Abstract: A flow-limiting device for a pipe carrying a fluid or gaseous medium, comprising a flap, means mounting the flap in the pipe for pivotal movement in a manner to vary the cross-sectional area of flow through the pipe, and spring means urging the flap in a direction to increase the cross-sectional area of flow and against the direction of flow through the pipe, so that the flap varies the cross-sectional area of flow through the pipe in dependence on the kinetic energy differential of the medium upstream and downstream of the flap. The spring means comprise a leaf spring one end of which is mounted in an upper part of a housing for insertion in the pipe and the other end of which carries the flap. There is a clearance beneath the lower edge of the flap to permit the passage of deposits in the medium past the flap in all positions thereof.

Abstract: Method and apparatus for cleaning gases, especially those generated by the pressurized gasification of coal, to remove impurities therefrom, especially tar, dust and salts, in which the gases are washed with a liquid, preferably water, in a scrubbing unit and the wash liquid is cleaned to yield a major clean liquid stream which is recycled by a circulating means to the scrubbing unit and a minor impurities concentrate stream from which the impurities are removed, in a separator unit. Preferably the wash liquid is cleaned using a plurality of hydrocyclones which may be arranged in series or in parallel. Optionally the liquid recovered from the impurities concentrate stream is returned to the scrubbing unit, although if the quantity of this liquid is equal to the quantity of liquid required for the de-salting of the wash liquid, no recovered liquid is returned to the scrubbing unit.