MANURE FROM ANIMAL WASTE. 257 



ment of all odoriferous products, and thus avoids costly gas con- 

 densation and denaturation processes. Before this new application, 

 this machine was already in use in distilleries to dry dregs, and 

 this use of it \vas described by the authoi' as far back as 1892. 

 The drying machine (Fig. 51) consists of a horizontal cast-iron cyhnder 

 2'5 m. in diameter by 2 5 m. long — say in round figures, 100 in. x 

 100 in., representing an interior volume of 12 cm. It rests on 

 two bearings by hollow pivots through which the heating steam 

 enters and the evaporation steam is ejected. The heating steam 

 enters a circular vertical steam chamber which forms the left side 

 of the cylinder. On this side are inserted a series of horizontal 

 tubes closed at the other extremity which form a heating surface of 

 59 square metres. The machine is fitted with the necessary ariange- 

 ments for ruaning off condensed water. The pivot placed at the 

 other end of the cylinder CDmmanicates by a wide pipe with a 

 double effect vacuum condensing pump into which the evaporation 

 vapour passes. The cylinder is fed and emptied through two man- 

 holes. The charge of moist material — containing 55 per cent of 

 water — is 5i tons. It makes three revolutions a minute. 



Method of Working. — The working is roost simple. The 

 machine is connected by a pipe with a tank containing the blood, 

 then by means of the vacuum pump the air in the cylinder is 

 rarefied so as to force the blood to precipitate itself by suction. 

 When 5^ tons have been fed into the machine, say an amount equal 

 to J the capacity of the machine, the aspiration is shut off and the 

 mass is heated under a pressure of li kilos whilst turning the 

 cylinder. The blood is then perfectly coagulated under the influence 

 of the heat without any pait escaping fiom the beating up. After 

 one hour forty miautes to one hour titty minutes, coagulation is 

 complete. The apparatus is emptied, the magma is run into cloths 

 and pressed under a press mounted on a truck. Each press takes 

 1 ton to 22 cwt. of dried blood as it comes from the curing machine. 

 After pressure, which is 3 kg., 400 kg. (880 lb.) of cake with 50 per 

 cent of water are taken out ; 3^ tons of these cakes are used to feed 

 another machine absolutely identical with the first, but which this 

 time acts the part of a drying machine. In a medium-sized factory 

 a siagle machine may act both as curing and drying machine. 



In factories with two machines the curer is altered by fitting 

 two steam circulation pipes perforated in the portion which dips into 

 the cylinder ; and used to bubble in steam during the coagulation, 

 they have the advantage of preventing the other heating pipes from 

 being leit bare. 



To dry the cakes the vacuum is stopped, for the vacuum pump 

 might entrain a portion of the extremely light powder to which the 

 blood is reduced by drying. During that time the vapours escape 

 through great w^ooden aspirators passing through the roof. As 



17 



