CN109307379A - Ultralow nitrogen lithium bromide absorption refrigerating set - Google Patents
Ultralow nitrogen lithium bromide absorption refrigerating set Download PDFInfo
- Publication number
- CN109307379A CN109307379A CN201811184195.4A CN201811184195A CN109307379A CN 109307379 A CN109307379 A CN 109307379A CN 201811184195 A CN201811184195 A CN 201811184195A CN 109307379 A CN109307379 A CN 109307379A
- Authority
- CN
- China
- Prior art keywords
- burner
- tube
- cooling tube
- lithium bromide
- absorption refrigerating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B15/00—Sorption machines, plants or systems, operating continuously, e.g. absorption type
- F25B15/02—Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas
- F25B15/06—Sorption machines, plants or systems, operating continuously, e.g. absorption type without inert gas the refrigerant being water vapour evaporated from a salt solution, e.g. lithium bromide
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/27—Relating to heating, ventilation or air conditioning [HVAC] technologies
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/62—Absorption based systems
Abstract
The present invention proposes that a kind of ultralow nitrogen lithium bromide absorption refrigerating set, including burner, burner hearth, absorber and generator, the burner are connected to by burner hearth with generator；The export pipeline of the absorber passes through the burner hearth and is connected to the generator, and the part that the export pipeline protrudes into the burner hearth is cooling tube；The cooling tube sequentially forms furnace grate tube, steady flame tube and solution conduit along the flow direction of mixed gas, and the mixed gas that the burner sprays is discharged after the steady flame of steady flame tube, solution conduit cooling through furnace grate tube after-combustion, burning gases.The present invention can not only be taken away flame heat regulating by the solution in cooling tube, can also utmostly reduce the discharge amount of NOx in flue gas by the way that multiple rows of cooling tube is arranged in the burner hearth of burner, and NOx discharge in flue gas is made to be less than 30mg/Nm3.Meanwhile lithium bromide absorption refrigerating set small volume of the present invention, refrigeration effect is preferable, has biggish marketing potentiality.
Description
Technical field
The present invention relates to field of refrigeration equipments, and in particular to ultralow nitrogen lithium bromide absorption refrigerating set.
Background technique
For lithium bromide chiller using water as refrigerant, lithium bromide water solution is absorbent, produces cold water or hot water, is chiefly used in center
Air-conditioning system.Lithium bromide chiller includes generator, absorber, condenser and evaporator.The heat that driving heat source issues is used to
Lithium-bromide solution in heating generator, so that lithium-bromide solution is concentrated.The type of driving heat source be divided into steam type, hot-water type,
Three kinds of direct combustion type.For direct combustion type driving heat source, the cigarette of most of direct-fired lithiumbromide absorption refrigerating machine groups in the market
Gas all cannot achieve low-nitrogen discharged.
Such as direct combustion dual effect type lithium bromide absorption of the patent disclosure with flue gas heat-exchange unit of Publication No. CN108518887A
Formula heat pump unit, including evaporator, absorber, Direct Fired High Pressure Generator, low pressure generator, condenser, high-temperature heat exchanger,
Flue gas heat-exchange unit, unit fortune is arranged in low temperature heat exchanger, solution pump and cryogenic fluid pump on the smoke exhaust pipe of unit or in external chimney
When row, although can make full use of flue gas heat, flue-gas temperature is reduced, the content of NOx in flue gas can not be reduced.Meanwhile
The volume of Direct Fired High Pressure Generator is larger, and internal structure is complex, it is difficult to promote in the market.
Summary of the invention
In order to solve the above-mentioned problems of the prior art, the application provides a kind of ultralow nitrogen lithium-bromide absorption-type refrigerating machine
Group, to realize the low-nitrogen discharged of lithium bromide chiller.
To realize the above-mentioned technical purpose, the invention adopts the following technical scheme:
Ultralow nitrogen lithium bromide absorption refrigerating set, including burner, burner hearth, absorber and generator, the burning
Device is connected to by burner hearth with generator；The export pipeline of the absorber passes through the burner hearth and is connected to the generator, described
The part that export pipeline protrudes into the burner hearth is cooling tube；The cooling tube sequentially forms fire grate along the flow direction of mixed gas
Pipe, steady flame tube and solution conduit, for the mixed gas that the burner sprays through furnace grate tube after-combustion, burning gases are steady through steady flame tube
It is discharged after flame, solution conduit cooling.
