and stable and reliable operation. Selection and Application in the Powder Conveying Industry (1): Vertical Kiln Blowers: Cement raw materials are fed into the top of the vertical kiln, while combustion air is supplied from the bottom or lower side of the kiln; the material falls vertically inside the kiln due to its own weight. The baked clinker is discharged from the lower part of the kiln, while the exhaust gases are expelled from the upper part of the kiln. Similar applications include supplying air to small iron smelting furnaces and cupola furnaces. Common models: RZ-65, RZ-80, RZ-100, etc. (2) Pneumatic ash transport: The large amount of fly ash generated in coal-fired power plants is first collected in a ash hopper using electrostatic precipitators; thereafter, the ash is fed into the transmission pipeline, where compressed air generated by blowers is used to propel the ash into the ash storage tank in a fluidized state ； The performance parameters of the fan are: a pressure increase of around 68.6 kPa and a flow rate of 5–16 m3/min; it can also be used to absorb negative pressure at the end of the ash transport system, thereby drawing the coal ash from the pipes and causing it to fall into the ash storage tank. Common models: RZ-80, RZ-100, RZ-125, etc. (3) Polymer powder transportation: In polymer processing, nitrogen is commonly used to transport granular raw materials such as polyethylene and polypropylene powders; the use of nitrogen is intended to prevent explosions caused by contact between the polymer powders and air or flammable volatile substances. To reuse nitrogen, the transportation system is a closed loop, with the filtered gas being returned to the blower for reuse. Common models: RZ-65, RZ-80, RZ-100, RZ-125, etc. Selection and Application in the Vacuum Packaging Industry (1): Product blister packaging; the valve is opened, and the plastic sheet is drawn towards the vacuum at the top, causing it to soften due to heat; the valve is then closed, and the sheet drops down to cover the product and the cardboard base plate. The suction force in the lower vacuum chamber is used to extract the air from the sheet and the product through the small holes in the base plate. Once the sheet is firmly attached to the product, it is heat-sealed to the base plate. Common models: RZV-65, RZV-80, RZV-100, etc. (2) Plastic blister forming: First, the plastic sheet is heated to soften it, and then a vacuum pump is used to create a vacuum at the bottom of the mold (only the female mold), causing the softened sheet to take on the shape of the female mold and thus form a blister. Blister packaging is a method of enclosing products between a pre-formed blister and a base sheet, and it is commonly used for packaging tablets, food items, daily necessities, and toys. Common models: RZV-65, RZV-80, RZV-100, RZV-125, etc. (3) Vacuum packaging of food: The food is placed inside a flexible packaging bag; an air extraction port is provided at the opening of the bag, and negative pressure is used to remove the air from within the bag. The opening of the bag is then sealed using a heat sealer, completing the packaging process. By removing most of the air from the bag and controlling the moisture levels, this method is often used to prevent food from becoming damp, moldy, or oxidized. Common models: RZV-65, RZV-80, RZV-100, etc. Selection and application in the water treatment industry: Aeration of wastewater – The function of blowers is to provide sufficient dissolved oxygen for aerobic bacteria in the water, as well as to generate the energy needed to stir the mixture in the aeration tank ； It is commonly used for aeration treatment of industrial wastewater such as that from the papermaking, textile, printing and dyeing, electroplating, viscose fiber, petrochemical, food processing, and fermentation industries, as well as urban domestic sewage. When selecting a fan, the wind pressure depends on water depth, pipe resistance, and water viscosity, while the air volume depends on the volume of water. Common models include: RZ65, RZ-80, RZ-100, RZSW5022, RZSW6537, etc. Selection and application in the aquaculture industry: In large-scale fish and shrimp farms, blowers are used to inject air into the breeding ponds, thereby increasing the dissolved oxygen level in the water, accelerating the oxidation and decomposition of certain harmful substances, improving water quality, and promoting the growth of fish and shrimp. Similar devices are also used for oxygen supply and mixing in aquariums and live fish tanks. The air supply rate per minute for the water volume used in shrimp fry rearing should be at least 1.5% of the total water volume. The selection of pressure should be based on: ① water depth; ② length and diameter of the gas pipeline; ③ local losses due