Dahlman OLGA

Solid removal choice

Solid particles (dust) can be separated from the product gas upstream OLGA by a cyclone or a hot gas filter system. When a cyclone is used only the coarse particles are removed, after which OLGA will remove the remaining fine particles. We compare both systems:

 

Solids removal with a cyclone & OLGA:

When a cyclone is placed upstream OLGA, fine particles will have to be captured in OLGA. Two mechanisms are important:

1. Direct impact
2. Condensation of oil and light tars on the particle.
   The particle forms a nuclei for tar condensation and will "grow" on his way to the column.

By these mechanisms the OLGA collector column will capture most of the particles. However, some particles will not grow enough to be captured and thus carry over this column. These particles / droplets will have to be removed by an ESP after the OLGA collector column. The collected ESP liquid will be recycled to the collector column. After the ESP the gas is free of heavy tars and solids.

 

Solids removal with a hot gas filter before OLGA:

A hot gas filter system is more efficient than a cyclone, coarse and fine particles are separated from the product gas. A hot gas filter therefore simplifies OLGA: 

1. The ESP is not necessary
2. Solid separation from scrubbing oil is not necessary

In other words; the investment in a Hot Gas Filter will (partially) be compensated by savings in the scope of the OLGA unit. More information can be found on "a ceramic hot gas filter"

 

Which choice should I make?

To our experience, solids capture by a cyclone & OLGA is often more interesting than an upstream hot gas filter.  For higher capacities the cyclone / OLGA combination will be considerably cheaper. Technically we also have a preference. A hot gas filter in biomass product gas is a delicate system in a critical position. Capture of fine particles in OLGA is a much more robust and reliable solution.

In some cases a hot gas filter can be of interest:

• Low capacities, where the hot gas filter might be economically interesting.
• Pre-coat filtration on a hot gas filter.
  In case the product gas contains contaminants like alkali metals, chlorine etc., adsorption on lime or activated carbon is an option to separate these contaminants. A hot gas filter precoated with an adsorption agent can do this job and will also take out all solids.