Systems and methods for high humidity curing within tablet coating system

1. A method of supplying a humid air flow to a pan coater of a tablet coating system, the method comprising:

providing the pan coater to apply one or more coatings to a tablet;

providing a recirculating air handler operably connected to the pan coater, the recirculating air handler comprising:

an inlet duct operable to receive exhaust air from the pan coater;

a humidifier to introduce moisture into the exhaust air in an amount resulting in an exit air having a relative humidity of up to about 94%;

a vent operable to release air from the recirculating air handler to the atmosphere via a vent valve, wherein the vent valve is opened as needed to maintain a pressure within the pan coater of at least 0.15 inches of water column below atmospheric pressure; and

an exit duct operable to deliver the exit air to the pan coater;

one or more configurable valves; and

a control system comprising a mode control operable to coordinate opening and closing of the one or more configurable valves to switch an air supply of the pan coater from a flow-through air handler to the recirculating air handler.

2. The method of claim 1 , further comprising:

establishing an air flow through the recirculating air handler operatively connected to receive exhaust air flow from the pan coater and to deliver a supply air flow to the pan coater;

heating the air flow to pre-heat the pan coater, a supply duct delivering air flow to the pan coater from the exit duct, and an exhaust duct receiving the exhaust air from the pan coater and delivering the exhaust air to the inlet duct;

establishing and maintaining a humid air flow within the pan coater for a duration of a humidification process; and

clearing the humid air flow from the pan coater.

3. The method of claim 2 , wherein the air flow is heated to a temperature ranging from about 50° C. to about 80° C. and a dew point ranging from about 45° C. to about 55° C.

4. The method of claim 2 , wherein the humid air flow is cleared from the pan coater by deactivating the humidifier and maintaining a pressure within the pan coater that is at least 0.25 inches of water column below atmospheric pressure.

5. The method of claim 2 , further comprising:

reestablishing air flow through the flow-through air handler operatively connected to the supply duct and configured to receive external air from the atmosphere, wherein reestablishing air flow through the flow-through air handler comprises closing a first and second valve operable to block flow entering and exiting the recirculating air handler, opening a third valve operable to direct air flow from the flow-through air handler into the supply duct, and directing the exhaust air flow from the pan coater through an exhaust stack into the atmosphere.

6. The method of claim 2 , further comprising:

removing particulate matter from an airflow entering the recirculating air handler via at least one inlet filter in the recirculating air handler situated upstream of the humidifier;

removing particulate matter from an airflow exiting the pan coater via at least one exit filter situated downstream of the humidifier;

monitoring an operational status of the at least one inlet filter or at least one exit filter via a filter monitor in the control system; and

issuing warnings to a system user when a filter is clogged and/or in need of cleaning or replacement.

7. The method of claim 1 , wherein the control system is further operable to modulate the air flow within the system, modulate temperature within the system, modulate humidity within the system, and/or modulate pressure within the pan coater.

8. The method of claim 1 , further comprising:

heating the pan coater via a heater;

measuring the temperature of the air flow downstream of the heater via a temperature sensor, wherein the control system reduces the heat output of the heater if the temperature of the air flow exceeds a maximum temperature; and

measuring air temperature within the pan coater via a temperature sensor, wherein the control system is operable to command increased heat output by the heater if the air temperature for the pan coater falls below a predetermined threshold temperature.

9. The method of claim 1 , further comprising:

measuring humidity introduced by the humidifier via a humidity sensor and an additional humidity sensor, the humidity sensor operatively connected to the exit duct of the recirculating air handler, wherein the control system is operable to increase or decrease the humidifier output if the measured humidity falls outside a minimum or maximum humidity level, and wherein the control system is operable to reduce clean steam flow entering the humidifier if the measured humidity at the additional humidity sensor exceeds a predetermined condensation threshold.

10. The method of claim 1 , further comprising:

monitoring a differential pressure between a first pressure sensor and a second pressure sensor, wherein the control system issues an alert or opens the vent valve if the differential pressure exceeds a threshold value.

11. The method of claim 10 , wherein the first pressure sensor is inside the pan coater and the second pressure sensor is within external atmosphere.

12. The method of claim 10 , wherein the first pressure sensor is upstream of a filter and the second pressure sensor is downstream of the filter.

13. The method of claim 1 , further comprising:

supplying a low humidity air flow to the pan coater via the flow-through air handler, wherein the low humidity air flow has a relative humidity less than the humid air of the recirculating air handler.

14. The method of claim 1 , wherein the one or more configurable valves is configured to:

cut off flow through the recirculating air handler and direct the air flow from the flow-through air handler to a supply duct of the pan coater and from an exhaust duct of the pan coater to an exhaust stack; or cut off flow from the flow-through air handler and direct the air flow from exit duct of the recirculating air handler to the supply duct of the pan coater and from the exhaust duct of the pan coater to the inlet duct of the flow-through air handler.