How to clean smoke emissions from a smokehouse. Installations for flue gas purification. Typical design and principle of operation of a smoke generator

Cooking meat and fish with cold smoke is becoming increasingly popular among smoked meat lovers. The process of cold smoking can be relatively easily organized with your own hands, even on the balcony of your apartment. The procedure for fumigating food with cold smoke does not require special technical knowledge or kitchen wisdom; you only need to make a smoke generator for smoking yourself. The rest of the equipment for cold smoking is a regular wooden box or cabinet, in which products hung on a hook or laid on a grid are simply smoked with cold or warm smoke.

How does the cold smoking process work?

Most people perceive cold smoking as an improved version of the classic processing of products with heat and steam. In fact, cold fumigation is a chemical processing method, so this scheme is closer to deep drying of meat and fish protein.

The basis of such processing is special device, a smoke generator for cold smoking that produces a vapor-gas mixture with special characteristics:

The flow of smoke and gas is saturated with vapors of chemically active substances, aldehydes, acids, alcohols, carbon monoxide and moisture. Also present are the decomposition products of lignin and cellulose in the form of tar water and resins;
The temperature of the steam-gas flow is relatively low, no more than 40 o C, therefore there is no thermal “cooking”, like hot smoking, in the smokehouse.

There is only one way to obtain a stable gas flow with similar characteristics - to make a smoke generator for cold smoking with your own hands. Smoke entering the smoking chamber saturates the surface layers of meat or lard with chemically active substances, and that’s it, the product can be removed and sent to “rest”, under a canopy or in a cool place where there are no flies, dust, drafts and sunlight. For about another day, the process of absorption of the settled products of sawdust decomposition into the tissue of meat products continues.

For your information! Only after a day can you begin tasting and assessing how successfully the cold smoking process went. Before the end of ripening, the product may disappoint true connoisseurs of smoked sausages and fish.

To get an excellent bouquet of smell and appearance smoked products, you need to not just select successful design smokehouse, it is better to make a smoke generator with your own hands. As practice shows, for a real cook, the process of improving a smokehouse with your own hands, in an amicable way, is never completed; amendments, modifications and improvements are constantly made to the design, so it is important to know the structure of the smoke generator and be able to adjust its basic parameters.

The effect of cold smoking can be achieved with the help of chemical additives, but the taste of meat treated with chemicals is fundamentally different from the product that has passed through a stream of smoke, so it is easier to make a smoke generator for a cold smokehouse with your own hands than to risk your health and the health of your family.

Typical design and principle of operation of a smoke generator

There are two main smoke generator designs - pyrolysis and designs with external heat supply. For a smoke generator with external heat supply, you will need a heater of at least 1000 W, a thick-walled cast iron or steel body and a special smoke cooling system from copper pipe. As a result, the design turns out to be heavier and bulkier, but the quality of cold smoking using such a smoke generator is many times better than in a pyrolysis scheme.

For efficient work For such a smoke generator, it will be necessary to install a cooling system, circulation and a heating control circuit, for example, a rheostat or a thyristor load regulator, which complicates the work, but allows you to obtain very stable parameters of the smoke flow. Essentially, this is high-tech in the field of cold smoking.

Optimal installation device for cold smoking

This is how a real cold smoking system works.

The products are kept in a cold smoking chamber. The smoke flow is cooled in a special heat exchanger to 30-35 o C, the most important thing is that it is freed from water vapor and the heaviest components of the vapor-gas mixture, and a dried mixture saturated with volatile substances enters the chamber. Moreover, the mixture regularly circulates through a closed cold smoking circuit, releasing excess water and being saturated with new substances. What does this give?

Firstly, thanks to the presence of a cooler, the most smelly and harmful part of the smoke is removed - tar water and phenols.

Secondly, the flow of gases moves around the fish or meat at a fairly high speed, which means it is possible to avoid two possible problems- cold hardening and characteristic bitterness of smoking. Cold hardening occurs in cases when the product, due to a temperature difference outside or insufficiently well-cleaned smoke from moisture, during cold smoking is covered with a thin layer of water, protecting the surface of the meat from deep penetration of valuable smoke components. The result is that outer part will become oversaturated with cold smoked products, and the inside of the product remains raw.

Home version of a smoke generator for a cold smoking chamber

You can make both at home, but most lazy lovers of cold smoked products prefer pyrolysis type smoke generator for quite objective reasons:

Simplicity of design; even tin cans and plumbing fittings can be used to assemble the most primitive generators;
The pyrolysis smoke generation system does not require powerful heaters to operate; 5-10 W is enough to power an electric fan or compressor;
In the flow flue gases significantly more active substances, lower temperature and more stable smoke flow.

Regardless of what diagrams and drawings of a smoke generator for cold smoking you use with your own hands, the smoke parameters will be approximately the same. The difference will concern the degree of smoke purification and the ease of maintenance of the device after its intended use.

The operation of the installation can be explained in the smoke generator diagram below.

Structurally, the gas generator consists of three main parts:

Containers made of heat-resistant material, most often the body is made of stainless steel or clad with aluminum cast iron pipe chimney;
Selection unit for hot gases formed due to the decomposition of sawdust at high temperatures;
A compressor for supplying air to the smoke generator and pressurizing the sawdust decomposition products inside the cabinet for cold smoking of products.

Small beech or cherry chips are poured into the bottom of the smoke generator housing. Apricot, cherry, and apple are ideal for cold smoking. Worse are alder and beech; it is strictly forbidden to use coniferous wood, birch, aspen, poplar and a tree grown on the shore of a reservoir with stagnant water.

This is the most suitable raw material for producing high-quality cold smoke. There is a hole at the bottom of the case for air suction. After ignition, the compressor turns on, which pumps air into two tubes. In this case, one tube is inserted coaxially inside another tube. This device is called an injection pump. As the air flow moves, smoke is sucked in and a vacuum occurs inside the smoke generator. Some of the air penetrates through the blower into the smoke generator housing and feeds the process of thermal decomposition of sawdust.

