RU2626852C1 - Way of wood torrefaction - Google Patents

Abstract

FIELD: timber conversional industry.

SUBSTANCE: way of wood torrefaction comprises the wood warming-up to 200°C in the airtight drying chamber, the following wood warm-up at a temperature of 200-300°C in the airtight torrefaction chamber, the torrefacated wood cooling-down inside the airtight atmosphere. At first the wood is sawed before the warming-up and then is ripped into wood blocks, the wood warm-up lasts for not less than 2 hours, the further wood warm-up in the torrefaction chamber lasts for 2.3-2.8 hours.

EFFECT: enhancement of process safety.

4 dwg, 1 tbl

Description

The invention relates to wood processing, in particular to torrefaction, and can be used in the forestry industry for the disposal of wood waste to obtain useful constituents used as fuel in the energy sector.

As a result of patent research, a number of technical solutions in this technical field were identified, for example, US 2015143742, CN 104471033, US 2014208995, KR 20140035866, US 2013318865, CA2798582, WO 2012158115, EP 2553050.

A known method and device for the torrefaction of biomass (patent for the invention of the Russian Federation No. 2559491, publ. 08/10/2015). According to the invention, the method of torrefaction (drying) of biomass at low temperature comprises the steps of:

- the creation of finely ground biomass,

- feeding finely divided biomass into at least one heater for drying and heating said biomass,

- supplying said dried biomass to at least one rotary torrefaction reactor, said reactor having a heated jacket and also cooling tubes spaced at equal distances in the circumferential direction located at a certain distance in the radial direction from the jacket, said cooling tubes arranged so that at least some of them in the process of rotation of the aforementioned at least one reactor are in contact with the torrefied biomass and cool it.

Preferably, torrefaction is performed in the absence of air or oxygen.

The disadvantages of this invention are crushing of biomass before frying, rotating reactors, a heated jacket, cooling pipes spaced equally apart, supplying cooling fluid to the cooling pipes partially or completely in contact with the torrefied biomass, low efficiency of heat penetration into the loaded wood mass. High power consumption. A lot of sophisticated equipment. Big power consumption. The duration of torrefaction is 6 hours, the long duration of the process, increased fuel consumption for heating.

The closest technical solution is the method of biomass torrefaction, which involves heating wood to 200 ° C without air in the drying chamber, further heating of wood at a temperature of 200-300 ° C without air in the torrefaction chamber, cooling of torrefied wood in the atmosphere without air ( http://www.infobio.ru/sites/default/files/alexandrova.pdf, publ. 2015, see the annex to the application).

The disadvantage of this method is that it uses crushed or pulverized wood.

An object of the invention is to expand the range of biofuels.

Achievable technical result - increasing the safety of the process of obtaining torrefied wood.

The technical problem is achieved by the fact that the method of torrefaction of wood includes heating wood to 200 ° C without air in the drying chamber, further heating of wood at a temperature of 200-300 ° C without air in the torrefaction chamber, cooling of torrefied wood in the atmosphere without air, before heating, the wood is first sawn and then split into firewood elements, the wood is heated in the drying chamber for at least 2 hours, the further wood heating in the torrefaction chamber is carried out for 2.3-2.8 hours

Comparison of the claimed technical solution with the prototype shows that it differs in the following features:

- before heating, the wood is first sawn;

- then split into firewood elements;

- heating of wood in the drying chamber is carried out for at least 2 hours;

- further heating of the wood in the torrefaction chamber is carried out for 2.3-2.8 hours

Therefore, we can assume that the claimed technical solution meets the criterion of "novelty."

The invention can be implemented using well-known technological equipment, therefore it meets the criterion of "industrial applicability".

Known methods of torrefaction of wood involve its grinding to a fine fraction or a pulverized mass and the use of various components, for example, inert gases (nitrogen), sulfuric acid, supersaturated steam, etc., depending on the technology features. Additional technological operations are also required for granulating or briquetting fuel after torrefaction. All this greatly complicates the biofuel production process, and there is also the possibility of serious accidents when working with pulverized fuel, which can lead to casualties among maintenance personnel.

When conducting patent research, the claimed combination of features was not identified, therefore, the claimed solution meets the criterion of "inventive step".

To obtain torrefied wood, the applicant first conducted experimental studies. For this, a mini-furnace was built with a furnace, a torrefaction chamber and a chimney. A mini retort was made with a diameter of 55 cm, a height of 30 cm, with a blank bottom. A pipe was welded to the bottom to divert the gas mixture into the furnace. The retort in the ball torrefaction chamber is mounted permanently. The top of the retort had a removable cover, the cover was hermetically sealed through a sheet of asbestos sheet and sealed by bolts and nuts. The torrefaction chamber was closed with a lid; tightness was achieved with an asbestos cord and the weight of the lid. The cover had thermal insulation from four layers of asbestos sheet, the thickness of the asbestos sheet was 5 mm. A bimetallic thermometer with a scale from 50 ° C to 350 ° C with a division value of 10 ° C was mounted on the sheet lid. The retort was loaded with birch tulles from plywood pencil with a diameter of 75 mm and a length of 270 mm. Flue gases entered the torrefaction chamber from the furnace, and were discharged from the chamber into the pipe due to the draft of the pipe. First, the temperature rose to 200 ° C and held for 2 hours, then rose sharply to 290 ° C and held for 2.5 hours. Then the lid of the chamber for cooling the biofuel retort was opened. After 1.5 hours, the retort lid was opened and the torrefied kilka, which had a brown color, was removed. The installation produced 5 experiments.

Later, to obtain torrefied firewood, the MPRU-22 pyrolysis furnace was used.

