Abstract: Concrete, especially for producing concrete blocks of high compressive strength, is formed from a hydraulic binder and an improved aggregate which consists of 0.1:1 to 1:0.1 parts of a sludge to comminuted slag. The sludge is a calcium-containing product of the scrubbing of the flue gases of a fossil-fuel boiler, preferably of a power plant, while the slag can be melting-chamber slag or ash obtained from the furnace. The composition may also contain sand or gravel. It is combined with water, to be cast into cement blocks of high compressive strength. Low proportions of the hydraulic binder are required with the improved aggregate.

Abstract: The gas-cleaning apparatus for a blast furnace operating under pressure using a differential-pressure washing arrangement whereby the differential-pressure washer comprises at least one annular gap with an annular-gap passage and an axially adjustable body received in the annular gap washer. The nozzle is disposed upstream of the annular-gap washer to spray the washing liquid into the gas which is accelerated through the annular gap. The position of this body is controlled in response to the gas pressure within the head of the blast furnace. The annular gap of the washer diverges in the direction of flow of the gas and the body has a complementary shape so that the gap width remains generally constant although its flow cross section increases with the diameter of the annular gap in the direction of flow of the gas.

Abstract: Dust-laden waste gases from a converter and from ancillary equipment are exhausted by respective blowers through a first and a second duct to a main and a secondary scrubbing station whence the purified gases escape through respective chimneys. The first duct is provided with two cascaded washing stages, the upstream stage being operable to throttle or block the flow of gases therethrough. An annular cowl for the interception of peripherally escaping converter gases is connected to a third duct which joins the first duct at a location between the two washing stages but is also connectable through a switching valve to the second duct.