Theoretically, the process is completely autonomous and does not require human participation in the cold smoking procedure. In fact, in some cases, the sawdust is “cemented” by the smoke and resinous vapors released, and it is often necessary to tap on the body in order to collapse the burnt-out arch of fuel in the smoke generator and continue the cold smoking process.

The most popular cold smoke generator designs

With rare exceptions, in most cases, your own homemade smoke generator makes it possible to smoke products at an acceptable level of quality. Therefore, there are absolutely no problems in how to make a smoke generator. You can take any smoke generator design for cold smoking you like, proven in practice, and build it in accordance with the developer’s recommendations.

As an example of classic smoke generators, we can cite two options - with upper smoke extraction and with gas intake directly from the combustion zone in the lower part of the housing.

Advice! For the body of the cold smoke generator, use only heat-resistant materials; a stainless steel chimney flame pipe with a diameter of 125 mm or 150 mm is best suited.

You can find out how suitable a cold smoke generator is from such a material from the video:

Upper version of the smoke generator

The cold smoke generator with upper selection of decomposition products is a cylindrical stainless steel body, Bottom part which is closed with a lid on thumbscrews, in the upper cold part there is an injection unit connected to an air compressor. The main thing is not so much to strictly adhere to the dimensions and design features of the smoke generator, but to make it controllable or customizable to the specific conditions of cold smoking. In this case, it is extremely important to accurately reproduce the injector at the top of the device. The chimney tube can be made of copper or aluminum, or any metal with high thermal conductivity.

To install the injector, a coupling with internal thread is welded to the body. A sleeve with external thread, which allows rotation to adjust the operation of the injection unit.

A mesh for ash is installed in the lower part of the smoke generator body, a hole is drilled for ignition and air intake into the combustion zone. To make the generator more efficient, an intermediate unit must be added to the design between the chimney and the cold smoking chamber, shown in the diagram.

This solution will allow you to control not only the consumption of smoke, but also its temperature; accordingly, the quality of cold-smoked meat or fish will be much higher, and the amount of phenols entering the chamber with smoke will be reduced by half or three.

Diagram of a smoke generator with bottom flue gas extraction

Additional smoke purification can be achieved using a copper pipe built into the generator housing, called a vapor-gas mixture elevator. In this case, the design of the smoke generator looks like this.

The body is made by welding from sheet metal, in the lower part of the structure the bottom is welded hermetically, leaving only a threaded hole for igniting sawdust, which is closed with a bolt after starting the smoke generator. Sawdust is filled to a level of ¾ of the height of the generator housing. Air is supplied from the compressor vertically copper tube, and combustion products are discharged through the side fitting in the upper part of the housing. The smoke generator can also operate in reverse order, if air is supplied through the chimney, then combustion products and smoke will rise through the copper elevator, cool and be freed from phenolic water. In addition, the sawdust in the smoke generator will be dried and loosened by smoke.

Compressor for smoke generator

In addition to the injector and cooler, the third adjustable component of the smoke generator is the compressor. Most often, converted low-power computer coolers or even aquarium compressors are used for these purposes. The most successful solution is a do-it-yourself compressor for a smoke generator based on a 12-volt beach device for inflating mattresses and inflatable sofas, as in the video:

Advice! You just need to add a speed controller to the standard device, and you get an ideal compressor for a smoke generator. All other options are either too low-power or cumbersome.

Conclusion

The smoke generator body must not be made from any painted or tin-plated containers, such as cans or other containers. Tin, lead, solder, paint - everything that comes into contact with the flow of smoke and heated vapors of acids and alcohols sooner or later turns into a volatile form and ends up inside the cold smoking chamber. In addition, if the design of the smokehouse plans to use an electrostatic field, it will be necessary to very carefully clean the smoke from tar and water.

Various types of smoking have long been used for heat treatment various types products. Smoking is not just a way to turn a perishable product into a dish with a longer shelf life, it is also an opportunity to add delicious aromas to food. taste qualities. Despite technical advances in terms of cooking products, cooking using smoking is still relevant and in demand.

Cold smoking - basics and principles of the process

The fundamental role during smoking is played by the smoke entering the product, which gives ready-made dish incredibly appetizing smell and amazing taste. There are many options for smokehouses on sale today, but not everyone can afford them.

So that the family budget is not damaged, and you and your loved ones can enjoy the smoked meats you prepare yourself, you can make DIY smoke generator.

Preparing cold smoked products is not a quick process, but does not require special skills.

Conditions that must be observed when cold smoking:

Before smoking, products must be processed - cleaned, washed, salted and slightly dried;
smoke treatment of products must be long-lasting - it takes from several hours to 5 days;
the temperature of the incoming smoke should be minimal;
Sawdust from fruit trees is mainly used, but in no case from coniferous trees, otherwise the dish will be hopelessly spoiled.

The process of cold smoking includes many different subtleties and nuances that should be learned. Depending on the skills of the cook and the accuracy of compliance with the smoking requirements, the result will differ.

Even a smoke generator (especially one made by yourself) has a significant value - depending on its design, it will different smoking intensity and, accordingly, the result.

The most important thing in a smoke generator is the correct location of all parts and the flow of low-temperature smoke. It is thanks to compliance with these requirements that the products acquire a presentable golden color and become incredibly tasty.

The smoke in the generator is formed from sawdust (sometimes wood chips), and it is recommended to use certain types of wood:

cherry;
alder;
Apple tree;
pear.

Flavor, aroma and color characteristics dishes will turn out different if you use one or another wood. By assembling a smoke generator with your own hands for cold smoking, you will have complete freedom in experimenting with cooking products and will be able to develop your own signature recipe.

How to make a smoke generator for a smokehouse with your own hands

Smoke generators may be different, but in general their designs are not particularly different. They consist of:

heat source;
fuel;
systems flue cooling;
systems for supplying cooled smoke to the smoking container.

Before deciding on the smoke generator model for your smokehouse, you need to choose heat source. It could be:

On own plot The most practical option would be to use the other options as fuel for a smoke generator for cold smoking. The best option, of course, is sawdust - you can prepare it yourself or purchase it ready-made.

