CN113431785A

CN113431785A - Intelligent sand-measuring mobile air stripping pump and use method thereof

Info

Publication number: CN113431785A
Application number: CN202110675350.8A
Authority: CN
Inventors: 不公告发明人
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-06-18
Filing date: 2021-06-18
Publication date: 2021-09-24

Abstract

The invention relates to the field of liquid treatment, in particular to an intelligent sand-measuring mobile air-lift pump and a using method thereof. Firstly, inventing a set of air lift pump with lifting and moving functions; sensing the amount of sand slag and dirt in the liquid by matching with a group of sensors for automatically measuring sand; and the other set of air lift pump sensors are matched to sense the running state of the air lift pump and lift the air lift pump. Namely, the two groups of automatic measuring and lifting devices can intelligently start and stop the air lift pump to discharge dirt according to the amount of sand slag dirt under liquid; when the blockage of the dirt is sensed, the dirt blocking the main liquid pipe can be cleaned out by lifting the air lift pump and backflushing; the function of intelligently controlling the air stripping pump is achieved. The invention solves the defects that the amount of dirt can not be sensed under liquid and the air stripping can not be carried out when the sand slag of the general air stripping pump is more than one air stripping pump opening is buried, and simultaneously well solves the problem of air stripping pump blockage. The invention reduces the carbon emission by the energy-saving pollution-reducing technology.

Description

Intelligent sand-measuring mobile air stripping pump and use method thereof

Technical Field

The invention relates to the technical field of liquid, in particular to an intelligent sand measuring mobile gas stripping pump and a using method thereof.

Background

During the liquid transportation process, it is often necessary to clean out the sediments and dirt under the liquid. The traditional method is to use electric pumps (dirt pump, submersible dirt pump, screw pump, etc.) for conveying, but the dirt cannot be lifted because the dirt often entangles the impeller; there is therefore a need for a bladeless lifting device.

Although a common air lift pump can lift dirt in an air lift mode, the common air lift pump is sometimes blocked and cannot be used, and the air lift pump needs to be manually disassembled for cleaning, so that time and labor are wasted.

Because the dirt pump and the common air lift pump cannot measure whether sediments and dirt needing to be lifted exist under the liquid or not, the air lift device can only be started continuously or at regular time, so that a large amount of electric energy is wasted, a large amount of water resources are wasted, and the direction of carbon emission and carbon neutralization advocated by the state is not met.

An aeration grit chamber is the most common sand removing facility in urban sewage treatment plants in China, sand suction equipment is generally arranged on a bridge type truss car, and the biggest problem is that the sand suction is not thorough. The reason for this is that sand is difficult to settle at the water inlet end and is deposited in a large amount at the water outlet end, and the sand suction device of the aeration grit chamber is fixed to move back and forth at the water inlet and outlet ends to suck sand, so that too much sand residue may cause damage to the sand suction device, and too little sand particle cannot achieve the sand suction effect. Therefore, in actual operation, more sand grains are accumulated at the water outlet end of the aeration grit chamber, especially sand slag is increased instantly when rain and snow fall, sand suction equipment is buried, the sand suction equipment cannot be stopped, and finally, only the chamber can be emptied and sand is manually cleaned. Therefore, during operation, the sand suction equipment is required to continuously adjust the sand suction height and the machine shutdown time according to the sand slag accumulation degree of the sand collection tank, so that the required sand suction effect is achieved while the equipment is protected.

In the second embodiment, a large amount of water is used for mixing asphalt, mud and slag in the existing stage of the petroleum sedimentation tank, and the mixture is pumped out by a sewage pump and then sent to a sewage plant for treatment; thus, the sewage pump needs fluidity, so that a large amount of water is needed to dilute the sewage for pumping, and a large amount of energy and capital are consumed; therefore, a device which can extract high-concentration dirt asphalt and can lift a small amount of water is needed. The efficiency is improved, the energy is saved, the emission is reduced, and the carbon emission is reduced.

Therefore, the prior art needs to be improved, and the intelligent sand-measuring mobile air stripping pump with a novel structure is invented to solve the problems.

Disclosure of Invention

The invention aims to: the intelligent sand measuring air stripping pump has the advantages of reasonable structural design, safety, convenience in operation and use, low maintenance cost, high automation intelligent degree and the like, can automatically clean up the sewage in the upper part, the middle part and the lower part of the liquid, and can be normally used in the severe environment.

