Carnot cycle

Sunday, January 24, 2010

Carnot cycle

Carnot engine
Carnot is an ideal engine it is consist of a cylinder with frictionless piston which is filled with ideal gas. The wall of cylinder and piston should be insulator and bottom should be good conductor. An infinite heat capacity of hot body and cold is used as source of heat and heat sink.
Carnot cycle
In which thermodynamic process Carnot engine works is called Carnot cycle. It is consist in the following four process.
1. Isothermal process
2. Adiabatic process
3. Isothermal compression
4. Adiabatic compression
Isothermal process

In this process an ideal gas filled cylinder is placed on the source of heat. The temperature of the system is kept constant during process when the piston is slightly moved upward the internal energy of the system becomes low because of doing work. To keep the temperature constant the heat Q₁ is supplied from the source of heat.

Consider the initial pressure of the gas = P₁

The initial volume of the gas = V₁

The initial temperature of the gas=T₁

At the final stage the pressure become =P₂

The final volume = V₂

But the temperature remain constant = T₁

Adiabatic expansion

to stop the heat absorbing and discharging to make the system isolated. Now the external pressure is reduced immediately the gas expands because of internal pressure this internal energy is used to work. In this process no external energy is provided to the system its temperature fall from T₁ to T₂ at the end of this process the pressure of gas is P₃ and its volume is V₃

Isothermal compression

At the 3^rd step cylinder is kept on a heat sink the temperature of the heat sink must be equal to the temperature of the gas now the external pressure applied on the cylinder is increased slowly. In this way by doing work on gas the internal energy of the system increased and as a result it temperature increased. To keep the gas temperature at constant some heat Q₂ insert in sink from the bottom of the cylinder. At the end of this process the pressure of the gas becomes P₄   

The volume of the gas V₄

The temperature of the gas T₂

Adiabatic compression

In the final step of Carnot cycle the cylinder is kept on an insulator and its external pressure is sharply increased in this way work is done on the system and the temperature of the system will be increased. The gas is compressed in adiabatic compression until it reaches in its initial stage so that it temperature become T₁volume V₁ and pressure P₁

Raw material for leather from different origin

Goat skins
Goats are hardly animals that can live on a wide variety of food s and can supply meat and milk. They are adaptable to difficult climates and are popular in Asia, Africa and South America. The original source of many of the goat skin is villages of widely diversified areas, so the quality varies greatly warm climate like Pakistan plain area the skin structure is firm and fine grain in leather making is obtain less fat content goat skin from Somalia, Tanzania and Kenya are of strength and firm structure they are preserved in dried condition less fatty. Also important in determining the quality of the goat skins are the type of animal, the method of slaughter, and the method of curing and the marketing practices of the area of origin. Between the villages and the world market there is a system of collector and dealers. The practices handling skin and business methods of each area have long been established by custom and tradition. These factors, different in each part of the world, are important in determining the equality, characteristics, and price of the skins. The skins are identified by the area of origin and are sold either on a size specification by the dozen or by the pound.
Sheepskins
Pickled, salted and dried sheepskins are available from many parts of the world, notably South America UK, Africa, Australia and New Zealand. Probably the largest single factor is the sheep skin industry of New Zealand, where the sheep are slaughtered and skin processed. As the value of the wool from the exceeds that of the skin, it is customary to remove the wool from the skin by wool pulling methods and the skins are soled in the pickled state. Because of the long wool and the high fat content (about 30-35 %) of the skin, curing of these skins in a salt pack is rather difficult. The slaughter of sheep and lambs in New Zealand follows the seasons and condition of pasture, creating a difficult purchasing situation for the tanner.
The slaughter of sheep in the United State does not follow this seasonal cycle as closely. Sheepskins are generally salted. Domestic sheepskins are salted and soled for use in grain leathers, suede, or shear lings. Since much of the weight of the sheepskin is made up in the wool and the grease associated with the wool, sheepskins are soled by the piece. Domestic sheepskin from Pakistan has short wool of low quality but less fat content compare to New Zealand and Australia.

News from China leather industry

Fujian tanners offered compensation
China


Construction at the proposed Fujian tanning cluster in South Eastern China came to an abrupt halt last Autumn after the local authorities in the Fujian province froze further construction and withdrew investment last Autumn despiet the fact that construction of the new tannery cluster and central treatment plant had already begun. The local government in Fuijan stopped construction and said that they wanted to use the land to attract high-tech companies, particularly from nearby Taiwan.

The authorities in the coastal region have also have said that they want to attract businesses with high-tech and clean production and in their minds this does not include tanneries.
A number of tanneries had already begun construction in the area and the Fujian government has said that it will fully compensate the companies for any financial investment they have made.
A spokesperson for the China Leather Industry Association (CLIA) confirmed that the ousted tanners from Fujian will be offered alternative locations to build their tanneries although nothing has happened yet on this matter.

China goes to WTO on footwear duties
China/European Union
Published: 09 February, 2010

China filed a complaint against European Union shoe tariffs at the World Trade Organization as Beijing continued its legal assault on what it says is unfair Western protectionism. Europe has grown increasingly concerned about China's balance of trade and what some critics view as its artificially weak currency.

China, which joined the WTO in 2001, filed its first unfair trade case against the European Union in July 2009, also involving antidumping duties.
The latest move appeared intended to increase pressure on the European Union, which had itself been sharply divided over extending the shoe tariffs.
In a statement issued by its mission in Geneva, where the WTO is based, the Chinese government said Europe's actions ‘violated various obligations under the WTO and consequently caused damage to the legitimate rights and interests of Chinese exporters.’ It added that China ‘had repeatedly consulted’ with the European Union but said that its concerns ‘had not been properly addressed or settled.’
In an eight-page legal complaint, the Chinese government requested consultations on both the original 2006 decision to impose the shoe duties and last year's move to extend them. The EU and the U.S. have sought to stem the flow of Chinese imports with special duties.
In the EU case, China is taking on one of the most important tariff increases ever levied, which has negatively impacted its shoe industry. The 16.5% tariffs are antidumping duties, meant to punish goods that are sold below cost and hurt the sales of domestic producers. The EU duties were inaugurated in 2006 and extended for 15 months in December 2009. At the same time, shoe imports from Vietnam were hit with a 10% tariff.
The EU dismissed the complaint. ‘Antidumping duties are not about protectionism’, said spokesman John Clancy. ‘They are about fighting unfair trade.’ The measures, he said, were imposed only on ‘evidence that dumping of Chinese products has taken place and that this is harming the otherwise competitive EU industry.’

Source: hidenet.com

Echo processes in leather making

TFL guidelines on salt & nitrogen reduction
Worldwide
TFL one of largest supplier of leather chemical including beamhouse chemicals, dyeing, fat liquoring has introduced new technical process and services to reduce salt and nitrogen content in leather making for environment aspects. The latest edition of leather chemical maker TFL part 2 of their ECO Guidelines has been published in order to enhance the understanding of ecological aspects in leather manufacturing.
The issue ‘Salt & nitrogen reduction in the Leather Making Process’ is a clear and easy to understand document focusing on tannery process steps where salt and nitrogen levels can be reduced by means of modifications to the process and the chemicals being used.
TFL say that the brochure is customized to the particular requirements of our direct customers and very useful for the whole leather processing industry.
The TFL ECO Guidelines brochure is now available. Please contact your local TFL partner for further details or have a look at www.tfl.com.
Reduction of salt in leather making
Preserved skin with salted should be desalted before soaking. Pickle float in which high amount of salt is used if recycled the amount of salt in effluent can be reduced.