Tableting process of pharmaceutical products

In a process which produces tablets, a mixture of solvents, containing MDC and methanol and binders is used. Solvents are emitted from the tableting unit. The following process is used to recover the emitted solvent.

Feed gas at 50°C from the tableting process is pre-treated by a filter to remove dusts and by a rotary wet scrubber to absorb mainly methanol. During the scrubbing MDC also dissolves in water, although at low concentration. This water is treated in two steps, by a degassing unit at room temperature and by an activated carbon filter so that the concentration of residual solvents is decreased below that of the environmental standard. The gas from the degassing unit is joined to the feed gas at the outlet of the demister of the MDC recovery unit. The gas, the pretreated feed, and gas from the degassing are cooled down to 30 - 40°C before feeding to the MDC recovery unit which consists of at least two columns for adsorption and desorption cycles. After processing the gas is released to the atmosphere.

Because little methanol is vaporized at room temperature, the water stream is fed to another degassing unit heated to 65°C to vaporize methanol. For safety purposes, the degassing air flow rate is controlled at 10 m3/min. The methanol laden gas from the heated degassing unit is fed to a catalytic oxidation unit where methanol is decomposed before exhausting the gas stream to the atmosphere. Table 22.2.8 shows the process performance.

Table 22.2.8. Performance of the solvent recovery in the tableting process



Flow rate at rotary scrubber

1,000 l/min

Feed concentration

MeOH 10,000 ppm MDC 2,000 ppm

Exhaust concentration

MeOH 150 ppm MDC 3 ppm

Catalytic oxidation flow rate

10,000 l/min

Feed concentration

MeOH 8,500 ppm MDC 1 ppm

Exhaust concentration

MeOH 10 ppm

This is a unique example of a process in which the recovery and the catalytic oxidation steps are combined. In addition to its use in the pharmaceutical industry, the adsorption is a suitable method for the separation of chlorine-containing solvents. Figure 22.2.11 shows the process flow diagram.

Pharmaceutical Flow Diagram

Figure 22.2.11. Flow diagram of tablet binder recovery process.

Drain ige

Figure 22.2.11. Flow diagram of tablet binder recovery process.

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