NL8102164A - LUBRICANTS FOR GAS COMPRESSORS. - Google Patents

Description

S'2909-532 f,? * 4

I '-F & C

Lubricants for gas compressors.

The invention relates to lubricants for gas compressors / in particular piston-type gas compressors used in the treatment of natural gas.

Non-lubricated compressors with liners - --- 5 have been used - for compressing gases, especially in applications where exhaust pressure is not excessively high and the wear of working parts is not too big. One of these applications is in the field of natural gas treatment, eg, the compression of the gases exiting the fast evaporation zones of a gas odor removal plant. In certain applications of this kind, it has been found that the gas from the rapid evaporation zones of the odor-free plant still containing H 2 S and CC> 2 may contain an unusually high solids content that is excessive causes severe wear on the piston rings and packing rings and requires the compressor to be taken out of service within a few days.

Several solutions to this problem are possible - and even technically feasible - but for various reasons these solutions are not attractive. For example, complete removal of the entrained Solid by filtration, centrifugation or precipitation may not be technically feasible due to spatial limitations of the equipment that would be necessary.

On the other hand, conventional oil lubrication of the compressor to control the wear problem would require the oil mist to be separated from the compressed gas, and even then complete exclusion of residual oil particles cannot be guaranteed, thus the following may exist. treatment steps with oil contamination and foaming. The technical difficulties and costs associated with this solution are therefore considerable.

It has now been found that the operation of any liner-type compressor used for treating gases can be improved by using a lubricant, namely one or more of the solvents, solvent components or drying solutions used in to treat the gas used. It is also possible to use a flowable lubricant that is compatible with the solvents and other materials used in the treatment downstream of the compressor, i.e., a liquid that does not react adversely with these materials. By using these liquids as lubricants, contamination and other handling problems are avoided in the following steps in the installation, such as:; : while simultaneously extending the useful life of the compressor and the length of time until maintenance of the compressor is required. compatibility of the flowable lubricant with the fluids used in subsequent treatment steps, Unwanted reactions between these materials are avoided - -s - · r -: -r: - The final choice of compressor lubricant depends on ... ....

-: of course, depending on the type of treatment installation after the compressor and of solvents or solutions used in this installation. Suitable.

Compressor lubricants for natural gas compressors therefore include - '- water fluids, physically active solvents, solvent components or drying solutions - which are used alone or in combination in the facilities for deodorizing or dehydrating gas. These lubricants generally do not contain components that chemically react with components of. dissolve the compressed gases or these components. -

The Lubricant can be introduced into the compressor by introducing it to the lubrication points provided for lubricating the cylinder in the compressor. The lubricants can be used to lubricate all parts of the compressor that come into contact with the gas being compressed, including the cylinders, cylinder raceways, pistons, piston rings, and stuffing boxes and glands.

Lubricants which are preferably used in natural gas treatment plants are described below, but the material used, as mentioned above, is selected according to the nature of the treatment steps downstream of the compressor, eg dehydration or deodorization.

The polyglycols or polyalkylene oxides are a preferred group of lubricants for the present purpose. The polyglycols are essentially linear polymers with the general formula R0- (CH2 -CHR '-0) X ~ R "30 wherein R' represents hydrogen and / or an alkyl group in different parts of the molecule. The terminal groups R and R" are usually hydrogen atoms or alkyl groups, generally lower alkyl groups, especially alkyl groups of 1-4 carbon atoms, although aromatic groups, such as phenyl, may be present in certain phenyl ether polyglycols. R and 35 R "are preferably hydrogen or methyl and R 'is preferably hydrogen, i.e. the preferred polyglycols according to the invention are polyethylene glycols and their dimethyl ethers.

In the above formula, x represents the degree of polymerization of the glycol. For the present purposes, poly- 8102 164 * - - «i - 3 -> glycols and polyglycol ethers of relatively low molecular weight are preferred, wherein x is 2-12 although higher molecular weight materials may also be used. The glycols and glycol ethers can of course be used in combination with each other.

- - -5 Examples of specific materials to be used are;

Name Formula

Diethylene glycol H0- (CH2-CH2-0) 2-H

Triethylene glycol H0- (CH2-CH2-0) 3-H

Tetraethylene glycol HO- (CH2rCH2-0) ^ -H

10 Triethylene glycol dimethyl ether CH 0- (CH_-CH -0) _- CHo 3 2 2 3 3

Tetraethylene glycol dimethyl ether CH ^ O- (CH2-CH2-0) ^ -CH3

Pentaethylene glycol dimethyl ether CH3O- (CH2-CH2-0) ^ - CH ^

Hexaethylene glycol dimethyl ether. CH-O- (CHo-CHo-0), -CH_ 3 2 2 o 3

Heptaethylene glycol dimethyl ether CH ^ O- (CHj-CHg-O) ^ - CH ^ 15 Octaethylene glycol dimethyl ether CH 0- (CH0-CH0-O) 0-CH, * 3 2 2 o 3

Nonaethylene glycol dimethyl ether CH30- (CH2-CH2-0) g-CH3

According to the invention, preference is given to polyglycols and polyglycol ether having a molecular weight of 62 to about 450. Other similar materials and mixtures of materials can also be used. Examples of these are described in the literature, eg, in "Synthetic Lubricants", Chapter 3, Gunderson and Hart, Reinhold, New York, 1962. These materials are also commercially available, eg under the name "UCON", a product from Union Carbide.

