RU2723865C1 - Method for synthesis gas production from plant biomass - Google Patents

Abstract

FIELD: oil, gas and coke-chemical industries.SUBSTANCE: invention relates to production of synthesis gas by processing vegetal biomass and can be used in oil refining, petrochemistry and power engineering. Method is implemented by grinding the initial biomass, mixing it with fine-dispersed oil shale with sulphur content 4.1–16.0 wt. %, having particle size of 10–100 mcm, and water taken in the following amount, wt. %: shale 3.0–5.0, water 10.0–30.0, biomass is balance up to 100. Then, the formed mixture is subjected to dispersion to obtain a suspension, followed by gasification of the obtained suspension at temperature of 800–1000 °C and direction of the formed gas stream for purification to obtain synthesis gas.EFFECT: technical result consists in improvement of efficiency of method of processing of biomass in order to obtain synthesis gas, namely in simplification of its technology, prevention of phenomenon of deposition of compounds of alkali metals on surfaces of equipment and effective prevention of alkali corrosion of equipment.1 cl, 2 tbl, 4 ex

Description

The invention relates to the field of production of synthesis gas by processing biomass of plant origin and can be used in oil refining, petrochemicals, energy.

Gasification is the most common of the thermochemical processes of biomass processing. The target product of biomass processing processes using gasification is synthesis gas, which is a gas mixture containing mainly carbon monoxide and hydrogen gas. Synthesis gas is used, in particular, for the production of methanol and hydrogen, in the Fischer-Tropsch process in order to obtain synthetic oil or raw materials for organic chemistry and petrochemicals.

Known methods for producing synthesis gas by gasification of biomass, described, for example, in patents US 9187704, 2015, EP 20090702727, 2009, RU 2631811, 2017, RU 2443626, 2012, RU 2519441, 2014, RU 2526387, 2017. One of the problems of the existing technology gasification of biomass is as follows. The biomass used contains significant amounts of alkalis - potassium and sodium compounds. These alkalis evaporate at temperatures above 800 ° C during gasification and partially penetrate into the pores of the lining of the gas generator. The introduction of alkalis destroys the structure of the lining. This phenomenon is known as alkaline degradation (alkaline corrosion). Part of the alkali in the gaseous state, formed during the biomass gasification, enters the colder part of the installation after the gas generator, where the gas condensation takes place, as well as the deposition process on the internal surfaces of the equipment, in particular, for example, heat exchangers and filters of heated gas of solid alkaline salts metals.

A known method of producing synthesis gas by gasification, in particular biomass of plant origin, in which the vaporous alkali contained in the synthesis gas is removed from the synthesis gas by contacting the getter ceramic material. In this case, the synthesis gas is sent without preliminary cooling to a slag separating device, in which droplets of slag are discharged in the form of liquid slag, and the hot synthesis gas after cleaning from slag, alkalis and, if necessary, from sulfur-containing substances is sent to a gas turbine driven into action of hot gas. Gasification is carried out at a temperature of 800-1800 ° C and a pressure of 0.1-10 MPa. (RU 2490314, 2016). The disadvantage of this method is the complex technological scheme.

A known method of gasification of biomass with the production of synthesis gas, in which the operation of mixing biomass and a catalyst ("accelerator") of gasification is preliminarily carried out, using clay having catalytic functions and / or a coolant function in the gasification reaction zone at elevated temperatures in the presence of gasification agent for converting organic raw materials into gas suitable for the production of liquid fuel (US 9187704, 2015). The gasification catalyst (“accelerator”) preferably contains at least one element selected from the group consisting of smectite clay, vermiculite clay, kaolin-serpentine clay, chlorite clay, and mixtures thereof; more preferably, at least one element selected from the group consisting of smectite clay, vermiculite clay, kaolinite clay, halloysite clay, and mixtures thereof.

In a gasification catalyst including clay as an indispensable component, if necessary, at least one element is selected from the group consisting of other minerals, diatomaceous earth, silicon oxide-alumina catalysts, transition metal inorganic catalysts , catalysts based on metal oxides and their mixtures.

