IMPROVING THE EFFICIENCY OF THE PYROLYSIS DEVICE FOR THERMAL PROCESSING OF MUNICIPAL SOLID WASTE

ABSTRACT

This article proposes a mine-auger drum pyrolysis device for thermal processing of solid domestic and organic waste by the pyrolysis method. Based on the geometric dimensions of the auger-drum pyrolysis device, the material and heat balance equations are constructed. In the reactor with a working volume of 1 m³, it was found that 243,360 mJ of heat energy was used to thermally process solid waste with a density of 300 kg / m³ and a mass of 180 kg to obtain alternative fuels. It was shown that the reduction of moisture content of solid waste from 45 ÷ 60% to 10 ÷ 15% due to the heat of the flue gases was carried out in the auger drum part of the device mounted on the recycling chamber, and the efficiency of the device was determined.

АННОТАЦИЯ

В статье предлагается пиролизная установка для термической переработки твердых бытовых и органических отходов методом пиролиза. На основании геометрических размеров пиролизного устройства построены уравнения материального и теплового баланса. В реакторе рабочим объемом 1 м³ установлено, что 243 360 мДж тепловой энергии было использовано для термической переработки твердых отходов плотностью 300 кг/м³ и массой 300÷350 кг для получения альтернативных видов топлива. Показано, что снижение влажности ТБО с 45 ÷ 60% до 10 ÷ 15% за счет тепла дымовых газов осуществлялось в шнековой барабанной части устройства, установленной на рециркуляционной камере, а КПД устройства было определено.

Keywords: solid waste, alternative fuel, pyrogas, thermal recycling, thermal energy, pyrolysis reactor.

Ключевые слова: твердые отходы, альтернативное топливо, пирогаз, термическая утилизация, тепловая энергия, реактор пиролиза.

Today, not only in our country but all over the world, the problem of waste is becoming one of the most pressing environmental, energy, and economic problems.

The analysis shows that the volume of solid domestic and industrial waste has been increasing year by year in recent years [1,2]. Especially in the XXI century, the growth of municipal solid waste (MSW) has begun to have a major negative impact on environmental sustainability and human health. Toxic compounds released as a result of the decomposition of MSWs under the influence of heat and humidity penetrate into surface and groundwater, atmospheric air, soil, and plants. As a result, man is exposed to fresh drinking water and lack of fresh air, degradation of fertile lands, as well as new outbreaks of various diseases. In recent years, the production of alternative liquid, gaseous and solid fuels using solid household waste for energy purposes has become more and more popular in our country, because MSWs are a source of cheap raw materials around the world. At the same time, the organization of the removal of MSW from the population in the cities and regions of the Republic of Uzbekistan is in an unsatisfactory state, practically in all cities the removal of solid household waste from the population is not carried out on a systematic basis, the material and technical base of specialized sanitary cleaning organizations is not equipped with special equipment [1-4]. In the required quantity, the existing landfills do not meet sanitary rules and regulations, in a number of places spontaneously formed landfills are used.

The problem of solid waste disposal is not only a technical problem but also a sanitary and ecological one.

MSW is divided into three categories:

1. Secondary raw materials that can be recycled. To do this, it must be separated from the general flow, separated, and put into further processing - 35%.

2. Biodegradable waste that can be put on compost - 35%.

3. Non-recyclable waste (tailings) - at present either cannot be processed into useful products, or the costs of such processing will be very high - 30%.

In 2017-2018, 13 state-owned unitary enterprises and their 172 branches in districts and cities, as well as 183 private and 9 clusters with a total capacity of 894 thousand tons of waste per year will be involved in improving the system of work related to MSW. This year, 20% of the waste generated in the country will be recycled, and the remaining 80% will be sent to landfills.

In Uzbekistan, about 200÷300 thousand tons of municipal solid waste are accumulated every day about 135÷150 million tons per year.

The accumulation of rotting solid waste in surface storage inevitably leads to the formation of biogas under the sun's rays, which is a product of the process of anaerobic decomposition, which pierces through the mass of waste collection. Biogas must be removed in order to prevent its migration from the landfill, as it is toxic and explosive. Its danger extends not only to the territory of the landfill but also beyond it due to the significant volume of education.

The methods of control and removal of biogas are currently quite developed and are widely used abroad. The gas is usually removed by suction and sent for combustion in an open flare or, in significant quantities and with appropriate quality, is utilized. Biogas is collected from vertical wells drilled at the site of already filled storages, or horizontal reservoir wells built in the process of waste storage.

The amount of biogas produced is influenced by:

- composition, age, density, temperature, and humidity of waste;

- area, depth, methods of operation and development of a solid waste storage facility;

- storage water balance.

More than a dozen methods for recycling solid household waste using a variety of methods are being implemented worldwide. The most common methods are direct combustion of MSW, anaerobic fermentation, pyrolysis, gasification, thermal processing, and so on. [5]. One of the most effective methods of thermal processing of MSWs is the pyrolysis method, pyrolysis technology is an innovative solution for waste management and leads to a significant reduction in the area of ​​landfills.