Preferably, the burner is that premix burner, combustion gas and the air mixing match in the burner form institute
State mixed gas.
Preferably, the furnace grate tube is made of a certain number of first cooling tube side-by-sides, between the first adjacent cooling tube
Form the first gap；The mixed gas is uniformly through first gap.
Preferably, the steady flame tube is made of a certain number of second cooling tube side-by-sides, each second cooling tube
Center is aligned setting with the first adjacent gap.
Preferably, the second gap is formed between adjacent second cooling tube, the mixed gas is stitched through described second
Stablize burning after gap.
Preferably, first cooling tube is rectangular, and the shape of second cooling tube is cylindrical.
Preferably, the solution conduit is made of multiple rows of third cooling tube arranged side by side, and the adjacent two rows third cooling tube is handed over
Mistake arrangement.
Preferably, the burner hearth is equipped with smoke outlet, and burning gases after the solution conduit from the smoke outlet by being discharged.
Preferably, the bottom of the generator is equipped with solution tank, the outlet of the entrance of the solution tank and the cooling tube
Connection, the outlet of the solution tank is connected to the entrance of the absorber；The top of the generator is equipped with steam outlet.
It preferably, further include condenser and evaporator, the burner, burner hearth, generator, condenser, evaporator and suction
Receive the integrated setting of device.
Compared with the prior art, the invention has the following advantages:
The present invention sequentially forms furnace grate tube, steady flame tube by the way that multiple rows of cooling tube, cooling tube are arranged in the burner hearth of burner
And solution conduit, mixed gas, which first cools down through furnace grate tube, burns, then through the steady flame of steady flame tube, the solution in finally heated solution conduit, no
It is only capable of taking away flame heat regulating by the solution in cooling tube, can also utmostly reduce the discharge amount of NOx in flue gas, make in flue gas
NOx discharge is less than 30mg/Nm3.Meanwhile lithium bromide absorption refrigerating set small volume of the present invention, refrigeration effect compared with
It is good, there are biggish marketing potentiality.
Detailed description of the invention
Fig. 1 is the schematic diagram of herein described lithium bromide absorption refrigerating set；
Fig. 2 is pipe structure for cooling figure in herein described burner hearth；
Fig. 3 is herein described pipe structure for cooling figure；
Fig. 4 is the left view of herein described lithium bromide absorption refrigerating set；
Fig. 5 is part A enlarged drawing in Fig. 4；
Fig. 6 is the right view of herein described lithium bromide absorption refrigerating set；
Fig. 7 is the main view of herein described lithium bromide absorption refrigerating set；
In figure: 1- burner, 2- burner hearth, 3- cooling tube, 31- furnace grate tube, the first cooling tube of 311-, the first gap 312-,
The steady flame tube of 32-, the second cooling tube of 321-, the second gap 322-, 33- solution conduit, 331- third cooling tube, 4- generator, 5- are cold
Condenser, 6- evaporator, 7- absorber, 8- heat exchanger.
Specific embodiment
Below by specific embodiment the technical scheme of the present invention will be further described explanation.
As shown in Figure 1, ultralow nitrogen lithium bromide absorption refrigerating set described in the present embodiment, including burner 1, burner hearth 2, hair
Raw device 4, condenser 5, evaporator 6 and absorber 7, the burner 1 are connected to by the burner hearth 2 with the generator 4；Institute
The export pipeline for stating absorber 7 passes through the burner hearth 2 and is connected to the generator 4；The export pipeline protrudes into the burner hearth 2
Part is cooling tube 3；Cooling tube 3 sequentially forms furnace grate tube 31, steady flame tube 32 and solution conduit 33 along the flow direction of mixed gas,
The mixed gas that burner 1 sprays is through 31 after-combustion of furnace grate tube, and burning gases are through the steady flame of steady flame tube 32, the cooling heel row of solution conduit 33
Out.
The generator of oil direct-fired absorption chiller is improved to the structure type with burner hearth 2 and cooling tube 3 by the application, combustion
For the mixed gas that burner 1 sprays through 31 after-combustion of furnace grate tube, burning gases first pass through steady flame tube 32, form stable flame, then go
Solution in heated solution pipe 33 can not only guarantee the high-efficiency heating of solution in generator 4, but also can reduce the row of nitrogen oxides
It puts.Preferably, the burner 1 in the present embodiment is premix burner, combustion gas and air the mixing match shape in the burner 1
At uniform mixed gas.