The disadvantage of the proposed method is the use of a complex catalyst composition and the presence in the gas composition of both volatile and non-volatile compounds of potassium and sodium, which are deposited on the walls in the reactor zone of the gas generator. Potassium and sodium compounds are deposited in the lining of the gas generator, on the walls of the equipment, which impairs their operation, complicates the gasification process, and leads to equipment failure (alkaline destruction). In addition, the low gasification temperature does not allow the complete conversion of biomass carbon into the target product.

Of the known technical solutions, the closest to the proposed technical essence and the achieved result is a method for producing synthesis gas by processing plant biomass by gasification in a fluidized bed to produce synthesis gas (RU 2639911, 2017). According to this method, in order to eliminate the formation of alkalis in the gaseous state during the synthesis gas production during gasification of biomass in the fluidized bed, the synthesis gas is brought into contact with the alkali binding gas-absorbing ceramic. The following substances are recommended to be used as gas absorption ceramics: kaolin, bauxite, bentonite, alumina, kieselguhr, pumice, diatomaceous earth, attapulgite, pyrophyllite, andalusite, sillimanite, mullite, barium sulfate, fuller’s earth, silicon oxide, activated alumina, silicon carbide or mixtures thereof. In this case, the contact of the biomass with the getter ceramic is carried out both in the device installed before the gas generator with the fluidized bed, and inside the latter. Ceramics deposited on the filter mounted on the gas stream exiting the gas generator are returned to the specified gas generator.

The disadvantages of the method are the complexity of the technological scheme associated with the need to organize recycling of the used getter ceramics, periodically replace the getter ceramics due to the accumulation of alkali metals in the latter. In addition, after the pores are completely filled with alkalis, the getter ceramic loses its absorption capacity and becomes an environmentally hazardous alkaline material, the disposal of which is a complex and expensive process.

Thus, this method is not effective enough.

The technical problem to which the present invention is directed is to increase the efficiency of the biomass processing method in order to obtain synthesis gas, namely, to simplify its technology, to prevent the deposition of alkali metal compounds on equipment surfaces and, as a result, to effectively prevent alkaline corrosion equipment.

This problem is solved by the described method of producing synthesis gas from biomass of plant origin by grinding the original biomass, mixing it with finely divided oil shale with a sulfur content of 4.1-16.0% by weight, having a particle size of 10-100 microns, and water taken in amount,% mass .: shale 1.0-5.0, water 10.0-30.0, biomass - the rest, up to 100, dispersing the resulting mixture to obtain a suspension, followed by gasification of the resulting suspension at a temperature of 800-1000 ° and directing the resulting gas stream to purification to produce synthesis gas.

Achievable technical result is to provide conditions for the formation of suspensions during heating prior to gasification of non-volatile, at a gasification temperature, alkali metal salts.

The essence of the method is as follows.

As a biomass of plant origin, it is possible to use any residues of agricultural production within the framework of this application, for example, corn cobs, corn straw and stalks, husk, cake and meal from sunflower processing, flax production wastes and other wastes generated during the processing of agricultural raw materials of plant origin or mixtures thereof, as well as waste from the forest industry and other similar waste. The total content of alkali metal compounds - oxides K ₂ O and Na ₂ O can reach 30-35% wt. In biomass.

Used shales in the framework of this application are various combustible shales with a high sulfur content - from 4.1 to 16.0 wt. -%, preferably shales of the Volga shale basin.

The initial biomass is ground sequentially, for example, in a screw mill or in a crushing machine, or in a drum grinder to a particle size of 1-3 mm and then in a homogenizer disperser to a particle size of 100-200 mm. The resulting crushed biomass is loaded into the hopper and stored in a nitrogen atmosphere.

Used oil shale is crushed to obtain fine shale with a particle size of 10-100 microns.

Then, the crushed initial biomass is mixed with finely divided oil shale (particle size 10-100 μm) with a sulfur content of 4.1-16.0% wt. and water in predetermined ratios (shale content of 3.0-5.0% wt., water 10.0-30.0% wt., biomass - the rest, up to 100% wt.) to obtain a mixture.

The resulting mixture is subjected to dispersion, for example, in a dispersant - homogenizer and sent to gasification.

In the described method, the gasification process can be carried out in the traditional way with air, air-oxygen and oxygen blasting. Due to the presence of a suspension of water used in the gasification process, the use of water vapor in addition to gasification is not practical.

