Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
  • B22C5/10—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose by dust separating

Definitions

• This invention concerns the reclamation of foundry sands.
• Foundry sand is used with suitable binding agents for making moulds and cores for casting metal.
• Various binders both inorganic and organic, are used to bond the foundry sand and, for many years, the sand after use was discarded.
• British Patent Specification No. 1,322,864 is also concerned with the problem of sand reclamation and discloses a process in which the used foundry sand is introduced into a blast of fluid under pressure, whereby the sand is projected against lateral walls of a hermetically sealed casing to cause a matrix of the binding agent to burst releasing the sand. The product of this process is then subjected to granulometric selection to remove the fines generated by the high impact.
• British Patent Specification No. 1,505,904 discloses a process in which coated sand particles are projected in a current of gas against the interior surface of a rotating drum.
• British Patent Specification No. 2,019,274 discloses a similar process in which, again, the coated sand is projected against a solid target.
• the essential problem to be overcome in the sand reclamation process is an adequate balancing of two objectives, namely the effective removal of a hard and tenacious coating and the avoidance of significant particle degradation of the clean sand particles to produce fines which are not useful in the reclaimed sand.
• the present invention provides a process which effectively balances these two objectives.
• the present invention provides a process for the reclamation of binder coated foundry sand, in which the coated foundry sand is fed to a fluid energy mill and fluid energy is imparted to the sand to a sufficient extent to substantially remove the binder coating without causing significant disintegration of the sand particles, and the reclaimed sand is separated from the binder debris.
• the specific energy imparted to the sand is less than 1,300 kilojoules per kilogramme of coated sand.
• the optimal energy range was from 400 to 1,200 kilojoules per kilogramme of sand.
• This work was carried out in a microniser having a diameter of 10 cm and containing 6 1.6 mm diameter inlet nozzles in the periphery of the chamber.
• the feed rate of the sand varied from 0.33 to 1.54 g per second and the optimum feed rate was of the order of 1 g per second for this apparatus.
• the sand feed rate can be increased in relation to the size of the mill and air throughput.
• the specific energy imparted to the sand should be of the same order of magnitude as previously defined but applied at a commercially useful sand feed rate.
• Fluid energy or jet mills (alternatively known as micronisers) suitable for use in the process of this invention are available from various suppliers in the market and are described in, for example, Chemical Engineering Handbook, Ed. J.H. Perry, 4th ed., McGraw Hill, p.8-42 and 43.
• the fluid energy imparted to the sand in the mill is determined by calculating the energy expended by the adiabatic expansion of the compressed fluid through the nozzles, and is given by:
• the specific energy input is obtained by dividing by the feedrate of sand (kg/s), i.e.
• Reynolds Number is the ratio of inertial force to the viscous force of the flowing fluid. It is a measure of the air fluid velocity in the jet stream which determines the drag force exerted on the individual particles and thus determines their acceleration and their impact velocity.
• the Reynolds Number does not exceed 6.5 x 10 4 and is preferably in the range 4.0 x 10 4 to 6.4 x 10 4 .

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Mold Materials And Core Materials (AREA)
• Disintegrating Or Milling (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=10524292

Family Applications (1)

Country Status (8)

Citations (7)

Family Cites Families (1)

• 1982
  • 1982-08-30 AU AU87845/82A patent/AU542894B2/en not_active Ceased
  • 1982-08-31 BR BR8205096A patent/BR8205096A/pt unknown
  • 1982-09-01 DE DE8282304595T patent/DE3268559D1/de not_active Expired
  • 1982-09-01 EP EP82304595A patent/EP0074755B1/fr not_active Expired
  • 1982-09-01 CA CA000410616A patent/CA1209784A/fr not_active Expired
  • 1982-09-02 ZA ZA826431A patent/ZA826431B/xx unknown
  • 1982-09-02 JP JP57153345A patent/JPS5853346A/ja active Pending
  • 1982-09-02 ES ES515460A patent/ES8308242A1/es not_active Expired

Patent Citations (7)

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