PROJECT PRESENTATION

Production of synthesis gas from solid combustible materials

A plant designed for the gasification of solid materials with carbon content (all types of biomass originating from farming and forestry, municipal, industrial and special/hazardous wastes, treatment plant slurries, charcoal, coal etc.) for the purposes of generation of pure synthesis gas.

Gasification of solid combustible materials is a process whereby a part of the input materials is burned and the generated heat is utilised to gasify the rest of the material. In the process, product gas is generated, a mixture of carbon monoxide, carbon dioxide, nitrogen (in the case air is used for oxidation), water, hydrogen, methane and, in minute or major concentrations, other hydrocarbons (tars). Gasification is in fact smouldering of combustible materials; hence the crucial technical issue is how to produce synthesis gas free of tar content. Normally, proper construction of the gasification plant is attempted, to prevent generation of tars, however, this, in most cases, this is achieved at the price to flexibility in terms of input material, which must be extremely homogeneous, pure and moisture-free. Since gasification without generation of tars cannot be achieved, the generated gas is usually post-treated, and tars are removed or decomposed into hydrogen and carbon monoxide.

The technological solution rests on the reverse logic, which reads:

higher content of tars = higher purity of the synthesis gas.

The process comprises two phases:

Gasification of materials with hydrocarbon content into the product gas characterised by a high tar content, in a counter-flow natural steam gasifier;
Full conversion of rich tars, organic steam and hydrocarbons into the corresponding volume of synthesis gas in a catalyst, via a partial oxidation process.

The principal and sufficient objective of phase “a” is merely the separation of inorganic matter, ash, minerals, salts and metals from the bulk of hydrocarbons, i.e. volatile substances, to produce product gas, as “dirty” as possible, i.e. product gas saturated by tars. Next, phase “b” converts all the complex hydrocarbon molecules fully into hydrogen and carbon monoxide (partial oxidation). A special characteristic of phase “b” is its selectivity: the reaction does not engage neither free hydrogen nor carbon monoxide in the product gas, but rather first decomposes complex organic molecules, thereby generating further amounts of synthesis gas. The precondition for the above described partial oxidation to take place is a 1% minimum content of any form of organic carbon in the product gas. A sufficient quantity of tars is also important for the catalyst energy balance, since the exothermic reaction maintains the catalyst operating temperature. Otherwise, a portion of the generated synthesis gas would have to be fully oxidised in order to maintain the temperature.

Technological objectives:

Gasification of damp or wet material
Gasification of material with high dust content
Minimal consumption of oxidant for gasification
Generation of product gas with high tar concentration
Preparation of the ideal product gas and oxidant mixture for the purposes of processing
Synthesis gas free of tar content
Process of product gas conversion to synthesis gas with a positive energy balance

ČLAN