In order to solve the problems in the background art and achieve the purpose, the invention adopts the following technical scheme:

firstly, the height of the sewage suction device is lifted for sewage suction according to the quantity of sand slag dirt through a measuring device for sensing the thickness of the sand slag dirt in a touch metering mode, so that the problems of sewage suction and energy saving are solved; when the extreme sand slag dirt is more buried in the suction device or the air stripping pump opening, the suction device or the air stripping pump is lifted to normally suck the dirt on the sand slag;

the diameter and the double-hole structure of the gas stripping liquid pipe are increased, and the gas stripping pump is matched with a lifting gas stripping pump and backflushing, so that the problem of blockage of the gas stripping pump is solved.

An intelligent sand-measuring mobile air-lift pump comprises a double-hole air-lift pump 1; 2. fixing a movable air stripping pump bracket; 3. an intelligent device of a gas stripping pump; 4. a fan; 5. an automatic control system; 6. a liquid pool;

the double-hole air stripping pump comprises: comprises a lift liquid pipe for lifting a gas-liquid mixture; 2 air pipes are connected with the bottom of the lifting liquid pipe at intervals, a proper amount of air is introduced to be mixed with liquid to lift dirt normally, and the lifting liquid pipe is dredged by increasing air flow and pressure when the lifting liquid pipe is blocked; 2 aeration pipes are arranged near the liquid lifting pipe, a proper amount of gas is introduced to be mixed with liquid dirt to perform a stirring action normally, so that the dirt is lifted, and when the liquid pipe is buried by the dirt, the dirt on the periphery of the liquid lifting pipe is cleaned by increasing the gas flow and the pressure, so that the liquid pipe can normally absorb sand; the gas stripping pump fixing plate plays a role in fixing the gas stripping pump pipe; the function of the double-hole air stripping pump is to cut the dirt and then to strip the dirt through the double-hole air pipe, so that the large dirt is effectively prevented from blocking the liquid lifting pipe, and the double-hole air stripping pump has a back flushing function, which is the main difference from the common air stripping pump.

The fixed mobile airlift pump bracket; the sand-measuring device comprises an air-lift pump support main board, an air-lift pump lower support, a sand-blowing pipe and a sand-measuring protection pipe, wherein the air-lift pump support main board is used for fixing an air-lift pump, the sand-measuring protection pipe moving lifting channel and the sand-blowing pipe; the air stripping pump upper bracket is used for fixing the lifting measuring device, the sand measuring power support, the sand measuring sensor, the sand measuring probe, the lifting channel of the fixed air stripping pump, the liquid pipe power device, the liquid pipe power support and the liquid pipe sensor; the manual movable air lift pump can be used by matching with the double-hole air lift pump.

The intelligent device of the air stripping pump comprises: the sand measuring device comprises a sand measuring power device, a sand measuring power support, a sand measuring sensor, a sand measuring probe and a sand measuring protection pipe; the method mainly comprises the steps of detecting signals of a sensor through a lifting probe, analyzing and comparing whether the liquid lifting pipe is about to be blocked by dirt around the liquid lifting pipe or not, and starting an air lift pump to lift the dirt; when the analysis contrasts that no dirt exists on the periphery of the lift pipe, the air lift pump is stopped; therefore, the start and stop of the gas stripping pump can be intelligently controlled, the energy is saved, and the carbon emission is reduced; and fundamentally solved and can't judge that the filth will bury the phenomenon that the air lift pump can't promote the filth on the air lift pump lift fluid pipe.

The intelligent device of the air stripping pump comprises: the automatic lifting device of the liquid lifting pipe is composed of a liquid pipe power device, a liquid pipe power support and a liquid pipe sensor; the main function is to lift the air stripping pump according to the signal of the sand detecting sensor; the second function can also automatically lift the air lift pump according to the quantity of sand slag dirt sensed by the liquid pipe sensor, so that the content of the lifted dirt is uniform, the efficiency of the air lift pump is improved, the blockage is avoided, and the application range of the air lift pump is expanded. The third function is that when the lifting liquid pipe is blocked and the double-hole back flushing pipe cannot be flushed, the air lift pump is lifted and then back flushed to clean dirt, and the air lift pump can be normally used in the lifting and lowering processes; this is not possible with conventional gas-lift pumps.