How to make smoke cold

Smokehouses for cold smoking have the same design:

A hole is dug out and lined, which will be the firebox.
The chimney is laid underground.
A filter is installed to prevent soot from getting on the food.
The smokehouse itself is installed.

But problems often arise in the form insufficient smoke cooling, that is, the products are cooked at high temperatures and instead of cold, hot or semi-hot smoking is obtained. You can solve this case like this:

Extend the chimney to such a size that the smoke passing through it cools down.
Use running water to cool the passing smoke in the generator. For this option, it will be necessary to modernize the source of smoke: into the container ( tin can, for example) sawdust is poured in and it is covered with tiles. If the distance from the firebox to the smokehouse exceeds a meter, then additional cooling is not necessary.

Electric generator for smokehouse It couldn't be easier to assemble cold smoked food with your own hands. In this case heating element An electric stove is used, and the smoke turns out cold due to a fairly long pipe.

Wood smokehouse is also assembled in the simplest way. Source of smoke in this option- potbelly stove. The smoke turns out cold due to the number of bends (elbows) of the pipe and its length.

Assembling a smoke generator with your own hands for the production of cold smoked products at home is not a difficult task, but requires a careful approach. Be sure to follow fire safety rules so that cooking is a joy and the resulting dishes are enjoyable.

Smoking products has been practiced by humanity since ancient times. This is due to the fact that this way you can preserve perishable products that acquire wonderful taste. Over the past few centuries, people have made great strides forward in terms of the technologies used, but they also continue to smoke meat and fish. Most main role During smoking, the smoke from the wood of fruit trees plays. It is this that gives the finished product a unique aroma. There is no need to worry about purchasing a smokehouse, since it is quite easy to build a smoke generator for smoking with your own hands. There are many designs that can be repeated even by people inexperienced in such matters.

Types and technologies of smoking

There are two types, different in size and hot. They differ in the temperature at which the product is prepared. If at can reach 95 0 C, then when cold it should not be higher than 35 0 C.

Hot smoking

The method is that the products are placed in a container, where they are treated with hot smoke, baked and smoked at the same time. The process is quite fast, usually takes several hours, and the end result is an unusually tender, aromatic and tasty product. However, such products cannot be stored for a long time, just a couple of days in the refrigerator.

Making a smoking device

How to make a smoke generator this way? Yes, very simple. In this case, the smoke generator and smoking chamber can be combined. Because no cooling of the smoke is required. A metal bucket with a lid, a large saucepan or a barrel will do. Sawdust or wood chips are poured onto the bottom, and the smokehouse is placed on a fire or electric stove.

Smoke emission and heating of the raw materials occur simultaneously. If the smokehouse is well sealed, or when a water lock is used, the smoking process does not require special control. All you have to do is pick temperature regime, in which the food will not burn.

Cold smoking

This method involves both more thorough preparation of the raw material and longer treatment with smoke. This is due to the use of cooled smoke, the temperature of which should not exceed 35 0 C. Before placing the products in the smokehouse, they must be well salted and then dried. The use of wet raw materials for cold smoking is unacceptable, because the smoke will dissolve in moisture, and the cooking process will take much longer.

Nuances when smoking

The cold smoking process is much more multifaceted. There are a lot of nuances, reservations, and a lot depends on the skill of the “chef.” Any of the technological operations can be reproduced in different ways, and each time the result will be different from the previous one.

Even a smoke generator made with your own hands for smoking can significantly affect the taste of products. Various designs smoke is produced with different intensities, and accordingly, smoking will take place differently. As at the dawn of mankind, the most important thing in smoking is the smoke. It is to him that the products owe their golden brown crust and unique taste. Let's look at this component in a little more detail.

How to get smoke

The smoke itself, as mentioned above, is obtained from chips or sawdust of certain types of wood. Typically this is fruit trees: cherry, apple, pear. But you can use both alder and willow for this. The smoke generator for cold smoking can handle any material. The taste, smell, and color of the resulting smoked meats depend on the type of smoke chosen. Here everyone decides for themselves which wood to choose, and, as a rule, settles on one thing.

Smoke generator designs

Homemade smoke generators for smoking vary in design, but they are all very simple to replicate. They are divided into two large groups depending on what heating source is used: electricity or open fire. The simplest smoke generator for smoking, made by yourself, is a small metal box with an outlet, which is put on to remove the smoke. Sawdust is placed in it and it is placed on an open fire. When exposed to high temperatures, wood chips begin to slowly smolder without access to oxygen. Despite their simplicity, these types of devices are quite difficult to use. Since the smoking process can take several days, and sometimes even several weeks, it is quite difficult to control the release of smoke, including its continuous supply.

Such designs do not allow you to quickly add sawdust and control the temperature of the smoke in the smokehouse. The smoke generator for cold smoking, having electrical element. In this case, you can control both the temperature of the incoming smoke and the process of igniting the sawdust - for this purpose the the electronic unit management. Structurally, it is the same small box with an outlet for a pipe, but inside it has a spiral or heating element from an electric stove. After a certain time (usually a couple of hours), the heating element heats up and the sawdust begins to smolder, releasing smoke. There are smoke generators made according to the muffle principle. In this case, a nichrome spiral is wound onto it. Each new turn is insulated with fiberglass, and this entire structure is covered with tin on top. This solution makes it easy to very quickly heat sawdust to a temperature at which they begin to smolder.

The muffle also maintains the temperature for some time, allowing smoke to be released after the heat is turned off. In this case, a temperature sensor can be built into the smokehouse itself, which will turn off the heating element when it reaches maximum temperature 35 degrees. This design does not require the constant presence of a person to control the process; it is enough to simply sometimes add sawdust to a homemade smoke generator for smoking. These are the most advanced devices for producing smoke. If planned constant use smokehouses, then such smoke generators are the best choice.

How to cool smoke

After the smoke is obtained, it must be cooled to the required temperature. It can be done different ways, the most popular of which is laying the chimney in a tank of cold water. Typically, in this case, a smoke generator for smoking, made with your own hands for an open fire, is used. The chimney can also be buried in the ground, which can also cool the smoke very well. There are designs where the chimney is represented by a trench in the ground, covered on top to prevent smoke from escaping.

