Method for producing vegetable carbon with high carbon content and plant for carrying out said method
For implementing startup and priming phases of a vegetable carbon production method, an installation includes a generator of hot gases with low oxygen content, and a fan downstream which boosts the hot gases into a lower part of a reactor. The reactor includes a column of substantial height whose upper inlet, with a temperature T 3 of less than 65° C., is used to continuously load and add biomass and whose lower part has a grid for support and removal of the load, an underlying injection chamber for the gases from the generator, and a mechanism for retrieving processed substances. The installation also includes, at the outlet for cold gases at temperature T 3 at the top of the reactor column, a thermal post-combustion chamber for the extracted gases, a heat exchanger, a fan, a second heat exchanger, a vent and connecting pipes. Another circuit located between the reactor and the fan includes a compressor unit to supply pressurized air at ambient temperature in the production phase and to replace the hot gases from the generator by compressed air.
1. A method for producing vegetable carbon with high carbon content from non-food agricultural biomass introduced at an upper inlet into a reactor column, comprising the following phases performed in sequence in an operating process:
(a) priming phase, comprising the steps of:
tiered pyrolytic distillation of the biomass through injection of hot gases at a temperature between 350° C. and 400° C. into a lower part of the reactor column through a grid supporting the biomass, and
removing processed biomass from the lower part of the reactor column when a temperature of a biomass layer just above the grid reaches the temperature of the injected gases;
(b) transition phase, comprising the steps of:
progressively adding air to the injected gases to enrich with oxygen,
oxidizing volatile components located on the grid with the oxygen to increase the temperature of the biomass layer just above the grid, and accelerate biomass mineralization; lowering the temperature of the injected gases into the lower part of the reactor column with the added air; and
(c) production phase, including the steps of:
when the temperature of the injected gases reaches ambient temperature, replacing the oxygen enriched gases exclusively with compressed air,
continuously injecting the compressed air into the lower part of the reactor column through the grid to increase heat transfer between the gases and the biomass to obtain vegetable carbon with high carbon content and to maintain the temperature in the biomass layer just above the grid between 600° C. and 750° C.,
removing biomass transformed into vegetable carbon from the lower part of the reactor column through the grid, and
adding non-food agricultural biomass through the upper inlet to the reactor column as the vegetable carbon is removed from the lower part of the reactor column through the grid while maintaining temperature at a top of the reactor column below 65° C.
2. The method as claimed in claim 1 , further comprising: implementing the priming phase with a generator of the hot gases, and a first fan downstream which boosts the hot gases into the lower part of the reactor, said reactor comprising a column of substantial height with an upper inlet to continuously load and add biomass, a grid in the lower part for support and removal of the processed biomass, and an underlying injection chamber for the injected gases, and further employing a mechanism for retrieving processed biomass, an outlet for cold gases at a top of the reaction column, a thermal post-combustion chamber for extracted gases, a heat exchanger, a second fan, a second heat exchanger, a vent and connecting pipes for recycling the gases with connections between a circuit defined by components on one side, and components on another side, and further employing another circuit located between the reactor column and the first fan, the another circuit including a compressor unit to supply the compressed air in the production phase and total replacement of the hot gases from the generator by the compressed air at ambient temperature.
3. The method of claim 1 wherein, in the priming phase, the hot gasses injected into the lower part of the reactor column contain approximately 1% oxygen.
4. The method of claim 1 , further including: employing the removed vegetable carbon to synthesize biofuel.