Gasification of the suspension is carried out in a continuous gas generator at 800-1000 ° C, the oxygen content in the blast from 20 to 95% vol. and an oxygen deficiency ratio of 0.3-0.5.

The resulting gasification products with a temperature of 800-1000 ° C, contaminated with solid organic (soot) and mineral impurities (ash), enter the cooling system.

Cooled gasification products are sent to the soot, ash and hydrogen sulfide purification system.

The cleaning of gasification products from soot is initially carried out by washing with a hydrocarbon fraction boiling above 250 ° C, with the release of a soot-hydrocarbon suspension and its subsequent return to gasification in a gas generator.

Subsequent purification of gasification products from soot and ash is carried out by water washing to separate an aqueous suspension of soot and ash components.

The final purification of gasification products from ammonia, thiocyanates and hydrogen sulfide is carried out with an aqueous solution of an alkaline sorbent, for example, an aqueous solution of ethanolamines to obtain purified synthesis gas.

The ash generated during gasification is cooled and collected in a hopper.

The presence of organic sulfur in shale during gasification allows the conversion of potassium and sodium compounds contained in the original biomass into non-volatile, at gasification temperature, salts, in particular, sulfite and sulfate. This process begins at temperatures below the gasification temperature of suspensions of mixtures of biomass, shale and water. Thus, the conversion of oil shale (for example, the Kashpirovsky field of the Volga region) during thermal gasification begins at a temperature of the feedstock equal to 450 ° C and ends with the almost complete conversion of shale into gas at 750 ° C. At this temperature, the volume of gas generated as a result of the conversion of oil shale reaches a maximum. In the process of thermolysis, almost complete decomposition of kerogen occurs, as a result of which this gas contains mainly hydrogen, carbon monoxide, carbon dioxide, methane, as well as hydrogen sulfide formed from organic sulfur shale.

Moreover, when the temperature reaches 750-800 ° C, alkali is sublimated - the sodium and potassium compounds contained in the biomass, with the formation of volatile sodium and potassium hydroxides. Volatile alkali hydroxides react with hydrogen sulfide, resulting in the formation of non-volatile, at gasification temperature, solid sulfates and sulfites of sodium and potassium.

The resulting sulfates and sulfites of sodium and potassium are removed from the reaction zone with the produced gas before the start of the main gasification process (occurring at temperatures of 800-1000 ° C) and, as a result, potassium and sodium compounds are not deposited on the walls of the equipment. Sulfates and sulfites of sodium and potassium are mixed with ash, formed during the biomass gasification process and consisting mainly of SiO ₂ (70% by mass and more), CaO (up to 6.0% by mass) and MgO (up to 8.0% by mass) .). At the same time, the sulfur-containing additive (shale), which promotes the binding of alkalis and prevents the occurrence of alkaline corrosion, does not need to be disposed of, since it almost completely turns into gas, slightly increasing the total volume of gasification gas generated.

The following are examples illustrating but not limiting the invention.

Table 1 shows the chemical analysis data for biomass samples that are used in the examples below.

Physico-chemical properties of oil shale used in the examples are shown in table 2.

Example 1

As the initial biomass, corn cobs are used. These rods are crushed sequentially in a screw mill to a particle size of 1-3 mm and then in a disperser - homogenizer to a particle size of 100-200 mm.

The oil shale of the Kashpirskoye field with a sulfur content of 4.1% by weight is used as oil shale.

Used oil shale is crushed to obtain fine shale with a particle size of 10-100 microns. Then, the crushed initial biomass is mixed with finely divided oil shale and water (taking into account the initial moisture content of the raw material), taken in the amount,% mass .: shale 5.0, water 10.0, biomass 85.0. the resulting mixture is subjected to dispersion in a dispersant - homogenizer to obtain a suspension. As a result of mechanical activation, the average particle size of water is 5-20 microns. This suspension is gasified by air blasting. Gasification is carried out with an oxygen deficiency coefficient of 0.3, at a temperature of 1000 ° C, without using pressure.

The gas formed during gasification is cooled, and is subjected to purification with the separation of soot and ash.

Then the gas is purified from hydrogen sulfide, ammonia and thiocyanates using monoethanolamine and get the target synthesis gas.