Passing along this path, it cools down, and smoking takes place in a normal cold mode. This method of cooling smoke is used in hiking conditions, where finding a corrugated pipe and a large container for water is very difficult. A smoke generator for smoking (assembled with your own hands) with an electric heating element, as a rule, does not need to cool the smoke. The temperature sensor is capable of turning off heating when a critical temperature is reached, maintaining the smoking process and not overheating the raw materials.

The technological properties of smoking smoke are largely determined by its chemical composition. The chemical composition of smoke depends on many factors, among which the most significant are: temperature of smoke formation; generation method; type of wood - wood moisture content; wood particle size; air access to the smoke generation zone; smoke transportation.

Wood requires heat to decompose and produce smoke. In the practice of smoking production, heat for generating smoke is obtained either by burning part of the wood used, or by supplying it from the outside.

The process of wood pyrolysis was studied on a laboratory device and presented in the form of a so-called “smoke thermometer” (Fig. 52).

Rice. 52. Smoke thermometer

When the wood temperature increases to 120 °C in upper layers sawdust, the formation of droplets of condensing water was observed. When the temperature reached about 185 °C, the color of the sawdust changed and a barely visible “thin” fog was observed. According to the researchers, this fog had a pungent odor, but could hardly be called smoke. For the first time, real smoke appeared in the temperature range of 220-300 °C.

The observed smoke formation continued up to a temperature of 500 °C, and the sawdust was completely charred. No smoke formation was observed in the combustion zone.

Here the burning of charcoal was observed, which had lost the ability to release gas. Smoke appeared near the combustion zone in wood that was not yet burning, but sufficiently heated.

Numerous studies of the influence of wood pyrolysis temperature on the chemical composition of smoke have led to the conclusion that the maximum yield of such chemical substances, like phenols, acids and carbonyl compounds, occur at temperatures of 550-650 °C.

With more high temperatures generation, as well as at lower levels, the content of phenols, acids and carbonyl compounds in the smoke is noticeably reduced.

The specified (optimal for given conditions) temperature when obtaining heat for the decomposition of wood due to combustion is ensured, as a rule, by changing the air supply to the combustion zone. With an increase in air supply, the temperature in the wood pyrolysis zone rises, and vice versa, limiting the air supply leads to a decrease in temperature.

It is easier and more accurate to regulate the temperature of smoke production, and therefore its chemical composition when using an external heat source for heating. In this case, the temperature is maintained and regulated by automation devices.

Examples where the heat required for pyrolysis is not generated by the combustion of charcoal, but is supplied externally, include heating superheated steam or using frictional heat. In practice, two similar smoke generators have been used, namely friction and steam. Friction operates at a pyrolysis temperature of about 380 °C, steam - from 320 to 380 °C. Smoke formation occurs when one or the other method is used in the lower temperature range required for lignin pyrolysis. At these temperatures, lignin is a source for the formation of flavoring components of smoke, such as phenols, and decomposes completely.

With many years of experience in the production of smoked fish products, preference has been given to wood when generating smoke. hardwood trees. The finished products, when processed in smoke from this wood, have high quality indicators, in particular a pleasant taste and smoky aroma. This fact is undoubtedly associated with the chemical composition of the smoke used and its condition.

It has been established that in the smoke generated when burning hardwood (oak, beech), the content of volatile acids is significantly higher than in the smoke generated from coniferous wood.

There is a difference in the structure of lignin in softwood and hardwood. The main components of phenolic compounds in smoke from soft wood is guaiacol, from hard wood - a mixture of guaiacol, syringol and its para-component derivatives. Hence the significant differences in the flavoring effect of these two types of smoke.

In the smoke from coniferous wood (spruce, pine) it was noted high content resinous substances and carbonyl compounds. Products treated with this smoke, as a rule, have an intense surface color and a pronounced resinous aroma.

Experimental work using an aerosol filter and a cascade impactor showed that the mass concentration of smoke smoke generated from birch sawdust is three times less than the mass concentration of smoke smoke generated from beech sawdust.

It was suggested that if the smoke from beech sawdust is more concentrated in the dispersed phase, then significantly less fuel from beech will be required to smoke the same amount of fish than from birch.

In practice, when producing smoked fish products, waste from wood processing enterprises is used as fuel to produce smoke. In most cases, this is a mixture of sawdust from various woods, most often hardwood.

Humidity of fuel (sawdust)

Research has been carried out on the influence of the moisture content of the material (sawdust) on the smoke formation process. The experiments considered sawdust with humidity levels of 0, 10, 20, 30, 40, 50% and smoke formation temperatures of 300, 500 and 700 °C. The time of onset of formation and the duration of smoke emission were recorded when burning the studied sawdust with different humidity levels and after cooling the mass of the remainder of the burnt wood. It has been established that at temperatures of 500 and 700 °C, complete decomposition of wood occurs and the mass of charcoal formed is almost the same for these temperatures.

In both cases, about 75% of the dry wood mass turns into smoke. At the same time, at a temperature of 300 °C, incomplete smoke formation was noted.

With subsequent heating for 1 - 2 hours, the mass of charcoal decreased, but did not reach the residual 25% that was observed at temperatures of 500 and 700 °C. Based on the work carried out, a number of conclusions were made. Firstly, water delays the onset of the smoke formation process, but this does not in any way affect the total amount of smoke produced at sufficiently high temperatures. Secondly, water evaporated from sawdust partially displaces oxygen from the combustion zone, as a result the temperature of the fire decreases and more smoke is produced. In addition, additional heat is required to evaporate water from sawdust, which also leads to a decrease in temperature in the smoke generation zone. Thirdly, a decrease in the pyrolysis temperature during the development of smoke affects chemical composition smoke and, as a result, on its sensory properties. Fourthly, the increased moisture content in sawdust leads to significant humidification of the smoke, reducing its moisture capacity.

