What is the difference between centrifugal compressor and screw compressor

What is the difference between centrifugal compressor and screw compressor? In the field of industrial power, centrifugal compressor and screw compressor are two mainstream compression equipment. Although they are all used to increase gas pressure, they are completely different from the core principle to the applicable scenarios. Understanding their differences is the key to efficient and economical equipment selection.
Difference between centrifugal compressor and screw compressor
I. Core principles
Working principle of centrifugal compressor: the motor drives the impeller to rotate at high speed, and the inhaled gas gains kinetic energy between the blades and is thrown to the outer edge of the impeller at high speed. Subsequently, the gas enters the “diffuser” with gradually expanding cross section, the speed is reduced, and the kinetic energy is converted into pressure energy according to Bernoulli principle, thus realizing pressurization. The whole process is continuous and non-contact, and the gas does not mesh with any parts.
Working principle of screw compressor: in the casing, a pair of female and male rotors (screws) rotate in opposite directions with a very small gap. With the meshing and separation of the rotor cogging, the closed volume of the inlet end moves to the exhaust end along the axial direction, and the volume decreases continuously, thus realizing the extrusion and compression of gas.
Second, the key performance parameters comparison
Centrifugal compressor and screw compressor are obviously different in core performance parameters such as pressure output, flow range and operation stability, which is the core basis for selection.
1. Pressure range: screw compressor is more suitable for medium and low pressure, and centrifugal compressor is good at gas transportation in high pressure scenes such as large chemical plants.
2. Flow output: centrifugal compressor is biased towards large flow, and screw compressor is adapted to medium and small flow. The throughput of centrifugal compressor is usually above 20m3/min, which is suitable for large-scale gas treatment scenes, such as large-scale air separation, wind tunnel experiment, air energy storage, etc. The flow rate of screw compressor is very small, which is suitable for compressed air supply in small factories.
3. Operation stability: When the centrifugal compressor runs under the design working condition, it has small vibration, low noise and excellent stability, but it needs to be equipped with anti-surge system; The start-stop operation of screw compressor is simple, but the maintenance is frequent.
Third, the application scenario
Application scenarios of centrifugal compressor;
1. Ultra-large flow, continuous and stable working conditions: such as process air/synthesis gas compression in large petrochemical and coal chemical industries, pressurization in large air separation units (oxygen and nitrogen) and long-distance natural gas pipelines.
2. Strict requirements for gas purity: such as oil-free process air in electronics, food and medicine industries.
3. Long-term full-load operation: it can always run near the designed high-efficiency point and give full play to its high-efficiency advantages.
Application scenarios of screw compressor;
1. Small and medium flow, variable pressure demand: such as general power air in factories, mining and construction sites.
2. Intermittent operation or large load fluctuation: because of its strong adaptability to load changes and no surge risk.
3. The gas is allowed to contain oil or the medium is special: the oil injection screw is widely used for refrigeration and compressed air; Oil-free screw is used for waste water treatment blast, biogas pressurization, etc.
4. Small and medium-sized projects with limited initial budget and high maintenance convenience requirements.
Four, the key considerations of type selection decision.
In the face of specific projects, it is suggested to follow the following decision-making path to choose which compressor:
1. Determine the core parameters: define the required flow range, intake/exhaust pressure, gas medium and purity requirements.
2. Evaluate the operation mode: is it full load continuously for 24 hours, or is it frequently started and stopped with large load fluctuation?
3. Conduct life cycle cost analysis: not only compare the initial purchase cost, but also calculate the long-term power consumption (energy efficiency), maintenance costs and possible downtime losses. For large-flow continuous operation, the high initial investment of centrifuge is often offset by its long-term excellent energy efficiency.
“The difference between centrifugal compressor and screw compressor” is introduced to you here. When selecting the type, enterprises need to abandon the misunderstanding of “blindly pursuing high performance”, and focus on their own pressure and flow demand, combined with the comprehensive judgment of operating scale, cost budget, media characteristics and other factors, in order to choose the compression equipment that meets the production needs.