Apparatus and method for solvent recovery from drying process
Method and apparatus for condensing a majority of the solvent in a process gas stream at low temperatures, e.g., below the freezing point of water, ca. −5° C. The gas stream exiting the condenser step may be further processed in one or more emission control devices, such as a single or multi-step series of concentrator devices, such as zeolite concentrator devices. One or more emission control operations can be carried out downstream of the single or multi-step concentrators. The aforementioned condensing process enables the one or more concentrators to operate in a favorable temperature range for removal of 99% or more of VOC, thereby meeting or exceeding strict environmental regulations.
1. A method for conditioning a circulation air laden with at least one condensable fluid, comprising:
a. providing the circulation air at a first volume flow and intake temperature level above 0° C. to a main condenser with at least one main condensation chamber;
b. gradually cooling the circulation air to a main temperature level of 0° C. or less inside the main condensation chamber;
c. splitting the volume flow of the circulation air into a high volume re-circulating flow and low volume off-gas side stream after reaching the main temperature level; and
d. providing the high-volume re-circulating flow to a circulation air intake of a dryer.
2. The method according to claim 1 , wherein the circulation air is cooled according to step b) with at least one cooling coil filled with a cooling medium, and whereby the cooling medium enters the coiling coil at the far end side of a circulation air entry with entry temperature of 0° C. or less and is heated while traveling through the cooling coil in a counter-flow direction to the circulating air.
3. The method according to claim 1 , further comprising:
a. feeding the circulation air at the first volume flow to a pre-condenser upstream said main-condenser with a pre-condensing temperature level below a first temperature level and above said main condensing temperature;
b. gradually cooling the circulation air to said pre-condensing temperature level in the pre-condenser; and
c. providing the cooled circulation air to an intake of said main condenser.
4. The method according to claim 2 , further comprising:
a. feeding the circulation air at the first volume flow to a pre-condenser upstream said main-condenser with a pre-condensing temperature level below a first temperature level and above said main condensing temperature;
b. gradually cooling the circulation air to said pre-condensing temperature level in the pre-condenser; and
c. providing the cooled circulation air to an intake of said main condenser.
5. The method according to claim 1 , further comprising pre-cooling said circulation air upstream of said main condenser.
6. The method according to claim 1 , further comprising re-heating said circulation air downstream of said main condenser.
7. The method according to claim 5 , further comprising re-heating said circulation air downstream of said main condenser.
8. The method according to claim 1 , further comprising:
a. feeding the off-gas side stream to an at least two-stage air pollution control device;
b. collecting and increasing the concentration of residual condensable fluid in an adsorptive concentrator as a first pollution control stage;
c. subsequently treating the remaining off gas stream in a second air pollution control device as a second stage further downstream of the first stage to a level of concentration of residual condensable in the air below a predetermined limit.
9. The method of claim 8 , wherein said predetermined limit is 1 mg/Nm 3 .
10. The method according to claim 8 , wherein said second air pollution control device is a second adsorptive concentrator.
11. The method according to claim 8 , wherein said second air pollution control device is a filtration device.
12. The method according to claim 11 , wherein said filtration device comprises an active carbon filter.