Selecting a flow meter for a dirty application

Hi all learned people, I need to select and install a flow meter to meaure infrequent flow of the following gas mixture (in-feed to a thermal incinerator)
Nitrogen Carbon Monoxide Carbon dioxide Carbonyl Sulphide Water (H2O)
The gas stream also contains micronised Titanium Oxide (pigment) which is capable of passing through a flame arrestor. The TiO2 makes the gas stream very sticky and gluey so that any in-line moving parts in contact with the gas stream (such as turbine meter) needs to be able to withstand this coating.
The pipe is a 400mm glass reinforced polyyester and the operating pressure is -1 to +6 kPag, operating temperature is ~ 45 deg C and the mass flow rate is ~18,000 kg/hr.
As mentioned before the flow is infrequent and the thermal incinerator is kept on hot-standby using natural gas. I have considered a V-cone flow meter (McCrometer), a thermal mass flow meter (FCI / Kurz) and an ultrasonic flow meter (Controlotron). Manufacturers have been contacted and I am awaiting their response.
In the mean time I would like to know if there are any other suitable flow meters that I have not considered. If so, can you please let me know? Thanks in advance for your replies. Regards, Raj
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