Skip to main content

Converting wood into pulp for paper-making

Wood is made up of two basic substances: cellulose (fibres) and lignin (which is essentially the glue that holds the fibres together). When the fibres are separated, the result is wood pulp.

The process of converting wood into pulp for paper-making is remarkably simple, there are two common processes for separating the fibres: mechanical pulping and chemical pulping. Mechanical pulping grinds the wood into individual fibres, while chemical pulping dissolves the lignin. The most common chemical pulp is kraft pulp, made through an alkaline cooking process that breaks the lignin down with the help of sodium sulphate. Bleached kraft pulp is known for its strength, absorbency and brightness.

The lopings, logs, or slabs, up to 11 inches square, are put into a hopper or feeder and guided under the cutter; this consists of a discplate, which, revolving at great speed, disintegrates the laminations of the wood. The wood falling on horizontal rollers. By packing in this manner, 60 cwt. of wood can be treated at one time in place of a limit of 32 cwt. of other material, and as nearly the same quantity of alkali or soda ash is required in dealing with either the large or the small weight. After boiling the wood about three hours, a pulp is produced from which paper can be made ,without the admixture of rags esparto, or any other material.

The basic process for making paper is simple. Pulp fibres are combined with water and other ingredients, forming a mixture that is similar in consistency to orange juice. The mixture is strained through a fine screen, which serves as a bed for the mat of wet fibres. The mat is dried with the help of heat, gravity, pressure and vacuum technologies, and the result is paper.

Modern papermaking machines can produce more than 700 tonnes a day at speeds of over 1,400 metres a minute. Equipment is customized to make many paper products, with different levels of quality. The machines and processes vary, but they do have things in common. They are all complex and they require the dedication of highly skilled workers.


Popular posts from this blog

Does pearls reproduce by itself through time

At the request of several families he and Mrs Legge gave a home for some months to a young Dutch girl, a granddaughter of the first Dutch governor of the Straits Settlements. She had several pearls of which the Dutch residents were great collectors, got from oysters found in a river of the Malay Peninsula, when she left them she gave Mrs Legge a small box containing a large pearl the size of a pea, with a blue spot on it, and two others not so large. This box was then put away and locked up. Several weeks later he took it out and on opening it discovered more than a dozen pearls, most of them very small. Astonished at the phenomenon he called his chief servant, a Portuguese, who happened to enter the room and who expressed no surprise but declared it to be a common occurrence. On enquiry he found that many of the Dutch people had jars of pearls, large and small, which had accumulated in this way. Some years later he related the incident at dinner on board ship. The captain was a cautio

Bidmas, Bedmas, Bodmas, Pedmas And Christmas

This BBC GCSE Bitesize post says, BODMAS stands for 'brackets', 'other', 'division', 'multiplication', 'addition' and 'subtraction'. It's the order in which we carry out a calculation. But another article says, the order of operations in Maths called BIDMAS. BIDMAS stands for Brackets, Indices, Division and Multiplication, Addition and Subtraction. The difference is that the second substitute 'o' with 'i', and we can understand that teacher normally chooses easy way to explain whose pupils can understand, exponent or power or indices are out of reach of foundation students, so teachers uses 'other' instead. And in this article , 'o' actually stands for 'order', as far as my memory can go, my English teacher never teach me 'order' actually means 'Powers and Square Roots, etc.' In United States, the mnemonic fo Order of Operation is PEMDAS, because brackets are called pa

Panic or panick

There is only one spelling for panic ; the verb is inflected 'panic, panics, panicked, and panicking’. The form panick is used for progressive tense, past tense and past participle. We don't write panick today, though English speakers from a few hundred years ago might have (in the same way they might have written musick). When the alternate spelling “panick” is used for the past participle: "I panicked last night at the disco." When it’s use for progressive tense: “Invariably, when markets are panicking, they sell the stocks quickly.” It's the rule for root words ending in "c" is that you have to add “k”, so the spelling is related with the pronunciation. If we don't add the <k>, it looks as if the <c> has to be pronounced /s/. If the "k" was not there, “panicing” would look like the word which is supposed to be pronounced as if it is ended in "sing," while “paniced” would be pronounced like “panised”. The same