The liquid pool can be various sewage pools (an inlet well, a sewage channel, a coarse grid channel, a fine grid channel, a primary sedimentation tank, a secondary sedimentation tank, an aeration tank, a grit chamber, a reaction tank, a rhodobacter tank, a sewage well, a sewer, a septic tank), a construction site puddle, a river channel, a deep well, seawater, a petroleum sedimentation tank and the like

The fan is mainly used for providing power for the gas stripping pump; the air hose is connected with the air pump pipe, so that the condition that the air pump can be lifted is achieved; the fan is controlled by the frequency converter, the fan normally runs at about 40Hz, the sand slag abnormally increases, the sand slag runs at 50Hz, and the sand slag blocks the backflushing, and the sand slag is run at 60Hz, so that the energy is saved. And the liquid dirt can be lifted out according to the adjustment of the adjusting frequency converter.

The automatic control system has the main function that the liquid pool dirt condition provided by the sand measuring device is analyzed through the PLC. When the measured dirt reaches the mouth of the lifting liquid pipe, a control air lift pump, a fan, a valve and the like are started to lift the dirt according to the discontinuous measured dirt of the sand measuring device in normal conditions; when it is measured that the sewage has reached the bottom of the tank, the lifting of the sewage is stopped. Thereby achieving the purpose of energy conservation and reducing carbon emission.

The automatic control system has the main functions that data provided by the liquid pipe sensor are analyzed through the PLC, if abnormal conditions occur, when the measured dirt is buried in the liquid lifting pipe opening, the liquid pipe is lifted, the liquid lifting pipe is exposed, and then the control air lift pump, the fan, the valve and the like are started to lift the dirt; when measuring the filth and reducing, control liquid pipe device and follow the reduction, the air lift pump is normally opened to the interim, promotes the filth, when measuring the filth and having reached the bottom of the pool, just stops to promote the filth.

The device achieves the main functions through experimental trial operation; the intelligent sand-measuring mobile air stripping pump can be operated automatically and manually, so that a large amount of manpower and material resources are saved; and because can adjust the volume of promoting the filth through filth perception system and fan converter at any time through PLC, make and promote filth concentration increase, avoided the original filth not regularly or the extravagant energy phenomenon of continuous operation promotion liquid, the energy of saving more than 60% than the original continuous operation air lift pump, be suitable for popularization and application.

The invention has the advantages and positive effects that:

the invention has the advantages that through the double-hole air stripping pump, the anti-blocking function is realized, and the gas back-flushing function is added; the problems of the background technologies of 0002 and 0003 are solved, and the application range of the gas stripping pump in various liquid environments is greatly improved; can replace sewage pumps, submersible sewage pumps, screw pumps and common air lifting devices;

according to the invention, the air stripping support is moved, so that the air stripping pump can move up and down manually or automatically, and the functions of installing, maintaining and maintaining the air stripping pump without stopping production are increased; the installation and maintenance cost is reduced; solves the problems of the prior art 0005 and 0006

According to the invention, the existence of dirt under liquid is sensed through the touch type sand measuring and measuring device, and a method for measuring the dirt under the liquid is added. Filling a gap. The self-control energy-saving air stripping pump becomes possible.

According to the invention, through automatic control, the air lift pump can be intelligently started to lift dirt when sand slag dirt exists, and the air lift pump can be stopped when sand slag dirt does not exist, so that the function of intelligently controlling the air lift pump is achieved, the minimum value of carbon emission is achieved, and energy is saved.

The invention overcomes the defects that the amount of dirt can not be sensed under liquid and the air stripping can not be carried out when the sand slag of the general air stripping pump is more than one air stripping pump opening is buried, and simultaneously, the problem of air stripping pump blockage is well solved. The problem of the background art 0005 is solved.

Drawings

FIG. 1 is a schematic diagram of a dual orifice air pump according to one embodiment of the present invention.

Fig. 2 is a schematic structural diagram of an intelligent sand-measuring mobile air-stripping pump according to an embodiment of the invention.

