B2. [20 marks] A coal-fired combustion system produces flue gas that contains particulate matter (mostly fly ash). To reduce the amount of particles, the flue gas is treated in a venturi scrubber. The measurement of the mass and size of the particles at the inlet and outlet of the scrubber yielded the size distribution data given in the following table: Table 1 - Size distribution data. a) Calculate the overall collection efficiency of the scrubber and the partial efficiency for each size interval (d,i) as a function of the particle geometric average diameter (dp,i). Present a table with the following information for each size interval: b) Calculate the mass-average diameter of the particles (dp) entering and leaving the scrubber. [6 marks] c) In recent years, venturi scrubbers have fallen out of favour as stand-alone particle removal systems. Explain the reasons why this happened. (maximum 100 words) [4 marks]