Product Description

Biomass carbon-vapor co-production is the process of producing carbonized materials and vapor with biomass materials, in which materials are heated in an air-isolation environment to reduce content of elements other than carbon. Main structure of the plant consists of a material bin, an elevator, a feeder, a furnace stack, refractories, a rotator, a temperature detector, a PLC cabinet, a cooler, a settling chamber, a waste heat boiler, a fan, and a deduster.

The carbonization process is an integration of material carbonization and vapor production based on end gas therefrom.

Carbonization Process

The carbonization process is actually a destructive distillation process at low temperature, in which materials are heated in a low-temperature and air-isolated environment to volatilize low molecular compounds, and then trigger a series of complicated physical and chemical changes in materials, which involves physical changes such as dehydration, degasification and drying. The process causes materials to discharge oxygen, hydrogen and other non-carbon substances, and recombine into substances in ordered graphite microcrystalline structure. Gaps among microcrystalline in these crystals formed with irregular hexagon carbon atomic planes are initial pores of the carbonized materials. Therefore, purposes of carbonization are changing materials into secondary pore structures adapted to activation, and rendering them with mechanical hardness required for undergoing the activation.

Requirements on carbonization of materials are obtained through carbonization.

 

 

Appearance of carbonized materials shall meet requirements in dimension

and shape. Inner structure of carbonized materials shall offer specific initial pores

and high mechanical hardness. The carbonization process may be divided into

the following sections.

 (1) Drying section at a temperature below **0°C. External and internal

moisture of materials evaporate in external heat, and shape of materials

remains.

 (2) Pyrolysis section at a temperature between ******0°C. Materials

decompose and release gaseous products (CO, CO2, H2 S, etc.), changes of

chemical composition of material initiates. Pyrolysis temperature varies with

specific materials, which is lower for low- metamorphic grade materials.

 (3) Carbonization section at a temperature between *******0°C.

Polycondensation and thermolysis cause materials to separate volatile

components out. The majority of tar, methyl alcohol, ethylene and other

products are separated in this section. Materials are gradually softened and

melted in this section, forming a plastic mass mixed by gas, liquid and solid

substance, which will be converted into semi- cokes in needle-shape or bulk.

Constant temperature and heating rate are key operable conditions

for carbonization process.

Heating rate is critical for productive ratio of carbonized products.

A high heating rate can separate out more tars and coal gas, and thereby

reduce productive ratio of carbonization. A lower heating rate may prolong

the duration of materials in low-temperature section, offering more options of

pyrolytic reactions which break weaker bonds in molecular in initial pyrolysis,

and form structures with higher thermal-stability in parallel sequential thermal

polycondensation, and thus reduce volatile productive rate of pyrolysis in

the high-temperature section, and achieve higher productive rate of solid

carbonized products (carbonized materials).

Quality of carbonized materials output from carbonization process shall

be evaluated considering volatiles content, moisture content and hardness.

Qualified carbonized materials shall be with a volatiles content of *2%- *6%,

a moisture content of *5%**5%, and a ball-pan hardness of *0%.

As measurements of the above indexes are time-consuming, and

immediate evaluation on carbonized materials are required in on-site debugging

for further adjustments on parameters, visual inspection and evaluation are

acceptable. Qualified carbonized materials shall have smooth and crack- free

surfaces, high hardness and uniform sections.

Treatments on End Gas and Generation of Vapor with Waste Heat

Carbonized end gas of the carbonization process consists of

high-temperature heating gas generated from combustions of external fuels,

which including CO2. H*0, N2 and a trace of SO2 and CO, and volatiles

generated from thermal decompositions, which including CO, H2, CH4, alkane,

olefin and tar. Traces of toxic matters in end gas of carbonization may cause

contamination without proper treatments.

With the burning method, end gas from carbonization are transfused into

a settling furnace at a high-temperature (******0°C) environment with excess

air, in which combustible gases and toxic substances will be burnt into CO2

and dumped. Heat generated by the such combustions may be recycled by the

waste heat boiler for vapor production. It is a low-cost simple method which

could eliminate most of environmentally harmful substances, and generate vapor

required for carbonization, therefore, the method is widely used in production of

activated carbons.

A large amount of vapor could be produced with the heat generated by

fume combustions.