GB2577672A

GB2577672A - Biomass conversion by treatment with acids and steam

Info

Publication number: GB2577672A
Application number: GB1812802.5A
Authority: GB
Inventors: Leopold Heinrich
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-08-06
Filing date: 2018-08-06
Publication date: 2020-04-08
Also published as: GB201812802D0

Abstract

A method for converting a biomass raw material into fibre or chemical products comprising treating the biomass with gaseous acid as a reactant and then heating it with steam to a reaction temperature. The process only requires a low chemical charge and can employ hydrochloric acid, sulphur dioxide, sulphur trioxide, formic acid or acetic acid. There may be a lower temperature when the gaseous acid is being used compared to when the raw material is being steam heated. The raw material may be lignocelluloses or agricultural residues including forest residuals or waste wood. The material may be washed to separate the fibre from chemical products for further refining. The approach is designed to concentrate reactants within the biomass leading to quicker disintegration based on the escape of chemical ions from hot steam into cooler aqueous environments. It can be used for producing paper and packaging and chemicals such as ethanol, xylitol, acetic acids and lignin.

Description

Biomass Conversion By Treatment with Acids And Steam Since over hundred years, Sulphite, Kraft and Alkaline pulping have been the standard technology for converting biomass for papermaking, packaging, hygienic materials and some basic chemicals such as ethanol, xylitol and acetic acids as well as lignin. The value of its products of 100 bn British Pound per year equals the worldwide steel industry and is-only second to the oil industry within the commodity based industries.

However, the above technologies require high chemical charge, which is expensive to recover. In addition; the use of sulphur is-a serious environmental concern for air quality and process residuals such as dregs and grids.

The invention relates to an improvement of conventional producing technologies through treatment with gaseous-acids followed by steaming at elevated temperature. Fibre yield and product quality as well as energy and reactants consumption will be improved. The yearly economic benefit of the invention may very likely reach billows of pounds in savings of more than ten times lower chemical and four times lower energy consumption as well as higher valuable fiber and chemical products. As the chemical charge in this process is very low, no recovery of chemicals is required anymore, leading to significant reductions in capital expense.

The invention is based on the observation that chemical ions tend to escape from hot steam into a-cooler aqueous environment This can be used to concentrate reactants within the raw material, leading to a much more efficient use of chemical reactants. Figure 1 depicts the conventional procedure which starts with the impregnation of the raw material 1 in a liquid phase. In the initial phase, the raw material 1 has not completely absorbed the reactants 2 -which are in this case protons: As the reaction should not start before the raw material -1 has fully absorbed the reactants, the temperature rises in most conventional production units slowly-until reaction temperature is reached. In some cases this may take up to-three hours. Assuming a liquid to solids ratio of 4:1, only half of reactants have been absorbed by the raw material when the reaction starts-at reaction temperature. Half of reactants-remain unused in the liquid phase, leading to side and condensation reactions as well as degradation of sugars and heraicelluloses. Conventional processes require therefore a high chemical rharge of up to 250 kg chemical reactants per ton of raw material. This turns conventional factories into large chemical factories in need to recover the high chemical-charge.

Figure 2 depicts the process according to the invention. The raw material 1 is initially treated with reactants -2. in a gas phase. The impregnated raw material is then heated up with steam 3. As ions escape from hot steam, they are compressed into the still cool raw material, which absorbs highly concentrated reactants 2. A high temperature gradient between-raw material at low temperature and the atmosphere surrounding the raw material at high temperature is beneficial. Due to the high concentration and evenly distribution of reactants; the raw material-is more quickly de-composed when the impregnated raw material is heated up by steam to reaction temperature.

The main feature of the process is the treatment of the raw material 1 with gaseous chemical reactants 2 below reaction temperature before the chemicals are further compressed with steam.

Furthermore, it is important to use the raw material in the first stage untreated at its natural humidity of 30-60% at mom temperature. No pre-heating or pre-steaming or drying is necessary as the natural water content in the raw material must absorb the chemical reactant at high concentration. Any possible excessive liquid has to be removed before the gaseous treatment The gaseous impregnation with chemicals is very effective -even at low temperature. Due to -the high concentration of reactants; the raw material is quickly decomposed when the reaction-temperature is-reached.

The first step and the reaction step are combined within one claim as it is the core of the invention that the gaseous rust step is immediately followed by a steaming step. If the second step would be a heating up in liquid phase, reactants would dissociate back into the liquid and the raw material would de-compose much slower.

Claims

Claims 1. A method for converting biomass ('raw material') into fibre and valuable chemical products wherein a) the raw material is treated in a first step with gaseous adds as reactants in a gas phase; (b) the such treated raw material is heated up with steam to reaction temperature.
2. A method according to claim 1, in which the chemical charge in step (a) is between 1kg and 20 kg per ton of raw material.
3. A process according to claim 1, in which the step (a) is between 10 and 90 min long.
4. A process according to claim 1, in which the temperature in step (a) is between 20 and 120 degree Celsius.
5. A process according to claim 1, in which said chemical reactants in step (a) are hydrochloric acid HC1, sulphur dioxide SO2 and sulphur trioxide SW as well as formic acid CH3COOH, acetic add CH3CH2COOH in gaseous condition.
6. A process according to claim 1, in which said heating step (b) is between 10 and 90 minutes long.
7. A process according to claim 1, in which said reaction temperature in heating step (b) is between 160 and 200 degree Celsius.
8. A process according to claim 1, in which said total liquid to solids ratio being between 0.5;1 and 2.011 in step (a) and (b).
9. A process according to claim 1, in which the steps (a) and (b) are practised discontinuously and continuously.
10. A process according to claim 1, in which the non-impregnated raw material being lignocelluloses including beech, eucalyptus, aspen; conifers (spruce, pine...) as well as agricultural residuals including straw, flax, bagasse, rice straw at a water content of 5 to 60% by weight This includes forest residuals and waste wood of a mix of said raw materials.
11. A process according to claim 1, in which said the remains of the treated raw material are washed to separate fibre from chemical products and treated for refining purpose according to state of the art procedures.