When studying the effect of fuel moisture on the dispersed composition of smoke smoke, it was noted that the mass concentration of smoke at a given temperature decreases with increasing relative humidity of sawdust.

The air entering the combustion zone during the formation of smoke has important, since to some extent it affects the chemical composition of the smoke. As air access increases during a certain period, an increase in the content of phenols is observed. The concentration of phenols, acids and carbonyl compounds increases with increasing proportion of decomposed wood and the amount of air supplied. With a large amount of incoming air, the generated smoke smoke contains an increased amount of resins and the content of phenols in it decreases.

In most modern smoking enterprises, smoke for fish processing is obtained in special devices - smoke generators, which are usually located at some distance from the smoking installations. In these cases, the centralized supply of smoke to the smoking chambers is carried out through chimneys. Transportation of smoke is reflected in its chemical composition; in this case, the degree of changes that occur depends on the distance of the generating device to the smoking chamber; changes in the cross-section of chimneys; changes in smoke temperature. When transporting smoke, accompanied by a decrease in temperature, a change in the ratio between the content of smoking components in the dispersed phase and the dispersion medium is observed. Main part chemical compounds concentrated in the dispersed phase.

During the movement of smoke, coagulation of particles and deposition of the latter on the walls of the air ducts are observed, and a significant part of the resinous substances is deposited in the air ducts. As a result general content smoking components in the smoke are reduced.

Since chemical compounds are distributed between the dispersed phase and the dispersion medium, the question of where more of them are located and which of the above smoke phases plays a decisive role in smoking is important.

An increase in relative humidity at the same temperature leads to an increase in the amount of phenolic compounds in the dispersed phase, and at a relative humidity of about 90 % Almost all phenols are concentrated in it. An increase in the temperature of the working environment promotes the redistribution of phenols between phases - part of the phenolic compounds from the dispersed phase passes into the vapor phase. However, even with maximum permissible temperatures cold smoking process (30-34 °C) the content of phenols in the vapor phase with a relative humidity of 20% did not exceed 50-55 % from their total content in the smoking environment.

Thus, it has been established that during cold smoking the phenolic components of smoke are mainly in the dispersed (droplet-liquid) phase. This is partly due to the fact that the boiling point of phenolic compounds is in the range of 182-260 °C.

Under hot smoking conditions at working environment temperatures from 80 to 140 °, the picture changes. Studies of model vapor environments regenerated from smoking products have shown that the bulk of smoke components of smoke in the lower temperature range are in the vapor phase. With an increase in temperature from 120 to 140 °C in the dispersed phase, the total amount of phenols, acids and carbonyl compounds decreases from 10 to 25%, depending on the type of drug used and its chemical composition.

Negative factors of smoke smoking and ways to eliminate them. Under the influence of individual components of smoke, in particular carbonyl compounds, the content of amino acids in the product, and especially lysine, decreases, resulting in a decrease the nutritional value products.

Among the carbonyl compounds in smoke, formaldehyde dominates. Free formaldehyde is one of the possible causes of the formation of cancerous tumors. Nevertheless, it has been proven that the human body is a system sufficiently protected from the effects of this substance, and its content in food is permissible up to 50 mg per 1 kg.

The main attention of specialists when studying issues related to smoke smoking is focused on finding ways to reduce the penetration of harmful chemical compounds into the processed products. Researchers have achieved certain positive results in this area. Thus, products with a reduced content of PAHs were obtained by using smoke generated under strictly defined conditions of pyrolysis and oxidation of volatile thermal decomposition products during the smoking process. As a result of numerous studies, it has been reliably proven that the smallest amount of polycyclic aromatic hydrocarbons contains smoke generated at temperatures of 300-400 o C.

Benzpyrene is concentrated mainly in the dispersed phase of smoke containing heavy resins. Separation of the dispersed phase and the use of exclusively steam media for smoking made it possible to significantly reduce the ingress of benzopyrene into the product.

The concentration of PAHs in smoked food products is significantly reduced when processed with chilled or filtered technological smoke. Studies of the composition of smoking media have confirmed that cooling promotes the condensation of high-boiling carcinogenic components of smoke, as well as coagulation and sedimentation of large particles of the dispersed phase containing benzopyrene.

Filtration is one of the simplest and most common methods of partially purifying smoke from undesirable compounds, based on removing large particles from the smoke-air mixture. Thus, one of the proposed methods for reducing PAHs is the use of an electrostatic air filter containing an ionizing section. Patent descriptions also contain recommendations for reducing PAHs in smoke using a cyclone. Filters are also used for these purposes mechanical removal from the smoke of resinous substances, but placing such a filter along the smoke path creates additional heat losses during hot smoking and contributes to an increase in wood fuel consumption.

Sensory evaluation of smoked products prepared with regular smoke compared to products processed with filtered smoke showed that they were similar in quality, but products smoked with filtered smoke were less intensely colored. Removing part of the dispersed phase during filtration leads to a decrease in the content of all smoke components, including aromatic and color-forming ones.

Steam smoked products are characterized by a low concentration of carcinogenic compounds, but they differ significantly in their organoleptic characteristics from the corresponding smoked products, in particular in the intensity of color and expressiveness of aroma, which are more pronounced during smoke smoking.

Most units for generating smoke include systems for partial purification of smoke from undesirable components. An example of a fairly effective method for purifying smoke is a device of the so-called water-inertial type, proposed by the Azcherryba Central Design Bureau (Fig. 53).

Thanks to inertia and effective contact with water, heavy smoke particles (soot, ash, tar) remain in it. Running water carries away particles of soot and ash, and the resin settles to the bottom of the device and is periodically removed through a hatch into a special container.

The methods and techniques listed above that help reduce the concentration of polycyclic aromatic hydrocarbons in smoked products do not lead to a noticeable decrease in nitrosamines, since one of the main sources of their formation in the product, nitrous oxide, is in the vapor phase of smoke, which does not undergo noticeable changes during the process. cleaning in smoking installations.

No less important issue associated with the use of smoke during smoking is the protection of the environment from air polluting smoke emissions containing a large number of organic substances.

