LV11994B - BIOMASS CARBONIZATION PROCESS FOR THE ENERGY SUPPLY AND / OR EXHAUST EMISSIONS - Google Patents

Abstract

The invention refers to chemical fuel technology and can be used for biomass (especially wood) processing, at the same time producing coke or charcoal and/or coal gas. The invention's goal is to provide autonomic energy, simply regulating, producing safe and ecologically clean heating energy for the biomass carbonization process, additionally producing coal gas.For method realization in one equipment there are no less than 3 (optimum 4-6) outer heating pyrolysis units, which start functioning gradually after similar time periods are united. Part of the biomass thermal decomposition products are burned for pyrolysis process upkeep, but the remaining part is burned in the utilization furnaces, producing additional heating energy, or is conveyed to the cracking unit, getting transportable and storable coal-gas. The changing pyrolysis steam-gas supply to the heating furnace and re-circulating the once used heating carrier makes the heating carrier temperature adjustment.<IMAGE>

Description

BIOMASS CARBONIZATION TECHNIQUES TO ENSURE PROCESSED ENERGY AND ADDITIONAL FUEL GASES

The invention relates to the chemical technology of fuels and can be used to process biomass (especially wood) to produce coke (or charcoal) and fuel gas at the same time.

The known biomass carbonation techniques [1] are implemented in two types of apparatus: (a) direct heating where the heat carrier is in direct contact with the material and (b) external heating where the heat carrier and the material are separated by a wall.

The advantage of direct heating of the carbonation material is that it is more intensive, takes place on large machines, and is easy to implement in continuous operation technology. The main disadvantage of this technique is that the heat carrier mixes with pyrolysis gases and vapors to reduce their concentration. In plants where dry distillation products (acetic acid, methanol, tar, etc.) are captured and released, this will seriously complicate the condensation system. In modern plants, which produce only charcoal, the problem is the provision of ecological requirements for production emissions. Typically, these high-yield, continuous-action apparatuses partially incinerate volatile pyrolysis products inside the apparatus in the presence of a limited amount of air, providing the required process temperature (e.g., Lambiotte and Lurgi apparatus, Hereshof furnaces, etc.). As a result, partial combustion products contain volatile pyrolysis products - carbon monoxide, methane, acetic acid, tar, and other compounds that cause atmospheric pollution in excess of the permitted concentrations. Because of the high water vapor content of the effluent mixture resulting from the drying of the biomass, the thermal decomposition reaction and the combustion process, and the low temperature (400-450 ^& C), the direct supply of air to the flue gases does not ensure combustion of these impurities. Therefore, the carbonizable material must be dried to a dry state (relative humidity <25%) or pyrolized using additional high calorific fuel (eg natural gas) prior to pyrolysis. As a result, these machines are highly sensitive to changes in the type of carbonate material (in the case of wood - even species) or moisture, and only work satisfactorily on homogeneous materials under constant mode. For ecological reasons, previously used Schwarz furnaces, charcoal burning in pinks, pits and various types of mobile equipment cannot be used for carbonization [2, 3],

External heaters typically use flue gas as a heat carrier, which is obtained by burning wood or other fuels in the furnace. The heat carrier heats the outer wall of the apparatus, which may be made of metal, bricks, refractory concrete, etc. etc., thus not mixing with volatile pyrolysis products, which can be condensed and further processed or incinerated as an additional fuel.

Known technical solutions for pyrolysis gas-vapor combustion in external heating plants without condensation of pyrolysis products have a number of disadvantages. Thus, the furnace with distinctive retorts described in USSR 311 072 (1987) and its analogous patent LV 10 631 (1993) is thermally irrational and does not ensure complete combustion of volatile products.

