硫酸盐制浆法是一种用于生产纸浆的工艺，在被称为蒸煮器的大型压力容器中，使用氢氧化钠和硫化钠将木质素从碎木片中分离，从而获得以纤维素为主要成分的纸浆。一些蒸煮器采用间歇蒸煮的方式，另一些如卡米尔（Kamyr）蒸煮器则采用连续的方式。

从纸浆液体中析取得被称为黑液的废液通过蒸发进行浓缩，并在回收锅炉中燃烧以回收其中的无机物再次在纸浆流程中使用。回收锅炉也为工厂产生高压蒸汽。黑液的无机物部分在被称为苛性华的过程中再生制浆所需的氢氧化钠和硫化钠。

如果使用软木（针叶树）作为木浆原材料，在黑液的蒸发过程中，可以回收一种类皂物质。类皂物质将被酸化以生产妥尔油（以生产树脂酸）、脂肪酸和其他化学物质。同时软木也会产生副产品——松节油。

The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibers, the main component of paper. The kraft process entails treatment of wood chips with a hot mixture of water, sodium hydroxide, and sodium sulfide, known as white liquor, that breaks the bonds that link lignin, hemicellulose, and cellulose. The technology entails several steps, both mechanical and chemical. It is the dominant method for producing paper. In some situations, the process has been controversial because Kraft plants can release smelly products and in some situations produce substantial liquid wastes.