Inspection of the inner surface of the gas generator reveals the presence of slight plaque on the walls and the absence of soot particles. According to the chemical analysis of ash obtained as a result of gas purification according to GOST 10538-87 Solid fuel. Methods for determining the chemical composition of ash (with Change No. 1) in the latter contains 8.8% of the mass. K ₂ O and 4.5% of the mass. Na ₂ O. Thus, more than 80% rel. compounds of potassium and sodium contained in the original biomass, during gasification were removed from the reaction zone with the resulting ash in the form of sulfates and sulfites and did not deposit on the surface of the equipment. The composition of the synthesis gas,% vol .: H ₂ - 23.4; СО - 10.3; CO ₂ - 8.6; N ₂ - 56.2; C ₁ - 1.5.

Example 2

As the initial biomass, sunflower husk is used. These rods are crushed sequentially in a drum grinder to a particle size of 1-3 mm and then in a disperser - homogenizer to a particle size of 100-200 mm.

As oil shale, oil shale from the Savelyevskoye field with a sulfur content of 16.0% by mass is used.

Physico-chemical properties of oil shale of the Savelyevsky field are shown in table 2.

Then, the crushed initial biomass is mixed with finely divided oil shale and water (taking into account the initial moisture content of the raw material), taken in the amount,% mass: shale 3.0, water 15.0, biomass 82.0. The resulting mixture is subjected to dispersion in a dispersant - homogenizer to obtain a suspension.

Moreover, as a result of mechanical activation processes taking place in a dispersant - homogenizer, the average particle size of water in suspension is 5-20 microns.

This suspension is gasified by air blasting. Gasification is carried out with an oxygen deficiency coefficient of 0.4 at a temperature of 800 ° C, without using pressure.

The gas formed during gasification is cooled, and is subjected to purification with the separation of soot and ash.

The gas is then purified from hydrogen sulfide, ammonia and thiocyanates using monoethanolamine.

Inspection of the inner surface of the gas generator reveals the presence of slight plaque on the walls and the absence of soot particles. According to the chemical analysis of ash obtained as a result of gas purification according to GOST 10538-87 Solid fuel. Methods for determining the chemical composition of ash (with Change No. 1) in the latter contains 17.8% of the mass. K ₂ O and 0.6% of the mass. Na ₂ O. Thus, about 90% rel. potassium and sodium compounds contained in the biomass, during gasification with shale, were removed from the reaction zone in the form of sulfates and sulfites with ash formed and did not deposit on the surface of the equipment.

The composition of the obtained synthesis gas,% vol .: H ₂ - 22.4; СО - 9.8; CO ₂ - 7.6; N ₂ - 58.9; C ₁ - 1.3.

Example 3 (comparative).

As the initial biomass, corn cobs are used. These rods are crushed sequentially in a drum grinder to a particle size of 1-3 mm and then in a disperser - homogenizer to a particle size of 100-200 mm.

The oil shale of the Leningrad field with a sulfur content of 0.91% by weight is used as oil shale.

Physico-chemical properties of oil shale of the Leningrad field, Slantsy are shown in table 2.

Used oil shale is crushed to obtain fine shale with a particle size of 10-100 microns.

Then, the crushed initial biomass is mixed with finely divided oil shale and water (taking into account the initial moisture content of the raw material), taken in the amount,% mass .: shale 5.0, water 30.0, biomass 65.0. The resulting mixture is subjected to dispersion in a dispersant - homogenizer to obtain a suspension. As a result of mechanical activation processes taking place in a dispersant-homogenizer, the average particle size of water in the latter is 5-20 microns.

The resulting suspension is gasified by air blasting. Gasification is carried out with a coefficient of air deficiency of 0.5 in terms of oxygen, at a temperature of 800 ° C, without using pressure. The gas formed during gasification is cooled, and is subjected to purification with the separation of soot and ash.

Then the gas is purified from hydrogen sulfide, ammonia and thiocyanates using monoethanolamine and get the target synthesis gas.