Rice. 53. Cleaning device for smoke generator N-10-ID2G-1;

1 - purified smoke output; 2 - fitting for connection to the water supply network; 3 - bottom of the device; 4 - central pipe; 5 - circular wall; 6 - a partition dividing the device into two compartments; 7 - drain tray; 8 - Luke; 9 - elbow

Amount emitted into the atmosphere organic compounds reaches 2 g/m 3 during cold smoking, and 10 g/m 3 during hot smoking.

Currently, methods of adsorption, absorption, high-temperature and catalytic combustion, liquid-phase oxidation, electrostatic deposition and combined methods are used to purify smoke and gas emissions from industrial enterprises.

In order to prevent environmental pollution from emissions from smoking industries, methods such as sedimentation of the dispersed phase of emissions in an electrostatic field are most often used and recommended. high voltage, catalytic and high-temperature combustion.

Of significant importance when assessing the effectiveness of a particular cleaning method is, in addition to the cost of the devices and their reliability in operation, the possibility of side effects and operating costs.

Afterburning of smoke emissions is the most effective way neutralization, which achieves a high degree of purification from toxic substances. The process can take place at a temperature of about 500 °C (catalytic afterburning) or 750 °C (thermal afterburning), resulting in the formation of water vapor and carbon dioxide. Regular fuel oil or gas is used as fuel in afterburning devices. It should be taken into account that when using fuel oil as fuel, sulfur dioxide is formed. If installations are used to burn smoke of relatively low density (density), then the amount of sulfur dioxide formed may be higher than the amount of organic carbon burned. In addition, at present, the use of these cleaning methods is becoming economically unprofitable due to the high energy (fuel) consumption of afterburning devices.

The method becomes economical if the combustion chambers of existing thermal units, such as boilers, are used for afterburning. However, thermal neutralization is complicated by the presence of tar substances in the emitted gases. The accumulation of resin disrupts the aerodynamics of chimneys and the operation of control and burner devices.

In Fig. Figure 54 shows an installation for thermal neutralization of smoke emissions containing resin. Smoke emissions from smoking stoves 1 and exhaust ventilation systems 2 pass through the resin pre-separation tank 3, reducing resin deflection in the fan 4. Gas duct 5 also serves as a condenser and is laid in the direction of the resin collector 10. The flue gases are then supplied by a blower 6 into the air path of the oil-gas burner 7, located in the boiler furnace. The separated resin is periodically heated by a coil 9 to reduce the viscosity of fuel oil, which is pumped 8 is supplied to the liquid path of a gas-oil burner for combustion in the same way as liquid fuel.

Rice. 54. Installation for thermal neutralization of exhaust gases:

I - smoking oven; 2 - suction channels of the exhaust ventilation system; 3 - resin pre-separation capacity; 4 - fan; 5 - gas duct; b - fan supplying gases to the burner; 7 - gas-oil burner; 8 - fuel oil pump; 9 - resin heating system; 10 - resin collector

Rice. 55. Circulation system of the Atmos-2000 smoking installation:

1 - smoking chamber; 2 - shower system; 3 - exhaust air outlet; 4 And 15 - valves for regulating temperature and humidity of the working environment; 5 - working medium circulation fan; 6 - air supply duct to the smoke generator; 7 - smoke generator; 8 - air supply to the combustion zone of the smoke generator; 9 - throttle valve; 10 - air supply bypassing the sawdust combustion zone; 11 - electric ignition of sawdust; 12 - supplying smoke to the chamber; 13 - condensate drain; 14 - working environment heating system

Reducing environmental pollution is also facilitated by a more complete use of smoke in a smoking installation due to its recirculation and the creation of closed (circulation) systems. Example of practical application closed system The Atmos-2000 installation can serve (Fig. 55). With this system of organizing the smoking process, most of the air required for the flow of chemical reactions during sawdust smoldering, it is taken from the working environment of the smoking chamber. Thanks to this, the amount of waste smoke during conventional smoking is reduced by 1/10.

In Figure 2.2. an installation for cleaning flue gases is shown, operating on the basis of inertial and absorption methods.

Flue gas cleaning in a Venturi scrubber is carried out as follows: the installation tank is filled with drinking water, then the fan is turned on and the flue gases enter the Venturi pipe, where their speed increases to the maximum value. At the same time, water is supplied into the Venturi tube through a nozzle. By atomizing water in the nozzle and pulsating the high-speed smoke flow, the water is finely atomized. The contact surface of water and smoke particles increases, therefore, the sorption process intensifies. Then the smoke-water flow passes through the diffuser, where its speed of movement decreases, as a result of which the duration of contact between water and smoke increases.

In a centrifugal swirler, water droplets are separated from the smoke flow, since they have greater inertia and do not keep up with changes in the flow movement.

Droplets are caught on the surface of the water. The smoke flow from the swirler is fed tangentially into the cyclone, water droplets are thrown to the walls of the cyclone and washed away by a film of water from the ring water supply, and the purified smoke emissions enter the atmosphere.

As the recirculating water becomes saturated with smoking components, it is drained into a container, cleaned of resinous compounds and can be used as a smoking preparation.

Figure 2.2 – Installation for producing the smoking preparation “VNIRO”:

1 – recirculation pump; 2 – solenoid valve; 3,9,15,17,23,25 – valves; 4 – flow meter total flow water; 5 – water tank; 6 – recirculation water flow meter; 7 – centrifugal swirler; 8 – cyclone; 10 – ring water supply; 11 – diffuser; 12 – Venturi pipe; 13 – neck; 14 – confuser; 16 – nozzle; 18 – gate; 19 - measuring tube; 20 – high water level indicator; 21 – low water level indicator; 22 – high pressure fan; 24 – recirculation water filter.

In the N10-IDG smoke generator, flue gases are purified using a water-inertial method (Fig. 2.3).

Figure 2.3. Water-inertial device of the N10-IDG smoke generator:

1- cover; 2-exhaust pipe; 3-tray for draining water; 4-knee; 5- partition; 6-boundary wall; 7-smoke pipe; 8-body; 9-water pipe.

