The gasification

Pezzolato turnkey equipment

The complete gasification equipment is turnkey delivered and includes a storage and biomass preparation system and a co-generation equipment, which transforms chipped material into electric Energy and heat.

Description of the storage and preparation system

The chipped material is charged from the top into a storage tank. Hot air flows upwards through this tank. Part of the heat coming from this hot air induces the evaporation of the chipped material humidity. This drying process takes some days and the dry chipped material is then pulled out from the bottom of the tank. The air is heated by means of an exchanger which uses part of the hot water produced by the co-generation system and blown upwards into the tank by means of a fan. The capacity and the temperature of the air flowing through the tank are checked so that the chipped material is dried up to a content of humidity not superior to 10%.

The dry chipped material is then screened in order to separate the fine particles before entering the gasification equipment. These particles are conveyed by an Archimedean screw system into a closed storage tank and then used for little boilers or for pellet production.

The dry screened chipped material is conveyed to the charging system by an Archimedean screw system.

 

Description of the cogeneration equipment

The charging system presents two shutters which open alternatively. This method avoids the unintentional air flowing in the gasifier. The equipment is completed by a motorised Archimedean screw system which regulates the necessary quantity of chipped material in order to keep it at a constant level in the gasifier.

The gasifier employed is the one currently defined “Co-current fixed bed” gasifier.

This type of gasifier consists of a closed tank; the chipped material is charged from the top. The syngas (produced gas) and the produced ashes leave from the reactor’s bottom.

In such a system the material moves downwards, due to the  gravity force.

During the descent the following reactions take place:

 

 

DEHYDRTTION OR DRYING PROCESS

In the dehydration zone, the water remaining in the chipped material evaporates. This step of the process takes place in air absence and needs heat energy. Temperature is inferior to 200°C.

 

THE PYROLYSIS (OR DEVOLATILIZATION) PROCESS

In this area, the wood separates at temperature between 200and  600°C by producing char and a gas mixture which includes also a great part of tar. Also this step of the process takes place in air absence and needs heat energy.

 

OXIDATION

In their descent inside the gasifier pyrolysis products enter in a narrowing where a controlled amount of air is injected. In this area the tar and a part of the charcoal are burned at temperatures above 1000 ° C.

This reaction provides the heat necessary in order the reactions in the remaining zones of the gasifier to take place.

This type of gasifier ensures an extremely low tar content in the syngas, in fact the tar generated in the pyrolysis is decomposed almost completely when passing the narrow and high temperature oxidation zone.

 

REDUCTION

In this area the charcoal, supported by a grid, reacts with the gas resulting from the oxidation zone that maintain temperatures above 700 ° C

. The reactions that occur in this area allow to obtain a further portion of combustible gases (mainly CO and H2), transforming the water vapour coming from drying and oxidation, the carbon dioxide generated in the oxidation zone and the charcoal.

After emerging from the gasifier the flow of gas and ash is cooled to about 130 ° C through a series of heat exchangers. The recovered heat is used in part to heat the air used for the oxidation. The remainder part heats a flow of hot water which is supplied from plant as cogenerated heat.

The gas flow then passes through a dry filter in which the ash is separated from the syngas. The filter is equipped with automatic extraction auger, which carries the ashes in a closed tank. .

The clean syngas is then burned in an Otto cycle engine to produce electricity. The engine cooling is done with a water-water exchanger, thereby further contributing to the production of hot water.

 

GASIFICATION UNITS: STANDARD MODELS

Pezzolato offers the following standard containerized models:

Modello

Chips consumption*

Rated output (electricity)

Rated output (heat energy)

PG50 45 Kg/h 50 kW electric 110 kW thermal
PG100 90 Kg/h 100 kW electric 220 kW thermal
PG200 180 Kg/h 200 kW electric 440 kW thermal
PG300 270 Kg/h 300 kW electric

660 kW thermal

 

 

* wood chips at 10% humidity and free of fine fraction. Forms are available complete with pretreatment system that allows the use of damp virgin wood's wood chips.

They are available on request customized solutions for the specific needs of our customers.

 

GASIFICATION UNITS: DETAILS

 

Figure 1 - Gasification unit SPANNER RE 2

 

Figure 2 - Cogenerator SPANNER RE2: GM engine and ABB generator

 

 

 

                                     

Figure 3 - V-8, 5.7 L cogeneration engine detail

 

 

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