RU2690477C1 - Device for torrification of granulated biomass with air heating - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to production of biofuel, namely to methods of thermal processing of biomass in order to obtain solid fuels with improved heat engineering characteristics. Main idea implemented in the design of the proposed invention consists in the fact that the biomass loaded into the reactor is heated and dried with a stream of hot air supplied through slots in the neck of the loading cone and directly into the loading hopper. Supply of hot air into loading unit ensures both heating of loaded raw material to temperatures preventing condensation of water vapor contained in heating heat carrier and pyrolysis gases, on surface of loaded granulated biomass, and does not pass these gases into cold zone of loading unit due to small excess pressure in front of slots of loading cone. Condensation of water vapor on cold pellets of biomass results in their swelling and clogging of the loading unit. Gases discharged from the reactor are fed into the afterburner where, under the action of the ignition flame, they are burnt, and the heat released is used to heat the air coming into the slit and hopper of the loading unit.EFFECT: increased thermal efficiency of torreification process and provision of reliable operation due to preliminary heating and drying of loaded raw material by hot air; at that, heat of gases leaving the reactor is used for air heating.1 cl, 1 dwg

Description

The invention relates to installations for the production of biofuels with enhanced thermal performance of granulated biomass.

At present, low-temperature pyrolysis (torrefaction) - heat treatment of biomass at temperatures of 230-300 ° C in an oxygen-free environment is considered as one of the methods for improving the quality indicators of biomass fuels. The end product of torrefaction is a solid hydrocarbon fuel with enhanced thermal performance. During torrefaction, the heat of combustion of fuels increases by 20–25%, the specific weight decreases by 20–30% and, what may be most important when using biomass as a fuel, the resulting product becomes hydrophobic, having a low hygroscopicity limit that do not require adherence to special conditions, precluding contact of the fuel with the environment).

Despite the seeming simplicity of the process, to date the torrefaction technology on an industrial scale has not been implemented.

The existing schematic and design solutions of the torrefaction process are rather complicated (Patents RU 161775 U1, 05/10/2016. RU 97727 U1, 09/20/2010. RU 144013 U1, 08/10/2014. EA 17739 V1, 02.28.2013). This concerns the heating of the processed material, which, as a rule, is carried out by burning natural gas. At the same time, it is necessary to reduce the temperature level of the resulting combustion products to the torrefaction required for the process, and to dispose of the heat released during cooling of the combustion products. A certain difficulty is associated with the disposal of waste gaseous reaction products, this applies, inter alia, to purification of the resulting gas mixture from harmful impurities: carbon monoxide, liquid high-molecular compounds, etc. The implementation of these activities requires a significant investment. One of the main reasons for the lack of industrially implemented torrefaction technology is the fact that, despite the obvious advantage of using torrefication in power plants, the cost of obtaining it does not pay off the benefits of the final product.

Closest to the claimed technical solution is a device for thermal conversion of biomass, RF patent RU 175131 U1, 09.12.2016.

This technical solution implements a cogeneration scheme for obtaining heat for heating the processed material. Heating is carried out in the environment of the combustion products of the gas piston unit. So, due to the combustion of natural gas, electrical energy is produced, then, using heat from the combustion gas exhaust products of the gas piston power unit, torrefaction is carried out directly. Thus, the energy of natural gas is used in this process to produce electrical and thermal energy, which from an economic point of view is more advantageous with respect to those schemes in which the combustion of natural gas is used only to heat the material being processed.

In addition, the use of an exothermic reaction to increase energy efficiency and plant capacity is organized in this unit due to the periodic discharge of self-heating biomass into the cooling zone.

A disadvantage of the known technical solution is that when loading biomass torrefaction into the reactor when it contacts the combustion gas exhaust power plant and torrefaction reaction products due to condensation of water vapor on the surface of the "cold" biomass it is possible to form agglomerates that prevent the movement of the processed biomass in the torrification reactor (blockage of the installation boot node). And for drying and preheating of the “cold” biomass being loaded, the heat of the heating coolant is used.

The aim of the invention is to increase the thermal efficiency of the process and ensure reliable operation of the torrefaction reactor due to preheating and drying the feed material with hot air, and to heat the air, the heat of the gases leaving the reactor is used. At the same time, the overpressure of the supplied air prevents the combustion products of the gas piston unit and pyrolysis gases containing a significant concentration of water vapor from entering the loading and preheating zone, thereby eliminating the possibility of the formation of agglomerates capable of disabling the charging unit.

