| 摘要 |
A process for controlling a gas phase polymerisation reaction in a reactor when changing from a first product (i) made at a first set of conditions to a second product (ii) made at a second set of conditions, comprises: (a) comparing (i) and (ii) reaction temperatures, and changing the product reaction temperature set point to the (ii) reaction temperature if this is lower than the (i) reaction temperature; (b) setting a melt index set point that is either 0-150 % higher or 0-70 % lower than the desired (ii) melt index value; (c) setting a reaction temperature set point that is 1-15 deg C above the desired (ii) reaction temperature if the (ii) melt index value is higher than the (i) melt index value, or 1-15 deg C below the actual (ii) reaction temperature if the (ii) melt index is lower than the (i) melt index; (d) setting a product rate-limiting reactant partial pressure set point that is 1-25 psig either below the (i) rate-limiting reactant partial pressure if the (ii) melt index value is higher than the (i) melt index value, or above the (i) rate-limiting reactant partial pressure if the (ii) melt index value is lower than the (i) melt index value; (e) maintaining the melt index set point, temperature set point and rate-limiting reactant partial pressure set point values until the polymerisation product exhibits an average melt index and average product density with an acceptable range from the desired (ii) melt index and density values; (f) changing the melt index set point to the desired (ii) melt index value; (g) changing the product reaction temperature set point to a value that is either 0-15 deg C above the desired (ii) reaction temperature if the (ii) melt index value is higher than the (i) melt index value, or 0-15 deg C below the desired (ii) reaction temperature of the (ii) melt index value is lower than the (i) melt index value; (h) changing the rate-limiting partial pressure set point to a value that is either 0-25 psig below the desired (ii) rate-limiting partial pressure if the (ii) melt index value is higher than the (i) melt index value, or 0-25 psig above the (ii) rate-limiting partial pressure if the (ii) melt index value is lower than the (i) melt index value; and (j) changing the reaction temperature set point and the rate-limiting partial pressure set point values to the desired (ii) reaction temperature and rate-limiting reactant partial pressure values when the reaction product exhibits an average melt index value within acceptable limits of the (ii) melt index value. |
