High efficiency material drying

Apparatus for drying material, comprising:

• a drying chamber for containing the material to be dried;
• material handling means, including means for introducing material to be dried and limited amounts of air associated therewith into said drying chamber, means for moving material through said drying chamber during the drying process, and means for removing dried material from said drying chamber;
• means for applying microwave radiation energy to the material within said drying chamber to remove vaporizable liquid therefrom;
• vacuum pump means connected to said drying chamber at an air outlet port thereof for exhausting air therefrom to maintain the lower pressure within said drying chamber;
• said means for introducing material and limited amounts of air to said drying chamber positioned at a location remote from said air outlet port to maintain a flow of air from the introducing means generally across the material being dried to said air outlet port to remove as vapor or aerosol the liquid removed from the material;
• and
• heat reclaim means connected to receive air, vaporized liquid and aerosol removed from said drying chamber and including heat exchanger means for recovering heat energy including heat of vaporization therefrom and for applying said heat energy to the material to be dried.

Apparatus for drying material comprising:

• a vacuum drying chamber for containing the material to be dried;
• means including air lock valves for introducing quantities of material to be dried and air into said drying chamber and for removing dried material from said drying chamber;
• means for applying microwave radiation energy to the material within said drying chamber to remove vaporizable liquid therefrom;
• vacuum pump means connected to said drying chamber at an air outlet port thereof for exhausting air therefrom to maintain lower pressure within said drying chamber;
• said air lock valves positioned for admitting air to said drying chamber at a location remote from said air oulet port to maintain a flow of air generally across the material being dried to said air outlet port to remove the resulting aerosol mixture;
• heat reclaim means connected to an outlet of said vacuum pump means to receive aerosol mixture removed from said drying chamber by said vacuum pump means and operative to recover heat energy added by said microwave energy means and by said vacuum pump means in pumping the aerosol mixture from the drying chamber;
• said heat reclaim means including a liquid-vapor separator connected to receive the aerosol mixture from said vacuum pump means;
• means for moving the material through said drying chamber including an auger having a hollow shaft connected to receive heated liquid from said separator so that said auger acts as a heat exchanger in applying heat to the material being dried within said drying chamber;
• and
• means defining a preheat zone including a passageway for directing the material to be dried to said drying chamber, means including air pathways in said preheat zone for circulating air therethrough, and a heat exchanger in thermal contact with said air circulating through said preheat zone so that the heat of the air and vapor from said separator is applied to the material in the preheat zone before the material enters said drying chamber.

Apparatus for drying material comprising:

• a vacuum drying chamber for containing the material to be dried, including first and second drying zones;
• a vacuum pump connected to an air outlet port of said drying chamber;
• means including air lock valves for introducing material to be dried into said drying chamber and means for removing dried material from said drying chamber;
• means for applying microwave radiation energy to the material within the first drying zone of said drying chamber to remove vaporizable liquid therefrom;
• a plurality of air inlets for admitting air to said drying chamber at locations proximate said first drying zone and proximate said second drying zone to maintain a flow of air from said inlet means generally across the material being dried to said air outlet port to remove the aerosol mixture, further including a pressure regulating air valve operative to maintain the pressure within said drying chamber in a predetermined range;
• a liquid-vapor separator connected to receive the aerosol mixture from the vacuum pump;
• means for moving the material through said drying chamber including an auger having a hollow shaft connected to receive liquid from said separator so that said auger acts as a heat exchanger in applying heat reclaimed from the liquid to the material to be dried within said drying chamber;
• means for defining a preheat zone including a passageway for directing the material to be dried from a hopper to one of said air lock valves for introduction to said drying chamber, means including air pathways for circulating air through said preheat zone, and a heat exchanger in thermal contact with said air circulating through said preheat zone so that the heat energy of the air and vapor from said separator is applied to the material in the preheat zone before the material enters said drying chamber;
• and
• an additional heat exchanger positioned in thermal contact with said air circulating through said preheat zone, and means for conveying the liquid to said additional heat exchanger after passage through said auger, so that residual heat energy of said liquid is applied to the material in the preheat zone.

A method for drying material contained in a chamber comprising the steps of:

• removing gas from the chamber to lower the pressure within said drying chamber;
• applying microwave radiation energy to the material within said drying chamber to vaporize liquid from the material;
• removing vaporized liquid from said drying chamber by admitting a limited amount of gas to said chamber to flow generally across the material to the gas removal location;
• recovering heat energy from the gas and liquid removed from the chamber, including heat of vaporization of the liquid;
• and
• applying the recovered heat to material to be dried.

A method for drying material, comprising the steps of:

• placing the material to be dried in a drying chamber;
• lowering the pressure within said drying chamber by removing air therefrom through an outlet;
• transporting the material to be dried through said drying chamber during the drying process;
• applying microwave energy to the material within said drying chamber to remove vaporizable liquid therefrom;
• admitting airflow into said drying chamber to entrain and remove from said drying chamber through the outlet, as vapor or aerosol, the liquid removed from the material;
• recovering heat energy from the vapor or aerosol removed from the drying chamber;
• and
• applying the recovered heat to material to be dried.

A method for drying material within a chamber comprising the steps of:

• preheating the material to be dried;
• transporting the material to be dried to a drying chamber after the preheating;
• maintaining a low pressure within said drying chamber by removing air from the drying chamber;
• moving the material through the drying chamber during the drying process;
• applying microwave radiation energy to the material within said drying chamber to remove vaporizable liquid therefrom;
• admitting air to said drying chamber at a location remote from the place of air removed therefrom to establish an air flow across the material being dried, thereby removing the vaporizable liquid as vapor or aerosol from the drying chamber;
• removing dried material from the drying chamber;
• reclaiming heat energy used in the drying process, including the heat of vaporization of the vaporized liquid;
• and
• applying at least a portion of the reclaimed heat to preheating the material.

A method of drying material, comprising the steps of:

• placing the material in a vacuum drying chamber;
• applying microwave energy to the material in the chamber to evaporate liquid from the material;
• admitting a limited amount of cool air to the chamber to mix with the vapor and form an aerosol mixture;
• maintaining low pressure within the vacuum drying chamber by removing the aerosol from the chamber;
• recovering heat energy from the removed aerosol, including latent heat of vaporization;
• and
• applying the recovered heat to the material.