This furnace belongs to stationary closed-loop pyrolysis plants with vertical extraction retorts and complete afterburning of pyrolysis gases in the furnace. The drying, torrefaction and furnace processes in the installation are combined. Combined-cycle gases formed during drying and soft pyrolysis of the feedstock are completely collected in gas collectors, discharged into the furnace, and burned there. This ensures the environmental cleanliness of the technology of torreficate used in this installation. The composition of atmospheric emissions is no different from emissions that occur during the use of firewood as fuel in domestic stoves and conventional boiler rooms. In addition, this technology provides a more complete combustion, since the combustion of soft pyrolysis products occurs in gaseous form, and not in the form of solid fuel, as when using firewood as fuel in conventional boiler houses.

In FIG. 1 shows a general view of the MPRU-22 pyrolysis furnace; FIG. 2 shows retorts before loading the raw material, FIG. 3 shows a cooling pad for retort with torreficate; FIG. 4 schematically shows the MPRU-22 furnace.

The MPRU-22 pyrolysis furnace for heat treatment of firewood contains (Fig. 4) a body 9 thermally insulated from the environment with hatches and covers 5 for loading and unloading retorts 4 into torrefaction chambers 2 and drying 3, connected to the combustion chamber 1 for pumping flue gases (coolant) ) from the combustion chamber (furnace) due to the draft of the chimney 6. For the implementation of the whole process in the housing are combined:

- combustion chamber 1, torrefaction chamber 2, drying chamber 3,

- systems for removing steam and gas from retorts through gas collectors (not shown conditionally) and pipes 7 located in the bottom of the furnace body.

- control thermocouples - temperature measurement and control sensors (not shown conditionally), the signals from which are fed to the control panel. Thermocouples are located at the inlet and outlet of the coolant (flue gas) in the torrefaction and drying chambers.

Firewood is loaded into retorts 4 and installed through a hatch with a removable heat-insulated lid 5 in a pyrolysis furnace vertically, first in a drying chamber 3, at the bottom of the drying chamber there is a layer of sand to seal the retorts from steam and gas gases, the hatch is sealed with a lid, the wood is heated through the wall flue gas retorts from the combustion chamber 1 (8 is the direction of flue gas movement). The drying time is 2.5 hours. Then the retorts are removed from the drying chamber 3 and loaded through the hatch with a lid 5 into the torrefaction chamber 2, the hatch is closed by a lid 5 hermetically with a layer of sand. The duration of torrefaction is 2.5 hours. After unloading the retorts from the drying chamber into the torrefaction chamber, retorts with new raw materials are immediately loaded into the drying chamber. And so the cycles are repeated after 2.5 hours. When heated in the retorts, an excess pressure of the vapor-gas mixture is created by about 10% above atmospheric. Due to overpressure, the vapor-gas mixture formed during the torrefaction of the feedstock is completely discharged through the trellised bottom cover of the retort, enters the gas collector, enters the combustion chamber from the gas collector through the gas exhaust pipes and burns there. This ensures the environmental cleanliness of the torrefaction technology. This technology provides a more complete combustion of the vapor-gas mixture, since the combustion of torrefaction products occurs in the vapor-gas form, and not in the form of solid fuel, as when using firewood as fuel in boiler rooms.

Next, the retorts are removed from the torrefaction chamber and placed on the site in a layer of sand to cool the retorts and torreficate (Fig. 3) to 90 ° C. After cooling, the torreficate is unloaded from the retorts and sent for packaging in bags of 10-20-40 kg, in MKRy or BIG-BENy. Retorts are sent to the loading pad.

The frequency of finished products - 2.5 hours for 6 retorts.

Previously, the wood is cut with a wood splitter with a saw for logs with a length of 200-300 mm.

To test for biofuel burning, 7 tyulka were burned in four open brick fireplaces. Burning lasted two hours. The flame was long, had the colors of white, blue and white-blue. Untreated firewood burns out within an hour. Treated firewood burns 1.5 hours longer.

Samples were taken for biofuel heat transfer tests. The tests were carried out in the laboratory of the joint-stock company “Eastern Research Coal Chemical Institute” (JSC “VUKHIN”) Testing Center, Yekaterinburg.

Test report No. 68 / Н-2015 dated December 09, 2015.

Compare the firewood torreficate with the following types of wood fuel:

Pellets: calorific value 4108 kcal / kg at a density of 1200-1400 kg / m ³ , ash content of 3%.

Dry birch firewood: calorific value 2930 kcal / kg at a density of 540 kg / m ³ , ash content of 6%.

Eurodrova: calorific value of 4400 kcal / kg at a density of 1100 kg / m ³ , ash content of 1.5%.

Torrefied firewood: calorific value 4488 kcal / kg at a density of 423-438 kg / m ³ , ash content 0.77%.

Industrial tests have also shown that the heating of wood in the torrefaction chamber must be carried out within 2.3-2.8 hours. If the wood is heated less than 2.3 hours, then it does not reach the required calorific value, and heating the wood for more than 2.8 hours to her charring.

Thus, the claimed invention allows to simplify the process, while excluding operations that can lead to explosive situations when working with fine and dusty raw materials. At the same time, an expansion of the biofuel assortment is achieved, which has sufficiently high operational indicators.

Claims (1)

Method of wood torrefaction, including heating wood to 200 ° C without access of air in the drying chamber, further heating of wood at a temperature of 200-300 ° C without access of air in the torrefaction chamber, cooling of torrefied wood in the atmosphere without access of air, characterized in that before heating the wood is first sawn and then chopped into logs, the wood is heated for at least 2 hours, further heating of the wood in the torrefaction chamber is carried out for 2.3-2.8 hours

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