In the conventional methods [4, 5], the maximum amount of wood pyrolysis vapor-gas mixture is burned during the exothermic reaction, where heating of the retorts is unnecessary and even undesirable, but unavoidable in the given solutions. The design of the furnace, which allows direct flame contact with the retorts as they are located in the furnace chamber, does not provide effective heat transfer to the walls and complete combustion of the fuel. This can be explained by the fact that the retort cools the combustion zone of the fuel and the furnace construction does not ensure a sufficiently long vapor-gas stay in the high temperature zone (> 750 ° C). As a result, flue gases contain very high concentrations of carbon monoxide (even above 7.5% by volume), particulates and other volatile pyrolysis products (acetic acid, methanol, acetone, ethyl acetate, tar, etc.), thus creating environmental problems.

From the point of view of the complete combustion and heat transfer of the pyrolysis vapor-gas mixture, a solution using a smokestack and external heating retorts with an organized heat carrier flow around them, as described, for example, in patent LV 11 333 (1996) (prototype). However, even in this case the thermal and technological solution is unsuccessful, because in its implementation additional fuel-firewood is needed, as well as in case when using only pyrolysis vapor-gas mixture (at wood relative humidity <20%), too high flue gas temperature (> 1000 ° C), ridge burns can occur, as well as masonry and smoke damage. By controlling the heating of the retorts with only the flue gas flow around the retorts, it is not possible to change the delivery of the vapor-gas mixture to the furnace during an exothermic process when the amount of vapor-gas released is twice as usual, especially if it occurs simultaneously in two retorts. In this case, wasteful use of heat and flue gas temperature rise in retort heating ducts above the allowable temperature, usually around 700 ° C, cannot be prevented.

It is known [6] that the heat consumption in the pyrolysis process and the amount of vapor-gas emitted depend mainly on the moisture and density of the biomass. However, the peculiarity of the batch process is that the vapor-gas release is not uniform over time, since pyrolysis occurs in several stages. During the drying (up to 120-150 ° C) and onset of thermal decomposition (120-275 ° C) volatile volatiles are released and the heat of burning these products is not enough to raise the temperature of wood or other biomass in the apparatus. At temperatures between 280-400 ° C t. s. the exothermic reaction and the amount of heat generated by the reaction heat itself and combustion of the volatile products is greater than that required to raise the temperature of the wood or other biomass in the apparatus and can be transferred to other apparatus where the wood or other biomass dries or is just beginning to decompose. During the annealing step (400-500 ° C), the combustion of volatile pyrolysis products provides the necessary amount of heat to raise the temperature in the apparatus and maintain it for a certain time.

The object of the invention is to eliminate the above-mentioned disadvantages of the preparation, supply and regulation of the heat carrier of the known external heating apparatus and to provide:

(a) complete heating of the biomass pyrolysis process by combustion of the volatile products from the thermal decomposition of biomass;

(b) prevention of overheating of pyrolysis apparatus;

(c) complete combustion of the volatile products from the thermal decomposition of biomass;

(d) rational use of the energy potential of all volatile products from the thermal decomposition of biomass.

To achieve this goal, a system of external heating pyrolysis apparatus and a portable furnace is proposed in which heating of the pyrolysis process is controlled not only by varying the flue gas flow around the apparatus but also by regulating the volatile biomass pyrolysis product feed by cracking according to known techniques (using charcoal, dolomite, etc. filling) and producing storage and transportable gaseous fuels.

In addition, it is proposed to partially recycle the recycled heat carrier to prevent the heat carrier temperature from rising above the allowable temperature (around 700 ° C for retorts made of non-alloy steel).

For the purpose of the invention, it is proposed to combine external heating biomass pyrolysis apparatus of any design into one system consisting of at least 3 apparatuses (optimally

4 - 6 apparatus), common portable furnaces for the production of heat carrier from a pyrolysis vapor - gas mixture, a recovery furnace and / or a vapor - gas cracker. The recovery furnace is designed to burn excess pyrolysis vapor - gas mixture to produce heat for local consumption (drying wood or other biomass, heating water or space heating). Steam

-Gas cracker for converting pyrolysis vapor-gas mixture into transportable and storage gas, which can also be used in internal combustion engines.