Wherein: 1 is a double-hole air-lift pump, 11 is a lifting liquid pipe, 12 is an air pipe 1, 13 is an

air pipe

2, 14 is an aeration pipe 1, 15 is an

aeration pipe

2, 16 is an air-lift pump fixing plate, and 17 is an air blowing pipe; 2, a fixed movable air-lift pump bracket, 21, an air-lift pump bracket main board, 22, an air-lift pump upper bracket and 23, an air-lift pump lower bracket; 3, an intelligent air stripping pump device, 31, a sand measuring power device, 32, a sand measuring power support, 33, a sand measuring sensor, 34, a sand measuring probe, 35, a sand measuring protective tube, 36, a liquid pipe power device, 37 and 38 are liquid pipe sensors; 4, a fan, 41, a wind hose; 5 is an automatic control system, 51 is a cable; 6 is a liquid pool;

Detailed Description

The intelligent sand-measuring mobile stripping pump and the use method thereof are further described in detail with reference to the accompanying drawings 1 and 2.

An intelligent sand-measuring mobile air-lift pump comprises a double-hole air-lift pump 1; 2. fixing a movable air stripping pump bracket; 3. an intelligent device of a gas stripping pump; 4. a fan, 5, an automatic control system; 6. a liquid pool;

the double-hole air stripping pump 1: a lift pipe 11 is included for lifting the gas-liquid mixture. The air pipe 12 and the air pipe 13 are connected with the bottom of the liquid lifting pipe at intervals, and a proper amount of air is introduced to be mixed with liquid to lift dirt normally, so that the dirt can be lifted by adjusting a valve; and dredging the liquid lifting pipe by increasing air flow and pressure during blockage. The aeration pipe 15 and the aeration pipe 16 are arranged near the liquid lifting pipe, and a proper amount of gas is introduced to be mixed with liquid to perform stirring action normally, so that the valve adjustment can be performed, and the lifting of dirt is facilitated; the peripheral filth of lifter liquid pipe is cleared up through increase tolerance and pressure when the liquid pipe is buried by the filth, guarantees that the liquid pipe can normally inhale sand. The stripper pump fixing plate 16 serves to fix the stripper pump tube. The function of the double-hole air stripping pump is to cut the dirt through the double-hole air pipe and then to strip the dirt, so that the large dirt is effectively prevented from blocking the lifting liquid pipe, and the double-hole air stripping pump has a back flushing function, which is the main difference from the common air stripping pump. The double-hole air stripping pump 1 can be used independently and can be used in the place of manually moving the air stripping pump.

The fixed mobile air stripping pump bracket 2; the device comprises a gas lift pump support main board 21 and a gas lift pump lower support 23, and is used for fixing a gas lift pump 1, a movable lifting channel of a sand detection protection pipe 35, a sand blowing pipe 17, an aeration pipe 14 and an aeration pipe 15; the air stripping pump upper bracket 22 is used for fixing a lifting measuring device, a sand measuring power device 31, a sand measuring power support 32, a sand measuring sensor 33, a sand measuring probe 34, a fixed air stripping pump lifting channel, a liquid pipe power device 36, a liquid pipe power support 37 and a liquid pipe sensor 38, and can be used for manually moving the air stripping pump by matching with the double-hole air stripping pump 1. And because the air lift pump with the fixed support can move up and down, the air lift pump can be used for installation and maintenance when dirt exists below liquid in the liquid pool, and the purpose of installing and maintaining the air lift pump without emptying the liquid is achieved.

The intelligent air stripping pump device 3 comprises a sand measuring power device 31, a sand measuring power support 32, a sand measuring sensor 33, a sand measuring probe 34 and a sand measuring protection pipe 35. Mainly through the lift probe, detect the signal of the measurement sensor, analyze and compare the liquid lift pipe 11 peripheral dirt will block up the lift pipe, thus send and start the air lift pump to lift the dirt; when the analysis contrasts that the periphery of the lift liquid pipe 11 is free from dirt, the air lift pump is stopped; therefore, the start and stop of the gas stripping pump can be intelligently controlled, the energy is saved, and the carbon emission is reduced; and fundamentally solved and can't judge that the filth will bury the phenomenon that the air lift pump can't promote the filth on the air lift pump lift fluid pipe.

