Device and method for collecting trace sulfur trioxide in industrial gasTechnical Field
The invention relates to a device and a method for collecting trace sulfur trioxide in industrial gas, belonging to the technical field of atmospheric pollution and treatment.
Background
Sulfur trioxide is an extremely harmful atmospheric pollutant, generally exists in tail gas discharged in industries such as electric power, chemical industry, metallurgy, building materials and the like, and the treatment and detection of the pollutant are highly regarded by the industry.
In the conventional method represented by the U.S. EPA 8 method, when such pollutants are detected, sulfur trioxide or sulfuric acid mist is usually sampled by impact adsorption, solution absorption, enrichment and the like, and the prepared solution is subjected to laboratory analysis. Due to the restriction of conditions such as strong corrosivity, adsorptivity, chemical instability and low content of sulfur trioxide and sulfuric acid mist, the accuracy of a sulfur trioxide measurement result is influenced by the problems of adsorption, air leakage, chemical reaction and the like generated in the sampling stage from a measurement point to absorption.
FIG. 1 is a schematic diagram of a sampling method of American EPA 8 sulfuric acid, the EPA 8 method is a sampling point of a heat tracing quartz tube 1 with a heat tracing function, which extends into a furnace wall (the heat tracing temperature is set to be 260 ℃), and industrial gas enters a system through the heat tracing quartz tube. The industrial gas passes through a quartzfilter material bottle 4, aspiral condensation pipe 9, a Teflon hose 6, an impact absorption bottle 7, a silica gel dryer 8, asuction pump 17, aflow meter 16, anaccumulation flow meter 15 and the like in sequence. The quartzfilter material bottle 4 is filled with a quartz filter material, is heated by theheating sleeve 5 and is matched with the heat preservation box 3 to maintain the working temperature of 260 ℃. When the industrial gas passes through the quartzfilter material bottle 4, dust is trapped on the quartz filter material in the bottle. The filtered gas enters thespiral condensation pipe 9, and the spiral condensation pipe is set at a constant temperature of 75-85 ℃, so that sulfur trioxide in the gas can be adsorbed on the pipe wall of the spiral condensation pipe, and a small part of the sulfur trioxide is adsorbed on the quartz filter material. Other gases including sulfur dioxide enter the impact type absorption bottle 7 after passing through the Teflon hose 6, the sulfur dioxide is absorbed by the solution in the absorption bottle, and the residual gas passes through the silica gel dryer 8, then passes through theair pump 17, theflowmeter 16, thethermometer 14 and theaccumulation flowmeter 15, and then the accumulated flow of the dry industrial gas can be measured.
After sampling, the filter material bottle 4 (including the quartz filter material therein) and thespiral condensation tube 9 are washed by deionized water. Collecting the leaching liquid, measuring the total sulfuric acid content in the liquid after constant volume, obtaining the total industrial gas amount through measurement, and calculating the content of sulfur trioxide (or sulfuric acid) in the industrial gas in unit volume.
The method has the disadvantages that because the flue gas flows in the quartz sampling tube, the temperature control in the sampling tube can not be uniform, a larger temperature gradient can be formed, dust is deposited, and sulfur trioxide is adsorbed on a pipeline or dust in a low-temperature area, so that the sulfur trioxide, sulfuric acid and the like can not reach the spiral condensation tube part through the sampling tube; meanwhile, the existing system has complex structure, more interfaces, complex leak detection and easy air leakage, and brings larger errors to test results; in the sulfuric acid condensation pipe part, because the temperature is lower than the boiling point of water, water in the industrial gas can condense and absorb sulfur dioxide, and the test results of various sulfides are influenced; a plurality of parts need to be washed in the later period, a cleaning dead zone is easy to form, the operation is complicated, and the solution is easy to remain; and the components such as sulfur trioxide and sulfuric acid adsorbed by the solid particles with adsorption in the industrial gas are not considered.
Disclosure of Invention
The invention aims to provide a device and a method for collecting trace sulfur trioxide in industrial gas, aims to solve the technical defects of complex structure and large sampling loss of a system for measuring trace sulfur trioxide in industrial gas in the industries of metallurgy, electric power, chemical industry, building materials and the like, and solves the problems of low test efficiency of sulfur trioxide, inaccurate measurement result and the like.