The principal scheme of the apparatus is shown in FIG. 1, wherein: R _{b is} R 2, R 3, R 1 - retort; K-furnace; S - smoke; Z- dryer; Utilization furnace; G- Cracking plant and scheme for charcoal production plant fig. 2, wherein: 1, 4 fans; 2- furnace, 3- disposal furnace; 5,6,7,8retortes; 9- smoke extractor; 10- Smoke.

In order to realize the invention, the work of the biomass pyrolysis unit must be organized in such a way that each of the retorts enabled in the system is implemented in different stages of the pyrolysis process. In the case of apparatus which does not differ significantly in their volume and in the biomass used, this is achieved by the introduction of a rhetorical apparatus at the same time intervals, defined by the formula:

T <j-> _ process.

n τ process - pyrolysis process duration, h; n - number of pyrolysis apparatus.

For heating the pyrolysis process, the amount of vapor gas to be burned in the furnace K is controlled by the flue gas temperature prior to the heating flues R1, R2, R3, R4. Exceeding the allowable temperature, the recycle heat carrier is fed to the cavity before retorting and a portion of the vapor / gas mixture is diverted to a recovery furnace U and / or cracker G, thus reducing the heat carrier temperature to the allowable temperature. The heating of individual pyrolysis apparatuses is controlled by dampers or shutters placed in the treated heat carrier line behind each apparatus. The recycled heat carrier is discharged through the chimney S, but part of the recycled heat carrier can be directed to the wood dryer Z.

The proposed biomass carbonation process, providing the energy required for the process and additionally obtaining the gas and its realization in one of its possible variants, is illustrated in FIG. 1 and 2, without limiting the possible embodiments of the invention.

Example.

The proposed charcoal production plant (Fig. 2) consists of 4 external heating intermittent retorts (5; 6; 7; 8), a furnace (2), a chimney (10) and a utilization furnace (3). The retorts are made of steel and are bricked with refractory bricks. The masonry houses spiral or ring chimneys, the bottom of which is made of fireclay bricks, the rest consisting of metal segments welded to the outside of the retort. The vertical stove of the furnace terminates in a horizontal divider stove, in which the heat carrier is fed to the chimneys of pairs (5; 6) and (7; 8) arranged in two opposite blocks in pairs. There is also an inlet for the processed heat carrier in the manifold. At both ends of the distributor groove, temperature gauges are used to measure the temperature of the heat carrier before entering the retort flue smoke.

From the retorts (5; 6, 7; 8), the recovered heat carrier enters the manifold, which is connected to the chimney (10). Exit the manifold from the recirculation duct through which the recycled heat transfer medium is fed through a smokestack (9) into the horizontal furnace groove and / or into the wood dryer. If the relative humidity of the charcoal is above 30%, it must be pre-dried by some known method. The pyrolysis vapor-gas mixture from the retorts (5, 6; 7; 8) converts through the outlet pipes into a common manifold, from where it is fed through a vapor-gas burner to the furnace (2). Fan (1) for forced air supply connected to the burner. From the vapor-gas collector, drain a piping through which part of the vapor-gas mixture is discharged through the burner connected to the fan (4) to the recovery furnace (3) for incineration. The resulting thermal energy is used for heating water, space heating or drying firewood.