Pyrolysis is one of the most promising ways to recycle solid waste. It allows you to get useful products from both environmentally safe and secondary energy resources. As a result of heat treatment of KMCs on the basis of the pyrolysis method in the temperature range of 350-600 0S, alternative, gaseous (pyrogas), liquid, and solid (poly coke) fuels are obtained. The pyrogas and liquid fuels obtained during the pyrolysis process can be used for the special needs of the pyrolysis unit. From an economic point of view, the use of pyrogas and liquid fuels as fuels is beneficial.

However, the use of such fuels depends on the morphological composition of the MSW, the pyrolysis technology, and the composition of the working mass of the fuels obtained.

The author proposes a schematic of a mine-auger drum pyrolysis device for thermal processing of solid waste by pyrolysis and obtaining alternative fuels (Figure 3). The pyrolysis device for thermal treatment of solid household waste consists of a mine (1), a tubular pyrolysis reactor (2), a valve (3,10,12,21), an auger drum (4), an auger drum cover (5). , mechanical auger (6), furnace (7), burner (8), gas holder (9), pipe (11,13), spiral heat exchanger (14), cold water inlet (15), hot water outlet ( 16), liquid fuel tank (17), filter (18), recycling chamber (19), smoke pipe (20) (1-Fig.).

Figure 1. The pyrolysis device for thermal processing of municipal solid waste

Pyrolysis devise for thermal processing of MSW works in the following order:

Unsorted municipal solid waste is loaded through the cover (5) of the auger drum (4) by opening the valve (3) to the tubular pyrolysis reactor (2) installed inside the mine (1), and the auger (6) is rotated by hand. MSW is crushed and moved along the auger drum. After loading the solid waste into the tubular pyrolysis reactor and auger drum, the valve (3) and cover (5) are fastened. For the pyrolysis process to take place, the burner (8) mounted on the furnace (7) is opened by opening the valve (10 and 12) from the gas holder (9), the gaseous fuel is fed through the pipe (11) and ignited. The high-temperature flue gases generated during combustion heat the solid domestic waste loaded into the tubular pyrolysis reactor uniformly from 450 ⁰C to 600 ⁰C over the entire surface, resulting in a vapor-gas mixture. The resulting vapor-gas mixture passes through a pipe (13) to a spiral heat exchanger (14). In the spiral heat exchanger (14), cold water (at ambient temperature) is supplied from the cold water inlet (15) to separate the steam-gas mixture into pyrolysis fuels, and the steam-gas mixture is heated from the hot water outlet (16) due to secondary heat. Water comes out and is passed to the consumer. As a result of heat exchange in the spiral heat exchanger (14), the vapor-gas mixture condenses to separate the liquid fuel and the liquid fuel is collected in the tank (17), while the pyrogas is cleaned through a filter (18) and collected in the gas holder (9) and used for special needs. Exhaust fumes from the tubular pyrolysis reactor in the temperature range 120 ° C to 125 ° C pass into the recycling chamber (19) and dry the solid household waste placed in the auger drum at a humidity of 50% to 60% to the humidity of 5% to 10%. Which in turn leads to an increase in the energy efficiency of the device, the prevention of excessive heat loss in the device, the sudden onset of the pyrolysis process and shortens the time of the pyrolysis process. When the work is done, the flue gases are released into the atmosphere through the smoke pipe (20). In a time interval of 240 to 280 minutes, the pyrolysis process is completed and the residual mass is removed from the tubular reactor through a valve (21), and the cycle is thus continued.

A comparative analysis with the prototype of the proposed technical solution revealed the following specific features:

- In contrast to the prototype, the reactor of the device is made in the form of a tube and installed inside the mine, which leads to a uniform distribution of heat in the tube pyrolysis reactor, heating the raw material throughout the volume and increasing the amount of pyrolysis fuel;

- the upper part of the device is divided into a recycling chamber, which efficiently uses the secondary energy resources of flue gases and increases the energy efficiency of the device;

- The device is equipped with an auger drum and it is mounted in the recycling chamber, which dries the moisture of solid waste (from 50-60% to 5-10%) due to the secondary heat of the flue gases, which in turn reduces excess heat consumption in the pyrolysis reactor. accelerates start-up and saves fuel resources;

- the device is equipped with a spiral heat exchanger, which receives hot water through heat utilization and provides heat energy to consumers;

- the device will be installed in solid waste landfills and transport costs will be saved.

The proposed pyrolysis unit allows to process of almost all types of waste except building materials and to obtain alternative pyrolysis fuel, and provides solutions to the following problems:

1. Reduces the impact of waste on environmental sustainability and human health.

2. Waste-free disposal (recycling without sorting waste).

3. Production of fuels (synthetic oil, pyrolysis fuel, diesel fuel, etc.) that meet the requirements of the "yashil tariff" for the production of heat and electricity.

The obtained fuels are used to save natural fossil fuels through the use of industrial boilers and furnaces, consumers with autonomous heat supply, greenhouses, country houses, field sheds, heating systems, and dryers. Material and heat balance equations for different temperature regimes of the pyrolysis process were constructed to determine the operating parameters of the auger-drum pyrolysis reactor and to evaluate its efficiency. When constructing the heat balance equation, the following was taken into account: the formation of ash-carbon residue during the thermal processing of MSW in the device by pyrolysis method does not exceed 5% and the obtained pyrogas is used in the combustion chamber. The thermal calculation of the device was performed based on the obtained research results.

References:

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