The technical scheme of the invention is as follows:
the utility model provides a gather trace sulfur trioxide's device in industrial gas which characterized in that: the device comprises a sampling pipe, a constant-speed sampling instrument, a temperature control device and an absorption bottle; the pitot tube in the sampling tube and the isokinetic sampling instrument is placed in industrial gas; the temperature control device is respectively connected with a heating wire and a thermocouple which are arranged in the sampling pipe through signal lines. The sampling tube comprises an outer protective sleeve and a sampling inner tube; the sampling inner tube consists of an air inlet tube section and an air outlet tube section, air holes and sharp protrusions are arranged on the tube wall of the air inlet tube section, and fiber winding wires are wound on the sharp protrusions; a sealing pipe is sleeved outside the air inlet pipe section, and a sampling desorption air inlet is arranged on the sealing pipe; the gas outlet of the sampling inner tube and the pitot tube are respectively connected with the constant-speed sampling instrument through gas pipelines; the air outlet pipe section is filled with an adsorption medium, and heat insulation tiles are arranged between the air outlet pipe section and the outer protective sleeve and between the outer protective sleeve and the sealing pipe. The absorption bottle is provided with a gas inlet pipe and a gas outlet pipe, and alkaline solution is filled in the absorption bottle.
Further, the air inlet end of the outer protective sleeve is provided with an air inlet pipe groove, and the sampling and desorption air inlet is communicated with the outside through the air inlet pipe groove.
Furthermore, the cross section of each heat-insulating tile is semicircular, and two heat-insulating tiles are oppositely arranged to form a cylinder shape; the inner wall surface of each heat-insulating tile is provided with a groove for placing a heating wire.
Furthermore, a gas inlet pipe of the absorption bottle adopts a double-layer sleeve structure, an outer layer sleeve is arranged at the bottle mouth, an inner layer sleeve is L-shaped, one end of the inner layer sleeve is inserted into the absorption bottle, and the other end of the inner layer sleeve penetrates through the outer layer sleeve and extends out of the bottle to be connected with a gas outlet of the sampling inner pipe; a sleeve sealing ring is arranged between the outer sleeve and the outer wall of the air outlet of the sampling inner tube.
In the above technical solution, the adsorption medium and the fiber winding are preferably quartz cotton. The heat-insulating tile is made of aluminum silicate; the sampling inner tube and the sealing tube are made of quartz glass.
The invention provides a method for collecting trace sulfur trioxide in industrial gas, which is characterized by comprising the following steps:
1) adsorption process
a. Placing the sampling pipe and the pitot tube into the industrial gas to be collected, and aligning a sampling desorption gas inlet to the direction of the industrial gas flow; controlling the temperature in the sampling pipe to be 130-150 ℃ by a temperature control device;
b. starting a constant-speed sampling instrument to perform constant-speed sampling, enabling industrial gas containing sulfur trioxide to enter a sealing pipe through a sampling desorption air inlet, intercepting solid particles in the gas by a fiber winding wire wound by a pointed part, then entering an inner pipe through an air hole, enabling the solid particles to flow out of the inner pipe after being adsorbed by an adsorption medium, and recording the total flow of the extracted gas by the constant-speed sampling instrument to enable the sulfur trioxide in the industrial gas to be adsorbed on the fiber winding wire and the adsorption medium;
c. after the collection is finished, taking out the sampling pipe from the industrial gas, and disconnecting the sampling pipe from theisokinetic sampler 22;
2) and (3) desorption process:
a. inserting an inner layer sleeve of a gas inlet pipe of an absorption bottle into a gas outlet of a sampling inner pipe, and introducing nitrogen or inert gas with the flow rate of 20-100 ml/min from a sampling desorption gas inlet; adjusting the temperature of the sampling pipe to 350-400 ℃ through a temperature control device, and continuously introducing nitrogen or inert gas for 10-20 minutes after the temperature is stable, so that the sulfur trioxide on the adsorption medium and the solid particles is completely absorbed by the alkali solution in the absorption bottle;
b. after the desorption process is finished, stopping introducing nitrogen or inert gas, disconnecting the absorption bottle from the sampling pipe, and collecting the solution in the absorption bottle into the volumetric flask; the absorption flask was rinsed with deionized water and the rinse was collected in the same volumetric flask and the solution in the flask was then subjected to laboratory analysis.