The intelligent device 3 of the air lift pump further comprises a liquid lifting pipe automatic lifting device consisting of a liquid pipe power device 36, a liquid pipe power support 37 and a liquid pipe sensor 38. The main function is to lift the air stripping pump 1 according to the signal of the sand detecting sensor 33; the second function can also sense the amount of sand slag and dirt according to the liquid pipe sensor 38, and the air lift pump 1 is automatically lifted, so that the content of the lifted dirt is uniform, the efficiency of the air lift pump is improved, the blockage is avoided, and the application range of the air lift pump is expanded; and the third function is that when the lifting liquid pipe 11 is blocked and the 12 and 13 double-hole back flushing pipes cannot be flushed, the air lift pump 1 is lifted and then back flushed to clean dirt, and the air lift pump 1 can be normally used in the lifting and lowering processes. This is not possible with conventional gas-lift pumps.

The fan 4 is mainly used for providing power for the gas stripping pump 1; and is connected with the air-lift

pump air pipes

12 and 13 through a 41-air hose, thereby achieving the condition that the air-lift pump can be lifted; an explosion-proof fan can be used in places with explosion-proof requirements. The fan is controlled by the frequency converter, the fan normally runs at about 40Hz, the sand slag abnormally increases, the sand slag runs at 50Hz, and the sand slag blocks the backflushing, and the sand slag is run at 60Hz, so that the energy is saved. And the liquid dirt can be lifted out according to the adjustment of the adjusting frequency converter.

The automatic control system 5 mainly has the function of analyzing the dirt condition of the liquid pool provided by the sand measuring device 33 through a PLC. In normal conditions, according to the intermittent measurement dirt of the sand measuring device for 5-10 minutes, when the measurement dirt reaches the mouth of the lifting liquid pipe, a control air lift pump, a fan, a valve and the like are started to lift the dirt; when it is measured that the sewage has reached the bottom of the tank, the lifting of the sewage is stopped. Thereby achieving the purpose of energy conservation and reducing carbon emission.

The automatic control system 5 has the main function of analyzing data provided by the liquid pipe sensor 38 through the PLC, if abnormal conditions occur, when the measured dirt is buried in the liquid lifting pipe opening, firstly lifting the liquid pipe to expose the liquid lifting pipe, and then starting and controlling the air lift pump, the fan, the valve and the like to lift the dirt; when measuring the filth and reducing, control liquid pipe device and follow the reduction, the normal air lift pump 1 that opens during, promote the filth, when measuring the filth and have reached the bottom of the pool, just stop promoting the filth.

The device achieves the main functions through experimental trial operation; the intelligent sand-measuring mobile air stripping pump can be operated automatically and manually, and a large amount of manpower and material resources are saved.

The device is tested through my experiment and run, and the amount of the lifting sewage can be adjusted at any time through the PLC through the sewage sensing system and the fan frequency converter, so that the concentration of the lifting sewage is increased, the phenomenon that the liquid is lifted by the original non-sewage timing or continuous operation is avoided, more than 60% of energy is saved compared with the original continuous operation air stripping pump, and the device is suitable for popularization and application.

While the invention has been described in terms of what are presently considered to be the preferred embodiments, it will be understood by those skilled in the art that the foregoing description is illustrative of the preferred embodiments of the invention, and is not intended to limit the invention in any way; those skilled in the art can make various changes, equivalents and modifications based on the above disclosure without departing from the scope of the invention.

The intelligent sand-measuring mobile air stripping pump can be applied to the liquid field, and comprises but is not limited to various sewage pools (water inlet wells, sewage channels, coarse grid channels, fine grid channels, primary sedimentation tanks, secondary sedimentation tanks, aeration tanks, grit chambers, reaction tanks, rhodobacter tank, sewage wells, sewers and septic tanks), construction site puddles, river channels, deep wells, seawater, petroleum sedimentation tanks and the like.

Claims

1. The utility model provides a sand removal air lift pump is surveyed to intelligence which characterized in that: the system comprises a double-hole air lift pump, a fixed movable air lift pump bracket, an intelligent air lift pump device, a fan and an automatic control system.

2. The dual orifice airlift pump of claim 1: comprises a lift liquid pipe for lifting a gas-liquid mixture; the double-hole air pipe is connected with the bottom of the lifting liquid pipe at intervals in a downward inclined manner; a plurality of aeration pipes are arranged near the lifting liquid pipe; the gas stripping pump fixing plate plays a role in fixing the gas stripping pump pipe; the air pipe is connected with the fan. This section can be used alone, and can be used in the place of manually moving the stripping pump.

