Desulfurization. The Roots blower is too noisy

This post was last edited by chen3jun on 2009-5-3 00:26. It is recommended that the original poster refer to the following papers； Discussion on Noise Reduction Measures for Roots Blowers (Click to enter) For blowers used in actual applications, different control measures can be adopted depending on the level of noise generated by the blower, the site conditions, and the noise reduction requirements. These measures generally include installing silencers, adding sound-insulating enclosures, modifying the blower room, or wrapping the pipes. 2.1 Mechanical noise control methods For the mechanical noise of Roots blowers, the main method of control is to improve the accuracy of assembly ； Replace the old ball bearings, or use sliding bearings in place of rolling bearings, to achieve dynamic balance of the rotor ； Connect the motor and blower with an elastic coupling ； Strengthen the maintenance of equipment, including refueling and lubrication, tightening connected bolts, replacing damaged components, and so on. These are effective against both weak and strong noises. 2.2 General methods for controlling aerodynamic noise 2.2.1 Installing silencers Since, under normal circumstances, the aerodynamic noise emitted from the fan’s intake and exhaust ports is 10–20 decibels(A) higher than the noise emitted from other parts, appropriate silencers should be installed on the intake and exhaust pipes in order to control the fan’s noise, as shown in Figure 3. Silencers are used on fans; currently, both domestically and internationally, resistive silencers are the preferred choice, while silencers that are large in size and have a narrow noise reduction range are rarely used. Of course, the selection, design, and installation of silencers should be based on actual conditions. 2.2.2 Installing a sound insulation enclosure: The measure of using a sound insulation enclosure involves enclosing the entire fan unit within a sealed acoustic enclosure. The key technical aspect lies in determining what cooling measures to use to ensure the proper operation of the fan. Currently, air cooling is the most common method used both domestically and internationally. The main cooling methods include: self-ventilated cooling, negative pressure suction cooling, air circulation ventilation cooling within a enclosure, and external mechanical ventilation cooling. The specific design principles, manufacturing methods, and details are described in the literature. 2.2.3 Renovating the fan room: If the fan unit has a dedicated fan room, it is possible to adapt the existing fan room into an acoustic isolation room, taking into account the specific conditions on site. In other words, the fan is enclosed within a fan room to prevent its noise from escaping. The main technical measures include the use of soundproof doors, soundproof windows, soundproof screens, and soundproof walls, as well as the application of appropriate sound-absorbing materials. 2.2.4 Pipe wrapping: To reduce the noise emitted from the fan ducts, the pipes can be wrapped in a spiral pattern, thereby blocking the pathways through which noise can propagate. 2.2.5 Vibration isolation: By taking into account factors such as safety, stability, and ease of maintenance, appropriate vibration isolators are selected and used to eliminate the rigid connections between machines and units, thus reducing solid-vibration noise. Ditching can also be used as a substitute for base vibration isolation, and it can achieve certain effects. The fundamental way to reduce noise from Roots blowers is to control noise by trying to avoid and minimize the noise radiation generated by the noise sources, that is, by reducing pulse forces as much as possible. The noise control methods mentioned above not only increase investment costs, but also result in energy losses during the operation of the fan due to pressure losses associated with silencers and similar components, which is detrimental to energy conservation. Therefore, the most fundamental approach to reducing the noise level of rotary vane fans is to improve their aerodynamic design, select the most suitable fans, and ensure proper installation and operation methods. Based on existing literature [7], there are many reports on reducing noise in centrifugal and axial flow fans through improvements to their structure, and significant results have been achieved. However, there are few reports related to rotary vane fans. Therefore, this paper explores the fundamental approaches to reducing noise in rotary vane fans. 3.1 Improving the aerodynamic and structural design of the fan 3.1.1 Making the impeller a twisted-blade impeller From the analysis of the mechanisms underlying fan noise, it can be seen that when the rotating wheel moves, the airflow in the area at the outlet of the blades is highly uneven. This uneven airflow acts periodically on the surrounding medium, resulting in pressure fluctuations that generate noise. Moreover, the greater the unevenness of the airflow, the louder the noise. Replacing the straight-blade impellers of the Roots blower rotor with twisted-blade impellers can improve the unevenness of the exhaust, thereby reducing noise. 3.1.2 Exhaust air from the inner circumferential surface of the casing I ； 3 is set at an angle of a certain magnitude relative to the tangent line at the tip of the impeller. The unevenness of the airflow along the circumferential direction of the impeller’s outlet generates pressure fluctuations that change over time; in turn, these fluctuations affect the airflow within the impeller, resulting in noise. Making the air outlet on the inner circumferential surface of the casing form an angle of a certain size with the tangent line at the top of the impeller can improve the unevenness of the airflow, thereby reducing the noise of the Roots blower. This method is limited by the geometric dimensions of two-blade impellers, but it can be fully applied to three-blade impellers. 3.1.3 Replacing the two-blade impeller with a three-blade impeller: By changing the two-blade impeller to a three-blade one, the number of blades on the rotor of the Roots blower increases, which in turn helps to reduce the unevenness in the exhaust flow from the blower; as a result, noise levels can be lowered. Changing a two-blade impeller to a three-blade one involves determining the pitch ratio of the involute three-blade impeller (K=D/A, where D is the impeller diameter and A is the distance between the centers of the two blades). The modified Roots blower features excellent properties such as low air flow pulsation and low noise, and it has now attracted the attention of various Roots blower manufacturers. 3.2 Controlling noise in fan selection, installation, and operation: The noise of rotary vane fans can be reduced not only through improved design but also, for a given task, by optimizing the fan’s design and size, as well as through proper installation and operation. 3.2.1 In actual piping systems, for the selection of fans, their operating modes, and installation layout, to ensure low noise levels, it is necessary to choose the most suitable fan type and size, install them properly, and maintain optimal operating conditions. For most fans, the operating point corresponding to the minimum sound power and optimal efficiency coincide; thus, making a proper choice of fan yields benefits both in terms of noise levels and cost ； The circumferential velocity at the top of the impeller should be as low as possible ； Ensure the fan inlet as much as possible ； Uniformity of airflow in 3 areas ； The matching of fans and piping systems must be considered not only from an aerodynamic perspective but also from an acoustic one; by appropriately selecting the fan diameter, speed, and number of blades, the radiation efficiency of blade-passing frequency noise can be minimized. 3.2.2 The sound power level or A-weighted sound level of the fan, when installed correctly, increases as flow rate and pressure increase; unnecessary resistance losses should be minimized during installation. Every effort should be made within the flow channel and in front of the impeller to prevent the wake generated by obstacles from being drawn into the impeller and causing noise. The silencer should be installed with a certain installation length from the impeller to avoid affecting it. 3.2.3 Selection of a suitable control method: Since most fans operate under variable conditions, both their air volume and pressure need to be adjusted according to the requirements of the piping system; therefore, efficient control systems such as variable speed control (e.g., frequency conversion speed control) should be preferred. These efficient adjustment methods are also those that generate the least additional noise. 4 Conclusions 4.1 Although the use of methods such as noise suppression, sound insulation, sound absorption, and vibration isolation can achieve certain results in comprehensive noise control, these measures are only taken at the level of noise transmission pathways; they increase costs and are also not conducive to energy conservation. 4.2 To achieve more effective noise control, it is necessary to address the problem at its source; that is, by selecting the optimal design, improving manufacturing precision and assembly quality, adopting appropriate adjustment methods, and implementing effective vibration reduction measures, satisfactory noise reduction results can be obtained. 4.3 Reducing the noise of rotary vane blowers can be achieved by making the impeller of the rotary vane blower a twisted-vane impeller, setting the outlet opening on the inner circumferential surface of the casing at an angle relative to the tangent line at the top of the impeller, and changing a two-vane impeller to a three-vane impeller. 4.4 In the future, theoretical research on the noise of rotary vane fans will continue, with the aim of predicting the noise level more accurately and establishing mathematical relationships between the fan’s airflow and structural parameters and the level of aerodynamic noise. In this way, during the design phase of the fan, these relationships can be utilized together with aerodynamic calculations to find solutions that minimize noise and achieve optimal aerodynamic performance, thereby reducing the noise generated by the fan itself at its core. 4.5 Measure the noise level of fans, establish corresponding databases, and use these databases to develop empirical design guidelines and mathematical models for predicting fan noise. By estimating the average performance of fans, it is possible to select fans appropriately from a noise perspective, while still meeting the user’s requirements regarding flow rate and pressure.

