This is a complex question without more details provided about the solids. Some solids may not be dosed to a batch reactor using automatic systems very easily. The reference to resins may indicate you are trying to put in cohesive solids and maybe solids of a wide size distribution. Also, you may have a formula that requires very small amounts of some of the different ingredients. These usually need to be added by hand or by using a pre-weighed container.

Most loss-in-weight feeders will work well for free-flowing solids and even on some less cohesive solids. If you have more than three components, it can be very costly. These can be incorporated into most automated control systems. If you have cohesive solids, the reactor can be placed on weight cells (in some cases) or an intermediate hopper can be used, which would be on weigh cells. In this case, only a volumetric feeder would be required. However, the solids flow properties need to be determined to insure proper design of the feeder and hopper. They need to be based on shear cell tests and the hopper needs to empty completely.