Specific and preferred mixtures of polyglycols and polyglycol ethers are listed below:

Lubricant A

A mixture of polyglycols with the following properties:

Density at 20 ° C 1.1254 kg / 1

Molecular weight 150.2

30 Boiling point at 760 mm Hg 287.4 ° C

Thickening point at 760 mm Hg -7.2 ° C

Viscosity at 20 ° C 47.8 cP.

Lubricant B *

A mixture of seven ethylene glycol dimethyl ethers with the following 35 properties:

Density at 25 ° C 1.031 kg / 1

Vapor pressure at 25 ° C 0.0001 kPa

Molecular weight 280-310

Freezing point - -22 ° to -29 ° C

8102164 * tr - 4 -

Specific heat ï - - - - - 'at 5 ° C 2.05 kJoule .kg ”1 ° C ~ 1 at 100 ° C 2.14 kJoule.kg loC_1

Viscosity at 25 ° C 5.8 cP

5 Surface tension at 25 ° C 343 h N / cm -1 - -1 - -1 -1

Thermal conductivity at 25 ° C 0.67 kJoule.m .iiur · ° C. - - - -

Flash point 151 ° C. - '· - ·, · A specific mixture that meets the specification of lubricant A, "is: 10 Lubricant A-1: ____

Component 'Weight% __

Diethylene glycol 1

Triethylene glycol 98

Tetraethylene Glycol 0.5 15 Other Ingredients 0.5 _ -: A mixture of 7 ethers meeting the specification for lubricant B is:

Lubricant B-1 - _______-;

Component Wt% 20 Triethylene glycol dimethyl ether 12

Tetraethylene glycol dimethyl ether 24

Pentaethylene glycol dimethyl ether 25

Hexaethylene glycol dimethyl ether 19

Heptaethylene glycol dimethyl ether 11. . - 25 Octaethylene glycol dimethyl ether 6 - - -

Nonaethylene glyco-dimethyl ether 3 - -

The invention is illustrated by the Examples below.

example i

A piston type stripping gas compressor was lubricated with the above lubricant A-1. The compressor properties were as follows:

Manufacturer: Klein, Schahzlin and Becker (KSB) 3 -1 '

Capacity: . 600 m. hour 3

Inlet pressure: 4.10 kPa 3 Outlet pressure: 7.10 kPa 35 Number of stages 1 -

The lubricant was supplied to the compressor at a flow rate -1 -1 of 4 l. For lubricating cylinder and piston rod.

Example ii

A recirculation compressor in a natural gas depletion plant * 8102164 * '', V> - 5 - - was lubricated with the above lubricant B-1. The compressor properties were as follows:

Manufacturer: Thomassen 3 -1

Capacity: 18,800 m. Hour 5 Inlet pressure: 100 kPa

Outlet pressure: 7 / 85.10 \ pa

Number of stages: 4 • - The lubricant was fed into the compressor at a throughput of 1 hour 1 for lubricating cylinder and piston rod.

Example III

A stripping gas compressor was lubricated with the above lubricant A-1. The compressor properties were as follows:

Manufacturer: Borsig 3 -1

Capacity: 9000 m. hour 3 15 Inlet pressure: 5.9.10 kPa 3

Outlet pressure: 11.9.10 kPa

Number of stages: 1

The lubricant was fed into the compressor at a throughput rate of 41 hours * for lubricating cylinder and piston rod.

By using the flowable lubricants of the invention, an undesired contamination of the downstream treatment steps is avoided and the problem of foaming that occurs with lubrication with conventional oil is eliminated. In addition, the useful life of the compressors and the time until maintenance of the compressors is required can be extended.

8102 164

Claims (7)

4r- -> V \ \ V - 6 - COJCLOSIONS; - Ir. Method of lubricating a piston type compressor which can be used for compressing natural gas, characterized in that a solvent, solvent component or drying solution is used as the lubricant, which is used for treating the gas stream -5 down from the compressor, or any material compatible with it. Method according to claim 1, characterized in that the lubricant is used for lubricating the cylinder tracks, pistons, piston rings and main packing sleeves of the compressor. 3. Process according to claim 1 or 2, characterized in that the lubricant used is a polyglycol, polyglycol ether or a mixture thereof. 4. Process according to claim 3, characterized in that a material of the following composition is used as lubricant: Diethylene glycol 1% by weight Triethylene glycol 98% by weight 15 Tetraethylene glycol 0.5 wt% Other ingredients 0.5 wt% 5. Process according to claim 3, characterized in that a material of the following composition is used as the lubricant: Triethylene glycol dimethyl ether 12% by weight 20 Tetraethylene glycol dimethyl ether 24 wt% Pentaethylene glycol dimethyl ether 25 wt% Hexaethylene glycol dimethyl ether 19 wt% Heptaethylene glycol dimethyl ether 11 wt% Octaethylene glycol dimethyl ether 6 wt% Nonaethylene glycol dimethyl ether 3 wt% 8102 164