A device for tangential flow filtration includes a filter unit having first and second fluid openings, a filter element and a permeate opening, a first flow connection to connect the first fluid opening to a reservoir, a second flow connection to connect the second fluid opening to the reservoir, a first centrifugal pump in the first flow connection to convey the fluid from the reservoir to the filter unit, a first controller to actuate the first centrifugal pump, the filter unit designed such that the fluid for tangential flow filtration is capable of flowing substantially parallel to the filter element, a second centrifugal pump in the second flow connection, with which a counter-pressure is capable of being generated at the second fluid opening, and a second controller to actuate the second centrifugal pump.

A stable discharge pressure of compressed hydrogen gas generated from the electrolysis of water is achieved and maintained at the outlet of a “hybrid” multistage compression system comprising at least a first section comprising at least one centrifugal compressor powered at least in part by electricity generated from at least one renewable energy source and a further section downstream of the first section, wherein the further section comprises at least one reciprocating compressor.

A stable discharge pressure of compressed hydrogen gas generated from the electrolysis of water is achieved and maintained at the outlet of a “hybrid” multistage compression system comprising at least a first section comprising at least one centrifugal compressor powered at least in part by electricity generated from at least one renewable energy source and a further section downstream of the first section, wherein the further section comprises at least one reciprocating compressor.

Operation of a multistage compression system comprising at least one centrifugal compressor having a dry gas seal with opposed seal faces, for compressing a gas feed having a variable flow rate is improved by operating the or at least one centrifugal compressor in a low power mode where the opposed faces of the dry gas seal are not in contact during periods when gas flow through the centrifugal compressor(s) is not sufficient for normal operation. Such operation not only reduces damage to the dry gas seals and hence improves reliability, but also reduces the overall power requirement of the overall compression system.

Operation of a multistage compression system comprising at least one centrifugal compressor having a dry gas seal with opposed seal faces, for compressing a gas feed having a variable flow rate is improved by operating the or at least one centrifugal compressor in a low power mode where the opposed faces of the dry gas seal are not in contact during periods when gas flow through the centrifugal compressor(s) is not sufficient for normal operation. Such operation not only reduces damage to the dry gas seals and hence improves reliability, but also reduces the overall power requirement of the overall compression system.

Energy efficiency and/or operational stability of a multistage compression system comprising a plurality (N) of centrifugal compressors that is compressing a gas feed having a variable flow rate is improved by adjusting reversibly the load on each compressor in response to changes in the flow rate of the gas feed using a main recycle system to enable operation of the centrifugal compressors at turndown capacity during periods when the flow rate is below total turndown capacity for all of the compressors, and if necessary, using the local recycle systems in order to avoid activation of anti-surge control, and switching one or more centrifugal compressors into low power mode or shutdown mode as required.

A method for determining the positions of a number of fans (V.sub.n,m) for generating an air flow in a preferably enclosed space. The fans (V.sub.n,m) have an acceleration sensor to determine their position. The fans (V.sub.n,m) are arranged in rows (R.sub.1, R.sub.2, . . . , R.sub.n) and columns (S.sub.1, S.sub.2, . . . , S.sub.m). At least the position (i, j) of one fan (V.sub.i,j) is known.

A magnetically attracted fan set comprises N+1 fans, the N≥1, and each of the N+1 fans has a fan frame and an airflow generating component disposed on the fan frame. Any two adjacent fans of the N+1 fans respectively have a joint surface, each of the joint surfaces has at least one fixing member capable of forming magnetic attraction, when the joint surface is close to the other joint surface at a distance sufficient for the two fixing members on the two joint surfaces to form magnetic attraction, two of the N+1 fans are joined together. Accordingly, the invention is capable of directly and quickly joining the N+1 fans without requiring complicated assembly gestures or other external components.

Disclosed is a fan. The fan includes a support; a first motor installed on the support, the first motor having a first rotation shaft; a first blade installed on the first rotation shaft; a second motor installed on the support, the second motor having a second rotation shaft and being coaxial with the first motor; a second blade installed on the second rotation shaft, a tilt direction of the second blade being opposite to a tilt direction of the first blade; and an electric control board electrically connected to the first motor and the second motor and configured to control a relative rotation of the first motor and the second motor.

A counter-rotating fan, comprising an impeller assembly and an air guide structure. The impeller assembly comprises a first stage impeller and a second stage impeller, of which the rotation directions are opposite. The pressure surfaces of first blades of the first stage impeller are configured to be opposite the suction surfaces of second blades of the second stage impeller, and from the blade root to the blade tip, each of the first blades and the second blades bends toward its own rotation direction. The air guide structure comprises a flow guide cover. The flow guide cover is provided at the center position of the air intake side of the first stage impeller, and the air intake side surface of the flow guide cover at least partially forms a flow guide surface, the flow guide surface extending along the axis of the first stage impeller in the direction away from the counter-rotating fan.