TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Process: The process may include a step of introducing a stream of additional diluent after the emulsion-breaking flash step (d) to enhance recovery of the oil from other components of the heavy crude oil. The amount of hydrocarbon diluent added is 10-35 vol.% based on the volume of oil in the crude stream. The process may be used for upgrading a heavy, high viscosity crude oil containing asphaltenes and resins, and include:(i) flashing the crude oil to break emulsion;(ii) adding additional solvent at 200-800 vol.% based on the separated oil content and using a 4-7C paraffinic or naphthenic hydrocarbon at a moderate temperature to obtain a continuous, single-phase oil-solvent solution;(iii) gently warming the blend to 5-25degreesF below the critical temperature of the solvent to cause a substantial part of the asphaltic or asphaltenic content to precipitate and settle from the lighter solvent-oil solution as (semi-)solid material;(iv) separating the solvent from the oil for recycling; and(v) recovering the extracted crude oil product.The solvent may also be separated from the asphaltic material for recycling. Precipitation is performed using a continuous counter-current contacting device (preferably a Rotating Disc Contactor), with the solvent introduced near the asphalt removal end and with the solvent-oil solution removed at the opposite end. A suitable heat-transfer means is used to maintain a temperature gradient with a higher temperature at the solvent-oil discharge end. The solvent is recovered from the oil in multiple stages using progressively lower pressures and supplying heat to vaporize the solvent. The process may include steam-stripping the solvent from the oil, condensing the vapors and decanting the condensed water from the recovered solvent. Solvent may also be recovered from the separated asphaltic material, preferably, while it still contains some solvent, by treating it using counter-current washing with water containing a chelating agent to remove heavy metals from the asphalt.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The diluent is a 3-7C paraffinic or naphthenic hydrocarbon, a 6-8C aromatic hydrocarbon, casing head gas condensate, light aromatic distillate or a mixture (preferably a mixture of light hydrocarbons of boiling point 10-180degreesF). The solvent is a mixture of 3-5C hydrocarbons or a 5-7C blend. SPECIFIC COMPOUNDS - The solvent is n-butane, isobutane, pentane, heptane. The chelating agent is ethylene diamine tetraacetic acid or one of its partial salts, nitrilotrisacetic acid or glycolic acid.    EXAMPLE - Heavy crude oil containing emulsions, and possibly inorganic salts, is pumped to a screening device (10) to remove gross contaminants, e.g. rocks. 10-20 vol.% of light hydrocarbon diluent from a storage tank (D) is injected into the crude oil line (16) with the pumps (14, 20) maintaining the mixture at a steady pressure of 100-350 psig. 100-1,000 ppm of other additives, e.g. de-emulsifiers, chelating agents and neutralizing agents, may also be injected (22). The mixture passes through an in-line mixer (24), a heat-exchanger (26) which transfers heat from condensing vapors from a flash drum (32) and a stripper (82). The mixture passes through a trim heater (28), which brings it to a preset temperature of 275-400degreesF, through a flash controller (30) and into a flash drum (32), where the pressure is released and a preset amount of the mixture vaporizes rapidly, rupturing emulsions, e.g. as described in (CIT)U.S. Pat. No. 4,938,8769(CIT). Water and light hydrocarbon vapors (5-20%) are removed to supply heat to the heat-exchanger (26), then they are passed to a cooler (37) where they are condensed into liquid water and hydrocarbons. The water separates and is removed from the bottom of the receiver (38) and the hydrocarbon is returned to the diluent storage tank (D). A small amount of non-condensible gas is released from the receiver (38) by a pressure control valve (46), which controls the pressure in the flash tank (32) and, indirectly, its liquid temperature (normally 210-260degreesF at 5-50 psig). The liquid and solids leaving the bottom of the flash tank (32) are diluted with 10-30 vol.% additional diluent and pumped to a first hydroclone desander (58). 5-20 wt.% solids in water leaves at the high specific gravity outlet (line 60) and the mixture is passed to a second hydroclone desander (64), where the solids are washed and then used either as full for making steam or for conversion to asphalt or coke. The overhead from the first hydroclone (58) is fed to a third hydroclone (74), which dewaters and desalts the crude oil, outputting a salty water stream (76). The dry oil is reheated in a heat exchanger (80) and fed to a diluent stripper column (82) through a flash control valve (84). The column bottom stream is clean, dry, salt-free oil, which has enhanced value as a feed crude oil at a refinery. The overhead from the stripper column (82) is ultimately returned to the diluent storage tank (D). Ideally, the system is kept in balance so that no light ends are lost from the diluent into the heavy oil product.