Process and apparatus for drying liquid-borne solid material

A method of continuously drying solid material borne in a liquid which method comprises:

• spraying a liquid bearing solid material upwardly into a drying zone,
• feeding a drying gas into the drying zone from below the spraying liquid in substantially parallel flow,
• removing the mixture of the drying gas and entrained dried particles from the drying zone,
• separating the entrained dried particles from their mixture with the drying gas,
• returning the separated dried particles to the drying zone, and
• collecting the dried particles continuously from below the spraying liquid,
• wherein a slower moving boundary layer is arranged to be formed within the feeding of the drying gas, through which boundary layer dried particles are allowed to fall under gravity to be collected.

A method of continuously drying and size-classifying solid material borne in a liquid which method comprises the steps of:

• converting a feed liquid bearing solid material into an aerosol mist of finely divided droplets by passing it through an atomizer located axially in an inlet gas throat below the bottom frusto-conical section of a drying vessel;
• concurrently passing through the throat a flow of gas heated to between 100 and 1000.degree. C. in substantially parallel flow;
• subjecting the combined streams of gas and aerosol to a rapid reduction in velocity by passing them into a drying vessel mounted on top of the frusto-conical section, so as to cause a boundary separation in the bottom part of the vessel;
• accumulating a layer of particles above the throat of the vessel;
• passing the resulting dispersion of gas and fine particles at the top of the vessel through one or a plurality of solid/gas separators to separate the solid residue from the gas;
• venting the gas to the atmosphere or recycling the gas to the process;
• returning the fine particles to the bottom of the vessel;
• passing the particles from the accumulated layer through the throat of the vessel counter-current to the upward flow of hot gas;
• collecting the size-classified product in the gas supply duct located below the throat of the atomizer;
• and
• removing the dried and size-classified particles continuously from the gas supply duct.

A method of continuously drying, size-classifying and coating dry particles, which method comprises the steps of:

• converting a feed solution of binder for the coating, which includes a coating material dissolved in a suitable liquid carrier or solvent, into an aerosol mist by passing it through an atomizer located axially in an inlet gas throat below the bottom frusto-conical section of a drying vessel;
• concurrently passing through the throat a flow of gas heated to between 100 and 1000.degree. C. in substantially parallel flow;
• subjecting the combined streams of gas and aerosol to a rapid reduction in velocity by passing them into a drying vessel mounted on top of the frusto-conical section, so as to cause a boundary separation in the bottom part of the vessel;
• simultaneously introducing the particles to be treated into the bottom of the vessel just above the frusto-conical section;
• passing the dispersion of gas and fine particles at the top of the vessel through at least one solid-gas separator to separate the solid residue from the gas;
• venting the gas to the atmosphere or recycling it to the process;
• returning the fine particles to the bottom of the vessel;
• accumulating a layer of particles above the throat of the vessel;
• passing the particles through the throat of the vessel counter-current to the upward flow of hot gas;
• collecting the size-classified product in the gas supply duct located below the throat of the atomizer;
• and
• removing the dried, size-classified, and coated particles continuously from the gas supply duct.