Process and apparatus for the production and/or treatment of particles

A process for at least one of producing and of treating particles within a process chamber, including the steps of circulating gas in a gas circulation that includes a process chamber and a gas circulation device, feeding a liquid, during circulation of gas, at least from time to time to at least one spray nozzle and spraying the liquid into the process chamber through a liquid outlet present in a mouthpiece of the spray nozzle, the process further comprising the steps of,

• moving the particles within the process chamber;
• feeding the liquid to the spray nozzle at a pressure of at least 500 kPa;
• wherein, at least during spraying of liquid, passing gas from the gas circulation to a gas passage of the spray nozzle, said gas passage having a section which, in cross-section surrounds the mouthpiece, and passing the gas into the process chamber through a section of the gas passage, wherein the pressure of the gas fed to the gas passage of the spray nozzle is at most 20 kPa greater than the pressure of the gas present in the process chamber, wherein the gas streaming through the gas passage into the process chamber forms a gas envelope for shielding the spray nozzle at least substantially against contact with the atomized liquid;
• wherein the sprayed liquid contains at least one of an organic solvent and of an organic dispersant, wherein the gas circulated in the gas circulation is brought, at least temporarily, to a temperature at which the at least one of an organic solvent and of a dispersant contained in the sprayed liquid is converted into vapor;
• and
• withdrawing gas, at least from time to time, from the gas circulation by means of a suction device so that, at least during spraying of liquid, the pressures of the gas circulated in the gas circulation and of the gas passed into the gas passage of the spray nozzle, at least during spraying of liquid, are below the ambient air pressure and lower than a minimum ignition pressure at which a mixture of air and vapor of the at least one of an organic solvent and of an organic dispersant present in the sprayed liquid can be caused to explode.

A process for at least one of producing and of treating particles within a process chamber, including the steps of circulating gas in a gas circulation that includes a process chamber and a gas circulation device, feeding a liquid, during circulation of gas, at least from time to time to at least one spray nozzle and spraying the liquid into the process chamber through a liquid outlet present in an end of a mouthpiece of the spray nozzle, the process further comprising the steps of,

• moving the particles within the process chamber;
• withdrawing the gas, at least from time to time, from the gas circulation by a suction device so that the pressure in the process chamber is continuously at a value of at most 50 kPa at least during spraying of liquid;
• feeding the liquid to the spray nozzle at a pressure of at least 500 kPa for atomizing the liquid;
• wherein the spray nozzle defines an axis and has a sleeve, wherein the sleeve has an end wall which is located along the axis a distance away from said end of the mouthpiece and has an outlet hole coaxial with the liquid outlet and has further an inner surface which is opposite to the mouthpiece, flat and at right angles to the axis, wherein the boundary of the narrowest part of the outlet hole surrounds the boundary of the narrowest point of the liquid outlet at a distance all around the axis in a direction of view parallel to the axis, wherein the spray nozzle has a gas passage having a section which is bounded by the sleeve and the mouthpiece and, in cross-section, encompasses the mouthpiece;
• wherein, at least during the spraying of liquid, passing gas from the gas circulation to the gas passage of the spray nozzle at a pressure which is at most 20 kPa greater than the pressure of the gas present in the process chamber;
• and
• passing the gas fed to the gas passage of the spray nozzle through said section of the gas passage, whereby the gas flows towards the axis between the end of the mouthpiece and said flat, inner surface of the sleeve and then through said outlet hole into the process chamber so that the gas streaming through the gas passage into the process chamber forms a gas envelope for shielding the spray nozzle at least substantially against contact with the atomized liquid.

An apparatus for at least one of the production and of the treatment of particles comprising,

• a process chamber for receiving the particles;
• a gas circulation device forming a gas circulation together with the process chamber to circulate gas through the gas circulation and the process chamber;
• a suction device connected to the gas circulation to extract gas from the gas circulation;
• a pressure sensor for measuring the pressure in the gas circulation;
• a control device connected to the pressure sensor and to the suction device;
• at least one spray nozzle for spraying a liquid into the process chamber, said spray nozzle including a mouthpiece and a liquid passage with a liquid outlet bounded by the mouthpiece, wherein the spray nozzle has a gas passage with a section which, in cross-section, surrounds the mouthpiece at the liquid outlet;
• a liquid supply device connected to the spray nozzle for supplying a liquid to said spray nozzle at a pressure of at least 500 kPa;
• wherein said control device including means to control the suction device so that the pressure in the process chamber is at a value of at most 50 kPa at least during the spraying of liquid;
• means for feeding a gas from the gas circulation to the gas passage of the spray nozzle at a pressure which is at most 20 kPa greater that the pressure in the process chamber and for passing this gas through the gas passage into the process chamber so that the gas streaming through the gas passage into the process chamber forms a gas envelope for shielding the spray nozzle at least substantially against contact with the atomized liquid.