Uses of Hot Gas Filtration

Why Filter Gases at High Temperature ?

There are a number of reasons why it may be desirable to remove solids from a process gas at an elevated temperature:

• the gas is already hot and subsequent process(es) also require it to be hot, but clean
• the hot gas contains condensable liquids or solids that are required to remain in the vapour phase i.e.
  • product liquids, such as oil from pyrolysis processes, that will be subsequently condensed and captured
  • acid gases, that would condense and corrode the process vessels
  • sticky liquids that would blind the filter medium
• the solids would compromise downstream processes e.g. by fouling a heat exchanger
• the gas will be recycled and solids are unacceptable
• the solids to be collected will change their properties if cooled down
• occasional loss of control, or sparks, require high temperature resistance
• a dry scrubbing sorbent in the gas stream reacts only at high temperature

Applications

Caldo has installed ceramic filters on processes including (links are to other pages on www.caldo.com):

• incineration of various materials
• burnout furnaces in lost wax foundries
• plasma melting of catalyst for precious metal recovery
• demilitarisation of munitions and chemical weapons
• production of nano materials
• gasification of waste wood and other materials
• pyrolysis of waste plastics and other materials
• manufacture of high performance ceramic fibres
• sulphuric acid recovery

Dry Scrubbing

Acid gases are a common gas phase pollutant and these can be very effectively removed by the addition of lime or sodium bicarbonate to the gas upstream of the ceramic filter. This acid gas removal technique is a dry scrubbing process.