Assessment of Sampling Error Associated with Collection and Analysis of Soil Samples at a Firing Ran

An improvement in a known process and apparatus for gasifying coal with water vapor and oxygen under pressure and at elevated temperature wherein coal is dropped onto a grate within a reactor supplied with gasifying agent from below, product gas being withdrawn above. In accordance with the invention an annular wall depends from the reactor top to form an annular gas space through which product gas is withdrawn. The annular space surrounds the top of the coal bed so the coal is preheated thereby. The wall is provided with apertures so that at least 20% of the product gas enters the annular space by traversing that part of the coal bed surrounded by the wall. This results in reduced product gas velocity and entrainment of coal dust.