Smoke comes out of pipe 7 at high speed, hits the surface of the water, heavy particles settle into the water, and the smoke, due to collisions with the restrictive wall, turns 90 degrees and through elbow 6 is again directed to the surface of the water, which partially captures the heavy fractions. Purified smoke enters the smoking chamber through pipe 2. Periodically, water saturated with resinous substances, soot and other contaminants is replaced.

Figure 2.4 shows a scrubber installation for cleaning smoke emissions smoking chambers. The installation works as follows. The smoke enters precipitation room 2, in which heavy resins and ash are separated from the smoke. The separation occurs in an inertial way. Then the smoke enters scrubber 3.

In scrubber 3, through nozzle 4 from Raschig rings, water moves towards the smoke and falls through nozzles 5.

Fig. 2.4. Device for obtaining an aqueous solution of smoke: 1-collector; 2-sediment chamber; 3-scrubber; 4-nozzle; 5- nozzles; 6-fan; 7-smoke solution; 8-reservoir; 9-filter; 10-pump; 11-cooler; 12-collector.

The water in the installation circulates according to the following scheme: tank 12, pump 10, nozzle 4, tank 12. The water temperature is maintained within 50 C 0. After saturation with smoking components, the aqueous solution is filtered through cellulose pulp. The purified aqueous solution can be used as a smoking preparation.

The All-Union Scientific Research Institute of Oceanography and Fisheries (VNIRO) has developed a number of installations that can be used both to purify harmful emissions and to obtain a smoking preparation (Fig. 2.5-2.7).

Fig. 2.5. Device for obtaining a smoking preparation.

1,3,6 - dampers; 2-smoke generator; 4-filter; 5-sorber; 7-fan.

Fig.2.6. Installation for cleaning the smoke-air mixture. 1-adapter; 2-cover; 3-chimneys; 4.8 fans; 5- prefilter; 6,7- sorbers; 9-tank for preparing the solution; 10-pump.

Distinctive feature installations is the presence of a movable nozzle made of rubber balls, made of acid-resistant rubber, with a diameter of 15-20 mm and a density of 1 g/cm 3 (Fig. 2.5-2.6). In the E01-3090 installation, the balls are made of polyethylene. VNIRO recommends a speed of the smoke-air mixture of 7.5±0.1 m/s with a ratio of the volumes of the moving nozzle and the water layer of 0.5: 0.1.

The installation for purifying the smoke-air mixture (Fig. 2.6) uses two sorbers with ball nozzles. Water is used as absorbents in the first sorber, and a solution of a chemically active substance is used in the second.

Fig. 2.7. Installation E01-3090 for cleaning smoke emissions

1- nozzle; 2-lattice; 3-absorber; 4-irrigator; 5-tee with valve; 6,7-drop catchers; 8-pipe for releasing purified smoke into the atmosphere; 9-flap; 10-fan; 11- drain pipe; 12-pipe for draining condensate into the sewer.

Installation capacity 6000 m 3 /h, installed power 27.5 kW, maximum hydraulic resistance 8.2 kPa (820 mm water column), purified smoke temperature 90 0 C. Water capacity 1.2 m 3, one-time consumption of soda 6 kg, potassium premanganate up to 20 kg, bleach - 12 kg. dimensions 6000×5600×2600 mm, occupied area 36.6 m2.

The E01-3090 installation (Fig. 2.7) consists of two autonomous drum-type sorbers. In sorbers there is a layer of polyethylene balls on perforated grids. The layer of balls is filled with water to a height of 350-400 mm. When passing through a layer of water and nozzle, a so-called “fluidized layer” is formed, as a result of which mass transfer between smoke and water increases.

The installation capacity is 10800-15000 m 3 /h, water consumption is 5 m 3 /h, steam consumption at a pressure of 200 kPa (2 kgf/cm 2) is 80 kg/h, electricity consumption is 28 kW∙h, weight is 4500 kg.

If water is constantly drained, then the degree of purification of smoke emissions for resinous substances increases to 50.5%, for benzopyrene - to 64.5%.

A high degree of purification is achieved if the absorbent is continuously drained into the sewer. In this case, it must be neutralized, that is, additional chemical cleaning. When recycling the absorbate for 5 hours, the degree of purification for benzopyrene decreases to 22%, and for resinous substances to 18.6%, i.e. cleaning is not carried out effectively if the smoking preparation is obtained using the E01-3090 installation.

At the Moscow fish complex, a Flakt (Denmark) installation is used to purify smoke emissions using the chemical absorption method. The installation consists of three stages. At the first stage, large smoke particles are captured from the smoke stream by flushing liquid (NaOH). The flushing liquid is sprayed into the showering devices, saturated with solid particles, filtered and sent back to the showering devices.

At the second stage, the washing liquid also circulates; as a result, sodium hydroxide hydrolyzes esters, converts phenols and organic acids into readily soluble phenolates and sodium salts. After a certain operating cycle, the flushing liquid is neutralized with 98% sulfuric acid to the required pH value, after which it is discharged into the sewer network.

Installation capacity 80,000 m 3 /h, water consumption 2-4 m 3 /, 20% NaOH 20-30 l/h, 98% H 2 SO 4 1-2 l/h, smoke temperature - up to 60 0 C. Overall dimensions 14000×3000×3700 mm.

In Fig. Figure 2.8 shows a schematic diagram of cleaning based on a three-stage tower scrubber from Flakt.

At the first stage, flue gases are exposed to hydrochloric acid, in this case, nitrogen compounds (ammonia, amines) are absorbed from the smoke. At the second stage, sulfur compounds (hydrogen sulfide and mercaptans), aldehydes, ketones, and fatty acids are absorbed and oxidized from the smoke by sodium hypochloride.

Rice. 2.8. Technological diagram of a three-stage installation

for emissions purification from Flakt

At the third stage, caustic soda (NaOH) removes excess chlorine and residual acid compounds from the smoke.

In Fig. 2.9 introduces the Geiloote scrubber. The scrubber consists of 4 reaction chambers containing layers of irrigated packing. After each reaction chamber there are layers of rain-fed packing that act as drop catchers, thereby achieving a more complete use of the washing liquid in each chamber and eliminating the carryover of the washing liquid with the flue gases.