As shown in Figures 2 and 3, cooling tube 3 forms Multi-row pipeline in burner hearth 2, and furnace grate tube 31 and steady flame tube 32 are set to furnace
The most upstream of thorax 2, solution conduit 33 are multiple rows of tube bundle, are set to the primary zone domain of burner hearth 2.
Furnace grate tube 31 is made of a certain number of first cooling tubes 311, and the first seam is formed between the first adjacent cooling tube
Gap 312, mixed gas is uniformly through burning is ignited behind first gap 312, due to being connected with bromination in the first cooling tube 311
Lithium solution, therefore, lithium-bromide solution can reduce the temperature of flame, while prevent back draft, inhibit the generation of NOx.Preferably,
The width in the first gap 312 is set as 0.5-1.5mm, to guarantee that effect is best.
Steady flame tube 32 is made of side by side a certain number of second cooling tubes 321, the center of each second cooling tube 321
Setting is aligned with the first adjacent gap 312.The second gap 322 is formed between adjacent second cooling tube 321, burning gases pass through
Behind second gap 322, the back side forms negative pressure, and strile-back new unburned gas again, so that flameholding, being carried out continuously.Together
When, the lithium-bromide solution in steady flame tube 32 can play the temperature for reducing flame, further decrease the discharge of NOx.
The center of first pipe group 31 and the center of the second pipe group 32 keep certain spacing, such as 1-2mm, so that from first
The mixed gas that gap 312 is flowed out forms a whole flame between 32 center of 31 center of the first pipe group and the second pipe group.
It burns to further increase stablizing for flame, the first cooling tube 311 is made to rectangular-shaped, the second cooling tube 312 system
At cylindric, to ensure the temperature with high efficiency of flame and stablize burning.
Herein described lithium bromide absorption refrigerating set realizes low-nitrogen discharged principle are as follows:
Burner 1 connection one have blower mixer, combustion gas mixed with air in the mixer proportion after through wind
Machine is sent into the burner hearth 2, and mixed gas is uniformly distributed in the first gap 312 between furnace grate tube 31.Pass through the first gap 312
Afterwards, air-flow velocity reduces, and pressure decline, temperature reduces, at this point, lighting mixed gas makes its burning.Combustion-gas flow is in the first seam
When between gap 312 and the second gap 322, gas volume increase, from each gap flow out fuel gas re-form one it is whole
Body flame, rekindles, and solves the problems, such as the de- fire of burner, the pressure of combustion-gas flow is P1 at this time.Combustion-gas flow is through the second seam
When gap 322 flows out, the pressure of formation is P2, and P2 is less than P1, and the one side of 321 air-flow of the second cooling tube outflow forms negative pressure, again
Strile-back unburned gas.Therefore combustion-gas flow is behind the second gap 322, and not only flame temperature is by the second cooling tube 321
Lithium-bromide solution reduces, and the second gap 322 that the second cooling tube 321 is formed makes combustion-gas flow stable burning again.Therefore,
Combustion-gas flow through the second cooling tube 321 after cooling, not only flameholding, but also the low discharge for utmostly reducing NOx in flue gas
Amount makes NOx discharge in flue gas be less than 30mg/Nm3。
Mixed gas burning velocity in the application is very fast, and blue, the length of flame is shorter, is usually no more than 150mm, leads to
Overregulate the gaseous mixture scale of construction in burner 1, the size of adjustable flame, to realize different burning output powers.
For improve solution conduit 33 in solution and burning gases heat transfer effect, by multiple rows of third cooling tube 331 interlock cloth
It sets, so that burning gases come into full contact with solution.
Preferably, the side of burner hearth 2 is equipped with smoke outlet, after burning gases and solution conduit 33 sufficiently exchange heat, through the smoke evacuation
Mouth discharge.Compared with traditional oil direct-fired absorption chiller, the flue-gas temperature of the application discharge is lower, NOx discharge in flue gas
Less than 30mg/Nm3, therefore, generator 4 no longer needs to setting smoke outlet and flue gas heat-exchange unit.Meanwhile the bottom of generator 4 is equipped with
Solution tank, the outlet of the entrance of the solution tank and the cooling tube 3, the outlet of the solution tank and the absorber 7
Entrance connection；The top of the generator 4 is equipped with steam outlet, ensure that the circulation of solution and the positive pressure of water vapour
Out, the volume for greatly reducing generator increases the heat transfer effect of solution in generator.