To implement the proposed method, a retort (5) with a geometric volume of 6 m ^{3 is} loaded with 1520 cm long wood cubes and the hermetically sealed bottom and top lids. Open the valve (7) on the steam gas line and the valve (8) in the recycled heat carrier line. The valve (9) is designed to shut off the retort heater in the event of an emergency or repair. The heating furnace (2) is fired with firewood to obtain thermal energy for starting the pyrolysis process by retorting (5). Upon reaching a temperature of 100 ° C, mainly water vapor, which enters the furnace via the vapor-gas line, begins to emit in the retort (2). Since one retort has a lifetime of 16 hours, the next retort (6, 7; 8) is connected for heating every 4 hours, as described above. Firewood heating is continued in parallel with the pyrolysis vapor-gas combustion to maintain the heat carrier temperature in the horizontal groove around 700 ° C. Gradually, with the increase of the calorific value of the vapor-gases, the wood-burning is stopped and the combustion of the vapor-gas mixture is completely switched over. When the heat carrier reaches 800 ° C, part of the vapor-gas mixture is directed to the recovery furnace (3) by opening the valve (3) and tightening the valve (2). By opening the valves (5) and (19) on the recycle heat carrier recirculation line and actuating the smoke extractor (9), a portion of the recycled heat carrier is fed to the furnace groove to reduce the heat carrier temperature to 800 ° C. The smoke extractor (9) is also designed to feed the processed heat carrier by opening the valve (6) to the wood dryer. The recycled heat carrier (flue gas) discharged into the chimney (10) is monitored visually by its appearance at the end of the chimney as well as by measurement of carbon monoxide concentration. The lack of air due to insufficient natural draft in the furnace (2) is eliminated by opening the valve (1) and supplying additional air with a fan (1) in the steam-gas burner. When the retort (5) reaches 450-500 ° C, close the valve (8) in the recycled heat transfer line and allow the temperature to drop by 50-100 ° C within 1.52 hours. The valve on the vapor-gas line (7) is then closed and, when the retort lower cover is opened, is discharged of finished charcoal in a charcoal cooler located below. Then, open the top hatch of the retort, close the bottom hatch, puncture the piebald retorts and start the process from scratch.

In the recovery furnace (3), the excess vapor-gas mixture is burned to produce a heat carrier which is used for space and water heating as well as for drying wood. The combustion air is supplied by opening the valve (4) via the fan (4). By controlling the supply of the pyrotechnic vapor-gas mixture to the furnace for heating (2) and utilization (3), as well as regulating the air supply to the respective furnaces with fans (1,4) and using partial recirculation of the recycled heat carrier in the furnace furnace via a smoke exhauster (9) achieve:

1) a constant temperature of the heat carrier (about 700 ° C) before entering the retort smoke, thus protecting them from thermal damage;

(2) the rational use of pyrolysis vapor-gases providing an energetically autonomous mode of carbonization,

3) complete combustion of fuel (firewood, vapor-gas mixture) and low level of harmful emissions into the atmosphere.

SOURCES OF INFORMATION

1. TexHOJioran jiecoxnMnnecKHx npon3BoztcTB.— 1987., JlecHan npoMbiuuieHHOcTb, MocKBa, 352 CTp.

2. Kalniņš A. Chemical Forest Technology.- Riga, 1944, 496pp.

3. Emrich W. Handbook of Charcoal Making.— Amsterdam, 1985, 278 pp.

4. SU 1. 312. 072, 1987.

5. LV 10 631, 1993.

6. LV 11 333, 1996.

7. UJyjibrHH IO.H., E <1> hmob JI.M. AHajiH3 3HepreTnnecKHX aarpaT b npon3BojicTBe apeBecHoro yrjw.— 1988., CSopmiK rpvnoB ΙΙΗΙΕΊΧΗ, JlecHan npoMbiniJieHHocTb, MocKBa, c. 5-16

Claims (2)

INVENTION FORMULA 1. A process for providing and obtaining the energy required for a biomass carbonation process, comprising heating the biomass in an airtight, external air-heated reactor, except that, in order to ensure an ecologically clean process, combustion of technological equipment and simultaneous production of the required quality coke or charcoal, in addition to heat carrier, as well as transportable and stored gaseous fuels, is carried out in a batch operation with not less than 3 apparatus, each carrying out different stages of the pyrolysis process, subjecting the temperature and volume control of the heat carrier to varying the amount of vapor-gas mixture fed to the furnace and / or feeding the processed heat carrier into the furnace furnace groove and the proliferation vapor-gas mixture, which v required for process maintenance, fed into a cracker to obtain transportable and stored gas. 2. An apparatus as claimed in claim 1, characterized in that it comprises a technological wood dryer, a recovery furnace and a steam-gas mixture cracker.