3. A stationary mobile stripper pump support according to claims 1 and 2; the device comprises a main board of a gas lift pump bracket and a lower bracket of the gas lift pump, and is used for fixing a gas lift pump and a movable lifting channel of a measuring device; the upper bracket of the air stripping pump is used for fixing a power device for lifting the air stripping pump and the measuring device; the manual movable air lift pump can be used by matching with the double-hole air lift pump. And because the air lift pump with the fixed support can move up and down, the air lift pump can be used for installation and maintenance when dirt exists below liquid in the liquid pool, and the purpose of installing and maintaining the air lift pump without emptying the liquid is achieved.

4. An intelligent device of an air lift pump as claimed in claim 1, 2 and 3, which comprises a sand measuring power device, a sand measuring power support, a sand measuring sensor, a sand measuring probe and a sand measuring protection tube, wherein the sand measuring function is realized by detecting signals of the sensor through a lifting probe, analyzing and comparing whether the dirt around the liquid lift pipe is about to block the lift pipe or not, and then starting the air lift pump to lift the dirt; when the analysis contrasts that no dirt exists on the periphery of the lift pipe, the air lift pump is stopped; therefore, the start and stop of the gas stripping pump can be intelligently controlled, the energy is saved, and the carbon emission is reduced; and fundamentally solved and can't judge that the filth will bury the phenomenon that the air lift pump can't promote the filth on the air lift pump lift fluid pipe.

5. The intelligent device of an air lift pump as claimed in claims 1, 2, 3 and 4, further comprising a liquid tube power device, a liquid tube power support and a liquid tube sensor, wherein the liquid tube sensor is formed into a liquid tube lifting automatic lifting device; the main function is to lift the air stripping pump according to the signal of the sand detecting sensor; the second function can also automatically lift the air lift pump according to the quantity of sand slag dirt sensed by the liquid pipe sensor, so that the content of the lifted dirt is uniform, the efficiency of the air lift pump is improved, the blockage is avoided, and the application range of the air lift pump is expanded. The third function is that when the lifting liquid pipe is blocked and the double-hole back flushing pipe cannot be flushed, the air lift pump is lifted and then back flushed to clean dirt, and the air lift pump can be normally used in the lifting and lowering processes; this is not possible with conventional gas-lift pumps.

6. The fluid tank as defined in claim 1, wherein the fluid tank is a sewage tank (intake well, sewage channel, coarse grid channel, fine grid channel, primary sedimentation tank, secondary sedimentation tank, aeration tank, sand sedimentation tank, reaction tank, rhodobacter tank, sewage well, sewer, septic tank), construction site puddle, river channel, deep well, seawater, petroleum sedimentation tank, etc.

7. The blower of claim 1, which is primarily for powering a gas lift pump; the air hose is connected with the air pump pipe, so that the condition that the air pump can be lifted is achieved; the fan is controlled by the frequency converter, the fan normally runs at about 40Hz, the sand slag abnormally increases, the sand slag runs at 50Hz, and the sand slag blocks the backflushing, and the sand slag is run at 60Hz, so that the energy is saved. And the liquid dirt can be lifted out according to the adjustment of the adjusting frequency converter.

8. The autonomous system of claim 1 wherein the primary function is to analyze the contamination of the fluid reservoir provided by the sand measuring device by means of a PLC. When the measured dirt reaches the mouth of the lifting liquid pipe, a control air lift pump, a fan, a valve and the like are started to lift the dirt according to the discontinuous measured dirt of the sand measuring device in normal conditions; when it is measured that the sewage has reached the bottom of the tank, the lifting of the sewage is stopped. Thereby achieving the purpose of energy conservation and reducing carbon emission.

9. The automatic control system according to claim 1, wherein the second main function is to analyze data provided by the liquid tube sensor through the PLC, if an abnormal condition occurs, when the measured dirt is buried in the liquid lifting tube opening, the liquid tube is lifted to expose the liquid lifting tube, and then the control air lift pump, the fan, the valve and the like are turned on to lift the dirt; when measuring the filth and reducing, control liquid pipe device and follow the reduction, the air lift pump is normally opened to the interim, promotes the filth, when measuring the filth and having reached the bottom of the pool, just stops to promote the filth.