I. The factory building design should be reasonable； II. Install auxiliary facilities such as soundproof walls ； III. When installing the equipment, pay attention to the installation accuracy.

Thank you all. To be more specific, we have a few new machines here that have just been put into use. The machines themselves don’t generate much noise or vibration, but once they are in operation, there is significant noise and vibration. I would like to ask for everyone’s advice on this matter

A few new units, one with a capacity of 40,000 tons of ammonia per year; together with the existing ones, the pipelines are large enough. It is recommended to strengthen the reinforcement of the export pipeline to reduce vibrations, and to use new types of silencers to further suppress noise. The pipeline from the fan outlet to the cooling tower has had its sound insulation enhanced using the method provided by the person in charge on the 2nd floor.

Is it caused by the high wind speed? Sound insulation measures should be applied to the ducts at the back, trying to avoid any rigid connections with the walls.

The two Roots blowers we installed in 2008 also had this problem at first; the loud noise was enough to make people feel anxious. Later, silencers were installed on the outlet pipes of each Roots blower, with very good results. Construction is also convenient, and the investment required is not high.

Sealing the Roots blower room is not a viable approach, as the Roots blowers in ammonia synthesis plants are used to transport and pressurize semi-water gas; any leakage in such a sealed room would inevitably lead to safety accidents.

This guy just makes a lot of noise; installing silencers and sound-absorbing walls can help to some extent. It’s also necessary to take proper sound-insulation measures for the operations.

The most direct way to reduce the noise generated by the Luo machine is to install a silencer at the outlet~ though the effect is only average~

The noise generated by rotary vane blowers consists mainly of mechanical noise, aerodynamic noise, and electromagnetic noise. Aerodynamic noise is primarily related to the intake and exhaust noises, with exhaust noise being the most significant. Mechanical noise is emitted from the casing, while electromagnetic noise is produced by the motor. How can the noise problem associated with rotary vane blowers be addressed? There are generally several methods available: 1) The noise from the casing and motor can be reduced by installing soundproof enclosures; the blower can be placed in a separate soundproof chamber, where sound absorption and insulation measures are applied. 2) Silencers can be installed at the blower’s exhaust outlet, equipped with internal silencing elements that help to reduce noise as it passes through these structures. Silencers are an effective way to minimize noise emitted from the intake and exhaust ports of aerodynamic devices or transmitted along pipes. 3) Where possible, sound-absorbing louvers should be used on the exterior of the floor covering. 4) Damped spring mounts can be used to suspend the blower, thereby reducing vibrations. 5) The blower’s foundation can be treated with overall vibration isolation measures.