An oil equalizing system for multiple compressors which does not require a particular machining process for shells of the compressors, thereby being capable of preventing an increase in costs, while maintaining oil in each compressor in a proper amount. In a refrigerant circuit, in which at least three compressors are connected in parallel, the oil equalizing system includes an oil equalizing tube adapted to communicate shells of the compressors with one another, and a bypass tube adapted to connect the oil equalizing tube to a discharge side refrigerant line for the compressors. The shell of each compressor is directly communicated with the shell of each of the remaining compressors by the oil equalizing tube.

An oil-free scroll compressor comprising a plurality of oil-free scroll compressing mechanism blocks, each for compressing a gas, and a motor or motors for driving the plurality of oil-free scroll compressing mechanism blocks. In operation, an air is suctioned into the compressor through a filter and a throttle valve and then divided and sucked into first and second oil-free scroll compressing mechanism blocks, which act to increase the pressure of the air to a predetermined pressure. The compressed air is cooled by an after-cooler and supplied to the compressed air user side. The scroll compressing mechanism blocks are driven by a dual-shaft motor through belts. Under no-load condition, the throttle valve is closed and a release valve is opened, whereby the compressed air held between the blocks and check valves is released.

Device for distributing suction gas for a parallel compressor installation, said installation having at least two refrigeration compressors, at least one oil level equalization tube providing a communication between the oil pans provided in the bodies of the compressors, at least one suction gas distribution device comprising an essentially straight distribution tube, and branch tubes. The branch tubes have at least one portion forming an angle of between 55.degree. and 65.degree. with the axis of the distribution tube. The present invention uses a special geometry for equalizing the pressures in the oil pans of each compressor and thus using simple equalization channels.

The system for controlling oxygen flow in a gasification process of the instant invention comprises a suction control valve located between the oxygen source and the oxygen compressor. The suction control valve is adapted in order to open to deliver oxygen from the source to the compressor through the first pipe and to move to a reduced flow position to prevent excess delivery of oxygen from the source to the compressor. The system also comprises a second pipe which operably connects the oxygen compressor to a port of a gasifier. The system comprises a normally closed vent valve located between the oxygen compressor and the port of a gasifier. The system comprises a means located in the gasifier or in the gasifier effluent for detecting when it is necessary to change the oxygen flow to the gasifier and to actuate the suction control valve sufficient to change the oxygen flow. Finally, the system comprises a means for a means of controlling the suction control valve and the vent valve to regulate the quantity of oxygen delivered to the gasifier.