Method and apparatus for recovering blowing agent in foam production

A process for recovering the volatile blowing agents employed in the production of expanded foam thermoplastic materials to permit their reuse in the production of the foam thermoplastic materials and to also reduce emissions of the blowing agents to the atmosphere, said process comprising

• discharging a pressurized solution of the thermoplastic material and volatile blowing agent from an extruder into the ambient atmosphere while volatilizing the blowing agent to thereby expand and foam the thermoplastic material,
• confining the air in a predetermined area surrounding the freshly extruded thermoplastic material while withdrawing from the confined area a stream of air containing the volatile blowing agent at a relatively low concentration,
• directing the stream of withdrawn air to an adsorber and adsorbing the volatile blowing agent on an adsorbent,
• desorbing the blowing agent from the adsorbent to thereby produce a stream of gas containing a relatively higher concentration of volatile blowing agent,
• compressing and condensing the concentrated stream of blowing agent-laden gas to form a liquid blowing agent phase and a gaseous phase containing air and blowing agent vapors,
• separating the liquid blowing agent phase from the gaseous phase and recovering the liquid blowing agent under pressure for reuse in the production of the foamed thermoplastic material, and
• recycling the gaseous phase to said adsorbing step for recovery of the blowing agent vapors contained therein.

A process for recovering the volatile blowing agents employed in the production of expanded foam thermoplastic materials to permit their reuse in the production of the foam thermoplastic materials and to also reduce emissions of the blowing agents to the atmosphere, said process comprising

• discharging a pressurized solution of the thermoplastic material and volatile blowing agent from an extruder into the ambient atmosphere while volatilizing the blowing agent to thereby expand and foam the thermoplastic material,
• moving an enclosure into surrounding relation to the freshly extruded thermoplastic material to form a confined area for receiving the volatile blowing agent vapors,
• withdrawing from the enclosure a stream of air containing the volatile blowing agent vapors,
• separating the withdrawn stream of air into a blowing agent-rich stream and a blowing agent-lean stream,
• compressing and condensing the concentrated stream of blowing agent-laden gas to form a liquid blowing agent phase and a gaseous phase containing air and blowing agent vapors,
• separating the liquid blowing agent phase from the gaseous phase and recovering the liquid blowing agent under pressure for reuse in the production of the foamed thermoplastic material, and
• recycling the gaseous phase to said adsorbing step for recovery of the blowing agent vapors contained therein.

An apparatus for recovering the volatile blowing agents employed in the production of expanded foam thermoplastic materials to permit their reuse in the production of the foam thermoplastic materials and to also reduce emissions of the blowing agents to the atmosphere, said apparatus comprising

• an extruder including means for discharging a solution of the thermoplastic material and volatile blowing agent so as to produce an expanded foam thermoplastic material,
• enclosure means located adjacent to the discharge of the extruder and defining a confined area surrounding the freshly extruded thermoplastic material,
• means for withdrawing from said enclosure means a stream of air containing the volatile blowing agent at a relatively low concentration,
• means for receiving the said stream of air and blowing agent and concentrating the stream to increase the blowing agent concentration by selective adsorption-desorption on an adsorbent,
• means for receiving the concentrated stream of blowing agent-laden air and for compressing and condensing the stream to form a liquid blowing agent phase and a gaseous phase containing air and blowing agent vapor, and
• means for separating the liquid blowing agent phase from the gaseous phase to recover the liquid blowing agent for reuse in the production of the foam thermoplastic material.

An apparatus for recovering the volatile blowing agents employed in the production of expanded foam thermoplastic materials to permit their reuse in the production of the foam thermoplastic materials and to also reduce emissions of the blowing agents to the atmosphere, said apparatus comprising

• an extruder including means for discharging a solution of the thermoplastic material and volatile blowing agent so as to produce an expanded foam thermoplastic material,
• enclosure means located adjacent to the discharge of the extruder and defining a confined area surrounding the freshly extruded thermoplastic material,
• means for withdrawing from said enclosure means a stream of air containing the volatile blowing agent at a relatively low concentration,
• adsorber means operatively connected to said enclosure means for receiving said stream of air and blowing agent and for concentrating the stream to produce a blowing agent-rich stream and a blowing agent-lean stream,
• said adsorber means including first and second adsorption chambers each containing therein an adsorbent for said blowing agent, and conduit means communicatively interconnecting the two chambers and cooperating therewith so that one of the chambers is operable in an adsorption mode while the other chamber is operable in a desorption mode to thereby provide for continuous operation,
• said conduit means being so constructed that the chamber which is in the adsorption mode has an inlet communicatively connected to said enclosure means for receiving the stream of air and blowing agent therefrom and an outlet communicating with the atmosphere for discharging said blowing agent-lean stream, and the chamber which is in the desorption mode having an inlet connected to a source of steam for being directed into contact with the adsorbent for desorbing the blowing agent and having an outlet for discharge of a blowing agent-rich stream containing blowing agent vapor, water vapor, and air,
• variable volume accumulator means communicatively connected for receiving and accumulating said blowing agent-rich stream,
• compresser means communicatively connected to said accumulator means and operable for receiving said blowing agent-rich stream therefrom and for compressing the blowing agent-rich stream to a pressure greater than critical pressure of the blowing agent,
• condenser means connected to said compressor means for receiving the compressed blowing agent-rich stream and for cooling and condensing the same to form a liquid blowing agent phase, a water phase, and a gaseous phase containing blowing agent vapor, water vapor and air,
• a receiver vessel operatively connected to said condenser means for receiving and separating as separate immiscible phases the liquid blowing agent, the water, and the gaseous phase,
• means for withdrawing the liquid blowing agent from said receiver vessel to permit reuse thereof in the production of the foam thermoplastic material, and
• means for venting the gaseous phase from the receiver vessel and for directing the gaseous phase to said adsorber means to permit recovery of the blowing agent vapors contained therein.