The first chamber is designed to remove solid particles.

In the second chamber, ionization of smoke particles occurs, so purification here occurs with absorption and electrostatic deposition. After passing through the high voltage zone, charged smoke particles are deposited on the surface of the nozzle or droplet separator as a result of the attraction of charged particles to the neutral surface under the influence of electromotive force self-induction or self-impact with a liquid or solid surface.

In the third chamber, acid washing with sulfuric acid occurs. In this case, alkaline components (amines) are removed from the smoke.

In the fourth chamber, the smoke is exposed to caustic soda, as a result of which acidic components are removed from it.

Installation capacity 40,000 m 3 /h, consumption of 20% NaOCl (in terms of active chlorine with a mass concentration of 150 g/l) 1.4 kg/h, electrostatic field voltage 20 - 30 kW, installed power 10 kW.

In Fig. Figure 2.10 shows the design of a smoke purification installation, the operating principle of which is based on absorption followed by post-combustion. Such installations are produced by Stork-Duke.

Rice. 2.9 Geiloote cross-flow scrubber:

1 – first stage of cleaning; 2 – ionization stage; 3 – third stage of purification; 4 – fourth stage of cleaning; 5, 6, 7 – viewing windows; 8, 9, 10 – absorbent recirculation systems; 11 – fan.

The installation consists of a scrubber with washing liquid and a furnace that runs on gas or fuel oil. The furnace can be cleaned using a recuperator.

After-combustion plants are also used by industry. Thermal catalytic devices are mainly used. In these devices, hydrocarbons and carbon monoxide are oxidized on a catalytic film to carbon dioxide. Aluminum-platinum, iron-chromium, and copper-chromium are used as catalysts.

It should be noted that the catalytic activity of various organic compounds is not the same. Therefore, the degree of purification of these compounds varies. In thermocatalytic installations, 75–97% of organic substances are usually oxidized.

In Fig. Figure 2.11 shows a schematic diagram of the installation for catalytic afterburning. If during thermal after-combustion the neutralization of organic substances occurs at a temperature of 700 - 800 0 C, then during catalytic after-combustion neutralization occurs at more low temperatures(up to 550 0 C).

The installation for catalytic combustion was tested at the Yalta fish processing plant (Fig. 2.12).

Catalyst basket 6 of the installation was made with various catalysts: AP-56 aluminum-platinum contacts (0.56% platinum on aluminum oxide); ShPK-2 (0.2% platinum on a ball carrier ShK-2); M-2 (chromium-nickel spiral with an active film containing thousandths of platinum).

The activity of contacts AP-56 and ShPK-2 at temperatures of 350 - 450 0 C and volumetric velocities of the smoke-air mixture of 5000 - 10000 m 3 / h is reduced due to deposits of carbon compounds on the surface.

Complete purification of flue gases is achieved using M-2 catalysts if the catalysis temperature is 500 0 C and the smoke-air mixture moves at a volumetric velocity of 15,000 m 3 /h.

Rice. 2.10. Combined treatment plant from Stork-Duke:

1 – drainage of washing liquid; 2 – air supply; 3 – gas supply; 4 – scrubber; 5 – supply of washing liquid; 6 – drop catcher; 7 – fan; 8 – air supply to the furnace; 9 – recuperator; 10 – chimney; 11 – air supply to the recuperator; 12 – combustion furnace; 13 – burner.

Figure 2.11 - Schematic diagram of an installation for catalytic afterburning: 1 – fuel oil or gas-burner; 2 – thermal insulation; 3 – cellular type catalyst; 4 – temperature sensor behind the catalyst; 5 – temperature sensor in front of the catalyst; 6 – fireproof pipe.

Figure 2.12 - Installation of catalytic after-combustion of smoke emissions:

1 – smoke supply fan; 2 – air supply fan; 3 – burners; 4 – reactor; 5 – air manifold; 6 – catalyst basket; 7 – chimney; 8 – smoke exhauster; 9 – waste heat boiler.

For deodorization of flue gases, NIIOGAZ specialists recommend NIIOGAZ-17D catalysts. The catalysis temperature should be 350-380 0 C, and the gas flow rate should be 15,000 - 20,000 m 3 /h.

The industry also uses so-called ionizing scrubbers, in which flue gases are purified using a high-voltage electrostatic field (Fig. 2.13).

In the zone of electrostatic charging of particles 1, ionization of smoke particles occurs. For ionization, irrigated electrode plates with a width of 200–300 mm are usually used. Small charged particles fall into layers of contact fillers (for example, Tellerette type). In contact fillers, small particles due to self-induction of reverse charge are attracted and deposited by the washing liquid. Harmful gases and gases from specific odors are absorbed by the washing liquid, react with it and turn into neutral compounds.

Figure 2.13 – Schematic diagram of an ionizing scrubber:

1 – zone of electrostatic charging of particles; 2 – spray nozzle; 3 – Tellerette type fillers; 4 – pump; 5 – tray for collecting washing liquid.

Scientists from the Moscow Institute of National Economy named after. G.V. Plekhanov developed a device for producing smoking liquid from flue gases (Fig. 2.14.)

In ionization chamber 1, soot is separated and relatively large resins are deposited; smoke particles acquire electrical charges. Finely dispersed water is introduced into the settling chamber 2 using a nozzle 3 connected to the negative pole of the voltage source. The aqueous solution circulates until it is saturated with smoking components according to the following scheme: receiver 5, pump 4, nozzle 3, sorption chamber 2, receiver 5.

Figure 2.14 – Device for producing smoking liquid using an electrostatic field:

1 – ionization chamber; 2 – sorption chamber; 3 – nozzle; 4 – pump; 5 – receiver.

The device can be used to obtain a smoking preparation and purify flue gases.

The performance of various types of scrubbers is given in Table 2.4.

Table 2.4

As can be seen from table. 2.4, the degree of flue gas purification using ionizing scrubbers (IWS) is quite high.