As shown in figs. 4-7, the present embodiment is by burner 1, burner hearth 2, generator 4, condenser 5, evaporator 6 and absorber
7, heat exchanger 8 becomes one, and forms ultralow nitrogen lithium bromide absorption refrigerating set, compact-sized, small volume has simultaneously
Higher refrigerating efficiency and lower nitrogen oxide emission, marketing potentiality are larger.
The embodiments of the present invention have been described in detail above, for those of ordinary skill in the art, according to this
The thought provided is provided, will change in specific embodiment, and these changes also should be regarded as protection model of the invention
It encloses.
Claims (10)
1. ultralow nitrogen lithium bromide absorption refrigerating set, feature are being: including burner (1), burner hearth (2), absorber (7)
And generator (4), the burner (1) are connected to by burner hearth (2) with generator (4)；
The export pipeline of the absorber (7) passes through the burner hearth (2) and is connected to the generator (4), and the export pipeline is stretched
The part for entering the burner hearth (2) is cooling tube (3)；
The cooling tube (3) sequentially forms furnace grate tube (31), steady flame tube (32) and solution conduit along the flow direction of mixed gas
(33),
The mixed gas that the burner (1) sprays is through furnace grate tube (31) after-combustion, and burning gases are through the steady flame of steady flame tube (32), molten
It is discharged after liquid pipe (33) cooling.
2. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 1, it is characterised in that: the burner (1)
For premix burner, combustion gas and air form the mixed gas in the burner (1) interior mixing match.
3. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 1, it is characterised in that: the furnace grate tube (31)
It is made of side by side a certain number of first cooling tubes (311), forms the first gap (312) between the first adjacent cooling tube；Institute
Mixed gas is stated uniformly through first gap (312).
4. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 3, it is characterised in that: the steady flame tube (32)
It is made of side by side a certain number of second cooling tubes (321), the center of each second cooling tube (321) and adjacent first
Gap (312) alignment setting.
5. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 4, it is characterised in that: adjacent described second
It is formed between cooling tube (321) the second gap (322), the burning gases stable burning after second gap (322).
6. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 4, it is characterised in that: first cooling tube
(311) rectangular, the shape of second cooling tube (321) is cylindrical.
7. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 1, it is characterised in that: the solution conduit (33)
It is made of multiple rows of third cooling tube (331) arranged side by side, adjacent two rows third cooling tube (331) interlaced arrangement.
8. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 1, it is characterised in that: the burner hearth (2) sets
There is smoke outlet, burning gases after the solution conduit (33) from the smoke outlet by being discharged.
9. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 1, it is characterised in that: the generator (4)
Bottom be equipped with solution tank, the outlet of the entrance of the solution tank and the cooling tube (3), the outlet of the solution tank and
The entrance of the absorber (7) is connected to；The top of the generator (4) is equipped with steam outlet.