In the method, the constant-speed sampling instrument records the total flow of the extracted gas and preferably records the total flow of the extracted gas to be 1 to 3 standard cubic meters. The alkaline solution is one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution and ammonium salt; the molar concentration of the alkali solution is 0.01-0.1 mol/L.
Compared with the prior art, the invention has the following advantages and prominent technical effects: the core of the invention lies in that the adsorption and desorption integrated sampling tube is applied, the sampling system is simplified, and the sampling error caused by air leakage generated by too many connectors is reduced; collecting sulfur trioxide by adopting a method of purging inert gas at high temperature, so that no cleaning dead zone is generated, the sampling precision is increased, and operations such as cleaning and drying of parts by using liquid are not needed in the later period; parts such as the quartz sampling inner tube and the like are easy to replace, multiple sets of parts are matched for use, continuous and multiple times of acquisition can be realized, and the working efficiency is effectively improved by carrying out sulfur trioxide collection in a centralized manner; the temperature stabilizing area of the sampling inner tube is long, condensation of sulfur trioxide on the tube wall due to the temperature gradient formed at the inlet and the outlet is reduced, and the sampling loss is reduced; the sulfur trioxide adsorbed on the industrial gas dust particles is also heated and flushed with inert gas in the desorption operation and is therefore also taken into the measurement range, which is not possible with other measurement methods.
Drawings
FIG. 1 is a schematic diagram of the sampling method of sulfuric acid from US EPA 8.
FIG. 2 is a schematic diagram of the structure of the collection adsorption process.
FIG. 3 is a schematic diagram of the desorption process.
Fig. 4 is a schematic structural diagram of the heat-insulating tile.
Fig. 5 is a schematic view of the connection structure of the absorption bottle and the sampling tube.
The labels in the figure are: 1-heat tracing quartz sampling tube; 2-furnace wall; 3, a heat preservation box; 4-quartz filter material bottle; 5, heating the outer sleeve; 6-Teflon hose; 7-impact absorption bottle; 8-silica gel dryer; 9-spiral condensation pipe; 14-a temperature detector; 15-a cumulative flow meter; 16-a flow meter; 17-an air pump; 18-needle type regulating valve; 19-a sampling tube; 20 — pitot tube; 21-gas connecting pipeline; 22-isokinetic sampler; 23-an exhaust tube; 24-temperature controller; 25-signal lines; 28-absorption bottle; 29-gas outlet pipe; 30-outer sleeve; 31-inner layer sleeve; 32-heat preservation tile; 33 — an adsorption medium; 34-an outer protective sleeve; 35-a sealing tube; 36-sampling and desorption air inlet; 37-air holes; 39-cuspate; 40-winding the fiber; 41-air inlet pipe groove; 42-a sealing ring; 43-sampling inner tube; 44-connecting a sealing ring; 45, sampling an air outlet of the inner pipe; 46-a groove.
Detailed Description
The principle structure and operation of the present invention will be further described with reference to the accompanying drawings and examples.
Referring to fig. 2 and 3, the device for collecting trace sulfur trioxide in industrial gas provided by the invention comprises a sampling pipe 19, anisokinetic sampler 22, atemperature control device 24 and anabsorption bottle 28; thepitot tube 20 using the tube 19 and isokinetic sampler is placed in the industrial gas; thetemperature control device 24 is respectively connected with a heating wire and a thermocouple arranged in the sampling pipe throughsignal lines 25.
The sampling tube 19 comprises an outerprotective sleeve 34 and a samplinginner tube 43; the samplinginner tube 43 is divided into an air inlet tube section and an air outlet tube section, asealing tube 35 is sleeved outside the air inlet tube section, and a samplingdesorption air inlet 36 is arranged on thesealing tube 35; the pipe wall of the air inlet pipe section is provided with anair hole 37 and apointed projection 39, and afiber winding wire 40 is wound on the pointed projection part; the sampling innertube air outlet 45 and thepitot tube 20 are respectively connected with theisokinetic sampler 22 through air pipelines.
The air outlet pipe section is filled with anadsorption medium 33, andheat preservation tiles 32 are arranged between the air outlet pipe section and anouter protection sleeve 34 and between the outer protection sleeve and asealing pipe 35. Theabsorption bottle 28 is provided with a gas inlet pipe and agas outlet pipe 29, and the inside of the absorption bottle is filled with alkaline solution. The alkaline solution is one or more of a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution, a potassium carbonate solution and an ammonium salt, and the molar concentration of the alkaline solution is 0.01-0.1 mol/L.