to bubbles. General conditions: The pressure rises to 19.6 kPa at a water depth of 1 m; ； When the water depth is 1~1.5m, the pressure is increased to 29.4kPa ； When it is over 1.5 m, the pressure is increased to 39.2 kPa or higher. Selection and Application in the Chemical Industry (1): Air supply for bubbling reactors: In the gas-solid two-phase contact involved in chemical reactions, solid particles are placed on a distribution plate; the air supplied by a blower is used to cause these particles to flow in a bubbling manner, thereby enabling them to come into full contact with other reactants or catalysts, which increases the speed and efficiency of the reaction ； Examples: Producing phthalic anhydride from naphthalene, producing sulfur dioxide by roasting pyrite, etc. Similar uses: Supplying air to combustion furnaces, etc. Common models: RZ-80, RZ-100, RZ-125, etc. (2) Ozone generation gas source: Inside the tubular ozone generator, there are dozens or even hundreds of identical discharge tubes. Each discharge tube consists of two concentric tubes – the outer tube being metal and the inner tube being glass (with a silver or graphite conductive layer coated on its inner wall). Oxygen or air supplied by a blower is used as the gas source for generating high-concentration ozone; as it passes through the discharge gap between the two tubes, part of it is converted into ozone. Common models: RZ-100, RZ-125, RZ-150, etc. (3) Air humidifier: Water is supplied to the center of the water dispersion disc, where it is scattered in all directions due to centrifugal force. The air expelled by the blower atomizes these water droplets, spreading the mist throughout various corners of the room. By adjusting the amount of mist generated, it is possible to control the humidity of the air. It is commonly used for humidifying environments in textile workshops, as well as for preventing static electricity in cigarette and printing factories. Common models: RZ-50, RZ-65, RZ-80, etc. (4) Pulp dewatering: A filter mesh is installed on the surface of the rotor, with multiple cavities arranged radially inside it; during operation, the mesh captures the pulp, and these cavities are connected in sequence to the vacuum pumping area and the blower pressure area through distribution valves. As the pulp passes through the pumping area, the waste liquid is separated from it, and once it reaches the pressure area, the pulp layer loosens and is eventually scraped off by a scraper. Common models include: RZ-80, RZ-100, RZ-125, RZ-150, etc. (5) Plating tank: To optimize the plating quality (uniform coating), gas is circulated within the electrolyte layer to move the electroplated parts around, and it is used as a gas source for this purpose. Due to the strict requirements regarding gas leaks in the chemical industry, stainless steel fans can be used when transporting highly corrosive gases such as nitric acid fumes, as they offer excellent sealing performance. Selection and application in other industries (1): Pressure transfer industry: Due to their pressure adaptability, three-blade Roots blowers are used in flour mills to transfer flour under pressure; once the flour is delivered to the silos, the pressure disappears. The selection of pressure is based on: ① pipeline length; ； ②Magnitude of resistance ； ③Material conveying ratio. The specific model is determined by the relevant design unit, generally: boost pressure of 49.0~78.4 kPa; flow rate of 2~45 m3/min. Similar uses: For pipeline cleaning, etc. (2) Urban gas pipeline industry: With the development of urban construction, gas pipelines are gradually being installed in households. Three-lobe Roots blowers, with their high pressure and excellent sealing properties, can meet the requirements of various applications. The typical performance parameters of fans used for transporting gas are: pressure of 68.6 kPa, and flow rates of 40, 60, and 80 m3/min. The available model options include RZW-65, RZW-80, RZW-100, RZ-80, RZ-100, etc. In the concluding section, taking into account the current status of three-lobe Roots blowers both domestically and internationally, the selection principles for new-type Roots blowers are presented, explanations on performance conversions for selection are provided, and classifications for selection and application in actual operating environments across various industries are given. It is of practical value for users and design firms to select the most ideal model specifications for three-lobe Roots blowers. To further address the issues of energy savings, reduced consumption, and operational safety in Roots blowers, a closed-loop control system for air pressure is implemented using variable frequency speed control and PLC devices, to meet the usage requirements to the greatest extent possible.