Patent GB-608595-A (GB)
Title: Distilling hydrocarbon tar and like oils and apparatus therefor
IPC: F28D7/02
Filed: 1945-05-23
Abstract: <PICT:0608595/III/1> <PICT:0608595/III/2> In the distillation of hydrocarbon, tar, and like oils by flowing the oils through a plurality of evaporator effects arranged in p  series and comprising calandria through the tubes of which the oils flow while being emulsified by vapours or gases, the oils are emulsified in the early effects by injecting into the tubes gases separated from the distilled vapours and in the later effects by live steam, preferably generated by heat exchange with the hot products of the distillation. Special evaporator effects, rectifiers, heat exchangers, and weight balance control of the inflow by the density of residua, are described.  The effects are heated to give progressive increase in temperature with corresponding decrease in pressure while the cross-sectional area of the calandria are successively reduced to compensate for reduction in volume of the oil treated.  The plant is shown in Figs. 1 and 2 and comprises a heat-exchanger recuperator A, effects D1-D7 surmounted by separators Y1-Y7, rectifiers U1-U6 (as described in Specification 517,550), centrifugal separators Z1-Z6 (as described in Specification 447,457, [Group II]), coolers E1-E4, gasometer Gs, syphon tubes T2-T7, barometric condenser C, purifier J and centrifugal separator K.  The path of the oil is from the pump O and tube T through the annular preheater on the outside of the recuperator to the first effect D1.  The oil flows in series through the effects D being emulsified at the bottom by jets of gases from the gasometer Gs in the effects D1-D3 and by jets of steam in the effects D4-D7, the whole of the oil in each effect being driven upwards in one pass through the calandria and separation of vapours and gases from residual liquid being effected in the separators Y, Z and rectifiers U from which liquids are returned through the pipes T2-T7 to the next effect while vapours and gases pass through pipes V4-V7 through the recuperator A and thence through cooler E4 to separators F.  Film evaporators.-The tubes a of the calandria are divided into central and peripheral sections by radial plates b, having apertures C through which the heating steam, fed in at St passes in series, the cross-sectional flow area of the sectors and the number of tubes therein being decreased successively as shown in plan in Fig. 3a.  The oil enters through a pipe T and is atomised into the tubes a by the steam or hydrocarbon gases injected from the line SG into a vessel f provided with a plurality of spouts d. The atomised gases and vapours emerge from the tubes into the separator Y provided with a baffle wall X which separates <PICT:0608595/III/3> <PICT:0608595/III/4> <PICT:0608595/III/5> <PICT:0608595/III/6> <PICT:0608595/III/7> <PICT:0608595/III/8> entrained liquid which is removed through line T1.  As shown in Fig. 4, the evaporators D may be arranged in nested fashion as a single unit, the separators Y being arranged segmentally so that their external surfaces form a single dome.  Evaporator D7, operating at the highest temperature is arranged centrally and the other evaporators surround it.  As shown in Fig. 7, the evaporating and fractionating zones may be combined by providing the evaporator D with a spiral coil having loops s, p, surrounding the evaporator and enclosed in a casing RC the vapours emerging from the separator being fed through a pipe V so that they flow upwardly through the spiral paths formed by the loops which are unequally spaced to vary the cross-sectional path of the vapours. Liquid separated in the previous evaporator is fed through line T to the loops p and falls from loop to loop through apertures r; a channel m is provided to conduct liquid to the lower spiral p.  Heat recuperators.-The recuperator A in which water used in the plant is evaporated to produce steam for heating the evaporator effects comprises inner and outer annular chambers B1, B2 down which the water drops from perforated plates p, so that it drips over the coils Sp, Sl through which the vapours generated in the various effects are passed, each stream passing first through chamber B1 and then through chamber B2, i.e. the vapour stream entering at V7 first passes through the coils Sp7 and is then fed by the pipe L7 through the coils Sl7, finally passing off through L17.  The diameter of the pipe forming each coil decreases with each coil throughout the entire length of the coils.  Residual oil from the last evaporator is passed through the coils SpR and SlR.  Automatic-flow regulation of the oil passed through the evaporator plant is operated in accordance with variations in the density of the liquid residue, whereby the density of the residue is maintained constant.  As shown in Fig. 6, the supply of crude oil by the pump O is regulated by a byepass pipe Tb having a valve By operated by a reversible motor Mo, the direction of the motor being governed according as the operating current enters wire 11 or 111 which wires are connected to relays Mg in circuit with a battery Pl and contact terminals aM, aM1 which make and break contact with one end In of a balance arm Ba. This arm is balanced at one end by the weight of the residual oil flowing constantly through a tank Pr and at the other end by a weight Cp adjustable on the arm according to the density required.  A simpler form of regulator comprises a float arranged in a tank through which the residue flows and provided with an arm regulating a valve on the pump byepass valve.