For convenience of installation and maintenance, an airinlet duct groove 41 is provided at the air inlet end of the outerprotective sleeve 34, and the sampling anddesorption air inlet 36 communicates with the outside through the airinlet duct groove 41. The airinlet duct slot 41 is a rectangular cut radially through the outerprotective sleeve 34 and the insulatingtile 32, and the sampling anddesorption air inlet 36 provided on thesealing tube 35 is clamped in the air inlet duct slot.
The gas inlet pipe of the absorption bottle adopts a double-layer sleeve structure, the outer-layer sleeve 30 is arranged at the bottle mouth, the inner-layer sleeve 31 is L-shaped, one end of the inner-layer sleeve is inserted into the absorption bottle, and the other end of the inner-layer sleeve penetrates through the outer-layer sleeve and extends out of the bottle to be connected with thegas outlet 45 of the sampling inner pipe; a sleeve sealing ring 44 (shown in figure 3) is arranged between the outer wall of theouter sleeve 30 and the outer wall of the sampling innertube air outlet 45.
Theadsorption medium 33 and the fiber winding 40 according to the present invention are preferably made of quartz wool. The material of the heat-insulatingtile 32 is preferably aluminum silicate; the samplinginner tube 43 and thesealing tube 35 are both made of quartz glass.
FIG. 4 is a schematic structural view of a heat-insulating tile; the cross section of theheat preservation tile 32 is semicircular, and two heat preservation tiles are oppositely arranged to form a cylinder shape; the inner wall surface of each heat insulation tile is provided with agroove 46 for placing a heating wire.
The invention provides a method for collecting trace sulfur trioxide in industrial gas, which is divided into two stages, namely an adsorption process and a desorption process.
The adsorption is to adsorb sulfur trioxide in the industrial gas on theadsorption medium 33 and the fiber winding 40. When the sampling device works, the sampling pipe is connected with the constant-speed sampling instrument through theexhaust pipe 23; connecting thepitot tube 20 with the isokinetic sampler through agas connecting pipeline 21; the temperature of the sampling tube is controlled to be 130-150 ℃ by atemperature controller 24; inserting a sampling pipe into the industrial gas inside thefurnace wall 2, wherein a samplingdesorption gas inlet 36 is aligned with the direction of the industrial gas flow; theisokinetic sampler 22 is turned on to begin isokinetic sampling and the isokinetic sampler records the total flow of air extraction, typically 1-3 standard cubic meters (see fig. 2). At the end of the adsorption process, the sampling tube 19 is removed from the industrial gas and disconnected from theisokinetic sampler 22.
The desorption process is to collect the sulfur trioxide adsorbed on the sulfur trioxide of theadsorption medium 33 and the sulfur trioxide on the solid particulate matter intercepted by the fiber wrapping 40 in the alkaline solution in theabsorption bottle 28. During work, a proper amount of alkali solution is added into the absorption bottle, theinner sleeve 31 of the absorption bottle is further inserted into the sampling innertube gas outlet 45, and asleeve sealing ring 44 is inserted into a gap between theouter sleeve 30 and the outer wall of the sampling innertube gas outlet 45 to ensure that sulfur trioxide enters theabsorption bottle 28 without loss; introducing nitrogen or inert gas with the flow rate of 20-100 ml/min from the samplingdesorption gas inlet 36; the temperature of the sampling pipe is adjusted to 350-400 ℃ through the temperature control device, nitrogen or inert gas is continuously introduced for 10-20 minutes after the temperature is stable, and the sulfur trioxide on the adsorption medium and the solid particles is completely absorbed by the alkali solution in the absorption bottle.
After the desorption is finished, the sulfur trioxide is absorbed by the alkali solution in theabsorption bottle 28; stopping introducing nitrogen or inert gas, disconnecting the absorption bottle from the sampling pipe, and collecting the solution in the absorption bottle into the volumetric flask; and (5) washing the absorption bottle by using the deionized water, and collecting the washing liquid in the same volumetric flask to finish the sampling process.
In subsequent work, the content of sulfur trioxide in the volumetric flask is measured in a laboratory, and the concentration of sulfur trioxide in the industrial gas is calculated by utilizing the standard condition gas extraction amount.