Experiments conducted at the Joint Institute for High Temperatures of the Russian Academy of Sciences have shown that when the processed biomass is heated to temperatures of 100-150 ° C, water vapor does not condense on its surface when the gas piston power station and the gaseous torrefaction reaction products come into contact with the exhaust gases.

This goal is achieved by hot air heated by the heat of hot gases from the reactor to a temperature of 100-150 ° C, with a pressure slightly higher than the pyrolysis gas pressure in the torrefaction zone, cutting off the feed bin and the slots of the loading block of the energy technology thermal biomass conversion unit. access to combustion products and pyrolysis gases in the feed hopper and providing pre-drying and preheating of the feed material.

Energy technology installation contains: gas piston installation (GPU) 1 (Fig. 1) and a programmer designed to control the operating modes of the power unit with the ability to generate electricity and heat simultaneously in various proportions by changing the operating modes of the power unit, the executive mechanism for controlling fuel consumption by the power unit to maintain set by the programmer air excess factor in the range of 0.95-1.00; gas-water heat exchanger 2, in which the medium being heated is water and the cooled one is the part of the exhaust gases of the power unit specified by the programmer; mixer 3 of the remaining part of the exhaust gases of the power unit and cooled in the heat exchanger, passed through the layer of pellets in the cooling section 4; reactor 5 thermal conversion of biomass, equipped with loading devices 6, 7 and unloading 8, in which the coolant is the gases obtained in the mixer 3; moreover, the unloading device 8 opens when a predetermined temperature is reached in the torrefaction zone, providing a continuous torrefaction process using the heat of an exothermic reaction; characterized in that it additionally contains a pipe 11 through which the loading hopper 7 and through perforations in the loading cone 6 are fed into the layer of the loaded “cold” biomass heated air with temperatures exceeding the pressure of pyrolysis gases in the zone to temperatures of 100-150 ° C torrefaction, cutting off access to the combustion products and pyrolysis gases in the hopper and providing pre-drying and heating of the feed material; for heating the air, the scheme additionally contains: a recuperative heat exchanger 9, using the heat of the waste gases from the reactor and the blower 10.

Thus, the biomass, before entering the thermal conversion zone, is preheated to temperatures of 100-150 ° C, which prevents condensation of moisture when contacting reaction products with it and the exhaust gases of a power unit.

The experiments performed on the semi-industrial thermal biomass conversion facility built at the Joint Institute for High Temperatures of the RAS showed that with a natural gas consumption of 14 m3 / h, the electrical power of the GPU was 25 kW, and the plant capacity was 150 kg / h of high-quality torrefaction. The installation worked in continuous mode for 6 hours. At the same time, the periodic unloading of pellets from the torrefaction zone was carried out upon reaching a temperature of 280 ° C. The specific productivity was 6 kg / h per kW of electrical power of the hcp, which is significantly higher than in the prototype. In addition, the absence in the prototype of preheating and drying of the feedstock did not allow for organizing a continuous long process of thermal conversion of biomass.

The invention provides a clear operation of the boot node installation, preventing the absorption of moisture in raw materials, reducing thermal energy spent on carrying out thermal conversion of biomass with a simultaneous increase in the performance of the installation.

Claims (1)

A biomass thermal conversion unit containing a gas piston power unit and a programmer designed to control power unit operation modes with the ability to generate electricity and heat simultaneously in different proportions by changing power unit operation modes, an executive unit controlling fuel consumption by the power unit to maintain the excess air ratio set by the programmer in the interval 0 , 95-1.00, gas-water heat exchanger, in which the heated medium is water, and cooled - back The programmer part of the waste gases of the power unit, as well as the mixer of the remaining part of the waste gases of the power unit and cooled in a heat exchanger, the installation contains a biomass thermal conversion reactor equipped with loading-unloading devices in which the heat carrier is gases produced in the mixer, characterized in that the loading unit the reactor is supplied with a pipeline through which hot air is fed into the unit hopper and into the slots in the loading cone, which, on the one hand, blocks access m of combustion and pyrolysis gases containing a large amount of water vapor in the layer of cold biomass, which can lead to condensation of moisture on the surface of the feedstock, its swelling and disruption of the loading unit, on the other hand, contributes to the drying and heating of the loaded biomass, and for Air heating uses heat from the exhaust gases from the reactor, which provides increased energy efficiency and plant capacity.

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