10. ultralow nitrogen lithium bromide absorption refrigerating set according to claim 1, it is characterised in that: further include condenser
(5) and evaporator (6), the burner (1), burner hearth (2), generator (4), condenser (5), evaporator (6) and absorber (7)
Integrated setting.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811184195.4A CN109307379A (en) | 2018-10-11 | 2018-10-11 | Ultralow nitrogen lithium bromide absorption refrigerating set |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811184195.4A CN109307379A (en) | 2018-10-11 | 2018-10-11 | Ultralow nitrogen lithium bromide absorption refrigerating set |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN109307379A true CN109307379A (en) | 2019-02-05 |
Family
ID=65224396
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811184195.4A Pending CN109307379A (en) | 2018-10-11 | 2018-10-11 | Ultralow nitrogen lithium bromide absorption refrigerating set |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109307379A (en) |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07318196A (en) * | 1994-05-27 | 1995-12-08 | Rinnai Corp | Absorption type refrigerating equipment |
| CN1188220A (en) * | 1997-01-10 | 1998-07-22 | 三洋电机株式会社 | High temp. regenerator |
| JP2000257819A (en) * | 1999-03-08 | 2000-09-22 | Sanyo Electric Co Ltd | Surface combustion burner |
| CN1828182A (en) * | 2006-04-13 | 2006-09-06 | 大连海事大学 | Air-preheating bromide-refrigerator fire-tube group cryogen steam regeneration method and device |
| CN107588421A (en) * | 2017-10-18 | 2018-01-16 | 力聚热力设备科技有限公司 | A kind of slit-aperture type flame combustion apparatus |
| CN209326133U (en) * | 2018-10-11 | 2019-08-30 | 浙江力聚热水机有限公司 | Ultralow nitrogen lithium bromide absorption refrigerating set |
-
2018
- 2018-10-11 CN CN201811184195.4A patent/CN109307379A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07318196A (en) * | 1994-05-27 | 1995-12-08 | Rinnai Corp | Absorption type refrigerating equipment |
| CN1188220A (en) * | 1997-01-10 | 1998-07-22 | 三洋电机株式会社 | High temp. regenerator |
| JP2000257819A (en) * | 1999-03-08 | 2000-09-22 | Sanyo Electric Co Ltd | Surface combustion burner |
| CN1828182A (en) * | 2006-04-13 | 2006-09-06 | 大连海事大学 | Air-preheating bromide-refrigerator fire-tube group cryogen steam regeneration method and device |
| CN107588421A (en) * | 2017-10-18 | 2018-01-16 | 力聚热力设备科技有限公司 | A kind of slit-aperture type flame combustion apparatus |
| CN209326133U (en) * | 2018-10-11 | 2019-08-30 | 浙江力聚热水机有限公司 | Ultralow nitrogen lithium bromide absorption refrigerating set |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN105333449B (en) | Low-carbon type smoke backflow formula steam boiler low oxygen combustion system | |
| CN103206711B (en) | The two snail flat flame burner of a kind of heat accumulating type | |
| CN104456537B (en) | Heat storage type porous medium burner assembly | |
| WO2019007001A1 (en) | Regenerative combustion type coal-based shaft furnace and direct reduction production method | |
| CN110360558A (en) | Cooling flame low nitrogen combustion apparatus and its combustion method | |
| CN207716416U (en) | The continous way Self-heat-storage flameless burner of the double preheatings of air/gas | |
| CN109297019A (en) | A kind of air suspended type fire row combustor with cylindrical fire face | |
| CN209326133U (en) | Ultralow nitrogen lithium bromide absorption refrigerating set | |
| CN209622792U (en) | Gas burner low nitrogen combustion apparatus | |
| CN110360568A (en) | A kind of low nitrogen combustion apparatus and method | |
| CN206724171U (en) | One kind uses coke-stove gas self-preheating type radiant tube combustion device | |
| CN109654491A (en) | A kind of interior axial water-cooled premixing combustion apparatus | |
| CN109307379A (en) | Ultralow nitrogen lithium bromide absorption refrigerating set | |
| CN107152672A (en) | Low NOXDouble drum gas fired-boilers | |
| CN207394904U (en) | A kind of straight way type flame front cooling structure | |
| CN109912188A (en) | A kind of combustion-type glass tempering heating device and operating method | |
| CN203177237U (en) | Energy-saving gas cooking appliance with rotary heat exchange device | |
| CN206755603U (en) | The heat exchanger of gas heater and there is its gas heater | |
| CN106766172A (en) | A kind of efficient energy-saving gas heating wall-hanging furnace | |
| CN210861719U (en) | Novel low-nitrogen energy-saving hot water unit | |
| CN205388316U (en) | Steam boiler waste heat utilization system | |
| CN210861032U (en) | Novel low-nitrogen energy-saving steam generator | |
| CN206112909U (en) | Metal surface combustion system | |
| CN208205406U (en) | A kind of burning energy-saving boiler | |
| CN208983615U (en) | A kind of ultralow nitrogen vacuum hot water boiler |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| TA01 | Transfer of patent application right | ||
| TA01 | Transfer of patent application right |
Effective date of registration: 20190313 Address after: 313000 Maowu Road, Maoxi Town, Wuxing District, Huzhou City, Zhejiang Province Applicant after: Zhejiang Unipower Boiler Co., Ltd. Address before: 313000 Shengye Street, Fuxi Street, Deqing County, Huzhou City, Zhejiang Province, 150 Applicant before: Zhejiang Li Ju thermal energy equipment Co., Ltd. |