Inspection of the inner surface of the gas generator reveals the presence of slight plaque on the walls and the absence of soot particles. According to the chemical analysis of ash obtained as a result of gas purification according to GOST 10538-87 Solid fuel. Methods for determining the chemical composition of ash (with Change No. 1) in the latter contains 7.8% of the mass. K ₂ O and 4.6% of the mass. Na ₂ O. Therefore, not more than 70% of the potassium and sodium compounds contained in the biomass, during gasification with shale in the form of sulfates and sulfites, were removed from the reaction zone with the resulting ash and did not deposit on the equipment surface. The rest was deposited on the walls of the equipment.

The composition of the obtained synthesis gas,% vol .: H ₂ - 20.7; СО - 9.8; CO ₂ - 8.0; N ₂ - 60.4; C ₁ - 1.1.

Example 4 (comparative).

The method is carried out analogously to example 1. The method is carried out without the use of oil shale.

As plant biomass, corn cobs or sunflower husks are used.

Ground corn cobs are mixed with water in an amount of 90% of the mass. biomass and 10 mass. water (taking into account the initial moisture content of the raw material). The specified mixture is subjected to dispersion in a dispersant-homogenizer.

The resulting suspension is gasified by air blasting. Gasification is carried out at a temperature of 800 ° C, an oxygen deficiency coefficient of 0.3, without using pressure.

The gas formed during gasification is cooled, and is subjected to purification with the separation of soot and ash.

Next, the gas is purified from hydrogen sulfide, ammonia and thiocyanates using monoethanolamine. The composition of the synthesis gas,% vol .: H ₂ - 18.4; СО - 10.5; CO ₂ - 7.9; N ₂ - 62.3; C ₁ - 0.9.

When examining the inner surface of the gas generator, the presence of ash deposits on the walls with the inclusion of individual soot particles is recorded. According to the chemical analysis of ash obtained by gas purification, the latter contains 2.4% of the mass. K ₂ O and 1.3% of the mass. Na ₂ O.

When using sunflower husk as biomass, the crushed sunflower husk is mixed with water in an amount of 85% of the mass. biomass and 15 mass. water (taking into account the initial moisture content of the raw material).

The specified mixture is subjected to dispersion in a dispersant-homogenizer.

The resulting suspension is gasified by air blasting. Gasification is carried out with an oxygen deficiency coefficient of 0.4 at a temperature of 800 ° C, without using pressure.

The gas formed during gasification is cooled, and is subjected to purification with the separation of soot and ash.

The gas is then purified from hydrogen sulfide, ammonia and thiocyanates using monoethanolamine. The composition of the obtained synthesis gas,% vol .: H ₂ - 17.4; СО - 9.3; CO ₂ 10.8; N ₂ 61.5; C ₁ - 1.0.

Inspection of the inner surface of the gas generator showed the presence of deposits on the walls with inclusions of individual soot particles. Chemical analysis of ash according to GOST 10538-87 Solid fuel. Methods for determining the chemical composition of ash (with Change No. 1) showed that it contains 4.1% of the mass. K ₂ O and 0% wt. Na ₂ O.

A comparison of the data on the content of potassium and sodium compounds in the initial biomass (table 1) and in the ash obtained as a result of gasification of the above biomass in a mixture with water without using shale shows that the latter contains about 20% of the potassium and sodium compounds from their initial content in biomass, therefore, at least 80% of the relative alkalis contained in the original biomass was deposited on the walls of the internal surfaces of the equipment.

Thus, the described method, carried out according to a simpler technological scheme, eliminating the need for recycling, replacing and disposing of an additive that helps to remove alkalis in a gaseous state, allows due to the possibility of converting alkali metal compounds - potassium and sodium contained in the raw material to be gasified to non-volatile , at a gasification temperature, alkali metal salts, it allows, almost completely (up to ~ 90% rel.) to prevent the occurrence of deposits of alkali metal compounds on the equipment surfaces and, as a result, effectively prevent alkaline corrosion of the equipment.

Claims (1)

The method of producing synthesis gas from plant biomass by grinding the original biomass, mixing it with finely divided oil shale with a sulfur content of 4.1-16.0 wt.%, Having a particle size of 10-100 microns, and water, taken in quantities, wt. .%: shale 3.0-5.0, water 10.0-30.0, biomass - the rest, up to 100, dispersing the resulting mixture to obtain a suspension, followed by gasification of the resulting suspension at a temperature of 800-1000 ° C and the direction of the gas purification stream to produce synthesis gas.